Obtaining and Characterization

**3**

**Chapter 1**

**Abstract**

of samples has not been revealed.

**1. Introduction**

Creating

Using of Magnetron Sputtering

*Konstantin V. Sergienko, Mikhail A. Kaplan, Ilya M. Fedyuk,* 

Biocompatible composites obtained using the magnetron sputtering for the production of minimally invasive implantation medical devices (stents) were investigated. Nano- and microdimensional surface layers of Ta, Ti, Ag, and Cu on flat and wire NiTi, Cu, Ti, and SiO2 substrates were created. The phase composition, surface morphology, and the layer-by-layer composition were investigated on an X-ray diffractometer, SEM, and Auger spectrometer. It was shown that the thickness and the structure of surface layers were affected by the sputtering distance, time, power, and the bias voltage at the substrate. The presence of the transition layer that contains both substrate and target elements and provides high adhesion of the surface layer to the substrate has been demonstrated. The material was tested for corrosion resistance under static conditions by dipping into solutions with various acidities (pH from 1.68 to 9.18) for 2 years, static mechanical properties, and biocompatibility in vitro and in vivo. A slight corrosive dissolution was observed only in a medium with a pH of 1.56. Dissolution in the other media is absent. An increase in strength and plasticity in comparison with substrate was attained depending on the nature of the sputtered substance and substrate. Toxicity

for Biocompatible Composites

*Elena O. Nasakina, Mikhail A. Sevostyanov,* 

*Alexander V. Leonov and Alexey G. Kolmakov*

**Keywords:** surface layer, magnetron sputtering, biocompatibility, corrosion resistance, shape memory effect and pseudoelasticity

In the modern world, an efficient manner of operational characteristic increase and of classical material shortcoming elimination is a formation on their basis of composite materials [1–6]. Development of the layered composite materials allowing to effectively combine desirable operational characteristics of the modified surface layers and the main material (substrate) at the present time is perspective in many areas of human activity: in optics (conducting, antireflecting, filtering, reflecting, and

*Alexander S. Baikin, Sergey V. Konushkin,* 

## **Chapter 1**

## Using of Magnetron Sputtering for Biocompatible Composites Creating

*Elena O. Nasakina, Mikhail A. Sevostyanov, Alexander S. Baikin, Sergey V. Konushkin, Konstantin V. Sergienko, Mikhail A. Kaplan, Ilya M. Fedyuk, Alexander V. Leonov and Alexey G. Kolmakov*

## **Abstract**

Biocompatible composites obtained using the magnetron sputtering for the production of minimally invasive implantation medical devices (stents) were investigated. Nano- and microdimensional surface layers of Ta, Ti, Ag, and Cu on flat and wire NiTi, Cu, Ti, and SiO2 substrates were created. The phase composition, surface morphology, and the layer-by-layer composition were investigated on an X-ray diffractometer, SEM, and Auger spectrometer. It was shown that the thickness and the structure of surface layers were affected by the sputtering distance, time, power, and the bias voltage at the substrate. The presence of the transition layer that contains both substrate and target elements and provides high adhesion of the surface layer to the substrate has been demonstrated. The material was tested for corrosion resistance under static conditions by dipping into solutions with various acidities (pH from 1.68 to 9.18) for 2 years, static mechanical properties, and biocompatibility in vitro and in vivo. A slight corrosive dissolution was observed only in a medium with a pH of 1.56. Dissolution in the other media is absent. An increase in strength and plasticity in comparison with substrate was attained depending on the nature of the sputtered substance and substrate. Toxicity of samples has not been revealed.

**Keywords:** surface layer, magnetron sputtering, biocompatibility, corrosion resistance, shape memory effect and pseudoelasticity

## **1. Introduction**

In the modern world, an efficient manner of operational characteristic increase and of classical material shortcoming elimination is a formation on their basis of composite materials [1–6]. Development of the layered composite materials allowing to effectively combine desirable operational characteristics of the modified surface layers and the main material (substrate) at the present time is perspective in many areas of human activity: in optics (conducting, antireflecting, filtering, reflecting, and absorbing media), electronics (conductors, semiconductors, dielectrics), machine engineering, building and household (tribological, durable, wear-resistant, functional, protective, resistant to action of aggressive environment, decorative, and other coatings for structural and utility materials), medicine (biocompatible materials), etc. [1–17].

An effective and fairly common method for such surfaces formation is physical vapor deposition, including variations of magnetron sputtering, since at relatively small expenditure of time and resources, it allows to efficiently receive qualitative thin films of a diverse nature on substrate of virtually any nature and geometry and to control properties of the created materials [7–17]. The deposition method developed at the Baikov Institute of Metallurgy and Materials Science allows one to produce [coating—transition layer—substrate] nanocompositions from thermodynamically nonmiscible elements with good adhesion and resistance to external thermal and mechanical influences [18] and at the same time to avoid substrate overheating with bombarding electrons by keeping them near the sputtering target, which is of high importance for substrate materials with low melting points or phase structure that is sensitive to temperature changes [7].

Among other things, this technology can be successfully used in the formation of medical composite materials that need to have complex properties, combining only the required characteristics of classical materials—for example, for the production of noninvasive stent implants designed to restore the patency of hollow parts of the cardiovascular, excretory, digestive, and respiratory systems [19, 20]. At the same time, the parameters of the resulting composites depend on a number of process conditions that can be conveniently varied over a wide range.

In addition, the initial choice of the components of the future composite is important. Materials with the shape memory effect are the best candidates for creation of medical implants plastically deformable in the cooled condition to extremely compact type promoting easier and less traumatic delivery to the necessary site of an organism without serious surgical intervention. Then, they independently take the functional form in set operational conditions without additional effect [20–23]. The most known medical material from this class is nitinol (NiTi) endowed with mechanical characteristics similar to behavior of living tissues that helps it to adapt to physiological loadings providing necessary service conditions [20–23]. But in addition to positive mechanical characteristics, this alloy possesses also a number of shortcomings: difficulty of processing in case of product production, the high content of a toxic element, disputable level of biocompatibility, and corrosion resistance. Research toward its improvement is actively conducted [23–25]. Thus, nitinol can be taken as the basis of the composite (substrate) and a biologically inert barrier at the contact between the metallic parts of the implant and active biological body fluids is needed. A new surface should be represented by a material with high corrosion resistance and biocompatibility. For example, tantalum and titanium is interesting due to high corrosion resistance in aggressive media, radiopacity, conductivity, wear resistance, nontoxicity, etc. [6]. Silver also exhibiting antitumor and antibacterial action is one of the suitable materials [26].

The purpose of this work was to investigate capabilities and regularities of production of layered biomedical composite materials based on an NiTi shape memory alloy with a surface layer from highly corrosion-resistant and biocompatible tantalum, titanium, or silver with strong adhesion between the components formed by magnetron sputtering and to study its operational properties.

**5**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

**2. Obtaining and investigating of biocompatible composites of medical** 

In this work, creation of layered composites was carried out by formation of tantalum, titanium, silver, etc., surface layers on flat and wire nitinol, titanium, glass/SiO2, etc., substrates (basis) by magnetron sputtering in an argon atmosphere by using a Torr International facility (United States). Working and residual pressure

The surface layers were produced under the following conditions of the process: (1) direct current magnetron, in the case of tantalum and titanium layers I ~ 400–1100 mA, U ~ 360–700 V; in the case of silver layers I ≈ 865 mA, U ~ 830 V; (2) with substrate rotation (rate was 9 rpm) and without it; (3) sputtering time t = 5 to 120 min; (4) bias voltage Ub ≈ 0–1000 V; and (5) sputtering

To avoid overheating, the substrate is critically important for substrate materials with phase structures that are sensitive to temperature changes as nitinol, for example—the thermal treatment allows one to vary static properties and cyclic loadings in operating conditions with a wide range of deformations and is extremely important for stabilization of the properties, constraining (shaping) the samples,

To determine the substrate surface temperature, we used special control samples from materials with various melting points: In (tm = 156.4°C), Sn (tm = 231.9°C), Pb (tm = 327.4°C, and Zn (tm = 419.5°C). Since none of the metals showed surface melting, we concluded that, under any conditions, the substrate surface tempera-

Disks made from chemically pure tantalum, titanium, silver, copper, etc., were used as the sputtered target. Plates made from nitinol, titanium, copper, steel, glass/ SiO2, etc., with a size of 10 × 10 × 0.5 mm and 280 μm diameter wires from nanostructured nitinol (with the composition 55.91 wt% Ni + 44.03 wt% Ti, having grains in the form of 30 to 70 nm diameter nanowires and a cubic crystal lattice (В2 phase)) were used as the basis for composites. Plates were treated with abrasive sandpaper (from 400 to 800 grit) and polished (until their surface became mirror-like) with the addition of diamond suspensions with a particle size of 3, 1, and 0.05 μm for the removal of flat indentations and defects. Nitinol wires were also polished consecutively with sandpaper from 180 to 1000 grit and subjected to finishing polishing with GOI (State Optical Institute) paste to a mirror surface. The decrease in the diameter was to 10 μm in comparison with the original. The depth of surface defects after the processing was less than 1 μm. Different substrates were selected to perfect the production of layered composites. Silicon, copper, and steel substrates are also of interest as a basis for production of functional materials for a wide range of applications (optics, electronics, construction materials, etc.). To clean, activate, and polish the substrate surface, before sputtering, it was bombarded with argon ions at Ue = 900 V

and Ie = 80 mA; i.e., preliminary ionic etching (PIE) was performed.

Phase structure of the deposited films was characterized by the Ultima IV X-ray

diffractometer (Rigaku Co., Japan) in Cu Kα—radiation on the base of Bragg— Brentano method. Phase analysis was prepared in the PDXL program complex using the ICDD database. The surface morphology and the layer-by-layer composition were investigated on a scanning election microscope (SEM) VEGA II SBU with the module INCA Energy for energy-dispersive analysis (TESCAN, Czech Republic), on a GDS 850A atomic emission spectrometer (JEOL Co., Japan), and on a JAMP-9500F Auger spectrometer (JEOL Co., Japan) in combination with ion etching at argon bombardment under an angle of 30°. In Auger electron spectroscopy,

distance (the distance from the target to the substrate) of 40–200 mm.

Pa, respectively.

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

in the vacuum chamber was 0.4 and 4 × 10<sup>−</sup><sup>4</sup>

and successful application of the product.

ture did not reach 150°C in any of the regimes used.

**appointment**

*Advances in Composite Materials Development*

[1–17].

changes [7].

wide range.

absorbing media), electronics (conductors, semiconductors, dielectrics), machine engineering, building and household (tribological, durable, wear-resistant, functional, protective, resistant to action of aggressive environment, decorative, and other coatings for structural and utility materials), medicine (biocompatible materials), etc.

An effective and fairly common method for such surfaces formation is physical vapor deposition, including variations of magnetron sputtering, since at relatively small expenditure of time and resources, it allows to efficiently receive qualitative thin films of a diverse nature on substrate of virtually any nature and geometry and to control properties of the created materials [7–17]. The deposition method developed at the Baikov Institute of Metallurgy and Materials Science allows one to produce [coating—transition layer—substrate] nanocompositions from thermodynamically nonmiscible elements with good adhesion and resistance to external thermal and mechanical influences [18] and at the same time to avoid substrate overheating with bombarding electrons by keeping them near the sputtering target, which is of high importance for substrate materials with low melting points or phase structure that is sensitive to temperature

Among other things, this technology can be successfully used in the formation of medical composite materials that need to have complex properties, combining only the required characteristics of classical materials—for example, for the production of noninvasive stent implants designed to restore the patency of hollow parts of the cardiovascular, excretory, digestive, and respiratory systems [19, 20]. At the same time, the parameters of the resulting composites depend on a number of process conditions that can be conveniently varied over a

In addition, the initial choice of the components of the future composite is important. Materials with the shape memory effect are the best candidates for creation of medical implants plastically deformable in the cooled condition to extremely compact type promoting easier and less traumatic delivery to the necessary site of an organism without serious surgical intervention. Then, they independently take the functional form in set operational conditions without additional effect [20–23]. The most known medical material from this class is nitinol (NiTi) endowed with mechanical characteristics similar to behavior of living tissues that helps it to adapt to physiological loadings providing necessary service conditions [20–23]. But in addition to positive mechanical characteristics, this alloy possesses also a number of shortcomings: difficulty of processing in case of product production, the high content of a toxic element, disputable level of biocompatibility, and corrosion resistance. Research toward its improvement is actively conducted [23–25]. Thus, nitinol can be taken as the basis of the composite (substrate) and a biologically inert barrier at the contact between the metallic parts of the implant and active biological body fluids is needed. A new surface should be represented by a material with high corrosion resistance and biocompatibility. For example, tantalum and titanium is interesting due to high corrosion resistance in aggressive media, radiopacity, conductivity, wear resistance, nontoxicity, etc. [6]. Silver also exhibiting antitumor and antibacterial action is one of

The purpose of this work was to investigate capabilities and regularities of production of layered biomedical composite materials based on an NiTi shape memory alloy with a surface layer from highly corrosion-resistant and biocompatible tantalum, titanium, or silver with strong adhesion between the components

formed by magnetron sputtering and to study its operational properties.

**4**

the suitable materials [26].

## **2. Obtaining and investigating of biocompatible composites of medical appointment**

In this work, creation of layered composites was carried out by formation of tantalum, titanium, silver, etc., surface layers on flat and wire nitinol, titanium, glass/SiO2, etc., substrates (basis) by magnetron sputtering in an argon atmosphere by using a Torr International facility (United States). Working and residual pressure in the vacuum chamber was 0.4 and 4 × 10<sup>−</sup><sup>4</sup> Pa, respectively.

The surface layers were produced under the following conditions of the process: (1) direct current magnetron, in the case of tantalum and titanium layers I ~ 400–1100 mA, U ~ 360–700 V; in the case of silver layers I ≈ 865 mA, U ~ 830 V; (2) with substrate rotation (rate was 9 rpm) and without it; (3) sputtering time t = 5 to 120 min; (4) bias voltage Ub ≈ 0–1000 V; and (5) sputtering distance (the distance from the target to the substrate) of 40–200 mm.

To avoid overheating, the substrate is critically important for substrate materials with phase structures that are sensitive to temperature changes as nitinol, for example—the thermal treatment allows one to vary static properties and cyclic loadings in operating conditions with a wide range of deformations and is extremely important for stabilization of the properties, constraining (shaping) the samples, and successful application of the product.

To determine the substrate surface temperature, we used special control samples from materials with various melting points: In (tm = 156.4°C), Sn (tm = 231.9°C), Pb (tm = 327.4°C, and Zn (tm = 419.5°C). Since none of the metals showed surface melting, we concluded that, under any conditions, the substrate surface temperature did not reach 150°C in any of the regimes used.

Disks made from chemically pure tantalum, titanium, silver, copper, etc., were used as the sputtered target. Plates made from nitinol, titanium, copper, steel, glass/ SiO2, etc., with a size of 10 × 10 × 0.5 mm and 280 μm diameter wires from nanostructured nitinol (with the composition 55.91 wt% Ni + 44.03 wt% Ti, having grains in the form of 30 to 70 nm diameter nanowires and a cubic crystal lattice (В2 phase)) were used as the basis for composites. Plates were treated with abrasive sandpaper (from 400 to 800 grit) and polished (until their surface became mirror-like) with the addition of diamond suspensions with a particle size of 3, 1, and 0.05 μm for the removal of flat indentations and defects. Nitinol wires were also polished consecutively with sandpaper from 180 to 1000 grit and subjected to finishing polishing with GOI (State Optical Institute) paste to a mirror surface. The decrease in the diameter was to 10 μm in comparison with the original. The depth of surface defects after the processing was less than 1 μm. Different substrates were selected to perfect the production of layered composites. Silicon, copper, and steel substrates are also of interest as a basis for production of functional materials for a wide range of applications (optics, electronics, construction materials, etc.). To clean, activate, and polish the substrate surface, before sputtering, it was bombarded with argon ions at Ue = 900 V and Ie = 80 mA; i.e., preliminary ionic etching (PIE) was performed.

Phase structure of the deposited films was characterized by the Ultima IV X-ray diffractometer (Rigaku Co., Japan) in Cu Kα—radiation on the base of Bragg— Brentano method. Phase analysis was prepared in the PDXL program complex using the ICDD database. The surface morphology and the layer-by-layer composition were investigated on a scanning election microscope (SEM) VEGA II SBU with the module INCA Energy for energy-dispersive analysis (TESCAN, Czech Republic), on a GDS 850A atomic emission spectrometer (JEOL Co., Japan), and on a JAMP-9500F Auger spectrometer (JEOL Co., Japan) in combination with ion etching at argon bombardment under an angle of 30°. In Auger electron spectroscopy,

the surface layer thickness was taken to be equal to the depth at which the atomic percentages of the constituent elements plateaued. Fracture surfaces were also examined on the TESCAN VEGA II SBU.

On the whole, similar results were obtained by examining the surface layer composition (**Figure 1**): the top surface layer was oxygen-enriched to a depth of 20 nm owing to active surface adsorption, a deeper layer consisted of only submitted element, and the transition layer was also oxygen enriched and resided on the substrate. The formation of the transition layer is connected with the fact that magnetron sputtering results in atoms and ions of the sputtered substance not only condensing on the substrate surface but also approaching it with some excess energy with their contact leading to a number of interparticle interactions: "knocking in" of sputtered atoms and ions, "knocking out" by them (upon elastic or inelastic interaction with or without transfer of their additional energy), and redeposition or, on the contrary, penetration of the surface particles (both of the substrate and earlier deposited elements) into the substrate structure, formation of radiation defects that stimulate mutual diffusion of elements of the deposited layer and substrate at their interface, etc. Thus, the mobilized particles, sputtered substance, and surface region of the substrate that are subjected to multiple collisions and set in chaotic motion at or near the substrate surface are constantly mixed. In the end, the surface region becomes so saturated by the sputtered substance that its interaction with new flows of atoms and ions leads to the formation of the surface layer of the composite.

**Figure 2a** shows dependence of tantalum surface layer thickness from time of magnetron sputtering on a nitinol substrate. Increasing the sputtering time to 20 min (at direct current of 865 mA, voltage of 700 V and distance 200 mm) increased the thickness of both the surface layer (consisting only of the deposited substance) and the transition layer (containing elements of both the substrate and deposited substance). Further increasing the sputtering time caused an increase only in the thickness of the surface layer, which varied nonlinearly, following a descending law, and up to 30 min more intensively, than at bigger time. This situation remains at all used materials and conditions. It occurs, most likely, because at the beginning of surface layer formation, atoms and ions of deposited substance, overcoming a sputtering distance, collide with particles of working gas, with each other and with new substrate surface and do not appear at each site of its surface in equal volume and at the beginning interact with it chaotically and unevenly. And further (at increase of sputtering time, and so of the time of influence on a surface), particles continue to collide, mixing up, try to reach thermodynamically more advantageous position and state, and a more uniform distribution of the deposited substance at the surfaces takes place. By consideration of cross section of samples, it

#### **Figure 1.**

*Composition depth profiles for a Ti-nitinol sample obtained by sputtering for 30 min at direct current of 865 mA, voltage of 700 V, and distance of 200 mm (a) and for Ag-nitinol obtained at a distance of 150 mm (b).*

**7**

**Figure 3.**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

is visible that at smaller time of a sputtering, the surface shows a big heterogeneity (**Figure 2b**). First, the layer had the form of isolated islands. Subsequently, a more

*Dependence of the surface layer structure on the time of magnetron sputtering of tantalum on a nitinol substrate at direct current of 865 mA, voltage of 700 V, and distance 200 mm (a) and microstructure changes (b).*

In case of thin films of tantalum, according to literary data, formation of both alpha and beta phases, which differ in properties, is possible [10–17, 27–29]. The X-ray diffraction patterns of our samples with nitinol basis (**Figure 3**) demonstrate that depending on sputtering, time tantalum is formed in two various crystal states—an alpha (a cubic crystal lattice) and a beta (a tetragonal lattice with the

*X-ray diffraction patterns of a composite on the basis of a nitinol received at magnetron sputtering time: (a) 5 min, (b) 10 and 20 min, (c) 29 min, (d) 30 min at direct current of 865 mA, voltage of 700 V and distance of 200 mm.*

uniform Ta distribution over the substrate surface was obtained.

small content of oxygen).

**Figure 2.**

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

#### **Figure 2.**

*Advances in Composite Materials Development*

examined on the TESCAN VEGA II SBU.

the surface layer thickness was taken to be equal to the depth at which the atomic percentages of the constituent elements plateaued. Fracture surfaces were also

On the whole, similar results were obtained by examining the surface layer composition (**Figure 1**): the top surface layer was oxygen-enriched to a depth of 20 nm owing to active surface adsorption, a deeper layer consisted of only submitted element, and the transition layer was also oxygen enriched and resided on the substrate. The formation of the transition layer is connected with the fact that magnetron sputtering results in atoms and ions of the sputtered substance not only condensing on the substrate surface but also approaching it with some excess energy with their contact leading to a number of interparticle interactions: "knocking in" of sputtered atoms and ions, "knocking out" by them (upon elastic or inelastic interaction with or without transfer of their additional energy), and redeposition or, on the contrary, penetration of the surface particles (both of the substrate and earlier deposited elements) into the substrate structure, formation of radiation defects that stimulate mutual diffusion of elements of the deposited layer and substrate at their interface, etc. Thus, the mobilized particles, sputtered substance, and surface region of the substrate that are subjected to multiple collisions and set in chaotic motion at or near the substrate surface are constantly mixed. In the end, the surface region becomes so saturated by the sputtered substance that its interaction with new flows of atoms and ions leads to the formation of the surface layer of the composite. **Figure 2a** shows dependence of tantalum surface layer thickness from time of magnetron sputtering on a nitinol substrate. Increasing the sputtering time to 20 min (at direct current of 865 mA, voltage of 700 V and distance 200 mm) increased the thickness of both the surface layer (consisting only of the deposited substance) and the transition layer (containing elements of both the substrate and deposited substance). Further increasing the sputtering time caused an increase only in the thickness of the surface layer, which varied nonlinearly, following a descending law, and up to 30 min more intensively, than at bigger time. This situation remains at all used materials and conditions. It occurs, most likely, because at the beginning of surface layer formation, atoms and ions of deposited substance, overcoming a sputtering distance, collide with particles of working gas, with each other and with new substrate surface and do not appear at each site of its surface in equal volume and at the beginning interact with it chaotically and unevenly. And further (at increase of sputtering time, and so of the time of influence on a surface), particles continue to collide, mixing up, try to reach thermodynamically more advantageous position and state, and a more uniform distribution of the deposited substance at the surfaces takes place. By consideration of cross section of samples, it

*Composition depth profiles for a Ti-nitinol sample obtained by sputtering for 30 min at direct current of 865 mA, voltage of 700 V, and distance of 200 mm (a) and for Ag-nitinol obtained at a distance of 150 mm (b).*

**6**

**Figure 1.**

*Dependence of the surface layer structure on the time of magnetron sputtering of tantalum on a nitinol substrate at direct current of 865 mA, voltage of 700 V, and distance 200 mm (a) and microstructure changes (b).*

is visible that at smaller time of a sputtering, the surface shows a big heterogeneity (**Figure 2b**). First, the layer had the form of isolated islands. Subsequently, a more uniform Ta distribution over the substrate surface was obtained.

In case of thin films of tantalum, according to literary data, formation of both alpha and beta phases, which differ in properties, is possible [10–17, 27–29]. The X-ray diffraction patterns of our samples with nitinol basis (**Figure 3**) demonstrate that depending on sputtering, time tantalum is formed in two various crystal states—an alpha (a cubic crystal lattice) and a beta (a tetragonal lattice with the small content of oxygen).

#### **Figure 3.**

*X-ray diffraction patterns of a composite on the basis of a nitinol received at magnetron sputtering time: (a) 5 min, (b) 10 and 20 min, (c) 29 min, (d) 30 min at direct current of 865 mA, voltage of 700 V and distance of 200 mm.*

In the case of a sample with a Ta surface layer obtained by sputtering for 5 min, the major phase was nitinol, but many peaks β-Ta in the 2-theta range from 33 to 81° were observed, which also corresponds to various crystal orientation. In the composites formed after sputtering for 10 and 20 min, β-Ta with O were a major phase, and only two main peaks were observed, but nitinol was also present. After 29 min, the strongest peak was that from α-Ta, and there were β-Ta with O and nitinol, due to the averaging of results over the entire probing depth; at further increase in time, α-Ta dominated and very weak peaks of β-Ta and nitinol were observed. Thus, it turns out that irrespective of summary sputtering time, the beta phase is formed in the beginning and at sputtering time, more than 20 min on it, alpha tantalum is deposited. The same regularities are observed in case of other substrates, which are united by availability of oxygen in a surface. In contrast to data available in the literature, the formation of α-Ta in this study cannot be due to an increase in temperature [10, 14, 27, 28].

Several theories of tantalum formation in α or β phase is developed, which are generally connected with working temperature and pressure (defining mobility and energy of atoms) and the substrate nature. However, different authors achieve often contradictory results.

It is noted that the alpha phase is formed at temperatures more than 400°C, promoting mobility increase in deposited atoms : initially at heating of a substrate or as a result of the annealing following sedimentation (then deposited β-Ta transforms in α-Ta) [10, 14, 27, 28]. However at a temperature about 400–500°C, β phase is also received (for example, in the form of the particles distributed in α) [10, 28], and α is also formed without heating [12, 15]. It is specified that with the growth of temperature, the size of grains, impurity amount in a surface layer (for example, the dissociation of oxides enhanced, i.e., the O contents lowered), and its amorphousness decreases.

Presence at the working atmosphere of the high oxygen content according to [16] leads to fast formation of oxides and, therefore, promotes formation of a tantalic layer in a beta state, whereas in [15], oxygen environment did not prevent the formation of alpha tantalum. At a deposition on silicon and glass substrates in [13, 16, 17], 0.5–0.7 Pa sputtering pressure led to α-Ta formation and smaller or bigger pressure—β-Ta, but in [15] already at 0.28 Pa, α phase was formed.

In [17], alpha tantalum was also formed at 0.3 and 1.4 Pa pressure, but at sputtering on earlier deposited α-Ta (110) layer. Also, it was specified that (110) is the most low-energy lattice for body-centered cubic (BCC) materials and provokes formation on itself of the same structure. Being a zone of a new surface nucleation, the substrate surface specifies the character of its structure formation. It was shown that on amorphous carboniferous or oxidic surfaces, the beta tantalum is formed, for example, on titanium without natural oxide or TaN substrates, the α-Ta is formed [11, 12, 14, 17].

And though availability of oxygen on a substrate surface not always prevented the formation of α-Ta, nevertheless, it is considered that it promotes formation of β-Ta. Therefore, its creation in this work in an initial time period on all substrates is quite expected, despite ionic etching.

In [14], as well as in this research, it was shown that longer time promotes layering of α-Ta on earlier formed β-Та, but authors connected it with a considerable warming up of a surface (more than 350°C), whereas in this work, temperature of a substrate did not rise higher than 150°C and so could not influence formation of alpha phase. It is worth noting that α-Та is a more thermodynamically stable phase. It is, therefore, reasonable to assume that, in this study, it results from a more uniform surface coverage with increasing sputtering time (because increasing the sputtering time increases the probability that a particle will find a more appropriate state and position), possible local surface heating (within several atomic layers,

**9**

**Figure 4.**

*for 30 min at a distance of 150 mm, 865 mA, and 400 V.*

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

time was too short for a purely metallic tantalum layer to form.

which cannot be detected visually), and the absence of oxygen (incorporated into

In combination with the above results of layer composition, this X-ray diffraction data lead us to assume that the surfaces of both the substrate and surface layer actively adsorbed oxygen and that, in the initial stage of the process, the sputtering

Purely silver or titanium layers in a single phase are formed on nitinol at all conditions, which is reflected in an X-ray pattern by characteristic peaks (**Figure 4**) [26].

*X-ray patterns of Ag-NiTi composites obtained by sputtering: (a) for 20 min, (b) for 30 min, and (c) Ti-NiTi* 

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

the β-Та sublayer) [11, 12, 14, 17].

#### *Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Advances in Composite Materials Development*

contradictory results.

phousness decreases.

[11, 12, 14, 17].

quite expected, despite ionic etching.

In the case of a sample with a Ta surface layer obtained by sputtering for 5 min, the major phase was nitinol, but many peaks β-Ta in the 2-theta range from 33 to 81° were observed, which also corresponds to various crystal orientation. In the composites formed after sputtering for 10 and 20 min, β-Ta with O were a major phase, and only two main peaks were observed, but nitinol was also present. After 29 min, the strongest peak was that from α-Ta, and there were β-Ta with O and nitinol, due to the averaging of results over the entire probing depth; at further increase in time, α-Ta dominated and very weak peaks of β-Ta and nitinol were observed. Thus, it turns out that irrespective of summary sputtering time, the beta phase is formed in the beginning and at sputtering time, more than 20 min on it, alpha tantalum is deposited. The same regularities are observed in case of other substrates, which are united by availability of oxygen in a surface. In contrast to data available in the literature, the formation of α-Ta in this study cannot be due to an increase in temperature [10, 14, 27, 28]. Several theories of tantalum formation in α or β phase is developed, which are generally connected with working temperature and pressure (defining mobility and energy of atoms) and the substrate nature. However, different authors achieve often

It is noted that the alpha phase is formed at temperatures more than 400°C, promoting mobility increase in deposited atoms : initially at heating of a substrate or as a result of the annealing following sedimentation (then deposited β-Ta transforms in α-Ta) [10, 14, 27, 28]. However at a temperature about 400–500°C, β phase is also received (for example, in the form of the particles distributed in α) [10, 28], and α is also formed without heating [12, 15]. It is specified that with the growth of temperature, the size of grains, impurity amount in a surface layer (for example, the dissociation of oxides enhanced, i.e., the O contents lowered), and its amor-

Presence at the working atmosphere of the high oxygen content according to [16] leads to fast formation of oxides and, therefore, promotes formation of a tantalic layer in a beta state, whereas in [15], oxygen environment did not prevent the formation of alpha tantalum. At a deposition on silicon and glass substrates in [13, 16, 17], 0.5–0.7 Pa sputtering pressure led to α-Ta formation and smaller or bigger

In [17], alpha tantalum was also formed at 0.3 and 1.4 Pa pressure, but at sputtering on earlier deposited α-Ta (110) layer. Also, it was specified that (110) is the most low-energy lattice for body-centered cubic (BCC) materials and provokes formation on itself of the same structure. Being a zone of a new surface nucleation, the substrate surface specifies the character of its structure formation. It was shown that on amorphous carboniferous or oxidic surfaces, the beta tantalum is formed, for example, on titanium without natural oxide or TaN substrates, the α-Ta is formed

And though availability of oxygen on a substrate surface not always prevented the formation of α-Ta, nevertheless, it is considered that it promotes formation of β-Ta. Therefore, its creation in this work in an initial time period on all substrates is

In [14], as well as in this research, it was shown that longer time promotes layering of α-Ta on earlier formed β-Та, but authors connected it with a considerable warming up of a surface (more than 350°C), whereas in this work, temperature of a substrate did not rise higher than 150°C and so could not influence formation of alpha phase. It is worth noting that α-Та is a more thermodynamically stable phase. It is, therefore, reasonable to assume that, in this study, it results from a more uniform surface coverage with increasing sputtering time (because increasing the sputtering time increases the probability that a particle will find a more appropriate state and position), possible local surface heating (within several atomic layers,

pressure—β-Ta, but in [15] already at 0.28 Pa, α phase was formed.

**8**

which cannot be detected visually), and the absence of oxygen (incorporated into the β-Та sublayer) [11, 12, 14, 17].

In combination with the above results of layer composition, this X-ray diffraction data lead us to assume that the surfaces of both the substrate and surface layer actively adsorbed oxygen and that, in the initial stage of the process, the sputtering time was too short for a purely metallic tantalum layer to form.

Purely silver or titanium layers in a single phase are formed on nitinol at all conditions, which is reflected in an X-ray pattern by characteristic peaks (**Figure 4**) [26].

#### **Figure 4.**

*X-ray patterns of Ag-NiTi composites obtained by sputtering: (a) for 20 min, (b) for 30 min, and (c) Ti-NiTi for 30 min at a distance of 150 mm, 865 mA, and 400 V.*

A composite with silver that is produced for 30 min has only Ag peaks observed because of natural growth of the thickness of the surface layer. At a sputtering time of 20 min or in Ti-NiTi composite produced for 20 and 30 min, the main phase is a sputtered metal, but also traces of the nitinol substrate are observed owing to data averaging over the depth. These results are repeated with all the used substrates.

**Figure 5** shows the dependence of the thickness of the surface tantalum layer (produced for 30 min at ~865 mA, ~700 V, a sputtering distance of 200 mm and with PIE on a flat nitinol substrate) on the applied negative bias voltage that was instrumental in the process of ion-atomic deposition [7, 18]. The bias voltage affected both the thickness and the structure of layers: a voltage of 100 V reduced (relative to zero voltage bias) the thickness of the surface and the complete layers supposedly because of the structure densification by the additional ionic bombardment. At higher voltages, the surface layer became thicker owing to an increase in the rate of deposition of the sputtered material, while the thickness of the transition layer was reduced somewhat (apparently because of further densification of its structure). The optimum conditions were attained at 500 V, and the further increase in the bias voltage probably led to certain sputtering of the surface: the thickness of the surface layer was reduced again, while the thickness of the transition layer remained the same.

Large corrugations with a length on the order of 20–10 μm and a width of 3–5 μm were observed at the surface of all samples (**Figure 6**). Their characteristic appearance did not change with applied bias voltage, and they did not disappear after a layer with a thickness of about 10 nm was etched out. Therefore, they may be interpreted as the initial microrelief of the sample surface. When the bias voltage was applied, smaller wavelike corrugations with a length of 6–10 μm and a width of 0.5–1 μm emerged at the surfaces of samples. An increase in the bias voltage from 100 to 1000 V led to the gradual smoothing of these corrugations, which were easily observable at first, but became virtually imperceptible at 1000 V. The surface after 1000 V did not differ from the one obtained under zero voltage bias (**Figure 6**). The emergence of smaller scale corrugations may probably be attributed to the presence of residual compressive stresses at the composite surface. A bias voltage of 500 V triggered a uniform distribution of point dimples that likely represented the traces of ion bombardment [9], but these pits and all other inhomogeneities of a similar scale disappeared after a layer with a thickness of about 10 nm was etched out.

**Figure 5.**

*Dependence of the thickness of the surface tantalum layer produced on a nitinol substrate at ~865 mA, ~700 V, a sputtering distance of 20 cm, and with PIE for 30 min on the bias voltage.*

**11**

**Figure 7.**

**Figure 6.**

*(d) 1000 V.*

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

The overall thickness of surface layers was increased almost linearly with sputtering power. The thicknesses of both the surface and the transition layers were raised to 30% of the maximum value (**Figure 7**). The thickness of the transition layer was reduced in the 30–50% power interval, while both the surface and the transition layers became thicker again at higher powers. The increase in their thicknesses may be attributed to the raised target sputtering rate [7], and the temporary reduction in the transition layers thickness may be associated with the structure

*Dependence of the thickness of the surface titanium layer produced on a glass substrate at ~865 mA, ~400 V, a* 

*sputtering distance of 150 mm, Ub ~ 0 V, for 30 min on the sputtering power.*

*Appearance of the surface tantalum layer produced on a titanium nickelide substrate at ~865 mA, ~700 V, and a sputtering distance of 15 cm (the sputtering process took 30 min) under Ub = (a) 100, (b) 500, (c) 800, and* 

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

#### **Figure 6.**

*Advances in Composite Materials Development*

tion layer remained the same.

10 nm was etched out.

A composite with silver that is produced for 30 min has only Ag peaks observed because of natural growth of the thickness of the surface layer. At a sputtering time of 20 min or in Ti-NiTi composite produced for 20 and 30 min, the main phase is a sputtered metal, but also traces of the nitinol substrate are observed owing to data averaging over the depth. These results are repeated with all the used substrates. **Figure 5** shows the dependence of the thickness of the surface tantalum layer (produced for 30 min at ~865 mA, ~700 V, a sputtering distance of 200 mm and with PIE on a flat nitinol substrate) on the applied negative bias voltage that was instrumental in the process of ion-atomic deposition [7, 18]. The bias voltage affected both the thickness and the structure of layers: a voltage of 100 V reduced (relative to zero voltage bias) the thickness of the surface and the complete layers supposedly because of the structure densification by the additional ionic bombardment. At higher voltages, the surface layer became thicker owing to an increase in the rate of deposition of the sputtered material, while the thickness of the transition layer was reduced somewhat (apparently because of further densification of its structure). The optimum conditions were attained at 500 V, and the further increase in the bias voltage probably led to certain sputtering of the surface: the thickness of the surface layer was reduced again, while the thickness of the transi-

Large corrugations with a length on the order of 20–10 μm and a width of 3–5 μm were observed at the surface of all samples (**Figure 6**). Their characteristic appearance did not change with applied bias voltage, and they did not disappear after a layer with a thickness of about 10 nm was etched out. Therefore, they may be interpreted as the initial microrelief of the sample surface. When the bias voltage was applied, smaller wavelike corrugations with a length of 6–10 μm and a width of 0.5–1 μm emerged at the surfaces of samples. An increase in the bias voltage from 100 to 1000 V led to the gradual smoothing of these corrugations, which were easily observable at first, but became virtually imperceptible at 1000 V. The surface after 1000 V did not differ from the one obtained under zero voltage bias (**Figure 6**). The emergence of smaller scale corrugations may probably be attributed to the presence of residual compressive stresses at the composite surface. A bias voltage of 500 V triggered a uniform distribution of point dimples that likely represented the traces of ion bombardment [9], but these pits and all other inhomogeneities of a similar scale disappeared after a layer with a thickness of about

*Dependence of the thickness of the surface tantalum layer produced on a nitinol substrate at ~865 mA, ~700 V,* 

*a sputtering distance of 20 cm, and with PIE for 30 min on the bias voltage.*

**10**

**Figure 5.**

*Appearance of the surface tantalum layer produced on a titanium nickelide substrate at ~865 mA, ~700 V, and a sputtering distance of 15 cm (the sputtering process took 30 min) under Ub = (a) 100, (b) 500, (c) 800, and (d) 1000 V.*

The overall thickness of surface layers was increased almost linearly with sputtering power. The thicknesses of both the surface and the transition layers were raised to 30% of the maximum value (**Figure 7**). The thickness of the transition layer was reduced in the 30–50% power interval, while both the surface and the transition layers became thicker again at higher powers. The increase in their thicknesses may be attributed to the raised target sputtering rate [7], and the temporary reduction in the transition layers thickness may be associated with the structure

**Figure 7.**

*Dependence of the thickness of the surface titanium layer produced on a glass substrate at ~865 mA, ~400 V, a sputtering distance of 150 mm, Ub ~ 0 V, for 30 min on the sputtering power.*

densification and a reduction in the available formation time with increasing energy and density of the flux of sputtered material. When the tantalum sputtering power was raised above 70%, the thickness of the surface layer increased only slightly, and the thickness of the transition layer remained the same (on a metal substrate) or was increased (on a glass substrate; see **Figure 7**) presumably owing to the influence of pores in the material. This also raised the target consumption rate and the potential to contaminate the surface of the composite with, among other things, elements of the walls of the working chamber that are knocked out by high energy particles.

On the one hand, with distance increasing at other equal conditions, the thickness of the tantalum surface layer naturally decreases (**Figure 8**) because larger volume of the sputtered substance is scattered away from the substrate; on the other hand, the thickness of the transition layer increases, which can be explained by a more intense flow of the sputtered substance at a shorter distance, uniformly but faster filling the surface and less diffusing into the substrate; and the total thickness of the layers eventually reaches a certain plateau, practically unchanged when the distance is more than 80–90 mm. Since the presence of a substantial transition layer is a presumable reason for the good adhesion of a new surface to the substrate [6], the surface layer must be adjusted to the mechanical properties of the substrate, and also considering the microdefects of the surface at small distances, the distances from the target to the substrate in the range of 100–150 mm are more optimum.

In contrast to tantalum, where the appearance of the surface layer thickness curve completely corresponds to the calculated models [7], in the case of a silver layer, two plateaus are observed (**Figure 9**): almost constant thicknesses at small sputtering distances can be attributed to saturation of the surface at high intensities of flux falling on the substrate. Unlike the previous case, both the surface layer and the transition layer are thinned with increasing distance, because a smaller volume of substance reached its goal, but the intensity of the flow did not affect the formation of the transition layer.

Visually, the layer thickness also was reduced (**Figure 10**) as the sputtering distance was increased under otherwise equal conditions. At smaller distances from the target to the substrate, no appreciable transition layer was observed in SEM images.

**Figure 8.**

*Change in the tantalum surface layers thickness as a function of the distance between the target and the substrate for composite obtained for 30 min at 400 V, 865 mA.*

**13**

*3.6 μm.*

**Figure 10.**

**Figure 9.**

*for composite obtained for 30 min.*

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

The morphology of a new surface repeats the substrate state regardless of the sputtering conditions (**Figure 11**). However, at small distances, surface microdefects appear as point depressions (**Figure 12**), recalling effect of high bias voltage and ion implantation [7, 9], which is correlated with a more intense flow of the sprayed material reaching the surface of the substrate, in comparison with larger distances. Formation of layers on the side that is opposite to the sputtered flow was noted. In this case, the structure and patterns of these layers changes are analogous to the straight side, but every 10–15 times thinner (**Figure 13**). This also could be accounted for by a large sputtering distance: when particles that are sputtered travel over large distances, they completely lose additional energy and directed movement, slow down to thermal velocities corresponding to the gas temperature, start to move like any atoms in a gaseous state, and can condense at the opposite side of the substrate upon collision with it [7]; there is also the possibility that sputtered atoms

*Dependence of the thickness of the surface tantalum layer distribution of elements in the structure of composites produced on a nitinol substrate for 120 min at ~865 mA, ~700 V, Ub ~ 1000 V, and with PIE on the sputtering distance. The sputtering distance was (a) 100 and (b) 200 mm, while the layer thickness was (a) 6.3 and (b)* 

*Change in the silver surface layers thickness as a function of the distance between the target and the substrate* 

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

#### **Figure 9.**

*Advances in Composite Materials Development*

densification and a reduction in the available formation time with increasing energy and density of the flux of sputtered material. When the tantalum sputtering power was raised above 70%, the thickness of the surface layer increased only slightly, and the thickness of the transition layer remained the same (on a metal substrate) or was increased (on a glass substrate; see **Figure 7**) presumably owing to the influence of pores in the material. This also raised the target consumption rate and the potential to contaminate the surface of the composite with, among other things, elements of the walls of the working chamber that are knocked out by high energy particles. On the one hand, with distance increasing at other equal conditions, the thickness of the tantalum surface layer naturally decreases (**Figure 8**) because larger volume of the sputtered substance is scattered away from the substrate; on the other hand, the thickness of the transition layer increases, which can be explained by a more intense flow of the sputtered substance at a shorter distance, uniformly but faster filling the surface and less diffusing into the substrate; and the total thickness of the layers eventually reaches a certain plateau, practically unchanged when the distance is more than 80–90 mm. Since the presence of a substantial transition layer is a presumable reason for the good adhesion of a new surface to the substrate [6], the surface layer must be adjusted to the mechanical properties of the substrate, and also considering the microdefects of the surface at small distances, the distances from the target to the substrate in the range of 100–150 mm are more optimum. In contrast to tantalum, where the appearance of the surface layer thickness curve completely corresponds to the calculated models [7], in the case of a silver layer, two plateaus are observed (**Figure 9**): almost constant thicknesses at small sputtering distances can be attributed to saturation of the surface at high intensities of flux falling on the substrate. Unlike the previous case, both the surface layer and the transition layer are thinned with increasing distance, because a smaller volume of substance reached its goal, but the intensity of the flow did not affect the formation of the transition layer. Visually, the layer thickness also was reduced (**Figure 10**) as the sputtering distance was increased under otherwise equal conditions. At smaller distances from the target to the substrate, no appreciable transition layer was observed in

*Change in the tantalum surface layers thickness as a function of the distance between the target and the* 

*substrate for composite obtained for 30 min at 400 V, 865 mA.*

**12**

**Figure 8.**

SEM images.

*Change in the silver surface layers thickness as a function of the distance between the target and the substrate for composite obtained for 30 min.*

The morphology of a new surface repeats the substrate state regardless of the sputtering conditions (**Figure 11**). However, at small distances, surface microdefects appear as point depressions (**Figure 12**), recalling effect of high bias voltage and ion implantation [7, 9], which is correlated with a more intense flow of the sprayed material reaching the surface of the substrate, in comparison with larger distances. Formation of layers on the side that is opposite to the sputtered flow was noted. In this case, the structure and patterns of these layers changes are analogous to the straight side, but every 10–15 times thinner (**Figure 13**). This also could be accounted for by a large sputtering distance: when particles that are sputtered travel over large distances, they completely lose additional energy and directed movement, slow down to thermal velocities corresponding to the gas temperature, start to move like any atoms in a gaseous state, and can condense at the opposite side of the substrate upon collision with it [7]; there is also the possibility that sputtered atoms

#### **Figure 10.**

*Dependence of the thickness of the surface tantalum layer distribution of elements in the structure of composites produced on a nitinol substrate for 120 min at ~865 mA, ~700 V, Ub ~ 1000 V, and with PIE on the sputtering distance. The sputtering distance was (a) 100 and (b) 200 mm, while the layer thickness was (a) 6.3 and (b) 3.6 μm.*

#### **Figure 11.**

*Morphology of the surface of a glass substrate, straight side (a) and opposite side (b), and a silver layer that is formed on it, straight side (c) and opposite side (d), by sputtering for 20 min at a distance of 70 mm.*

**15**

**Figure 14.**

*400 V and distance of 150 mm.*

**Figure 13.**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

without complete loss of their kinetic energy fall to the opposite side of the substrate

The study of the composites after static breakdown (metal wire) or brittle fracture (glass) showed that their components (the surface layer and the base) were not separated from each other even in the area of failure (**Figure 14**). It was assumed that the presence of the transition layer was the reason for good adhesion between

The mechanical properties of samples with a working part length of 45 mm were determined under the conditions of static stretching on an Instron 3382 (Instron, USA) universal testing machine with a loading speed of 2 mm/min. The base diameter was used in the calculation of strength properties. Three to five samples were tested per one experimental point. Micro-Vickers hardness measurements determined at loading 1–2 N by the WOLPERT GROUP 401/402 device—MVD (WILSON Instruments, USA) equipped with a light microscope. The conventional yield strength σ0.2, the ultimate strength σu, the relative elongation δ, and microhardness were determined (**Table 1**). Six types of samples were studied: TiNi in the initial state (as-received),

*Surface layer in a Ta-nitinol sample on a wire substrate after 80 min of sputtering with rotation at 865 mA,* 

as a result of multiple collisions and reflections on atoms of the working gas.

*Change in the tantalum surface layers' thickness as a function of the distance between the target and the substrate on the opposite side of the substrate for composite obtained for 30 min at 400 V, 865 mA.*

the surface layer and the base. Preliminary ion etching improved adhesion.

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

#### **Figure 13.**

*Advances in Composite Materials Development*

**14**

**Figure 12.**

**Figure 11.**

*Morphology of the surface of a glass substrate, straight side (a) and opposite side (b), and a silver layer that is formed on it, straight side (c) and opposite side (d), by sputtering for 20 min at a distance of 70 mm.*

*Morphology of the silver surface layer sputtered for 20 min at a distance of 40 mm.*

*Change in the tantalum surface layers' thickness as a function of the distance between the target and the substrate on the opposite side of the substrate for composite obtained for 30 min at 400 V, 865 mA.*

without complete loss of their kinetic energy fall to the opposite side of the substrate as a result of multiple collisions and reflections on atoms of the working gas.

The study of the composites after static breakdown (metal wire) or brittle fracture (glass) showed that their components (the surface layer and the base) were not separated from each other even in the area of failure (**Figure 14**). It was assumed that the presence of the transition layer was the reason for good adhesion between the surface layer and the base. Preliminary ion etching improved adhesion.

The mechanical properties of samples with a working part length of 45 mm were determined under the conditions of static stretching on an Instron 3382 (Instron, USA) universal testing machine with a loading speed of 2 mm/min. The base diameter was used in the calculation of strength properties. Three to five samples were tested per one experimental point. Micro-Vickers hardness measurements determined at loading 1–2 N by the WOLPERT GROUP 401/402 device—MVD (WILSON Instruments, USA) equipped with a light microscope. The conventional yield strength σ0.2, the ultimate strength σu, the relative elongation δ, and microhardness were determined (**Table 1**). Six types of samples were studied: TiNi in the initial state (as-received),

#### **Figure 14.**

*Surface layer in a Ta-nitinol sample on a wire substrate after 80 min of sputtering with rotation at 865 mA, 400 V and distance of 150 mm.*


#### **Table 1.**

*Mechanical properties of composites based on nanostructured nitinol with surface layers of tantalum and titanium.*

TiNi after polishing and annealing, TiNi after PIE, and composites with Ta and Ti layers. Wires after polishing were annealed at 450°C for 15 min in air as this treatment is needed for end stabilization of the nitinol structure that caused SME and superelasticity and product shaping. Composites were produced at 865 mA, 400 V, a sputtering distance of 150 mm and the conventional sputtering time listed in the **Table 1**.

Results of mechanical stretching tests show positive influence of 1 μm thickness surface layers of Та and Ti on static properties of a nanostructural alloy, which promotes increase of yield strength and tensile strength by 2–4%. Relative elongation of all samples was of 55%. During preliminary ion etching of the surface of the substrate, bombardment with argon ions is carried out, which facilitates the removal of the surface oxide and the riveted layer with residual surface stresses and defects. Apparently, this explains a slight decrease in the microhardness of the samples immediately after PIE. Two types of composites were studied with a tantalum surface layer obtained for 10 (the main phase β-Ta) and 30 min (the main phase α-Ta formed on the beta phase). The surface of the composite material is distinguished by large microhardness values in comparison with the samples after PIE, since the hardness of both β-Ta and α-Ta is higher than that of nitinol. A thicker surface layer corresponds to higher microhardness values. With respect to the nanostructured substrate, a Ta layer of the order of 1 μm thick, consisting of a mixture of beta and alpha phases, shows an increase in the microhardness by about 26%. In this case, the effect of mechanical surface treatment and annealing on the surface microhardness can be practically neglected in connection with the PIE being carried out. The surface of the titanium layer less significantly affects the microhardness of the nanostructured substrate, but still increases it by 18%.

An object for investigations of corrosion resistance was wires of nanostructural nitinol and composites based on it with tantalum or titanium surface layers. Six types of samples were studied: (1) TiNi in the initial state (as-received), (2) TiNi after annealing, (3) TiNi after polishing, (4) TiNi after polishing and annealing, (5) TiNi-4 with Ta surface layer (Ta-TiNi), and (6) TiNi-4 with Ti surface layer (Ti-TiNi). Composites were produced at 865 mA, 400 V, a sputtering distance of 150 mm, a sputtering time 80 min on the main surface with rotation and 30 min on end faces after PIE. The researched composite materials had layered structure "a surface layer from the deposited substance (thickness ~ 0.9 microns)—the transitional layer containing elements both of the surface layer and of a basis (thickness ~ 0.2 microns)—a basis."

The material was tested for corrosion resistance under static conditions by dipping into solutions with various acidities because pH in the human body changes from 1 to 9. Neutral 0.9 wt% sodium chloride solution, artificial plasma and saliva, and four standard buffer solutions to reproduce acidic and alkaline media at the given level, and prepared from corresponding standard trimetric substances

**17**

**Table 2.**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

(fixanals) made by Merck, were used and listed in **Table 2**. Wire samples with a weight by 32.6 mg (separately from each other) were placed into flasks with 100 mL of the selected solution and aged totally in a dark place for up to 730 days. Sampling from flaks for analysis was after a selected period (7, 14, 30, 60, 90, 180, 360, or 730 days). The initial buffer solutions were used as reference solutions. Analysis was carried out by an ULTIMA 2 sequential atomic emission spectrometry (HORIBA Jobin Yvon, Japan) for using atomic emission spectrometry (AES) with inductively coupled plasma (ICP) for direct simultaneous determination of titanium and nickel in solutions. After immersion, the surface morphology and layer-by-layer composi-

In **Figures 15** and **16**, an release of metal ions in model media depending on holding time, material treatment, nature, and temperature of the environment is shown. There are no results about all samples in the alkaline environment, artificial plasma and saliva, and also about TiNi-3, TiNi-4, Ta-TiNi, and Ti-TiNi samples in solutions with acidity 3.56–6.31, since in these cases, dissolution of elements was zero or below a limit of detection for all the time of a research. So, all further results

In the remained cases, elements' concentration in solutions increases (**Figures 15** and **16**) over time, but leaching of elements in medium considerably slows down. It can be related to sequential processes of the destruction and renewal of the protective film (de- and repassivation) on defect areas [30, 31]. Medium temperature growth insignificantly increases concentration of elements in solution (varies depending on immersion time and metal nature), but at the same time, the gradual inhibition of material dissolution is also observed, and at different temperatures, it occurs almost at the same time (**Figure 15**). It allows to assume that after initial increase in corrosion due to temperature increase in the following, with the surface repassivation, the degree of the material dissolution practically does not

In solution with Ti-TiNi (**Figure 15a**), titanium concentration is approximately twice more than nickel that is explained by chemical interaction of surface layer material with potassium tetraoxalate [31]. In case of composite material with a tantalum surface layer, Tа concentration was also considered (**Figure 15b**). Insignificant dissolution of material is also observed only in the most acidic environment (most likely on possible defective sites of a surface with an incomplete surface layer that requires separate studying), and concentration of tantalum is

7.36 Artificial plasma: NaCl (92.3 mМ), NaHCO3 (26.3 mМ), K2HPO4 (0.9 mМ), KCl (2.7 mМ),

7.55 Artificial saliva: NaCl (13.34 mМ), NaHCO3 (7.4 mМ), K2HPO4 (4.4 mМ), KCl (10 mМ), NaH2PO4 (1.2 mМ), CaCl2 (1.4 mМ), MgSO4·7H2O (0.7 mМ), Na2SO4 (0.13 mМ), Na2S (0.021 mМ),

NaH2PO4 (0.22 mМ), CaCl2 (2.5 mМ), MgSO4·7H2O (0.82 mМ), Na2SO4 (1.48 mМ), D-glucose

much less than of titanium, which, respectively, is less, than of nickel.

1.68 Potassium tetraoxalate: КН3С4О8×2Н2О, 0.05 М 3.56 Acid potassium tartrate: С4Н5О6К, 0.025 М 4.01 Acid potassium phthalate: С8Н5О4К, 0.05 М

9.18 Acid sodium tetraborate: Nа2В4О7×10Н2О, 0.05 М

*The composition and acidity of modeling solutions used for immersion test.*

С6Н12О6 (5.55 mM) [23, 30, 31]

carbamide (1 g/l) [23, 30, 31]

6.31 Sodium chloride: NаСl, 0.9 wt.%

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

concern only a solution with a pH of 1.68.

tion were also investigated.

depend on temperature.

**рН** С**omposition**

### *Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

*Advances in Composite Materials Development*

TiNi after mechanical surface treatment and annealing

**Table 1.**

*titanium.*

TiNi after polishing and annealing, TiNi after PIE, and composites with Ta and Ti layers. Wires after polishing were annealed at 450°C for 15 min in air as this treatment is needed for end stabilization of the nitinol structure that caused SME and superelasticity and product shaping. Composites were produced at 865 mA, 400 V, a sputtering

*Mechanical properties of composites based on nanostructured nitinol with surface layers of tantalum and* 

distance of 150 mm and the conventional sputtering time listed in the **Table 1**.

surface layers of Та and Ti on static properties of a nanostructural alloy, which promotes increase of yield strength and tensile strength by 2–4%. Relative elongation of all samples was of 55%. During preliminary ion etching of the surface of the substrate, bombardment with argon ions is carried out, which facilitates the removal of the surface oxide and the riveted layer with residual surface stresses and defects. Apparently, this explains a slight decrease in the microhardness of the samples immediately after PIE. Two types of composites were studied with a tantalum surface layer obtained for 10 (the main phase β-Ta) and 30 min (the main phase α-Ta formed on the beta phase). The surface of the composite material is distinguished by large microhardness values in comparison with the samples after PIE, since the hardness of both β-Ta and α-Ta is higher than that of nitinol. A thicker surface layer corresponds to higher microhardness values. With respect to the nanostructured substrate, a Ta layer of the order of 1 μm thick, consisting of a mixture of beta and alpha phases, shows an increase in the microhardness by about 26%. In this case, the effect of mechanical surface treatment and annealing on the surface microhardness can be practically neglected in connection with the PIE being carried out. The surface of the titanium layer less significantly affects the

microhardness of the nanostructured substrate, but still increases it by 18%.

both of the surface layer and of a basis (thickness ~ 0.2 microns)—a basis."

The material was tested for corrosion resistance under static conditions by dipping into solutions with various acidities because pH in the human body changes

from 1 to 9. Neutral 0.9 wt% sodium chloride solution, artificial plasma and saliva, and four standard buffer solutions to reproduce acidic and alkaline media at the given level, and prepared from corresponding standard trimetric substances

An object for investigations of corrosion resistance was wires of nanostructural nitinol and composites based on it with tantalum or titanium surface layers. Six types of samples were studied: (1) TiNi in the initial state (as-received), (2) TiNi after annealing, (3) TiNi after polishing, (4) TiNi after polishing and annealing, (5) TiNi-4 with Ta surface layer (Ta-TiNi), and (6) TiNi-4 with Ti surface layer (Ti-TiNi). Composites were produced at 865 mA, 400 V, a sputtering distance of 150 mm, a sputtering time 80 min on the main surface with rotation and 30 min on end faces after PIE. The researched composite materials had layered structure "a surface layer from the deposited substance (thickness ~ 0.9 microns)—the transitional layer containing elements

Results of mechanical stretching tests show positive influence of 1 μm thickness

**Sample σy, МПа σu, МПа δ, % Microhardness, HV** TiNi 547 ± 5 1585 ± 7 47 ± 1 332 ± 3

TiNi after PIE — — — 310 ± 6 Ta@TiNi, 10 min of sputtering — — — 330 ± 4 Ta@TiNi, 30 min of sputtering 652 ± 7 1884 ± 8 55 ± 1 418 ± 4 Ti@TiNi, 30 min of sputtering 648 ± 6 1879 ± 8 55 ± 1 391.4 ± 5

641 ± 6 1815 ± 9 54 ± 1 399 ± 3

**16**

(fixanals) made by Merck, were used and listed in **Table 2**. Wire samples with a weight by 32.6 mg (separately from each other) were placed into flasks with 100 mL of the selected solution and aged totally in a dark place for up to 730 days. Sampling from flaks for analysis was after a selected period (7, 14, 30, 60, 90, 180, 360, or 730 days). The initial buffer solutions were used as reference solutions. Analysis was carried out by an ULTIMA 2 sequential atomic emission spectrometry (HORIBA Jobin Yvon, Japan) for using atomic emission spectrometry (AES) with inductively coupled plasma (ICP) for direct simultaneous determination of titanium and nickel in solutions. After immersion, the surface morphology and layer-by-layer composition were also investigated.

In **Figures 15** and **16**, an release of metal ions in model media depending on holding time, material treatment, nature, and temperature of the environment is shown. There are no results about all samples in the alkaline environment, artificial plasma and saliva, and also about TiNi-3, TiNi-4, Ta-TiNi, and Ti-TiNi samples in solutions with acidity 3.56–6.31, since in these cases, dissolution of elements was zero or below a limit of detection for all the time of a research. So, all further results concern only a solution with a pH of 1.68.

In the remained cases, elements' concentration in solutions increases (**Figures 15** and **16**) over time, but leaching of elements in medium considerably slows down. It can be related to sequential processes of the destruction and renewal of the protective film (de- and repassivation) on defect areas [30, 31].

Medium temperature growth insignificantly increases concentration of elements in solution (varies depending on immersion time and metal nature), but at the same time, the gradual inhibition of material dissolution is also observed, and at different temperatures, it occurs almost at the same time (**Figure 15**). It allows to assume that after initial increase in corrosion due to temperature increase in the following, with the surface repassivation, the degree of the material dissolution practically does not depend on temperature.

In solution with Ti-TiNi (**Figure 15a**), titanium concentration is approximately twice more than nickel that is explained by chemical interaction of surface layer material with potassium tetraoxalate [31]. In case of composite material with a tantalum surface layer, Tа concentration was also considered (**Figure 15b**). Insignificant dissolution of material is also observed only in the most acidic environment (most likely on possible defective sites of a surface with an incomplete surface layer that requires separate studying), and concentration of tantalum is much less than of titanium, which, respectively, is less, than of nickel.


#### **Table 2.**

*The composition and acidity of modeling solutions used for immersion test.*

**Figure 15.**

*Dependence of concentration of the elements dissolved from TiNi-Ti (a) and TiNi-Ta (b) composites in buffer solution with acidity 1.68 on immersion time of sampling and temperature of solution: the marked curves correspond to temperature of 21°C, curves without tags—37°C.*

Depending on material treatment (**Figure 16**), ion release decreases in the following order: TiNi-2 > TiNi-1 > TiNi-4 > TiNi-3 > Ti-TiNi (if to look on nickel concentration) > Та-TiNi. According to the literature, the thermal treatment at a temperature from 400 to 1000°C, which is required for stabilization of the mechanical properties, always results in a significant worsening of the corrosion resistance [31]. At the same time, the surface treatment, which facilitates the formation of the most perfect and homogeneous passive film, increases the corrosion resistance. Because of chemical interaction of Ti with acid media composite with its surface layer obviously less corrosion resistant than with Ta, but they are both more resistant than nitinol without a protective layer.

Composites Ta-TiNi and Ti-TiNi were also tested for biocompatibility.

The effect on the formation of H2O2 in the phosphate buffer (pH 6.8) on heating (37°C) for 200 min in the enhanced chemiluminescence system (luminol–piodophenol–peroxidase) [32] was studied. Sputtering of titanium and tantalum decreases the concentration of hydrogen peroxide formed by approximately 40 (6.5 ± 0.5 nM) and 60% (4.5 ± 0.3 nM), respectively, both close to the media concentration 3.2 ± 0.2 nM. By using a fluorescence probe specific to the OH radicals,

#### **Figure 16.**

*Dependence of nickel concentration in buffer solution with acidity 1.68 at 21°C on immersion time and a sample type.*

**19**

Ta-NiTi surfaces.

**3. Conclusions**

composite materials.

tering conditions.

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

prevent the excessive generation of reactive oxygen species.

coumarin-3-carboxylic acid (Aldrich, USA) [33], it was found that all types of barrier coatings decrease the amounts of these radicals formed in a 20 mM phosphate buffer solution (pH 6.8) on heating (80°C) for 2 h. Titanium and tantalum coatings decreased the amount of the hydroxyl radicals by about 70 and 80% (30.9 ± 2.0 and 26.1 ± 1.3 nM), respectively, in comparison with NiTi plates (120.7 ± 4.9 nM). The test systems we used showed that the titanium or tantalum surface composite layers

The biocompatibility was measured in vitro using standard test systems [34]. Then, the samples were examined under a DM 6000 fluorescence microscope (Leica, Germany). In the case of myofibroblasts from peripheral vessels, the percentages of vital cells for Ta-NiTi and Ti-NiTi were 95 ± 2 and 97 ± 2%, respectively. In the case of the human bone marrow mesenchymal stromal cells (MSC), the percentages of vital cells for Ta-NiTi and Ti-NiTi were 96 ± 3 and 96 ± 2%, respectively. Thus, none of the material surface samples used in the study had a short-term toxic effect on the cells that overgrew these surfaces de novo. The mitotic activity of the cells was assessed considering the mitotic index of the cells in the logarithmic growth phase (the third day after inoculation). The number of mitotic cells was determined by fluorescence microscopy using the vital staining with the Hoechst 33342 fluorescent dye (Sigma, USA). The MI value for the cells growing on the NiTi (reference) surface was 3.1% for the myofibroblast culture and 1.8% for the MSC culture. In the case of Ta-NiTi, the MI was 6.1% for the myofibroblasts and 4.3% for the bone marrow MSC. For the myofibroblasts and MSC cultured on Ti-NiTi, the mitotic indices were 5.8 and 4.7%, respectively. Morphological analysis of the myofibroblasts from peripheral vessels and bone marrow MSC on the surface of materials after 5 days of culturing were performed. Both myofibroblasts and MSC form a merged monolayer on the Ti-NiTi and

Nano- and microdimensional surface layers of α- and β-Ta, Ti, Ag, and Cu on flat and wire NiTi, Cu, Ti, and SiO2 substrates were created by vacuum magnetron sputtering aimed to investigate regularities of production of layered biomedical

It was shown that the thickness and the structure of surface layers were affected by the sputtering distance, time, power, and the bias voltage at the substrate. The presence of the transition layer that contains both substrate and target elements and provides high adhesion of the surface layer to the substrate has been demonstrated. The morphology of a new surface repeats the substrate state regardless of the sput-

With increase in deposition time, surface layer thickness does not linearly increase. Irrespective of summary sputtering time, the β phase is formed in the beginning, and at summary, surface layer thickness more than 0.6 μm on it α tantalum is deposited, while temperature remains below 150°C. The optimum bias voltage (500 V) for ion-atomic deposition was determined. It was demonstrated that an increase in power from 50 to 70% enhanced the thickness and uniformity of

A nonlinear increase in the thickness of the growing surface layers with decreasing sputtering distance under otherwise equal conditions was demonstrated. But the thickness of the transition layer and the dependence of the thickness change as a whole depend on the nature of the sputtered substance. It has been shown that at distances of 40–160 mm, insignificant deposition on the substrate side that is

both the surface and the transition layers without their contamination.

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

#### *Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

coumarin-3-carboxylic acid (Aldrich, USA) [33], it was found that all types of barrier coatings decrease the amounts of these radicals formed in a 20 mM phosphate buffer solution (pH 6.8) on heating (80°C) for 2 h. Titanium and tantalum coatings decreased the amount of the hydroxyl radicals by about 70 and 80% (30.9 ± 2.0 and 26.1 ± 1.3 nM), respectively, in comparison with NiTi plates (120.7 ± 4.9 nM). The test systems we used showed that the titanium or tantalum surface composite layers prevent the excessive generation of reactive oxygen species.

The biocompatibility was measured in vitro using standard test systems [34]. Then, the samples were examined under a DM 6000 fluorescence microscope (Leica, Germany). In the case of myofibroblasts from peripheral vessels, the percentages of vital cells for Ta-NiTi and Ti-NiTi were 95 ± 2 and 97 ± 2%, respectively. In the case of the human bone marrow mesenchymal stromal cells (MSC), the percentages of vital cells for Ta-NiTi and Ti-NiTi were 96 ± 3 and 96 ± 2%, respectively. Thus, none of the material surface samples used in the study had a short-term toxic effect on the cells that overgrew these surfaces de novo. The mitotic activity of the cells was assessed considering the mitotic index of the cells in the logarithmic growth phase (the third day after inoculation). The number of mitotic cells was determined by fluorescence microscopy using the vital staining with the Hoechst 33342 fluorescent dye (Sigma, USA). The MI value for the cells growing on the NiTi (reference) surface was 3.1% for the myofibroblast culture and 1.8% for the MSC culture. In the case of Ta-NiTi, the MI was 6.1% for the myofibroblasts and 4.3% for the bone marrow MSC. For the myofibroblasts and MSC cultured on Ti-NiTi, the mitotic indices were 5.8 and 4.7%, respectively. Morphological analysis of the myofibroblasts from peripheral vessels and bone marrow MSC on the surface of materials after 5 days of culturing were performed. Both myofibroblasts and MSC form a merged monolayer on the Ti-NiTi and Ta-NiTi surfaces.

## **3. Conclusions**

*Advances in Composite Materials Development*

**Figure 15.**

tant than nitinol without a protective layer.

*correspond to temperature of 21°C, curves without tags—37°C.*

Depending on material treatment (**Figure 16**), ion release decreases in the following order: TiNi-2 > TiNi-1 > TiNi-4 > TiNi-3 > Ti-TiNi (if to look on nickel concentration) > Та-TiNi. According to the literature, the thermal treatment at a temperature from 400 to 1000°C, which is required for stabilization of the mechanical properties, always results in a significant worsening of the corrosion resistance [31]. At the same time, the surface treatment, which facilitates the formation of the most perfect and homogeneous passive film, increases the corrosion resistance. Because of chemical interaction of Ti with acid media composite with its surface layer obviously less corrosion resistant than with Ta, but they are both more resis-

*Dependence of concentration of the elements dissolved from TiNi-Ti (a) and TiNi-Ta (b) composites in buffer solution with acidity 1.68 on immersion time of sampling and temperature of solution: the marked curves* 

Composites Ta-TiNi and Ti-TiNi were also tested for biocompatibility.

*Dependence of nickel concentration in buffer solution with acidity 1.68 at 21°C on immersion time and a* 

The effect on the formation of H2O2 in the phosphate buffer (pH 6.8) on heating (37°C) for 200 min in the enhanced chemiluminescence system (luminol–piodophenol–peroxidase) [32] was studied. Sputtering of titanium and tantalum decreases the concentration of hydrogen peroxide formed by approximately 40 (6.5 ± 0.5 nM) and 60% (4.5 ± 0.3 nM), respectively, both close to the media concentration 3.2 ± 0.2 nM. By using a fluorescence probe specific to the OH radicals,

**18**

**Figure 16.**

*sample type.*

Nano- and microdimensional surface layers of α- and β-Ta, Ti, Ag, and Cu on flat and wire NiTi, Cu, Ti, and SiO2 substrates were created by vacuum magnetron sputtering aimed to investigate regularities of production of layered biomedical composite materials.

It was shown that the thickness and the structure of surface layers were affected by the sputtering distance, time, power, and the bias voltage at the substrate. The presence of the transition layer that contains both substrate and target elements and provides high adhesion of the surface layer to the substrate has been demonstrated. The morphology of a new surface repeats the substrate state regardless of the sputtering conditions.

With increase in deposition time, surface layer thickness does not linearly increase. Irrespective of summary sputtering time, the β phase is formed in the beginning, and at summary, surface layer thickness more than 0.6 μm on it α tantalum is deposited, while temperature remains below 150°C. The optimum bias voltage (500 V) for ion-atomic deposition was determined. It was demonstrated that an increase in power from 50 to 70% enhanced the thickness and uniformity of both the surface and the transition layers without their contamination.

A nonlinear increase in the thickness of the growing surface layers with decreasing sputtering distance under otherwise equal conditions was demonstrated. But the thickness of the transition layer and the dependence of the thickness change as a whole depend on the nature of the sputtered substance. It has been shown that at distances of 40–160 mm, insignificant deposition on the substrate side that is

opposite to the sputtered flow is observed, with the thickness of formed layers also depending on the distance between the target and the substrate.

A slight corrosive dissolution was observed only in a medium with a pH of 1.56 for 2 years of a research. Dissolution in the other media is absent. Concentration of metals increases in solution over time, but the considerable slowdown of a metal ion release in solutions is observed over time. An increase in strength and plasticity in comparison with substrate was attained depending on the nature of the sputtered substance and substrate. Toxicity of samples has not been revealed.

Thus, the growth of a thin surface layer with high corrosion resistance and good biocompatibility by magnetron sputtering allows one to obtain a barrier to nitinol contact with physiological medium, which can withstand loads when nitinol exhibits superelasticity and an SME, with the formation of a transition layer, but no nitinol phase state changing.

## **Acknowledgements**

The authors wish to thank Dyomin K Yu, Mikhailova AB, Gol'dberg MA, Kargin Yu F, and Gudkov SV for their help in sample analysis. The work was partially carried out under state assignment no. 007-00129-18-00 and was supported by the Russian President Program for Young Scientists (MK-4521.2018.8).

Chapter is partially based on the results of earlier published works [35–37], and authors have the permission to re-use it.

## **Conflict of interest**

There is no conflict of interest to declare.

## **Author details**

Elena O. Nasakina\*, Mikhail A. Sevostyanov, Alexander S. Baikin, Sergey V. Konushkin, Konstantin V. Sergienko, Mikhail A. Kaplan, Ilya M. Fedyuk, Alexander V. Leonov and Alexey G. Kolmakov A.A. Baikov Institute of Metallurgy and Material Science, Moscow, Russia

\*Address all correspondence to: nacakina@mail.ru

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**21**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

2014;**48**(4):477-486. DOI: 10.1134/

[7] Kuz'michev AI. Magnetronnye raspylitel'nye sistemy. Kn. 1. Vvedenie v fiziku i tekhniku magnetronnogo raspyleniya [Magnetron Scattering Systems. Book 1. Introduction into Physics and Technique of Magnetron Scattering]. Kiev: Avers; 2008. 244 p.

[8] Bunshah RF. Deposition

Publications; 1982

New York: Plenum; 1983

vacuum.2011.04.012

tsf.2013.09.055

[11] Bernoulli D, Müller U, Schwarzenberger M, Hauert R, Spolenak R. Magnetron sputter deposited tantalum and tantalum nitride thin films: An analysis of phase, hardness and composition. Thin Solid Films. 2013;**548**:157-161. DOI: 10.1016/j.

[12] Zhou YM, Xie Z, Ma YZ, Xia FJ, Feng SL. Growth and characterization of Ta/Ti bi-layer films on glass and Si (111) substrates by direct current magnetron sputtering. Applied Surface Science. 2012;**258**:7314-7321. DOI: 10.1016/j.apsusc.2012.03.176

[13] Navid AA, Chason E, Hodge AM. Evaluation of stress during and after sputter deposition of Cu and Ta films. Surface and Coating Technology.

Technologies for Films and Coating. Park Ridge, New Jersey (USA): Noyes

[9] Poate JM, Foti G, Jacobson DC. Surface Modification and Alloying by Laser, Ion and Electron Beams.

[10] Dorranian D, Solati E, Hantezadeh M, Ghoranneviss M, Sari A. Effects of low temperature on the characteristics of tantalum thin films. Vacuum. 2011;**86**:51-55. DOI: 10.1016/j.

S0040579514040071

(Russian)

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

[1] Stolin АM, Bazhin PM. Manufacture of multipurpose composite and ceramic materials in the combustion regime and high-temperature deformation (SHS extrusion). Theoretical Foundations of Chemical Engineering. 2014;**48**(6):751- 763. DOI: 10.1134/S0040579514060104

[2] Bazhin PM, Stolin AM, Alymov MI.

[3] Maho A, Kanoufi F, Combellas C, Delhalle J, Mekhalif Z. Electrochemical investigation of nitinol/tantalum hybrid surfaces modified by alkylphosphonic

Electrochimica Acta. 2014;**116**:78-88. DOI: 10.1016/j.electacta.2013.11.008

[4] Krivoshapkin PV, Mikhaylov VI, Krivoshapkina EF, Zaikovskii VI, Melgunov MS, Stalugin VV. Mesoporous Fe-alumina films prepared via sol–gel route. Microporous and Mesoporous Materials. 2015;**204**:276-281. DOI: 10.1016/j.micromeso.2014.12.001

[5] Kononova SV, Romashkova KA, Kruchinina EV, Gusarov VV, Potokin IL, Korytkova EN, Maslennikova TP. Polymer-inorganic nanocomposites based on aromatic polyamidoimides effective in the processes of liquids separation. Russian Journal of General Chemistry. 2010;**80**(6):1136-1142. DOI:

10.1134/S1070363210060162

[6] Nasakina EO, Baikin AS, Sevost'yanov MA, Kolmakov AG, Zabolotnyi VT, Solntsev KA. Properties of nanostructured titanium nickelide and composite based on it. Theoretical Foundations of Chemical Engineering.

self-assembled monolayers.

Preparation of nanostructured composite ceramic materials and products under conditions of a combination of combustion and high-temperature deformation (SHS extrusion). Nanotechnologies in Russia. 2014;**9**(11-12):583-600. DOI: 10.1134/

S1995078014060020

**References**

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

## **References**

*Advances in Composite Materials Development*

nitinol phase state changing.

authors have the permission to re-use it.

There is no conflict of interest to declare.

**Acknowledgements**

**Conflict of interest**

**Author details**

opposite to the sputtered flow is observed, with the thickness of formed layers also

Thus, the growth of a thin surface layer with high corrosion resistance and good biocompatibility by magnetron sputtering allows one to obtain a barrier to nitinol contact with physiological medium, which can withstand loads when nitinol exhibits superelasticity and an SME, with the formation of a transition layer, but no

The authors wish to thank Dyomin K Yu, Mikhailova AB, Gol'dberg MA, Kargin

Chapter is partially based on the results of earlier published works [35–37], and

Yu F, and Gudkov SV for their help in sample analysis. The work was partially carried out under state assignment no. 007-00129-18-00 and was supported by the

Russian President Program for Young Scientists (MK-4521.2018.8).

Elena O. Nasakina\*, Mikhail A. Sevostyanov, Alexander S. Baikin,

A.A. Baikov Institute of Metallurgy and Material Science, Moscow, Russia

A slight corrosive dissolution was observed only in a medium with a pH of 1.56 for 2 years of a research. Dissolution in the other media is absent. Concentration of metals increases in solution over time, but the considerable slowdown of a metal ion release in solutions is observed over time. An increase in strength and plasticity in comparison with substrate was attained depending on the nature of the sputtered

depending on the distance between the target and the substrate.

substance and substrate. Toxicity of samples has not been revealed.

**20**

provided the original work is properly cited.

Alexander V. Leonov and Alexey G. Kolmakov

\*Address all correspondence to: nacakina@mail.ru

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Sergey V. Konushkin, Konstantin V. Sergienko, Mikhail A. Kaplan, Ilya M. Fedyuk,

[1] Stolin АM, Bazhin PM. Manufacture of multipurpose composite and ceramic materials in the combustion regime and high-temperature deformation (SHS extrusion). Theoretical Foundations of Chemical Engineering. 2014;**48**(6):751- 763. DOI: 10.1134/S0040579514060104

[2] Bazhin PM, Stolin AM, Alymov MI. Preparation of nanostructured composite ceramic materials and products under conditions of a combination of combustion and high-temperature deformation (SHS extrusion). Nanotechnologies in Russia. 2014;**9**(11-12):583-600. DOI: 10.1134/ S1995078014060020

[3] Maho A, Kanoufi F, Combellas C, Delhalle J, Mekhalif Z. Electrochemical investigation of nitinol/tantalum hybrid surfaces modified by alkylphosphonic self-assembled monolayers. Electrochimica Acta. 2014;**116**:78-88. DOI: 10.1016/j.electacta.2013.11.008

[4] Krivoshapkin PV, Mikhaylov VI, Krivoshapkina EF, Zaikovskii VI, Melgunov MS, Stalugin VV. Mesoporous Fe-alumina films prepared via sol–gel route. Microporous and Mesoporous Materials. 2015;**204**:276-281. DOI: 10.1016/j.micromeso.2014.12.001

[5] Kononova SV, Romashkova KA, Kruchinina EV, Gusarov VV, Potokin IL, Korytkova EN, Maslennikova TP. Polymer-inorganic nanocomposites based on aromatic polyamidoimides effective in the processes of liquids separation. Russian Journal of General Chemistry. 2010;**80**(6):1136-1142. DOI: 10.1134/S1070363210060162

[6] Nasakina EO, Baikin AS, Sevost'yanov MA, Kolmakov AG, Zabolotnyi VT, Solntsev KA. Properties of nanostructured titanium nickelide and composite based on it. Theoretical Foundations of Chemical Engineering.

2014;**48**(4):477-486. DOI: 10.1134/ S0040579514040071

[7] Kuz'michev AI. Magnetronnye raspylitel'nye sistemy. Kn. 1. Vvedenie v fiziku i tekhniku magnetronnogo raspyleniya [Magnetron Scattering Systems. Book 1. Introduction into Physics and Technique of Magnetron Scattering]. Kiev: Avers; 2008. 244 p. (Russian)

[8] Bunshah RF. Deposition Technologies for Films and Coating. Park Ridge, New Jersey (USA): Noyes Publications; 1982

[9] Poate JM, Foti G, Jacobson DC. Surface Modification and Alloying by Laser, Ion and Electron Beams. New York: Plenum; 1983

[10] Dorranian D, Solati E, Hantezadeh M, Ghoranneviss M, Sari A. Effects of low temperature on the characteristics of tantalum thin films. Vacuum. 2011;**86**:51-55. DOI: 10.1016/j. vacuum.2011.04.012

[11] Bernoulli D, Müller U, Schwarzenberger M, Hauert R, Spolenak R. Magnetron sputter deposited tantalum and tantalum nitride thin films: An analysis of phase, hardness and composition. Thin Solid Films. 2013;**548**:157-161. DOI: 10.1016/j. tsf.2013.09.055

[12] Zhou YM, Xie Z, Ma YZ, Xia FJ, Feng SL. Growth and characterization of Ta/Ti bi-layer films on glass and Si (111) substrates by direct current magnetron sputtering. Applied Surface Science. 2012;**258**:7314-7321. DOI: 10.1016/j.apsusc.2012.03.176

[13] Navid AA, Chason E, Hodge AM. Evaluation of stress during and after sputter deposition of Cu and Ta films. Surface and Coating Technology.

2010;**205**:2355-2361. DOI: 10.1016/j. surfcoat.2010.09.020

[14] Myers S, Lin J, Martins Souza R, Sproul WD, Moore JJ. The β to α phase transition of tantalum coatings deposited by modulated pulsed power magnetron sputtering. Surface and Coating Technology. 2013;**214**:38-45. DOI: 10.1016/j.surfcoat.2012.10.061

[15] Cacucci A, Loffredo S, Potin V, Imhoff L, Martin N. Interdependence of structural and electrical properties in tantalum/tantalum oxide multilayers. Surface and Coating Technology. 2013;**227**:38-41. DOI: 10.1016/j. surfcoat.2012.10.064

[16] Navid AA, Hodge AM. Nanostructured alpha and beta tantalum formation—Relationship between plasma parameters and microstructure. Materials Science and Engineering A. 2012;**536**:49-56. DOI: 10.1016/j.msea.2011.12.017

[17] Navid AA, Hodge AM. Controllable residual stresses in sputtered nanostructured alpha-tantalum. Scripta Materialia. 2010;**63**:867-870. DOI: 10.1016/j.scriptamat.2010.06.037

[18] Zabolotnyi VT. Ionnoe peremeshivanie v tverdykh telakh [Ion Intermixing in Solids]. Moscow: MGIEM (TU); 1997 (Russian)

[19] Bose A, Hartmann M, Henkes H. A novel, self-expanding, nitinol stent in medically refractory intracranial atherosclerotic stenosis. The Wingspan Study, Stroke. 2007;**38**:1531-1537. DOI: 10.1161/STROKEAHA.106.477711

[20] Stoeckel D. Nitinol medical devices and implants. Minimally Invasive Therapy & Allied Technologies. 2000;**9**:81-88. DOI: 10.3109/13645700009063054

[21] Petrini L, Migliavacca F. Biomedical applications of shape memory alloys. Journal of Metallurgy. 2011;**2011**:1-15. DOI: 10.1155/2011/501483

[22] Zabolotnyi VT, Belousov OK, Palii NA, Goncharenko BA, Armaderova EA, Sevost'yanov MA. Materials science aspects of the production, treatment, and properties of titanium nickelide for application in endovascular surgery. Russian Metallurgy. 2011;**5**:437-448. DOI: 10.1134/S003602951105017X

[23] In: Ebrahim F, editor. Shape Memory Alloys—Fundamentals and Applications. Croatia, Rijeka: InTech d.o.o.; 2017. 134 р. Chapter 4. pp. 81-104. DOI: 10.5772/intechopen.69238

[24] Choi J, Bogdanski D, Köller M, Esenwein SA, Müller D, Muhr G, Epple M. Calcium phosphate coating of nickel–titanium shape-memory alloys. Coating procedure and adherence of leukocytes and platelets. Biomaterials. 2003;**24**:3689-3696. DOI: 10.1016/ S0142-9612(03)00241-2

[25] Tan L, Dodd RA, Crone WC. Corrosion and wear-corrosion behavior of NiTi modified by plasma source ion implantation. Biomaterials. 2003;**24**:3931-3939. DOI: 10.1016/ S0142-9612(03)00271-0

[26] Chen Y-H, Hsu C-C, He J-L. Antibacterial silver coating on poly (ethylene terephthalate) fabric by using high power impulse magnetron sputtering. Surface and Coating Technology. 2013;**232**:868-875. DOI: 10.1016/j.surfcoat.2013.06.115

[27] Cheng Y, Cai W, Li HT, Zheng YF. Surface modification of NiTi alloy with tantalum to improve its biocompatibility and radiopacity. Journal of Materials Science. 2006;**41**:4961-4964. DOI: 10.1007/s10853-006-0096-6

**23**

*Using of Magnetron Sputtering for Biocompatible Composites Creating*

2014;**127**:163-170. DOI: 10.1016/j.

[35] Nasakina EO, Sevost'yanov MA, Mikhailova AB, Gol'dberg MA, Demin KY, Kolmakov AG, Zabolotnyi VT. Preparation of a nanostructured shape memory composite material for biomedical applications. Inorganic Materials. 2015;**51**(4):400-404

[36] Nasakina EO, Sevostyanov MA,

Sergienko KV, Leonov AV, Kolmakov AG. Formation of alpha and beta tantalum at the variation of magnetron sputtering conditions. IOP Conference

[37] Nasakina EO, Seregin AV, Baikin AS, Kaplan MA, Konushkin SV, Sergiyenko KV, et al. Formation of biocompatible surface layers depending on the sputtering distance. IOP Conference Series: Journal of Physics: Conference

Mikhaylova AB, Baikin AS,

Series: Materials Science and Engineering. 2016;**110**:012042

Series. 2017;**857**:012032

jenvrad.2012.12.009

*DOI: http://dx.doi.org/10.5772/intechopen.79609*

[28] Zhang M, Yang B, Chu J, Nieh TG.

nanocrystalline tantalum thin films. Scripta Materialia. 2006;**54**:1227-1230. DOI: 10.1016/j.scriptamat.2005.12.027

[29] Zhou YM, Xie Z, Xiao HN, Hu PF, He J. Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering. Journal of Vacuum Science and Technology A. 2009;**83**:286-291. DOI:

[30] Nasakina EO, Sevostyanov MA, Golberg MA, et al. Long term corrosion tests of nanostructural nitinol of (55.91 wt% Ni, 44.03 wt% Ti) composition under static conditions: Composition and structure before and after corrosion. Inorganic Materials: Applied Research. 2015;**6**(1):53-58. DOI:

10.1134/S2075113315010104

2015;**6**(1):59-66. DOI: 10.1134/

[32] Shtarkman IN, Gudkov SV, Chernikov AV, Bruskov VI. Effect of amino acids on X-ray-induced hydrogen peroxide and hydroxyl radical formation in water and 8-oxoguanine in DNA. Biochemistry (Moscow). 2008;**73**:470-478. DOI: 10.1134/

S2075113315010116

S0006297908040135

[33] Bruskov VI, Karp OE, Garmash SA, et al. Free Radical Research. 2012;**46**:1280-1290. DOI: 10.3109/10715762.2012.709316

[34] Garmash SA, Smirnova VS, Karp OE, et al. Pro-oxidative, genotoxic and cytotoxic properties of uranyl ions. Journal of Environmental Radioactivity.

[31] Nasakina EO, Sevostyanov MA, Golberg MA, et al. Long term corrosion tests of nanostructural nitinol of (55.91 wt% Ni, 44.03 wt% Ti) composition under static conditions: ion release. Inorganic Materials: Applied Research.

Hardness enhancement in

10.1116/1.304614

*Using of Magnetron Sputtering for Biocompatible Composites Creating DOI: http://dx.doi.org/10.5772/intechopen.79609*

[28] Zhang M, Yang B, Chu J, Nieh TG. Hardness enhancement in nanocrystalline tantalum thin films. Scripta Materialia. 2006;**54**:1227-1230. DOI: 10.1016/j.scriptamat.2005.12.027

*Advances in Composite Materials Development*

[21] Petrini L, Migliavacca F. Biomedical applications of shape memory alloys. Journal of Metallurgy. 2011;**2011**:1-15.

[22] Zabolotnyi VT, Belousov OK, Palii NA, Goncharenko BA, Armaderova EA, Sevost'yanov MA. Materials science aspects of the production, treatment, and properties of titanium nickelide for application in endovascular surgery. Russian Metallurgy. 2011;**5**:437-448. DOI: 10.1134/S003602951105017X

[23] In: Ebrahim F, editor. Shape Memory Alloys—Fundamentals and Applications. Croatia, Rijeka: InTech d.o.o.; 2017. 134 р. Chapter 4. pp. 81-104.

DOI: 10.5772/intechopen.69238

S0142-9612(03)00241-2

S0142-9612(03)00271-0

[25] Tan L, Dodd RA, Crone WC. Corrosion and wear-corrosion behavior of NiTi modified by plasma source ion implantation. Biomaterials. 2003;**24**:3931-3939. DOI: 10.1016/

[26] Chen Y-H, Hsu C-C, He J-L. Antibacterial silver coating on poly (ethylene terephthalate) fabric by using high power impulse magnetron sputtering. Surface and Coating Technology. 2013;**232**:868-875. DOI: 10.1016/j.surfcoat.2013.06.115

[27] Cheng Y, Cai W, Li HT, Zheng YF. Surface modification of NiTi alloy with tantalum to improve its biocompatibility and radiopacity. Journal of Materials Science. 2006;**41**:4961-4964. DOI: 10.1007/s10853-006-0096-6

[24] Choi J, Bogdanski D, Köller M, Esenwein SA, Müller D, Muhr G, Epple M. Calcium phosphate coating of nickel–titanium shape-memory alloys. Coating procedure and adherence of leukocytes and platelets. Biomaterials. 2003;**24**:3689-3696. DOI: 10.1016/

DOI: 10.1155/2011/501483

2010;**205**:2355-2361. DOI: 10.1016/j.

[14] Myers S, Lin J, Martins Souza R, Sproul WD, Moore JJ. The β to α phase transition of tantalum coatings deposited by modulated pulsed power magnetron sputtering. Surface and Coating Technology. 2013;**214**:38-45. DOI: 10.1016/j.surfcoat.2012.10.061

[15] Cacucci A, Loffredo S, Potin V, Imhoff L, Martin N. Interdependence of structural and electrical properties in tantalum/tantalum oxide multilayers. Surface and Coating Technology. 2013;**227**:38-41. DOI: 10.1016/j.

surfcoat.2010.09.020

surfcoat.2012.10.064

[16] Navid AA, Hodge AM. Nanostructured alpha and beta tantalum formation—Relationship between plasma parameters and microstructure. Materials Science and Engineering A. 2012;**536**:49-56. DOI:

10.1016/j.msea.2011.12.017

residual stresses in sputtered

[18] Zabolotnyi VT. Ionnoe peremeshivanie v tverdykh telakh [Ion Intermixing in Solids]. Moscow: MGIEM (TU); 1997 (Russian)

[17] Navid AA, Hodge AM. Controllable

nanostructured alpha-tantalum. Scripta Materialia. 2010;**63**:867-870. DOI: 10.1016/j.scriptamat.2010.06.037

[19] Bose A, Hartmann M, Henkes H. A novel, self-expanding, nitinol stent in medically refractory intracranial atherosclerotic stenosis. The Wingspan Study, Stroke. 2007;**38**:1531-1537. DOI: 10.1161/STROKEAHA.106.477711

[20] Stoeckel D. Nitinol medical devices and implants. Minimally Invasive Therapy & Allied Technologies. 2000;**9**:81-88. DOI: 10.3109/13645700009063054

**22**

[29] Zhou YM, Xie Z, Xiao HN, Hu PF, He J. Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering. Journal of Vacuum Science and Technology A. 2009;**83**:286-291. DOI: 10.1116/1.304614

[30] Nasakina EO, Sevostyanov MA, Golberg MA, et al. Long term corrosion tests of nanostructural nitinol of (55.91 wt% Ni, 44.03 wt% Ti) composition under static conditions: Composition and structure before and after corrosion. Inorganic Materials: Applied Research. 2015;**6**(1):53-58. DOI: 10.1134/S2075113315010104

[31] Nasakina EO, Sevostyanov MA, Golberg MA, et al. Long term corrosion tests of nanostructural nitinol of (55.91 wt% Ni, 44.03 wt% Ti) composition under static conditions: ion release. Inorganic Materials: Applied Research. 2015;**6**(1):59-66. DOI: 10.1134/ S2075113315010116

[32] Shtarkman IN, Gudkov SV, Chernikov AV, Bruskov VI. Effect of amino acids on X-ray-induced hydrogen peroxide and hydroxyl radical formation in water and 8-oxoguanine in DNA. Biochemistry (Moscow). 2008;**73**:470-478. DOI: 10.1134/ S0006297908040135

[33] Bruskov VI, Karp OE, Garmash SA, et al. Free Radical Research. 2012;**46**:1280-1290. DOI: 10.3109/10715762.2012.709316

[34] Garmash SA, Smirnova VS, Karp OE, et al. Pro-oxidative, genotoxic and cytotoxic properties of uranyl ions. Journal of Environmental Radioactivity. 2014;**127**:163-170. DOI: 10.1016/j. jenvrad.2012.12.009

[35] Nasakina EO, Sevost'yanov MA, Mikhailova AB, Gol'dberg MA, Demin KY, Kolmakov AG, Zabolotnyi VT. Preparation of a nanostructured shape memory composite material for biomedical applications. Inorganic Materials. 2015;**51**(4):400-404

[36] Nasakina EO, Sevostyanov MA, Mikhaylova AB, Baikin AS, Sergienko KV, Leonov AV, Kolmakov AG. Formation of alpha and beta tantalum at the variation of magnetron sputtering conditions. IOP Conference Series: Materials Science and Engineering. 2016;**110**:012042

[37] Nasakina EO, Seregin AV, Baikin AS, Kaplan MA, Konushkin SV, Sergiyenko KV, et al. Formation of biocompatible surface layers depending on the sputtering distance. IOP Conference Series: Journal of Physics: Conference Series. 2017;**857**:012032

Chapter 2

Solution

Rais Ahmad

bionanocomposite.

1. Introduction

25

Abstract

Polyaniline/ZnO Nanocomposite:

Removal of Cr(VI) from Aqueous

In recent years with the rapid economic globalization, pollution by industries and agriculture has increased, which results in decrease in the quality of ground and surface water. Pollution by heavy metals has become a serious health issue worldwide due to their nonbiodegradable and persistent nature. Therefore, extensive research has been done to develop ecofriendly and effective methods for removal of heavy metals, such as chemical precipitation, ion exchange, electrodialysis, membrane filtration, and adsorption. Among these methods, adsorption is the most recognized technique for wastewater treatment due to high-removal efficiency and ease in operation without yielding harmful by-products. Recently, nanocomposites based on biopolymer-grafted synthetic adsorbent have been used in various industrial applications including wastewater treatment. Therefore, the present chapter will be devoted for the removal of toxic heavy metals from wastewater by using

Keywords: heavy metals, bionanocomposite, adsorption, desorption

and pulmonary congestion and regarded as carcinogenic also [5–7].

In today's era, the industrialization, agriculture, and domestic activities have led

Various conventional methods have been developed for the adsorption of Cr(VI) in wastewater, including electrochemical precipitation, ion exchange, membrane ultrafiltration, reverse osmosis, reduction, and adsorption [8–10]. Adsorption has

to a large amount of wastewater having toxic elements such as lead, mercury, cadmium, copper, arsenic, chromium, etc., and dyes which has adversely affected human lives, animal lives, and environment. Among various heavy metals, Cr(VI) is one of the most important and toxic heavy metals due to its vast applications in industries [1, 2]. In aqueous medium, two forms of chromium exist, i.e., Cr(III) and Cr(VI), and the toxicity and reactivity of both the forms mainly depend on oxidation state of the chromium [3]. In trace amounts, Cr(III) is an essential nutrient for humans and to mammals for their maintenance of normal glucose tolerance factor, lipid, and protein metabolism [4]. On the other hand, Cr(VI) is very toxic to human as well as marine life and poses serious health problems such as liver damage

A Novel Adsorbent for the

## Chapter 2

## Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous Solution

Rais Ahmad

## Abstract

In recent years with the rapid economic globalization, pollution by industries and agriculture has increased, which results in decrease in the quality of ground and surface water. Pollution by heavy metals has become a serious health issue worldwide due to their nonbiodegradable and persistent nature. Therefore, extensive research has been done to develop ecofriendly and effective methods for removal of heavy metals, such as chemical precipitation, ion exchange, electrodialysis, membrane filtration, and adsorption. Among these methods, adsorption is the most recognized technique for wastewater treatment due to high-removal efficiency and ease in operation without yielding harmful by-products. Recently, nanocomposites based on biopolymer-grafted synthetic adsorbent have been used in various industrial applications including wastewater treatment. Therefore, the present chapter will be devoted for the removal of toxic heavy metals from wastewater by using bionanocomposite.

Keywords: heavy metals, bionanocomposite, adsorption, desorption

## 1. Introduction

In today's era, the industrialization, agriculture, and domestic activities have led to a large amount of wastewater having toxic elements such as lead, mercury, cadmium, copper, arsenic, chromium, etc., and dyes which has adversely affected human lives, animal lives, and environment. Among various heavy metals, Cr(VI) is one of the most important and toxic heavy metals due to its vast applications in industries [1, 2]. In aqueous medium, two forms of chromium exist, i.e., Cr(III) and Cr(VI), and the toxicity and reactivity of both the forms mainly depend on oxidation state of the chromium [3]. In trace amounts, Cr(III) is an essential nutrient for humans and to mammals for their maintenance of normal glucose tolerance factor, lipid, and protein metabolism [4]. On the other hand, Cr(VI) is very toxic to human as well as marine life and poses serious health problems such as liver damage and pulmonary congestion and regarded as carcinogenic also [5–7].

Various conventional methods have been developed for the adsorption of Cr(VI) in wastewater, including electrochemical precipitation, ion exchange, membrane ultrafiltration, reverse osmosis, reduction, and adsorption [8–10]. Adsorption has

been widely used for the removal of chromium from contaminated groundwater out of these methods [11] due to its low initial cost and ease of operation and high efficiency to remove toxic heavy metals. This technique can be harnessed at large scale for the treatment of polluted water as it can handle fairly large flow rates, producing a high quality of water without producing notorious sludge and residual contaminants [12–14].

2.3 Synthesis of polyaniline/ZnO nanocomposite

DOI: http://dx.doi.org/10.5772/intechopen.85868

meter was used to adjust the pH of the solutions.

PAZO was calculated by a mass balance relationship:

2.5 Adsorption experiments

(from 10, 50, 100 mg L�<sup>1</sup>

adsorbent (mg g�<sup>1</sup>

solution (mg L�<sup>1</sup>

27

of unreacted aniline.

2.4 Instrumentation

The material was synthesized by methods already reported elsewhere [20]. The detailed procedure is as follows: 1 g of above synthesized ZnO nanoparticles were taken in 100 ml of 0.1 M HCl solution and sonicated for 1 h at 30°C. Now, 10 ml of distilled aniline monomer taken in 400 ml of 0.1 M HCl solution was poured in the above colloidal solution of ZnO. The mixture was allowed to stir for 2 h for complete mixing at 5°C. The reaction was proceeded with the addition of 15 g of APS. The reaction was allowed to stand for 12 h at 5°C and product obtained was washed with 0.1 M HCl solution five to six times in order to remove excess amount

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

The FTIR spectra of the adsorbent materials were recorded with a Perkin Elmer

The adsorption experiments were performed using batch equilibrium technique in aqueous solutions in the temperature range of 30–50°C at pH 2. For this, 0.04 g of adsorbents was added to 20 ml of Cr(VI) solution of various concentrations

at 120 rpm. After equilibrium was attained, the adsorbent was removed and the supernatant was collected after attaining equilibrium. The concentrations of Cr(VI) in supernatant were measured using atomic absorption spectrophotometer (AAS). The kinetic experiments were performed at three different Cr(VI) ion concentrations mainly at 10, 50, and 100 mg L�<sup>1</sup> at pH 2 and 3. The effect of time on the adsorption of Cr(VI) ions on PAZO nanocomposite was studied at 10–300 min and the equilibrium was reached at 120 min. The effect of adsorbent dose and initial metal ion concentration was also studied. The amount of metal ions adsorbed onto

qe <sup>¼</sup> <sup>ð</sup>Co � CeÞ<sup>V</sup>

); Co and Ce are the concentrations of the metal ion in the initial

) and after adsorption, respectively; V is the volume of the

where qe is the amount of metal ion adsorbed per unit weight of the

adsorption medium (L); and W is the amount of the adsorbent (g).

) and shaken in a thermostatic water-bath shaker operated

<sup>W</sup> (1)

1800 model IR spectrophotometer operating at frequency range from 400 to 4000 cm�<sup>1</sup> using KBr pallets. X-ray diffraction (XRD) patterns of the samples were obtained using Siemens D 5005 X-ray unit Cu Kα (λ = 1:5406 Å) radiation, generated at a voltage of 40 kV and a current of 40 mA was used as the X-ray source. Scanning electron microscopy and electron diffraction scattering (SEM/EDS) analysis were done using GSM 6510LV scanning electron microscope. The particle size and structure of the synthesized nanocomposite were observed by using JEM 2100 transmission electron microscope (TEM). The thermal stability was determined by derivative thermal analysis (DTG, Perkin Elmer Pyris 6) and DTA (Perkin Elmer model, STA 6000). The thermograms were recorded for 20 mg of powder sample at a heating rate of 10°C min�<sup>1</sup> in the temperature range of 30–800°C under nitrogen atmosphere. The concentration of metal ions in the solution was measured by atomic absorption spectrophotometer (AAS) model GBC-902. Elico Li 120 pH

Conducting polymer with metal oxide has nowadays emerged as an attractive alternative for the sequestration of wastewater, as it mainly provide larger surface area for the adsorption, interfacial adhesion between the surface of nanocomposite and metal ions, it is easily tractable and cost effective. Due to large amount of amine and imine functional groups PANI has strong affinity with metal ions and can remove heavy metal contaminants from aqueous solutions effectively [15, 16]. The stability of polymer matrix can be enhanced by addition of fillers such as natural clays, metal oxide nanoparticles, etc. [17]. Zinc oxide is known to be a potential adsorbent of Cr(VI) at high temperatures as well as at low temperatures [18]. So, the incorporation of ZnO nanoparticles in the PANI matrix not only provides thermal and mechanical strength, but also improves its adsorption properties. This improvement was attributed to the increase in the number and high dispersion of active terminal OH groups of ZnO nanoparticles with amine groups of PANI.

In the present chapter, polyaniline zinc oxide nanocomposite was synthesized by oxidative free radical polymerization of aniline monomer in presence of zinc oxide nanoparticles. The material was characterized by various analytical techniques such as FT-IR, XTD, TGA-DTG, SEM, and TEM. The nanocomposite material was further explored for the removal of Cr(VI) from aqueous solution. The effects of various adsorption parameters viz. agitation time, solution pH, adsorbent dose, initial metal ion concentration, and temperature was observed and optimized by preliminary experiments.

## 2. Materials and methods

#### 2.1 Chemicals

Zinc acetate and ammonium persulfate (APS) were procured from Sigma Aldrich, India. Sodium hydroxide and potassium dichromate were procured from Merck, India. Aniline monomer was procured from Fisher Scientific, India and was distilled before use. About 1000 mg L<sup>1</sup> stock solutions of were prepared by dissolving appropriate amount of metal salts in double distilled water.

#### 2.2 Synthesis of zinc oxide nanoparticles

ZnO nanoparticles were synthesized by direct precipitation method using zinc acetate and KOH as precursors [19]. The aqueous solution (0.2 M) of zinc acetate (Zn(CH3COO)2 2H2O) and the solution (0.4 M) of KOH were prepared with deionized water, respectively. The KOH solution was slowly added into zinc nitrate solution at room temperature under vigorous stirring, which resulted in the formation of a white suspension. The white product was centrifuged at 5000 rpm for 20 min and washed three times with distilled water, and washed with absolute alcohol at last. The obtained product was calcined at 500°C in air atmosphere for 3 h.

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

### 2.3 Synthesis of polyaniline/ZnO nanocomposite

The material was synthesized by methods already reported elsewhere [20]. The detailed procedure is as follows: 1 g of above synthesized ZnO nanoparticles were taken in 100 ml of 0.1 M HCl solution and sonicated for 1 h at 30°C. Now, 10 ml of distilled aniline monomer taken in 400 ml of 0.1 M HCl solution was poured in the above colloidal solution of ZnO. The mixture was allowed to stir for 2 h for complete mixing at 5°C. The reaction was proceeded with the addition of 15 g of APS. The reaction was allowed to stand for 12 h at 5°C and product obtained was washed with 0.1 M HCl solution five to six times in order to remove excess amount of unreacted aniline.

#### 2.4 Instrumentation

been widely used for the removal of chromium from contaminated groundwater out of these methods [11] due to its low initial cost and ease of operation and high efficiency to remove toxic heavy metals. This technique can be harnessed at large scale for the treatment of polluted water as it can handle fairly large flow rates, producing a high quality of water without producing notorious sludge and residual

Conducting polymer with metal oxide has nowadays emerged as an attractive alternative for the sequestration of wastewater, as it mainly provide larger surface area for the adsorption, interfacial adhesion between the surface of nanocomposite and metal ions, it is easily tractable and cost effective. Due to large amount of amine and imine functional groups PANI has strong affinity with metal ions and can remove heavy metal contaminants from aqueous solutions effectively [15, 16]. The stability of polymer matrix can be enhanced by addition of fillers such as natural clays, metal oxide nanoparticles, etc. [17]. Zinc oxide is known to be a potential adsorbent of Cr(VI) at high temperatures as well as at low temperatures [18]. So, the incorporation of ZnO nanoparticles in the PANI matrix not only provides thermal and mechanical strength, but also improves its adsorption properties. This improvement was attributed to the increase in the number and high dispersion of active terminal OH groups of ZnO nanoparticles with amine groups

In the present chapter, polyaniline zinc oxide nanocomposite was synthesized by oxidative free radical polymerization of aniline monomer in presence of zinc oxide nanoparticles. The material was characterized by various analytical techniques such as FT-IR, XTD, TGA-DTG, SEM, and TEM. The nanocomposite material was further explored for the removal of Cr(VI) from aqueous solution. The effects of various adsorption parameters viz. agitation time, solution pH, adsorbent dose, initial metal ion concentration, and temperature was observed and optimized by

Zinc acetate and ammonium persulfate (APS) were procured from Sigma Aldrich, India. Sodium hydroxide and potassium dichromate were procured from Merck, India. Aniline monomer was procured from Fisher Scientific, India and was distilled before use. About 1000 mg L<sup>1</sup> stock solutions of were prepared by dissolving appropriate amount of metal salts in double

ZnO nanoparticles were synthesized by direct precipitation method using zinc acetate and KOH as precursors [19]. The aqueous solution (0.2 M) of zinc acetate (Zn(CH3COO)2 2H2O) and the solution (0.4 M) of KOH were prepared with deionized water, respectively. The KOH solution was slowly added into zinc nitrate solution at room temperature under vigorous stirring, which resulted in the formation of a white suspension. The white product was centrifuged at 5000 rpm for 20 min and washed three times with distilled water, and washed with absolute alcohol at last. The obtained product was calcined at 500°C in air

contaminants [12–14].

Advances in Composite Materials Development

of PANI.

preliminary experiments.

2.1 Chemicals

distilled water.

atmosphere for 3 h.

26

2. Materials and methods

2.2 Synthesis of zinc oxide nanoparticles

The FTIR spectra of the adsorbent materials were recorded with a Perkin Elmer 1800 model IR spectrophotometer operating at frequency range from 400 to 4000 cm�<sup>1</sup> using KBr pallets. X-ray diffraction (XRD) patterns of the samples were obtained using Siemens D 5005 X-ray unit Cu Kα (λ = 1:5406 Å) radiation, generated at a voltage of 40 kV and a current of 40 mA was used as the X-ray source. Scanning electron microscopy and electron diffraction scattering (SEM/EDS) analysis were done using GSM 6510LV scanning electron microscope. The particle size and structure of the synthesized nanocomposite were observed by using JEM 2100 transmission electron microscope (TEM). The thermal stability was determined by derivative thermal analysis (DTG, Perkin Elmer Pyris 6) and DTA (Perkin Elmer model, STA 6000). The thermograms were recorded for 20 mg of powder sample at a heating rate of 10°C min�<sup>1</sup> in the temperature range of 30–800°C under nitrogen atmosphere. The concentration of metal ions in the solution was measured by atomic absorption spectrophotometer (AAS) model GBC-902. Elico Li 120 pH meter was used to adjust the pH of the solutions.

#### 2.5 Adsorption experiments

The adsorption experiments were performed using batch equilibrium technique in aqueous solutions in the temperature range of 30–50°C at pH 2. For this, 0.04 g of adsorbents was added to 20 ml of Cr(VI) solution of various concentrations (from 10, 50, 100 mg L�<sup>1</sup> ) and shaken in a thermostatic water-bath shaker operated at 120 rpm. After equilibrium was attained, the adsorbent was removed and the supernatant was collected after attaining equilibrium. The concentrations of Cr(VI) in supernatant were measured using atomic absorption spectrophotometer (AAS). The kinetic experiments were performed at three different Cr(VI) ion concentrations mainly at 10, 50, and 100 mg L�<sup>1</sup> at pH 2 and 3. The effect of time on the adsorption of Cr(VI) ions on PAZO nanocomposite was studied at 10–300 min and the equilibrium was reached at 120 min. The effect of adsorbent dose and initial metal ion concentration was also studied. The amount of metal ions adsorbed onto PAZO was calculated by a mass balance relationship:

$$q\_{\epsilon} = \frac{(\mathbf{C}\_{\bullet} - \mathbf{C}\_{\epsilon})V}{W} \tag{1}$$

where qe is the amount of metal ion adsorbed per unit weight of the adsorbent (mg g�<sup>1</sup> ); Co and Ce are the concentrations of the metal ion in the initial solution (mg L�<sup>1</sup> ) and after adsorption, respectively; V is the volume of the adsorption medium (L); and W is the amount of the adsorbent (g).

## 3. Results and discussion

## 3.1 Characterization of PAZO

## 3.1.1 XRD analysis

XRD analysis of bulk composite was done and it was seen that the characteristic peak of ZnO nanoparticles were obtained at 2θ values of 8.03, 11.87, 31.71, 34.38, 38.18, 47.47, 58.51, 62.77, and 68.98° given in Figure 1 which corresponds to Miller indices (100), (002), (101), (102), (110), (103), and (201), respectively. The crystalline size calculated using Scherer formula was found to be 31 nm which is also confirmed by TEM micrograph. The PANI peak diffracted at an angle of 25.72°, respectively, in the XRD pattern showing low crystallinity for conductive polymers due to the repetition of benzenoid and quinoid rings in PANI chains. Peaks of PANI-ZnO composites shift slightly higher values of 2θ. It can be seen that the XRD patterns of nanocomposites represent the peaks from ZnO and PANI. This is because of the presence of ZnO nanoparticles which is equal to 5% and it has significant effect on diffraction pattern of PANI. According to Figure 1, two distinct sharp peaks at 2θ = 19.311 and 25.721 with planes of (010) and (200), respectively, are shifted negligibly but their intensity increases by the reinforcement of the ZnO nanoparticles in PANI matrix. Additionally, one peak at 2θ = 23.21 with plane of (102) appears which is related to PANI-CSA and its intensity is increased by adding ZnO nanoparticles. XRD results confirm the effect of ZnO nanoparticles in PANI-ZnO nanocomposites. Figure 1 shows that intensity of the peaks was increased by incorporation of 5% ZnO nanoparticles, which means that there is an interaction of ZnO nanoparticles and PANI by formation of hydrogen bonding between H–N and oxygen of ZnO [21].

degradation of weight in the range of 30–800°C. The first weight loss of at around 109.47°C is due to evaporation of water. The second stage of weight loss starting at around 140°C up to 370°C almost 60% substance weight loss which represents the degradation of low molecular weight polymers and almost 45% weight loss for PANI was observed at 700°C [22]. From 370°C onward, degradation of PANI chains takes place up to 800°C, in which almost 90% mass loss is observed. The PAZO also shows same stages of weight loss with little bit of higher thermal stability as compare to pure PANI due to incorporation of ZnO in PANI matrix and a weight loss of

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

Morphologies of the PANI-ZnO nanocomposite with its EDX image before and after adsorption of Cr(VI) are shown in Figure 3. Nanocomposite reveals flaky fibrous structure shaped structure. These nanocomposites should give the opportunity to obtain improved capacitance due to surface effects. The size of the flakes and fibers decreased due to adsorption of Cr(VI). The SEM images help us to draw a conclusion that the doping of ZnO nano-rods has a strong effect on the morphology of PANI, since PANI has various structures such as granules, nanofibers, nanotubes,

Due to the low magnification in SEM micrographs, it is difficult to observe ZnO nanoparticles in the nanocomposite matrix; thus, an appropriate way for observing them in polymer matrix is by the use of TEM. According to the TEM micrographs in Figure 4, PANI and ZnO nanoparticles have formed a nanocomposite in which the nanoparticles are embedded in the polymer matrix. It is obvious that ZnO nanoparticles were uniformly coated by PANI. The average size

PANI and PAZO nanocomposite were characterized by using the FTIR technique. Figure 5 shows the FTIR pattern of ZnO nanoparticles, PANI and PAZO nanocomposite. The characteristic absorption bands of PANI are 515.71 cm<sup>1</sup>

28% was observed at 800°C.

TGA thermograms of PANI and PAZO.

DOI: http://dx.doi.org/10.5772/intechopen.85868

Figure 2.

3.1.3 Surface analysis (SEM with EDX)

nanospheres, microspheres, and flakes.

3.1.4 Transmission electron microscope (TEM) analysis

of ZnO nanoparticles was observed as 31.2 nm.

3.1.5 FTIR analysis

29

### 3.1.2 Thermal analysis

Thermal stability of PANI and PAZO was analysed by TGA and the thermograms are given in Figure 2. The TGA thermogram of pure PANI shows three-step

Figure 1. XRD spectra of ZnO, PANI and PAZO.

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

#### Figure 2. TGA thermograms of PANI and PAZO.

3. Results and discussion

3.1.1 XRD analysis

oxygen of ZnO [21].

3.1.2 Thermal analysis

Figure 1.

28

XRD spectra of ZnO, PANI and PAZO.

3.1 Characterization of PAZO

Advances in Composite Materials Development

XRD analysis of bulk composite was done and it was seen that the characteristic peak of ZnO nanoparticles were obtained at 2θ values of 8.03, 11.87, 31.71, 34.38, 38.18, 47.47, 58.51, 62.77, and 68.98° given in Figure 1 which corresponds to Miller indices (100), (002), (101), (102), (110), (103), and (201), respectively. The crystalline size calculated using Scherer formula was found to be 31 nm which is also confirmed by TEM micrograph. The PANI peak diffracted at an angle of 25.72°, respectively, in the XRD pattern showing low crystallinity for conductive polymers due to the repetition of benzenoid and quinoid rings in PANI chains. Peaks of PANI-ZnO composites shift slightly higher values of 2θ. It can be seen that the XRD patterns of nanocomposites represent the peaks from ZnO and PANI. This is because of the presence of ZnO nanoparticles which is equal to 5% and it has significant effect on diffraction pattern of PANI. According to Figure 1, two distinct sharp peaks at 2θ = 19.311 and 25.721 with planes of (010) and (200), respectively, are shifted negligibly but their intensity increases by the reinforcement of the ZnO nanoparticles in PANI matrix. Additionally, one peak at 2θ = 23.21 with plane of (102) appears which is related to PANI-CSA and its intensity is increased by adding ZnO nanoparticles. XRD results confirm the effect of ZnO nanoparticles in PANI-ZnO nanocomposites. Figure 1 shows that intensity of the peaks was increased by incorporation of 5% ZnO nanoparticles, which means that there is an interaction of ZnO nanoparticles and PANI by formation of hydrogen bonding between H–N and

Thermal stability of PANI and PAZO was analysed by TGA and the thermograms are given in Figure 2. The TGA thermogram of pure PANI shows three-step degradation of weight in the range of 30–800°C. The first weight loss of at around 109.47°C is due to evaporation of water. The second stage of weight loss starting at around 140°C up to 370°C almost 60% substance weight loss which represents the degradation of low molecular weight polymers and almost 45% weight loss for PANI was observed at 700°C [22]. From 370°C onward, degradation of PANI chains takes place up to 800°C, in which almost 90% mass loss is observed. The PAZO also shows same stages of weight loss with little bit of higher thermal stability as compare to pure PANI due to incorporation of ZnO in PANI matrix and a weight loss of 28% was observed at 800°C.

## 3.1.3 Surface analysis (SEM with EDX)

Morphologies of the PANI-ZnO nanocomposite with its EDX image before and after adsorption of Cr(VI) are shown in Figure 3. Nanocomposite reveals flaky fibrous structure shaped structure. These nanocomposites should give the opportunity to obtain improved capacitance due to surface effects. The size of the flakes and fibers decreased due to adsorption of Cr(VI). The SEM images help us to draw a conclusion that the doping of ZnO nano-rods has a strong effect on the morphology of PANI, since PANI has various structures such as granules, nanofibers, nanotubes, nanospheres, microspheres, and flakes.

### 3.1.4 Transmission electron microscope (TEM) analysis

Due to the low magnification in SEM micrographs, it is difficult to observe ZnO nanoparticles in the nanocomposite matrix; thus, an appropriate way for observing them in polymer matrix is by the use of TEM. According to the TEM micrographs in Figure 4, PANI and ZnO nanoparticles have formed a nanocomposite in which the nanoparticles are embedded in the polymer matrix. It is obvious that ZnO nanoparticles were uniformly coated by PANI. The average size of ZnO nanoparticles was observed as 31.2 nm.

### 3.1.5 FTIR analysis

PANI and PAZO nanocomposite were characterized by using the FTIR technique. Figure 5 shows the FTIR pattern of ZnO nanoparticles, PANI and PAZO nanocomposite. The characteristic absorption bands of PANI are 515.71 cm<sup>1</sup>

(C–N–C bonding mode of aromatic ring); 592.85 and 700.84 cm<sup>1</sup> (C–C, C–H bonding mode of aromatic ring); 831.98 cm<sup>1</sup> (C–H out of plane bonding in benzenoid ring); 1040.26, 1302.53, and 1503.09 cm<sup>1</sup> (C–N stretching of benzenoid ring), and 1572.52 cm<sup>1</sup> (C–N stretching of quinoid ring). The PAZO nanocomposite shows the same characteristic peaks. However, there is an evidence of peak displacement when ZnO nanoparticles are added to the PANI. These shifts include 1572.51–1587.94, 1503.09–1510.81, 1155.97–1148.25, 1040.26–1047.97, 831.98–

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

ZnO nanoparticles and PANI by formation of hydrogen bonding between H–N and oxygen of ZnO. So, the peak displacement that was observed in FTIR spectra may be ascribed to the formation of hydrogen bonding between ZnO and the N–H group

One the most important parameter that directly affects the adsorption of Cr(VI) is pH of the solution. The effect of the initial solution pH on the removal of Cr(VI) was studied with 0.04 g of PAZO nanocomposite, 20 ml of 10, 50, and 100 mg L<sup>1</sup> Cr(VI) solution with different pH in the range 2–7 at 30°C. The effect of pH on

Effect of pH on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion concentrations.

. Furthermore, in PAZO nanocomposite, a broad

, which can be associated to the interaction between

862.84, and 592.85–600.23 cm<sup>1</sup>

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of PANI on the surface of the ZnO nanoparticles.

3.2 Adsorption behavior of PAZO toward Cr(VI)

peak appeared in 3470 cm<sup>1</sup>

3.2.1 Effect of pH

Figure 5.

Figure 6.

31

FTIR spectra of (a) PANI and (b) PAZO.

Figure 3.

SEM images of PAZO before and after adsorption of Cr(VI) with its EDX image.

Figure 4. TEM image of PAZO. Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

(C–N–C bonding mode of aromatic ring); 592.85 and 700.84 cm<sup>1</sup> (C–C, C–H bonding mode of aromatic ring); 831.98 cm<sup>1</sup> (C–H out of plane bonding in benzenoid ring); 1040.26, 1302.53, and 1503.09 cm<sup>1</sup> (C–N stretching of benzenoid ring), and 1572.52 cm<sup>1</sup> (C–N stretching of quinoid ring). The PAZO nanocomposite shows the same characteristic peaks. However, there is an evidence of peak displacement when ZnO nanoparticles are added to the PANI. These shifts include 1572.51–1587.94, 1503.09–1510.81, 1155.97–1148.25, 1040.26–1047.97, 831.98– 862.84, and 592.85–600.23 cm<sup>1</sup> . Furthermore, in PAZO nanocomposite, a broad peak appeared in 3470 cm<sup>1</sup> , which can be associated to the interaction between ZnO nanoparticles and PANI by formation of hydrogen bonding between H–N and oxygen of ZnO. So, the peak displacement that was observed in FTIR spectra may be ascribed to the formation of hydrogen bonding between ZnO and the N–H group of PANI on the surface of the ZnO nanoparticles.

## 3.2 Adsorption behavior of PAZO toward Cr(VI)

### 3.2.1 Effect of pH

Figure 3.

Figure 4.

30

TEM image of PAZO.

SEM images of PAZO before and after adsorption of Cr(VI) with its EDX image.

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One the most important parameter that directly affects the adsorption of Cr(VI) is pH of the solution. The effect of the initial solution pH on the removal of Cr(VI) was studied with 0.04 g of PAZO nanocomposite, 20 ml of 10, 50, and 100 mg L<sup>1</sup> Cr(VI) solution with different pH in the range 2–7 at 30°C. The effect of pH on

Figure 5. FTIR spectra of (a) PANI and (b) PAZO.

Figure 6. Effect of pH on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion concentrations.

sorption of Cr(VI) has been shown in Figure 6. It was found that the maximum adsorption capacity for Cr(VI) was in the pH value of 2 and as the pH value increases the adsorption capacity decreases. Various forms of Cr(VI) in water such as HCrO4 in acidic medium, CrO4 <sup>2</sup> in neutral and basic medium are predominant factor for the adsorption of Cr(VI) onto PAZO nanocomposite.

3.2.3 Effect of adsorbent dose and temperature

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adsorbent dose for all the experiments.

temperature for all the adsorption experiments.

3.3 Adsorption isotherms

applied to the experimental data.

3.3.1 Langmuir isotherm

Figure 8.

33

concentrations.

The adsorption of metal ions in the solution is greatly affected by the dose of adsorbent used. A range of adsorbent dose from 0.01 to 0.07 g was used with 20 ml of 10, 50, and 100 mg L<sup>1</sup> of metal ion solution for 120 min to investigate the effect of dose on removal of Cr(VI), and the results are shown in Figure 8. It was found that the adsorption efficiency for Cr(VI) ion increases as the amount of adsorbent increase up to 0.04 g, but on further increasing the adsorbent dose, the adsorption capacity decreases. This trend can be explained as the adsorbent dose increases, the number of adsorbent particles also increases facilitating more active sites for adsorption but on further increase in adsorbent dose adsorption capacity decreases due to partial aggregation of adsorbent particles. So, 0.04 g was taken as optimum

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

The effect of temperature on adsorption of Cr(VI) was observed in the temperature range of 30–50°C (plot not given). It was observed that on increasing the temperature, the adsorption capacity also increases due to increase in diffusion rate of metal ions across the external boundary layer and within the pores of PAZO nanocomposite. Furthermore, at high temperature, the energy of the system also facilitated the binding of Cr(VI) on the surface of PAZO indicating the adsorption of Cr(VI) is controlled endothermic process. So, 50°C was selected as the optimum

The adsorption isotherms describe the effect of metal ion concentrations on the amount of metal ion adsorbed on the adsorbent surface leading to find the best equilibrium position in the adsorption process. In the present study, Langmuir [26], Freundlich [27] Dubinin-Radushkevich [28], and Temkin [29] models have been

The Langmuir isotherm is used to describe the equilibrium between the surface of solid and the solution as a reversible chemical equilibrium. Langmuir isotherm model is valid for adsorption onto a surface containing a finite number of identical

sites. The Langmuir treatment is based on the assumption that a maximum

Effect of adsorbent dose on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion

At pH < 4, due to presence of excess of H+ ions in the solution, the adsorbent surface becomes positively charged due to protonation and HCrO4 form of Cr(VI) ions are dominant at lower pH [23], so strong electrostatic attraction between positively charged adsorbent surface and negatively charged HCrO4 ions led to higher removal efficiency. However, as the pH increases, deprotonation of surface of the adsorbent was observed due to decrease in number of H+ ions. So, lower adsorption capacity results due to less interaction between Cr(VI) ions and adsorbent surface at higher pH value. The point of zero charge of adsorbent surface is found to be 5.5.

#### 3.2.2 Effect of contact time and initial metal ion concentration

The effect of retention time on removal efficiency of Cr(VI) was carried out by varying the contact time in the range of 10–300 min at three different metal ion concentrations 10, 50, and 100 mg L<sup>1</sup> at pH 2 at adsorbent dose of 0.04 g. The effect of contact time on PAZO for Cr(VI) removal is depicted in Figure 7 indicating an initial increase in adsorption capacity with increase in time and attaining the equilibrium time at 120 min after that little change in adsorption capacity for Cr (VI) is seen which indicates that the system has already achieved equilibrium. No change in adsorption capacity after equilibrium reveals that the adsorption sites are completely occupied by metal ion. So, the equilibrium time 120 min was chosen as optimum time in subsequent experiments.

The initial metal ion concentration provides an important driving force to overcome all mass transfer resistance of metal ions between the aqueous and solid phases [24]. Three different concentrations 10, 50, and 100 mg L<sup>1</sup> of the metal ions were chosen to see the effect of initial metal ion concentration on adsorption capacity of PAZO. Figure 7 also shows the effect of initial metal ion concentration in which by increasing Cr(VI) ions concentration the adsorption capacity also increases. The maximum adsorption capacity at 10, 50, and 100 mg L<sup>1</sup> was found to be 9.31, 25.11, and 31.89 mg g<sup>1</sup> , respectively, which might be due to the fact that increasing metal ion concentration increased the number of collision between the adsorbent and metal ion species, this leads to an increased metal ion uploading [25].

Figure 7. Effect of contact time on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion concentrations.

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

### 3.2.3 Effect of adsorbent dose and temperature

sorption of Cr(VI) has been shown in Figure 6. It was found that the maximum adsorption capacity for Cr(VI) was in the pH value of 2 and as the pH value increases the adsorption capacity decreases. Various forms of Cr(VI) in water such

At pH < 4, due to presence of excess of H+ ions in the solution, the adsorbent

higher removal efficiency. However, as the pH increases, deprotonation of surface of the adsorbent was observed due to decrease in number of H+ ions. So, lower adsorption capacity results due to less interaction between Cr(VI) ions and adsorbent surface at higher pH value. The point of zero charge of adsorbent surface is

The effect of retention time on removal efficiency of Cr(VI) was carried out by varying the contact time in the range of 10–300 min at three different metal ion concentrations 10, 50, and 100 mg L<sup>1</sup> at pH 2 at adsorbent dose of 0.04 g. The effect of contact time on PAZO for Cr(VI) removal is depicted in Figure 7 indicating an initial increase in adsorption capacity with increase in time and attaining the equilibrium time at 120 min after that little change in adsorption capacity for Cr (VI) is seen which indicates that the system has already achieved equilibrium. No change in adsorption capacity after equilibrium reveals that the adsorption sites are completely occupied by metal ion. So, the equilibrium time 120 min was chosen as

The initial metal ion concentration provides an important driving force to over-

come all mass transfer resistance of metal ions between the aqueous and solid phases [24]. Three different concentrations 10, 50, and 100 mg L<sup>1</sup> of the metal ions were chosen to see the effect of initial metal ion concentration on adsorption capacity of PAZO. Figure 7 also shows the effect of initial metal ion concentration in which by increasing Cr(VI) ions concentration the adsorption capacity also increases. The maximum adsorption capacity at 10, 50, and 100 mg L<sup>1</sup> was found

increasing metal ion concentration increased the number of collision between the adsorbent and metal ion species, this leads to an increased metal ion uploading [25].

Effect of contact time on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion

ions are dominant at lower pH [23], so strong electrostatic attraction between

<sup>2</sup> in neutral and basic medium are predominant

, respectively, which might be due to the fact that

form of Cr(VI)

ions led to

as HCrO4

found to be 5.5.

in acidic medium, CrO4

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optimum time in subsequent experiments.

to be 9.31, 25.11, and 31.89 mg g<sup>1</sup>

Figure 7.

32

concentrations.

factor for the adsorption of Cr(VI) onto PAZO nanocomposite.

3.2.2 Effect of contact time and initial metal ion concentration

surface becomes positively charged due to protonation and HCrO4

positively charged adsorbent surface and negatively charged HCrO4

The adsorption of metal ions in the solution is greatly affected by the dose of adsorbent used. A range of adsorbent dose from 0.01 to 0.07 g was used with 20 ml of 10, 50, and 100 mg L<sup>1</sup> of metal ion solution for 120 min to investigate the effect of dose on removal of Cr(VI), and the results are shown in Figure 8. It was found that the adsorption efficiency for Cr(VI) ion increases as the amount of adsorbent increase up to 0.04 g, but on further increasing the adsorbent dose, the adsorption capacity decreases. This trend can be explained as the adsorbent dose increases, the number of adsorbent particles also increases facilitating more active sites for adsorption but on further increase in adsorbent dose adsorption capacity decreases due to partial aggregation of adsorbent particles. So, 0.04 g was taken as optimum adsorbent dose for all the experiments.

The effect of temperature on adsorption of Cr(VI) was observed in the temperature range of 30–50°C (plot not given). It was observed that on increasing the temperature, the adsorption capacity also increases due to increase in diffusion rate of metal ions across the external boundary layer and within the pores of PAZO nanocomposite. Furthermore, at high temperature, the energy of the system also facilitated the binding of Cr(VI) on the surface of PAZO indicating the adsorption of Cr(VI) is controlled endothermic process. So, 50°C was selected as the optimum temperature for all the adsorption experiments.

#### 3.3 Adsorption isotherms

The adsorption isotherms describe the effect of metal ion concentrations on the amount of metal ion adsorbed on the adsorbent surface leading to find the best equilibrium position in the adsorption process. In the present study, Langmuir [26], Freundlich [27] Dubinin-Radushkevich [28], and Temkin [29] models have been applied to the experimental data.

#### 3.3.1 Langmuir isotherm

The Langmuir isotherm is used to describe the equilibrium between the surface of solid and the solution as a reversible chemical equilibrium. Langmuir isotherm model is valid for adsorption onto a surface containing a finite number of identical sites. The Langmuir treatment is based on the assumption that a maximum

#### Figure 8.

Effect of adsorbent dose on adsorption of Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> initial metal ion concentrations.

adsorption corresponds to a saturated monolayer of solute molecules on the adsorbent surface which is represented as follows:

$$\frac{C\_{\epsilon}}{q\_{\epsilon}} = \frac{1}{q\_{m}K\_{L}} + \frac{C\_{\epsilon}}{q\_{m}} \tag{2}$$

adsorption capacities (qm) calculated by Langmuir model were found to be 120.92, 134.22, and 139.47 mg g�<sup>1</sup> at 30, 40, and 50°C, respectively. The regression coefficient values calculated are 0.99, 0.99, and 0.99, respectively, which suggest that the Langmuir model is best fitted to the experimental data at all temperature ranges.

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The Freundlich isotherm model is the earliest empirical equation based on the adsorption on reversible heterogeneous surfaces. The mathematical expression of

and 1/n is the adsorption intensity and an indicator for the favorability of adsorption. The values of n > 1 represent favorable adsorption condition. The linear plot (Figure 10) of ln qe versus ln Ce gives slope of value 1/n and an intercept ln KF. When Ce equals unity, ln KF is equal to ln qe. In the other case, when 1/n = 1, the KF value depends on the units in which qe and Ce are expressed. A favorable adsorption tends to give Freundlich constant n value between 1 and 10. Larger value of n

Langmuir adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

Freundlich adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

lnC<sup>e</sup> þ lnKF (4)

) is approximately an indicator of the adsorption capacity,

ln qe <sup>¼</sup> <sup>1</sup> n

3.3.2 Freundlich isotherm

the model is given as follows:

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where KF (mg g�<sup>1</sup>

Figure 9.

Figure 10.

35

where qm is maximum monolayer adsorption capacity of the adsorbent (mg g�<sup>1</sup> ) and KL is the Langmuir constant (L mg�<sup>1</sup> ) related to the adsorption free energy. The qm and KL values are reported in Table 1. The essential feature of the Langmuir adsorption can be expressed by means of RL, a dimensionless constant referred to as separation factor for predicting whether an adsorption system is favorable or unfavorable. RL is calculated using equation

$$R\_L = \frac{1}{1 + K\_L C\_o} \tag{3}$$

where C<sup>0</sup> is the initial metal ion concentration (mg L�<sup>1</sup> ). The parameter RL indicates the favorability of adsorption as follows:


The linearized plot (Figure 9) of Ce/qe versus Ce are obtained for Cr(VI). The Langmuir constants qm and KL can be determined from the slope and intercept of the linear line, respectively. As can be seen from Table 1, the maximum monolayer


#### Table 1.

Isotherm parameters for Cr(VI) removal by PAZO at 30, 40, and 50°C.

### Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

adsorption capacities (qm) calculated by Langmuir model were found to be 120.92, 134.22, and 139.47 mg g�<sup>1</sup> at 30, 40, and 50°C, respectively. The regression coefficient values calculated are 0.99, 0.99, and 0.99, respectively, which suggest that the Langmuir model is best fitted to the experimental data at all temperature ranges.

## 3.3.2 Freundlich isotherm

adsorption corresponds to a saturated monolayer of solute molecules on the adsor-

where qm is maximum monolayer adsorption capacity of the adsorbent (mg g�<sup>1</sup>

(2)

(3)

) related to the adsorption free energy. The

30°C 40°C 50°C

) 120.92 134.22 139.47

) 0.06 0.08 0.12 R2 0.99 0.99 0.99

) 5.69 6.29 6.62 R<sup>2</sup> 0.98 0.98 0.98

) 59.05 62.18 68.70

) 10.48 11.71 12.65 R<sup>2</sup> 0.97 0.98 0.97

) 0.55 0.60 0.64

) 63.10 62.97 56.09 R<sup>2</sup> 0.98 0.98 0.98

) 1.85 � <sup>e</sup>�<sup>6</sup> 1.47 � <sup>e</sup>�<sup>6</sup> 1.25 � <sup>e</sup>�

). The parameter RL

)

<sup>¼</sup> <sup>1</sup> qmKL þ Ce qm

qm and KL values are reported in Table 1. The essential feature of the Langmuir adsorption can be expressed by means of RL, a dimensionless constant referred to as separation factor for predicting whether an adsorption system is favorable or unfa-

RL <sup>¼</sup> <sup>1</sup>

where C<sup>0</sup> is the initial metal ion concentration (mg L�<sup>1</sup>

Model Parameters Cr(VI)

KL (L mg�<sup>1</sup>

KL (mg g�<sup>1</sup>

kD-R (mol<sup>2</sup> KJ�<sup>2</sup>

E (KJ mol�<sup>1</sup>

b (J mol�<sup>1</sup>

Isotherm parameters for Cr(VI) removal by PAZO at 30, 40, and 50°C.

indicates the favorability of adsorption as follows:

1 þ KLCo

The linearized plot (Figure 9) of Ce/qe versus Ce are obtained for Cr(VI). The Langmuir constants qm and KL can be determined from the slope and intercept of the linear line, respectively. As can be seen from Table 1, the maximum monolayer

Freundlich n 1.18 1.22 1.35

Ce qe

bent surface which is represented as follows:

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and KL is the Langmuir constant (L mg�<sup>1</sup>

vorable. RL is calculated using equation

• RL > 1, unfavorable adsorption

• 0 < RL > 1, favorable adsorption

• RL = 0, irreversible adsorption

• RL = 1, linear adsorption

Langmuir qm (mg g�<sup>1</sup>

D-R qm (mg g�<sup>1</sup>

Temkin A (L mg�<sup>1</sup>

Table 1.

34

The Freundlich isotherm model is the earliest empirical equation based on the adsorption on reversible heterogeneous surfaces. The mathematical expression of the model is given as follows:

$$\ln q\_{\epsilon} = \frac{1}{n} \ln \mathbb{C}\_{\epsilon} + \ln K\_F \tag{4}$$

where KF (mg g�<sup>1</sup> ) is approximately an indicator of the adsorption capacity, and 1/n is the adsorption intensity and an indicator for the favorability of adsorption. The values of n > 1 represent favorable adsorption condition. The linear plot (Figure 10) of ln qe versus ln Ce gives slope of value 1/n and an intercept ln KF. When Ce equals unity, ln KF is equal to ln qe. In the other case, when 1/n = 1, the KF value depends on the units in which qe and Ce are expressed. A favorable adsorption tends to give Freundlich constant n value between 1 and 10. Larger value of n

#### Figure 9.

Langmuir adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

Figure 10. Freundlich adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

(smaller value of 1/n) implies strong interaction between sorbent and metal ions, while 1/n equal to 1 indicates linear adsorption leading to identical adsorption energies for all the sites. It can be observed from Table 1 that for all the temperature ranges, the values of n is >1 and hence favorable adsorption.

## 3.3.3 Dubinin-Radushkevish (D-R) isotherm

The Dubinin-Radushkevish (D-R) isotherm can be used to describe adsorption on both homogeneous and heterogeneous surfaces. This isotherm can be described by the following equation:

$$\ln q\_{\epsilon} = \ln q\_{m} - k\_{D-R} \mathbf{e}^{2} \tag{5}$$

3.3.4 Temkin isotherm

high temperature.

Figure 12.

37

3.4 Adsorption kinetics

3.4.1 Lagergren pseudo-first-order model

expressed by the following equation:

isotherm has been used in the following forms:

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where R is gas constant 8.314 J mol�<sup>1</sup> K�<sup>1</sup>

Temkin constant related to the heat of adsorption (J mol�<sup>1</sup>

Temkin isotherm considers the effects of the heat of adsorption that decreases linearly with coverage of the adsorbate and adsorbent interactions. The Temkin

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

<sup>B</sup> <sup>¼</sup> RT

rium binding constant corresponding to the maximum binding energy (L g�<sup>1</sup>

ions. The value of binding constant A given in Table 1 as 0.55, 0.60, and

order, Elovich, and Webber-Morris intra-particle diffusion models.

log qe � qt

liner plots (Figure 12) of qe versus ln Ce enable to determine the constant A and B. The Temkin constant given in Table 1 clearly suggests that the adsorption involves chemisorption and physisorption of the Cr(VI) rather than an ion exchange mechanism. The Temkin isotherm gives a satisfactory linear fit data with all the metal

0.64 L mg�<sup>1</sup> also support the high affinity of Cr(VI) toward adsorbent surface at

Kinetics of the adsorption process is a vital parameter which provides essential information on the solute uptake rate and the reaction pathways. To determine the rate-determining step during the adsorption process, the kinetic data of heavy metals onto PAZO were simulated with the pseudo-first-order and pseudo-second-

The pseudo-first-order kinetics model is based on the assumption that adsorption was controlled by diffusion steps [30] and the rate of adsorption is in direct proportion to the difference value of equilibrium adsorption capacity and the adsorption capacity at any time t. The linear equation for this model can be

<sup>¼</sup> log qe � <sup>k</sup><sup>1</sup>

Temkin adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

qe ¼ Bln A þ BlnC<sup>e</sup> (8)

<sup>b</sup> (9)

. T is absolute temperature (K), b is the

<sup>2</sup>:<sup>303</sup> <sup>t</sup> (10)

), and A is the equilib-

). The

where qm is the D-R monolayer capacity (mg g�<sup>1</sup> ) obtained by a plot between ln qe and ε <sup>2</sup> (Figure 11), kD-R is a constant related to the adsorption energy, and ε is Polanyi potential which is related to the equilibrium concentration as follows:

$$\varepsilon = RT\left(1 + \frac{1}{C\_{\epsilon}}\right) \tag{6}$$

where R is the gas constant (8.314 Jmol�<sup>1</sup> K�<sup>1</sup> ) and T is the absolute temperature (K). The constant k gives the mean free energy E of adsorption per molecule of the adsorbate when it is transferred to the surface of the solid from infinity in the solution and can be computed using the relationship:

$$E = \frac{1}{\sqrt{2k\_{D-R}}}\tag{7}$$

The magnitude of E is useful for estimating the mechanism of the adsorption reaction. From Table 1, the maximum adsorption capacities for Cr(VI) calculated by D-R model at 30, 40, and 50°C was found to be 59.05, 62.18, and 68.70 mg g�<sup>1</sup> , respectively. The mean free energy per molecule (E) was estimated to be 10.48, 11.71, and 12.65 KJ mol�<sup>1</sup> at 30, 40, and 50°C, respectively, which confirms that the adsorption reaction follows chemisorption process. The values of D-R constant kD-R were found to be 1.85 � <sup>10</sup>�<sup>6</sup> , 1.47 � <sup>10</sup>�<sup>6</sup> , and 1.25 � <sup>10</sup>�<sup>6</sup> for Cr(VI) at 30, 40, and 50°C, respectively.

Figure 11. D-R adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

#### 3.3.4 Temkin isotherm

(smaller value of 1/n) implies strong interaction between sorbent and metal ions, while 1/n equal to 1 indicates linear adsorption leading to identical adsorption energies for all the sites. It can be observed from Table 1 that for all the temperature

The Dubinin-Radushkevish (D-R) isotherm can be used to describe adsorption on both homogeneous and heterogeneous surfaces. This isotherm can be described

<sup>2</sup> (Figure 11), kD-R is a constant related to the adsorption energy, and ε is

1 Ce � �

Polanyi potential which is related to the equilibrium concentration as follows:

ε ¼ RT 1 þ

(K). The constant k gives the mean free energy E of adsorption per molecule of the adsorbate when it is transferred to the surface of the solid from infinity in the

<sup>E</sup> <sup>¼</sup> <sup>1</sup>

respectively. The mean free energy per molecule (E) was estimated to be 10.48, 11.71, and 12.65 KJ mol�<sup>1</sup> at 30, 40, and 50°C, respectively, which confirms that the adsorption reaction follows chemisorption process. The values of D-R constant kD-R

, 1.47 � <sup>10</sup>�<sup>6</sup>

D-R adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

The magnitude of E is useful for estimating the mechanism of the adsorption reaction. From Table 1, the maximum adsorption capacities for Cr(VI) calculated by D-R model at 30, 40, and 50°C was found to be 59.05, 62.18, and 68.70 mg g�<sup>1</sup>

ffiffiffiffiffiffiffiffiffiffiffiffi 2kD�<sup>R</sup>

ln qe <sup>¼</sup> ln qm � kD�Rε<sup>2</sup> (5)

) obtained by a plot between ln

) and T is the absolute temperature

p (7)

, and 1.25 � <sup>10</sup>�<sup>6</sup> for Cr(VI) at 30, 40, and

(6)

,

ranges, the values of n is >1 and hence favorable adsorption.

where qm is the D-R monolayer capacity (mg g�<sup>1</sup>

where R is the gas constant (8.314 Jmol�<sup>1</sup> K�<sup>1</sup>

solution and can be computed using the relationship:

3.3.3 Dubinin-Radushkevish (D-R) isotherm

Advances in Composite Materials Development

by the following equation:

were found to be 1.85 � <sup>10</sup>�<sup>6</sup>

50°C, respectively.

Figure 11.

36

qe and ε

Temkin isotherm considers the effects of the heat of adsorption that decreases linearly with coverage of the adsorbate and adsorbent interactions. The Temkin isotherm has been used in the following forms:

$$q\_{\epsilon} = B \ln A + B \ln \mathbf{C}\_{\epsilon} \tag{8}$$

$$B = \frac{RT}{b} \tag{9}$$

where R is gas constant 8.314 J mol�<sup>1</sup> K�<sup>1</sup> . T is absolute temperature (K), b is the Temkin constant related to the heat of adsorption (J mol�<sup>1</sup> ), and A is the equilibrium binding constant corresponding to the maximum binding energy (L g�<sup>1</sup> ). The liner plots (Figure 12) of qe versus ln Ce enable to determine the constant A and B. The Temkin constant given in Table 1 clearly suggests that the adsorption involves chemisorption and physisorption of the Cr(VI) rather than an ion exchange mechanism. The Temkin isotherm gives a satisfactory linear fit data with all the metal ions. The value of binding constant A given in Table 1 as 0.55, 0.60, and 0.64 L mg�<sup>1</sup> also support the high affinity of Cr(VI) toward adsorbent surface at high temperature.

#### 3.4 Adsorption kinetics

Kinetics of the adsorption process is a vital parameter which provides essential information on the solute uptake rate and the reaction pathways. To determine the rate-determining step during the adsorption process, the kinetic data of heavy metals onto PAZO were simulated with the pseudo-first-order and pseudo-secondorder, Elovich, and Webber-Morris intra-particle diffusion models.

#### 3.4.1 Lagergren pseudo-first-order model

The pseudo-first-order kinetics model is based on the assumption that adsorption was controlled by diffusion steps [30] and the rate of adsorption is in direct proportion to the difference value of equilibrium adsorption capacity and the adsorption capacity at any time t. The linear equation for this model can be expressed by the following equation:

Figure 12. Temkin adsorption isotherm for Cr(VI) on PAZO at 30, 40, and 50°C (dose = 0.04 g and pH = 2).

where k<sup>1</sup> is the pseudo-first-order rate constant (min�<sup>1</sup> ), qe is the amount of heavy metal ions adsorbed at equilibrium (mg g�<sup>1</sup> ), and qt is the amount of the adsorption at any time t (mg g�<sup>1</sup> ). Such an equation should yield a straight line, as given in Figure 13, with intercept equal to log qe and slope equal to (k1/2.303).

#### 3.4.2 Pseudo-second order

The linear equation for pseudo-second-order kinetics [31] is given by the following equation:

$$\frac{t}{q\_t} = \frac{1}{k\_2 q e^2} + \frac{t}{q\_e} \tag{11}$$

3.4.3 Elovich model

DOI: http://dx.doi.org/10.5772/intechopen.85868

stant (g mg�<sup>1</sup>

tion rate α.

and Morris [33]:

plot given in Figure 16.

Figure 15.

pH = 2).

39

3.4.4 Intra-particle diffusion model

If the process is a chemisorption on highly heterogeneous sorbents, the sorption

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

), and qt is the adsorption capacity at any time t in mg g�<sup>1</sup>

When adsorbate transmits from solution into solid phase of absorbents, pore and intra-particle diffusion are often rate limiting in a batch reactor system. The intraparticle diffusion was explored by using the following equation suggested by Weber

qt ¼ Kintt

intra-particle diffusion equation constant (mg g�<sup>1</sup> min�1/2), and t is the time.

straight line, when diffusion plays a role in the sorption rate, and should cross the origin if intra-particle diffusion is the rate-determining step. The intra-particle diffusion parameters can be calculated from the slope and intercept of the linear

The kinetic parameters obtained by the sorption of heavy metal ions on PAZO nanocomposite are summarized in Table 2. It is found that the correlation coefficients R<sup>2</sup> for the pseudo-second-order kinetic model are 0.99 for 10, 50, and 100 mg L�<sup>1</sup> Cr(VI) concentration at 50°C, respectively, is higher than the correlation coefficient obtained for other models. Also, the qcal values obtained through this model 9.79, 25.46, and 38.44 mg g�<sup>1</sup> are much closer to qexp values 9.31, 25.11, and 37.89 mg g�<sup>1</sup> for 10, 50, and 100 mg L�<sup>1</sup> Cr(VI) solution. The pseudo-secondorder kinetic model assumes that the rate limiting step may be chemical adsorption,

Elovich model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration (dose = 0.04 g and

where the parameter qt is the amount adsorbed at time t (mg g�<sup>1</sup>

According to the Weber-Morris model, the plot of qt, against t

shows a plot of linearization form of Elovich model. The slopes and intercepts of plots of qt versus ln t were used to determine the constant β and the initial adsorp-

ln ð Þ αβ (12)

<sup>1</sup>=<sup>2</sup> <sup>þ</sup> <sup>C</sup> (13)

), β is the adsorption con-

. Figure 15

), Kint is the

1/2, should give a

kinetics could be interpreted by Elovich equation [32] as follows:

where α is the initial adsorption rate (mg g�<sup>1</sup> min�<sup>1</sup>

qt <sup>¼</sup> <sup>1</sup> β ln t þ 1 β

where k<sup>2</sup> is the pseudo-second-order rate constant (g mg�<sup>1</sup> min�<sup>1</sup> ), qe is the amount of heavy metal ions adsorbed at equilibrium (mg g�<sup>1</sup> ), and qt is the amount of the adsorption at any time t (mg g�<sup>1</sup> ). The linear plot of pseudosecond-order model is given in Figure 14, from which constant k<sup>2</sup> and qe can be calculated.

#### Figure 13.

Pseudo-first-order model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration (dose = 0.04 g and pH = 2).

#### Figure 14.

Pseudo-second-order model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration (dose = 0.04 g and pH = 2).

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

#### 3.4.3 Elovich model

where k<sup>1</sup> is the pseudo-first-order rate constant (min�<sup>1</sup>

given in Figure 13, with intercept equal to log qe and slope equal to (k1/2.303).

t qt

where k<sup>2</sup> is the pseudo-second-order rate constant (g mg�<sup>1</sup> min�<sup>1</sup>

amount of heavy metal ions adsorbed at equilibrium (mg g�<sup>1</sup>

amount of the adsorption at any time t (mg g�<sup>1</sup>

The linear equation for pseudo-second-order kinetics [31] is given by the fol-

t qe

<sup>¼</sup> <sup>1</sup> <sup>k</sup>2qe<sup>2</sup> <sup>þ</sup>

second-order model is given in Figure 14, from which constant k<sup>2</sup> and qe can be

Pseudo-first-order model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration

Pseudo-second-order model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration

heavy metal ions adsorbed at equilibrium (mg g�<sup>1</sup>

adsorption at any time t (mg g�<sup>1</sup>

Advances in Composite Materials Development

3.4.2 Pseudo-second order

lowing equation:

calculated.

Figure 13.

Figure 14.

38

(dose = 0.04 g and pH = 2).

(dose = 0.04 g and pH = 2).

), qe is the amount of

(11)

), qe is the

), and qt is the

). The linear plot of pseudo-

), and qt is the amount of the

). Such an equation should yield a straight line, as

If the process is a chemisorption on highly heterogeneous sorbents, the sorption kinetics could be interpreted by Elovich equation [32] as follows:

$$q\_t = \frac{1}{\beta} \ln t + \frac{1}{\beta} \ln \left(a\beta\right) \tag{12}$$

where α is the initial adsorption rate (mg g�<sup>1</sup> min�<sup>1</sup> ), β is the adsorption constant (g mg�<sup>1</sup> ), and qt is the adsorption capacity at any time t in mg g�<sup>1</sup> . Figure 15 shows a plot of linearization form of Elovich model. The slopes and intercepts of plots of qt versus ln t were used to determine the constant β and the initial adsorption rate α.

### 3.4.4 Intra-particle diffusion model

When adsorbate transmits from solution into solid phase of absorbents, pore and intra-particle diffusion are often rate limiting in a batch reactor system. The intraparticle diffusion was explored by using the following equation suggested by Weber and Morris [33]:

$$q\_t = K\_{\text{int}} t^{1/2} + \mathcal{C} \tag{13}$$

where the parameter qt is the amount adsorbed at time t (mg g�<sup>1</sup> ), Kint is the intra-particle diffusion equation constant (mg g�<sup>1</sup> min�1/2), and t is the time. According to the Weber-Morris model, the plot of qt, against t 1/2, should give a straight line, when diffusion plays a role in the sorption rate, and should cross the origin if intra-particle diffusion is the rate-determining step. The intra-particle diffusion parameters can be calculated from the slope and intercept of the linear plot given in Figure 16.

The kinetic parameters obtained by the sorption of heavy metal ions on PAZO nanocomposite are summarized in Table 2. It is found that the correlation coefficients R<sup>2</sup> for the pseudo-second-order kinetic model are 0.99 for 10, 50, and 100 mg L�<sup>1</sup> Cr(VI) concentration at 50°C, respectively, is higher than the correlation coefficient obtained for other models. Also, the qcal values obtained through this model 9.79, 25.46, and 38.44 mg g�<sup>1</sup> are much closer to qexp values 9.31, 25.11, and 37.89 mg g�<sup>1</sup> for 10, 50, and 100 mg L�<sup>1</sup> Cr(VI) solution. The pseudo-secondorder kinetic model assumes that the rate limiting step may be chemical adsorption,

#### Figure 15.

Elovich model for Cr(VI) on PAZO at 10, 50, and 100 mg L�<sup>1</sup> metal ion concentration (dose = 0.04 g and pH = 2).

enthalpy change (ΔH°), and entropy change (ΔS°) were calculated using the Gibbs

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

R þ

ΔS<sup>o</sup>

lnKc ¼ � <sup>Δ</sup>H<sup>o</sup>

tion coefficient; T is the temperature of the solution in Celsius. ΔG° and ΔS° were calculated from the slope and intercept of a plot of ln Kc as a function of 1/T, as shown in Figure 17. The free energy change (ΔG°) can be determined from the

Thermodynamic parameters associated with the Cr(VI) adsorption by the nanocomposite are listed in Table 3. The positive value of ΔH° confirmed the endothermic nature of the adsorption process of Cr(VI) on PAZO. The values of ΔG° are all negative, and the negative value of ΔG° increases as the temperature increase

from 30 to 50°C, which indicates that the Cr(VI) adsorption process of the nanocomposite is spontaneous and spontaneity increases with temperature [34]. The positive value of ΔS° revealed the increased randomness and an increase in the degrees of freedom at the adsorbent-solution interface during the immobilization of the heavy metal ions on the active sites of the adsorbent, which indicate the partial liberation of the salvation metal ions from solvent molecules before adsorption (liberation of water molecules from solvated-heavy metals), therefore, enabling

<sup>Δ</sup>G<sup>o</sup> ¼ �RTlnKc (14)

<sup>Δ</sup>G<sup>o</sup> <sup>¼</sup> <sup>Δ</sup>H<sup>o</sup> � <sup>T</sup>ΔS<sup>o</sup> (16)

RT (15)

. Kc (Cad/Ce) is the distribu-

equation and the Van't Hoff equation, listed as follows:

DOI: http://dx.doi.org/10.5772/intechopen.85868

The gas constant R is defined by 8.3145 J mol�<sup>1</sup> K�<sup>1</sup>

commonness of randomness and spontaneity in the system.

Thermodynamic plot for removal of Cr(VI) on PAZO at 30, 40, and 50°C.

) ΔS° (KJ mol�<sup>1</sup> K�<sup>1</sup>

10 mg L�<sup>1</sup> 1.66 0.014 �2.75 �2.89 �3.04 50 mg L�<sup>1</sup> 3.74 0.021 �2.91 �3.13 �3.35 100 mg L�<sup>1</sup> 3.74 0.023 �3.26 �3.50 �3.73

) ΔG° (KJ mol�<sup>1</sup>

)

30°C 40°C 50°C

Concentration ΔH° (KJ mol�<sup>1</sup>

Thermodynamic parameters for Cr(VI) removal by PAZO.

following equation:

Figure 17.

Table 3.

41

#### Figure 16.

Intra-particle diffusion model for Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> metal ion concentration (dose = 0.04 g and pH = 2).


#### Table 2.

Kinetic parameters for Cr(VI) removal by PAZO at 50°C.

and the adsorption behavior of PAZO may involve valence forces through sharing of electrons between transition metal cations and the PAZO. Because of the fact that diffusion and adsorption are often experimentally inseparable, the uptake of metal ions onto nanocomposite may be a complicate process including diffusion, coordinating bond formation or chemical reaction simultaneously. However, from the results obtained, it can be observed that good fits to the experimental data are obtained with pseudo-second-order model for the metal ion at all concentration ranges at 50°C.

#### 3.5 Adsorption thermodynamics

To substantiate our prediction about the endothermic nature of the adsorption process, thermodynamic parameters such as Gibbs free energy change (ΔG°),

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

enthalpy change (ΔH°), and entropy change (ΔS°) were calculated using the Gibbs equation and the Van't Hoff equation, listed as follows:

$$
\Delta G^{\circ} = -RT\ln K\_{\circ} \tag{14}
$$

$$
\ln Kc = -\frac{\Delta H^{\circ}}{R} + \frac{\Delta S^{\circ}}{RT} \tag{15}
$$

The gas constant R is defined by 8.3145 J mol�<sup>1</sup> K�<sup>1</sup> . Kc (Cad/Ce) is the distribution coefficient; T is the temperature of the solution in Celsius. ΔG° and ΔS° were calculated from the slope and intercept of a plot of ln Kc as a function of 1/T, as shown in Figure 17. The free energy change (ΔG°) can be determined from the following equation:

$$
\Delta G^{\circ} = \Delta H^{\circ} - T\Delta \text{S}^{\circ} \tag{16}
$$

Thermodynamic parameters associated with the Cr(VI) adsorption by the nanocomposite are listed in Table 3. The positive value of ΔH° confirmed the endothermic nature of the adsorption process of Cr(VI) on PAZO. The values of ΔG° are all negative, and the negative value of ΔG° increases as the temperature increase from 30 to 50°C, which indicates that the Cr(VI) adsorption process of the nanocomposite is spontaneous and spontaneity increases with temperature [34]. The positive value of ΔS° revealed the increased randomness and an increase in the degrees of freedom at the adsorbent-solution interface during the immobilization of the heavy metal ions on the active sites of the adsorbent, which indicate the partial liberation of the salvation metal ions from solvent molecules before adsorption (liberation of water molecules from solvated-heavy metals), therefore, enabling commonness of randomness and spontaneity in the system.

Figure 17. Thermodynamic plot for removal of Cr(VI) on PAZO at 30, 40, and 50°C.


Table 3. Thermodynamic parameters for Cr(VI) removal by PAZO.

and the adsorption behavior of PAZO may involve valence forces through sharing of electrons between transition metal cations and the PAZO. Because of the fact that diffusion and adsorption are often experimentally inseparable, the uptake of metal ions onto nanocomposite may be a complicate process including diffusion, coordinating bond formation or chemical reaction simultaneously. However, from the results obtained, it can be observed that good fits to the experimental data are obtained with pseudo-second-order model for the metal ion at all concentration

Intra-particle diffusion model for Cr(VI) on PAZO at 10, 50, and 100 mg L<sup>1</sup> metal ion concentration

30°C 40°C 50°C

) 9.31 25.11 37.89

) 5.88 6.57 8.77

) 9.31 25.11 37.89

) 9.79 25.46 38.44

) 3.59 3.88 7.57

) 0.65 0.61 0.48 R<sup>2</sup> 0.90 0.89 0.93

min 1/2) 0.32 0.35 0.45

) 4.75 20.21 31.30 R<sup>2</sup> 0.69 0.70 0.79

R<sup>2</sup> 0.99 0.99 0.99

) 2.19 <sup>10</sup><sup>3</sup> 2.17 <sup>10</sup><sup>3</sup> 2.18 <sup>10</sup><sup>3</sup>

) 0.02 0.02 0.02 R<sup>2</sup> 0.97 0.98 0.97

Model Parameters Cr(VI)

qe (cal) (mg g<sup>1</sup>

k1 (min<sup>1</sup>

qe (cal) (mg g<sup>1</sup>

k2 (g mg<sup>1</sup> min<sup>1</sup>

β (g mg<sup>1</sup>

C (mg g<sup>1</sup>

To substantiate our prediction about the endothermic nature of the adsorption process, thermodynamic parameters such as Gibbs free energy change (ΔG°),

ranges at 50°C.

40

Table 2.

Figure 16.

(dose = 0.04 g and pH = 2).

Pseudo-first-order qe (exp) (mg g<sup>1</sup>

Advances in Composite Materials Development

Pseudo-second-order qe (exp) (mg g<sup>1</sup>

Elovich α (mg g<sup>1</sup> min<sup>1</sup>

Kinetic parameters for Cr(VI) removal by PAZO at 50°C.

Intra-particle Kint (mg g<sup>1</sup>

3.5 Adsorption thermodynamics

## 4. Conclusion

In this chapter, polyaniline/zinc oxide nanocomposite was synthesized by oxidative free radical polymerization of aniline monomer in presence of zinc oxide nanoparticles. The material was characterized by various analytical techniques, such as FT-IR, XTD, TGA-DTG, SEM, and TEM. The nanocomposite material was further explored for the removal of Cr(VI) from aqueous solution. The effect of various adsorption parameters such as agitation time, solution pH, adsorbent dose, initial metal ion concentration, and temperature was observed and optimized by preliminary experiments. The adsorption of metal ions is highly pH-dependent and the maximum removal efficiencies and adsorption capacities of the selected metal ions were obtained at pH 2. The experimental data were tested using Langmuir, Freundlich, D-R and Temkin models and the data were best followed by Langmuir model. The maximum monolayer adsorption capacity was found to be 120.92 mg g<sup>1</sup> at 30°C, 134.22 mg g<sup>1</sup> at 40°C, and 139.47 mg g<sup>1</sup> at 50°C. All kinetic parameters suggest that the adsorption of metal ion by PAZO followed the second-order kinetics and chemisorption is the rate-determining step. The positive values of ΔH° and negative value of ΔG° indicate the adsorption process to be endothermic and spontaneous in nature.

BT Temkin constant related to heat of adsorption (J mol<sup>1</sup>

)

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

)

)

)

Environmental Research Laboratory, Department of Applied Chemistry, Aligarh

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

β constant related to the adsorption energy (mol<sup>2</sup> kJ<sup>2</sup>

E mean free energy of adsorption (kJ mol<sup>1</sup>

ΔG free energy change (kJ mol<sup>1</sup>

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ΔS entropy change (kJ mol<sup>1</sup> K<sup>1</sup>

R universal gas constant (J mol<sup>1</sup> K<sup>1</sup>

ΔH enthalpy change (kJ mol<sup>1</sup>

T absolute temperature (K)

V volume of solution (liter)

ε Polanyi potential

t time (min)

°C degree celsius

mg g<sup>1</sup> milligram per gram

mg L<sup>1</sup> milligram per liter μg L<sup>1</sup> microgram per liter

rpm revolutions per minute

Muslim University, Aligarh, India

provided the original work is properly cited.

\*Address all correspondence to: rais45@rediffmail.com

μg microgram Å angstrom nm nanometer

Author details

Rais Ahmad

43

K kelvin cm centimeter g gram mg milligram

L liter ml milliliter

M molar N normality h hours min minute J joule kJ kilo joule mol mole

Units

)

)

)

## Nomenclature


Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868


## Units

4. Conclusion

Advances in Composite Materials Development

spontaneous in nature.

(mg L<sup>1</sup> )

XRD X-ray diffraction

m amount of adsorbent (g) DDW double distilled water

SEM scanning electron microscopy EDX energy dispersive X-ray analysis TEM transmission electron microscopy

TGA thermogravimetric analysis

A and B Elovich constants (mg g<sup>1</sup>

Kc equilibrium constant

42

Nomenclature

In this chapter, polyaniline/zinc oxide nanocomposite was synthesized by oxidative free radical polymerization of aniline monomer in presence of zinc oxide nanoparticles. The material was characterized by various analytical techniques, such as FT-IR, XTD, TGA-DTG, SEM, and TEM. The nanocomposite material was further explored for the removal of Cr(VI) from aqueous solution. The effect of various adsorption parameters such as agitation time, solution pH, adsorbent dose, initial metal ion concentration, and temperature was observed and optimized by preliminary experiments. The adsorption of metal ions is highly pH-dependent and the maximum removal efficiencies and adsorption capacities of the selected metal ions were obtained at pH 2. The experimental data were tested using Langmuir, Freundlich, D-R and Temkin models and the data were best followed by Langmuir model. The maximum monolayer adsorption capacity was found to be 120.92 mg g<sup>1</sup> at 30°C, 134.22 mg g<sup>1</sup> at 40°C, and 139.47 mg g<sup>1</sup> at 50°C. All kinetic parameters suggest that the adsorption of metal ion by PAZO followed the second-order kinetics and chemisorption is the rate-determining step. The positive values of ΔH° and negative value of ΔG° indicate the adsorption process to be endothermic and

Ce equilibrium adsorbate concentration in the solution (mg L<sup>1</sup>

Cab equilibrium concentration of adsorbate on the adsorbent surface

qe amount of adsorbate adsorbed per unit mass of adsorbent at equilib-

)

)

)(L mg<sup>1</sup>

)

) 1/n

)

C0 initial adsorbate concentration in the solution (mg L<sup>1</sup>

qe(exp) adsorption capacity determined experimentally (mgg<sup>1</sup>

qe(cal) adsorption capacity calculated from model (mg g<sup>1</sup>

k<sup>2</sup> pseudo-second-order rate constant (g mg<sup>1</sup> min<sup>1</sup>

kid intra-particle diffusion rate constant (mg g<sup>1</sup> min1/2) C intra-particle constant related to thickness of boundary layer

b Langmuir constant for energy of adsorption (L mg<sup>1</sup>

)

qm theoretical maximum monolayer adsorption capacity (mg g<sup>1</sup>

rium or adsorption capacity (mg g<sup>1</sup>

AAS atomic absorption spectrophotometer FTIR Fourier-transform infrared spectroscopy

k<sup>1</sup> pseudo-first-order rate constant (min<sup>1</sup>

qt adsorption capacity at time t (mg g<sup>1</sup>

KF Freundlich isotherm constant (mg g<sup>1</sup>

n Freundlich exponent, dimensionless factor KT Equilibrium binding constant (L mg<sup>1</sup>

)

)

)

)

)

)

)


## Author details

Rais Ahmad Environmental Research Laboratory, Department of Applied Chemistry, Aligarh Muslim University, Aligarh, India

\*Address all correspondence to: rais45@rediffmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## References

[1] Li H, Li J, Chi Z, Ke W. Kinetic and equilibrium studies of Cr (III) removal from aqueous solution by IRN-77 cationexchange resin. Procedia Environmental Sciences. 2012;16:646-655

[2] Chen S, Yue Q, Gao B, Xu X. Equilibrium and kinetic adsorption study of the adsorptive removal of Cr (VI) using modified wheat residue. Journal of Colloid and Interface Science. 2010;349:256-264

[3] Jain M, Garg VK, Kadirvelu K. Adsorption of hexavalent chromium from aqueous medium onto carbonaceous adsorbents prepared from waste biomass. Journal of Environmental Management. 2010;91: 949-957

[4] Kocaoba S, Akcin G. Removal and recovery of chromium and chromium speciation with MINTEQA2. Talanta. 2002;57:23-30

[5] Pang Y, Zeng G, Tanga L, Zhang Y, Liu Y, Lei X, et al. Preparation and application of stability enhanced magnetic nanoparticles for rapid removal of Cr (VI). Chemical Engineering Journal. 2011;175:222-227

[6] AL-Othman ZA, Ali R, Naushad M. Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: Adsorption kinetics, equilibrium and thermodynamic studies. Chemical Engineering Journal. 2012;184:238-247

[7] AL-Othman ZA, Ali R, Naushad M. Kinetic, equilibrium isotherm and thermodynamic studies of Cr (VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid. Environmental Science and Pollution Research. 2013; 20:3351-3365

[8] Shin K, Hong J, Jang J. Heavy metal ion adsorption behaviour in nitrogendoped magnetic carbon nanoparticles: Isotherms and kinetic study. Journal of Hazardous Materials. 2011;190:36-44

A novel adsorbent for the removal of amido black 10B. Journal of Chemical & Engineering Data. 2010;55:3489-3493

DOI: http://dx.doi.org/10.5772/intechopen.85868

comparison study of adsorption of Cr (VI) from aqueous solutions onto alkyl-

[24] Ajouyed O, Hurel C, Ammari M, Allal LB, Marmier N. Sorption of Cr (VI) onto natural iron and aluminum (oxy) hydroxides: Effects of pH, ionic strength and initial concentration. Journal of Hazardous Materials. 2010;

[25] Monier M, Ayad DM, Sarhan AA. Adsorption of Cu (II), Hg (II), and Ni (II) ions by modified natural wool chelating fibers. Journal of Hazardous

[26] Langmuir I. Adsorption of gaseous on plane surface of glass, mica and platinum. Journal of the American Chemical Society. 1918;40:1361-1403

[28] Dubinin MM. The potential theory of adsorption of gases and vapours for adsorbents with energetically nonuniform surface. Chemical Reviews.

[29] Temkin MJ, Pyzhev V. Kinetics of ammonia synthesis on promoted iron catalysts. Acta Physicochimica. 1940;12:

[30] Lagergren S. About the theory of socalled adsorption of soluble substances.

[31] Ho YS. Review of second-order models for adsorption systems. Journal of Hazardous Materials. 2006;136:

[32] El-Ashtoukhya E-SZ, Amina NK, Abdelwahab O. Removal of lead (II) and copper (II) from aqueous solution using

Materials. 2010;176:348-355

[27] Freundlich HMF. Over the adsorption in solution. Zeitschrift für Physikalische Chemie. 1906;57:385-470

1960;60:235-266

The Hand. 1898;24:1-39

217-222

681-689

substituted polyaniline/chitosan composites. Desalination. 2011;279:

325-331

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous…

174:616-622

[16] Kanwal F, Rehman R, Anwar J, Saeed M. Batchwise removal of

1134-1139

239-244

chromium (VI) by adsorption on novel synthesized polyaniline composites with various brans and isothermal modelling of equilibrium data. Journal of the Chemical Society of Pakistan. 2012;34:

[17] Zhu J, He H, Zhu L, Wen X, Deng F. Characterization of organic phases in them interlayer of montmorillonite using FTIR and 13C NMR. Journal of Colloid and Interface Science. 2005;286:

[18] Khan TA, Nazir M, Ali I, Kumar A. Removal of chromium(VI) from aqueous solution using guar gum-nano zinc oxide biocomposite adsorbent. Arabian Journal of Chemistry. 2013

[19] Vigneshwaran N, Kumar S, Kathe AA, Varadarajan PV, Prasad V. Functional finishing of cotton fabrics using zinc oxide-soluble starch nanocomposites. Nanotechnology.

characterization of new biocompatible copolymer: Chitosan-graft polyaniline. International Nano Letters. 2014;4:1-6

[21] Shi L, Wang X, Lu L, Yang X, Wu X.

[22] Sharma AL, Saxena V, Annopoorni

2006;17:5087-5095

2009;159:2525-2529

1460-1466

45

[20] Sedaghat S. Synthesis and

Preparation of TiO2/polyaniline nanocomposite from a lyotropic liquid crystalline solution. Synthetic Metals.

S, Malhotra BD. Synthesis and characterization of a copolymer: Poly (aniline-co-fluoroaniline). Journal of Applied Polymer Science. 2001;81:

[23] Yavuz AG, Dincturk-Atalay E, Uygun A, Gode F, Aslan E. A

[9] Noreen S, Bhatti HN, Nausheen S, Sadaf S, Ashfaq M. Batch and fixed bed adsorption study for the removal of Drimarine Black CL-B dye from aqueous solution using a lignocellulosic waste: A cost effective adsorbent. Industrial Crops and Products. 2013;50: 568-579

[10] Noreen S, Bhatti HN, Nausheen S, Zahid M, Asim S. Biosorption of Drimarine Blue HF-RL using raw, pretreated and immobilized peanut hulls. Desalination and Water Treatment. 2014;52:7339-7353

[11] Tofighy MA, Mohammadi T. Adsorption of divalent heavy metal ions from water using carbon nanotube sheets. Journal of Hazardous Materials. 2011;185:140-147

[12] Gupta VK, Jain R, Saleh TA, Nayak A, Malathi S, Agarwal S. Equilibrium and thermodynamic studies on the removal and recovery of Safranine-T dye from industrial effluents. Separation Science and Technology. 2011;46: 839-846

[13] Shahat A, Awual MR, Khaleque MA, Alam MZ, Naushad M, Chowdhury AMS. Large-pore diameter nanoadsorbent and its application for rapid lead (II) detection and removal from aqueous media. Chemical Engineering Journal. 2015;273:286-295

[14] Nausheen S, Bhatti HN, Furrukh Z, Sadaf S, Noreen S. Adsorptive removal of Drimarine Red HF-3D dye from aqueous solution using low-cost agricultural waste: Batch and column study. Chemistry and Ecology. 2015;30: 376-392

[15] Ahmad R, Kumar R. Conducting polyaniline/iron oxide composite:

Polyaniline/ZnO Nanocomposite: A Novel Adsorbent for the Removal of Cr(VI) from Aqueous… DOI: http://dx.doi.org/10.5772/intechopen.85868

A novel adsorbent for the removal of amido black 10B. Journal of Chemical & Engineering Data. 2010;55:3489-3493

References

[1] Li H, Li J, Chi Z, Ke W. Kinetic and equilibrium studies of Cr (III) removal from aqueous solution by IRN-77 cationexchange resin. Procedia Environmental

Advances in Composite Materials Development

doped magnetic carbon nanoparticles: Isotherms and kinetic study. Journal of Hazardous Materials. 2011;190:36-44

[9] Noreen S, Bhatti HN, Nausheen S, Sadaf S, Ashfaq M. Batch and fixed bed adsorption study for the removal of Drimarine Black CL-B dye from aqueous solution using a lignocellulosic waste: A cost effective adsorbent. Industrial Crops and Products. 2013;50:

[10] Noreen S, Bhatti HN, Nausheen S, Zahid M, Asim S. Biosorption of Drimarine Blue HF-RL using raw, pretreated and immobilized peanut hulls. Desalination and Water Treatment. 2014;52:7339-7353

[11] Tofighy MA, Mohammadi T. Adsorption of divalent heavy metal ions from water using carbon nanotube sheets. Journal of Hazardous Materials.

[12] Gupta VK, Jain R, Saleh TA, Nayak A, Malathi S, Agarwal S. Equilibrium and thermodynamic studies on the removal and recovery of Safranine-T dye from industrial effluents. Separation Science and Technology. 2011;46:

[13] Shahat A, Awual MR, Khaleque MA, Alam MZ, Naushad M, Chowdhury AMS. Large-pore diameter nanoadsorbent and its application for rapid lead (II) detection and removal from aqueous media. Chemical Engineering

[14] Nausheen S, Bhatti HN, Furrukh Z, Sadaf S, Noreen S. Adsorptive removal of Drimarine Red HF-3D dye from aqueous solution using low-cost agricultural waste: Batch and column study. Chemistry and Ecology. 2015;30:

[15] Ahmad R, Kumar R. Conducting polyaniline/iron oxide composite:

Journal. 2015;273:286-295

2011;185:140-147

839-846

376-392

568-579

Sciences. 2012;16:646-655

2010;349:256-264

949-957

2002;57:23-30

[2] Chen S, Yue Q, Gao B, Xu X. Equilibrium and kinetic adsorption study of the adsorptive removal of Cr (VI) using modified wheat residue. Journal of Colloid and Interface Science.

[3] Jain M, Garg VK, Kadirvelu K. Adsorption of hexavalent chromium

carbonaceous adsorbents prepared from

Environmental Management. 2010;91:

[4] Kocaoba S, Akcin G. Removal and recovery of chromium and chromium speciation with MINTEQA2. Talanta.

[5] Pang Y, Zeng G, Tanga L, Zhang Y, Liu Y, Lei X, et al. Preparation and application of stability enhanced magnetic nanoparticles for rapid removal of Cr (VI). Chemical

Engineering Journal. 2011;175:222-227

[6] AL-Othman ZA, Ali R, Naushad M. Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: Adsorption

thermodynamic studies. Chemical Engineering Journal. 2012;184:238-247

[7] AL-Othman ZA, Ali R, Naushad M. Kinetic, equilibrium isotherm and thermodynamic studies of Cr (VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid. Environmental Science and Pollution Research. 2013;

[8] Shin K, Hong J, Jang J. Heavy metal ion adsorption behaviour in nitrogen-

kinetics, equilibrium and

20:3351-3365

44

from aqueous medium onto

waste biomass. Journal of

[16] Kanwal F, Rehman R, Anwar J, Saeed M. Batchwise removal of chromium (VI) by adsorption on novel synthesized polyaniline composites with various brans and isothermal modelling of equilibrium data. Journal of the Chemical Society of Pakistan. 2012;34: 1134-1139

[17] Zhu J, He H, Zhu L, Wen X, Deng F. Characterization of organic phases in them interlayer of montmorillonite using FTIR and 13C NMR. Journal of Colloid and Interface Science. 2005;286: 239-244

[18] Khan TA, Nazir M, Ali I, Kumar A. Removal of chromium(VI) from aqueous solution using guar gum-nano zinc oxide biocomposite adsorbent. Arabian Journal of Chemistry. 2013

[19] Vigneshwaran N, Kumar S, Kathe AA, Varadarajan PV, Prasad V. Functional finishing of cotton fabrics using zinc oxide-soluble starch nanocomposites. Nanotechnology. 2006;17:5087-5095

[20] Sedaghat S. Synthesis and characterization of new biocompatible copolymer: Chitosan-graft polyaniline. International Nano Letters. 2014;4:1-6

[21] Shi L, Wang X, Lu L, Yang X, Wu X. Preparation of TiO2/polyaniline nanocomposite from a lyotropic liquid crystalline solution. Synthetic Metals. 2009;159:2525-2529

[22] Sharma AL, Saxena V, Annopoorni S, Malhotra BD. Synthesis and characterization of a copolymer: Poly (aniline-co-fluoroaniline). Journal of Applied Polymer Science. 2001;81: 1460-1466

[23] Yavuz AG, Dincturk-Atalay E, Uygun A, Gode F, Aslan E. A

comparison study of adsorption of Cr (VI) from aqueous solutions onto alkylsubstituted polyaniline/chitosan composites. Desalination. 2011;279: 325-331

[24] Ajouyed O, Hurel C, Ammari M, Allal LB, Marmier N. Sorption of Cr (VI) onto natural iron and aluminum (oxy) hydroxides: Effects of pH, ionic strength and initial concentration. Journal of Hazardous Materials. 2010; 174:616-622

[25] Monier M, Ayad DM, Sarhan AA. Adsorption of Cu (II), Hg (II), and Ni (II) ions by modified natural wool chelating fibers. Journal of Hazardous Materials. 2010;176:348-355

[26] Langmuir I. Adsorption of gaseous on plane surface of glass, mica and platinum. Journal of the American Chemical Society. 1918;40:1361-1403

[27] Freundlich HMF. Over the adsorption in solution. Zeitschrift für Physikalische Chemie. 1906;57:385-470

[28] Dubinin MM. The potential theory of adsorption of gases and vapours for adsorbents with energetically nonuniform surface. Chemical Reviews. 1960;60:235-266

[29] Temkin MJ, Pyzhev V. Kinetics of ammonia synthesis on promoted iron catalysts. Acta Physicochimica. 1940;12: 217-222

[30] Lagergren S. About the theory of socalled adsorption of soluble substances. The Hand. 1898;24:1-39

[31] Ho YS. Review of second-order models for adsorption systems. Journal of Hazardous Materials. 2006;136: 681-689

[32] El-Ashtoukhya E-SZ, Amina NK, Abdelwahab O. Removal of lead (II) and copper (II) from aqueous solution using

pomegranate peel as a new adsorbent. Desalination. 2008;223:162-173

[33] Weber WJ Jr, Morris JC. Kinetics of adsorption on carbon from solution. Journal of the Sanitary Engineering Division: American Society of Civil Engineers. 1963;89:31-59

[34] Ahmet Sari A, Mendil D, Tuzen M, Soylak M. Biosorption of palladium(II) from aqueous solution by moss (Racomitrium lanuginosum) biomass: Equilibrium, kinetic and thermodynamic studies. Journal of Hazardous Materials. 2009;162:874-879

**47**

Section 2

Mechanical and Wear

Behaviour

Section 2
