**2.4 Co, Cu, and Ni adsorption isotherm**

The different isotherm models used to describe the adsorption of Ni, Co, and Cu are concentrated in **Table 1**, for each one of the regression coefficients was

**95**

nDCPD (g).

*The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes*

calculated to evaluate the adjustment of each nonlinear model and the separation factor, *RL*, which allows to predict the affinity between the adsorbent and adsor-

1 + *KLC*<sup>0</sup>

where *KL* is the constant of the Langmuir model and *C0* is the initial concentration of Ni, Co, and Cu ions. To know the thermodynamics of the adsorption process, the free-energy parameters of apparent Gibbs were determined. Δ*G* (kJ/mol), Δ*H* (kJ/mol), and Δ*S* (kJ/mol K), which are directly related to changes in temperature, and help to understand the mechanism of adsorption of metal ions, by using

∆*G* = −*RTln*(k) (2)

*k* = 55.5*KL* (3)

∆*H RT* <sup>+</sup> \_\_\_ ∆*S*

where *KL* is the constant of the Langmuir model (L/mol), *R* is the constant of the ideal gases, and *T* is the absolute temperature (K). The values of Δ*H* and Δ*S* can be determined with the slope and ordered to the origin of the graph ln *k* as a function

For the study of the adsorption isotherms of the different metals in nDCPD, 1 g of sorbent was put in contact with 50 ml of the aqueous solution of the metal ions Co, Cu, and Ni, varying the concentration between 0 and 1000 ppm in a shaker (ZHWY-200D) with an agitation of 200 rpm at 25, 35, and 45°C for 24 h of

The experiments to establish the kinetics of metal ion removal in nDCPD and to know the evolution of the adsorption of Ni, Co, and Cu ions in the biomaterial were carried out in batches. They were carried out varying the concentration of nDCPD (Cads), from 0 to 40 g/L, during 24 h at a speed of 200 rpm and at 25, 35, and 45°C. At specific times aliquots of aqueous solution were taken to separate the adsorbent material and the liquid supernatant by centrifugation at 10,000 rpm. The supernatant was analyzed with the help of a spectrophotometer (JENWAY 6705) to know the concentration of the different ions present in the solution. The amount of

*qe* <sup>=</sup> *<sup>V</sup>*(*C*<sup>0</sup> <sup>−</sup> *<sup>C</sup>*) \_\_\_\_\_\_\_\_ *<sup>m</sup>* (5)

where *C0* and *C* represent the initial concentration and the concentration at time t or in equilibrium (mg/L), *V* is the volume of solution (L), and *m* is the mass of

× 100 (6)

ions removed (*qe*) by nDCPD was obtained by applying Eq. 5 [4]:

The percentage of removal (%*R*) was calculated as Eq. 6 [5]:

%*<sup>R</sup>* <sup>=</sup> (*C*<sup>0</sup> <sup>−</sup> *Ce*) \_\_\_\_\_\_\_ *<sup>C</sup>*<sup>0</sup>

*<sup>R</sup>* (4)

(1)

*DOI: http://dx.doi.org/10.5772/intechopen.86803*

*RL* <sup>=</sup> \_\_\_\_\_\_ <sup>1</sup>

ln(*k*) = −\_\_\_\_

bate, using Eq. 1 [5]:

Eqs. 2, 3, and 4 [27, 36]:

of 1/*T*.

contact time.

**2.5 Batch removal kinetics**

*The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes DOI: http://dx.doi.org/10.5772/intechopen.86803*

calculated to evaluate the adjustment of each nonlinear model and the separation factor, *RL*, which allows to predict the affinity between the adsorbent and adsorbate, using Eq. 1 [5]:

$$R\_L = \frac{1}{1 + K\_L C\_0} \tag{1}$$

where *KL* is the constant of the Langmuir model and *C0* is the initial concentration of Ni, Co, and Cu ions. To know the thermodynamics of the adsorption process, the free-energy parameters of apparent Gibbs were determined. Δ*G* (kJ/mol), Δ*H* (kJ/mol), and Δ*S* (kJ/mol K), which are directly related to changes in temperature, and help to understand the mechanism of adsorption of metal ions, by using Eqs. 2, 3, and 4 [27, 36]:

$$
\Delta G = -RTln\,\text{(k)}\tag{2}
$$

$$k = \texttt{55.5}K\_{L} \tag{3}$$

$$
\ln \text{(\&)} = -\frac{\Delta H}{RT} + \frac{\Delta S}{R} \tag{4}
$$

where *KL* is the constant of the Langmuir model (L/mol), *R* is the constant of the ideal gases, and *T* is the absolute temperature (K). The values of Δ*H* and Δ*S* can be determined with the slope and ordered to the origin of the graph ln *k* as a function of 1/*T*.

For the study of the adsorption isotherms of the different metals in nDCPD, 1 g of sorbent was put in contact with 50 ml of the aqueous solution of the metal ions Co, Cu, and Ni, varying the concentration between 0 and 1000 ppm in a shaker (ZHWY-200D) with an agitation of 200 rpm at 25, 35, and 45°C for 24 h of contact time.

#### **2.5 Batch removal kinetics**

The experiments to establish the kinetics of metal ion removal in nDCPD and to know the evolution of the adsorption of Ni, Co, and Cu ions in the biomaterial were carried out in batches. They were carried out varying the concentration of nDCPD (Cads), from 0 to 40 g/L, during 24 h at a speed of 200 rpm and at 25, 35, and 45°C. At specific times aliquots of aqueous solution were taken to separate the adsorbent material and the liquid supernatant by centrifugation at 10,000 rpm. The supernatant was analyzed with the help of a spectrophotometer (JENWAY 6705) to know the concentration of the different ions present in the solution. The amount of ions removed (*qe*) by nDCPD was obtained by applying Eq. 5 [4]:

$$q\_e = \frac{V(C\_0 - C)}{m} \tag{5}$$

where *C0* and *C* represent the initial concentration and the concentration at time t or in equilibrium (mg/L), *V* is the volume of solution (L), and *m* is the mass of nDCPD (g).

The percentage of removal (%*R*) was calculated as Eq. 6 [5]:

 %*<sup>R</sup>* <sup>=</sup> (*C*<sup>0</sup> <sup>−</sup> *Ce*) \_\_\_\_\_\_\_ *<sup>C</sup>*<sup>0</sup> × 100 (6)

*Water Chemistry*

**2. Experimental**

**2.2 Preparation of the adsorbent**

**2.3 Characterization of natural brushite**

**2.4 Co, Cu, and Ni adsorption isotherm**

**2.1 Reagents**

been one of the most used metal ion removal techniques, since it is a simple, effective, and inexpensive process compared to other methods [13–17]. Adsorption processes have been experimented with an extensive amount of materials such as adsorbents, among which activated carbon stands out due to its high capacity for capturing metal ions; however, this material has the disadvantage of generating large quantities of sludge, since the removal of metals trapped in activated carbon can only be done with processes that are often expensive such as leaching [5, 9, 18, 19]. For this reason, the use of different materials that are economical, are easy to obtain, and have high efficiency in the removal of metal ions has been investigated. In recent decades, these studies have focused on the waste derived from the agricultural industry that produces large amounts of waste such as biomass, wheat husks, rice, orange, etc. [2, 4, 8, 9, 16, 18–30]; the use of residues from other industries has also been investigated, such as the case of apatites derived from the bone tissue of animals, which have been used for removal of dyes and metal ions obtaining promising results. The use of apatites in particular hydroxyapatite and brushite for the adsorption of heavy metals such as Cd, Cu, Ni, Pb, Co, Mn, and Fe, to name a few, has already been reported [31–35]; however, in most of the studies carried out, only the process of adsorption of metallic solutions of a single component has been analyzed, so the objective of the present work is to evaluate the capacity of brushite (nDCPD), obtained from bovine bone to remove Ni (II), Co (II), and Cu (II) of aqueous solutions, analyzing the selectivity of removal of metal ions in aqueous solutions with two or three different metals, determining the kinetic models and in equilibrium in which the removal of metals takes place and the structural changes suffered by nDCPD during the development of the different tests.

All the reagents that were used were of analytical grade. The water used for the preparation of solutions in the experiment was deionized. The solutions to be evaluated were prepared by dissolution of salts of nickel (Ni(NO3)2 6H2O), cobalt (Co(NO3)2⋅6H2O), and copper (Cu(NO3)2) in concentrations from 0 to 1,000 ppm.

Brushite natural (nDCPD) was obtained from bovine bone, which was washed with hot water several times to remove tissue debris, and then it was dried at 353 K for 24 h. Next, the bones were crushed and sieved to obtain a particle size of 150 mesh (104 μm).

The X-ray diffraction patterns (XRD) were obtained in a Rigaku diffractometer (Ultima IV). The Fourier transform infrared studies of the samples were performed in an IR 100 Analyzer spectrophotometer (PerkinElmer), in a range of

The different isotherm models used to describe the adsorption of Ni, Co, and Cu are concentrated in **Table 1**, for each one of the regression coefficients was

. The scanning electron microscopy (SEM) images were obtained in

M, respec-

Then, the powder obtained was treated with HCl and NaOH solution, 10<sup>−</sup><sup>2</sup>

tively, using a ratio of 30% w/v. Finally nDCPD was stored until its use [1].

**94**

400–4000 cm<sup>−</sup><sup>1</sup>

a JOEL equipment (6510-Plus).


*SIPS: KS (L/mg), qm (mg/g), nS (dimensionless); Redlich-Peterson: KR (L/g), aR (L/mg)<sup>β</sup> , β (dimensionless); Langmuir: KL (L/mg), qm (mg/g), RL (dimensionless); Freundlich: KF [(mg/g)(L/mg)]1/n, n (dimensionless); Temkin: A (L/mg), B (kJ/mol).*

#### **Table 1.**

*Nonlinear adsorption isotherm models [40, 41].*
