**1. Introduction**

Increased use of metals and chemicals in process industries has led to the production of large volumes of effluent containing high levels of toxic heavy metals and their presence, due to their non-degradable and persistent existence, poses problems with disposal. World Health Organization (WHO)-based aluminum, cobalt, chromium, iron, cadmium, nickel, zinc, copper, lead and mercury are the most toxic metals [1–3].

Leather tanning, mining, electroplating, textile dyeing, coating operations, aluminum conversion, and pigments are the main industries that introduce water contamination by chromium. Owing to the decreasing availability of natural resources and the rising contamination in the atmosphere, the removal of ions from their effluents has taken on greater significance in the recent past [4–6]. For environmental purposes, the removal of copper (Cu) from aqueous solutions requires an effective method (toxic ions if they are beyond the WHO limits). The minimization of liquid effluents containing hazardous metals is a general concern. The solvent extraction process is a conventional method to eliminate Cu from solutions. A well-established Cu extract, such as diketones or hydroxytoxic agents [7], should be used in this technique. Both are LIX acid (Cognis) and phosphoric acid (D2EHPA) di- (2-ethylhexyl) [8–11].

Liquid surfactant membrane (LSM) for the isolation of solvents, such as phenols, biochemical products and metal pollutants [2, 12–19], has been considered as an alternative to solvent extraction. LSM is a form of triple dispersion, where a primary emulsion (water/oil or oil/water) is dispersed to be processed in the feed process (E). The liquid membrane consists of three phases: I internal, ii) external and iii) organic. The organic phase includes a diluent, an emulsifier to stabilize the emulsion and, in the case of metal ion separation [10], an extractant. The solution is transferred through the membrane through the stripping phase droplets during the mixing between the feed phase (E) and the emulsion (organic + internal) and is concentrated [20]. After extraction, the emulsion is isolated from the raffinate process and the emulsion is typically demulsified by high voltage or heat application. There are several advantages to LSM, such as single-stage re-extraction, large specific surface area for extraction, concurrent extraction and the need for an expensive extractant in small quantities [10, 21, 22].

The aim of this research was to investigate the potential of a liquid surfactant membrane (LSM) to extract copper ions from the feed solution. Despite studies in this area, the study examined different experimental parameters, such as extractant concentration, ratio of treatment, rate of agitation, and initial feed concentration, to determine the best conditions that would give the LSM the greatest efficiency.

#### **2. Experimental protocols**

#### **2.1 Reagents**

The phosphoric acid di-(2-ethylhexyl) (D2EHPA) worked as a shuttle and the nonionic emulsifier was Sorbitan monooleate (Span 80 C24H44O6), both of which were supplied by Sigma-Aldrich (Merck, Darmstadt, Germany). The Southern Oil Company (SOC) (Al Basra-Iraq) supplied kerosene used as a diluent, while the removing agent was sulfuric acid (H2SO4) and was purchased from the acid and base factory (Babylon, Iraq). Copper solutions were prepared from nitrate of copper (Chemical, Company, Co., Ltd. Korea).

#### **2.2 Procedure**

The experimental work consists of four parts: emulsion preparation as a first step, stock solution preparation, extraction process execution, and emulsion demulsification. In this article, **Figure 1** shows the LSM process.

#### *2.2.1 Emulsion preparation*

Mixing those volumes of kerosene, Span80, and D2EHPA using SR30 digital Homogenizer, (model: 670/340 W, 10-2000 ml, 3000–27,000 rpm) at a speed of 17,500 rpm to reach the oil process. The sulfuric acid (H2SO4) solution was applied dropwise to the oil process as a stripping agent until the necessary volume ratio was obtained from the oil solution to the stripping solution. To achieve a stable Water/ Oil LSM, the solution was continuously stirred for 10 minutes.

**137**

*2.2.2 Feed phase preparation*

*2.2.3 Extraction*

**Figure 1.**

and then adding some drops of sulfuric acid to pH 4.

*Removal of Copper Ions from Aqueous Solution Using Liquid Surfactant Membrane Technique*

This stage was prepared to obtain the necessary concentrations (200 ppm) of copper by adding distilled water (conductivity, 1 μs/m) to Cu (NO3)2 (solid form)

*LSM technique: (1) droplets, (2) organic phase, (3) globules, (4) emulsifier, (5) internal phase and Cu.*

At a temperature of 25 ± 1°C, all experiments were performed. The prepared emulsion (2.2.1) has been added to a specific feed solution volume. The production of double emulsions of water / oil/water was obtained by stirring the contents with a digital stirrer (12,700 rpm) for 12 minutes. The external solution (E) was drawn from the syringe and filter syringe and then analyzed by AAS (atomic absorption spectrophotometry). The resulting solution was allowed to be separated by gravity into an emulsion (water/oil) and an external solution (E) in a 24-hour separation funnel. The external phase was drawn after two-phase separation and the concentration of Cu was analyzed using AAS (Atomic Absorption Spectrophotometer) in the internal phase. The Cu(II) ions remain in membrane process can be determined by mass balance. The extractant concentration, initial Cu concentration, treatment

*DOI: http://dx.doi.org/10.5772/intechopen.95093*

*Removal of Copper Ions from Aqueous Solution Using Liquid Surfactant Membrane Technique DOI: http://dx.doi.org/10.5772/intechopen.95093*

**Figure 1.** *LSM technique: (1) droplets, (2) organic phase, (3) globules, (4) emulsifier, (5) internal phase and Cu.*

### *2.2.2 Feed phase preparation*

This stage was prepared to obtain the necessary concentrations (200 ppm) of copper by adding distilled water (conductivity, 1 μs/m) to Cu (NO3)2 (solid form) and then adding some drops of sulfuric acid to pH 4.

#### *2.2.3 Extraction*

*Colloids - Types, Preparation and Applications*

(D2EHPA) di- (2-ethylhexyl) [8–11].

expensive extractant in small quantities [10, 21, 22].

The solvent extraction process is a conventional method to eliminate Cu from solutions. A well-established Cu extract, such as diketones or hydroxytoxic agents [7], should be used in this technique. Both are LIX acid (Cognis) and phosphoric acid

Liquid surfactant membrane (LSM) for the isolation of solvents, such as phenols, biochemical products and metal pollutants [2, 12–19], has been considered as an alternative to solvent extraction. LSM is a form of triple dispersion, where a primary emulsion (water/oil or oil/water) is dispersed to be processed in the feed process (E). The liquid membrane consists of three phases: I internal, ii) external and iii) organic. The organic phase includes a diluent, an emulsifier to stabilize the emulsion and, in the case of metal ion separation [10], an extractant. The solution is transferred through the membrane through the stripping phase droplets during the mixing between the feed phase (E) and the emulsion (organic + internal) and is concentrated [20]. After extraction, the emulsion is isolated from the raffinate process and the emulsion is typically demulsified by high voltage or heat application. There are several advantages to LSM, such as single-stage re-extraction, large specific surface area for extraction, concurrent extraction and the need for an

The aim of this research was to investigate the potential of a liquid surfactant membrane (LSM) to extract copper ions from the feed solution. Despite studies in this area, the study examined different experimental parameters, such as extractant concentration, ratio of treatment, rate of agitation, and initial feed concentration, to determine the best conditions that would give the LSM the greatest

The phosphoric acid di-(2-ethylhexyl) (D2EHPA) worked as a shuttle and the nonionic emulsifier was Sorbitan monooleate (Span 80 C24H44O6), both of which were supplied by Sigma-Aldrich (Merck, Darmstadt, Germany). The Southern Oil Company (SOC) (Al Basra-Iraq) supplied kerosene used as a diluent, while the removing agent was sulfuric acid (H2SO4) and was purchased from the acid and base factory (Babylon, Iraq). Copper solutions were prepared from nitrate of cop-

The experimental work consists of four parts: emulsion preparation as a first step, stock solution preparation, extraction process execution, and emulsion

Mixing those volumes of kerosene, Span80, and D2EHPA using SR30 digital Homogenizer, (model: 670/340 W, 10-2000 ml, 3000–27,000 rpm) at a speed of 17,500 rpm to reach the oil process. The sulfuric acid (H2SO4) solution was applied dropwise to the oil process as a stripping agent until the necessary volume ratio was obtained from the oil solution to the stripping solution. To achieve a stable Water/

demulsification. In this article, **Figure 1** shows the LSM process.

Oil LSM, the solution was continuously stirred for 10 minutes.

**136**

efficiency.

**2.1 Reagents**

**2.2 Procedure**

*2.2.1 Emulsion preparation*

**2. Experimental protocols**

per (Chemical, Company, Co., Ltd. Korea).

At a temperature of 25 ± 1°C, all experiments were performed. The prepared emulsion (2.2.1) has been added to a specific feed solution volume. The production of double emulsions of water / oil/water was obtained by stirring the contents with a digital stirrer (12,700 rpm) for 12 minutes. The external solution (E) was drawn from the syringe and filter syringe and then analyzed by AAS (atomic absorption spectrophotometry). The resulting solution was allowed to be separated by gravity into an emulsion (water/oil) and an external solution (E) in a 24-hour separation funnel. The external phase was drawn after two-phase separation and the concentration of Cu was analyzed using AAS (Atomic Absorption Spectrophotometer) in the internal phase. The Cu(II) ions remain in membrane process can be determined by mass balance. The extractant concentration, initial Cu concentration, treatment

ratio (TR) and stirring speed were varied to observe their effects on Cu extraction in order to understand the important variables relating to the extraction of Cu.

#### *2.2.4 Demulsification of the emulsion*

After the extraction experiment, the loaded emulsion was broken into the internal Cu concentrated phase and the organic phase by means of a hot plate magnetic stirrer (70° C for 43 minute). The internal phase (I) was analyzed and the Cu concentration determined after that.

#### **2.3 Extraction mechanism in the ELM system**

The prepared emulsion (Section 2.2.1) containing a certain concentration of copper ions at pH 4 (adding some drops of 0.2 M H2SO4) was transferred to the external process. For 0–12 minutes, a robotic mixer was used to stir the solution. Eqs. 1 and 2 elucidate the extraction and stripping reactions of the copper ions.

Here, RH refers to an extractant's protonated form (D2EHPA in this paper) [23]. **Figure 2** [24, 25] reveals the D2EHPA structure.

Extraction reaction of the copper ions:

$$\text{Ca}^{\ast 2}\text{}\_{\text{(S)}} + 2\text{(RH)}\_{\text{(L)}} \rightarrow \text{PbR}\_2\text{(RH)}\_2 + 2\text{H}^+\tag{1}$$

Stripping reaction of the copper ions:

$$\text{CuR}\_2\text{(RH)}\_2 + 2H^+ \rightarrow \text{Cu}^{\ast 2}\_{\text{(S)}} + 2\text{(RH)}\_{\text{2(L)}}\tag{2}$$

At the membrane (O)-external (E) interface, Eq. (1) denotes the reaction, whereas Eq. (2) shows the reaction where the copper ions are stripped at the oil (O)-internal (W) interface. **Figure 3** describes the movement of Cu (II) ions by an extractant from the external phase to the internal phase. Based on the Eq. (3), the extraction percentage (E percent) is found:

$$\mathbf{E}\mathfrak{W}\mathbf{\tilde{o}} = \frac{\mathbf{C\_{in}} - \mathbf{C\_{out}}}{\mathbf{C\_{in}}} \times \mathbf{100}\mathfrak{W}\mathfrak{W} \tag{3}$$

**139**

**Figure 4.**

*Removal of Copper Ions from Aqueous Solution Using Liquid Surfactant Membrane Technique*

**3.1 Effect of changes in carrier concentration on copper removal efficiency**

*Effect of D2EHPA concentration on the Cu extraction at optimal conditions using LSM. (O/I = 1/1, span 80 = 4 v/v%, H2SO4 = 0.5 M, feed concentration*≈ *200 mg/L, pH = 4, TR = 1:10, mixing speed = 250 rpm).*

As expected, this paragraph presented in **Figure 4**, as soon as the mixing began, the extraction efficiency increased in the first 0.5 minutes due to the efficacy of the carrier in carrying the copper ions and the increase of the shuttle D2EHPA concentration from 6–8% (v / v) provides only a 2% increase in the quantity extracted using LSM. At 10% D2EHPA, the E percentage decreased significantly. It should be noted that the D2EHPA concentration in the membrane process was observed to decrease the rate of copper extraction in the range of 2% (v / v) to 4% (v/v) under optimum conditions for copper extraction from nitrate solution, as observed by [2, 23]. An improvement of 2 percent from an economic point of view is very low,

*DOI: http://dx.doi.org/10.5772/intechopen.95093*

**3. Results and discussion**

*Depicts the transfer mechanism of LSM.*

**Figure 3.**

so 6 percent of D2EHPA is used in the experiments.

In the external phase, where Cin is the initial copper concentration, and Cout is the concentration of copper ions after the extraction phase.

$$\begin{aligned} \mathop{\rm C\_{2}H\_{8}}\_{\begin{subarray}{c}\text{CH}\_{3}(\text{CH}\_{2})\_{3}\text{CH}(\text{CH}\_{2})\\\text{C}\_{2}\text{H}\_{5}\end{subarray}}\mathop{\rm P\_{\begin{subarray}{c}\text{O}^{-},\text{H}^{+},\text{O}^{-}\\\text{O}^{-},\text{H}^{+}\end{subarray}}}^{\text{C}\_{2}\text{H}\_{5}}\mathop{\rm P\_{\begin{subarray}{c}\text{O}^{-},\text{H}^{+},\text{O}^{-}\\\text{O}^{-},\text{H}^{+}\end{subarray}}\mathop{\rm P\_{\begin{subarray}{c}\text{O}^{-},\text{H}^{+},\text{H}^{+}\\\text{O}^{-},\text{H}\_{5}\end{subarray}}}^{\text{C}\_{2}\text{H}\_{5}}\mathop{\rm P\_{\begin{subarray}{c}\text{O}^{-},\text{H}^{+},\text{O}^{-}\\\text{O}^{-},\text{H}\_{5}\end{subarray}}}^{\text{C}\_{2}\text{H}\_{5}}\begin{aligned}\mathop{\rm P\_{\begin{subarray}{c}\text{O}^{-},\text{H}^{+},\text{O}^{-}\\\text{O}^{-},\text{H}^{+}\end{subarray}}^{\text{C}\_{2}\text{H}\_{5}}\\\end{aligned}$$

**Figure 2.** *Depicts the structure of D2EHPA.*

*Removal of Copper Ions from Aqueous Solution Using Liquid Surfactant Membrane Technique DOI: http://dx.doi.org/10.5772/intechopen.95093*

*Colloids - Types, Preparation and Applications*

*2.2.4 Demulsification of the emulsion*

Cu concentration determined after that.

**2.3 Extraction mechanism in the ELM system**

**Figure 2** [24, 25] reveals the D2EHPA structure. Extraction reaction of the copper ions:

Stripping reaction of the copper ions:

extraction percentage (E percent) is found:

ratio (TR) and stirring speed were varied to observe their effects on Cu extraction in order to understand the important variables relating to the extraction of Cu.

After the extraction experiment, the loaded emulsion was broken into the internal Cu concentrated phase and the organic phase by means of a hot plate magnetic stirrer (70° C for 43 minute). The internal phase (I) was analyzed and the

The prepared emulsion (Section 2.2.1) containing a certain concentration of copper ions at pH 4 (adding some drops of 0.2 M H2SO4) was transferred to the external process. For 0–12 minutes, a robotic mixer was used to stir the solution. Eqs. 1 and 2 elucidate the extraction and stripping reactions of the copper ions.

Here, RH refers to an extractant's protonated form (D2EHPA in this paper) [23].

( ) ( ) ( ) ( ) 2 <sup>2</sup> 2 2 2 2 *<sup>S</sup> <sup>L</sup> CuR RH H Cu RH* + + +→ + (2)

<sup>2</sup> <sup>2</sup> 2 2 *<sup>S</sup> <sup>L</sup> Cu RH PbR RH H* + + +→ + (1)

<sup>C</sup> = × - (3)

( ) ( )( ) ( ) <sup>2</sup>

At the membrane (O)-external (E) interface, Eq. (1) denotes the reaction, whereas Eq. (2) shows the reaction where the copper ions are stripped at the oil (O)-internal (W) interface. **Figure 3** describes the movement of Cu (II) ions by an extractant from the external phase to the internal phase. Based on the Eq. (3), the

> in out in C C E% 100%

the concentration of copper ions after the extraction phase.

In the external phase, where Cin is the initial copper concentration, and Cout is

**138**

**Figure 2.**

*Depicts the structure of D2EHPA.*
