Separation of Zinc Ions from an Acidic Mine Drainage using a Stirred Transfer Cell–Type Emulsion Liquid Membrane Contactor

Abstract

This is a report on the separation and recovery of zinc ions from an acidic mine drainage using a stirred transfer cell‐type emulsion liquid membrane contactor. Di(2‐ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. A study was made of the effect on the extraction extent and initial extraction rate of the following variables: pH and initial metal concentration of the feed phase, carrier content in the organic solution, a stripping agent concentration in the receiving phase, and stirring speed in the transfer cell. The content of sulfuric acid as a stripping agent did not show in the studied range any significant influence on metal permeation through the SLM, although a minimum hydrogen ion concentration of 100 g/L is suggested in the internal aqueous solution to ensure an acidity gradient between both aqueous phases to promote the permeation of metal ions toward the strip liquor. Results show that using a pH of 4.0 in the feed acid solution, a concentration of 3% w/w_o of phosphoric carrier in the organic phase and a H₂SO₄ content of 100 g/L in the strip liquor, the extent and rate of extraction through the liquid membrane can be highly favored, pointing to the potential of this method for extracting heavy metals from many kinds of dilute aqueous solutions.     

Extraction and recovery of rhodamine B,methyl violet and methylene blue from industrial wastewater using D2EHPA as an extractant

The extraction behavior of cationic dyes namely rhodamine B (RB), methyl violet (MV) and methylene blue (MB) from industrial wastewater has been investigated using di-(2-ethylhexyl) phosphoric acid (D2EHPA) in hexane as a carrier. The extraction of cationic dyes increases with decreasing feed phase pH and increasing D2EHPA concentration in organic phase. The stripping percentage of dyes using acetic acid as the stripping agent from loaded D2EHPA was found to increase with increasing acid concentration. 98% stripping efficiency of dyes was achieved with 8.5 mol/L acetic acid solution at an organic:aqueous phase ratio (O/A) of 2:1. Parameters examined include D2EHPA concentration, effect of diluents, effect of pH, effect of initial dye concentration, equilibration time, and various stripping agents, aqueous to organic phase ratio in extraction and organic to aqueous phase ratio in stripping.     

Recovery of Chloroform from Effluent with Solvent Extraction–Distillation Process

Abstract

A solvent extraction–distillation process for recovery of chloroform in aqueous effluent was developed. Sutfonated kerosene was used for extraction of chloroform. When the flow ratio of organic phase to aqueous phase is 0.1, the chloroform concentration in the aqueous effluent can be decreased from 10 g/L to about 100 mg/L by 3-stage countercurrent extraction. The distribution ratio of chloroform between sulfonated kerosene and water is about 50. Sodium sulfate in the aqueous effluent will enhance the distribution. A small amount of water was added to the distillation column for stripping chloroform in sulfonated kerosene. RPC was used as a commercial extractor. Scale-up from the data of the pilot test was based on the Karr correlation. Recovery of chloroform was over 90%, and residual kerosene in the aqueous effluent from the extraction was lower than 70 mg/L. It is expected that the technique can be used for the recovery of other organic solvents miscible with kerosene.     

Solvent Extraction Studies of Zinc and Cadmium with Aliquat 336-S in Aqueous Chloride Solutions

Abstract

New solvent extraction systems have been developed for the extraction of zinc and cadmium from aqueous chloride solution using Aliquat 336-S dissolved in the nonpolar solvents heavy aromatic naphtha and xylene as the extractant. Moderately high concentrations of the metalions (1 mg/ml zinc and 2 mg/ml Cd) can be extracted quantitatively from acid solutions with an equal volume of 5% Aliquat 336-S solution in 15 sec. Both zinc and cadmium can be stripped from the organic phase with a series of aqueous stripping solutions. When comparing zinc and cadmium, cadmium is the easier to extract and the more difficult to strip under the same experimental conditions.     

Synergistic Solvent Extraction and Transport of Zn(II) and Cu(II) across Polymer Inclusion Membranes with a Mixture of TOPO and Aliquat 336

Separation of zinc(II) and copper(II) ions from aqueous solutions by synergistic extraction and transport through polymer inclusion membranes (PIMs) has been investigated. A mixture of trioctylphosphine oxide (TOPO) and trioctymethylammonium chloride (Aliquat 336) was used as a selective extractant as well as an ion carrier in polymer membranes. The effects of hydrochloric acid concentration in the aqueous phase and extractants concentration in the organic phase on the separation process of zinc(II) and copper(II) ions have been studied. Zn(II) ions were successfully separated from Cu(II) ions in solvent extraction process using 0.025 M TOPO and 0.06 M Aliquat 336 in kerosene. Polymer inclusion membranes (PIMs) containing a mixture of TOPO and Aliquat 336 as the ion carrier have been prepared and the facilitated transport of Zn(II) and Cu(II) ions has been studied. The influence of membrane composition on the transport kinetic of Zn(II) and Cu(II) has been evaluated. Zn(II) ions were preferably transported from the aqueous solutions containing Cu(II) and above 87% of Zn(II) ions were effectively recovered from the 0.5 M HCl solution as the source phase through PIM into 0.5 M H₂SO₄ as the stripping phase.     

Performance of hollow fiber supported liquid membrane on the extraction of mercury(II) ions

The extraction and recovery or stripping of mercury ions from chloride media using microporous hydrophobic hollow fiber supported liquid membranes (HFSLM) has been studied. Tri-n-octylamine (TOA) dissolved in kerosene was used as an extractant. Sodium hydroxide was used as a stripping solution. The transport system was studied as a function of several variables: the concentration of hydrochloric acid in the feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium hydroxide in the stripping solution, the concentration of mercury ions in the feed solution and the flow rates of both feed and stripping solutions. The results indicated that the maximum percentages of the extraction and recovery of mercury ions of 100% and 97% were achieved at the concentration of hydrochloric acid in the feed solution of 0.1 mol/l, the concentration of TOA at 3% v/v, the concentration of sodium hydroxide at 0.5 mol/l and the flow rates of the feed and stripping solutions of 100 ml/min. However, the concentration of mercury ions from 1–100 ppm in the feed solution had no effect on the percentages of extraction and recovery of mercury ions. Thus, these results have identified that the hollow fiber supported liquid membrane process has high efficiency on both the extraction and recovery of mercury (II) ions. Moreover, the mass transfer coefficients of the aqueous phase (k _i ) and membrane or organic phase (k _m ) were calculated. The mass transfer coefficients of the aqueous phase and organic phase are 0.42 and 1.67 cm/s, respectively. The mass transfer coefficient of the organic phase is higher than that of the aqueous phase. Therefore, the mass transfer controlling step is the diffusion of the mercury ions through the film layer between the feed solution and the liquid membrane.     

Interfacial mass transfer in stripping of phenylalanine in a liquid-liquid extraction process

Stripping of L-phenylalanine from organic phase containing ALIQUAT 336 (tri-octyl-methyl-ammonium chloride) as complexing agent was studied using a stirred transfer cell. The study investigated the effects of concentration of the stripping agent, potassium chloride, in strip solution and temperature on mass transfer rates. A two-film model based on organic and aqueous phases mass transfer resistances was proposed to estimate mass transfer coefficients and it predicted adequately the experimental time-concentration data at different conditions studied. A comparison of mass transfer coefficients for stripping and previously published results on extraction for the same system was made.     

Response Surface Modelling and Optimization of Mercury Extraction through Emulsion Liquid Membrane

Mercury(II) is a very harmful metal, highly toxic, and carcinogenic in nature. Experiments were carried out using the emulsion liquid membrane (ELM) technique in order to evaluate the maximum extraction of mercury(II) from aqueous solutions of mercuric chloride using 3³ factorial design. The ELM consisted of di-2-ethylhexylphosphoric acid as a carrier, toluene as an organic solvent, span 80 as a surfactant, and sulphuric acid with thiourea solution as stripping phase. The three factors for the factorial design were mercury(II) concentration in the aqueous solution, that is, feed phase concentration, carrier concentration in the membrane phase, and sulphuric acid concentration in the stripping phase. The study has also highlighted the effects of various other parameters, such as pH of the feed phase and thiourea concentration on mercury(II) extraction. The optimization of the factors to obtain maximum extraction were carried out by incorporating main effect plots, interaction plots, analysis of variance (ANOVA), normal probability plots, residual plots, surface plots, and contour plots. A reduced model developed by regression analysis was suggested in which the experimental data were fitted very well. The results showed that it is possible to extract mercury(II) up to 98% from aqueous solutions at the optimum conditions.     

Determination of the heat change in solvent extraction of metals. The extraction of zinc (II) from hydrochloric acid solutions by high molecular weight amines in various organic solvents

The heat change associated with the uptake of zinc (II) has been examined by using a twin type isoperibol calorimeter in the extraction of zinc (II) from hydrochloric acid solutions by trioctylamine hydrochloride (TOAHCl) and trioctylmethyl-ammonium chloride (TOMAC) in various organic solvents such as benzene, chlorobenzene, o-dichlorobenzene, toluene, m-xylene, nitrobenzene, carbon tetrachloride and 1, 2-dichloroethane. It was found that the dependence of apparent molar heat change (the value of the heat change detected with regard to the concentration of zinc (II) reacted) on the aqueous chloride concentration could be attributed to the change in the distribution of zinc (II) chloride species in the aqueous phase. Taking account of this fact, variable Y, which constitutes the sum of the change in enthalpies for the relevant steps in the extraction of zinc (II), except the transformation of ZnCl_j^(2-j)+ to ZnCl₄^2-, in the aqueous phase, is introduced. From the values of Y obtained, it is concluded that in the extraction by TOMAC, Y correlates with the solubility parameter of diluent, suggesting that the organic phases may be regarded as regular solutions, while in the extraction by TOAHCl, no clear-cut relation holds between Y and the physico-chemical constants of the diluent such as dipole moment, dielectric constant and solubility parameters.     

Solvent Extraction of Au(I) from Auro‐Cyanide Solution with Cetyltrimethylammonium Bromide/Tri‐n‐Butyl Phosphate System using Column‐Shaped Extraction Equipment

Abstract

Solvent extraction of Au(I) from alkaline cyanide solution containing several milligram per liter of gold was investigated with column‐shaped extraction equipment using tri‐n‐butylphosphate (TBP) as extractant with addition of quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), directly into the aurous aqueous phase in advance. The influences of the volume of TBP and the NaCl concentration in the aurous aqueous phase on Au(I) extraction were investigated. The experimental results for treating 50 L of synthetic auro‐cyanide solution containing 10 mg/L Au(I) and for treating real auro‐cyanide leaching liquor by CTAB/TBP system were reported. The results obtained establish that the column‐shaped extraction equipment was suitable for extracting Au(I) from low content auro‐cyanide solution at high aqueous/organic phase ratio, and that more than 97% of gold(I) could be extracted while the Au(I) concentration in the raffinate was less than 0.3 mg/L. In addition, the stripping of Au(I) from the loaded organic phase and the recycle of the organic phase were also discussed.     

Extraction of Thallium with Butyl Acetate

ABSTRACT

Experimentally obtained extraction isotherms of the system thallium-sulfuric acid-sodium chloride-butyl acetate are presented. The influence of the sulfuric acid and chloride anion concentrations on the extraction equilibria of thallium was investigated. An increase in the acidity of the aqueous phase results in steeper extraction isotherms, and the amount of thallium extracted generally increases. The influence of chloride anions on the equilibrium is more complex. It was found that the extraction equilibria is not influenced by the chloride ion concentration, provided that the Cl/T1 ratio in the aqueous phase is ? 4. If this ratio is less than 4, the concentration of chloride anions significantly influences the extraction isotherms. The results obtained are discussed in terms of the composition of the complex in the organic phase. An apparent reaction constant equation is proposed for the prediction of the extraction equilibria.     

Stripping of Au(I) from a Loaded Cetyltrimethylammonium Bromide/Tributyl Phosphate Organic Solution: Conversion and Reduction

The recovery of Au(I) from cyanide leaching solutions by solvent extraction techniques has attracted wide interest in the past decades. However, no substantial progress in industries has been reported yet, because of the difficulties concerning gold stripping from loaded organic phases, such as the quaternary amines extraction systems. In this work, a new technique for the recovery of Au(CN)₂ ^? from the loaded cetyltrimethylammonium bromide / tributyl phosphate organic solution by a two‐step stripping procedure is suggested first by Au(CN)₂ ^? conversion by HCl into corresponding chloride complex ions, and then by chemical reduction of auro‐chloride complex ions in TBP organic phases to give metal gold powder. The influences of HCl concentrations, reaction time, and various reducing agents used on the percent gold conversion and reduction were investigated. About 33% of Au(CN)₂ ^? in the initial TBP organic phase could be precipitated as metal gold powder in the conversion step, while 67% was converted into AuCl₂ ^? or AuCl₄ ^? and held in the organic phase. Subsequently, the loaded organic phase after conversion was contacted with reducing agents such as sodium sulfite, ammonium oxalate, or hydrazine hydrate. Most (>98%) of the auro‐chloride complex ions could be effectively reduced as metal gold. As a result, the total gold recovery from the initial TBP organic phases after the two stripping procedures achieved more than 98%. The ¹⁹⁸Au radioactive tracer was employed to determine the concentration and distribution behavior of gold in both organic and aqueous solutions. In addition, the experiment on the reuse of the organic phase after gold stripping showed that there was no obvious loss in percent gold(I) recovery after one cycle of the extraction‐ stripping‐ regeneration process no matter what reducing agent was used.     

褐藻糖胶的萃取和反萃

研究了无机盐种类和浓度对N263萃取褐藻糖胶的影响. 结果表明,无机盐浓度是影响褐藻糖胶萃取的最主要因素, 褐藻糖胶的萃取率随盐浓度的增加而迅速降低,在无机盐存在下,增加萃取剂浓度并不能增加对褐藻糖胶的萃取. 用盐水溶液反萃不同条件下萃取的褐藻糖胶,结果表明,反萃率随盐浓度的增加而增加,在相同的氯离子浓度下,钠盐的反萃效率优于钙盐,随有机相中褐藻糖胶浓度的增加, 盐的反萃效率降低. 比较了不同溶剂作为稀释剂对用盐溶液反萃褐藻糖胶的影响,表明CCl4作为稀释剂时盐的反萃效率最低.     

Liquid-Liquid Extraction of Zinc with Aliquat 336-S-Br from Aqueous Bromide Solutions

Abstract

A new solvent extraction system has been developed for zinc in aqueous bromide solution using Aliquat 336-S-Br-xylene solution as an extractant. A 1 mg/ml zinc solution is extracted essentially quantitatively with an equal volume of 5% Aliquat 336-S-Br-xylene solution in 15 sec. The extracted zinc can be stripped from the nonaqueous layer with a series of aqueous solutions including Na₂SO₃ (≥m 1.0 M) NaOH (≥m 0.5 M), NH₃ (≥m 0.5 M), ethylenediamine (≥m 0.3%), and EDTA (≥m0.5%). The extraction is quantitative only from acidic solutions. High aqueous to organic phase ratios can be utilized without loss of extraction efficiency.     

Extraction Kinetics of Rare Earth Metals with 2-Ethylhexyl Phosphonic Acid Mono-2-ethylhexyl Ester Using a Hollow Fiber Membrane Extractor

Abstract

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively, were investigated to clarify the permeation mechanism. From the experimental results it was predicted that the permeation rate is controlled by diffusion of the chemical species in aqueous and organic phases and by interfacial chemical reaction. The experimental data were analyzed by the diffusion model accompanied with an interfacial reaction, taking into account the velocity distributions of the aqueous and organic phases through the inner and outer sides of the hollow fiber.     

Facilitated Transport of Gold through a Membrane via Complexation to Thiourea-Based Reagents

Abstract

The facilitated transport of Au(III) from hydrochloric acid solutions through double solid supported liquid membranes (SSLMs) is reported. The organic phase consisted of a chloroform solution of thiourea-based extraction reagents, dodecyl-thiourea (DTH) or nonylthiourea (NTH), physically absorbed onto microporous polypropylene films, Celgard 2500 or Celgard 2400 (Celanese Plastic Inc.). A cell composed of three compartments, including a reservoir of organic solution, with double SSLM was used in this study. Aqueous solutions of thiourea, KSCN, or Na₂S₂O₃ were used for removing Au(III) from the membrane phase. The permeability coefficient, P, of the SSLM was determined from the slope of Iog[Au]/[Au]_o or log A/A_o vs time plot. The influences of the stirring rate in aqueous feed and organic solutions, of the stripping reagents and their concentration, of the carrier concentration, and of the concentration of HCl in the aqueous feed on the permeability coefficient were determined. A model describing the transport mechanism consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion through the membranes is reported. The study also demonstrates the suitability of the liquid membrane technique to use reagents with low solubility in organic solutions for the permeation of Au³⁺ without problem of solid-phase formation.

     

THE SOLVENT EXTRACTION OF ZINC FROM LITHIUM CHLORIDE BY ALIQUAT 336 CHLORIDE,BROMIDE AND IODIDE IN CHLOROFORM: AN ANALYTICAL INVESTIGATION

ABSTRACT

The extraction of zinc by Aliquat CI in chloroform is studied as a function of LiCl concentration. A plot of log D versus total [Cl] shows that log D increases sharply from 0-2 M LiCl, then remains constant over a considerable range of concentrations ( 2-8 M ), before shooting up again from 8-14 M. Further work is carried out at 4 M LiCl to determine the extraction equation, and quantitative aspects determined such as a plot of log D versus log [Aliquat Cl]_free, giving a ratio of 2:1 for extractant: metal, and the ratio [Cl / Zn]_extracted, which is 2.

In order to follow the exchange of halides across the interface, Aliquat Br and Aliquat I are used as extractants in chloroform to study the extraction of zinc chloride from 4 M LiCL Organic and aqueous phases are analysed for halides and zinc, and the ratio [ΔCl] / [Zn] in the organic phase determined to be 3 for both Aliquat Br and I at 4M LiCl, indicating extraction of ZnCl₃,' and not ZnCl₄ ² at this concentration. Further work with these extractants based on plots of log D versus log [Aliquat X]_free ( X = Br, I ) is presented and extraction equations are proposed for these extractants, which fit the data.

Extraction of zinc at 4 M LiCl by Aliquat Cl is then considered in terms of the extraction of the trichlorozincate (II) species, ZnCl₃,“, and the extraction constant determined.     

The Solvent Extraction of Boron with Synthesized Aliphatic 1,3‐Diols: Stripping and Extraction Behavior of Boron by 2,2,5‐Trimethyl‐1,3‐hexanediol

Abstract

A variety of aliphatic 1,3‐diols (4a–c, 5a–c, 6a–c) was synthesized from β‐hydroxy carbonyl compounds (1–3) for potential use in the solvent extraction of boron. Primary‐secondary and primary‐tertiary alcohol structures of 1,3‐diols substituted with isopropyl, isobutyl, and isopentyl groups have been demonstrated to be very efficient for the solvent extraction of boric acid from aqueous solutions. The extraction ability of 2,2,5‐trimethyl‐1,3‐hexanediol (5b) was investigated as a function of 5b concentration, solution pH, solvent properties, and stripping conditions. Extraction efficiency increased with increasing concentration of 5b, and the best extraction of boron (96.8%) was found to be at an equilibrium pH of 2 with 0.5 M of 5b. Chloroform, toluene, chlorobenzene, 2‐octanol, and n‐amyl alcohol were found to be suitable solvents for the solvent extraction of boron. The boron complex can be recovered from the organic phase by treatment with an aqueous solution of sodium hydroxide. The highest ratio (96.7%) of boron was recovered by 0.1 M of sodium hydroxide solution.     

Process for the Recovery of Cobalt and Nickel from Sulphate Leach Liquors with Saponified Cyanex 272 and D2EHPA

Abstract

In this paper, a process is reported for the recovery of cobalt and nickel from copper raffinate solutions using partially saponified Cyanex 272 and D2EHPA as the extractants. The aqueous feed contains 1.65 g/L cobalt and 16.42 g/L nickel. More than 99.9% cobalt separation was achieved with 0.13 M Cyanex 272 (60% neutralized with alkali) in two counter‐current stages at an aqueous to organic phase ratio of 1.1:1. Co‐extraction of nickel was 0.18% only. Stripping of cobalt from a loaded organic phase was carried out with synthetic spent electrolyte solution at an organic to aqueous phase ratio of 2.5 in two counter‐current stages to generate a pregnant electrolyte solution to produce cobalt metal by electrowinning. Similarly, optimum conditions for nickel extraction with 60% neutralized 1 M D2EHPA at O/A ratio of 1.4 in 2 two stages and stripping of metal with synthetic spent electrolyte at O/A ratio of 1.6 in two stages were standardized. Extraction and stripping efficiencies were >99% and the flowsheet of the process is demonstrated.     

Application of N,N′‐Dimethyl‐N,N′‐Di(4‐Chlorophenyl)Tetradecyl Malonamide for the Selective Recovery of Iron(III) from Concentrated Chloride Solutions

Abstract

The feasibility of using two new diamides namely; N,N′‐dimethyl‐N,N′‐di(4‐chlorophenyl)malonamide (DMDPhClMA) and N,N′‐dimethyl‐N,N′‐di(4‐chlorophenyl)tetradecylmalonamide (DMDPhClTDMA), as agents for the selective extraction of iron(III) from chloride solution was investigated. A systematic investigation has been carried out on the detailed extraction properties of iron(III) with these extractants from chloride media. The extraction of iron(III) from an aqueous chloride solution in the presence of metal ions, such as Zn(II), Co(II), Mn(II) Cu(II), Pb(II), Ni(II) and Ag(I) was carried out using DMDPhClMA or DMDPhClTDMA in binary and multicomponent mixtures. The quantitative extraction of iron(III) with DMDPhClMA and DMDPhClTDMA in toluene is observed at 4 and 7 M HCl, respectively. The quantitative stripping of Fe(III), from the loaded organic phase was successfully achieved by simple contact with water.