THE KINETICS OF COBALT AND NICKEL EXTRACTION USING HEHEHP

The kinetics of the extraction of cobalt and nickel using purified mono 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester (HEHEHP) were studied using the Rotating Diffusion Cell (RDC) apparatus. The extraction of cobalt was Investigated over a wide range of cobalt concentration, extractant concentration, pH and temperature conditions. Nickel extraction was examined over a wide range of nickel concentrations.

The kinetic data were treated according to both interfacial and mass transfer with chemical reaction (MTWCR) models. The MTWCR model adequately described the kinetic data for both the cobalt and nickel extraction experiments. No variation of an interfacial model was adequate to describe the data. In the MTWCR model, the extraction rate was shown to be controlled by a mechanism involving diffusion of the extractant into the aqueous phase boundary layer with subsequent reaction involving the addition of the first ligand to the cobalt or nickel ion. This extraction mechanism was substantiated by supplementary results including the activation energy determination which indicated mixed diffusion and chemical reaction control, the significant measured rate of partition of the extractant to the aqueous phase, and the values of the cobalt and nickel complex formation constants in the aqueous phase.     

THE COMPETITIVE PERMEATION OF COBALT AND NICKEL WITH SUPPORTED LIQUID MEMBRANES

In this paper, the competitive permeation of cobalt and nickel from nitrate solutions through supported liquid membranes was studied, in which contained 2-ethylhexyIphosphonic acid mono-2-cthylhexyl ester (HEHEHP) dissolved in kerosene as a mobile carrier. The permeation rate equations were derived taking into account the aqueous film diffusion of metal ions towards and out of the membrane and the membrane diffusion of HEHEHP and its metal complexes. The mass transfer coefficients of metal ions and metal-HEHEHP complexes were also determined using the permeation cell. It was found that the calculated permeation rates were in good agreement with the measured ones.     

The separation and recovery of copper(Ⅱ), nickel(Ⅱ), cobalt(Ⅱ), zinc(Ⅱ),and cadmium(Ⅱ) in a sulfate-based solution using a mixture of Versatic 10 acid and Mextral 984H

We studied the separation and recovery of copper(Ⅱ), nickel(Ⅱ), cobalt(Ⅱ), zinc(Ⅱ), and cadmium(Ⅱ) from magnesium and calcium, using synergistic solvent extraction(SSX) in a typical hydrometallurgical waste solution. A mixture of Versatic 10 acid and Mextral 984 H, diluted with Mextral DT100, was used to obtain fundamental data on p H and distribution isotherms, as well as the kinetics of extraction and stripping. We also investigated the main effects and interactions of common solvent extraction factors: the extraction p H at equilibrium, the temperature, and the extractant concentration. The synergistic effect for extracting metals was confirmed. The results showed that the addition of Mextral 984 H enhanced the separation factors of copper, nickel, cobalt,zinc, and cadmium over magnesium and calcium. Compared with Versatic 10 acid alone, for a mixture of0.5 mol·L~(-1) Versatic 10 acid/0.5 mol·L~(-1)Mextral 984 H, Δp H50 values of copper, nickel, cobalt, zinc, and cadmium were found to be N 2.0, 3.30, 2.85, 0.95, and 1.32 p H units, respectively. The Δp H_(50)(Zn–Mg)and Δp H_(50)(Zn–Ca)values were 3.27 and 2.25, respectively, indicating easy separation and recovery of copper, nickel, zinc, cobalt,and cadmium. The extraction and stripping of copper, cobalt, zinc, and cadmium were fast, with 90% of the metal transferred in 2 min. We next studied whether the metals could be stripped from the extracted liquid selectively in sequence, by using sulfuric acid at different concentrations. The influence of the molecular structure of the oxime and carboxylic acid components upon the synergistic effects was identified by numerical analysis.Excellent separation of copper, nickel, cobalt, and zinc over magnesium and calcium was achieved with this synergistic solvent extraction system.     

Critical Evaluation of Different Mass Transfer Models Taking Zinc Extraction as an Example

Different mass transfer models were evaluated on the basis of zinc extraction with the liquid ion exchanger di(2‐ethylhexyl)phosphoric acid. Comparison of the models showed that the film model inadequately describes the time dependence of zinc concentration in aqueous solution. The best match of the measured time‐concentration profiles was achieved by adapting the film‐penetration model. Studies were carried out in a stirred cell with a planar interface stabilized by the mixing conditions. Under the chosen experimental conditions mass transfer was limited by zinc transfer in the aqueous phase. The mass transfer equations of each model were solved analytically using empirical correlations for the modeling parameters.     

EXTRACTION OF NICKEL FROM AQUEOUS SULFATE SOLUTION INTO BIS(2,2,4-TRIMETHYLPENTYL)PHOSPHINIC ACID,CYANEX 272TM -EQUILIBRIUM AND KINETIC STUDIES

ABSTRACT

Equilibrium and kinetic studies have been carried out on the extraction of nickel from sulfate solutions using bis(2,2,4 trimethylpentyl) phosphinic acid HDTMPP, “Cyanex 272tm”- It was found that nickel extraction in HDTMPP was favored by the presence of sodium in the organic phase and that equilibrium nickel concentration could be written in terms of the pre-equilibrated extractant concentration

Kinetic studies were carried out using the rising drop method, reaction orders were determined with respect to the aqueous phase nickel concentration, Ni²⁺, the aqueous phase sodium concentration, Na ⁺ the pH, the organic phase dimer concentration ------ and the organic phase sodium salt concentration ---- In addition, it was found that the extraction kinetics could be explained in terms of an aqueous phase interfacial reaction accompanied by diffusion through the interface. Mass transfer coefficient values were determined indicating extraction rates for metal extraction into HDTMPP were the same order of magnitude as those found for HDEHP.     

Separation of Zinc by a Non‐dispersion Solvent Extraction Process in a Hollow Fiber Contactor

Abstract

A process for recovery of zinc from acid solution with di(2‐ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso‐dodecane was carried out at 20°C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1–1.0 g/L), pH 0.1–2.1, and D2EHPA concentrations (2–8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38–0.80 L/min) and organic flow rate (0.22–0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2×10^?6 m/s to 25.3×10^?6 m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer.     

Separation of Cobalt and Nickel with Phenylphosphonic Acid Mono-4-tert-octylphenyl Ester by Liquid Surfactant Membranes

Abstract

The separation of cobalt and nickel with liquid surfactant membranes (LSMs) was carried out in a stirred cell using a newly synthesized extractant. The effect of a surfactant on the kinetics of cobalt and nickel extraction was investigated to elucidate the role of a surfactant used in LSMs. The extraction equilibrium of these metals was also examined. Further, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of a surfactant. It was found that the interfacial activity of the extractant is as high as that of a surfactant. In the extraction equilibrium study of these metals, extraction equilibrium constants were obtained for cobalt and nickel for the following equations:

Co²⁺ + 2(HR)₂=CoR₂(HR)₂ + 2H⁺ Ni²⁺ + 3(HR)₂=NiR₂2(HR)₂ + 2H⁺ The effects of the extractant and surfactant on the extraction rate of cobalt and nickel in LSMs were studied. The results were analyzed by a proposed model with an interfacial reaction, and rate constants were obtained for each metal. It was found that the new extractant has a very strong extractability for each metal compared with a conventional commercial extractant such as 2-ethylhexylphosphonic acid mono-2-elhylhexylester (commercial name, PC-88A) or di(2-ethylhexyl)phosphoric acid (D2EHPA). Further, a surfactant strongly affected the extraction rate and the separation of these metals, and a cationic surfactant was selected.     

Liquid extraction of metals from sulphate solutions by alkylphosphoric acids. II. Kinetics of the extraction of copper and cobalt with di-(2-ethyl hexyl) phosphoric acid

Kinetic studies of the transfer of copper and cobalt (separately) between aqueous solutions of their sulphates and organic phases consisting of solutions of di(2-ethyl hexyl) phosphoric acid (EHPA) in kerosene were made by an ‘equilibrium extraction’ technique, in which radioactive isotopes of the metals were transferred between phases which were otherwise in equilibrium. The total resistance to mass transfer was found to be greater than that predicted from the mass-transfer resistances of the aqueous and organic phases, the additional resistance to mass transfer being between 30 and 75% of the total resistance. When the concentration of free EHPA in the organic phase was greater than 0·01 g mole/l (which is approximately equivalent to a ratio of the metal concentration in the organic phase to the initial organic-phase EHPA concentration of less than 0·25), expressions for these additional resistances were obtained from consideration of the kinetics of the extraction reaction, with a rate-controlling step equivalent to the reaction of a metal ion with an EHPA dimer to form a metal-EHPA compound and a hydrogen ion. At lower organic-phase-free EHPA concentrations, the additional resistances were lower and did not show any marked dependence on pH or reactant concentrations.     

Treatment of wastewater containing copper,zinc, nickel and cobalt using Duolite ES‐467

Duolite ES‐467 was used to treat wastewater containing heavy metal ions. Sorption experiments were carried out at varying pH values, agitation speeds, reaction times, and metal ion and sorbent concentrations. Each of the parameters affects the sorption behaviour of individual metal ions. Copper sorption was greater compared with other metal ions such as zinc, nickel and cobalt. The presence of other metal ions affects copper sorption. Equilibrium isotherm curves were developed. These were used to predict that the metal ion concentration would be reduced from 100 to less than 1 mg dm^?3. Fixed bed tests were conducted to investigate the efficiency of Duolite ES‐467 for the selective removal of copper ions from multi‐metal solutions. Breakthrough curves were obtained using Duolite ES‐467 for solutions containing copper, nickel and copper, zinc, nickel and cobalt. Elution studies were also carried out using sulfuric acid. © 2002 Society of Chemical Industry     

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.     

Mass Transfer and Immobilized Organic Phase Instability Studies for Cobalt(II)–Nickel(II) Separation by PEHFSD

Pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD) technique was examined as an alternative to solvent extraction for simultaneous separation and concentration of cobalt(II)–nickel(II) mixture using Cyanex-272 as the extractant. Experiments were carried out by continuous recirculation of the feed and pseudo-emulsion phases through a hollow-fiber module. The separation factor increased rapidly after 60 min of operation. The maximum value after 120 min of operation was ～128 (pH = 6.5) for the operating conditions studied. The mass transfer resistance from the extraction reaction appeared to be dominant. The results of mathematical modeling of the mass transfer process indicated that higher separation factor and extraction rate can be achieved using PEHFSD in comparison to solvent extraction. Mixing of the stripping and the feed solution was observed at high dispersed phase volume fraction in the pseudo-emulsion and low flow rate of this phase. The maximum value of backtransport flux from the stripping phase due to mixing was estimated to be approximately two orders lower than the initial extraction rates.     

EXTRACTION KINETICS OF ZINC BY TRILAURYLAMM0NIUM CHLORIDE AT DIFFERENT CHLORIDE CONCENTRATIONS

The rate of the extraction of zinc by trilaurylammonium chloride (TLAHC1) dissolved in toluene was investigated at different aqueous chloride concentrations, using lithium chloride as bulk electrolyte, ranging from 0.5 mol.dm -3 to 2.0 mol dm -3. The experiments were performed using a modified Lewis cell at 25?°C. The rate of metal extraction was found to increase by increasing the aqueous chloride concentration. The data treatment indicated that ZnCl₂ and ZnCl₄ ^2- are both kinetically active species. The addition reaction with ZnCl₂ is favoured at low chloride concentration while the anion exchange of ZnCl₄ ^2- prevails at high chloride concentration. The addition reaction was explained in terms or interfacial reaction steps. The anion exchange reaction, due to its fast nature, seems to be controlled by diffusion.     

Development of Spiral-Type Supported Liquid Membrane Module for Separation and Concentration of Metal Ions

Abstract

Experiments on the single permeation of cobalt, nickel, and zinc, and the simultaneous permeation of cobalt and nickel were performed using newly developed spiral-type supported liquid membrane modules. These metal ions were successfully separated and concentrated. EHPNA (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) was used as the carrier of cobalt and nickel, and D2EHPA (di-(2-ethylhexyl)phosphoric acid) for the recovery of zinc. In these modules the flow pattern of both feed and stripping solutions is plug flow, which led to very high recovery of metal ions. For example, 99.97% of cobalt in the feed was recovered in a once-through operation, and cobalt could be pumped against its concentration gradient even if the ratio of the metal concentration in the strip phase to that in the feed phase was as high as 70,000. It was confirmed by a life test of the module that the membrane was stable for more than one month without appreciable decrease in metal flux, and that the degraded membrane could be easily and rapidly regenerated without interrupting the permeation of metal ions by re-impregnating the module with the organic membrane solution. The degree of removal for both single and simultaneous permeation of cobalt and nickel was satisfactorily simulated by design equations of the module and the flux equations in which the formation of aggregates of metal-carrier complexes was taken into account.     

Separation of cobalt and zinc from concentrated nickel sulfate solutions with Cyanex 272

BACKGROUND: Removal of cobalt and zinc from concentrated nickel solutions separately using two Cyanex 272 circuits has been practised in the nickel industry. However, no detailed study has been conducted and data are scarce for further improvement. This study aims to optimise the operating conditions and to simplify the process flowsheet. RESULTS: With a synthetic solution containing 100 g L^?1 Ni, 1.4 g L^?1 Co and 0.8 g L^?1 Zn and the organic solution containing Cyanex 272 and TBP in Shellsol D70, the operating conditions of extraction, scrubbing and stripping were optimised. McCabe–Thiele diagrams were constructed to determine the theoretical extraction and stripping stages and a flowsheet to separate cobalt and zinc from nickel was proposed. With this flowsheet, more than 99% cobalt and zinc could be separated, resulting in a pure nickel solution with less than 10 mg L^?1 of cobalt and zinc. CONCLUSIONS: The current study shows that Cyanex 272 can be used to separate cobalt and zinc in one Cyanex 272 circuit effectively from concentrated nickel solutions to obtain very pure nickel solutions suitable for nickel electrowinning or hydrogen reduction. The cobalt and zinc in the loaded strip liquor were concentrated over 10 times and can be separated readily in another much smaller solvent extraction circuit. Copyright © 2010 Society of Chemical Industry     

Recycling of nickel–metal hydride batteries. II: Electrochemical deposition of cobalt and nickel

A combination of hydrometallurgical and electrochemical processes has been developed for the separation and recovery of nickel and cobalt from cylindrical nickel–metal hydride rechargeable batteries. Leaching tests revealed that a 4 mol dm^?3 hydrochloric acid solution at 95 °C was suitable to dissolve all metals from the battery after 3 h dissolution. The rare earths were separated from the leaching solution by solvent extraction with 25% bis(2‐ethylhexyl)phosphoric acid (D2EHPA) in kerosene. The nickel and cobalt present in the aqueous phase were subjected to electrowinning. Galvanostatic tests on simulated aqueous solutions investigated the effect of current density, pH, and temperature with regard to current efficiency and deposit composition and morphology. The results indicated that achieving an Ni? Co composition with desirable properties was possible by varying the applied current density. Preferential cobalt deposition was observed at low current densities. Galvanostatic tests using solutions obtained from treatment of batteries revealed that the aqueous chloride phase, obtained from the extraction, was suitable for recovery of nickel and cobalt through simultaneous electrodeposition. Scanning electron micrography and X‐ray diffraction analysis gave detailed information of the morphology and the crystallographic orientation of the obtained deposits. Copyright © 2004 Society of Chemical Industry     

Purification of nickel sulphate solutions containing iron,copper, cobalt,zinc and manganese

Acidic nickel-bearing solution containing iron, cobalt, manganese, zinc and copper was processed through a solvent extraction and precipitation technique to obtain a pure nickel sulphate solution. Iron was extracted using 0.2M Cyanex-272 (partially neutralised) as the extractant. Stripping of iron from the loaded organic has also been studied. After iron recovery through solvent extraction the raffinate still contained 0·25 g dm^?3 of iron which was quantitatively separated by a lime precipitation technique. During this iron precipitation there was no loss of cobalt and nickel but copper, manganese and zinc were coprecipitated to some extent. From the iron-free nickel sulphate solution the other impurities were extracted using the same extractant (Cyanex-272) in a single stage. The metal ions from the loaded organic were stripped using a 0·5% (v/v) H₂SO₄ solution in a single stage. The entire operation needs only seven stages: two stages for iron extraction, three stages for iron stripping from the loaded organic, and one stage each for extraction and stripping of other impurities. In the entire operation the loss of nickel was less than 0·5%.     

PART 3. THE EXTRACTION OF Co2+, Ni2+, Cu2+ AND Zn2+ USING NOVEL DITERTIARY-AMINEEXTRACTANTS

The syntheses of N-N-octyl-2-2'-pyridylimidazole and N,N'-di-n-octyl-(a)-aminopicoline are presented. Their extraction properties are compared with that of an aliphatic diamine N,N,N',N'-tetraoctylethylene-diamine. The reagents, dissolved in chloroform, were used to extract divalent cobalt, nickel, copper and zinc from aqueous chloride medium. Two extraction mechanisms are postulated for the extraction of these metals, and extraction data are discussed in terms of these postulates.

Extraction of the copper(II) ion at low pH values with amines is best effected by the inclusion of aromatic nitrogen atoms into a diamine extractant.     

Mechanistic study of cobalt,nickel and copper transfer across a supported liquid membrane

The mechanism of cobalt, copper and nickel transport through supported liquid membranes containing di(2-ethylhexyl)phosphoric acid as a mobile carrier has been studied. An equation describing the permeation rate has been derived, taking into account stagnant layer aqueous diffusion, interfacial resistance due to solvatation reaction and liquid membrane diffusion as simultaneous controlling factors. The validity of this model is evaluated with experimental data of mass transfer coefficient measured employing a permeation cell. For these ions it was found that at low stirring conditions the stagnant layer resistance mainly controlled the processes, but it is controlled by diffusion of the ion complex through the supported liquid membrane when the stagnant layer resistance is negligible.     

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.