Emulsion liquid membrane extraction of Ni(II) and Co(II) from acidic chloride solutions using bis-(2-ethylhexyl) phosphoric acid as extractant

An emulsion liquid membrane process using bis-(2-ethylhexyl) phosphoric acid (D2EHPA) to extract and separate Ni(II) and Co(II) from acidic chloride solutions is described. Liquid membrane consists of a diluent, a surfactant (Span 80), and an extractant (D2EHPA). Hydrochloric acid was used as the stripping solution. The important parameters governing the permeation of nickel and their effect on the separation process have been studied. These parameters are stirring speed, feed phase pH, surfactant concentration, extractant concentration, stripping phase concentration, phase ratio, initial concentration of metal, and treatment ratio. The optimum conditions have been determined. The separation factors of Ni(II) with respect to Co(II), based on initial feed concentration, have been experimentally determined. Furthermore, the extraction selectivity for Co(II) over Ni(II) has been improved by using D2EHPA during the initial minutes.     

Extractive separation of Cu<Superscript>2+</Superscript>–Co<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript>–Co<Superscript>2+</Superscript> mixtures using <Emphasis Type="Italic">N</Emphasis>-salicylideneaniline

A study on the extraction of copper(II), cobalt(II), and nickel(II) from solutions containing ions of both metals with N-salicylideneaniline(SAN) in chloroform has been realized. Distribution of the metal ions in wide range of pH has been studied. Extraction of copper(II) was always favored over that of cobalt(II). Extraction of copper(II) from binary metal solution is selective and it can be quantitatively separated from cobalt(II). The equilibrium constant of the extraction of cobalt and nickel from an aqueous solution containing both metals using SAN were evaluated. The separation factors for cobalt and nickel were expressed as a function of the distribution of nickel and cobalt. From these results, salicylideneaniline is an adequate extractant for extractive separation of such mixtures.     

Application of emulsion liquid membranes to recover cobalt ions from a dual-component sulphate solution containing nickel ions

Emulsion liquid membranes (ELMs) containing 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) have been applied to recover cobalt II ions from a dilute sulphate solution containing equal amounts of nickel II ions (0.16 g/l). We focused on the study to develop an effective technique to recover cobalt as a target metal. It is found that polyamine (PX 100) membranes allow better permeation rates of cobalt ions than sorbitan monooleate (Span 80) membranes. The separation factor (β_Co/Ni) in polyamine membranes averaged 70 at a carrier concentration of 12 mol/m³ and feed solution pH 5.5. The permeation rate of Co II was found to increase proportionately with feed pH while for Ni II it decreased substantially at pH above 5.5 indicative of slower interfacial reaction rate. We found that short contact time (4–6 min) of feed solution and emulsion improved separation factor (β_Co/Ni) at feed pH above 5.5 and also minimized chances of emulsion break up. We have also observed that Span 80 membranes are hydrolyzed readily in a moderate acidic sulphate solution (pH 4.0–5.5) to form viscous gels. Results have shown that excess carrier [(HR)₂] affects the stability of emulsion and thus the separation factor. The critical ratio of carrier to emulsifier [(HR)₂]/[C_sf] was found to be approximately 0.5. This paper concludes with a discussion on the prospects of ELM system in practical use.     

Studies on extraction of chromium (VI) from acidic solutions containing various metal ions by emulsion liquid membrane using Alamine 336 as extractant

The extraction of chromium (VI) ions from acidic solutions containing various metal ions by emulsion liquid membrane (ELM) was studied. Liquid membrane consists of a diluent, a surfactant, and an extractant. 0.5 M ammonium carbonate solution was used as stripping solution. Effects of acid concentration in feed solution, type and concentration of stripping solution, mixing speed, surfactant concentration, phase ratio and the influence of membrane characteristics were studied and optimum conditions were determined. Under the optimum conditions, extraction of chromium (VI) was tested and it was possible to selectively extract 99% of chromium from the acidic feed solution. This study also examined the effect of extractant concentration and acid type in the feed solution on the extraction of Cr (VI) ions and almost all of Cr (VI) from the acidic feed solution containing 500 mg/L from each of Co (II), Ni (II), Cd (II), Zn (II), and Cu (II) ions, and 100–500 mg/L Cr (VI) was extracted within 5–10 min.     

Separation of Trivalent Samarium through Facilitated Stripping Dispersion Hollow Fiber Liquid Membrane Using p204 as Mobile Carrier

The separation of Sm(III) through stripping dispersion hollow fiber liquid membrane system (SDHFLM) containing feed phase adding acetate buffer solution and dispersion solution with HCl solution as the stripping solution and membrane solution of di(2‐ethylhexyl) phosphoric acid (p204) dissolved in kerosene, has been studied. A set of factors were studied, including pH value, initial concentration of Sm(III) and different ionic strength of feed phase, volume ratio of membrane solution and stripping solution (O/W), HCl concentration, carrier concentration, different stripping agents of dispersion phase on Sm(III) separation. Experimental results indicate that the optimum separation conditions of Sm(III) were obtained as that HCl concentration was 4.00 mol/L, p204 concentration was 0.150 mol/L, and volume ratio of membrane solution and stripping solution (O/W) was 1.00 in the dispersion phase, and pH value was 4.60 in the feed phase. Ionic strength had no obvious effect on separation of Sm(III). When initial Sm(III) concentration was 1.00×10^?4 mol/L, the separation rate of Sm(III) was up to 93.5% in 85 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The modeled results were in good agreement with the experiment data.     

Simultaneous reactive extraction separation of amino acids from water with D2EHPA in hollow fiber contactors

Reactive extraction separation of binary amino acids from water using a microporous hollow fiber has been studied, in which the acidic extractant di(2-ethylhexyl)phosphoric acid (D2EHPA) was selected as an active carrier dissolved in kerosene. l-Phenylalanine (Phe) was extracted from an aqueous solution through the shell side of module to the organic phase through the lumen of fiber in the extraction module, in which l-Phe was then back-extracted to stripping phase in stripping module. Experiments were conducted as a function of the initial feed concentration of equimolar Phe and l-aspartic acid (l-Asp) (5 mol/m³), feed pH (3–5), the carrier concentration (0.1–0.5 mol/dm³), and stripping acidity (0.1–2 mol/dm³). The effect of process variables on the separation factor of Phe/Asp and the possible transport resistances including aqueous-layer diffusion, membrane diffusion, organic-layer, and interfacial chemical reaction were quantitatively studied and discussed. The high separation factor (β) of Phe/Asp was obtained to be 18.5 at feed pH 5 and 2 mol/dm³ of strip solution (HCl). The extraction and stripping processes appear to rely on pH dependence of the distribution coefficient of amino acids in reactive extraction system. The separation factor (β) was enhanced in hollow fiber membrane (HFM) process compared with conventional solvent process, which was a result of the counter transport of hydrogen ions.     

Performance Evaluation of Nickel Separation and Extraction Process from Simulated Spent Cr/Ni Electroplating Bath Solutions by ELM Process Using LIX63 and PC88A

The study was conducted to investigate synergistic extraction of nickel from simulated spent Cr–Ni electroplating bath solutions by emulsion liquid membrane (ELM) process using 5,8-diethyl-7-hydroxydodecan-6-one oxime (LIX 63) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A) as carriers. The importance of ELM composition and the properties of simulated spent electroplating bath solution have been optimized to synergistically extract nickel. The important parameters affecting the nickel extraction efficiency and ELM stability, such as acid concentration, stripping solution type and concentration, extractant concentration, surfactant concentration, and phase ratio, were experimentally studied. Along with obtained results, higher than 99% of nickel was selectively extracted within 30 minutes from simulated electroplating bath solutions that their metal concentrations was in the range of 100–500 mg/L. in the optimum conditions. The higher separation factor value of nickel over chromium (β_Ni/Cr) was obtained as 898. As a result, the nickel extraction kinetic was found to depend on PC88A, since extraction mechanism of PC88A is slower than that of LIX63. So, the combined use of LIX63 and PC88A improved the selective extraction of nickel in that process.     

Investigation and characterization of PVA-g-AAc/Zol membranes for possible practical use in separation processes

Poly(vinyl alcohol) films were grafted with two monomers (acrylic acid and N-vinyl imidazole) using the gamma irradiation technique. The melting temperature (T_m) and glass transition temperature (T_g) of the grafted membranes were determined with respect to the grafting yield. The ability of these membranes to separate cobalt from nickel has been investigated. The diffusion of cobalt and nickel ions from the feed compartment to the receiver compartment depends on the grafting yield and the pH of the feed solution. Cobalt ions do not diffuse through the membrane when the pH of the feed solution is >4.5. Thus, the prepared membranes could be considered for the separation of cobalt ions from nickel ions. The temperature of thermal decomposition of pure PVA-g-AAc/Zol membrane, PVA-g-AAc/Zol membranes containing cobalt ions, and PVA-g-AAc/Zol membranes containing nickel ions are determined using TGA analyzer; it was shown that the presence of cobalt and nickel increases the decomposition temperature. Also the membranes bonded with cobalt ions are more stable than the membranes containing nickel ions.     

Electrodialytic separation of cobalt(II) and nickel(II) using liquid membranes based on tri-n-octylamine and trialkylbenzylammonium chloride

Electrodialytic separation of Co(II) and Ni(II) in the course of their transfer from 3–4 M HCl solutions into dilute solutions of various acids using liquid membranes that contain anion-exchange carriers was studied. The influence exerted on the metal transport rate and separation efficiency by the compositions of the feed and receiving aqueous solutions and of liquid membranes and by the electrodialysis current density was examined. Under optimal conditions, in metal recovery from a solution containing an equimolar mixture of 0.01 M CoCl₂ and NiCl₂, the separation factor β_Co/Ni is 147; when nickel in the feed solution is in excess, it reaches 330, and when cobalt(II) is in excess, it exceeds 400.     

Separation of cobalt and nickel by emulsion liquid membrane with the use of EDTA as masking reagent

EDTA was used to complex nickel to allow a separation of trace amounts of nickel and cobalt in an emulsion liquid membrane (ELM), which contains P204, L-113A, liquid paraffin, kerosene and HCl. Separation time is about 20 min. Separated cobalt and nickel can be easily determined by spectrophotometer. The favorable range of pH is 4.4–5.2. The total separation coefficient is over 220 and the recoveries of cobalt and nickel are more than 95% and less than 8%, respectively. Among the coexisting ions investigated, only copper ion affects the separation.     

Bismuth film electrode for simultaneous adsorptive stripping analysis of trace cobalt and nickel using constant current chronopotentiometric and voltammetric protocol

Bismuth film electrode (BiFE) is presented as a promising alternative to mercury electrodes for the simultaneous determination of trace cobalt and nickel in non-deoxygenated solutions. The preplated BiFE was employed under adsorptive stripping constant current chronopotentiometric and adsorptive stripping voltammetric conditions in the presence of dimethylglyoxime complexing agent. BiFE exhibited well-defined and undistorted signals with favorable overall resolution for cobalt and nickel cations, with the signals for both metal cations being practically independent of each other. The stripping performance of BiFE is characterized by good reproducibility (RSD 1.4% for Co(II), and 4.3% for Ni(II)), low detection limits of 0.08 μg l⁻¹ for Co(II) and 0.26 μg l⁻¹ for Ni(II) employing a deposition time of 60 s, in addition to good linearity. The non-toxic character of bismuth imparts the possibility of tailoring disposable and one-shot electrochemical sensors for decentralized environmental, clinical and industrial monitoring of trace cobalt and nickel.     

Micellar enhanced ultrafiltration of cadmium

The preconcentration of cadmium from aqueous colloid solution containing 8-hydroxyquinoline as extractant, laurylsulphate natrium as surfactant,n-butanol as co-surfactant was performed using micellar ultrafiltration technique. Filters with different pore size and materials were used to achieve a separation from liquid solutions. The cadmium recoveries depending on different conditions (pH, concentration of surfactant) were determined and the results are explained in the terms of colloidal parameters in the compare with the classical solvent extraction.     

Extraction of cobalt by the AOT microemulsion system

The extraction of cobalt by Winsor II microemulsion system was studied. In the bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT)/n-pentanol/n-heptane/NaCl system, AOT was used as a anionic surfactant to form microemulsion in n-heptane, n-pentanol was injected in the microemulsion as a cosurfactant. Co(II) was found to be extracted into the microemulsion phase due to ion pair formation such as Co²⁺(R–SO₃ ⁻)Cl. The influence of different parameters such as the volume ratio of aqueous phase to microemulsion, surfactant concentration, pH of the feed solutions, cosurfactant concentration as well as temperature on the extraction yield (E%) were investigated. The results showed that it was possible to extract 95% of cobalt by the AOT Winsor II microemulsion.     

Spectrophotometric determination of cobalt with 1-(2-pyridylazo)-2-naphthol and surfactants

A simple and highly selective spectrophotometric method for the determination of cobalt based upon the rapid reaction with PAN in the presence of surfactants and minute amounts of ammonium persulphate at pH 5.0 is described. The cobalt(III) chelate is made water-soluble by a neutral surfactant. Triton X-100, combined with sodium dodecylbenzene sulphonate (DBS). Iron(III), bismuth, tin(IV) and aluminium are masked with oxalate or citrate. Iron(II) must be absent. The other metal-PAN chelates, except that of nickel, are readily decomposed by EDTA. Up to 150 microg of nickel does not interfere. When larger amounts up to 625 microg are present, the absorbance can be corrected by measurements at two wavelengths. In a strongly acid medium (below pH 0.5) the nickel and other metal chelates are completely and instantaneously decomposed, while the cobalt(III) chelate remains unchanged. When, in place of EDTA, several ml of 6M hydrochloric acid are added after the colour development, nickel in quantities up to 1250 microg can be tolerated. A several hundredfold excess of zinc and manganese does not interfere. At 620 nm Beer's law is obeyed over the cobalt concentration range 0.4-3.2 microg/ml. The precision (95% confidence) is +/- 1.0 microg for 100 microg of cobalt. The molar absorptivity is 1.90 x 10(4) l. mole(-1) .cm(-1).     

Spectrophotometric determination of cobalt in iron-, cobalt- and nickel-base alloys

A spectrophotometric method has been developed for the accurate determination of cobalt at milligram level, based on oxidation of the cobalt(II)-EDTA complex with gold(III) chloride at pH 4.0-6.5 and 100 degrees and measurement of the absorbance of the resultant violet cobalt(III)-EDTA complex at 535 nm. The precision is not affected by the presence of several metal ions; including coloured ones such as Cu(II), Ni(II) and Fe(III). However, chromium(III) interferes since it also forms a violet complex with EDTA, but can be removed by separation with pyridine. Practical application of the method is illustrated by the determination of cobalt in alloys based on iron, cobalt and nickel. Over the cobalt range 8-52% the error ranges from 0.1 to 0.3%.     

Anion-exchange separation of cobalt from nickel

An anion-exchange method has been developed for the separation of cobalt from nickel, based on the observation that from a malonic acid solution containing sodium nitrite, cobalt is preferentially adsorbed by the exchanger but nickel passes through. The cobalt is eluted with 2M ammonium chloride in dilute ammonia solution. Prom an ammonium malonate solution containing chloride and nitrate, cobalt is quantitatively electro-deposited on a platinum cathode to give a bright, adherent deposit. Nickel is deposited from a solution of similar composition.     

Spectrophotometric determination of copper as a dithiocarbamate by flow injection analysis

Copper(II) ions (1–20 mg l^?1) are determined at 385 nm by injection into an aqueous carrier solution containing EDTA (0.05 M), carbon disulphide (0.03%) and diethanolamine (0.1%) in aqueous ammonia solution (0.5%) adjusted to pH 8.0. Chromium(VI) and, to a minor extent, iron(III) interfere. In the absence of EDTA, cobalt, iron(II), nickel, and manganese ions interfere but the sensitivity to copper is higher.     

Electrodeposition of zinc + cobalt alloys.: Relation between the electrochemical response and the composition and morphology of the deposits

The electrodeposition of cobalt and zinc + cobalt alloy in aqueous chloride solution has been studied on vitreous carbon electrodes under different concentration conditions (total concentration of metallic ion 0.1 mol dm ⁻³, chloride ion 1 mol dm ⁻³, pH = 3), particularly during the initial stages of the deposition process. For the alloy a relation has been found between the shape of the current-time transients, the morphology of the deposits, the stripping analysis and the results of X-ray microanalysis. The different alloy phases present in the deposits were identified using X-ray microanalysis data, stripping voltammetry results and literature data.The results indicate that the electrocrystallization of cobalt is inhibited even at very low concentrations of zinc in solution: voltammetric and galvanostatic results indicate that the deposition potentials always correspond to more negative values than those for cobalt deposition. This inhibition depends strongly on both the metallic ion ratio in solution and the applied overpotential (or current density). For Zn(II)/Co(II) ratios greater than 1/9, low overpotentials (or low current densities) favoured homogeneous and compact deposits that were rich in zinc and were mainly composed of γ-phases of zinc + cobalt alloy. However, when high overpotentials or current densities were used and/or when the Zn(II)/Co(II) ratio was very low (< 1/9), dendritic and non-homogeneous cobalt-rich deposits were obtained.     

Separation and preconcentration of cadmium ions in natural water using a liquid membrane system with 2-acetylpyridine benzoylhydrazone as carrier by flame atomic absorption spectrometry

A method for the determination of Cd in natural water by flame atomic absorption spectrometry after separation and preconcentration with a bulk liquid membrane containing 2-acetylpyridine benzoylhydrazone as mobile carrier dissolved in toluene has been developed. Effects of carrier concentration, volume of organic phase and pH of feed and receiving solutions on the flux for Cd across the membrane have been studied, being optimized by the modified simplex method. Optimum values for these variables were: carrier concentration of 0.84 g l⁻¹, 74 ml of toluene, pH 7.8 in the feed solution and 0.06 mol l⁻¹ of HNO₃ in the receiving solution, allowing a preconcentration factor of 17.9. The preconcentration step required 7 h to be accomplished. The recovery of Cd at optimum conditions was 101.0±2.7%, even with saline matrix, with good relative standard deviation (2.5%) at 95% confidence level. The detection limit of blank sample was 6 ng l⁻¹ of Cd. The method was validated using a certified reference material (TMDA-62) and also applied successfully to the analysis of Cd in four samples of seawater collected from the coast of Huelva (Spain). The relative errors of determinations were −7.6% for certified reference material and ranging between +2.4 and +7.1%, for samples of seawater (obtained between the results of the proposed and differential pulse anodic stripping voltammetry methods).     

液膜法分离钴和镍

钻、镍的分离一直受到关注，人们先后利用离子交换法［’‘、色谱法［’‘、苹取法「’‘等方法对它们在水溶液中共存时进行了分离．本文利用液膜法将共存的微量钻、镍一步分离开，同时富集了钻离子．利用液膜富集和分离钻、镍，大量工作是针对它们的富集；对其实施分离，报道甚少［‘·’‘，且分离效果不够满意．将EDTA作为掩蔽剂应用于钻、镍的分离，尚未见报道·仪器为721型分光光度计（上海第三分析仪器厂），PHS－ZC精密酸度计（上海雷磁仪器厂）．试剂为2一乙基已基单2一乙基己基磷酸酯（P507，中国科学院上海有机化学研究所），…