Solvent extraction of cadmium from sulfate solution with di-(2-ethylhexyl) phosphoric acid diluted in kerosene

In the present paper, solvent extraction process has been used for extraction of cadmium from sulfate solution using di-(2-ethylhexyl) phosphoric acid (D2EHPA) with 1% isodecanol in kerosene diluent expected from industrial effluents or leaching of ores/secondary materials. Different process parameters such as pH, contact time, extractant concentration, O/A ratio etc. were investigated. Results demonstrated that quantitative extraction of cadmium was feasible from 4.45 mM cadmium feed solution in single stage at equilibrium pH 4.5, time 2 min and O/A ratio 1:1 with 0.15 mM D2EHPA. The extraction mechanism of cadmium from sulfate solution by D2EHPA in kerosene could be represented at equilibrium by Cd²⁺ + 3/2 (H₂A₂)_org ⇔ CdA₂(HA)_org + 2H⁺. The loading capacity of 0.15 mM D2EHPA in sulfate solution was determined to be ∼ 8.9 mM cadmium. The loaded cadmium was effectively stripped using 180 g/L sulfuric acid. The metal or salt could be produced by electrolysis or crystallization from the stripped solution.     

Recovery of Al(III) and Fe(III) from mixed chloride solutions containing platinum(IV)

The sorption of Fe(III), Al(III) and Pt(IV) from the individual and mixed chloride solution was investigated by using PC88A resin. With the increase of HCl concentration to 5 M, the distribution coefficient of Fe decreased slowly, while that of Al decreased rapidly and the distribution coefficient of Pt was nearly zero in our experimental range. Batch experiments showed that it was possible to extract both Fe and Al simultaneously by adjusting HCl and PC88A resin concentrations. However, continuous extraction chromatographic experiments indicated that simultaneous sorption of Al as well as Fe was difficult in our experimental range. Two extraction chromatographic steps would extract most of Fe and 90% of Al from the mixed solution, while Pt was not extracted. Extraction chromatography of the mixed chloride solution with PC88A resin was found to be fast and simple.     

The extraction of copper(II) and iron(III) from chloride and sulphate solutions with LIX 64N in kerosene

A comparison has been made of the extraction of Cu(II) and Fe(III) from chloride and sulphate solutions with LIX 64N in kerosene. The effects on extraction of pH, anion concentration, and temperature were examined, and attention was paid to the ionic strength of the aqueous media, some of which contained aluminium and magnesium; extraction was carried out under ‘practical’ rather than ‘ideal’ conditions. Extraction of both Cu and Fe was enhanced from chloride solutions compared with sulphate; although separation of Cu from Fe was slightly reduced, extraction of Cu from chloride liquors appears to be applicable to commercial leach solutions.     

Comparative studies on Y(III) and Dy(III) extraction from hydrochloric and nitric acids by Cyanex 572 as a novel extractant

Extraction of Y(III) and Dy(III) from hydrochloric and nitric acids by Cy-572 in kerosene was studied. The factors affecting the extraction were separately investigated. The stoichiometry of the extracted species was deduced on the basis of slope analysis method. Evaluation of extraction equilibrium and stripping investigation was studied as well as saponification effect of Cy-572. The composition of the extracted metal species in the organic phase was found to be $\overline{{[\text{MA}}_3·{\left(\text{HA}\right)}_3]}$ for Y(III) or Dy(III) in both media. 1.0 mol/L HCl is the best stripping agent for each metal ion from the studied acidic media in one step. Saponified Cy-572 does not exhibit any selectivity towards the extraction of Y(III) or Dy(III) from both HCl and HNO₃ solutions. Based on the obtained results, the data were compared and the separation feasibility between lanthanides and Y(III) in the two media was discussed.     

A comparative study on extraction of Fe(III) from chloride leach liquor using TBP, Cyanex 921 and Cyanex 923

A comparative study on extraction of Fe(III) from the HCl leach liquor of low grade iron ore tailings has been carried out using Tri-n-butyl phosphate (TBP), Cyanex 921 and Cyanex 923 in distilled kerosene. The percentage extraction of iron increased with increasing HCl and extractant concentrations. The extracted species in each case was found to be HFeCl₄·S. The extraction isotherms for the above extractants indicated quantitative extraction of Fe(III) in 3-stages at O:A ratio of 3:2 with TBP, and in 2-stages at O:A ratio of 1:1 with Cyanex 921 and Cyanex 923. The stripping studies of the loaded organic phases were carried out with 0.4 M HCl. The stripping isotherms indicated 2-stages at O:A ratio of 5:2 for TBP, and 3-stages at O:A ratio of 2:3 for Cyanex 921 and Cyanex 923. From the extraction studies, the extraction efficiency of the extractants for Fe(III) was in the order TBP < Cyanex 921 < Cyanex 923. Although Cyanex 923 was found to be the best extractant, the percentage stripping of Fe from the loaded Cyanex 923 was the least. The stripping of Cyanex 923 was 94.9%, but with TBP and Cyanex 921, it was 99.8% and > 99.9%, respectively.     

用三烷基氧化膦从氰化浸出液中萃取低浓度金

研究了三烷基氧化膦(TRPO)-磷酸三丁酯(TBP)-煤油萃取体系对氰化浸金液中低浓度金(Ⅰ)的萃取和反萃取能力,结果表明,尽管TRPO体系中添加TBP对金(Ⅰ)的萃取率影响很小,但一定量的TBP能提高体系的反萃效果。考察了料液pH值、硫酸锂浓度等因素对萃取率的影响,探讨了不同的反萃温度、反萃相比对负载有机相中金(Ⅰ)的反萃效果。结果表明,采用TRPO-TBP-煤油组成的有机相,对金(Ⅰ)质量浓度为9.5 mg/L、盐析剂硫酸锂浓度为1.0 mol/L的碱性氰化液在相比A/O=1∶1条件下进行萃取时,金(Ⅰ)的单级萃取率可达95%以上;反萃温度越高,相比(A/O)越大,反萃效果越好,可以将大部分金(Ⅰ)反萃出来。     

The extraction of Zinc(II) from sulphate and chloride solutions with kelex 100 and versatic 911 in kerosene

Zinc(II) is extracted from sulphate or chloride solutions by Kelex 100 (HX) in kerosene, comparable extraction taking place under more acid conditions from chloride media. The addition of Versatic 911 (HA) leads to synergistic enhancement of extraction; equilibrium studies with the mixed extractants indicate that a mixed complex of the form ZnX₂ · (HA)₂ is extracted, and infra-red spectra suggest that Versatic is present as a solvating agent. The effect of chloride ion concentration on extraction was examined, and tracer studies showed that chloride takes no part in the constitution of the extracted zinc complex.     

Ethyl-bis-triazinylpyridine (Et-BTP) for the separation of americium(III) from trivalent lanthanides using solvent extraction and supported liquid membrane methods

The present paper deals with the solvent extraction and supported liquid membrane studies on Ln(III)/An(III) separation using ethyl-bis-triazinylpyridine (Et-BTP) as the extractant. The solvent extraction studies involved evaluation of a) diluents, b) phase modifiers, c) stripping agents and d) role of feed acidity. Though reasonably high separation factor values were obtained when Et-BTP was used along with α-bromo carboxylic acids, the mixtures could not be used for liquid membrane studies due to unsatisfactory stripping. On the other hand, a combination of Et-BTP with chlorinated cobalt dicarbollide (CCD) in nitrobenzene resulted in significant Am(III) mass transfer when used in the solvent extraction as well as SLM studies. Improved transport, membrane stability, and decontamination from lanthanides were observed when the organic phase diluent composition was 60% nitrobenzene + 40% n-dodecane. Using 0.02 M Et-BTP along with 0.005 M CCD in 60% nitrobenzene + 40% n-dodecane, the SLM studies on a mixture of ²⁴¹Am, ¹⁵²Eu and ¹⁴⁷Nd in a feed containing 0.1 M HNO₃, indicated quantitative Am³⁺ transport in 3.5 h with co-transport of about 8% Nd³⁺ and 22% Eu³⁺.     

Solvent extraction of heavy metals contained in phosphoric acid solutions by 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline in kerosene diluent

The solvent extraction of zinc, cadmium and chromium contained in 5.5 mol/L phosphoric acid solutions (30% P₂O₅) was investigated using 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline-Kelex 100® as extractant and treated kerosene as diluent. At organic-to-aqueous phase ratio (1/1) and at room temperature, 58% of zinc, 34% of chromium and 15% of cadmium were recovered in 240 min. In order to improve the kinetics of extraction, a modifier reagent was added to the organic phase. The addition of n-decanol (10 vol.%) increased the rate metals extraction by reducing the equilibrium time from 240 min to 30 min, along with 60% recovery of metals. Extraction of metal ions increased with increasing aqueous phase pH. The pH_0.5 values difference of 0.1 M with Kelex 100® indicates the possible separation of cadmium, zinc and chromium. Increasing the concentration of Kelex 100® increased the percentage extraction of metal ions. The loading capacity values were found to be 83%, 80% and 71% for zinc, chromium and cadmium, respectively, at 0.4 M Kelex 100® concentration, indicating that the extractant is highly selective for the metal ions considered.     

Solvent extraction-separation of La(III), Eu(III) and Er(III) ions from aqueous chloride medium using carbamoyl-carboxylic acid extractants

N,N-dibutyldiglycol amic acid(HLI) and N,N-dioctyldiglycol amic acid(HLII) were synthesized and characterized by conventional spectroscopic methods. These molecules were examined as extractants for extraction-separation of La(III), Eu(III) and Er(III), as representative ions of light, middle and heavy rare earths, from aqueous chloride solutions. The analysis of the extraction equilibria revealed that the extracted species of lanthanum and europium ions by both of the extractants had a 1:3 metal to ligand ratio. It was suggested that erbium ions were extracted into the organic phase via the formation of Er(LI or II)2Cl complexes. The effect of the organic diluents on the extraction-separation efficiency of the studied rare earths by HLI and HLII was investigated by comparing the results obtained in dichloromethane and carbon tetrachloride. Regardless to the diluent used, the order of selectivity presented by the investigated extractants was Er(III)Eu(III)La(III). It is noteworthy that, a significant enhancement in separation of the studied rare earths by the extractants was achieved in their competitive extraction experiments with respect to that obtained in single component extraction experiments. Applicability of the extractants for the removal of rare earth ions from spent Ni-MH batteries was tested by removal of La(III), Eu(III) and Er(III) ions from simulated leach solution of such batteries.     

Mixed solvent systems for the extraction and stripping of iron(III) from concentrated acid chloride solutions

The extraction of concentrated iron(III) from acid chloride solutions has been investigated with methyl isobutyl ketone (MIBK), tri-n-butyl phosphate (TBP), di(2-ethylhexyl) phosphoric acid (D2EHPA), and their mixtures in various proportions, at different acid concentrations. On comparing the extraction of iron(III) with mixed and individual extractant, it was found that both D2EHPA-MIBK and D2EHPA-TBP mixtures exhibit synergism, the latter having better extraction ability. The synergistic coefficients, at different initial acid concentrations for each mixed extractant system, were evaluated and compared. An increase in the concentration of MIBK and TBP in the mixed organic resulted in higher synergistic coefficient. The stripping of iron(III) from loaded D2EHPA was found to increase with the strip feed acid concentration, while from loaded organic mixtures, it initially increased and then decreased. Stripping of iron(III) from D2EHPA-MIBK loaded solvent is better then D2EHPA-TBP. The extracted iron species formed and the stripping reactions have been proposed. Ultraviolet visible spectra of the stripped organic phase support the result and the proposed mechanisms.     

Solvent extraction of Ti(IV), Fe(III) and Fe(II) from acidic sulfate medium with di-o-tolyl phosphoric acid-benzene — hexan-1-ol system: A separation and mechanism study

The extraction of Ti(IV), Fe(III) and Fe(II) with di-o-tolyl phosphoric acid (HDTP, HA)-benzene-20% hexan-1-ol system was studied as function of contact time, concentrations of extractant in the organic phase and of H₂SO₄ in the aqueous phase, and temperature. The order of extractability under identical conditions is: Ti(IV) > Fe(III) ? Fe(II). The relative separations of these metal ions are also dependent on the above four factors. The maximum values of the separation factors, $\text{β}{}_1\text{=}\text{E}{}_{\mathrm{<mtext>Ti(IV)</mtext>}}{}^0\text{E}{}_{\mathrm{<mtext>Fe(IlI)</mtext>}}{}^0\text{= 175}$ at 0.10 M HDTP and 3.50 M H₂SO₄ concentrations, and $\text{β}{}_2\text{=}\text{E}{}_{\mathrm{<mtext>Ti(IV)</mtext>}}\text{E}{}_{\mathrm{<mtext>Fe(II)</mtext>}}{}^0\text{= 7800}$ at 0.10 M HDTP and 0.50 M H₂SO₄ concentrations, indicate that the separation of Ti(IV) from iron seems to be promising if iron is present in the divalent state. The mechanisms of extraction are discussed.     

Solvent extraction of rhodium from aqueous solution of Rh(III)–Sn(II)–Cl system by TBP

In this paper, the results of a systematic study on the solvent extraction of rhodium with TBP in hydrochloric acid are given. The optimum extraction conditions are as follows: The amount of added stannous chloride is four times that of Rh according to the mole ratio of Sn and Rh, the temperature of complex reaction 60°C, aging time 2 h, phase ratio 1:1, contact time 5 min. A highly efficient method of stripping Rh from the loaded organic phase of TBP is also proposed. The percentage of stripping may reach to 100% through one stage with 4 M hydrochloric acid containing chlorine. The mechanism of extracting Rh(III) with the addition of stannous chloride is described and the reaction equation of extraction is deduced.     

Development of a microfluidic-chip system based on parallel flow for intensified Gd(III) extraction from nitrate media using cationic extractant

Microfluidic solvent extraction (micro SX) of gadolinium was conducted using a mono- and di-ester mixture (MDEHPA) as the cationic extractant. A microfluidic YY channel was fabricated using CO₂-laser technique in a glass microchip used as the extraction system. Compared with batch extraction, extraction kinetic is found fast, and extraction equilibrium is attained within 15 s. Stoichiometry of the extracted complex is found to be Gd(NO₃)₃·3MDEHPA using log–log plot method. Additionally, the operating parameters and overall volumetric mass transfer coefficient $\left(k_{\mathrm{L}}\alpha \right)$ were investigated to determine the mass transfer performance. Optimal condition of microextraction for gadolinium using response surface methodology was determined (feed solutions 31 mg/L adjusted to pH value 2.5, extractant concentration 2.9 vol% and extraction time 13.5 s). In optimal condition, gadolinium extraction yield is obtained 95.5%. Findings of this study approve simplicity, portability, effectiveness, swiftness, and environmental friendliness microfluidic solvent extraction process and reveal that micro SX is useful in the field of extraction strategic metals present at low concentrations, which are otherwise not technically amenable or economically feasible to extract using current traditional methods.     

The behaviour of lix 63 in the extraction of Cu(II) and Fe(III) from chloride media

Investigation of the extraction of copper from chloride solutions using the commercial Lix reagents has shown that Lix 64N extracts small amounts of chloride whereas Lix 65N does not. The extraction of chloride is due to a minor component of the Lix 64N, the aliphatic α-hydroxyoxime Lix 63. This latter reagent extracts copper as a neutral chlorocomplex, probably of the form CuCl₂ · HCl or CuCl₁ · 2HCl₁ at low pH values and extracts the metal ion directly at higher pH. Under similar conditions iron is apparently extracted as the mono-chloro complex, entering the organic phase as FeCl · Lix₂. Following this behaviour, it appears that, in a solvent extraction operation involving chloride leach solutions, Lix 65N, which exhibits no tendency to extract chloride ions, might be a preferable extractant.     

Separation of In3+ and Fe3+ from sulfate solutions using D2EHPA in a laminar microreactor

A microfluidic solvent extraction method is put forward to solve the problems existing in the conventional solvent extraction of indium, such as large waste of extractant, fire hazards, etc. Experiments were performed in a series of microreactors to separate In³⁺ and Fe³⁺ from sulfate solutions using D2EHPA as the extractant. The effect of main parameters such as different contact times, microchannel sizes, interface to volume ratios and pH values on the indium extraction efficiency was investigated. The results show that the smaller the channel size, the more the beneficial diffusion and mass transfer. Specifically, in a microchannel, with a size of 100?μm?×?50?μm?×?120?mm, almost 100% extraction efficiency was reached with contact time about 0·5?s. The mean mass transfer rate can be as high as 0·291?g?m^??2?s^??1, and the ratio of mean mass transfer rate of In³⁺ to that of Fe³⁺ can be as high as 29·76.     

Studies on the recovery of uranium from phosphoric acid medium using synergistic mixture of (2-Ethyl hexyl) Phosphonic acid,mono (2-ethyl hexyl) ester (PC88A) and Tri-n-butyl phosphate (TBP)

This paper describes the extraction of uranium from aqueous phosphoric acid medium using (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and tri-n-butyl phosphate (TBP) individually as well as their synergistic mixture in different diluents. The various experimental parameters are investigated to optimize optimise the suitable extraction conditions. Results indicate that a synergistic mixture of 0.90 M PC88A + 0.15 M TBP in xylene, can be used for the extraction of uranium from low phosphoric acid medium. Back extraction studies reveals that among all the common strippants used, 0.50 M solution of (NH₄)₂CO₃ was most suitable. The synergistic mixture of 0.90 M PC88A + 0.15 M TBP as extractant system and 0.5 M (NH₄)₂CO₃ as strippant is used to recover uranium from a conditioned wet process phosphoric acid and from actual radioanalytical waste generated during uranium analysis by modified Davies–Gray method. The recovery is found to be around 80% from conditioned WPA whereas better than 90% from modified Davies–Gray waste.     

Uphill permeation model of gold(III) and its separation from base metals using thiourea derivatives as ionophores across a liquid membrane

This work deals with carrier-facilitated membrane transport of Au(III) from chloride media across a polymer-immobilised liquid membrane (PILM) using as organic reagents N-(thiocarbamoyl)benzamide derivatives and N-benzoylthiourea derivatives, denoted as 2a–c and 3a–f, respectively. Both the composition of the organic membrane solvent and the type of carrier have a marked effect on gold permeation. Recovery and permeability of gold using 2a–c and 3a–f across a PILM proceed in the following order: 3e≈3d≈3c?3f>3b≈3a≈2a≈2b≈2c. In view of the performance of these carriers, 3c was selected as a metal receptor for detailed studies of Au(III) in permeation. A model is presented for the permeation of Au(III) (61 μM) in 0.5 M Cl⁻ at pH 2.5 using 3c as a membrane carrier. The mathematical equations describing the rate of permeation are derived to correlate the membrane permeability coefficient with diffusional and equilibrium parameters. The mass transfer coefficient was calculated from the described model as 1.1×10⁻⁵ m s⁻¹, and the thickness of the aqueous boundary was later calculated to be 65 μm. Several polymeric supports were tested for impregnation of the organic extractant, and Durapore (Millipore) afforded the maximum flux for Au(III), yielding a value of 1.1×10⁻¹⁴ mol m⁻² s. The relationship between flux and support characteristics is derived and a mathematical equation is presented. Of the several diluents used, cumene had the most satisfactory performance in terms of PILM stability and metal transport. Of the different reagents used, 0.5 M sodium thiocyanate in 0.5 M NaCl at pH 2.5 served most efficiently as the stripping agent. More than 80% of the Au(III) could be readily separated using 3c in the presence of various metals such as Cu(II), Fe(III) and Zn(II).     

Use of mixed-metals isotherm and log–log McCabe Thiele's diagram in solvent extraction—A case study

Nickel and cobalt are invariably associated with other transition element impurities like copper, zinc, iron, etc. It is essential to remove these impurities in order to attain the high standards of purity required for specific applications. Solvent extraction is a well-tested route for this purpose. The present paper describes the application of two novel concepts, viz. mixed-metals isotherm and log–log McCabe Thiele's (MT) diagram in solvent extraction. Mixed-metals isotherms can be applied to a system in which two metal ions compete for a single extractant. If these two metal ions are required to be extracted as a group, mixed-metals isotherms can precisely predict their behavior. Log–log MT diagrams are useful in determining the requirement of the number of stages in counter current extraction, especially when the feed and raffinate concentrations differ by several orders of magnitude. The two concepts have been successfully applied to develop a process for the separation of high purity cobalt and nickel from ocean nodules leach liquor.