Use of Binary Extractants for Extraction and Separation of Noble Metals

The distribution of platinum metals and gold in the systems with binary extractants (salts of amines, quaternary ammonium bases (QAB), and organic acids) in toluene has been studied. It was shown that anion exchange mechanism complicated by interactions of components in organic phase is realized during metal extraction from 1–3 M HCl solutions. When acidity of aqueous phase decreases distribution coefficients of noble metals are decreased according to binary extraction regularities of mineral acids in (he systems with salts of trioctylamine and QAB. In the systems with caprylate and alkylphenolate of dioctylamine in the region of high pH values of aqueous phase, palladium distribution coefficients are increased due to formation in the organic phase of complexes with direct coordination of amine molecules to atoms of palladium and their stability is, obviously, higher than that of dioctylamine salts with corresponding organic acids. From the investigated binary extractants, the salts of quaternary ammonium bases and strong organic acids (alkylphosphoric, alkylbenzolsulfonic acids) are of great interest for practice. It was shown during extraction of Pt (IV), Pd (II), Ir (IV) and Au (III) chlorocomplexes by 0.1 M solutions of trialkylbenzylammonium alkylsulphonate, metal distribution coefficients in the acidic region are changed from 5 to 150 while distribution coefficients for Rh(III) and Ir(III) did not exceed 0.1 and that creates possibilities for separation of platinum metals. Noble metals are lightly stripped from organic phase by water that it is impossible for initial systems with mineral salts of quaternary ammonium bases. The comparison of the systems with binary extractants and TBP has shown the advantage of binary extraction for obtaining more concentrated stripping solutions.     

Reductive-Sorption Methods for Noble Metals Extraction from Solutions

Active carbons combining the properties of ion exchangers and reductive sorbents, take a special place among sorption materials for noble metal extraction from solution. Electrochemical mechanism is the specific feature of the noble metals sorption by active carbons. In the present work on the natural phenomena of reductive sorption of electropositive metals (Cu sub-group, platinoids) using synthetic active carbons of SCN or SCS type are studied. Synthetic carbons have been indicated to extract electropositive metal ions both from concentrated and diluted media (solutions of hydrometallurgy conversion, sewage and rinse flushes of galvanic production, etc.)

Synthetic carbons were shown to have high selectivity in extracting gold and silver from alkaline cyanide solutions of gold-containing raw material processing. Synthetic carbons of SCN type make it possible to extract palladium and platinum from hydrochloric acid solutions up to the overflow decantation level 100-fold against the background. Using the technique of internal electrolysis (systems: Carbon/Zn, Carbon/Al) gives the possibility, with reductive sorption method, to select rhodium and ruthenium from solutions of complex salt composition with the formation of metallizing carbon granules.

It was indicated that the selectivity and high extraction of these metals from fluid media are connected with the possibility of using sorption to reduce ions to metallic phase formation. Carbons coated by noble metals or metal complexes can be used as a catalyst. The proposed approach (reductive sorption) and applied new materials (synthetic carbon) give the possibility to solve important tasks of noble metal hydrometallurgy, environmental protection, and catalyst production.     

The extraction of noble metals by macrocyclic compounds

This is analytical article devoted to the extraction of noble metals by acyclic analogs of crown ethers (podands) covering the period from 1980 to 2007. Most attention is given to the extraction of noble metals by phosphoryl-containing podands from hydrochloric acid solutions. The efficiency of extraction depends mostly on the number and nature of donor centers in a reagent molecule. It is shown that the use of podands as noble metal extractants does not help to solve the problem of selective separation of noble metals from complex solutions.     

The extraction of noble metals by macrocyclic compounds: II. The extraction by crown compounds

Our review on the extraction of noble metals by macrocyclic compounds, i.e., by crown ethers containing donor atoms O, S, and N, continues. The literary data for the period from 1984 to 2008 are summarized. It is noted that no systematic investigations have been carried out until now. On the whole, the information is incomplete. The solution compositions are far from technological ones, and the chemical state of extracted ions in aqueous solutions is not taken into account. It is emphasized that there is only desultory information on the reextraction in the literature. The problem of selectivity for noble metal extraction by crown compounds is discussed.     

Mechanism and kinetics of sulfite-thiosulfate dissolution of gold

Dissolution mechanisms of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating the medium) in alkali and acidic media are described. The conditions of intensifying the dissolution process are evaluated. The reaction rates are investigated. Based on the obtained data, it is concluded that it is rational to apply the sulfite-thiosulfate solvents of noble metals to recover them from concentrates under the usual conditions.     

Binary Extraction in Hydrometallurgy

Abstract

Results obtained during technological application of binary extraction (extraction by salts of organic acids and organic bases) for recovery and separation of non-ferrous, rare, noble and associated metals are presented in the paper. The method of extraction of copper, especially from leaching solutions of oxidised ores, with the use of tertraoc-tylammonium dialkyldithiophosphate has been developed- The binary extractant is characterized by high separation coefficients of copper and iron, large capacity according to copper and high rate of its extraction and stripping by solutions of ammonia. The technology has also been tested in the sorption-extraction mode.

Possibilities of the use of binary extractants for the purification of sulphate solutions containing copper and iron, and also chloride solutions containing iron, have been discussed. The technological scheme developed for the purification of aluminium from iron in chloride solutions with the application of carboxylate of trialkylamine is characterized by a more concentrated strip solution obtained in comparison with the system based on trialkylamine.

The technology of the extraction of indium from Zn-containing sulphate solutions with the use of binary extraction by dialkylphosphate of trioctylamine has been developed and adopted at the Chetaybinsk zinc factory. The use of hydrochloric acid has been avoided in the stripping stage by the application of binary extractant. The technological scheme worked out for the extraction of cadmium from Zn-containing sulphate solutions with the use of carboxylate of trialkylamine allows one to achieve objectives of cadmium recovery in the form of chloride anion, cadmium concentration and conversion with the generation of cadmium sulphate solution suitable for cementation and also simultaneous purification of zinc sulphate solution from chloride ion with the production of concentrated solution of natrium chloride. Possible uses of binary extractants for the recovery of molybdenum as well as extraction and separation of platinum metals are also discussed.

In hydrometallurgy the extraction processes are most effectively applied to solve the following tasks:

?extraction (and usually simultaneous concentration) of valuable components in processing solutions with complex composition; - separation of elements with similar properties and their isolation into corresponding products;

?purification of aqueous technological solutions from elements - impurities; synthesis of inorganic compounds using, stripped solutions with definite element composition;

?purification of industrial sewage.

Obviously, an extractant is selected depending on the objectives. A search of extractants is a continuing process and a wide circle of specialists in the field of extraction chemistry and technology, organic synthesis, physical chemistry, and others take part inthis process. Recently processes of the so-called binary extraction have attracted re- searcher's attention considerably. A review of results obtained by us on the use of binary extraction for technological applications is given in the present paper.     

Cyanex有机膦类萃取剂在贵金属溶剂萃取中的研究和应用

介绍了近年来Cyanex有机膦类萃取剂在贵金属溶剂萃取中的研究状况及应用进展，展望了该类萃取剂在贵金属分离提取中的应用前景。     

Thermodynamics of interaction between sulfite-thiosulfate solutions and noble metals

The thermodynamic probability of dissolution of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating of the solution) is considered. The influence of impurities and catalysts (divalent copper, elemental sulfur, oxygen access into the solution, and ammonia) is evaluated. Theoretical calculations of reaction rates are performed. As a result of theoretical investigations, a conclusion about the usefulness of applying sulfite-thiosulfate solvents of noble metals from ores and concentrates is made.     

萃取分离Pt,Rh,Pd,Ir的工艺研究

实验研究了从铂族金属溶液中草取分离Pt，Pd，Rh，Ir的工艺，较好地分离除去了残金属离子；提出了采用铜试剂＋氯仿螯台萃取Pd的新方法．实验证明，采用连续萃取工艺取代部分沉淀法，可提高铑的直收率（＞85％），简化工艺，缩短生产周期．     

Purification of Cobalt Solutions from Manganese by Extraction with Mixture of Organic Acids

extraction on pH and composition of the aqueous phase, and concentration of extractants have been investigated. D2EHPA was shown to extract the metals, but monocarboxylic acids took part in extracting the complex formed by means of additional solvation.

Electronic adsorption spectra of extracts of cobalt and manganese di (2-ethylhexyl) phosphates in SMA show that there are mainly octahedral complexes in extracts. It confirms the formation of a mixed extracted complex in organic phase. In contrast to the systems with “inert” solvents, manganese oxidation by air does not occur due to stabilization of manganese (II) in octahedral complex. The conditions of purification of cobalt chloride and cobalt sulphate solutions from manganese were determined and tested on a pilot scale. According to the technological scheme the cobalt solution after purification from iron was purified from manganese by extraction with 0.6-0.8 M D2EHPA in a monocarboxylic acids (C₁-C₉ solution. Scrubbing of extracts from cobalt and stripping of manganese were conducted by hydrochloric or sulhpuric acids depending on the type of initial solution. Purified cobalt solution practically does not contain manganese and cobalt recovery was 99.5%. The suggested scheme of purification has been applied at the Norilsk Mining and Metallurgical plant for processing of manganese by-product.     

Extraction of Nonferrous Metals and Arsenic from Thin Dusts of Copper Fuel Production by Combined Technology

Russian Journal of Non-Ferrous Metals - Thin dust from copper smelting production is a valuable raw material for the extraction of heavy nonferrous, noble, and rare metals. One feature of dusts is...     

Extraction of nickel,cobalt and other metals [Cu,Zn, Fe(III)] with a commercial β-diketone extractant

The extraction of nickel, cobalt, copper and zinc from ammoniacal solutions of ammonium carbonate or ammonium sulphate by solutions of Hostarex DK-16 in kerosene has been investigated as a function of phase contact time, aqueous-phase pH and organicphase reagent concentration. Besides copper, Hostarex DK-16 also partially extracts iron (III) from moderately acidic solutions whereas nickel, cobalt(II), copper and zinc are extracted from neutral or ammoniacal ammonium sulphate and ammonium carbonate solutions. Extraction decreases in the following order of metals: Cu > Co > Ni > Zn. Cobalt(III) is not extracted, but the complex of cobalt(II) with Hostarex DK-16 is slowly oxidized to a cobalt(III) complex which cannot be stripped even when 10 N sulphuric acid is used. Absorption spectra for cobalt complexes with Hostarex DK-16 (purified by preparative thin-layer chromatography) in benzene also suggest oxidation of cobalt(II) to cobalt(III) in the organic phase. Nickel, cobalt(II), zinc and copper can be stripped easily from organic solution with dilute solutions of sulphuric acid. Hostarex DK-16 extracts iron very slowly, nickel moderately rapidly and copper, cobalt(II) and zinc rapidly. Slope analysis and extraction isotherms suggest that the complexes CuR₂, NiR₂ ·HR and CoR₂·HR are present in the organic phase. Nickel can easily be separated from cobalt by extraction with Hosterex DK-16 after oxidation of cobalt in aqueous ammoniacal solution by hydrogen peroxide; however, LIX 64N seems to be a more promising extractant owing to the higher extraction of nickel under analogous conditions and the poorer extraction of zinc in comparison with Hostarex DK-16.     

Extraction Separation of Scandium，Iron and Lutetium with Isopropyl Phosphonic Acid Mono（1－hexyl－4－ethyl）OctylEster

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Metals extraction with carboxylic acids. II. Effect of temperature on the extraction of Cu,Ni, Co(II), Zn,Fe(III) and Co(III)

The relation between the extraction temperature and the coefficient of distribution of various metals between aqueous phases and kerosene solutions of Versatic acid has been investigated.Using a mathematical procedure, it was established that with increasing temperature the distribution coefficient changes if the composition of the metal-Versatic complex is temperature-dependent. In the case of trivalent iron a reversible increase in distribution coefficient occurs when the temperature is raised. It is suggested that this is due to a reversible depolymerization of the complex. The distribution coefficient of trivalent cobalt also increases with temperature, but here the increase is irreversible, possibly because the number of covalently bound carboxylate groups changes.In general, the distribution coefficient of metals which do not show variations in the composition of their complexes with Versatic, such as Cu, Ni, Co(II) and Zn, does not change appreciably with temperature.     

The extraction of iron(III) from aqueous acid solutions by di(2-ethylhexyl)phosphoric acid

The extraction of iron(III) from aqueous solutions containing sulphuric, hydrochloric and nitric acids by di(2-ethylhexyl)phosphoric acid (DEHPA) in kerosene has been investigated under different conditions. As a result, it is found that although extraction is dominated by an ion-exchange reaction, the rate of iron(III) extraction from sulphuric acid solutions to reach equilibrium is relatively slow in comparison with that from hydrochloric or nitric acid solutions. In the extraction from aqueous solutions containing hydrochloric or nitric acid, however, the DEHPA combines with iron(III) according to the solvating reaction at higher aqueous acidity. From studies on the rate of the extraction from sulphuric acid solutions, examined under non-equilibrium, it is confirmed that dependencies of extraction rate on hydrogen ion and DEHPA concentrations are in the first and inverse first orders, respectively. The hydrolyzed species is considered to interpret the extraction mechanism in this system.     

Extraction With Liquid Surfactant Membranes

Abstract

Liquid surfactant membranes, noted as a novel separation technique, have potential applications in many fields, especially in extractive metallurgy. High separation efficiency with the membranes can be achieved by using type I and type II facilitated transport mechanisms to maximize both the flux through the membranes and the capacity of the internal receiving phase for the diffusing species. Mass transfer models for both facilitated transport mechanisms are developed by taking into account the mass transfer and the reactions both inside and outside the emulsion globules, and perturbation solutions to the resulting nonlinear equations are presented. A Carrier Facilitated Transport Factor, defined as the ratio of the extraction rate constant for type II facilitation to that of type I facilitation, is proposed to account for the effect of carriers in the membrane on the extraction rate. Model predictions are in good agreement with the experimental data on batch extraction of acetic acid and auric chloride from their respective aqueous solutions.     

活化-溶剂萃取技术分离铑的研究进展

铑在氯化物溶液中的化学性质十分复杂，它的分离与纯化一直是贵金属提取冶炼中的难题。概述了近十年来国内外活化．溶剂萃取技术分离铑的研究进展。指出含铑料液经某些试剂活化处理后，能提高铑的被萃取性能，并讨论了溶剂萃取体系中加入SnCl2，SCN^-，l^-，Br^-等不同试剂的活化条件及铑的分离回收情况。指出了活化．溶剂萃取技术分离回收铑的应用发展前景。     

Extraction of heavy metals and ammonium from waters by unsaturated fatty acids and their soaps

The process including heavy metals and ammonium extraction from waters by an extraction medium based on unsaturated fatty acids and their soaps, up-concentration of the extracted metals, and regeneration of the extraction medium was investigated. The process corresponds to current hydroxides-precipitating, coagulation and biotreatment processes. The two synergistically effective ways are described: the basic process with the pretreatment of feed water by sodium or calcium hydroxide and extraction with unsaturated fatty acids, and the advanced process exploiting the extraction through sodium and/or calcium unsaturated fatty acids soaps. Oleine as a commercially available extraction medium was used. High bonding capacity and metals removal efficiency, fast kinetics and selectivity for the extraction process, and the self-adjustment of the pH value after the extraction process, as well as the high up-concentration of the metals salts limiting to saturated solutions, and the complete regeneration of the extraction medium were reached. Heavy metals hydroxides precipitation behaviour was investigated. Chemical and hydrophobisation metals-bonding mechanisms for the extraction process were observed. Regeneration and up-concentration behaviour, Oleine stability and organics residues in the water phases were investigated.     

A Review on Separation of Gallium and Indium from Leach Liquors by Solvent Extraction and Ion Exchange

Considering the growing demand for In(III) and Ga(III) for the manufacture of advanced materials, it is necessary to develop efficient separation processes for recovery of these metals from primary and secondary resources. In the present work, separation of In(III) and Ga(III) from different aqueous mediums by solvent extraction, ion exchange, and solvent-impregnated resins/gels was reviewed. Although complete separation of In(III) from Ga(III) is possible using ion exchange or solvent-impregnated resins/gels, these methods are limited in industrial applications due to low adsorption capacity for metals. Solvent extraction with amines, acidic, and neutral extractants is commonly employed to separate these two metal ions. Amines and neutral extractants can extract both In(III) and Ga(III) and then these metals are separated by selective stripping. By contrast, solvent extraction with acidic extractants including commercial and synthetic extractants results in complete separation of In(III) and Ga(III). Compared to common commercial extractants such as D2EHPA, PC88A, Cyanex 272, and Cyanex 301, synthetic extractants offer higher extraction and separation efficiency, but extraction kinetics and stripping efficiency in these systems should be improved in the future.     

A Review on the Separation of Niobium and Tantalum by Solvent Extraction

Niobium and tantalum are found together in natural minerals. Leaching with concentrated acid solution or alkaline roasting followed by water/dilute acid leaching results in a solution containing these two metals. In this work, we reviewed the extraction and separation of Nb(V) and Ta(V) from leach liquors in the absence and presence of hydrofluoric acid by acidic, neutral extractants and amines. Several solvent extraction systems were compared in the light of the requirement of hazardous chemicals, extraction/separation efficiency, and stability/solubility of extractants. Since the cationic species of Nb(V) and Ta(V) are unstable in the aqueous solution, the application of acidic extractants for extraction and separation of these metals is limited. Amines can extract Nb(V) as well as Ta(V) irrespective of the presence of fluoride ion but the separation of these metals from the loaded amines should be carried out in stripping process, resulting in process complexity. Another disadvantage encountered for amine is related to high viscosity in extraction process. Neutral extractants are considered as promising extractants which are effective to separate Ta(V) and Nb(V) from either non-fluoride or to moderate fluoride ion concentration in terms of extraction, separation and stripping efficiency. Compared to the traditional methyl iso-butyl ketone (MIBK) based system, methyl isoamyl ketone (MIAK) is found to be a promising extractant to separate Nb(V) and Ta(V).