G. L. Pashkov

Application of binary extraction in hydrometallurgy

Abstract The results of a series of fundamental and applied researches into mineral acid and metal salt extraction by salts of organic acids and organic bases (binary extractants) have been generalized and systematized. The scientific study of binary extraction and distribution regularities in systems with binary extractants results in a wide spectrum of practical uses for new extractants with various properties in the technology of extraction, separation, concentration and refinement of non-ferrous and rare metals.

Nickel(II) Extraction from Sulphate Media with Bis (2,4,4‐Trimethylpentyl)Dithiophosphinic Acid Dissolved in Nonane

The paper presents data on nickel(II) extraction from sulphate solutions with nonane‐diluted bis(2,4,4‐trimethylpentyl)dithiophosphinic acid (HR). An IR spectroscopy method is used to examine the state of HR in nonane, and it was shown to exist as a monomer up to a concentration of 0.1 M. With a further increase in concentration, the acid forms associated species. The value of the concentration of the monomeric form is determined as a function of the total HR concentration in nonane in the range of 0.0–1.0 M. Based on the comparative analysis of the extraction equilibrium data together with information from the visible and IR absorption spectra of the nickel extract, the configuration of the nickel(II) complex in the organic phase was determined to be a low‐spin, square‐planar complex. The complex composition was found to correspond to the formula NiR2. The complex is hydrated, with the water very likely being bonded in the outer coordination sphere.

Investigation of the State of Bis(2,4,4-trimethylpentyl)dithiophosphinic Acid in Nonane in the Presence of Electron-Donor Additives

Abstract An IR-spectroscopy method is used to examine the state of nonane diluted bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HR) in the presence of various electron-donor additives (L). Trioctyl amine (TOA), n-octanol, trioctylphosphine oxide (TOPO), tributylphosphate (TBP), and triisobutylphosphine sulfide (TIBPS) were used as additives. The formation of hydrogen bonded complexes (H-complexes) via proton transfer and a [TOAH+][R−] ion pair was shown to occur in the system containing HR and TOA. For the other additives, except n-octanol, during the formation of the H-complexes, hydrogen bonding without proton transfer takes place. In the HR and n-octanol mixture H-complexes having a structure in which the acid exhibits both proton and electron-donor properties are formed. The concentrations of the monomers (CHR ) and the activity coefficients for the dithiophosphinic acid (γ HR(tot) ) in the presence of the additives were calculated. It was shown that CHR and γ HR(tot) depend essentially on the type of additive and that their values decrease when passing from n-octanol to TOA. The strength of the interaction between HR and L decreases in the series TOA > TOPO > TBP > TIBPS > n-octanol. This series coincides with the basicity series of the additives. An antagonistic effect takes place when zinc is extracted with the HR and L mixture, where L is the trialkyl amine (TAA), the trialkyl phosphine oxide (TAPO), TBP, and n-octanol. A decrease in extraction is observed in the series TAA > TAPO > TBP > n-octanol. This series coincides with the series for decreasing HR activity in the presence of additives. Thus a decrease in the extractant activity resulting from the interaction between HR and L is the determinant factor during zinc extraction with bis(2,4,4-trimethylpentyl)dithiophosphinic acid in the presence of the electron-donor additives.

Cobalt and Nickel Recovery from Sulfate Media Containing Calcium, Manganese, and Magnesium with a Mixture of CYANEX 301 and a Trialkylamine

Abstract Data are presented on the solvent extraction of nickel and cobalt from sulfate solutions imitating the composition of partially neutralized liquors from the leaching of oxidized nickel ores using mixtures of 0.4 M CYANEX 301 (HR) with 0.4–0.5 M C7–C9 fraction of a trialkyl amine (R′3N) as the extractant. Nickel and cobalt are efficiently extracted in the pH range 6.2–6.5 and separated from Mn, Mg, and Ca in the extraction step. The separation factors for Co and Ni are high (102–103). Due to the formation of the stable adduct [R′3NH]+[R]− between the extractant components, nickel and cobalt can be stoichiometrically stripped with H2SO4 (1.0–2.0 M), allowing the production of concentrated solutions (> 100 g/L of total Co and Ni). The nickel strip liquors contain only a small amount of free acid (pH 1.5–2.0) after purification from cobalt, so they can be further processed using traditional technologies. A proposed flowsheet for nickel and cobalt recovery from such leach liquors has the advantages of ease of production of concentrated nickel and cobalt strip liquors in sulfate media and the stability of the extractant and strip liquor to oxidation by air or oxygen compared to other variants of CYANEX 301 applications.

Investigation of the State of Bis(2,4,4‐Trimethylpentyl)dithiophosphinic Acid in Nonane and Toluene Solutions

An IR spectroscopy method is used to examine the state of nonane and toluene diluted bis(2,4,4‐trimethylpentyl)dithiophosphinic acid (HR) in the concentration range of 0.025–1.0 M. It was found that in contrast to the “inert” solvent nonane, in which marked self‐association of the dithiophosphinic acid due to the formation of intermolecular SH…S hydrogen bonds begins at an HR concentration of ∼0.1 M, in the aromatic diluent toluene this process begins at HRtotal ⩾0.4 M. This result is explained by the interaction of the proton of the S‐H group of the dithiophosphinic acid with the π‐electron system of the toluene aromatic ring and the formation of SH…π hydrogen bonds, preventing the self‐association of the organic acid. The presence of the monomeric, dimeric, and tetrameric forms of the extractant in solution was shown to best describe the bis(2,4,4‐trimethylpentyl)dithiophosphinic acid‐nonane system. The formation constants of the dimers (K2 = 0.78 ± 0.07) and tetramers (K4 = 3.42 ± 0.26) have been calculated.

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- searchers attention considerably. A review of results obtained by us on the use of binary extraction for technological applications is given in the present paper.

EXTRACTION OF INDIUM FROM SULFURIC ACID SOLUTIONS BY MIXTURES OF DI-(2-ETHYLHEXYL)PHOSPHORIC AND OCTANOIC ACIDS

ABSTRACT The extraction of indium from sulfuric acidic solutions by mixtures of di(2-ethylhexyl)phosphoric (D2EHPA, HR) and octanoic (HA) acids was studied. The state of D2EHPA in octanoic acid was investigated by IR-spectroscopy. It was shown that the nonideal behavior in this system occurs due to the partial dimerization of D2EHPA in organic phase. A strong antagonistic effect observed during the extraction of indium is caused by a HR–HA interaction at the expense of formation of intermolecular hydrogen bonds. Low indium concentrations and high excess of extracting agent, as well as application of “inert” diluents, result in the formation of In(HR2)3 compound in organic phase.

Peculiarities of the subchloride metallurgy of titanium

Conditions of the gas-phase reactions of reducing titanium tetrachloride to metal with aluminum subchloride are investigated in the approximation of equilibrium thermodynamics. It is established that the reduction process has a threshold character by three parameters: temperature, the amount of subchloride, and the radius of the metallic surface. Above the threshold values that were found, these parameters, along with the amount of inert gas in the gas mixture, unambiguously determine the yield of titanium and its aluminide. The conditions for obtaining aluminum-free titanium are determined. A comparative analysis of the advantages and disadvantages of subchloride and vapor-phase metallothermic methods of reducing titanium is carried out.

Extraction of nickel from sulfurous digestion solutions of oxide-type nickel ores by mixtures of monocarboxylic acids and Lix 54

The extraction of nickel from sulfurous solutions by various mixtures of monocarboxylic acids with β-diketone (Lix 54, 1-phenyl-1,3-decadione) in the presence of magnesium and calcium is reported. The extraction of nickel by the complex agents was proven to proceed more effectively than in the case of individual agents, which stipulated the formation of mixed complexes of nickel in the organic phase. The use of mixtures of various monocarboxylic acids (HR) with Lix 54 (HA) (molar ratio HR: HA = 1: 1−0.5) led to a substantial increase of the coefficients of nickel separation with the main contaminants (Ca and Mg). Using the mixtures of HR and HA, a technological scheme for the extractive isolation of nickel from a sulfurous solution with a high content of calcium (0.5−0.55 g/l) and magnesium (≥7 g/l) was developed. The resulting nickel concentrate was applicable for isolation by means of electrolysis or the preparation of nickel sulfate. The extraction degree was achieved at a level not less than 99.7%.

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 stri...