L. K. Nikiforova

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.

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.

Manganese extraction with mixtures of bis(2,4,4-trimethylpentyl)dithiophosphinic acid and trioctyl phosphine oxide

ABSTRACT It was shown that a strong synergistic effect (S ≈ 4000) takes place when extracting manganese (II) from sulfate solutions with mixtures of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (CYANEX 301) and trioctyl phosphine oxide (TOPO. The synergistic effect is caused by the formation of the mixed complex Mn-HR-TOPO. Analysis of the manganese partition between organic and aqueous phase as well as of the IR and electron paramagnetic resonance spectra of the extracts showed that manganese forms a hexacoordinated complex with the dithiophosphinate ions and TOPO with an octahedral geometry. The composition of the complex can be presented as MnR2∙2TOPO. Examples of the possible use of the CYANEX 301 and trialkyl phosphine oxide (TAPO, CYANEX 923) mixtures when processing manganese-containing liquors are given.

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%.