The Use of Liquid Extraction for the Purification of Solutions from the Nickel Production of JSC Kola MMC from Impurities

Abstract

Studies of the extraction of impurities of calcium(II), magnesium(II), boron(III), and chloride ions from sulfate-chloride nickel solutions have been carried out. As extractants, we used di-2-ethylhexylphosphoric acid (D2EHPA), di-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), trialkylamine (TAA), tributyl phosphate (TBP), and aliphatic alcohols: octanol-1, 2-ethylhexanol, and a by-product of its production—distillation residue (TPRD). According to the results of research, it was established that a mixture of 40% TAA in 2-octanone and TPRD exhibits a high extraction ability with respect to boron(III); the degree of boron extraction is 60.7 and 74.5%, respectively. The effect of the acidity of the aqueous phase and the composition of organic mixtures on the extraction ability of organophosphorus acids D2EHPA and Cyanex272 in the extraction of calcium(II) and magnesium(II) was studied. The optimal concentration of individual extractants was found to be 20 vol % in Escaid 100 solvent and the composition of the mixture (vol %) 15 (D2EHPA) + 5 (Cyanex 272). Individual D2EHPA predominantly extracts calcium(II): extraction of 62% Ca(II) and 15% Mg(II). When using Cyanex272, the extraction of magnesium(II) predominates: extraction of 59% Mg(II) and 20% Ca(II). It is shown that the extraction mixture has higher performance than individual extractants for the extraction of Ca(II) and Mg(II) from nickel solutions in the range of pH 3.0–3.5, at which the coextraction of nickel(II) is negligible. With increasing pH values, the extraction of Ca(II) decreases owing to the increasing extraction of nickel and the displacement of calcium by it from the organic phase. The results of the extraction purification of the nickel electrolyte of JSC Kola MMC with an extraction mixture in the Ni form to exclude pH adjustment at each stage of the process are presented. The experimental data obtained make it possible to conclude that the extraction purification of nickel electrolytes of JSC Kola MMC is promising, as a result of which pure solutions of nickel sulfate with a residual content of ≤0.010 g/dm³ B(III), Ca(II), Mg(II), and chloride ions were obtained.