Using liquid extraction to clean JSC «Kola MMC» nickel production solutions from impurities

Studies of the extractive recovery of Ca(II), Mg(II) и B(III) impurities from nickel production solutions at JSC «Kola Mining and Smelting Company» were conducted. As extraction agents, we used di-(2-ethylhexyl)phosphoric acid (D2EHPA), di-(2,4,4-trime-thylpentyl)phosphinic acid (Cyanex 272), trialkylamine (TAA), tributyl phosphate (TBP), aliphatic alcohols: octanol-1, 2-ethylhexanol and a by-product of its production – heavy product of 2-ethylhexanol distillation (TPRD). In order to assess the effect of conditions used to extract impurities from solutions, laboratory studies on the effect of aqueous phase acidity, extraction agent concentration, composition of organic impurities on their extractability were conducted. According to the research results, it was found that the optimal concentration of individual extraction agents is 20 vol.% each in the Escaid 100 solvent, and the mixture composition is 15 vol.% D2EHPA + 5 vol.% Cyanex 272 at Ca(II) and Mg(II) extraction. Individual D2EHPA predominantly extracts calcium (II): extraction of 62 % Ca(II) and 15 % Mg(II). When using Cyanex 272, the extraction of magnesium (II) predominates: extraction of 59 % Mg(II) and 20 % Ca(II). It was found that the extraction mixture has higher performance than individual extraction agents for Ca(II) and Mg(II) extraction from nickel solutions in the pH range of 3.0÷3.5, at which Ni(II) coextraction is negligible. With increasing pH values, Ca(II) extraction decreases due to the increasing extraction of nickel and the displacement of calcium by it from the organic phase. It was established that a mixture of 40 % TAA + + 60 % 2-octanone and heavy product of 2-ethylhexanol distillation exhibits high extraction ability with respect to B(III): the degree of boron extraction is 60.7 and 74.5 %, respectively. The paper provides the results of the extraction purification of the nickel electrolyte from JSC «Kola Mining and Smelting Company» with an extraction mixture in the Ni-form to exclude pH adjustment at each stage of the process. Based on the results of the studies conducted, a flowchart is recommended for obtaining pure NiSO4 solutions with a residual total B(III), Ca(II), Mg(II) and Cl– content of £0.010 g/dm3 .