Isolation of Zinc, Copper, and Nickel from Glutamate Media by Solvent Extraction

Abstract

Solvent extraction scheme to isolate Zn, Cu, and Ni from glutamate media as hypothetical product of electric arc furnace dust alkaline leaching was developed, with concentrations being 17.6, 0.35, and 0.14 g/L, respectively. Three extractants were investigated: Cyanex 272, DEHPA, and Acorga M5640 selectively separated Zn, Ni, and Cu from each other. Aside from pH, parameters investigated included O/A ratio, extractant concentration in kerosene as diluent, and sulfuric acid concentration as stripping agent. pH was the most critical factor in determining the separation factor among three metals since pH controlled metal speciation in pregnant leach solution and regulated the interaction between metal ions and extractant. Based on previous studies, a flowsheet for Zn, Cu, and Ni isolation is proposed, which obeys the following sequence: Zn separated from Cu and Ni by Cyanex 272 (in pregnant leach solution at pH 8, log separation factor Zn–Cu 4.78, Zn–Ni 2.51), followed by Ni separation from Cu by DEHPA (in raffinate at pH 7, log separation factor Ni–Cu 3.92), and finally Cu extraction (in raffinate at pH 4, log distribution coefficient 3.19). Sulfuric acid was proved to be a suitable stripping agent with optimum concentrations of Zn, Ni, and Cu being 0.5, 0.25, and 2 M, respectively.