Selective recovery of zinc from mining sulfuric liquor employing aqueous two-phase systems

•Selective extraction of Zn+2 from mining liquor in ATPS.•Reuse of ATPS components with high extraction efficiency.•Concentrated mining sulfuric liquor as a stock solution for in situ preparation of an ATPS.•Methodology applied for zinc recovery. Zinc recovery is extremely important due to the chemical and physical properties of this metal. Liquid-liquid extraction technique allows the selective recovery of zinc, leading to a high purity product. For the first time, a concentrated mining sulfuric liquor as a stock solution for in situ preparation of an Aqueous Two-Phase System (ATPS) in a hydrometallurgical process. This liquor is an overly complex solution with a high content of metal ions, especially Zn2+ and Mg2+. ATPS technique has already shown good results when compared to traditional solvent extraction techniques and can be considered a greener technique. The proposed method was optimized to obtain selective Zn2+ extraction by studying the parameters: the nature of the ATPS-forming polymer and their concentration in the stock solution; the effect of the salt added to the system; the concentration of extractant agent and the mass ratio between both phases. The optimized methodology made it possible to extract (91.5 ± 0.1)% of Zn2+ and (18.2 ± 0.1)% of Mg2+ from the liquor in three extraction steps. In the stripping step which used NaOH as the precipitating agent, about 65 % of Zn2+ was selectively recovered at pH = 6.00 and at pH = 9.00 the recovery of Zn2+was close to 80 %. Furthermore, for the first time it was proven that the polymer and the extracting agent (following the stripping step) are reusable components of the ATPS. A high extraction efficiency (%EZn ∼ 45 %) was achieved in one extraction step using the recycled extraction phase without any adjustment.