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

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 Zn(2+)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 similar to 45 %) was achieved in one extraction step using the recycled extraction phase without any adjustment.

Automated summary

The importance of zinc recovery due to its chemical and physical properties led to the study of liquid-liquid extraction technique for selective recovery. Using a concentrated mining sulfuric liquor as a stock solution, an Aqueous Two-Phase System (ATPS) was prepared in situ, showing promising results in extracting Zn2+. The optimized methodology achieved high Zn2+ extraction efficiency and demonstrated the reusability of the polymer and extracting agent in the ATPS.