A feasible strategy for the multi-stage separation of valuable metals from zinc hydrometallurgy leaching solution

Given the irreplaceability of tin, germanium, and indium in high-tech field, along with the widespread use of zinc in everyday life, effectively and efficiently recovering these metals from the leaching solution in zinc hydrometallurgy is crucial for advancing global science and technology and enhancing living standards. However, existing methods such as P204 extraction for indium, tannin precipitation for germanium, and zinc electrowinning encounter numerous unresolved challenges, leading to low recovery rates. To address these issues, this study presents a system that utilizes a trioctylamine-tributyl phosphate-sulfonated kerosene mixture for the selective extraction and separation of tin and germanium. Following this, oxalic acid was used as a precipitant to selectively isolate zinc from the raffinate. Finally, an ammonium sulfide solution was added to the precipitate to extract and separate indium. The results showed optimal separation yields of 99.54 % for zinc, 95.63 % for tin, 95.27 % for germanium, and 99.42 % for indium. Tin and germanium were stripped from the organic phase using sulfuric acid over three cycles, achieving maximum stripping yields of 91.52 % and 96.63 %, respectively. Characterization of the oxalic acid precipitate revealed only trace amounts of impurities, indicating it can be classified as high-purity zinc oxalate. Additionally, sulfur and certain arsenides can be eliminated by oxidizing roasting the sulfide precipitate in air, resulting in a solid phase primarily composed of oxides such as zinc, tin, iron, cadmium, and indium, with indium content reaching approximately 11 %. If zinc, iron, and cadmium are dissolved through a sulfuric acid neutral leaching process, products rich in indium and tin can be obtained.