Recovery of Germanium via H<sub>2</sub>SO<sub>4</sub>/MnO<sub>2</sub> Leaching–NaAc Leaching/Na<sub>2</sub>CO<sub>3</sub> Precipitation–Tri(octyl-decyl) Amine Stepwise Solvent Extraction
Tao Jiang, Tao Zhang, Zhihong Liu
Abstract
Zinc and germanium are typically recovered by sulfuric acid leaching–tannin precipitation from germanium-bearing secondary zinc oxide (SZO). However, low recovery rate of Ge and large consumption of tannin are the obvious limitations. Herein, we propose a novel recovery process involving three main steps: (1) SZO is leached by H2SO4 solution (pH 2.0 ± 0.5), and MnO2 oxidation leaching is conducted for the residue (H2SO4: 10–40 g/L); (2) the oxidation leaching residue is treated with NaAc solution and, subsequently, Na2CO3 (or CO2) to precipitate lead and obtain PbCO3; the resulting solution is reused for the leaching process (step 2); (3) a tri(octyl-decyl) amine(N235)/tributyl phosphate/sulfonated kerosene system (no preacidification) is used to recover germanium from the oxidation leachate; the loaded organic phase is employed as an extractant to recover germanium from the leachate obtained in step 1. The raffinate could be sent to a zinc plant, and the loaded organic phase could be reused after stripping and washing. Up to 98% zinc and germanium leaching efficiencies, 98% germanium extraction efficiency, >90% lead recovery, and 97.87% purity PbCO3 product were achieved. Therefore, a relatively sustainable treatment involving closed-circuit circulation of leaching agents and extractants for SZO was proposed.