Investigation on the Extraction Process of Zinc and Germanium from Germanium-Rich Zinc Concentrate by Hydrothermal Method

A hydrothermal acid leaching process is employed to extract Zn and Ge from germanium-rich zinc concentrate (GRZC), and X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) are conducted to characterize the raw material, and it indicated that the main phase composition of the GRZC is sphalerite ZnS, accompanied by a small amount of pyrite FeS2. Subsequently, the effects of key process parameters on the leaching efficiencies of Zn and Ge are systematically investigated, including oxidant type, sulfuric acid concentration, liquid-to-solid ratio, hydrothermal temperature, hydrothermal duration, and grinding particle size. Through a series of single-factor experiments, the optimal hydrothermal process conditions are determined as follows: ferric sulfate as the oxidant, grinding particle size of 150 mesh, H2SO4 concentration of 2 mol/L, liquid-to-solid volume-mass ratio of 8: 1, hydrothermal temperature of 180 °C, and hydrothermal duration of 4 h. Under these optimized conditions, the leaching rates of Zn and Ge reached 93.57% and 93.81%, respectively. Phase analysis of the residue indicated that iron was effectively fixed in the solid phase. Compared with traditional leaching processes, the proposed hydrothermal method not only retains the high recovery rates of Zn and Ge but also significantly mitigates environmental pollution. Thus, it provides a novel and selective approach for the green and efficient utilization of GRZC, offering theoretical and technical support for its industrial application.