Enhancing the extraction of germanium from zinc oxide dust through microwave roasting and the underlying mechanism

In this study, a microwave roasting-sulfuric acid leaching process was proposed to increase the efficacy of extracting germanium (Ge) from Ge-bearing zinc oxide (ZnO) dust. Microwave energy has a selective cleavage effect on ZnO dust. Proper microwave roasting of Ge-bearing ZnO dust can fracture the ZnO dust, reduce the particle size, increase the particle size uniformity and specific surface area, and transform the phase of Fe₄Ge₃O₁₂, thus improving the leaching percentage of Ge from the ZnO dust. The optimized conditions were as follows: microwave heating temperature of 290°C, microwave heating time of 5 min, liquid-solid ratio of 6 mL/g, leaching time of 4 h, initial concentration of sulfuric acid of 9 mol/L, and leaching temperature of 60 °C; the leaching percentage of Ge was 84.4 %. In contrast, the leaching percentage of Ge was found to be 62.4 % under the same conditions without roasting. In this study, we described a promising strategy for leaching Ge from ZnO dust via the microwave roasting-sulfuric acid leaching process.