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

•Demonstrating the efficacy of microwave roasting on the properties of ZnO dust.•Analyze the phase transformations and structural changes by microwave roasting.•Offering a comparison between the microwave-assisted process and conventional methods.•The leaching percentage of germanium increase by 22 % after proper microwave roasting. 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. [Display omitted]