Leaching behavior of germanium presented in different phases from zinc oxide dust under atmospheric acid leaching conditions

Recovering germanium from zinc oxide dust (ZOD) produced from Pb-Zn smelter is an important pathway to extract germanium. However, the leaching efficiency of industrial germanium production is not satisfactory (usually less than 75 %). Therefore, the leaching behavior of Ge in different phases was discovered in this work. Ge in the ZOD mainly occurs in oxide, sulfide, silicate, and solid insoluble. The potential decides the oxidative dissolution of sulfide. The leaching recovery of zinc and germanium were 90 % and 80 % with oxidant, and 78 % and 80 % without oxidant, respectively. The effect sequence of oxidant type on the Zn leaching efficiency was MnO2 > H2O2 approximate to oxygen > air, but the type and addition of oxidant had no obvious effect on the leaching recovery of germanium. The final pH of leaching slurry limits the dissolution of oxide and hydrolysis-polymerization of impurity ions (such as Fe(III) and Si). Decreasing the final pH is beneficial to the leaching reaction of Zn and Ge. The germanium presented in oxide and sulfide is easy to leach, while the leaching of germanium existed in silicate and solid insoluble is relatively difficult. The structure of aluminate can be destroyed effectively using a 40 g/L HF solution. When the leaching percent of SiO2 is 86.82 %, the leaching recovery of Ge is 96.57 %. For the ZOD with higher content of Fe and Si, germanium leaching is negatively correlated with the content of Fe and Si in the ZOD. The results provide a scientific basis for improving the leaching recovery of germanium.