Efficient extracting germanium and gallium from zinc residue by sulfuric and tartaric complex acid

This paper introduces an efficient extraction method based on organic and sulfuric complex acid system, to achieve the clean recovery of scattered metals from zinc leaching residue. The tartaric (TAR) and sulfuric complex acid significantly improved the leaching of Ge but had little effect on the leaching efficiency of Ga. A maximum extraction efficiency of 93.1% of Ge and 84.3% of Ga, was obtained at a sulfuric acid concentration of 100 g/L, TAR concentration of 20 g/L, leaching time of 1 h, and temperature of 80 °C, with a liquid-solid ratio of 10 mL/g, and a mixing rate of 250 rpm. The leaching process and mechanism were investigated by XRD, SEM, EPMA and UV–Vis. The findings showed that TAR acid plays a key role in the dissociation of the mineral phase containing Ge, as well as the promotion of Ge dissolution. Compared with the conventional sulfuric acid system, the TAR containing complex acid could effectively promote the decomposition of some iron ore phases, like beaverite, in which Ge tends to be embedded and enriched, in association with Fe. Additionally, the improved leaching efficiency of Ge was attributed to the formation of soluble TAR-Ge complexes, which were confirmed by UV–Vis.