The evolution of Ge occurrence state and Si-Ge relationship during precipitation-dissolution enrichment to recover scattering metals from Zn concentrate leaching solution

Abstract

Germanium is one of the strategic scattering metals, and recovering a minor concentration of scattering metals from zinc concentrate’s leaching solution is an essential resource worldwide. Practically, neutralizing precipitation and the subsequent dissolution are implemented to enrich scattering metals from zinc leaching solution, facilitating further extraction of Ge and others. Silicon poses significant challenges to the efficient extraction of Ge due to their similar chemical property and the inert nature of silica. However, the evolution of the Ge occurrence state, especially its relationship with Si, during the precipitation and dissolution process in zinc hydrometallurgy is unclear, and there is a lack of an effective method to separate Si/Ge. This paper started with a detailed characterization and leaching behavior of Ge-enriched residue obtained from the plant, followed by a systematic investigation of Ge behavior in synthetic Si/Ge binary and Fe/Si/Ge ternary systems. Eventually, options for Ge enrichment from zinc leaching solution and Si/Ge separation are recommended, providing a practical framework for mitigating the negative influence of Si on the extraction of Ge in zinc hydrometallurgy. The significant findings are that Ge/Si are both presumably co-adsorbed by Fe(OH)₃ colloids upon neutralization to pH 5 of zinc leaching solution, which could be acid redissolved at the unrealistically high liquid-to-solid ratio of 200/1 at the practically meaningful liquid-to-solid ratio of 5/1, Si concentration is high enough to quickly condense and polymerize, resulting the formation of silica precipitate and permanent encapsulating of Ge into silica; interestingly, the Si-O-Ge bonding becomes weakened with pH increasing up to alkaline region and Ge leaching rate exceeding 80% at pH 10, effectively separating Ge from SiO₂.