Gallium Electrowinning in Complex Solutions Produced by a Zinc Hydrometallurgy System

Gallium metal is scattered within Fankou lead-zinc ore, and the existing zinc hydrometallurgy process includes a leaching-extraction-electrowinning sequence to recover the gallium metal. However, impurities from lead-zinc ore have many adverse effects on the gallium electrowinning process such as strong hydrogen evolution reaction and low mass transfer rate, which lead to low current efficiencies and poor quality cathode gallium during gallium electrowinning process. In order to achieve efficient separation and recovery of gallium from zinc hydrometallurgy system, the effects of Al, Zn, and OH^- impurities on gallium electrowinning were systematically investigated in this study. The research results indicate that the Al impurity did not affect the cathode gallium product, but do affect the current efficiency of the gallium electrowinning process. The Zn impurity had a greater impact on the gallium electrowinning process than the other impurities, and deposition of Zn at the cathode led to a low current efficiency and directly affected the quality of the cathode gallium product. When the Zn concentration exceeded 1 g/L, the purity of the cathode gallium product was reduced to approximately 99%. Both excessively low and high OH^- concentrations had negative effects on the gallium electrowinning process, and the maximum value of current efficiency of gallium electrowinning is 54.14% when the alkali concentration was 120 g/L NaOH. The optimized main conditions for gallium electrowinning provide suggestions for realization of gallium production in zinc hydrometallurgy system.