Bioleaching of GaAs metal hydroxide sludge: a biohydrometallurgical alternative to conventional acid leaching

The economically important metal gallium (Ga) is considered to be a critical raw material with a potentially high supply risk. The industrial semiconductor production process generates multiple waste streams that contain Ga in economically significant amounts. This study explores bioleaching for Ga recycling from a waste metal hydroxide sludge originating from industrial GaAs-wafer production. Previous studies have demonstrated that hydrometallurgical recycling of this sludge provides an effective approach for gallium recovery. Furthermore, it was shown that reducing the ferric iron in the leaching solution has a beneficial effect on downstream processing, enabling less consumption of chemicals. Based on these results, the present study investigates the potential of biohydrometallurgy as an innovative recycling method for Ga recovery, addressing both ecological and economic concerns associated with traditional acid leaching techniques. The results indicate promising outcomes in terms of Ga extraction efficiency and reductions in harmful chemical use, making a compelling case for further research and development in this field.