Reviving Riches: Unleashing Critical Minerals from Copper Smelter Slag Through Hybrid Bioleaching Approach

Due to the emission of hazardous chemicals and heat, the traditional smelting method used to extract critical minerals from ore and mine slag/tailings is considered bad for the environment. An environmentally friendly procedure that can stabilize sulfur emissions from mine waste without endangering the environment is bioleaching. In the present study, sequential oxidative (Oxi) and reductive (Red) bioleaching of acid-pretreated copper smelter slag using iron-oxidizing/reducing Acidithiobacillus ferrooxidans was applied to investigate critical minerals’ recovery for the dissolution of copper smelter slag. In this batch flask experiment, up to 55% Cu was recovered on day 11 during the Oxi stage, which increased to 80% during the Red stage on day 20. A sequential oxidative and reductive bioleaching of an acid-pretreated copper smelter slag at pH (1.8) and 30 °C positively affects the extraction of Cu (80%), Zn (77.1%), and Al (65.3%). In contrast to the aerobic bioleaching experiment, the reduction of Fe3+ iron under anaerobic conditions resulted in a more significant release of Fe2+ and sulfate, limiting the development of jarosite, surface passivation, and the subsequent loss of metal recovery due to co-precipitation with Fe3+. Overall, the Oxi-Red bioleaching process combined with acid pretreatment showed promising results toward creating a method for recovering valuable metals from metallurgical waste that is economical and environmentally beneficial.