Improving bioleaching of Cu and Zn from e-waste with graphene and activated carbon with Acidithiobacillus bacteria

The rapid growth of e-waste generation poses significant environmental hazards and represents a potential source of valuable metals. This study investigates the bioleaching of copper (Cu) and zinc (Zn) from television printed boards (TVPCBs) using Acidithiobacillus ferrooxidans (A. ferrooxidans) and Acidithiobacillus thiooxidans (A. thiooxidans), both separately and mixture of them. The use of graphene and powdered activated carbon as catalysts was investigated to enhance metal recovery. Response surface methodology (RSM) with a central composite design (CCD) was applied to optimize critical variables, including initial pH, graphene concentration, and activated carbon concentration. The mixed bacterial culture improved Cu recovery, reaching values 18 % higher than those obtained with A. ferrooxidans alone and 15 % higher than with A. thiooxidans alone. Cu recovery increased by approximately 20 % when using graphene and powdered activated carbon as catalysts. Under optimal conditions (initial pH 2.0, 1.5 g/L graphene, and 1.5 g/L activated carbon), 100 % simultaneous recovery of Cu and Zn was achieved within 12 days. Catalysts greatly enhanced bacterial activity, which was evidenced by the increased metal recovery. This effect may be attributed to the increased concentrations of sulfate and ferric ions.