Utilization of industrial by-products as nutrients for gold bioleaching from waste random access memory

Gold (Au) recovery from waste random access memory (WRAM) was successfully achieved through a bioleaching process utilizing Chromobacterium violaceum. In this study, condensed distiller solubles (CDS), a by-product of industrial ethanol fermentation, was used to stimulate cyanide production, thereby enhancing Au dissolution. Prior to bioleaching, selective removal of base metals was conducted using 100 mM Fe₂(SO₄)₃, achieving 99.7 % copper removal without impacting Au content and effectively minimizing competition for cyanide ions. Subsequently, the treated material was used for the Au bioleaching. Bioleaching parameters, including pulp density, CDS concentration, glycine dosage, and pH, were optimized. The highest Au leaching efficiency of 98.6 % was achieved at WRAM pulp density of 10 g/L, CDS concentration of 8 %, glycine concentration of 3 g/L, and pH of 7.0. This integrated strategy, combining selective chemical pretreatment with CDS-enhanced bioleaching, presents a simple, cost-effective, and environmentally sustainable method for efficient Au recovery from electronic waste.