Performance of Fluidized-Bed Bioreactor in Copper Bioleaching from Printed Circuit Boards using Alcaligenes aquatilis

Technological advancements have led to a demand for modern electronic gadgets and outdated ones discarded as electronic waste (e-waste). The printed circuit boards (PCBs) constitute a significant portion of these wastes that contain hazardous substances that mandate e-waste management. The rich source of precious and base metals makes it a resource for urban mining. Bioleaching, a process of biohydrometallurgy, an alternative to conventional heat and chemical-based metal recovery processes, can be efficiently applied for metal recovery from these wastes in an environmentally safe manner. The process parameters like particle size, inoculum size (v/v), and e-waste load (w/v) for bioleaching of Cu from PCBs in a Fluidized-Bed bioreactor (FBR) and shake flask using Alcaligenes aquatilis as bioleaching agent were optimized. The bioleaching of 47.99% and 37.54% of Cu from PCBs were achieved in shake flask and FBR, respectively. The optimal conditions of Cu bioleaching were 0.175 mm particle size, 5% (v/v) inoculum, and 2% (w/v) e-waste load with 169.45 mg/g and 132.55 mg/g of Cu recovery in shake flask and FBR at 84 and 96 h, respectively. Further, the Cu bioleaching was carried out in sequential batches to improve the recovery with the optimized conditions. There was a prominent increase in the cumulative %Cu bioleaching of about 80.02% after three sequential batch experiments from PCBs with an initial Cu concentration of 353.09 mg/g. The present study proves that sustainable heterotrophic bioleaching of Cu can be efficiently achieved in a Fluidized-bed bioreactor operated in sequential batch mode by Alcaligenes aquatilis . Graphical Abstract