Bioleaching of zinc from e-waste by A. aquatilis in fluidised bed bioreactor

Technological advancements with the use of new-generation electronic devices and accumulated electronic wastes (e-wastes) raise environmental concerns. E-waste, especially mobile phone Printed Circuit Boards (PCBs) is a rich source of metals. Bioleaching, a microbe-mediated metal dissolution process is employed for the recovery of metals. The operational parameters like particle size, inoculum percentage (v/v) and e-waste load (w/v) were optimised for Zn bioleaching by Alcaligenes aquatilis in shake flasks and fluidised bed bioreactor (FBR). The e-waste feed particle size of 0.175 mm and 5% inoculum was found to be the optimum for Zn bioleaching in both the shake flask and FBR. The optimum e-waste load was 5% in the shake flask and 2% in FBR. The maximum recovery of Zn was 0.6 mg/g (13.73%) in the shake flask and 0.57 mg/g (13%) in FBR, implying that FBR exhibits similar efficiency of Zn bioleaching as in the shake flask. Further three sequential batch runs increased the recovery to a maximum of 1.66 mg/g from 4.37 mg/g Zn present in the PCBs ie., 38% Zn recovery. This shows that efficient bioleaching of Zn on a larger scale can be achieved with sequential batches and applied for the simultaneous recovery of metals from PCBs.