Investigating critical parameters for bioremoval of heavy metals from computer printed circuit boards using the fungus Aspergillus niger

Abstract

In this article, bioleaching of computer printed circuit boards (CPCBs) was examined using Aspergillus niger with one-step, two-step, and spent-medium bioleaching methods. Four effective parameters were optimized using response surface methodology (RSM) to achieve maximum recovery of Cu and Ni. Under optimal conditions – pH of 5.15, pulp density of 10 g/l, 1E+007 spores of A.niger, and 4.5 days for the sample adding time − 97% and 74% of Cu and Ni were recovered, respectively. Two-step bioleaching and spent medium bioleaching were respectively identified as the best methods for maximizing Cu and Ni recovery. Fungi deteriorate the sample mainly by it is chemical action like producing acids. Surface morphology results confirmed the metabolites produced by the fungus—corrosive chemicals—eroded the particles of the e-waste sample during the bioleaching time. The mapping and energy dispersive X-ray (EDAX) of the initial sample and the processed sample validated that bioleaching was quite effective. The overall results indicate that Cu and Ni from e-waste can be recovered through the bioleaching process using A. niger. The addition time (day) of the sample to the solution plays an important role in metal recovery using A. niger. Acid production by the fungi increases the metal recovery, while biocrystallization of heavy metals decreases the recovery. This paper proved the great potential of the biohydrometallurgical route mediate by Aspergillus niger strain for recovering heavy metals from electronic wastes under defined optimal condition, two-step process, 30 °C, and shaking rate of 130rpm.