Bioleaching of Metals from Printed Circuit Boards

Abstract

Electronic waste or E-waste refers to the discarded electrical or electronic devices which have neared their useful life. Because of the toxicity and carcinogenicity of some compounds, the proper management and safe disposal of these electronic wastes have become serious challenges in recent years. Printed Circuit Boards (PCBs) are found almost in every other electronics these days, hence the present study focuses on bioleaching of metals from Printed Circuit Boards (PCBs) using bacterial and yeast strains (Stenotrophomonas maltophilia, Bacillus sp. and Candida tropicalis) isolated from heavily contaminated soil samples. A two-step bioleaching procedure was followed for maximum mobilization of metals. The isolated strains were able to mobilize metals from PCBs with different efficiencies depending on their ability to utilize the E-waste a carbon source when cultivated in minimal media. Bioleaching potential of isolated microbes on eight heavy metals (Cu, Ni, Mn, Pb, Fe, Cr, Zn & Co) in the sample were studied using AAS and SEM analysis before and after the two-step bioleaching process and found to be efficient. The study concludes that isolated bacterial and fungal species from the study can be further standardized with regard to the growth parameters and used on large scale to carry out the efficient recovery of metals that can help in recycling E-waste in the digital world.