Environmental Impact Assessment and Bioleaching of Metals from Electronic Waste

Abstract

The electronic industry is the largest and fastest growing industry in the world. newlineThe increasing market penetration in developing countries, replacement market in newlinedeveloped countries and high obsolescence rate are prominent reasons for rapid growing newlineelectronic waste (E-waste) streams. The increasing volumes of E-waste, in combination newlinewith the complex composition of these items and the resulting difficulties in treating them properly, are the cause of concern. In present scenario, gravity of the E-waste problem has increased due to the heterogeneity of the metals present, because of which the reprocessing of electronic waste is quite limited. Bioleaching is an eco-friendly approach to recover metals; uses lesser energy as compared to roasting and smelting. Metal recovery from E-waste by bioleaching process showed a good potential in present study. Both single and newlinemixed cultures of cyanogenic bacteria were able to mobilize metals from E-waste of newlinePrinted Circuit boards (PCBs) with different efficiencies. Chromobacterium violaceum was newlinecapable to leach 79%, 69%, 46%, 9%, and 7% of Cu, Au, Zn, Fe, and Ag, respectively at newlinean E-waste concentration of 1% w/v. Whereas mixture of Chromobacterium violaceum and newlinePseudomonas aeruginosa exhibited leaching of metals more than 83%, 73%, 49%, 13%, newlineand 8% of total Cu, Au, Zn, Fe, and Ag, respectively. The optimum pulp density for the Ewaste newlineleaching with Aspergillus niger occurred at 1% (w/v) in one-step and two-step newlineleaching process. An increase in the pulp density led to a decrease in the leaching yields. At 1% pulp density, A. niger leached 86%, 74%, 80%, and 50% of Al, Zn, Cu and Fe newlinerespectively in two-step bioleaching. At 5% pulp density, the bioleaching efficiency for Al,Zn, Cu and Fe decreased to 50 60%, 20-25%, 25-30% and 30-35%, respectively in both newlineone step and two step bioleaching process. Mixed culture of acidophilic bacteria (MCAB) newlinewas used as inoculants in two step bioleaching to recover metals from metal concentrate of waste motherboards of personal computer