10 - Process engineering for bioleaching of metals from waste electrical and electronic equipment

Abstract

Waste electrical and electronic equipment (WEEE), also known as electronic waste (e-waste), is considered as a secondary reservoir of metals because of their tremendous metal content. Conventional approaches for the extraction of metals from WEEE are basically pyrometallurgy and hydrometallurgy. However, both of these techniques have their own limitations, which have led to a shift toward biometallurgical technique. Biometallurgy or bioleaching technique, involving mostly acidophilic microorganisms, is an eco-friendly, cost-effective technique but is inherently time-consuming. This necessitated the need for the application of bioprocess engineering for the development of suitable bioreactors as mechanized systems for fast, efficient, and improved metal extraction from WEEE. The bioleaching process operated in batch or continuous mode in specialized bioreactors is reported to be promising on the quantitative extraction of various metals from WEEE. Metal extraction is further reported to improve by implementing the optimized process parameters. In these contexts, process engineering aspects, including the applicability of bioreactors and bioprocess engineering for bioleaching of metals employing chemolithotrophic and organotrophic microbes from WEEE are comprehensively presented. Mechanism of bioleaching, potential microbes, metal extraction ability, operational strategies, and process development with future research perspectives are outlined.