An overview of the potential of eco-friendly hybrid strategy for metal recycling from WEEE

Most waste electrical and electronic equipment (WEEE or E-waste) is recycle in the informal sector, even though—many more sophisticated recycling technologies are available. Mechanical recycling, usually the first step, can achieve maximum metal extraction, however has direct or indirect health effects, higher capital costs, and results in the loss of numerous secondary metal resources. The second most commonly used approach is the chemical method, which is much faster than the biological one, but chemical hydrometallurgy is metal-specific and also causes secondary pollution. The third approach—microbial metal recovery—is an eco-friendly and promising technology for WEEE processing. This comprehensive review evaluates and provides details of recent trends and developments in various technologies, including: physical, chemical and biological methods for the recycling and recovery of secondary resource materials, such as valuable metals. Although no single approach by itself is adequate, and as it cannot achieve ecofriendly high extraction rates of metals from WEEE, it is possible to develop a combined process, such as the initial use of mechanical treatment followed by leaching with either easily biodegradable reagents or organic acids produced by microbes—this would be more ecofriendly and economically feasible. Therefore, this article highlights specific gaps in the available technology for solving the e-waste issue, and recommends a hybrid strategy as the best available approach.