A review on sustainable approach of bioleaching of precious metals from electronic wastes

The development and widespread use of biomining are the result of the rising demand for metals. The depletion of organic resources, the abundance of low-grade metallic ores, and the vast production of metallic waste during mining and beneficiation processes have enhanced the need for biomining. Compared to high-energy-demanding and environmentally unsafe traditional mining techniques, the biomining approach is a revolutionary biotechnological technique. It is a sustainable alternative for extracting valuable metals from low-grade ores and waste materials by using microbes. Microbes have the capacity to catalyze biochemical processes, making it easier to solubilize and extract target metals from complicated mineral matrices. Notably, the redox processes, creation of organic or inorganic acids, and the release of complex agents are all necessary for biomining metals. Metal recovery is achieved from metallic grade ores, mine tailings, municipal solid waste disposal sites, incinerator ash, electronic wastes, tars, etc., all effectively processed via biomining. Biomining is also advantageous as it prevents the emission of harmful gases released from e-waste dump sites, including sulfur dioxides, nitrogen oxides, and carbon dioxide, which are of major concern. These gases may be released into the environment when open-air burning and acid baths are used for the recovery of valuable metals. Nowadays, both base metals (copper, and to a lesser extent, nickel and zinc) and precious metals (mainly gold) are extracted from ores and mineral concentrates in heaps, stirred-tank bioreactors, dumps, and other locations via microbial processing, or biomining. In the ongoing boom of the electronics industry, there is increasing pressure to handle huge amounts of electronic waste. This is also important considering the use of precious metals in the electronics sector and the need to extract them. The present review discusses biomining and bioleaching principles, methods, and also talks about e-waste in general, providing a worldwide overview. The review primarily concentrates on the use of biomining to recover valuable metals from electronic waste.