Green electrochemical redox mediation for valuable metal extraction and recycling from industrial waste

Abstract

The global consumption of critical metals has significantly grown in recent decades. However, their natural sources are depleting; valuable metal recycling and recovery from industrial material flows is needed to guarantee reliable and sustainable access to metal production, which is in line with the concept of green manufacturing and process innovation to develop green chemical processes. Compared with conventional hydrometallurgical or pyrometallurgical processes, the electrochemical strategy has been extensively investigated and applied to the extraction of metals from industrial wastes, owing to its advantages of high efficiency and selectivity, easy operation, low energy consumption, and environment friendliness. This review provides an overview of the present status and outlook on electrochemical technologies, based on the electrochemical redox mediation mechanism, used to extract valuable metals from industrial wastes, including metallurgical slag, electronic scrap, spent batteries, spent catalysts, fly ash, alloy scrap, and nuclear waste, from the perspective of technical, mechanistic, and environmental impact. Special focus is given to electrochemical redox mediation technologies including electrochemical oxidation and reduction, slurry electrolysis, membrane electrolysis, molten salt electrolysis, electrokinetic separation, and external field-intensified electrochemical extraction. Furthermore, challenges and future strategies for electrochemical extraction of valuable metals from the perspective of a coupled green process and highly efficient regeneration/extraction, to technological improvement and environmental impact evaluation were proposed.