Novel approaches for solid waste utilization as sacrificial electrodes in wastewater treatment by electrocoagulation: a critical review

Utilization of waste materials as sacrificial electrodes for wastewater treatment (WWT) by electrocoagulation (EC) technology is a novel and promising application for closing resource loops. This work comprises the first known review focused on waste-derived electrodes for WWT, covering trends and research gaps. Analysis of the compiled literature shows that a wide range of wastewater types were successfully treated using waste-derived electrodes, including industrial, urban, and landfill leachate wastewater, as well as contaminated natural waters. Average removals ranged from 90 to 100% for most indicators, including organic loads, dyes, and heavy metals. A wide range of waste sources have been tested as electrode materials, including medical wrappers, metallic foils, machine shop turnings, beverage cans, and demolition waste, amongst other types. The works were primarily WWT-driven and not focused on waste management, and the majority of studies used bench-scale batch mode setups, suggesting this research area remains in the early stages. Electrode preparation from waste materials included varying degrees of processing, such as smelting and compression, and less intensive methods like cleaning and cutting, and direct reuse for smaller scraps via novel customized reactors with special submerged casings. Several drawbacks were noted, such as rapid passivation and inconsistent performance due to different scrap compositions. Important research gaps not addressed include streamlining scrap metal reuse in continuous pilot operations and the environmental and social impacts of this waste utilization framework. However, there is sufficient evidence to suggest that EC using waste-derived electrodes is a potentially disruptive application, and further works are strongly encouraged.