From Wastewater Treatment to Energy Recovery: Advances and Perspectives in Electrochemical Oxidation—A Critical Review

Abstract

Electrochemical oxidation (EO) is a versatile, advanced oxidation process (AOP) for the treatment of persistent and recalcitrant pollutants in wastewater. This critical review examines recent advances in EO, with emphasis on oxidation mechanisms, electrode materials, reactive species, reactor configurations, operational parameters, and energy efficiency. Direct electron-transfer reactions and indirect oxidation mediated by electrogenerated reactive species are discussed in relation to pollutant degradation, mineralization, and process selectivity. Attention is given to active and non-active anodes, classified according to their interaction with electrogenerated oxidizing species and their catalytic behavior toward organic pollutant oxidation, as well as to electrode stability and oxygen evolution competition. The effects of parameters such as current density applied potential, pH, electrolyte composition, conductivity, temperature, mass transfer, and electrolysis time on treatment performance and energy consumption are critically evaluated. The review also examines the integration of EO with microbial electrochemical technologies, anaerobic digestion, hydrogen production, and other resource-recovery pathways, distinguishing direct electrochemical energy recovery from downstream energy generation. Photo-electrooxidation is considered as a complementary light-assisted electrochemical approach. Importantly, the available evidence does not yet support generalized claims of positive net energy recovery, highlighting the need for complete system-level energy balances. Finally, key challenges related to real wastewater, electrode durability, transformation products, toxicity, scale-up, techno-economic feasibility, and environmental sustainability are discussed, together with future perspectives for efficient and scalable EO-based wastewater treatment.