A Critical Review of Electrode Materials, Reaction Mechanisms, and Reactor Designs in Electrocoagulation for Wastewater Treatment

Electrocoagulation (EC) is a well-established wastewater treatment technique that has been extensively investigated for a variety of wastewater contaminants. This paper reviews electrocoagulation (EC) as a wastewater treatment method. Recent developments in reactor geometries and scale-up, electrode material and modification, reaction mechanism and kinetics, and operating parameters (current density, pH, conductivity, inter-electrode distance, temperature) are summarised and explained. The review covers coupled, hybrid EC-based systems, including comparative performance by wastewater type, and evaluates techno-economic and environmental factors influencing field implementation. The Key findings are: (1) iron- and aluminum-based electrodes still prevail, but non-metallic and modified electrodes show promise for improved selectivity and reduced passivation; (2) primary removal mechanisms are anodic electro-dissolution followed by hydrolysis and adsorption/sweeping flocculation, and kinetic behavior varies by pollutant category and reactor operation mode; (3) reactor design (A/V ratio, electrode geometry, flow regime) exerts a pronounced impact on mass transfer, energy consumption, and scale-up potential; (4) practical limitations are passivation of electrodes, energy consumption, and sludge management. The review concludes with targeted research trajectories (anti-passivation material design, standard pilot-scale test procedures, lifecycle assessments, biological and membrane system integration approaches) and outline where future work will optimally fill knowledge gaps.