Recent advancements in the catalytic electro-fenton process for sustainable and effective degradation of hazardous organic compounds in wastewater

Recalcitrant organic pollutants (ROPs), including persistent perfluorinated chemicals (PFCs) and polycyclic aromatic hydrocarbons (PAHs) from industrial activity, are widespread in wastewater and pose a significant environmental threat. Conventional treatment methods, such as activated sludge digestion, often struggle to degrade these stubborn contaminants due to their complex chemical structures and resistance to biological breakdown. This review examines advancements in electro-Fenton processes (EFP), a promising technology that utilizes iron-based catalysts (e.g., Fe²⁺/Fe³⁺ ions) and external electricity to enhance ROP degradation. Additionally, other Fenton-based processes—including the photo-Fenton process (pFP), sono-Fenton process (sFP), and photo-electro-Fenton process (peFP)—have demonstrated higher mineralization rates, as well as reduced operational costs and toxicity in treated wastewater. The total operating cost (expressed as cost per kilogram of COD removed) was assessed, including energy requirements (kWh per kilogram of COD removed), as well as the regeneration and reusability of the Fenton catalyst. Furthermore, novel kinetics based on the widely recognized EFP reaction mechanism were explored, providing clarity on the effects of critical operational parameters—such as pH, current density, dissolved oxygen concentration, and initial ferrous ion concentration—on hydroxyl radical (•OH) generation, pollutant interactions, and overall degradation efficiency. By critically analyzing existing research and highlighting promising optimization strategies, this work aims to reinforce EFP's position as a robust and sustainable solution for wastewater decontamination, paving the way for cleaner and healthier water bodies.