Synergistic Roles of Direct Electron Transfer and ^• OH-Mediated Electrooxidation Mechanisms Using a TiOx-REM Electrode

This study investigates the electrochemical reactivity of a novel TiOx reactive electrochemical membrane (TiOx-REM) at pilot scale. The material is fabricated through a simple and scalable dip-coating process in which Ti4O7 powder is deposited onto a low-cost commercial silicon carbide (SiC) ceramic membrane serving as the substrate. The work focuses on distinguishing between direct electron transfer (DET) and hydroxyl radical (•OH)-mediated electrooxidation mechanisms. Oxalic acid (OA) and salicylic acid (SA) were selected as probe molecules for DET and •OH-mediated oxidation, respectively. The TiOx-REM’s performance was evaluated under various current densities (2–6 mA·cm–2) in recirculation mode. Significant mineralization rates were achieved, reaching 55% for OA and 42% for SA after 1872 mA·h. Electrolysis of an OA/SA mixture showed competitive behavior, with preferential degradation of SA (95% removal) over OA (52%), confirming the predominance of •OH-driven oxygen transfer over DET and demonstrating the greater efficiency of •OH attack for complex molecules. Energy consumption was below 0.05 kWh g–1COD, falling within the same order of magnitude as values reported in previous studies. These results underscore the potential of the TiOx-REM for effective wastewater treatment, particularly for complex matrices containing refractory contaminants.