PEDOT Particle Electrodes in a 3D Electrochemical Reactor for Degradation of Organic Contaminants in Water

Current electrochemical systems for contaminant degradation using conventional two-dimensional (2D) electrodes face mass-transfer and scalability limitations, especially for persistent organics. To address these limitations, we fabricated a three-dimensional (3D) reactor operated with a dilute, well-mixed suspension of poly(3,4-ethylenedioxythiophene) (PEDOT) particles and evaluated its performance, energy, and reusability, with hexazinone (HEX), a persistent triazine herbicide, as a model recalcitrant organic compound. PEDOT particles, synthesized via chemical polymerization, acted simultaneously as adsorbents, electrodes, and catalysts, achieving HEX removal efficiencies exceeding 98% at 5 V and 1 g/L particle loading (EE/O = 7 kWh/m³). Influencing factors, including applied voltage, electrolyte concentration, pH, PEDOT particle concentration, and initial HEX concentration, were systematically investigated. Radical quenching experiments identified hydroxyl radicals (^•OH) as the primary reactive species responsible for HEX degradation. Adsorption–desorption experiments revealed simultaneous adsorption and degradation processes. Reusability tests indicated particle loss as the primary challenge, but embedding a Fe₃O₄core in PEDOT particles enabled their magnetic recovery and stable performance over five cycles. A detailed degradation pathway involving multiple intermediates was proposed based on LC–MS/MS analysis. The research demonstrates the applicability of PEDOT suspensions in water treatment for the removal of recalcitrant organic micropollutants.