Anodic oxidation of paraquat herbicide on BDD electrode: comparative evaluation of variable effects and degradation mechanisms

This work investigates the electrochemical degradation of paraquat (30 mg L^-1) in aqueous medium using a boron-doped diamond (BDD) anode, with a graphite cathode. The influence of operational variables including the effect of the anode material, current density, type of supporting electrolyte, and initial pH was systematically examined. BDD electrodes exhibited the most efficient performance, achieving COD and TOC removal rates of 99% and 98.6%, respectively, under optimal conditions (15 mA cm^-2, pH = 3, 50 mmol per L Na₂SO₄). Degradation followed pseudo-first-order kinetics (<i>k</i> = 3.14 × 10^-2 s^-1). While faradaic efficiency peaked at 70.14%, energy demand increased to 66 kWh m^-3 over time. Analysis of reaction intermediates revealed the formation of aromatic and carboxylic acid by-products, which were tracked to elucidate a complete mineralization pathway. These findings demonstrate the potential of BDD driven electrochemical oxidation as a promising and sustainable technique for the treatment of persistent organic contaminants in water systems.