Electrocatalytic Oxidation Performance and Mechanism of Porous Active Metal Oxide Coated Anode for Congo Red Degradation
To address the challenges of high salinity, recalcitrance, limited mass transfer, and coating detachment in traditional anodes for textile wastewater treatment, a porous RuO2@r-TiO2 nanotube array (NTA) anode was fabricated via anodic oxidation, electrochemical reduction, and thermal decomposition. A flow-through electrochemical oxidation system was constructed using this anode and a graphite felt cathode. The material's morphology and physicochemical properties were characterized by SEM, XRD, and XPS. Congo red (CR) was used as a model pollutant to evaluate degradation performance under various conditions. Optimal conditions were identified as current density 5 mA·cm−2, permeate flux 480 L·(m2·h)−1, initial CR concentration 0.15 mmol·L−1, and NaCl concentration 75 mmol·L−1. Under these conditions, the system achieved 91% decolorization within 20 min and 82% mineralization within 60 min. Mass transfer tests showed a rate constant of 2.23×10−4 m·s−1 in flow-through mode, three times higher than conventional mode, with active chlorine and H2O2 production increased by 32.8% and 66.7%, respectively. Radical quenching experiments indicated that singlet oxygen (1O2) was the primary reactive species. The degradation mechanism was proposed based on quenching and UV spectral analysis. The system achieved >90% decolorization for five typical dye pollutants with an energy consumption of only 0.16 kWh·m−3. Cyclic voltammetry confirmed long-term stability. These findings provide theoretical support for applying electrochemical advanced oxidation to high-salinity textile wastewater.