Electrochemical degradation of synthetic wastewater containing Reactive Red 4 using mixed metal oxide composite electrodes

The textile industry is a major contributor to global water pollution due to the release of recalcitrant dye effluents and large volumes of wastewater, with an estimated 10–15% of dyes lost through effluent streams. Such contamination diminishes water quality and creates anoxic conditions that threaten aquatic ecosystems. Electrochemical treatment has emerged as an efficient and environmentally friendly method for wastewater remediation, offering simple process control through adjustable operational parameters (such as applied voltage, dye concentration, pH, type and concentration of supporting electrolyte). Mixed metal oxide (MMO) electrodes are particularly attractive owing to their catalytic activity, stability, and corrosion resistance. However, the reliance on noble metal oxides such as TiO₂, RuO₂, and IrO₂ raises costs, limiting large-scale applications. This study aimed to fabricate cost-effective MMO composite electrodes and evaluate their performance in degrading Reactive Red 4 (RR4). Three composite electrodes namely CuO-PbO₂/Ni, CuO-NiO/Ni, and CuO-NiO-PbO₂/Ni were successfully synthesized via electrodeposition technique. ATR-FTIR, XRD, and EDX analyses confirmed the formation of metal oxides on the electrode surfaces. Under optimized electrolysis conditions (500 ppm RR4, 0.1 M NaCl, 10 V, pH 6.88, stainless-steel cathode), CuO-PbO₂/Ni and CuO-NiO/Ni electrodes achieved 99.80% and 98.27% degradation within 10 min, respectively, while the CuO-NiO-PbO₂/Ni electrode required 15 min to reach 99.91%. Reusability tests showed stable performance, with all electrodes maintaining ~ 100% degradation over five consecutive cycles. Overall, the findings demonstrate that MMO composite electrodes can be fabricated as low-cost electrodes with excellent pollutant removal efficiency and long-term stability, making them promising candidates for sustainable wastewater treatment.

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