Efficient electro-oxidation of diclofenac persistent organic pollutant in wastewater using carbon film-supported Cu-rGO electrode

Gradually increasing concentrations of diclofenac (DCF), a widely used anti-inflammatory drug, in water bodies is an emerging concern because of the persistent characteristics and harmful environmental impact of the drug molecule. In this study, electro-oxidation using a novel copper (Cu) - reduced graphene oxide (rGO) electrode is indicated to be an efficient technology for treating DFC-laden wastewater. The Cu-rGO dispersed carbon film (∼1 mm thickness) is synthesized by carbonization and H2-reduction of a phenolic polymeric film in situ dispersed with a Cu salt and GO. The synthesized self-standing carbon film electrode is used for electro-oxidation of aqueous DCF. Analytical microscopic techniques are used to study the physicochemical properties of the material. Cyclic voltammetry analysis shows the prepared electrode generating a high oxidative current response. Approximately 100% DCF degradation is measured within 1 h at 1 V constant biased potential. Dual roles of Cu-rGO are presented as rGO facilitating direct oxidation via enhanced electron mobility at the electrode surface and Cu nanoparticles (NPs) participating in indirect oxidation by generating OH radicals in aqueous phase. The Cu NPs show an over-potential of -0.5 V vs. Ag/AgCl (100 mM KCl) for oxygen evolution, indicating indirect oxidation of DCF. The high non-faradic current density of 4 mA cm-2 generated at the positive potential (1 V) indicates direct oxidation of DCF. This study clearly indicates electro-oxidation using the Cu-rGO-dispersed carbon film electrode to be an efficient technique for remediation of pharmaceutical pollutants-contaminated wastewater.