Photoelectrocatalytic water treatment systems: degradation, kinetics and intermediate products studies of sulfamethoxazole on a TiO2–exfoliated graphite electrode

Abstract

Sulfamethoxazole is an antibacterial agent which is commonly prescribed for the treatment of infections in humans and animals. The detection of this drug in the aqueous environment has raised considerable health concerns. Herein, we report the photoelectrocatalytic degradation of sulfamethoxazole at a TiO₂–exfoliated graphite (TiO₂–EG) anode. The TiO₂–EG nanocomposite, synthesised by sol–gel and microwave methods, was characterised by XRD, Raman and FTIR spectroscopies, SEM and TEM. The cyclic voltammograms of the fabricated electrodes were obtained in [Fe(CN)₆]³⁻ redox probe. Concentration abatement of the antibiotic was monitored using a UV-vis spectrophotometer and the possible intermediates were investigated using LCMS. After 6 h of the photoelectrocatalytic process, almost 100% of the drug had been degraded and a 90% COD decay was achieved. The photoelectrocatalytic degradation of sulfamethoxazole entailed γ-, β-, δ- and ε-cleavages, hydroxylation and rings opening. The outcome of this study shows that the EG–TiO₂ anode can be applied for the photoelectrocatalytic remediation of water contaminated by pharmaceuticals.