Plasma–photocatalytic degradation of dyeing wastewater: comparison of titanium oxide, zinc oxide, and graphene oxide

Non-thermal plasma combined with photocatalysis is a viable technique for the degradation of organic impurities in wastewater. In this work, a specially devised dielectric barrier discharge plasma reactor system coupled with photocatalysis was applied to the degradation of CI Acid Red 4 which is commonly used as a textile dye. Dye degradation in the combined system was evaluated with three different photocatalysts: titanium oxide, zinc oxide, and graphene oxide. The photocatalysts were characterised by X-ray diffraction, particle size analysis, and Brunauer–Emmett–Teller specific surface area. It was found that the combination of photocatalysis with plasma substantially improved dye degradation by comparison with plasma alone. To identify which photocatalyst exhibited the best performance, the influence of photocatalysis alone on dye degradation was separately determined using an ultraviolet lamp, which showed that graphene oxide, which has a broad band gap, degraded the dye most effectively.