Sunlight-assisted photocatalytic degradation of azo-dye using zinc-sulfide embedded reduced graphene oxide

Abstract

Herein, Zinc sulfide embedded reduced graphene oxide nanocomposites (ZnS-rGO) have been prepared using a simple precipitation method. The as-prepared ZnS-rGO has been applied for sunlight-promoted selective degradation of Congo Red (CR), an azo dye in a short time and even when combined with spiking industrial wastewater. The ZnS-rGO shows ~98% degradation of CR dye with a rate constant of 0.0266 min−1 by following pseudo-first-order kinetics. Sunlight as a sustainable energy source produces the best results (~three times higher) than experiments done in artificial bulb light, during photocatalytic degradation of similar concentrations of CR dye. The effect of dye concentration and loading of catalyst on photocatalytic degradation efficiency has also been explored. The role of reactive oxygen species responsible for photocatalytic degradation is examined by employing trap experiments, confirms the significant contribution of superoxide radicals. Additionally, ZnS-rGO is able to degrade CR dye in a broad pH range and used to degrade CR from industrially spiked wastewater samples to demonstrate the photocatalyst's potential for their use in the real-world applications. Moreover, comparative NMR and FTIR analysis support the photocatalytic degradation of CR dye.