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

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 similar to 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 (similar to three times higher) than experiments done in artificial bulb light, during photocatalytic degradation of similar concentra-tions 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. Addi-tionally, 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.

Automated summary

Zinc sulfide embedded reduced graphene oxide nanocomposites (ZnS-rGO) were prepared via a simple precipitation method. The as-prepared ZnS-rGO exhibited efficient sunlight-promoted selective degradation of Congo Red (CR) in a short time, even in the presence of spiking industrial wastewater. Under pseudo-first-order kinetics, the ZnS-rGO achieved similar to 98% degradation of CR dye with a rate constant of 0.0266 min-1. Sunlight as a sustainable energy source outperformed artificial bulb light by producing better results (approximately three times higher) during photocatalytic degradation of similar concentrations of CR dye. The study also investigated the effect of dye concentration and catalyst loading on the photocatalytic degradation efficiency.