(169e) Harnessing Green Nanosilver Supported on Reduced Graphene Oxide for Photocatalytic Degradation of Methylparaben

Methylparaben (MeP) is a hazardous water pollutant found in the effluent from cosmetic industries. It has been reported to cause disruption in various organisms' endocrine or hormonal systems, and its extensive use has led to its increased discharge into water bodies, posing a significant threat to the environment and human health. Therefore, there is a pressing need to develop effective techniques to remove MeP from contaminated water sources.

Plasmonic nanoparticles have emerged as a promising pathway for the removal of pollutants from water treatment processes due to their ability to perform direct visible-light-driven photocatalysis. In this study, a hybrid catalyst of silver nanoparticles on reduced graphene oxide (rGO/AgNPs) was fabricated using a biobased in-situ reduction process and employed as a visible light photocatalyst to treat MeP. The use of green reducing agents during the synthesis process reduces the overall cost and environmental impact of the process. The synthesized catalyst demonstrated significantly enhanced adsorption and photocatalytic degradation of MeP than rGO or AgNPs, individually. The conditions that influence the kinetics of the photocatalytic degradation by rGO/AgNPs were comprehensively studied using response surface methodology (RSM), including solution pH, catalyst dose, persulfate concentration, MeP initial concentration, and time. The catalyst showed good stability and reusability and could induce up to 97.6% MeP degradation efficiency.

Furthermore, the mechanism of the photocatalytic reaction was investigated by scavenger tests and density functional theory (DFT) study. The results indicated that hydroxyl radicals (•OH) played a crucial role in the photocatalytic degradation of MeP. Additionally, the DFT calculations revealed that the adsorption and electron transfer mechanism of MeP on the rGO/AgNPs surface was more favorable than that on the individual components. This study provides a novel approach for the development of low-cost photocatalysts for cosmetic wastewater treatment utilizing visible light irradiation. The biobased synthesis of rGO/AgNPs and the insights into the photocatalytic mechanism could pave the way for the future development of eco-friendly and effective catalysts for the removal of MeP from contaminated water sources.