Green Synthesis of SnO₂/Bentonite Nanocomposite Using Murraya koenigii Leaf Extract for Photocatalytic Degradation of Rhodamine B Dye and Carbofuran Pesticide in Aqueous Solution

Water contamination by synthetic dyes and pesticides is a major environmental concern because of their persistence, toxicity, and adverse effects on aquatic ecosystems and human health. The present study focused on the green synthesis of SnO₂ nanoparticles and the preparation of a SnO₂/bentonite nanocomposite (SBT-NC) using Murraya koenigii leaf extract and its application for the photocatalytic degradation of Rhodamine B (RhB) dye and Carbofuran (CBF) pesticide in aqueous solutions. Bentonite was used as a supporting material to improve the adsorption capacity, surface area, and dispersion of SnO₂ nanoparticles. The synthesized materials were characterized using UV–visible spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR). The characterization results confirmed the successful formation and incorporation of SnO₂ nanoparticles onto the bentonite matrix. The effects of important experimental parameters, including solution pH, initial pollutant concentration, contact time, and catalyst dosage, were investigated under light irradiation. The SBT-NC showed considerably higher photocatalytic degradation efficiency than pure bentonite and SnO₂ nanoparticles. Under optimized conditions, the degradation efficiency of Rhodamine B reached approximately 92–94%, while Carbofuran degradation reached approximately 90–91%. The optimum conditions included alkaline pH for Rhodamine B and acidic pH for Carbofuran, with a catalyst dosage of approximately 0.1 g and a reaction time of about 90–120 min. The enhanced performance of SBT-NC was attributed to the synergistic effect of the adsorption properties of bentonite and the photocatalytic activity of SnO₂, which provided additional active sites and promoted the formation of reactive oxygen species. Kinetic analysis indicated that the degradation of both pollutants was generally better described by the pseudo-first-order kinetic model. Overall, the green-synthesized SnO₂/bentonite nanocomposite demonstrated strong potential as an efficient, economical, and environmentally friendly photocatalyst for the removal of organic pollutants from contaminated water.