Novel nanocomposite thin films for efficient degradation of Rhodamine B and Rhodamine 6G under visible light irradiation: Reaction Mechanism and Pathway studies

The present investigation aims to synthesize the novel nanocomposite thin film and utilize the material to remove emerging dyes efficiently (i.e., Rhodamine B (R-B) and Rhodamine 6G (R-6G)), in an aqueous solution using LED visible light and UV-A light. A facile synthetic route was adopted to obtain the TiO2-supported bentonite and in situ decorated with Au nanoparticles (NPs) thin film. The advanced analytical techniques characterizes the materials. The laboratory scale reactor was utilized for efficient degradation of R-B and R-6G using thin film catalysts. The percentage removal of R-B was 54.13% (visible light) and 76.26% (UV-A light) and the R-6G, was removed 60.37% (visible light) and 84.68% (UV-A light) at the initial pollutant concentration of 0.5 mg/L and at pH 6.0 using the thin film photocatalyst. The parametric studies demonstrated the insights of degradation mechanisms in photocatalytic operations. A significant mineralization of these dyes is achieved, and the repeated use in reactor operations indicated the catalysts' stability. After six repeated cycles of photocatalytic reaction, the efficacy of catalyst was decreased by 1.02% only (for R-G) and 0.93% only (for R-6G). A plausible reaction pathway was proposed, and the real implications showed higher selectivity of the catalyst.