Green AgNPs/TiO2 for sustainable photocatalytic degradation of AO10 azo dye under eco-friendly white LED illumination: experimental, DFT calculations, and machine learning-guided study.

Water and wastewater contamination by organic micropollutants remains a critical global environmental issue, necessitating the development of efficient and sustainable treatment strategies. In this work, we report a simple and eco-friendly approach for the biosynthesis of silver-decorated titanium dioxide nanocomposites (green AgNPs/TiO2) using phytochemicals derived from Rosmarinus officinalis. The successful formation of the AgNPs/TiO2 nanocomposites was confirmed through comprehensive characterization using UV-Vis, XRD, SEM, and FTIR. The photocatalytic performance of green AgNPs/TiO2 was systematically evaluated for the degradation of Acid Orange 10 (AO10) under mild and energy-efficient white LED irradiation. The effect of each parameter on the photocatalytic activity of the green AgNPs/TiO2 nanocomposite, including solution pH, catalyst loading, H2O2 concentration, and the initial AO10 concentration, was thoroughly investigated, together with kinetic analyses to gain insight into the degradation mechanism. In parallel, a polynomial regression-based machine learning model was used to capture the relationships among the experimental parameters affecting the concentration ratio (C/C0), enabling the identification of optimal conditions that minimize C/C0 in the shortest reaction time. Pareto optimization (λ = 1) predicted optimum conditions of, pH 1.50, 3.35 × 10-3 M H2O2, 80.24 mg L-1 catalyst loading, and 26.40 mg L-1 AO10, yielding a predicted complete dye degradation in 15.81 min. Furthermore, DFT calculations were performed to estimate the relative adsorption energies (Eads) of AO10 on the AgNPs/TiO2 surface. The results indicate that the SO3-Ag adsorption orientation is energetically more favorable than N-Ag and OH-Ag possible adsorption orientations. In addition, the DFT analysis reveals a strong influence of pH on the adsorption process. Notably, at very high pH values, the adsorption becomes endergonic, which provides a molecular-level explanation for the experimentally observed decrease in the photocatalytic activity of green AgNPs/TiO2 under strongly alkaline conditions.