Methyl orange degradation using Ag-doped TiO2, H2O2, andhydrodynamic cavitation

This study investigates the photocatalytic degrada?tion of Methyl Orange (MO) using doped photocatalysts, specifically Ag-TiO2 synthesized via a novel solid-state method, with varying silver concentrations (0%, 0.5%, 1%, 1.5%, and 2.5% w/ w relative to TiO2) under different UV light intensities (60 and 200 W). The photocatalysts were characterized using XRD, SEM-EDS, and BET. The optimal performance was observed with a 0.5% Ag?TiO2 concentration, achieving a degradation efficiency of 59% under 200 W UV light over 180 min of treatment. The effect of photocatalyst loading was then optimized, followed by an investigation of the synergistic effects of photocatalysis (PC) coupled with hydrogen peroxide (H2O2). The highest degradation efficiency of 94% was achieved at 0.01% v/v H2O2 with a synergistic coefficient of 24, within 60 min. Further enhancement was observed when combining PC, H2O2, and hydrodynamic cavitation (HC), achieving complete degradation of MO in just 3 min (1.5 passes) with a high synergistic coefficient of 42. The degradation process was represented as pseudo-first-order kinetics for PC alone and combined with H2O2, and a per-pass degradation model for HC. The impact of various scavengers on the photocatalytic process was examined, highlighting the crucial roles of hydroxyl radicals (•OH) and photogenerated holes (h+ ) in the degradation mechanism. The influence of anions and the water matrix on the reactive oxygen species (ROS) generation and efficiency, as well as the environmental fate of Ag-TiO2 catalysts, is also discussed. This research underscores the importance of optimizing doped photocatalyst composition and operational conditions to maximize pollutant degradation efficiency, demonstrating significant advancements in advanced oxidation processes through synergy.