Methyl Orange Degradation Using Ag-Doped TiO<sub>2</sub>, H<sub>2</sub>O<sub>2</sub>, and Hydrodynamic Cavitation
Ryma Merdoud, Farid Aoudjit, Lotfi Mouni, Vaishnavi G. Honavar, Roja P. Moghadam, Manoj Palabathuni, Vivek V. Ranade
Abstract
High Resolution Image Download MS PowerPoint Slide This study investigates the photocatalytic degradation of Methyl Orange (MO) using doped photocatalysts, specifically Ag-TiO 2 synthesized via a novel solid-state method, with varying silver concentrations (0%, 0.5%, 1%, 1.5%, and 2.5% w/w relative to TiO 2 ) 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-TiO 2 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 (H 2 O 2 ). The highest degradation efficiency of 94% was achieved at 0.01% v/v H 2 O 2 with a synergistic coefficient of 24, within 60 min. Further enhancement was observed when combining PC, H 2 O 2, 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 H 2 O 2, 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-TiO 2 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.