Theoretical-experimental design of TiO2 photocatalysts for removal of emerging pollutants from water: The effect of Ga doping on photodegradation of methyl orange

Abstract

Complementary experimental and theoretical approaches were used to evaluate the effect of Ga doping on the photocatalytic performance of TiO2. Pristine and Ga-doped anatase nanoparticles were synthesized with varying Ga/TiO2 ratios and characterized by techniques such as electron microscopy, UV-VIS and fluorescence spectroscopy, XRD, BET surface area analysis, and Density Functional Theory (DFT) calculations. Adsorption and photodegradation tests were performed against methyl orange (MO) under UV and solar light irradiation. Results revealed that 1% Ga doping, under solar irradiation, achieved a remarkable mineralization efficiency (over 85%), aligning with DFT and spectroscopy results. pH was a critical factor in influencing both the decomposition rate and photodegradation mechanism since the adsorbed MO decreased TiO2 photoactivity but degraded via an alternative pathway. The presence of multiple scavengers revealed that the decomposition proceeds via both TiO2(e-)/O2•- and TiO2(h+) routes. All data were best fitted using pseudo-first-order kinetics, and the catalyst remained highly efficient for at least 5 cycles. The impact of the water source on the catalyst performance and the potential formation of MO metabolites during the photocatalytic process were analyzed and discussed.