Photooxidation of ethylene glycol and methanol in water solutions over P25 modified with Au, Pt, and Pd

One of the actual pollutants of water resources is ethylene glycol, which is part of deicing liquids, high concentrations of which are harmful to humans and nature. This paper describes investigation of the kinetic patterns of photooxidation of ethylene glycol (EG) and methanol (MeOH) as model oxidizable substances on TiO2 P25 modified with Au, Pt, Pd, under UV irradiation. The study of processes using TOC analysis made it possible to determine the total mineralization of organic substrates, and the analysis of the mixture composition by HPLC, supplemented by modeling the kinetics of oxidation, made it possible to visualize probable transformation routes. Formaldehyde conversion to formic acid showed the lowest surface reaction rate constant in both methanol and ethylene glycol oxidation processes. Acceleration of this step is observed when Pt nanoparticles are applied to the TiO2 surface. The application of Au has little effect on the rate of decomposition, while the addition of Pd in most cases reduces the observed rates. The study has shown the effect of the metal nature on the course of stepwise ethylene glycol and methanol decomposition and oxidation in aqueous solutions, revealed the ratio between rate constants of these processes, and highlighted the critical need to consider the distribution of the reaction participants between the bulk solution state and the adsorbed one on the surface of the catalyst.