Hierarchical mesoporous TiO2 microspheres for the enhanced photocatalytic oxidation of sulfonamides and their mechanism

Abstract

Sulfonamides, a group of antibacterial agents, are not readily biodegradable and as a result have often been detected in wastewater effluents, rivers and lakes. This work investigated the photocatalytic degradation of sulfadimethoxine (SDM) and related sulfonamides in H₂O₂ containing aqueous suspensions of mesoporous TiO₂ microspheres exposed to simulated solar light irradiation. The three-dimensional mesoporous TiO₂ microsphere catalyst was fabricated by a facile method via a one-step solvothermal process without templates. The performance of mesoporous TiO₂ microspheres exceeded the commercially available P25 TiO₂ catalyst in the photocatalytic degradation of sulfonamides. Sulfadimethoxine degradation increased and reached the optimal H₂O₂ concentration of 5.9 mM. Particularly, the disappearance of SDM as well as the formation and decomposition of some degradation intermediates were determined by high-performance liquid chromatography-mass spectroscopy (HPLC-MS) and high-performance liquid chromatography-selective ion recording (HPLC-SIR) data modules, and possible photocatalytic degradation mechanisms were proposed. The hydroxylation and cleavage of the S–N or C–N bonds through ^•OH attacks on the aromatic rings and aminopyrimidine rings under simulated solar light irradiation with the assistance of H₂O₂ played important roles during SDM photocatalytic degradation.