Molybdenum Telluride-Promoted BiOCl Photocatalysts for the Degradation of Sulfamethoxazole Under Solar Irradiation: Kinetics, Mechanism, and Transformation Products

This work examines the solar photocatalytic degradation of the antibiotic sulfamethoxazole (SMX) using molybdenum telluride (MoTe2)-promoted bismuth oxychloride (BiOCl). Different loadings of molybdenum telluride in the 0–1% range on BiOCl were synthesized and evaluated. Although the presence of MoTe2 did not alter either the adsorption capacity or the energy gap of BiOCl, the synthesized photocatalyst demonstrated higher photocatalytic activity due to the enhanced separation of photogenerated pairs. The 0.5MoTe2/BiOCl photocatalyst achieved a kinetic constant nearly 2.8 times higher than that of pure BiOCl, leading to the elimination of 500 μg/L SMX within 90 min. The system’s performance was enhanced under neutral to acidic conditions and lower SMX concentrations. Based on experiments with radical scavengers, photogenerated holes appeared to be the dominant species, with the contribution of reactive species following the order h+>O2•−/e−>1O2>HO•. Interestingly, in different water matrices, photocatalytic activity was not diminished and even increased by 20%, likely because of the action of photogenerated holes and the selectivity of secondary generated radicals. The photocatalyst retained > 90% of its activity after three sequential experiments. Finally, four transformation products from SMX photodegradation were identified via UHPLC-TOF-MS, and a degradation pathway is proposed.