Individual and simultaneous degradation of antibiotics sulfamethoxazole and trimethoprim by UV and solar radiation in aqueous solution using bentonite and vermiculite as photocatalysts

This work is aimed at studying the utilization of bentonite and vermiculite as a photocatalyst in the individual and simultaneous degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) by UV and solar light radiation. The clays were characterized by various analytical techniques, and it was corroborated that the photoactivity and textural properties of clays remained unaffected by the UV radiation. The band gap energy (E-g) of both clays was less than 4 eV, revealing that they could behave as semiconductor materials and could act as photoactive materials in the presence of UV radiation. The photodegradation rate and the maximum percentage of degradation for SMX and TMP were markedly enhanced by the presence of the clays. The reaction rate constant for SMX and TMP degradation in UV radiation was increased 11.4 and 46.4 times, respectively, when 10 mg of vermiculite were added to the UV system. Better degradation results were observed by using vermiculite, and this trend could be attributed to the higher percentage of doping ions in the vermiculite. In the UV radiation and UV/Clay systems, the rate constants for single degradation were faster than those for simultaneous degradation of SMX and TMP; this was due to the competition of SMX and TMP for the generated oxidant radicals. The photoactivity of the reutilized clays was similar to that of the original clays.