Application of TiO2-ceramic/UVA photocatalyst for the photodegradation of sulfamethoxazole

Abstract

Sulfamethoxazole (SMX) is one of the most antibiotic compounds detected in the aquatic environment. The potential concentration of SMX could raise the ecotoxicological effects on microbial. The photocatalyst based on TiO2 has been demonstrated as the effective material for the elimination of SMX in water. However, due to the non-selected attack of hydroxyl radical derived from photocatalysis to S–N, C–N bond, –NH2 group, or isoxazole ring, therefore SMX could be transferred to different intermediate products. In this study, SMX at 5 mg L−1 has been removed up to 84.7% after 7 h of irradiation by TiO2-ceramic photocatalyst. The highest removal efficiency could maintain at pH (5–6) where SMX existed in neutral form and the TiO2 reached to point of zero charge (PZC). On the other hand, environmental parameters such as bicarbonate ions and the dissolved organic matter (DOM), which are generally existing in ambient water, have negative effects on the elimination of SMX. Therefore, we investigated the effect of these factors on SMX photocatalyst removal. The efficiency of TiO2-ceramic was stable for 15 cycles of the experiment. In addition, the intermediate products were identified by UPLC-MS/MS and the degradation pathways were proposed. There were 11 intermediates detected with a molecular mass higher than 254. The result suggested that there was the recombination of free radicals to form new compounds. Therefore, although TiO2-ceramic is a promising photocatalyst for SMX removal an ecotoxicity test still needs to be evaluated for a deeper understanding of transformation products.