Selective photocatalytic removal of sulfonamide antibiotics: The performance differences in molecularly imprinted TiO2 synthesized using four template molecules

Four types of molecularly imprinted TiO2 photocatalysts named MIP-TiO2/sulfadiazine (SD), MIP-TiO2/sulfamethoxazole (SMX), MIP-TiO2/sulfonamide (SN) and MIP-TiO2/aniline (AN), were synthesized. The five catalysts exhibited different degrees of selectivity for two types of sulfonamide antibiotics (SAs), SD and SMX. In the systems of NIP–TiO2, MIP-TiO2/SD, MIP-TiO2/SMX, MIP-TiO2/SN and MIP-TiO2/AN, the degradation rate constants of SD were 0.0789, 0.1031, 0.0859, 0.1034 and 0.1051 min−1, respectively. Moreover, the removal rate constants of SMX on the mentioned catalysts were 0.1076, 0.3250, 0.4260, 0.3885 and 0.5848 min−1, correspondingly. The single bond cleavage (C–S, C–N, and S–N bonds), hydroxylation, ring-opening, oxidation, and deamination were the major transformation pathways of SAs. With the presence of MIP-TiO2/SN and MIP-TiO2/AN, more low molecular weight products were generated, and the intermediates preferred to go through further hydroxylation and oxidation reactions. Therefore, besides MIP-TiO2/SD and MIP-TiO2/SMX, the novel MIP-TiO2/SN and MIP-TiO2/AN, which were prepared by using substances with the similar main functional groups as SAs as template molecules, had excellent catalytic abilities and less byproducts formed in the situation. The results may provide an effective idea to level up the SAs degradation rates, control the generation of intermediates, and reduce environmental risks.