间歇超声波强化ZVI/PS体系氧化降解磺胺抗生素

Sulfonamide antibiotics (SAs) are one of the first chemically synthesized antibiotics used. The widely application and discharge of SAs have caused serious pollution to the environment and aroused people's attention. Therefore, five characteristic SAs with relatively high detection rate in the water environment were selected as target pollutants, namely sulfamethazine (SMR), sulfamethazine (SMT), sulfamethoxazole (SMX), sulfaisoxazole (SIX), and sulfathiazole (STZ). High performance liquid chromatography-mass spectrometry (HPLC-MS-MS) was used to detect the intermediate products of the five SAs in the degradation process. The degradation efficiency and reaction pathways of SAs by ultrasound (US) enhanced ZVI/PS (US-ZVI/PS) process was further investigated. The results showed that: (1) Under the conditions of ultrasonic intensity, pH, ZVI and PS concentrations of 0.25 W/cm³, 6.0, 0.6 mmol/L and 1.4 mmol/L, and reaction time of 30 minutes, the degradation rates of five SAs were all above 95%. (2) The degradation process of five SAs accorded with the pseudo-first-order kinetic equation. The order of the degradation rate constant was SMR (0.223) > SMT (0.215) > STZ (0.203) > SIX (0.181)> SMX (0.119). (3) The degradation sites of the five SAs were No.3 of C atom on the benzene ring, No.7 of N atom on the phenylamino group, No.8 of S atom and No.11 of N atom on the sulfonamide group. The common degradation pathways of the five SAs included S-N bond cleavage, C-N bond cleavage, benzene ring hydroxylation, oxidation of aniline and R substituents. Compared with the five-membered ring SAs, the six-membered ring SAs had a special oxidation process. The extraction of the SO₂ group in the molecular structure led to N-N rearrangement to form new intermediates. The results showed that the US-ZVI/PS process can effectively achieve the rapid degradation of SAs with different structures. It is a green and efficient advanced oxidation technology.