Enhancement of sulfadiazine degradation by TiO2 addition in a simulated sunlight induced periodate activation system: Influence parameter, degradation process and solution toxicity analysis

This study applied the advanced oxidation process of simulated sunlight-induced periodate activation (SSL/PI) to degrade antibiotics. In order to enhance degradation, TiO 2 was also added to the SSL/PI system to create a synergistic effect (SSL/PI/TiO 2 ) and boost the degradation process. Sulfadiazine (SDZ) was selected as the target pollutant to investigate the enhancement from TiO 2 addition and the influential parameters on degradation. The obtained results showed that PI concentration was the most important parameter affecting SDZ degradation, while TiO 2 dosage and solution pH had less impact. Adding Fe 2+ and CO 3 2− inhibited SDZ degradation, while Cu 2+ and Cl − had minimal effect. DFT analysis indicated that the C4, C5, N23, N26, and N27 sites of the SDZ molecule were susceptible to be attacked by the formed reactive species. The key reactive species responsible for SDZ degradation in the SSL/PI/TiO 2 system were •O 2 − , 1 O 2 , IO 3 •, and •OH. LC-MS analysis identified 10 main byproducts during SDZ degradation, then three possible degradation pathways were predicted. The concentration detection of I 2 , I 3 − , and HOI, along with lettuce seed germination experiments, verified that the toxicity of the SDZ solution reduced after treatment with the SSL/PI/TiO 2 process.