Sulfonamide antibiotics in water have raised public concern, owing to their stability and capacity to induce microbial resistance. We investigated the degradation efficiencies of photolysis by ultraviolet light and photolysis combined with hydrogen peroxide treatment. Combining ultraviolet light irradiation with hydrogen peroxide treatment was more effective at removing sulfadimethoxine than irradiation alone or UV/persulfate system. We also assessed the effects of hydrogen peroxide concentrations, reaction time, and the composition of the water matrix. The removing efficiency of sulfadimethoxine was negatively affected by high concentrations of hydrogen peroxide and with increasing alkalinity (pH 7.5–9.0). A tentative degradation pathway was proposed, involving the initial one-electron oxidation of sulfadimethoxine by ·OH and further reactions of the formed cation intermediate. We assessed the acute toxicity of the transformation products to Vibrio fischeri, and found that combining ultraviolet light irradiation with hydrogen peroxide treatment exerted lower toxicity to the bacterium than irradiation alone.

水中的磺酰胺类抗生素由于其稳定性和诱导微生物耐药性的能力而引起了公众的关注。我们研究了紫外线和光解结合过氧化氢处理的光解降解效率。将紫外线照射与过氧化氢处理相结合，比单独照射或紫外线/过硫酸盐体系更能有效地去除磺胺二甲嘧啶。我们还评估了过氧化氢浓度，反应时间和水基质组成的影响。高浓度的过氧化氢和碱度的增加（pH 7.5-9.0）对磺胺嘧啶的去除效率有不利影响。提出了一种初步的降解途径，涉及由·OH进行的磺胺二甲氧嘧啶的初始单电子氧化，以及形成的阳离子中间体的进一步反应。我们评估了转化产物对费氏弧菌，发现紫外线照射与过氧化氢处理相结合对细菌的毒性比单独照射低。