紫外活化过硫酸盐工艺降解水中磺胺二甲氧嘧啶动力学特征与机理

Degradation kinetics and mechanism of SDM by UV/PS process in water

采用紫外活化过硫酸盐(UV/PS)工艺降解典型磺胺类抗生素磺胺二甲氧嘧啶(SDM),比较单一紫外(UV)、单一过硫酸盐(PS)和UV/PS对SDM的去除效果,考察各因素对降解动力学的影响,并探究其降解机理,对SDM及其中间产物进行毒性测定和风险评价。结果显示,UV/PS可以加速SDM降解,反应速率常数分别是单一UV和单一PS的4、20倍;反应速率常数随PS浓度和UV光强的增加而增大;酸性条件更有利于SDM降解;背景无机阴离子(HCO^(-)_(3)、Cl^(-)、NO^(-)_(3)、SO^(2-)_(4)、CO^(2-)_(3))能促进UV/PS降解SDM,其中HCO_(3)^(-)的促进效果最明显。基于高分辨质谱法(HRMS)解析出了8种降解中间产物,涉及氨基氧化、羟基化和键断裂等反应路径。降解过程中溶液急性毒性并没有随着SDM去除而降低,可能是生成了生态风险更大的中间产物。

Sulfadimethoxine(SDM),a typical sulfonamide antibiotic,was degraded by ultraviolet activated persulfate(UV/PS)process.The removal effects of single ultraviolet(UV),single persulfate(PS)and UV/PS on SDM were compared.The effects of various factors on the degradation kinetics were investigated to explore the degradation mechanism of SDM,and conduct toxicity determination and risk assessment for SDM and its intermediate products.The results showed that UV/PS could promote SDM degradation.The degradation rate constant was 4 and 20 times of those under single UV and single PS,respectively.The degradation rate constants increased with the increasing UV intensity and PS dosage.SDM degradation could be improved under acidic conditions.Background inorganic anions(HCO_(3)^(-),Cl^(-),NO^(-)_(3),SO^(2-)_(4)and CO^(2-)_(3))would accelerate the degradation process,and HCO_(3)^(-) had the most obvious promotion effect.Based on HRMS,8 degradation intermediates were identified,which involved amino oxidation,hydroxylation and bond breakage.The acute toxicity of the solution did not decrease with the removal of SDM during the degradation process,which might be the formation of intermediates with greater ecological risk.