间歇超声波强化ZVI/PS体系氧化降解磺胺抗生素

Degradation of Sulfonamide Antibiotics by Intermittent Ultrasound Enhanced ZVI/PS Process

磺胺抗生素(SAs)作为最早应用的一类化学合成抗菌药,其大量使用和排放对水环境造成严重污染,引起了人们对于水环境安全的高度关注.因此,选取了水环境中检出率较高的5种特征SAs作为目标污染物,分别为磺胺甲基嘧啶(SMR)、磺胺二甲基嘧啶(SMT)、磺胺甲恶唑(SMX)、磺胺异恶唑(SIX)和磺胺噻唑(STZ).利用高效液相色谱质谱联用仪(HPLC-MS-MS)对降解过程产生的中间产物进行检测和分析,深入研究了间歇超声波(US)强化ZVI/PS体系(简称“US-ZVI/PS体系”)降解5种SAs的效能和反应路径.结果表明:①在US强度、pH、ZVI(零价铁)浓度和PS初始浓度分别为0.25 W/cm^(3)、6.0、0.6 mmol/L和1.4 mmol/L条件下,30 min反应时间内,US-ZVI/PS体系对5种SAs的降解效率均超过95%.②US-ZVI/PS体系降解5种SAs的过程均符合拟一级反应动力学,5种SAs降解速率常数大小依次为SMR(0.223)>SMT(0.215)>STZ(0.203)>SIX(0.181)>SMX(0.119).③5种SAs的降解活性位点为苯环上邻位的3号C原子、苯氨基上的7号N原子、磺酰胺基上的8号S原子和11号N原子,US-ZVI/PS体系降解5种SAs的相同反应路径包括S—N键断裂、C—N键断裂、苯环羟基化、苯胺氧化和R取代基氧化过程,与五元环SAs相比,六元环SAs反应路径多一个N—N重排过程.研究显示,US-ZVI/PS体系能够实现不同结构SAs的快速降解,是一种绿色、高效的高级氧化技术.

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/cm^(3),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 SO_(2) 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.