紫外/过二硫酸盐对组胺H_(2)受体拮抗剂的降解特性及自由基模拟

Degradation of histamine H_(2)-receptor antagonists by UV/PDS:Kinetics and radical modeling

研究了基于硫酸根的高级氧化技术UV/过二硫酸盐(UV/PDS)对水体中组胺H2受体拮抗剂(HRAs)的降解,并选取HRAs中的典型物质西咪替丁(CMTD)为目标污染物.采用竞争动力学方法得到了HRAs和·OH及SO_(4)^(−)反应的二级速率常数,k·OH/HRAs为(2.8—14.6)×10^(9)L·mol^(−1)·s^(−1),kSO_(4)^(−)/HRAs为(0.81—8.10)×10^(9)L·mol^(−1)·s^(−1).研究在实验基础上建立了UV/PDS的自由基拟稳态模型,模拟结果表明,UV/PDS对污染物的降解,其间接光解起主要作用,体系中·OH和SO_(4)^(−)是间接光解的主导自由基.在(0.1—0.5)mmol·L^(−1)PDS投加量下,·OH和SO_(4)^(−)的浓度分别为(3.85—5.16)×10^(−16)mol·L^(−1),(1.21—1.68)×10^(−13)mol·L^(−1),SO_(4)^(−)对污染物的降解起主导作用.酸性条件下自由基浓度相对更高,从而促进了CMTD的去除.水体基质(Cl^(−)、HCO_(3)^(−)和NOM)存在条件下,CMTD的降解受到一定的抑制,模拟结果表明自由基浓度显著降低;但是模拟结果与实验结果有一定偏差,主要是基质存在下生成了衍生自由基,由于衍生自由基的复杂性而未计入模型计算中导致.在实际水样中应用的研究表明,UV/PDS可以有效降解地表水(SW)和实际废水(WW)中的CMTD,具有良好的应用前景.

The degradation of histamine H2-receptor antagonist(HRAs)by sulfate radical based advanced oxidation processes(SR-AOPs)of UV/peroxydisulfate(UV/PDS)was investigated in this study.Cimetidine(CMTD),a typical compound of HRAs,was selected as the target pollutant.The second-order rate constants between HRAs with·OH and SO_(4)^(−)were obtained by competition kinetic approaches,with kžOH/HRAs in the range of(2.8—14.6)×10^(9)L·mol^(−1)·s^(−1)and kSO_(4)^(−)/HRAs in the range of(0.81—8.10)×10^(9)L·mol^(−1)·s^(−1),respectively.Based on experimental results,a pseudo steady-state kinetic model was developed to calculate the radical concentration.The modeling results showed that CMTD degradation was mainly caused by indirect photolysis,which dominated by·OH and SO_(4)^(−).With the dosage of(0.1—0.5)mmol·L^(−1)PDS,the·OH and SO_(4)^(−)concentrations were in the range of(3.85—5.16)×10−16 mol·L^(−1)and(1.21—1.68)×10^(−13) mol·L^(−1),respectively.Thereby,SO_(4)^(−)was deemed as the major contributor to CMTD degradation.The radical concentration was relatively higher under acidic conditions,which promoted the degradation of CMTD.In the presence of water matrices,i.e.,Cl^(−),HCO_(3)^(−)and NOM,the degradation of CMTD was inhibited to some extent.Modeling results confirmed that the radical concentration decreased significantly.However,a certain deviation between modeling and experimental results was observed in the presence of water matrices,which might be caused by the secondary radicals derived from·OH and SO_(4)^(−)reacting with water matrices.Due to the complexity of secondary radicals,the reactions of derived radicals were not included in the model.The application of UV/PDS in real water samples showed that CMTD could be effectively degraded by UV/PDS in surface water(SW)and wastewater(WW),which is promising in water treatment.