不同离子对Dinoseb氯化降解及消毒副产物生成的影响

以水体中常见的污染物地乐酚(Dinoseb)为研究对象,分析了水中4种不同离子(Br^-、NH4⁺、NO3^-、NO2^-)背景浓度下Dinoseb氯化动力学及生成消毒副产物(DBPs)的情况。结果表明,4种离子对Dinoseb氯化反应的影响顺序为:Br^->NH4⁺>NO2^->NO3^-。产生的消毒副产物主要有三氯甲烷(CF)、三氯硝基甲烷(TCNM)、二氯乙腈(DCAN)、三氯丙酮(TCP)、二氯一溴甲烷(DCBM)等,其中TCNM浓度最高,Dinoseb是TCNM的典型前体物。当水中有Br^-存在时,Dinoseb降解反应非常复杂,降解速率不符合拟一级反应规律,还会产生大量溴代THMs,如二氯一溴甲烷(DCBM)、一氯二溴甲烷(DBCM)、三溴甲烷(TBM)等,它们的浓度均随着Br^-/Cl2值的增加而迅速增加,浓度高低顺序为:DCBM>DBCM>TBM>CF。在相同p H值下,Dinoseb的氯化降解速率随着Br^-浓度的增大而增加;在相同Br^-浓度下,pH值越低,Dinoseb的氯化反应速率越快。与Br^-相比,pH值是更重要的氯化速率影响因素。当水体中有NH4⁺存在时,TCNM产率会提高较多;NO3^-对Dinoseb的氯化反应有一定的抑制作用,各DBPs浓度都有降低;NO2^-可以被水中的次氯酸氧化成NO3^-,消耗水中部分次氯酸,DBPs浓度总体都会降低。

Effect of Different Ions on Chlorination Degradation of Dinoseb and Formation of Disinfection By-products

Chlorination kinetics of dinoseb(a common pollutant in water bodies)and disinfection by-products(DBPs)formation were analyzed under background concentrations of four different ions(Br^-,NH4⁺,NO3^-and NO2^-).The order of four ions influencing dinoseb chlorination reaction from strong to weak was as follows:Br^-,NH4⁺,NO2^-and NO3^-.The main DBPs generated were trichloromethane(CF),trichloronitromethane(TCNM),dichloroacetonitrile(DCAN),trichloroacetone(TCP),dichloromethane(DCBM),etc.Among them,the concentration of TCNM was the highest,and dinoseb was a typical precursor of TCNM.When Br^-existed in the water,the degradation reaction of dinoseb was very complex,and the degradation rate did not conform to pseudo-first-order reaction model.In addition,various bromination nitromethane emerged,such as DCBM,dibromochloromethane(DBCM)and tribromomethane(TBM).Their concentrations increased rapidly with the increase of Br^-/Cl2 value,and the order of concentration from high to low was DCBM,DBCM,TBM and CF.The chlorination rate increased with the increase of Br^-concentration at the same pH.If the same initial dosages of Br^-were applied,the faster degradation rates of dinoseb were found at lower pH.Compared with Br^-,p H was a more important factor affecting the chlorination rate.When there was NH4⁺in the water,the yield of TCNM increased greatly.NO3^-had a certain inhibitory effect on chlorination of dinoseb,and the concentrations of DBPs were slightly reduced.NO2^-could be oxidized to NO3^-by HOCl,which consumed part of HOCl,and the concentrations of DBPs decreased overall.