纳米零价铁对γ-HCH的降解效果及机理研究

Degradation efficiency and mechanisms of γ-hexachlorocyclohexane by nanoscale zero valent iron particles

采用液相还原法制备纳米零价铁(nZVI),透射电镜表征显示,其粒径<20nm,在介质中处于团簇状态.利用所合成的nZVI对γ-HCH进行了还原脱氯研究,结果表明,nZVI具有很高的表面反应活性,当用量为0.5g/L时,反应90min,对2.5mg/L的γ-HCH去除率达90%以上.nZVI对γ-HCH的去除符合准一级反应动力学方程,其反应速率和去除率与pH值、nZVI添加量、γ-HCH初始浓度、共存离子等因素有关.反应速率随pH值的减小而增大,NO3-对反应速率有较强的抑制作用,Ca2+,Mg2+和SO42-对反应速率影响不大.利用GC-MS检测到降解产物四氯环己烯(TeCCH)和氯苯(CB)的存在,推测反应机制为双氯脱除反应和脱氯化氢反应.

Nanoscale zero valent iron particles（nZVI） were synthesized using liquid phase reduction method.TEM analysis indicated that the size of nZVI was 20 nm,and clustered in the medium.It displayed high reactivity to decompose γ-hexachlorocyclohexane（γ-HCH）.More than 90% of γ-HCH was removed in 90 min with 0.5 g/L of nZVI in the solution.The degradation reaction followed a pseudo-first order kinetic.The reaction rate coefficient and removal efficiency were affected by many factors,such as the amount of nZVI,pH,the initial concentration of γ-HCH and coexisting ions.The reaction rate decreased with increasing initial pH.NO3-greatly inhibited the degradation reaction,but Ca2＋,Mg2＋ and SO42-had little effect on it.Degradation products such as tetrachlorocyclohexene（TeCCH） and chlorobenzene（CB）,were identified by GC/MS.Based on this,the main reaction mechanism was suggested as dehydrochlorination and dichloroelmination.