臭氧化去除水中敌敌畏效能及机理

Effieiency and mechanism of dichlorvos removal by ozonation

摘要:

为及时处理进入水体中的诸如敌敌畏(DDV)的有机磷类农药,采用臭氧氧化方式对水中的DDV去除进行研究,探讨DDV氧化去除的影响因素及臭氧化机理.结果表明:臭氧能有效降解水中的DDV;增加溶液pH值,能提高DDV的降解效率;90%以上的DDV都是在臭氧化反应初期的5 min内被去除;DDV在臭氧化过程中,有机氯大都被矿化变成无机氯离子,在反应初期DDV矿化程度较快,反应5 min之后,TOC变化幅度就明显减弱;TOC变化同臭氧质量浓度有关,臭氧质量浓度越高,TOC降低幅度越大;GCMS分析发现DDV降解过程中的中间产物主要有磷酸三甲酯、二氯乙酸、二氯乙醛;对二氯乙酸的定量分析发现,pH值及反应时间对溶液中二氯乙酸的质量浓度都没有明显的影响,溶液中二氯乙酸的质量浓度呈高低交替波动状.研究认为水溶液中的DDV臭氧化的降解过程可能存在水解、直接分子臭氧氧化反应、自由基反应3种方式,其中以羟基自由基(.OH)反应为主,.OH与DDV反应首先可能夺取乙烯双键上的氢原子,生成磷酸二甲酯和二氯乙烯自由基,然后进一步被氧化生成各种产物或矿化为磷酸、CO2、氯离子.

Abstract:

The efficiency and mechanism of ozonation of dichlorvos(DDV) had been studied,and experimental result showed that ozone could effectively decompose DDV in the water,and the removal efficiency of DDV could be increased under basic condition.More than 90% of the DDV was removed within the initial 5 min.During the DDV ozonation degradation process,organic chlorine was almost completely converted into chloride.In the initial reaction stage,most of the TOC decomposition was finished during the first 5 min.The TOC removal rate increased with the increasing of ozone concentration.The analysis of GSMS showed that the main intermediate products were trimethyl phosphate,dichloroacetic acid(DCAA) and dichloro acetaldehyde.The quantitative analysis of DCAA showed that pH and reaction time had no obvious influence on the formation of DCAA.During the DDV ozonation process,there were three reaction modes: hydrolysis,direct ozone molecular oxidation and free radical reaction.The double bond of ethylene in the DDV molecule was first attacked by hydroxyl radical(·OH) to form dimethyl phosphate and dichloroethylene radical,which were further oxidized to other kinds of product or mineralized to phosphoric acid,carbondioxide and chloride.