EDTA对Pd/Fe体系还原脱氯2,4-D的影响  

Effects of EDTA on the Reductive Dechlorination of 2,4-D by Pd/Fe

作　　者：周红艺[1] 聂亚中 陈勇[1] 雷双健[1] 

机构地区：[1]浙江工业大学环境学院,杭州310014

出　　处：《环境科学》2016年第2期595-601,共7页Environmental Science

摘　　要：针对Pd/Fe体系对含氯有机物催化还原脱氯过程中,零价铁易腐蚀并在颗粒表面形成钝化层,阻碍目标污染物的进一步脱氯去除,本研究利用乙二胺四乙酸(EDTA)与Fe2+和Fe3+的络合作用,消除Pd/Fe颗粒表面的钝化层,使还原脱氯过程得到持续进行.实验考察了EDTA的投加方式和投加量、p H、钯负载率、温度等因素对2,4-二氯苯氧乙酸(2,4-D)还原脱氯的影响.结果表明:1EDTA浓度为25.0 mmol·L-1、投加速率为20 m L·h-1时,苯氧乙酸(PA)生成率在20 min达到了90.7%.而未加EDTA的反应体系,反应210 min后,PA的生成率仅为74.5%;2EDTA可以络合Pd/Fe体系在催化脱氯过程中生成的Fe2+和Fe3+,防止或减缓了Pd/Fe颗粒表面钝化层的形成,提高了反应活性;3适宜的2,4-D催化脱氯条件为:浓度25.0mmol·L-1的EDTA溶液,投加速率20 m L·h-1、初始p H为4.2、钯负载率0.050%、温度30.0℃、搅拌速率200 r·min-1,反应210 min,20.0 mg·L-1的2,4-D几乎可完全转化为PA;42,4-D催化脱氯的中间产物主要是2-氯苯氧乙酸及微量的4-氯苯氧乙酸,最终产物为苯氧乙酸.In Pd / Fe system,zero-valent iron（ ZVI） passivation layer is easily formed on the particle surface during the catalytic reductive dechlorination of chlorinated organics,hindering further dechlorination of target contaminants. In this paper,the passivation layer on the Pd / Fe particle surfaces could be eliminated by the chelation of disodium edetate（ EDTA） with Fe2 ＋,Fe3 ＋,making the reductive dechlorination continue. The experiment investigated the effects of EDTA addition manner and dosage,p H,Pd loading and temperature on dechlorination of 2,4-dichlorophenoxyacetic acid（ 2,4-D） by Pd / Fe. The conclusions can be summarized as follows： 1Phenoxyacetic acid（ PA） generation ratio reached 90. 7% within 20 min with EDTA concentration of 25. 0 mmol·L- 1and flow rate of 20 m L·h- 1,while it was only 74. 5% after 210 min in the system without EDTA. 2The EDTA could chelate the Fe2 ＋and Fe3 ＋generated from the process of 2,4-D dechlorination by Pd / Fe,preventing or slowing down the formation of passivation layer,and accelerating the reduction efficiency. 3The appropriate experimental parameters for 2,4-D removal were as follows： EDTA flow rate of 20 m L·h- 1,cEDTA of 25. 0 mmol·L- 1,Pd loading of 0. 050%,200 r·min- 1,p H 4. 2 and 30. 0℃. The removal percentage of 20. 0 mg·L- 12,4-D reached nearly up to 100% within 210 min under these conditions. 4 The intermediates of 2,4-D catalytic dechlorination included 2-chlorophenoxyacetic acid（ 2-CPA） and trace 4-chlorophenoxyacetic acid（ 4-CPA）,and the end product was PA.

关 键 词：PD/FE 脱氯 EDTA 2 4-D 苯氧乙酸 

分 类 号：X131[环境科学与工程—环境科学]