摘要
传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O_(2)和H_(2),配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O_(2)产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从0~2 mg/L增加到4~14 mg/L,黏土区域较高。通电过程中,循环井促进O_(2)、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O_(2)提高了氧化剂利用率,有望应用于有机污染地下水修复。
Traditional groundwater remediation by in-situ chemical oxidation has the problem of short transport distance and low utilization efficiency for oxidants.In this study,a two-well groundwater circulation mode was applied to enhance mass transfer;and electrolysis in the injection well was utilized to generate O_(2)and H_(2)in-situ.In order to use Fe(Ⅱ)in sediments for TCE degradation,ethylenediamine tetraacetic acid(EDTA)was added to chelate Fe(Ⅱ)and increase•OH production.The system performance was evaluated in a two-dimensional sandy tank filled with interlayers of sand and clay.The current was set to 0.2 A and the flow rate was 72 cm/d.Results from a 9-day experiment showed that~3 mg/L TCE was degraded down to~1 mg/L(67%removal).Addition of 0.5 mmol/L EDTA before electrolysis increased the dissolved Fe(Ⅱ)concentration in the aquifer from 02 mg/L to~414 mg/L after a day of hydraulic circulation,with the higher concentrations around clay fillings.During electrolysis,groundwater circulation promoted the effective contacts and reactions of O_(2),Fe(Ⅱ)-EDTA and TCE for TCE degradation.In the early stage,the rates of Fe(Ⅱ)oxidation and TCE degradation were slower around clay fillings than in other areas,but the gap gradually decreased in the later stage.Adding acetate upon completion of electrolysis promoted Fe cycling and utilization in the aquifer.This remediation process improved the oxidant transport distance through groundwater circulation and the oxidant utilization efficiency through use of relatively stable O_(2)and Fe(Ⅱ)-EDTA from aquifer,demonstrating its potential application in the remediation of organic pollution in groundwater.
作者
刘洋
谢雯静
郑云松
张耀强
蔡其正
袁松虎
LIU Yang;XIE Wenjing;ZHENG Yunsong;ZHANG Yaoqiang;CAI Qizheng;YUAN Songhu(State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Wuhan),Wuhan 430074,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2021年第5期197-207,共11页
Earth Science Frontiers
基金
国家重点研发计划项目(2018YFC1802504)。
关键词
电化学
循环井
化学氧化
二价铁
三氯乙烯
electrochemistry
circulation well
chemical oxidation
ferrous iron
trichloroethylene
