摘要
在氯代烃污染场地修复中,电阻加热技术因不受地层条件影响、污染物修复效率高等特点在氯代烃污染地块修复中得到了广泛关注,但仍存在用电量大、能耗较高等问题.通过创建基于脉动直流电的电热耦合修复体系,以三氯乙烯为模拟污染物,比较了其与传统基于交流电模式的电阻加热技术在修复非均质介质三氯乙烯重质非水相液体(DNAPL,dense nonaqueous-phase liquid)时的去除效率及能耗,分析了造成其修复差异的原因.结果表明:电热耦合体系下介质的增温幅度明显优于交流电体系,最高温度可达100℃,而交流电体系最高温度仅为70℃,这表明脉动直流电通过引入电极水电解反应提高了介质电导率,从而达到更高的温度,进一步促进了污染物的加热挥发作用.反应结束后,电热耦合体系中三氯乙烯主要集中在阴极侧,而交流电体系中三氯乙烯无定向分布特征,表明电热耦合体系中的直流电场可通过电渗析作用增强三氯乙烯向阴极的定向迁移.经过48 h持续反应,脉动直流电体系对三氯乙烯DNAPL的去除率为88%,可较同等电压下交流电体系提升2.2倍,而能耗仅为1.92kW·h/(log·kg),是交流电体系的32%.研究显示,利用脉动直流电加热可通过强化相变迁移和电渗析定向迁移效应共同作用于三氯乙烯去除,有效提高三氯乙烯DNAPL的去除率,降低体系修复能耗.
Electrical resistance heating technology has been widely applied in the site remediation of chlorinated hydrocarbons because of its high efficiency regardless of site heterogeneity,but it requires high energy input. In this study,we proposed a system that combines electrical resistance heating (ERH) process with electrokinetic migration for enhanced remediation based on pulsed direct current (PDC).Trichloroethylene was used as a model pollutant,and its removal efficiency and energy consumption were compared with the traditional ERH technology based on alternating current (AC). As a result,faster temperature increase was achieved by PDC compared with the conventional AC. The highest temperature in PDC system was 100 ℃ while only 70 ℃ was achieved by the conventional AC. PDC could increase the electrical conductivity of silica sand by introducing water electrolysis reactions into the remediation process. After 48 h of treatment,88% of TCE was removed from fine silica sand using PDC,which was 2. 2 times that of AC mode. The highest concentration of TCE with PDC mode was found near the cathode,indicating electroosmosis also contributed to TCE migration and removal from fine sand.The normalized energy consumption in PDC system was 1. 92 kW·h/ (log·kg),only 32% of that in the AC system. The results indicated that PDC is a promising remediation approach to improve the energy-efficiency and effectiveness of ERH.
作者
耿竹凝
刘波
黄菀
李广贺
张芳
GENG Zhuning;LIU Bo;HUANG Wan;LI Guanghe;ZHANG Fang(State Key Joint Laboratory of Environment Simulation and Pollution Control,School of Environment,Tsinghua University,Beijing 100084,China;National Engineering Laboratory for Site Remediation Technologies,Beijing 100015,China)
出处
《环境科学研究》
EI
CAS
CSCD
北大核心
2020年第8期1911-1918,共8页
Research of Environmental Sciences
基金
国家重点研发计划项目(No.2018YFC1802500)。
关键词
三氯乙烯
重质非水相液体
原位热修复
脉动直流电
trichloroethylene
dense nonaqueous-phase liquid
in situ thermal remediation
pulsed direct current
