两种改性剂对多氯联苯污染土壤协同热脱附影响研究

采用热脱附技术处理多氯联苯污染土壤已经成为了一种主要的场地修复方式。为提高热脱附效率,降低能耗,以典型电力电容器污染土壤为对象,采用2种改性剂(零价纳米铁和氢氧化钠)研究协同热脱附下多氯联苯的去除效率、分布特性及毒性当量。结果表明纳米铁和NaOH存在的条件下,有效提高了多氯联苯和毒性当量的去除效率,在较低温度下尤其显著,因此添加改性剂能够有效地促进热脱附过程。纳米铁的协同热脱附机理为显著强化了热脱附过程的传质传热,同时伴有一定的脱氯降解。NaOH的添加在较低温度下实现了较强的脱氯降解作用,加氢脱氯机理可用来解释协同热脱附过程中多氯联苯的脱氯反应过程。上述研究结果为多氯联苯污染土壤的场地修复提供理论基础。

Effect of Two Additives on Thermal Desorption of PCBs Contaminated Soil

Thermal desorption has become an effective site remediation technology for treating polychlorinated biphenyls (PCBs) contaminated soil. In order to increase efficiency and reduce energy consumption, synergetic thermal desorption of PCB-contaminated soil collected from typical soil contaminated by waste capacitors and transformers was studied. By two additives (nano zerovalent iron and sodium hydroxide) addition, removal efficiency (RE), composition and toxic equivalency quantity (TEQ) of PCBs were investigated. The results showed nano zerovalent iron and NaOH effectively increased the RE of PCBs and TEQ, especially at lower temperature, thus additives strengthened the process of thermal desorption. The synergetic mechanism of nano zerovalent iron on thermal desorption is significant promotion on mass and heat transfer process, accompanied by dechlorination and decomposition. The addition of NaOH realized strong dechlorination and destruction at lower temperature. The hydrogenation/dechloriantion mechanism is proposed to explain the PCBs pathways during the thermal desorption. The results presented in this study will provide theoretical basis for site remediation of PCBs contaminated soil.?