处理温度和时间对六氯苯污染土壤热解吸修复的影响

以山东潮土作为供试土壤,模拟HCB(六氯苯)污染土壤的热解吸试验研究. 考察处理温度和时间2个主要影响因素对热解吸后土壤中HCB的去除率及其热解产物变化的影响. 结果表明:随处理温度的升高和处理时间的延长,HCB的去除率逐渐增大,在处理温度400 ℃、处理时间10 min时,HCB的去除率达到94.2%；在处理温度450 ℃、处理时间60 min时,HCB 的去除率达到99.4 %,去除效果明显,w(HCB)达到HJ 350—2007《展览会用地土壤环境质量评价标准》的A级标准限值(≤0.66 mg/kg)；继续升高处理温度和延长处理时间对HCB的去除率改变不大. HCB的热解吸过程不仅是HCB的物理分离过程,也存在HCB的还原脱氯过程,HCB的热解产物主要为1,3,5-TCB(1,3,5-三氯苯)和1,2,4-TCB(1,2,4-三氯苯)；处理温度450 ℃、处理时间60 min为该污染土壤较为合适的热解吸运行参数. 

Effects of Treatment Temperature and Time on Thermal Desorption of Hexachlorobenzene-Contaminated Soil

A fluvo-aquic soil from Shandong Province was artificially contaminated with hexachlorobenzene (HCB), and thermally treated under different temperatures and times to study the removal efficiencies of HCB and its decomposition products. The results indicated that thermal desorption could effectively remove hexachlorobenzene from the soil. The removal rates of HCB increased with increasing temperature and extending treatment time. The removal rate of HCB was 94.2% when the soil was treated at 400 ℃ for 10 min, and increased to 99.4% when the soil was treated at 450 ℃ for 60 min. The residual concentration was less than the Class A standard of soil quality assessment for exhibition sites (≤ 0.66 mg/kg). Further increases of temperature and/or treatment time had no effects on the removal rate of HCB. The thermal desorption process of HCB was not only a physical separation process, but also a reductive dechlorination process. The residual contaminants in soil after thermal desorption were HCB, 1,3,5-trichlorobenzene and 1,2,4-trichlorobenzene. The optimal operating conditions of thermal desorption were 450 ℃, 60 min.