FeCl3强化汞污染土壤热解吸修复

目前采用的热解吸技术修复汞污染土壤所需热解吸温度(600~800 ℃)较高,导致修复成本很高,也造成土壤本身结构的破坏. 采用在土壤中加入添加剂的方式来降低土壤修复的热解吸温度和热解吸时间, 分析了热解吸修复汞污染土壤时FeCl₃的最佳投加量、热解吸时间和热解吸温度,并且对试验条件进行优化. 结果表明:在土壤中添加FeCl₃能够有效提高汞的去除率,可降低热解吸所需的温度和时间. 当热解吸温度为400 ℃、热解吸时间为30 min时,随着c(FeCl₃)/c(Hg)的增加,汞的去除率逐渐提高. c(FeCl₃)/c(Hg)、热解吸温度、热解吸时间分别为150、450 ℃、20 min下,是汞污染土壤热解吸修复的最佳条件. 在热解吸过程中添加FeCl₃,可以使土壤中的w(Hg)在较低热解吸温度、较短的热解吸时间下降至GB 15618—1995《土壤环境质量标准》三级标准限值(1.5 mg/kg)以下. 

Thermal Desorption of Mercury from Contaminated Soil with the Addition of FeCl3 as Enhancement

Current thermal desorption methods for remediating mercury contaminated soil are expensive and destructive to soil characteristics due to high treating temperatures (600-800 ℃). In the present study, relatively low temperature thermal desorption treatments with different additives for mercury contaminated soil were developed. The operating parameters including the amounts of additive, temperature and heating time were optimized. The results showed that high removal efficiency of mercury from soil could be obtained with FeCl₃ as an additive during the thermal desorption process with a lower temperature and less time. The removal efficiency increased with increasing c(FeCl₃)/c(Hg) when the soil was treated at 400 ℃ for 30 minutes. The addition of FeCl₃ at 150 times the mole concentration of mercury in the soil was needed to effectively remove Hg from contaminated soils compared with no addition of FeCl₃. The parameters were further optimized for thermal treatment at 450 ℃ for 20 minutes. With the addition of FeCl₃, the mercury content in the contaminated soil could be reduced at relatively low temperature and short time to less than the limit of the environmental quality standard for soils of China.