温度和停留时间对DDT污染土壤热脱附效果的影响

采用热处理方法分别对自配DDT及其衍生物(DDTs,包括p,p'-DDT、o,p'-DDT、p,p'-DDD和p,p'-DDE)污染土壤在5个温度(100,200,300,400,500℃),6个停留时间(5,10,20,30,40,50 min)下的DDTs去除率及热处理前后的DDTs残留浓度变化进行了研究。研究结果表明:热脱附对DDTs污染土壤修复效果显著。当温度达到300℃以上时,热脱附技术的优势开始显现。300℃下40 min时的DDTs去除率与400℃及500℃处理10 min时相当,均能达到97%以上。对热处理前后土壤中DDTs的残留浓度进行检测,结果表明:土壤中的主要污染成分p,p'-DDT在200℃以上时大量减少,主要转化为p,p'-DDE。p,p'-DDE在200～300℃时大量生成,400～500℃被去除。根据能耗分析结果得出较佳热处理条件为400℃,10 min。

EFFECT OF TEMPERATURE AND RESIDUE TIME ON TREATMENT OF DDTS CONTAMINATED SOIL BY THERMAL DESORPTION TECHNOLOGY

Thermal desorption technology was adopted to study the removal rates and residual concentrations of DDTs(p,p′-DDT,o,p′-DDT,p,p′-DDD,p,p′-DDE) in the artificially contaminated soil under five temperature levels(100,200,300,400,500 ℃,respectively) and six levels of residue time(5,10,20,30,40,50 min,respectively).The removal rates of DDTs increased sharply when the temperature was above 300 ℃.The removal rate(more than 97%) of DDTs under a temperature of 300 ℃ and 40 min was close to those under temperature of 400 ℃ and 500 ℃ with the residue time of 10 min.As for the residual concentrations of DDTs in the soil,the main pollutant,p,p′-DDT decreased significantly when the temperature was above 200 ℃ and mainly transferred to p,p′-DDE.The concentrations of p,p′-DDE increased sharply when the temperature was between 200 ℃ and 300 ℃.Also,it was removed when the temperature was above 400 ℃.According to the results of energy consumption analysis,the optimum temperature and residue time were 400 ℃ and 10 min,respectively.