有机-重金属复合污染土壤的热处置工艺探索

Exploration on the Thermal Treatment Technology of Organic and Heavy Metal Co-contaminated Soil

为了解决有机-重金属复合污染土壤处置工艺较为复杂、处置成本较高等问题,考察了加热温度和加热时间对有机-重金属复合污染土壤的影响,确定了最佳热处置工艺参数。试验研究结果显示,随着加热温度的提高,多环芳烃、多氯联苯和石油烃的含量逐渐下降,铜、镍、铅、镉、砷和汞的浸出浓度出现先增加后减少的趋势,弱酸提取态含量占比逐渐下降。400℃下加热,随着加热时间的增加,各重金属的浸出浓度逐渐降低。加热后土壤粘粒含量下降、粗砂粒含量升高,土壤有机质含量和pH值有所降低,水溶性盐总量显著提高。最佳热处置工艺为400℃下加热4 h,各重金属的浸出浓度均达到地下水Ⅳ类水质标准,有机污染物含量满足一类建设用地要求。

In order to solve the problems of complex disposal process and high disposal cost of organic and heavy metal co-contaminated soil,the effects of heating temperature as well as heating time on the treatment of organic matter and heavy metal compound polluted soil were investigated,the best thermal treatment parameters were determined.The experimental results show that with the increase of heating temperature,the contents of polycyclic aromatic hydrocarbons,polychlorinated biphenyls and petroleum hydrocarbons gradually decrease,the leaching concentrations of cadmium,copper,nickel,lead,arsenic and mercury first increase and then decrease,and the proportion of weak acid extracted content gradually decrease.When heated at 400℃,the leaching concentration of heavy metals and arsenic increase gradually with the decreasing of heating time.It is found that after heating,the content of soil clay decrease,the content of coarse sand increase,the content of soil organic matter and the pH value of soil decrease,while the total amount of soil water-soluble salt increase significantly.It is concluded that the best thermal treatment parameters are heated at 400℃for 4 hours,the leaching concentrations of heavy metals and arsenic meet the class IV quality standard of groundwater,and the content of organic pollutants meet the requirements of class I construction land.