调理剂对多环芳烃污染黏性土壤热脱附的影响

Effects of Conditioners on Thermal Desorption of Clay Soil Contaminated with Polycyclic Aromatic Hydrocarbons

黏性土壤具有颗粒细小和通透性弱等特点,会影响受多环芳烃(PAHs)污染的黏性土壤的热脱附效率,因此本研究选择6种调理剂(CaO、MgO、Al2O3、Fe2O3、K2CO3和沸石)来改良黏性土壤,考察调理剂对PAHs污染黏性土壤热脱附的影响,分析了调理剂对黏性土壤塑性指数、pH、阳离子交换量、粒径的影响,探讨了调理剂对PAHs污染黏性土壤热脱附的影响机制.结果表明:(1)添加6种调理剂均提高了PAHs污染黏性土壤的热脱附效率,可有效去除总PAHs,并显著降低超标物质苯并[a]蒽(Baa)和苯并[a]芘(Bap)的残留浓度,其中在添加10%CaO条件下,总PAHs去除率最高,达97.48%.(2)分别添加6%的CaO、MgO、K2CO3调理剂后,黏性土壤塑性指数由18.55%分别降至14.38%、13.58%和15.25%,但添加Al2O3、Fe2O3和沸石均增加了黏性土壤的塑性指数.(3)综合分析,调理剂改良黏性土壤主要通过阳离子交换作用和絮凝作用.研究显示,调理剂改变了黏性土壤的细粒含量和阳离子交换量,进而影响其塑性指数,提升了PAHs热脱附去除效率,CaO、MgO、K2CO3可作为调理剂的合适选择.

Clay soil with fine particles and low permeability affects the thermal desorption efficiency of polycyclic aromatic hydrocarbons(PAHs) in contaminated clay soil. Therefore, six conditioners(CaO, MgO, Al2O3, Fe2O3, K2CO3and zeolite) were selected to improve the clay soil and the thermal desorption efficiency of the PAHs-contaminated clay soil in this study. The effects of the conditioners on the plasticity index, pH, cation exchange capacity, and particle size of the modified clay soil were investigated, and the mechanisms of the effects of the conditioners on the thermal desorption of the PAHs-contaminated clay soil were discussed. The results showed that:(1) The addition of the six conditioners improved the thermal desorption efficiency of the PAHs-contaminated clay soil, effectively increased the removal of the total PAHs, and significantly reduced the residual concentrations of benzo[a]anthracene(Baa) and benzo[a]pyrene(Bap).The highest removal rate of total PAHs was up to 97.48% when 10% CaO was added to the clay soil.(2) After adding 6% CaO, MgO, and K2CO3to the clay soil, the plasticity index of the clay soil decreased from 18.55% to 14.38%, 13.58%, and 15.25%, respectively. However,the addition of Al2O3, Fe2O3, and zeolite increased the plasticity index of the clay soil.(3) The improvement of the clay soil by the conditioners was mainly attributed to the cation exchange and flocculation. The results showed that the conditioners changed the fine grain content and cation exchange capacity of the clay soil, which affected the plasticity index and improved the thermal desorption efficiency of PAHs. In summary, CaO, MgO and K2CO3could be suitable conditioners.