填埋场覆盖土对典型氯代烃的吸附特性

Adsorption of chlorinated hydrocarbons in landfill cover soil

覆盖土吸附能力的有效评估对填埋场中挥发性氯代烃(VCHs)污染物的控制有重要意义.全面考察了二氯甲烷(DCM)、三氯甲烷(TCM)、1,1,2-三氯乙烷(1,1,2-TCA)、四氯化碳(CT)、顺-1,2-二氯乙烯(c-1,2-DCE)、三氯乙烯(TCE)、四氯乙烯(PCE)和氯苯(CB)8种VCHs在填埋场覆盖层中的吸附特性.结果显示,氯代烷烃和氯代芳烃在覆盖层土壤中吸附等温线符合Freundlich模型(R^2=0.65~0.87),氯代烯烃在覆盖层土壤中吸附等温线符合Langmuir模型(R^2=0.87~0.96).基于拟合结果预测了覆盖土对VCHs的吸附能力,结果表明VCHs的吸附速率随氯取代数的增多而增大;具有相同氯原子取代数目的氯代烃,覆盖土对氯代烯烃和氯苯的吸附量大于氯代烷烃.因此,在填埋场运行管理中,VCHs中浓度较高的氯代烷烃应该是优先治理的污染物之一.覆盖土中VCHs的吸附平衡时间约为20h,吸附速率变化范围为26~250μg/(gsoil·h),远高于文献报道中覆盖土对VCHs的最大降解速率.可以推断,强化覆盖土的生物氧化活性可更有效减少VCHs对环境的不利影响.

The evaluation for adsorption ability of landfill cover soil is significantly important to pollution control of volatile chlorinated hydrocarbons(VCHs).Adsorption characteristics of 8VCHs in landfill cover soil,such as dichloromethane(DCM),trichloromethane(TCM),1,1,2-trichloroethane(1,1,2-TCA),carbon tetrachloride(CT),cis-1,2-dichloroethylene(c-1,2-DCE),trichloroethylene(TCE),tetrachloroethylene(PCE)and chlorobenzene(CB),was completely investigated by static adsorption experiments in this work,respectively.The results demonstrated that adsorption isotherm of chlorinated alkanes and chlorinated aromatic hydrocarbons in the landfill cover soil were both consistent with the Freundlich model(R2=0.81~0.87),and the adsorption isotherm of chloroalkene in the soil was consistent with the Langmuir model(R2=0.87~0.96).The adsorbing capacity of VCHs in cover soil predicted via fitting results were showed as follows.The adsorption rate of VCHs was increased with the increasing number of chlorine substitution;the absorption capacity of chlorinated alkanes was greater than chloroalkene and chlorinated aromatic hydrocarbons in the same number of chlorine substitution.Consequently,the prior pollution control of chlorinated alkanes with higher concentration should be considered in the landfill operation management.Moreover,in this study,the 8VCHs adsorption equilibrium time were all about 20h,but the result of adsorption rate in the range of 26~250μg/(gsoil·h)was much higher than those reported by references.The bioaugmentation soil potential could effectively reduce the adverse effect of VCHs on the environment.