Cabbar H C, Bostanci A
Department of Chemical Engineering, Gazi University, Maltepe, 06570 Ankara, Turkey.
J Hazard Mater. 2001 Apr 20;82(3):313-22. doi: 10.1016/s0304-3894(01)00177-7.
Vapor-phase affects the transport, lifetime, and fate of volatile organic contaminants in soils. Furthermore, it has an effect on the assessment and the selection of a remediation approach. The diffusion of dichloromethane (DCM), 1,1,1-trichloroethane (TCE) and carbon tetrachloride (CTC) in dry and wet sand media were investigated using a packed column at room temperature. The apparent diffusion coefficients, D(app), which accounts for effective diffusion and sorption of DCM, TCE and CTC were determined by fitting the experimental data to a diffusion model. The apparent diffusion coefficients of DCM, TCE and CTC for wet sand were found to be larger than the corresponding values for dry sand. The presence of water reduced retardation factors expressed in terms of the sorption capacity for each compound. The results indicated that dry mineral surface provided dominant sorption sites. This is reflected in greater amounts of organic vapors adsorbed under dry conditions. On the other hand, lower sorption capacities for organic compounds on vapor-water interface than on vapor-mineral interface and their low solubilities resulted in smaller retardation factors in wet sand. The experiments clearly demonstrate the role of humidity in sorption and transport of vapors in sand.
气相影响土壤中挥发性有机污染物的迁移、寿命和归宿。此外，它还会影响修复方法的评估和选择。在室温下，使用填充柱研究了二氯甲烷（DCM）、1,1,1-三氯乙烷（TCE）和四氯化碳（CTC）在干砂和湿砂介质中的扩散。通过将实验数据拟合到扩散模型，确定了表观扩散系数D(app)，该系数考虑了DCM、TCE和CTC的有效扩散和吸附。发现湿砂中DCM、TCE和CTC的表观扩散系数大于干砂中的相应值。水的存在降低了以每种化合物的吸附容量表示的阻滞因子。结果表明，干燥的矿物表面提供了主要的吸附位点。这体现在干燥条件下吸附的有机蒸汽量更多。另一方面，有机化合物在气-水界面上的吸附容量低于气-矿物界面，且它们的低溶解度导致湿砂中的阻滞因子较小。实验清楚地证明了湿度在砂中蒸汽吸附和传输中的作用。
