Transport of volatile organic compounds through PVC and LLDPE geomembranes from both aqueous and vapour phases

The diffusive migration in the aqueous and vapour phases of four volatile organic compounds (VOCs: benzene, toluene, ethylbenzene and xylenes) through samples of 0.76 mm (30 mil) thick flexible poly-vinyl chloride (PVC) and 0.76 mm (30 mil) linear low-density polyethylene (LLDPE) geomembranes are compared based on both sorption and diffusion tests. Diffusion coefficients for the PVC geomembrane were in the range of 5.0-10 x 10(-13) m(2)/s for diffusion from both the aqueous and vapour states. The range for LLDPE was 2.5-5.0 x 10(-13) m(2)/s. Diffusive transport of VOC contaminants through geomembranes in a simulated landfill environment (i.e. in the presence of water vapour) is identical despite the phase they originated from, simplifying the analysis of contaminant transport. The partitioning (sorption) coefficients for PVC were in the range 100-1075 with respect to aqueous phase concentrations. The corresponding values with respect to vapour phase concentrations were 22-290. LLDPE partitioning (sorption) coefficients were 200 475 with respect to aqueous phase concentrations and 44-123 with respect to vapour phase concentrations.