Sorption and Diffusion of BTEX through Thin-Film EVOH

The diffusive properties of thin-layer ethylene vinyl alcohol (EVOH) thin-films often used in vapour barriers and co-extruded geomembranes were studied. Sorption, diffusion and permeation were studied for benzene, toluene, ethylbenzene and xylenes (BTEX) contaminants in dilute aqueous solutions. Films with 32 and 44 mol% EVOH were studied, showing a decrease in permeability with higher EVOH content. Sorption was studied for the EVOH thin-films at room temperature, as well as 30, 40 and 50°C. An increase in sorption of BTEXs was observed at elevated temperatures. Results show that the permeability of these non-polar hydrocarbons decreases with decreasing EVOH content from the 32 mol% thin-film (P_g=15–57 x 10^{– 14}m²s^–1), to the 44 mol% thin-film (P_g=3–5 x 10^–14m²s^–1). When compared with the EVOH inner barrier layer of a co-extruded LLDPE/EVOH geomembrane, the co-extruded geomembrane has the lowest P^g (0.7–0.9 x 10^minus;14m²s^–1). P^g values are significantly lower for EVOH thin-films and co-extruded geomembranes when compared with standard LLDPE, HDPE and PVC geomembranes.