Equivalent Transport Parameters for Volatile Organic Compounds in Coextruded Geomembrane–Containing Ethylene-Vinyl Alcohol

Abstract

A method to estimate the equivalent diffusion coefficient and partition coefficient of a coextruded ethylene-vinyl alcohol (EVOH) geomembrane (GM) is presented. The method is based on the weighted harmonic mean of diffusion coefficients of each layer and the partition coefficient of the outer layers. The method was evaluated using experimental data obtained with five volatile organic compounds (VOCs) typically found in landfill leachate [methylene chloride (MC), methyl tertiary butyl ether (MTBE), trichloroethylene (TCE), toluene (TOL), and chlorobenzene (CB)] and a coextruded GM composed of outer layers of low-density polyethylene (LLDPE) or high-density polyethylene (HDPE), an adhesive tie layer (maleic anhydride), and a core of EVOH. Equivalent diffusion coefficients computed with the recommended equation were found to be no different statistically from equivalent diffusion coefficients measured using a modified double-compartment apparatus. VOC transport through a composite liner using a coextruded EVOH GM was predicted using a finite-difference model with the equivalent transport parameters as input. Good agreement was obtained between predictions from the model and measured concentrations from a column test simulating a composite liner.

The Ubiquitous Issue of Cross-Mass Transfer: Applications to Single-Use Systems

“…The walls of each bag were modeled as trilayer materials including a central EVOH layer (see Table 6) and by neglecting tie layers. As EVOH is known to be partly a barrier to organic vapors with diffusion coefficients of dry EVOH 10 to 30 times lower than in LDPE [82,83,84,85], factor thirty was applied as an acceptable estimate. Contacts took place, indeed, in dry conditions as the relative humidity (RH) of the air in the bags ca.…”

Review of the Anti-Pollution Performance of Triple-Layer GM/GCL/AL Composite Liners

“…The diffusion of organic pollutants through the GM has been studied to reveal that the diffusion coefficients of polar molecules, such as water molecules and inorganic ions in the GM, are very small, while those of the organic pollutants are quite large [ 47 ]. Eun et al [ 48 ] and Mcwatters [ 6 ] showed that the diffusion rate of organic compounds in the GM is quite high. Mcwatters et al [ 7 ] further showed that the breakthrough time of organic chemical transport through a GM was only 24 h, and the pollutant flux reached a steady state after approximately one week.…”