Permachor Method To Predict Diffusivity Coefficients of Organics in Aqueous Solutions in Flexible Membrane Liners

Abstract

The diffusion of organic contaminants through plastic Flexible Membrane Liners (FMLs) used in landfills and surface impoundments is an important criteria for evaluating synthetic liner performance. An experimental method has been developed and used to measure diffusivities of organic contaminants commonly found in landfill leachate from an aqucous solution through High Density Polyethylene (HDPE). These data were utilized to evaluate the applicability of the Permachor Method developed by Salame (1961) to predict the diffusion of other organics through FMLs. The Permachor equation can be used in combination with the relationship between the partition coefficients of organics in aqueous organic solution and the octanol-water partition coefficients to predict permeability factors which in turn can be used to calculate the diffusion coefficients of a range of organic chemicals in a plastic FML. Once the relationship between permeability and Permachor are determined for a given plastic FML for a few organic chemicals, the method can be used to predict the permeability of many other organic chemicals. The properties of the plastics and the additives used in its formulation including carbon black appear to influence the diffusion rates.

Non-Fickian diffusion in systems with complex interfaces

“…65 August and Tatsky 66 measured the transmission rates of six solvents through a 1.0 mm thick HDPE geomembrane. 70 The results from this work and similar experiments by Haxo, and Barrett and Stessel with gasoline and HDPE geomembranes indicate that strong selectivity by the geomembrane causes very different permeation rates for components of mixtures. The upper compartment contained the solvent mixture, the composition of which was held constant, and the lower compartment was partially evacuated.…”

Viscoelastic (Non‐Fickian) Diffusion

“…144,145 For example, even though the ratio between the concentrated toluene and the dilute solution was 1000:1, the ratio between the permeation rates through the geomembrane was 20:1. 146 The results from this work and similar experiments with gasoline and HDPE geomembranes indicate that the strong selectivity by the geomembrane may lead to very different permeation rates for the components of mixtures. 139,[147][148][149] The results from these studies allow one to conclude that significant quantities of an organic can permeate through a geomembrane due to selective permeation, even when the organics are present at low concentration.…”