Coupled effect of UV ageing and temperature on the diffusive transport of aqueous, vapour and gaseous phase organic contaminants through HDPE geomembrane

Abstract

High-density polyethylene geomembranes (HDPE GMBs) are indispensable in constructing composite barriers of modern engineered landfills. GBMs would be exposed to various weathering conditions apart from the interaction of organic pollutants in landfill gas and leachate. Though many studies have investigated the contaminant's migration, the transport of volatile organic compounds (VOCs) concerning the synergistic effect of thermal and UV exposure has not been thoroughly explored. Given this, the present study investigated the diffusive transport of four VOCs (aqueous and vapour phase) at 10 °C, 25 °C, 40 °C, and methane diffusion through an HDPE GMB subjected to accelerated UV weathering. The results indicated that the contaminant phase (aqueous, vapour, gaseous), its properties (aqueous solubility, molar mass, polarity), temperature, and the extent of ageing significantly influenced the transport behaviour. The standard oxidative induction time decreased appreciably with ageing duration following a first-order exponential decay. The change in tensile properties and melt flow index indicated the dominance of UV degradation by cross-linking, resulting in an increased crystallinity of GMB that was identified using Fourier transforms infrared (FTIR) spectroscopy and Differential scanning calorimeter (DSC). The crystallinity increased with UV ageing and caused the sorption and diffusion coefficients to decrease.