An analytical solution for organic pollutant diffusion in a triple-layer composite liner considering the coupling influence of thermal diffusion

摘要

This study provides an analytical solution for forecasting one-dimensional molecular diffusion of organic pollutants in triple-layer composite liner system considering the coupling effect of thermal diffusion. The solution is appropriate for two typical bottom boundaries, i.e., Dirichlet and Neumann boundaries. The solution is verified against experimental data and a numerical method. Using the present model, the performances of nine typical barrier liner systems are investigated. The results show that (1) when the Soret coefficient ST increases from 0.01 to 0.1 K-1, given ignoring the effect of thermal diffusion, breakthrough times tb would be overestimated by 7%70%; (2) replacing AL with CCL of the same thickness, the breakthrough time increases by at least 130%; (3) the increase rate of tb due to additional deployment of GCL is generally below 8%; (4) with Dsl decreasing by two thirds (from 9 x 10-10 to 3 x 10-10 m2/s), the breakthrough times increase by 157%-200%; (5) the breakthrough times are improved by 30-80% for Dgmb reduced from 1 x 10-13 to 0.1 x 10-13 m2/s; (6) inversely, the thermal conductivity of GCL and SL, and Dgcl have negligible effect on barrier performances.