Effect of chemico-osmosis on solute transport in clay barriers

Abstract

The significance of chemico-osmosis on solute transport through clay barriers exhibiting membrane behaviour was investigated by conducting coupled solute transport model simulations in which the effect of chemico-osmosis was either included or omitted. Results show that percentage reductions in solute flux (P RF) through a clay barrier increase with increasing membrane efficiency coefficient, ω; decreasing Péclet number, P e (representing the relative importance of advection to diffusion); and increasing osmotic number, N π (representing the relative importance of chemico-osmosis to diffusion). Predicted P RF values under diffusion-dominated conditions (P e = 0·01) based on experimental data reported for bentonite barriers in contact with monovalent salt solutions (0·015 ≤ ω ≤ 0·73; 0·049 ≤ N π ≤ 0·30) ranged from 3·8 to 74% when the effect of chemico-osmosis was omitted (i.e. by setting N π = 0). When the effect of chemico-osmosis was included, P RF increased by 0·5–10%, indicating that chemico-osmosis has only a minor influence on solute transport in bentonite barriers exhibiting N π ≤ 0·30.