Membrane behaviour of clay soils permeated with multi-electrolyte aqueous solutions

Osmosis is known to play a key role in reducing the transport rate of contaminants through the natural and engineered clay barriers that are used for a number of geoenvironmental applications, such as the lining of waste disposal facilities. Although a significant body of experimental research has focused on the quantification of osmotic phenomena in smectite clays permeated with single-electrolyte solutions, no evidence has been provided about the membrane behaviour of clays in solute mixtures and, specifically, about the so-called osmotic anomalies that have been documented in the biological and chemical literature for fine-porous charged diaphragms in the presence of two or more electrolytes. In view of the similarities between such fine-porous media and smectite clays, the aim of the paper is to illustrate the physico-chemical mechanisms that govern semipermeable membrane behaviour in multi-electrolyte systems, and to identify suitable test conditions for the experimental assessment of the aforementioned phenomena in clay soils.