Effect of the solution concentration on the ion permeation through the montmorillonite membranes

The montmorillonite (MMT) membranes were prepared by vacuum filtration method and the MMT membrane surface was covered with a poly vinyl alcohol (PVA) layer. Compared with the uncovered MMT membrane, the covered membrane exhibited excellent stability in water. The ion diffusion results confirmed that the covered PVA layer almost exhibited little effect on the ion permeation. The MMT layer can effectively suppress the permeation of ion, and the retention effect is more obvious for the membrane with thicker MMT layer. Moreover, higher concentration gradient could lead to a lower diffusion coefficient through the MMT layer, which suggested the surface charge of MMT sheet would play an important role in ion diffusion through the MMT layer. The results implied that the Donan effect is predominant for MMT membrane at low concentration.