Effect of layer charges on exfoliation of montmorillonite in aqueous solutions

In this work, the exfoliation of montmorillonite related with electric charges on the layers in aqueous solutions were investigated through the measurements of zeta potential, turbidity and atomic force microscopy, as well as molecular dynamics simulation. The charge amount on montmorillonite layers was adjusted by blocking or neutralizing the layer charges with tetraethylenepentaminecopper (II) ([Cu(tetren)]2+) through cation exchange reaction. The experimental results have shown that the exfoliation closely correlated to the amount of the layer charges. The larger are the charge amount on montmorillonite layers, the more easily the montmorillonite is exfoliated. This observation might be attributed to the repulsive energy (electrostatic and hydration repulsion) was stronger between the high charged montmorillonite layers than low charged ones.