The standard reaction Gibbs energy of the cation exchange reaction of the biionic (Mg,Na)-form of montmorillonite

Abstract

The aim of this paper is to contribute to the knowledge of the quantitative formulation of the ion exchange reaction in clays. The equilibrium was studied at 11 degrees C in a system of solutions of NaCl and MgCl2, the concentrations of which never exceeded 0.1 mol/dm(3), and the "Jelenkovac" montmorillonite, the particle size of which was below 2 mu m. The standard reaction Gibbs energy of the Mg-Na exchange determined by applying the Gapon equation (Delta(r)G(Mg)(0Na) = 11.9 kJ/mol) and that obtained according to Levy-Shainberg (Delta(r)G(Mg)(0Na) = 10.5 kJ/mol) showed a large degree of concordance. The latter method also includes the exchangeable ion activity coefficient obtained from ion-clay interaction data which includes data on the thickness of the intel layer space in the montmorillonite structure, as well as the thickness of the basis montmorillonite layer itself.