Specific adsorption of lithium, sodium, potassium, and strontium to montmorillonite: observations and predictions.

The adsorption of Li, Na, K, Cs and Sr onto montmorillonite is studied within the framework of a model that accounts for specific binding as well as adsorption in the double-layer region. Variations in solution concentrations of cations due to adsorption are considered. Experimental data include adsorption measurements in binary and ternary systems of cations and adsorption data taken from the literature. Solution and adsorbed concentrations of cations are well simulated and predicted by the calculations for a wide range of variations of cation ratios, ionic strengths and clay concentrations. The values determined for the binding coefficients are: K_Li = 0.6 M^-1, K_Na = 1 M^-1, K_K = 2 M^-1, K_Ca = 200 M^-1. (Authors' abstract)-C.N.