To Distinguish Electrostatic, Coordination Bond, Nonclassical Polarization and Dispersion Forces on Cation-Clay Interactions

Recent researches have suggested inorganic ions give rise to complex interfacial adsorption effects, but people do not fully understand the mechanisms at present. In this study, the interface adsorption energies of H+ (without extranuclear electron), Li+ and Cs+ (with extranuclear electrons but possessing a large difference in ionic radius) on montmorillonite surface were estimated to elucidate the contribution of electrostatic, coordination bond, nonclassical polarization and dispersion forces to interface adsorption energies. The results showed that under given cationic concentrations, the equilibrium adsorption energies followed the sequence of Cs+ > H+ > Li+. Moreover, the adsorption energies of H+ (with minimum ion-radius) was close to Cs+ (with largest ion-radius) but much larger than that of Li+ under relative low cationic concentrations, whereas the adsorption energies of Cs+, H+ and Li+ approached each other under the highest cationic concentration of 0.1 mol L-1, although their ionic sizes are i...