Objective On the basis of orbital asymmetric hybridization, this study investigated the adsorption kinetics characteristics of alkali metal ions (Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ ) on the surface of kaolinite particles.

Method The ion exchange adsorption kinetic model was used to calculate the ion diffusion distance from the soil / liquid interface and the surface potential of the kaolinite particles under different conditions. Further characterize the different adsorption types of ions on the surface of kaolinite particles and quantitatively evaluate the strength of different types of adsorption forces.

Result ① Only first-order adsorption kinetic characteristics are presented when alkali metal ions (Li ⁺ , Na ⁺ , Cs ⁺ ) are adsorbed on the exchange surface of kaolinite particles, but there are significant differences in the equilibrium adsorption volume, which manifested as Cs ⁺ > Li ⁺ > Na ⁺ . ② On the surface of the kaolinite particles, Li ⁺ is subject only to electrostatic adsorption, and Na ⁺ subjected to electrostatic adsorption and non-classical polarization, Cs ⁺ subjected to electrostatic adsorption, nonclassical polarization and polarization-induced covalent effect. The electrostatic adsorption and nonclassical polarization was weakened with the increase of electrolyte concentration and polarization induced valence effects enhanced with the increase of electrolyte concentration. ③ Ions are subjected to different polarization on the particle surface. The effective charge of electrostatic adsorption(β_e), non-classical polarization(β_p) and polarization induced valence effects(β_c) are manifested as β_eLi = βe_Na = β_eCs = 1, β_pNa << β_pCs , β_c are only showed in the adsorption process of ion Cs ⁺ on whose surface of the kaolinite particles.

Conclusion The adsorption kinetics characteristics of alkali metal ions (Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ ) on the surface of kaolinite particles are obviously different, which are influenced by the mineral surface potential. The alkali metal ions generate different ion polarization effects on mineral surfaces, resulting in various types of adsorption forces experienced by the alkali metal ions on the surface of kaolinite particles. This study will provide new ideas for the improvement of the soil / liquid interface reaction theory on variable charge mineral surfaces.