Mechanism of sodium adsorption on metakaolinite surfaces: MD investigation

XY Liu and J Long and RP Chen and HB Chen and W Yang, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 686, 133275 (2024).

DOI: 10.1016/j.colsurfa.2024.133275

High salt environment will be unfavorable to the permeability of the liner material, and metakaolinite as an additive can effectively adsorb sodium ions. In order to explore the adsorption mechanism, we estimated the molecular structure, dynamics properties, and adsorption behavior of sodium ions on metakaolinite surfaces with different dehydroxylation degrees by molecular dynamics simulations. We determined the adsorption regions, then compared trajectories and self -diffusion coefficients of sodium ions in different regions. The change in the microstructure of metakaolinite leads to an increase in the adsorption sites, which is the ultimate reason for the improvement of its adsorption capacity. The inner -sphere trajectory of sodium ions preferentially diffuses only in a small area near the defect sites, while the outer -sphere trajectories are very dispersed on the whole surface and readily dissociate from the mineral surface and permeate into the free region. Al(IV)-Metakaolinite gibbsite surface has the best adsorption capability on sodium ions and its content might be a useful index for the selection of various aluminosilicates as efficient adsorbents for liner materials.

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