Reaction activity of kaolinite surfaces: Quantum chemistry calculations

Abstract

The anion-kaolinite surface interactions and AuS⁻ adsorption onto the surfaces of kaolinite were studied using the self-consistent-field discrete variation (SCF-X_α-DV) method. Electronic structure and energies of the system of anion AuS⁻ adsorbed on an atomic cluster of kaolinite were calculated. The results show that the systems with lower total energy are those AuS⁻ adsorbed on the edge surfaces, which indicates that the systems of adsorption of AuS⁻ on the edges are more stable relative to those adsorbed on the basal plane. On the other hand, bond order data suggest that significant shifting of atomic charge and the overlapping of electronic cloud between Au (I) of the AuS⁻ and the surface ions of kaolinite would take place in the systems with AuS⁻ being adsorbed on the edges, especially at the site near Al octahedra. Therefore, it can be concluded that edge sites will dominate the complexation reactions of the surfaces of kaolinite, with negligible contributions from other functional groups on the basal plane, which are dominated by either siloxane sites in silica layers or aluminol sites in gibbsite layers.

Keywords

quantum chemistry / kaolinite / surface reaction / adsorption / functional group

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