Mechanism insights into the hydrated Al ion adsorption on talc (001) basal surface: A DFT study

Abstract

Al ion was reported to have an enhanced depression of Carboxymethyl cellulose (CMC) on talc flotation. However, how Al ion is adsorbed on talc surface remains unclear. Herein, the hydrated Al ion adsorption on talc (001) basal surface was creatively studied by DFT calculations. The effective number of H2O ligands in hydrated Al ion was probed and the optimal adsorption structure was investigated. We found that Al(OH)3(H2O) was the preferred hydrate structure, and the top O site was its optimal adsorption position on talc surface. Furthermore, Al-O chemical bond was not formed, and H2O was found to act as a bridge to connect the Al(OH)3(H2O) to talc surface by H-bond between H of H2O ligand and surface O instead of H-bond between H of Al(OH)3 in Al(OH)3(H2O) and surface O. However, [Al(OH)4]− cannot form the H2O bridge due to the electrostatic repulsion, and its adsorption on talc surface was energetically unsupportive. Moreover, we found that the formation of H-bond was due to the hybridization reaction between O 2p and H 1s orbitals, and slight electron transfers between O and H atoms were also observed. Finally, the Al(OH)3(H2O) was adsorbed on talc surface, which is consistent with the performed experimental result.