Adsorption of hydrated [Y(OH)2]+ on kaolinite (001) surface: Insight from DFT simulation

Abstract Yttrium (Y) is a crucial rare earth element, and it is found in the ion-adsorption rare earth ore of Jiangxi province, China, at a percentage of up to 64.9%. This study used density functional theory calculations to investigate the adsorption behaviour and bonding mechanisms of the Y ion on the surface of kaolinite (001). Understanding these would be beneficial for its mineralisation processing and exploitation. [Y(OH)2(H2O)7]+ was studied as the initial adsorption structure with the lowest binding energy of −1629.19 kJ/mol in an aqueous system. The adsorption models were divided into outer-layer and inner-layer adsorption models based on the adsorption energy and bonding mechanisms. It was found that [Y(OH)2(H2O)7]+ preferred to adsorb on the Al-OH surface with inner-layer adsorption mainly via the coordination bond of Y Os, and through hydrogen bonds for outer-layer adsorption. In the outer-layer adsorption, the adsorption energy of [Y(OH)2(H2O)7]+ on the Al-OH surface was higher than that on the Si O surface because of the steric hindrance effect of the H in the hydroxyl of the Al-OH surface. The Mulliken bond populations of Y Os for inner-layer adsorption showed that it was primarily dominated by the bonding orbital.