Molecular Dynamics Simulations of Quartz (101)–Water and Corundum (001)–Water Interfaces: Effect of Surface Charge and Ions on Cation Adsorption, Water Orientation, and Surface Charge Reversal

Abstract

Quartz and corundum surfaces in water are capable of adsorbing and releasing protons, a behavior attributed to the amphoteric character of their silanol and ab initio calculations are used to obtain different charge densities on crystalline (101) quartz and (001) corundum surfaces and the corresponding charge delocalization after deprotonation of the silanol and aluminol groups, respectively. Then, classical molecular dynamics simulations are used to study the interaction of water with the charged quartz and corundum surfaces in the presence of aqueous solutions of monovalent alkali and alkaline-earth metal chlorides. Results include density profiles of adsorbed cations, and the effect of cations on the orientation profiles of water molecules close to the mineral surfaces and the distance at which such surfaces become neutral or reverse their charges. In all cases where there are experimental or simulation data, the results here compare very well. The adsorption density of cations on quartz increases with...