Hydrogen bonds at silica-CO2 saturated water interface under geologic sequestration conditions

To investigate the effects of sequestration condition on hydrogen bonds between mineral and water, molecular dynamics simulations have been performed. The simulations were conducted at conditions related with geologic sequestration sites: pressure (3.1-32.6 MPa), temperature (318 and 383 K), salinity (0-3 M), salt (NaCI and CaCl2) and silica surface models Q(2) (geminal), Q(3) (isolated) and amorphous Q(3). The hydrogen bonds were classified into four types: silica-silica, silica-dissolved CO2, silica-water as donors and silica-water as acceptors. The mean numbers of hydrogen bonds for each type were analysed. The results show that: (1) silica surface silanol groups do not form H-bonds with dissolved CO2 molecules in water (brine); (2) The mean number of hydrogen bonds between silanol groups follows the order: Q(2) > amorphous Q(3) > Q(3); (3) The mean number of hydrogen bonds between silanol and water molecules follows the order: Q(3) > amorphous Q(3) > Q(2).