Aqueous Hydrogen Sulfide in Slit-Shaped Silica Nanopores: Confinement Effects on Solubility, Structural, and Dynamical Properties

Confinement in nanometer-size pores affects structural and transport properties of water and coexisting volatile species. It has for example been reported that confinement can enhance the solubility of gases in water. We report here equilibrium molecular dynamics simulations for aqueous H2S confined in slit-shaped silica pores at 313 K We investigated the effect of pore width on the H2S solubility in water. We quantified the molecular distribution of the fluid molecules within the pores, the hydration structure for solvated H2S molecules, and the dynamical properties of the confined fluids. The results show that confinement reduces the H2S solubility in water and that the solubility increases with the pore size. Our analysis suggests that these results are due to perturbations on the coordination of water molecules around H2S due to confinement. Confinement is found to dampen the dynamical properties of aqueous H2S as well. Comparing the results obtained for aqueous H2S to those, reported elsewhere, for aqueous CH we conclude that H2S permeates hydrated slit shaped silica nanopores faster than CH4. These observations contribute to understand fluids in the subsurface and could have important implications for applications in catalysis and perhaps for developing new natural gas sweetening technologies.