jp305529d_si_001.pdf (1.5 MB)
Influence of Hydrated Silica Surfaces on Interfacial Water in the Presence of Clathrate Hydrate Forming Gases
journal contribution
posted on 2012-11-29, 00:00 authored by S. Alireza Bagherzadeh, Peter Englezos, Saman Alavi, John A. RipmeesterWe study the hydrated silica–water interface in
the presence
of methane or carbon dioxide gas with molecular dynamics simulations.
The simulations are performed with a limited amount of water, which
forms a meniscus between two hydroxylated silica surfaces separated
by 40 to 60 Å. Simulations were performed with the remaining
space of the simulation cell left empty or filled with different numbers
of methane or carbon dioxide gas molecules. The meniscus is used to
determine the contact angle between water and silica in the absence
and presence of the gases. The distribution profiles of the water
and gas phases are determined over the duration of the simulation.
The water number density in the layers adjacent to the silica is higher,
and these layers are more structured and less mobile compared with
water layers far from the surface. Additionally, the concentrations
of the gases are significantly higher at the liquid and silica interfaces
than in other locations in the gas phase. We speculate that the enhanced
concentration of gases at the interface along with the extended contact
area (curved meniscus compared with flat interface in the absence
of silica surfaces) between water and guest molecules at the meniscus
as well as lesser mobility of water molecules near the silica surface
may provide a mechanism for the heterogeneous nucleation of the clathrate
hydrate in water-wetting porous medium.
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Interfacial Watercontact areasilica interfacescontact anglesimulation cell60 Å. SimulationsHydrated Silica Surfaceswater moleculescarbon dioxide gas moleculessilica surfacemeniscugas phasehydroxylated silica surfacesgas phasesclathrate hydratewater number densityClathrate Hydrate Forming GasesWe studycarbon dioxide gassilica surfaceswater layersguest moleculesdynamics simulationsdistribution profiles
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