Proyectos

Water confined in Å- to nm-scale pores is volumetrically and chemically important in surficial and near surface geological environments. Partitioning of water between bulk liquid and vapor phases and water confined in spaces within and between minerals plays a critical role in determining the fate of geochemical and geobiological processes. Despite considerable effort over the past several decades focused on the properties of confined water, rigorous thermodynamic models permitting simultaneous consideration of confined water stability relative to bulk water that are consistent with widely employed geochemical models are generally not available. In part, this is due to a paucity of physical chemical models permitting quantitative description of the hysteresis that is commonly observed between sorption and desorption of confined water. The present study addresses these needs through a combination of equilibrium observations, calorimetric measurements, and thermodynamic modeling of a selected suite of systems containing confined water. Model zeolite and nanoporous systems exhibiting hysteretic sorption/desorption behavior will be studied in order to test a newly developed thermodynamic model that shows promise in predicting hysteretic behavior. In addition, two other types of systems will be studied to fill in gaps currently present in the understanding of the factors controlling the stability of confined water: a) pure silica zeolites in which water molecules do not solvate ions; and c) zeolite systems containing confined water that is only bonded to ions. Water in these systems exhibits ?endmember? structural states, that when combined form the environments found in most previously studied microporous confined water systems (that is, those containing water molecules that both solvate ions and interact with the confining medium).

Water confined in Å- to nm-scale pores is volumetrically and chemically important in surficial and near surface geological environments. Partitioning of water between bulk liquid and vapor phases and water confined in spaces within and between minerals plays a critical role in determining the fate of geochemical and geobiological processes. Despite considerable effort over the past several decades focused on the properties of confined water, rigorous thermodynamic models permitting simultaneous consideration of confined water stability relative to bulk water that are consistent with widely employed geochemical models are generally not available. In part, this is due to a paucity of physical chemical models permitting quantitative description of the hysteresis that is commonly observed between sorption and desorption of confined water. The present study addresses these needs through a combination of equilibrium observations, calorimetric measurements, and thermodynamic modeling of a selected suite of systems containing confined water. Model zeolite and nanoporous systems exhibiting hysteretic sorption/desorption behavior will be studied in order to test a newly developed thermodynamic model that shows promise in predicting hysteretic behavior. In addition, two other types of systems will be studied to fill in gaps currently present in the understanding of the factors controlling the stability of confined water: a) pure silica zeolites in which water molecules do not solvate ions; and c) zeolite systems containing confined water that is only bonded to ions. Water in these systems exhibits ?endmember? structural states, that when combined form the environments found in most previously studied microporous confined water systems (that is, those containing water molecules that both solvate ions and interact with the confining medium).

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