Surface forces in thin aqueous films: Applications to wettability and membrane transport

The objective of this work is to fundamentally understand the short range structural forces in thin aqueous films and examine their role in dewetting of water and oil on mineral surfaces and in transport of aqueous electrolyte through charged microcapillaries.;A theoretical model has been formulated to investigate the origin of hydration forces in thin aqueous films confined between charged mica and silica surfaces. It is shown that the increase in free energy of ions in the film, due to the structural alignment of solvent molecules, gives rise to additional repulsive hydration forces in thin aqueous electrolyte films. The model results show remarkable agreement, both qualitatively and quantitatively, with experimental observations.;Film stability tests have been conducted using an AFM to study the physics of wetting and dewetting of oil/brine/mineral systems. Surface forces between oil phase (pure and crude oil) and mineral surfaces in brine were directly measured to quantify the effects of capillary pressure, surface morphology, and composition of the liquid phases that leads to the wettability alteration of water-wet mineral surfaces. The role of physical heterogeneity (surface roughness) on wettability reversal phenomenon is demonstrated.;Theoretical studies were conducted to investigate the effect of structural forces on the steady-state electrohydrodynamic flow in charged capillary membranes. The existing Space Charge model has been modified to include the variation in dielectric constant, ion solvation, variation in surface charge and surface potential, and finite ion sizes. The improved model results show good agreement with measured electrokinetic data for membranes with well-defined structures.