Hydrogen-Bonding Liquids at Mineral Surfaces: From Fundamentals to Applications

Molecular-level understanding of properties of hydrogen-bonding liquids and their mixtures at solid-liquid interfaces plays a significant role in several applications including membrane-based separations, shale gas production, etc. Liquid water and ethanol are common hydrogen-bonding fluids. All-atom equilibrium molecular dynamics simulations were employed to gain insights regarding the structure and dynamics of these hydrogen-bonding liquids on various free-standing solid surfaces. Models for silica, alumina, and magnesium oxide were used in these works. The results show a highly well-ordered layer of the hydrogen-bonding liquids near solid substrates and a pronounced dipolar orientation of the hydrogen-bonding molecules found in this layer, which is dependent on the surface chemistry of the substrate. Our simulated results are in good agreement with the experimental data. Many studies have paid attention to mixtures of hydrogen-bonding fluids such as liquid water-ethanol mixtures due to their critical roles in industrial applications. We have conducted simulations to examine the sorptivity, structure and dynamics of liquid water-ethanol mixtures confined in alumina pores. Analysis of the structure and dynamics suggests the possibility of using alumina as perm-selective membranes to produce anhydrous ethanol from liquid water-ethanol solutions. In addition, it is important to understand properties of mixtures of water and volatile hydrocarbons under confinement as recently water is used as fracturing-fluid to stimulate subsurface formations in the practice of hydraulic fracturing. We have investigated the behaviour of aqueous methane confined in 1 nm-wide pores obtained from materials such as silica, alumina, and magnesium oxide. Our results show that methane solubility in confined water strongly depends on the confining material, with silica yielding the highest solubility. Studying dynamical properties of confined aqueous methane suggests a direct proportional coupling between methane and water dynamics. These results help refer to multiple possible applications for fluid transport