Macroscopic Thermodynamics of Interfaces at Water Pore Scales: Effects on Water-Rock Interactions and Mass Transfer

The possible role of liquid-air and solid-liquid interfacial curvature on water-rock mass transfer in natural settings is here studied by macroscopic thermodynamics that includes the Young-Laplace interphase pressure gradient. Capillary water in non-saturated soils (liquid-air concave curvature toward air), and curved solid as a function of pore sizes (solid-liquid concave curvature towards infilling solution) exemplify what can be expected in terms of solubility. Gas solubilities in capillary water increase with curvature, promoting gas uptake and so modifying chemical equilibria in solutions (e.g., redox and/or acido-basic) accordingly. Applied to solid solubility, the macroscopic thermodynamics of interface treatment highlights the versatility offered by crystalline shaping with respect to the capillary degree (if any) of the surrounding aqueous solution. Additionally, the solid curvature associated with decreasing pore sizes makes the solid less soluble in the infilling bulk solution.