HOW ROUGHNESS AND CLEANLINESS OF ROCK MINERAL SURFACES CONTROL ITS WETTABILITY

To evaluate wettability of geologic minerals and rocks, their surfaces, at first, are subjected to a polishing routine, which involves sequential polishing from a coarse to a fine grit papers. The polishing routine introduces a degree of ‘surface roughness’, which likely affects the surface wettability measurements. Likewise, differences in surface cleaning procedures, such as usage of DI water, Acetone, Ethanol, and plasma cleaning lead to differences in degree of ‘cleanliness’ or contamination, which influences wettability measurements.

In this study, we systematically subject Quartz, Calcite, and Glass samples to different degrees of polishing, and quantify surface roughness using ‘Confocal Microscopy’. The samples are then subjected to different cleaning procedures, followed by wettability determination from contact angle measurement of air-water system at ambient conditions. Our preliminary results show that polishing from coarse to fine size, which decreases the ‘surface roughness’, transforms the wettability of quartz and calcite minerals from intermediately low wetting to strongly wetting characteristics. Furthermore, we have been able to show control of surface cleanliness through a cleansing procedure, which contributes to tens of degrees of variation in measured contact angles.