Surface-Sensitive Characterization of Nujol Interaction with CaCO₃ (104) Surfaces

In this study, we investigated the adsorption of Nujol, composed mainly of n-dodecane molecules, on pristine and hydrated CaCO₃ (104) surfaces by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and infrared reflection-absorption spectroscopy (IRRAS). Our results reveal changes in the molecule-calcite interaction connected to differences in the substrate surface chemical composition upon hydration. XPS analysis suggests that the ideal pristine calcite forms a Ca²⁺ -deficient surface under hydration as a consequence of the dissolution process, whose traces were identified in the AFM topography images. Upon Nujol adsorption, both interface's chemical composition and topography indicate the formation of a continuous versus a discontinuous film (several patches and 3D islands) on pristine and hydrated calcite surfaces, respectively. Finally, the IRRAS spectral analysis allowed us to correlate the distinct film's topography to a specific binding geometry of the molecule. These findings provide clear evidence of the modification of the hydrocarbon molecule-calcite interaction that is essential for optimizing key parameters (surface composition, surface hydration, and oil adhesion) to improve technologies related to wettability alteration, particularly in the field of oil recovery process.