The Origin of Surface Energy of Calcite and Its Wettability

The microstructure and anisotropy of the solid-liquid interface hold significant importance in a wide range of fields, such as rock mechanics, mineral processing, and powder technology. Despite the prevalence of anisotropic properties in calcite, the underlying physical mechanisms remain poorly understood. Focusing on surface energy, we established a quantitative relationship for surface broken bonds density (D_b) and interlayer spacing (d) on surface energy: γ_dry = 0.021D_b - 1.036d + 0.77, which provided a novel approach to evaluating surface stability and reactivity of calcite. Examination of anisotropic surface properties revealed the (104) calcite surface as the most common cleavage surface owing to its lower surface energies, smaller D_b, and larger d. Furthermore, the effects of water coverage and salinity on surface energy were explored, indicating a negative relationship between water coverage and surface energy of (104) calcite. The interaction of water with calcite was observed to affect surface energy, with water adsorption sites being occupied by salt ions. By incorporating contact angle measurements and charge transfer analyses, we elucidated the interaction mechanisms governing surface wettability and offered new insights into the adsorption behavior of water on calcite surfaces, which contributed to advancing the field of mineral surface science and the interaction processes at solid-liquid interfaces.