Salinity-Induced Reduction of Interfacial Energies and Kinetic Factors during Calcium Carbonate Nucleation on Quartz

Nucleation is a crucial nanoscale process during the formation of new phases. This study employs CaCO₃ nucleation on quartz as an example system and investigates the effects of salinity on thermodynamic and kinetic factors in CaCO₃ nucleation. In situ grazing incidence small-angle X-ray scattering was used to obtain the nucleation rates of CaCO₃ at different supersaturations (IAP/K_sp(calcite) = 10^1.40 to 10^2.00) and NaCl-adjusted ionic strengths (i.e., salinities). From a salinity value of 0.15 to 0.85 M, the effective interfacial energy (α) dropped from 48 to 35 mJ/m² because of the decrease in water-CaCO₃ and CaCO₃-quartz interfacial energies, and the kinetic factor was reduced by ∼13 times. Further, high salinity triggered faster nucleation, shorter induction time, and smaller nuclei. Our findings provide new insights for predicting and improving such important processes as CO₂ mineralization during geologic carbon sequestration, desalination membranes, nanoparticle synthesis, and contaminated environments.