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 (alpha) dropped from 48 to 35 mJ/m(2) because of the decrease in water-CaCO3 and CaCO3-quartz interfacial energies, and the kinetic factor was reduced by similar to 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.