Ion migration at the ice–water interface during the freezing process of salt solution – Numerical investigation

This study applies phase-field theory, introducing the concept of solid–liquid dispersion into the freezing process of salt solutions. A mathematical model for the complex physical processes of heat and mass transfer at the ice–water phase transition interface was established and validated to address the issue of ion migration during the freezing process of salt solutions. The model considers the effects of salt crystallization and ion release in ice, elucidating the microinteractions among the phase field, temperature field, and concentration field. The results show that during the phase transition, the main region of heat exchange occurs at the ice-water phase transition interface, and the formation of a temperature diffusion layer and increased ion concentration will inhibit the growth of dendrites. The ions expelled from the ice–water interface accumulate at the tips and roots of the dendrites, leading to competitive growth among dendrites, which eventually develop into saline channels and brine pockets, resulting in ions being recaptured within the ice. Under identical simulation conditions, the migration patterns of different ions are consistent with those obtained from experimental studies, indicating that the constructed model can accurately depict the migration patterns of different ions under freezing conditions.