Molecular dynamics simulation studies elucidating interaction mechanisms and structures of salt–brine interfacial systems derived from magnesium sulfate subtype salt lakes

Abstract

Salt–brine interfacial systems widely occur in the process of salt crystallization and separation, where the interfacial interaction plays a crucial role in influencing salt crystal growth, product purity and brine recovery rates. In the present study, molecular dynamics simulations were employed to investigate the interaction mechanisms and structures of salt–brine interfacial systems derived from the magnesium sulfate–subtype salt lakes. The results indicate that the type of salts was the key factor that affects salt–brine interfacial interactions. The strength of interfacial interaction in hydrated salt–brine systems was found to be more than twice that of ionic salt–brine systems. This can be attributed to two characteristics observed in hydrated salt–brine systems: the incompact and undulating surface structure of hydrated salts and the hydrogen bonding between water molecules on hydrated salt and brine surfaces. In all the seven interfacial systems, no accumulation of Li+ ions at the interface was observed, and there were no significant structure changes in bulk brines except the variations in hydration numbers of K+ ions. These findings provide insights into atomic-level mechanisms governing the interfacial interactions between different types of salts and brines, thus providing a theoretical guidance for enhancing the salt crystallization and separation process.