Desalination of seawater via the freeze-thaw method based on density functional theory

In the context of a severe global water scarcity, seawater desalination technologies have undergone rapid advancements. Among these, the freeze-thaw method, as a novel and emerging desalination technique, has garnered increasing attention.In this study, we investigated the desalination of seawater using the freeze-thaw method. Specifically, we systematically analyzed the migration patterns of inorganic ions and organic matter during the desalination process, aiming to elucidate the underlying mechanisms. Our findings indicate that the freeze-thaw method can effectively reduce the typical salinity levels in seawater through the freezing and thawing cycles. The freezing process facilitates the concentration of a substantial portion of inorganic ions and organic substances in seawater into subglacial water. Meanwhile, pollutants that remain trapped within the ice can be effectively expelled during the initial thawing phase.The results indicate that initial freezing alone can achieve a salinity reduction of 63.75%, prior to the melting process. Futhermore, when the ice undergoes an initial melting process, the salinity removal rate increases significantly to 86.62%. Microscopic examination of the ice revealed the presence of "brine channels" within the ice matrix, which facilitate the discharge of pollutants during the melting process. This ensures the production of subsequent clean ice meltwater. The binding energies of three common ions in seawater with ice molecules and water clusters were calculated using density functional theory (DFT). Furthermore, the mechanism of seawater desalination was elucidated from the perspective of energy-driven processes. This study provides a theoretical framework for the application of the freeze thaw method in seawater desalination, thereby, advancing .the development of efficient desalination techniques.