(501d) Molecular Aspects of Temperature Swing Solvent Extraction for Brine Desalination Using Imidazole-Based Solvents.

Solvent extraction desalination has shown to be a promising energy-efficient technique when compared to separation processes usually employed. In this context, freshwater from brine is obtained by solubilizing the water in an organic phase followed by a later recovery process induced by a temperature swing. Despite the remarkable impact of the organic solvent's molecular characteristics on this process, few studies have been carried out so far to explicitly ascertain the influence of these characteristics on the solubility of water in the solvent. Here, we assess the viability of four different imidazole-based solvents and compare to an amine compound for solvent extraction desalination of high salinity brines. All-atom molecular simulations of pure solvent and water-solvent bulk mixtures are used to ascertain the influence of the solvents' molecular structures on solvent-solvent and solvent-water interaction. Our results show that water solubilization in imidazole-based solvents is an exothermic process, while for a secondary amine (diisopropylamine) it is an endothermic process. Notably, we explicitly show that imidazole-based solvents can be designed to provide characteristics favorable to brine desalination, namely, dependence on the solubility of water in the solvent within a narrow temperature range, high water solubility, and minimal solvent solubility in the aqueous phase.