Phase Equilibria, Critical Phenomena, and Extractive Crystallization of the Salt in the Sodium Chloride–Water–Diisopropylamine Ternary System
Д. Г. Черкасов, Veronica V. Danilina, K. K. Il’in
Abstract
Extractive crystallization is a promising method for preparing salts from their aqueous solutions. It is topical to carry out extractive crystallization so that reuse the solvent. One aim of our study was to find optimal conditions for the extractive crystallization of sodium chloride via studying phase equilibria and critical phenomena in the sodium chloride–water–diisopropylamine ternary system in the range 10.0–90.0°C. One more aim was to decide whether sodium chloride is useful for salting-out diisopropylamine from its aqueous solutions. The water–diisopropylamine system has a lower critical solution temperature (27.3°C). The phase-transition temperatures were evaluated by the visual polythermal method, and polythermal phase diagrams of mixtures of ternary system’s components were plotted. Temperature dependences of the critical solution composition and the distribution coefficient (Kd) of diisopropylamine between the aqueous and organic monotectic phases were elucidated. The maximum value of Kd (480) was reached at 90.0°С. The yield of NaCl crystals was found to increase with increasing amine concentration in the ternary mixtures. The highest sodium chloride yield (49%) from a water–salt solution containing 26 wt % salt was observed at 27.3°С after 90.0 wt % diisopropylamine was added.