Separation of 1,3-dioxolane, 1,4-dioxane, acetonitrile and tert-butanol from their aqueous solutions by using Good's buffer HEPES-Na as an auxiliary agent

The biological buffer 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid sodium (HEPES-Na) was found that can induce liquid-liquid phase splitting in the aqueous solutions of 1,3-dioxolane, 1,4-dioxane, acetonitrile, and tert-butanol at ambient conditions. To prepare the phase diagrams, we measured the solid-liquid equilibrium (SLE), solid-liquid-liquid equilibrium (SLLE), and liquid-liquid equilibrium (LLE) data for the ternary systems containing water+1,3-dioxolane, 1,4-dioxane, acetonitrile, or tert-butanol+HEPES-Na at 298.2 K under atmospheric pressure. The effective excluded volume model (EEV) was used to fit the experimental LLE phase boundary data. The consistency of the experimental LLE tie line data was confirmed by Othmer-Tobias equation. These tie-line data were also correlated with the NRTL model. By using the HEPES-Na as an auxiliary agent, the maximum concentrations of 1,3-dioxolane (97.7 wt%), 1,4-dioxane (97.4 wt%), acetonitrile (93.9 wt%), and tert-butanol (92.7 wt%) in the organic-rich phase are greater than the azeotropic compositions of the corresponding aqueous systems. These results indicate that HEPES-Na can be served as a high efficiency, non-corrosive, and biocompatible green agent for the separation of 1,3-dioxolane, 1,4-dioxane, acetonitrile, and tert-butanol from their aqueous solutions. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.