Buffering-out: Separation of tetrahydrofuran, 1,3-dioxolane, or 1,4-dioxane from their aqueous solutions using EPPS buffer at 298.15 K

Buffering-out phase separation technique was performed to obtain 98.01 wt.% of tetrahydrofuran (THF), 96.63 wt.% of 1,3-dioxolane, and 94.85 wt.% of 1,4-dioxane from their aqueous solutions using a biological buffer. The phase separation was carried out at room temperature under atmospheric pressure; and the biological buffer is 3-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid (EPPS). The solid–liquid equilibrium (SLE), liquid–liquid equilibrium (LLE), and solid–liquid–liquid equilibrium (SLLE) data have been measured for EPPS + tetrahydrofuran + water, EPPS + 1,3-dioxolane + water, and EPPS + 1,4-dioxane + water systems. Phase diagrams were then constructed for these new phase separation systems. The solubility mass fractions were fitted to an empirical equation as a function of the cyclic ether and buffer concentrations. The effective excluded volume (EEV) model was applied to the solubility mass fractions as well in order to evaluate the phase-separation ability of the investigated cyclic ethers. The consistency of the LLE tie-line data was verified with the Othmer−Tobias correlation. For the process simulations purpose, these experimental tie-line data were also correlated satisfactorily with the NRTL activity coefficient model. The NRTL binary interaction parameters of the investigated systems were reported. By taking advantage of the buffering-out effect, a conceptual process flowsheet for recovery of the cyclic ethers from their aqueous solutions was proposed.

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► EPPS buffer induces phase separation for aqueous solutions of cyclic ethers.
► We constructed the phase diagrams of EPPS + water + cyclic ether systems.
► The liquid–liquid equilibrium data were correlated satisfactorily with the NRTL model.
► We proposed a conceptual process flowsheet for recovery the cyclic ethers from water.