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. ? 2012 Elsevier B.V. All rights reserved.