Liquid−Liquid and Liquid−Liquid−Solid Equilibrium of the Poly(ethylene glycol) Dimethyl Ether 2000 + Sodium Sulfate + Water System

Abstract

The phase diagram for the poly(ethylene glycol) dimethyl ether (PEGDE) + Na 2 SO 4 + H 2 O system at 298.15 K using PEGDE with a molar mass of 2000 was determined. Compositions of the liquid-liquid and the liquid-liquid-solid equilibria were determined using calibration curves of refractive index of the solutions, and atomic absorption (AA) and X-ray diffraction analyses were made on the solids. The solid phase in equilibrium with the biphasic region was anhydrous Na 2 SO 4 . An empirical nonlinear three-parameter expression developed by Merchuk was used for reproducing the experimental binodal data at T ) (288. 15, 298.15, 308.15, and 318.15) K, and the fitting parameters were obtained for the corresponding temperatures. The effects of temperature on the binodal curve were also studied, and it was observed that the area of the biphasic region increased slightly with an increase in temperature. The experimental tie-line compositions at the aforementioned temperatures were fitted to both the Othmer-Tobias and Bancroft and Setschenowtype equations. Correlation coefficients for all equations are reported.

(Liquid+liquid) and (liquid+solid) equilibrium of aqueous two-phase systems containing poly ethylene glycol di-methyl ether 2000 and di-sodium hydrogen phosphate

“…Additionally, to show the effect of temperature on the equilibrium phase compositions for the investigated system, the experimental tie-lines are compared in figure 1, for the temperatures 298.15 K and 318.15 K. As shown in figure 1, the slope and the length of the tie-lines increase with an increase in temperature, similar to the one observed in our previous works [6,7,12]. This is because the PEGDME 2000 becomes more hydrophobic with increase in temperature [13].…”

“…To see the effectiveness of the anion in forming an aqueous two-phase system with PEGDME 2000 , the experimental binodal curves of the {PEGDME 2000 (1) + Na 2 H-PO 4 (2) + H 2 O (3)} obtained in this work are shown in figure 2 together with the binodal curves of the {PEGDME 2000 (1) + Na 2 SO 4 + H 2 O (3)} and {PEGDME 2000 (1) + Na 2 CO 3 (2) + H 2 O (3)} systems studied previously [6,7] at T = 298.15 K. Also to see the effect of other phosphate anions, the binodal curves for aqueous PEG-DME 2000 containing Na 3 PO 4 and NaH 2 PO 4 have also been determined at T = 298.15 K and are shown in figure 2. The corresponding binodal data are given in table 3.…”

“…The number average molar mass of the polymer previously determined [6] to be 2305 g Á mol À1 , using gel permission chromatography (GPC, Agilent, USA). Di-sodium hydrogen phosphate with mass fraction purity >0.99 was supplied from Merck.…”

“…Recently, the above equation has been successfully used for the correlation of binodal data of some aqueous (0PEG or PEGDME + salt systems) [6,7,12]. We also used this equation as temperature dependence function for correlation and prediction of some ATPSs [18].…”

“…water structure) salts. However as far as we know there is a few experimental (liquid + liquid) equilibrium (LLE) data for ATPSs with this polymer [6,7].…”