Phase Equilibria of Aqueous Two-Phase Systems of PEG with Sulfate Salt: Effects of pH, Temperature, Type of Cation, and Polymer Molecular Weight

Abstract

The present work reports the liquid–liquid equilibrium (LLE) measurements and the construction of binodal curves for polyethylene glycols (PEG) + zinc sulfate/ammonium sulfate + water at three different temperatures (298.15, 303.15, and 308.15 K) and pH values (3.00, 4.70, and 5.21). PEGs with different molecular weights of 2000 g·mol–1 (PEG 2000), 3000 g·mol–1 (PEG 3000), and 8000 g·mol–1 (PEG 8000) were chosen for this study. The phase composition was obtained by measuring the refractive index (n D) and density (ρ) and was further used to obtain the tie-line length (TLL) and the slope of tie-line (STL). The tie-lines are reported at different polymer lengths, pH values, and temperatures. The values of the effective excluded volume (EEV) were employed to analyze the effect of the parameters on the binodal curves. Moreover, the impact of those parameters on the TLL and STL and plait point are discussed and compared with the results of the literature. Furthermore, the binodal curves data and the tie-lines’ ends were fitted using some semiempirical equations with satisfactory results. Finally, the UNIFAC is used to calculate the LLE data of the above system and the adjusted binary group interaction parameters of the model were reported.

Temperature Effect on the Phase Equilibrium of Polyethylene Glycol 2000 + Trilithium Citrate + Water Aqueous Two-Phase Systems at T = 288.15, 298.15, 308.15, and 318.15 K

“…Pirdashti et al measured the effect of the polymer molecular mass, pH, and temperature on the phase equilibrium of ATPSs of the ternary systems of PEG 2000 , PEG 3000 , and PEG 8000 + zinc sulfate or ammonium sulfate + water at T = 298.15, 303.15, and 308.15 K. The results proved that the two-phase region has been extended by increasing the temperature. In other studies, Pirdashti’s group reported the pH effect on the binodal curves and tie-line compositions of PEG 1500 and PEG 6000 + MgSO 4 + water ATPSs at room temperature. , …”

“…In other studies, Pirdashti's group reported the pH effect on the binodal curves and tie-line compositions of PEG 1500 and PEG 6000 + MgSO 4 + water ATPSs at room temperature. 35,36 In this study, the effect of temperature on the binodal curves and tie-lines of the ternary system containing PEG 2000 + trilithium citrate + water has been measured experimentally and modeled using some appropriate thermodynamic models. Three-parameter nonlinear equations 31 were used to fit binodal curves at the studied temperatures.…”

Simple Approach for Reliable Prediction of Solubility of Polymers in Environmentally Compatible Solvents

“…This approach cannot be applied for polymers of very high crystallinity because they are insoluble in solvents whose solubility parameters perfectly match their own. Statistical assessments of the new model as compared to the methods of Koc−Koç2 5 and Goudarzi et al 24 confirmed that eq 5 has significant reliability.…”

“…Thus, the new model covers any kind of polymer with high reliability because reliable forecasts always that the coverages are greater than 90%. 46 those predicted by complex QSPR models of Koc−Koç2 5 and Goudarzi et al 24 The predicted absolute percent error (APE) values of eq 5 for 97 polymers were compared with those of the two QSPR methods of Koc−Koç2 5 and Goudarzi et al 24 (Tables S1 and S2). Figure 4 compares the results of eq 5 and the Koc− Koç2 5 and Goudarzi et al 24 methods with the measured data.…”

“…Solvent selection for polymers has wide applications in industries to recycle degraded polymers with environmentally compatible byproducts and to avoid phase separation during the synthesis of polymers as well as to improve stable formulations with high-quality standards for entering the environment . Solubility parameters can be used to select compatible solvents for coating resins, estimating the swelling of cured elastomers by solvents, predicting the vapor pressure of the solvent in polymer solutions for reaction systems and the removal of volatile substances, as well as forecasting phase equilibria for polymer–binary, random copolymer, polymer–polymer, and multicomponent solvents . Since the cohesive energy density shows the energy required to break all intermolecular physical links in a unit volume of the material, the solubility parameter quantifies the interactions between polymers and solvents …”