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.

The liquid−liquid equilibriums (LLEs) for 2-propanol + tripotassium phosphate + water at 298.15, 308.15, and 318.15 K and 2propanol + dipotassium hydrogen phosphate + water at 298.15 K were measured. The binodal curves of 2-propanol + potassium sulfate/potassium sulfite + water at 298.15 K were measured and compared. Accordingly, the experimental binodal data were correlated using Merchuk, Hu, and Pirdashti equations, and the tie-line compositions were correlated using Othmer− Tobias and Bancroft equations. The effect of temperature, anion type, and length of alcohol chain on the binodal curve, tie-line length (TLL), slope of tie-line (STL), and phases' physical properties were studied. It was found that an increase in salt's hydrophobicity and alcohol's carbon number in low temperature led to the expanding biphasic region and approaching the binodal curve to the origin. The phase-forming ability of different anions was studied using effective excluded volume (EEV) model, and the relation between the EEV value, saturation solubility, anion's surface charge density, and salt solubility in water was investigated. It was found that kosmotropic ions with higher surface charge density and lower solubility in water have a higher EEV value and are able to form a wider two-phase area. Finally, the salting-out ability of different alcohols was compared with the Setschenow-type equation, and it was found that increasing the carbon number of alcohols enables the ATPS to salt out effectively.

The phase diagram and liquid−liquid equilibrium data for poly(vinyl pyrrolidone) (PVP) of different molecular weights (10,000, 24,000, or 40,000) + potassium formate (KCHO 2 ) or sodium formate (NaCHO 2 ) aqueous two-phase systems were determined experimentally at different temperatures (298.15, 308.15, and 318.15 K). The phase composition and the tie-line ends were obtained by measuring and correlating the density (ρ) and refractive index (n D ) of binary and ternary mixtures within the range of 0−46.6 wt % of PVP and 0−30 wt % of used salts. Furthermore, the binodal data were fitted to both the Pirdashti and Merchuk equations. The cloud point of PVP solutions was determined in the presence of salt at different concentrations. Additionally, the influence of the polymer's molecular weight and temperature on the binodal curve, tie-line length, and slope of tie-line is discussed and compared with the literature data. Moreover, the impact of the Hofmeister series on the separation factor of formate ion was determined. Finally, the extended NRTL and modified UNIFAC-NRF were used to compute the phase compositions of the studied systems, and the adjusted parameters of the models were reported. Results show that both models provide satisfactory agreement with experimental data.

No abstract

No abstract