Temperature, Polymer Molecular Weight, and Salt Effects on Phase Equilibria of PVP + Formate Salts + Water: Experimental Measurements, Correlations, and Thermodynamic Modeling

Abstract

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.

Liquid–Liquid Equilibrium Data for [Mmim][DMP] + Salt Aqueous Biphasic Systems and Their Application for [Mmim][DMP] Recovery

“…These two kinds of salts have the same potassium ion, but the anion of K 3 PO 4 has higher valence, showing higher surface charges. The hydrogen bonds of the H 2 O structure are strengthened by the ionic electrical field . Therefore, the anion of K 3 PO 4 with higher surface charge reconstructs the H 2 O molecules to make a stronger biphasic system.…”

“…The hydrogen bonds of the H 2 O structure are strengthened by the ionic electrical field. 66 Therefore, the anion of K 3 PO 4 with higher surface charge reconstructs the H 2 O molecules to make a stronger biphasic system. As a boosted surface charge, kosmotropic ions in Hofmeister series, 66 the required quantity of electrolyte for PO 4 3− cations is significant and leads to a higher separation factor.…”

“…66 Therefore, the anion of K 3 PO 4 with higher surface charge reconstructs the H 2 O molecules to make a stronger biphasic system. As a boosted surface charge, kosmotropic ions in Hofmeister series, 66 the required quantity of electrolyte for PO 4 3− cations is significant and leads to a higher separation factor. In addition, we compared the data on LLE among a plenty of data for other ABSs in Figure 4.…”

Phase Equilibria of the Ternary System of Lithium Sulfate + Polyethylene Glycol (PEG3000) + Water at Different pH: Experiment Determination, Correlation, and Thermodynamic Modeling

“…Accordingly, an important consideration in the LLE of polymer solutions is the percentage of compressibility or free-volume in polymers when the low-molecular-weight compounds are employed . Additionally, the modified UNIFAC-NRF model was satisfactorily used to correlate the coexistence phase compositions of the same ATPSs. , …”

“…34 Additionally, the modified UNIFAC-NRF model was satisfactorily used to correlate the coexistence phase compositions of the same ATPSs. 35,36 It is widely acknowledged that pH and temperature are some of the most critical factors in separating the biological compounds. 25 Lithium is the one of the kosmotropic cations that is able to give better salting-out impacts.…”