Liquid–Liquid Equilibria Determination and Modeling of ATPS Based on PEG4000 and PVP29000 at 298.15 K and 0.1 MPa

Additionally to the known nontoxicity and eco-friendliness of aqueous two-phase systems (ATPS), polymeric ATPS, which are composed of at least one polymer [e.g., poly(ethylene glycol) or poly(vinylpyrrolidone)], provide extractive media with enhanced potential for drug delivery and biomolecule extraction. Nevertheless, the lack of liquid–liquid equilibria (LLE) data concerning these systems still limits their large-scale application and hampers proper thermodynamic modeling, delaying advancements in the design of novel materials and processes based on polymers. In this work, the LLE, i.e., solubility curves and tie-line compositions, of the ATPS {PEG4000 (1) + NaFormate (2) + Water (3)} and {PVP29000 (1) + NaFormate or Na2Tartrate or K2Tartrate (2) + Water (3)} were determined at 298.15 K and 0.1 MPa. The estimation of tie-line composition using third-degree polynomials of liquid density (ρ) and electrical conductivity (κ) allowed to better understand the influence of composition on these thermophysical properties, and the tie-line data were successfully correlated using the models of Othmer–Tobias and Bancroft–Hubard, achieving determination coefficients (R2) larger than 0.9575 and 0.9676, respectively. Moreover, the obtained compositions were effectively described using the UNIversal QUAsi-Chemical (UNIQUAC) model, with standard deviations (σ) lower than 6.84 × 10–3.