Experimental and Theoretical Studies on ATPSs Containing Ethyl Lactate or Propan-1-ol: Phase Equilibria, eNRTL Modeling, and Intermolecular Potentials

This work was focused on the experimental and theoretical study of the Aqueous Two-Phase Systems (ATPSs) {ethyl lactate or propan-1-ol (1) + sodium formate (2) + water (3)}, at 298.15 K and 0.1 MPa. Solubility curves were obtained using the “cloud-point” method and correlated using empirical equations. The results revealed broad two-phase regions. In particular, the system composed of propan-1-ol exhibited a larger biphasic domain due to the lower polarity of this solvent. Tie-line compositions were determined based on third-degree polynomials of thermophysical properties and modeled using the electrolyte Non-Random Two-Liquid (eNRTL) model. This model achieved low standard deviations (6.62 × 10–4 < σSD < 1.27 × 10–1) considering multiple approaches for the nonrandomness factor (α) Finally, intermolecular potential energies for the constituent chemicals of the studied ATPSs were determined by quantum mechanical calculations. The molecular geometries were optimized using DFT, and intermolecular potential energies were computed and correlated with established potential models. Mie potential provided the best results (0.96 < σSD / kJ·mol–1 < 196.28) and these findings also highlighted the need for a trade-off between model complexity and computational feasibility in molecular simulations.