Vapor–Liquid and Solid–Liquid Modeling with a Universal Quasichemical Segment-Based Activity Coefficient Model

A segment-based activity coefficient model is developed through the Universal Quasichemical (UNIQUAC-SAC) approach and is applied for vapor–liquid and solid–liquid equilibrium calculations. We incorporated the conceptual segment approach of the NRTL-SAC activity coefficient model with modification of binary interaction parameters for the conceptual segments. The conceptual segments are represented by n -hexane, dimethyl sulfoxide, nitromethane, and water as hydrophobic, polar attractive, polar repulsive, and hydrophilic, respectively. The UNIQUAC-SAC molecular parameters are obtained for 82 common solvents, 62 of which are common solvents in the pharmaceutical industry. The UNIQUAC-SAC and NRTL-SAC models are employed to compute the vapor–liquid equilibrium of binary, ternary, and quaternary systems. In most cases, the UNIQUAC-SAC model gives a better prediction than the NERL-SAC model. Moreover, the UNIQUAC-SAC model is extended to modeling the solubility of organic nonelectrolyte solute in common solvents. Finally, using the UNIQUAC-SAC and NRTL-SAC models, the solubility data of several pharmaceutical solutes is calculated in one- and two-solvent systems and compared with experimental results.