Experimental and Theoretical Study of the Solvent Activity in Aqueous Polyvinyl Pyrrolidone Solution by Direct/Indirect Methods and Presentation of A New Eyring-Flory Huggins Model

One of the most important thermodynamic properties of a solution is solvent activity, which indicates intermolecular interaction and deviation from the ideal state. Four different temperatures (298.15, 308.15, 318.15, 328.15) Kelvin and a concentration range of 0.001 to 0.1 weight fraction at eight different concentrations were used to measure the water activity of solution PVP (K30) +  by VPO method in the experimental part. Besides the VPO direct method, solvent activity was determined through viscosity measurements. In this method, the viscosity of PVP solution (K30) + H2O, at the mentioned temperatures and in the concentrations of 0.013, 0.025, 0.050, 0.075, 0.100, 0.150, 0.200 Polymer weight fractions were obtained. Then for the prediction of solvent activity, using viscosity data a new model was proposed through the use of Eyring’s absolute rate theory and Flory Huggins’s model in combination. Water activity in thermodynamic modeling was calculated for two PVP solutions, K30+ and K15+, using four thermodynamic models with varying approaches, including ASOG, NRTL, NRTL-NRF, and Flory-Huggins. Fminsearch, Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) were the three algorithms used for optimizing the thermodynamic model parameters. The results of the used models and the presented model in this work have revealed that it is consistent well with the experimental data. AAD% is about 0.5% for the four reported models and 0.9% for the presented model.