Thermodynamic characterization and modeling of aqueous two-phase systems composed of cholinium chloride and salts

Aqueous two-phase systems (ATPS) are liquid-liquid extraction platforms effectives for the separation and purification of bioactive products. Therefore, as other downstream operation units, its scaling up requires a proper evaluation of the process variables, to understand how each variable affect the performance of the entire process. The application of predictive models, which enable to simulate ATPS behavior at different conditions, has been presented as an alternative to the experimental analysis, a procedure that can often be time-consuming and costly. Thus, aiming a future implementation of ATPS at industrial scale, in the present project the modeling of the liquid-liquid equilibrium of salt/salt ATPS composed of cholinium chloride ([Ch]Cl) and phosphate inorganic salts (K2HPO4 or K3PO4) using the thermodynamic model Non-Random-Two-Liquid (NRTL) was carried out. Firstly, the respective phase diagrams and tie-lines (TLs) were determined. Then, the NRTL model was implemented in Matlab® software, using optimization strategies to reduce the possibility of local minimum. Finally, the experimental results were correlated with the NRTL model, obtaining good fitting results for both ATPS, i.e., low RMSD values in comparison with the results reported in the literature. The NRTL model provides a good representation (fitting) of the experimental data for the salt/salt ATPS.