Research On Thermodynamic Model Of Imidazole Ionic Liquid-inorganic Salt Aqueous Two-phase System

Ionic Liquid(IL),as a green solvent,is environmentally friendly and designable.It is highly likely to be a substitute for traditional organic solvents.The IL-inorganic salt aqueous two-phase system(ATPS)consists of two immiscible aqueous solutions that can be used for the separation of biomolecules and for the recovery of IL as a potential method.At present,there has been many experimental works involving the phase behaviors of IL-inorganic salt ATPS.However,the study of the thermodynamic model of the IL ATPS is rare.Therefore,the model of imidazole IL-inorganic salt aqueous two-phase system is explored based on the traditional activity coefficient model.The results will provide the necessary parameters for unit operation and process optimization of system that contain IL and promote the industrial application.According to the imidazole IL-inorganic salt aqueous two-phase system to be studied,the permeability coefficient of the corresponding imida zole IL([Hmim]Cl and [O mim]Cl)aqueous solution was determined by isobaric method.The relationship between the vapor pressure drop,(NaCl-H2O)>([Hmim]C l-H2O)≈([O mim]C l-H2O),indicating that most IL is present in an ionic state in aqueous solution.The experimental data are correlated with the extended Pitzer model,and the corresponding binary interaction parameters are obtained.In this work,the Extended UNIQUAC model is modified to calculate the equilibrium of [Bmim]Cl-K2HPO4-H2 O ATPS at 298.15 K.IL is considered as an entirety,and all the interaction parameters of the model are salt specific.The results show that the experimental compositions of tie lines are correlated successfully by the proposed model.The root mean square deviation of the mass fraction is 0.0256.In addition,a new simplified parameter is proposed for the first time based on the modified e-NRTL model,that is,the interaction parameter of anion-water and large-sized ion-water is zero according to the solvation theory.The obtained parameters can be used to correlate the single electrolyte system well.For the low-valent potassium salt system,the permeability coefficient and the activity coefficient are correlated with high accuracy,and the consistency of the model is also verified.For the high-valent potassium salt,some correlation of the permeability coefficient is poor.The binary parameters obtained by the above binary system were applied to the calculation of liquid-liquid equilibrium of imidazole IL-inorganic salt ATPS.However,the parameters of IL were obtained from the experimental data of ternary system.The calculation results of seven kinds of ATPS are very good,and the model has predictability to some extent.