Construction Of Ternary And Quaternary Aqueous Two-phase Systems Based On Ionic Liquids/Small Molecule Organic Solvents And Their Phase-forming Mechanism Study

Aqueous two-phase system,as an efficient,convenient,low-cost environmental friendly pretreatment technology,has been the common separation and purification technique in areas like chemical engineering,bioengineering,medical industry and material science.Of these,the most studied and most widely-used aqueous two-phase systems are mostly base on ionic liquid,polymer or small molecule organic solvent.Nevertheless,the three kinds have respectively shown deficiencies like high viscosity,high cost and difficulty in discharging waste water in the practical application,which slowed down their industrialization process.This work structured quaternary aqueous two-phase systems by combining ionic liquid-based ternary systems and small molecule alcohol-based systems.This could well reduce the viscosity of the systems,cut down the cost of production and meanwhile keep the admirable properties for phase-forming and extraction.It is of important theoretical and practical significance.The work severally established ionic liquid-salt-water ternary systems and ionic liquid/ small molecular alcohol-ethanol-water quaternary systems employing ionic liquid,small molecular alcohol,inorganic/organic salts and water.The binodal and tie-line data were systematically collected and the liquid-liquid equilibrium behavior of each system was investigated.The influences of several factors on the phase-separation properties of studied systems were thoroughly discussed and the conditional parameters for preliminary operations of separation and extraction were screened out,which provided theoretical basis for the extended application of these aqueous two-phase systems.The conclusions are drawn:(1)The binodal curves of [BPy]BF4-salt-water ternary aqueous two-phase systems at different temperatures were determined and associated with numeral nonlinear equations.The universally applicable equation was sorted.The tie-line data of each system were obtained based on the binodal data equipped with detecting instruments and were successfully related to Othmer-Tobias and Bancroft equations.(2)The effect of salt type and temperatures on the liquid-liquid equilibrium of [BPy]BF4-salt-water ternary aqueous two-phase systems were discussed and conclusions have been reached:(1)the salting-out capabilities of phase-forming salts follow Na2SO4>(NH4)2SO4>(NH4)3C6H5O7>CH3COONa;(2)the phase-separation abilities of each system at different temperatures follow 35?>45?>55?.The effective exclude values and Gibbs free energy theory were applied to validate the conclusions.(3)The binodal curves of [Bmim]BF4/2-proponal-ethanol-salt-water quaternary aqueous two-phase systems at different temperatures and organic component ratios were determined and associated with numeral nonlinear equations.The universally applicable equation was sorted.The tie-line data of each system were calculated by the optimal equation and “lever arm rule” based on the binodal data and were successfully related to Othmer-Tobias and Bancroft equations.(4)The effect of salt type,temperatures,organic component ratio and system architecture on the liquid-liquid equilibrium of [Bmim]BF4/2-proponal-ethanol-salt-water quaternary aqueous two-phase systems were discussed and conclusions have been reached:(1)the salting-out capabilities of anions follow CO32->SO42-,the salting-out abilities of cations follow Na+>NH4+;(2)the phase-separation abilities of 2-proponal-ethanol-(NH4)2SO4 system at different temperatures follow 35?>45?>55?;(3)the higher the proportion of ionic liquid(2-proponal)in the organic mixture,the higher the phase-separation ability of an ionic liquid(2-proponal)-ethanol system;(4)The phase-separation capabilities of different systems follow ionic liquid-ethanol system > 2-propanol-ethanol system.The effective exclude values,the Hofmeister series and Gibbs free energy theory were applied to validate the conclusions.