Functionalized Choline Ionic Liquid-polymer Aqueous Two-Phase Systems And Their Separation Performance For Some Phytochemicals

As a new separation technology,ionic liquids?ILs?based aqueous two-phase systems?ATPSs?are attracting the attention of a growing number of scientists and engineers in recent years.However,most of such studies was focused on the use of imidazolium ILs,which are toxic and may have possible impact on the environmental and ecosystems.An alternative approach for overcoming these drawbacks is the development of ILs from their components which have well cha racterized biodegradable and toxicological properties.Biodegradable choline-based ILs have been used to form environmentally friendly ATPSs.However,only a few of compounds c an form ATPSs with choline-based ILs because of the relatively simple structure of these ILs,which may limit the wide application of these ATPSs.As a part of the researches of the project supported by the National Natural Science Foundation of China?No.21133009?,a series of ionic liquids with choline structure have been designed and synthesized from environmentally friendly ethylene glycol derivatives.The phase equilibrium of ATPSs formed by these choline-based ILs and temperature responsive polymers?EOPO?was studied systematically.Then,partition behavior of selected phytochemicals in these ATPSs w as studied.The major content of the present work is as follows.1.24 kinds of functionalized choline ILs were synthesized and pur ified,and then characterized by.¹H NMR,¹³C NMR,differential scanning calorimetry?DSC?and thermogravimetric analysis?TGA?.It was shown that theses ionic liquids have excellent low temperature performance and good thermal stability.They belong to the scope of room temperature ionic liquids.2.Based on the liquid-liquid equilibr ia data determ ined for the ATPSs formed by the functionalized choline ILs and thermal responsive polymer?EOPO1900,EOPO2000,EOPO2700 and EOPO5800?,liquid-liquid equilibrium phase diagrams were constructed for these ATPSs.The effects of the structures of the ILs and the polymers as well as the system temperatures on the phase equilibrium of the ATPSs were investigated systematically,and phase formation regularity was analyzed in such ATPSs.3.The partition behavior of chlorogenic acid and caffeic acid in the ATPSs were investigated,and the effects of the composition of ATPSs,structure of the ILs,polymers and phytochemicals on the partitioning of chlorogenic acid and caffeic acid were examined.Based on these results,green extraction strategies were established for chlorogenic acid and caffeic acid.It was found that under the optimized condition,the single extraction efficiency of chlorogenic acid and caffeic acid in the ATPSs was as high as 97.0% and 96.7%,respectively.4.The selective separation of chlorogenic acid from caffeine by the functionalized choline ILpolymer ATPSs was studied.The effects of the concentrations of the ionic liquids and polymers,structure of the chlorogenic acid and caffeine,and the temperature of the systems on the selective separation were examined in detail.Under the optimized conditions,the selectivity separation coefficient of chlorogenic acid and caffeine in the ATPSs could be reached to 195 by one-step extraction.A selective separation strategy was then proposed for chlorogenic acid and caffeine.