Preparation And Extraction Properties Of Ionic Liquid Gel Microspheres Using Pickering Emulsion Drops As Template

Emulsion refers to a system composed of two immiscible liquids（such as water and oil）,in which one liquid is dispersed in the form of small droplets in the other liquid.The former is called the dispersed phase,and the latter is called the continuous phase.Traditional emulsions are emulsion systems formed by small molecular surfactants as emulsifiers,while Pickering emulsions refer to emulsion systems formed by using solid particles as emulsifiers.Room temperature ionic liquids（IL or ILs）are ionic compounds composed of organic cations and inorganic or organic anions.Ionic liquids are considered as"designer solvents"and"future solvents".They are called"designer solvents"because they can adjust their properties by changing the composition of the ionic liquids.By changing the structure of the cation or anion,the type of substituent group,and the length of the alkyl chain,the properties of the ionic liquids can be changed.They are called"future solvents"because they have been found to be suitable for various fields such as extraction processes,electrochemistry,analytical chemistry,and nanotechnology.Ionic liquid gel is a new type of hybrid material that limits ionic liquids in a three-dimensional cross-linked network through different internal interactions,and fills the space between the network with cations and anions.The ionic liquid gel contains free ionic liquid units,so it retains the original properties of the ionic liquid,while stably confining the ionic liquid in the polymer network without leakage.This article combines ionic liquid gel with Pickering emulsion droplets,uses Pickering emulsion to disperse the ionic liquid in the form of droplets in water,and polymerizes the ionic liquid to form an Ionic liquid gel microsphere complex to investigate the extraction performance of the Ionic liquid gel microsphere complex for dyes.The specific contents are as follows:（1）Firstly,Si O₂nanospheres were prepared by the sol-gel method,and the diameter of Si O₂nanospheres was about 150 nm.GO nanosheets were prepared by an improved Hummers method.Two emulsifiers were used to emulsify[BMIm][PF₆]and[VEIm][PF₆]mixed ionic liquids to form Pickering emulsions of water-in-mixed ionic liquids.Irgacure-2959 was used as a photoinitiator,and ultraviolet light was used to polymerize[VEIm][PF₆]inside the Pickering emulsion droplets to form P[VEIm][PF₆],and[BMIm][PF₆]existed in the three-dimensional network of P[VEIm][PF₆]as a solvent,thus forming an Ionic liquid gel microsphere complex with particle-containing surface emulsifiers.The Pickering emulsion was stable and the droplets were small when the volume ratio of oil to water was 1:3 and the dosage of Si O₂microspheres was 14 mg.The Pickering emulsion was placed in a petri dish and irradiated discontinuously by ultraviolet light.The ionic liquid gel microspheres were easily monodisperse.Only when n[BMIm][PF₆]/n[VEIm][PF₆]is 5:5 and 6:4,ionic liquid gel microspheres can be formed.n[BMIm][PF₆]/n[VEIm][PF₆]is 5:5,the morphology of ionic liquid gel microspheres is good.Pickering emulsion can be formed only when the volume ratio of oil to water is 1:4,the dosage of GO nanosheet is 10 mg,n[BMIm][PF₆]/n[VEIm][PF₆]is 5:5.The monodisperse ionic liquid gel microspheres were formed when the Pickering emulsion was placed in a petri dish and irradiated discontinuously by ultraviolet light.The particle size of ionic liquid gel microspheres is about 200μm.The Ionic liquid gel microsphere complex were characterized by FT-IR,SEM,TG.（2）The stability of the emulsifiers on the surface of the Ionic liquid gel microsphere complex was investigated,and the stability of the Ionic liquid gel microsphere complex in deionized water,methanol,acetonitrile,and DMF was explored.It was found that the stability of the Ionic liquid gel microsphere complex without crosslinking agent was poor in acetonitrile and DMF.Then,ionic gel balls with divinylbenzene as a crosslinking agent were prepared,and the stability of the ionic gel balls with crosslinking agent in different solvents was explored again.It was found that adding a crosslinking agent improved the stability of the Ionic liquid gel microsphere complex in acetonitrile and DMF compared with the Ionic liquid gel microsphere complex without cross linking agent.（3）This study investigated the effects of extraction time,solution p H,Na Cl concentration,and polymerization time on the extraction efficiency of ion-imprinted gel beads.The optimal extraction performance was achieved when the extraction time was 80 min,the p H was 7,the Na Cl concentration was 0.0 mol·L^-1,and the polymerization time was 6 min.The influence of different emulsifiers,crosslinkers,and[BMIm][PF₆]content of the ion-imprinted gel beads on the extraction performance was also discussed.The ion-imprinted gel beads with GO as the emulsifier showed better extraction performance than those with Si O₂as the emulsifier,and the addition of a small amount of crosslinker or an increase in[BMIm][PF₆]content enhanced the extraction ability of the ion-imprinted gel beads.Additionally,the extraction performance of the ion-imprinted gel beads for different dyes was investigated.