The Extraction And Capture Performance Of Phenol And Iodine By Choline-based Ionic Liquids

Aromatic compounds in crude oil and radioactive iodine in nuclear wastesareunneglectableenergy byproducts casusing environmental pollution.With wide liquid temperature range,ionic liquids（ILs）perform excellent application prospects in the field of extraction and separation.However,most researches focus their attention on the traditional ionic liquids,which lack of special design and theinteraction sitesare limited,thus contribute to the low separation efficiency andlarge dosage.As part of the researches of the project supported by the National Natural Science Foundation of（No.21673068）,anions with special functional groups were choose to synthesize the 43 kinds of choline-based ionic liquids because of the fact thathydroxyl group in choline cation could interact withsome environmental pollutants.These ionic liquids were used for the separation of phenol and the capture of radioactive iodine,and the main contents are as follows.1.43 kinds of choline-based ionic liquids were synthesized and characterized by ¹H NMR,thermogravimetric analysis（TGA）and differential scanning calorimetry（DSC）,Thermal poperities and their structural effect were studied.It was found that the melting point or glass transition temperature of most choline-based ILs were below 100℃,which means that most of the synthesized ILs belong to room-temperature ILs.The decomposition temperature of choline carboxylic-based ILs was atabout 200℃.Their thermal properities weremainly influenced by the position,sizeof substituent and heteroatom numbers.2.Extraction and separation performance of phenol from the model oil（toluene）bycholine carboxylic-based ILs were investigated.The effects of IL structure,system temperature,and molar ratio ofIL to phenolic on distribution coefficient were exmined.It was shown that choline carboxylic-based ionic liquidsexhibit the excellent performance whenused for the separation/extraction of phenolic compounds from toluene.Under the optimized conditions,the separation efficiency of 13 kinds of ionic liquids can reach up to 99%.The transfer of phenol from toluene phase to ILs phase is a thermodynamically favorable process.3.Capture performance of radioactive iodine from cyclohexane solution by choline heterocylic-based ionic liquidswas investigated.Ultraviolet and visible spectroscopy（UV-vis）,nuclear magnetic resonance(¹H NMR,¹³C NMR,COSY,DOSY),mass spectrometry（ESI-MS）and DFT simulation were adopted to analyze the trapping process and mechanism.It was found thatat 30℃,the adsorption capacity of choline heterocylic-based ionic liquids could reach up to 3.1 mol/mol within 15minutes,and the formation of C-I bonds was the main driving force for such a high capacity.4.Captureperformance of radioactive iodine from iodine vapourwas also studied and the stability of the system after capture of radioactive iodine was estimated by TGA,binary phase diagrams of the systemswere determined by DSC,and the possible iodine species in capturing system were analyzed by electrospray ionization mass spectrometry（ESI-MS）.It was found thatthe capture capacity of iodine by choline imidazolium ionic liquidincreased with the increase of temperature in the range of 40-100℃,and up to 11.8 mol/molcapacity was achived at 100℃.Besides,radioactive iodine can be stablystored in choline heterocylic-based ionic liquids.With the sweeping rate of 5 mL/min with N₂at 100℃,the loss amount of iodine vapour in thecholine-imidazole ionic liquid is less than 5%after 10 hours of sweeping.