J. Mem. SCI.: the wanyinhua research group of the Institute of process engineering, Chinese Academy of Sciences has made important progress in the recovery of ionic liquids by membrane distillation technology

As a green solvent, ionic liquid plays an important role in separation, catalysis and electrochemistry However, ionic liquids are generally expensive and cannot be discharged directly, so they need to be recycled Pressure driven membrane separation technology (such as nanofiltration and reverse osmosis) is one of the effective methods to recover ionic liquid from aqueous solution Compared with nanofiltration or reverse osmosis technology, membrane distillation technology, which is not affected by osmotic pressure, has excellent retention performance for non-volatile substances, and is expected to make a breakthrough in the application of ionic liquid recovery However, in the new process of separation and concentration of ionic liquid aqueous solution by membrane distillation, the problems of membrane material selection, membrane fouling and wetting, process mass transfer and heat transfer need to be studied In view of the above problems, wanyinhua research team of the Institute of process engineering, Chinese Academy of Sciences has carried out a systematic study on the process of membrane distillation and concentration of ionic liquid aqueous solution from the aspects of membrane preparation, membrane pollution, process optimization, etc The schematic diagram of membrane distillation technology (source: Institute of process engineering, Chinese Academy of Sciences) uses plasma technology to hydrophobically modify the surface of hydrophilic polyacrylonitrile membrane (Pan), and a high-performance hydrophobic porous membrane is prepared It is found that it can efficiently concentrate high concentration of 1-butyl-3-methylimidazolium chloride ([bmim] Cl) aqueous solution Meanwhile, the process of concentration is clarified The evolution mechanism of membrane pollution Based on the above results, the thermodynamic mechanism of membrane fouling in the separation of ionic liquid aqueous solution by membrane distillation was further explored from the perspective of the interaction between ionic liquid and membrane surface The interaction energy between different membranes and different ionic liquids was calculated by xdlvo (extended Derjaguin Landau Verwey Overbeek) theory The results show that this kind of membrane fouling is mainly controlled by the polarity of adsorption; at the same time, the higher the roughness of membrane surface, the higher the polarity of membrane surface, the less the negative charge of membrane surface, the higher the concentration of ionic liquid, and the stronger the interaction between ionic liquid and membrane surface, which results in the aggravation of membrane fouling Finally, the mass transfer and heat transfer model of the separation of ionic liquid water mixture by vacuum membrane distillation is established The results show that the effect of concentration polarization on membrane flux is greater than that of temperature polarization The project is supported by the national high technology research and development plan (No 2012aa021202, No 2014aa021005), the National Natural Science Foundation (No 21106153) and the solar thermal driven seawater desalination technology project (kgcx2-yw-380) Paper link: https://www.sciencedirect.com/science/article/pii/s037673881323608 correspondence Author: Wan Yinhua researcher http://sourcedb.cas.cn/sourcedb_ipe_cas / ZW / zjrc / 200906 / t20090611_974209.html Shen Fei associate researcher http://sourcedb.cas.cn/sourcedb_ipe_cas / ZW / zjrc / 200906 / t20090611_974133.html