Janus membranes with opposite wettability prompting the synchronous synthesis and separation of hydrophobic ionic liquids

• Published in: Journal of membrane science 2023-12, Vol.687, p.122037, Article 122037
• Main Authors: Wu, Qian, Zhang, Wen-Ting, Li, Hao-Nan, Cao, Ye, Weng, Rui-Bin, Li, Yong-Jin, Yang, Jing
• Format: Article
• Language: English
• Subjects: Emulsion separation; Ionic liquids; Janus membrane; Membrane reactor; Unidirectional liquid delivery
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2023.122037

Traditional production of ionic liquids (ILs) includes isolated processes of synthesis followed by extraction purification with organic solvents. A remained challenge is to produce these green solvents by a simultaneous synthesis and separation procedure disusing volatile organic solvents. Herein, we describe a framework for the synchronous synthesis and separation of hydrophobic ILs based on an environmentally benign membrane reactor system. A Janus hollow fiber membrane reactor (JHFMR) with a thin and charged inner surface (IL-phobic) and an IL-philic outer surface is prepared by mussel-inspired co-deposition technique. The hydrophilic lumen surface supplies a reaction zone for anion metathesis. The inner surface charge destabilizes the emulsified target ILs dispersed in water. The deemulsified ILs actively pass through the JHFMR from IL-phobic side to IL-philic side driven by the gradient of surface energy. Multiple JHFMRs are ultimately assembled to prepare a JHFMR module for achieving a continuous and large-scale production of hydrophobic ILs in a cross-flow mode. The final ILs yield under a low reactant concentration (l.0 mol/L) is enhanced to reach 96% after 30 h by doubling the packing density of module. The residual water content in IL products is below 1.0 wt%. Other ion impurity is negligible (Li+