Ultrathin Poly(Ionic Liquid) Nanomembranes for High Performance Mg²⁺/Li⁺ Separation

Abstract

The fragility and brittleness of glassy poly(ionic liquid)s (PILs) hinders the processing of ultrathin PILs membranes. This work is reported the interfacial polymerization of PILs, which enables the first preparation of defect‐free PIL nanomembranes for high flux separation of lithium (Li+, 3.8 Å) and magnesium (Mg2+, 4.3 Å) ions mixture. Aqueous solution of an amine‐functionalized PIL is brought in contact with trimesoyl chloride (TMC) hexane solution. The “amine ≈ acyl chloride” condensation reaction occurs at the “water ≈ hexane” interface to form ≈50 nm thin PILNH2‐TMC nanomembranes consisting of water‐stable nanoaggregates (≈20 nm in size). Water permeance of the PIL nanomembrane is 3 times as high as the state‐of‐the‐art polyamide nanofiltration membranes, while its MgCl2 rejection is as high as 95%. Both the structures and separation performance of PIL nanomembranes are stable versus operation time and pressure. This work opens a new avenue to process fragile PILs, such as into functional nanomembranes for ion separation.

Alternative materials for interfacial polymerization: recent approaches for greener membranes

“…Lastly, in most cases, the IL is used as an additive. 48,49 2.1.2 Bio-based solvents. Ong et al 21 used decanoic acid in the IP organic phase, which is a medium chain fatty acid found in coconut oil, palm kernel oil, and animal fats.…”

Ionic liquids membranes for liquid separation: status and challenges

“…For example, Ni et al found that the long chain nature of PILNH 2 polymers contributed to the stable microstructures in PILNH 2 -TMC nanomembranes with stable flux versus pressure. 151 In their study, Chen et al analyzed how the different amounts of [EMIM][B(CN) 4 ] impacted the mechanical properties of ILPMs made with PVDF. They found that as the IL content increased, the Young's modulus, tensile strength, and extension at break decreased.…”

A Selective Separation Mechanism for Mono/divalent Cations and Properties of a Hollow-Fiber Composite Nanofiltration Membrane Having a Positively Charged Surface

“…Apart from PEI and PIP as aqueous monomers, researchers [ 18 , 19 ] have also used other chemicals as monomers during interfacial polymerization. For example, recently, Peng et al [ 18 ] synthesized a quaternized-spiral piperazine (QSPIP) featuring a spiral conformation and quaternary/secondary amines and used it as an aqueous monomer to react with TMC via interfacial polymerization and fabricated a kind of QSPIP-TMC membrane, which achieved an approximately five-times-improved water permeance (220 LMH/MPa) compared with analogous polyamide membranes and a good Mg/Li selectivity of 8.7.…”