Ionic liquid regulated interfacial polymerization process to improve acid-resistant nanofiltration membrane permeance

Abstract

In order to enhance the permeance of the acid resistance membrane, an ionic liquid (IL) regulating strategy was proposed to rearrange the interfacial polymerization process. Herein, we revisited polyethylenimine (PEI) and cyanuric chloride (CC) as the pristine acid-resistant membrane. 1-aminopropyl-3-methylimidazolium chloride ([AEMIm][Cl]) and 1-aminopropyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([AEMIm][Tf2N]) ILs were used to regulate the interfacial polymerization process. Molecular dynamic (MD) simulation was used to reveal IL and PEI diffusion behavior in aqueous solution, membrane pore size distribution, and porosity. The effects of ILs on membrane surface morphology, surface zeta potential, chemical composition, and separation property were analyzed. The IL regulating strategy endow the membrane with uniform smaller pore and higher porosity, thus improved membrane permeance and selectivity simultaneously. For the [AEMIm][Cl] IL, the corresponding AEMIC-PEI-CC membrane showed high permeance of 79.1 L m−2h−1bar−1, which is 1.36 times the pristine PEI-CC membrane, combined with high Y3+ rejection of 97.5%, low H+ rejection of 1.35%. In addition, this membrane showed good acid stability in 30 days long-term test.