High-flux and anti-fouling cellulose nanofiltration membranes prepared via phase inversion with ionic liquid as solvent

It is well-known that cellulose is difficult to dissolve in common organic solvent and be directly processed into porous membrane. In this work, using ionic liquid, 1-allyl-3-methylimidazolium chloride (AMIMCl) as solvent, high flux and anti-fouling cellulose nanofiltration (NF) membranes were fabricated by phase inversion method from 8.0 wt.% of cellulose/AMIMCl solutions. Pure water was employed as the non-solvent in phase inversion process. From the result of polarized light microscopy, we found that cellulose was completely dissolved in the AMIMCl at 90 °C. The characterizations of Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopies showed that no obvious changes occurred in the chemical structure of cellulose after membrane formation, but the crystallinity had a remarkable decreased. Membrane morphologies of the fabricated cellulose membranes including the cross-section and the surface were analyzed by scanning electron microscopy (SEM). It was found that the AMIMCl had a distinctive effect on phase inversion process and the cellulose selective layer displayed a macrovoid-free and relatively dense layered structure. Based on the filtration experimental results, the pure water permeation flux of the membranes reached 128.5 L/m2h under 0.4 MPa, and the molecular weight cut-off was less than 700 Da. The membranes exhibited a good stability and anti-fouling ability in water-phase separation process, and were suitable as NF membranes to separate the organic compounds with a medium molecular weight.

► Cellulose NF membranes were fabricated using ionic liquid as solvent. ► The pure water flux of membrane reached to 128.5 L/m2h under 0.4 MPa. ► The molecular weight cut-off was less than 700 Da. ► The membranes exhibited a good stability and anti-fouling capability.