Preparation of a PES/PFSA-g-MWCNT ultrafiltration membrane with improved permeation and antifouling properties

In this study, perfluorosulfonic acid (PFSA) was firstly grafted on multi-walled carbon nanotubes (MWCNTs) to obtain PFSA-g-MWCNT nanocomposites. The combination of MWCNTs with PFSA effectively prevents the interactions among them, so that the dispersion of PFSA-g-MWCNTs in N,N-dimethylacetamide (DMAc) was greatly improved. Then, polyethersulfone (PES)/PFSA-g-MWCNT ultrafiltration (UF) membranes were prepared via a non-solvent induced phase separation (NIPS) method using different contents of PFSA-g-MWCNT nanocomposites as additives. The nanocomposites and membranes were characterized using techniques including Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). The SEM images show that the PFSA-g-MWCNTs no longer agglomerate and entangle, and exist as individual nanotubes in the PES/PFSA-g-MWCNT membrane. The mechanical and thermal properties of the composite membranes were enhanced with the increasing PFSA-g-MWCNT nanocomposite content. The performance of the UF membrane was evaluated using bovine serum albumin (BSA) as a model system. The results show that the permeation and antifouling performances of the PES/PFSA-g-MWCNT membranes were enhanced. For example, the pure water flux, BSA rejection and pure water flux recovery rate of the PES (M0) membrane were 80.49 L m−2 h−1, 86.29%, and 70.96%, respectively, while for the PES/PFSA-g-MWCNT (M6) membrane, they were 447.83 L m−2 h−1, 87.47%, and 92.10%, respectively. Long-term stability experiments show that the PES/PFSA-g-MWCNT membrane still maintains a high pure water flux.