Carbon nanotubes regulated polyamide membrane by intercalation to improve the organic solvent nanofiltration performance

Abstract

Carbon nanotubes (CNT) are considered as promising materials for enhancing thin-film composite (TFC) membranes by introducing an intermediate layer. However, the specific function of the CNT intermediate layer in the formation of the selective polyamide (PA) layer using interfacial polymerization (IP) remains unclear. Consequently, in this study, a network of CNT was applied as a coating on a polyketone (PK) substrate to control its surface characteristics and act as an intermediate layer for PA formation. By adjusting the amount of CNT, the PK surface became less hydrophilic and had smaller surface pores. The CNT intermediate layer facilitated PA formation by expediting the release of IP monomers, reducing the interaction between PK and the monomers. Nevertheless, excessive CNT loading could lead to the retreat of large leaf-like structures, which are essential for achieving high performance in organic solvent nanofiltration (OSN). OSN tests revealed that the optimal TFC-0.5 membrane displayed a methanol permeance of 5.34 L m−2 h−1/bar with an extremely low molecular weight cut-off (MWCO) of 170–180 g/mol. This result was attributed to the reduced PA intrusion, enlarged PA filtration area, and the gutter layer effect brought about by the CNT intermediate layer.