Fabrication of microporous polyamide selective layer on macroporous ceramic hollow fibers via direct interfacial polymerization for nanofiltration applications

Polyamide (PA) thin-film composite (TFC) membranes have been widely applied to nanofiltration applications and separation processes due to their high water permeability and solute rejection. However, commercial PA-TFC membranes with organic flat-sheet substrates, such as polysulfone, have a low resistance to organic solvents and a maximum operating temperature no higher than 50 °C. To alleviate this problem, recent research has focused on the development of ceramic substrates to provide robust membrane support. In this study, we successfully developed a novel alumina hollow fiber (AHF) substrate for PA-TFC membrane synthesis via interfacial polymerization. For the first time, a PA thin film was directly fabricated on a macroporous ceramic hollow fiber substrate without an intermediate layer. Herein, to make the support compatible with the PA thin film, AHF with a smooth, hydroxyl group-abundant, and ultrahydrophilic surface was prepared. The HF substrate demonstrated a porous structure with a mean pore size of 219.4 nm and high pure water permeability of 4593 ± 139 LMH/bar. In addition, the nanofiltration performance of the PA-TFC membrane was thoroughly evaluated in this study and compared to previous reports, and it was found that it possessed a molecular weight cut-off (MWCO) of 340 g/mol, pure water permeability (PWP) of 9.5 ± 0.4 LMH/bar, and high rejection of dyes (>97.0%). Our AHF substrate demonstrated its potential as an ideal material for fabricating high-performance PA-TFC membranes for nanofiltration applications. Moreover, our enhanced process of synthesizing PA-TFC membranes via direct interfacial polymerization promises wide applicability in future membrane studies.