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 & PLUSMN; 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 & PLUSMN; 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.