Fabrication and Modification of Thin-Film Composite Hollow Fiber NF Membranes

This study focuses on the preparation and modification of a thin-film composite (TFC) hollow fiber polyamide membrane fabricated by the interfacial polymerization of Piperazine (PIP) and trimesoyl chloride (TMC) on a porous polysulfone substrate. The effects of triethylenetetramine (TETA) and silica nanoparticles (SiO2) contents in the aqueous phase (as the additives) on the morphology and performance of the hollow-fiber composite membranes were studied. The morphologies, chemical composition and the surface image of membranes were investigated by using FTIR, SEM, AFM and contact angle analyzes. TETA resulted a more hydrophilic as well as lower surface roughness in the modified membranes. In addition, the active layer of the membranes had uniform, smooth and dense structures compared with the neat membrane (control sample). In case of the SiO2 nanoparticles, AFM images showed rougher surfaces in the modified membranes. However, the nanoparticles’ size is close to the membrane pore size. As a result, the silica particles block a few pure water channels of the membranes. The obtained results showed that the water flux increased with increasing the silica contents in the aqueous phase. Furthermore, the NaCl rejection increased by increasing the TETA concentration. This showed that adding optimal concentration of the both SiO2 and TETA in the aqueous phase would increase the both flux and rejection, as well as prepared appropriate hollow fiber TFC membrane. The hollow fiber composite membrane possessed a salt (NaCl) rejection of about 26 % and flux of about 31 L.m-2.h-1.