Fabrication of novel functionalized multi-walled carbon nanotube immobilized hollow fiber membranes for enhanced performance in forward osmosis process

A novel functionalized multi-walled carbon nanotube (MWCNT) immobilized polyethyleneimine–poly(amide–imide) (PEI–PAI) hollow fiber membrane was designed and fabricated using an easily scalable method. PAI hollow fiber was spun via phase inversion, followed by functionalized MWCNTs immobilization via vacuum filtration before a chemical post-treatment using PEI was applied to obtain a positively charged selective layer. The resulting membranes were evaluated in the forward osmosis (FO) process. The membrane prepared using a 0.62 mg/L of MWCNTs solution shows a pure water permeability of 4.48 L/m2h bar with a MgCl2 rejection of 87.8% at 1 bar. This is a 44% enhancement in water permeability without significant compromise on the salt permeability when compared to membranes without MWCNTs. In addition, FO water flux of membranes prepared using 0.31 and 1.25 mg/L of MWCNTs solutions have also been enhanced up to 29% without compromising the solute flux in the active layer facing feed water orientation using 0.5 M MgCl2 solution as the draw solution and deionized water as the feed water. These encouraging results suggest that hollow fiber membranes immobilized with commercial MWCNTs exhibit good potential to be further developed for applications in the FO process.