Development of nanofiltration dual-layer hollow fiber membranes for forward osmosis

Abstract

Forward osmosis (FO) has been attracting growing attention in many applications in the recent years. FO has not been as well-studied as compared to pressure driven membrane process. The main advantages of FO include low or no hydraulic pressure, low tendency of fouling and high water recovery. The key challenges faced by FO are draw solution and the need for new membrane development. Therefore, the current study aims to fabricate nanofiltration dual-layer hollow fiber membranes suitable for FO applications.The provided polyamide-imide (PAI)/ polyethersulfone (PES) hollow fiber ultrafiltration (UF) substrates were cross-linked with 1% wt polyethylenimine (PEI) of different molecular weight at 70ᵒC for 75 mins to prepare the NF membrane. The PEI modified membranes were further modified with cross-linked layer-by-layer (LbL) assembly. The LbL consists of layers of polyanion (polystyrenesulfonate, PSS) and polycation (polyallylamine hydrochloride, PAH), cross-linked with glutaraldehyde solution. The modified membranes were subsequently characterized in terms of morphology, FTIR, surface charge, pore size distribution, water permeability and salt rejection. The same modified membranes will then undergo FO performance test. In FO, draw solution of 0.5M MgCl2 and feed water of DI water were used.