Effect of added NaX nano-zeolite into polyamide as a top thin layer of membrane on water flux and salt rejection in a reverse osmosis process

The thin film nanocomposite of polyamide and nano-NaX zeolite (40-150 nm) membranes was coated via interfacial polymerization of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) monomers over porous polyethersulfone ultrafiltartion support. Different types of nanocomposite films were synthesized by two levels of monomer concentrations and nanozeolite loading into the polyamide film. The prepared nanocomposite membranes had higher thermal stability and more water permeability than the pure polyamide membranes. The results showed that addition of nano-NaX zeolite to the polyamide membrane led to improvement of surface properties such as RMS roughness, contact angle and solid-liquid interfacial free energy, a decrease in film thickness and an increase in pore size and water flux. The nanocomposite membranes with high concentration of monomers in interfacial polymerization exhibited a high water flux and low salt rejection. Excellent membrane performance was observed for the nanocomposite membrane containing about 0.2% (w/v) nano-NaX zeolite, 0.1% (w/v) TMC and 2% (w/v) MPD which its flux was higher by 1.8 times than the flux value of the neat polyamide membrane without any change in salt rejection. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.