Preparation, Characterization and Evaluation of Some Reverse Osmosis Membranes for Water Desalination

Abstract

Preparation of thin film composite polyamide (PA) reverse osmosis (RO) membranes and their modification with zwitterionic polymer [poly [2- (methacryloyloxy) ethyl- dimethyl- (3-sulfopropyl) ammonium hydroxide] (P(MEDSAH)] were studied. The results showed successful incorporation of P(MEDSAH) coating layer on the PA membrane and the membrane surface was more hydrophilic. The membrane modification tended to enhance significantly both the water permeability and salt rejection. The experimental results of fouling tests showed that the coating layer of zwitterionic polymer improved the bacterial fouling resistance of membrane. The flux recovery rate of modified membrane after cleaning by de-ionized water was 87%, which was much higher than that of virgin membrane 59%. The results are of great importance in enhancing antifouling properties and this approach would be of particular interest from a practical point of view as the membranes can be treated in their original module assembly. These results were confirmed by the various applied testing methods and highly sophisticated instrumental techniques applied through this study. Asymmetric reverse osmosis membranes of cellulose acetates (CA) with and without nano-chitosan were prepared by the phase-inversion technique. Different parameters affecting on the properties of the polymer membrane such as polymer composition, amount and type of solvent, non solvent, evaporation time and annealing temperature were investigated.Water flux and salt rejection of 35g/L aqueous sodium chloride solution were monitored over time at different applied pressures in a dead end module. The results showed that the addition of nano-chitosan to the casting solution enhances both water flux and salt rejection properties for pure cellulose acetate and largely enhanced water flux but decline salt rejection for cellulose triacetate membranes. All membranes containing nano-chitosan exhibited remarkable antifouling to bacterial attack. Key Words: Reverse Osmosis Membrane, Thin Film Composite, Asymmetric membrane, Antifouling, Polyamide, Cellulose acetate, Zwitterionic polymer