Preparation and selected properties of ion-containing reverse osmosis membranes

Abstract

Ion-containing reverse osmosis membranes were prepared by the post radiation grafting of 4-vinylpyridine onto low density polyethylene films, followed by quaternization of the pyridine rings in the graft chains to confer ionic character to the membranes. The effect of some preparation conditions on the grafting yield was investigated. Different quaternizing agents such as methyl iodide, allyl bromide, and hydrochloric acid were used for the quaternization of the graft chains. The effect of quaternizing agent and degree of grafting on the properties of the membranes such as swelling behaviour, specific electric resistance, water flux and salt rejection, was investigated. The complete quaternization of pyridine rings in the graft chains with methyl iodide and allyl bromide was achieved and the membranes, thus obtained, possess good hydrophilic properties. It was found that the methyl iodide and allyl bromide quaternized membranes gave reasonable water flux and salt rejection. HCl-quaternized membrane, however, gave higher water flux and somewhat lower salt rejection as compared with those obtained for methyl iodide and allyl bromide quaternized ones. The properties of these ionic membranes did not deteriorate with the operation time and they show a great promise for the use in the field of reverse osmosis desalination of sea water.