Chemical Modification of Polyamide Thin-Film Composite Membrane by Surface Grafting of a Vinyl-Based Monomer

Currently, the use of membrane techniques has undergone dynamic growth, particularly due to the diversification of their fields of application. This trend is expected to increase owing to new environmental protection requirements and thanks to the increasingly competitive energy and technical-economic performances offered by membrane processes. New research is constantly being carried out to better understand the functioning of membranes, to create more efficient or more specific membranes, and also to develop processes for new applications. The aim of this work is to improve the performance of a polyamide reverse osmosis membrane by chemical modification of its surface. Thin film polyamide reverse osmosis membranes are widely used for desalination. However, these membranes face a fouling issue that results in low permeation flux, which is undesirable in the reverse osmosis process. An interesting alternative to improve the properties of these polyamide composite membranes is the use of chemical surface modification. In this context, we studied the chemical grafting of vinyl acetate monomer on the surface of a polyamide membrane in order to improve the selectivity towards sodium ion. The chemical grafting was carried out by radical polymerization of vinyl acetate monomer in the presence of benzoil peroxide as an initiator in an organic medium. Unmodified, modified membranes and evolution of the polymerization reaction were analyzed by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), interferometric electron microscopy, and contact angle. An application with a front filtration module was investigated to confirm the improved selectivity for sea water. This study revealed an improved efficiency of the reverse osmosis PA membrane after the grafting of polyacetate monomer on the active layer of this membrane.