Interfacially synthesized thin film composite RO membranes for seawater desalination

A composite RO membrane with high salt rejection and high flux for the desalination of seawater was prepared by treating a porous polysulfone (PS) support sequentially with a di-amine and then with a polyfunctional acid chloride, thereby forming a thin film of polyamide (PA) on the PS support. In order to establish conditions for the development of suitable thin film composite (TFC) membranes on a coating machine, various parametric studies were carried out which included varying the concentration of reactants, reaction time, curing temperature and curing time for thin film formation by the interfacial polymerization technique. By suitable combination of these factors,a desired thin film of polyamide with improved performance for seawater desalination could be obtained. Moreover, the product water fluxes were considerably enhanced by post-treatment of the TFC membrane. Continuous sheets of TFCs were developed on the mechanical coating unit and tested for RO performance in a plate-and-frame configuration with synthetic seawater. The performance of these composite membranes was also determined for the separation of organics and compared with cellulose acetate (CA) membranes.