The chlorination and chlorine resistance modification of composite polyamide membrane

Abstract

ABSTRACTMembrane‐based separation technology is one of the most active separation technologies being employed in water treatment. Polyamides (PA) are widely used membrane materials because they exhibit excellent performance, such as high flux with high salt rejection, and enhanced stability against wide range of pH and temperature. Unfortunately, PA membranes exhibit extremely poor resistance to chlorine leading to increased operation costs and decreased membrane lifetime. In this study, we find new ways for prolonging membrane lifetime and reducing the operating costs by investigating the chlorination and modification of PA membranes. Varying concentrations of hypochlorite were used to chlorinate a commercial reverse osmosis membrane (BW‐30, DOW). The results showed that short‐time exposure to high concentrations of hypochlorite could cause more serious problems to membranes than long‐time exposure to low concentrations under the similar total exposure. The performance of the chlorinated membranes was recovered to some extent after treatment with NaOH solution (pH 10), indicating that the alkali treatment could initiate the reversible regeneration of chlorinated membranes. Furthermore, an industrial grade epoxy resin was used to modify the membranes to enhance the chlorine resistance via the reaction between the amide nitrogen and epoxy bond. The successful modifications were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Moreover, the chlorination tests showed that the modifications performed in these experiments enhanced the chlorine resistance of the membranes, especially for the membranes exposed to low concentration of chlorine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41584.