Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

Heat curing was devised in temperature-controlled steam and water environments to synthesize reverse osmosis (RO) polyamide (PA) membrane. The effect of new curing media on the physicochemical properties and RO performance of the synthesized polyamides was fully investigated using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and water drop contact angle. The results show a reduction in amide linkage content on the surface of the steam-cured polyamide and surface and bulk of the water-cured polyamide. Additionally, it was revealed that heat curing in the humidity-controlled environment can be considered as a chemical modification process with the ability to change the cross-linking degree in adjustable depth and intensity. Heat curing in steam provided the membrane with great surface hydrophilicity, permeate flux, and salt rejection, which are required for treating dilute solutions. Moreover, the water-cured membrane exhibited extra high surface hydrophilicity and salt rejection that are necessary for treating solutions with high inorganic fouling tendency and high osmotic pressure.