Preparation of polyamide thin film nanocomposite membranes containing silica nanoparticles via an in-situ polymerization of SiCl4 in organic solution

Thin film nanocomposite (TFN) membranes with improved permeability is important in the energy-efficient reverse osmosis membrane processes. In this paper, we demonstrate a facile method for the formation of polyamide/silica TFN membranes by an in-situ interfacial polymerization of aqueous amine and acid chloride/silicon tetrachloride (SiCl 4 ) solutions. Water permeability is greatly enhanced with minimal loss in NaCl rejection. Polyamide/silica TFN membranes with 0.04% w/v SiCl 4 exhibit a pure water permeability up to 9.7 L m −2 h −1 bar −1 , which is 2.02 times more than that of the pristine thin film composite (TFC) membranes, while high rejection to NaCl (96.5%) is maintained. TEM tomograms confirm the existence of silica nanoparticles (NPs) in the thin PA film. More permeable voids are created in the cross-section of TFN membranes. Outer voids are buried underneath the PA protuberances and overhanging crumples. Inner voids and silica NPs are both encapsulated by polyamide . Top surfaces become more hydrophilic and negatively charged. With the optimal amount of SiCl 4 loading, the formation of non-selective voids around the particles is minimized. Covalent and hydrogen bonds are formed between SiCl 4 and PA polymers. These polyamide/silica nanocomposite membranes outperform many other TFN membranes in water permeability and salt rejection.