Clay nanosheets as charged filler materials for high-performance and fouling-resistant thin film nanocomposite membranes

Abstract

Montmorillonite (MMT), a cationic clay, and layered double hydroxide (LDH), an anionic clay were prepared through “top-down” and “bottom-up” methods, respectively, with lateral dimension on hundred-nanometer scale as well as high aspect ratio. These two types of nanosheets, served as additives in interfacial polymerization process, were utilized to fabricate thin film nanocomposite (TFN) reverse osmosis (RO) membranes containing cationic and anionic clay nanosheets. The properties of TFN membranes were effectively modified with the advantage of unique charged properties and hydrophilic nature of these nanoclay filler materials,. Both MMT and LDH filled TFN membranes showed increased hydrophilicity and improved desalination performance. More importantly, the incorporation of MMT and LDH nanoclays resulted in a more and less negatively charged membrane surface, respectively, and thus exhibited different electrostatic repulsion effects and improved antifouling performances towards protein, cationic surfactant, and natural organic matter foulants. The results indicate that clay nanosheets are effective filler materials to tailor membrane surface properties and fouling resistance. Since the modification by nanoclays can be achieved in the membrane preparation process without altering existing procedures, this approach can be considered as a facile way to produce novel high-performance and fouling-resistant TFN RO membrane for desalination.