Next-generation thin-film composite nanofiltration membranes for water remediation: a review

One of the most daunting challenges faced by the planet is a reliable and accessible supply of water in sufficient quantity. The membrane technology has emerged as a cost-effective alternative for water purification. One such pressure-driven membrane separation process is nanofiltration (NF), where the interfacial polymerization (IP) is predominantly used to prepare the thin polyamide selective layer. Over the last decade, a wide variety of novel/modified IP techniques have been explored to improve the performance of the polyamide (PA) thin-film composite and thin-film nanocomposite (TFN) membrane in both pressure-driven and osmotic driven applications. This paper explores different IP fabrication techniques viz. support-free IP technique, filtration-assisted IP technique, reverse IP technique, electrospray-based IP technique, etc. The thickness of the PA layer can be precisely monitored by many of these modified IP techniques. The incorporation of nanoparticles on the PA layer and membrane matrix could enhance the fouling resistance, increase the rejection efficiency and improve the water permeability. The efficiency of these membranes has been explored for the separation/removal of emerging contaminants, divalent/multi-valent ions, low molecular weight organics, micropollutants, and inorganic salts. Several advantages of these IP techniques are discussed in detail; however, the various associated challenges must be overcome before these techniques can be transferred from lab-scale to commercial applications.