Recent advancements in the application of new monomers and membrane modification techniques for the fabrication of thin film composite membranes: A review

Thin film composite (TFC) membranes have been experiencing significant modifications recently aiming to improve their structure, properties and separation efficiency. One of the promising modifications to tailor the membranes more efficient is changing the materials used. m-phenylene diamine (MPD), piperazine (PIP), and trimesoyl chloride (TMC) are the most common monomers used to fabricate TFC membranes. Recent studies have introduced several alternatives to these traditional monomers showing significant contribution of these monomers to the physicochemical properties of the membranes (e.g., surface roughness, hydrophilicity, cross-linking density, chemical structure) as well as membranes' separation efficiency. Emergence of more favorable functional groups such as carboxylic and amine groups due to the new materials integration facilitates the polymerization process and is beneficial to the membrane properties. Here, a critical review on the new interfacial polymerization monomers applied for reverse osmosis (RO) and nanofiltration (NF) membranes fabrication is presented. The membrane molecular structure and fabrication mechanism are investigated in details. This is followed by a review of the recent surface modification methods including grafting, coating and additive incorporating into the thin layer of membranes. The application of alternative monomers to MPD, PIP and TMC are investigated and the benefits of using these monomers or co-monomers are discussed.