Polyamide layer modulation for PA-TFC membranes Optimization: Developments, Mechanisms, and implications

Polyamide thin film composite (PA-TFC) membrane featured with triple-layer structure including polyamide (PA), substrate, and nonwoven support is playing critical roles in dealing with freshwater crisis via desalination technologies such as reverse osmosis (RO) and nanofiltration (NF). Although with good performance, further strengthening of PA-TFC membrane efficacy would contribute to further decreasing desalination cost. As the core part, PA layer modulation gradually comes into researchers’ sight. PA layer is usually fabricated by interfacial polymerization (IP), which occurs at liquid interface and is a diffusion-dependent process. Thus, Regulating interface properties and/or controlling diffusion process could tune IP and further modulate PA layer structure and performance. Herein, we reviewed and discussed currently reported strategies for IP tuning and PA layer modulation with emphasis on interlayer intercalation, additive introduction, co-solvent assisted IP (CAIP), and novel IP. Combined with analysis on the reported works, we emphasize on the common and distinctive features of these methods in modulating PA layer structure and membrane performance. We also make discussions on the shortage of the present study. It is anticipated that we could provide some insight on how to further refine these methods by analyzing the underlying mechanism and by comparing the different results. Furthermore, based on analysis and discussions we also give our perspective on future research in this area. The information here is believed to be able to contribute to push the development of more advanced PA-TFC membranes via PA layer modulation.