Robust thin film composite membrane with Cu2+ integrally-crosslinking for organic solvent nanofiltration

Thin film composite (TFC) membranes are commonly used for organic solvent nanofiltration (OSN) application. However, these membranes normally suffer from the layer delamination under harsh conditions. Chemically integral crosslinking is a common method to address this problem, but the resultant tightened polymeric chains and denser microstructure will inevitably bring the reduced solvent permeance. In this work, a facile metal integral crosslinking strategy, which has minimal adverse effect on the solvent permeance, was developed to improve the tolerance to the majority of organic solvents as well as enhance the adhesions of upper selective layers and underlying substrates simultaneously for the first time. The as-developed Cu2+ integrally-crosslinked membranes demonstrated a high permeance for organic solvents and a high rejection towards rose bengal. In comparison to the Cu2+ partially-crosslinked membranes (with substrate crosslinked only), the integrally-crosslinked ones exhibited superior solvent resistance and OSN performance. This improvement was attributed to the enhanced interactions and a defect-free PA layer. Additionally, the effects of solvent activation, crosslinking solution concentration as well as crosslinking time were also studied. It is believed that metal integral crosslinking strategy will offer a novel approach to develop promising TFC membranes with satisfactory OSN performance for practical applications.