Antifouling and chlorine-resistant cyclodextrin loose nanofiltration membrane for high-efficiency fractionation of dyes and salts

Antifouling loose nanofiltration membranes are prepared for effective fractionation of dyes and salts by the construction of a porous cyclodextrin polymer layer on membrane substrate. Octopus-shaped cyclodextrin macromonomers with pendant vinyl groups can be facilely prepared via a union of controlled radical polymerization and esterification reaction, which are then used to fabricate membrane. The surface-initiated photopolymerization of β-cyclodextrin-centered macromonomers could yield a porous polymer layer on the surface of the PVDF substrate. The porous structure could be well-tuned by adjusting the concentration of macromonomers or regulating the polymerization time. The optimal loose nanofiltration membranes have demonstrated high-efficiency separation ability for different dyes and low rejection ability for salts (<10%), owing to the selective layer of porous cyclodextrin polymer. Meanwhile, it maintains a high Congo red (CR) retention (∼99%) in a long-term filtration test. Furthermore, the cyclodextrin polymer layer also endows the membranes with predominant chlorine-resistance performance even after 15 days of immersion in sodium hypochlorite solution. The flux recovery ratio value of optimal membrane towards bovine serum albumin is 97.6% even after 5 antifouling cycles, and the antifouling ability is more than 10 times higher than that of the pristine PVDF membrane depending on the degree of membrane fouling by CR. The proposed strategy could provide helpful guidance in preparing antifouling loose nanofiltration membranes.