In-situ formation of epoxy derived polyethylene glycol crosslinking network on polyamide nanofiltration membrane with enhanced antifouling performance

Abstract

Nanofiltration (NF) membrane fouling is still an inevitable main challenge, which leads to the reduction of membrane performance. The large number of aliphatic chains in the poly (vinyl alcohol) (PVA) skeleton will reduce the increase in hydrophilicity. Therefore, the existing PVA grafting technology has certain limitations in the application of anti-fouling modification. A facile and effective strategy for enhancing membrane surface hydrophilicity and antifouling performance becomes very important. In this study, epoxy derived polyethylene glycol crosslinking network was in situ introduced on polyamide nanofiltration membrane through ring-opening reaction of poly(ethylene glycol) diglycidyl ether (PEGDGE) to enhance membrane hydrophilicity and antifouling performance. The large amount of ether units in PEGDGE endowed this crosslinked network with hydrophilicity and relative loose structure. Results of FTIR, XPS and WCA indicated that PEGDGE-polyether crosslinking network was successfully formed on the surface of the NF membrane. Water contact angle of the modified membrane was decreased to 23.7 ± 1.2° compared with pristine NF membrane (45.7 ± 2.1°). For the performance test, humic acid (HA) was used to evaluate the fouling resistance of membranes. FRR (Flux Recovery Ratio) value was as high as 91% (e.g., NF–10 S membrane) compared with the pristine membrane (71%). Meanwhile, NF–10 S membrane showed lower FDR (Flux Decline Ratio) (41%) than the pristine NF membrane (68%). Both the low FDR and high FRR of NF–10 S membranes indicated an excellent long-term anti-fouling property. The coating can provide a large number of ether bonds to improve hydrophilic properties, and the proposed strategy in the current study can offer a facile and effective method for membrane antifouling modifications.