Synthesize of in-situ polymerized PVDF/Fe-MILs membranes for highly efficient organic pollutants degradation and photocatalytic self-cleaning

Catalytic membrane combined with advanced oxidation processes (AOPs) could overcome the problem of secondary pollution that is caused by the difficulty of powder catalyst recovery. In this work, Fe-based metal-organic frameworks (MIL-101(Fe) or NH2-MIL-101(Fe)) were immobilized on polyvinylidene fluoride (PVDF) membrane to construct the photocatalytic membrane for organic pollutants degradation. Herein, the in-situ polymerization of PVDF/MIL-101(Fe) and PVDF/NH2-MIL-101(Fe) membranes were synthesized via non-solvent induced phase conversion method. The experimental results showed that all the catalytic membranes exhibit enhanced photocatalytic activity compared to pristine PVDF membrane. Among them, PVDF/NH2-MIL-101(Fe) (M3) showed the best photocatalytic activity. 90% of methylene blue (MB) was degraded by M3 under 90 min simulated solar irradiation. Moreover, the M3 has excellent stability, the degradation efficiency remained almost unchanged after repeated use 4 times. Free radical trapping experiments showed that superoxide radical (center dot O-2(-)) is the main reactive species in the photocatalytic degradation of MB. Furthermore, the flux recovery ratio (FRR) of M3 was 83% after 10 min of simulated solar irradiation. MIL-101(Fe) and NH2-MIL-101(Fe) with excellent hydrophilicity and photocatalytic performance can not only endow the photocatalytic membranes with an excellent anti-fouling ability for pollutants but also endow the photocatalytic membranes with good self-cleaning ability for the degradation of the foulants deposited on the membrane. In this study, the PVDF/Fe-MILs membranes show excellent photocatalytic performance, stability and self-cleaning ability, which have broad application prospects in the field of water treatment.