Constructing visible-light-driven self-cleaning UF membrane by quaternary ammonium-functionalized Ti-MOFs for water remediation

Abstract

In this study, quaternary ammonium-functionalized MIL-125 (Me3N+-MIL-125) decorated polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was fabricated by a facile two-step assembly method to remove rhodamine B (RhB, a model dye). For comparison purpose, MIL-125 and amino-functionalized MIL-125 (NH2-MIL-125) based membranes were also prepared. Porous Ti-MOFs layer was firmly anchored on membrane surface by crosslinking reaction between polyethyleneimine and epichlorohydrin, which caused higher hydrophilicity, more positive charge and efficient thermal stability of membrane. Compared to MIL-125 and NH2-MIL-125, Me3N+-MIL-125 endows the membrane with superior water flux (192.7 L m−2 h−1, transmembrane pressure = 0.2 MPa), RhB rejection ratio (60.4%) and antibacterial efficiency against E. coli (99.98%) and S. aureus (99.95%). In addition, Me3N+-MIL-125 decorated membrane exhibits excellent visible-light photocatalytic activity. Membrane performance can be fully recovered by visible light irradiation due to the oxidation degradation by reactive oxygen species (ROS, •OH and O2•-) that generated on Me3N+-MIL-125 with the wider visible-light response range and narrower bandgap energy (1.65 eV). This novel multifunctional UF membrane is promising in the application of dye-contaminated water remediation.