Effective strategy for UV-mediated grafting of biocidal Ag-MOFs on polymeric membranes aimed at enhanced water ultrafiltration

Abstract

Ultrafiltration membranes with antifouling and antibacterial properties are greatly beneficial for all industrial applications and to supply safe water worldwide. Improving these properties while maintaining both high productivity and high water quality remains a challenge. This work proposes the surface functionalization of an ultrafiltration membrane obtained via UV-initiated grafting polymerization of acrylic acid (AA) and silver-containing metal–organic frameworks (Ag-MOFs), with the goal to achieve combined bactericidal and hydrophilic properties. The effectiveness of different modification pathways is evaluated, including Ag-MOFs blending into the AA solution followed by grafting, as well as in-situ synthesis of Ag-MOFs over the surface of AA-grafted membranes, with in-depth characterization of the resulting materials. The steady-state water fluxes with a feed water laden with organics are improved from two to three-fold for the functionalized membranes compared to the commercial one, while the rejection of macromolecules is maintained at greater than 99%. Significantly, fouling is partly reversible with all enhanced surfaces: the flux recovery ratio following cleaning varies between 3.8% and 20% compared to near zero for the pristine membrane. Noteworthy bacterial inactivation reaches up to 90% for E. coli and 95% for S. aureus, respectively, for surface-grafted membranes. Silver leaching and surface characterization analyses indicate a strong immobilization of Ag-MOFs on membranes and imply long-lasting antimicrobial as well as antifouling activities.