Physical–chemical properties, separation performance, and fouling resistance of mixed-matrix ultrafiltration membranes

Herein we report on the formation and characterization of mixed-matrix ultrafiltration (UF) membranes hand-cast by nonsolvent induced phase inversion. We evaluated nanometer-to-micrometer sized inorganic fillers (silver, copper, silica, zeolite, and silver-zeolite) materials with polysulfone (PSf) as the polymeric dispersing matrix. In general, mixed-matrix membranes were rougher, more hydrophilic, and more mechanically robust. Only sub-micron zeolite-PSf mixed-matrix membranes exhibited simultaneous improvements in water permeability and solute selectivity; all other mixed-matrix membranes were more permeable, but less selective due to defects associated with poor polymer-filler binding. Protein and bacterial fouling resistance of mixed-matrix membranes containing silver, zeolite, and silver-zeolite nanoparticles were compared to a low-fouling, poly(acrylonitrile) (PAN) UF membrane. Zeolite and silver containing membranes exhibited better protein fouling resistance (due to higher hydrophilicity), whereas silver and silver-zeolite based membranes produce better bacterial fouling resistance due to antimicrobial properties. Overall, zeolite-PSf and silver exchanged zeolite-PSf membranes offered the best combination of improved permeability, selectivity, and fouling resistance — superior to the commercial PAN membrane.

Research highlights
► Mixed-matrix UF membranes formed by nonsolvent induced phase inversion.
► Ag, Cu, SiO2, zeolites were used as inorganic fillers in mixed-matrix UF membranes.
► Mixed-matrix membranes were more hydrophilic, rough, and mechanically robust.
► Zeolite nanoparticle based membranes had both higher permeability and selectivity.
► Zeolite and silver based membranes exhibited improved fouling resistance.