Nanoparticle incorporation into porous polymeric membranes has received continued attention with the concurrent continued development of reactive metallic and metal oxide nanoparticles for water treatment applications. Nanoparticles comprised of metals such as iron, nickel, palladium, silver, aluminum, and copper have been shown to remove both organic and inorganic water contaminants, and novel multi-metallic nanoparticle combinations and morphologies continue to be reported. Iron nanoparticles (Fe NPs) remain at the forefront of efforts focused on water remediation due to the low cost of the metal and the versatility of Fe NPs in addressing a wide variety of water contaminants. The incorporation of these nanoparticle materials into a support material such as a polymeric membrane immobilizes the nanoparticles, preventing movement within the treatment system, and may also provide enhanced contaminant removal. In particular, there is an interest in embedding nanoparticles in phase inversion polymeric membranes, where the nanoparticles can be incorporated into the membrane casting solution and retained in the solid membrane phase when the membrane polymer precipitates.
In this work, the incorporation of iron nanoparticles in a polyethersulfone membrane was studied. Nanoparticle stabilizer type, casting solution additives, and nanoparticle processing by centrifugal or magnetic separation were varied, and specific membrane characteristics were evaluated. Specifically, membrane casting solution viscosity, cast membrane thickness, pure water flux, and internal morphology were evaluated. While the addition of the additives ethanol and polyvinylpyrrolidone to a polyethersulfone-dimethylacetamide solution causes an expected increase in viscosity, the addition of nanoparticles can cause an increase or decrease in viscosity depending on the ligand stabilizer used during nanoparticle synthesis and casting solution additive concentration. Viscosity can also be affected by nanoparticle separation method, but again, changes are also dependent on casting solution composition. Varying changes in membrane thickness are observed and can be correlated to viscosity. Pure water flux decreases for all samples when nanoparticles are added, but the extent of the change is affected by casting solution composition. Internal morphology can partially explain the decrease in flux for nanoparticle-embedded membranes.