Synthesis of Catalytic Nanoporous Metallic Thin Films on Polymer Membranes

This work deals with the creation of bimetallic thin films on porous polymer membrane surfaces. Metal-polymer composite membranes have been produced through magnetron sputtering. Commercially available membranes with both micrometer and nanometer scale pores were used as supports for deposition. Continuous alloy films of ∼110 nm thickness were deposited to produce the top layer of the composite structure. These films were dealloyed with sulfuric acid creating a nanoporous film structure with a ligament size of 7.7 ± 2.5 nm. The resulting composite membranes were permeable to water at all stages of production, and an polysulfone ultrafiltration membrane with 90 nm of nanoporous Fe/Pd on top showed a flux of 183 L/m²/h (LMH)/bar. The films were evaluated for dechlorination of toxic polychlorinated biphenyls from water. At a loading of 6.6 mg/L Pd attached to 13.2 cm² support in a 2.5 ppm PCB-1 solution with 1.5 ppm dissolved H₂, over 90% of PCB-1 was removed from solution in 30 min, which produced the expected product biphenyl from the dechlorination reaction. The permeation of a 5 ppm PCB-1 solution resulted in a 28% degradation at a single pass through the composite membrane under H₂ pressurization at a flux of 75 LMH.