Mixed matrix membranes (MMMs) synthesized by polymers and inorganic particles have been widely used in gas separation. With surface modification techniques, ion exchange polymers and reactive nanoparticles have been in-situ synthesized in the commercial microfiltration (MF) membranes for toxic metal and organic remediation from complicated water matrices (surface and groundwater). We developed polymer-nanoparticle based MMMs with stimuli-responsive pores and high metal adsorption capacity, which allows the subsequent synthesis of metal/metal oxide nanoparticles for catalytic degradation of environmental pollutants in water.
Surface and pore functionalization of commercial membranes was achieved by in-situ polymerization. Acrylic acid was polymerized via free radicals and stabilized via cross-linkers, forming pH responsive polyacrylic acid (PAA) in porous polyvinylidene fluoride (PVDF) membranes. Iron and iron oxide nanoparticles were synthesized directly inside the polymer matrix, which provides added benefits of eliminating the particle aggregation and leaching. This membrane nanocomposite shows robust performance in reductive and oxidative degradation of chlorinated organic compounds (e.g. trichloroethylene, TCE and polychlorinated biphenyls, PCBs). The combined pathway (i.e. reduction followed by free radical oxidation) can further reduce the toxicity of intermediations and byproducts. By collaborating with a membrane company, this membrane has been scale up from lab-scale flat sheet to full-scale spiral wound module. Iron nanoparticles were also synthesized in the membrane module. By integration of nanofiltration and functionalized membranes, toxic metal oxyanions (e.g. selenium and arsenic) were significantly removed from the coal-fired power plant scrubber water. Selenium concentration as low as 10 µg/L was obtained via iron/iron oxide reduction and adsorption. The effects of total dissolved salt (TDS) concentration and reaction temperature were also investigated.
This research project is supported by NIH-NIEHS Superfund Research Program under award no. P42ES007380, NSF KY EPSCoR program under award no. 1355438, and Southern Company in Birmingham, AL. We thank Nanostone/Sepro Membranes, Inc. for the joint development of full-scale functionalized membranes.
See more of this Group/Topical: Environmental Division