(197a) New Membranes for CO2 Separation/Capture and Water Purification
This presentation covers two types of new membranes: (1) carbon dioxide-selective membranes for hydrogen purification for fuel cells and carbon capture from flue gas and (2) interfacially polymerized reverse osmosis membranes for water purification. We have synthesized CO2-selective membranes by incorporating amino groups into polymer networks. The membranes have shown high CO2 permeability and selectivity vs. hydrogen, carbon monoxide and nitrogen up to 180oC. We have elucidated the effect of amine steric hindrance in the solid membrane, showing significant enhancement for CO2 transport. Hydrogen sulfide permeates through the membrane much faster than CO2, allowing H2S removal in the treated synthesis gas before water-gas-shift (WGS) reaction. Our initial experiments have shown a nearly complete removal of H2S from 50 ppm in synthesis gas to about 10 ppb in the hydrogen product. Using the membrane, we have obtained <10 ppm carbon monoxide in the hydrogen product in WGS membrane reactor experiments via CO2 removal. The data have been in good agreement with our modeling predictions. The membrane is being scaled up for commercial development. We will also discuss a new concept of inorganic/polymer composite membranes for CO2 capture from flue gas in coal-fired power plants for sequestration. On interfacially polymerized reverse osmosis membranes, the state-of-the-art membranes in the thin-film-composite (TFC) structure prepared by interfacial polymerization are reviewed and discussed. Recent advances have been in high flux TFC interfacially polymerized membranes for increasing water productivity and decreasing energy consumption. We have synthesized high flux membranes by incorporating a hydrophilic additive in the aqueous amine solution during interfacial polymerization, resulting in increasing water flux significantly through an additional pathway for water transport while maintaining high salt rejection via charge repulsion. The membranes synthesized for seawater desalination showed a very high flux of 1.81 m3/m2/day (44.4 gallons/ft2/day (gfd)) and a salt rejection of 99.41% using 3.28% NaCl solution. The high-flux membrane was further tested using seawater from Port Hueneme, CA and exhibited a very good and stable desalination performance for 30 days. FTIR confirmed the good membrane stability. The membrane synthesized with hydrophilic additive showed significantly improved fouling resistance. Analysis using atomic force microscopy (AFM) showed a smoother membrane surface for the membrane incorporated with the hydrophilic additive.