New Developments on Membranes for CO2 and Water Separations

Reporter： W.S. Winston Ho
                 William G. Lowrie Department of Chemical and Biomolecular Engineering,Department of
                 Materials Science and Engineering,The Ohio State University, USA
Time: 15:00 p.m., June 25th (Tues.)
Place: 2nd Floor Meeting Room,Chemistry Building

Abstract

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 commercialization.  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 membrane has shown 100% increase in water flux vs. the industry standard Film-Tec FT-30 membrane while maintaining a high NaCl rejection of about 99% for brackish water desalination.  Initial scale-up of the membrane to commercial size has been successful.  Also discussed is the fouling-resistant property of the synthesized membrane enhanced by physically coating a cross-linked polyethylene glycol layer on top of the thin film.