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Porous Support (porous + support)
Selected AbstractsEnhanced Photocatalytic Activity using Layer-by-Layer Electrospun Constructs for Water RemediationADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Jung Ah Lee Abstract Endocrine disruptors such as bisphenol A (BPA) are environmental pollutants that interfere with the body's endocrine system because of their structural similarity to natural and synthetic hormones. Due to their strong oxidizing potential to decompose such organic pollutants, colloidal metal oxide photocatalysts have attracted increasing attention for water detoxification. However, achieving both long-term physical stability and high efficiency simultaneously with such photocatalytic systems poses many challenges. Here a layer-by-layer (LbL) deposition approach is reported for immobilizing TiO2 nanoparticles (NPs) on a porous support while maintaining a high catalytic efficiency for photochemical decomposition of BPA. Anatase TiO2 NPs ,7,nm in diameter self-assemble in consecutive layers with positively charged polyhedral oligomeric silsesquioxanes on a high surface area, porous electrospun polymer fiber mesh. The TiO2 LbL nanofibers decompose approximately 2.2,mg BPA per mg of TiO2 in 40,h of illumination (AM 1.5G illumination), maintaining first-order kinetics with a rate constant (k) of 0.15,h,1 for over 40,h. Although the colloidal TiO2 NPs initially show significantly higher photocatalytic activity (k,,,0.84,h,1), the rate constant drops to k,,,0.07,h,1 after 4,h of operation, seemingly due to particle agglomeration. In the BPA solution treated with the multilayered TiO2 nanofibers for 40,h, the estrogenic activity, based on human breast cancer cell proliferation, is significantly lower than that in the BPA solution treated with colloidal TiO2 NPs under the same conditions. This study demonstrates that water-based, electrostatic LbL deposition effectively immobilizes and stabilizes TiO2 NPs on electrospun polymer nanofibers for efficient extended photochemical water remediation. [source] High-Performance Oxygen-Permeable Membranes with an Asymmetric Structure Using Ba0.95La0.05FeO3,, Perovskite-Type OxideADVANCED MATERIALS, Issue 21 2010Ken Watenabe High oxygen permeability was achieved using an asymmetric Ba0.95La0.05FeO3,, membrane. In this membrane, oxygen diffuses physically through pores of a porous support and oxygen permeates electrochemically through a dense layer. The oxygen permeation flux of the asymmetric Ba0.95La0.05FeO3,, membrane reached more than 10,cm3 (STP) min,1,cm,2 from a test gas containing 50% oxygen at 930,°C. [source] Hybrids of poly(ethylene oxide- b -amide-6) and ZrO2 sol,gel: Preparation, characterization, and application in processes of membranes separationADVANCES IN POLYMER TECHNOLOGY, Issue 1 2002Rita Aparecida Zoppi Abstract Hybrids consisting of poly(ethylene oxide- b -amide-6), PEBAXTM, and zirconium oxide were prepared from hydrolysis and condensation of zirconium tetraisopropoxide in solution containing the dissolved organic polymer. These hybrids were characterized by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy, and electron microscopy. Results show that the incorporation of the inorganic phase seems to promote the degradation of the organic polymer. Composite membranes consisting of a porous support of poly(vinylidene fluoride), PVDF, and a filter layer of PEBAX/ZrO2 were prepared and characterized by electron microscopy. Permeation tests of water or aqueous solutions containing poly(ethylene glycol) of different molar masses were carried out to determine the permeation rate and the membrane cutoff respectively. To determine the phosphate retention, permeation tests using a KH2PO4 aqueous solution were carried out. Independent of composition of the filter layer, values of phosphate retention were nearly equivalent to 80%. © 2002 John Wiley & Sons, Inc. Adv Polym Techn 21: 2,16, 2002; DOI 10.1002/adv.10011 [source] Streaming potential characterization of LBL membranes on porous ceramic supportsAICHE JOURNAL, Issue 4 2007Yiwei Chen Abstract An in-situ characterization of the growth of the self-assembled polyelectrolyte membranes on the porous support was conducted by applying transmembrane streaming potential measurement via surface charge monitoring. The membranes were prepared by layer-by-layer alternative deposition of poly (allylamine hydrochloride) and poly (styrenesulfonate) on porous ceramic supports. The surface charge variations of membranes as functions of different top-assembled materials and numbers of deposited cycles were investigated. Different top-assembled materials make isoelectric points of the as-prepared membranes drift in opposite directions and also lead to symmetrical signal changes of zeta-potential in salt solutions at the isoelectric points of the supports. Ex-situ characterizations, including scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray spectroscopy, also confirm the alternative deposition of polyelectrolytes. It is demonstrated that the transmembrane streaming potential measurement is effective in studying the growth of layer-by-layer membranes on porous support. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Pd membranes formed by electroless plating with osmosis: H2 permeation studiesAICHE JOURNAL, Issue 2 2002Razima S. Souleimanova The synthesis of fully dense Pd-Vycor glass composite membranes by electroless plating with or without osmosis is reported. Use of osmotic flux allows one to rapidly form thin (a few microns), fully dense palladium films, which have submicron size microstructure. These features significantly enhance hydrogen permeability as compared to the conventional method. By accounting for resistance of the porous support, it is confirmed that for membranes prepared by the same technique, with gradually changing microstructural characteristics, those with smaller palladium crystallites exhibit larger hydrogen flux. Pd-stainless steel composite membranes were also prepared using electroless plating, either with or without osmosis. Membranes synthesized using osmosis exhibit superior thermal stability. [source] Metallocyclo- and Polyphosphazenes Containing Gold or Silver: Thermolytic Transformation into Nanostructured MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 48 2009Josefina Jiménez Dr. Abstract A cyclotriphosphazene bearing two 4-oxypyridine groups on the same phosphorus atom, gem -[N3P3(O2C12H8)2(OC5H4N-4)2] (I), and its analogous polymer [{NP(O2C12H8)}0.7{NP(OC5H4N-4)2}0.3]n (II), have been used to prepare gold or silver, cyclic and polymeric, metallophosphazenes. The following complexes, gem -[N3P3(O2C12H8)2(OC5H4N-4{ML})2] (ML=Au(C6F5) (1) or Au(C6F5)3 (2)), [N3P3(O2C12H8)2(OC5H4N-4{AuPPh3})2][NO3]2 (3), and [N3P3(O2C12H8)2(OC5H4N-4{AgPPh2R})2][SO3CF3]2 (R=Ph (4) or Me (5)) have been obtained. Complexes 1 and 4 are excellent models for the preparation of the analogous polymers [{NP(O2C12H8)}0.7{NP(OC5H4N-4{ML})2}0.3]n (ML=Au(C6F5) (P1), Ag(OSO2CF3)PPh3 (P2)). All complexes have been characterized by elemental analysis, various spectroscopic methods, and mass spectrometry. The polymers were further investigated by thermochemical methods (thermogravimetric analysis) and differential scanning calorimetry. For compounds 1,5 and for the starting phosphazene I, a mixture of different stereoisomers may be expected. The stereochemistry in solution has been studied by variable-temperature NMR spectroscopy studies, which provided evidence for interconversion processes that involve changes in the chirality of a 2,2,-dioxybiphenyl group. A single-crystal X-ray analysis of the gold complex 2 confirmed not only the proposed structure, but also S,S and R,R configurations at the two biphenoxy-substituted phosphorus centers, in contrast to those observed for the precursor I. Pyrolysis of these new metallophosphazenes was also studied. Notably, pyrolysis of the gold derivatives gave macroporous metallic gold sponges without the requirement of either an external reducing agent or a porous support. These materials were all characterized by XRD, TEM, SEM, and energy-dispersive X-ray spectroscopy. En este trabajo se ha usado el ciclotrifosfazeno que tiene dos grupos 4-oxipiridina en el mismo átomo de fósforo, gem -[N3P3(O2C12H8)2(OC5H4N-4)2] (I), y su polímero análogo, [{NP(O2C12H8)}0.7{NP(OC5H4N-4)2}0.3]n(II), para preparar nuevos compuestos de oro o plata, cíclicos o polímeros. Se han obtenido los siguientes complejos, gem -[N3P3(O2C12H8)2(OC5H4N-4{ML})2] [ML=Au(C6F5) (1), Au(C6F5)3 (2)], [N3P3(O2C12H8)2(OC5H4N-4{AuPPh3})2][NO3]2 (3) and [N3P3(O2C12H8)2(OC5H4N-4{AgPPh2R})2][SO3CF3]2 [R=Ph (4) or Me (5)], que a su vez han resultado ser excelentes modelos para preparar los polímeros análogos de oro o plata, [{NP(O2C12H8)}0.7{NP(OC5H4N-4{ML})2}0.3]n[ML=Au(C6F5)(P1), Ag(OSO2CF3)PPh3 (P2)]. Todos los complejos, cíclicos o polímeros, se han caracterizado por análisis elemental, por métodos espectroscópicos y por espectrometría de masas. Los polímeros, además, se han caracterizado por métodos termoquímicos (TGA y DSC). Para 1,5 y para el fosfazeno de partida (I) puede esperarse una mezcla de varios estereoisómeros. Se ha estudiado su estereoquímica en disolución por RMN a temperatura variable, lo que ha indicado la presencia de un proceso de interconversión que implica cambios de quiralidad del grupo 2,2,-dioxibifenilo. La resolución de la estructura cristalina del complejo 2, por difracción de Rayos X, no sólo ha confirmado la estructura propuesta sino que, además, indica una configuración (S,S)- y (R,R)- , a diferencia de lo observado para el precursor I. Se ha estudiado también la pirólisis de estos nuevos metalofosfazenos. Cabe destacar que la pirólisis de los derivados de oro, trímero (1) y polímero (P1), dio esponjas macroporosas de oro metálico sin utilizar un agente reductor externo ni un soporte poroso. Todos estos materiales se han caracterizado por XRD, TEM, SEM y EDAX. [source] A new nano-(2Li2O/MgO) catalyst/porous alpha-alumina composite for the oxidative coupling of methane reactionAICHE JOURNAL, Issue 3 2010Behrooz Fallah Abstract The present work discloses a new methodology for the production of detached nanorods of 2Li2O/MgO catalyst particles on the internal surface of ,-Al2O3 porous supports to be used as efficient catalysts for the oxidative coupling of methane reaction (OCM). The peculiarity of our preparatory recipe is the success in producing "detached" nanosized entities on the support surface. The performance of the new catalyst/support system for the OCM reaction has been evaluated using a special reactor assembly with cross flow of methane and oxygen gas streams. Under the optimum process conditions, the yield of C product is 25% at an average reaction temperature of 750°C. Under the optimum conditions, the yield of ethylene reaches 8%. It is shown that the enhanced catalytic properties of the new catalyst/support composite may be attributed to nanoeffects. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] | |||||||||||||