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Membrane Characteristics (membrane + characteristic)
Selected AbstractsRemoval of H2S and volatile organic sulfur compounds by silicone membrane extractionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2009I. Manconi Abstract BACKGROUND: This study explores an alternative process for the abatement and/or desulfurization of H2S and volatile organic sulfur compounds (VOSC) containing waste streams, which employs a silicone-based membrane to simultaneously remove H2S and VOSC. An extractive membrane reactor allows the selective withdrawal of VOSC and H2S simultaneously from the waste stream, while preventing direct contact between the waste stream and the absorbing solution and/or the biological treatment system. The influence of the sulfur compounds, membrane characteristics, extractant and pH was studied. RESULTS: Sulfide and the VOCS studied, i.e. methanethiol (MT), ethanethiol (ET) and dimethylsulfide (DMS) were removed from the synthetic wastewater using a silicone rubber membrane. Methanethiol showed the highest (8.72 × 10,6 m s,1) overall mass transfer coefficient (kov) and sulfide the lowest kov value (1.23 × 10,6 m s,1). Adsorption of the VOCS into the silicone membrane reduced the overall mass transfer coefficient. The kov when using Fe(III)EDTA, as extractant (5.81 × 10,7 m s,1) for sulfide extraction was one order of magnitude lower than with anaerobic water (2.54 × 10,6 m s,1). On the other hand, the sulfide removal efficiency with Fe(III)EDTA, was higher (84%) compared with anaerobic water (60%) as extractant. An additional mass transfer resistance was formed by elemental sulfur which remained attached to the membrane surface. CONCLUSIONS: Extraction of sulfide and VOCS from a synthetic wastewater solution through a silicone rubber membrane is a feasible process as alternative to the techniques developed to treat VOSC emissions. Optimizing the aqueous absorption liquid can increase the efficiency of extraction based processes. Copyright © 2008 Society of Chemical Industry [source] ,-Tocopheryl phosphate , An active lipid mediator?MOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 5 2010Jean-Marc Zingg Abstract The vitamin E (,-tocopherol, ,T) derivative, ,-tocopheryl phosphate (,TP), is detectable in small amounts in plasma, tissues, and cultured cells. Studies done in vitro and in vivo suggest that ,T can become phosphorylated and ,TP dephosphorylated, suggesting the existence of enzyme(s) with ,T kinase or ,TP phosphatase activity, respectively. As a supplement in animal studies, ,TP can reach plasma concentrations similar to ,T and only a part is dephosphorylated; thus, ,TP may act both as pro-vitamin E, but also as phosphorylated form of vitamin E with possibly novel regulatory activities. Many effects of ,TP have been described: in the test tube ,TP modulates the activity of several enzymes; in cell culture ,TP affects proliferation, apoptosis, signal transduction, and gene expression; in animal studies ,TP prevents atherosclerosis, ischemia/reperfusion injury, and induces hippocampal long-term potentiation. At the molecular level, ,TP may act as a cofactor for enzymes, as an active lipid mediator similar to other phosphorylated lipids, or indirectly by altering membrane characteristics such as lipid rafts, fluidity, and curvature. In this review, the molecular and cellular activities of ,TP are examined and the possible functions of ,TP as a natural compound, cofactor and active lipid mediator involved in signal transduction and gene expression discussed. [source] Mechanisms of Action of Dietary Fatty Acids in Regulating the Activation of Vascular Endothelial Cells during AtherogenesisNUTRITION REVIEWS, Issue 8 2003Raymond A. Christon PhD Dietary long chain omega-3 polyunsaturated fatty acids from fish oil appear to be clearly efficient in regulating endothelial dysfunction (or activation), which is the first stage of atherogenesis. Studies on endothelial cells in vitro have shown that the main dietary PUFA and oleic acid may prevent endothelium activation either by inhibiting the expression of adhesion molecules or by improving the nitric oxide production. Saturated fatty acids and also linoleic acid do not inhibit endothelium activation. The mechanisms involved in this inhibition could be related to endothelial cell membrane characteristics or redox status. However, these findings need to be confirmed in vivo. [source] Studies on cellulose acetate,carboxylated polysulfone blend ultrafiltration membranes,Part IIPOLYMER INTERNATIONAL, Issue 1 2003J Sajitha Abstract Hydrophilic polysulfone ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones of 0.43 and 0.75 degrees of carboxylation. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, water content and membrane hydraulic resistance, have been investigated to evaluate the performance of the membranes. The influence of the degree of carboxylation on the performance of the blend membranes of various blend polymer compositions has been investigated and also compared with earlier reports on blend membranes prepared from cellulose acetate and polysulfone or carboxylated polysulfone of 0.14 degree of carboxylation. © 2003 Society of Chemical Industry [source] Effect of molecular structure of hybrid precursors on the performances of novel hybrid zwitterionic membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Junsheng Liu Abstract Three types of novel hybrid zwitterionic membranes were prepared via a coupling reaction between two silane-coupling agents in a nonaqueous system and a subsequent reaction with 1,4-butyrolactone to create ion pairs in the hybrid precursors. FT-IR spectra corroborated the corresponding reactions. The synthesized membranes were characterized by thermal analyses, ion-exchange capacities, streaming potentials, and pure water flux. Thermal analyses exhibited that the degradation temperature of the hybrid precursors decreased with an increase in zwitterionic extent because of the introduction of ion pairs. Ion-exchange capacity measurements revealed that the anion-exchange capacities and cation-exchange capacities were in the range of 0.023,0.05 and 0.32,0.58 mmol g,1, respectively. Streaming potentials displayed that when the membranes coated for one or three times, the isoelectric points were in the pH range of 6.6,7.58 and 6.58,7.7, respectively. The pure water flux showed that it could be affected by the coating times and the ingredients of these zwitterionic membranes. This difference in membrane's characteristics can be ascribed to the effect of molecular structure of the hybrid precursors. Both the Coulombic interactions of ion pairs between the polymer chains and the hydrophilicity of these membranes were proposed to clarify the above phenomena. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Effect of surface modifying macromolecules stoichiometric ratio on composite hydrophobic/hydrophilic membranes characteristics and performance in direct contact membrane distillationAICHE JOURNAL, Issue 12 2009M. Qtaishat Abstract The stoichiometric ratio for the synthesis components of hydrophobic new surface modifying macromolecules (nSMM) was altered systematically to produce three different types of nSMMs, which are called hereafter nSMM1, nSMM2, and nSMM3. The newly synthesized SMMs were characterized for fluorine content, average molecular weight, and glass transition temperature. The results showed that fluorine content decreased with increasing the ratio of ,,,-aminopropyl poly(dimethyl siloxane) to 4,4,-methylene bis(phenyl isocyanate). The synthesized nSMMs were blended into hydrophilic polyetherimide (PEI) host polymer to form porous hydrophobic/hydrophilic composite membranes by the phase inversion method. The prepared membranes were characterized by the contact angle measurement, X-ray photoelectron spectroscopy, gas permeation test, measurement of liquid entry pressure of water, and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation and the results were compared with those of commercial polytetraflouroethylene membrane. The effects of the nSMM type on the membrane morphology were identified, which enabled us to link the membrane morphology to the membrane performance. It was found that the nSMM2/PEI membrane yielded the best performance among the tested membranes. In particular, it should be emphasized that the above membrane was superior to the commercial one. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] | |||||||||||||