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Hydrophobic Membranes (hydrophobic + membrane)
Selected AbstractsKinetics of the Extraction of Succinic Acid with Tri- n -octylamine in 1-Octanol SolutionBIOTECHNOLOGY PROGRESS, Issue 6 2005Young-Si Jun Kinetic studies for the extraction of succinic acid from aqueous solution with 1-octanol solutions of tri- n -octylamine (TOA) were carried out using a stirred cell with a microporous hydrophobic membrane. The interfacial concentrations of species were correlated and thus the intrinsic kinetics was obtained. The overall extraction process was controlled by the chemical reaction at or near the interface between the aqueous and organic phases. The formation reaction of succinic acid-TOA complex was found to be first order with respect to the concentration of succinic acid in the aqueous phase and the order of 0.5 with respect to that of TOA in the organic phase with a rate constant of (3.14 ± 0.6) × 10,8 m2.5·mol,0.5·s,1. The dissociation reaction of succinic acid-TOA complex was found to be the second-order with respect to that of succinic acid-TOA complex in the organic phase and the order of ,2 with respect to that of TOA in the organic phase with a rate constant of (1.44 ± 1.4) × 10,4 mol·m,2·s,1. [source] Hypertonicity-induced decrease in aquaporin-4 expression in retinal pigmented epithelial cellsACTA OPHTHALMOLOGICA, Issue 2009F WILLERMAIN Purpose Osmotic gradients regulate subretinal water content and might be acutely changed during macular oedema. Moreover, since RPE cells express tight junctions, water molecules must use specific channels to cross their hydrophobic membrane. Aquaporins (AQP) are good candidates to assume this function. In this work, we investigated the effects of osmotic stress on the expression of AQP in RPE cells. Methods ARPE-19 cells were grown in different hypertonic conditions. AQP1 and AQP4 expressions were assessed by Western blot and RT-PCR. Chemical inhibitors were used to specifically block lysosomes and proteasome function. Cell proliferation was investigated by BRDU incorporation, and cell viability by flow cytometry. Cell cycle was studied by Western blot and flow cytometry. Results Hypertonic stress rapidly decreased AQP4 expression on ARPE cells. The effect was reversed by proteasome inhibition, but was likely ubiquitinylation-independent. At 24h post-hypertonic stress, cell viability was not affected but cell proliferation was decreased. Cell cycle was also modified as the percentage of cells in G0/G1 phase decreased and the percentage of cells in S and G2/M phase increased. Conclusion Hypertonic stress strongly reduced AQP4 expression and RPE cell proliferation. Those results might contribute to our understanding of macular oedema formation. [source] Translocation of proteins across archaeal cytoplasmic membranesFEMS MICROBIOLOGY REVIEWS, Issue 1 2004Mechthild Pohlschröder Abstract All cells need to transport proteins across hydrophobic membranes. Several mechanisms have evolved to facilitate this transport, including: (i) the universally-conserved Sec system, which transports proteins in an unfolded conformation and is thought to be the major translocation pathway in most organisms and (ii) the Tat system, which transports proteins that have already obtained some degree of tertiary structure. Here, we present the current understanding of these processes in the domain Archaea, and how they compare to the corresponding pathways in bacteria and eukaryotes. [source] Adsorption separation of terpene lactones from Ginkgo biloba L. extract using glass fiber membranes modified with octadecyltrichlorosilaneJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2005I-Fang Su Abstract In this study porous glass fiber membranes were modified by reaction with octadecyltrichlorosilane to form C18 hydrophobic membranes. The contact angle and the CH2 vibration bands at 2855 and 2920 cm,1 found by FTIR measurements verified the successful immobilization of C18 groups on the glass fiber membranes. The resulting C18 hydrophobic membranes were used to adsorb terpene lactones from crude Ginkgo biloba L. extracts. In batch adsorption processes, the modified C18 membranes exhibited a better adsorption performance than commercial C18 solid phase extraction adsorbents. Different desorption solvents were tested and ethyl acetate was found to preferentially desorb terpene lactones from the modified C18 membranes. In flow adsorption experiments at 1 mL/min, terpene lactone contents higher than 6 wt% (the standardized content) could be achieved in the elution step using ethyl acetate. [source] Development of thin film composite for CO2 separation in membrane gas absorption applicationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009A.L. Ahmad Abstract The thin film composite (TFC) membrane based on polypropylene (PP) and polyvinylidenefluoride (PVDF) was prepared using glutaraldehyde as the selective layer. The percentages of glutaraldehyde were optimized to maximize the permeability of carbon dioxide (CO2) and selectivity as well. The TFC with 6% w/v of glutaraldehyde based on PVDF achieved the highest permeance of 881.70 GPU and 18.08 for selectivity through the increase in effective layer and skin layer thickness. This TFC promises to provide porous and hydrophobic membranes for use in membrane gas absorption (MGA) processes. The absorption of CO2 in deionized water was studied in MGA system in which the mass transfer coefficient (K) and CO2 flux decreased with increasing CO2 concentration in feed stream. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Precipitants and additives for membrane crystallization of lysozymeBIOTECHNOLOGY JOURNAL, Issue 11 2006Xinmiao Zhang Abstract Membrane crystallization is a newly developed crystallization technique that has proven to be superior in producing good crystal forms under operating conditions that are not appropriate to perform the crystallization process by other traditional techniques. In this work, static membrane crystallization was carried out on lysozyme, with hollow-fiber microporous hydrophobic membranes. Numerous precipitant and additive types and concentrations were employed in the crystallization processes in order to select the most appropriate precipitant and additive types and to find their corresponding concentration levels that can yield the best crystal forms. The crystallization processes were analyzed in two ways: firstly, by evaluation of the transmembrane fluxes obtained by using different precipitants and additives; secondly, by utilization of the images and results obtained from the micrography and IR spectra in comparisons and evaluations of the crystals formed under all kinds of conditions. Moreover, the size distributions of the crystals yielded under several typical crystallization conditions were analyzed, and turbidity and induction time periods obtained during typical crystallization experiments were also measured. Amongst the numerous precipitants and additives tested, the most appropriate precipitant type and additive were chosen and their concentrations were optimized. Good lysozyme crystals were obtained using a certain precipitant and additive. The obtained results from this work further support the advantages of utilizing the membrane crystallization technique for macromolecule crystallizations. [source] Experimental Study and Design of a Submerged Membrane Distillation BioreactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2009J. Phattaranawik Abstract A hybrid process incorporating membrane distillation in a submerged membrane bioreactor operated at elevated temperature is developed and experimentally demonstrated in this article. Since organic particles are rejected by an ,evaporation' mechanism, the retention time of non-volatile soluble and small organics in the submerged membrane distillation bioreactor (MDBR) is independent of the hydraulic retention time (mainly water and volatiles). A high permeate quality can be obtained in the one-step compact process. The submerged MD modules were designed for both flat-sheet membranes and tubular membrane configurations. The process performance was preliminarily evaluated by the permeate flux stabilities. The module configuration design and air sparging used in the MDBR process were tested. Flux declines were observed for the thin flat-sheet hydrophobic membranes. Tubular membrane modules provided more stable permeate fluxes probably due to the turbulent condition generated from air sparging injected inside the tubular membrane bundles. The experiments with the submerged tubular MD module gave stable fluxes of approximately 5,L/m2 h over 2,weeks at a bioreactor temperature of 56,°C. The total organic carbon in the permeate was consistently lower than 0.7,mg/L for all experiments. [source] | |||||||||||||