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Matrix Membranes (matrix + membrane)
Selected AbstractsGas sorption in polymers, molecular sieves, and mixed matrix membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Theodore T. Moore Abstract Gas sorption has been an underutilized technique for characterizing organic,inorganic hybrid (mixed matrix) membranes. Sorption in these membranes, which are composed of rigid inorganic domains, such as zeolites, dispersed in a polymer matrix, should be approximately additive. Sorption in the neat polymers and zeolites were first measured to demonstrate that sorption in mixed matrix membranes is approximately additive in the absence of other effects. Sorption in mixed matrix membranes was demonstrated to be additive. This extends to cases where sorption in one or both phases of the mixed matrix membrane is affected by an outside contaminant. For example, zeolite 4A is extremely hydrophilic and easily affected by contaminants from processing or from the test gases. Zeolite 4A encapsulated within a polymer matrix can still be affected by these same components, and this causes sorption lower than predicted based on that in unaffected polymers and sieves. This sorption analysis has proven to be very important in understanding the permeabilities and selectivities of mixed matrix membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4053,4059, 2007 [source] Cancellous Bone Remodeling Occurs in Specialized Compartments Lined by Cells Expressing Osteoblastic MarkersJOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2001Ellen M. Hauge Abstract We describe a sinus, referred to as a bone remodeling compartment (BRC), which is intimately associated with cancellous bone remodeling. The compartment is lined on its marrow side by flattened cells and on its osseous side by the remodeling bone surface, resembling a roof of flattened cells covering the bone surface. The flat marrow lining cells are in continuity with the bone lining cells at the margins of the BRC. We examined a large number of diagnostic bone biopsy specimens received during recent years in the department. Furthermore, 10 patients (8 women and 2 men, median age 56 [40,69] years) with the high turnover disease of primary hyperparathyroidism who were treated with parathyroidectomy and followed for 3 years were included in the histomorphometric study. Bone samples for the immuno-enzyme staining were obtained from an amputated extremity of child. The total cancellous bone surface covered by BRC decreases by 50% (p < 0.05) following normalization of turnover and is paralleled by a similar 50% decrease in remodeling surface (p < 0.05). The entire eroded surface and two-thirds of the osteoid surface are covered by a BRC. BRC-covered uncompleted walls are 30% (p < 0.05) thinner than those without a BRC. This indicates that the BRC is invariably associated with the early phases of bone remodeling, that is, bone resorption, whereas it closes during the late part of bone formation. Immuno-enzyme staining shows that the flat marrow lining cells are positive for alkaline phosphatase, osteocalcin, and osteonectin, suggesting that they are bone cells. The first step in cancellous bone remodeling is thought to be the lining cells digesting the unmineralized matrix membrane followed by their disappearance and the arrival of the bone multicellular unit (BMU). We suggest that the lining cell barrier persists during bone remodeling; that the old lining cells become the marrow lining cells, allowing bone resorption and bone formation to proceed under a common roof of lining cells; that, at the end of bone formation, new bone lining cells derived from the flattened osteoblasts replace the marrow lining cells thereby closing the BRC; and that the two layers of lining cells eventually becomes a single layer. The integrity of the osteocyte-lining cell system is reestablished by the new generation of lining cells. The BRC most likely serves multiple purposes, including efficient exchange of matrix constituents and minerals, routing, monitoring, or modulating bone cell recruitment, and possibly the anatomical basis for the coupling of bone remodeling. [source] Novel Thorium Membrane Sensors with Anionic Response Based on Trioctylphosphine Oxide and Toluate IonophoresELECTROANALYSIS, Issue 19 2008Abstract Two novel potentiometric polymeric membrane sensors for rapid and accurate determination of thorium are described. These are based on the use of trioctylphosphine oxide (TOPO) and thorium toluate (Th-TA) as ionophores dispersed in poly(vinyl chloride) matrix membranes plasticized with nitrophenyloctyl ether. In strong nitric acid medium, Th(IV) nitrate is converted into [Th(NO3)6]2, complex and sensed as anionic divalent ion which exclude most cationic effect. Validation of the assay methods using the quality assurance standards (linearity range, accuracy, precision, within-day variability, between-day-repeatability, lower detection limit and sensitivity) reveals excellent performance characteristics of both sensors. The sensors exhibit near-Nernstian response for 1.0×10,6,1.0×10,1 M Th over the pH range 2.5,4.5. Calibration slopes of ,32.3±0.3 and ,27.2±0.2,mV/decade, precision of ±0.5 and ±0.8% and accuracy of 98.8±0.9 and 97.9±0.7% are obtained with TOPO and Th-TA based sensors, respectively. Negligible interferences are caused by most interfering mono-, di-, tri-, tetra-, penta-, and hexa-valent elements commonly associated with thorium in naturally occurring minerals and ores. High concentrations of Cl,, F,, SO42,, and NO3, ions have no diverse effect. Complete removal of the effect of the interferents in complex matrices is achieved by retention of [Th(NO3)6]2, complex from 5,M nitric acid/methanol mixture (1,:,9,v/v) on a strong anion exchanger, washing out the cationic interferents followed by stripping off thorium anion complex and measurements. Both sensors are used for determining thorium in certified thorium ore samples (20,120,mg Th/kg) and some naturally occurring ores (200,600,mg Th/kg). The results obtained agree fairly well with the certified labeled values or the data obtained using X-ray fluorescence spectrometry [source] Preparation of novel ZSM-5 zeolite-filled chitosan membranes for pervaporation separation of dimethyl carbonate/methanol mixturesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Bingbing Liu Abstract Novel mixed matrix membranes were prepared by incorporating ZSM-5 zeolite into chitosan polymer for the pervaporative separation of dimethyl carbonate (DMC) from methanol. These membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) to assess their morphology, intermolecular interactions, and crystallinity. Sorption studies indicated that the degree of swelling for zeolite-filled membranes increased with zeolite content in the membrane increasing and the separation selectivity of DMC/methanol was dominated by solubility selectivity rather than diffusivity selectivity. The characteristics of these membranes for separating DMC/methanol mixtures were investigated by varying zeolite content, feed composition, and operating temperature. The pervaporation separation index (PSI) showed that 5 wt % of ZSM-5 zeolite-filled membrane gave the optimum performance in the PV process. From the temperature-dependent permeation values, the Arrhenius activation parameters were estimated. The resulting lower activation energy values obtained for zeolite-filled membranes contribute to the framework of the zeolite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Gas sorption in polymers, molecular sieves, and mixed matrix membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Theodore T. Moore Abstract Gas sorption has been an underutilized technique for characterizing organic,inorganic hybrid (mixed matrix) membranes. Sorption in these membranes, which are composed of rigid inorganic domains, such as zeolites, dispersed in a polymer matrix, should be approximately additive. Sorption in the neat polymers and zeolites were first measured to demonstrate that sorption in mixed matrix membranes is approximately additive in the absence of other effects. Sorption in mixed matrix membranes was demonstrated to be additive. This extends to cases where sorption in one or both phases of the mixed matrix membrane is affected by an outside contaminant. For example, zeolite 4A is extremely hydrophilic and easily affected by contaminants from processing or from the test gases. Zeolite 4A encapsulated within a polymer matrix can still be affected by these same components, and this causes sorption lower than predicted based on that in unaffected polymers and sieves. This sorption analysis has proven to be very important in understanding the permeabilities and selectivities of mixed matrix membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4053,4059, 2007 [source] Novel Poly(vinyl alcohol)-tetraethoxysilane hybrid matrix membranes as oxygen barriers,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Mallikarjunagouda B. Patil Abstract Novel type of membranes based on poly(vinyl alcohol) crosslinked with tetraethoxysilane have been prepared by solution casting and solvent-evaporation method. The membranes thus formed were characterized by Fourier transform infrared spectroscopy (FTIR) to study the chemical interactions, X-ray diffraction (XRD), and thermogravimetry (TGA) to investigate morphological and thermal properties. Membranes were prepared in two different thicknesses (30 and 55 ,m) and used for measuring the oxygen permeability under varying feed pressures (maintaining the desired pressure differential across the membrane) in the range from 1 to 50 kg/cm2 pressure. Oxygen permeability of the membranes ranged from 0.0091 to 1.6165 Barrer for 30 ,m and 0.0305 to 0.1409 Barrer for 55-,m thick membranes by increasing the feed pressures on the feed side. Except at 50 kg/cm2 pressure, the observed oxygen permeability values are almost close to total permeability. Membranes of this study could be useful as oxygen barriers for applications in food packaging industries. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 273,278, 2007 [source] A novel primer to prevent nanoparticle agglomeration in mixed matrix membranesAICHE JOURNAL, Issue 9 2007Yi Li First page of article [source] Matrimid®/MgO mixed matrix membranes for pervaporationAICHE JOURNAL, Issue 7 2007Lan Ying Jiang Abstract For the first time, porous Magnesium oxide (MgO) particles have been applied to generate mixed matrix membranes (MMM) for the dehydration of iso-propanol by pervaporation. A modified membrane fabrication procedure has been developed to prepare membranes with higher separation efficiency. FESEM and DSC characterizations confirm that the MMMs produced have intimate polymer/particle interface; the nanosize crystallites on MgO surface may interfere with the polymer chain packing and induce chains rigidification upon the particle surface. It is observed that Matrimid®/MgO MMMs generally have higher selectivity, but lower permeability relative to the neat Matrimid® dense membrane. The highest selectivity is obtained with MMM containing 15 wt. % MgO. The selective sorption and diffusion of water in the MgO particles, and the polymer/particle interface properties combine to lead to the earlier phenomena. The investigation on the effect of feed water composition on the pervaporation performance reveals that the addition of MgO can show the selectivity-enhancing effects if the feed water concentration is lower than 30 wt. %. In the dehydration of isopropanol aqueous solution with 10 wt. % water, the selectivity of the MMMs is around 2,000, which is more than twice of 900 of neat polymeric membrane. This makes MMMs extremely suitable for breaking the azeotrops of water/iso-propanol. Gas permeation tests are also conducted using O2 and N2 to determine the microscopic structure of the MMMs, and to investigate the relationship between pervaporation and gas separation performance. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Co-permeability of 3H-labelled water and 14C-labelled organic acids across isolated Prunus laurocerasus cuticles: effect of temperature on cuticular paths of diffusionPLANT CELL & ENVIRONMENT, Issue 9 2002L. Schreiber Abstract Co-permeability of 3H-labelled water and 14C-labelled benzoic acid or 2,4-dichlorophenoxyacetic acid across isolated cuticular membranes of Prunus laurocerasus L. was measured at temperatures ranging from 15 to 50 °C. The water and benzoic acid permeances were highly correlated over the whole temperature range investigated, whereas water and 2,4-dichlorophenoxyacetic acid permeances were only correlated between 15 and 30 °C. The activation energies of cuticular permeability calculated from Arrhenius plots were 40 kJ mol,1 for water and benzoic acid and 115 kJ mol,1 for 2,4-dichlorophenoxyacetic acid. The slopes of the Arrhenius plots of 2,4-dichlorophenoxyacetic acid were linear between 15 and 50 °C, whereas pronounced phase transitions around 30 °C were observed for water and benzoic acid permeability. However, with isolated polymer matrix membranes, where cuticular waxes forming the transport-limiting barrier of cuticles have been extracted, phase transitions were not observed for water and benzoic acid. It is concluded that temperatures above 30 °C caused structural changes in the transport-limiting barrier of the cuticles leading to additional paths of diffusion for water and benzoic acid but not for 2,4-dichlorophenoxyacetic acid. [source] Fractionation of ,-Lactoglobulin from whey by mixed matrix membrane ion exchange chromatographyBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Syed M. Saufi Abstract Mixed matrix membranes (MMMs), which incorporate adsorptive particles during membrane casting, can be prepared simply and have performances that are competitive with other membrane chromatography materials. The application of MMM chromatography for fractionation of ,-Lactoglobulin from bovine whey is described in this article. MMM chromatography was prepared using ethylene vinyl alcohol polymer and lewatit anion exchange resin to form a flat sheet membrane. The membrane was characterized in terms of structure and its static and dynamic binding capacities were measured. The optimum binding for ,-Lactoglobulin was found to be at pH 6.0 using 20 mM sodium phosphate buffer. The MMM had a static binding capacity of 120 mg/g membrane (36 mg/mL membrane) and 90 mg/g membrane (27 mg/mL membrane) for ,-Lactoglobulin and ,-Lactalbumin, respectively. In batch fractionation of whey, the MMM showed selective binding towards ,-Lactoglobulin compared to other proteins. The dynamic binding capacity of ,-Lactoglobulin in whey solution was about 80 mg/g membrane (24 mg ,-Lac/mL of MMM), which is promising for whey fractionation using this technology. This is the first reported application of MMM chromatography to a dairy feed stream. Biotechnol. Bioeng. 2009;103: 138,147. © 2008 Wiley Periodicals, Inc. [source] | |||||||||||||