Top PDF ION CONDUCTING MEMBRANES MEMBRANE SEPARATIONS pdf

ION CONDUCTING MEMBRANES   MEMBRANE SEPARATIONS pdf

ION CONDUCTING MEMBRANES MEMBRANE SEPARATIONS pdf

The principle of using a dense ceramic ionic conductor to separate the ion-conducting species is, in itself, not new. The idea has been around since the turn of the century when Nernst R rst investigated solid electrolyte compositions for use as incandescent R laments in his glower devices. Since then ion-con- ducting ceramics have been used to separate a num- ber of elements, for example oxygen, hydrogen and gallium, but mainly as a scienti R c curiosity and only on a laboratory scale. The current industrial interest in membrane separators was instigated by a Japanese group, who, in 1985, investigated dense oxide mem- branes, which were able to permeate substantial S uxes of oxygen at temperatures of 800 } 1000 3 C, with 100% selectivity. Since then there has been a rapid growth of both scienti R c and industrial inter- est in the use of these membranes for the separation of oxygen. The industrial interest has been driven by the possibility of providing compact oxygen separation plants for a number of applications including aero- space and medical, petrochemical and manufacturing industries.
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Gas Separations with Polymer Membranes pdf

Gas Separations with Polymer Membranes pdf

Measuring the permeability of gas mixtures is more complex. Usually a S ow of a pre-blended source is passed over the feed side of the membrane. The steady state permeate S ux can be measured by em- ploying an inert gas such as helium to sweep the permeating components into a gas chromatograph, for example, for compositional analysis. Preferably the experiment is conducted such that back-diffusion of the helium sweep is insigni R cant and where the feed gas composition is not altered by permeation. Additionally, nuances in the S ow patterns within test cells not speci R cally designed for mixed gas experi- ments can lead to erroneous results.
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Ion Conducting Nanocomposite Membranes Based on PVA-HA-HAP for Fuel Cell Application: II. Effect of Modifier Agent of PVA on Membrane Properties

Ion Conducting Nanocomposite Membranes Based on PVA-HA-HAP for Fuel Cell Application: II. Effect of Modifier Agent of PVA on Membrane Properties

FTIR spectra were recorded by (EQUINOX 55, BRUKER Germany) using KBr transparent discs. IR spectra were recorded at 64 scans between 4000–400 cm −1 with a resolution of 2 cm −1 . Vacuumed-dried samples were pressed by applying a force 105 N into transparent disk (disk weight and diameter ~ 125 mg and 14 mm), respectively. KBr-sample discs were measured in the absorbance mode. The mechanical stability measurements of composite membranes e.g. the maximum tensile- strength and the elongation-at-break were carried out with a universal tensile testing machine (model: AG-I/ 50N-10KN, Japan). PVA-HA-HAP membranes were cut into the specific shape of a dog-bone- shape-dimension (~ 5 cm long × 1.5 cm wide-the ends × 1 cm middle). The measurements were carried out at stretching rate 10 mm/min with pre-load of 0.5 N to determine load for each sample. Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) thermograms were carried out with a 204 Phoenix TGA/DSC instrument (NETZSCH, Germany), at a heat-scan rate 5 °C min -1 at 25–600 o C in N 2 for TGA and 10 °C min -1 at 25– 400 °C with N 2 gas for DSC analysis.
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Amphiphilic nanocomposite proton conducting membrane

Amphiphilic nanocomposite proton conducting membrane

Composite membranes formed of zeolitic fillers embedded in Nafion were made by evaporating the solvents from a suspension of small zeolite crystals in a Nafion solution [23]. Two natural zeolites were selected as filler: chabazite and clinoptilolite. This work was carried out in order to exploit the molecular sieving properties of the natural zeolites to improve selectivity of Nafion ion conducting membranes. However, the performances of chabazite-Nafion and of clinoptilolite- Nafion composite membranes were inferior to that of zeolite-free recast Nafion membranes with regard to both ion conductivity and transport selectivity. These results were due to the properties of the chosen zeolites, which proved inadequate to the authors’ purpose. Besides, a new solid inorganic proton conductor was developed based on Yzeolite [24] and mesoporous molecular sieves (MCM-41) [26] loaded with tungstophosphoric acid and molybdophosphoric acid. These new materials combine the high thermal and structural stability of Y-zeolite and MCM-41 with outstanding conductivity of heteropolyacids, which places them among the one of the most promising solid proton conductors. The highest proton conductivity of around 0.01 S/cm was obtained at room temperature for fully hydrated 50 wt% heteropolyacids loaded Y-zeolite and MCM-41.
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METAL MEMBRANES   MEMBRANE SEPARATIONS pdf

METAL MEMBRANES MEMBRANE SEPARATIONS pdf

Another bene R t of membrane reactors, particularly for fuel cell applications that require high-purity hydrogen from source gases like methanol or gaso- line, is that a membrane changes the way pressure affects extent of reaction and product recovery. Without the membrane in the reactor, a reforming reaction of this type would require low pressure op- eration to achieve high conversion, and would require a dif R cult hydrogen puri R cation for the intended use. A membrane reactor allows the reaction to be driven by high pressures, greatly increasing the ease of hydrogen product recovery. At present, several membrane reactors are in trial and one at the pilot-plant scale for the production of hydrogen. Typical pressures of operation are at 17 atm, with operation temperatures dictated by the catalyst and material of construction. The size of the fuel cell market is currently small, but is believed to be rising fast.
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An Electrochemical Cell Configuration Incorporating an Ion Conducting Membrane Separator between Reference and Working Electrode

An Electrochemical Cell Configuration Incorporating an Ion Conducting Membrane Separator between Reference and Working Electrode

Figure 4 clearly demonstrates the serious effect of chloride contamination of the electrolyte on the ORR activity, when no modified reference electrode side compartment is used. During the first ORR measurement, after only approximately 10 minutes the half-wave potential had already shifted negatively by about 150 mV, despite thoroughly rinsing of the reference electrode with Millipore water beforehand. Note that part of this lower initial activity observed in Figure 3 compared to Figure 2, is due to the difference in uncompensated resistance. Over the course of the experiment chlorides continuously diffuse through the porous frit, a process observed in the corresponding decrease in ORR activity. If, however, the reference electrode is placed into the ‘Tschurl Modification’ with only one Nafion membrane, no chloride contamination is initially evident and the deterioration in the ORR activity over time is significantly reduced. A superior chloride diffusion inhibiting effect can be achieved by employing 3 membranes in the reference electrode compartment. In this case the ORR activity remains almost unaltered after 290 minutes, with a negative shift of the half-wave potential of only 10 mV. However, it is clear that the Nafion membranes do not completely prevent the diffusion of chlorides into the cell electrolyte. There is the possibility that other types of ion conducting membranes with different polymer chain length, equivalent weight and thickness can be used in order to optimize the reference electrode compartment [10].
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Cyclones for oil Water Separations pdf

Cyclones for oil Water Separations pdf

Even though the reservoir pressure is often high enough to remove the need for pumps this factor tends to limit size As the hydrocyclone size reduces to a DR of approximately 20 mm impro[r]

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ISOTOPE SEPARATIONS   Gas Centrifugation pdf

ISOTOPE SEPARATIONS Gas Centrifugation pdf

A centrifuge designed for binary separations with uranium hexa S uoride cannot be ef R ciently used for nonuranium isotope separation with differ- ent chemical compounds. Therefore, centrifuges with speci R c characteristics must be designed for particular separation problems. For some isotopes, specially synthesized gaseous chemical compounds must be prepared for use as the process gas. The basic condi- tion for the applicability of the process gas in these newly designed centrifuges is that the gas vapour pressure is not less than 5 } 10 mmHg under normal operating temperatures. In addition to the condition that this substance should not corrode the structural material of the centrifuge, it has to be suf R ciently resistant to temperature dissociation, and preferably must possess the maximum possible content of the desired element in the molecule. The list of such substances includes S uorides and oxy S uorides of metals and nonmetals, metal } organic and complex compounds, phosphorus hydrides, boron hydrides, Freons and some others. Signi R cant differences in the chemical and physical properties of process gases leads to the necessity to create a set of gas centrifuge designs for various ranges of molecular masses. The internal circulating S ow must be opti- mized for each of these designs.
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Quantitative Analysis of Prazosin Hydrochloride in Pharmaceutical Formulation by Prazosin Potentiometric Sensor Based on Computational Investigation

Quantitative Analysis of Prazosin Hydrochloride in Pharmaceutical Formulation by Prazosin Potentiometric Sensor Based on Computational Investigation

The general procedure to prepare the PVC membrane was as follow: Different amounts of the Prazosin-tetraphenyl borate ion-pair along with appropriate amounts of PVC, plasticizer and additive were dissolved in tetrahydrofuran (THF), and the solution was mixed well. The resulting mixture was transferred into a glass dish of 2 cm diameter. The solvent was evaporated slowly until an oily concentrated mixture was obtained. A Pyrex tube (3-5 mm o.d.) was dipped into the mixture for about 10 s so that a transparent membrane of about 0.3 mm thickness was formed. The tube was then pulled out from the mixture and kept at room temperature for about 10 h. The tube was then filled with an internal filling solution (1.0×10 -3 mol L -1 Prazosin hydrochloride). The electrode was finally conditioned for 24 h by soaking in a 1.0×10 -3 mol L -1 Prazosin hydrochloride solution [44-46].
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PERFORMANCE OF THE OPTIMIZED TREE-TYPE CYLINDRICAL-SHAPED NANOPOROUS FILTERING MEMBRANES WITH 9 OR 10 BRANCH PORES IN EACH PORE TREE

PERFORMANCE OF THE OPTIMIZED TREE-TYPE CYLINDRICAL-SHAPED NANOPOROUS FILTERING MEMBRANES WITH 9 OR 10 BRANCH PORES IN EACH PORE TREE

Nanoporous filtering membranes are a new direction of the development of filtration membranes due to their super purification capability (Adiga et al., 2009; Hinds et al., 2004). They have been successfully applied in ordinary and medical purifications (Baker and Bird, 2008; Biffinger et al., 2007; Fissel et al., 2009; Jackson and Hillmyer, 2010). One of the challenges to the development of these membranes is that it is not easily reconciled among the filtration capability, flux and mechanical strength of the membranes. In the past, it was tried to overcome it such as by manufacturing very thin membranes with the use of the material of grapheme, taking the filtration pore as conical, and taking the membrane as mixed and consisted of both nanopores and micropores (Li et al., 2004; Surwade et al., 2015; Yang et al., 2006).
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CHIRAL SEPARATIONS   Chiral Derivatization pdf

CHIRAL SEPARATIONS Chiral Derivatization pdf

It is indisputable that the direct chromatographic enantioseparations based on chiral stationary phases has greatly surpassed the importance of indirect sep- arations based on covalent chiral derivatization. The fact that the overwhelming majority of papers report- ing on the development and application of chiral separations are from these R elds does not necessarily re S ect the real of the contribution of covalent chiral derivatization in the solution of practical problems in pharmaceutical and biomedical analysis. In some areas (e.g. the determination of small concentrations of D -amino acids in various biological samples, etc.)
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CHIRAL SEPARATIONS   Capillary Electrophoresis pdf

CHIRAL SEPARATIONS Capillary Electrophoresis pdf

forming a ternary metal complex with an enantiomer of a chiral amino acid. In an enantiomeric mixture the metal complexes can have differential stability, and therefore mobility differences between the enantio- mers result. In the case above, a neutral pH buffer was used, which gives a positively charged metal } histidine interaction and the enantiomer forming the higher stability complex migrates faster. One draw- back of this procedure is the requirement that the amino acid in the metal } amino acid interaction has to be of very high purity to stop enantiomeric impurities being introduced into the assay. Following the initial research, the same group impressively resolved 14 racemic amino acids by this procedure where the complex was Cu(II) } aspartame. At present the pro- cedure is limited to amino acids, with some extension to peptides and additional separations, and most ap- plications appeared in the early years of CE.
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Santiago_unc_0153D_16080.pdf

Santiago_unc_0153D_16080.pdf

The high sensitivity and rapid analysis times of mass spectrometry have led to its importance as an analytical technique; however, low signal-to-background ratios and isomeric/isobaric interferences can be problematic during the analysis of complex mixtures. Separation techniques such as chromatography and electrophoresis are often coupled to mass spectrometry prior to ionization to reduce the complexity of the subsequent mass analysis but these separations can be time consuming [1]. Post-ionization separation techniques such as ion mobility spectrometry (IMS) are much more rapid and can also be used prior to mass analysis, either as a stand-alone separation method or as a complementary separation step after a liquid phase separation [2-5]. A commonly used ion mobility technique, drift tube ion mobility spectrometry (DT-IMS), is depicted in Figure 1.1 and uses an electric field to force ions the length of a drift tube filled with a buffer gas [5]. The ion mobility (K) through the buffer gas depends directly upon the collisional cross-section of the ion and buffer gas by the Mason- Schamp equation:
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Metabolic inactivation of the circadian transmitter, pigment dispersing
factor (PDF), by neprilysin like peptidases in Drosophila

Metabolic inactivation of the circadian transmitter, pigment dispersing factor (PDF), by neprilysin like peptidases in Drosophila

have considered the possibility that temporal variation in the expression of the PDF-degrading neprilysin(s) might contribute to the circadian functions of PDF, especially since one neprilysin gene (CG8550) was shown to cycle in a microarray analysis of circadian gene expression (McDonald and Rosbash, 2001). In four separate experiments, PDF-degrading neprilysin activity was assayed in head membranes prepared from adult w1118 flies collected at 4·h intervals for 24·h in a 12·h:12·h light:dark cycle. Fluctuations in neprilysin-like activity were apparent; however, the results lacked statistical significance (results not presented). While these results do not demonstrate a role for PDF degradation in regulation of circadian behaviours, we cannot exclude the possibility that localized peptidase activity is under clock control and masked by other peptidases present in whole head extracts.
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Cell membrane lipid composition and distribution: implications for cell function and lessons learned from photoreceptors and platelets

Cell membrane lipid composition and distribution: implications for cell function and lessons learned from photoreceptors and platelets

process (i.e. a thermodynamic process). Model membrane (Yeagle and Young, 1986; Backer and Dawidowicz, 1981) and biological membrane (House et al. 1989) studies have found that the introduction of phosphatidylethanolamine into membranes creates a thermodynamically unfavorable environment for cholesterol. The thermodynamic constraints when cholesterol and phosphatidylethanolamine coexist predict an unfavorable entropy, causing the translocation of cholesterol from the phosphatidylethanolamine-rich lipid environment as a compensatory mechanism. It is proposed that such partitioning of cholesterol is due to the increased ordering of water molecules on the membrane surface. Chaotropic agents relieve the constraint on the membrane by disrupting the interstitial hydrogen-bonded water and, thereby, allow both lipids to coexist within the same bilayer. In fact, cholesterol translocation is blocked by exposure of platelets to the chaotropic agents urea and guanidine–HCl (Boesze-Battaglia et al. 1996). However, the participation of an enzymatic activity in cholesterol translocation has not been investigated. Platelet responses culminating in aggregation are strongly influenced by the cholesterol content of the platelet membrane and are positively correlated with the membrane cholesterol content. Carvalho et al. (1974) reported increased sensitivity to epinephrine, ADP- and collagen-initiated aggregation and increased nucleotide release in platelets from patients with hypercholesterolemia. Supporting the view that the increased sensitivity of platelets removed from hypercholesterolemic individuals is a consequence of their elevated cholesterol levels are data from studies by Shattil et al. (1975) and Tomizuka et al. (1990) reporting increased sensitivity of platelets to epinephrine, ADP and thromboxane A 2 when the platelets had
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Gas Separation Properties of the Dense Polymer — Zeolite Powder Composite Membranes

Gas Separation Properties of the Dense Polymer — Zeolite Powder Composite Membranes

In this paper, the possibility of the construction of the mixed matrix membrane based on the polymer matrix and surface treated inorganic powder was tested. The constructed membranes are dense, mixed-matrix membranes. The membranes were constructed with polyether-b-amide with 60% of PEG as a matrix and one of the four different zeolite particles as the dispersed inorganic phase. As an additive, the n-tetradecane trimethyl ammonium bromide (n-C14-TMABr) was tested. By the observation of the membranes after their construction, it was concluded that the presence of the C14- TMABr provides better contact between the polymer chains and zeolyte particles. Therefore, the gaps at the contact surface are avoided which improves overall separation performance of the membrane. The membrane with the acceptable quality could not be achieved without the addition of the C14-TMABr. The obtained permeability of the carbon dioxide, and the membranes’ selectivity of carbon dioxide versus hydrogen (as the main research interest of the experiments) were 120 Barrer and approximately 9, respec- tively. Those values are slightly lower in comparison with other systems. The permeability of the membranes con- structed with 3-dimensionals zeolite pores are slightly higher in comparison with analogous 1- and 2-dimensional systems. One of the possible reasons for that could be that the orientation of the pores play significant role in the permeability of the membrane.
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Supporting Polyvinylchloride Polymeric Blend Membrane with Coated Woven Fabric

Supporting Polyvinylchloride Polymeric Blend Membrane with Coated Woven Fabric

To produce a polymeric flat sheet membrane, the polymer solution can be cast on a support such as a glass plate or on a supporting material (woven or nonwoven support) and then immersed into a coagulation bath for membrane formation to occur. Most flat sheet membranes are prepared in the lab without supporting materials that provided weak mechanical properties of prepared membranes compared with supported membranes. For example, the tensile strength of polyethersulfone membrane without support is 25.8 MPa, while the tensile strength of the supported polyethersulfone membrane with woven fabric is 148 MPa [26]. Also, using supporting materials in membrane preparation reduces the shrinkage that often occurs when the membranes are unsupported [26].
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The Effects of Ability Grouping on Gifted & Talented Third, Fourth, and Fifth Grade Students in Selected South Carolina Public School Districts

The Effects of Ability Grouping on Gifted & Talented Third, Fourth, and Fifth Grade Students in Selected South Carolina Public School Districts

Zeolites are crystalline aluminosilicates with uniform pore structure and a minimum channel diameter range of 0.3-1.0 nm as shown in Figure 1.6. The presence of molecular-sized cavities and pores make the zeolites effective as shape-selective materials for a wide range of separation applications. Separation occurs in zeolite membranes by both molecular sieving and surface diffusion mechanisms. Zeolites are typically employed at elevated pressures (above 2 bar), and their adsorption capacity has been shown to be greatly reduced by the presence of moisture in the gas, thereby necessitating very high regeneration temperatures (often in excess of 300 o C). 27, 28 These additional recovery costs for their regeneration pose a significant disadvantage.
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Mixed anion materials and compounds for novel proton conducting membranes

Mixed anion materials and compounds for novel proton conducting membranes

Mixed anion materials and compounds for novel proton conducting membranes Abstract The present invention provides new amorphous or partially crystalline mixed anionchalcogenide compounds[r]

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Compounds for novel proton conducting membranes and methods of making same

Compounds for novel proton conducting membranes and methods of making same

As noted above, the present invention provides, in one embodiment, measurable proton conductivity in hydrous and anhydrous chalcogenide samples and further demon Uses As noted above the [r]

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