Home About us Contact
|
Home About us Contact | ||
|
|
||
Polymeric Membranes (polymeric + membrane)
Selected AbstractsSurface Resistance and Potentiometric Response of Polymeric Membranes Doped with Nonionic SurfactantsELECTROANALYSIS, Issue 19 2004Liya Muslinkina Abstract The influence of lipophilic, electrically neutral surfactants added to the membrane on the ion transfer resistance between an aqueous sample and a polymeric ion-selective membrane has been studied by electric impedance spectroscopy and potentiometry. An increase in the surface resistance and a shift of the apparently super-Nernstian response to lower sample ion activities has been observed when using the nonpolar bis(2-ethylhexyl) sebacate as plasticizer. [source] Time/Space-Resolved Studies of the Nafion Membrane Hydration Profile in a Running Fuel CellADVANCED MATERIALS, Issue 5 2009Valerio Rossi Albertini The hydration profile of proton-exchange membranes (PEM) in running fuel cells (FC) are obtained through an original method that employs very-high-energy synchrotron-radiation X-ray diffraction in space/time-resolved measurements. Determining the amount and spatial distribution of water in the polymeric membrane of PEMFCs under working conditions is of utmost importance in PEMFC technology, since FC performances are strongly dependent on PEM hydration. [source] Modeling and simulation of polymeric nanocapsule formation by emulsion diffusion methodAICHE JOURNAL, Issue 8 2009M. Hassou Abstract The objective of this work is to develop a predictive dynamical model of a nanoencapsulation process using an emulsion diffusion method. This model describes the formation of the polymeric membrane around the oil droplet and its size reduction due to the solvent diffusion. To this end, we assume that the phase separation is only due to purely diffusive mechanism. This work is illustrated on the formation of poly-,-caprolactone (PCL) around the oily core formed of labrafac from the initial homogeneous polymer-solvent-nonsolvent solution (PCL, ethyl acetate, and labrafac). The polymeric membrane formation, the size reduction of the nanocapsule after the solvent diffusion, and the morphology of nanocapsules are experimentally investigated. It is shown that the results obtained in simulation from the dynamical model are in agreement with the experimental ones. The model is then used to predict the effect of the initial composition on the nanocapsule morphology. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [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] Modelling and process development for gaseous separation with silicone-coated polymeric membranesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008Xin Jiang Abstract This paper proposes a permeance equation for vapour,permanent gas mixtures in a silicone-coated polymeric membrane. The equation was derived from the Arrhenius relationship by combining an apparent activation energy and interaction parameter. Accurate values of transmembrane flux were obtained by incorporating this proposed equation, which was dependent on temperature and feed composition. The equation parameters were correlated with the experimental data of eight mixtures consisting of hydrocarbons such as ethylene, ethane, propylene and propane with nitrogen covering a broad range of temperature and concentration. A numerical integration scheme was used for developing a crossflow model utilizing the above equation, which allowed the estimation of product properties including the membrane plasticization cases. The study also reports examples of implementation of this approach in potential industrial applications for the recovery of ethylene and propylene from nitrogen. Cet article propose une équation de permeance pour les mélanges vapeur,permanents de gaz dans une membrane polymère enduite de silicone. L'équation a été dérivée du rapport d'Arrhenius en combinant une énergie d'activation et un paramètre apparents d'interaction. Des valeurs précises du flux de transmembrane ont été obtenues en incorporant cette équation proposée, qui dépendait de la composition en température et en alimentation. Les paramètres de l'équation ont été corrélés avec les données expérimentales de huit mélanges se composant des hydrocarbures tels que l'éthylène, l'éthane, le propylène et le propane avec de l'azote couvrant une large gamme de la température et de concentration. Un arrangement numérique d'intégration a été employé pour développer un modèle de croisement de flux utilisant l'équation ci-dessus, qui a permis l'évaluation des propriétés de produit comprenant les cas de plasticization de membrane. L'étude indique également des exemples d'exécution de cette approche dans des demandes industrielles potentielles de rétablissement d'éthylène et de propylène de l'azote. [source] Gas permeation properties of Seragel membraneASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010M. Saeidi Abstract Gas permeation behavior through a specific type of polymeric membrane was investigated in this work. The main objective of our study was to determine gas permeation properties of a specific polymeric membrane over a range of operating pressures. The diffusive layer of this membrane consists of Butadiene,Sulfone block copolymer and demonstrates high chemical stability in corrosive media. Permeances were determined at the temperature of 35 °C and pressures of 760, 1520, and 3040 cmHg for methane, carbon dioxide, and nitrogen. Gas permeances were also determined for actual binary mixtures of H2S/CH4. Average permeances of 23.17 and 3.75 GPU for H2S and CO2 were achieved respectively, at the pressure range of 380,1140 cmHg. Calculated permeances by a model developed for this membrane in previous literatures have been compared with experimental data in this study and the agreement of the model with H2S/CH4 mixture was also investigated. The results show that the agreement between the pure gas experimental permeances and the data from the model is more in comparison with the experimental gas mixture results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Catalysis in polymeric membrane reactors: the membrane roleASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010M.G. Buonomenna Abstract Polymeric catalytic membrane reactors (PCMRs) combine a polymeric membrane that controls transfers and a catalyst that provides conversion. This review focuses on the polymeric membrane. Depending on the application, the micro-environment of the catalyst in the PCMR may be quite different from that existing in conventional reactors. This could originate different performances of the catalyst properties compared to its use without membrane. In some cases, catalysts for use in PCMR might require a specific design. In particular, the study of PCMR is a multidisciplinary activity, including material science, chemistry, and chemical engineering. Membrane based reactive separation processes, which combine two distinct functions, i.e. reaction and separation, have been around as a concept since the early stages of the membrane field itself, but have only attracted substantial technical interest during the last decade or so. Liquid phase catalytic oxidations are involved in numerous industrial processes ranging from fine to bulk chemical synthesis. PCMR polymeric membranes may also play a significant role in this field. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Visible and FTIR Microscopic Observation of Bisthiourea Ionophore Aggregates in Ion-Selective Electrode MembranesELECTROANALYSIS, Issue 22 2005Katherine Abstract Since conventional response models for ionophore-based ISEs are based on the assumption of a homogeneous membrane phase, they cannot accurately predict the response of membranes containing self-aggregating ionophores. However, meaningful conclusions about the relationship between ionophore structure and potentiometric responses can only be drawn if ionophore aggregation is properly recognized. This study demonstrates that dark field visible microscopy and FTIR microspectroscopy are valuable tools for the observation of such ionophore self-aggregation and, thereby, the development of new ionophore-based ISEs. Sulfate selective electrodes with solvent polymeric membranes containing bisthiourea ionophores that differ only by peripheral nonpolar substituents were shown to exhibit very different interferences from the sample pH. On one hand, optimized electrodes based on an ionophore with a phenyl substituent on each thiourea group (1) do not respond to pH at all and function well as sulfate-selective electrodes. On the other hand, membranes containing a more lipophilic ionophore with two additional hexyl-substituted adamantyl groups (2) exhibit severe pH interference at pH values as low as pH,5. The observation of membranes containing ionophore 2 with dark field visible microscopy and FTIR microspectroscopy shows supramolecular aggregation, and explains the startling difference between the potentiometric responses of the two types of electrodes. [source] Monodisperse, Polymeric Nano- and Microsieves Produced with Interference HolographyADVANCED MATERIALS, Issue 17 2009An Maria Prenen Monodisperse microfiltration membranes are fabricated using interference lithography. The versatility of this technique to produce polymeric membranes optimized for flow and selectivity characteristics with a wide variety of pore geometries and dimensions is demonstrated. [source] Purification of Aspergillus carbonarius polygalacturonase using polymeric membranesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008E. Nakkeeran Abstract BACKGROUND: Microfiltration (MF: 70,450 nm) and ultrafiltration (UF: 10,500 kDa) membranes were used to eliminate carbohydrates and other non-protein impurities from Aspergillus carbonarius culture broth containing polygalacturonase enzyme (EC 3.2.1.15) that would otherwise interfere with the purification processes and lead to enzyme loss. Further, diafiltration was attempted to improve the elimination of impurities as well as recovery of enzymes. RESULTS: MF resulted in removal of 2,25% carbohydrates with an enzyme recovery of 69,82% from the crude culture broth owing to the secondary layer formation. UF with 10 kDa membrane eliminated most of the carbohydrates (96%), phosphate salts and total acids with a recovery of 96% polygalacturonase and resulted in greater productivity. Using the above procedure, the enzyme was concentrated nearly 10-fold while the purity improved from 4.6 to 49.4 U mg,1 of dry matter. CONCLUSIONS: The results of this study focused on the elimination of carbohydrates and other non-protein impurities showed that UF could be used efficiently as a primary purification step during downstream processing of microbial culture broths containing enzymes. The present approach will ensure complete elimination of non-protein impurities thereby reducing the losses and difficulties in the subsequent purification steps. Copyright © 2008 Society of Chemical Industry [source] Ultrathin polymeric interpenetration network with separation performance approaching ceramic membranes for biofuelAICHE JOURNAL, Issue 1 2009Lan Ying Jiang Abstract Biofuel has emerged as one of the most strategically important sustainable fuel sources. The success of biofuel development is not only dependent on the advances in genetic transformation of biomass into biofuel, but also on the breakthroughs in separation of biofuel from biomass. The "separation" alone currently accounts for 60,80% of the biofuel production cost. Ceramic membranes made of sophisticated processes have shown separation performance far superior to polymeric membranes, but suffers fragility and high fabrication cost. We report the discovery of novel molecular engineering and membrane fabrication that can synergistically produce polymeric membranes exhibiting separation performance approaching ceramic membranes. The newly discovered Polysulfone/Matrimid composite membranes are fabricated by dual-layer coextrusion technology in just one step through phase inversion. An ultrathin dense-selective layer made of an interpenetration network of the two materials with a targeted and stable interstitial space is formed at the interface of two layers for biofuel separation. The combined molecular engineering and membrane fabrication approach may revolutionize future membrane research and development for purification and separation in energy, environment, and pharmaceuticals. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Effect of Concentration Gradient on the Morphology Development in Polymer Solutions Undergoing Thermally Induced Phase SeparationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007Bai Tao Jiang Abstract Anisotropic porous polymeric materials fabricated from the phase separation method via spinodal decomposition are used in various practical engineering applications. We studied the formation of anisotropic porous polymeric materials numerically, by imposing an initial linear concentration gradient across a model polymer solution. The initial concentration gradient is placed at three different regions of the polymer sample for comparison purposes. All the simulation results are in good agreement with published experimental observations, which are reported from the applications of porous polymeric membranes. The structure development shows that an anisotropic porous morphology forms when an initial linear concentration gradient is applied to the model polymer solution. [source] Influence of the Non-Perfect Step Input Concentration at the Feed Side of the Membrane Surface on the Diffusion Coefficient EvaluationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2006Jirina Cermakova Abstract Summary: Vapor diffusion coefficients in polymeric membranes were evaluated from dynamic permeation experiments. A membrane separated the diffusion cell into two parts , upstream and downstream. At the start of the experiment the concentration change in the upstream part (feed side) was made by substituting the input stream of pure nitrogen by the stream of permeant vapors. The solution of the Fick's second law with the step input concentration function is used for the evaluation of diffusion coefficients. The realization of the step input function can be difficult and its imperfection can negatively influence the evaluation process. This contribution deals with the description of the experimentally obtained input function and the study of its influence on evaluated values of diffusion coefficients. The mathematical model, which includes the non-perfect step input concentration function and the transport through a polymer was developed. The results of this study enable the estimation of diffusion coefficient evaluation errors as dependence on the experimental arrangements and on the membrane transport properties. Diffusion apparatus for measurement of the steady-state permeation process. [source] Synthesis, stability and electrocatalytic activity of polymer-stabilized monometallic Pt and bimetallic Pt/Cu core,shell nanoparticlesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008D. N. Muraviev Abstract In this paper we report the results obtained for inter-matrix synthesis (IMS) and characterization of monometallic and bimetallic polymer-stabilized metal nanoparticles (PSMNPs). The IMS procedure is based on the use of appropriately functionalized polymeric membranes as nanoreactors, which allows both synthesis and characterization of the composition and morphology of PSMNPs inside the membranes. The membranes were prepared by using noncrosslinked sulfonated poly(etherether ketone) (SPEEK) of desired degree of sulfonation, which provided insolubility of the polymer in water and solubility in some organic solvents (e.g. dimethylformamide). The IMS of PSMNPs involved loading of the membrane with metal ions or complexes followed by metal reduction inside the membrane resulting in the formation of either monometallic (Cu or Pt) or bimetallic (Pt/Cu) PSMNPs with core,shell structure. The electrocatalytic activity of the PSMNPs was estimated by measuring the electrochemical response of amperometric sensors prepared by using SPEEK-Pt-PSMNP and SPEEK-Pt/Cu-PSMNP nanocomposite membranes as sensing elements to detect H2O2. At the same values of Pt loading the response of Pt/Cu-PSMNP-based sensors appeared to be far higher than that of sensors modified with Pt-PSMNP membranes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polymer electrolyte membranes for high-temperature fuel cells based on aromatic polyethers bearing pyridine unitsPOLYMER INTERNATIONAL, Issue 11 2009Joannis K Kallitsis Abstract This review is focused on the design and synthesis of new high-temperature polymer electrolytes based on aromatic polyethers bearing polar pyridine moieties in the main chain. Such materials are designed to be used in polymer electrolyte fuel cells operating at temperatures higher than 100 °C. New monomers and polymers have been synthesized and characterized within this field in respect of their suitability for this specific application. Copolymers with optimized structures in order to combine excellent film-forming properties with high mechanical, thermal and oxidative stability and controlled acid uptake have been synthesized which, after doping with phosphoric acid, result in ionically conducting membranes. Such materials have been studied in respect of their conductivity under various conditions and used for the construction of membrane-electrode assemblies (MEAs) which are used for fuel cells operating at temperatures up to 180 °C. New and improved, in terms of oxidative stability and mechanical properties in the doped state, polymeric membranes have been synthesized and used effectively for MEA construction and single-cell testing. Copyright © 2009 Society of Chemical Industry [source] Modelling and process development for gaseous separation with silicone-coated polymeric membranesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008Xin Jiang Abstract This paper proposes a permeance equation for vapour,permanent gas mixtures in a silicone-coated polymeric membrane. The equation was derived from the Arrhenius relationship by combining an apparent activation energy and interaction parameter. Accurate values of transmembrane flux were obtained by incorporating this proposed equation, which was dependent on temperature and feed composition. The equation parameters were correlated with the experimental data of eight mixtures consisting of hydrocarbons such as ethylene, ethane, propylene and propane with nitrogen covering a broad range of temperature and concentration. A numerical integration scheme was used for developing a crossflow model utilizing the above equation, which allowed the estimation of product properties including the membrane plasticization cases. The study also reports examples of implementation of this approach in potential industrial applications for the recovery of ethylene and propylene from nitrogen. Cet article propose une équation de permeance pour les mélanges vapeur,permanents de gaz dans une membrane polymère enduite de silicone. L'équation a été dérivée du rapport d'Arrhenius en combinant une énergie d'activation et un paramètre apparents d'interaction. Des valeurs précises du flux de transmembrane ont été obtenues en incorporant cette équation proposée, qui dépendait de la composition en température et en alimentation. Les paramètres de l'équation ont été corrélés avec les données expérimentales de huit mélanges se composant des hydrocarbures tels que l'éthylène, l'éthane, le propylène et le propane avec de l'azote couvrant une large gamme de la température et de concentration. Un arrangement numérique d'intégration a été employé pour développer un modèle de croisement de flux utilisant l'équation ci-dessus, qui a permis l'évaluation des propriétés de produit comprenant les cas de plasticization de membrane. L'étude indique également des exemples d'exécution de cette approche dans des demandes industrielles potentielles de rétablissement d'éthylène et de propylène de l'azote. [source] Catalysis in polymeric membrane reactors: the membrane roleASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010M.G. Buonomenna Abstract Polymeric catalytic membrane reactors (PCMRs) combine a polymeric membrane that controls transfers and a catalyst that provides conversion. This review focuses on the polymeric membrane. Depending on the application, the micro-environment of the catalyst in the PCMR may be quite different from that existing in conventional reactors. This could originate different performances of the catalyst properties compared to its use without membrane. In some cases, catalysts for use in PCMR might require a specific design. In particular, the study of PCMR is a multidisciplinary activity, including material science, chemistry, and chemical engineering. Membrane based reactive separation processes, which combine two distinct functions, i.e. reaction and separation, have been around as a concept since the early stages of the membrane field itself, but have only attracted substantial technical interest during the last decade or so. Liquid phase catalytic oxidations are involved in numerous industrial processes ranging from fine to bulk chemical synthesis. PCMR polymeric membranes may also play a significant role in this field. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Performance Characteristics of Nanoporous Carbon Membranes for Protein UltrafiltrationBIOTECHNOLOGY PROGRESS, Issue 5 2007Tapan N. Shah Nanoporous carbon membranes could be very attractive for applications of ultrafiltration in the biotechnology industry because of their greater mechanical strength and longer membrane life. The objective of this study was to obtain quantitative data on the performance characteristics of nanoporous carbon membranes formed within a stainless steel support that was first modified by deposition of silica particles within the macroporous support. The nanoporous carbon membrane effectively removed small solutes from a protein solution using diafiltration, with performance comparable to that of commercial polymeric membranes. Protein fouling was evident, although the nanoporous carbon membranes were easily regenerated; cleaning with 0.5 N NaOH at 50 °C completely restored the water permeability for multiple cycles. The nanoporous carbon membranes were also compatible with steam sterilization. Significant increases in process flux could be obtained using periodic back-pulsing, with no evidence of any structural alterations in the membrane. These results clearly demonstrate the potential benefits and opportunities for using nanoporous carbon membranes for protein ultrafiltration. [source] | ||||||||||||||||