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Membrane Performance (membrane + performance)
Selected AbstractsEvaluation of factors influencing membrane performanceENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2005Weihua Peng Abstract Three commercial water treatment membranes, TFC-S (Koch membranes, San Diego, CA), ESPA1, and NTR7450 (Hydranautics, San Diego, CA), were tested under various physical and chemical conditions to investigate their fouling behaviors. It was found that TFC-S always displayed the greatest rate of flux decline, ESPA1 displayed a mild trend in flux decline, and NTR7450 presented a nearly stable flux. Multivariable regression models showed that the flux decline rates for TFC-S and ESPA1 were controlled by the initial permeate flux, whereas their initial (that is, instantaneous) foulings were controlled by the interaction between permeate drag and electrostatic repulsions. Feed bacteria concentration also contributed to the initial fouling of ESPA1 as a result of cell deposition on the membrane surface. NTR7450 showed an initial decline in flux followed by a steady flux, and its initial fouling was significantly affected by feed water total organic carbon (TOC) arising from the initial accumulation of colloidal organic particles on the surface. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Chemical modification of polyethersulfone nanofiltration membranes: A reviewJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009B. Van der Bruggen Abstract Polysulfone (PS) and poly(ether)sulfone (PES) are often used for synthesis of nanofiltration membranes, due to their chemical, thermal, and mechanical stability. The disadvantage for applying PS/PES is their high hydrophobicity, which increases membrane fouling. To optimize the performance of PS/PES nanofiltration membranes, membranes can be modified. An increase in membrane hydrophilicity is a good method to improve membrane performance. This article reviews chemical (and physicochemical) modification methods applied to increase the hydrophilicity of PS/PES nanofiltration membranes. Modification of poly(ether)sulfone membranes in view of increasing hydrophilicity can be carried out in several ways. Physical or chemical membrane modification processes after formation of the membrane create more hydrophilic surfaces. Such modification processes are (1) graft polymerization that chemically attaches hydrophilic monomers to the membrane surface; (2) plasma treatment, that introduces different functional groups to the membrane surface; and (3) physical preadsorption of hydrophilic components to the membrane surface. Surfactant modification, self-assembly of hydrophilic nanoparticles and membrane nitrification are also such membrane modification processes. Another approach is based on modification of polymers before membrane formation. This bulk modification implies the modification of membrane materials before membrane synthesis of the incorporation of hydrophilic additives in the membrane matrix during membrane synthesis. Sulfonation, carboxylation, and nitration are such techniques. To conclude, polymer blending also results in membranes with improved surface characteristics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Pervaporation of tertiary butanol/water mixtures through chitosan membranes cross-linked with toluylene diisocyanate,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2005Smitha Biduru Abstract Membranes made from 84% deacetylated chitosan biopolymer were cross-linked by a novel method using 2,4-toluylene diisocyanate (TDI) and tested for the separation of t -butanol/water mixtures by pervaporation. The unmodified and cross-linked membranes were characterized by Fourier transform infra red (FTIR) spectroscopy, X-ray diffraction (XRD) studies and sorption studies in order to understand the polymer,liquid interactions and separation mechanisms. Thermal stability was analyzed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) while tensile strength measurement was carried out to assess mechanical strength. The membrane appears to have good potential for breaking the aqueous azeotrope of 88.2 wt% t -butanol by giving a high selectivity of 620 and substantial water flux (0.38 kg m,2 hr,1). The effects of operating parameters such as feed composition, membrane thickness and permeate pressure on membrane performance were evaluated. Copyright © 2005 Society of Chemical Industry [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] Separation of light gas mixtures using SAPO-34 membranesAICHE JOURNAL, Issue 4 2000Joseph C. Poshusta Continuous SAPO-34 membranes were prepared on porous alumina tubular supports, and shown to be useful for light gas separations at low and high temperatures. Single-gas permeances of CO2, N2 and CH4 decreased with increasing kinetic diameter. For the best membrane at 300 K, the He and H2 permeances were less than that of CO2, because He, H2, and CO2 were small compared to the SAPO-34 pore, and differences in the heat of adsorption determined the permeance order. The smaller component permeated the fastest in CO2/CH4, CO2/N2, N2/CH4, H2/CH4 and H2/N2 mixtures between 300 and 470 K. For H2/CO2 mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400 K. The CO2/CH4 selectivity at room temperature was 36 and decreased with temperature. The H2/CH4 mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness. [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Analysis presented in Part 1 of this paper indicated the importance of optimization of the transport properties of the interfacial region to achieve ideal mixed matrix materials. This insight is used in this paper to guide mixed matrix material formation with more conventional gas separation polymers. Conventional gas separation materials are rigid, and, as seen earlier, lead to the formation of an undesirable interphase under conventional casting techniques. We show in this study that if flexibility can be maintained during membrane formation with a polymer that interacts favorably with the sieve, successful mixed matrix materials result, even with rigid polymeric materials. Flexibility during membrane formation can be achieved by formation of films at temperatures close to the glass transition temperature of the polymer. Moreover, combination of chemical coupling and flexibility during membrane formation produces even more significant improvements in membrane performance. This approach leads to the formation of mixed matrix material with transport properties exceeding the upper bound currently achieved by conventional membrane materials. Another approach to form successful mixed matrix materials involves tailoring the interface by use of integral chemical linkages that are intrinsically part of the chain backbone. Such linkages appear to tighten the interface sufficiently to prevent "nonselective leakage" along the interface. This approach is demonstrated by directly bonding a reactive polymer onto the sieve surface under proper processing conditions. [source] Computational Evaluation of Dialysis Fluid Flow in Dialyzers With Variously Designed JacketsARTIFICIAL ORGANS, Issue 6 2009Ken-ichiro Yamamoto Abstract Dialyzer performance strongly depends on the flow of blood and dialysis fluid as well as membrane performance. It is necessary, particularly to optimize dialysis fluid flow, to develop a highly efficient dialyzer. The objective of the present study is to evaluate by computational analysis the effects of dialyzer jacket baffle structure, taper angle, and taper length on dialysis fluid flow. We modeled 10 dialyzers of varying baffle angles (0, 30, 120, 240, and 360°) with and without tapers. We also modeled 30 dialyzers of varying taper lengths (0, 12.5, 25.0, and 50.0 mm) and angles (0, 2, 4, and 6°) based on technical data of APS-SA dialyzers having varying surface areas of 0.8, 1.5, and 2.5 m2 (Rexeed). Dialysis fluid flow velocity was calculated by the finite element method. The taper part was divided into 10 sections of varying fluid resistances. A pressure of 0 Pa was set at the dialysis fluid outlet, and a dialysis fluid flow rate of 500 mL/min at the dialysis fluid inlet. Water was used as the dialysis fluid in the computational analysis. Results for dialysis fluid flow velocity of the modeled dialyzers indicate that taper design and a fully surrounded baffle are important in making the dialysis fluid flow into a hollow-fiber bundle easily and uniformly. However, dialysis fluid flow channeling occurred particularly at the outflowing part with dialyzers having larger taper lengths and angles. Optimum design of dialysis jacket structure is essential to optimizing dialysis fluid flow and to increasing dialyzer performance. [source] | |||||||||||||