The Experts below are selected from a list of 15498 Experts worldwide ranked by ideXlab platform
A.e. Yaroshchuk - One of the best experts on this subject based on the ideXlab platform.
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Osmosis and reverse osmosis in fine-porous charged diaphragms and Membranes
Advances in Colloid and Interface Science, 1995Co-Authors: A.e. YaroshchukAbstract:Abstract The theory of osmosis and reverse osmosis in fine-porous charged Membranes and diaphragms is presented in a deductive way with several well-structured levels of consideration. The analysis starts from the discontinuous version of irreversible thermodynamics where the Membrane is considered as an absolutely black box without any information needed about its internal structure. As a trade-off for generality, however, the thermodynamic forces must be small. A number of qualitative conclusions is drawn proceeding from rather evident assumptions about the order of magnitude of various phenomenological coefficients. In the case of electrolyte mixtures those conclusions turn out surprisingly numerous and non-trivial including predictions of reflection coefficients larger than unity and strong negative osmosis. Both those anomalous phenomena are confirmed by experimental findings. The next step is the introduction of a ‘uniformly black’ box, namely a macroscopically Homogeneous Membrane with otherwise unspecified internal structure. That permits to employ the continuous version of irreversible thermodynamics thus allowing to drop the restriction of small thermodynamic forces. In the case of binary electrolytes general solutions in quadratures are obtained for the problems of apparent osmotic pressure and of reverse osmosis, and a very accurate approximate solution in quadratures is obtained for the problem of osmosis. Some of the theoretical predictions are compared with experimental data on the reverse osmosis of binary electrolytes in track-etched Membranes with the pore size of 8 nm. In the case of electrolyte mixtures a semi-quantitative asymptotic analysis is performed in the limiting case of reverse osmosis at sufficiently large Peclet numbers, and in the particular case of one dominant electrolyte in the mixture an exact solution in quadratures is obtained. Those analyses make possible to predict a number of non-trivial regularities that are confronted with experimental data on the pressure-driven transport or ternary electrolyte mixtures across various charged porous Membranes. A good qualitative agreement between the theory and experiments is recorded. The next step is the specification of phenomenological coefficients within the scope of a general capillary model. That makes the box grey but not transparent, yet, as the shape of capillary cross-section as well as the nature of surface forces are not specified. General expressions for phenomenological coefficients derived in terms of ion distribution and diffusion coefficients make possible a qualitative analysis of the effect of inhomogeneity of ion distribution inside pores. Finally, the capillary space charge model is introduced making the analysis completely mechanistic. Several approaches are considered to the approximate description of the structure of overlapped diffuse parts of double electric layers in fine pores. Since qualitative effects of microscopic heterogeneity appear to be not dependent on the details of the pore geometry sample numerical calculations are performed for slit-like capillaries where there is a general solution of Poisson-Boltzmann equation in quadratures. A more general model of pores in an electrically conducting gel is introduced in an attempt to quantitatively describe the results of complete characterization of cation-exchange Membranes in terms of irreversible thermodynamics.
Robert Y M Huang - One of the best experts on this subject based on the ideXlab platform.
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pervaporation with chitosan Membranes ii blend Membranes of chitosan and polyacrylic acid and comparison of Homogeneous and composite Membrane based on polyelectrolyte complexes of chitosan and polyacrylic acid for the separation of ethanol water mix
Journal of Membrane Science, 1997Co-Authors: Jyhjeng Shieh, Robert Y M HuangAbstract:Abstract Three different types of blend Membranes based on chitosan and polyacrylic acid were prepared from Homogeneous polymer solution and their performance on the pervaporation separation of water-ethanol mixtures was investigated. It was found that all Membranes are highly water-selective. The temperature dependence of Membrane permselectivity for the feed solutions of higher water content (>30 wt%) was unusual in that both permeability and separation factor increased with increase in temperature. This phenomenon might be explained from the aspect of activation energy and suggested that the sorption contribution to activation energy of permeation should not always be ignored when strong interaction occurs in the pervaporation Membrane system. A comparison of pervaporation performance between composite and Homogeneous Membranes was also studied. Typical pervaporation results at 30°C for a 95 wt% ethanol aqueous solution were: for the Homogeneous Membrane, permeation flux = 33 g/m 2 h, separation factor = 2216; and for the composite Membrane, permeation flux = 132 g/m 2 h, separation factor = 1008. A transport model consisting of dense layer and porous substrate in series was developed to describe the effect of porous substrate on pervaporation performance.
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pervaporation dehydration of isopropanol with chitosan Membranes
Journal of Membrane Science, 1997Co-Authors: M Ghazali, Mohd Ghazali Mohd Nawawi, Robert Y M HuangAbstract:Homogeneous and composite chitosan based Membranes were prepared by the solution casting technique. The Membranes were investigated for the pervaporation dehydration of isopropanol-water systems. The effects of feed concentration and temperature on the separation performance of the Membranes were studied. In terms of the pervaporation separation index (PSI), the composite Membrane was more productive than the Homogeneous Membrane for pervaporation of feed with high isopropanol content. It was observed that permeation increased and the separation factor decreased with the temperature. Modification of the Homogeneous chitosan Membrane by chemical crosslinking with hexamethylene diisocyanate improved the permselectivity but reduced the permeation rate of the Membrane.
Ivan Roche - One of the best experts on this subject based on the ideXlab platform.
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Anhydrous proton motion study by solid state NMR spectroscopy in novel PEMFC blend Membranes composed of fluorinated copolymer bearing 1,2,4- triazole functional groups and sPEEK
RSC Advances, 2014Co-Authors: Benjamin Campagne, Gilles Silly, Ghislain David, Bruno Ameduri, Deborah Jones, Jacques Roziere, Ivan RocheAbstract:The proton mobility in a new family of PEMFC blend Membranes containing 1,2,4-triazole groups is studied by infrared spectroscopy and particularly by 1H Magic Angle Spinning Solid State NMR spectroscopy. These Membranes are usually used for fuel cell operation at low relative humidity (RH < 25%). The studied Membrane contains 40%-wt of a partially fluorinated alternating poly(2-iodoethyl vinyl ether-altchlorotrifluoroethylene)- g-1H-1,2,4-triazole-3-thiol95% copolymer (II) and 60%-wt of sulfonated poly(ether ether ketone), sulfonated PEEK (IEC ¼ 1.3 meq g 1) (r ¼ n-NH/n-SO3H ¼ 1.7). In this study, the 1D 1H MAS spectrum of copolymer (II) was fully determined. Following acidification of a suspension of this copolymer leading to acidified (II0) copolymer, the 1D 1H MAS spectrum showed two populations corresponding to triazole and triazolium groups. The 2D 1H EXchange SpectroscopY spectrum of (II0) showed faster proton dynamics of the triazolium protonated form than in the copolymer containing only non protonated triazole groups. Inhomogeneity of (II0) sample was confirmed by the different spin dynamics of triazole and triazolium ring protons. In the Homogeneous Membrane, spin dynamics were further increased (i.e. very short mixing time to observe proton diffusion). Hence, this work provides confirmation that protonation acts in favour of proton mobility in the material at room temperature, and provides experimental evidence for the increase of proton mobility due to triazole protonation from the sulfonic acid groups of sPEEK.
Qu Wenjuan - One of the best experts on this subject based on the ideXlab platform.
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Comparison of the property of Homogeneous and heterogeneous ion exchange Membranes during electrodialysis process
Ain Shams Engineering Journal, 2020Co-Authors: Shaoxiang Lee, Wenqiao Meng, Yupeng Wang, Dong Wang, Meng Zhang, Guohui Wang, Jiaji Cheng, Yue Zhou, Qu WenjuanAbstract:Abstract Recently, electrodialysis technology has received widespread attention in the fields of water resource utilization. The core of the electrodialysis technology is the structure and performance of the ion exchange Membrane. This study uses the single variable method to investigate the effects of energy consumption, current efficiency, and other parameters of Homogeneous and heterogeneous Membranes, then by chemical analysis method and scientific numerical analysis to determine the best operating parameters for the electrodialysis process of different ion exchange Membranes. The experimental results show that the current efficiencies of heterogeneous and Homogeneous Membrane can reach 0.9295 and 0.9577 respectively. The highest concentration in the concentration chamber by using heterogeneous and Homogeneous Membrane can reach 149.30 g/L, 191.24 g/L, respectively. Meanwhile, the structural stability of the two ion exchange Membranes was compared by concentration experiment and system stability analysis. These experimental results indicated the direction of Homogeneous and heterogeneous Membrane in electrodialysis engineering.
Kailash Chandra Khulbe - One of the best experts on this subject based on the ideXlab platform.
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Comparison of gas separation performance and morphology of Homogeneous and composite PPO Membranes
Journal of Membrane Science, 2005Co-Authors: F. Hamad, Kailash Chandra Khulbe, Takeshi MatsuuraAbstract:Abstract Composite Membranes, prepared by coating PPO on top of a 12 kDa MWCO ultrafiltration Membrane (Osmonics-HO51), showed enhanced gas permeability ratio and separation factor for CO 2 /CH 4 gas system, as well as some decrease in the permeability of CO 2 gas, in comparison to the dense Homogeneous PPO Membrane. Average permeability ratio, CO 2 /CH 4 , being reported in this paper is 37 for composite Membranes, and 17 for Homogeneous Membranes. The CO 2 permeability obtained for composite and Homogeneous PPO Membranes were 80 and 92 Barrer, respectively. AFM observations showed that the coated layer of the composite Membrane possessed graded compactness across the depth, rough and large polymer aggregates on top surface while smooth and fine polymer aggregates on bottom surface. This morphology profile was opposite to that observed for the dense Homogeneous Membrane. Based on AFM observations and solvent evaporation kinetics, it is postulated that the enhancement in the selectivity and the drop in the gas permeability of the coated layer, in comparison to that of the dense Homogeneous Membrane, is due to the densification and compaction of the polymer adjacent to the support Membrane interface. This is the direct result of the migration of solvent toward the support Membrane and the partial draw of the solvent into the support Membrane pores. This has produced a smoother bottom surface as a result of (i) the formation of small nodules, and (ii) the fusion of these small nodules by the compressive forces that have developed due to the shrinkage of the swollen support substrate. These compressive forces have caused the bottom surface to wrinkle.
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Study of the structure of asymmetric cellulose acetate Membranes for reverse osmosis using electron spin resonance (ESR) method
Polymer, 2001Co-Authors: Kailash Chandra Khulbe, Takeshi Matsuura, G. Lamarche, A.-m. Lamarche, C. Choi, S.h. NohAbstract:Electron spin resonance (ESR) technique was used to study the structure of the skin layer of asymmetric cellulose acetate Membranes for reverse osmosis. TEMPO (2,2,6,6-tetramethyl-1-piperridinyloxy-free radical) was used as a spin probe that was brought into the Membranes either by reverse osmosis experiments with feed solutions involving TEMPO, or by blending TEMPO into casting solutions. It was found that the mobility of TEMPO in the asymmetric Membrane shrunk at 90°C was the same as TEMPO in a dense Homogeneous Membrane prepared from the same casting solution as that used for the preparation of the asymmetric Membranes. On the other hand, TEMPO was more mobile in the asymmetric Membranes when they were shrunk at lower temperatures and less mobile in a dense Homogeneous Membrane when the latter is prepared from a casting solution without pore former (magnesium perchlorate and water). Reverse osmosis experiments were also performed using feed aqueous solutions of sodium chloride and/or TEMPO.
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Surface morphology of Homogeneous and asymmetric Membranes made from poly(phenylene oxide) by tapping mode atomic force microscope
Journal of Applied Polymer Science, 1996Co-Authors: Kailash Chandra Khulbe, Boguslaw Kruczek, Geeta Chowdhury, S. Gagné, Takeshi MatsuuraAbstract:Surface morphology of asymmetric and Homogeneous Membranes prepared from poly(phenylene oxide) (PPO) was studied by tapping mode atomic force microscopy (TM AFM). As expected, a significant difference in the morphology between the top and the bottom surfaces of the asymmetric Membrane was observed. The images of the top surface revealed a small variation in the vertical direction (6.7 nm), compared to the mean diameter of nodules (62 nm), while the images of the bottom surface were very porous (microfiltration structure). On the other hand, the observed difference in morphology between the top and the bottom surfaces of the Membrane prepared by the complete evaporation of the solvent (Homogeneous Membrane) was rather unexpected. The nodules on the bottom surface were twice as large as those on the top surface. These studies also revealed some differences in the morphology of the top surface of asymmetric and Homogeneous Membranes. Both surfaces were made up of nodules having a similar size (62-64 nm) ; however, roughness parameters calculated for the top surface of the asymmetric Membrane were approximately two times greater than those for the top surface of the Homogeneous Membrane.