Blending, membrane

Several selective interactions by MIP membrane systems have been reported. For example, an L-phenylalanine imprinted membrane prepared by in-situ crosslinking polymerization showed different fluxes for various amino acids [44]. Yoshikawa et al. [51] have prepared molecular imprinted membranes from a membrane material which bears a tetrapeptide residue (DIDE resin (7)), using the dry phase inversion procedure. It was found that a membrane which contains an oligopeptide residue from an L-amino acid and is imprinted with an L-amino acid derivative, recognizes the L-isomer in preference to the corresponding D-isomer, and vice versa. Exceptional difference in sorption selectivity between theophylline and caffeine was observed for poly(acrylonitrile-co-acrylic acid) blend membranes prepared by the wet phase inversion technique [53]. 

Mathai, A.E., Singh, R.P., and Thomas, S. Transport of Aromatic Solvents through Nitrile Rubber/Epoxidized Natural Rubber Blend Membranes, Polym. Eng. Set 43(3), 704—712, March 2003. 

Polyanion Blend Polycation Blend Membrane Type Comment Blend Nos. from Table 1... 

PVA-PAcr.Ac.blends membranes are suitable also for separation of components in cthanol/benzene mixtures. Reported data are presented in table 9. 

Methanol/toluene mixtures could be separated by pervaporation technique using PVA/PAcr.Ac. blend membranes. Reported data are presented in table 10. 

The blend membranes are permselective for different organic isomers. So, these could be used for the separation of n-propanol from a mixture of n-propanol (n-PrOH) and i-propanol (i-PrOH) [84] and the separation of p-xylene from a p-xylene and o-xylene mixture [35], It was evidenced that, in both cases, the separation was better by applying the evapomeation technique than that of the pervaporation. 

Also, the PVA/Poly(l,l Dimethylenepiperidinium chloride) (PDMeDMPCl) blend membrane evidenced ion exchange capacity that increased with the time of crosslinking (tc) from 0,92 to 1,2 meq/g after tc= 15min respectively 120 min and showed a maximum capacity value, function of the weight fraction of PDMeDMPCl at 0.45 [44],... 

The PVA/PDMeDMPCl blend membranes evidenced a lower permselectivity than PVA/PSSNa membranes, probably because of a possible phases separation during the solvent evaporation, as it can see from table 15 [44],... 

The effect of annealing temperatures (65 - 250 °C) and blend composition of Nafion 117, solution-cast Nafion , poly(vinyl alcohol) (PVA) and Nafion /PVAblend membranes for application to the direct methanol fuel cell is reported in [148], These authors have found that a Nafion /PVAblend membrane at 5 wt% PVA (annealed at 230 °C) show a similar proton conductivity of that found to Nafion 117, but with a three times lower methanol permeability compared to Nafion 117. They also found that for Nafion /PVA (50 wt% PVA) blend membranes, the methanol permeability decreases by approximately one order of magnitude, whilst the proton conductivity remained relatively constant, with increasing annealing temperature. The Nafion /PVA blend membrane at 5 wt% PVA and 230 °C annealing temperature had a similar proton conductivity, but three times lower methanol permeability compared to unannealed Nafion 117 (benchmark in PEM fuel cells). 

PVA/chitosan blend membranes can be applied for the synthesis of monoglyceride, when used as a membrane enzyme reactor [277]. 

PVA/acrylamide blend membranes prepared on cheese cloth support by y-irradiation induced free radical polymerization can be used for urease entrapment. The enzyme urease is entrapped in the membrane during polymerization process and using glutaraldehyde as cross-linking agent. The main advantage of this blend to this process is that it can be reused a number of times without significant loss of urease activity [292],... 

Schematic representation of ionically cross-linked acid-base blend membranes. (From Kerres, J. A. 2005. Fuel Cells 5 230-247.)...

Jung, B., Kim, B. and Yang, J. M. 2004. Transport of methanol and protons through partially sulfonated polymer blend membranes for direct methanol fuel cell. Journal of Membrane Science 245 61-69. 

Kerres, J., Cui, W., Disson, R. and Neubrand, W. 1998. Development and characterization of cross-linked ionomer membranes based upon sulfinated and sulfonated PSU-cross-linked PSU blend membranes by disproportionation of sulfinic acid groups. Journal of Membrane Science 139 211-225. 

Fu, Y. Z., Manthiram, A. and Guiver, M. D. 2006. Blend membranes based on sulfonated poly(ether ether ketone) and polysulfone bearing benzimidazole side groups for proton exchange membrane fuel cells. Electrochemistry... 

Kerres, J., Ullrich, A., Haring, T., Baldauf, M., Gebhardt, U. and Preidel, W. 2000. Preparation, characterization and fuel cell application of new acid-base blend membranes. Journal of New Materials for Electrochemical Systems 3 229-239. 

In another report polyphosphazene copolymers were synthesized from bis (2-methylphenoxy) phosphazene, which was sulfonated after polymerization. Polymers such as polyvinylidene fluoride, polyhexa-fluoropropylene, and polyacrylonitrile were used to produce a blended membrane system. Polymer blends, cross-linking, and other means of re-enforcement are... 

Problems of desorption and loss of activity encountered with natural heparin have led numerous workers to explore synthetic heparin-like polymers or heparinoids, as reviewed by Gebelein and Murphy [475, 514, 515]. The blood compatibility of 5% blended polyelectrolyte/polyfvinly alcohol) membranes was studied by Aleyamma and Sharma [516,517]. The membranes were modified with synthetic heparinoid polyelectrolytes, and surface properties (platelet adhesion, water contact angle, protein adsorption) and bulk properties such as permeability and mechanical characteristics were evaluated. The blended membrane had a lower tendency to adhere platelets than standard cellulose membranes and were useful as dialysis grade materials. 

Ultrathin (about 400 A thick), polymer-blend membrane prepared from poly(styrenephosphonate diethyl ester) and cellulose acetate Size-quantized CdS particles generated in membranes... 

A.G. Boricha and Z. Murthy, Acrylonitrile butadiene styrene/chitosan blend membranes Preparation, characterization and performance for the separation of heavy metals, J. Membr. Sci., 339(l-2) 239-249, September 2009. 

Fig. 12. Relative integral permeability P/PFDMS of propane through polydimethyl siloxane (PDMS) — poly(ethylene-copropylene) rubber (EPR) blend membranes as a function of blend...

H.C. Park, R.M. Meertens, M.H.V. Mulder, C.A. Smolders, Pervaporation of alcohol-toluene mixtures through polymer blend membranes of poly(acrylic acid) and poly(vinyl alcohol), J. Membr. Sci. 90 (1994) 265-274. 

U.S. Toti, M.Y. Kariduraganavar, K.S. Soppimath, T.M. Aminabhavi, Sorption, diffusion and pervaporation separation of water/acetic acid mixtures through the blend membranes of sodium alginate and guar gum-g-poly(acrylamide), J. Appl. Polym. Sci. 83 (2002) 259-272. 

W.M. King, D.L. Hoemschemeyer and C.W. Saltonstall, Jr, Cellulose Acetate Blend Membranes, in Reverse Osmosis Membrane Research, H.K. Lonsdale and H.E. Podall (eds), Plenum Press, New York, pp. 131-162 (1972). 

Figure 9.19 Fraction of benzene in permeate as a function of feed mixture composition for pervaporation at the reflux temperature of a binary benzene/cyclohexane mixture. A 20-qm-thick crosslinked blend membrane of cellulose acetate and polystyrene phosphate) was used [54]. Reprinted with permission from I. Cabasso, Organic Liquid Mixtures Separation by Selective Polymer Membranes, Ind. Eng. Chem. Prod. Res. Dev. 22, 313. Copyright 1983 American Chemical Society...

From a functional point of view, Nguyen et al. examined the pervapora-tion characteristics of CA/P(VP-co-VAc) blends for application as alcohol-selective membrane materials [107]. The blend membranes were shown to be very efficient in the removal of ethanol from its mixture with ethyl tert-butyl ether (ETBE). ferf-butyl ethers are octane-value enhancers for gasoline, and the synthesis requires an excess of alcohol in the reaction to reach high... 

Nam, K. et al., Acid-Base Proton Conducting Polymer Blend Membrane, U.S. Patent Application 2003/0219640, November 27, 2003. 

Chen X, Liu JH, Feng ZC, and Shao ZZ. Macroporous chitosan/carboxymethylclellulose blend membranes and their application for lysozyme adsorption. J. Appl. Polym. Sci. 2005 96 1267-1274. 

Matsuyama H, Terada A, Nakadawara T, Kitamura Y, and Teramoto M. Facilitated transport of CO2 through polyethylenimine/ polyfvinyl alcohol) blend membrane. J. Membr. Sci. 1999 163 221-227. 

A significant number of works are concerned with the development of new membranes for the separation of mixtures of aromatic/alicyclic hydrocarbons [10,11,77-109]. For example, the following works can be mentioned. A mixture of cellulose ester and polyphosphonate ester (50 wt%) was used for benzene/cyclohexane separation [113]. High values of the separation factor and flux were achieved (up to 2 kg/m h). In order to achieve better fluxes and separation factors the attention was shifted to the modification of polymers by grafting technique. Grafted membranes were made of polyvinylidene fluoride with 4-vinyl pyridine or acrylic acid by irradiation [83]. 2-Hydroxy-3-(diethyl-amino) propyl methacrylate-styrene copolymer membranes with cyanuric chloride were prepared, which exhibited a superior separation factor /3p= 190 for a feed aromatic component concentration of 20 wt%. Graft copolymer membranes based on 2-hydroxyethyl methylacrylate-methylacrylate with thickness 10 pm were prepared [85]. The membranes yielded a flux of 0.7 kg/m h (for feed with 50 wt% of benzene) and excellent selectivity. Benzene concentration in permeate was about 100 wt%. A membrane based on polyvinyl alcohol and polyallyl amine was prepared [87]. For a feed containing 10 wt% of benzene the blend membrane yielded a flux of 1-3 kg/m h and a separation factor of 62. 

Prausnitz JM, Lichtenthaler RN, de Azevedo EG, Eds., Polymers solutions, blends, membranes and gels. In Molecular Thermodynamic of Fluid-Phase Equilibria, 3rd edition. Prentice-Hall, Int. Series in the Phys Chem Eng Science, 1996 417-505. 

Van Zyl AJ and Kerres JA. Development of new ionomer blend membranes, their characterization and their application in the perstractive separation of alkene-alkane mixtures. II. Electrical and facilitated transport properties. J Appl Pol Sci 1999 74 422-427. 

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