Composite oxide membranes

Konno, M., M. Shindo, S. Sugawara and S. Saito. 1988. A composite palladium and porous aluminum oxide membrane for hydrogen gas separation, J. Membr, Sci. 37 193-97. 

All oxidants used must be removed in the final stage of the pretreatment process, as they are known to damage most polymer membranes used for desalination. In particular, chlorine is known to be harmful to commonly used thin-film composite polyamide membranes. 

These membranes have exceptional properties, including seawater salt rejections of up to 99.6 % and fluxes of 23 gal/ft2 day at 800 psi. Unfortunately, they are even more sensitive to oxidants such as chlorine or dissolved oxygen than the polyamide/polyurea interfacial composites. The membranes lose their excellent properties after a few hundred hours of operation unless the feed water is completely free of dissolved chlorine and oxygen. A great deal of work was devoted to stabilizing this membrane, with little success. 

First, the thermal stabilities of the membranes are improved by the addition of other oxide(s). Specifically, the mixed oxide membranes will retain their pore sizes and porosities when heated to a temperature at least about lOO C higher than the temperatures which would degrade the pore size and porosity of single oxide membranes. TiOz-ZtOz membranes with varying compositions have been proven to be the case. Moreover, other mixed oxide membranes containing Ti-Nb and Ti-V [Anderson et al., 1993] and AbBa and Al-La [Chai et al., 1994] are additional examples. 

Lin Y.S., de Vries K.J., Brinkman H.W. and Buiggraaf A.J., Oxygen semipermeable solid oxide membrane composites prepared by electrochemical vapor deposition, 7. Membr. ScL 66 211 (1992). 

In other respects, we can consider zeohte membranes as pertaining to the ceramic material category. Indeed zeolites are classified for the most part as microporous, crystalline silico-aluminate stmctures with different alumininum/silicon ratios. Thus, the chemical compositions are close to those of ceramic oxide membranes, in particular of microporous silica and alumina membranes. On the other hand, zeohtes are crystalline materials and they have a structural porosity very different from microporous amorphous silica [124]. Zeohte membranes are well adapted to the separation of gases, in particular H2 from hydrocarbons, but these membranes are not very selective for the separation of mixtures of noncondensable gases. 

Composite metal membranes are most often the structure of choice when a reactive group 3-5 metal or alloy is the principle constituent of the membrane. The relative chemical reactivity of these metals dictates that an inert coating must be applied to at least the feed surface of the membrane. Palladium, or better yet a palladium alloy, customarily serves as the coating layer. If it can be guaranteed that the permeate side of the membrane will never be exposed to reactive gases (e.g., water, carbon oxides, and hydrocarbons), then a two-layer composite membrane is a satisfactory choice. However, normal operating procedures and the potential for process upsets typically favors the selection of a three-layer composite structure. 

Y.S. Lin, K.J. de Vries, H.W. Brinkman and A.J. Burggraaf, Oxygen semipermeable solid oxid membrane composites prepared by electrochemical vapor deposition. J. Membr. Sci, 66 (1992) 211-226. 

Matsuura, T. Reverse osmosis and nanofiltration by composite polyphenylene oxide membranes. In Polyphenylene Oxide and Modified Polyphenylene Oxide Membranes, Gas, Vapor and Liquid Separation Chowdhury, G., Kruczek, B., Matsuura, T., Eds. Kluwer Academic Boston, 2001 181-212. 

Since TTA is poorly oxidizable it is likely to be esterified into other lipids, primarily phospholipids. Thus, TTA readily enters the cell membrane in which it influences membrane properties. Moreover, TTA treatment influences the PUFA composition of membranes. As TTA changes the membrane PUFA content and possesses antioxidant properties, it may influence the susceptibility to lipid peroxidation. In addition to functioning as an antioxidant itself, TTA changes the antioxidant defense system in hepatocytes. This indicates that TTA affects the cellular oxidative situation. 

Sforca M, Nunes SP, and Peinemann KV, Composite nanofiltration membranes prepared by in-situ polycondensation of amines in a poly(ethylene oxide-b-amide) layer. Journal of Membrane Science 1997,135,179-186. 

Use of nanofiltration for non-aqueous separations is limited by membrane compatibility - a common material in composite nanofiltration membranes used for aqueous separations is polysulfone which possesses limited solvent resistance [134]. However, during the past two decades a number of materials have emerged with improved solvent resistance that have enabled a broad range of organic solvent nanofiltration (OSN) applications. These materials include polydimethylsiloxane, polyphenylene oxide, polyacrylic acid, polyimides, polyurethanes, and a limited number of ceramics. Commercial products are offered by Koch Membrane Systems, W.R. Grace, SolSep, and Hermsdorfer Institut fur Technische Keramik (HITK) [135]. 

Chemical in Japan where membrane cells are now dominant. Because of their Teflon -like chemical composition, perfluorinated membranes resist chemical and thermal degradation better than any of the hydrocarbon ion-exchange membranes that preceded them. For most of them the starting materials are perfluorinated monomers such as tetrafluoroethylene (TFE) CF2=CF2 and hexa-fluoropropylene oxide (FIFPO)... 

Hoehn HH (1985) Aromatic polyamide membranes. In Lloyd DR (ed) Materials science of synthetic membranes. ACS Symposium Series 269. American Chemical Society, Washington, DC, p 81 Matsuura T (2001) Reverse osmosis and nanofiltration by composite polyphenylene oxide membranes. In Chowdhury G, Kruczek B, Matsuura T (eds) Polyphenylene oxide and modified polyphenylene oxide membranes. Kluwer, Dordrecht, p 181... 

Yang CC, Chiu SJ, Lee KT, Chien WC, Lin CT, Huang CA (2008) Study of poly(vinyl alcohol)/titanium oxide composite polymer membranes and their application on alkaline direct alcohol fuel cell. J Power Sources 184 44-51... 

Yang CC, Chien WC, Li YJ (2010) Direct methanol fuel cell based on poly(vinyl alcohol)/ titanium oxide nanotubes/poly(styrenesulfonic acid)(PVA/nt-Ti02/PSSA) composite polymer membrane. J Power Sources 195 3407-3415... 

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