Applications synthetic membranes

The possibility of having membrane systems also as tools for a better design of chemical transformation is today becoming attractive and realistic. Catalytic membranes and membrane reactors are the subject of significant research efforts at both academic and industrial levels. For biological applications, synthetic membranes provide an ideal support to catalyst immobilization due to their biomimic capacity enzymes are retained in the reaction side, do not pollute the products and can be continuously reused. The catalytic action of enzymes is extremely efficient, selective and highly stereospecific if compared with chemical catalysts moreover, immobilization procedures have been proven to enhance the enzyme stability. In addition, membrane bioreactors are particularly attractive in terms of eco-compatibility, because they do not require additives, are able to operate at moderate temperature and pressure, and reduce the formation of by-products. 

For biotechnological applications, synthetic membranes entrapping enzymes, bacteria, or animal cells are used in membrane bioreactors disclosing new important developments mainly due to the increased stability of immobilized enzymes, the possibility of their continuous reuse and the absence of pollution of the products. Membrane bioreactors are of great interest as well for the possibility of continuously removing metabolites whose presence in the reaction environment could reduce the productivity of the reactor. 

P. M. Bungay, H. K. Lonsdale, and M. N. de Pinho, eds.. Synthetic Membranes Science and Engineering Applications, D. Reidel Pubhshers, Dordrecht, the Nethedands, 1986. 

G. Belfort, ed.. Synthetic Membrane Processes Fundamentals and Water Applications, Academic Press, Inc., New York, 1984. 

A spinning molecule on a copper surface and a soccer-ball molecule tethered to a protein may seem no more useful than a spinning ice-skater or a tetherball. Nonetheless, advocates of nanotechnology cite a wealth of potential applications for this new field, including tailored synthetic membranes that can collect specific toxins from industrial waste and computers that process data much faster than today s best models. The list of possible benefits from nanotechnology is limited only by our imaginations. 

Application of Synthetic Membranes in Water Supply Systems in Israel... 

Sourlrajan, S., Plenary Lecture, Symposium on Synthetic Membranes and Their Application, Las Vegas, Nevada, August 25, 1980. 

P.M. Bungay, Transport Principles-Porous Membranes, in Synthetic Membranes Science Engineering and Applications, P.M. Bungay, H.K. Lonsdale and M.N. dePintio (eds), D. Reidel, Dordrecht, pp. 109-154 (1986). 

A. Golomb, Application of Reverse Osmosis to Electroplating Waste Treatment, in Reverse Osmosis and Synthetic Membranes, S. Sourirajan (ed.), National Research Council Canada, Ottawa, Canada, pp. 481-494 (1977). 

Figure 6.20 Purchase price in 2003 US dollars for ultrafiltration plants as a function of plant capacity. Data of Rogers corrected for inflation [20]. Reprinted from Synthetic Membrane Processes, A.N. Rogers, Economics of the Application of Membrane Processes, p. 454, G. Belfort (ed.), Copyright 1984, with permission from Elsevier...

The discussion of synthetic membranes can be structured in terms of the function or the structure of the membrane used in a particular application. For instance, one can consider whether a membrane is used to separate mixtures of gas molecules vs particles from liquids (function) vs whether the membrane structure is primarily microporous or dense (structure). In fact, function and stmcture are linked, but to facilitate the consideration of physical science issues related to membranes appropriate for this reference, emphasis on functional aspects are probably most appropriate. This approach reflects the fact that the use of a membrane generally involves one or more physical sci-... 

In use, most synthetic membranes involve a transport of one or more components from an upstream side of the membrane to a downstream side. Although microscopic interpretations differ between the various applications, description of the transport process for a component, A, from the upstream to the downstream side of the membrane is possible in terms of Eq. (1) ... 

TABLE I Primary Synthetic Membrane Applications and Driving Forces... 

Lonsdale, H. K., "Reverse Osmosis," in Synthetic Membranes Science, Engineering and Applications, Bungay, P.M., H.K. Lonsdale, and M.N. de Pinho eds., D. Reidel Publishing Company, Dordrecht, Holland, 1986. 

However, in view of the high-temperature capabilities of thermoplastic materials based on aromatic rings linked by thermally and oxidatively stable units such as ether, ketone, sulfone, or direct bonds,3 we have attempted to develop linear, carborane-copolymers of this same general type. We here describe synthetic and crystallographic studies of such materials, and report on their potential applications in membrane separation and in ceramic-precursor chemistry. 

Langmuir-Blodgett films may have value in many applied areas of traditional interest to the industrial chemist, such as adhesion, encapsulation, and catalysis. The permeability characteristics of monolayer assemblies may also find application as synthetic membranes for ultrafine filtration, gas separation, and reverse osmosis. For example, Albrecht et al. (44) proved the eflSciency of polymeric diacetylene monolayers on semipermeable supports in reducing the flow of CH4. One interesting possibility lies in using LB monolayers as lubricants in magnetic tape technology. Unpublished reports have indicated that frictional coeflScients can be reduced markedly when the tape is coated with a few monolayers. In applications such as those listed previously, difiSculties may well be encountered with the mechanical stability of the films. To date, relatively little research has been carried out in this area. 

The range of available membrane materials used in water and wastewater treatment is quite broad, but most of them are synthetic membranes. Synthetic membranes can be organic or inorganic however, the most important class of membrane materials is organic or polymer membrane. The choice of a given polymer as a membrane material is not arbitrary (13). Inorganic materials generally possess superior chemical and thermal stability relative to polymeric materials. However, both types of membranes have different applications. A list of common membranes is shown in Table 2. 

Lembrane science has recently received considerable attention. Membranes for industrial separations, therapeutic medical applications, and controlled release, as well as membrane barriers for packaging, have all moved from the laboratory bench to the world of commerce. Forecasts call for additional applications and expanded markets in the future. However, for membranes to proceed beyond the present level of success, further advances must be made in the materials science of membranes. The objective of this book is to compile state-of-the-art reviews of several aspects of the materials science of synthetic membranes. It is hoped that this compilation will serve as a useful reference regarding past and present developments, and that it will provide the impetus for future advances in membrane materials science. 

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