Synthetic membrane technology

More recendy, two different types of nonglass pH electrodes have been described which have shown excellent pH-response behavior. In the neutral-carrier, ion-selective electrode type of potentiometric sensor, synthetic organic ionophores, selective for hydrogen ions, are immobilized in polymeric membranes (see Membrane technology) (9). These membranes are then used in more-or-less classical glass pH electrode configurations. 

PhenoHc-based resins have almost disappeared. A few other resin types are available commercially but have not made a significant impact. Inorganic materials retain importance in a number of areas where synthetic organic ion-exchange resins are not normally used. Only the latter are discussed here. This article places emphasis on the styrenic and acryHc resins that are made as small beads. Other forms of synthetic ion-exchange materials such as membranes, papers, fibers (qv), foams (qv), and Hquid extractants are not included (see Extraction, liquid-liquid Membrane technology Paper.). 

Orofino, T. A. (1977). Technology of hollow fiber reverse osmosis systems. In Reverse Osmosis and Synthetic Membranes (S. Sourirajan, eds.), pp. 313-341 National Research Council, Ottawa, Canada. 

As discussed by Lonsdale , since the 1960s a new technology using synthetic membranes for process separations has been rapidly developed by materials scientists, physical chemists and chemical engineers. Such membrane separations have been widely applied to a range of conventionally difficult separations. They potentially offer the advantages of ambient temperature operation, relatively low capital and running costs, and modular construction. In this chapter, the nature and scope of membrane separation processes are outlined, and then those processes most frequently used industrially are described more fully. 

For general reading on membranes see a. T. Matsuiua, Synthetic Membranes and Membrane Separation Processes, CRC Press, Boca Raton, 1994 b. RW. Baker, in Kirk-Othmo" Encyclopedia of Chemical Technology, Vol. 16, (1995), 13... 

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. 

Wadhwani, P., Tremouilhac, P., Strandberg, E., el al. (2007) Using fluorinated amino acids for structure analysis of membrane-active peptides by solid-state 19F-NMR, in Current Fluoroorganic Chemistry New Synthetic Directions, Technologies, Materials, and Biological Applications (eds. V. A. Soloshonok, K. Mikami, T. Yamazaki, et al.), American Chemical Society, Washington, D.C., pp. 431 —446. 

Strathmann, H. Synthetic membranes and their preparation. In Handbook of Industrial Membrane Technology, Porter, M.C., Ed. Noyes Publications Westwood, New Jersey, 1990 1 pp. 

Rozelle, L.T. Cadotte, J.E. Cobian, K.E. Kopp, C.V., Jr. Nonpolysaccharide membranes for reverse osmosis NS-lOO membranes. In Reverse Osmosis and Synthetic Membranes, Theory—Technology— Engineering , Sourirajan, S., Ed. National Research Council of Canada Ottawa, 1977 249-261. 

Sourirajan, S. (ed.) (1977). Reverse Osmosis and Synthetic Membranes Theory—Technology— Engineering, National Research Council. 

Membrane separation is a relatively new and fast-growing field in supramolecular chemistry. It is not only an important process in biological systems, but becomes a large-scale industrial activity. For industrial applications, many synthetic membranes have been developed. Important conventional membrane technologies are microfiltration, ultrafiltration, electro- and hemodialysis, reverse osmosis, and gas separations. The main advantages are the high separation factors that can be achieved under mild conditions and the low energy requirements. 

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