High performance membrane

The electrolysis of potassium chloride [7447-40-7] KCl, to produce chlorine and potassium hydroxide in membrane cells requires similar but unique membranes. Commercial membranes currendy employed in high performance membrane electroly2ers include Du Pont s Nafion 900 series and Asahi Glass s Plemion 700 series. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

Podgornik, A., Barut, M., Jancar, J., and Strancar, A., High-performance membrane chromatography of small molecules, Anal. Chem., 71, 2986, 1999. 

Tennikov, M. B., Gazdina, N., Tennikova, T. B., and Svec, F., Effect of porous structure of macroporous polymer supports on resolution in high-performance membrane chromatography of proteins, J. Chromatogr. A, 798, 55, 1998. 

Tennikova TB, Freitag R (1999) High-Performance Membrane Chrommatography of Proteins. In Aboul-Einen HY (ed) Analytical and Preparative Separation Methods of Macromolecules. Marcel-Dekker Inc, New York-Basel, p 255... 

Tennikova, T. B., Svec, F., and Belenkii, B. G. (1990). High-performance membrane chromatography. A novel method of protein separation. J. Liquid Chromatogr. Related Technol. 13 63-70. 

Several factors contribute to the successful fabrication of a high-performance membrane module. First, membrane materials with the appropriate chemical, mechanical and permeation properties must be selected this choice is very process-specific. However, once the membrane material has been selected, the technology required to fabricate this material into a robust, thin, defect-free membrane and then to package the membrane into an efficient, economical, high-surface-area module is similar for all membrane processes. Therefore, this chapter focuses on methods of forming membranes and membrane modules. The criteria used to select membrane materials for specific processes are described in the chapters covering each application. 

The technology to fabricate ultrathin high-performance membranes into high-surface-area membrane modules has steadily improved during the modem membrane era. As a result the inflation-adjusted cost of membrane separation processes has decreased dramatically over the years. The first anisotropic membranes made by Loeb-Sourirajan processes had an effective thickness of 0.2-0.4 xm. Currently, various techniques are used to produce commercial membranes with a thickness of 0.1 i m or less. The permeability and selectivity of membrane materials have also increased two to three fold during the same period. As a result, today s membranes have 5 to 10 times the flux and better selectivity than membranes available 30 years ago. These trends are continuing. Membranes with an effective thickness of less than 0.05 xm have been made in the laboratory using advanced composite membrane preparation techniques or surface treatment methods. 

The prospects for facilitated transport membranes for gas separation are better because these membranes offer clear potential economic and technical advantages for a number of important separation problems. Nevertheless, the technical problems that must be solved to develop these membranes to an industrial scale are daunting. Industrial processes require high-performance membranes able to operate reliably without replacement for at least one and preferably several years. No current facilitated transport membrane approaches this target, although some of the solid polymer electrolyte and bound-carrier membranes show promise. 

There is also continuing research into higher-performance (high flux and high rejection) membranes to further reduce the size and cost of RO systems. Nanotechnology shows promise for having a role in the development of these high-performance membranes. 

Josic, D., Reusch, J., Loster, K., Baum, O., and Reutter, W. (1992). High-performance membrane chromatography of serum and plasma membrane proteins. J. Chromatogr. 590, 59-76. 

McMaster, R., Kruk, J., Christianson, G., Gomez, P., Warner, T., Demmer, W., and Nussbaumer, D. (1998). Purification of clinical vaccine proteins by high performance membrane chromatography. Proceedings of 18th Int. Symp. on Sep. and Anal, of Prot., Pep. and Polynucleotides (ISPPP 98), p. 29, abstract 114, Vienna. 

Tennikova TB and Svec H. High-performance membrane chromatography Highly efficient separation method for proteins in ion-exchange, hydrophobic interaction and reversed-phase modes. J. Chromatogr. 1993 646 279-288. 

Zhou D, Zou H, Ni J, Yang L, and Jia L. Fast assay and minipurification of proteins by high performance membrane affinity chromatography. Chin. J. Biotechnol. 1998 14 389-391. 

Giovannini R, Freitag R, and Tennikova TB. High-performance membrane chromatography of supercoiled plasmid DNA. Ana/. Chem. 1998 70 3348-3354. 

Josic D and Lim Y-P. Application of high-performance membrane chromatography for separation of annexins from the plasma membranes of liver and isolation of monospecific polyclonal antibodies. J. Chromatogr. B 1994 662 217-226. 

Tennikova, T.B. Freitag, R. High-Performance Membrane Chromatography of Proteins. In Analytical and Preparative Separation Methods of Biomacromolecules Aboul-Enein, H.Y., Ed. Marcel Dekker, Inc. New York-Basel, 1999 255-300. 

Hong, S.B. Row, K.H. Separation characteristics of whey protein by high performance membrane chromatography. Korean J. Chem. Eng. 2001, 16 (6), 314-537. 

The precise perovskite composition may be tailored for a specific application. To obtain a high performance membrane, however, many technical and material problems remain to be solved. This final section will focus on several issues, which are not yet well understood, but are thought to be of importance for further development of the membrane devices. 

High performance membranes can be made by immobilizing a liquid phase containing a complexation agent (carrier) in a thin porous support. 

This article aims at describing the microstructure and transport properties of these polymeric membranes from an electrochemical point of view. It is intended to provide some direction for the future development of high-performance membrane cells in industrial electrolytic or separation processes. 

Perfluorinated ionomer membranes have been developed for use as separators in chlor-alkali electrolysis cells. Using an automated test apparatus, the current efficiency and voltage drop of such a high performance membrane were evaluated as a function of several cell parameters. Results are plotted as three dimensional surfaces, and are discussed in terms of current theories of membrane permselectivity. 

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