Liquid emulsion membrane applications

All the novel separation techniques discussed in this chapter offer some advantages over conventional solvent extraction for particular types of feed, such as dilute solutions and the separation of biomolecules. Some of them, such as the emulsion liquid membrane and nondispersive solvent extraction, have been investigated at pilot plant scale and have shown good potential for industrial application. However, despite their advantages, many industries are slow to take up novel approaches to solvent extraction unless substantial economic advantages can be gained. Nevertheless, in the future it is probable that some of these techniques will be taken up at full scale in industry. 

In this paper an overview of the developments in liquid membrane extraction of cephalosporin antibiotics has been presented. The principle of reactive extraction via the so-called liquid-liquid ion exchange extraction mechanism can be exploited to develop liquid membrane processes for extraction of cephalosporin antibiotics. The mathematical models that have been used to simulate experimental data have been discussed. Emulsion liquid membrane and supported liquid membrane could provide high extraction flux for cephalosporins, but stability problems need to be fully resolved for process application. Non-dispersive extraction in hollow fib er membrane is likely to offer an attractive alternative in this respect. The applicability of the liquid membrane process has been discussed from process engineering and design considerations. 

Draxler, J. and Marr, R. (1986) Emulsion liquid membranes part I Phenomenon and industrial application. Chemical Engineering and Processing, 20, 319. 

A liquid membrane configuration, which is much used for technical applications, is the emulsion liquid membrane (ELM) systems where the acceptor phase is dispersed as a colloid phase, each colloid drop surrounded by a thin organic, surface active phase. This principle does not seem to have been used for analytical sample preparation, probably due to the difficulty of quantitatively recovering the disperse acceptor phase. 

Noble RD and Way ID Eds. Liquid Membranes. Theory and Applications. ACS symposium series 347, ACS, Washington DC 1987. Strzelbicki J and Schlosser S. Influence of surface-active substances on pertraction of cobalt(II) cations through bulk and emulsion liquid membranes. Hydrometallurgy, 1989 23(1) 67-75. 

Cahn RP and Li NN. Commercial applications of emulsion liquid membranes. In Li NN, Calo JM, eds. Separation and Purification Technology, New York Marcel Dekker, 1992 195-212. 

Cahn, R. P., and Li, N. N., "Commercial Applications of Emulsion Liquid Membranes, presented at The Third Chemical Congress of North America, Toronto, Ontario, Canada, June 5-10, 1988. 

Emulsion Liquid Membranes Definitions and Classification, Theories, Module Design, Applications, New Directions AND Perspectives... 

Kasaini, H., Nakashio, F. and Goto, M. (1998). Application of emulsion liquid membranes to recover cobalt ions from a dual-component sulphate solution containing nickel ions. J. Membr. Sci., 146, 159-68. 

Emulsion liquid membranes (ELM) are double emulsions formed by mixing two immiscible phases and then dispersing the resulting emulsion in another continuous phase under agitation. Proposed applications for emulsion liquid membranes have included selective recovery of metal ions (1-12), separation of hydrocarbons (13 16), removal of trace organic contaminants (17-27), and encapsulation of reactive enzymes or whole cells (28-36). 

A recent study with biotechnology applications relates to amino acid extraction. Schugerl and co-workers (71 ) used a quaternary ammonium carrier in an emulsion liquid membrane system for enzyme catalyzed preparation of L-amino acids. Frankenfield et al. (72) discuss a wide variety of biomedical ELM applications including enzyme encapsulation, blood oxygenation, and treatment of chronic uremia. 

J>) reported on the application of emulsion liquid membrane technology to the recovery of uranium from wet process phosphoric acid. 

In Chapter 6, characteristic features of emulsion liquid membrane systems are examined by Yurtov and Koroleva. The effects of surfactant and carrier concentrations and external and internal phase compositions upon the properties of the extracting emulsions are discussed. Several mathematical models for the rheological curves are considered, and regions of applicability for the models are evaluated. An influence of nanodispersion formation on mass transfer through the interface and on the properties of extracting emulsions for cholesterol is demonstrated. 

In Chapter 15, Ho and Li briefly review recent advances in the theory for emulsion liquid membranes and applications in more detail. Commercial applications include the removal of zinc, phenol, and cyanide from wastewaters. Potential applications in wastewater treatment, biochemical processing, rare earth metal extraction, radioactive material removal, and nickel recovety are described. 

There is an ever increasing interest in the use of liquid membranes for performing chemical separations. Emulsion liquid membrane (ELM) systems in which the targeted chemical species in an aqueous solution is extracted with a multicomponent emulsion have a variety of applications. These include isolation and concentration of valued or harmful substances in industrial chemistry, separation of substances for determination in analytical chemistry, separation of pollutants in environmental remediation, and detoxification of biological fluids by removal of harmful substances of exogenic and endogenic origins (7). 

Carrier-facilitated transport of actinides across bulk, supported, and emulsion liquid membranes, as well as plasticized membranes and recently developed emulsion-free liquid membranes, are reviewed. The discussion includes the effects of important experimental variables upon the solute flux for various types of liquid membranes. Applications of liquid membranes in the recovery and removal of radiotoxic actinides from the nitric acid wastes generated during reprocessing of spent fuel by the PUREX process and wastes produced by other radiochemical operations are surveyed. 

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