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After a brief introduction to liquid membranes, studies of supported liquid membranes (SLM) and their applications in separations of various metal species relevant to nuclear research centers are described. Aspects of coupled transport in SLM and the transport model first proposed by Danesi are outlined. Choices of membrane material and solvent which improve membrane stability in a SLM system are discussed. Recent modifications of the SLM process are mentioned. Applications of SLMs in hydrometallurgy for the separation and concentration of actinides, lanthanides, and transition metals, are reviewed. A few pilot-scale studies of SLM are described which show the potential for large-scale utilization in the future.Membrane processes, including reverse osmosis, ultrafiltration, and electrodialysis, are finding increased use in the treatment of the large volumes of low-level radioactive liquid effluents which are generated at various stages of fuel reprocessing for the nuclear fuel industry (1). These membrane processes are primarily used to achieve a significant volume reduction of the liquid wastes for subsequent processing by conventional methods. This strategy helps to reduce the equipment size for conventional plants, as well as the amount of energy and chemicals required. However, many of these membranes do not possess adequate selectivity for the separation of various radionuclides from the liquid streams. Conversely, inorganic ion exchangers and liquid membrane processes show good potential for such applications ( /).In our laboratories, research and development studies have been conducted on the separation of uranium and various lanthanides by common extractants (carriers) and of actinides by crown ether carriers using different types of liquid membrane systems. Also our studies have been directed toward determining optimal support systems for supported liquid membranes (SLM) which may offer improved flux

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pounds of water and 0.6 pound of methyl ethyl ketone, the other containing 99.4 pounds of methyl ethyl ketone and NOMENCLATURE Ffluid phase existing above critical pressure of ethylenesolvent binary at temperature of diagram L =* single liquid phase existing over entire range of watersolvent compositions, usually at low ethylene concentrations Lj * water-rich or more dense liquid phase La = solvent-rich or less dense liquid phase Pl * low pressure, about 1 to 5 atm.