Refractory metals such as vanadium, chromium, molybdenum, wolfram and rhenium are widely used as a catalyst component in the petroleum refining industry. Recycling of those materials generates solutions containing combinations of these metals together with catalytic elements such as cobalt, nickel and platinum group metals. The separation and recovery of those metals from leach solutions by the use of liquid-liquid extraction is well documented. Liquid-liquid extraction for the treatment of solutions containing only minor concentrations of metals, as in effluents, is not recommended because of the high ratio of solvent inventory towards the metal content of the solutions to be treated. Liquid-liquid extraction also may lead to contamination of the effluent with organic components or other entrained chemicals, which have to be avoided if the treated solution is to be drained into a common sewage purification unit. Presentation of the liquid ion exchanger as a thin membrane between feed and receiving solution reduces considerably the solvent inventory while keeping the excellent separative and concentrating capacities of the liquid ion exchange solution. In this paper results will be presented concerning the recvoery of molybdenum and rhenium from an effluent generated ina molybdenumsulphide roaster unit. From these results it may be concluded that a Supported Liquid Membrane (SLM) configuration can be used to recover both metals from the gaswash effluent. It will also be demonstrated that by pH control of the feed, rhenium can be recovered selectively from this effluent as a concentrated sodiumperrhenate solution.
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