Development of efficient separation process of rare earth metals utilizing interfacial area

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The separation process for rare earth metals requires a huge energy, because the separation of adjacent elements in the rare earth series is very difficult. Thus a new method to enhance the separation efficiency is desirable to simplify the separation process. In this study, we have developed several new separation techniques for rare earth metals utilizing an interfacial area such as an oil-water or a solid-water, and the following results were obtained :1. New synergistic agents have been developed for the selective separation of rare earth metals. By the addition of a small amount of the agent, the selectivity of rare earth metals was enhanced remarkably. The difference in interaction between the synergistic agent and rare earth ions at the oil-water interface results in an increase in the separation efficiency.2. A plasma-graft polymerization technique made it possible to modify the surface of a porous hollow-fiber membrane of poly (tetrafluoroethylene) with polyacrylamide layr. Separation of rare earth metals was conducted in the hollow-fiber membrane extractor modified by plasma-graft polymerization. When the surface-modified membrane was used, the separation factor increased by the interaction between the grafted layr and metal ions. The hollow-fiber membrane modified by plasma-graft polymerization was found to be very useful as a separator of rare earth metals.3. A novel molecular imprinting technique has been developed for a metal ion-selective resin. A surface-templated resin is prepared by an emulsion polymerization using a metal ion-binding (host) monomer, a resin matrix-forming comonomer and a targer (guest) metal ion. In this study, we have prepared several metal ion-imprinted resins by the novel technique. The interfacial activity of the host monomer was found to be a key factor to produce the imprinting effect.