The Use of Lanthanide Triflates as a Method for Reducing Ytterbium(III) to Ytterbium(II)

High purity lutetium (99.999%) is employed in the manufacture of cerium-doped lutetium oxyorthosilicate. Such lutetium is in high demand because the cerium-doped lutetium oxyorthosilicate is the best gamma-detecting scintillator known. Solvent extraction is the most widely used method for separating the rare earths on an industrial scale at 99.999% purity. However, this process is time consuming and requires 80-100 separation stages. The major difficulty in pure lutetium production is the separation from the adjacent element, ytterbium. If ytterbium(III) could be reduced to ytterbium(II), this would permit a different chemistry between ytterbium(II) and the trivalent state elements, allowing a more facile separation process by opening the separation gap between ytterbium and lutetium. This has been previously achieved through the use of mercury cathodes or amalgams. Unfortunately, any process involving mercury is unacceptable industrially because of the toxicity of mercury. Literature has shown that reduction with magnesium metal can be carried out with proper selection of solvent. A maximum amount of 85% ± 5% can be obtained. The ideal system would be one which would remove all of the ytterbium(III). This project was performed to develop a more efficient reduction by the use of the triflate system. Anhydrous solutions were used in the project because of the capability of water to oxidize ytterbium(II) to ytterbium(III). With the set of systems that were attempted, about 50% ytterbium(II) was achieved. The hypothesis that the absence of water would increase the percent recovery of ytterbium did not solve the problem.