Separation of metals

Abstract

The invention provides a process for the separation of metals, the metals being comprised as the metal oxides in a mixed oxide sample, the process comprising: (i) adding the mixed oxide to a molten salt electrolyte and cathodically electrolysing the oxide, the potential of the cathode being controlled so as to favour oxygen ionisation over deposition of metal from the cations present in the molten salt, and the applied potential difference being such as to facilitate selective reduction of one metal oxide at the expense of other metal oxides; and (ii) separating the metal from the remaining metal oxides, wherein the metal oxides comprise oxides of metals from at least one of the transition metal, lanthanide or actinide series The process is applicable to mixed oxide samples comprising mixtures of two or more metal oxides, and a particular application is in the separation of zirconium and hafnium comprised in mixed zirconium and hafnium oxides, the removal of hafnium facilitating the use of the zirconium in fuel cladding for use in the nuclear power industry.

Description

FIELD OF THE INVENTION [0001] This invention relates to a method for the separation of metals from mixtures of metal oxides and relies on the selective reduction of certain oxides to the metals, whilst the other metals remain in the form of the oxides. The method of the present invention finds particular application in the separation of transition metals, lanthanides and actinides. BACKGROUND TO THE INVENTION [0002] The prior art teaches the use of molten salts in the separation of metals and metal oxides in molten salt media. As used herein, the term “molten salts” is intended to cover salts such as lithium chloride which melts at an elevated temperature and also ionic liquids which typically are liquid at room temperature or which melt at a temperature up to about 300° C. Such techniques have found particular application in the nuclear industry, where two well-established processes are available for the treatment of irradiated nuclear fuel. [0003] The first of these processes, the...

AI Technical Summary

Benefits of technology

[0017] The process may be applied to the separation of a wide variety of metals of the transition, lanthanide and actinide series which are comprised as the oxides in mixed oxide samples. The broad usefulness and versatility of the method is illustrated by its applicability to the separation of metals from mixtures of two or more metal oxides. Thus, it is possible to apply the method of the invention to the separation of metals of the transition, lanthanide and actinide series comprised as the oxides in mixed oxide samples comprising oxides of one, two or three of the said series. In other words, the method of the invention facilitates the separation of metals from mixed oxide samples which comprise any of the following combinations:

Problems solved by technology

This process has both technical and environmental limitations.

A disadvantage of the lithium reduction process for producing a metallic feed from an oxide is the production of Li2O by-product.

Thus mixtures of uranium and plutonium oxides, together with the oxides of other actinide metals, may additionally be contaminated with oxides of other, chemically active, metals such as, for example, those associated with fission products.

The present inventors, however, recognised that there is frequently the requirement, both within the nuclear industry and the wider chemical industry, for the separation of metals from mixtures of metal oxides, and that the established technologies within these industries often provide inadequate means for the performance of such separations.