Electrolysis: processes – compositions used therein – and methods – Electrolytic process involving actinide series elements or... – Plutonium
Patent
1996-04-25
1998-07-28
Phasge, Arun S.
Electrolysis: processes, compositions used therein, and methods
Electrolytic process involving actinide series elements or...
Plutonium
25 46, 25768, C25D 2110, C21F 900
Patent
active
057858365
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the electrolytic treatment of material. In particular, it relates to apparatus and a method for treating a body of conducting material.
The use of gas bubbling or sparging in electrochemical process is known. Examples of such processes are disclosed inn Patent Specifications GB 1091157, GB 1392705, GB 2182259A, U.S. Pat. No. 3,875,041 and U.S. Pat. No. 4,263,120. However, in the constructions described the bubbling or sparging is carried out in a controlled manner at electrode surfaces in order to promote processes such as electrodeposition or electrolytic etching.
Applicants' GB 2269601A describes a method of treating scrap graphite contaminated with metal electrolytically whereby graphite and metal may be separated and treated or disposed of in different ways. The use of sparging is proposed.
However, GB 2269601A does not envisage a practical arrangement for carrying out the sparging and it is therefore an object of the present invention to provide such a practical arrangement. The present invention provides an apparatus and method for electrolytically treating bodies of conducting material such as graphite in a manner similar to that described in GB 2269601A.
According to the present invention there is provided a method of treating a body of conducting material electrolytically which comprises the steps of placing the material to be treated in an aqueous oxidising electrolyte, passing an electric current through the electrolyte and the material to be treated and sparging the electrolyte with gas, characterised in that the material to be treated is placed in a basket comprising a conducting frame having an insulating container fitted therein, the basket being insertable in and removable from the electrolyte as desired, wherein the insulating container is removable from the conducting frame, the frame having retaining means for receiving the insulating container, the container including a base having perforations to allow electrolyte to contact the material to be treated and wherein the electrolyte is sparged with gas in the region where the material to be treated is in contact with it, the gas being supplied by a plurality of pipes extending across the electrolyte at a location beneath the perforated base of the insulating container, the pipes each having a plurality of gas outlet holes directed towards the material to be treated.
Sparging of the electrolyte in the manner described allows a substantial surface area of the electrolyte around the material to be treated to be sparged simultaneously.
The material to be treated may comprise a porous mass. It may comprise scrap graphite to be separated from metal adhered thereto. The metal may for example comprise one or more hazardous, eg toxic or radioactive, elements such as uranium and or plutonium. Such elements may be present in compound form, eg as oxides.
The electric current may be a directional current.
The conducting material to be treated, eg graphite body, disintegrates in the electrolyte and any metal present dissolves at an accelerated rate under the influence of the electric current. The metal can also break off from the graphite and may dissolve over a longer time period in the electrolyte. The graphite so treated may therefore be separated by filtering and washing. Where the graphite has been contaminated with uranium and/or plutonium the separation by this process is sufficiently successful to allow the graphite to be disposed of in a conventional manner rather than by special means required for hazardous, radioactive materials.
Where scrap graphite is treated by the method of the present invention the scrap graphite may contain less than 40 percent, in most cases less than 10 percent by weight, eg from 2 to 6 percent by weight of contaminant metal so that the metal is a minor by-product to the separation process (in terms of its quantity).
The electrolyte is desirably a strong acid, eg nitric and/or sulphuric acid. Its concentration is preferably in the range 5 to 70 percent by weight of acid: aqueous soluti
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patent: 429386 (1890-04-01), Parrish
patent: 1600730 (1926-09-01), Haffner
patent: 2903402 (1959-09-01), Fromm, Jr.
patent: 3875041 (1975-04-01), Harvey et al.
patent: 4263120 (1981-04-01), Berndt et al.
British Nuclear Fuels PLC
Phasge Arun S,.
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