US3025224A - Process for isolating isotopes of alkali metals - Google Patents

Process for isolating isotopes of alkali metals Download PDF

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Publication number
US3025224A
US3025224A US781084A US78108458A US3025224A US 3025224 A US3025224 A US 3025224A US 781084 A US781084 A US 781084A US 78108458 A US78108458 A US 78108458A US 3025224 A US3025224 A US 3025224A
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cathode
isotopes
anode
electrolyte
nitric acid
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Expired - Lifetime
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US781084A
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English (en)
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Kepes Andre
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/228—Terminals
    • H01G4/236—Terminals leading through the housing, i.e. lead-through
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D59/00—Separation of different isotopes of the same chemical element
    • B01D59/38—Separation by electrochemical methods
    • B01D59/42—Separation by electrochemical methods by electromigration; by electrophoresis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G2/00—Details of capacitors not covered by a single one of groups H01G4/00-H01G11/00
    • H01G2/02—Mountings
    • H01G2/04—Mountings specially adapted for mounting on a chassis

Definitions

  • the electrolyte When, in the case, for example, of two isotopic cations the electrolyte is moved against the flow of the cations at a speed between the speeds of the cations, the faster of the cations will continue to progress upstream while the slower cation will be carried downstream.
  • This is the principle upon which the process of separating isotopes by electromigration against a stream of electrolyte is based. This is more eflicient and the yields is higher than in the case of simple electromigration of the known types.
  • the movement of the electrolyte from the cathode toward the anode is generated by regenerating the electrolytic medium, which is preferably a molten salt, from the metal which has been deposited on the cathode.
  • the flow of electrolyte will be from the cathode toward the anode, and the flow of cation will be from the anode toward the cathode.
  • the isotopes which migrate more rapidly will thus be deposited on the cathode, while those which migrate less rapidly will be carried downstream by the flow of the current of electrolyte.
  • the flow may be maintained by regenerating the metal deposited on the cathode.
  • apparatus of vertical type is particularly inefiicient because of the presence of gas bubbles which inevitably appear during the electromigration and pass upwardly through the electrolytic medium. These bubbles disturb the selective migration of the ions by their irregular ascension through the molten salts.
  • the vertical disposition of the apparatus is especially ineflicient because it is difficult to establish the same temperature in all of the salts, and this also disturbs the selective migration of the ions.
  • Another object of the invention is to replace the unsatisfactory mixture of N0 and O in the regeneration of nitrate salt of the electrolyte.
  • Another object is to overcome the disadvantages inherent in the vertical apparatus heretofore employed.
  • the electrolyte may be horizontally arranged, nitric acid should be employed to regenerate the nitrate salt by reaction with the metal deposited on the cathode, and the rate of flow of the electrolyte should be controlled either by the rate of admission of HNO to the electrode, or by inclining the electrolyte toward the anode, or both.
  • a particularly advantageous method of carrying out the invention is to put the electrolyte into a horizontal apparatus of a novel type, which constitutes a part of the present invention.
  • This apparatus is comprised essentially of anode and cathode compartments connected by a substantially horizontal channel, or by a plurality of channels.
  • the apparatus may have dilterent forms, elongated or otherwise, always on the condition that the position of the electrolyte between the electrodes and the channels shall, at the beginning be on the same level, and that thereafter permanent current shall be set up from the cathode toward the anode which is opposed to the direction of electromigration.
  • This movement of the electrolyte is naturally established by the electrolytic decomposition of the nitrate which, by loss of matter on the anode in the form of nitrous vapors and by increase of the electrolytic medium at the cathode by chemical recombination with the nitric acid, establishes a permanent inclination between the opposite ends of the eleectrolyte.
  • this movement is generally retarded and is regulated by changing the inclination of the apparatus with respect to the horizontal, thus making it possible to control the speed of flow of the electrolyte.
  • the canal which connects the compartments and contains the electrode, is preferably filled with some inert granular material, through which the molten nitrate extends in order to reduce convection currents.
  • Inert satis factory materials are powders of steatite, zirconia, polytetrafluorethylene. No particular size of granule is necessary, although the granules should not be too coarse, as they would probably atfect the opposition to convection currents; neither should they be too fine, as they might interrupt the regularity of the fiow. It follows that the movement of the electrolyte can be controlled by altering the size of the granules which fill the channel and also by the inclination of the apparatus.
  • the anode and cathode compartments in which the electrodes are situated, immersed in the molten nitrate, are preferably deeper than the canal.
  • the electrodes, and more particularly the cathode are preferably provided with a large surface. They can also be made of metals which are resistant to nitric acid, such as a chemically resistant steel for the cathode and platinum for the anode.
  • the cathode compartment is supplied with nitric acid, preferably in vapor phase, by gravity or by siphon from a reservoir of concentrated nitric acid (commercial grade) through a heating tube at 120-130 C.
  • this tube is beneficially filled with a material inert to nitric acid, for instance, in granular form.
  • the nitric acid is brought to a temperature at which the water azeotrope of nitric acid boils, and in this way it is vaporized without appreciable decomposition. It is advantageous to admit an excess of acid with respect to the quantity of water deposited at the cathode with which the acid is to react.
  • FIG. 1 is a longitudinal vertical section through apparatus representative of the invention
  • FIG. 2 is a cross-section on the line IIII of FIG. 1, and
  • FIG. 3 is an enlarged detail of the cathode end of the apparatus of FIG. 1, in vertical-longitudinal section.
  • the apparatus comprises a parallel pyrolitic block 1 of high-frequency steatite, elongated and of rectangular section, having very low porosity and fired at about 1400 C.
  • a block Prior to the firing, a block was provided with a channel 2 relatively deep compared to its width and with two cylindrical cavities 3 and 4 at its extremities. These cavities were deeper than the canal and communicate with it by a series of oblique holes 5.
  • the block itself is contained in a cylindrical furnace 8 which may be made of a glass tube about which is coiled an electrical heating coil 9.
  • the tube is closed at its extremities by closures; at the anode side, two appendages 10 permit the entrance of air, or of a thermometer if desired.
  • the tubular furnace 8 above the cathode has a large opening extended by a tube 12 which is fixed or not to the tube 8 which holds the cathode in place and permits the introduction of lithium nitrate at the beginning and during the operation.
  • a cover 13 of polytetrafluorethylene closes the tube at its upper end.
  • the tube itself may be covered with a heating coil if desired.
  • the two extremities of the furnace, or only one of them, may be separable as indicated at 8-a.
  • the anode 7 may be composed of a platinum wire ending in a spiral immersed in the molten salt. Its upper end is connected to a generator of direct current, either through the end of the tube or through the tube itself.
  • the cathode 6 (FIG. 3) plays the roles of electrode, cathode and supply tube for nitric acid vapors. It is constituted of a central tube 15 carrying at its lower extremity a receptable 16 which is pierced with a number of holes 17 and filled with small metallic fragments 18. Orifices 15-a allow the tube 15 to communicate with the interior of the receptacle 16.
  • the tube, receptacle and metallic fragments may be composed of refractory steel sulficiently high melting to Withstand the temperature and sufiiciently inert to the acid to remain unaffected by disruption.
  • the metallic tube of the cathode at its upper part is connected by connection 19 to the tube which receives the liquid nitric acid 20.
  • This tube has a heating zone 21 at the temperature which vaporizes the nitric acid.
  • the valve 22 interrupts the feed of liquid nitric acid it necessary.
  • the central part of the cathode tube the part serving for the introduction of acid extending between the connection 19 and the valve 22, is filled with quartz wool 23.
  • the upper part of the cathode compartment is covered by a cylindrical lid 24- mounted in the block and of the same interior diameter as the compartment itself.
  • a cover 25 closes the upper part except for the central hole through which the electrode passes and several oblique holes which permit the escape of nitric acid vapors.
  • the cylindrical lid and its cover are of calcined steatite, the same as the block.
  • the anode compartment is closed in the same way by a small steatite cover 26 having a central hole for the passage of the electrode and small lateral holes for the escape of gases.
  • the channel 2 contains a fill 27 of small depth, for example several millimeters, constituted by calcined steatite particles of sizes AFNOR 35 to 60.
  • the block in which the electromigration takes place need not be of a single piece but of conforming elements and profile which are united with each other by plastic joints, for example of polytetrafluorethylene.
  • This structure permits the dismounting and facilitates the entering of the anode and cathode compartments at the end of the operation.
  • heating which may be obtained by the introduction of heating wires into the interior of the furnace and exteriorly provided with temperature regulating means.
  • a number of units such as described above may be used in cascade to carry out the process continuously. This is accomplished by a system of supply and interconnection having as an object to continue the separation of isotopes until one has attained an enrichment of the desired magnitude.
  • Example 1 The apparatus having been assembled but with the electrodes not yet energized, the heating coil was energized and the apparatus was brought to the temperature at which lithium nitrate had been fused and was poured into the cathode compartment, from which it flowed to and filled the anode compartment.
  • the addition of molten salt was ended when the level approached the top of the granular steatite which filled the channel and of which the size of particle was between AFNOR 35 and 60.
  • the cathode cover was replaced.
  • a difference of potential was applied to the electrode so as to produce a flow of about 0.3 ampere.
  • the nitric acid was passed through the vaporizer and into the cathode compartment, the rate of supply being regulated either by valve 22 or by tilting the apparatus so as to produce an inclination of the channel.
  • the acid was supplied in an excess with respect to the lithium deposited at the cathode, which is to say, about 200 cm? concentrated acid for 24 hours.
  • Li was equal to 11.35. At the end of the 72 hours the proportion was 11.95 at the anode and 10.8 at the cathode. The factor of accretion of the apparatus was consequently equal to 11.95/ 10.8 for a mass of lithium nitrate of the order of 20 grams.
  • the invention includes a process for separating isotopes of the alkali metals, of which lithium has been given hereinabove as a specific example.
  • the separation is carried out by migration against a stream of electrolyte flowing at a speed between the speeds of migration of the isotope ions.
  • the electrolyte is the nitrate of the metal whose isotopes are desired.
  • a distinguishing feature of the invention is the regeneration of the alkali metal nitrate in the cathode compartmen-t by means of nitric acid acting on one of the deposited isotopes.
  • the nitric acid is preferably vaporized before introduction into the cathode compartment, the preferred temperature of vaporizaiton being that of the boiling point of its water azeotrope.
  • Another distinguishing feature of this invention is the horizontal flow of the electrolyte.
  • the invention also involves novel apparatus in which anode and cathode compartments are connected by one or more horizontal channels in which a current of electrolyte flows from the cathode to the anode, the speed of flow being controlled by tilting the channels appropriately.
  • the channels are lined with an inert granular filler which reduces convection currents, controls horizontal flow, and tends to maintain uniformity of current flow through the electrolyte.
  • the anode and cathode compartments are preferably deeper than the connecting canal.
  • the cathode may conveniently be in refractory steel and the anode in platinum.
  • the nitric acid is supplied in vapor form from an acid reservoir containing concentrated nitric acid and flows to the cathode compartment through a heating tube at a temperature of l20-l30 C.
  • the apparatus is enclosed ina heated tube which maintains the molten condition of the electrolyte and from which the vapors rising from the system can be removed.
  • the method of separating isotopes that comprises fusing lithium nitrate at about 280 C., flowing electrolytic current through the lithium nitrate, between an anode and a cathode immersed in the electrolyte, thereby dissociating it and providing ions Li and Li, the difference in potential between the points of entrance and exit of the current producing about 0.3 ampere, flowing the electrolyte toward the anode at a rate similar to that produced by a physical gradient of 1 in 400, and regenerating the Li deposited on the cathode -by bringing vaporized nitric acid in contact therewith, the quantity of HNO added being in excess with respect to the Li deposited on the cathode by about 200 cm.
  • the method of separating isotopes of an alkali metal that comprises forming an electrolytic bath of molten alkali metal nitrate, flowing the bath from the cathode to the anode, through inert, finely divided material, at a speed between the speeds of migration of the isotope ions, passing an electrolytic current through the electrolyte between the electrodes, regenerating substantial quantities of the metal deposited at the cathode by reacting it with nitric acid vapor, and removing the gases released by the electrolysis and the reaction.
  • the step of separating isotopes of an alkali metal comprises forming an electrolytic bath of molten alkali metal nitrate between electrodes, flowing the electrolyte toward the cathode at a speed between the speeds of migration of the isotopes and passing an electrolytic current between the electrodes through the electrolyte, the step of regenerating substantial quantities of the alkali metal nitrate from the metal deposited at the cathode, by introducing nitric acid in the cathodic compartment.
  • a method of separating isotopes which comprises fusing an alkali metal nitrate, passing an electrolytic current through the molten salt, flowing the salt from a cathode toward an anode at a speed between the speeds of migration of the isotopes, regenerating an alkali metal nitrate at the cathode by reacting the metal deposited at the cathode with HNO and subjecting the regenerated alkali metal nitrate to electrolysis in a stream of an alkali metal nitrate proceeding toward an anode at a speed between the speed of migration of the isotopes.
  • the method of separating the metal isotopes of an alkali metal nitrate that comprises fusing the nitrate, passing an electrolytic current therethrough, flowing the fused nitrate toward the anode at a speed between the speeds of migration of the isotopes, and reacting the isotopes at the cathode with nitric acid, thereby restoring alkali metal nitrate to the fused electrolyte and subjecting the cathodic concentration of isotopes to further separation.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electrochemistry (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Molecular Biology (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
US781084A 1957-12-20 1958-12-17 Process for isolating isotopes of alkali metals Expired - Lifetime US3025224A (en)

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FR754308 1957-12-20

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US (1) US3025224A (xx)
CH (1) CH377789A (xx)
DE (1) DE1081439B (xx)
FR (1) FR1207421A (xx)
GB (1) GB888884A (xx)
LU (1) LU36689A1 (xx)
NL (1) NL112924C (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257293A (en) * 1959-04-03 1966-06-21 Commissariat Energie Atomique Process and apparatus for controlling a counter-current electromigration installation
US3382164A (en) * 1965-01-26 1968-05-07 Atomic Energy Commission Usa Separation of cesium and strontium by electrodialysis
US3508968A (en) * 1962-05-28 1970-04-28 Energy Conversion Devices Inc Thermoelectric device
US3620958A (en) * 1968-09-30 1971-11-16 Philips Corp Device for electrophoretic analysis using a capillary tube with detection means

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4603664B2 (ja) * 2000-09-08 2010-12-22 独立行政法人 日本原子力研究開発機構 リチウム同位体分離方法とその装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1018802A (en) * 1910-10-27 1912-02-27 Nitrogen Company Method of producing nitrogen compounds.
US2566308A (en) * 1947-02-07 1951-09-04 Aubrey K Brewer Process and apparatus for the electrochemical separation of chemicals by ion migration
US2645610A (en) * 1942-02-25 1953-07-14 Atomic Energy Commission Process for the separation of isotopic ions
US2813064A (en) * 1952-03-18 1957-11-12 Clark Albert Isotopic fractionation process of uranium

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1018802A (en) * 1910-10-27 1912-02-27 Nitrogen Company Method of producing nitrogen compounds.
US2645610A (en) * 1942-02-25 1953-07-14 Atomic Energy Commission Process for the separation of isotopic ions
US2566308A (en) * 1947-02-07 1951-09-04 Aubrey K Brewer Process and apparatus for the electrochemical separation of chemicals by ion migration
US2813064A (en) * 1952-03-18 1957-11-12 Clark Albert Isotopic fractionation process of uranium

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257293A (en) * 1959-04-03 1966-06-21 Commissariat Energie Atomique Process and apparatus for controlling a counter-current electromigration installation
US3508968A (en) * 1962-05-28 1970-04-28 Energy Conversion Devices Inc Thermoelectric device
US3382164A (en) * 1965-01-26 1968-05-07 Atomic Energy Commission Usa Separation of cesium and strontium by electrodialysis
US3620958A (en) * 1968-09-30 1971-11-16 Philips Corp Device for electrophoretic analysis using a capillary tube with detection means

Also Published As

Publication number Publication date
NL112924C (xx) 1966-06-15
CH377789A (fr) 1964-05-31
LU36689A1 (xx) 1959-06-17
GB888884A (en) 1962-02-07
DE1081439B (de) 1960-05-12
FR1207421A (fr) 1960-02-16

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