US1462421A

US1462421A - Electrolytic treatment of metalliferous materials containing metals of the chromium group

Info

Publication number: US1462421A
Application number: US565209A
Authority: US
Inventors: Pearson Richard Edgar
Original assignee: METAL PATENTS Ltd
Current assignee: METAL PATENTS Ltd
Priority date: 1922-06-01
Filing date: 1922-06-01
Publication date: 1923-07-17
Anticipated expiration: 1940-07-17

Description

July 17, 1923.

- R. E. PEARSON .ET AL ELECTROLYTIC TREATMENT OF METALLIFEROUS MATERIALS CONTAINING METALS OF THE CHROMIUM GROUP Filed June '1. 1922 Patented July 17, 1923.

UNITED STATES RICHARD EDGAR PEARSON, OF LONDON,

PATENT OFFICE.

AND EUSTACE NEVILLE CRAIG, OF HAM COMMON, ENGLAND, ASSIGNORS TO METAL PATENTS LIMITED, OF LONDON, ENG- LAND, A BRITISH COMPANY.

ELECTROLYTIC TREATMENT OF METALLIFEROUS MATERIALS CONTAINING METALS OF THE CHROMIUM GROUP.

Application filed June 1,

To all whom it may concern:

Be it known that we, RICHARD. EDGAR PEARSON, residing at Hanwell, London, England, and EUSTACE NEVILLE CRAIG, residing at Ham Common, Surrey, England, both subjects of the King of England, have invented certain new and useful Improvements in the Electrolytic Treatment of Metalliferous Materials Containing Metals of the Chromium Group, of which the following is a specification.

This invention is for improvements in or relating to the electrolytic treatment of metalliferous materials containing metals of the chromium-group, more particularly for use in the production of metallic powder, to be employed in the preparation of pressed and sintered bars and the like.

In classifying the metallic elements the term chromium-group is commonly used to embrace the metals chromium, tungsten, molybdenum and uranium, which have certain properties in common, and where this term occurs in the present specification and claims, it is to be interpreted in its ordinary sense as signifying the aforesaid metals.

In many ores, waste products or the like, one or other of these metals, either in a free or a combined state, is contained in substantial proportion, but may be much contaminated with other metals or substances. One object of this invention is to provide simple electrolytic means for concentrating or purifying such ores, waste products or the like.

Broadly stated, the process employed is one in which the anode reactions in. an electrolytic cell are utilized to oxidize certain materials. 1

According to this invention, a process for concentrating or purifying metalliferous material (such, for example, as crude wolframite, crude molybdenlte, or crude metallic powder) containing a chromiumgroup metal consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble, but in which the anode products to be isolated are soluble and passing a current from the anode into the electrolyte.

It is to be understood that the electrolyte 1922. Serial No. 565,209.

may be so chosen that the oxide of the chromium-group metal which is formed during electrolysis, is soluble in the electrolyte, whereas the oxides of contaminatmg metals are insoluble. In this case the oxide of the chromium'metal comes within the term anode products to be isolated. On the other hand, as more particularly described hereinafter, the electrolyte may be such that the oxides of contaminating metals are soluble in the electrolyte, whereas the oxide of the chromium-group metal is insoluble. In the latter case it will be appreciated that it is the oxides of the contaminating metals that are meant when the term anode products to be isolated is used.

When the material to be treated is an ore or the like, it is preferably powdered and intimately mixed, (for example in the form of a paste) with the electrolyte.

The metalliferous material may be agitated during the passage of current.

A suitable apparatus for carrying out one form of the process according to the present invention is one in which the metalliferous material rests upon and is supported by an anode in the form of a plate within an electrolytic cell.

It is within the scope of this invention to apply the process herein described to the treatment of waste metal (such as scrap molybdenum wire or the like) whereby powdered metallic oxide (for example molybdic oxide) is formed.

The process may also be advantageously applied to the purification of crude tungsten or molybdenum powder, as will be more fully described hereinafter.

Either an acid or an alkaline electrolyte may be employed. In the former case, when for example an ore is treated, the tungstic or molybdic oxide formed is insoluble in the electrolyte, whereas the oxides of metals (such as iron, manganese, tin, magnesium and the like) which usually contaminate the ore are, in general, soluble in the electrolyte. On the other hand, if an alkaline electrolyte be used it is the tungstic or molybdic oxide which is soluble in the electrolyte and the oxides of the contaminating metals insoluble. In both cases be dealt with and the use in the process of an acid electrolyte will be considered. Molybdenite is one of the most readily available ores of molybdenum but it contains in addition to a siliceous gangue, iron, alumina, and the like. Before this material can be utilized for the production of metallic molybdenum, it is desirable to remove the sulphur, and also to eliminate the iron,

alumina and the like. The apparatus which it is preferred to employ is shown in Figure 1 and comprises any desired number of electrolytic cells, each containing an acid electrolyte (for example an aqueous solution of sulphuric acid). Conveniently each cell is in the form of an inverted bell jar 5 into which the cathode projects from above, while the anode is a plate 6 located in the region of the bottom of the cell. The anode may be of any conducting material which is less easily oxidized than molybdenum and the cathode conveniently comprises a pertorated plate 7 of acid-resisting metal. The plate -7 is connected to a central vertical rod 8, which also forms part of the cathode.

The crude molybdenite crushed to a fine powder (for example 200 mesh) is mixed into a paste (like paint) with the electrolyte, and this paste is then introduced into each cell (which also contains the electrolyte) so that it rests upon the anode plate therein. Current at a suitable voltage, say 4-7 volts, is then passed through the cells and oxidation is continued to the desired extent, the paste if required being agitated from time to time in order to keep the surface of the anode plate clean and to bring fresh portions of the paste into contact therewith. One result of the reaction is that the iron is oxidized and selectively passes into solution in the electrolyte. Alumina is similarly eliminated. The sulphide of molybdenum is converted into oxide which is substantially insoluble in the electrolyte and therefore remains upon the anode plate, contaminated only with inert material such as silica ngue from which the molybdic oxide may easily separated, say, by ammonia treatment.

The use of an alkaline electrolyte and the application of the process to the treatment of wolframite will now be considered;

The apparatus is substantially the same as in the previous example, the electrolyte in this case, however, being a caustic soda solution (for example a 25% solution). The anode is preferably not a metal (such as iron) which is oxidized under the conditions of the operation, but an anode of nickel has been successfully used, so also has an anode of an alloy of nickel with molybdenum, (12% Mo). As before, the ore is finely powdered, mixed into a paste with the electrolyte and introduced on to the anode plate. Current is passed through the cell and oxidation is carried on to the desired extent, the paste being agitated if required during oxidation.

Wolframite is a tungstate of iron and manganese. i. e., a compound of oxide of tungsten (W0 with ferrous oxide (Feb) and manganese oxide (MnO), and the ore may contain other metals as well. Asa result of-the anode reaction, the chemical combination of the wolframite is broken up, and the iron and manganese, thus freed, are converted into higher oxides (such as Fe,(), and M11 0 which are insoluble in caustic alkali and remain as a sludge on the anode plate.

Meanwhile the tungstic oxide becomes dissolved in the electrolyte and is obtained in solution as sodium tungstate. In this way it is possible to obtain a product freed from contaminating metals and gangue, and particularly suitable for use in the production of tungsten or molybdenum powder, and finally of metallic tungsten or molybdenum.

In the third example of the application of the present invention the starting material is crude metallic tungsten (or molybdenum) powder. In the example under consideration an impure metallic powder was obtained by reduction of the commercial yellow oxide of tungsten with hydrogen in the usual way. a a- A suitable iorm of apparatus is illustrated in Figure 2 and comprises any desired number of electrolytic cells 11 each containing a sulphuric acid electrolyte, of specific gravity 1.2. In each cell is a porous pot 12 for the anode and a porous pot 13 for the cathode. Into the anode pot the crude tungsten powder mixed with electrolyte is introduced. The anode to be inserted in the anode pot, consists of a platinum wire 14, and the cathode is a stout rod 15 of lead.

The electrodes are connected to a source of direct current at a voltage of say 5 volts, the current being in the region of 3 amperes. The current density at the anode is kept as low as possible in order to avoid excessive oxidation of the metallic powder. The process is continued to the desired extent, the electrolyte being controlled so that it remains substantially acid throughout. The result of the reaction is that all those substances which migrate to the cathode, or which are oxidized at the anode into compounds soluble in the electrolyte, are removed from the tungsten powder, thereby effecting a substantial purification of the latter. The oxy-compounds of sodium, iron and manganese are removed in this way. The soda which passes to the cathode crystallizes out and the major portion of it adheres to the cathode rod with which it may be easily removed from the cell.

Preferably the contents of the anode pot on completion of the anode reaction, are washed and then transferred to the cathode compartment of an eletrolytic cell again containing a sulphuric acid electrolyte. Treatment at the cathode is carried out under substantially the same conditions as to concentration of electrolyte, voltage and current as governed the anode reaction. Conveniently, the cathode -in this case is a group of nickel-chromium rods, and the anode a rod of lead. The object of the cathode treatment is to reduce any tungsten which may have become oxidized during the anode reaction. Moreover substances which wander from the cathode to the anode (e. g. sulphur and arsenic) are removed by this treatment. Soluble silica also passes into solution and is thus eliminated. The contents of the cathode pot are washed, dried and submitted to a final reduction in hydrogen, after which the powder is ready for use in the formation of ressed and sintered bars.

f the impurities to be dealt with in the preparation of metallic powder suitable for the above use, soda usually presents very considerable difiiculties and elaborate steps have hitherto been necessary to eflect its removal. It will be seen that the process described above affords a ready and efficient means of eliminating soda from the resultant product.

The acid (or alkali) used in the electrolyte is chosen to suit the impurities to be removed, e. g. oxalic acid may be successfully used when sodium is the only predominat ing impurity; hydrochloric acid may be used if iron is the chief impurity; sulphuric acid is advantageous if one or more carbides be present; or electrolytes containing these acids may be used successively.

We claim:

1. A process for concentrating metalliferous material containing a chromiumgroup metal, which process consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble but in which the anode products to be isolated are soluble, and passing a current from the anode into the electrolyte.

2. A process for concentrating metalliferous material containing a chromiumg'roup metal which process consists in preparing an intimate pasty mixture of the metalliferous material in a powdered form with an electrolyte in which said material is insoluble, but in which the anode products to be isolated are soluble, immersing an anode in said mixture, and passing a current from the anode into the electrolyte.

3. A process for concentrating metalliferous material containing a chromiumgroup' metal which process consists in surrounding an anode with said metalliferous material and with an acid electrolyte in which the material is insoluble but in which the contaminating anode products are soluble, and passing a current from the anode into the electrolyte.

4. A process for concentrating metalliferous material containing a chromiumgroup metal which process consists in surrounding an anode with said metalliferous material and with an alkaline electrolyte in which the material is insoluble, but in which the anode products of the chromium-group metal are soluble, and passing a current from the anode into the electrolyte.

5. A process for concentrating metalliferous material containing a chromiumgroup metal, which process consists in surrounding an anode with said metalliferous material and with an electrolyte consisting of an aqueous solution of sulphuric acid, and passing a current from the anode into the electrolyte.

6. A process for concentrating metalliferous material containing a chromiumgroup metal which process consists in surrounding an anode with said metalliferous material and with an electrolyte consisting of a solution of caustic soda, and passing a current from the anode into the electrolyte.

7 A process for concentrating metalliferous material containing a chromiumgroup metal which process consists in introducing said metalliferous material on to an anode plate within an electrolytic cell containing an electrolyte in which the material is insoluble, but in which the anode products to be isolated are soluble, and passing a current from the anode into the electrolyte.

8. A process for concentrating metalliferous material containing a chromiumgroup metal which process consists in introducing into a porous anode chamber within an electrolytic cell, an intimate mixture of said metalliferous material and an electrolyte in which it is insoluble, but in which the anode products to be isolated are soluble, immersing an anode in said mixture, and passing a current from the anode into the electrolyte.

9. A process for concentrating metalliferous material containing a chroniumgroup metal which process consists in introducing into a porous anode chamber within an electrolytic cell an intimate mixture of said metalliferous material and an electrolyte in which it is insoluble, but in which the anode products to be isolated are soluble, immersing an anode in said mixture, passing a current from the anode into the electrolyte, and agitating said mixture during the passage of current.

10. A process for concentrating metalliferous material containing a chromiumgroup metal in the form of waste metal, which process consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble, but in which the anode products to be isolated are soluble, and passing a current from the anode into the electrolyte.

11. A process for concentrating metalliferous material containing a chromiumgroup metal said material being in the form of crude metallic powder, which process consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble, but in which the contaminating anode products are soluble, and passing a current from the anode into the electrolyte.

12. A process for concentrating metalliferous material containing a chromuimroup metal, said material being in the orm of crude metallic powder, which process consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble, but in which the contaminating anode products are soluble, passing a current from the anode into the electrolyte, thereafter subjecting the powder to the reducing action of the cathode of an electrolytic cell, and finally washing the reduced product and heating it in hydrogen in known manner to complete the reduction.

13. A process for purifying crude metallic tungsten powder, which process consists in surrounding an anode with said metalliferous material and with an electrolyte in which the material is insoluble. but in which the contaminating anode products are soluble, and passing a current from the anode into the electrolyte.

14. A process for purifying crude metallic tungsten powder which consists in preparing an intimate pasty mixture of said powder with an electrolyte in which it is insoluble, but in which the contaminating anode products are soluble, immersing an anode in said mixture, and passing a current from the anode into the electrolyte.

15. A process for purifying crude metallic tungsten powder which consists in surrounding an anode with said powder and with an electrolyte comprising an aqueous solution of sulphuric acid, and passing a current from the anode into the .electrolyte.

16. A process for purifying crude metallic tungsten powder which process consists in introducing an intimate mixture of said powder with an electrolyte in which it is insoluble, but in which the contaminating anode products are soluble, into a porous pot within an electrolytic cell also containing the electrolyte, immersing an anode in said mixture, passing a current from the anode into the electrolyte, and agitating the mixture during the passage of the current.

17. A process for the production of tungsten powder for use in the manufacture therefrom of pressed and sintered bars which process consists in reducing commer cial trioxide of tungsten to an impure metallic powder by reduction in known manner with hydrogen, introducing said impure powder into the anode compartment of an electrolytic cell containing an electrolyte in which said powder is insoluble. but in which the contaminating anode products are soluble, passing a direct current from the said anode into the electrolyte, thereafter subjecting the powder to the reducing action of an electrolytic cell and finally washing the reduced product and heating it in hydrogen in known manner to complete the reduction.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

RICHARD EDGAR PEARSON. EUSTAOE NEVILLE CRAIG. Witnesses:

HARRY S. GREELY, THos. ELBERT.