US1345846A - Process of extracting metals from their ores - Google Patents

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w. E. GEEENAWALT. PROCESS OF EXTRACTING METALS FROMTHEIR ORES.

' APPLICATION FILED DEC. 13, 1 915. RENEWED SEPT. 15, 1919. 1,345,846.

. Patented July 6, 1920.

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WILLIAM E. GREENAWALT, OF DENVER, COLORADb.

PROCESS OF EXTRAC'IING METALS FROM THEIR ORES.

To all whom it may concern:

lie it known that I, WILLIAM E. GREENA WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful Improvements in Processes of Extracting Metals from Their Ores, of which the following is a specification.

This invention relates generally to processes ofextracting metals from their ores, and more particularly to those methods involving electrolytic deposition of the metals extracted from the ore by solvent of the metal. lts object is to render the process more efficient and to overcome, or reduce, the effect of deleterious salts in the solution during electrolysis.

The process will be described more particularly in its application to the extraction of copper from its ores, to the conditions of which it is eminently adapted. although it is in no wise intended to limit it to this use alone.

In the electrolysis of impure copper solutions, asfor example those obtained from leaching copper ores with a sulfate solution,

there is always present iron sulfate which injuriously affects the operation. Ferrous sulfate in the electrolyte is not particularly harmful, but the ferric sulfate is highly detrimental.

If a solution of copper sulfate, containing ferrous sulfate, is electrolyzed, copper is deposited at the cathode While sulfuric acid and ferric sulfate are produced at the anode, as represented by the following equations:

The ferric sulfate, finding its way back to the cathode, combines with the deposited copper and is again reduced to the ferrous condition, thus representing a loss of efficiency, as represented by the equation:

if, however, the ferric sulfate can be reduced at the expense of a comparatively cheap reducing agent, such as hydrogen sulfid, copper sulfid, or sulfur dioxid, then the iron in the electrolyte loses its ability to combine with the deposited copper, while at Specification of Letters Patent.

Patented July 6,1920.

7 Application filed December 13, 1915, Serial No. 66,621. Renewed September 15, 1919. Serial No. 323,997.

the same time, an equivalent of acid is regenerated, as shown by the following equations:

The present method of carrying out these reactions will now be described, as applied to the treatment of copper ores.

The ore, treated raw if an oxid and roasted if a sulfid, isleached with water or a sulfate solution, such as dilute sulfuric acid. The rich copper sulfate solution, resulting from the leaching, is electrolyzed to deposit the copper, while at the same time an equivalent of acid is regenerated. The rich copper solution will inevitably contain some iron sulfate, and in the electrolytic deposition of the copper will give trouble. To overcome this there is introduced into the electrolyte a substance capable of reacting with the ferric salts, by first combining the substance with an insoluble carrier, such as sulfur or charcoal. To carry this out, cop per is combined with the sulfurfand sulfur dioXid with the charcoal.

Tf copper is combined with the sulfur, the ore after having been leached and filtered for the rich copper solutions to be electrolyzed, is then washed to remove the remaining soluble copper, which results in a lean copper solution. This lean copper sulfate solution cannot be effectively electrolyzed and is precipitated in some other way. For the purpose of this process the lean, or very foul, copper solutions, which cannot be effectively electrolyzed are treated with hydrogen sulfid, when the copper in the solution combines with the sulfur of the hydrogen sulfid to form'copper sulfid. This copper sulfid is finely divided, and when filtered from the solution is in a comparatively pure and concentrated form, and in an ideal condition to react with the ferric salts in the electrolysis of the rich solutions. This cop per sulfid is then applied to the electrolyte, or rich copper solutions, to react with the variable valent compounds, such as the ferric salts. The method of applying it will be described later.

If sulfur dioxid is to be used, either alone or in connection with the copper sulfid, it cannot be effectively applied in its gaseous condition, for, the gas, per se, is only slightly soluble in water and the reaction with the variable valent salts is slow. To more effectively apply it,'it 1s first combined with finely pulverized charcoal.-

v the chemical industry. ,The'charcoal, heavily charged with sulfur dioxid, can then be applied to the electrolyte, or rich copper solutions, with no perceptible liberation of the free gas. In this way the gas may be brought in intimate and effective contact with the variable valent elements, while the charcoal remains unaffected and may be re used as often as desired.

.In applying the copper sulfid, or sulfurdioxid and charcoal, to the electrolyte, or rich copper solutions, an apparatus such as shown in the accompanying drawings is preferred. .In these drawings Figure 1 represents a cross section of an electrolyzer; Fig. 2 partlongitudinal section and elevationyFigs. 3 and 4 a detail elevation and section of the diaphragm; Fig. 5 a detail section of the bottom of the electrolyzer, and Fig. 6 a detail section of cathodes.

In the drawings, 1 represents an electrolytic tank, 2 the diaphragms, 3 the anode, 4 the cathodes, 5 a pipe having perforations 6 by means of which air or other gas is introduced into the anode compartment of the electrolyzer and is regulated by the valve 7. 8 and 9 represent respectively the pipes by means of which the electrolyte is introduced into the anode and cathode compartments of the electrolyzer, and 10 and 11, respectively the pipes through which the electrolyte is withdrawn. V

A suitable diaphragm is somewhat difiicult of construction. A preferred arrangement is that shown in the drawings, in which the diaphragm is composed of suitable porous slabs 2, assembled and held in place by a metal rod 12 fitted in the grooved joints 14: of the porous slabs, and protected from the action of the electric current'and the corrosive electrolyte by the rubber tubing or covering 13. This stiffening and supporting rod is very conveniently'made by inserting a metal rod into hard rubber tubing and cementing it in position. The metal will give the desired stiffness and strength while the rubber will give the desired insulating and acid resisting qualities. In this way a diaphragm may be constructed which will resist the action of the current and the solution indefinitely.

' The anodes 3 may preferably be made of lead or carbon, and fixed in position by the sumed as being a lead cathode surrounded.

by a perforated franfe 15, in which the perforations are shown by 16; the cathode and surrounding frame are fixed in position by the strips 18. The object of thisarrangement is to give uniformity to the catholyte and make it possible to use permanent lead sheets for the cathodes. The edges of the cathode are embedded in the surrounding frame and thereby insulated, so that no deposition of copper will take place on the edges. This cathode sheet may be made, say of one quarter inch thick hard antimonial lead. When the copper has been deposited on this cathode sheet of the desired thickmess, the cathode and frame are removed from the tank together, the frame removed from the edges, and the copper removed from the face of the sheet. This avoids the necessity of starting sheets, and ischeaper and more convenient. i

In the operation of the process, the concentrated copp'er sulfid precipitate obtained *from the weak and extremely foul solutions,

as already described, is introduced into the anode compartment of the electrolyzer, while the rich copper solutions are introduced into the a cathode compartment. When the current is turned'on copper-is deposited on the cathode while sulfuric acid and ferric sulfate are produced in the anode. The electrolyte in the anode compartment is preferably agitated, as with compressed air introduced through the perforated pipe 5: this reduces the voltage required in the process and makes the depolarization more effective. Any attempt of the ferric salts to get to the cathode is frustrated by the reaction shown in equation 5, if copper sulfid is used, and by the reaction shown in equation 6 if sulfur dioXid combined with charcoal is used.

In this way a high current efficiency is obtained in the deposition of the copper and in the regeneration of the solvent, while the operation is practically unaffected by the amount of iron in the electrolyte. A tight of any reasonable size Bil till

rsaaeac diaphragm is not essential to successful operation: the diaphragm acts largely to keep the insoluble reducing agent in the anode compartment from getting to the cathode, so that even if some of the reduced solution from the anode compartment gets into the cathode compartment no perceptible harm will be done. Tt is preferred to circulate the electrolyte in the two compartments separately, although this is not necessary. The sulfid sludge in the anode compartment will not need much circulation, and will be required only as the elemental sulfur, or charcoal, shown by equations 5 and 6 becomes excessive.

This method of procedure, serves two important purposes: The lean solutions which could not be advantageously treated electrolytically are taken care of chemically, while the resulting copper sulfid is used to make effective the electrolytic treatment of the rich solutions, and allthe copper is in the end converted into the pure electrolytic metal by the process in its regular working. The copper sulfid, as precipitated from the lean solutions, is light, highly effective, and is easily maintained in suspension as a sludge in the anode compartment, as disclosed in theBprcferred method of operation. rouri ding the cathode a uniform supply of electrolyte at the surface of the cathode is assured.

The electrolyte in the cathode may also be agitated, but this is not essential, as the copper is never very closely extracted from the electrolyte, and the regular circulation of the comparatively rich solution will bring the copper ions in suiiicient contact with the cathode to obtain a high etliciency.

This application may he considered as a continuation in part of my cop-ending application, SerialNo. 15,583, filed March 19, 1915.

T claim:

1. A process of extracting copper from its ores which consists in treating the ore with an acid solution to dissolve the copper, separating the rich copper solution from the gangue, washing the residue and thus obtaining a lean copper solution, electrolyzing the solution rich in copper to deposit the metal and regenerate acid, precipitating the lean copper solution with hydrogen sullid means of the perforated frame surand thus obtaining copper sulfld precipitate from the lean copper solutions, and then applying the copper sulfid precipitate to the electrolyte to reduce the variable valent salts in the electrolyte to their lowest valencg.

2. process ofextracting copper from its ores which consists in treating the ore with an acid solution to dissolve the copper, electrolyzing a portion of the dissolved copper to deposit the metal and regenerate the acid combined with the copper, precipitating some of the copper as the sulfid with hydrogen sulfid, filtering the sulfid precipitate from the precipitated solution, adding the sulfid precipitate sludge to the anolyte of the electrolyte, and agitating the copper sulfid sludge in contact with the anode while maintaining it separate from the cathode.

3. A process of extracting copper from its ores which consists in treating the ore with an acid solution to extract the copper, separating the rich copper solution from the gangue, washing the residue and thus obtaining a lean copper solution, electrolyzing the rich copper solution to deposit the metal and regenerate the combined acid, precipitating the lean copper solution with hydro gen 'sulfid and thus obtaining a copper sul fid precipitate from the lean solutions, and then applying the copper sulfid precipitate to the rich solutions to reduce the ferric salts to the ferrous salts produced by the electrolysis or the rich copper solutions.

4:. A process of extracting copper: from its ores which consists in treating the ore with a dilute acid solution to dissolve the copper, separating the resulting impure rich copper solution containing salts of iron from the gangue, washing the residue and thus obtaining a lean copper solution, electrolyzing the rich copper solution to deposit the copper with the simultaneous regeneration of acid and the production of ferric salts, chemically precipitating the copper from the lean solution, and then applying the chemical precipitate to the rich copper solution to reduce the ferric salts produced by the electrolysis from a higher to a lower valency.

VVTLLTAM GBEENAWALT. fitnesses Faun L. Scorn, Conn snnawam.

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