US2580681A

US2580681A - Method of treating the electrolyte in the electrodeposition of iron

Info

Publication number: US2580681A
Application number: US45967A
Authority: US
Inventors: Erich H Konrad; Warren H Kaye
Original assignee: SULPHIDE ORE PROCESS Co I
Current assignee: SULPHIDE ORE PROCESS Co I; SULPHIDE ORE PROCESS COMPANY Inc
Priority date: 1948-08-24
Filing date: 1948-08-24
Publication date: 1952-01-01
Anticipated expiration: 1969-01-01

Description

1952 E. H. KONRAD ETAL 2,580,681

METHOD OF TREATING THE ELECTROLYTE IN THE ELECTRODEPOSITION OF IRON Filed Aug. 24, 1948 FEED TANK ELEC YTIC TANK LEACH TANK mmmalzxcrmcmm:

FILTER 1 SULPHATE REMOVAL H s REMOVAL This filtrate is accordingly further treated for the elimination and removal of the hydrogen sulphide and colloidal sulphur. This may be completely effected by contacting it with activated charcoal, either by adding the charcoal to it and agitating, or by passing the solution through a suflicient mass of activated charcoal,

and then filtering. The adsorbent charcoal thus.

acquires and retains a high percentage of sulphur, both as free sulphur and as hydrogen sulphide, which may be recovered' As thus completely liberated from both hydrogen sulphide and free sulphur, the resulting clear, strongly acid solution offerrous chloride (or other ferrous salt) is especially adaptable-to the continued electrodeposition of electrolytic iron therefrom.

If the liberated hydrogen sulphide or ,the free sulphur are oxidized, as they often are during the prolonged leaching treatment or re-cycling of the solution, so as to form sulphuric acid or soluble sulphur compounds in the electrolyte, these may be precipitated as calcium sul phate, by the addition of calcium chloride to the liquor during the leaching operation, and subsequently separated. with the coagulated sulphur on the activated charcoal, or by separate precipitation and filtration. a

The leaching liquor or solution containing hydrogen sulphide and colloidal sulphur may also be liberated of these components .by agitating with a stream of compressed airor by allowing the solution to stand quiescent for a prolonged period of time (24 to 36 hours) -'followed in either case by filtering out the thus coagulated sulphur.

The filtered, clarified solution of electrolyte,

as diagrammatically shown in the accompanying drawings in which Fig. 1 is a diagrammatic flow sheet oi the sequence of process steps; and

Fig. 2 is a diagrammatic showing of supple mentary process steps which may be associated and conducted with the steps of Fig. l.

The tank i may contain the initial supply of an aqueous solution of the ferrous salt, such as ferrous chloride, or a supply of acid such as hydrochloric acid, or both. The conventional electrolysis tank 2, with diaphragm 2a and anode 4 defining the anolyte portion, and cathode 3 is provided with the aqueous electrolyte 5 from tank I (or by recirculation as pointed out below) which is characterized, during electrolysis, by containing water, 12% to 20% of iron, in the form of a ferrous salt, such as ferrous chloride, an acid such as hydrochloric acid to a pH value of 1.2 to 2.0, and in the cathode portion not more than approximately 0.4% of iron in the form of a ferric salt, such as ferric chloride, and in the anode portion approximately 3.5% to 10.0% or iron in the form of a ferric salt such as ferric chloride.

In operation the electrolyte .5 may be withdrawn from the anolyte portion by the pipe 5 and circulated in the leach tank I having an agi-' tator 1a over sulphide iron ore, such as pyrrhotite.

as thus obtained, is then returned to the electrolytic cell, for the continued electrodeposition of iron therefrom, and directed either into the electrolytic bath as a whole .(if a non-diaphragm cell is used, as it may be) or into the catholyte compartment, in the case of a diaphragm cell. It may require some addition of acid to adjust the pH value to the desired degree of acidity as indicated above. But if sulphuric acid is formed in the leaching operation and the sulphate radical thereof precipitated by calcium chlorides, this will liberate freehydrochloric acid into the solution, which will in part' or wholly compensate for the lo s of acid due to solvent action of the acid of the solution upon the iron sulphide or the formation of hydrogen sulphide.

This invention accordingly provides a method of leaching sulfide ores or concentrates containing iron and copper sulfides in varying proportions and a variety of minor constituent metals in such a manner as to produce:

1. A solution of iron suitable for the production of smooth deposits of electrolytic iron of high purity;

2. A residue containing a high percentage of characterized by containing a sulphide or sulphides of other metals such as of the copper or tin group, nickel or'cobalt, the ore being fed to the leach tank in a conventional manner. The reduced leach liquor may be drawn off, with or without separation from attendant solids. through pipe 8, to the filter 9, from which the filtrate may be drawn off by pipe I 0 and led into tank H, for treatment for removal of hydrogen sulphide. e. g., by contact with activated char coal. The thus treated liquor is then passed through pipe I2 to filter 13, to remove the charcoal with adsorbed gases and colloidal residues, and the resulting filtrate drawn off through pipe M and conducted back into the cathode portion of the electrolyte 5, as shown.

In the case of oxidized ores or leach liquors which may otherwise acouire the pre ence of sulphates, as above-described, the leach liquor. after being removed from the ore in leach tank I and passed throu h the filter 9, may be bypassed from pipe Hi to pipe I5 and thence into tank [6 for treatment with calcium chloride. The resulting mixture then maybe withdrawn through pipe I! to filter I8, the filtered solution then being returned through pipe l9 to pipe 10 and thence into the treating tank II.

It should be'understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

We claim:

1. Method of treating the anolyte in the electro-deposition of iron, which anolyte has a pH of 1.2 to 2.0 and contains 35 to grams per liter of iron in ferric condition, comprising contacting the anolyte with an excess of an acid soluble iron sulphide ore containing another metal whose sulphide is insoluble in said anolyte after the ferric ions have been reduced to ferrous ions, such excess of ore being sufiicient to completely reduce all ferric iron present in the anolyte to ferrous iron and to subsequently react with the free acid present in the anolyte to form hydrogen sulphide, dissolving the iron and other metals soluble in the anolyte and continuing the leaching of the ore by the anolyte until the ferric iron is completely reduced to ferrous iron and hydrogen sulphide is then formed from the free acid and precipitates the other metal as insoluble sulphide, separating the resulting mixture of solution and solids, treating I the solution portion therefrom to remove the hydrogen sulphide and the free sulphur content, and returning the clear solution as catholyte to the electrolytic cell.

2. The method according to claim 1 in which the anolyte has a pH of 1.2 to 2.0 and contains 35 to 100 grams per liter of iron as ferric chloride 3. The method according to claim 1 wherein separating of the resulting mixture of solution and solids is conducted by filtering the mixtureand treating the filtrate with activated charcoal I to remove the hydrogen sulphide content.

4. The method according to claim 1 wherein separating of the resulting mixture of solution,

and solids is conducted by filtering the mixture and treating the filtrate with compressed air liter of iron as ferric chloride, comprising con-' tacting the anolyte with an excess of an acid soluble iron sulphide ore containing another metal whose sulphide is insoluble in said anolyte after the ferric ions have been reduced to ferrous ions, such excess of ore being suflicient to completely reduce all ferric iron present in the anolyte to ferrous iron and to subsequently react with the free acid present in the anolyte to form hydrogen sulphide, dissolving the iron and other metals soluble in the anolyte and continuing the leaching of the ore by the anolyte until the ferric iron is completely reduced to ferrous iron and hydrogen sulphide is then formed from the free acid and precipitates the other metal as insoluble sulphide, separating the resulting mixture of solution and solids, treating the solution portion therefrom with calcium chloride to precipitate any sulphate ion content in the solution portion, filtering, treating the clear solution to remove hydrogen sulphide, filtering and returning the clear solution as catholyte to the electrolytic cell.

ERICH H. KONRAD. WARREN H. KAYE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,432,543 Eustis et al Oct. 17, 1922 1,456,615 Belcher et a1 May 29, 1923 1,567,916 Conder Dec. 29, 1925 1,751,099 Pike Mar. 18, 1930 1,945,107 Cain Jan. 30, 1934 1,980,381 Cain Nov. 13, 1934 2,273,036 Heise et a1 Feb. 17, 1942 2,503,234 Cain Apr. 11, 1950 OTHER REFERENCES Filtration and Filters, by J. A. Pichard, 1929. pages 28, 374, 405.

Claims

1. METHOD OF TREATING THE ANOLYTE IN THE ELECTRO-DEPOSITION OF IRON, WHICH ANOLYTE HAS A PH OF 1.2 TO 2.0 AND CONTAINS 35 TO 100 GRAMS PER LITER OF IRON IN FERRIC CONDITION, COMPRISING CONTACTING THE ANOLYTE WITH AN EXCESS OF AN ACID SOLUBLE IRON SULPHIDE ORE CONTAINING ANOTHER METAL WHOSE SULPHIDE IS INSOLUBLE IN SAID ANOLYTE AFTER THE FERRIC IONS HAVE BEEN RECUCED TO FERROUS IONS, SUCH EXCESS OF ORE BEING SUFFICIENT TO COMPLETELY REDUCE ALL FERRIC IRON PRESENT IN THE ANOLYTE TO FERROUS IRON AND TO SUBSEQUENTLY REACT WITH THE FREE ACID PRESENT IN THE ANOLYTE TO FORM HYDROGEN SULPHIDE, DISSOLVING THE IRON AND OTHER METALS SULUBLE IN THE ANOLYTE AND CONTINUING THE LEACHING OF THE ORE BY THE ANOLYTE UNTIL THE FERRIC IRON IS COMPLETELY REDUCED TO FERROUS IRON AND HYDROGEN SULPHIDE IS THEN FORMED FROM THE FREE ACID AND PRECIPITATES THE OTHER METAL AS INSOLUBLE SULPHIDE, SEPARATING THE RESULTING MIXTURE OF SOLUTION AND SOLIDS, TREATING THE SOLUTION PORTION THEREFROM TO REMOVE THE HYDROGEN SULPHIDE AND THE FREE SULPHUR CONTENT, AND RETURNING THE CLEAR SOLUTION AS CATHOLYTE TO THE ELECTROLYTIC CELL.