US2755241A

US2755241A - Electrowinning of manganese

Info

Publication number: US2755241A
Application number: US301382A
Authority: US
Inventors: Glen D Bagley; Michael C Carosella
Original assignee: Union Carbide and Carbon Corp
Current assignee: Union Carbide Corp
Priority date: 1952-07-28
Filing date: 1952-07-28
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17

Description

, a 2,755,241 mted States Patent Ofice P........ ant-1,1956

ELECTROWINNING F MANGANESE Glen D. Bagley, Lewiston, and Michael C. Carosella, Niagara Falls, N. Y., assignors to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application July 28, 1952, Serial No. 301,382

4 Claims. (Cl. 204-105) The present invention relates to cathodes for use in the electrowinning of manganese from aqueous solutions and more particularly to a method for the preparation and use of such cathodes.

The characteristics required of successful cathodes for the electrowinning of manganese, some of which are stated in United States Patent No. 2,325,660, are exacting and, heretofore, no metal or metal alloy has been discovered which satisfies all of the characteristics to a sufficient degree.

It is, therefore, the main object of the present invention to provide process for the electrowinning of manganese employing cathodes capable of effectively serving for long periods of time Without extensive treatment and from which deposited metal is easily removed.

Another object is to provide a method for fabricating and conditioning such materials to make them suitable for use as cathodes for the electrowinning of manganese.

Other aims and advantages will be apparent from the following description and appended claims.

It has been discovered that nickel-base alloys containing molybdenum, chromium, iron and Wolfram are very highly resistant to corrosion by aqueous solutions of manganese and ammonium mineral salts, the electrolyte employed in most commercial processes for the electrowinning of manganese. Additionally, it has been found that such alloys, when used as cathodes for the electrowinning of manganese, have maintained their polished surfaces for much longer periods of time than was heretofore believed possible of cathodes. These characteris tics, together with the fact that such cathodes permit much easier stripping of the deposited manganese metal serve to make the cathodes of the present invention ideal for use in the electrolytic depositing of manganese from manganese and ammonium mineral salt solutions.

In accordance with the present invention a nickelbase alloy containing 2% to 20% molybdenum, to 25% chromium, 4% to 25% iron, 0.5% to 10% wolfram and to 83.5% nickel is provided in rolled, annealed sheets of the desired thickness having smooth surfaces. Thereupon, the sheets are surface polished with abrasive paper or other suitable equivalent. The asformed sheet is then degreased prior to its employment as a cathode in a diaphragm cell for the electrowinning of manganese.

It has been found that in many cases metallic manganese can easily be deposited and stripped from cathodes prepared in accordance with the present invention without precoating the cathode surfaces. Inthose cases where easier stripping is desired the cathode may be precoated with a dilute solution of sodium silicate, or suitable equivalent. It is preferable to wash and degrease the cathode plates prior to their use in the electrolytic cell to remove dirt and other contaminants, as well as to improve adherence of the deposited metal to the cathode plates.

Cathodes prepared in accordance with the present invention have been found to be far superior to any heretofore employed for the electrowinning of metallic manganese from aqueous solutions due especially to their properties of high resistance to corrosion by the electrolyte and ease of stripping of deposited metal therefrom. Because of the two aforementioned properties the cathodes maintain their polished surfaces for longer periods of time, thereby reducing the frequency of the surface polishing treatment and consequently increasing the period of use of a given cathode.

Metal alloy cathodes having the two following compositions have been prepared in accordance with the present invention and have fulfilled the requirements for use in the electrowinning of manganese with greater success than all of the prior art cathodes tested:

Cathode I.15% Cr, 17% Mo, 5% W, 6% Fe, 55% Ni.

Cathode II.22% Cr, 9% Mo, 2% W, 25% Fe, 39% Ni, 0.1% Ta, 0.5% Nb.

For example, surface polished, washed, degreased cathodes having the composition given for Cathode 1 above were used in the cathode compartment of a diaphragm cell for the electrowinning of metallic manganese in which liters of solution containing 27.2 grams per liter of manganese, 128.5 grams per liter of ammonium sulphate, 0.68 gram per liter of sulphur dioxide and some magnesium was continuously introduced as catholyte cell feed. Electrolysis was maintained at a cathode current density of 41 amperes per square foot and high purity manganese metal was deposited on the cathode. The current efiiciency was 64.8% for a deposition time of 24 hours. The deposited metal was easily removed, leaving a mirror polished surface on the cathode which was used for further deposition of manganese metal without further polishing.

It is, of course, to be understood that minor amounts, not in excess of 5%, of metals usually found in alloys of this type may be contained in the alloy. Metals such as tantalum, niobium, vanadium, titanium and aluminum are but a few of the metals normally found in minor amounts in such alloys.

In addition, metallic and non-metallic impurities of the order of approximately 2% may be, and ordinarily are, contained in such alloys without substantially altering the composition or properties of such alloys when used as cathodes for the electrowinning of manganese.

Manganese metal deposited on cathodes in accordance with the present invention may be treated to prevent oxidation by dipping the cathodes and deposited metal in a dilute solution of sodium bichromate prior to the stripping operation.

What is claimed is:

l. A process for the electrowinning of manganese from an aqueous solution of a manganese and ammonium mineral salt in a diaphragm cell comprising electrolytically depositing metallic manganese from said aqueous solution on at least one thin alloy sheet cathode having rolled, annealed, polished, degreased surfaces and containing 10 per cent to 25 per cent chromium, 0.5 per cent Wolfram, 4 per cent to 25 per cent iron, 2 per cent to 20 per cent molybdenum, and 20 per cent to 83.5 per cent nickel; removing said cathode from said cell and removing said deposited metallic manganese from said cathode; and returning said cathode to said cell for further deposition of metallic manganese.

2. A process for the electrowinning of manganese from an aqueous solution of a manganese and ammonium mineral salt in a diaphragm cell comprising electrolytically depositing metallic manganese from said aqueous solution on at least one thin alloy sheet cathode having rolled, annealed, polished, degreased surfaces and containing 10 per cent to 25 per cent chromium, 0.5 per cent to 10 per cent Wolfram, 4 per cent to 25 per cent with a dilute solution of sodium bicl'n'emate to prevent 3. A process for the eiectrowinning of manganese iron an aqueous solution of a manganese and :nnrnoninn: nineral salt in a diaphragm cell comprising electrolytically depositing metallic manganese from said non-cons solution on at least one thin alley sheet cathode having rolled, annealed, polished, degreased surfaces and composed oi: approximately 15 per cent chromium, 5 per cent wolfram, 6 per eent iron, 17 per cent molybdenum and 55 per cent nickel; removing said cathode from said cell and treating said deposited metallic manganese with a dilute solution of sodium bichromate to prevent o/."lation thereof; removing said deposited metallic inang nese from said cathode; and returning said cathode to said cell for further deposition of metallic manganese.

4. A process for the electrowinning of manganese from an aqueous solution of a manganese and ammonium mineral salt in a diaphragm cell comprising electrolytically depositing metallic manganese from said aqueous solu' tion on at least one thin alloy sheet cathode being rolled, annealed, polished, degreased surfaces and composed of approximately 22 per cent chromium, 2 per cent Wolfram, 25 per cent iron, 9 per cent molybdenum, 39 per cent nickel, 0.1 per cent tantalum, and 0.5 per cent niobium; removing said cathode from said cell and treating said deposited metallic manganese with a dilute solution of sodium bichromate to prevent oxidation thereof; T011101 ing said deposited metallic manganese from said cathode; and returning said cathode to said cell [or further deposition of metallic manganese.

References Cited in the file of this patent UNITED STATES PATENTS Chamberlain Aug. 3, 1943 Jacobs Jan. 24, 1950 OTHER REFERENCES

Claims

1. A PROCESS FOR THE ELECTROWINNING OF MANGANESE FROM AN AQUEOUS SOLUTION OF A MANGANESE AND AMMONIUM MINERAL SALT IN A DIAPHRAGM CELL COMPRISING ELECTROLYTICALLY DEPOSITING METALLIC MANGANESE FROM SAID AQUEOUS SOLUTION ON AT LEAST ONE THIN ALLOY SHEET CATHODE HAVING ROLLED, ANNEALED, POLISHED, DEGREASED SURFACES AND CONTAINING 10 PER CENT TO 25 PER CENT CHROMINUM, 0.5 PER CENT WOLFRAM, 4 PER CENT TO 25 PER CENT IRON, 2 PER CENT TO 20 PER CENT MOLYBDENUM, AND 20 PER CENT TO 83.5 PER CENT NICKEL; REMOVING SAID CATHODE FROM SAID CELL AND REMOVING SAID DEPOSITED METALLIC MANGANESE FROM SAID CATHODE; AND RETURNING SAID CATHODE TO SAID CELL FOR FURTHER DEPOSITION OF METALLIC MANGANESE.