US1252654A - Electrodeposition of metals. - Google Patents

Description

A. G. BETTS.

ELECTRODEPOSITION 0F METALS.

APPLICATION FILED MAY 15- I916.

Patented Jan. 8, 1918.

caries.

ANSON Gr. IBETTS, OF ASHEVILLE, NORTH CAROLINA.

ELEGTRODEPOSITION 0F METALS.

Specification of Letters Patent.

Patented Jams, 1918.

' Application filed May 15, 1916. Serial No. 97,544.

To all whom it may concern:

Be it known that I, ANsoN G. Bn'rrs, a citizen of the United States, residing at Asheville, in'the county of Buncombe and State of North Carolina, have invented certain new and useful Improvements in Electrodeposition of Metals, of which the following is a full, clear, and exact description.

This inventionrelates to the electrolytic recovery of metals from soluti0ns,of salts thereof, particularly zinc from acid sulfate solutions. In the electrolyticmethod of zinc recovery the zinc sulfate is electrolyzed with suitable anodes;-and cathodes, with deposit of metallic zinc on the cathodes, thus liberating sulfuric acid and making the electrolyte more acid until it is finally removed from the electrolytic cell as a solution of sulfuric acid containing only a little zinc sulfate. i Y

It is well known that the ambunt of zinc deposited for a given consumption of current is always considerably less than the amount that would be expected from theoretical considerations. In short, the efficiency of the process is undesirably low, and hence the cost undesirably high. It isaccordingly the object of my present invention to provide an electrolytic process by which the amount of zinc deposited with iven current consumption will be increased.

nother object is to diminish the amount of hydrogen liberated along with the zinc at the'cathode. These objects I attain by the simple expedient of giving the inner surface of the electrolytic tank, in contact with the solution, (which surface is usually metallic lead), an electric potential of its own, relative to the solution, so thatsome current willflow from the solution to the tank as well as to the cathode: This has the effect of increasing the efliciency'of the cell, that is, it permits the use of less current for a given amount of zinc deposited, or, conversely, permits more zinc to be deposited with the same amount of current.

It is my present belief that the abovementioned potential (which for convenience can be referred to as the tank potential) accomplishes the result described by (1) opposing the formation of a lead salt, more or less soluble in the zinc solution, by the acid of the zinc solution attacking the lead surface of the tank, Whichsalt,'when present in the solution, exerts an unfavorable efiect, probably catalytic, upon the deposition of the zinc; (2) diminishing the amount of hydrogen liberated at the cathode along with the zinc, which hydrogen tends to cling to the cathode and thereby increase the resistance of the cell, causing some of the current to be wasted in heating effects; and (3) hindering re-dissolving of zinc from thercathode by the free acid of the solution, that is, hindering re-formation of the zinc salt by attack of the free acid upon the metallic zinc deposited on the cathode.

In the accompanying drawing I have shown diagrammatically a simple electrolytic cell for practising my method in the preferred manner. In the cell illustrated, 1 is the tank, which may be made of wood, 2 is the'lead lining, and 3 designates the electrolyte, preferably an acid zinc sulfate solution. The anode and cathode are designated A and C respectiyely, and may be of any suitable material, for example aluminum. The cathode is electrically connected to the lead lining by wire 4. This gives the lead surface a negative potential with respect to the anode or positive electrode A, with the result that current flows to the lead and thence to the negative pole as well as direct to the latter. This has the effect, in general, of opposing the formation of a lead salt, which effect may possibly be explained on the theory that as fast as the lead salt is formed it is reducedby electrolytic action and the lead re-deposited on the lead surface. It also tends to deposit zinc on the lead surface, and if enough current were allowed to flow to the lead the amount of zinc there deposited would be considerable. I therefore prefer to include a suitable resistance R'in the connection, of such value that" sufficient current can HOW to prevent formation of lead salt. The current ma even be large enough to deposit a smal amount of zinc on thelead surface,but such deposit can easily be removed from time to time by means of sulfuric acid solution.

' It is to be understood that the invention 1s not limited tothe specific details herein described but can be practised in other ways "without departure from its spirit. Nor is the invention limitedto zinc recovery, but is in general applicable to other metals that are more soluble in the acid electrolyte used than is the metal (for example lead) used for the inner surface of the tank.

I claim:

1. The method of electrodepositing metals of greater solubility in the acid of the salt contained in the electrolyte than lead, comprising the step of electrolyzing a solution of a salt of the metalwith suitable anode and cathode in a vessel having an inner surface of lead while passing current to the lead inner surface.

'2. The method of electrodepositing metals of greater solubilit in the acid of the salt contained in the-e ectrolyte than lead, comprising the step of electrolyzing a solution of a salt of the metal with suitable anode and cathode in a vessel having an inner surface of lead, while passing current from the anode to the said lead innerjsurface of the vessel.

3.. The method of electrodepositing metal in a vessel having a lead inner surface, comprising electrolyzing in such vessel a solution of a salt of the metal While maintaining at the said lead. surface a negative potential high enough to substantially prevent the formation of a lead salt thereat.

4. The method of electrodepositing zinc from its sulfate solutions, comprising electrolyzing the solution with suitable anode and cathode in a vessel having a lead inner surface, While passing current from the electrolyte to the said lead inner surface.

5. An apparatus for electrodeposition comprising a lead lined receptacle, an anode and a cathode therein, each spaced from said receptacle, a positive terminal connected to said anode and a negative terminal con- .nected to said cathode; and an independent connection between the lead lining of said receptacle and the said negative terminal, said independent connection offering a relativel electric current.

In testimony whereof I hereunto affix my signature. v

ANSON G. BETTS.

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