US2325201A - Electrolytic cell and anode - Google Patents

Description

Patented July 27, 1943 ELECTROLYTIC CELL AND ANQDE John L. Young,

Pittsburgh, Pa., assignor to Plastic Metals, Inc., a corporation of New York No Drawing. Application September 28, 1939,

Serial No. 296,939

50mins. (Cl. 204-280) In Letters Patent of the United States 2,043,823, I have described and claimed the electrolytic deposit of metallic iron, using a soluble iron anode and ammonium and ferrous sulfate as the electrolyte. It is characteristic of the anode in the various forms in which I have there shown and described it that it is essentially of granular will be reacted upon and go into solution, andv or porous structure. I have there. claimed such an anode in two specific forms. In one the granular material rests upon a,suriace oi mercury. In another it is held to a supporting body by magnetic attraction. Manifestly these are .very particular ways of forming the anode, and an anode so formed does not readily lend itself to conditions of commercial operation.

I have pursued an inquiry, looking to an anode possessing these essential features, and yet capable of being used under ordinary industrial conditions.

In the specification of the patent alluded to I said that I had found that sponge iron, compressed sufiiciently to form a coherent mass of permanent shape, and yet retaining its finely divided character, would be found effective. And it is measurably eiTective, but not wholly so; at least, not without the further qualifications that here'I shall disclose.

Inevitably it is true of such -a metal as iron, which is very active chemically, that refining operations are very expensive, and that, at best, purity is only attained in approximation. And in such a situation as this, where the anode is itself consumed and its very substance goes to make up the end product, the anode must be inexpensive of production. If inexpensively produced the anode will necessarily contain a very appreciable content of adulterant, oxide, mineral matter, alloy, etc. It is a first requisite of .a soluble iron anode that it shall, in the course of A the electrolytic operation, keep itself' free of dross, and its surfaces accessible to the continu ing electrolytic action. While it is true that. a

the surface of the anodewill be free. The action of solution of iron inthe electrolyte will be intensified at the surface. The iron at the surface the dross will fall away as it is progressively exposed, so that the surface will continue to be clean and accessible to. the electrolyte.

I take finely divided iron in such form as may be available, and, within limits, the finer the better. It may, for instance", be the tumings or scrap of prior fabrication; it may be in the form of reduced scale from rolling mills and such places; it may be the product of the various known sponge-iron procedures; and inevitably it will under practical conditions-be impure. It will carry an appreciable adulteration of nonmetallic substance. Such materials under compression and at elevated temperature in a reducing atmosphere will give me my desired product. Inevitably, in all these cases, the finely divided material will at the-beginning of operation contain iron oxide, and particularly the'surfaces of the particles will bear oxide coatings. At elevated temperature and in a reducing atmosphere the oxide will be reduced; the content of combined iron will be brought to minimum; and

the iron oxide that in any case coats the granules at the points of meeting ofgranule with granule will be reduced, and bridges of pure iron .will be formed between the bodies of essentially pure iron that constitute the granules. Par

bodyof sponge iron compressed to coherence will 1 serv as a soluble anode, it will not unless it be possessed of other peculiar features continue to serve efficiently during protracted operation.

I have found, and herein is my present invention, that if a granular and porous body of essentially pure iron (the content of combined iron I having been reduced to a minimum), necessarily carrying a burden of dross, be compressed to coherence; and if in addition to that the granules of iron be united granule to granule by bridges of metallic iron, my desideratum is gained, and my problem is solved. The current flow, then, to

ticles of non-metallics will remain interspersed in the porous structure, between the iron granules. Thus my anode body will be perfected because as a consequence of the uniting of the particles of iron by bridges-of metallic'iron formed "by reduction of iron oxide, the particles,- or granules, are integrated into a mechanically strong structure that embodies to a high degree the desiderata of an anode. Such an anode is highly porous and thus presents a desiredly large surface area for solution of the iron. The bridges act to holdthe particles in place until they have been whollycorroded by the electrolytic action,.

which is in contrast to anodes made from similar materials without such bridge formation and in whose use particles of'metallic iron .fall away from the anode into the slimes, which is economically undesirable. v

I am aware of the fact that iron oxide has been reduced at elevated temperatures in a reducing atmosphere. I am aware that coherence has been given by heat and pressure to granular material, and particularly to sponge iron. I am not aware that ever Deters h sponge iron, carrying such a practically inevitable content of non-metallic adulterant; been pressed to coherence in a reducing atmosphere, with the substantial elimination of combined iron and with the production of bridges of metallic iron connecting the bodies of the granules of metallic iron, and I am not aware that ever before in an electrolyte of ammonium and ferrous sulfate has a soluble anode been used that is porous, that is made up of granules, in which the granules themselves of essentially pure iron are united granule to granule by bridges of pure iron, with the nonmetalliccontent interspersed between the granules. This I believe to be new; and I have found it to be useful. a

I claim as my invention:

ierrous and ammonium sulfate with a soluble anode consisting of granules of metallic iron united granule to granule by bridges of metallic iron which act to integrate said granules into a 1. A soluble anode for an electrolytic cell con- I sisting of a coherent and porous mass of'granules of substantially pure iron connected granule to granule by bridges of iron in metallic state and being thereby of high porosity and electrical conductivity, of high and maintained coherence in use whereby the iron is dissolved substantially completely under the influence of the electric current with substantially no disintegration and loss of particles of free iron.

, it is exposed while the iron is dissolved substan-' 2. An anode for the electrolytic refining of iron formed of an impure grade of iron powder containing mechanically held non-metallic impurities but having a minimum of combined iron, the

structure of the anode being porous, the nonmetallic impurities being distributed between the granules'of iron, and the granules of iron being electrically united granule to granule by bridges of metallic iron, whereby the action of solution of the iron is intensified at the surface of the anode, the released'non-metallic impurities fall away as they are exposed, and the iron of the anode is dissolved substantially completely under the influence of the electric current with substantially no loss of particles of free iron.

3. In an electrolytic cell for the electro-deposition of iron, the combination of an electrolyte of porous structure of high electrical conductivity and maintained coherence and from which nonmetallic impurities fall away as they are exposed while the iron is dissolved substantially completely with substantially no disintegration and loss of granules of metallic iron.

4. In an electrolytic cell for the electro-deposition of iron, the combination of an electrolyte of ferrous and ammonium sulfate with a soluble anode of porous structure composed of iron of normal adulteration with non-metallic matter and in the form of granules united granule to granule by bridges of metallic iron, granules of non-metallic matter being dispersed through the iron granules, said bridges acting to integrate said granules into a porous structure of high electrical conductivity and maintained coherence and from which said non-metallic material falls away as tially completely with substantially no disintegration and loss of particles of metallic iron.

5. In an electrolytic cell for the electro-deposition of iron, the combination of an electrolyte of ferrous and ammonium sulfate with a soluble anode composed of granules of metallic iron containing the normal non-metallic adulterating material and united granule to granule by bridges of metallic iron to form a porous structure, particles of adulterating material insoluble in the