US1491498A - Method of electrolysis - Google Patents

Description

Patented Apn 22, 1924.

UNITED STATES PATENT OFFICE.

UBYLN CLIFTON minimum, of JOHANNESBURG, TRANSVAAL, soo'rn AFRICA.

METHOD OF ELECTROLYSIS.

No Drawing.

In the electrolysis of aqueous solutions with insoluble anodes it frequently happens that incrustations or insoluble deposits are formed over the active surface of the anode which is in contact with the electrolyte; Such deposits or incrustations are frequently a source of serious trouble, causing as theydo the intervention of a poorly conducting medium between the anode and the electrolyte and thus raising the ohmic resistance of the circuit. Moreover, since these deposits possess usually a lower overvoltage than the anode material itself it sometimes happens that desirable reactions which depend for their continuance upon the maintenance of a high overvoltage are interfered with or even completely inhibited.

As an example of the conditions above described we may take the case of the electrolysis of solutions derived from the leaching of zinc ores with sulphuric acid. These solutions, after the ordinary processes of purification have been carried out, usually con-- ried out with an anode of lead or lead perox ide, all of the three metals in question are precipitated as insoluble oxidesin the vicinthe further precipitation of the oxides of manganese, cobalt and antimony is thus prevented. Moreover, since the resistance of this layer of scale is considerable, a substanillustration Application filed January 5, 1921. Serial No. 435,158.

tially higher voltage must be employed with consequent lossof power.

The object of this invention is to provide means whereby the above mentioned disadvantages can be obviated without the neces sity of mechanical cleaning of'th e anodes by hammering or scraping which is the method usually used. Accordin to the present invention, this effect may be accomplished by making use of the expansive. effect of the bubbles of gas liberated at the surface of anelectrode during electrolysis. By so arranging the conditions that bubbles of gas are liberated behind the scale at the true anode surface, the scale is'broken oif and the.

anodes thus kept continuously in good condition.

In order to attain this result it is necessary, firstly, to surround the anode with a solution of high electrical conductivity. Since the adhering scale is always to some extent porous the electrolyte will permeate it and come in contact with the anodejsurface beneath. Secondly, there must be employed a current of great intensity in proportion to the area .of the anode surface.

If these twoconditions are carried out it is found that the evolution of gas occurs not only at the surface-of the scale but also to i some extent behind it, with the result that the adhering scale is detached and falls away leaving the anode surface clean.

A solution of suitably hi h conductivity is one containing a considera le percentage of free acid, for example 10% or more. The density of current at the anode should be 50 amperes per square foot or 'higher.- As an example-of the application of the invention to the case. mentloned above. That of the electrolysis of zinc sulphate solutions, the

free acid concentration in the electrolyte may I conveniently be 250 grams of sulphuric acid per litre and the current density at the anode 100 amperes per square foot.- It. is understood that these figures are given merely in to their use.

- These conditions may be applied intermittently 'in order to. remove .adhering scale which has formed, or they. may be used continuously and the anode thus kept permanently .clean. The latter case is preferable since the ohmic resistance of the'circuit is thus'kept low and, moreover, objectionable constituents of the electrolyte such as antiand the invention is not limited Q mony, cobalt and manganese are continuously precipitated and removed from solution. 7

Having thus described my invention, what I claim and desire to secure by Letters Patcurrent of high density in proportion to its tion containing a acld content approximating 100 surface the currentdensity approximating 5O amperes or more per square foot of anode surface immersed. 2. In the electrolysis of zinc sulphate solutions with insoluble anodes, surrounding the anode with a solution containing a high percentage of free sulphuric acid, the rams or more of free acid per litre, and t e simultaneous ap lication to the anode of a current of big densit in proportion to its surface, the current ensity approximating 50 amperes or more per square foot of anode surface immersed.

3. In the electrolysis of aqueous solutions containing manganese, a method of keeping the anode free of encrustations, which consists in surroundingl the anode with a soluigh percentage of free acid, the acid content approximating 10 per cent, or more, and the simultaneous a plication to the anode of a current of high ensity in proportion to its surface, the current density approximating 5O amperes or more per square foot of anode surface immersed.

' 4. In the electrolysis of aqueous solutions containing manganese, a method of removing encrustations formed'on the anode surfaces, which consists in intermittentl surrounding the anode with a solution 0 high menace electrical conductivity, and simultaneously applying to the anode a current of high density in proportion to its surface, the current density approximatin 50 amperes or more per square foot of ano e surface immersed.

5. In the electrolysis of aqueous solutions containing manganese, antimony and cobalt a method of continuously precipitating said metals as insoluble oxides during the electrolysis of the-solution, which consists in surrounding the anode with a solution containing a high percentage of free sulphuric acid, the acid content approximating 100 grams or. more of free acid per litre, and simultaneously applying to the anode a current of high density in proportion to its surface,

the current density approximating 50 amperes or more per square foot'of anode surface immersed,

6. In the electrolysis of aqueous solutions containing manganese, antimony and cobalt, a method of continuousl precipitating said metals as insoluble oxi es during the electrolysis of the solution, which consists in surrounding the anode With a solution containing approximately 10 or cent or more of free sulphuric acid, an simultaneously applying to the anode a current of high density. approximating 5O amperes or more per square foot of submer ed surface".

7 In the electrolysis of zinc sulphate solutions containing manganese, a method of preventing encrustation of the anode, which consists in surrounding the anode with a solution containing a high percentage of free sulphuric acid, the acid content approximating 100 grams or more of free acid per litre, and simultaneously applying to the anode a current of high density 1n proportion to its surface, the current density approximating 50 amperes or more per square foot of anode surface immersed in the electrol te.

LYN CLIFTON T INTON.