US2480771A - Process for the electrolytic recovery of nickel - Google Patents

Description

2,480,771 PROCESS FOR THE ELECTROLYTIC RECOVERY OF NICKEL Filed May '18, 1946 L. S. RENZONI Aug. 30, 1949.

4 Sheets-Sheet 2 IN VENT OR.

Lou/s 5. RENZO 1w.

\ I ATTORNEK PROCESS FOR THE ELECTROLYTIC RECOVERY OF NICKEL Filed May 18, 1946 C L. S. RENZONI Aug. 30, 1949.

4 Sheets-Sheet 3 INVENTOR ATTORNEY.

PROCESS FOR THE ELECTROLYTIC RECOVERY OF NICKEL Filed May 18, 1946 L. S. RENZONI Aug. 30, 1949.

4 Sheets-Sheet 4 INVENTOR.

Lou/.5 LSHEENZONI.

ATTORNEY.

Patented Aug.'3 0, 1949 PROCESS FOR THE ELECTROLYTIC RECOVERY OF NICKEL Louis Secondo Renzoni, Port Colborne, Ontario,

Canada, assignor to The International Nickel Company, Inc., of Delaware New York, N. Y., a corporation Application May 18, 1946, Serial No. 670,774 1 In-Canada April 12, 1946 v 9 claims. (or. 204-112) The present invention relates to a nickel liberator cell and a process of electrolysis carried out in that cell.

In the normal course of recovering nickel by electrodeposition from electrolytes containing chloride ions and. utilizing soluble anodes, an

excess of nickel entersthe system over that amount of nickel which is removed at the cathode. In such a system of nickel recovery, it is necessary, in order to maintain a balance between the nickel entering the system and the nickel removed at the cathode, to decrease the amount of nickel entering the electrolyte at the soluble anode without decreasing the amount of nickel removed at the cathode. In systems for recovery of nickel wherein all-sulfate electrolytes are employed, i. e. substantially free of chloride ion, the nickel balance of the system is maintained by replacing some of the soluble anodes with insolubleanodes. However, the practice of replacing soluble-anodes with insoluble anodes to maintain a nickel balance, when utilized in a chloride ion-bearing electrolyte I system, has proved to be unsatisfactory as, when insoluble anodes are employed in contact with a chloride ion-bearing electrolyte, molecular chlorine is liberated at the anode during electrolysis and leads to numerous operating difiiculties. Attempts have been made heretofore to operate cells producing nickel at the cathode and chlorine at the anode, but such attempts have been unsuccessful due to difficulties encountered in handling the chlorine. Furthermore, to provide adequate cathodeefilciency for economical operation, it has been found necessary to use either cathode or anode diaphragms to prevent alarge percentage of the current from beingutilized for hydrogen ion discharge and chlorine reduction. Any such .diaphragm arrangements, suitable for nickel electro-refining, have however, been found to deteriorate rapidly due to the action of molecular chlorine, resulting in numerous chlorine leaks, necessitating frequent changes of diaphragms'and tank linings. Even more objectionable than the hcreinbefore mentioned difiiculties has been the resulting addition of chlorinated, water soluble, organic compounds to the nickel electrolyte which resulted in production of strained, warped cathodes throughout the tank house.

It is apparent, therefore, that in order to satisfactorily operate a balanced nickel system, when employing a chloride ion-containing electrolyte, 'it' would be necessary to provide an electrolysis cell and a method for operating the cell in a mannerwhereby chlorine would not be liberated at an insoluble anode during the electrolysis. In view ofthe foregoing remarks, it will be apparent that the art of nickel recovery by electro-deposition, up to the time of the present discovery, was confronted with the problem of obtaining an electrolysis cell. that could be operated with insoluble anodes and a chloride-ion containing electrolyte in a manner whereby the system could be operated in balance with respect to nickel, and nickel recovered efllciently. at a cathode without liberation of chlorine at an insoluble anode. Furthermore, in providing an electrolysis cell that would operate in a satisfactory manner without liberation of chlorine at aninsoluble anode, it was desired that the cell operate satisfactorily without necessity. of adding cations or anions to the electrolyte system, which cations or anions would be deleterious to the -2o electrolytic production, of the cathode.

I have discovered a novel liberator cell and a method employing the novel cell with insoluble anodes and a chloride-ion-containing electrolyte whereby the electrolytic system can be operated inbalance, with respect to nickel, during electrolysis, and wherein nickel is recovered by electrodeposition at a cathode without liberation of chlorine at an insoluble anode. It is an object of the present invention to provide a liberator cell capable of maintaining a high purity nickel: at

catholyte substantially free of anolyte and anolyte substantially free of catholyte.

It is stillanother object of the present invention to provide a liberator cell having an anode compartment and a cathode compartment. separated by an intervening compartment, i. e., a middle compartment, whereby during operation of the novel cell, the cathode compartment is maintained substantially free of anolyte and the anode compartment maintained substantially free of catholyte.

The present invention contemplates the provision of a liberator cell having an insoluble anode whereby chlorine is not liberated at the anode during operation of the cell when employing a chlorine-ion-bearing electrolyte.

The, present invention further contemplates a method for recovery of nickel by electro-deposition from a chloride-ion-bearing electrolyte by employing the novel liberator vcell embodied in the present invention.

It is within thecontemplation of the present invention to provide a method for recovery of nickel by electrodeposition from a chloride-ionanodes and cathodes.

' cathodes;

ing description taken in conjunction with the V drawings in which: Fig. l is a diagrammatic illustration'ofanin stallation such as may be employed in carrying out the present inventionp;

Fig. 2 is a sectional view of Fig. 1;

Fig. 3 is a view partly in section of a: cathode compartment;

Fig. 4 is a sectional view taken on line 4 5 of Fig. 3;

Fig. 5 is an elevational view of a manifold feed 'gassembly such as may be employed for feeding electrolyte to the novel' liberator cell such as provided by the present invention?v l 1 I I Fig.- dis a sectional elevational view taken on linefi-efi in Fig. 7 and showing in detail a suitable means 'of assembly. for busloar connections for Fig. 7 isa plan view of-a suitable means of assemblyfor bus bar connections for anodes and Fig. 8 is an elevational view of an anode compartment frame;

Fig.9 is a sectional view of Fig.8; and} I Figs. 10 and .11 are elevational views of a. cathodeand an ano'derespectively. J

Generally speaking, the novel apparatus of the present invention comprises an electrorefining tank in which are suspended-a plurality of alternating anodes and cathodes, each electrode being contained within a compartment 'the refo'r,- each compartment comprising a diaphragm at each side of the electrode" with suitable 'fttme'workfor maintaining the diaphragms in substantially parallel, spaced-apart relationship-{ and each compartment being-maintained in spaced apart relationship with each adjoining compartmentby suitable framework thus providing diffusimrzones i. e.; intervening compartments,betweenadjacent electrode compartments. Anolyte and catholyte are introduced into the respective anode and cathode compartments-at rates suflicient-to provide the hydrostatic heads required in each compartment toinsu'reflow of both anolyte and cathoiyte into the intervening -difiusion zones; an overflow being provided in the diiiusion'zo ne'for the mixture of a'nolyte and catholyteat asuitable level to assist in maintaining the preferred hydrostatichead. I'Ihe anolyte employed is an acid solution substantially devoid of chlorideion and is;v preferably a dilute sulphuric acid solution, Whilethe catholyte is a sulphate-chloride=nickel electrolyte. During operationof the novel-cell, nickel is removed. from the catholyte -at-the cathode hand the electrolyte, depleted in nickel con tent, flows through the cathode diaphragm to the middle compartment. At the anode, meanwhile, oxygen isliberated at 100%currentefiiciency with the simultaneous liberation of hydrogen ions, The liberation of hydrogen'ions' results in the '2 continuous production ot-sulfuric acid. Thus, the anolyte passing through the anode diaphragm has an increased-1acid-content: Inthe middle compartmentpf the cell, the twosolutions, i. e., anolyte and catholyte; are mixed to form acid liquor which is subsequently used for pH correction. The mixing of the two liquors in the middle compartment is not efficient, however,

5 and there is a tendency for the heavy liquor from the cathode compartment to segregate near the tank' bottom. For this freasonfiit is air essential feature of the present invention that the overflow from the electro-refining tank be taken ofi in the 10 .lower regions thereof so that this heavy mixture is withdrawn. The mixture withdrawal outlet gwiltoffc'durse be brought to the proper level for overflow in order to maintain the proper relative t level's" within the .anolyte and catholyte compartmeritsand the intervening diffusion zone and this bringing to proper level may be by goose-neck bend or other means well known to those skilled i n the art; -;Itisgalso an essential feature of the ipresentinvention that infiltration of the heavy anolyte-catholyte mixture into the anolyte compartment should be avoided and for this reason the suspended anodes-and anode compartments should not'extend to the bottom of' thetarikyand *in the preferred embodiment theyshould attestend more than about two-thirds of tlie depth of the tank: By this arrangement-contact between the anodes and the heavy anolyte ca'tl'iolyte mixture'with the undesirable volutio fit free chlorine which would result thief rohriis an avoided: It will thus be apparent fror'xi the 'forgoing that the-port of withdrawal of the heavy liquor should be preferably in that'portion 'cf 'the tank beneath the bottom 'oftheanodess i f In reference torespective ,depths'of'the *a'jn'cd'e and cathode compartments, 'althoug-hthe pr eferred embodiment of the present"invention-is that such compartments-shouldnotextend more than about two-thirds of the depth'f oithe tank, it is also preferred but notessential; that the cathode compartments are of the samefdepth as the anode compartments? The -depth-"o he cathode compartments can be varied'; 'fliowever, particularly made deeper, without materially trfecting the operation of the-"tank; "HoweyenjI as have found that there is no particular aunts;-

tage in employing a short" anode a flong cathode in practicing the present inventi'onfialthough the use of a cathode longerin length than the anode wouldbe'zof advantage in a pro 'cess requiring a high anode current density and a lower cathode cur'rentdensity. Referringto the drawings; Figpl'dsa'di'agrammatic illustration of an installation such as may be employed'in carrying out the presenmnvention'. In Fig. 1, a multi-compartmentelectrmre: fining tank 32, containing amixed acidelec't'rolyte, is shown having suspended-in each"of"the compartments a plurality of alternating anode compartments 34; and cathode "cbm'partme'ntsfi which are more clearly illustrated inFlg QZfi The anode compartments 34 and cathode "compart mcnts 35 are 'supportedby compartment-bearing supports 38 in a'spaced-apart relationship with each adjoining compartment wherebya diffusion zone is provided betweenadjacent compartments. Suitable'means, such 'as'supports '39 and 40,'mor'e clearly shown in Fig, 2; maintainithe' compartment-bearing supports 38 in desired position. An acid 2|, substantially free of chloride ions, and. preferably concentratedsulphuric acid,""is contained-in 'asuitable acid tank 20. By means of gravity, the acid 2| is allowed to fiow through a conduit, such as pipe 24, and controlvalven, into an anolyte supply tank in which theacid Z I 1 flowing therein-' is diluted to provide an all) aqueous anolyte 26, preferably containing about 10 grams per liter of sulfuric acid. By means of gravity, the'anolyte 26 is allowed to fiow through a conduit, such as pipe 21 and control orifice 28 into the anode compartments 34. Similarly a suitable nickel electrolyte containing chloride ions and sulfate ions is fed through a main feed line, such as pipe 29 and riser 36 into the cathode compartments 35. By means of an orifice, such as shown by reference numeral 3|, the rate of flow of catholyte is controlled to a desired rate. In order to maintain a hydrostatic head in the anode compartments 34 and cathode compartments 35, an overflow system, such as overflow system 36, is provided to allow for withdrawal of mixed electrolyte liquor from the tank and diffusion zones in a manner whereby the surface level of the mixed electrolyte solution in the diffusion zones and tank is maintained at a lower surface level than the surface levels of the anolyte in the anode compartments 34 and the catholyte in the cathode compartments 35. The mixed electrolyte solution flowing through overfiow system 36 flows by gravity through a conduit such as pipe 37 into an acid liquor tank 4|. The acid liquor 41a is pumped by a suitable means such as pump 43 through a conduit, such as pipe 44, into a pH correction tank 45. The acid liquor 4 la may be used for pH correction of purifiednickel catholyte or may be employed for other purposes as desired. 7

" Fig. 2 is a sectional view taken on line 2-2 of Fig. 1 and shows the preferred embodiment of a nickel liberator cell such as contemplated by the present invention. In Fig. 2, a refining tank 32 is provided having a suitable lining 33 and an overflow system, such as a goose-neck overflow system 36. A plurality of alternating cathode compartments 35 and anode compartments 34 are suspended in tank 32 in a manner such as shown in Fig. 2 whereby the bottom 4'! of each anode compartment 34 rests in a slot 48 of compartment-bearing support 38, and, similarly, the bottom 49 of each cathode compartment 35 rests in a slot 56 of compartment-bearing support 38.

The compartment-bearing support 38 is supported in the desired position by means of a suitable support system, such as supports 39 and 40. By means of wood spacers 5i in compartment-bearing support 38, the anode comparti ments 34 and cathode compartments 35 are spaced apart to provide an intervening compartment 52, i. e., diffusion zone, between adjacent anode and cathode compartments.- Each anode compartment 34 has a suitable insoluble anode suspended therein, such as anode 53, and each cathode diaphragms in substantially parallel,

spaced-apart relationship. As shown in Fig. 2, the anode compartment 34 and cathode compartments 35 do not extend to the bottom of tank 32, and in the preferred embodiment, the anode compartments 34 and cathode compartments do not extend more than about two-thirds of the depth of the tank. Such an arrangement of the anode compartments and cathode compartments substantially inhibits the infiltration of heavy anolyte-catholyte mixture from the intervening compartments 52 into the anode compartments 34, and thus the heavy anolyte-catholyte mixture does not come in contact with the anodes. The heavy anolyte-catholyte mixture in the intervening compartments 52 is withdrawn from the lower portion of the tank by means of the overflow system 36. As shown in Fig. 2, the surface level of anolyte in the anode compartments 34 and catholyte in the cathode compartments 35 is maintained at a higher surface level than the mixed electrolyte in the intervening compartments 52- and tank 32, thus providing a hydrostatic head in the anode and cathode compartments. In other words, by cone trolling the rate of now of anolyte into the anode compartment and catholyte into the cathode compartment, and by proper adjustment of the overflow system 36, the surface level of anolyte in anode compartments 34 and the surface level of catholyte in cathode compartments 35 are maintained at a higher level than that of the mixed acid solution in the intervening compartment 52, thereby providing a hydrostatic head in the anode compartments 34 and cathode compartments 35 with relation to the intervening compartments 52, and providing flow of anolyte and catholyte into the diffusion zones in the intervening compartments.

Fig. 3 is a view partly in section of a cathode compartment, and Fig. 4 is a sectional view taken on line 44 of Fig. 3, showing a suitable means of assembly for a cathode compartment such as may be employed in a nickel liberator tank such as shown in Fig. 2. In Figs. 3 and 4, a suitable cathode bus bar 60 supports the cathode 54 in the compartment by means of a cathode connection such as shown by the reference numeral 59. Reference numeral 58 shows a suitable frame construction for the compartment for maintaining cathode diaphragms 56 in substantially parallel, spaced-apart relationship. The bottom 49 of the cathode compartment provides for the resting of the compartment in slots 50 of compartment bearer-support 33, shown in Fig. 2, for maintaining the cathode compartments in spaced-apart relationship with each adjoining compartment, whereby a diffusion zone, i. e., intervening compartment, is provided between adjacent compartments.

Fig. 5 is an elevational view of a manifold feed assembly such as may be employed for feeding anolyte or catholyte to the respective compartments of the novel liberator cell such as shown in Fig. 2. In Fig. 5, a tank 32 having a suitable lining 33 is shown provided with an overflow system 36 hereinbefore described in connection with Figs. 1 and 2. A riser 35 carries catholyte from a main feed line into a header such as pipe 6| which has a series of outlets 52 arranged in a manner such as shown in Fig. 5. Risers 63, preferably soft rubber tubes, are connected to each outlet 62 on pipe 6! and the free end of each riser 63 is curved over the top of tank 33 whereby the catholyte flowing through riser 30, pipe 6|, and risers 63 flows into th cathode compartments suspended in tank 32. Orifice 3i connecting riser 30 to pipe 6! maintains the rate of flow of catholyte at the desired rate into the cathode compartments. For feeding anolyte to the anode compartments 34, a manifold system such as l hereiribeforedescribed for thecatholyte feedmay be employed: 'Ihus,ain-.Fig-15,.a conduit such as cmiduit 2l', is shown which carries anolyte, and whiclrr'conduit may-beconnectedto a suitable orificeaandcaassembly of risers, to maintain the desired rate of flower anol-yteto the anode com partments a manner similar .to the assembly otccnduitiw, orifice 3|, pipe 6! and risers 63 for feeding of catholyte to the cathode compart- K161513355 "Figs? isa plan view at he bus bars and electrode suspension means and la. 6 is an elevation thereof taken on the line Set of Fig; 7 showing theraaede and cathode bus bars nd the means ier: obtaiiiiril; emperlearances for the sheds andz cathogie chnihartmehts suspended in the tank In Figs. 6 and 'Y- reieience nii'meral 32 a rytaleompartmentta k. having a suitable 1i mgss; in which comr'iartmnts theanode and athode pomliai'tznnts aie susiinded as shewnin Fig.2. i Cathode bus bar 'subb'oits, 'siiiih as wcad strips as, support the cathode bus ba'is tifll fimilailijithodbus bar supports, such as wood strip 65, support the anode bus bars 655,

The anode bus bars 56 and cathode bus bars 513 are assembled in amass-r; such as shown in 6 and 7 whereby a spaced-apart relationshi'p ie maintained thereby roviding the intervening-eemp'artment 52; shown in Fig. 2, between adjacent compartments. Furthermore Figs. 6

a ridsh'ow a suitable mea ns of a'ss'enr bly for eurrent ear'ryine membe s ma, connecting to anode bus cars 63, jivhieli carry current to the anode-builders: Similarly, current carrying members fi'lEconnecting tothe cathode-bus bars fill-,harr'y current to the cathode bus bars.

Ii'-iny-"1iractice-of the bresent invention, the elct o-refiningtanks; such as the mumen tank er Fig. '1, are connected to each other in series and enorm ty of slieh tank c'oh'r'iectd in this manner constitutes electrical circuit, With reference to Fig. 7-, in the tank cell 32 A,the anode bus bar s 155 are in-contact with the anode current carrying members 61A.- The cathode bus bars 60, intank cell 32A, are not in contact with i a cathode-current carrying member, but only with a conductor, 1. e. copper, such as shown by reference numeral 68, having no outside electrical contacts." The conductor 68 serves to dis tributethe current uniformly and, to form an electrical contact betweenthe two' tank cells, i-.=e.--3'2A and 32B, such as shown in Fig. 7. Conrenew; intankcell 32B, the cathode busbalfs so make contact with cathode current carrying member 67B, and the anode bus bars 66 contact conductor 68. Thus in an arrangement such as shown by Fig. 7', consideringthe new. of current through the solution from anode, to. cathode, the current enteringat the anodes in tankcell 32A flow-s through the solution to the cathodes in tank bell 32A, and out through the cathode bus bars in'tank'cell 32A to conductor 68. Thence, the" current flows through the anode bus bars 66 and anodes in tank cell 323, through the solu; ti'cn to'the cathode, andthrough the cathode bus ba'r fifl tocathode current carrying member 5113 Fig. 8 is an elevational view, and Fig. 9 is a sectional View of an anode compartment frame such as may be employed in practicing the present invention. In Figs. 8 and 9, reference nuineral' 34 shows a suitable anode compartment having diaphragms 55 maintained, in the manner shown, in su stantiany parallel, spaced-apart ielationshirf. Fig. 11 is an elevational View of an anode 53, attached by suitable means, such as lugs,.:5l,.to. an anode husbar 5.6. .lntm pl iirf. ticeof the present invention, an anode assembly such .as shown inFig. 11 is suspended in an. anode compartment frame such asshowninzfiigs, 8 and9 to comprisean anode compar ment fo suspension in a tank, such astank 32, in Fig.2.

Fig-10is an elevational view. of; a, cathode a p sembly. comprising cathode 54 attaqhedby. suit: able. means, such. as, cathode connection 5,9, hol d-, ing the cathode tathebus bar. in my mac; tice of thepresent invention, thecathode assem: bly shown in Fig. missuspended in the cathode compartment in a manner such as shown in- Figs.

.The. anode emp oi ed if; the antes, empart= ments of-th novel liberatr cell dtth eres'at invention is insoluble node. satisfactory .ii'= ample's 'of -whichare lead nodes or sweetness of inshluble anodes normally emnloyed all sat-rate lectrolytes n pr cesses for reeeveqefhickeh In my practice 6f the piesentiiiviitioii, I ri'rere to emslo lead anodes containing sheet 6% antimony, as I have found that theseanedes fierform;-satis'factorily and lead is not added to the electrolyte system as a result of the use of such moses .irhediap'hr'agms e eloyjed for the antderaiii cathode corniiartment-s of the novel lib'eiatgr cell are 'generallyorthe acid-resistant typ'e. In'my preferred embodiment or the present invention, a dura-lilad fabric ervinyi resin is e emyea'ror theanode and cathode compartment a aehragms; sun another type of di phragm, that has fieii found to e satisfactory" in; racticing i'ny' iii-yention is a diaphragm consisting of glass cloth:

In practicing the resent invention, when during operation of the cell it isd's ired to remove the anodes and cathodes from their respective comb'artmen't's, the anodes and cathodes are removed single from the comiiaitmntsiiy siiitable means, such as a traveling crane, the hook 6? which is-attached to the anode or cathode bar of theelectrode to be removed and the electrode is lifted out of the compartment. Similarly, anodes and cathodes are lowered'into place singly into the respective comliar'trhe'nt's.

The cathodes employed in the cathode com partments of the novel liberator cell may be of suitable types generally used in electro-Wiiming of nickel by ele'ctrodepositio'n. In my referred embodiment of the present invention, I employ nickel starting sheets, such as are Well known to those skilled in the art, for the cathodes in the cathode compartments. I i In my novel process for recovery or nickel from a chloride-ion containing cath'ol yte, employing a novel liberator cell, such aspi'ovided by the present invention, an aqueous acid solution substanmany free of chloride-ion is employed as the 'aildlyte. A Suitable shown: is an aeueoussoiution containing sulphuric acid. The acid Content if the anolyte is determined loythe and equire; ments of the electrolyte system as a whole but sufiicient acid should be present to make the present invention, the acid requiremeatser the liter of sulphuric acid, and preferably seen 1 te s I have found that at this and concentration, the

other appneauens, wherein the and requir ments peratures exceeding about 140 Rare employed,

the diaphragm fabrics and tank linings may be deleteriously affected. Lower temperatures than about 100 F. may be employed, but use of such lower temperatures results in higher power consumption in operation of the novel process described herein for recovery of nickel. A temperature range of about 120 F. to 130 F. has been found to be satisfactory for the anolyte, as use of temperatures within this range provides the desired results and also allows for absorption of heat generated in the event that local short circuits may occur in the system.

In my particular application of the novel process embodied in the present invention, current densities within the range of about to 50 amperes per square foot have been found to be entirely satisfactory, and preferably, are employed in practicing the present invention. Although current densities less than about 20 amperes per square foot may be employed, the use of such lower current densities necessitates employing a large number of tanks to remove the desired quantity of nickel. As for current densities exceeding about 50 amperes per square foot, I have found that use of such high current densities results in production of exceedingly rough cathodes, and therefore, it is preferred that a current density of less than about 50 amperes per square foot may be employed.

In general, the catholytes that may be employed in practicing the present invention are similar to those set forth in my application, Serial No. 472,471, now United States Patent No. 2,394,874, relating to the electro-refining of nickel with sulfate-chloride electrolyte. Thus, an aqueous catholyte that can be satisfactorily employed in the present invention contains about to 60 grams per liter of nickel, about 27 to 30 grams per liter of chloride ion, and about 71 to 120 grams per liter of sulfate ion. The pH of the catholyte is preferably maintained at pH 4.0 to 5.0 at a temperature of 100-120 F. In my preferrcd embodiment of the present invention, I

employ an aqueous catholyte having the following composition:

Constituent Grams per Liter Abo 0.0001 About 0.0002 to 0.0005

About 0.0001 About 0.0001

10 e1 results obtained by employing the present invention. In the cathode compartment of the novel liberator cell, the conditions to be fulfilled to allow the flow of current through the catholyte are that either cations or anions or both anions and cations pass through the cathode diaphragm. In the present application, I impose the condition that all the current must be carried through the cathode diaphragm by the anions. This, I believe takes place in the following manner: at the instant of discharge of a nickel ion, giving up its two positive charges, a sulfate anion or two chloride anions must migrate out of the oathode compartment to maintain ionic equilibrium within the compartment. This flow of free anions through the diaphragm constitutes a flow of electrons or negative electricity towards the anode. Similarly, at the anode compartment, I impose the condition that all the current must be carried through the anode diaphragm by the cations. The mechanism, I believe, is as follows: within the anode compartment, oxygen is liberated at the anode at current efiiciency as a result of hydroxyl ion discharge. At the instant of discharge of a hydroxyl ion, giving up its unit of negative charge, a hydrogen ion carrying a unit of positive charge must migrate through the anode diaphragm to maintain ionic equilibrium within the compartment. The continuous flow of these free positive ions towards the cathode constitutes a flow of positive electricity. Combining the two compartments by placing between them a middle compartment containing an electrolyte constitutes an electrolytic cell, the overall operation of which may be described as follows: in the middle compartment, the ions are free to move under the influence of the electric current and the cations will migrate towards the cathode while the anions will move in the opposite direction. The fraction of the total current carried by either the cations or the anions will be determined by their respective mobilities. Thus when current is flowing through the cell, there is a transfer of cations in the direction of the cathode and of anions in the direction of the anode. At any given plane in the middle compartment, the net transfer of cations at the plane is equivalent to the sum of the cations migrating into the plane and of the cations migrating out of the plane. The quantity of matter transferred must be equivalent to one equivalent weight per Faraday. There is, therefore, a boundary of cations moving towards the cathode and a similar boundary of anions advancing towards the anode. In the vicinity of either diaphragm, the advancing boundaries of anions and cations meet a flow of oppositely charged ions which stream through the diaphragm, and a narrow diffusion zone is thus set up in the immediate vicinity of both diaphragms. These diffusion zones form the actual boundaries between the electrode compartments and the middle compartment. At these boundaries, a free exchange of ions can take place and the electrical circuit is completed between the anode and the cathode. Hence it may be considered that the diaphragms act as mechanical barriers preventing the diffusion of ions, while the diffusion Zones form the permeable boundaries which allow the free ionic exchange and thus allow for an unhindered flow of current. Although the believed reasons hereinbefore given for the novel results obtained by practicin the present invention are recited above, it is to be understood that the theory for these reasons may change. However, regardless of the reasons unilerlying the improved*rsultsobtained'with the fpfresent'invention, has'heen found 'that'by'en earing the novel cell andlprocess employing that ear, I have provided for 'efiici ent recovery'of nicke1; at a cathode from a' chloride -ion' containing electrolyte without liberation of chlorineat insoluble anodes. n r

order that-those skilled in'the art may have abetter understanding of the presentinvention, the following example is given, employing a novel fnbemmmen; such is-described in Fig; 2, for "recovery oini ckel from a sulfate-chloride nickel electrolyte without liberation of chlorine at the anode.

Example --in an arrangement,=such-as shown in Fig. 2, an electro-refiningtank having an overflow system is-filledwith a mixed acid-electrolyte in the following manner:

An aqueous solution containing about grains per liter of sulfuric acid is run into the tank until the liquor level reaches the top of the compartment' supports 38; AnoIyte; an aqueous solution "'containing alaout 10 grams per liter of sulfuric acid; is-then-introduced into the anode compart- "merits 3fiand catholytai e. an aqueous solution containing sulfate-,chloricleand nickel ions, is introduced into-cathode compartments 35. 1 Both anolyte and catholyte areintroduced into the respective compartments at rates of flow su ficiently rapid to maintain ate-adequate flow through the respectivadiaphragrn to prevent infiltration of foreign ions intothe anode-and cathode cornpartmentsfl Sulfuric acid solutions, similar to that introduced into the tank; are introduced into "the middle compartmets 5?. at the same time as the anolyte isintroduced-into the anode compartments and cathol-yte' into the cathode compartments; at a reduced rate of flow to=inaintain thel-iquor level in the middle compartments below theliquorlevels in the cathodeand anode com- :partments, to such as-about-z inches below the liquor levels in-the anode and cathodecompartinentsw' As soon as-the liquor'levels in'the three compartments-anode compartments 3-3, cathode compartments 85: and middle compartments 52, have reached the desired operating levels; thefiow of sulfuric acid solution to the-middle compartments is stopped {and-the flow of 'anolyte and catholyte is allowed to-proceedat the desiredrates through the respective orifices;- The tank is then ready for operation. The anode: compartments,

containing 6% antimony-lead anodes, andcathode compartments, containing nickel starting sheets as cathodes are arranged in the tank in the inanner shown in Fig. 2. In nay-practice of the present invention, thenovel liberatorcell contains; cathode and anode compartments.

A one inch space separates the anode compartjn ents ifrorn" the" cathode corn partments and the intervening -sp acesconstitute the middle comtea u -The purified nickel electrolyte containing about setter-ems per liter of nickel, 27-30- gramsv per lit of chloride ion and 71 129 grams per liter of sulfate ion area-imp the cathode compart- "r'fieiits'ata rate'o'f 300 milliliters per minute-While an aqueous solution containing. 19 grains per liter ZQ'fH'zSOi is fed into the anode compartments at rat ofsoo ministers per minute. During opei'at ri'o'f fine 0e11,thenuxedaeidiiqubr'from the mid ecdfipartinents and tanks continuously efn'oved by "Ineansf of the overflow "system, .The rate o'f ffioiv of anolyte at" about milliliters per in'i'nut'e 'irito theanode compartments; and

Arequired for the purpose. present invention, each nickel liherator cel]. of

catholyt e'at 300 milliliters per minute minding :cathode compartment has been found to he a "sufficient rate of flow to provide a hydrostati'c head in these compartments with respctto the intervening. compartments and to provide ajll'ow of anolyte and catholyte into" the intervening compartments. ,The; satisfactory rate oiiloiv oi' 'anolyteintothe anode-compartments and catholyteinto the cathode compartments, whereby a hydrostatic head is maintained in these co npartments with relation to the electrolyte inthe -inte'rwning compartments toinsure flow of anthe diaphragms.

' The: temperature of the anolyte and catholyte is maintained at about- F.' The total current flowing through the tank is 650,0 ampere's-and a voltage of 6.5, volts providing anano'de and with- "ode current density. of approximately 30 amperes per square foot. v 4

' Durin'g operation of thecell the catholyte containing 56 5'?" grams per liter o'f nickel, flovvs" to each cathode compartment at 300 niilliliters per minute. At each cathode,4.9 grains of nickel 'arerernoi' e'd iron 1 solutionper, m'inut'a'" Thus the depleted nickel electrolyte flowing through the cathode diaphragm has a nickel content of approiiimately d0 grains per liter; At eachjanod, oxygen is liberated at 109% current efficiency withasimultaneous liberation of hydrogen ions. This results in the production at" each anode of aquantity of acid equivalent to 7.9 grains (if perrn'inute." Since anolyte containing 1'0 grains per liter of H2804, flows to each anode compartment at the, rate of 50:3 rnfillil-iters per "minute, the anol yte flowing through the anode diaphragm has a total acid content equivalent to 25:8 gra ns'pe'r liter of H2804. v

The anolyte and catholyte flovgin'g throughthe diaphragm are nixec'lin the middle con'1par nie'nts to for n an acideleotrclyte liquor containing app roxi'in'ately l 5-- gran s p'er liter of nickel and 16 grams per literof H2504. The acid liquor flows from t'he:tanlr by means of the overflow system and is' used; forpH correction of thelp'uri fied nickel electrolyte andrepl'ac'es an: equivalent quantity or fl-Iz'SOlt which would otherwise be In my .operationoi the thetype shown in 2, operating at a total current of 6500 amperes per square foot, removes approximately 375 lbs. of nickel per day from the eledtrolytesystem and produces a quantity of acid approximately equivalent to 625 lbs. of I- I2S O'4 per day; .--During electrolysis, heavy liquoi 'infiL tratio'nfroin' the middle compartments intothe lower portions of the anode compartments isi s uh stantiallyeliminated, and thus, the anode :com' partments are substantially free of chloride. ions, and as. a result, chlorine is not liberated-at; tlie anode. Hence, nickel is removed efficiently a'tthc cathodes Without liberation of chlorine at the divisional application Serial No.-r5,925, filed .o'n Marbh 1991948.

embodiments thereof, those skilled in the art will readily recognize that variations and modifications can be made. Such variations and modifications are to be considered to be within the purview of the specification and the scope of the appended claims. Thus, although the present invention has been described in conjunction with a multicell arrangement, as shown in Figs. 1 and 2, it is within the scope of the present invention to include unit nickel liberator cells, as for example a liberator cell comprising a suitable receptacle provided with a suitable overflow and having an anode compartment and cathode compartment suspended therein separated in a manner whereby the space separating the two compartments constitutes a middle compartment, thereby forming a 3-compartment cell. Furthermore, although the present invention has been describedin conjunction with an aqueous sulphuric acid anolyte and a chloride-ion-bearing catholyte, it is within the scope of the present invention to include the electrolysis of solutions containing two or more difierent anions where it is desired to prevent the anodic reaction of one or more of the anions. However, in employing a solution containing one or more anions, the anolyte employed and the product of the anode reaction must be compatible with the electrolyte and process as a whole. Conversely, it is within the scope of the present invention to include electrolysis of a solution where it is desired to prevent cathodic reaction of one of the constituents of the solution.

I claim:

1. A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essentially of water with hydrogen ions to provide a pH of about 4 to about 5 and with about 56 to about 57 grams per liter of nickel, about 27 to about 30 grams per liter of chloride ions, about 71 to about 120 grams per liter of sulfate ions, and about to about grams per liter of boric acid, said solution being at a temperature between about 100 F. and about 120 F.; introducing into an adjacent, acid-resistant, diaphragmous-walled anode compartment containing an insoluble lead anode having a content of about 6% antimony and spaced apart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment 2. solution consisting essentially of water with about 10 grams per liter of sulfuric acid but substantially devoid of chloride ions, said solution being at a temperature between about 100 F. and about 140 F.; maintaining the level of each of said solutions in the respective compartments suificiently high to cause each of said solutions to flow through the respective diaphragmous walls to form mixed solutions in said intervening compartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the depths of both the anode compartment and the cathode compartment at a rate suficient to maintain the level of the mixed solutions in said intervening compartment below the respective levels of the solutions in said anode compartment and said cathode compartment and to maintain the respective flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode 1 and said cathode at an anode current density between about 20 and about amperes per square foot to deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

2. A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essentially of water with hydrogen ions to provide a pH of about 4 to about 5 and with about 40 to about grams per liter of nickel, about 20 to about 30 grams per liter of sodium, about 2'1to about 30 grams per liter of chloride ions, about '71 to about 120 grams per liter of sulfate ions and about 15 to about 25 grams per liter of boric acid; introducing into an adjacent, acidresistant, diaphragmous-walled anode compartment containing an insoluble lead anode and spacedapart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment a solutionconsisting essentially of water with sulfuric acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufiiciently high to cause each of said solutions to flow through the respective diaphragmous walls to form mixed solutions in an intervening compartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervenin compartment at a level below the anode at a rate sufiicient to maintain the level of the mixed solutions in the intervening compartment below the respective t levels of the solutions in the anode compartment and the cathode compartment and to maintain the respective flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode and said cathode to deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas atthe insoluble anode.

3. A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essentially of water with hydrogen ions to provide a pH of about 4 to about 5 and with about 40 to about 60 grams per liter of nickel, about 20 to about 30 grams per liter of sodium, about 27 to about 30 grams per liter of chloride ions and about '71 to about grams per liter of sulfate ions; introducing into an adjacent, acid-resistant, diaphragmous-walled anode compartment containing an insoluble anode and spaced apart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially of water with about 10 to about 20 grams'per liter of sulfuric acid but substantially devoid of chlo ride ions; maintaining the level of each of said solutions in the respective compartments sufiiciently high to cause each of said solutions to flow through the respective diaphragmous, walls to form mixed solutions in an intervening compartment located between-and connecting said anode compartment and.- said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the anode at a rate suflicient to maintain the level of the mixed solutions inthe intervening compartment below the respective levels of the solutions in the anode compartment and the cathode compart-- ment and to maintain the respective'flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode and said cathode to deposit nickel on the cathode whereby nickel is electrol-yti'ca-lly recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

" A process for the electrolytic recoveryof nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essentially or water with hydrogen ionsto provide a pH of about 45 to about and with about 40 to about 60: grams per liter of nickel, about 27 to about 3'0 gramsper liter of chloride ions and about '11 to about 120 grams per' liter of sulfate ions; introduping into an adjacent, acid-resistant, diaiphrag-mous-wa-llcd anode compartment containing an insoluble anode and spaced apart from said cathode-compartment by an intervening oompar-lament having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially 01 water with about to about grams per liter of sulfuric acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufiicientl'y'highto cause each of said solutions to flowthrough the respective diaphragmous walls to form mined solutions in an intervening comb part-ment located between and connectingsaid anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the depth of the anode compartment at a rate suflicient to maintain the level of the mixed solutions inthe intervening compartment bi-EIOWthGIBSlJGC- tive levels of the solutions inthe anode compartment and the cathodecompartme'nt andtomaintain. the respective flows of said solutionsinto the intervening compartment; and: passing electric current through the solutions between said anode and said cathode to deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

5. A process for the electrolytic recoveryof nickel from aqueous nickel containing solutions which comprises introducing: into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essen tially of water with hydrogen ionstoprovidea pH of about 4 to about 5' and with about 40 to about (lo-grams per-liter of' nickel, about 2'? to about 36 grams per liter of chloride ions andabout 71 to about 1-20 grams per liter of sulfate ions; intro ducing into an adjacent, acid-resistant, diaphragmous-walled anode compartment containing an insoluble anode and spaced apart fromsaid cathode compartment by an intervening cumpartment having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially of water with asmall amount/up to about grams 16 7 per liter of sulfuricacid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufiiciently high to cause each of said solutions to flowthrough the respective diaphragmous walls toform mixed solutions in an intervening compartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the anode at a rate su-iiicient to maintain the'level of the mixed solutions in the intervening com-- part-merit below the respective levels of the-solutions in the anode compartment and the cathode compartment and to maintain the respective flows of said solutions intotheintervening compartment; and passing electric current through'the solutionsbetween said anode and said cathodeto deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickelgand chloride ions while substantiallypreventing evolution of chlorine gas at the insoluble anode.

6; A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resist diapliragmcue-walledcathode compartment containing a cathode a solution consisting essentially of water with hydrogen ions to provide a pH" of about 4 to about 5' and with about 40 to about 60 grams per liter of" nickel, about 2'7 to about 30 grams per liter of chloride ions, about '71 to about 129 grams per liter of sulfate ions and about 15- to about 25 grams per liter of-boric acid; introducing into anad-jacent, acid-resistant, 'diaphrag-mous-wal-led' anode compartment containing an insoluble anode and spaced apart from said cathode compartment by" an intervenl ng compartment having common diaphragmous walls with said anode compartment and. said cathode compartment a; solution consisting essen-tially of water with sulfuric acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufiici'ently high to cause each of said solutions to flow through the respective diaphragmous walls to form mixed solutions in an interveningcompartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at alevel' below the anode at a rate sufficient' to maintain the level of the mixed solutions in the intervening compartment below the respective levels of the solutions. in the anode compartment and the cathodecompartment and to maintain therespective flows ofisai'd solutions into themtervening compartment; and passing electric current through the solutions between saidanode and said cathode to deposit nickel. onthe cathode whereby nickel is electrolytically recovered from aqueous. solutionscontaining nickel and chloride ions while, substantially preventing evolution. of chlorine gas at the insoluble anode.

T; A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises, introducing. into an acid-re.- sistant, diaphragm'ous-walled cathode compartment containing a cathode a solution consisting essentially of' water withhydrogen ions to provide a pH of ab cutj' l to} about 5 andwith nickel; sodium"; chloride ions,.su1fate ions andl boric acid} introducin into an adjacent, acijdrresistant. diaphragmousewalled anode, compartment con-- training an insoluble anode and spaced apart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially of water with sulfuric acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufficiently high to cause each of said solutions to flow through the respective diaphragmous walls to form mixed solutions in an intervening compartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the anode at a rate sufiicient to maintain the level of the mixed solutions in the intervening compartment below the respective levels of the solutions in the anode compartment and the cathode compartment and to maintain the respective flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode and said cathode to deposit nickel n the cathode whereby nickel is electrolytically recovered from aqueous solutions containin nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

8. A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode a solution consisting essentially of water with hydrogen ions, nickel, chloride ions, sulfate ions and boric acid; introducing into an adjacent, acid-resistant, diaphragmous-walled anode compartment containing an insoluble anode and spaced apart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially of water with sulfuric acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufiiciently high to cause each of said solutions to flow through the respective diaphragmous walls to form mixed solutions in an intervening compartment located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the anode at a rate sufficient to maintain the level of the mixed solutions in the intervening compartment below the respective levels of the solutions in the anode compartment and the cathode compartment and to maintain the respective flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode and said cathode to deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

9. A process for the electrolytic recovery of nickel from aqueous nickel-containing solutions which comprises introducing into an acid-resistant, diaphragmous-walled cathode compartment containing a cathode an acid solution consisting of water, hydrogen ions, nickel and chloride ions as essential ingredients; introducing into an adjacent, acid-resistant, diaphragmouswalled anode compartment containing an insoluble anode and spaced apart from said cathode compartment by an intervening compartment having common diaphragmous walls with said anode compartment and said cathode compartment a solution consisting essentially of water with acid but substantially devoid of chloride ions; maintaining the level of each of said solutions in the respective compartments sufficiently high to cause each of said solutions to fiow through the respective diaphragmous walls to form mixed solutions in an intervening com partnient located between and connecting said anode compartment and said cathode compartment; withdrawing the mixed solutions from said intervening compartment at a level below the anode at a rate sufiicient to maintain the level of the mixed solutions in the intervening compartment below the respective levels of the solutions in the anode compartment and the oathode compartment and to maintain the respective flows of said solutions into the intervening compartment; and passing electric current through the solutions between said anode and said cathode to deposit nickel on the cathode whereby nickel is electrolytically recovered from aqueous solutions containing nickel and chloride ions while substantially preventing evolution of chlorine gas at the insoluble anode.

LOUIS SECONDO RENZONI.

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

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1900 Number Number

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