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AU652179B2 - Insoluble anode for electrolyses in aqueuos solutions - Google Patents
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AU652179B2 - Insoluble anode for electrolyses in aqueuos solutions - Google Patents

Insoluble anode for electrolyses in aqueuos solutions Download PDF

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Publication number
AU652179B2
AU652179B2 AU84896/91A AU8489691A AU652179B2 AU 652179 B2 AU652179 B2 AU 652179B2 AU 84896/91 A AU84896/91 A AU 84896/91A AU 8489691 A AU8489691 A AU 8489691A AU 652179 B2 AU652179 B2 AU 652179B2
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Australia
Prior art keywords
anode
bimetallic
framework
bus bar
anode according
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Application number
AU84896/91A
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AU8489691A (en
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Pierluigi Fracchia
Marco Olper
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Ecochem AG
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B U S Engitec Servizi Ambientali Srl
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Assigned to ECOCHEM AKTIENGESELLSCHAFT reassignment ECOCHEM AKTIENGESELLSCHAFT Alteration of Name(s) in Register under S187 Assignors: B.U.S. ENGITEC SERVIZI AMBIENTALI S.R.L.
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02Electrodes; Connections thereof

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)

Description

C V P/0o/oil 28/91 Regulation 3.2(2)
AUSTRALIA
Patents Act 1990
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT o 0* o p 0000 0000 V 00 40 0 O 00 0 0 4 00 9009 0000 9 00 00 0 0 00 Application Number: Lodged: Invention Title: INSOLUBLE ANODE IFOR ELECTROLYSES IN AQUEOUS SOLUTIONS a 0 06 Ie The following statement Is a full description of this Invention, including the best method of performing it known to 0~us "INSOLUBLE ANODE FOR ELECTROLYSES IN AQUEOUS SOLUTIONS" The extraction of heavy metaLs from the aqueous solutions of the salts which contain them, by electroLysis (electrowinning), requires the use of insoluble anodes which are good electrical conductors, and simultaneously are endowed with a high enough resistance to the electrolyte used and to the products from the relevant anodic reactions, and, finally, favour the development of oxygen.
For those metals which are more commonly produced 10 by this route: copper, nickel, manganese, zinc, cadmium, and so forth, the present art preferably uses j anodes of bonded Lead (with antimony, silver, calcium, and so forth).
In the usual sulfuric baths used to electrowin the above said metals, the lead anodes get coated with a Sthin Layer of lead sulfate which, by oxidation, is transformed into a layer consisting of Pb dioxide, which protects them from further corrosion and which, o.o by being conductive, uses the development of 02 with a i; o" 20 suitably Low oxygen overvoltage.
In order to electrowin copper and nickel from the solutions of their sulfates, anodes have being used for many years, which consists of Lead containing 6-8% of Sb, and which are consumed very slowly, unless chloride ions are present in the electrolyte. Unfortunately, the anode of Pb/Sb does not prevent Pb from polluting of cathode.
On the contrary, for zinc electrowinning, anodes of Pb with 0.5-1% of Ag are used, which are obtained by 2.
casting or Lamination, and sometimes are provided with grooves to favour oxygen development and other times are provided with circular holes to favour the circulation of the electrolyte. The conduction of electrical current throughout the anode is secured by inserting the copper bar inside the body of the same anode, by melting. The resistance of these anodes to the chemical attack by the electrolyte is undoubtedly good, and the useful operating Life of such electrodes 10 is often longer than 2-3 years.
A negative characteristic consists in that, owing to the presence in the zinc-containing solution, of a *94o Scertain level of manganous ions, adhering scales of MnO2 are foried on the anode, which become thicker and thicker with time.
When these scales get detached, owing to natural processes, they release particles of Pb02 and/or of ar PbS04, which increase the Pb level in the cathodic 6 09 zinc.
0 20 Another common problem displayed by the lead anodes used in the above cited electrolyses, is the Slarge amount of immobilized metal (the weight of an 4 t anode of the cells known from the prior art is always higher than 100 kg), and the costs deriving from the periodic restoration of the anodes. Furthermore, in many facilities, the burden should be taken into consideration, which derives from the periodic removal of the scales (every 2-4 weeks), which is carried out in order to improve the quality of produced zinc, and reduce the cell voltage.
3.
The production of lead by the etectrolytic route is presently in the focus of interest of the big metallurgical industry: the fluoroboric and fLuorosiLicic electroLytes, preferred owing to the higher quality of deposits which can be obtained, cai,;ses serious problems of resistance of the anodic material to arise.
E.R. Cole et at., USP-42 72 340, uses an anode constituted by a titanium sheet electroLyticaLLy coated O 10 with a thin-texture Layer of PbOz, with a particularly compact structure.
0 ,o M. Ginatta, USP-4 098 658, uses anodes made from 113 graphite bars, which get naturally coated with PbOz, 3' and are sheltered by it.
R.D. Prengaman et aL., USP-4 236 978 uses anodes made from a graphite plate wrapped in a net made from a plastics material, which serves as a reinforcement for the deposit of PbOz, and counteracts the brittLeness thereof.
oo 20 All these types of anodes display a poor o o, o electrical conductivity, are rather brittle', and their useful operating life is rather short.
Also the probLems caused by the anodic materials used to produce oxidizer halogenated salts (at present, activated Ti or Pt are used), are not completeLy solved.
In EP Public. No. 328 189 to the same Applicant's name, an electricaL conductor is disclosed, which is suitable, in particuLar, for use as an insoluble anode in electrowinning processes and i -PX I a a 0 a 00 0 00 0 0 0 0 0 0 0 09 0600 0 0 00 electrochemical processe in general, which is characterized in that it is constituted by a bimetallic wire composed by an inner copper core, coated by a thinner, external Layer of a transition metal preferably selected from tantalum, titanium and niobium.
The present invention proposes to use an electrical conductor of the above said EP Public.No. 328189 to the same Applicant's name and, as its main purpose, aims at supplying, with it, an anodic structure which is particularly able to resist to the electrolytes and to the very aggressive products from the anodic reaction, which are found in the electrowinning of the main heavy metals (copper, nickel, zinc, cadmium, lead, and so forth) from the aqueous solutions of their salts.
In particular, the anodic structure of the present invention should also be suitable for being advantageously used for the electrolytic production of 20 a large number of oxidizer halogenated salts (chlorates and perchlorates, bromates and perbromates, iodates and periodates), which require that an anodic material is used, which displays a particularly high resistance to corrosion.
In order to achieve such purposes, the present invention proposes an insoluble anode for the electrolysis of aqueous solutions, h a r d in that z- id n dc eompriz s-a framework which supports a bus bar of copper provided with vertical holes, and a plurality of electrical conductors, constituted by 0 0 0 4 0 00 0 0 0 01 0 0i 00 0 0i 0 1 ,x .4* N 6; ii .i 4.
*0 00 0 0 000 o 0; 0 0 0 00 bimetallic wires consisting of an inner copper core coated by an outer, thinner Layer of a transition metal, with each of said bimetallic wires being given a fork shape, which fork is fastened in a vertical position onto said framework, so that the free ends of each of said fork-shaped elements pass through the above said vertical holes provided in said bus bar.
The transition metals preferably are tantalum titanium niobium (Nb).
In order to better describe the features and advantages of the instant invention, an exemplifying form of practical embodiment thereof which in no way should be construed as being limitative thereof is disclosed in the following, with reference to the figures of the accompanying drawings.
Figure 1 shows a front elevation view of an anode according to the present invention.
Figure 2 shows a schematic perspective view of a detail of the anode according to the present invention.
Figure 3 shows a sectional view made along the section line III-III of figure 1.
Referring to such figures, an anode according to the present invention comprises a copper bar 1 with a rectangular cross-section, which acts as a bus bar a current bearing bar), provided with vertical holes 11 for inserting through, and horizontal screwthreaded holes for fastening onto, said bus bar, the U- shqe4 free ends of 4t- haped elements 2 made from a 4bimetallic conductor CuTa (or CuNb or CuTi), coated with a catalytic layer of Pt and/or PbO 2 Said fork- 0 QO 0'0.0 4 0 P 00 4 0 0 0 *L i t i n~ r~n~, X-1: shaped elements behave as an electrode witl preferential oxygen development, and are positioned on a same plane, so as to form a plurality of longitudinal, co-planar wires.
U -s Aped The bus bar 1 and the f4rk-hpcd elements 2 are
A
all supported by a framework 3, which comprises a pair of uprights made from an insulating plastics material, which performs the function of stiffening the overall structure, so as to make it possible the same anode to 10 be precisely positioned inside the cell.
oo In the accompanying figures, the following are moreover displayed: a structural shape made from a plastic material 4, which constitutes the upper horizontal side of the framework 3, and also performs the function of protecting the copper bar from the acidic mists which ,c can be evolved from the surface of the electrolytic 4 4 bath; a structural shape made from a plastics material 20 which constitutes the lower horizontal side of the framework, inside which the "U"-shaped ends of the U-shaced S--e-pr-k-'h-ap d- elements of bimetallic conductor enter; upper joints 6 and lower joints 7 between the vertical and horizontal sides of the framework; spacers 8 made from a plastics material, slid through, and fastened at determined levels onto, the vertical uprights of the framework, which keep each anode exactly spaced apart from the adjacent cathodes.
In figure 3, the details are shown of the pJ $I U- skaped insertion of the bent ends of the Af rk- shapd- elements of bimetaLLic conductor inside the structural shape and of the fastening, by means of a relevant compression screw, of the free ends of said fork- h:p elements inside the copper bus bar, through the holes 9. A structural shape made from a plastics material is superimposed, as a cover, to the copper bar, in order to protect it against the electrolyte drops which otherways would strike said copper bar during the 0 QQ 10 removal of the cathodes.
o o0 The advantages of the anodic structure according 0 to the present invention can be summarized as follows:
I,
Hiah eLectricalconductivty: *Copper constitutes approximately 90% of the surfacearea of the cross-section of the bimetallic wire; each anode is capable of allowing currents of many Shundreds of amperes to circulate without losses; 0 0 Light-weight: As compared to the corresponding anodes made from Pb, °oo 20 this structure has a weight which is approximateLy 1/10 of the weight thereof. As a consequence, the structure of the electrolysis ceLL is very simplified; Riduced overall dimensions of the metal comoonents of the anode: The distance between opposite-sign electrodes can be reduced to a minimal value; InalterabilitY of the anodic surfaces: Tantalum which coats, with a continuous and compact coat, the metal parts of the anode, is the best f /y'i 8.
solution offered by the present state of the art, for providing corrosion-preventing coats; Ltgssen overvoLtage:' The catalytic layer of Pt and/or Pb02, with which the tantalum anode is coated, secures the development of oxygen at the minimal possible voltage from the technical viewpoint; The structure consisting of vertical, parallel wires, well spaced apart from each other, favours the rising 0 A.
10 of the small bubbles of anodic gas, the free circulation of the electrolyte, and the continuous °o renewal of the solution at cathode/soLution oo interface. The cathodic current density can hence be a .a *o increased up to the maximum levels, as allowed by the concentration of the ions of the metal to be deposited; Owing to the same structure of the anode, the anodic o 9 0 current density results to be 3-4 times as large as the cathodic current density.
20 This situation of high anodic density is favourable when at the anode solid products are formed.
O t. In the case of Zn-containing electrolyte, manganese dioxide, which is formed on the anode of the Scell, is preferentially formed in powder form.
Therefore, the scales which adhere to lead anodes which scales must be frequently removed from said anodes are not formed.
This peculiarity can be applied to the production of electrolytic MnOz for dry batteries, in that MnO2 is obtained in continuous mode by filtering the solution .4 contained inside the caLL, without that the eLectroLysis has to be discontinued in order to remove the anodes coated with MnO2, therefore the manuaL removal of the Latter, and the expensive mitLing thereof~, being both avoided.
00 0 o 00 0 f 00 0 boo.
O 0 *000 9 00 .0 0 0 *000 0 0.4*00 0 0 '0 4 14 to

Claims (5)

1. Insoluble anode for the electrolysis of aqueous solutions, including a framework which supports a bus bar of copper provided with vertical holes, and a plurality of electrical conductors, constituted by bimetallic wires ieluding an bo4 o -f Ae free eds of inner copper core coated by an outer, thinner layer of a transition metal, with each of said bimetallic wires being fastened in a vertical position onto said framework, so that the upper ends of each of said bimetallic wires pass through the above said vertical holes provided in said bus bar.
2. Anode according to claim 1, wherein said transition metal selected from the group containing tantalum, titanium, niobium.
8. Anude according to claim I or 2, wherein said bimetallic wire is coated by a catalytic layer of pla.tinum, or of lead dioxide, or of both of them. 4. Anode according to any one of the preceding claims, wherein said bimetallic wires are located within a common plane, parallel to one another. 00 o Anode according to any one of the preceding claims, wherein said bus bar is also provided with horizontal holes for the passage of compression screws for fastening the bimetallic wires. 0 0 S" 6. Anode according to any one of the preceding claims, wherein said framework includes a pair of uprights connected with a pair of horizontal, upper S4", and lower, structural shapes. 9* 7. Anode according to claim 6, wherein said horizontal structural shapes are provided with holes through which said bimetallic wires pass. **V 1) "i. I. cl 4a1. 11 8. Anode according to any one of the preceding claims, wherein said anode includes spacers fastened in a predetermined position upon said framework, so as to keep said anode spaced apart from the adjacent cathodes inside the cell.
9. Anode according to any one of the preceding claims, wherein said bus bar is provided with a sheltering cover. Anode according to any one of the preceding claims, wherein the bimetallic wires are in the form of a plurality of U-shaped elements.
11. Anode substantially as hereinbefore described with respect to what is shown in the accompanying drawings. DATED this 18th day of August, 1993 B.U.S. ENGITEC SERV!ZI AMBIENTALI S.r.I. I r~s e t 4 I t i t 44 44 C WATERMARK PATENT TRADEMARK ATTORNEYS S THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA S 4 SI SKP/MCQ:EK AU8489691 .WPC[DOC. 39] 4, 04 0 :U1 o 0o Sr 0 a 0 0~ a; o 04 ao a "INSOLUBLE ANODE FOR ELECTROLYSES IN AQUEOUS SOLUTIONS" Abstract The present invention relates to an insoLubLe anode for the e aqueous solutions electrolytic produ The anode is a bus bar with vertical and shaped elements, inserted and fast elements, made conductor, coated PbO2, acting as a development; by plastics material, lectrowinning of heavy metals from which contain them, and for the ction of oxidizer halogenated salts. constituted by a copper bar acting as as a current-bearing bar), provided horizontal holes through which fork- made from a bimetallic conductor, are ened; by a plurality of fork-shaped from said filamentary bimetallic by a catalytic layer of Pt and/or n electrode with preferential oxygen a framework made from an insulating which is used to support and stiffen the structure, and for the precise anode inside the cell. positioning of the
AU84896/91A 1991-10-02 1991-10-02 Insoluble anode for electrolyses in aqueuos solutions Ceased AU652179B2 (en)

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Application Number Priority Date Filing Date Title
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AU8489691A AU8489691A (en) 1993-04-08
AU652179B2 true AU652179B2 (en) 1994-08-18

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4108756A (en) * 1973-10-30 1978-08-22 Oronzio De Nora Impianti Electtrochimici S.P.A. Bipolar electrode construction
US4767519A (en) * 1985-03-07 1988-08-30 Oronzio De Nora Impianti Elettrochimici Monopolar and bipolar electrolyzer and electrodic structures thereof
EP0328189A2 (en) * 1988-02-11 1989-08-16 Engitec S.P.A. Process for producing an electrical conductor, in particular suitable for use as an insoluble anode in electrowinning processes, and in electrochemical processes in general, and intermediate product thereof.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4108756A (en) * 1973-10-30 1978-08-22 Oronzio De Nora Impianti Electtrochimici S.P.A. Bipolar electrode construction
US4767519A (en) * 1985-03-07 1988-08-30 Oronzio De Nora Impianti Elettrochimici Monopolar and bipolar electrolyzer and electrodic structures thereof
EP0328189A2 (en) * 1988-02-11 1989-08-16 Engitec S.P.A. Process for producing an electrical conductor, in particular suitable for use as an insoluble anode in electrowinning processes, and in electrochemical processes in general, and intermediate product thereof.

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