CA1321971C - Fluidized bed electrolysis cell with particulate anode - Google Patents
Fluidized bed electrolysis cell with particulate anodeInfo
- Publication number
- CA1321971C CA1321971C CA000546800A CA546800A CA1321971C CA 1321971 C CA1321971 C CA 1321971C CA 000546800 A CA000546800 A CA 000546800A CA 546800 A CA546800 A CA 546800A CA 1321971 C CA1321971 C CA 1321971C
- Authority
- CA
- Canada
- Prior art keywords
- cell
- anode
- valve metal
- electrolysis
- bed electrolysis
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Electrolytic Production Of Metals (AREA)
Abstract
ABSTRACT
FLUID BED ELECTROLYSIS CELL
A fluidized bed electrolysis cell comprising one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide; the cell is useful for electrowinning metals from electrolytes by fluid bed electrolysis; in particular the protective film of valve metal oxide provides an insoluble current feeder and reduces undesirable dissolution of the current feeder thereby improving the performance of the cell.
FLUID BED ELECTROLYSIS CELL
A fluidized bed electrolysis cell comprising one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide; the cell is useful for electrowinning metals from electrolytes by fluid bed electrolysis; in particular the protective film of valve metal oxide provides an insoluble current feeder and reduces undesirable dissolution of the current feeder thereby improving the performance of the cell.
Description
1321~7~
FLUID BED ELECTROLYSIS CELL
This invention is concerned with a fluidized bed electrolysis cell of improved design, as well as with the use of such an elec-trolys~s cell, especially for the dissolution of metal particulates to prepare metal salt solutions.
Fluidized bed electrolysis cells are known in the art, cf.
US-A 4,244,795 and "Chemistry and Industry", 1st July 1978, p 465-467. The fluidized bed electrolysis cells described in these references comprise a particulate metal cathode, one or more conventional anodes and one or more diaphragms, preferably the latter are conceived as tubes or pipes surrounding the anodes. The particulate cathode is fluidized by ad~usting the flow of catholyte, a convenient method for assessing the state of fluidization is by measuring bed expansion. One or more current feeders, e.g. wires, rods, strips, plates, tubes or pipes, that are `
dipped into the particulate cathode, ensure adequate distribution of current over all metal particles. In addition to the fluidized bed electrolysis cells described above, it is also possible to use a particulate metal anode, together with one or more conventional cathodes and one or more diaphragms, preferably the latter con-ceived as tubes or pipes surrounding the cathodes. The particulate anode is fluidized by ad~usting a flow of anolyte. One or more current feeders, e.g. wires, rods, strips, plates~ tubes or pipes, that are dipped into the particulate anode, ensure adequate distri-bution of current over all metal particles.
It will be appreciated that the fluidized bed electrolysis cell may be provided with a particulate metal cathode as well as with a particulate metal anode.
Whilst it has been proposed to employ f1uid bed electrolysis using particulate cathodes for the winning of metals from suitable electrolytes such as hydrometallurgical process streams, most of - , " ,,~ , ' ~32i97~
the practical development work that has been carried out to date has been directed towards another use, i.e., the removal o~ metal ions from waste water streams. As a result of the electrowinning of metals by fluid bed electrolysis is to date at best at the initial stage of development and no practical commercial method is available today~ Fluid bed electrolysis using particulate metal anodes may be used for the preparation of metal salt solutions b~
dissolution of the particulate anode-metal.
One of the problems associated with the electrowinning of metals is the need for an undisturbed continuous operation. Deposition of metal on parts or elements of the cell other than the particulate cathode can lead to interruption of the smooth operation of the cell and continued deposition in undesired locations may lead to shortcircuiting of the cell or immobilisation of the fluidized bed of cathode particles, it also adversely affects efficient use of current. Particularly undesirable is the deposition of metal on the current feeders.
One of the problems associated with the dissolution of particulate metal anodes is the need for an insoluble current feeder to allow undisturbed continuous operation.
The present invention is therefore concerned with means for improving the operation of fluidized bed electrolysis cells, particularly when these are employed for the preparation of metal salt solutions.
Thereto this invention provides a fluidized bed electrolysis cell comprising one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide.
. . ., : , , . !.
' ~
' . . ' , 132197~
- 2a -According to the invention there i8 provided a fluidized bed electrolysis cell comprising: one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide, one or more cathodes, one or more anode compartments and one or more cathode compartments, each anode compartment being associated with an anode, and each cathode compartment being associated with a cathode, and one or more diaphragms for separating the one or more anode compartments from the one or more cathode compartments.
In another aspect of the invention there is provided a process for the dissolution of metals by fluid bed electrolysis in an electrolysis cell of the invention.
Valve metals are defined in this specification to comprise any and all metals or metal alloys which may form a protective oxide layer. Depending on the particular application envisaged suitable cathode valve metals are à.o. Al, Bi, Ge, Hf, Mg, Mo, Nb, Ta, Sn, Ti, W and Zr. Preferred are Ta, Ti and Zr.
Depending on the particular application envisaged suitable anode valve metals are a.o. Al, Mg, Nb, Ta, Ti and Zr, particularly Ta, Ti and Zr.
-- `
' 1321~7~
A method for constructing the special current feeders to be applied in this invention is by employing the feeder as anode in an electrolysis cell with an electrolyte consisting, for instance, of a dilute oxidizing mineral acid, such as sulphuric acid. This technique, known in the art as "anodizing", will produce - by oxidation of the valve metal on the surface of the current feeder -a protective film of the valve metal oxide which is coherent, non-porous and well-adhering to the surface, such film being referred to herein as "anodic" film. It will be appreci~ted that the core of the current feeder may be constructed from a different materal than the valve metal forming the surface of the current feeder. The core may be constructed for instance, from another ~etal, or from graphite. When anodizing ~he current feeder a suitable anode potential is 1 to 30 V, preferably 1.5 to 10 V.
The anodic films on anode feeders can also be formed in situ.
The valve metal oxide film can also be formed by suitable chemical oxidation processes, for instance programmed temperature oxidation in an oxygen containing atmosphere.
Investigations by the Applicants have shown that the thickness of the oxide surface layer has a clear influence on the performance of the current feeder used in the particulate electrode. They have also found that the thickness is closely related to the anode-potential applied during anodizing, the higher this potential, the thicker the metal oxide deposit.
Examples Testing of current feeders was carried out in a fluidized bed electrolysis system of 8 l capacity. Electrolyte was circulated from a central holding tank through a cell of rectangular cross-section (~ 1.5 l capacity) that was divided into two compartments (cathode and fluidized bed anode) with a diaphragm of 10 ~m pore size.
The current feeders of the material tested consisted of 2 mm diameter wires insulated with heat-shrunk pvc tubing leaving only a surface area of 2.0 cm2 uncovered. 3 Feeders were used in the cell in a triangular arrangement with one nearest the diaphragm.
.-~, . :
: :
- . ~..
, -; .~. ;,, : ~
; . ?, ~ .:. . .
:': : ,~. ~ :
- :,. .,. ,:
:' , . ,: .
., ~. :
~32~71 Titanium feeders had been anodized at 2,5 and 20 ~ anode-potential for three minutes, while tantalum and zirconium feeders had been anodlzed at 10 V, each for 20 minutes, all in deoxygenated 0.5 mol.l H2S04 electrolyte.
The cell was operated at a bed expansion of 27% (measured by observing the bed height), at a nominal current density on the beads of 1 mA.cm 2 (a current of 5.0 A). The cell was run for 6 hours. Then the feeders and the granules were withdrawn, washed with water and acetone, and air dried before weighing to determine the amounts of metal dissolved from the feeder and from the granules.
The particulate anode contained Cu-beads, and a Ti current feeder was used. The cathode was a Cu-plate and a polyethylene diaphragm was used. The electrolyte was of nominal concentration of 100 g/l H2S04 and 10 g/l Cu. The Ti feederplate was prepared as described above or in situ anodized in the fluidized bed electrolysis cell. After addition of the Cu-beads the anodic dissolution was carried out with quantitative current efficiency.
~o dissolution of the current feeder occurred, Application of the novel electrolysis cell of this invention for the preparation of metal salt solution involves the dissolution of particulate metal anodes. This may be effected baechwise or in continuous operation, in the latter event metal particles e.g.
beads, shot or chopped wire, are more or less continuously introduced into the anode compartment. Gas evolving from the cathode compartment is also continuously withdrawn from the cell.
The cell would normally be operated at room temperature, although elevated temperatures, e.g. up to 70 C, may also be employed, especially in case that the solubility of the metal salt to be prepared is relatively low. The electrolyte solution is circulated through the anode chamber at flow rates that would give a bed expansion of 0 to 50~, usually up to 20~.
All kinds of particulate anode metals may be used, for instance Cu, Zn and Sn, provided that the metals will dissolve under the conditions employed. The metal salt solution obtained may ... .
, .~
-` 1321~71 be used for electrodepositing purposes (electrorefining) as described above, or for other purposes.
Anolyte concentration may vary widely. Metal concentrations may be obtained for instance in the case of the preparation of Cu-solutions of up to 40 g/l. A typical anolyte will comprise from 35 to 135 g H2S04, preferably 50 to 100 g.
Cell voltage and electrode potentials are adjusted to the various electrolytes and electrodes employed, those skilled in the art will appreciate which combinations can be employed. Selecting the right values forms no part of this invention since the prior art on electrolysis contains enough guiding information.
Since the invention solves the problem of undesired dissolution of metal current feeders, the life time of the cell is dramatically increased, and continuous operation for several months is possible.
- , : :. . ::,, ~ ... :.
~: - - . " . -. ~ . :; .
",, , ~ " ~ :
- . . , ~ .: ~ .
FLUID BED ELECTROLYSIS CELL
This invention is concerned with a fluidized bed electrolysis cell of improved design, as well as with the use of such an elec-trolys~s cell, especially for the dissolution of metal particulates to prepare metal salt solutions.
Fluidized bed electrolysis cells are known in the art, cf.
US-A 4,244,795 and "Chemistry and Industry", 1st July 1978, p 465-467. The fluidized bed electrolysis cells described in these references comprise a particulate metal cathode, one or more conventional anodes and one or more diaphragms, preferably the latter are conceived as tubes or pipes surrounding the anodes. The particulate cathode is fluidized by ad~usting the flow of catholyte, a convenient method for assessing the state of fluidization is by measuring bed expansion. One or more current feeders, e.g. wires, rods, strips, plates, tubes or pipes, that are `
dipped into the particulate cathode, ensure adequate distribution of current over all metal particles. In addition to the fluidized bed electrolysis cells described above, it is also possible to use a particulate metal anode, together with one or more conventional cathodes and one or more diaphragms, preferably the latter con-ceived as tubes or pipes surrounding the cathodes. The particulate anode is fluidized by ad~usting a flow of anolyte. One or more current feeders, e.g. wires, rods, strips, plates~ tubes or pipes, that are dipped into the particulate anode, ensure adequate distri-bution of current over all metal particles.
It will be appreciated that the fluidized bed electrolysis cell may be provided with a particulate metal cathode as well as with a particulate metal anode.
Whilst it has been proposed to employ f1uid bed electrolysis using particulate cathodes for the winning of metals from suitable electrolytes such as hydrometallurgical process streams, most of - , " ,,~ , ' ~32i97~
the practical development work that has been carried out to date has been directed towards another use, i.e., the removal o~ metal ions from waste water streams. As a result of the electrowinning of metals by fluid bed electrolysis is to date at best at the initial stage of development and no practical commercial method is available today~ Fluid bed electrolysis using particulate metal anodes may be used for the preparation of metal salt solutions b~
dissolution of the particulate anode-metal.
One of the problems associated with the electrowinning of metals is the need for an undisturbed continuous operation. Deposition of metal on parts or elements of the cell other than the particulate cathode can lead to interruption of the smooth operation of the cell and continued deposition in undesired locations may lead to shortcircuiting of the cell or immobilisation of the fluidized bed of cathode particles, it also adversely affects efficient use of current. Particularly undesirable is the deposition of metal on the current feeders.
One of the problems associated with the dissolution of particulate metal anodes is the need for an insoluble current feeder to allow undisturbed continuous operation.
The present invention is therefore concerned with means for improving the operation of fluidized bed electrolysis cells, particularly when these are employed for the preparation of metal salt solutions.
Thereto this invention provides a fluidized bed electrolysis cell comprising one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide.
. . ., : , , . !.
' ~
' . . ' , 132197~
- 2a -According to the invention there i8 provided a fluidized bed electrolysis cell comprising: one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide, one or more cathodes, one or more anode compartments and one or more cathode compartments, each anode compartment being associated with an anode, and each cathode compartment being associated with a cathode, and one or more diaphragms for separating the one or more anode compartments from the one or more cathode compartments.
In another aspect of the invention there is provided a process for the dissolution of metals by fluid bed electrolysis in an electrolysis cell of the invention.
Valve metals are defined in this specification to comprise any and all metals or metal alloys which may form a protective oxide layer. Depending on the particular application envisaged suitable cathode valve metals are à.o. Al, Bi, Ge, Hf, Mg, Mo, Nb, Ta, Sn, Ti, W and Zr. Preferred are Ta, Ti and Zr.
Depending on the particular application envisaged suitable anode valve metals are a.o. Al, Mg, Nb, Ta, Ti and Zr, particularly Ta, Ti and Zr.
-- `
' 1321~7~
A method for constructing the special current feeders to be applied in this invention is by employing the feeder as anode in an electrolysis cell with an electrolyte consisting, for instance, of a dilute oxidizing mineral acid, such as sulphuric acid. This technique, known in the art as "anodizing", will produce - by oxidation of the valve metal on the surface of the current feeder -a protective film of the valve metal oxide which is coherent, non-porous and well-adhering to the surface, such film being referred to herein as "anodic" film. It will be appreci~ted that the core of the current feeder may be constructed from a different materal than the valve metal forming the surface of the current feeder. The core may be constructed for instance, from another ~etal, or from graphite. When anodizing ~he current feeder a suitable anode potential is 1 to 30 V, preferably 1.5 to 10 V.
The anodic films on anode feeders can also be formed in situ.
The valve metal oxide film can also be formed by suitable chemical oxidation processes, for instance programmed temperature oxidation in an oxygen containing atmosphere.
Investigations by the Applicants have shown that the thickness of the oxide surface layer has a clear influence on the performance of the current feeder used in the particulate electrode. They have also found that the thickness is closely related to the anode-potential applied during anodizing, the higher this potential, the thicker the metal oxide deposit.
Examples Testing of current feeders was carried out in a fluidized bed electrolysis system of 8 l capacity. Electrolyte was circulated from a central holding tank through a cell of rectangular cross-section (~ 1.5 l capacity) that was divided into two compartments (cathode and fluidized bed anode) with a diaphragm of 10 ~m pore size.
The current feeders of the material tested consisted of 2 mm diameter wires insulated with heat-shrunk pvc tubing leaving only a surface area of 2.0 cm2 uncovered. 3 Feeders were used in the cell in a triangular arrangement with one nearest the diaphragm.
.-~, . :
: :
- . ~..
, -; .~. ;,, : ~
; . ?, ~ .:. . .
:': : ,~. ~ :
- :,. .,. ,:
:' , . ,: .
., ~. :
~32~71 Titanium feeders had been anodized at 2,5 and 20 ~ anode-potential for three minutes, while tantalum and zirconium feeders had been anodlzed at 10 V, each for 20 minutes, all in deoxygenated 0.5 mol.l H2S04 electrolyte.
The cell was operated at a bed expansion of 27% (measured by observing the bed height), at a nominal current density on the beads of 1 mA.cm 2 (a current of 5.0 A). The cell was run for 6 hours. Then the feeders and the granules were withdrawn, washed with water and acetone, and air dried before weighing to determine the amounts of metal dissolved from the feeder and from the granules.
The particulate anode contained Cu-beads, and a Ti current feeder was used. The cathode was a Cu-plate and a polyethylene diaphragm was used. The electrolyte was of nominal concentration of 100 g/l H2S04 and 10 g/l Cu. The Ti feederplate was prepared as described above or in situ anodized in the fluidized bed electrolysis cell. After addition of the Cu-beads the anodic dissolution was carried out with quantitative current efficiency.
~o dissolution of the current feeder occurred, Application of the novel electrolysis cell of this invention for the preparation of metal salt solution involves the dissolution of particulate metal anodes. This may be effected baechwise or in continuous operation, in the latter event metal particles e.g.
beads, shot or chopped wire, are more or less continuously introduced into the anode compartment. Gas evolving from the cathode compartment is also continuously withdrawn from the cell.
The cell would normally be operated at room temperature, although elevated temperatures, e.g. up to 70 C, may also be employed, especially in case that the solubility of the metal salt to be prepared is relatively low. The electrolyte solution is circulated through the anode chamber at flow rates that would give a bed expansion of 0 to 50~, usually up to 20~.
All kinds of particulate anode metals may be used, for instance Cu, Zn and Sn, provided that the metals will dissolve under the conditions employed. The metal salt solution obtained may ... .
, .~
-` 1321~71 be used for electrodepositing purposes (electrorefining) as described above, or for other purposes.
Anolyte concentration may vary widely. Metal concentrations may be obtained for instance in the case of the preparation of Cu-solutions of up to 40 g/l. A typical anolyte will comprise from 35 to 135 g H2S04, preferably 50 to 100 g.
Cell voltage and electrode potentials are adjusted to the various electrolytes and electrodes employed, those skilled in the art will appreciate which combinations can be employed. Selecting the right values forms no part of this invention since the prior art on electrolysis contains enough guiding information.
Since the invention solves the problem of undesired dissolution of metal current feeders, the life time of the cell is dramatically increased, and continuous operation for several months is possible.
- , : :. . ::,, ~ ... :.
~: - - . " . -. ~ . :; .
",, , ~ " ~ :
- . . , ~ .: ~ .
Claims (10)
1. A fluidized bed electrolysis cell comprising:
one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide, one or more cathodes, one or more anode compartments and one or more cathode compartments, each anode compartment being associated with an anode, and each cathode compartment being associated with a cathode, and one or more diaphragms for separating the one or more anode compartments from the one or more cathode compartments.
one or more particulate anodes provided with one or more current feeders carrying on their surfaces a protective film of valve metal oxide, one or more cathodes, one or more anode compartments and one or more cathode compartments, each anode compartment being associated with an anode, and each cathode compartment being associated with a cathode, and one or more diaphragms for separating the one or more anode compartments from the one or more cathode compartments.
2. A cell as claimed in claim 1, in which the protective film of valve metal oxide has been made by anodizing a valve metal film.
3. A cell as claimed in claim 2, in which the anodizing was carried out employing an anode potential of 1 to 30 V.
4. A cell as claimed in claim 2 or 3, in which the protective film of valve metal oxide has been made by anodizing the valve metal film in situ.
5. A cell as claimed in claim 1, 2 or 3, in which the valve metal is tantalum, titanium or zirconium.
6. A cell as claimed in claim 5, in which the current feeder is made of titanium.
7. A cell as claimed in claim 1, in which the valve metal oxide is formed by a chemical oxidation process.
8. A process for the dissolution of metals by fluid bed electrolysis in an electrolysis cell, in which said cell is as claimed in claim 1, 2, 3, 6 or 7.
9. A process for the dissolution of metals by fluid bed electrolysis in an electrolysis cell, in which said cell is as claimed in claim 4.
10. A process for the dissolution of metals by fluid bed electrolysis in an electrolysis cell, in which said cell is as claimed in claim 5.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB878705471A GB8705471D0 (en) | 1987-03-09 | 1987-03-09 | Fluid bed electrolysis cell |
| GB8705471 | 1987-03-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1321971C true CA1321971C (en) | 1993-09-07 |
Family
ID=10613581
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000546800A Expired - Fee Related CA1321971C (en) | 1987-03-09 | 1987-09-14 | Fluidized bed electrolysis cell with particulate anode |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1321971C (en) |
| GB (1) | GB8705471D0 (en) |
-
1987
- 1987-03-09 GB GB878705471A patent/GB8705471D0/en active Pending
- 1987-09-14 CA CA000546800A patent/CA1321971C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB8705471D0 (en) | 1987-04-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4778572A (en) | Process for electroplating metals | |
| EP0114085B1 (en) | Molten salt electrowinning method, anode and manufacture thereof | |
| US4085016A (en) | Method and apparatus for the oxidation of organic material present in concentrated sulfuric acid | |
| US4039403A (en) | Electrowinning metals | |
| US4468305A (en) | Method for the electrolytic regeneration of etchants for metals | |
| US3957600A (en) | Method of and anodes for use in electrowinning metals | |
| US2828251A (en) | Electrolytic cladding process | |
| US2817631A (en) | Refining titanium alloys | |
| US2872405A (en) | Lead dioxide electrode | |
| EP0234727A1 (en) | Porous anodic aluminium oxide films | |
| US3236756A (en) | Electrolysis with precious metalcoated titanium anode | |
| US3974058A (en) | Ruthenium coated cathodes | |
| JPS59166689A (en) | Cathode for electrolytic production of hydrogen | |
| US4364807A (en) | Method of electrolytically recovering zinc | |
| KR101298072B1 (en) | The impurity control specialization electrolytic refining devide for the salt manufacture and for nuclear reactor waste salt manufacturing method using the same | |
| RU2181150C2 (en) | Method of pickling steel | |
| Moskalyk et al. | Anode effects in electrowinning | |
| US4824541A (en) | Fluid bed electrolysis cell | |
| US4832812A (en) | Apparatus for electroplating metals | |
| US4285784A (en) | Process of electroplating a platinum-rhodium alloy coating | |
| CA1321971C (en) | Fluidized bed electrolysis cell with particulate anode | |
| US2453757A (en) | Process for producing modified electronickel | |
| CA1321972C (en) | Fluidized bed electrolysis cell comprising particulate cathode | |
| JP2000256898A (en) | Copper plating method of wafer | |
| US4118291A (en) | Method of electrowinning titanium |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |