EP1560948A1 - Procede d'electrolyse et cellule utilisee dans celui-ci - Google Patents

Procede d'electrolyse et cellule utilisee dans celui-ci

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Publication number
EP1560948A1
EP1560948A1 EP03753140A EP03753140A EP1560948A1 EP 1560948 A1 EP1560948 A1 EP 1560948A1 EP 03753140 A EP03753140 A EP 03753140A EP 03753140 A EP03753140 A EP 03753140A EP 1560948 A1 EP1560948 A1 EP 1560948A1
Authority
EP
European Patent Office
Prior art keywords
deposition
cathode
areas
metal
deposition surface
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.)
Withdrawn
Application number
EP03753140A
Other languages
German (de)
English (en)
Other versions
EP1560948A4 (fr
Inventor
Chung Ho Lam
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Intec Ltd
Original Assignee
Intec Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Intec Ltd filed Critical Intec Ltd
Publication of EP1560948A1 publication Critical patent/EP1560948A1/fr
Publication of EP1560948A4 publication Critical patent/EP1560948A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/12—Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/16—Electrolytic production, recovery or refining of metals by electrolysis of solutions of zinc, cadmium or mercury
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/18—Electrolytic production, recovery or refining of metals by electrolysis of solutions of lead
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00—Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/02—Electrolytic production, recovery or refining of metal powders or porous metal masses from solutions
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/06—Operating or servicing
    • C25C7/08—Separating of deposited metals from the cathode
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B15/00—Obtaining copper
    • C22B15/0063—Hydrometallurgy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention relates generally to an electrolysis process for the recovery of metals from an aqueous solution and to an improved cathode for use in such a process.
  • the primary application of the invention disclosed herein is in relation to the recovery of copper, although the invention finds equal application with electro-recovery of other metals such as nickel, lead, zinc etc.
  • This process is multi-stage and produces a pregnant liquor stream following leaching of the mineral in a chloride medium.
  • the pregnant liquor stream is electrolysed in an electrolysis cell to recover the metal from the solution which deposits on a cathode of the cell. Under high current densities, dendritic copper of high purity is produced on the cathode . In the past it has been necessary to regularly remove the cathodes to strip the plates of the metal deposits so as to maintain current efficiency in the cell.
  • Optimisation of the electrowinning operation is a function of the purity of the pregnant liquor stream , and general cell parameters such as current density, stripping cycle, cell configuration and the degree of agitation. Accordingly, an aim of the present invention is to improve the efficiency of the elecfrowi- ing operation. In particular, an aim is to provide an electrolysis process and cell configuration which is able to better control current density across the deposition surface of the cathode so as to assist in both formation and removal of the metal deposit.
  • the present invention provides an electrolysis process for the recovery of metal from an aqueous solution wherein on electrolysing the solution metal is caused to deposit on a deposition surface of a cathode, the process including the step of
  • the deposition surface maybe of unitary structure or alternatively may be formed from discrete elements which may be spaced apart or in direct contact with one another.
  • Providing a non-uniform current density across the deposition surface provides a mechanism by which the deposition of metal on that surface can be controlled.
  • it allows the metal deposition to be concentrated in certain areas (i.e. the areas of high current density) so as to promote non-uniform deposition across the surface.
  • Non-uniform deposition of the metal is beneficial as it is easier to remove from the cathode which assists in the metal recovery process.
  • the metal deposition is heavily concentrated on the areas of high current density so that the metal deposition is effectively discontinuous across the deposition surface.
  • the concentration of metal deposition in operation of the cell is greater than 80% in the areas of high current density and more preferably greater than 95%.
  • the areas of high current density and low current density extend along the surface in one direction and alternate across the surface in an opposite direction.
  • the metal deposits in a series of generally linear bands which is ideally suited for removal using a wiping action as will be described in more detail below.
  • the electrolysis process induces a non-uniform current density across the deposition surface by providing a cathode which in operation of the cell, creates a non-uniform electrical field having areas of strong electrical field and weak electrical field.
  • the areas of strong electrical field induce the areas of the high current density and the areas of weak electrical field induce the areas of low current density.
  • the non-uniform electrical field can be created through numerous mechanisms, including the geometry of the surface, and by varying the electrical resistance between the cathode and anode along the deposition surface, or by a combination of both these mechanisms.
  • the geometry of the surface influences the electrical field and is related to its surface curvature. Electrical fields are always parallel to the surface so that, sharp edges, or peaks at the deposition surface induce areas of high electrical field as compared to areas of flat surface, or valleys.
  • the electrical resistance can be varied by using different materials along the deposition surface (e.g. providing sections with insulating material) or by changing the current path length between the cathode and the anode.
  • the non-uniform electrical field is induced at the deposition surface by the geometry of the surface and in particular by forming a series of alternate ridges and valleys across the surface.
  • this geometry in operation of the cell, there is a higher electrical field along the ridges as compared to the valleys.
  • the current path length at the ridges is shorter as compared to the valleys thereby creating a situation where there is less resistance at the ridges as compared to the valleys.
  • the variation in current density across the deposition surface may be such that there is a sharp demarcation between the areas of high current density and low current density, or alternatively there may be a more gradual transition between the areas of highest current density and lowest current density.
  • the applicant has found that inducing a gradual transition between the areas of highest and lowest current density still provides good deposition patterns so as to promote substantially discontinuous growth across the deposition surface.
  • the applicant has found that using a cathode which includes a deposition surface having ridges and valleys which do not include a sharp transition between the ridge and valleys so that there is a more gradual change between the highest current density and the lowest current density provides excellent performance.
  • This arrangement induces secondary effects which assist in concentration of the metal deposition at the ridges as described in more detail below and also provides for easier removal of the metal as it allows easier access to the entire deposition surface in contrast to a sharp transition between the ridge and the valley may provide areas which are difficult to access 1 .
  • the current density in the areas of high current density is in the range of 500 to 2,500A/m 2 and more preferably l,000A/m 2 .
  • the areas of low current density is in the range of 0 to 2,05 OA/m 2 and more preferably 0 to 500A/m 2 .
  • the demarcation between an area of "high current density” and “low current density” is somewhat arbitrary.
  • the transition region may be regarded as an area of moderate current which in turn is located between areas of adj acent "high current density” and areas of "low current density”.
  • the process further includes the step of removing deposited metal from the deposition surface by passing an element over the surface.
  • the element is moved in the direction in which the areas of high and low current density extend.
  • the deposited metal is removed by the element whilst maintaining current flow in the aqueous solution. In this way, the process can be substantially continuous.
  • the present invention relates to an electrolysis cell for the electrorecovery of metal from an aqueous solution, the cell including a cathode which includes a deposition surface on which metal is deposited on electrolysing of the aqueous solution, wherein in operation of the cell, the deposition surface has a non- uniform electrical field so as to have areas of strong electrical field interspaced by areas of low electrical field, the difference between the areas of high electrical field and low electrical field being sufficient to cause metal deposition to be concentrated on the areas of high electrical field so as to promote non-uniform deposition of metal on the surface.
  • the areas of high electrical field and low electrical field extend along the surface in one direction and alternate across the surface in an opposite direction.
  • the deposition surface of the cathode includes an array of alternate ridges and valleys, with the ridges forming areas of high electrical field and the valleys forming the areas of low electricalfield.
  • Profiling the deposition surface to have an array of alternate ridges and valleys has significant benefit in promoting substantially discontinuous metal deposition on the cathode.
  • profiling promotes metal deposition as a dendrite growth on each of the ridges.
  • the resulting dendrites are easy to remove (as described below). Not only does the profile provide, in the initial operation of the cell, the appropriate non-uniform current density to concentrate metal deposition as dendrites on the ridges, but it also assists in maintaining discontinuous growth as the process continues.
  • the deposited metal forms an extension of a deposition surface.
  • An advantage of having an arrangement of ridges and valleys is that as the dendrites grow on the ridges, they tend to "shadow" the valleys which further inhibits metal deposition in the valleys. In addition, the aqueous solution tends to stagnate in the valleys which further inhibits deposition of metal in the valleys. In tests conducted by the applicant, using a profile of alternate ridges and valleys, more than 98.8% of metal was deposited on the ridges of the deposition surface.
  • the applicants have found that a regular profile where the surfaces between the top of the ridge and the base of the valley is substantially linear and have an internal angle of approximately 60° between adjacent surfaces provides good results. Furthermore preferably the pitch distance between adjacent ridges is in the order of 10-40mm, and more preferably 15-25mm, and the depth between the ridge and the valley is in the order of 8-32mm and more preferably in the range of 12-20mm.
  • a deposition surface having these characteristics has been found to produce substantially discontinuous metal deposits.
  • this profile enables the surface to be substantially cleaned without creating "hot spots" of current density which would lead to impure metal deposits.
  • the current density at a site is too high, as the deposition progresses, it leads to concentration polarisation (which takes place around the growing deposit). When this phenomenon occurs, a relative increase in impurity inclusions in the depositing metal (e.g. in copper) can occur. Thus it is important to control the current density at the site.
  • the advantage of the profile mentioned above is that the areas of high current density where metal deposits still takes up a substantial part of the total area of the cathode (i.e. in the vicinity of 25-35% of the total area of the deposition surface). With this arrangement, the current is able to be maintained at a substantially constant rate regardless of whether the surface is clean of metal deposits or whether deposition has already occurred. As such, there is no need to ramp up the current on initiating the cell as the profile itself does not tend to induce strong "hot spots" of current density which is likely to cause problems in initial metal deposition.
  • the cathode includes a sheet having at least one major surface which forms the deposition surface of the cathode, the sheet being preformed so as to incorporate the alternate ridges and valleys.
  • the sheet may thus define a corrugated profile.
  • this preforming operation is achieved by folding of the sheet but it could be made by any other appropriate process such as a stamping, milling, swaging, casting process or combinations thereof.
  • the sheet is formed from titanium or similar oxidation resistant material. Whilst other oxidation resistant materials may be used, such as platinum, stainless steel, corrosion resistant metal alloys, titanium is most preferred because of its excellent oxidation resistance, its capacity to resist fo ⁇ riing a metallurgical bond with metals such as copper, and because of its relative availability.
  • a further advantage of using a corrugated profile is that it assists in maintaining dimensional stability for the sheet.
  • Such an arrangement can assist in overcoming the disadvantages of prior art arrangements where sheet cathodes had a tendency to flex and buckle.
  • the dimensional stability of the sheet enables wiping methods to be used to easily remove the deposit from the sheet. The applicants have found that titanium sheets in the order of 1.6mm thickness provide sufficient dimensional stability for this process.
  • the sheet is adapted in use for attachment to a conductive header bar.
  • This header bar supports the cathode in use and supplies electrons to it.
  • the opposite major surfaces of the folded sheet are used as deposition surfaces in operation of the cathode.
  • the cathode is made from a composite structure and further includes a conducting element which extends along the sheet.
  • the conducting element is in elecfrocommunication with the sheet so as in use to supply the deposition surface with electrons in the electrolysis process.
  • One advantage of using a conducting element which extends along the sheet is that it minimises ohmic drop which occurs when the electrons are supplied solely from one edge of the sheet.
  • a second advantage of using a conducting element is that is may be of sufficient size to provide rigidity to the sheet to further assist in maintaining dimensional stability of the cathode. With the composite arrangement it may thus be possible to use thinner sheet structures for the deposition surface(s).
  • the cathode includes a second sheet which is connected to the first sheet and which has a major surface which forms a second deposition surface of the cathode, the second sheet being preformed so as to incorporate the alternate ridges and valleys along that deposition surface.
  • the second sheet is connected to the first sheet of the cathode so as to form a plurality of pockets which extend in the direction of the alternate ridges and valleys. At least some of these pockets are operative to receive the conducting element of the cathode.
  • the wiping device is operative to pass over a deposition surface of the cathode so as to remove deposited material from the deposition surface.
  • the wiping device includes a plurality of projections which are operative to locate within respective valleys of the deposition surface.
  • these projections are made from a ceramic material but can be made of any other corrosive resistant material.
  • the projections are movable between a first and a second position and are operative to pass over the surface in either of these positions.
  • the element In a first position, the element is in contact or in close proximity to the deposition surface so as to remove substantially all of the deposition material from that surface.
  • the element In the second position, preferably the element is spaced from the deposition surface and is operative to remove deposited material which extends a predetermined distance from the deposition surface.
  • the present invention relates to a cathode for use in a process or electrolysis cell as defined in any form above.
  • the present invention relates to a wiping system for use in an electrolysis cell in any form as defined above.
  • the present invention relates to a cathode for use in an electrolysis cell for the elecfrorecovery of metal from an aqueous solution, the cathodes including a deposition surface having a plurality of ridges which are interspaced by a plurality of valleys, the profile of the cathode being operative on operation of the cell to cause metal deposition to be concentrated on the ridges so as to promote non-uniform deposition of metal on that surface.
  • FIG. 1 is a generalised flowchart for processing and recovery of copper
  • Figure 2 is a sectional elevation of an electrolysis cell in accordance with one embodiment of the invention with wiper sets of the cell in a closed position;
  • Figure 3 is a sectional side view of the cell of Figure 2;
  • Figure 4 is a sectional elevation of the cell of Figure 2 with the wipers in an open position
  • Figure 5 is a detailed view of the linkage assembly in the cell of Figure 2;
  • Figure 6 is a cut-away perspective view of the cell of Figure 2;
  • Figure 7 is a schematic view to an enlarged scale showing the wipers located in an open position at the top of the cathode plates;
  • Figure 8 is a detailed view to an enlarged scale of the wipers in a closed position;
  • Figure 9 is a front elevation of a cathode panel used in the cell of Figure 2;
  • Figure 10 is an end view of the panel of Figure 9;
  • Figure 11 is a schematic perspective view of a wiper engaging a cathode in the cell of Figure 2;
  • Figure 12 is a sectional view along section line XIE-XT in Figure 11;
  • Figure 13 is a detailed view of the blade construction of the wipers used in the cell of Figure 2;
  • Figures 14 and 15 are variations of the blade instruction shown in Figurel3;
  • Figure 16 is a schematic perspective view of an alternative cathode designed for use in the cell of Figure 2;
  • Figure 17 is a cross sectional view along section line XVII-XVII of the cathode of Figure 16.
  • FIG. 1 a schematic representation of a combined process 100 including leach and elecfrorecovery 104 of metal is depicted.
  • ground copper sulfide 106 is fed to a multistage counter current leaching process in which the metals are solubilised through oxidation by a lixiviant.
  • the lixiviant includes a complex halide species which is formed in the anode of the subsequent electrolysis stage and is fed back into the leach stage as part of the electrolyte recycle 108.
  • Dissolved metals in desirable oxidation states are removed at various stages from the leach process in the leachate.
  • the leachate is passed through filtration 110 to remove unwanted solids such as sulfur and ferric oxide.
  • the leachate is then passed to purification 112 to remove metals which may otherwise contaminate subsequent electrolysis (such as silver and mercury).
  • the contaminant metals may be precipitated as the metal oxide or carbonate form.
  • the purified leachate is then fed to the electrolysis stage 104 which may include a plurality of electrolysis cell groups in series and/or in paralleLIn each group, a different metal may be produced, with typically copper metal being electrorecovered in a first cell group and metals such as zinc, lead and nickel being recovered in subsequent or parallel cell groups.
  • the electrolysis process is typically operated such that a highly oxidising lixiviant (such as a complex halide species) is produced at the anode.
  • the spent electrolyte (anolyte) is then recycled to the leaching stage and includes the highly oxidising lixiviant which participates in further counter current leaching.
  • the present invention is concerned with optimising the elecfrorecovery of metals and relates to significant design improvements in the electrolysis process, including improved cathode design and geometry.
  • the electrolysis cell 10 for use in the process 100 includes a series of cathode plates 11 which are disposed within the electrolysis cell tank 50 and interspaced by anodes 12. Electrolyte fed to the cell enables current flow between the anodes and the cathodes.
  • the outer surfaces 13, 14 of the respective cathodes form a deposition surface for the cell on which the metal to be recovered deposits in operation of the cell 10.
  • the cathode plates are formed from a generally corrugated profile having alternate ridges and valleys so as to influence the mode of deposition of the metal on the respective deposition surfaces 13 and 14.
  • the cell 10 includes a wiper system 15 which includes a plurality of wiper sets
  • the wipers 17 are arranged to be wiped down the respective deposition surfaces 13 and 14 at predetermined intervals to cause the dislodged metal to drop to the bottom of the cell 10 wherein it is transferred to a conveyor 18 for removal from the cell.
  • the wiping system 15 includes two principle movements; the first being a vertical movement to allow the wiper sets 16 to move between the top and the bottom of the respective cathodes 11, the second being to allow the wipers 17 in each set 16 to move from an open position (as best illustrated in Figure 7) to a closed position (as best illustrated in Figure 8).
  • the wiper sets 16 are mounted on a frame 32 which is secured at its upper end to four supporting struts 19, 20, 21 and 22.
  • Each of the struts include a helical track 23 which cooperates with a worm gear 24 connected to the frame 32.
  • An electric motor 25 mounted on a cross beam 26 is operative to drive the worm gears 24 so as to achieve the vertical movement of the wiper sets relative to the deposition surfaces 13 and 14. Under this action, the wipers are able to move between a lower position as disclosed in Figure 2 to an upper position as disclosed in Figure 4.
  • the frame 32 supports a linkage assembly 27 which in turn is connected to the wiper sets 16.
  • the linkage assembly 27 includes a pair of link plates 28 at each end of the wiper sets 16 which are connected to respective link arms 29.
  • a crank 30 is pivotally connected to respective pairs of the link plates 28 through pivot points 31.
  • Crank arms 40 extend from the crank 30 to the wiper sets 16 so as to support each end of the wiper sets.
  • the link arms 29 are capable of vertical movement through a second actuator 41.
  • the second actuator is in the form of worm gears which cooperate with helical tracks formed on the respective link arms.
  • the worm gears rotate which impacts the rotation to the the link arms 29 to cause vertical displacement of those arms relative to the frame 18 which in turn drives the crank 30 so as to move the wipers between their open and closed positions.
  • the second activator can be damped to prevent over-tightening and jamming of the wipers against the cathode. Damping can be provided by a spring-loaded coupling or by using a pneumatic cylinder in place of the worm gear.
  • each line of cathodes in the cell 10 is formed from a plurality of cathode plates 11 which are connected to a header bar 34 so that the individual plates are suspended in the tank 50.
  • the header bar 34 is conductive and connected to a power source so as to supply electrons to the cathode.
  • the electrolyte is highly corrosive, resulting from typically a 5 molar or greater concentration of alkali or alkaline-earth metal halides.
  • the wiper system 15 is made from a corrosion resistant material which is preferably titanium.
  • suitable materials include platinum, stainless steel, corrosion resistant metal alloys (such as Hastalloy C 22), or even some plastics.
  • titanium is most preferred for the cathode because of its excellent corrosion resistance and its capacity to resist forming a metallurgical bond with metal such as copper, and because of its relative availability (hence cost benefit). Its resistance to forming a metallurgic bond improves the ability of the plates to be stripped using the wiper system described above.
  • FIGS 9 and 10 illustrate the construction of the individual cathode plates 11.
  • the cathode plate 11 is formed from a titanium sheet having a thickness which is preferably about 1.6mm. Sheets of this thickness have been found by the applicant to give adequate rigidity to the cathode plate to prevent buckling in use.
  • the titanium sheet is folded to form a generally corrugated profile so as to provide on each deposition surface 13, 14 alternate valleys and ridges 35, 36 respectively. These corrugations run along the entire length of the cathode between its upper and lower edges 37, 38.
  • the distance between adjacent ridges 36 is 20mm, whereas the depth between the top of the ridges 36 and the bottom of the valleys 35 is approximately 16mm.
  • the wall surfaces 43 formed on the corrugated sheet are generally linear and have an internal angle at the top at the ridges and bottom of the valleys of approximately 60°.
  • a primary purpose for incorporating the corrugations in the cathode is to influence the current density on the deposition surfaces 13, 14 under operation of the cell.
  • the corrugations on the deposition surface cause a non-uniform electrical field across that surface in operation of the cell.
  • the corrugated deposition surface on the cathode creates bands of high current density along the ridges of the cathode due to its corresponding high electrical field at those areas and relatively low current densities in the valleys. This causes metal deposition to be concentrated in the areas of high current density and promotes non- uniform deposition across the surface so that the vast majority of the deposition includes in the ridge regions 35 of the deposition surface. Creating substantially discontinuous deposition improves the ability to be able to remove recovered metal from the cathode using the wiping system 15.
  • the profile of the deposition surface with the valleys and ridges causes the non-uniform electric field by two mechanisms. Firstly, in view of the geometry of the profile, the electrical field will be stronger at the ridges than the valleys because of its surface curvature. In general, the electric field lines are always parallel to the surface. Therefore, at each ridge there will be a concentration of a field along those points. Secondly, the current flow path at the ridges is less than the current flow path at the valleys. As a result, there is less resistance at the ridges than there is at the valleys. In addition, the use of the corrugated profile of the cathode allows better control at the main sites of deposition (i.e. along the ridges).
  • the current density at a site is too high, as deposition progresses, it leads to concentration polarisation (which takes place around the growing deposit). When this phenomenon occurs, a relative increase in impurity inclusion in the depositing metal (e.g. in copper) can occur.
  • the main sites of deposition account for approximately 25-35% of the total surface area of the cathode.
  • the current at the deposition surface should be in the vicinity of l,000A/m 2 or less. As the dend ⁇ tes grow on the surface, the actual area of deposition surface increases as metal is deposited on the previously deposited metal.
  • the current density at the deposition sites both on initial operation of the cell and after dendritic growth has occurred, it is able to be maintained m the vicinity of 1 ,000A/m so as to provide high quality metal deposition. As such, there is no need to vary the current during the process.
  • a further advantage of using the corrugated profile on the cathode is that it improves the rigidity of the cathode plate, as the corrugated profile is inherently stiffer than a flat plate along the direction of the ridges and valleys.
  • the corrugated profile is ideally suited to be cleaned using the wiping blade system as is described in more detail below.
  • the wipers 17 include fingers 39 which are mounted between a pair of rails 42.
  • each of the individual fingers are formed from a ceramic material with the rails being made of titanium.
  • Each of the fingers is spaced along the rail 42 so that the wipers 17 conform generally to the shape of the corrugated cathode plate 11, with the individual fingers locating within the valleys 35 of the deposition surface and over the associated ridges 36.
  • the wiping system 15 is designed so that when the wiper sets 16 are in their closed position, the wipers 17 are angled to the cathode plate 11 so that the individual fingers 39 are in a trailing position relative to the line of movement of the wiper 17 down the cathode plate 11. This arrangement is preferred as it inhibits jamming of the fingers in the valleys as may occur if the fingers 39 were in a leading position relative to the direction of movement of the wipers down the cathode plate.
  • the metal recovered from the electrolysis cell is concentrated on the ridges of the respective deposition surfaces of the cell.
  • the wiper 17 when the wiper 17 is moved across the deposition surface the dislodged material from the ridges tends to move into the adjacent valleys of the deposition surface. This causes an accumulation of the metal within the valleys which tends to envelop the fingers 34 thereby protecting the ceramic fingers 39 from wear.
  • the wipers 17 can be operated to remove the bulk of the deposited material on the deposition surfaces by dragging across those surfaces when in their closed position.
  • the wipers can also be moved across the deposition when in their open position. This is used not to fully clean the deposition surface but rather to ensure that there is no extended dendritic growth on part of the deposition surface which could otherwise grow to an extent that it contacts the anode and thereby causes short circuiting of the electrolysis cell. Also, this allows for more consistent growth across the ridges of the cathode, which aids in control of the current density along the deposition surface.
  • FIGS 14 and 15 illustrate some variations in the design of the wipers 17.
  • each of the wipers 17 include ceramic fingers 39.
  • the fingers 39 are interconnected by an internal connecting bar 44.
  • the bar 44 is formed as a square section, whereas in Figure 15 the connecting bar is made up of two cylindrical bars 45.
  • the cathode is formed as a composite structure wherein the outer deposition surfaces 13, 14 are defined by separate sheets which are fastened together along their respective lateral edges 60, 61, and which may optionally be fastened together at intermittent regions 62.
  • a plurality of conducting bars 63 form part of the construction and extend downwardly from the header bar 34, the conducting bars typically also being formed from titanium (or a titanium coated copper bar to further improve conductively).
  • the conducting bars extend for the full length the plates 13, 14 through each of the passages defined between a plate and are fastened thereto.
  • Such an arrangement provides enhanced distribution of electrons through the assembly, thereby minimising ohmic drop which can occur when the electrons are supplied solely to one edge of the sheet.
  • the composite arrangement including the arrangement of the conducting bars in the passages, enhances the dimensional stability of the sheet so that thin plate structures (e.g. as small as 1mm) or alternatively wide plate structures can be employed for the cathode. Otherwise, the principles of operation of the cathode of Figures 16 and 17 are described above.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Cell Electrode Carriers And Collectors (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Abstract

Un procédé d'électrolyse permettant la récupération de métal d'une solution aqueuse est défini. Lors de l'électrolyse, le métal de la solution est amené à se déposer sur une surface de dépôt d'une cathode. Le procédé comprend l'étape consistant à induire une densité de courant non uniforme sur la surface de dépôt afin de former des zones de haute densité de courant intercalées par des zones de basse densité de courant. La différence entre les zones de haute densité de courant et de basse densité de courant est suffisante pour faire en sorte que le dépôt de métal se concentre sur les zones de haute densité de courant, afin de favoriser le dépôt non uniforme de métal sur la surface de dépôt. Une cellule d'électrolyse pour l'électro-récupération de métal à partir d'une solution aqueuse est également définie. La cellule comprend une cathode comportant une surface de dépôt sur laquelle le métal est déposé lors de l'électrolyse de la solution aqueuse. Lors du fonctionnement de la cellule, la surface de dépôt présente un champ électrique non uniforme présentant des zones de fort champ électrique intercalées avec des zones de faible champ électrique. La différence entre les zones de fort champ électrique et de faible champ électrique est suffisante pour faire en sorte que le dépôt de métal se concentre sur les zones à champ électrique élevé afin de favoriser le dépôt non uniforme de métal sur la surface.
EP03753140A 2002-10-21 2003-10-21 Procede d'electrolyse et cellule utilisee dans celui-ci Withdrawn EP1560948A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AU2002952181 2002-10-21
AU2002952181A AU2002952181A0 (en) 2002-10-21 2002-10-21 Electrolysis process and cell for use in same
PCT/AU2003/001393 WO2004035868A1 (fr) 2002-10-21 2003-10-21 Procede d'electrolyse et cellule utilisee dans celui-ci

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EP1560948A1 true EP1560948A1 (fr) 2005-08-10
EP1560948A4 EP1560948A4 (fr) 2006-02-22

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EP (1) EP1560948A4 (fr)
JP (1) JP2006503978A (fr)
KR (1) KR20050062632A (fr)
CN (1) CN1705773A (fr)
AR (1) AR041685A1 (fr)
AU (1) AU2002952181A0 (fr)
BR (1) BR0314904A (fr)
CA (1) CA2502650A1 (fr)
MX (1) MXPA05004201A (fr)
PE (1) PE20040433A1 (fr)
RU (1) RU2331721C2 (fr)
SA (1) SA04250008B1 (fr)
TW (1) TWI334664B (fr)
WO (1) WO2004035868A1 (fr)
ZA (1) ZA200503694B (fr)

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US8900439B2 (en) 2010-12-23 2014-12-02 Ge-Hitachi Nuclear Energy Americas Llc Modular cathode assemblies and methods of using the same for electrochemical reduction
US8956524B2 (en) 2010-12-23 2015-02-17 Ge-Hitachi Nuclear Energy Americas Llc Modular anode assemblies and methods of using the same for electrochemical reduction
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US8945354B2 (en) * 2011-12-22 2015-02-03 Ge-Hitachi Nuclear Energy Americas Llc Cathode scraper system and method of using the same for removing uranium
US9150975B2 (en) * 2011-12-22 2015-10-06 Ge-Hitachi Nuclear Energy Americas Llc Electrorefiner system for recovering purified metal from impure nuclear feed material
US8968547B2 (en) 2012-04-23 2015-03-03 Ge-Hitachi Nuclear Energy Americas Llc Method for corium and used nuclear fuel stabilization processing
CN107112606B (zh) * 2014-11-18 2020-01-21 艾库伊金属有限公司 改进的用于铅酸电池无熔炼回收的装置和方法
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WO2016183431A1 (fr) 2015-05-13 2016-11-17 Aqua Metals Inc. Composition de plomb déposée par électrolyse, procédés pour sa production, et utilisations
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KR20050062632A (ko) 2005-06-23
US20060091017A1 (en) 2006-05-04
TW200411963A (en) 2004-07-01
CA2502650A1 (fr) 2004-04-29
EP1560948A4 (fr) 2006-02-22
AR041685A1 (es) 2005-05-26
JP2006503978A (ja) 2006-02-02
RU2005115463A (ru) 2005-10-27
BR0314904A (pt) 2005-08-02
MXPA05004201A (es) 2005-09-20
WO2004035868A1 (fr) 2004-04-29
TWI334664B (en) 2010-12-11
AU2002952181A0 (en) 2002-11-07
SA04250008B1 (ar) 2008-05-20
RU2331721C2 (ru) 2008-08-20
PE20040433A1 (es) 2004-07-12
ZA200503694B (en) 2006-08-30
CN1705773A (zh) 2005-12-07

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