DD206567A5 - NETWORK ELECTRODE FOR THE RECONSTRUCTION OF METALLIONS AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

THE INVENTION INVOLVES A CATHODE ARRANGEMENT FOR USE IN AN ELECTROLYTIC CELL FOR THE RECOVERY OF METALS FROM SOLUTIONS CONTAINING LONES OF THESE METALS. THE CATHODE ORDER SHALL CONSTITUTE A CARRIER STRUCTURE AND A CARBONATED POLYMERIC FOAM OR MATERIAL PRESENTED BY CARBON, WHICH HAS BEEN MOUNTED ON THE CARRIER AND IN ELECTRICAL CONTACT WITH THE CARRIER. THE CONDUCTIVITY OF THE CATHODE OF POLYMERIC FOAM OR TISSUE SHOULD IN GENERAL BE MORE GREAT THAN APPROX. 10,000 OHM / CM, AND, PREFERABLY, GREATER THAN 5000 OHM / CM, IN PARTICULAR MATERIALS OF AVERAGE 3000 OHM / CM OR GREATER PREFERRED.

Description

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Mesh-shaped electrode for the recovery of metal ions and method for its production ·

Field of application of the invention

The invention relates to electrolytic cells, especially for electrical metal extraction. More particularly, the invention relates to methods and apparatus for electrolytically recovering metals on reticulated electrodes from solutions containing the ions of these metals.

Characteristic of the known technical solutions

It is well known that many metals from solutions containing ions of the metals can be recovered electrolytically. In general, the solution containing the metal ions is contacted with an anode-cathode pair in an electrolytic cell, with the metal precipitating from the ionic solution at the cathode. On such metal recovery cells known for electrolytic cell processes features such as power efficiency and current density are applicable to the cathode. In addition, for the electrowinning of metals, the recovery of the metal from the cathode, particularly at a relatively low cost and with relative ease, is important.

Conventionally, the metal recovery cathode consisted of a substrate of an electrically conductive, abundant metal on which the metal ions of the metal

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Solution were deposited. The separation normally required the melting of the deposited metal and substrate and subsequent separation of the two metals. In some cases, it was possible to separate the electrodeposited metal from the substrate by physical cleavage. When the substrate metal and the metal to be electrodeposited were the same, the problems associated with the subsequent separation of the cathode substrate and recovered metals were often reduced. The surface of these conventional cathodes has often been limited in their ability to hold the deposited metal.

Recently, it has been found that open-pored plastics, especially polymers, can be used as reticulated electrodes in metal ion recovery because they provide a larger surface area. In using these polymers for metal ion recovery, it has been found that it is essential that these plastics be conductive and sufficiently rigid for use in electrolytic cells at the same time. Without conductivity, electrolytic recovery can be difficult. Without strength, maintaining an effective small anode-cathode distance within the electrolytic cell can be complicated.

In an earlier proposal, to produce an open-cell reticulated electrode that was both electrically conductive and relatively rigid, a metal was deposited on an open cell polymeric foam or fabric or nonwoven fabric.

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deposited substance. In general, a preliminary metal deposition is performed on the polymer by treatment in a chemical bath and subsequent electroless deposition of a metal such. B. copper on the polymer. The electrolessly metal-coated polymer, which is now somewhat conductive, is then subjected to electrodeposition of relatively large amounts of the metal to produce a relatively rigid, conductive electrode structure for recovering metal ions from solutions.

The combination of electroless and electrolytic deposition of conductive metals on the polymer to make a cathode for recovering metals from solutions can be economically burdensome. These cathodes, when fully charged with the recovered metals, are generally destroyed upon removal of the recovered metal. Therefore, a completely new cathode is required each time.

In particular, where a polymer structure, generally for use as a cathode in an electrolytic cell, is provided with a metal to render the polymer structure conductive, it is necessary to attach at least one current feeder. In particular, in an acidic solution, when the electric current in cells using electroless and electrolytic deposition polymeric cathodes is interrupted, and thus eliminates cathodic protection generally present at the cathode during electrolysis, this junction and also the conductive metal may be eliminated be subject to corrosion. By a

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such corrosive action can weaken the electrical connection to the cathode, thereby reducing the efficiency of electrolytic metal recovery from solution or interrupting recovery.

Object of the invention

The aim of the invention is to avoid the disadvantages of the prior art,

presentation; the essence of the invention;

An object of the present invention is to provide a net-like cathode for use in the recovery of metal ions from a solution containing these ions.

Another object of the invention is to provide an easily replaceable polymeric cathode which does not require electroless and / or electrolytic deposition of a conductive metal on the polymeric material for electrical conductivity and rigidity.

Another object of the invention is to provide a cathode configuration or assembly that includes a separable, electrical current distributing and rigidity-imparting portion and at least one polymeric cathode portion.

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The present invention therefore provides a cathode assembly for use in the electrolytic recovery of metal ions from solutions containing these ions. The cathode contains an open carrier structure that is electrically conductive and slightly permeable to fluids. A part of this structure is to be immersed in the solution from which the metal ions are recovered, and is connected to a connection part through which electric current is transferred between the support structure and an electric power source.

An open cell, electrically conductive, carbon impregnated polymeric membrane cathode coversably attaches at least a portion of at least one surface of the submerged mesh structure. The polymeric cathode is in electrical contact with the support structure. The polymer cathode is bonded to the carrier using a conductive adhesive or using fasteners such as staples.

The open-pore, carbon-impregnated polymeric membrane consists of an open cell foam or an open-pored mat of the polymer. The polymer is made of a polyurethane or a polyester. The open-cell foam consists of carbon impregnated polyurethane or polyester foams · The fiber mats cathode is made of polyester "The support structure has an open area of between 10 and 95 ^J / o and the foam or · the woven polymer has a thickness between about _e 0.05 inch ( 0.127 cm) and 1.0 inch (2.54 cm). The process for producing an electrode assembly for recovering metals from ions of the metal-containing solutions is characterized by selecting a carrier which conducts electrical current.

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structure having a part for at least partially immersing in the solution, and a connection part through which electric current is transmitted between the support structure and an electric potential source, and mounting an open-pore, electrically conductive carbon cathode membrane covering at least a part of at least The open-pore electrically conductive polymeric membrane is one of carbon-impregnated polyurethane or polyester foams. The open-pore, electrically conductive polymeric membrane is woven polyester The membrane is fabricated using a electrically conductive epoxy resin binder, an electrically conductive latex, clips and mixtures thereof.

The cathode assemblies are used to form anode-cathode pairs contained in an electrolytic metal recovery cell. In general, a plurality of cathode arrays are arranged along the entire length of an electrolytic cell, each spanning the width of the electrolytic cell. The solution containing the metal ions is introduced at one end of the cell and flows through a cell length, successively through the open-pored polymers Cathodes located inside the cell flow »

The use of the open cell polymeric cathode according to the present invention provides a cathode assembly that is relatively inexpensive in cost and has a large surface area available for electrodeposition of metal ions out of the solution. The support structure provides a relatively rigid cathode assembly

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facilitates the maintenance of the anode-cathode space within the cell, thereby helping to maintain a desirably low consumption of electrical energy during operation of the electrolytic cell.

The cathode assemblies according to the present invention can be relatively easily arranged by covering the polymer with at least one side of the reticulated structure. Once assembled, their unitary construction allows for easy replacement when the porous structure is clogged by accumulated metal precipitates. In a preferred embodiment, a portion of the reticulated structure located above the normal level of the solution within the electrolytic cell remains uncovered by the polymeric material. When polymer cathode clogging occurs, the metal-laden solution flowing through the cell overflows the plugged polymeric cathode through the uncovered support structure above the normal or conventional level of the metal-loaded solution within the cell, thus providing a visible indication of cathode clogging.

Ausführun ^ SExample

By the following detailed description of the invention and in conjunction with the accompanying drawings, which together form a part of the specification, the above and other features and advantages of the invention will become apparent. In the drawing ze igenι

FIG. 1s is a perspective view of a cathode assembly according to the present invention. FIG.

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Pig. 2; a cross-section of a cathode assembly according to the invention containing on both surfaces of the support structure polymeric cathodes j

FIG. 3: a cross section through a typical electrolytic cell using cathode arrangements according to the invention »

1 and 2 show perspective and cross-sectional views of a cathode arrangement 10. The cathode assembly 10 includes an open, fluid-permeable support structure 12 and a polymeric cathode 14 connected to the structure 12 and in electrical contact with the structure 12 »

The support structure 12 may be made of any electrically conductive, relatively rigid material. It can, for. B * an electrically conductive metal mesh, a perforated plate, a woven wire mesh, one of an electrically conductive plastic, such. B, Gaprez polypropylene or conductive polyvinyl chloride formed grid. Other suitable or conventional materials, through the structure of which electrical current easily flows and which allow easy fluid passage, may be used.

The support structure 12 fulfills a dual function. Electricity is distributed by the structure to the polymeric cathode 14 and the structure serves to locate and support the cathode 14 within an electrolytic cell and to maintain the cathode 14 at a desired distance from the anodes used in the electrolytic cell.

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The cathode 14 is formed of a flexible polymer. Three polymeric forms have been found to be well suited, namely foams, pasque fabrics and non-woven mats. The polymer used should be resistant to corrosive and dissolving influences by solutions loaded with any metal ions which are to be deposited by electrolytic use of the cathode assembly of the invention.

A preferred form of the conductive polymer is a foam. It has been found that polyurethanes and polyesters provide effective cathodes, although other conductive foams may be sufficient. The foam should be open-pored, d. h., fluid should pass through its thickness relatively freely. The open cell foam should allow liquid flow across the surface of the cathode assembly through the foam at least equal to the flow rate of the solution from which the metal ions are to be recovered.

Another preferred embodiment of the invention is an open-pore, woven fiber mat of a polymer or a non-woven mat of the polymer, which mat allows fluid flow through the mat across the surface of the cathode assembly that is at least equal to the flow rate of the solution from which metal ions are to be recovered. In particular, polyester fiber webs have been found to work well, although other electrically conductive polymeric fibers can be used.

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The fiber mat or polymeric foam cathode 14 is rendered conductive by incorporation of carbon into the polymeric cathode 14. Carbon may be incorporated by incorporation into the system of the foam or mat during formation or by impregnation of the foam or mat after formation. Carbon entrapment or impregnation techniques are well known. The following materials have been found to be suitable for use as a polymeric cathode; 202 urethane foam and CG-F-1 / 8-35PPI-1OO, CC-F-1 / 8-35EPI-65 and CC-F-7 / 32-30PPI-65 foams,

The conductivity of the polymeric foam or mat cathode should generally be greater than about 10 000 ohms / cm, and preferably greater than 5,000 ohms / cm, with particular preference for materials averaging 3,000 ohms / cm or greater.

The cathode 14 may vary in thickness over a substantial range. Typically, a foam of 0.05 to 1.0 inches (0.127 to 2.54 cm) is used, and preferably between 1/16 to 1/2 inches (0.16 up to 1.27 cm). Thicker foam cathodes 14 contribute to a distance of anode and cathode within the cell to an extent whereby a significant drop in voltage efficiency can occur during operation of a metal recovery cell. Thinner cathodes 14 are rapidly loaded with reclaimed metal and require undesirably frequent removal and replacement,

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The porosity of the foam or mat can vary between about 10 and 100 pores / square inch (PPI) (10 and 100 pores / 6.45 cm). Preferred are materials of about 25 to 40 PPI (25 to 40/6 , 45 cm ² ) ·

The polymeric cathode 14 may be attached to the support structure 12 in any suitable or conventional manner that establishes an electrical connection between them. Conductive iQeber such. B »Crest 2014A and B or Crest 173Λ and B, two-part epoxy resins or 52-04-4130 conductive latex, staples 16 or U-bolts are used to keep the structure 12 and the polymeric cathode 14 in intimate electrical contact.» It is important in that the electrical current between the net-like structure 12 and the cathode is transmitted over a substantial part of the surface parts of the cathode opposite the structure »

When a permeable polymeric reticulated structure is used, it is sometimes desirable to mount an electrically conductive metal foil (not shown) along an upper edge of the support structure which allows electrical current to be transferred from an electrical power source along the length of the cathode assembly to the cathode assembly 10 at one or more locations along the support structure. In a preferred embodiment, one or more flange portions 18 of the support structure are mounted upward from the cathode assembly and may be used to secure the cathode assembly 10 in an electrolyte.

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The flange portions 18 may be made in any suitable or conventional manner, eg, by forming the flange from the support structure and bending the part, or by attaching separately shaped flange portions 18,

3, an electrolyte cell 24 is shown that includes a plurality of cathode assemblies 10 and a plurality of anodes 26 spaced across the width of the cell 24. The cathode assemblies 10 generally divide the cell 24 into compartments 28. The cell includes a fluid inlet 30 and outlet 32,

The solution containing metal ions to be recovered enters the cell through the fluid inlet and exits through the outlet. The solution as it flows through the cell passes through each cathode assembly, with. Metal ions are brought into intimate contact with the cathode assembly for deposition.

When a cathode is charged with decreasing the flow of the solution with recovered metal ions, the solution level begins to rise in compartments that are behind the solution flow, as shown at 38 in FIG. In the preferred embodiment, the polymeric cathode 14 does not fully cover the support structure, whereby the rising solution level may overflow the cathode 14 through a region 40 of the support structure. The determination of the cathode arrangements requiring replacement.

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Anodes and the surfaces of the cathodes 14 within the electrolytic cell are advantageously maintained at a distance of between 1/4 inch and 1/2 inch (1.27 and 0.63 cm). A lesser spacing is feasible, but the formation of dendrites Cathodes 12 placed a short distance from anodes can cause a short circuit. A greater distance is feasible, but can lead to unacceptable energy losses. Generally, anode-cathode spacings above about 5 inches (12.7 cm) and below about 1/16 inch (0.16 cm) are not desirable. "

The polymeric cathode 14 may be applied to one or both surfaces of the conductive support structure 12, as shown at 14 in FIG. Whether one or both surfaces of the structure are to be coated depends in part on factors such. As the concentration of metal ions in the solution to be treated, the rate of flow of the solution through the cell, the thickness of the applied cathode 14 and the arrangement of the anodes "Each application is therefore somewhat individual and should be determined individually.

The following examples serve to further illustrate the invention _;

example 1

An open-topped electrolytic cell with the approximate

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6 inches χ 8 inches in height (15.24 cm χ 20.32 cm χ 20.32 cm) made of Lucite® was provided with an eluate inlet and outlet. Two squares of RPM ΦΦ 202 of capable urethane foam approximately 6 inches χ 6 inches χ 3/8 inch thick (15.24 χ 15.24 χ 0.95 cm) each were placed in a three-sided cavity 6 inches in dimension χ 6 inches (15.24 χ 15.24 cm). The cavities were pressed for 25 μs to hold the foam. A strip of aluminum foil was pressed into the foam along the unframed side. The effective open foam area was then about 5x5 inches (12.7 x 12.7 cm).

The foam squares were installed in the lucite cell with the enclosing framing adjacent to the walls and bottom of the cell. Three metal grid anodes of approximately 5 inches by 5 inches (12.7 × 12 × 7 cm) in thickness with TIR radiation. 2000, a mixture of tantalum, titanium and iridium oxides, were placed alternately with the foam squares in the cell. A distance of about 1/2 inch (1.27 cm) was maintained between the surface of each foam square and an opposite electrode. A power supply was connected to the aluminum foil strip attached to each foam square, the square being made cathodic by connection to a power source,

15 L of a copper sulfate solution of concentration 250 ppm in sulfuric acid was repeatedly circulated through the cell, passing through each of the foam cathodes. The

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The pH of the solution was about 1 »5 * A current of 5 amperes per square foot (929» 029 cm) flowed between the anodes and the cathodes »The solution circulated at 3 gallons / min / square foot of the foam cathode (11,35 l / min / 929.029 cm ² ).

Circulation continued for approximately 1 hour during which time the copper concentration in the circulating solution dropped to 73 ppm. The voltage between anodes and cathodes during this time dropped from approximately 3.8V to approximately 2.4V.

Example 2

A cathode was prepared by depositing two squares of RFM ΦΦ 202 conductive foam and measuring 6 inches χ 6 inches χ 1/4 inches (15 24 24 χ 15.24 χ 0.63 cm) on both surfaces of a patterned aluminum mesh a substantially open area and dimensions 6 inches χ 6 inches χ 8 inches (15.24 x 15.24 x 20.32 cm). The attachment was done using staples. A 2 inch (5.08 cm) wide strip of aluminum remained free.

The cathode was installed in the cell between two mesh anodes of the type used in Example 1 at intervals of 1/2 inch (1.27 cm). The cathode and the free aluminum part of the anodes were connected to an electric power source. An amount of 15 liters of a copper sulphate solution with a concentration of 210 ppm and a pH of about 1.75

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was circulated through the cell at a rate of 6 gallons / min / square foot of the foam cathode (22.71 l / min / 929.029 cm ² ),

After about 1 hour, the copper content of the circulating solution had been reduced to 100 ppm. The voltage between anode and cathode decreased from initially 2.5V to 2.3V.

Example 3

A cathode assembly was made by placing an expanded 18 inch x 15 inch (45 x 72 x 38.1 cm) expanded aluminum foil web between two 18 inch x 15 inch x 1/8 inch cathodes formed from carbon impregnated polyurethane foam Thickness (45.72 x 38.1 x 0.32 cm) »The three-component cathode assembly was fixed by attaching the foam to the aluminum with a conductive epoxy adhesive. The cathode was placed in an open electrolytic cell between two TIR-2000 metallic anodes with the inter-anode to foam surface spacing of about 1/2 inch (1.27 cm).

A wastewater stream with a concentration of about 150 ppm copper sulfate was passed through the electrolysis cells without recycle for about 200 hours at a flow rate of 2 gallons / min / square foot free cathode area (7.57 l / min / 929.029 cm ² ). The cell was given a DC of 3 A / square at a constant voltage of 2.8V

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foot free cathode area (3 A / 929.029 cm ² ) applied. At the end of the experiment, 300 grams of metallic copper were removed from the copper sulfate solution.

Ea, a preferred embodiment of the invention has been shown and described in detail; but it is obvious that various modifications are possible without departing from the scope of the claimed invention

Claims (5)

L 4 H DI Ο / " ₁₈ .. 19.8.1983 61 607/13 Erfindungaanapruch 1 _e net shaped electrode for the recovery of metal ions, characterized by an electrically leit capable Trägeratruktur containing an at least partially in the solution immersed portion and a connecting portion, is transmitted through the elektriacher current between the support structure and a source of electrical potential, and an open-pore, with A carbon-impregnated polymeric cathode membrane which, when applied, covers at least a portion of at least one surface of the support structure and is in electrical contact with the support structure. 2, arrangement according to item 1, characterized in that the open-pore, carbon-impregnated polymeric membrane consists of an open-cell foam or an open-pored fiber mat of the polymer, 3 »arrangement according to item 1, characterized in that the polymer consists of a polyurethane or a polyester, 4, arrangement according to point 3, characterized in that the open-pore foam consists of carbon-impregnated polyurethane or polyester foams » Arrangement according to point 2, characterized in that the i'asermatten cathode is made of polyester. 24 4 6 1 6 7 -19. 19.8.1983 61 607/13 6. Arrangement according to item 4 or 5, characterized in that the carrier structure has an open area of between 10 and 95 % and the foam or the woven polymer has a thickness between about 0.05 inch (0.127 cm) and 1, 0 inch (2.54 cm) has « A method of making an electrode assembly for recovering metals from ions of the metal-containing solutions, characterized by selecting a support structure conducting the electrical current having a part for at least partial immersion in the solution and a connection part by the electric current between the support structure and applying an electric potential source, and mounting an open-pore, electrically conductive carbon cathode membrane having at least a portion of at least one surface with the support structure in a correlation transmitting the electric current. 8. The method according to item 7, characterized in that the open-pored, electrically conductive polymeric membrane is one made of impregnated with carbon polyurethane or polyester foams. 9. The method according to item 7, characterized in that the open-pore, electrically conductive polymeric membrane is woven polyester. -20- 19.8.1983 61 607/13 10, method according to item 7 », characterized in that the membrane is attached using an electrically conductive epoxy resin binder, an electrically conductive latex, staples and mixtures thereof. For this 2 pages drawings