WO2010080761A1

WO2010080761A1 - System for electrolytic recovery of metals with improved connection interface

Info

Publication number: WO2010080761A1
Application number: PCT/US2010/020131
Authority: WO
Inventors: Randolph L. Epner
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-01-06
Filing date: 2010-01-05
Publication date: 2010-07-15
Anticipated expiration: 2011-07-06

Abstract

A metal extraction apparatus for recovering metal from a solution. The apparatus includes a recovery tank that houses a plurality of anodes and is configured to have metal containing solution pumped therethrough. The tank is configured to hold a plurality of removable cathodes. During operation, a voltage difference is applied between the anodes and the cathodes so that the metal within the solution collects on the cathode. When an amount of metal has accumulated on a cathode, that cathode may be removed so that the metal can be collected. The cathodes can include a connector element of a plug-and-receptacle connector for electrically connecting the cathode to a voltage potential. The cathodes can alternatively, or in addition, include supports configured to be held in saddles disposed on side walls of the recovery tank.

Description

SYSTEM FOR ELECTROLYTIC RECOVERY OF METALS WITH IMPROVED

CONNECTION INTERFACE

Cross Reference to Related Applications

[0001] The present application claims the priority to the U.S. provisional patent application no. 61/142,790 entitled "SYSTEM FOR ELECTROLYTIC RECOVERY OF METALS WITH IMPROVED CONNECTION INTERFACE" filed 6 January 2009, which is incorporated herein by reference in its entirety.

Field of the Invention

[0002] The present invention relates to an apparatus configured to extract metal from a liquid for recovery of the metal or purification of the liquid.

Background

[0003] There are many applications where it is desirable to recover a metal from a solution. For example, precious metals such as gold or silver that are incorporated in a plating or rinse solution may be recovered from the solution for their intrinsic value. The recovery of expensive metals from so-called waste solution can yield significant economic benefits. Another application in which removal of metals from solution is beneficial are those where metal pollutants such as mercury, cadmium, copper, nickel, zinc, or other heavy metals, should be removed in order to meet or exceed environmental standards. These pollutants typically are contained in waste streams from such industrial sources as metal finishing, metal plating or mining operations. Generally, even a small quantity of a heavy metal can render an otherwise innocuous waste into a hazardous waste, severely complicating disposal. While the removal of these contaminants is desirable from waste solutions, it is usually difficult to achieve separation of just the metals from the solution due to the presence of other waste contained within the stream. For example, the waste stream may include various solid contaminants dispersed therein. [0004] Recovery of metals from solution has generally been directed to methods and apparatus for electroplating the metal dissolved in the solution onto a cathode in an electrolytic recovery cell or tank. Such electrolytic recovery systems typically comprise at least one anode and at least one cathode mounted in spaced apart relationship within a housing and are connected to a source of DC current. The recovery rate of the metal from the solution is dependent on the concentration of metal in the solution and the surface area of the anode and cathode. The cathode may be formed of a base material that may or may not be conductive, surrounded by a layer of conductive metal. The cathode is periodically removed from the recovery cell and the recovered metal is separated from the cathode by methods well known in the art. [0005] Several systems for the recovery of metals from solution are disclosed in U.S.

Patent Nos. 4,276,147, 4,863,580 and 4,960,500 incorporated by reference herein. These systems include anodes and cathodes that are energized by a DC power source. A solution containing a metal is pumped through the system and the metal is captured by the cathodes. The present invention provides improvements over the systems disclosed in these patents.

Summary of the Invention

[0006] The present invention provides a metal extraction apparatus for recovering metal from a solution. The apparatus includes a recovery tank that houses a plurality of anodes and is configured to have metal-containing solution pumped therethrough. The tank is configured to hold a plurality of removable cathodes. During operation, a voltage difference is applied between the anodes and the cathodes so that the metal within the solution collects on the cathode. When a desirable amount of metal has accumulated on a cathode, that cathode may be removed so that the metal can be collected.

[0007] In one embodiment, the cathodes can be connected to a cathode conductor of the tank using a plug-and-receptacle connector. Accordingly, each of the cathode and cathode conductor has one connector element of the plug-and-receptacle connector. For example, the cathode conductor may have the plug connector element and the cathode may have the corresponding receptacle connector element. The plug-and-receptacle connector provides both a strong mechanical and electrical connection between the cathode and the cathode conductor. Moreover, in an embodiment of using the metal extraction apparatus, the connector element of the cathodes can be used to secure the cathodes to a mechanical hoist for removing the cathodes from the tank and transporting the cathodes. In this embodiment, the mechanical hoist includes a similar connector element as the cathode conductor so that the mechanical hoist can be attached to the cathode in the same manner as the cathode conductor. The secure mechanical connection between the connector element of the cathode and the connector element of the hoist allows the cathode to be easily removed from the tank and transported. Additionally, the cathode only needs one connector element for both electrical connection and connection to the mechanical hoist.

[0008] In another embodiment of the apparatus, each cathode can include both a holder portion and a metal recovery plate. The metal recovery plate may have a large surface area to provide efficient collection of the metal on the cathode. The holder is configured to both supply the voltage potential to the metal recovery plate and also to help secure the metal recovery plate in place. Accordingly, the holder can include supports that extend outward toward side walls of the tank. Corresponding saddles fixed to the tank side walls are configured to hold the supports in place, thereby securing the cathodes in a desired position.

[0009] As a combination of these embodiments of the invention, the holder may include the plug-and-receptacle connector to connect to the cathode conductor.

Brief Description of the Drawings

[0010] Exemplary embodiments of the invention will be described in the following with reference to the drawings, in which:

[0011] Fig. 1 is a top view of a recovery cell tank in accordance with an embodiment of the invention;

[0012] Fig. 2 is a side view of the recovery cell tank shown in Fig. 1;

[0013] Fig. 3 is a cross-sectional view of the recovery cell tank shown in Fig. 1, taken along line 3—3; and

[0014] Fig. 4 is a perspective view of particular features shown in Fig. 1.

Detailed Description of Illustrated Embodiments

[0015] As shown in Figs. 1-3, the present invention provides a metal extraction apparatus, for recovering metal from a solution. In the illustrated embodiment, the apparatus is substantially contained in an electrolytic recovery cell tank 2 which includes an inlet end 4, an outlet end 6, a first side 8, and a second side 10. The walls of the tank 4, 6, 8 and 10 are formed of a non-conductive material and may be corrosion resistant. For example, the tank walls can be made of a plastic material such as polyethylene or polypropylene. The tank can include a support 11 providing a downward slope through the tank. The slope provided by the support 11 may be between 6° and 30°, for example about 10°.

[0016] In operation, the metal-containing solution is pumped through the tank from an inlet opening 12 to an outlet opening 14. The recovery tank 2 includes a plurality of anodes 16 and cathodes 18 spaced apart from one another. As the solution is pumped through the tank, the metal therein accumulates on the cathodes 18. Each of the anodes 16 is fixed in the tank 2 while the cathodes 18 are removable. Accordingly, when the cathodes 18 have accumulated an amount of metal thereon, they may be removed from the recovery tank 2 and the metal can be collected. Each of the anodes 16 are electrically connected to an anode bus bar 20 disposed on an outside of the first side 8 while each of the cathodes 18 are electrically connected to a cathode bus bar 22 disposed on an outside of the second side 10. As described further below, Figs. 1 and 2 show the three cathodes on the left side removed.

[0017] The anodes 16 are formed of solid metal plates and extend up from the floor 24 of the recovery tank 2 from the first side 8 to the second side 10. The solid metal anodes 16 help direct the flow of the metal-containing solution and, in conjunction with the cathodes and the voltage difference between the anodes and cathodes provide the electric field for attracting the metal onto the cathodes. In the illustrated embodiment, the solid anodes 16 direct the solution through the recovery tank 2 along a serpentine flow path as indicated by the arrows in Fig. 1. As shown, the anodes 16 are fixed to baffles 26 at one side of the tank 2 and a flow gap 28 is left between the anode 16 and the opposite side of the tank 2. To create the serpentine flow path, adjacent anodes 16 are fixed to baffles on opposite sides of the tank 2 so that the flow gap 28 switches from one side of the tank to the other and back. For example, anode 16a is fixed to baffle 26a at the second side 10 of the tank and the following anode 16b is fixed to baffle 26b at the first side 8 of the tank. Accordingly, the solution is forced to flow through the flow gap 28 at the first side 8 and then cross the entire tank 2 to the flow gap 28 at the second side 10. The baffles 26 help direct the solution so that it flows more efficiently along the serpentine path. Alternatively, the baffles 26 may be omitted and the solid metal anodes 16 can be fixed directly to a respective side wall 8, 10 of the recovery tank. The metal anodes 16 effectively separate the recovery tank 2 into a plurality of recovery chambers 30 that are surrounded on each side by an anode 16. In combination with the serpentine flow path, the sloped angle provided by the support 11 allows solid contaminants in the solution to be separated out from the flow and slowly accumulate at the bottom of the tank 2.

[0018] Each of the anodes 16 are connected to the anode bus bar 20 with an anode conductor 32. Preferably, the anode conductor 32 and the anode bus bar 20 are enclosed by insulation. For example, the anode conductor 32 may be formed of an insulated wire and the anode bus bar 20 can be covered by an insulating material, such as plastic. For example, the exposed end of the anode conductor 32 can be electrically connected to the anode bus bar 20 and the entire anode bus bar 20 and exposed end of the anode conductor 32 can be covered with a PVC material such as plastisol. Each of the anodes 16 are provided with an electrical potential through the anode bus bar 20 which is connected to a voltage source. [0019] Each of the recovery chambers 30 is configured to hold a cathode 18. The cathode 18 is positioned in the center of the chamber 30 between two anodes 16 such that the cathode 18 is exposed to the solution as it flows past it on either side. In Fig. 1, the cathodes 18 have been removed from the three chambers on the left. The recovery tank is configured such that the cathodes 18 can be removed easily to allow metal to be retrieved. The illustrated cathode 18 shown in Figs. 3 and 4 includes a holder 34 and a metal recovery plate 36. Each metal recovery plate 36 is held in place in the tank 2 by the holder 34 and a series of posts 40 that each include slot 42 (Fig. 4). As shown in Fig. 3, the metal recovery plate may be positioned in the posts 40 so as to be disposed at a distance from the bottom 44 of the tank 2. This ensures that any deposits at the bottom of the tank 2 do not produce a short circuit between the anode 16 and the cathode 18. The posts 40 are formed of a non-conductive material and can have a simple construction, such as a plastic pipe, for example PVC, with a slot 42 cut therein. [0020] The metal recovery plate 36 is formed to have a large surface area so as to hold a large amount of recovered metal and provide high efficiency for extracting metal from the solution. In a preferred embodiment, the metal recovery plates are made of a sheet of non- conductive cellular base layer with a conductive plating thereon. Examples of this type of conductive cathode structure are described in U.S. Patent No. 4,276,147 which, as stated above, is incorporated by reference herein. The use of a cellular non-conductive base layer provides increased turbulence as the solution flows through the cellular structure, thereby increasing the recovery efficiency.

[0021] In addition to the posts 40, each metal recovery plate 36 is held in place by a holder 34 which also supplies a voltage potential to the recovery plate 36. The holders 34 each include a pair of conductive metal forks 46 having two conductive legs 48 spaced apart at a predetermined distance. Preferably, the legs 48 of the fork 46 are spaced apart a distance that is slightly smaller than the width of the metal recovery plates 36 so that the metal recovery plates 36 can fit snuggly in the forks 46 without any additional attachment mechanism. However, additional attachments may be used to secure the metal recovery plate 36 in the fork 46. The pair of conductive metal forks 46 may both be attached to the ends of a conductive beam 50, which may be made of a highly conductive material, such as copper. The forks may be attached to the beam by any method that will provide an electrical connection, such as welding or bolting the legs of 48 of the forks 46 to a side face of the beam 50. As described in more detail below, the holder also includes an electrical connector 52 coupled to the conductive beam 50. This coupling may also be of any type that allows a conductive coupling, such as welding or bolting. The electrical connector 52 is configured to couple the cathode 18 to the cathode bus bar 22 by a cathode conductor 54 so as to provide a voltage potential to the cathode 18. For safety, all of the conductive surfaces of the holder may be covered in an insulator 60, such as plastic or plastisol except the inner sides of the fork legs 48 and a connection portion of electrical connector 52. [0022] For increased stabilization, the holders 34 can include supports 56 that extend out from either side of the conductive beam 50. Preferably, the supports 56 are formed of a non- conductive material, such as plastic or natural polypropylene. The supports 56 can be bolted or adhered to the conductive beam 50 in order to fix them together securely. The near end of the supports 56 may also be covered by the insulator 60 in order to guarantee that no conductive portion of the holder 34 is exposed. Each of the supports 56 are held in place at the side wall 8, 10 of the tank 2 by a saddle 58. The saddle 58 can be formed of a non-conductive material, such as natural polypropylene and include a slot 62 configured to receive the support 56. The saddles 58 are attached to the side walls 8, 10 of the tank 2 and can be fixed with attachments such as bolts or with an adhesive. The weight of the cathode 18 may rest on the bottom of the slot 62 or can rest on the walls 8, 10 of the tank itself. Aside from securing the cathodes 18 in place, the saddles 58 also help guide the placement of the metal recovery plates 36 as the cathodes are inserted into the tank 2.

[0023] The electrical connector 52 of the cathode 18 includes a plug connector 64 and the cathode conductor 54 has a corresponding receptacle connector 66 to receive the plug connector 64. Alternatively, the plug connector 64 may be provided on the cathode conductor 54 and the receptacle connector 66 provided on the cathode 18. The respective plug and receptacle connectors 64, 66 provide a strong electrical connection as well as a secure mechanical connection between the cathode 18 and the cathode conductor 54. The plug connector of electrical connector 52 is in the form of a shaft 64 and the receptacle connector 66 is in the shape of a conductive connector that includes a bore 68 configured to receive the shaft 64 of the plug connector. In order to lock the shaft 64 within the bore 68, a slot 70 can extend around a portion of the shaft at distance from the end 72 of the shaft and the bore 68 can have a corresponding projection 74 configured to be held within the slot 70. In order to allow the projection 74 to pass the end of shaft 72 so that it can be fit into the slot 70, a portion of the end of the shaft 72 can be cut out in order to provide a path for the projection 74. In the illustrated embodiment, the path is formed by a flat section 76 in the side of the shaft. To lock the shaft 64 in place within the bore 68, the projection 74 of the bore and the flat section 76 of the shaft are aligned and the shaft 64 is inserted into the bore 68. The receptacle connector 66 is then turned such that the projection 74 is moved into the slot 70. In one embodiment, the slot 70 may be tapered such that further turning of the receptacle connector 66 results in a tighter fit of the projection 74 within the slot 70. The dimensions of the slot and projection may be configured so that friction between these elements results in a secure connection.

[0024] Opposite the electrical connector 52, the cathode conductor 54 corresponding to each cathode 18 is attached to the cathode bus bar 22. As shown in Figs. 1 and 2, each of the cathode conductors 54 may include over-current protection between the cathode bus bar 22 and the cathode 18. The illustrated embodiment includes a series of housings 78 corresponding to each cathode conductor 54 adjacent the cathode bus bar 22. An over-current protection device is disposed in each housing 78 in series between the cathode bus bar 22 and each cathode 18. This over-current protection may be in the form of a fuse, or a circuit breaker. The housings 78 are formed of a non-conductive material, such as polypropylene, and isolate the cathode conductor 54 from having direct electrical connection with the cathode bus bar 22. By having each cathode 18 have its own over-current protection, if one of the cathodes 18 fails, for example due to a short between the cathode 18 and an adjacent anode 16, the remaining cathodes 18 and corresponding recovery chambers 30 can continue to operate without decreased efficiency. Like the anode bus bar 20, the cathode bus bar 22 may be covered in an insulating material. [0025] To operate the metal extraction apparatus, a cathode 18 including a holder 34 and a metal recovery plate 36 is inserted into each recovery chamber 30 between two anodes 16. The cathodes 18 are positioned so that the metal recovery plates are disposed within the slots 42 of posts 40 and so that each support 56 of the holders 34 is disposed within the slot 62 of a saddle 58. The electrical connector 52 of each holder 34 is electrically connected to the cathode bus bar 22 by securing plug connector 64 within receptacle connector 66 of a respective cathode conductor 54. A voltage potential is then supplied between the anodes 16 and cathodes 18 and metal containing solution is pumped through the tank 2 so that metal accumulates on the metal recovery plates. Once an amount of metal has accumulated on a metal recovery plate 36, the corresponding cathode is disconnected from the cathode conductor 54. The cathode 18 is then removed from the tank 2 for collecting the metal deposited thereon. In an advantageous embodiment, the cathode 18 can be connected to a mechanical hoist using the plug connector 64 that is used for the electrical connection of the cathode. Accordingly, the mechanical hoist can include a receptacle connector 66 that receives the plug connector 64 of the cathode. The mechanical connection provided by the plug connector 64 and receptacle connector 66 is sufficiently secure to allow the cathode 18 to be removed from the tank and transported using the electrical connector of the cathode 64. In an alternative embodiment, the plug connector 62 may be included on the hoist and the receptacle connector 64 included on the cathode. [0026] Although the preferred form of the invention has been shown and described, many features may be varied, as will readily be apparent to those skilled in this art. For example, the illustrated embodiment includes six recovery chambers but the invention is not limited to this number. Similarly, the posts holding the metal recovery plates are illustrated and described as circular pipes but are not limited to that description. Thus, the foregoing description is illustrative and not limiting, the invention being defined by the following claims.

Claims

We Claim

1. A metal recovery apparatus comprising: a tank configured to receive a metal-containing solution and having an inlet opening and an outlet opening; a plurality of anodes disposed in the tank; a plurality of removable cathodes each insertable in the tank between two respective anodes, each removable cathode including a first connector element of a plug-and- receptacle connector; and a plurality of cathode conductors attached to the tank, each cathode conductor including a second connector element of the plug-and-receptacle connector configured to mate with the first connector element of the plug-and-receptacle connector.

2. The metal recovery apparatus of claim 1 wherein one of the first connector element and the second connector element is a plug connector and the other of the first connector element and the second connector element is a receptacle connector, the plug connector including a shaft and the receptacle connector including a bore configured to receive the shaft.

3. The metal recovery apparatus of claim 2 wherein the shaft includes a distal end and a slot disposed at a distance from the distal end, the slot extending around a portion of the circumference of the shaft, and wherein the bore includes a projection configured to be held within the slot.

4. The metal recovery apparatus of claim 3 wherein the distal end of the shaft includes a cut-out portion providing an access path for the projection of the bore to reach the slot as the shaft is inserted into the bore.

5. The metal recovery apparatus of claim 2 wherein the shaft and bore are configured to be locked together by relative twisting when the shaft is inserted in the bore.

6. The metal recovery apparatus of claim 1 further comprising a cathode bus bar attached to the tank and operable to provide an electrical connection to each of the cathode conductors.

7. The metal recovery apparatus of claim 6 further comprising a over-current protection between each of the cathode conductors and the cathode bus bar.

8. A metal recovery apparatus comprising: a tank configured to receive a metal-containing solution and having a first side, a second side, an inlet opening and an outlet opening; a plurality of anodes disposed within the tank along a length of the tank; a plurality of pairs of first saddles and second saddles, the first saddles being disposed on the first side of the tank and the second saddles being disposed on the second side of the tank, each pair of saddles being disposed between adjacent anodes along the length of the tank; a plurality of removable cathodes insertable in the tank, each removable cathode including a holder and a metal recovery plate, each holder having a first support and a second support respectively configured to be held by a respective pair of the plurality of pairs of first and second saddles.

9. The metal recovery apparatus of claim 8 wherein the tank includes a support providing a downward slope along a length of the tank.

10. The metal recovery apparatus of claim 8 wherein the tank includes a plurality of baffles cooperating with the anodes so as to form a serpentine flow path for the metal-containing solution through the tank.

11. The metal recovery apparatus of claim 8 further comprising: a cathode bus bar attached to the tank and operable to provide an electrical connection to each of the removable cathodes; and an anode bus bar attached to the tank and operable to provide an electrical connection to each of the anodes.

12. The metal recovery apparatus of claim 11 wherein an insulating material covers the anode bus bar.

13. The metal recovery apparatus of claim 8 wherein the tank includes at least one post corresponding to each metal recovery plate, each at least one post including a slot configured to hold a respective metal recovery plate therein.

14. The metal recovery apparatus of claim 8 wherein each metal recovery plate includes a non-conductive cellular base layer and a conductive plating disposed on the non- conductive cellular base layer.

15. The metal recovery apparatus of claim 8 wherein each holder includes a pair of conductive metal forks including two spaced apart conductive legs, each conductive metal fork being configured to hold the metal recovery plates between the spaced apart conductive legs.

16. The metal recovery apparatus of claim 15 wherein an outer portion of each conductive metal fork is covered with an insulating material and an inner portion of each conductive metal fork is uncovered such that it directly contacts the metal recovery plate.

17. The metal recovery apparatus of claim 8 wherein the first and second supports include an insulating material and are fixed to opposite ends of a conductive beam of the holder.

18. The metal recovery apparatus of claim 8 further comprising a plurality of cathode conductors attached to the tank, each cathode conductor including a first connector element of a plug-and-receptacle connector, wherein each removable cathode includes a second connector of the plug-and- receptacle connector configured to mate with the first connector.

19. A method of removing metal from a solution comprising: providing a tank with a first side, a second side, an inlet opening and an outlet opening; disposing a plurality of anodes within the tank along a length of the tank; disposing a plurality of removable cathodes within the tank with each cathode being between two respective anodes, each removable cathode including a first connector element of a plug-and-receptacle connector; connecting the first connector element of each cathode to a corresponding second connector element of a plug-and-receptacle connector disposed on a respective conductor so as to provide an electrical potential between the cathodes and anodes; providing the tank with a metal-containing solution such that metal collects on each cathode; disconnecting the first connector element of each cathode from the corresponding connector element of each conductor; connecting the first connector element of each cathode to a corresponding second connector element disposed on a mechanical hoist; and removing each cathode from the tank using the mechanical hoist.