WO2004079840A2 - Eletrode a flux traversant tridimensionnelle et cellule electrochimique - Google Patents

Eletrode a flux traversant tridimensionnelle et cellule electrochimique Download PDF

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Publication number
WO2004079840A2
WO2004079840A2 PCT/US2004/005902 US2004005902W WO2004079840A2 WO 2004079840 A2 WO2004079840 A2 WO 2004079840A2 US 2004005902 W US2004005902 W US 2004005902W WO 2004079840 A2 WO2004079840 A2 WO 2004079840A2
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Prior art keywords
flow
electrode
ore
solution
water
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PCT/US2004/005902
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English (en)
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WO2004079840A3 (fr
Inventor
Arden L. Larson
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Evat, Inc.
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Publication of WO2004079840A2 publication Critical patent/WO2004079840A2/fr
Publication of WO2004079840A3 publication Critical patent/WO2004079840A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F1/46114—Electrodes in particulate form or with conductive and/or non conductive particles between them
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C25B9/65—Means for supplying current; Electrode connections; Electric inter-cell connections
    • 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
    • C22B11/00—Obtaining noble metals
    • C22B11/04—Obtaining noble metals by wet processes
    • 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
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/02—Apparatus therefor
    • 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
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/045—Leaching using electrochemical processes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • 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
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
    • C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
    • C02F1/4674—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation with halogen or compound of halogens, e.g. chlorine, bromine
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46152—Electrodes characterised by the shape or form
    • C02F2001/46157—Perforated or foraminous electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/4618—Devices therefor; Their operating or servicing for producing "ionised" acidic or basic water
    • C02F2001/4619—Devices therefor; Their operating or servicing for producing "ionised" acidic or basic water only cathodic or alkaline water, e.g. for reducing
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/18—Removal of treatment agents after treatment
    • C02F2303/185—The treatment agent being halogen or a halogenated compound
    • 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
    • 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
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
    • Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy

Definitions

  • the present invention relates to electrodes and, more specifically, to the use of three-dimensional flow-through electrode and electromechanical cells used for a number of applications, including water purification, improving crop yields, metal processing, chemical manufacturing and environmental cleanup.
  • Electrolytic processes are commonly conducted using planar electrodes. Electrodes are well known in the art and include a conductor which is in contact with a plate, in which various types of solutions flow-by the electrode. A number of specific electrodes have been designed in which the solutions flow-through one or more electrodes. These electrodes have been made from a variety of materials and material shapes.
  • One problem addressed by the present invention relates to the method of feeding electrical current into an electrode; specifically into a three-dimensional electrode composed of graphite felt material which provides a large surface area for electrochemical reactions.
  • Previously used graphite felt electrodes typically feed electrical current through contact of a conductor metal either on the edges of a thin graphite felt electrode, as disclosed, for example, in U.S. Patent No.
  • Patent No.5,376,240 both of which are incorporated herein by reference in their entirety.
  • Still other known graphite felt electrodes feed current by inducing an electrical charge in a thicker graphite felt electrode by inserting it between two oppositely charged electrodes so the graphite felt becomes bi-polar with regard to electrical charge.
  • Such an electrode is disclosed in U.S. Patent No. 5,744,028 to Goto et al., issued on April 28, 1998 entitled “Water treating apparatus,” which is also incorporated herein by reference in its entirety. All of these methods work to some degree for their specific intended purpose; unfortunately, they all fail in their ability to handle significant current flows.
  • an electrode which is relatively large, which can provide a large surface area for efficient chemical reactions which can be used in water purification, metal processing, chemical manufacturing and environmental cleanup, to name a few possible applications. Furthermore, it would be advantageous for such an electrode to be capable of handling relatively large current flows.
  • an efficient method for feeding current into a three-dimensional, flow-through electrode preferably utilizing a graphite felt material.
  • Rods of a conducting material, preferably graphite are inserted at predetermined spacing into a block of graphite felt electrode as current feeders. The spacing of these conductor materials throughout the graphite felt block allows for efficient current distribution despite the electrical resistance of the graphite.
  • the large surface area provided by the graphite felt makes it possible to expose solutions or gases to electrical charges instituting electrochemical reactions.
  • This large surface area providing approximately 17,000 square feet of graphite surface for each cubic foot of graphite felt, makes it possible to perform electrochemical reactions on minute traces of elements in solutions such as contaminants in water, and additionally makes it possible for the mass transfer of electrons in chemical reactions allowing for the high throughput of solutions in industrial applications such as the production of chlorine from salt water.
  • a flow-through electrolytic cell is provided using the flow-through electrodes.
  • a number of methods of feeding solutions or gases into the flow-through electrolytic cell are introduced depending upon the direction of solution flow through the electrodes. Solutions or gases can be either first oxidized in one electrode or reduced or the solution can be fed between the electrodes so that one portion flows through the oxidizing electrode while the other portion flows through the reducing electrode. This methodology allows the elimination of diaphragms in some electrolytic cells.
  • one aspect of the present invention is an electrochemical cell, comprising: at least a first and a second three-dimensional flow-through electrode wherein said first three-dimensional flow-through electrode is a positive electrode and said second three-dimensional flow-through electrode is a negative electrode; a current feeder associated with each of said three-dimensional flow-through electrodes, wherein at least a substantial portion of each of said current feeders is located within said three-dimensional flow-through electrode associated with said current feeder; a power supply coupled to each of said current feeders to create an electrical potential therebetween; and wherein the electrochemical cell is operable to facilitate a chemical reaction on a feed solution which is flowing through said electrodes.
  • FIGURE 1 is a front perspective view of a basic flow-through electrode in one embodiment of the present invention
  • FIGURE 2 is a front perspective view of a large flow-through electrode in one embodiment of the present invention.
  • FIGURE 3 is a front perspective view of a flow-through electrode in another embodiment of the present invention.
  • FIGURE 4 is a cross-sectional view of a flow-through electrolytic cell according to one embodiment of the present invention
  • FIGURE 5 is a cross-sectional view of a flow-through electrolytic cell according to another embodiment of the present invention.
  • FIGURE 6 is a cross-sectional view of a flow-through electrolytic cell according to another embodiment of the present invention
  • FIGURE 7 is a cross-sectional view of a flow-through electrolytic cell according to another embodiment of the present invention.
  • FIGURE 8 is a cross-sectional view of a flow-through electrolytic cell according to another embodiment of the present invention.
  • FIGURE 9 is a flow chart diagram illustrating the operational steps for one embodiment of the present invention.
  • FIGURE 10 is a flow chart diagram illustrating the operational steps of another embodiment of the present invention.
  • FIGURE 11 is a flow chart diagram illustrating the operational steps of another embodiment of the present invention.
  • FIGURE 12 is a front elevation view of a mineral processing apparatus of another embodiment of the present invention.
  • FIGURE 13 is a front sectional schematic diagram showing the layout of a series of E-VATs arranged in a train-like setting
  • FIGURE 14 is a plan view schematic which illustrates a preferred embodiment of this invention for processing ores and particularly ores containing gold;
  • FIGURE 15 depicts a flow chart showing another embodiment of this invention; a method of recovering metal, in particular, gold, from ores requiring finer particle size preparation for liberation of their mineral values;
  • FIGURE 16 is a cross section of a typical in situ leaching method for production of uranium from subterranean deposits using another embodiment of this invention for regenerating oxidizing lixiviants in a cost effective manner;
  • FIGURE 17 is a cross section illustration of in irrigation treatment system of one embodiment of the present invention.
  • FIGURE 1 illustrates one embodiment of the present invention having a flow-through electrode 1 into which a current feeder 2 is inserted.
  • the flow-through electrode 1 can be any conducting material that is porous to the flow of liquids or gases, and, in one embodiment, is graphite felt such as that manufactured by National Specialty Products of Fostoria, Ohio.
  • the current feeder 2 can be any conductor material capable of conducting an electrical current, and, in one embodiment, is a graphite rod having a diameter of about one-quarter inch or larger, and being capable of conducting a current in the range of about 0.01 to 5.0 amperes.
  • Other current feeders may include, for example, copper, steel, or a noble metal such as platinum, palladium, gold, as well as allows of metals such as tantalum, tungsten, and titanium.
  • the current feeder may also separate base material which is plated with any of the previously mentioned materials.
  • the current feeder 2 is inserted into the flow- through electrode 1 by boring a hole of lesser diameter than the current feeder 2 in the flow-through electrode 1 such that when the current feeder 2 is inserted, the fibers of the graphite felt are in intimate contact with the current feeder 2, forming a good electrical connection.
  • a current feeder as referred to herein, is a device which facilitates the supply of electrical current to, or the conduction of electrical current from, an associated electrode.
  • porous conducting materials could be used for the electrode material such as, for example, steel wool, copper wool, or wool composed of the noble metals such as platinum, palladium or gold, as well as exotic alloys of metals such as tantalum, tungsten and titanium.
  • Graphite felt is utilized in one embodiment for this invention because of its low cost when compared to most alternatives, chemical resistance and its high hydrogen overvoltage potential property.
  • FIGURE 2 is a front perspective view of a flow-through electrode 100 in one embodiment of the present invention which includes a plurality of current feeders 2.
  • An electrode of this design containing one cubic foot of graphite felt would have a surface area for electrochemical reactions of about 17,000 square feet. This large surface area allows for relatively efficient reactions to take place. These types of electrochemical reactions are especially useful in numerous applications for removing trace elements from solutions or gases, or the reduction and recovery of valuable metals such as gold, silver, platinum and palladium.
  • the flow-through electrode 150 is used to produce electrodes for industrial applications requiring large current flows.
  • the flow- through electrode 100 in another embodiment is used for a fuel cell electrode where the graphite felt is first coated with a suitable catalyst.
  • the current feeders 2 are also used to remove electricity generated within the electrode.
  • the number and spacing of the current feeders 2 is dependent upon the application and the amount of current required for the application. For example, current of up to at least 50 amperes per square foot (600 amperes per cubic foot) is preferred for chlorine production, while current of about 100 milliamps per square foot is preferred for removal of trace elements from water.
  • the number, size, and spacing of the current feeders vary as necessary for the desired current density.
  • the current feeders 2 are covered by a polypropylene geotextile having precut holes. This embodiment is useful when the current feeders 2, have a relatively high voltage applied to them, which may act to pull the carbon felt apart and cause a cell containing the electrode to short-circuit.
  • FIGURE 3 is a perspective view of an alternative method of achieving electrical flow into a flow-through electrode 1 where a conductive bar 104 is placed in intimate contact with up to four sides of the flow-through electrode 1.
  • This bar 104 can be any conductive material, and in one embodiment is a graphite bar and the flow-through electrode is graphite felt, similar to the flow-through electrode depicted in FIGURE 1.
  • a drawback of this method of feeding electrical current into flow-through electrode 1 is that as the dimensions of the flow-through electrode increases, the resistance to electric current flow also increases due to the resistance of the carbon felt. Accordingly, this design is most advantageous in applications requiring relatively small current flows in the range of about 5 milliamps per square foot up to one ampere per square foot.
  • FIGURE 4 is a cross-sectional front elevation view of a flow-through electrolytic cell 108 using the basic electrode described in FIGURE 1, where two such flow-through electrodes 1 and la, with current feeders 2 and 2a, are placed in a container 3 made from inert material, such as a variety of plastics including PVC, HDPE, Acrylic, or any other suitable material that is not a conductor of electricity and is not chemically reactive with any of the gases or liquids used in the electrolytic cell 108.
  • Such containers may be either open-top or totally enclosed, depending on the application.
  • the flow-through electrodes 1 and la separate the electrolytic cell 108 into three specific chambers 4, 5, 6.
  • a solution, or gas enters the flow-through electrolytic cell 108 from stream 7 (under sufficient hydraulic pressure to induce flow) through a valve (not shown) into chamber 4 where it passes through a negatively-charged electrode la into chamber 5 and then through a positively-charged electrode 1 and into chamber 6 where the product stream 8 exits through an exit valve (not shown).
  • Both the current feeders 2, 2a are connected to a direct current power supply (not shown). In this unit a direct electrical current is applied through current feeder 2 into positive electrode 1 and negative electrode la and into current feeder 2a to complete the circuit. The amount of current and voltage is dependent upon solution composition and desired results.
  • One application for a flow-through electrode 108 of this embodiment includes stream 7 which is composed of a solution of water and sodium chloride.
  • stream 7 which is composed of a solution of water and sodium chloride.
  • the negative electrode la under sufficient voltage of at least about 3 volts, and, more preferably about 5-10 volts, some of the water is elecfrolytically separated into hydrogen gas and hydroxide ions.
  • the hydrogen gas is vented from chambers 4 and 5 (not shown), while the solution, with its increased hydroxide ion level passes into chamber 5 and then through the positive flow-through elecfrode 1 where some of the chloride ions are oxidized to free chlorine which immediately reacts with the hydroxide to form a hypochlorite ion within the flow-through electrode 1 and within chamber 6 so that the product leaving the flow-through electrolytic cell is a solution of water, sodium chloride and sodium hypochlorite (a common chemical used as household bleach, swimming pool disinfectant and numerous industrial processes).
  • FIGURE 5 is similar to FIGURE 4 as to the design and construction of the flow- through electrolytic cell.
  • the primary distinction is in the direction of flow of solutions or gases to be processed.
  • solutions or gases to be processed in the flow stream 9 are introduced into chamber 5 through a valve (not shown) where a portion of the solution passes through a negative electrode la and the remainder of the solution passes through the positive electrode 1.
  • a direct electrical current is applied through current feeders 2, 2a into positive electrode 1 and negative electrode la, the amount of current and voltage is dependant upon solution composition and desired results.
  • stream 9 is separated into two different products, including stream 7 and stream 8.
  • a solution of sodium chloride and water is fed into chamber 5 as stream 9. A portion of the solution passes through the negative flow- through electrode la into chamber 4 and the remaining portion of solution passes through the positive electrode 1 into chamber 6.
  • the amount of each product stream 7 and 8 is regulated by a valve (not shown) on chambers 4 and 6.
  • water is elecfrolytically separated into hydrogen gas and into hydroxide ions while in the positive flow-through elecfrode 1 the chloride ion is oxidized to chlorine gas which dissolves into water to form hypochlorous acid.
  • the solution in chamber 4 is enriched in sodium hydroxide while the solution in chamber 6 is enriched in hypochlorous acid.
  • the pH of the solution in chamber 4 is substantially basic while that of the solution in chamber 6 is substantially acidic.
  • the inventor has conducted tests where the pH in chamber 4 reached in excess of pH 13, while the pH of chamber 6 was as low as 1. These results can be varied by controlling the voltage to the electrodes, the solution flow rate through each electrode and the composition of the original solution. For example, in one test, a voltage of 9 volts, with a starting solution of 2 percent sodium chloride was used, resulting in a flow rate of 70 ml/min for each electrode, and each electrode was 4 inches by 4 inches by 1 inch thick.
  • the resulting solution in chamber 6 had a pH of 3.8 and an ORP of 1,045 millivolts, and a solution in chamber 4 had a pH of 11.7 with an ORP of 37 millivolts. It will be obvious to one skilled in the art that this is a fundamental electrochemical cell with the ability to separate any salts into their original acidic and basic components. It will also be obvious to one skilled in the art that this embodiment allows electrochemical processes to be conducted without the use of a diaphragm to separate anode and cathode products.
  • the flow-through nature of the electrodes la and 1 used within substantially prevents the back-flow of products due to the fact that electrical charge on the flow-through electrodes la and 1 repels ions or products with the same charge.
  • FIGURE 6 is similar to FIGURE 4 in the construction of the flow-through electrolytic cell.
  • the solutions or gases to be processed as depicted as stream 11, first enter chamber 6 where they first flow through the positive elecfrode 1, then into chamber 5 where they flow through the negative electrode la into chamber 4 and exit as product stream 10.
  • a direct electrical current is applied through current feeders 2, 2a into positive elecfrode 1 and negative electrode la, the amount of current and voltage is dependant upon solution composition and desired results.
  • One specific application of this embodiment is in the treatment of contaminated water to provide water suitable for human consumption.
  • Untreated water, with sediments removed, is processed as depicted in stream 11 where it enters chamber 6 and passes through the positively charged flow-through electrode 1.
  • some existing chloride ions (which are common to all natural water) are oxidized to chlorine and micro-organisms are subjected to an electric current. Both the electric current and the chlorine act to kill substantially all of the disease-causing micro-organisms. Trace organic harmful compounds are oxidized as well.
  • the oxidized solution flows into chamber 5 and then through the negative electrode la where the chlorine produced within the positive electrode is reduced back to chloride and fransition metals present in the original untreated water are electro-deposited within the negative flow-through electrode la.
  • the resulting solution in chamber 4 and exiting as stream 10 is potable water.
  • the current and voltages necessary for this embodiment can readily be produced by an inexpensive solar cell, which produces at least about 1.7 amp, 9 volts, and 15 watts. Most any other means of electricity generation, such as wind power or a small hydroelectric generator could also readily produce the current and voltages necessary for this embodiment. Voltage is the most important factor and is preferably at least about 3 volts. It is contemplated that this embodiment may have widespread usage worldwide to provide potable water in remote locations not in proximity to a power grid.
  • FIGURE 7 is similar to FIGURE 6 with the addition of the option of removing a stream 12 from the inter-electrode chamber 5 through a valve (not shown). This embodiment allows the removal of an additional product.
  • FIGURE 8 is similar to FIGURE 4 with the addition of stream 12 removed from the inter-electrode chamber 5 through a valve (not shown). This embodiment allows the production of two products from a process stream 10.
  • This embodiment would be the processing of a solution of water and sodium chloride entering chamber 4 as process sfream 10, where it first passes through the negative flow-through electrode la.
  • a direct electrical current is applied through current feeders 2, 2a into positive electrode 1 and negative elecfrode la, the amount of current and voltage is dependant upon solution composition and desired results. More specifically, this application may be used to produce sodium hypochlorite from low concentration salt solutions.
  • An optional circulating loop 13 of solution raises the pH of the product in chamber 5 to the point where it will dissolve all of the chlorine produced in elecfrode 1.
  • the production of chlorine from low salt solutions is generally hampered by the competing production of oxygen at the electrode. As will be understood, this embodiment may have important usage in other electrochemical processes.
  • h electrode la water is elecfrolytically separated into hydrogen gas and hydroxide ions.
  • the hydrogen gas may be removed from chambers 4 and 5 through valves (not shown) while the hydroxide ion enriched solution passes into chamber 5 where a portion of it may be withdrawn through process sfream 12 for further usage, including recycling it back to process sfream 10 by process sfream 13 in order to increase the strength of the incoming solution 10 in hydroxide ions.
  • the concentration of hydroxide ions in input sfream 10 can be increased by the recycling the solution from chamber 5.
  • the solution moving through the positive flow-through elecfrode 1 is thus more concentrated in hydroxide ions.
  • a solution process stream 10 of water and sodium chloride can be separated into three products, hydrogen gas, sodium hydroxide and sodium hypochlorite.
  • FIGURE 9 illustrates another embodiment of the present invention. It is a generalized flow diagram of a process to treat industrial waste water containing cyanide and metals in solution.
  • One such source of this type of metal laden solution is, for example, from electroplating operations.
  • Another source is from mining operations, such as gold and silver heap leaching operations such as the one at the Florida Canyon Mine located in Humboldt County, Nevada.
  • a source solution 20 containing a cyanide and dissolved metals is pumped into a closed mixing tank 22 through process line 24.
  • an oxidizing solution containing chlorine and oxygen from process line 8 is mixed with the source solution 20.
  • the chlorine and oxygen destroy the cyanide by oxidizing it to nitrogen and carbon dioxide.
  • oxidized are metals in a reduced state such as ferrous iron and arsenic compounds.
  • This oxidized solution leaves the mixing tank 22 through process line 10 where it enters the inner-electrode chamber 5 of the flow-through electrolytic cell 3. h this unit, a direct electrical current is applied through current feeders 2, 2a into positive electrode 1 and negative electrode la.
  • the natural amount of current and voltage applied to electrodes 1, la is dependant upon solution composition and desired results. More specifically, the voltage must be high enough to produce either chlorine or oxygen or both, and in one embodiment is above about 3 volts.
  • the current is dependent upon the concentration of the dissolved salts, a salt solution of 500 ppm or more would draw a much larger current than a solution with only 50 ppm dissolved salts.
  • a portion of the solution passes through the positive charged three-dimensional flow-through electrode 1, in which chloride ions present in the original solution are oxidized to chlorine and some water molecules are oxidized to produce oxygen.
  • This oxidizing solution passes from the flow-through electrode 1 into chamber 4 of the flow- through electrolytic cell 3 and then into process line 8 through a regulating valve (not shown).
  • the remaining solution in chamber 5 passes through flow-through electrode la which, in this embodiment, is made of a wire mesh of a conducting material such as copper, lead, or stainless steel. This electrode la has sufficient openings to allow passage of precipitated metals and metal compounds.
  • the electro-chemical reactions occurring in and around this electrode are of a reducing nature such that some metals are electro-deposited on the wire mesh while water is reduced to produce hydrogen and hydroxide ions. Some metals precipitate as hydroxides, others as oxides and some are further reduced by the action of the dissolved and entrained hydrogen in chamber 6.
  • the electro-chemical reactions in, at, and around electrode la will depend upon metal concentration, applied voltage, current flow, solution flow rate and solution composition.
  • the solution passing through this elecfrode la virtually boils with hydrogen gas bubbles and has an Oxidation-Reduction Potential of minus 1000 millivolts or lower.
  • This reduced solution leaves chamber 6 through process line 7 and may be stored in a treated solution tank 26.
  • Another embodiment of the present invention is used in an agricultural setting.
  • water used for irrigation of plants is generated by an elecfrolytic cell of the present invention.
  • the electrolytic cell includes a negatively charged electrode of copper wire screen and a positively charged electrode of graphite felt.
  • the copper wire screen elecfrode of this embodiment allows irrigation water to pass through without removing substantial amounts of transported nutrients. Standard irrigation water is fed into the inter-electrode spacing and most of it, approximately ninety percent in one embodiment, is allowed to pass through the negatively charged copper wire screen elecfrode and collected in an inert tank. The water passing through the positively-charged elecfrode is discarded in one embodiment.
  • the cell of this embodiment is operated at a direct current of about 9 volts and approximately 3 to 5 amperes of current. Each elecfrode was 12 inches square and one inch thick.
  • the water produced through the negative electrode has an oxidation-reduction potential of approximately -300 to -600 millivolts. This is by definition, an anti-oxidant water, as it donates electrons to reduce oxidants and free-radicals. This water is then taken from the inert tank and used as irrigation water.
  • a test garden was planted by the inventor.
  • the garden was divided into two substantially identical sides. One side was irrigated with water directly from a pond while the other side was irrigated with pond water that had passed through the above-described elecfrolytic cell.
  • Two tanks of 300 gallons capacity were filled for each irrigation event, normally three days apart. One tank was filled with the raw pond water, while the other tank was filled with hydrogen-rich water generated by the flow-through electrolytic cell.
  • FIG. 5 Another example involves numerous other flow-through elecfrolytic cells which have been constructed and tested using tap water as a source using the scheme depicted in FIGURE 5.
  • the tap water was fed into the inter-electrode space and allowed to flow through each side of the elecfrolytic cell without restriction. Approximately forty percent of the water passed through the negatively-charged electrode while approximately sixty percent of the water passed through the positively-charged elecfrode.
  • the electrodes were connected to a direct current power supply with a 9 volt potential.
  • the cells drew an average of 1 ampere per square foot of elecfrode.
  • FIGURE 10 illustrates another embodiment of the present invention.
  • the solution source 30 is a liquid containing dissolved metals including, but not limited to, gold, silver, copper, lead and zinc, but does not contain cyanide.
  • a solution could originate from many industrial processes, such as, for example, metal plating, ore processing or scrap recycling, and would most likely be acidic.
  • the solution could also be from polluted sources such as acid mine drainage.
  • This solution may contain chlorides, nitrates, sulfates or phosphates.
  • solution 30 flows through process line 34 to mixing tank 32 where it is mixed with a reducing alkaline solution from chamber 6 in the flow-through electrolytic cell 3 which flows through process line 7 to the mixing tank 32.
  • mixing tank 32 can be drawn out into individual reactions in separate mixing tanks by first separating the hydrogen gas in process stream 7 from the hydroxide rich liquid so that the original solution can have its pH raised in increments by addition of hydroxide rich liquid separated from process stream 7 to allow individual metal hydroxides to precipitate.
  • the Oxidation-Reduction Potential of the process stream 34 could also be regulated with the addition of controlled amounts of the separated hydrogen gas, thus sequentially reducing dissolved metals according to their respective oxidation-reduction potentials.
  • the reduced alkaline solution from mixing tank 32 flows through process line 34 into filter 36 where solids 38 containing metal powders, metal oxide powders and/or metal hydroxides are removed for environmentally safe disposal or metal recovery.
  • the resulting metal-free liquid from the filter 36 flows through process line 10 into chamber 5 of flow-through electrolytic cell 3.
  • a direct electrical current is applied through current feeders 2, 2a into positive elecfrode 1 and negative electrode la. The amount of current and voltage is dependant upon solution composition and desired results.
  • FIGURE 11 illustrates another embodiment of this invention which generally depicts a process diagram for recovering metals from ores, including, but not limited to gold, silver, copper, lead, zinc, tin, cobalt, platinum and palladium.
  • crushed ore 50 is conveyed by conveyor 54 into device 56, herein called the E-VAT, which is a continuous flow, counter-current leaching system.
  • Lixivating solution 8 such as a solution of 1/10% to 30% sodium chloride and 0% to 15% sodium bromide, is added to the ore in the E-VAT 56 after first passing through the electrode 1 where it is oxidized to produce sufficient chlorine, bromine or compounds of both so that it dissolves the targeted metal contained within the ore resulting in a pregnant solution which leaves the E-VAT 56 through process line 58.
  • leached ore is transported through rinsing mechanism 60 where fresh water from process line 62 is added to displace entrained liquids in the leached ore so that a rinsed and leached ore 64 is produced for further environmentally safe disposal.
  • the fresh water 62 is derived from a portion of lixiviant solution in process line 8 through a salt/water separator 66 using reverse osmosis, electro-dialysis or another effective method to produce fresh water from salt water.
  • the waste solution 68 from the salt/water separator 66 is added back to the lixiviant solution in line 8 through process line 70.
  • the pregnant solution containing the targeted metals flows through process line 58 into mixing tank 72, where a solution coming from chamber 6 of flow-through electrolytic cell 3 is added through process line 7.
  • this mixing tank 72 at least two chemical reactions occur, the first being the reduction of metals by hydrogen gas entrained in the solution from process line 7, and the second reaction being the precipitation of metal hydroxides and oxides by the hydroxide ions in the solution from process line 7. It will be understood by one skilled in the art as to which type of these reactions occur depends upon the metals present, their concentration, the pH and Eh of the pregnant solution.
  • the precipitated solution leaves mixing tank 72 through process line 74 where it passes into filter 76 where the precipitated metals and metal compounds are removed as filter cake 78 which can be mixed with fluxes such as borax, sodium carbonate, fluorite, silica, and lime, and melted to produce metal bullion, if desired.
  • the barren solution filtrate from the filter 76 leaves through process line 10 where it enters chamber 5, the inter-electrode chamber, of flow-through electrolytic cell 3.
  • a direct electrical current is applied through current feeders 2, 2a into positive electrode 1 and negative electrode la, the amount of current and voltage is dependant upon solution composition and desired results.
  • the flow rate through process line 10 is about 100 mL/min and the flow-through elecfrodes 1, la are each about 4 inches per side and one inch thick. It will be understood that flow rates may vary based on the size of the electrodes, the current and voltage, and the solution being fed into the elecfrolytic cell. A portion of the barren solution passes through flow-through elecfrode la where water is separated into hydrogen gas and hydroxide ions and enters chamber 6 where it is recycled to mixing tank 72 for metal precipitation.
  • the remaining barren solution passes through flow-through elecfrode 1 where it is oxidized by the elecfrolytic process so that any chloride or bromide ions are oxidized to chlorine and bromine and their compounds which dissolve in the solution in chamber 4 to form hypochlorous acid or hydrobromous acid, dependant upon solution chemistry.
  • the pH of this solution may also be lowered by the oxidation of water to produce oxygen and hydrogen ions.
  • This solution is now the lixiviant which flows through process line 8 back to the E-VAT leaching system.
  • this embodiment of the invention is a closed system to recover metals from their ores, waste materials or scrap using the flow-through electrodes 1 in a flow-through elecfrolytic cell.
  • FIGURE 12 is a sectional, front elevation view of one embodiment of the continuous-flow counter-current leaching system, referred to as the E-VAT, of FIGURE 11.
  • E-VAT continuous-flow counter-current leaching system
  • two round cone-bottomed tanks 150 and 154 made from rotary molded hi-density polyethylene or other suitable material are positioned vertically above each other and supported by a structural steel silo 158.
  • the tanks are connected by a feed tube 162 through which crushed ore 166 stored in tank 150, used as an ore bin passes into tank 154, used as a leaching reactor, where the ore is contacted with a lixiviant solution which enters through pipe 170.
  • the lixiviant solution 172 flows up through the crushed ore in tank 154 where it dissolves the desired elements and becomes pregnant solution 174, which exits through pipe 178 (equivalent to process line 11 of FIGUREl l).
  • the crushed ore flows down through tank 154 (the leaching reactor) by gravity where it flows through outlet pipe 182 into auger 186. It moves up auger 186, powered by variable speed motor drive mechanism 190.
  • Fresh water is injected into the auger through pipe 194 where it displaces entrained solutions. The fresh water is injected at a point above the liquid level 198 in tank 154 (the leaching reactor) so that the fresh water flows down the auger by gravity.
  • the leached and rinsed ore then exits the auger 186 through discharge pipe 202 where it falls to the ground as pile 206 for further environmentally safe disposal.
  • the auger 186 is fitted with a clean-out plug 210 and drain pipe 214. h this system, the crushed ore flows by gravity down through the leaching reactor 154 while the lixiviant flows up through the ore.
  • the sfrongest solution therefore contacts the weakest (lowest metal content) ore which is the ideal metallurgical condition to maximize metal recoveiy and minimize reagent consumption.
  • the flow rate of ore through the E-VAT is easily regulated by adjusting the speed of the auger through the variable speed motor drive mechanism 190.
  • the solution flow rate, and thus the residence time, in the leaching reactor is readily regulated by the injection rate of the solution.
  • FIGURE 13 is a front sectional schematic diagram showing the layout of a series of E-VATs arranged in a train-like setting. Only major components are depicted.
  • crushed ore is fed into ore hopper 301 where it is conveyed via auger 302 into ore hopper 303.
  • E-VAT unit 304 The ore flows by gravity down through E-VAT unit 304, is conveyed via auger 305 into E-VAT unit 306, where it flows by gravity into auger 307 which conveys it into E-VAT unit 308 where it flows by gravity into auger 309 which conveys it into E-VAT unit 310 where it flows by gravity into auger 311 which conveys it into E-VAT unit 312 where it flows by gravity into auger 313 where it is conveyed for disposal.
  • the ore can flow either continuously, or in batches, depending upon the processing needs. Lixiviants are injected into the bottom of each E- VAT unit and removed from the upper portion of the same unit as depicted more fully in FIGURE 12.
  • FIGURE 14 is a plan view schematic which illustrates an embodiment of this invention for processing ores and particularly ores containing gold, i this embodiment, crushed ore is placed into ore hopper 401.
  • the fineness of crushing is dependent upon the particular leaching requirements of the ore.
  • the ore enters an auger 403 where it is conveyed into E-VAT unit 404.
  • an agglomerating agent such as Portland cement, long-chained polymers, flocculates or other suitable binding agent is added from tank 402.
  • the addition of the agglomerating agent coupled with the rotary action of the auger 403 while conveying the ore has the effect of agglomerating the ore by attaching fine particles to larger ones.
  • the auger 403 can also be discharged into an ore bin vertically above E-VAT 404 as depicted by 303 in FIGURE 13.
  • This ore bin can be sized to allow curing time for the agglomerating agent, or if necessary, an additional E-VAT unit without any liquid additions can be used at this point in the process for longer curing times, h E-VAT unit 404 a lixivating agent is injected into the bottom of the unit where it percolates up through the crushed and agglomerated ore reacting with, and dissolving metals.
  • This metal-laden pregnant solution flows from the upper portion of the E-VAT unit 404 into pregnant storage tank 414.
  • the pregnant solution is then pumped through flow-through electrolytic cell 419 as depicted in FIGURE 4.
  • the contained metals of the pregnant solution are deposited in the negatively-charged flow-through electrode.
  • the lixiviant is restored when it passes through the positively-charged flow-through electrode.
  • the restored and regenerated lixiviant flows into storage tank 423 from which it is then pumped back into E-VAT unit 404, this forming a completed closed circuit of solution flow.
  • E-VAT unit 404 From E-VAT unit 404 the partially leached ore passes into transfer auger 405 where it is conveyed into E-VAT unit 406 where the leaching cycle is repeated as described above for E-VAT unit 404. These steps are repeated in E-VAT units 408, 410 and finally in 412 at which point substantially all of the metal is leached out. As will be understood, additional E-VATs may be added in series, or in parallel, to the apparatus illustrated in FIGURE 14. A rinsing solution of clean water can be added at the end of auger 413 as shown in 194 of FIGURE 12.
  • the Inventor operated the apparatus for leaching an ore containing polymetallic sulfides, with solutions containing both sodium chloride and sodium bromide which, when passed through a positively-charged flow-through electrode, were partially converted in chlorine and bromine and their compounds. It was observed that the metals in the sulfides were leached in the following order. First, the lead sulfides dissolved, followed by the zinc sulfides and then the copper sulfides dissolved. This was followed by dissolution of gold while the contained silver remained in the ore as silver chloride and silver bromide.
  • a polymetallic ore containing metal sulfides can be treated in sequence.
  • the lead is leached in E-VAT unit 404 and recovered in flow-through electrolytic cell 419
  • the zinc is leached in E-VAT unit 406 and recovered in flow-through elecfrolytic cell 420.
  • the copper is leached in E- VAT unit 408 and recovered in flow-through electrolytic cell 421.
  • Gold is then leached in E-VAT unit 410 and recovered in flow-through electrolytic cell 422.
  • silver is leached in E-VAT unit 412 and recovered in flow-through electrolytic cell 423.
  • the lixiviants used in a multiple stage process can be diverse.
  • a starting solution containing only sodium chloride could be used while the addition of sodium bromide may increase the recovery of copper in the next stage and increases the recovery of gold in the gold stage.
  • Silver requires the use of a different lixiviant than used in the previous stages as the silver halides are insoluble in water, but the silver can be recovered in this stage by the use of solutions containing thiosulfate, ammonia, salt brine, or a number of organic compounds.
  • the solutions could also flow through multiple units in a counter-current direction with or without passing through an elecfrolytic cell. Such a flow scheme may be of use to increase the metal content of the pregnant solution prior to stripping in an electrolytic cell. It also should be understood by one skilled in the art, that other methods of removing metals from pregnant solutions could be used prior to lixiviant regeneration including cementation with another metals, ion exchange, or crystallization of a metal salt such as lead chloride recovered by simply cooling a saturated hot solution.
  • this multiple stage process can be used to treat a vast variety of solids whereby the solids are treated by different lixiviants for different objectives.
  • the solids could be ores containing metals or scrap materials such as granulated electronic circuit boards.
  • the solids could also be contaminated soils where there is a need to remove environmentally hazardous compounds as simple as salty soil to that containing radioactive compounds.
  • the liquids used need not be confined to water solutions but could as well be any number of organic liquid compounds.
  • FIGURE 15 illustrates yet another embodiment of the present invention. It depicts a flow chart of the operational steps for a method of recovering metal, in particular, gold, from ores requiring finer particle size preparation for liberation of their mineral values.
  • Crushed ore prepared by any number of conventional methods, enters ball mill 501 through process stream 500 and discharges through process sfream 502 where additional water is added from process stream 509.
  • the ground ore slurry enters classifier 503 where oversize material is separated and returned to the ball mill 501 through process sfream 504 while diluted undersize material flows through process line 505 into thickener 506 where the ore slurry is thickened to a pulp density between 40 to 70 percent, more preferably 60 to 70 percent.
  • the excess water from the thickener is decanted through process line 507 into storage tank 508 while the thickened slurry is pumped (pump not shown) through process line 510 into mixing tank 511 where lixiviant is added.
  • the lixiviant should have a pH between 3 and 8 (dependent upon the chemistry of the ore), a sodium chloride content of between 0.1 and 25 percent, a sodium bromide content between 0.05 and 5 percent and an oxidation-reduction potential (as measured with a calomel-platinum probe) in excess of +650 millivolts, more preferably +850 to +950 millivolts, due to the generation of dissolved chlorine and bromine and their compounds.
  • This lixiviant is generated in the positively charged flow-through elecfrode of electrolytic cell 529. Sufficient lixiviant is added to dilute the pulp density of the incoming ground ore slurry to between 10 and 35 percent solids, more preferably to 25 percent solids. It should be noted that all equipment from the mixing tank 511 to the end of the process should be constructed of non-corroding material, and in an embodiment is constructed of HDPE plastic, and should be totally enclosed to prevent any loss of chlorine or bromine vapors.
  • mixing tank 511 leaves mixing tank 511 through process line 512 into pump 513 where it is injected into the bottom of reactor 515 through process line 514, it departs reactor 515 through process line 516 where it enters pump 517 and is injected into the bottom of reactor 519 through process line 518. It departs through process line 520 into pump 521 where it is injected into the bottom of reactor 523 through process line 522.
  • mixing tank 511 and reactors 515, 519, 523 are cone-bottomed covered vessels of rotary-cast hi- density polyethylene (HDPE). The conical shape of the bottom insures that all of the ore particles are in motion and subject to the action of the lixiviant.
  • HDPE rotary-cast hi- density polyethylene
  • each reactor 515, 519, and 523 is from less than 30 minutes to about 4 hours, preferably about 1 hour, dependant upon the natural chemistry of the ore.
  • the ore slurry, with dissolved metals, leaves reactor 523 through process line 524 into pump 525 which fransfers it to thickener 527 through process line 526.
  • thickener 527 the solids are separated from most of the liquid containing the dissolved metals.
  • This pregnant solution leaves through process line 528 where it is joined with additional pregnant solution from filter 544 through process line 543.
  • the combined streams flow into flow-through elecfrolytic cell 529 where gold and other metals are deposited in and on the negatively charged flow-through electrode, as also depicted in FIGURE 7.
  • the thickened leached ore is pumped from thickener 544 (pump not shown) into filter 544 where additional pregnant solution is removed through process line 543.
  • the filter cake is rinsed with fresh water (source not shown) to removed any entrained lixiviant.
  • the rinsed filter cake, which is the leached ore residue, is then sent to disposal shown as 545. This disposal should be upon a liner to prevent any migration of trace amounts of metals into the environment.
  • the rinse solution from the filter 544 leaves through process line 542 and enters flow-through electrolytic cell 541. It enters between the positive and negative charged flow-through elecfrodes as shown in FIGURE 5. Any residual gold and other metal is recovered within the negatively-charged flow-through electrode which also generates an excess of dissolved hydrogen gas.
  • This solution leaves through process line 540.
  • a portion of the process sfream flows through the positively-charged flow-through elecfrode where some of the residual chloride and bromide is oxidized to chlorine and bromine and their compounds and leaves through process line 539 where it is mixed with the solution from process line 540 in tank 538 where the dissolved hydrogen reduces the chlorine and bromine contained in process line 539 back to harmless chloride and bromide.
  • the now neutralized dilute saline solution leaves tank 538 through process line 537 into evaporator 536.
  • evaporator 536 This could be any commercial evaporator or simply a series of small evaporation ponds.
  • the purpose of this step is to increase the concentration of dissolved salts to match that of the lixiviant.
  • the now concentrated salt solution is fed into lixiviant tank
  • the amount of solution entering the evaporation step from line 546 can be dramatically reduced by grinding the ore in a spent lixiviant solution rather than fresh water.
  • the E-VAT continuous-flow counter-current leaching system of the present invention has the ability to replace current heap-leaching technology commonly used in the mining industry.
  • heap-leaching technology a large pile of ore is placed on an impervious leach pad and sprayed or irrigated with leaching solutions which migrate down through the ore, dissolving metals. In many cases, the heaps continue to have additional ore added to them until they reach enormous size, over hundreds of millions of tons. These pads are saturated with the leaching solution.
  • the leaching solution contains cyanide.
  • the leaching solution contains sulfuric acid and iron salts.
  • FIGURE 16 illustrates another embodiment of this invention.
  • the figure is a cross section of a typical in-situ leaching situation for uranium similar to those discussed by Hard et al. in US Patent 3,708,206 and Habib, Jr., et al. in US Patent 4,312,840 and Camp, et al. in U. S Patent 4,476,099.
  • a porous ore horizon 601 containing valuable uranium deposits is sandwiched between two impermeable beds 602 and 603 which protect underlying rock formation 605 and overlying gravel 604 from contamination by solutions originating in ore horizon 601.
  • a lixiviant containing alkali metal bicarbonate, or carbonate and hypochlorite solutions at a pH in excess of 7, more preferably between 8-10 is injected through process line 615 into Injection Well 606 where it enters porous ore horizon 601 wherein the lixiviant dissolves uranium minerals .
  • the metal-laden lixiviant is withdrawn from the porous ore horizon 601 by Recovery Wells 1 and 2, 607 and 608, where it flows through process line 607 into pregnant solution tank 608 and then through process line 609 into precipitation apparatus 610 where the pH of the pregnant solution is lowered and sufficient phosphate is added to precipitate the contained uranium values as discussed, for example, by Camp, et al. in U. S Patent 4,476,099.
  • the mechanism of recovering the precipitate is not shown in this diagram.
  • the now barren solution leaves the precipitation apparatus 610 through process line 611 where it enters flow-through electrolytic cell 612.
  • FIGURE 4 The details of this particular embodiment of the flow-through cell 612 are depicted in FIGURE 4.
  • the pH of the lixiviant is increased and restored to the range of 8-10 within the negatively charged flow-through elecfrode by the electrolytic reduction of the water according to the equation 2H 2 0 + 2e " - H 2 + 2OH " , the lixiviant then flows through the positively charged flow-through elecfrode where contained chloride ions are oxidized to chlorine according to the equation 2C1 " - 2e " - Cl 2 which dissolves in the alkaline solution to form hypochlorite according to the following equation Cl 2 + H 2 0 ⁇ CI " + H " + HOCl.
  • the power source to provide the direct electric current for the flow-through elecfrolytic cell can be, for example, solar cells, wind generators or conventional power grid.
  • the now regenerated lixiviant with pH and hypochlorite content restored leaves the flow- through electrolytic cell 612 through process line 613 into lixiviant storage tank 615, thus completing a closed chemical circuit for the production of uranium.
  • This embodiment is particularly applicable to, for example, the Anderson uranium mine in Yavapai County, Arizona.
  • this embodiment specifically refers to the recovery of uranium by in-situ methods, this is not intended to limit this use of this invention to uranium as numerous other metals such as gold, silver, copper, lead, zinc, or cobalt, to name a few, using appropriate lixiviants that can be generated or regenerated using a flow-through electrolytic cell of this invention.
  • FIGURE 17 is a schematic diagram showing one embodiment of this invention whereby treated irrigation water is used to irrigate growing crops, h this diagram, untreated water in pond 701 is pumped through intake line 702 by pump 703 through line 704 into the inter-electrode chamber of flow-through elecfrolytic cell 705.
  • the negatively charged elecfrode 706 is composed of a conducting wire mesh or screen such as copper or stainless steel, while the positively charged elecfrode 707 is a flow-through electrode of graphite felt as depicted in FIGURE 1.
  • the majority of the water passes through electrode 706 where it undergoes reduction by the electrochemical process of decomposing water where 2H 2 0 + 2e " -» H 2 (gas) + 2OH " thereby also increasing the pH of the water.
  • the water becomes saturated in dissolved hydrogen gas.
  • This water flows through line 708 and either through line 709 to line 711, or alternatively is stored in storage tank 710 prior to flowing into line 711 and then to a field of irrigated crops 712 where it is used as irrigation water.
  • storage tank 710 is preferably made from an electrical non-conductor such as HDPE, otherwise electrons may flow from the water to the tank.
  • the mechanism of controlling flow rate through each electrode can either be controlled by valves (not shown) but normally is self-regulating by the difference in permeability between the open wire mesh or screen of the negative elecfrode and the tight spacing in the graphite felt of the positive electrode.
  • the graphite felt is preferred due to its resistance to attack by the oxidants generated with the positively charged elecfrode where metals would rapidly con-ode.

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Abstract

L'invention concerne une électrode à flux traversant tridimensionnelle comprenant un mécanisme d'alimentation par courant efficace, des conduits d'alimentation comprenant des tiges en matière conductrice, notamment le graphite, qui sont insérées à des intervalles spatiaux prédéterminés dans une électrode à flux traversant, notamment un bloc de feutre de graphite. Les conduits d'alimentation de courant sont espacés de manière appropriée à travers l'électrode pour permettre une distribution efficace du courant. La grande zone de surface dotée de l'électrode à flux circulant permet d'exposer des solutions ou des gaz sur des zones relativement grandes de charges électriques, pour provoquer des réactions électriques et chimiques. Un certain nombre de procédés chimiques électrolytiques faisant appel à des cellules électrolytiques comprennent le traitement de l'eau, le traitement chimique et la production chimique, des applications hydrométallurgiques et un nettoyage écologique. L'invention concerne une méthode de remplacement de l'utilisation de cyanure dans des opérations de traitement d'or et d'argent.
PCT/US2004/005902 2003-02-28 2004-02-27 Eletrode a flux traversant tridimensionnelle et cellule electrochimique WO2004079840A2 (fr)

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