Classifications

• • 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
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0084—Treating solutions
  • C22B15/0089—Treating solutions by chemical methods
  • C22B15/0093—Treating solutions by chemical methods by gases, e.g. hydrogen or hydrogen sulfide
• • 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
  • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
  • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical 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
  • C22B43/00—Obtaining mercury
• • 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
  • C22B47/00—Obtaining manganese
• • 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
  • C22B5/00—General methods of reducing to metals
  • C22B5/02—Dry methods smelting of sulfides or formation of mattes
  • C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S204/00—Chemistry: electrical and wave energy
  • Y10S204/03—Auxiliary internally generated electrical energy

Definitions

• the present invention relates to the hydrogen reduction, at porous hydrophobic catalytic, barriers of hydrogen-reducible ions in solution, and more particularly, though not exclusively, to the recovery of metals from aqueous solutions of such metal ions at ordinary temperatures.
• hydrogen-reducible ion means an ion producing a positive potential when it is reduced in aqueous solution in the electrochemical reaction in which hydrogen gas goes to hydrogen ion, i.e. H 2 ⁇ 2H + + 2e; that is, the reduced ion has an oxidation potential below that of hydrogen.
• Recoverable metal ions yielding "hydrogen-reduced metals" in this reaction include such metals as copper, silver, gold, the platinum metals and the like; whereas “partially hydrogen-reducible ions”, include the ferric, mercuric, permanganate and similar ions which are re ⁇ ced in solution from a higher valence state to a lower valence state without normally being reduced to the metal.
• "ordinary temperature” as used in the spec ification and claims, is intended to connote ambient tempera tures and above; but in any event, temperatures below about the boiling point of water.
• An object of the invention accordingly, is to provide a new and improved process and apparatus for the recovery of hydrogen-reduced metals and ions, employing hydrogen reduction at hydrophobic catalytic barriers.
• a further object is to provide such a novel process and apparatus that is particularly useful for the recovery of metals from aqueous solutions thereof.
• Still another object is to provide for the improved recovery of metals by depositing the same upon such barriers from a dilute aqueous solution thereof and to enable the subsequent removal of the deposited metal by well-known techniques.
• An additional object is to provide an improved process whereby the metal deposited on the barrier may also be dissolved from the barrier by catalytic or electrochemical oxidation in the presence of a small volume of electro lyte to produce a concentrated aqueous solution thereof which can then be subjected to metal electrowinning or electrorefining and the like.
• the invention embraces a process for recovering hydrogen-reduced metals or ions from an aqueous solution of an ionized salt thereof, that comprises, providing a porous hydrophobic catalytic barrier, contacting one surface of the barrier with said solution, and applying hydrogen gas to said other surface, thereby to produce the hydrogen-reduced metals or ions at said one surface.
• a porous hydrophobic catalytic barrier contacting one surface of the barrier with said solution, and applying hydrogen gas to said other surface, thereby to produce the hydrogen-reduced metals or ions at said one surface.
• Fig.1 of which is a schematic longitudinal section of a preferred apparatus for carrying out the process of the invention
• Fig. 2 is a similar view of a modification
• Fig. 3 is a graph demonstrating the rate of metal deposition attainable with the invention in specific examples involving copper.
• suitable barriers for the purpose of this invention are porous to hydrogen and at the same time hydrophobic to the agueou ⁇ solutions so that the liguid and gas phases remain separate while permitting the hydrogen ionization reaction to take place on the catalyst of the barrier.
• the barrier prevents intermingling of hydrogen and solution, thereby allowing separate control of flow rates and easy confinement of hydrogen gas, at or near atmos pheric pressure, for good hydrogen utilization (for example by recycling the hydrogen).
• platinum catalysts are preferred because of their corrosion resistance and durability.
• the platinum catalysts having a particle size substantially between 15 ⁇ and 25 ⁇ when deposited on finely divided high surface area carbon carriers, (herein referred to as 15-25
• the hydrogen-ionizing catalyst is preferably deposited, together with a hydrophobic agent such as a fluorinated hydrocarbon polymer (herein referred to as Teflon) on an electrically-conducting porous substrate such as a metal screen, a porous carbon, and, especially a carbon yarn cloth as described in our copending application Serial No. 074,470 , comprising, for example, PANEX-type carbon cloth of the Stackpole Fibers Company.
• Teflon fluorinated hydrocarbon polymer
• the hydrogen reduction thereon is carried out in the absence of an external electrical circuit. It is often advantageous to use such a hydrogen electrode in the case of, for example, copper recovery because the copper deposited on the barrier can then be removed from the barrier by an electrolytic process, such as in a copper refining cell in which the copper-covered barrier is used as the anode.
• the recovery of silver from, for example, a silver nitrate solution can benefit similarly from the use of barriers of such carbonbased substrates.
• electrically insulating porous substrates such as a porous ceramic, a glass cloth, or a porous glass fiber mat, are also suitable substrates for the illustrative platinum-on-carbon-Teflon mixture (or other catalyst hydro phobic mixture).
• uniformly deposited thereon since the reduc tion of the present invention, as before stated, takes place in the absence of external circuitry.
• copper is deposited on such a barrier from a dilute copper sulfate solution, it can then be removed from the barrier by contacting the coppered face with a small volume of a solution of sulfuric acid and contacting the gas face with air or oxygen, whereby the.
• the removal of, for example, copper by anodic redissolution or by oxidation can be carried out by keeping the barrier in a fixed position and alternating (1) the flows of dilute and concentrated solutions and (2) the flow of hydrogen and D.C. current or air/oxygen, respectively.
• the barrier may conveniently be continuously moved from the dilute solution with hydrogen behind the barrier, to effect copper deposition on said barrier, to, for example, a tank containing concentrated solution to effect copper removal therefrom, as above explained.
• the metal deposited on the barrier if the barrier substrate is combustible as in the case of the before-mentioned carbon cloth , may be removed by incinerating the same. Scraping or mechanical stripping may also be useful in some instances.
• the recovery of platinum metals, especially of platinum and palladium, which are excellent catalysts for the H 2 ⁇ 2H + + 2e reaction, is advantageously carried out on a barrier which bears a platinum-on-carbon- Teflon mixture or a palladium-on-carbon-Teflon mixture, respectively. There is then built up on said barrier, by the hydrogen reduction of this invention, a deposit of platinum or palladium, respectively, in amount far in excess of the initial amount present on said barrier.
• the rate at which the hydrogen-reduced metal, for example, copper, is deposited on the barrier is diffusioncontrolled.
• dilute solutions of metal for example, copper sulfate solutions containing between about 0.1 and about 5 grams/liter copper
• the apparatus is advantageously provided with means to agitate the solution as by directing the flow of solution onto said barrier under rapid flowing conditions.
• a typical circuitry-free apparatus suitable for the purpose of this invention comprises the barrier assembly, a cross section of which is schematically shown in Fig. 1.
• a gas plenum 1 is bounded on one side by, for example, a flat sheet of plastic 3, such as of Lucite and on the other side by the flat hydrophobic catalytic barrier 2 of the invention , with the two sides of the plenum being kept apart by gaskets 4 as of rubber, plastic or the like.
• the gaskets are provided with gas inlet and outlet ports 5 and 5 ' , respectively , with hydrogen applied to the right-hand face of the barrier 2 through the inlet 5.
• a gasket 6 holds the hydrophobic barrier 2 in place , with the assembly being clamp together by means , for example , of clamp 7.
• the gasket 6 can be of any material , flexible or stiff , enabling the holding of the hydrophobic barrier 2 in place.
• a pump 8 feeds the metal or other ion solution through piping 8 ' to a distributor head 9 , the latter being designed to permit even (and , when turbulent flow is desired , rapid ) flow of solution onto the preferably total left-hand face of the barrier on which the metal , for example , is to be deposited.
• Fig . 2 shows , in cross section , an alternate assembly for flowing the aqueous solution onto the barrier 2 under controlled and, when desired , rapid flow rates.
• the barrier 2 with its gasket 6 constitutes one side (the right side) of a solution plenum 10 bounded on the other side by a plastic sheet 11.
• the solution plenum 10 is provided with a solution inlet 12 and an outlet 12 ' , with the solution being circulated through the plenum 10 at turbulent flow rates when desired, by means of the pump 8.
• a porous carbon or ceramic tube or pipe can be made into a porous hydrophobic catalytic barrier by coating its outside with the hydrogen-ionizing catalyst-tefloimixture.
• a hydrogen-reducible metal ion-bearing solu tion is flowed over the outside of such a tube or pipe barrie and hydrogen gas is fed to the inside thereof, the metal is deposited on the outside of the tube or pipe.
• Other flow and barrier configurations will also occur to those skilled in the art.
• One case of special importance that is particularlay useful with the invention is the recovery of copper from dilute copper-bearing leach solutions such as are obtained by sulfuric acid leaching of low grade mine and waste dump materials.
• Such solutions contain less than about two grams per liter of copper and also small amounts of the order of 3 grams or less of total iron per liter, the iron being present as ferric and ferrous ions in the approximate ratio of, for example, about 1:2.
• Copper is now commonly recovered from such solutions by cementation; i.e. by reduction of Cu ++ and Fe +++ with scrap iron, which recovery is costly and causes accumulation of iron in dumps.
• a two—plenum apparatus consisting of the gas plenum shown schematically in Fig. 1 and the solution plenum shown schematically in Fig. 2 was provided with a porous hydrophobic catalytic barrier having an exposed area 2" by 2" in size, said barrier having been prepared by the following procedure.
• a platinum-on-carbon sample was prepared substantially in accordance with Example 1, col. 9 of U.S. Patent No. 4,044,193, the pH being adjusted to 3 during the preparation.
• the air-dried material containing 9.9% by weight of platinum on Vulcan XC-72 carbon, which carbon has a surf ace area of approximately 200 m 2 /g, was compounded with 50% by weight of wet-proofing fluorinated hydrocarbon, herein referred to as Teflon, whereby a typical catalytic carbon Teflon mixture was formed.
• Teflon wet-proofing fluorinated hydrocarbon
• 1.0 gram of the platinum-on-Vulcan carbon was suspended in 60 ml of distilled water containing 1.4 g/1 of lanthanum sulfate.
• the suspen sion was ultrasonically dispersed and 11.75 ml of the aqueous colloidal Teflon dispersion described in col. 1 lines 35-44 of U.S. Patent No. 4,166,143, containing 85 g/1, was added and the stirring was continued for 5 minutes, whereby the Teflon was completely flocced, forming the uniform catalytic carbon-Teflon mixture.
• the floc-containing liquid sus pension was then filtered, leaving, on the filter, the mix ture in a form of a paste suitable for coating the substrate.
• the coating procedure consisted in applying 0.38 gms of the paste to 9 sq. inches of the above-described carbon cloth PANEX PWB-3, the paste being spread uniformly on the surface and into the open pores of the cloth.
• the coated fabric is then heated to 340°C for about 20 minutes.
• the resulting electrode-type structure had a platinum loading of 0.32 mg/cm 2 of electrode area, the platinum being in the form of particles predominantly in the 15-25 Angstrom range.
• Hydrogen was fed to the gas plenum at the rate of about 50 ml/min. under a pressure of 5 inches of water above atmospheric.
• the barrier was weighed initially and after com pletion of the test, and it was found that about 0.135 grams of copper had been deposited, in substantial agreement with the experimentally determined loss of copper in the solution.
• Example 2 shows the concentrations of Fe produced by this reduction as a function of time. The reduction is associated with the formation of hydrogen ions, the pH column of Table 2 showing the increasing acidity of the solution accompanying the increase in Fe ++ concentration. In this experiment, the ferrous ion produced by the reduction remained in solution, in contrast to the deposited copper of Example 1.
• Example 2 The method of Example 1, using the apparatus and barrier thereof, was repeated except that the sulfate sol ution contained 0.30 gm/1 of copper and 3.00 gm/1 of ferric ion. The appearance of a film of copper was again observed after 12 seconds on the left-hand solution face of the bar rier 2. The rate of Fe +++ to Fe ++ reduction is shown in
• Example 1 The method of Example 1 was repeated with the apparatus thereof, using a glass-cloth based barrier 2 having a glass cloth substrate 12 mils thick and having about 19 yarns per inch in each of the warp and fill direc tions, and provided with a catalyzed and hydrophobic coat ing by the method of Example 1.
• the barrier was thus sub stantially the same as the barrier of Example 1 with respect to platinum particle size, platinum loading and Teflon loading.
• Example 1 The method of Example 1 was again repeated with the apparatus thereof, except that a conventional platinum on-carbon catalyst was substituted for the 15-25 ⁇ platinumon-carbon catalyst of Example 1.
• the conventional catalyst was prepared by the known technique of impregnating a sample of Vulcan XC-72 carbon with a solution of chloroplatinic acid, followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a platinum on-carbon containing 10% of Pt by weight.
• the barrier of this example was then prepared by the method described in Example 1 using this platinum-on-carbon and loading the barrier with 34 mg Pt/cm , i.e. about the same as that of Example 1.
• the copper deposition rate on this barrier using the solution of Example 1, is depicted in curve 4 of the graph of Fig. 3. It is seen that the copper ion reduction is catalyzed by this conventional platinum catalyst but that it is less effective than the preferred 15 - 25 ⁇ platinum-on-carbon catalyst, when both are used in substantially equal amounts.
• Example 1 The method of Example 1 was further repeated except that a palladium-on-carbon catalyst was substituted for the 15 - 25 ⁇ platinum catalyst of Example 1.
• the palladium-on-carbon catalyst was prepared by impregnating a sample of Vulcan XC-72 carbon with an aqueous palladium sol, followed by evaporation, drying and hydrogen reduction, the ingredients being selected in amounts to produce a palladium-on-carbon containing 10% palladium.
• the palladium sol was prepared by solvent extraction, with an organic amine of an aqueous palladium nitrate solution.
• the barrier 2 of this example was then prepared by the method described in Example 1, using this palladium-on-carbon catalyst and loading the barrier with 0.25 mg Pd/cm 2 ; i.e.
• Example 7 The copper deposition rate on the barrier using the solution of Example 1 is depicted in Fig. 3, curve 5. It is seen that the copper ion reduction is catalyzed by the palladium catalyst but that it is significantly less effective than the platinum on-carbon catalysts, when all are used in amounts of the same order. (Note that more gram-atoms of Pd per square inch were on the barrier than gram-atoms of Pt per square inch).
• Example 1 The method of Example 1, using the apparatus and barrier thereof was repeated except that 2 liters of a silver nitrate solution containing 1.5 g/1 Ag was recirculated. Build-up of silver was extremely rapid. A loosely adhering silver deposit of 0.53 grams was obtained on the left face of the barrier in 15 minutes.
• Example 2 The method of Example 1 was repeated except that 2 liters of a chloroplatinic acid solution containing 1.5 g/1 Pt was recirculated. About 600 mg of firmly adher ⁇ ing platinum was deposited on the barrier in two hours. The 2" x 2" barrier had an initial platinum loading of about 10 mg as the 15 - 25 ⁇ platinum-on-carbon catalyst.
• Example 1 The method of Example 1 was repeated except that
• metal deposited on the barrier adheres thereto and needs therefore to be removed therefrom to be put into useable form.
• a suf ficiently thick deposit on the barrier such as the silver deposit of Example 7
• mechanical stripping is one such tech nique which is especially useful when the original silver ion-containing solution is not contaminated by other hydrogen
• Example 1 the coppered barrier of Example 1 was used in a conventional electroref ining cell as the anode .
• the copper deposit was redissolved into the conventional electrorefining electrolyte, a substantially equivalent amount of copper being electrodeposited as massive cathodic copper .
• Typical experimental conditions for such an electrode refining operation are , for example , shown in Table 27 , pages 150-151 of Electrochemical Engineering , by C . L. Man tell , 4 th Edition , McGraw-Hill Book Company, New York , 1960 .
• the redissolution of copper from the barrier by means of air or oxygen as illustrated above is applicable to barriers having either a conducting or a nonconducting substrate
• the stripping of the copper from the barrier by electrorefining requires that the barrier comprise an electrically-conducting substrate that is the barrier having the structure of a hydrogen anode .
• the above-described incineration technigue is the preferred method of removing platinum or the like from the barrier.
• the barrier of Example 8 with its platinum deposit was incinerated at about 800oC leaving a residue of platinum weighing 0.5812 grams.

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• 1979
  • 1979-10-26 US US06/088,373 patent/US4331520A/en not_active Expired - Lifetime
• 1980
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