Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/20—Electrolytic production, recovery or refining of metals by electrolysis of solutions of noble metals
• • 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
  • C22B11/00—Obtaining noble metals
  • C22B11/04—Obtaining noble metals by wet processes
  • C22B11/042—Recovery of noble metals from waste materials
• • 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
  • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
  • C22B3/065—Nitric acids or salts thereof
• • 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
  • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
  • C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
• • 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
  • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
• • 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
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F1/00—Etching metallic material by chemical means
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/16—Acidic compositions
  • C23F1/30—Acidic compositions for etching other metallic material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the present invention relates generally to processes for recycling/reclaiming of noble metals, such as ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold from source materials.
• noble metals such as ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold from source materials.
• noble metals such as gold, silver and platinum group metals which offer the opportunity for economical recovery.
• gold is available from ores and numerous scrap sources, including industrial wastes, gold plated electronic circuit boards, and in alloys with copper, zinc, silver or tin in the karat gold used in jewelry.
• Silver is available from photographic and x-ray film emulsions, scrap sterling, and numerous industrial sources.
• Platinum group metals are available from industrial sources, such as catalysts. There are numerous instances in which it is desirable to recover these metals from an aggregate material.
• Platinum is a silvery, white, ductile metal which is insoluble in mineral and organic acids, but soluble in aqua regia. Platinum does not corrode or tarnish, and forms strong complexes with halides (i.e., chloride, bromide, fluoride and iodide). Platinum is used as a catalyst (nitric acid, sulfuric acid, and high-octane gasoline production; automobile exhaust gas converters), in laboratory ware, spinnerets for rayon and glass fiber manufacture, jewelry, dentistry, electrical contacts, thermocouples, surgical wire, bushings, electroplating, electric furnace windings, chemical reaction vessels, anti-cancer drugs and permanent magnets.
• halides i.e., chloride, bromide, fluoride and iodide
• Platinum is used as a catalyst (nitric acid, sulfuric acid, and high-octane gasoline production; automobile exhaust gas converters), in laboratory ware, spinnerets for rayon and glass fiber manufacture, jewelry, dentistry,
• Palladium is similarly a silvery, white, ductile metal which does not tarnish in air. It is the least noble (e.g., most reactive) of the platinum group, is insoluble in organic acids, but soluble in aqua regia and fused alkalies. Palladium is used as a catalyst for chemical processes including reforming cracked petroleum fractions and hydrogenation, for metallizing ceramics, as “white gold” in jewelry, in protective coatings, and in hydrogen valves (in hydrogen separation equipment). Both platinum and palladium are good electrical conductors and are used in alloys for electrical relays in switching systems and telecommunication equipment, resistance wires and aircraft spark plugs. Further, platinum group metal applications include industrial radiography, catalysts, pen points, electrical contacts, jewelry, coatings and headlight reflectors.
• the present disclosure is directed to methods and processes that use halide-based compositions at room temperature to efficiently remove noble metals from the source comprising same.
• the present invention relates generally to compositions and processes for leaching noble metals from sources comprising same including, but not limited to, ores, jewelry, scraps comprising said noble metals, waste materials, alloys, catalyst materials, and various industrial sources. More specifically, the compositions for leaching noble metals from sources are acidic, halide-based compositions that efficiently remove noble metals from the source at room temperature.
• a leaching composition comprising at least one oxidizing agent, at least one halide, at least one acid, and at least one solvent.
• a method of removing noble metals from a source comprising contacting said source under conditions with the leaching composition, wherein said noble metals are dissolved or otherwise solubilized in the leaching composition, and wherein the leaching composition comprises at least one oxidizing agent, at least one halide, at least one acid, and at least one solvent.
• the present invention relates generally to compositions and processes for leaching noble metals from sources comprising same including, but not limited to, ores, jewelry, scraps comprising said noble metals, waste materials, alloys, catalyst materials, and various industrial sources. More specifically, the compositions for leaching noble metals from sources are acidic, halide-based compositions that efficiently remove noble metals from the source at low temperatures.
• non-noble metals refers to the group of metals including gold, silver, the platinum group metals, alloys comprising same, and combinations thereof
• platinum group metals include ruthenium, osmium, rhodium, iridium, palladium and platinum.
• base metals corresponds to iron, nickel, zinc, copper, aluminum, tungsten, molybdenum, tantalum, magnesium, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium, thallium, alloys comprising same, and combinations thereof.
• Substantially devoid is defined herein as less than 2 wt. %, preferably less than 1 wt. %, more preferably less than 0 5 wt. %, and most preferably less than 0 1 wt. %. “Devoid” corresponds to 0 wt. %.
• halide corresponds to fluoride, chloride, bromide or iodide-containing species such as salts or acids.
• the “source” is a noble metal-containing material including, but not limited to, ores, jewelry, scraps comprising said noble metals, waste materials comprising said noble metals including electronic waste, alloys, catalyst materials, various industrial sources, and combinations thereof
• “to remove” noble metals from a source means that the noble metal is substantially dissolved or solubilized or the like in the leaching composition, while base metals are not substantially dissolved or solubilized or the like.
• “Substantially dissolved” is defined herein more than 95 wt. % of the material originally present is dissolved or solubilized or the like, preferably more than 98 wt. %, more preferably more than 99 wt. %, and most preferably more than 99.9 wt. %.
• “Not substantially dissolved” is defined herein less than 5 wt. % of the material originally present is dissolved or solubilized or the like, preferably less than 2 wt. %, more preferably less than 1 wt. %, and most preferably less than 0.1 wt. %.
• the term “leaches” or “leaching” corresponds to the complete or partial removal or extraction of the gold and/or other noble metals from the source into the leaching composition.
• the gold or other noble metal is dissolved or otherwise solubilized in the leaching composition, preferably dissolved.
• crushing corresponds to any method that substantially exposes the gold and other noble metals of the source material to the leaching composition, e.g., crushing, cracking, pulverizing, shredding, or grinding.
• agitation means include, but are not limited to, physical agitation such as mixing, recirculation, turbulence, and combinations thereof.
• compositions may be embodied in a wide variety of specific formulations, as hereinafter more fully described.
• specific constituents of the composition are discussed in reference to weight percentage ranges including a zero lower limit, it will be understood that such constituents may be present or absent in various specific embodiments of the composition, and that in instances where such constituents are present, they may be present at concentrations as low as 0.001 weight percent, based on the total weight of the composition in which such constituents are employed.
• a method of removing noble metals from a source wherein said noble metals are dissolved or otherwise solubilized in a leaching composition. More specifically, the method of removing noble metals from a source comprises contacting said source with a leaching composition, wherein said noble metals are dissolved or otherwise solubilized in the leaching composition. Preferably, noble metals are selectively removed relative to base metals also present in the source.
• new volumes of the source can be added to the leaching composition and the process of removing the noble metals can be repeated again and again until the leaching composition is saturated with noble metals.
• a “feed and bleed” process may be used wherein clean leaching composition is periodically introduced to the working leaching composition with simultaneous withdrawal of some of the working leaching composition.
• the leaching composition comprising the noble metals can be processed to obtain useful forms of said noble metals (e.g., electrochemically, by electrowinning, or using reducing agents).
• the leaching composition is contacted in any suitable manner to the source, e.g., by spraying the leaching composition on the source, by dipping the source in a volume of the leaching composition, by contacting the source with another material, e.g., a pad, or fibrous sorbent applicator element, that has the leaching composition absorbed thereon, by contacting the source with a recirculating composition, or by any other suitable means, manner or technique, by which the leaching composition is brought into contact with the source.
• a suitable manner or technique by which the leaching composition is brought into contact with the source.
• the source i.e., noble metal containing material
• the leaching composition can be added to the leaching composition as is, pulverized into a powder, shredded into pieces, crushed, or in any other form so long as the metals contained in the source are readily exposed for removal from the source.
• the leaching composition and the source can be agitated such that the source is substantially exposed to the leaching composition.
• the leaching composition typically is contacted with the source for a time of from about 1 min to about 120 minutes, preferably about 3 min to 60 at temperature in a range of from about 20° C. to about 100° C., preferably in a range from about 20° C. to about 60° C., more preferably about 20° C. to about 40° C., and most preferably about room temperature.
• Such contacting times and temperatures are illustrative, and any other suitable time and temperature conditions may be employed that are efficacious to remove the noble metals from the source comprising same.
• a leaching composition comprising, consisting of, or consisting essentially of at least one oxidizing agent, at least one halide, at least one acid, and at least one solvent.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one chloride salt, at least one acid, and at least one solvent.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one chloride salt, at least one sulfur-containing acid, and at least one solvent.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one alkaline chloride salt, at least one sulfur-containing acid, and at least one solvent.
• the leaching composition comprises, consists of, or consists essentially of at least one nitrate salt oxidizing agent, at least one alkaline chloride salt, at least one sulfur-containing acid, and at least one solvent.
• the leaching composition is aqueous in nature and has a pH less than about 2, more preferably less than about 1.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one halide salt, at least one acid, and at least one solvent, present in the following weight percentages, based on the total weight of the composition:
• oxidizing agent about 40 wt % about 30 wt % about 20 wt % at least one about 1 wt % to about 2 wt % to about 3 wt % to halide about 40 wt % about 30 wt % about 15 wt % at least one about 1 wt % to about 2 wt % to about 7 wt % to acid about 50 wt % about 40 wt % about 30 wt % at least one about 1 wt % to about 1 wt % to about 35 wt % to solvent about 93 wt % about 87 wt % about 86 wt %
• the leaching composition comprises, consists of, or consists essentially of at least one nitrate salt oxidizing agent, at least one alkaline chloride salt, at least one sulfur-containing acid, and at least one solvent, present in the following weight percentages, based on the total weight of the composition:
• Oxidizing agents are included in the composition to oxidize the metals to be removed into an ionic form and accumulate highly soluble salts of dissolved metals.
• Oxidizing agents contemplated herein include, but are not limited to, ozone, nitric acid (HNO 3 ), bubbled air, cyclohexylaminosulfonic acid, hydrogen peroxide (H 2 O 2 ), oxone (potassium peroxymonosulfate, 2KHSO 5 .KHSO 4 .K 2 SO 4 ), ammonium polyatomic salts (e.g., ammonium peroxomonosulfate, ammonium chlorite (NH 4 ClO 2 ), ammonium chlorate (NH 4 ClO 3 ), ammonium iodate (NH 4 IO 3 ), ammonium perborate (NH 4 BO 3 ), ammonium perchlorate (NH 4 ClO 4 ), ammonium periodate (NH 4 IO 3 ), ammonium persul
• the oxidizing agent comprises a nitrate ion including, but not limited to, nitric acid, sodium nitrate, potassium nitrate, ammonium nitrate, tetraalkylammonium nitrate, and combinations thereof.
• the at least one halide is preferably a chloride-containing compound including, but not limited to, hydrochloric acid, and alkaline chlorides (e.g., sodium chloride, potassium chloride, rubidium chloride, cesium chloride, magnesium chloride, calcium chloride, strontium chloride, ammonium chloride, quaternary ammonium chloride salts), and combinations thereof, with the proviso that the chloride-containing compound cannot include copper chloride, chlorine gas, or a second, different halide.
• the at least one halide is devoid of compounds such as CuCl 2 , Cl 2 , and BrCl 2 ⁇ .
• the at least one halide comprises an alkaline chloride, even more preferably an alkali metal chloride such as sodium chloride.
• the at least one halide can also include salts and/or acids comprising bromide and iodide including, but not limited to, sodium bromide, sodium iodide, potassium bromide, potassium iodide, rubidium bromide, rubidium iodide, cesium bromide, cesium iodide, magnesium bromide, magnesium iodide, calcium bromide, calcium iodide, strontium bromide, strontium iodide, ammonium bromide, ammonium iodide, quaternary ammonium bromide salts, and quaternary ammonium bromide salts.
• the at least one halide is preferably substantially devoid of fluoride ions.
• the at least one acid is preferably a sulfur-containing species such as sulfuric acid, sulfate salts (e.g., sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate), sulfonic acid, sulfonic acid derivatives, and combinations thereof.
• sulfuric acid e.g., sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate
• sulfate salts e.g., sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulf
• Sulfonic acid derivatives contemplated include methanesulfonic acid (MSA), ethanesulfonic acid, 2-hydroxyethanesulfonic acid, n-propanesulfonic acid, isopropanesulfonic acid, isobutenesulfonic acid, n-butanesulfonic acid, n-octanesulfonic acid), benzenesulfonic acid, benzenesulfonic acid derivatives, and combinations thereof.
• the at least one acid comprises sulfuric acid, preferably concentrated sulfuric acid.
• the at least one solvent includes, but is not limited to, water, methanol, ethanol, isopropanol, butanol, pentanol, hexanol, 2-ethyl-1-hexanol, heptanol, octanol, ethylene glycol, propylene glycol, butylene glycol, tetrahydrofurfuryl alcohol (THFA), butylene carbonate, ethylene carbonate, propylene carbonate, dipropylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, propy
• the leaching composition further comprises a corrosion inhibitor, specifically a base metal corrosion inhibitor, so as to ensure that the leaching composition selectively removes noble metals from the source relative to base metals.
• the leaching composition can comprise, consist of, or consist essentially of at least one oxidizing agent, at least one halide, at least one acid, at least one solvent, and at least one corrosion inhibitor.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one chloride salt, at least one acid, at least one solvent, and at least one corrosion inhibitor.
• the leaching composition comprises, consists of, or consists essentially of at least one oxidizing agent, at least one chloride salt, at least one sulfur-containing acid, at least one solvent, and at least one corrosion inhibitor.
• Corrosion inhibitors for passivating the base metals include, but are not limited to, ascorbic acid, adenosine, adenine, L(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives, citric acid, ethylenediamine, gallic acid, oxalic acid, tannic acid, ethylenediaminetetraacetic acid (EDTA), uric acid, 1,2,4-triazole (TAZ), triazole derivatives (e.g., benzotriazole (BTA), tolyltriazole, 5-phenyl-benzotriazole, 5-nitro-benzotriazole, 3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole
• the leaching composition of the second aspect can further comprise noble metal chelators, surfactants, defoamers, and combinations thereof, as readily determined by the person skilled in the art.
• the leaching composition comprises, consists of, or consists essentially of sodium chloride, sulfuric acid, nitric acid, and water, with the proviso that the leaching composition is substantially devoid of hydrogen peroxide, copper (II) chloride, chlorine gas, BrCl 2 ⁇ , fluoride-containing compounds, hydroxide-containing compounds, ferrous ions, a sulfur compound comprising a sulfur atom with an oxidation state in the range of ⁇ 2 to +5, and cyanides.
• the leaching composition comprises a nitrate such as nitric acid
• NO x gases can be emitted.
• the leaching process is carried out in a system comprising a condenser, wherein the NO x gases can be collected and converted back into nitric acid, as readily known to the person skilled in the art.
• NO x corresponds to mononitrogen oxides such as NO and NO 2 .
• the leaching composition is easily recyclable and can be employed in a closed-loop process generating minimal waste.
• the resulting leaching composition including the noble metals can be recycled by reclaiming the noble metals.
• the recycled leaching solution can be reused, with or without the addition of fresh leaching composition chemistry.
• the leaching composition is essentially non-toxic once the noble metals are reclaimed and the excess acidity neutralized.
• the leaching compositions described herein are easily formulated by simple addition of the respective ingredients and mixing to homogeneous condition. Furthermore, the leaching composition may be readily formulated as single-package formulations or multi-part formulations that are mixed at or before the point of use, e.g., the individual parts of the multi-part formulation may be mixed at the tool or in a storage tank upstream of the tool.
• concentrations of the respective ingredients may be widely varied in specific multiples of the composition, i.e., more dilute or more concentrated, and it will be appreciated that the compositions described herein can variously and alternatively comprise, consist or consist essentially of any combination of ingredients consistent with the disclosure herein.
• the leaching composition described herein is capable of substantially removing noble metals from a source at room temperature without the use of high temperatures (e.g., temperatures greater than about 100° C.), high pressures (e.g., pressures greater than atmospheric pressure) or electrodes to maintain the voltage of the composition in a specific range.
• the leaching composition is more environmentally friendly than the prior art cyanide compositions and more inexpensive than tri-iodide compositions.
• the vessel that is used to process the source to remove the noble metals can comprise any material without any concern of corrosion or degradation.
• the noble metals can be reclaimed from the leaching composition using a number of methods including, but not limited to, electrochemical techniques such as electrowinning, and chemical reduction processes.
• a reducing agent can be added to the leaching composition containing noble metals to cause their precipitation.
• various reducing agents can be applied to cause selective or non-selective precipitation of noble metals. Precipitation can be done in a manner to avoid the contamination of the leaching composition, so that the leaching composition can be regenerated and reused in the next leaching cycle after the noble metals have been removed.
• the reducing agent is a so-called environmentally friendly chemical.
• the reduction occurs rapidly with minimal heating requirements.
• precipitation with SO 2 is known to be selective for gold, non-contaminating to the leaching composition and inexpensive.
• Gold is precipitated as a fine powder that is separated from the leaching solution by filtration.
• a flocculating agent can be added to the solution at the same time as the reducing agent, if the reducing agent is in liquid or gaseous form. If the reducing agent is in the form of powder, a flocculating agent can be added after complete dissolution of the reducing agent to prevent collection of particles of the reducing agent.
• commercially available MAGNAFLOK-351 that is typically used for concentrating finely ground gold ores, can be used. The use of a non-ionic flocculating agent is preferred to avoid the possible undesirable recovery of iodine from the composition.
• the reducing agents can include, but are not limited to, sodium borohydride, ascorbic acid, diethyl malonate, sodium metabisulfite, polyphenon 60 (P60, green tea extract), glucose, and sodium citrate.
• ascorbic acid introduced to a composition comprising Au 3+ ions at pH 1 produces highly pure gold metal.
• Sodium metabisulfite (SMB) can be added to a composition comprising Au 3+ ions at pH 1 or pH 7 and produce highly pure gold metal.
• the noble metal ions can be converted to noble metals via electrowinning or electrochemical techniques. Any suitable means can be used to remove the precipitated noble metals. Settling and decanting, filtering the solution through a filter press or centrifuging are convenient procedures for such removal.
• the leaching composition may still include leached silver and palladium ions.
• a selective reducing agent may be added for precipitation of silver, such as hydroxylamine.
• the use of a flocculating agent is suggested to facilitate filtration.
• palladium can be precipitated, for example, with the use of a stabilized alkali metal borohydride and a flocculating agent.
• the source material subsequent to leaching can be rinsed (e.g., with water) to further recover the residual leaching composition on the surface of the source material, which can contain very significant amounts of dissolved noble metals.
• Electrowinning is a common way of gold recovery from solutions, but if the rinse water comprising dissolved gold is recovered, conventional electrowinning becomes ineffective as gold is present in rinse water in small concentrations.
• the removal of gold from rinse water solutions can become effective if high surface area (HSA) electrodes are used for electrowinning HSA electrowinning may economically remove gold having a concentration greater than 10 ppm down to ppb level.
• HSA high surface area
• Iodide can also be oxidized and recovered using the same process if an undivided electrowinning cell is used.
• a leaching composition comprising 30 wt % water, 29 wt % sulfuric acid (96%), 18 wt % nitric acid (70%) and 23 wt % saturated sodium chloride was prepared.
• the leaching composition was divided into four test tubes containing 10 g each of the leaching composition. Gold fingers, pure Pd, pure Pt and pure Ag were added to each of the test tubes and processed as indicated and the pre- and post-weight of the noble metals determined, as summarized in Table 1.
• the leaching composition effectively and efficiently dissolved gold and palladium and could be loaded with additional metal as more source is added to said composition.

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• 2015
  • 2015-02-23 EP EP15755407.2A patent/EP3110982A4/fr not_active Withdrawn
  • 2015-02-23 CN CN201580020472.6A patent/CN106661663A/zh active Pending
  • 2015-02-23 CA CA2943992A patent/CA2943992A1/fr not_active Abandoned
  • 2015-02-23 WO PCT/US2015/017088 patent/WO2015130607A1/fr active Application Filing
  • 2015-02-23 US US15/121,622 patent/US20160362804A1/en not_active Abandoned
  • 2015-02-23 KR KR1020167026584A patent/KR20160127088A/ko unknown
  • 2015-02-25 TW TW104106023A patent/TW201602357A/zh unknown

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