EP4192986A1 - Method for extracting gold and/or silver and/or at least one platinum metal - Google Patents

Method for extracting gold and/or silver and/or at least one platinum metal

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Publication number
EP4192986A1
EP4192986A1 EP21754726.4A EP21754726A EP4192986A1 EP 4192986 A1 EP4192986 A1 EP 4192986A1 EP 21754726 A EP21754726 A EP 21754726A EP 4192986 A1 EP4192986 A1 EP 4192986A1
Authority
EP
European Patent Office
Prior art keywords
solution
gold
ozone
silver
starting material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21754726.4A
Other languages
German (de)
French (fr)
Inventor
Claudio Baldizzone
Niklas Maier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP4192986A1 publication Critical patent/EP4192986A1/en
Pending legal-status Critical Current

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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
    • C22B1/00—Preliminary treatment of ores or scrap
    • 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
    • C22B11/08—Obtaining noble metals by cyaniding
    • 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
    • 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
    • C22B3/16—Extraction of metal compounds from ores or concentrates by wet processes by leaching in organic solutions
    • 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
    • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
    • 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 to a method for extracting gold and/or silver and/or at least one platinum group metal from at least one starting material.
  • Gold, silver and platinum metals are essential raw materials. Their recovery from recyclable waste, for example as part of catalyst materials or electronic devices, can be pyrometallurgical or hydrometallurgical. Pyrometallurgical reclamation is done by melting the scrap metal and then treating it through various processes. However, this is very energy-intensive and associated with the formation of toxic emissions.
  • hydrometallurgical recovery the metals to be recovered are brought into an aqueous solution by complex formation.
  • An example of such a process is alkaline cyanide leaching for gold recovery. This process is carried out at very high pH values, i.e. using aggressive bases.
  • the complexing agent cyanide used is very toxic, so this process can also lead to dangerous emissions.
  • the pH value of a cyanide-containing solution can increase so much, for example, by absorbing carbon dioxide from the ambient air that hydrogen cyanide outgasses from the solution.
  • WO 2016/168933 A1 describes a method in which gold is extracted from starting materials using an organic solution.
  • acetonitrile can be used as a solvent.
  • the method is used to extract gold and/or silver and/or at least one platinum metal from at least one starting material, in particular from scrap metal or from naturally occurring ores.
  • Platinum metals platinum group metals; PGM are understood to mean the light platinum metals ruthenium, rhodium and palladium and the heavy platinum metals iridium and platinum.
  • Scrap metals are processed metals of any form, for example metals as part of catalytic converters or metals as part of electronic devices.
  • the at least one starting material, which contains gold and/or silver and/or at least one platinum metal is introduced into an aqueous solution which contains at least one nitrile.
  • the nitrile is selected from the group consisting of acetonitrile, isobutyronitrile and propionitrile, with acetonitrile being particularly preferred.
  • Ozone is introduced into the solution in at least two initiation phases. No ozone is introduced into the solution between the introduction phases.
  • the ozone can react with water to form oxygen and hydroxyl radicals, the reaction being carried out in particular photocatalytically.
  • the ozone required for this can be generated, for example, by corona discharges or electrochemically.
  • By reacting the hydroxyl radicals with the nitrile just as many cyanides (ions or radicals) can be generated in situ as are required to dissolve the metal to be extracted.
  • the hydroxyl radicals can act as oxidizing agents towards the metal. As a result, it is not necessary to work with large excesses of cyanides, nor is it necessary to use large amounts of strong bases.
  • An initiation phase is preferably started when a concentration of cyanide ions and/or cyano radicals in the solution falls below a first threshold is. This means that the process starts with the introduction of ozone, since the solution initially contains neither cyanide ions nor cyano radicals. Each time the concentration falls below the first threshold due to complexation with the metal to be extracted, another initiation phase is started.
  • An introductory phase is preferably carried out for a predeterminable period of time.
  • the predefinable period of time is preferably in the range from 5 minutes to 15 minutes. Such a period of time is sufficient, on the one hand, to enrich the solution with cyanide ions and/or cyano radicals to such an extent that these bring the metal to be extracted into solution. On the other hand, excessive formation of cyanide ions, which can result from oxidation of cyanide ions with ozone, is avoided.
  • Oxygen is preferably introduced into the solution at least between the introduction phases. This supports the oxidation of unreacted hydroxyl radicals still present in the solution with the metal to be obtained or the nitrile. Additional oxygen can also be introduced into the solution during the introduction of the ozone. This is carried out in particular when the ozone is generated by corona discharges and is therefore present as an ozone/oxygen mixture.
  • a final initiation phase of the process is preferably performed until a concentration of cyanide ions and/or cyano radicals in the solution has fallen below a second threshold. In this way, cyanide ions and cyano radicals still contained in the solution can be oxidatively converted into less toxic cyanate. In the process, the remaining nitrile still in the solution is also used up.
  • the final initiation phase is preferably only started when all of the metal to be extracted has gone into solution. In one embodiment of the method, this can be recognized by the fact that the concentration of the metal in the solution no longer increases. In another embodiment of the method, it is recognized that an amount of a gradient of a decreasing the concentration of cyanide ions and/or cyano radicals in the solution falls below a gradient threshold.
  • the solution contains at least 0.1 mol/l of the at least one nitrile to provide a sufficiently large source for the generation of cyanides (ions or radicals). Furthermore, it is preferred that the concentration of the at least one nitrile does not exceed 0.5 mol/l. This avoids large amounts of nitrile remaining at the end of the process, which must also be oxidized in the final oxidation of cyanide ions, cyano radicals and nitrile and thus prolong the process time.
  • the solution preferably contains 0.1 mol/l to 1.0 mol/l of at least one alkali metal hydroxide, in particular sodium hydroxide or potassium hydroxide. Due to the targeted formation of cyanides (ions or radicals) and the oxidizing effect of the hydroxyl radicals, this amount of alkali metal hydroxide is sufficient to effectively prevent the formation of gaseous hydrocyanic acid.
  • the solution contains at least one substance selected from the group consisting of alcohols, surfactants and activated carbon.
  • alcohols preference is given to the short-chain alcohols methanol, ethanol and isopropanol.
  • surfactants the alcohols bring about improved wetting of the at least one starting material by the aqueous solution.
  • the activated carbon has a high surface area on which the formation of hydroxyl radicals can take place.
  • the ozone is introduced into the solution through a porous diffuser below the feedstock. In this way it flows around the feedstock and the formation of the hydroxyl radicals occurs near the surface of the feedstock.
  • the solution is irradiated with UV light.
  • the UV light preferably has a wavelength of less than 310 nm.
  • FIG. 1 schematically shows a reactor in which a process according to an exemplary embodiment of the invention takes place.
  • FIG. 2 shows in a diagram the change in concentration over time of several substances in an exemplary embodiment of the invention.
  • FIG. 3 shows in a diagram the change in concentration of gold(I) complexes over time in an exemplary embodiment of the invention and in a comparative example.
  • FIG. 1 shows how, in an exemplary embodiment of the invention, gold can be detached from a nickel substrate from a starting material 10, which in this case is a printed circuit board.
  • the starting material 10 is fastened in a frame 11 for this purpose.
  • This is covered by an aqueous solution 20 stored in a reactor 21 .
  • the aqueous solution 20 contains 0.11 mol/l acetonitrile and 0.50 mol/l sodium hydroxide. It also contains methanol, surfactants and activated carbon.
  • Ozone 30 is introduced into reactor 21 through a porous diffuser 31 located in reactor 21 below feedstock 10 and below inlet port 22 at initiation stages. It mixes with the fresh solution 20, which is fed into the reactor 21 through the inlet opening 22, and flows around the starting material 10.
  • the reactor 21 consists of a transparent material and is illuminated from the outside by means of a UV lamp 40 with light having a wavelength of irradiated less than 310 nm.
  • the ozone 30 according to formula 1 also forms here
  • a mixture 32 of unreacted ozone and the oxygen formed leaves the reactor 21 through a gas outlet 22 at its top.
  • hydroxyl radicals react with the acetonitrile to form methanol to form cyano radicals. These oxidize metallic gold to gold(l)cyanide:
  • hydroxyl radicals according to formula 3 can themselves oxidize gold to gold(I) hydroxide on the metal surface. This is highly reactive and reacts with the acetonitrile to form methanol to form gold(l) cyanide:
  • cyanide ions that have already formed are oxidized by the ozone to cyanate ions according to formula 4:
  • the reactor 21 contains sensors (not shown) for measuring the concentrations c(CH3CN) of acetonitrile, c(CN') of free cyanide ions, c(CNO') of cyanide ions and c(Au + ) of complex-bound gold(I) cations. If no starting material 10 is added to the reactor 21, as shown in FIG. 2, the concentration c(CH3CN) of the acetonitrile drops significantly during a first introductory phase 51 which lasts 10 minutes. In the process, free cyanide ions are formed and cyanide ions are already oxidized to form cyanate ions.
  • the concentrations c(CH3CN) of acetonitrile, c(CN') of free cyanide and c(CNO') of cyanide ion remain essentially constant for 30 minutes, since without the presence of a starting material 10 no free cyanide is available complexing of gold is consumed. If a second introductory phase 52 is started, which, like the first introductory phase 51, also lasts 10 minutes, the cyanide ion concentration c(CN') begins to drop, since the cyanide ion concentration c(CN'), which is still high without consumption of cyanide ions, now causes a strong formation of cyanation takes place.
  • the second introductory phase 52 was started after a specified period of time. Within another 10 minutes after the end of the second introductory phase 52 would be in the presence of a
  • Starting material 10 is to be expected that all of the gold is removed and no further metal goes into solution, since nickel forms an inert protective layer of nickel hydroxide under alkaline conditions.
  • a third initiation phase 53 is now started, which is continued until the concentration c(CN') of the free cyanide ions has fallen below a second threshold value and has thereby reached a value of almost zero. This is achieved within 20 minutes. The concentration c(CHsCN) of the acetonitrile also falls to zero. If the process is carried out in the presence of the starting material, the gold could then be precipitated from the solution using methods known from cyanide leaching.
  • FIG. 3 shows the course of the concentration c(Au + ) of the complex-bound gold(I) cations relative to the surface of the starting material 10 with time t. It can be seen that in the period of 80 minutes in which the gold is completely dissolved in exemplary embodiment B according to the invention, in the comparative example only half of the concentration c(Au + ) of the complex-bound gold(I) cations in the solution achieved according to the invention is reached. This means that only half of the gold was dissolved in the starting material 10 in the comparative example.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geochemistry & Mineralogy (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Catalysts (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)

Abstract

The invention relates to a method for extracting gold and/or silver and/or at least one platinum metal. At least one starting material, which contains gold and/or silver and/or at least one platinum metal, is introduced into an aqueous solution that contains at least one nitrile. Ozone is introduced into the solution in at least two introduction phases (51, 52, 53). No ozone is introduced into the solution between the introduction phases (51, 52, 53).

Description

Beschreibung description
Titel title
Verfahren zur Gewinnung von Gold und/oder Silber und/oder mindestens einem Platinmetall Method for extracting gold and/or silver and/or at least one platinum group metal
Die vorliegende Erfindung betrifft ein Verfahren zur Gewinnung von Gold und/oder Silber und/oder mindestens einem Platinmetall aus mindestens einem Ausgangsmaterial. The present invention relates to a method for extracting gold and/or silver and/or at least one platinum group metal from at least one starting material.
Stand der Technik State of the art
Gold, Silber und Platinmetalle sind essentielle Rohstoffe. Ihre Rückgewinnung aus Wertstoffabfall, beispielsweise als Teil von Katalysatormaterialien oder von elektronischen Geräten kann pyrometallurgisch oder hydrometallurgisch erfolgen. Die pyrometallurgische Rückgewinnung erfolgt, indem die Altmetalle geschmolzen und dann durch verschiedene Verfahren aufbereitet werden. Dies ist allerdings sehr energieintensiv und mit dem Entstehen toxischer Emissionen verbunden. Bei der hydrometallurgischen Rückgewinnung werden die zurückzugewinnenden Metalle durch Komplexbildung in eine wässrige Lösung gebracht. Ein Beispiel für ein solches Verfahren ist das alkalische Cyanidlaugen zur Goldgewinnung. Dieses Verfahren wird bei sehr hohen pH-Werten, also unter Verwendung aggressiver Laugen, durchgeführt. Der verwendete Komplexbildner Cyanid ist sehr toxisch, sodass auch dieses Verfahren zu gefährlichen Emissionen führen kann. Insbesondere kann der pH-Wert einer cyanidhaltigen Lösung durch Aufnahme von Kohlendioxid aus der Umgebungsluft beispielsweise so stark ansteigen, dass Blausäure aus der Lösung ausgast. Gold, silver and platinum metals are essential raw materials. Their recovery from recyclable waste, for example as part of catalyst materials or electronic devices, can be pyrometallurgical or hydrometallurgical. Pyrometallurgical reclamation is done by melting the scrap metal and then treating it through various processes. However, this is very energy-intensive and associated with the formation of toxic emissions. In hydrometallurgical recovery, the metals to be recovered are brought into an aqueous solution by complex formation. An example of such a process is alkaline cyanide leaching for gold recovery. This process is carried out at very high pH values, i.e. using aggressive bases. The complexing agent cyanide used is very toxic, so this process can also lead to dangerous emissions. In particular, the pH value of a cyanide-containing solution can increase so much, for example, by absorbing carbon dioxide from the ambient air that hydrogen cyanide outgasses from the solution.
Die WO 2016/168933 Al beschreibt ein Verfahren, in dem Gold mittels einer organischen Lösung aus Ausgangsmaterialien gewonnen wird. Dabei kann Acetonitril als Lösungsmittel verwendet werden. Dieses enthält eine Säure, wie beispielsweise Chlorwasserstoff, ein Oxidationsmittel, wie beispielsweise Wasserstoffperoxid, und einen organischen Komplexbildner, um Gold(lll)- Kationen in dem organischen Lösungsmittel in Lösung zu bringen. WO 2016/168933 A1 describes a method in which gold is extracted from starting materials using an organic solution. In this case, acetonitrile can be used as a solvent. This contains an acid, such as for example hydrogen chloride, an oxidizing agent such as hydrogen peroxide and an organic complexing agent to solubilize gold(III) cations in the organic solvent.
Offenbarung der Erfindung Disclosure of Invention
Das Verfahren dient zur Gewinnung von Gold und/oder Silber und/oder mindestens einem Platinmetall aus mindestens einem Ausgangsmaterial, insbesondere aus einem Altmetall oder aus natürlich vorkommenden Erzen. Unter Platinmetallen (platinum group metals; PGM) werden dabei die leichten Platinmetalle Ruthenium, Rhodium und Palladium und die schweren Platinmetalle Iridium und Platin verstanden. Unter Altmetallen werden verarbeitete Metalle jeglicher Form verstanden, beispielsweise Metalle als Teil von Katalysatoren oder Metalle als Teil von elektronischen Geräten. Das mindestens eine Ausgangsmaterial, welches Gold und/oder Silber und/oder mindestens einem Platinmetall enthält, wird in eine wässrige Lösung eingebracht, welche mindestens ein Nitril enthält. Das Nitril ist insbesondere ausgewählt aus der Gruppe, die aus Acetonitril, Isobutyronitril und Propionitril besteht, wobei Acetonitril besonders bevorzugt ist. Ozon wird in mindestens zwei Einleitungsphasen in die Lösung eingeleitet. Zwischen den Einleitungsphasen wird kein Ozon in die Lösung eingeleitet. The method is used to extract gold and/or silver and/or at least one platinum metal from at least one starting material, in particular from scrap metal or from naturally occurring ores. Platinum metals (platinum group metals; PGM) are understood to mean the light platinum metals ruthenium, rhodium and palladium and the heavy platinum metals iridium and platinum. Scrap metals are processed metals of any form, for example metals as part of catalytic converters or metals as part of electronic devices. The at least one starting material, which contains gold and/or silver and/or at least one platinum metal, is introduced into an aqueous solution which contains at least one nitrile. In particular, the nitrile is selected from the group consisting of acetonitrile, isobutyronitrile and propionitrile, with acetonitrile being particularly preferred. Ozone is introduced into the solution in at least two initiation phases. No ozone is introduced into the solution between the introduction phases.
Das Ozon kann mit Wasser unter Bildung von Sauerstoff und Hydroxylradikalen reagieren, wobei die Reaktion insbesondere photokatalytisch durchgeführt wird. Das hierfür benötigte Ozon kann beispielsweise durch Koronaentladungen oder elektrochemisch erzeugt werden. Durch Reaktion der Hydroxyl radikale mit dem Nitril können in situ gerade so viele Cyanide (Ionen oder Radikale) erzeugt werden, wie erforderlich sind, um das zu gewinnende Metall in Lösung zu bringen. Gleichzeitig können die Hydroxylradikale gegenüber dem Metall als Oxidationsmittel fungieren. Hierdurch muss weder mit großen Überschüssen an Cyaniden gearbeitet werden, noch ist die Verwendung großer Mengen starker Laugen erforderlich. The ozone can react with water to form oxygen and hydroxyl radicals, the reaction being carried out in particular photocatalytically. The ozone required for this can be generated, for example, by corona discharges or electrochemically. By reacting the hydroxyl radicals with the nitrile, just as many cyanides (ions or radicals) can be generated in situ as are required to dissolve the metal to be extracted. At the same time, the hydroxyl radicals can act as oxidizing agents towards the metal. As a result, it is not necessary to work with large excesses of cyanides, nor is it necessary to use large amounts of strong bases.
Eine Einleitungsphase wird vorzugsweise gestartet, wenn eine Konzentration von Cyanidionen und/oder Cyanoradikalen in der Lösung unter einem ersten Schwellenwert liegt. Dies bedeutet, dass das Verfahren, mit dem Einleiten von Ozon beginnt, da die Lösung anfangs weder Cyanidionen noch Cyanoradikale enthält. Jedes Mal, wenn die Konzentration durch Komplexbildung mit dem zu gewinnenden Metall wieder unter den ersten Schwellenwert fällt, wird eine weitere Einleitungsphase gestartet. An initiation phase is preferably started when a concentration of cyanide ions and/or cyano radicals in the solution falls below a first threshold is. This means that the process starts with the introduction of ozone, since the solution initially contains neither cyanide ions nor cyano radicals. Each time the concentration falls below the first threshold due to complexation with the metal to be extracted, another initiation phase is started.
Eine Einleitungsphase wird vorzugsweise für einen vorgebaren Zeitraum durchgeführt wird. Der vorgebbare Zeitraum liegt bevorzugt im Bereich von 5 Minuten bis 15 Minuten. Ein solcher Zeitraum reicht einerseits aus, um die Lösung so sehr mit Cyanidionen und/oder Cyanoradikalen anzureichern, dass diese das zu gewinnende Metall in Lösung bringen. Andererseits wird eine Übermäßige Bildung von Cyanationen vermieden, welche durch eine Oxidation von Cyanidionen mit Ozon entstehen können. An introductory phase is preferably carried out for a predeterminable period of time. The predefinable period of time is preferably in the range from 5 minutes to 15 minutes. Such a period of time is sufficient, on the one hand, to enrich the solution with cyanide ions and/or cyano radicals to such an extent that these bring the metal to be extracted into solution. On the other hand, excessive formation of cyanide ions, which can result from oxidation of cyanide ions with ozone, is avoided.
Zumindest zwischen den Einleitungsphasen wird vorzugsweise Sauerstoff in die Lösung eingeleitet. Dieser unterstützt die Oxidation von noch in der Lösung vorhandenen nicht abreagierten Hydroxylradikalen mit dem zu gewinnenden Metall oder dem Nitril. Auch während der Einleitung des Ozons kann zusätzlich Sauerstoff in die Lösung eingeleitet werden. Dies wird insbesondere dann durchgeführt, wenn das Ozon durch Koronaentladungen erzeugt wird und dadurch als Ozon/Sauerstoff-Gemisch vorliegt. Oxygen is preferably introduced into the solution at least between the introduction phases. This supports the oxidation of unreacted hydroxyl radicals still present in the solution with the metal to be obtained or the nitrile. Additional oxygen can also be introduced into the solution during the introduction of the ozone. This is carried out in particular when the ozone is generated by corona discharges and is therefore present as an ozone/oxygen mixture.
Eine letzte Einleitungsphase des Verfahrens wird bevorzugt durchgeführt, bis eine Konzentration von Cyanidionen und/oder Cyanoradikalen in der Lösung unter einen zweiten Schwellenwert gefallen ist. Auf diese Weise können noch in der Lösung enthaltene Cyanidionen und Cyanoradikale oxidativ in weniger toxisches Cyanat überführt werden. Dabei wird auch das noch in der Lösung befindliche restliche Nitril aufgebraucht. A final initiation phase of the process is preferably performed until a concentration of cyanide ions and/or cyano radicals in the solution has fallen below a second threshold. In this way, cyanide ions and cyano radicals still contained in the solution can be oxidatively converted into less toxic cyanate. In the process, the remaining nitrile still in the solution is also used up.
Die letzte Einleitungsphase wird vorzugsweise erst dann gestartet, wenn das gesamte zu gewinnende Metall in Lösung gegangen ist. Dies kann in einer Ausführungsform des Verfahrens daran erkannt werden, dass die Konzentration des Metalls in der Lösung nicht mehr steigt. In einer anderen Ausführungsform des Verfahrens wird es daran erkannt, dass ein Betrag eines Gradienten eines Sinkens der Konzentration der Cyanidionen und/oder Cyanoradikale in der Lösung unter einen Gradientenschwellenwert fällt. The final initiation phase is preferably only started when all of the metal to be extracted has gone into solution. In one embodiment of the method, this can be recognized by the fact that the concentration of the metal in the solution no longer increases. In another embodiment of the method, it is recognized that an amount of a gradient of a decreasing the concentration of cyanide ions and/or cyano radicals in the solution falls below a gradient threshold.
Es ist bevorzugt, dass die Lösung mindestens 0,1 mol/l des mindestens einen Nitrils enthält, um eine ausreichend große Quelle für die Erzeugung von Cyaniden (Ionen oder Radikale) zur Verfügung zu stellen. Weiterhin ist es bevorzugt, dass die Konzentration des mindestens einen Nitrils 0,5 mol/l nicht überschreitet. Hierdurch wird vermieden, dass am Ende des Verfahrens große Mengen des Nitrils verbleiben, welche bei der abschließenden Oxidation von Cyanidionen, Cyanoradikale und Nitril mitoxidiert werden müssen und so die Verfahrensdauer verlängern. It is preferred that the solution contains at least 0.1 mol/l of the at least one nitrile to provide a sufficiently large source for the generation of cyanides (ions or radicals). Furthermore, it is preferred that the concentration of the at least one nitrile does not exceed 0.5 mol/l. This avoids large amounts of nitrile remaining at the end of the process, which must also be oxidized in the final oxidation of cyanide ions, cyano radicals and nitrile and thus prolong the process time.
Die Lösung enthält vorzugsweise 0,1 mol/l bis 1,0 mol/l mindestens eines Alkalimetallhydroxids, insbesondere Natriumhydroxids oder Kaliumhydroxids. Aufgrund der gezielten Bildung von Cyaniden (Ionen oder Radikale) und der oxidierenden Wirkung der Hydroxylradikale ist diese Menge des Alkalihydroxids ausreichend, um eine Bildung von gasförmiger Blausäure wirksam zu unterbinden. The solution preferably contains 0.1 mol/l to 1.0 mol/l of at least one alkali metal hydroxide, in particular sodium hydroxide or potassium hydroxide. Due to the targeted formation of cyanides (ions or radicals) and the oxidizing effect of the hydroxyl radicals, this amount of alkali metal hydroxide is sufficient to effectively prevent the formation of gaseous hydrocyanic acid.
Weiterhin ist es bevorzugt, dass die Lösung zumindest eine Substanz enthält, die ausgewählt ist, aus der Gruppe bestehend aus Alkoholen, Tensiden und Aktivkohle. Unter den Alkoholen sind dabei die kurzkettigen Alkohole Methanol, Ethanol und Isopropanol bevorzugt. Ebenso wie die Tenside bewirken die Alkohole eine verbesserte Benetzung des mindestens einen Ausgangsmaterials durch die wässrige Lösung. Die Aktivkohle weist eine hohe Oberfläche auf, an welcher die Bildung von Hydroxylradikalen ablaufen kann. Furthermore, it is preferred that the solution contains at least one substance selected from the group consisting of alcohols, surfactants and activated carbon. Among the alcohols, preference is given to the short-chain alcohols methanol, ethanol and isopropanol. Like the surfactants, the alcohols bring about improved wetting of the at least one starting material by the aqueous solution. The activated carbon has a high surface area on which the formation of hydroxyl radicals can take place.
Es ist bevorzugt, dass das Ozon durch einen porösen Diffusor unterhalb des Ausgangsmaterials in die Lösung eingeleitet wird. Auf diese Weise umströmt es das Ausgangsmaterial und die Bildung der Hydroxylradikale erfolgt in der Nähe der Oberfläche des Ausgangsmaterials. It is preferred that the ozone is introduced into the solution through a porous diffuser below the feedstock. In this way it flows around the feedstock and the formation of the hydroxyl radicals occurs near the surface of the feedstock.
Weiterhin ist es bevorzugt, dass die Lösung mit UV-Licht bestrahlt wird. Bei der Bildung von Hydroxylradikalen durch Einleitung von Ozon in die Lösung kann hierdurch eine Photokatalyse der Reaktion erreicht werden. Hierzu hat das UV- Licht bevorzugt eine Wellenlänge von weniger als 310 nm. Furthermore, it is preferred that the solution is irradiated with UV light. In the formation of hydroxyl radicals by introducing ozone into the solution a photocatalysis of the reaction can thereby be achieved. For this purpose, the UV light preferably has a wavelength of less than 310 nm.
Kurze Beschreibung der Zeichnungen Brief description of the drawings
Ausführungsbeispiele der Erfindung sind in den Zeichnungen dargestellt und werden in der nachfolgenden Beschreibung näher erläutert. Embodiments of the invention are shown in the drawings and are explained in more detail in the following description.
Figur 1 zeigt schematisch einen Reaktor, in dem ein Verfahren gemäß einem Ausführungsbeispiel der Erfindung abläuft. FIG. 1 schematically shows a reactor in which a process according to an exemplary embodiment of the invention takes place.
Figur 2 zeigt in einem Diagramm die zeitliche Konzentrationsänderung mehrerer Substanzen in einem Ausführungsbeispiel der Erfindung. FIG. 2 shows in a diagram the change in concentration over time of several substances in an exemplary embodiment of the invention.
Figur 3 zeigt in einem Diagramm die zeitliche Konzentrationsänderung von Gold(l)-Komplexen in einem Ausführungsbeispiel der Erfindung und in einem Vergleichsbeispiel. FIG. 3 shows in a diagram the change in concentration of gold(I) complexes over time in an exemplary embodiment of the invention and in a comparative example.
Ausführungsbeispiele der Erfindung Embodiments of the invention
Figur 1 zeigt, wie in einem Ausführungsbeispiel der Erfindung aus einem Ausgangsmaterial 10, bei dem es sich vorliegend um eine Leiterplatte handelt, Gold von einem Nickelsubstrat gelöst werden kann. Hierzu ist das Ausgangsmaterial 10 in einem Rahmen 11 befestigt. Dieser wird von einer wässrigen Lösung 20 bedeckt, die in einem Reaktor 21 bevorratet ist. Die wässrige Lösung 20 enthält im vorliegenden Ausführungsbeispiel 0,11 mol/l Acetonitril und 0,50 mol/l Natriumhydroxid. Weiterhin enthält sie Methanol, Tenside und Aktivkohle. Ozon 30 wird in Einleitungsphasen durch einen porösen Diffusor 31, der im Reaktor 21 unterhalb des Ausgangsmaterials 10 und unterhalb der Einlassöffnung 22 angeordnet ist, in den Reaktor 21 eingeleitet. Es vermischt sich mit der frischen Lösung 20, die durch die Einlassöffnung 22 in Reaktor 21 geleitet wird, und umströmt das Ausgangsmaterial 10. Zwischen den Einleitungsphasen wird durch den porösen Diffusor 31 Sauerstoff in den Reaktor 21 eingeleitet. Der Reaktor 21 besteht aus einem transparenten Material und wird von außen mittels einer UV-Lampe 40 mit Licht mit einer Wellenlänge von weniger als 310 nm bestrahlt. Dabei bildet das Ozon 30 gemäß Formel 1 mitFIG. 1 shows how, in an exemplary embodiment of the invention, gold can be detached from a nickel substrate from a starting material 10, which in this case is a printed circuit board. The starting material 10 is fastened in a frame 11 for this purpose. This is covered by an aqueous solution 20 stored in a reactor 21 . In the present exemplary embodiment, the aqueous solution 20 contains 0.11 mol/l acetonitrile and 0.50 mol/l sodium hydroxide. It also contains methanol, surfactants and activated carbon. Ozone 30 is introduced into reactor 21 through a porous diffuser 31 located in reactor 21 below feedstock 10 and below inlet port 22 at initiation stages. It mixes with the fresh solution 20, which is fed into the reactor 21 through the inlet opening 22, and flows around the starting material 10. Between the introduction phases, oxygen is introduced into the reactor 21 through the porous diffuser 31. The reactor 21 consists of a transparent material and is illuminated from the outside by means of a UV lamp 40 with light having a wavelength of irradiated less than 310 nm. The ozone 30 according to formula 1 also forms here
Wassermolekülen photokatalytisch Sauerstoff- und Hydroxylradikale: h ■ v water molecules photocatalytically oxygen and hydroxyl radicals: h ■ v
O3 + H2O - > O2 + 2 OH' (Formel 1) O 3 + H 2 O -> O 2 + 2 OH' (Formula 1)
Ein Gemisch 32 aus nicht abreagiertem Ozon und dem gebildeten Sauerstoff verlässt den Reaktor 21 durch einen Gasauslass 22 an seiner Oberseite. A mixture 32 of unreacted ozone and the oxygen formed leaves the reactor 21 through a gas outlet 22 at its top.
Die Hydroxylradikale gehen in der Lösung 20 im Wesentlichen zwei Reaktionen ein: The hydroxyl radicals essentially undergo two reactions in the solution 20:
Gemäß Formel 2 reagieren Hydroxylradikale mit dem Acetonitril unter Bildung von Methanol zu Cyanoradikalen. Diese oxidieren metallisches Gold zu Gold(l)cyanid: According to formula 2, hydroxyl radicals react with the acetonitrile to form methanol to form cyano radicals. These oxidize metallic gold to gold(l)cyanide:
OH' + CH3CN + AU - CN' + Au - > AuCN (Formel 2) OH' + CH 3 CN + AU - CN' + Au - > AuCN (Formula 2)
— C H30H - CH30H
Weiterhin können die Hydroxylradikale gemäß Formel 3 an der Metalloberfläche selbst Gold zu Gold(l)hydroxid oxidieren. Dieses ist hoch reaktiv und reagiert mit dem Acetonitril unter Bildung von Methanol zu Gold(l)cyanid: Furthermore, the hydroxyl radicals according to formula 3 can themselves oxidize gold to gold(I) hydroxide on the metal surface. This is highly reactive and reacts with the acetonitrile to form methanol to form gold(l) cyanide:
OH' + CH3CN + Au - > AuOH + CH3CN > AuCN (Formel 3) OH' + CH 3 CN + Au - > AuOH + CH 3 CN > AuCN (Formula 3)
— CH3OH — CH3OH
Das Gold(l)cyanid mit weiteren Cyanidionen als Cyanokomplex in Lösung. Gold(I) cyanide with other cyanide ions as a cyano complex in solution.
Als Nebenreaktion werden bereits gebildete Cyanidionen von dem Ozon gemäß Formel 4 zu Cyanationen oxidiert: As a side reaction, cyanide ions that have already formed are oxidized by the ozone to cyanate ions according to formula 4:
CN~ + O3 - > CN0~ + O2 (Formel 4) CN~ + O 3 -> CN0~ + O 2 (formula 4)
Der Reaktor 21 enthält nicht dargestellte Sensoren zur Messung der Konzentrationen c(CH3CN) von Acetonitril, c(CN') von freien Cyanidionen, c(CNO') von Cyanationen und c(Au+) von komplexgebundenen Gold(l)-Kationen. Wenn dem Reaktor 21 kein Ausgangsmaterial 10 zugefügt wird, sinkt, wie in Figur 2 dargestellt ist, die Konzentration c(CH3CN) des Acetonitrils während einer ersten Einleitphase 51, die 10 Minuten dauert, deutlich ab. Dabei bilden sich freie Cyanidionen und es kommt auch schon zu einer Oxidation von Cyanidionen zu Cyanationen. Vor Beginn einer zweiten Einleitphase 52, bleiben die Konzentrationen c(CH3CN) des Acetonitrils, c(CN') des freien Cyanids und c(CNO') der Cyanationen für 30 Minuten im Wesentlichen konstant, da ohne Anwesenheit eines Ausgangsmaterials 10 kein freies Cyanid zur Komplexierung von Gold verbraucht wird. Wenn eine zweite Einleitphase 52 gestartet wird, die wie die erste Einleitphase 51 ebenfalls 10 Minuten dauert, beginnt die Cyanidionenkonzentration c(CN') zu sinken, da nun aufgrund der ohne Verbrauch von Cyanidionen noch hohen Cyanidionenkonzentration c(CN') eine starke Bildung von Cyanationen erfolgt. Da in diesem Experiment kein Ausgangsmaterial 10 vorahnden ist, und die Cyanidionenkonzentration c(CN') deshalb nach Ende der ersten Einleitphase 51 nicht sinkt, also auch nicht unter einen ersten Schwellenwert sinken kann, wurde die zweite Einleitphase 52 nach einem festgelegten Zeitraum gestartet. Innerhalb von weiteren 10 Minuten nach Ende der zweiten Einleitphase 52 wäre bei Anwesenheit einesThe reactor 21 contains sensors (not shown) for measuring the concentrations c(CH3CN) of acetonitrile, c(CN') of free cyanide ions, c(CNO') of cyanide ions and c(Au + ) of complex-bound gold(I) cations. If no starting material 10 is added to the reactor 21, as shown in FIG. 2, the concentration c(CH3CN) of the acetonitrile drops significantly during a first introductory phase 51 which lasts 10 minutes. In the process, free cyanide ions are formed and cyanide ions are already oxidized to form cyanate ions. Before beginning a second initiation phase 52, the concentrations c(CH3CN) of acetonitrile, c(CN') of free cyanide and c(CNO') of cyanide ion remain essentially constant for 30 minutes, since without the presence of a starting material 10 no free cyanide is available complexing of gold is consumed. If a second introductory phase 52 is started, which, like the first introductory phase 51, also lasts 10 minutes, the cyanide ion concentration c(CN') begins to drop, since the cyanide ion concentration c(CN'), which is still high without consumption of cyanide ions, now causes a strong formation of cyanation takes place. Since no starting material 10 is present in this experiment and the cyanide ion concentration c(CN') therefore does not drop after the end of the first introductory phase 51, i.e. cannot drop below a first threshold value either, the second introductory phase 52 was started after a specified period of time. Within another 10 minutes after the end of the second introductory phase 52 would be in the presence of a
Ausgangsmaterials 10 zu erwarten, dass das gesamte Gold abgetragen wird und kein weiteres Metall in Lösung geht, da Nickel unter alkalischen Bedingungen eine inerte Schutzschicht aus Nickelhydroxid bildet. Starting material 10 is to be expected that all of the gold is removed and no further metal goes into solution, since nickel forms an inert protective layer of nickel hydroxide under alkaline conditions.
Nun wird eine dritte Einleitphase 53 gestartet, die fortgesetzt wird, bis die Konzentration c(CN') der freien Cyanidionen unter einen zweiten Schwellenwert gesunken ist und dabei einen Wert von nahezu Null erreicht hat. Dies wird innerhalb von 20 Minuten erreicht. Dabei sinkt auch die Konzentration c(CHsCN) des Acetonitrils auf null. Bei Durchführung des Verfahrens in Gegenwart des Ausgangsmaterials könnte anschließend das Gold mittels aus der Cyanidlaugerei bekannter Methoden aus der Lösung ausgefällt werden. A third initiation phase 53 is now started, which is continued until the concentration c(CN') of the free cyanide ions has fallen below a second threshold value and has thereby reached a value of almost zero. This is achieved within 20 minutes. The concentration c(CHsCN) of the acetonitrile also falls to zero. If the process is carried out in the presence of the starting material, the gold could then be precipitated from the solution using methods known from cyanide leaching.
Ein erfindungsgemäßes Ausführungsbeispiel B, in dem tatsächlich das Ausgangsmaterial 10 behandelt wurde, wurde mit einem Vergleichsbeispiel VB verglichen, in dem unter ansonsten identischen Verfahrensbedingungen kontinuierlich Ozon 30 in den Reaktor 21 eingeleitet wurde, anstatt es nur in den Einleitphasen 51, 52, 53 einzuleiten. In Figur 3 ist der Verlauf der Konzentration c(Au+) der komplexgebundenen Gold(l)-Kationen bezogen auf die Oberfläche des Ausgangsmaterials 10 mit der Zeit t dargestellt. Dabei ist erkennbar, dass in dem Zeitraum von 80 Minuten, in welchem das Gold im erfindungsgemäßen Ausführungsbeispiel B vollständig aufgelöst wird, in dem Vergleichsbeispiel lediglich die Hälfte der erfindungsgemäß erreichten Konzentration c(Au+) der komplexgebundenen Gold(l)-Kationen in der Lösung erreicht wird. Dies bedeutet, dass in dem Vergleichsbeispiel nur die Hälfte des Goldes in dem Ausgangsmaterial 10 aufgelöst wurde. An inventive embodiment B, in which the starting material 10 was actually treated, was compared with a comparative example VB, in which ozone 30 was continuously introduced into the reactor 21 under otherwise identical process conditions, instead of introducing it only in the introduction phases 51, 52, 53. FIG. 3 shows the course of the concentration c(Au + ) of the complex-bound gold(I) cations relative to the surface of the starting material 10 with time t. It can be seen that in the period of 80 minutes in which the gold is completely dissolved in exemplary embodiment B according to the invention, in the comparative example only half of the concentration c(Au + ) of the complex-bound gold(I) cations in the solution achieved according to the invention is reached. This means that only half of the gold was dissolved in the starting material 10 in the comparative example.

Claims

- 9 - Ansprüche - 9 - Claims
1. Verfahren zur Gewinnung von Gold und/oder Silber und/oder mindestens einem Platinmetall, worin mindestens ein Ausgangsmaterial (10), welches Gold und/oder Silber und/oder mindestens ein Platinmetall enthält in eine wässrige Lösung (20) eingebracht wird, welche mindestens ein Nitril enthält und wobei Ozon (30) in mindestens zwei Einleitungsphasen (51, 52, 53) in die Lösung (20) eingeleitet wird und zwischen den Einleitungsphasen (51, 52, 53) kein Ozon (30) in die Lösung (20) eingeleitet wird. 1. A method for extracting gold and/or silver and/or at least one platinum metal, wherein at least one starting material (10) containing gold and/or silver and/or at least one platinum metal is introduced into an aqueous solution (20) which contains at least one nitrile and wherein ozone (30) is introduced into the solution (20) in at least two introductory phases (51, 52, 53) and no ozone (30) is introduced into the solution (20 ) is initiated.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass eine Einleitungsphase (51, 52) gestartet wird, wenn eine Konzentration (c(CN')) von Cyanidionen und/oder Cyanoradikalen in der Lösung (20) unter einem ersten Schwellenwert liegt. 2. Method according to claim 1, characterized in that an initiation phase (51, 52) is started when a concentration (c(CN')) of cyanide ions and/or cyano radicals in the solution (20) is below a first threshold value.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass eine Einleitungsphase (51, 52) für einen vorgebaren Zeitraum durchgeführt wird. 3. The method according to claim 1 or 2, characterized in that an initiation phase (51, 52) is carried out for a predetermined period of time.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass zumindest zwischen den Einleitungsphasen (51, 52, 53) Sauerstoff in die Lösung (20) eingeleitet wird. 4. The method according to any one of claims 1 to 3, characterized in that at least between the introduction phases (51, 52, 53) oxygen is introduced into the solution (20).
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass eine letzte Einleitungsphase (53) des Verfahrens durchgeführt wird, bis eine Konzentration (c(CN')) von Cyanidionen und/oder Cyanoradikalen in der Lösung unter einen zweiten Schwellenwert gefallen ist. 5. Method according to any one of claims 1 to 4, characterized in that a final initiation phase (53) of the method is carried out until a concentration (c(CN')) of cyanide ions and/or cyano radicals in the solution falls below a second threshold value is.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass die letzte Einleitungsphase (53) erst dann gestartet wird, wenn das gesamte zu gewinnende Metall in Lösung gegangen ist. 6. The method according to claim 5, characterized in that the last initiation phase (53) is only started when all the metal to be extracted has gone into solution.
7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass die Lösung (20) 0,1 mol/l bis 0,5 mol/l des mindestens einen Nitrils enthält. 7. The method according to any one of claims 1 to 6, characterized in that the solution (20) contains 0.1 mol/l to 0.5 mol/l of the at least one nitrile.
8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Lösung (20) 0,1 mol/l bis 1,0 mol/l mindestens eines Alkalihydroxids enthält. 8. The method according to any one of claims 1 to 7, characterized in that the solution (20) contains 0.1 mol/l to 1.0 mol/l of at least one alkali metal hydroxide.
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass das Ozon (30) durch einen porösen Diffusor (31) unterhalb des Ausgangsmaterials (10) in die Lösung (20) eingeleitet wird. 9. The method according to any one of claims 1 to 8, characterized in that the ozone (30) through a porous diffuser (31) below the starting material (10) is introduced into the solution (20).
10. Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, dass die Lösung (20) mit UV-Licht bestrahlt wird. 10. The method according to any one of claims 1 to 9, characterized in that the solution (20) is irradiated with UV light.
EP21754726.4A 2020-08-05 2021-07-21 Method for extracting gold and/or silver and/or at least one platinum metal Pending EP4192986A1 (en)

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GB851552A (en) * 1958-03-04 1960-10-19 Fairweather Harold G C Process for extracting gold and silver from their ores
US3635697A (en) 1969-09-30 1972-01-18 Us Interior Recovery of gold
GB0318017D0 (en) * 2003-08-01 2003-09-03 Shipley Co Llc Methods for recovering metals
CN1556050A (en) * 2003-12-31 2004-12-22 大连海事大学 Method of producing hydroxy free radical from reaction of ozone and exutad water
WO2016168933A1 (en) * 2015-04-21 2016-10-27 University Of Saskatchewan Methods for selective leaching and extraction of precious metals in organic solvents
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