EP1061144B1 - Method of preparing high purity gold from precious metal bearing nitrate solutions - Google Patents

Method of preparing high purity gold from precious metal bearing nitrate solutions Download PDF

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Publication number
EP1061144B1
EP1061144B1 EP00111133A EP00111133A EP1061144B1 EP 1061144 B1 EP1061144 B1 EP 1061144B1 EP 00111133 A EP00111133 A EP 00111133A EP 00111133 A EP00111133 A EP 00111133A EP 1061144 B1 EP1061144 B1 EP 1061144B1
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Prior art keywords
gold
solution
nitrate
ppm
high purity
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EP00111133A
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German (de)
French (fr)
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EP1061144A1 (en
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Martin Stettner
Horst Dr. Meyer
Matthias Dr. Grehl
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WC Heraus GmbH and Co KG
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WC Heraus GmbH and Co KG
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    • 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

Definitions

  • the invention relates to a method for producing gold of high purity from nitrate Precious metal solutions.
  • a method for producing a gold powder from particles of certain Size and shape revealed which is characterized in that a gold salt solution with a reducing agent, namely 1) hydroquinone or bromine, chlorine or low Alkyl substitution products of hydroquinone or mixtures thereof or 2) oxalic acid, one Alkaline salt of oxalic acid or mixtures thereof or 3) combinations of 1) and 2) in the presence of a protective colloid is reduced at a temperature in the range of 20 to 100 ° C.
  • a reducing agent namely 1) hydroquinone or bromine, chlorine or low Alkyl substitution products of hydroquinone or mixtures thereof or 2) oxalic acid, one Alkaline salt of oxalic acid or mixtures thereof or 3) combinations of 1) and 2) in the presence of a protective colloid is reduced at a temperature in the range of 20 to 100 ° C.
  • JP-A-09272927 describes the nitrate destruction with formaldehyde or formic acid in solutions containing precious metals, the redox potential being kept at ⁇ 800 mV and gold is precipitated at the same time as the nitrate removal.
  • the problem that arises is in particular in providing a method of producing high purity gold using just a few steps.
  • the nitrate in the noble metal solution is destroyed in a first step, for example by adding a reducing agent to the heated solution.
  • the gold ions are then reduced to gold by adding an acidic Fe 2+ solution, the concentration of H + of the Fe 2+ solution being at least 4 mol / l.
  • the precious metal solution previously prepared free of nitrates has a concentration of H + ions of at least 4 mol / l.
  • step b that is to say the addition of an acidic Fe 2+ solution to the nitrate-free processed noble metal solution, is carried out in a potential-controlled manner, since in this way the end of the reduction is relatively easy to recognize and targeted process control is thus possible.
  • nitrate destruction with formic acid or ascorbic acid is carried out because these substances specifically reduce nitrate to NO, but not gold ions.
  • the end of the reduction is announced by a significant drop in potential.
  • the end point is at 560 mV vs. Pt // Ag / AgCl to determine the necessary purity of the gold at the same time to achieve optimal gold yield.
  • the residual gold content in the mother liquor was 7 ppm or 0.08% of the gold used.
  • the purity of the gold sponge produced meets the 99.99% fine gold criteria according to the Amercian standard.
  • the following were found as impurities by means of GDL analysis: Ag 11 ppm Cu 1 ppm Pt ⁇ 3 ppm Fe 12 ppm Pd 25 ppm Mg ⁇ 2 ppm Rh ⁇ 1 ppm Mn ⁇ 1 ppm Ru ⁇ 1 ppm Ni ⁇ 1 ppm Al ⁇ 1 ppm Pb ⁇ 3 ppm Be ⁇ 1 ppm Sb ⁇ 5 ppm Bi ⁇ 5 ppm Si 15 ppm Ca ⁇ 1 ppm Sn ⁇ 5 ppm Cd ⁇ 5 ppm Te ⁇ 5 ppm Co ⁇ 3 ppm Zn 2 ppm Cr 1 ppm Total: 67 ppm corresponding to> 99.99% gold purity.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Gold hoher Reinheit aus nitrathaltigen Edelmetall-Lösungen.The invention relates to a method for producing gold of high purity from nitrate Precious metal solutions.

In DE-Z.: T. Havlik u.a.: "The leaching behaviour of tetrahedrite concentrate in nitrate solution" in: Metall, 52, 1998, 4, Seiten 210 bis 213, ist u. a. offenbart, dass aus Nitratlösungen Metalle in Anwesenheit von Eisenionen besonders gut durch Zementation herauslösbar sind.In DE-Z .: T. Havlik et al .: "The leaching behavior of tetrahedrite concentrate in nitrate solution" in: Metall, 52, 1998, 4, pages 210 to 213, is u. a. discloses that from nitrate solutions metals in Presence of iron ions can be removed particularly easily by cementation.

In DE 21 54 093 wird u. a. ein Verfahren zur Herstellung eines Goldpulvers aus Teilchen bestimmter Grösse und Gestalt offenbart, das dadurch gekennzeichnet ist, dass man eine Goldsalzlösung mit einem Reduktionsmittel, nämlich 1) Hydrochinon oder Brom-, Chlor- oder niedrig Alkyl-Substitutionsprodukte von Hydrochinon oder Gemischen davon oder 2) Oxalsäure, einem Alkalisalz von Oxalsäure oder Gemischen davon oder 3) Kombinationen von 1) und 2) in Gegenwart eines Schutzkolloids bei einer Temperatur in dem Bereich von 20 bis 100 °C reduziert.In DE 21 54 093 u. a. a method for producing a gold powder from particles of certain Size and shape revealed, which is characterized in that a gold salt solution with a reducing agent, namely 1) hydroquinone or bromine, chlorine or low Alkyl substitution products of hydroquinone or mixtures thereof or 2) oxalic acid, one Alkaline salt of oxalic acid or mixtures thereof or 3) combinations of 1) and 2) in the presence of a protective colloid is reduced at a temperature in the range of 20 to 100 ° C.

JP-A-09272927 beschreibt die Nitratzerstörung mit Formaldehyd oder Ameisensäure in Edelmetalle enhaltenden Lösungen, wobei das Redoxpotential bei < 800 mV gehalten und gleichzeitig mit der Nitratentfernung Gold ausgefällt wird.JP-A-09272927 describes the nitrate destruction with formaldehyde or formic acid in solutions containing precious metals, the redox potential being kept at <800 mV and gold is precipitated at the same time as the nitrate removal.

In RU-A-2120485 wird ein Verfahren zur Trennung von Platinmetalle aus goldhaltigen Lösungen beschrieben. Im laufe des Verfahrens wird nach der Thiosulfat-Fallüng Nitrat mit Urea zerstört. Nach der Abtrennung von Silber- und Bleichlorid durch Filtration wird dem Filtrat Eisen(II)-Sulfat zugegeben zur Fällung von Gold als Goldschlamm.In RU-A-2120485 a process for the separation of platinum metals from gold-containing Solutions described. In the course of the process, after the thiosulfate fall Nitrate destroyed with urea. After the separation of silver and lead chloride by filtration, iron (II) sulfate is added to the filtrate Precipitation of gold as gold sludge.

Es ist seit langem bekannt, Gold hoher Reinheit mittels SO2 aus nitrathaltigen Edelmetall-Lösungen zu gewinnen. Nachteilig bei diesen Verfahren ist die Notwendigkeit, die erhaltenen Produkte mehrfach umzulösen. Die hierdurch anfallende Vielzahl der einzelnen Verfahrensschritte bedingt einen hohen Kosten- und Zeitaufwand.It has long been known to obtain high purity gold from nitrate-containing precious metal solutions using SO 2 . A disadvantage of these processes is the need to redissolve the products obtained several times. The resulting large number of individual process steps requires a high cost and time.

Aus dem Vorgenannten ergibt sich das Problem, mit Hilfe eines neuartigen Verfahrens die oben genannten Nachteile zumindest teilweise zu beseitigen. Das sich ergebende Problem liegt insbesondere darin, ein Verfahren zur Herstellung von Gold hoher Reinheit bereitzustellen, das mit wenigen Arbeitsschritten auskommt. The problem arises from the above, with the aid of a novel method the above to at least partially eliminate the disadvantages mentioned. The problem that arises is in particular in providing a method of producing high purity gold using just a few steps.

Dieses Problem wird erfindungsgemäß durch ein Verfahren nach Anspruch 1 gelöst.According to the invention, this problem is solved by a method according to claim 1.

Beim erfindungsgemäßen Verfahren wird in einem ersten Schritt das in der Edelmetall-Lösung befindliche Nitrat zerstört, beispielsweise durch Zugabe eines Reduktionsmittels in die aufgeheizte Lösung. Anschließend werden die Goldionen durch Zugabe einer sauren Fe2+-Lösung zu Gold reduziert, wobei die Konzentration an H+ der Fe2+-Lösung mindestens 4 mol/l beträgt. Die vorher nitratfrei aufbereitete Edelmetall-Lösung weist eine Konzentration an H+-Ionen von mindestens 4 mol/l auf.In the method according to the invention, the nitrate in the noble metal solution is destroyed in a first step, for example by adding a reducing agent to the heated solution. The gold ions are then reduced to gold by adding an acidic Fe 2+ solution, the concentration of H + of the Fe 2+ solution being at least 4 mol / l. The precious metal solution previously prepared free of nitrates has a concentration of H + ions of at least 4 mol / l.

Von besonderem Vorteil ist es, wenn die Reduktion des Schrittes b), also die Zugabe einer sauren Fe2+-Lösung zur nitratfrei aufbereiteten Edelmetall-Lösung, potentialgesteuert durchgeführt wird, da auf diese Art und Weise das Ende der Reduktion relativ leicht zu erkennen und somit eine gezielte Verfahrenssteuerung möglich ist.It is particularly advantageous if the reduction in step b), that is to say the addition of an acidic Fe 2+ solution to the nitrate-free processed noble metal solution, is carried out in a potential-controlled manner, since in this way the end of the reduction is relatively easy to recognize and targeted process control is thus possible.

Weiterhin ist es von Vorteil, wenn die Nitratzerstörung mit Ameisensäure oder Ascorbinsäure durchgeführt wird, da diese Substanzen spezifisch Nitrat zu NO reduzieren, nicht jedoch Goldionen.Furthermore, it is advantageous if the nitrate destruction with formic acid or ascorbic acid is carried out because these substances specifically reduce nitrate to NO, but not gold ions.

Die Nitratzerstörung wird vorteilhafterweise bei einer Temperatur von T = + 80 ° C bis + 90 °C durchgeführt, um so eine effiziente Zerstörung des Nitrats zu gewährleisten.The nitrate destruction is advantageously at a temperature of T = + 80 ° C to + 90 ° C carried out so as to ensure efficient destruction of the nitrate.

Schließlich wird die in Schritt a) aufbereitete Lösung, also die nitratfrei gemachte Edelmetall-Lösung, vor Zugabe der Fe2+-Ionen-Lösung auf eine Temperatur von T = + 60 °C aufgeheizt, da auf diese Art und Weise das Gold feinkörniger und mit weniger Einschlüssen ausfällt.Finally, the solution prepared in step a), i.e. the nitrate-free noble metal solution, is heated to a temperature of T = + 60 ° C. before adding the Fe 2+ ion solution, since in this way the gold is finer-grained and fails with fewer inclusions.

Das nachfolgende Beispiel dient zur Erläuterung der Erfindung.The following example serves to explain the invention.

Verwendete ChemikalienChemicals used

  • Goldlösung in Königswasser
    c(Au) = 33,508 g/l, c(Pd) = 9,861 g/l, c(Pt) = 10,612 g/l    Gold solution in aqua regia
    c (Au) = 33.508 g / l, c (Pd) = 9.861 g / l, c (Pt) = 10.612 g / l
  • Eisen(II)sulfat, techn. FeSO4 . 7 H2O in 10 n HCI gelöstIron (II) sulfate, techn. FeSO 4 . 7 H 2 O dissolved in 10 n HCl
  • Salzsäure, techn., 10 nHydrochloric acid, technical, 10 n
  • Ameisensäure, techn., 85 %Formic acid, technical, 85%
Nitratzerstörungnitrate destruction

In einem heizbaren 1 l Laborreaktor mit Rückflußkühler und Glasrührer wurden 500 ml der goldhaltigen Ausgangslösung vorgelegt und mit 285 ml konz. Salzsäure versetzt, um eine Säurenormalität von 4 mol/l einzustellen. Anschließend ist die Lösung unter Rühren auf eine Temperatur von 100 °C erhitzt und die Temperatur während der Ameisensäurezugabe gehalten worden. Nun wurden mit Hilfe einer Schlauchpumpe über eine Zeitraum von 1 Stunde 45 ml Ameisensäure zudosiert. Während der Ameisensäurezugabe traten intensive NOx-Dämpfe auf, die am Ende der Nitratzerstörung nicht mehr zu beobachten waren. Das Redoxpotential ist während der Ameisensäurezugabe von einem Anfangspotential von 854 mV vs. Pt//Ag/AgCl auf einen Endwert von 723 mV vs Pt//Ag/AgCl abgefallen. Die Lösung wurde im Anschluß auf Raumtemperatur abgekühlt.In a heatable 1 liter laboratory reactor with reflux condenser and glass stirrer, 500 ml of the gold-containing starting solution and 285 ml conc. Hydrochloric acid added to an acid normality of 4 mol / l. The solution is then brought to a temperature with stirring heated from 100 ° C and the temperature maintained during the addition of formic acid Service. Now, with the help of a peristaltic pump, 45 ml Formic acid added. Intensive NOx vapors occurred during the addition of formic acid, which could no longer be observed at the end of the nitrate destruction. The redox potential is during the formic acid addition from an initial potential of 854 mV vs. Pt // Ag / AgCl a final value of 723 mV vs Pt // Ag / AgCl dropped. The solution was subsequently on Cooled to room temperature.

Au-ReduktionAu reduction

Die Lösung nach der Nitratzerstörung wurde in ein Becherglas überführt, wobei beobachtet wurde, daß bereits eine geringe Menge Gold ausgefallen war. Der Rückstand wurde komplett mit der Lösung in das Becherglas gegeben. Es ergab sich ein Lösungsvolumen von 1500 ml. Nun wurde auf dem Magnetrührer auf 60 °C aufgeheizt und unter ständiger Potentialkontrolle innerhalb von 2 Stunden 495 ml 0,5 n FeSO4-Lösung mit Hilfe einer Schlauchpumpe zudosiert. Das Redoxpotential fiel während der Reduktion von einem Anfangswert von 723 mV vs. Pt//Ag/AgCl auf den Endwert von 560 mV vs. Pt//Ag/AgCl ab. Nach Erreichen des Redoxpotentials von 560 mV vs. Pt//Ag/AgCl wurde die Eisensulfatzugabe gestoppt. Es wurde auf Raumtemperatur abgekühlt und der Rührer ausgeschaltet. Zum Teil haftete das ausreduzierte Gold am Rührer bzw. an der Redoxelektrode an, der Hauptteil jedoch befand sich am Boden des Becherglases. Der ausreduzierte Au-Schwamm wurde über eine Nutsche abfiltriert und mit 100 ml VE-Wasser gewaschen. Es wurden feine, blättrige Goldflitter erhalten. Diese wurden im Trockenschrank bei 100 °C getrocknet (Auswaage: 16,74 g) und zur Reinheitsanalyse per Röntgenfluoreszenz gegeben. Das Filtrat und das Waschwasser wurden vereinigt, gemischt, ausgelitert (2000 ml) und eine Standard-DCP-Analyse veranlaßt.The solution after the nitrate destruction was transferred to a beaker, and it was observed that a small amount of gold had already precipitated out. The residue was completely added to the beaker with the solution. The result was a solution volume of 1500 ml. The mixture was then heated to 60 ° C. on a magnetic stirrer and 495 ml of 0.5 n FeSO 4 solution were metered in with the aid of a peristaltic pump over the course of 2 hours, with constant monitoring of the potential. The redox potential fell during the reduction from an initial value of 723 mV vs. Pt // Ag / AgCl to the final value of 560 mV vs. Pt // Ag / AgCl. After reaching the redox potential of 560 mV vs. Pt // Ag / AgCl the iron sulfate addition was stopped. It was cooled to room temperature and the stirrer was switched off. Some of the reduced gold adhered to the stirrer or redox electrode, but the main part was on the bottom of the beaker. The reduced Au sponge was filtered through a suction filter and washed with 100 ml of demineralized water. Fine, flaky gold flakes were obtained. These were dried in a drying cabinet at 100 ° C. (weight: 16.74 g) and added for X-ray fluorescence for purity analysis. The filtrate and wash water were combined, mixed, filtered (2000 ml) and a standard DCP analysis was carried out.

Es werden für die nachfolgende Versuchsauswertung folgende Reaktionsgleichungen zugrunde gelegt: 1. 3 HCOOH + 2 HNO3 ↑ + 2 NO ↑ + 4 H2O oder 2. HCOOH + 2 HNO3 = CO2 ↑ + NO2 ↑ + H2O 3. H[AuCl4] + 3 FeSO4 = Au ↓ + FeCl3 + Fe2(SO4)3 + HCI The following reaction equations are used for the following test evaluation: 1. 3 HCOOH + 2 HNO 3 ↑ + 2 NO ↑ + 4 H 2 O or 2. HCOOH + 2 HNO 3 = CO 2 ↑ + NO 2 ↑ + H 2 O 3. H [AuCl 4 ] + 3 FeSO 4 = Au ↓ + FeCl 3 + Fe 2 (SO 4 ) 3 + HCl

Für die Nitratzerstörung wurden in diesem Versuch für 500 ml Ausgangslösung 45 ml 85%ige Ameisensäure verbraucht. Am Ende der Nitratzerstörung war wenig Gold ausgefallen, welches jedoch nicht separat gehalten werden braucht.For the nitrate destruction, 45 ml of 85% strength were used in this experiment for 500 ml of starting solution Formic acid consumed. At the end of the nitrate destruction, little gold had failed but does not need to be kept separately.

Das Ende der Reduktion kündigt sich durch einen deutlichen Potentialabfall an. Der Endpunkt ist bei 560 mV vs. Pt//Ag/AgCl festzulegen, um die nötige Reinheit des Goldes bei gleichzeitiger optimaler Goldausbeute zu erzielen.The end of the reduction is announced by a significant drop in potential. The end point is at 560 mV vs. Pt // Ag / AgCl to determine the necessary purity of the gold at the same time to achieve optimal gold yield.

Die zugesetzte Menge Eisensulfatlösung (495 ml) mit 0,5 mol/l entspricht nach Gleichung (3) einer theoretischen Goldmenge von 16,25 g. Im Versuch wurden 16,74 g Gold ausreduziert, so daß die tatsächlich benötigte Menge Eisensulfat ca. 97 % der Stöchiometrie entspricht.The added amount of iron sulfate solution (495 ml) with 0.5 mol / l corresponds to equation (3) a theoretical amount of gold of 16.25 g. In the experiment, 16.74 g of gold was reduced, so that the amount of iron sulfate actually required corresponds to approximately 97% of the stoichiometry.

Der Restgehalt Gold in der Mutterlauge betrug 7 ppm oder 0,08 % des eingesetzten Goldes. Die Reinheit des erzeugten Goldschwammes erfüllt die Kriterien von Feingold 99,99 % nach dem Amercian Standard. Es wurden als Verunreinigungen mittels GDL-Analyse festgestellt: Ag   11 ppm Cu   1 ppm Pt <   3 ppm Fe   12 ppm Pd   25 ppm Mg <   2 ppm Rh <   1 ppm Mn <   1 ppm Ru <   1 ppm Ni <   1 ppm Al <   1 ppm Pb <   3 ppm Be <   1 ppm Sb <   5 ppm Bi <   5 ppm Si   15 ppm Ca <   1 ppm Sn <   5 ppm Cd <   5 ppm Te <   5 ppm Co <   3 ppm Zn   2 ppm Cr   1 ppm Summe: 67 ppm entsprechend > 99,99 % Goldreinheit. The residual gold content in the mother liquor was 7 ppm or 0.08% of the gold used. The purity of the gold sponge produced meets the 99.99% fine gold criteria according to the Amercian standard. The following were found as impurities by means of GDL analysis: Ag 11 ppm Cu 1 ppm Pt <3 ppm Fe 12 ppm Pd 25 ppm Mg <2 ppm Rh <1 ppm Mn <1 ppm Ru <1 ppm Ni <1 ppm Al <1 ppm Pb <3 ppm Be <1 ppm Sb <5 ppm Bi <5 ppm Si 15 ppm Ca <1 ppm Sn <5 ppm Cd <5 ppm Te <5 ppm Co <3 ppm Zn 2 ppm Cr 1 ppm Total: 67 ppm corresponding to> 99.99% gold purity.

Claims (5)

  1. Process for the preparation of gold having a high purity of ≥ 99.99% from nitrate-containing noble metal solutions, comprising the following steps:
    a) destruction of nitrate in the noble metal solution,
    b) addition of an acidic Fe2+ solution, the H+ ion concentration of which is at least 4 mol/l, with reduction of gold ions,
    to the solution which is prepared in step a) and the H+ ion concentration of which is at least 4 mol/l.
  2. Process according to Claim 1, characterized in that the reduction of step b) is carried out with potential control.
  3. Process according to either of Claims 1 and 2, characterized in that the nitrate destruction is carried out using formic acid or ascorbic acid.
  4. Process according to any of Claims 1 to 3, characterized in that the nitrate destruction is carried out at a temperature of T = +80 to +90°C.
  5. Process according to any of Claims 1 to 4, characterized in that the solution prepared in step a) is heated to a temperature of T = +60°C before addition of the Fe2+ ion solution.
EP00111133A 1999-06-18 2000-05-24 Method of preparing high purity gold from precious metal bearing nitrate solutions Expired - Lifetime EP1061144B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19928028A DE19928028C1 (en) 1999-06-18 1999-06-18 High purity gold is recovered from nitrate solution by nitrate decomposition to obtain a highly acidic solution from which gold is recovered by ferric ion addition
DE19928028 1999-06-18

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EP1061144A1 EP1061144A1 (en) 2000-12-20
EP1061144B1 true EP1061144B1 (en) 2003-10-29

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US (1) US6331200B1 (en)
EP (1) EP1061144B1 (en)
DE (2) DE19928028C1 (en)
ZA (1) ZA200003019B (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2103659A (en) * 1981-08-12 1983-02-23 Robert Henry Perrin Recovery of precious metals from solutions
JPH05222465A (en) * 1992-02-10 1993-08-31 Sumitomo Metal Mining Co Ltd Method for removing nox from palladium-containing solution
JPH09272927A (en) * 1996-04-08 1997-10-21 Sumitomo Metal Mining Co Ltd Removing method of nitrogen oxides from palladium-containing solution
RU2120485C1 (en) * 1997-07-03 1998-10-20 Щелковский завод вторичных драгоценных металлов Method of removing platinum metals from material containing these metals

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ZA200003019B (en) 2001-01-09
EP1061144A1 (en) 2000-12-20
DE19928028C1 (en) 2000-08-17
US6331200B1 (en) 2001-12-18
DE50004219D1 (en) 2003-12-04

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