DE2340157B2 - Process for the separation and purification of gold which is present in a mixture with the metals of the platinum group - Google Patents

Description

The present invention relates to the separation and purification of gold in a mixture with the Metals of the platinum group is present.

In general, the five metals ^ platinum group, ie platinum, palladium, iridium, ruthenium and rhodium are, in nature, together with gold before, and these six elements must be separated and purified from each other to find a useful application in trade and industry can. As a rule, a separation of these elements into two groups is first carried out by treating the base mixture, which generally consists of a rough stone leach residue or sludge, with aqua regia, and in this case the platinum, palladium and gold go in solution, while the iridium. Ruthenium and rhodium essentially remain in the residue that is obtained in this process. The two groups of metals thus obtained are then subjected to separation procedures, which are generally lengthy and complicated, in order to separate and purify the individual metals.

The present invention relates to a method for separating gold from the metals Platinum group, which is easier to carry out, at least in the case where the end product is gold higher Purity is needed, and / or which is the separation of the metals of the platinum group and gold relieved.

The method according to the invention for separating and cleaning gold from a work-up concentrate that contains money in addition to metals of the platinum group, by means of treating the concentrate with aqua regia and further work-up of the lead-free solution, which contains gold and one or more metals of the platinum group, by reducing the gold compound with H- ¹ O: now consists in evaporating the solution to dryness, taking up the residue at least once in nitric acid and evaporating to dryness, and redissolving the residue in nitric acid. Hydrogen peroxide is added, the resulting lot-ing is heated to boiling, and the gold precipitate obtained is collected and subjected to a cleaning treatment.

Another feature of the invention is that the gold precipitate can be cleaned in Aqua regia dissolves, the solution evaporates to dryness, the salts obtained with ammonium hydroxide solution boils, the solution is cooled and filtered, the residue is dissolved in boiling nitric acid and filtered, the filtrate passes through a cation exchanger, which washes the gold out of the cation exchanger, the process with Hydrogen peroxide boils and the gold precipitate obtained is isolated.

The filtrate can also be obtained from the gold powder obtained after boiling with hydrogen peroxide Boil the solution with formic acid to recover the remaining gold and bring the solution to pH 5 adjust and return the filtered precipitate to the work process.

Finally, the solution, evaporated to dryness, can contain gold and one or more metals the platinum group in aqua regia taken up twice with nitric acid and evaporated to dryness will.

It is useful when treating the residue dissolved in nitric acid with hydrogen peroxide to use an amount of hydrogen peroxide of about 1 ml per gram of gold to be felled.

Evaporation to dryness with nitric acid is carried out to remove the nitrosochloride complexes existing metals to form.

Still further features of the invention are evident from the following description of a preferred embodiment the same, which includes a specific example in which the quantities of reagents used are given in brackets.

Generally, concentrates of the platinum group metals and gold are used as raw rock leachate or sludge obtained, which - starting from this stage - process! be to the desired Metals, and for this reason the following description continues with the processing of a such raw stone leach residue or sludge.

In the course of the description, reference is made to the flow charts of which

Fig. 1 is a flow diagram illustrating the general, not part of the invention processing of the raw stone leaching residue illustrates, and

Fig. 2 shows a flow diagram, welch.s the further inventive separation and purification of the Gold explained.

The sludge used as the starting material had the following composition:

element (Pt) % 6.92 platinum (Pd) 3.04 palladium (Au) 0.59 gold (Rh) 0.32 Rhodium (Ru) 0.60 Ruthenium (Ir) 0.08 iridium (Ag) 0.03 silver (AhO ₁ ) 3.60 Aluminum oxide (Sb) 0.05 antimony (Bi) 0.11 bismuth (CaO) 0.49 Calcium oxide (Cu) 6.91 copper (Co) 0.19 cobalt (Fe) ■ 1.57 iron (MgO) 0.35 Magnesia (Ni) 3.50 nickel [Cn (H2O) _m J 23.1 Organic substances (K) 0.03 potassium (SiO ₂ ) 12.92 Silicon dioxide (N / A) 9.25 sodium (S) 19.63 Sulfur (total) (Te) 0.29 Tellurium (Zn) <0.001 zinc Other components (as difference) 3.43 + 02 + H2O

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First, 2.5 kg of the slurry into a stream of air for two hours at 600 ⁰ C ge / östet, in order to transfer all the sulfides and the free sulfur in this stage 1 into oxides.

The roasted material was refluxed and stirred with 20% H2SO4 (3 liters) in stage 2 for two hours cooked, then cooled to about 55 ° C and filtered to remove most of the base metals present to detach.

Calcium oxide (CaO) was added to the filtrate in stage 3 to remove all of the nickel contained in the filtrate, Precipitate copper and the platinum group metals and gold. This precipitate was collected, and so did you contained 30 mg platinum, 100 mg palladium, 10 mg gold, 50 mg rhodium and 40 mg iridium. This precipitation would be fed back into the raw stone melting plant in practical operation.

The residue left after the sulfuric acid treatment was then used in stage 4 for three hours Aqua regia (1.5 liters) leached out. This aqua regia leach and all other aqua regia leaches were carried out in the following way:

The material was boiled with the required amount ^ ₅ hydrochloric acid (HCI) for 30 minutes under reflux. The required amount of nitric acid (HNOj) was gradually added to Hann over a period of 60 minutes.

55 The mixture was left on for the remainder of the time (i.e. 1/2 hour) left to simmer.

Sodium bromide (NaBrO3) (30 g) was then added to the solution, which was boiled for an additional 30 minutes after the solution was diluted with water (1.5-3 liters) to make the platinum group metals and gold most stable Oxidation stages to oxidize. The pH was then adjusted (about 6O ⁰ C) (1 kg) to 6.5 with sodium carbonate to all metals - with the exception of platinum - to precipitate as oxides hydraiisierte. The solution was left to stand for 20 minutes and then filtered or suction filtered under vacuum. In this manner, the fla.in was removed so as to reduce by about 50% the majority of the platinum group metals and gold which had to be alloyed with lead.

Formic acid (0.2 liters) was added to the filtrate (+ 90% platinum [Pt] in the feed) in step 5, and the solution was refluxed with stirring for 5 hours. In stage 6, sodium carbonate (NasCO}) (0.3 kg) was added in portions over 1 hour until a pH of 5.0 was reached. After that it was the solution was boiled for a further 60 minutes, cooled to 60 ° C. and filtered under vacuum. These stages 5 and 6 were performed to precipitate the platinum in the solution.

The filtrate was in step 7 over an anion exchange column managed and the process eliminated. This process contained 100 mg Pt, 10 mg Pd, 10 mg Au, 1 mg Rh and 25 mg Ir.

The precipitate was dissolved in aqua regia (1.0 liter) in step 8, the solution was cooled and filtered. Of the The residue obtained consisted of silver chloride (AgCl).

This aqua regia filtrate contained most of the platinum. This platinum was with the bulk of palladium and gold are united in the manner described below, and the separation of these Platinum group metals was performed by a separate procedure.

The combination of residue and precipitation - accrued during the initial aqua regia leaching and the sodium carbonate precipitation in stage 4 (+ 140Og) - was with a flux A and a Flux B, which are defined below, mixed and in stage 9 75 minutes at 1140 ° C melted together. The consequence of this is that the rhodium predominantly consists of a aqua regia-insoluble form is converted into e'.ne aqua regia-soluble form. At the same time, the Solubility of the iridium and ruthenium in aqua regia continues to be hot. 2.5 kg of the Flux A per kg of residue and 335 g of flux B per 100 g of the metals to be collected Platinum group plus gold used. These fluxes had the following compositions:

Flux A (active flux) (3.5 kg)

(1) Borax Na2ß4O? 20% (0.75 kg)

(2) Sodium carbonate NaKXb 80% (2.75 kg)

Flux B (collector) (0.55 kg)

(1) Black lead PbO 90% (0.5 kg)

(2) Charcoal C 10% (0.05 kg)

The molten material was poured into iron molds and allowed to cool in them. The thus obtained Lead regulus was separated from the slag, and the

Slag was crushed and collected, but in practical operation it would become a raw stone smelting plant to be led back. The slag contained 520 mg Pt. 230 mg Pd, 45 mg Au, 24 mg Rh, 45 mg Ru (ruthenium) and 5 mg of Ir.

The lead regulus was crushed and then put into Stage 10 5 hours under reflux with 20% HNOi (5.5 liters) boiled to remove the lead. The solution was cooled to 55 ° C and under vacuum filtered. The residue was used in a later aqua regia leaching stage, which is designated as stage 11, supplied.

In stage 12, formic acid (0.05 liters) was added to the filtrate from the nitric acid leach of stage 10 added and the pH adjusted to 2.0 with sodium carbonate Na2CCb (0.3 kg) to avoid all metals To precipitate the platinum group and the gold that had been dissolved by the nitric acid. The solution was then stirred for 5 hours at room temperature and filtered under vacuum.

The resulting precipitate was combined with the residue obtained from the nitric acid leach step in Level 10 was accrued, and this combination of materials was considered the level 11 aqua regia leach level Feeding supplied. In stage 13, ΝΗίΟΗ was added to the filtrate to remove the lead and any To precipitate platinum group metals plus gold, and that precipitate was dried and annealed, and it would recycled to the melt bleaching stage in practical operation, d. H. to level 9.

The combination of residue and precipitation was in stage 11 with aqua regia (0.75 liters) Boiled under reflux for 3 hours. The solution was cooled to 55 ° C and filtered under vacuum. Of the Residue formed part of the feed to the rhodium, iridium and separation process Ruthenium from each other. This residue contained 850 mg Pt, 700 mg Pd, 100 mg Au, 5000 mg Rh. 14 720 mg Ru and 1420 mg Ir. The precious metals usually make up approximately 50% of this as metal concentrate while the remaining 50% consists of lead chloride (PbCb).

The stoichiometric amount of H2SO4 plus became the filtrate from the aqua regia leaching stage of stage 11 10% excess (100 ml of a 50% H2SO4) was added in stage 14 to reduce the amount contained in this solution Precipitate lead. The solution was boiled for 30 minutes, cooled to 55 ° C and filtered.

The precipitated lead sulfate was converted into hot lead (PbO) by annealing in stage 15 and was again ready for use for the return to the stage of fused enamel.

The filtrate from the lead precipitation step was evaporated to dryness in stage 16, and the resulting salts were annealed for 2 hours at 600 ⁰ C. As has been found, this temperature is important in order to make the rhodium in the residue insoluble in aqua regia.

The glow product was refluxed with aqua regia (0.75 liters) for three hours in step 17. The solution was cooled and filtered under vacuum.

The residue was with the residue from the aqua regia leach stage of stage 11, which after alloying was carried out, combined to give a combined feed for the Separation of the secondary group of platinum group metals, namely rhodium. Ruthium and iridium, which had the following contents of platinum metals and gold: 1130 mg Pt, 850 mg Pd, 120 mg Au. 7480 mg Rh. 14,920 mg Ru and 1,720 mg Ir.

That in the last aqua regia leaching stage of the The filtrate obtained from stage 17 was with that Filirai combined that in the aqua regia leach stage of stage 8, which had been carried out with the metals, which had been dissolved in the leaching stage 4 carried out at the beginning, had accumulated. so one Charging material for the processes for the separation of platinum, palladium and gold (stages 18 and 19) too to win. This charge had the following levels of platinum group metals and gold: 171,210 mg Pt, 74,790 mg Pd, 14 560 mg Au, 200 mg Rh, 25 mg Ru and 210 mg Ir.

The filtrates from the aqua regia leaching (1.75 l) were dried in polyfluoroethylene dishes evaporated. The residue was heated in stage 18 for 30 minutes, with 2 times 0.55 l of concentrated nitric acid taken up and again evaporated to dryness. The salts were heated again for 30 min and in step 19 with 21 boiled 10% nitric acid. The solution obtained, which contained 150 g / l noble metals, was with once 2 l and then 3 l of water diluted. 300 ml H2O2 were added, the solution boiled for 30 min, aul Chilled 55 ° C and filtered under vacuum.

The precipitate was transferred to gold purification stage 20.

This precipitate obtained through the practice of the present invention. contained the following ingredients: 50 mg Pt. 10 mg Pd. 13,750 mg Au, 40 mg Rh and a trace of ruthenium.

This impure gold was dissolved in aqua regia (0.06 liters) in stage 20. The solution turned to dryness evaporated and the salts were boiled in step 21 with Nr-UOH (0.06 liters) to remove all silver chloride in Bring solution. The solution was cooled to 55 "C and filtered. The filtrate, which contained only a trace of silver, was discarded, but would in the technical Scale can be traced back.

₄ q The residue was dissolved in boiling 5% HNO3 (0.6 liters) in stage 22. The insoluble residue was filtered off and in practical operation it would be returned to a suitable point in the work-up process.

The filtrate was in step 23 over a cation exchange resin directed; the resin held back the base metals, and the gold became with water washed out.

In step 24, H2O2 (0.03 liter; added and cooked for 30 minutes to get there; Fell goid. After cooling to 55 ° C, the Solution filtered.

The dried precipitate consisted of the finished gold, which had a purity of over 99.97% gold.

_5S The total yield of gold was 9000 mg, wa; corresponds to a value of approximately 60%.

The gold in the filtrate was removed in step 25 by boiling the solution with formic acid (12 ml) and adjusting the pH of the solution was precipitated to 5.0 with Na2CO3 (10 g)

5ο The solution was cooled and filtered. The Filtra was discarded; it did not contain any precious metals. Since: precipitated metal would in practical operation zi to a suitable stage of the separation process.

By using the method according to the invention, gold of high purity can thus be obtained in a way that is easy and effective to perform.

For this purpose 2 sheets of drawings

Claims (5)

Patent claims: 1. Process for separating and purifying gold from a concentration concentrate. which contains gold in addition to platinum group metals, by treating the concentrate with aqua regia and further processing the lead-free solution, which contains gold and one or more platinum group metals, by reducing the gold compound with H2O2. characterized in that the solution is evaporated to dryness, the residue is taken up at least once in nitric acid and evaporated to dryness, the residue is redissolved in nitric acid, hydrogen peroxide is added, the resulting solution is heated to boiling and the resulting gold precipitate is collected and subjected to a cleaning treatment. 2. The method according to claim 1, characterized in that that the gold precipitate is dissolved in aqua regia for cleaning, the solution evaporated to dryness, the salts obtained with it Ammonium hydroxide solution boils, the solution cools and filtered, the residue in boiling nitric acid dissolves and filtered, the filtrate passes through a cation exchanger, the gold from the Washes out the cation exchanger, the process boils with hydrogen peroxide and the obtained Gold precipitate isolated. 3. The method according to claim 1 or 2. characterized ^ o characterized in that the filtrate is obtained from gold precipitate obtained after boiling with hydrogen peroxide to obtain residual gold boils with formic acid and adjusts the pH of the solution to 5 with sodium carbonate and the filtered off precipitate in the processing process returns. 4. The method according to claim 1 to 3, characterized in that the evaporated to dryness Dissolve gold and one or more platinum group metals in aqua regia twice takes up with nitric acid and evaporates to dryness. 5. The method according to claim 1 to 4, characterized in that in nitric acid dissolved residue from treatment with nitric acid with about 1 ml of hydrogen peroxide per gram of the gold to be dropped.