DE2340157C3 - 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 platinum group metals, platinum, palladium, iridium, ruthenium, and rhodium, occur naturally with gold, and these six elements must be separated and purified in order to find useful commercial and industrial uses . ^ ₀ As a rule, these elements are first separated into two groups, namely by treating the basic mixture, which generally consists of a raw stone leach residue or sludge, with aqua regia, and in this case the platinum, palladium and the Gold in solution, while the iridium, ruthenium and rhodium essentially remain in the residue which is obtained in this process Separate and clean individual metals.

The present invention relates to a method for separating gold from the metals Platinum group, which is to be carried out more densely, at least in the case in which the end product is gold higher Purity is needed, and / or which is the separation of the metals of the platinum group and gold facilitated.

The method according to the invention for separating and cleaning gold from a processing plant, which contains gold in addition to metals of the platinum group, 'by treating the concentrate with Aqua regia and further processing of the blcifrci made solution, the gold as well as one or more Metali- · * of the platinum group, by reduction of the The gold compound with H2O2 consists in evaporating the solution to dryness, the residue at least once in nitric acid and evaporated to dryness, the residue again in nitric acid dissolves, hydrogen peroxide is added, the resulting solution is heated to boiling and the resulting solution GoldnieJerschlag collects and subjects it 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 precipitated from the GoIcI precipitate 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 evaporated solution of 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.

Steaming 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, which - starting from this stage - are processed to produce 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 diagram Referenced by those

fig-1 e> n is a flow diagram showing the »!! mean work-up not belonging to the invention of the raw leach residue tj is illustrated and

Figure 2 is a flow diagram illustrating the further separation and purification of the gold according to the invention explained.

The sludge used as the starting maierial showed the following composition:

Element Λ-,

platinum
palladium

Rhodium

Ruthenium

iridium

silver

Aluminum oxide

antimony

bismuth

Caleium Oxide

copper

cobalt

Magnesia

nickel

Organic substances

potassium

Silicon dioxide

sodium

Sulfur (total)

Tellurium

Other components

+02 + H2O

(Pt) 6.92 (Pd) 3.04 (Au) 0.59 (Rh) 0.32 (Ru) 0.60 (Ir) 0.08 (Ag) 0.03 (AIjOi) 3.60 (Sb) 0.05 (Bi) 0.11 (CaO) 0.49 (Cu) 6.91 (Co) 0.19 (Fe) 4.57 (MgO) 0.35 (Ni) j, 50 ten [Cn (H-O) π.] 23.1 (K) 0.03 (SiO ₃ ) 12.92 (N / A) 9.25 (S) 19.63 (Te) 0.29 (Zn) <0.001 (as difference) 3.43

15th

100.00

40

First, 2.5 kg of the sludge was roasted in a stream of air for two hours at 600 "C to all In this stage 1, sulfides and the free sulfur are converted into oxides.

In stage 2, the roasted material was refluxed with stirring with 20% H> SO4 (3 liters) for two hours cooked, then cooled to about 55 ° C and filtered to order to extract most of the base metals present.

In stage 3, calcium oxide (CaO) was added to the filtrate in order 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 of 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 refluxed with the required amount of hydrochloric acid (HCl) for 30 minutes. The required amount of nitric acid (HNOi) was gradually added to Hann over a period of 60 minutes.

45

55 /: hours The mixture was used for the rest of the time (i.e. let the) boil further.

Sodium bromate (NaBrOs) (30 g) was then added to the solution, which was boiled for an additional 30 minutes after the solution had been diluted with water (1.5 to 3 hours) to make the platinum group metals and gold most stable Oxydaiionsiufen to oxidize. The pH was then adjusted with sodium carbonate (about 60'C) [I kg; set to 6.5. in order to precipitate all metals - with the exception of platinum - as hydrated oxides. The solution was left to stand for 20 minutes and then filtered or suction filtered under vacuum. In this way the platinum 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 liter) was added to the filtrate (+ 90% platinum [Pt] in the feed) in stage 5, and the solution was refluxed with stirring for 5 hours. In stage 6, sodium carbonate (Na ^ COj) (0.3 kg) was added in portions over the course of 1 hour until a pH of 5.0 had been 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 fe were done to keep the platinum in solution to fell.

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

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

This aqua regia filirate 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 royal water leaching and the sodium carbonate precipitation in stage 4 (+1400 g) - was mixed with a flux A and a flux B, which are defined below, and in stage 9 75 Melted together at 1140 ^c C for minutes. The consequence of this is this. that the rhodium is mainly converted from an aqua regia insoluble form into an aqua regia soluble form. At the same time, the solubility of iridium and ruthenium in aqua regia is further reduced. 2.5 kg of flux A per kg of residue and 335 g of flux B per 100 g of platinum group metals plus gold to be collected were used. These fluxes had the following compositions:

Flux A (active flux) (3.5 kg)

(1) Borax Na2B1 O; 20% (0.75 kg)

(2) Sodium carbonate NarCOs 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 would can be returned to the raw stone melting plant in practical operation. The slag contained 520 mg Pt. 230 mg Pd, 45 mg Au, 24 mg Rh, 45 mg Ru (ruthenium) and 5 mg Ir.

The lead regulus was crushed and then put into Stage 10 refluxed with 20% HNOt (5.5 liters) for 5 hours to remove the lead. the Solution was cooled to 55 ° C and filtered under vacuum. 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 with sodium carbonate Na2COj (0.3 kg) adjusted to 2.0 to include all metals of the platinum group and the goid, which are caused by the nitric acid had been resolved to fail. The solution was then stirred for 5 hours at room temperature and under Vacuum filtered.

The resulting precipitate was combined with the residue obtained from the nitric acid leach step in Level 10 was incurred. and this combination of materials was considered the Stage 11 aqua regia leach Feed added In stage 13, NH4OH was added to the filter to remove the lead and any To precipitate platinum group metals plus gold, and that precipitate was dried and annealed, and it would be returned to the fused lead tank 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. 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 out. while the remaining 50% consists of lead chloride (PbCb).

To the filtrate from the aqua regia leach step 11, the stoichiometric amount of H2SO4 was plus 10% excess (100 ml of a 50% H2SO4) ₄₅ In stage 14 is added to the solution contained in these lead precipitate. 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, as was found for 2 hours at ⁰ C 6OO, this temperature is important to make königswasserunlöslich to the rhodium in the residue.

The glow product was refluxed with aqua regia (0.75 liters) for three hours in step 17. ^ ₀ 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, ruthinm 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.

The filtrate obtained in the last aqua regia leaching stage of stage 17 became with that filtrate combined, that in the aqua regia leach stage of level 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 Feed material for the processes for the separation of platinum, palladium and gold (stages 18 and 19) 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 (1.751) were evaporated to dryness in polyfluoroethylene dishes. The residue was heated in stage 18 for 30 min, taken up with 2 times 0.55 l of concentrated nitric acid and again evaporated to dryness. The salts were heated again for 30 minutes and boiled in stage 19 with 21 10% strength nitric acid. The solution obtained, which contained 150 g / l noble metals, was diluted with once 2 liters and then 3 liters of water. 300 ml of H2O2 were added, the solution was boiled for 30 min, ^{cooled to 55 °} C. and filtered under vacuum.

The precipitate was transferred to the 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 NH4OH (0.06 liter) to remove all silver chloride in Bring solution. The solution was cooled to 55 ° C and filtered. The filtrate, which only contained a trace of silver, was discarded, but would be technically Scale can be traced back.

The residue was dissolved in boiling 5% HNO3 (0.6 liter) in step 22. The insoluble residue was filtered off, and in practical operation it would become a suitable point in the work-up process to be led back.

The filtrate was passed over a cation exchange resin in stage 23; the resin kept the more ignoble Metals returned, and the gold was washed out with water.

H2O2 (0.03 liters) was added to the drain in step 24 and the whole thing boiled for 30 minutes in order to: Fell goid. After cooling to 55 ° C., the solution was filtered off.

The dried precipitate consisted of the finished gold, which had a purity of over 9957% gold.

The total gold yield was 9000 mg, which 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) The solution was cooled and filtered. The filter was discarded; it did not contain any precious metals. There precipitated metal would be returned to an appropriate stage of the separation process in practical operation be guided.

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

For this purpose 2 sheets of drawings

Claims (5)

Claims:> "' 1. Process for separating and purifying gold from a work-up concentrate, the gold in addition to metals of the platinum group, by treating the concentrate with aqua regia and further processing of the lead-free solution, the gold and one or more metals of the Contains platinum group, by reducing the gold compound with H2O2, characterized that the solution is evaporated to dryness, the residue at least once in nitric acid absorbs and evaporates to dryness, redissolve the residue in nitric acid, hydrogen peroxide adds, the resulting solution is heated to boiling and collects the resulting gold precipitate and subjected to a cleaning treatment. 2. The method according to claim 1, characterized in that the gold precipitate for Purification dissolves in aqua regia, the solution evaporates to dryness, the salts obtained with 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 in that the filtrate from after Boiling the gold precipitate obtained with hydrogen peroxide to recover the remaining gold boils with formic acid and the pH of the solution is adjusted to 5 with sodium carbonate and the the precipitate filtered off is returned to the work-up process. 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 precipitated.