DE2340192B2 - Process for separating iridium from the other platinum group metals and gold and for cleaning iridium - Google Patents

Description

The present invention relates to the separation of iridium from mixtures of platinum group metals and gold and the purification of iridium.

In general, the five platinum group metals, platinum, palladium, iridium, ruthenium, and rhodium, occur in nature with Gofd, and these six elements must be separated and purified to find useful commercial and industrial uses . In general, these elements are first separated into two groups by trading the basic substance, which usually consists of a raw stone leach residue or sludge, ίο with aqua regia, and in this case platinum, palladium and gold go into solution, while iridium, Ruthenium and rhodium essentially remain in the residue. The two groups of metals obtained in this way are then subjected to separation processes, which are generally lengthy and complicated, in order to separate and purify the individual metals.

192 y

The present invention relates to a method for separating the iridium from the others Platinum group metallers and gold, which is more convenient to perform and which enables a product of higher purity.

In the context of the present invention, a process for separating the iridium from the other metals of the platinum group and from gold is accordingly claimed, which consists in converting the dissolved metals of the platinum group and gold into their lower oxidation levels by adding hydrogen peroxide to the solution treated in an acidic medium at elevated temperatures, adjusts the pH of the solution to approximately 9, separates the precipitation from the iridium and platinum remaining in solution and then converts the platinum and iridium ia their highest valence levels, through the action of sodium bromate in acid Medium at elevated temperatures, and then adjust the pH of the solution to about 6.5 to 7.5 to precipitate the iridium and keep the platinum in solution.

Another feature of the invention is that one starts with a feed which is iridium contains in a mixture with relatively small amounts of the other metals of the platinum group and gold, in which the iridium through previous work stages. has already been enriched.

Further features of the present invention will be apparent from the description below.

Reference is made to the flow charts of which

F i g. 1 is a flow diagram showing the first separation of the metals in FIG Platinum group and gold from a rough stone leach residue illustrates, and

F i g. Figure 2 is a flow diagram illustrating the purification of iridium according to the invention.

The sludge used as the starting material in this embodiment of the invention contained the the following components:

Element%

Platinum (Pt) 6.92

Palladium (Pd) 3.04

Gold (Au) 0.59

Rhodium (Rh) 0.32

Ruthenium (Ru) 0.60

Iridium (Ir) 0.08

Silver (Ag) 0.03

Aluminum oxide (Al ₂ O ₃ ) 3.60

Antimony (Sb) 0.05

Bismuth (Bi) 0.11

Calcium Oxide (CaO) 0.49

Copper (Cu) 6.91

Cobalt (Co) 0.19

Iron (Fe) 4.57

Magnesium oxide (MgO) 0.35

Nickel (Ni) 3.50

Organic substances [C _n (H ₁ O) _n ,]. · 23.1

Potash (K) 0.03

Silica (SiO ₁ ) 12.92

Sodium (Na) 9.25

Sulfur (Total) (S) 19.63

Tellurium (Te) 0.29

Zinc (Zn) <0.001

Other components + O ₂ + H, 0 ^w .

(as difference) 3.43

100.00

In general, the iridium is made from rough die-casting residues which are usually the other platinum group metals and likewise Contain gold.

Initially, in stage 1, 2.5 kg of the sludge were used

Roasted for 2 hours in a stream of air at 600 ° C, xaa converting all sulfides and the free sulfur into oxides.

The roasted material was boiled in step 2 with 20% ι H ₁ SO * (31) for 2 hours under reflux and stirring to ™, then ^{cooled to about 55 0} C and filtered, xaa to dissolve out most of the base metals present.

Calcium oxide (CaO) was added to the FUtrate in stage 3 to remove all nickel, copper, the metals Platinum group and the gold in the FUtrat to precipitate. This precipitate was collected and it contained 30 mg Platinum, 100 mg palladium, 10 mg gold, 50 mg rhodium and 40 mg iridium. In practical operation it would this precipitation back to the raw stone crushing plant- αο · be guided.

The residue remaining after the sulfuric acid treatment was treated with aqua regia (1.51) in stage 4

Leached for 3 hours. This aqua regia leach and all other aqua regia leaches were carried out as follows:

The material was refluxed for 30 minutes with the required amount of acidic acid (HCl). The required amount of nitric acid (HNO ₃ ) was then gradually added over 60 minutes. The mixture was then left to boil for the remainder of the time (ie Ι ^{1 / hours).}

Sodium bromate (NaBrO ₃ ) was then added to the solution, which was then kept boiling for a further 30 minutes after the solution had been diluted with water (1.5 to 3 liters) in order to stabilize the metals of the platinum group and gold to their highest level Oxidation stages to oxidize. The pH was then adjusted (about 6O ⁰ C) (1 kg) to 6.5 with sodium carbonate to precipitate all the metals other than platinum as hydrated oxides. The solution was allowed to stand for 20 minutes and then filtered under vacuum. In this manner the platinum was removed so as to reduce by about 50% the majority of the platinum group metals and gold which were leaded.

To the filtrate, which contained more than 90% platinum (Pt) of the feed, was added formic acid (0.2 L) in step 5 and the solution was refluxed with stirring for 5 hours. In stage 6, sodium carbonate (Na ₂ CO ₃ ) (0.3 kg) was added in portions over the course of one hour until a pH of 5.0 had been reached. The solution was then boiled for a further 60 minutes, then cooled to 60 ° C. and nitrated under vacuum. These steps 5 and 6 were performed to precipitate the platinum in the solution.

The filtrate was then passed through an anion exchange column in step 7 passed, and the process was 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 (1.01) in step 8, the solution cooled and filtered. Of the The residue consisted of silver chloride (AgCl).

This Köaigswasser 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 these metals of the platinum group carried out by means of a separate process.

The residue and the precipitate obtained from the aqua regia leaching carried out at the beginning and from the sodium carbonate filling stage 4 (+1400 g) were mixed with a flux A and a flux B, which are defined below and melted together in stage 9 for 75 minutes at 114O ^{0 C.} Most of the rhodium is converted from a water-insoluble form into a water-soluble form. At the same time, the solubility of iridium and ruthenium ίο 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 recovered were used. These fluxes had the following compositions:

Flux A (active flux) (3.5 kg)

(1) Borax Na ₂ B ₄ O ₇ 20% (0.75 kg)

(2) Sodium carbonate Na ₂ CO ₃ .... 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 therein. The thus obtained Lead regulus was separated from the slag, and the slag was crushed and collected, but would be returned to the rough stone smelting plant in practical operation. The slag contained 520 mg Pt, 230 mg Pd, 45 mg Au, 24 mg Rh, 45 mg Ru and 5 mg Ir.

The lead regulus was crushed and then _{refluxed with 20% HNO S} (5.51) for 5 hours in step 10 to remove the lead. The solution was ^{cooled to 55 °} C. and filtered under vacuum. The residue was sent to a later aqua regia leach stage, designated Stage 11.

In stage 12, formic acid (0.05 l) was added to the filtrate of the nitric acid leach of stage 10 and the pH was _{adjusted to 2.0 with sodium carbonate Na 2} CO ₃ (0.3 kg) in order to avoid all metals of the platinum group and the To precipitate gold that had been dissolved by the nitric acid. The solution was then stirred at room temperature for 5 hours and filtered under vacuum.

The resulting precipitate was combined with the residue that had accumulated in the nitric acid leaching stage of stage 10, and the combination of materials was fed to the aqua regia leaching stage of stage 11. In stage 13, NH ₄ OH was added to the filtrate to precipitate the lead and any platinum group metals and gold present, and this precipitate was dried and calcined and would in practical operation be returned to the stage 9 enamel bleaching stage.

The combination of residue and precipitation was taken in stage 11 with aqua regia (0.75 1) for 3 hours Refluxed. The solution was cooled to 55 ° C and filtered under vacuum. The residue

Formed part of the feed material for the double, and then filtered under vacuum (1 + 21). Process for the separation of rhodium, iridium and The filtrate was used as starting material for pure ruthenium from each other. This residue contained supply of the rhodium used, and it contained 300 mg, 850 mg Pt, 700 mg Pd, 100 mg Au, 5000 mg Rh, Pt, 2000 mg Pd, 20 mg Au, 14 500 mg Rh, 60 mg Ru, 14 720 mg Ru and 1420 mg Ir. The precious metals make 5 and 40 mg of Ir. The residue was in stage 20 with approximately 50% of this as a metal concentrate, three times its own weight, while the remaining 50% consisted of lead chloride (PbCl,) Na ₄ O ₂ (0.25 kg) in an iron crucible for 2 hours. Sintered at 500 ^° C. The melt was in stage 21 in

50% HCl (1.5 l) dissolved in the filtrate from the aqua regia leaching stage.

step 11, the stöehiometfische amount io Thereafter, H ₄ O H ₄ (0.071) was added to the solution, SO ₄ plus 10% excess (by weight 100ml of a 50% and the mixture refluxed for 30 minutes to sulfuric acid) added in stage 14 to which is heated in this boiling in order to precipitate the metals present in their lower solution. The solution was to reduce valence levels. The pH of the solution was boiled for 30 minutes, ^{cooled to 55 °} C. and filtered. was then increased to 9.0 in stage 21 with NaOH (0.7 kg)

The precipitated lead sulfate was set in stage 15 through 15 to remove all platinum group metals that do not contain The glow was converted into litharge (PbO) and was then platinum and no iridium, as well as the gold from fall ready for use again for the return to the stage. The solution was cooled to 55 ° C and the enamel bleaching. filtered under vacuum.

The filtrate obtained in the lead precipitation stage

was evaporated to dryness in stage 16, and the purification of the ruthenium, and it contained 90 mg Pt, the salts obtained in this way were calcined for 2 hours at 600 ^° C. 500 mg Pd, 330 mg Au, 7900 mg Rh, 44650 mg Ru . This temperature was found to be and 1620 mg of Ir. The filtrate was the starting point for rendering the rhodium in the residue material for purifying the iridium, and it contained aqua regia. 300 mg Pt, 50 mg Pd, 10 mg Au, 40 mg Rh, 50 mg Ru

The annealing product was in stage 17 with Königs- »s and 350 mg Ir.

water (0.751) refluxed for 3 hours. These? iridium-containing feed material was used

The solution was cooled and first filtered under vacuum in step 23 with sodium bromate NaBrO _3. (7 g) treated, the solution with HCl to a pH of

The residue was adjusted with the residue from the 2.0 and then the solution for 30 minutes Aqua regia leaching stage of the stage, which had been boiled after 30 in order to oxidize the iridium to a higher valence, combined, stage to oxidize.

so as to use a combined feed for separation. The pH of the boiling solution was then adjusted to

of the secondary group of platinum metals, namely Na ₄ CO ₃ , adjusted to 7.0, and the solution was made of rhodium, ruthenium and iridium, boiled for 1 hour, then cooled, and the iridium and it had the following contents of metals Platinum hydroxide was filtered off, the platinum remaining in the group and on gold on: 1130 mg Pt, 850 mg Pd, solution.

120 mg Au, 74G0 mg Rh, 14 920 mg Ru and 1720 mg The noble metals remaining in the filtrate were

Ir. precipitated in step 24 by boiling with formic acid,

That in the last aqua regia leaching stage and this precipitation would be used in practical operation the filtrate obtained from stage 17 was returned to that roasting stage, agrees that at the aqua regia leach stage of the iridium hydroxide precipitation was in stage 25

Stage 8 was incurred, which had been dissolved in 50% HCl (0.071) with the metals colored iridium chloride form had been converted into a brown iridium charge to separate platinum, palladium and 45 chloride form. Gold. This charge had the following levels. Then H ₂ O ₂ (7 mL) was added and that

Platinum group metals and gold: 17-210 mg. Cooking continued for another 15 minutes. The pH of the Pt, 74,790 mg Pd, 14 560 mg Au, 200 mg Rh, 25 mg Ru solution was adjusted to 9.0 in step 26 with NaOH. and 210 mg of Ir. then the solution is cooled and filtered. The fall

The infiltration materials that would be drawn from the three 50 would initially be in practical use Cycles of the above procedures are obtained wor- roasting stage are returned, den were and the rhodium, ruthenium and iridium The iridium hydroxide was in step 27 from the

were combined with each other to precipitate the solution in the manner described above. Starting material for the separation of the iridium to The hydroxide was in stage 28 by annealing, at to win. This starting material then contained 55 1000 ° C. converted into the metal and the annealing j 3390 mg Pt, 2550 mg Pd, 360 mg Au, 22 440 mg Rh, product cooled in a nitrogen stream This] 44 760 mg Ru and 5160 mg Ir. Metal then represented the finished Iridium product,

This feed was in stage 18 and it was 99.9% pure. The iridium with an amount of NaHSO ₄ · 1 H ₂ O (0.8 kg), the yield was 2000 mg, which corresponded to 33.33% of the load j five times its own weight, 1 hour 60 kung. j

melted at 600 ⁰ C in a quartz vessel. The present invention is therefore an effective!

Melt was in stage 19 in boiling hydrochloric acid same method for separating the iridium (11) solved. The solution was then made with water mixing the platinum group metals with gold diluted to reduce their original volume and to purify the iridium.

For this purpose 2 sheets of drawings

Claims (7)

2 claims: 1. Process for separating the iridium from the other metals of the plate group and gold, S, characterized in that the dissolved metals of the platinum group and the gold are converted to their lower oxidation levels by treating the solution with hydrogen peroxide in an acidic medium at elevated temperature , adjusts the pH of the solution to approximately 9, separates the precipitate from the iridium and platinum remaining in solution, then converts the platinum and iridium to their highest valence levels by the action of sodium bromate in an acidic medium at an elevated temperature and the pH of the solution to about 6.5 to 7.5 adjusts to precipitate the iridium and keep the platinum in solution. 2. The method according to claim 1, characterized in that the iridium is mixed with relatively small amounts of the other platinum group metals are used. 3. The method according to claim 2, characterized in that the iridium is in the form of an as Residue is used, as in an aqua regia leaching of a mixture of metals of the platinum group with gold. 4. The method according to claim 3, characterized in that that said residue is subjected to a treatment for the purpose of removing the majority of the rhodium therefrom, before the Treatment with water jeroxide takes place. 5. The method according to any one of the preceding claims, characterized in that the pH the solution is increased by using sodium hydroxide. 6. The method according to any one of the preceding claims, characterized in that the Treatment with hydrogen peroxide is carried out in a hydrochloric acid medium. 7. Iridium, characterized in that it is according to a method as in any one of the claims 1 to 6 is claimed has been obtained.