FI58161C - FOERFARANDE FOER SEPARERING AV GULD FRAON METALLER TILLHOERANDE PLATINAGRUPPEN - Google Patents

Description

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National Board of Patents and Registration / 44) Date of Publication and Hearing. -

Patent · och reglsterstyrelsen AnatHan utlagd och utl. * KrlfMn publlnrkd 29.0δ. 8θ ~ (32) (33) (31) Requested • oioikwt — Begird prterltet 10,08.72

Republic of South Africa-South Africa (ZA) 72/5488 (71) Swarsab Mining, Exploration & Development Company (Proprietary)

Limited, 56 Main Street, Johannesburg, Transvaal Province,

Republic of South Africa, South Africa (ZA) (72) Willem Hubert Pittie, Roodeport, Transvaal, Gerhardus Overbeek,

Florida, Transvaal, Kingsley Ferguson Doig, Johannesburg, Transvaal, South Africa, South Africa (ZA) (7 * 0 0y Heinänen Ab (54) Method for separating gold from metals belonging to the platinum group The present invention relates to a process for separating gold from metals belonging to the platinum group.

Five metals belonging to the platinum group, namely, platinum, palladium, iridium, ruthenium, and rhodium, usually coexist in nature with gold, and these six elements must be separated and purified in order to be useful in trade and industry. Generally, the initial separation of these elements into two groups is accomplished by treating the masterbatch, which is usually a lime leaching slurry or sludge, with aqua regia, in which case platinum, palladium, and gold dissolve while iridium, ruthenium, and rhodium remain predominantly in the process residue. The two groups of metals thus obtained are then usually subjected to a long and complex separation process designed to separate and purify the private metals.

2,581 61

It is an object of the nuclear invention to provide a method for separating gold from platinum group metals which is easier to implement at least if very pure gold is required as the final product and / or which facilitates the separation of the platinum group metals present from gold.

The process according to the invention is characterized in that the nitric acid solution containing gold and at least one platinum group metal is evaporated to dryness at least once, preferably twice, the residue is redissolved in nitric acid and hydrogen peroxide is added to the resulting solution, followed by boiling to coagulate and precipitate gold.

Evaporation of the nitric acid solution to dryness is performed to form nitrosochloride complexes of the metals present.

The concentrates of the platinum group metals and gold are usually obtained as leaching waste or sludge from the metal rock, which is further treated to separate the desired metals.

The invention is described in serum with reference to the accompanying diagram. The description includes an example in which the amounts of reagents used are given in parentheses.

An aqueous solution of platinum group metals (1.75 L) containing 171210 mg Pt, 74790 mg Pd, 14560 mg Au, 200 mg Rh, 25 mg Ru and 210 mg Ir was evaporated to dryness in Teflon crucibles, after which the evaporation residue was heated on a hot plate. minutes. The residue was then evaporated to dryness in step 1 with two equal volumes (2 x 0.55 L) of concentrated nitric acid. _

The salts were then heated again for 30 minutes.

The dried salts were dissolved by boiling in step 2 in 10% nitric acid (2 L) to obtain a solution containing 150 g / l of precious metal.

The solution was then diluted with cold water (21 + 31) to contain 100 g / l of valuable metal.

then 1 ml per gram of precious metal (300 ml) was added to the solution and the solution was allowed to boil for 30 minutes. The solution was cooled to 55 ° C and filtered in vacuo.

58161

The precipitate was fed to the gold refining process which began in step 3 of the scheme.

This precipitate obtained using this invention contained the following ingredients: 50 mg Pt, 10 mg Pd, 13750 mg Au, 40 mg Rh and traces of ruthenium.

This crude gold was dissolved in royal water (0.06 L) in Step 3. The solution was evaporated to dryness and the salts were boiled in Step 4 with NH 4 UlH (0.06 L) to dissolve any silver chloride. The solution was cooled to 55 ° C and filtered. The filtrate containing only traces of silver was discarded.

The residue was dissolved in boiling 5% HNO 2 (0.6 L) in step 5.

The insoluble residue was filtered off and would have been practically returned to the appropriate previous step.

The filtrate was passed through a cationic resin Dowex 50 x 8 in step 6. The resin traps the base metals and the gold is washed away with water.

Step 7 (0.03 L) is added to the liquid and this is allowed to boil for thirty minutes to precipitate gold. After cooling to 55 ° C, the solution was filtered.

The dried precipitate was the final gold with a purity exceeding 99.97% Au.

The total gold yield was 9000 mg, which is about 60% of the original amount of gold, which was 14560 mg.

v The gold in the filtrate was precipitated in step 8 by boiling the masonry with odoric acid (12 ml) and adjusting the pH of the solution to 5.0 ^ 200 ^^ (10 g) The solution was cooled and filtered, the filtrate was discarded and did not contain any precious metals.

The process according to the invention thus gave very pure gold, the procedure being easy and efficient compared to the prior art. To demonstrate this, the following experiments were performed:

Three solutions containing chlorine complexes of platinum group metals and gold were evaporated to dryness in a Teflon vessel. The resulting salts were heated on a hot plate for 30 minutes at 4 0 581 61.

mode 130 C.

Each solution contained precious metals as follows: 17121 mg Pt, 7479 mg Pd, 1456 mg Au, 200 mg Rh, 25 mg Ru and 210 mg Ir.

The dry salts were treated as follows: a) the salts were dissolved in 250 ml of boiling water, then 25 ml of hydrogen peroxide was added and cooking was continued for 30 minutes. The solution was allowed to cool to 55 ° C and the resulting precipitate was filtered.

b) the dry salts were evaporated to dryness with 25 ml of 55% nitric acid and then dissolved in 250 ml of 5% boiling nitric acid. Then 25 ml of hydrogen peroxide was added and cooking was continued for 30 minutes. The solution was allowed to cool to 55 ° C and the resulting precipitate was filtered.

c) the dry salts were treated as in b), but evaporation with 55% nitric acid was followed by evaporation in two 25 ml portions.

The distribution of precious metals in the precipitate and filtrate in cases a) to c) is shown in the following table.

Metal Pt Pd Au Rh Ru Ir (mg) (mg) (mg) (mg) (mg) (mg) _ v Precipitation 11 23 376 534 a)

Sludge 17,110 7,456 1.0B0 20 22 206 ^ j Precipitation 90 1 1,275 40 0 0

Soda 17,031 7,478 181,160 25,210. Precipitation 95 1 1.387 32 0 0 c)

Soda 17,026 7,478 69,168 25,210

It can be seen from the table that the gold yield in case a) was 25.8%, in case b) 87.5% and in case c) 95.3%. In addition, the purity of the gold obtained in case c) was 91.6%, which was achieved by precipitation from a solution with a gold content of only 5.5%.

Claims (2)

5,581 61 A process for separating gold from platinum group metals, characterized in that a nitric acid solution containing gold and at least one platinum group metal is evaporated to dryness at least once, preferably twice, the residue is redissolved in nitric acid and hydrogen peroxide is added to the resulting solution. and precipitating as a metal. Process according to Claim 1, characterized in that about 1 ml of hydrogen peroxide is used per gram of gold to be doped.