Method for breaking down a mixture of solid particles comprising ruthenium

Abstract

A method for breaking down a mixture, which is present in the form of solid particles, consisting of: (A) 0 to 99% by weight of metallic ruthenium, (B) 0 to 50% by weight of at least one element other than ruthenium, which is present in elementary form, selected from the group of elements of the atomic numbers 13, 21-30, 39-42, 45-52, and 72-83, (C) 0 to 99% by weight of ruthenium oxide, (D) 0 to 70% by weight of at least one solid element oxide other than ruthenium, (E) 0 to 30% by weight of at least one inorganic substance other than (A) to (D), and (F) 0 to 3% by weight of at least one organic substance, wherein the sum of the % by weight of the compounds (A) to (F) is 100% by weight and the ruthenium content of the mixture is 2 to 99% by weight, and wherein the method comprises the steps of: (1) optionally mixing said mixture with alkali carbonate by forming a blend, (2) alkaline oxidizing breakdown of the mixture or of the blend, respectively, formed in optional step (1) into molten potassium hydroxide using a gaseous oxidizing agent selected from the group consisting of air, oxygen, and air/oxygen mixtures, and without use of nitrate, and (3) cooling down the breakdown material formed in step (2) to a temperature below its solidification temperature, wherein the gaseous oxidizing agent is introduced into the melt in step (2).

Claims

1. A method for breaking down a mixture, the mixture in the form of solid particles, the mixture consisting of: (A) 0 to 99% by weight of metallic ruthenium, (B) 0 to 50% by weight of at least one element other than ruthenium, wherein the at least one element is in elementary form and is selected from the group of elements of the atomic numbers 13, 21-30, 39-42, 45-52, and 72-83, (C) 0 to 99% by weight of ruthenium oxide, (D) 0 to 70% by weight of at least one solid element oxide other than ruthenium oxide, (E) 0 to 30% by weight of at least one inorganic substance other than (A) to (D), and (F) 0 to 3% by weight of at least one organic substance, wherein the sum of the % by weight of the compounds (A) to (F) is 100% by weight and the ruthenium content of the mixture is 2 to 99% by weight, wherein the method comprises: (1) alkaline oxidizing breakdown of the mixture in molten potassium hydroxide using a gaseous oxidizing agent selected from the group consisting of air, oxygen, and air/oxygen mixtures, and (2) cooling down a breakdown material formed in step (1) to a temperature below its solidification temperature to form a solidified broken down material, wherein the gaseous oxidizing agent is only introduced below a surface of the molten potassium hydroxide in step (1), wherein the gaseous oxidizing agent is the only oxidizing agent used in the method, and wherein the methods provide a ruthenium recovery ratio of at least 90%.

2. The method according to claim 1, wherein step (1) is performed with the mixture blended with an alkali carbonate.

3. The method of claim 2, wherein the mixture and the alkali carbonate are blended in amounts that provide a weight ratio of 1 part by weight of the mixture to 0.05 to 0.5 parts by weight of the alkali carbonate.

4. The method of claim 1, wherein the mixture is an ore concentrate or a mixture of a plurality of different ore concentrates of an ore dressing and/or a residue or a mixture of a plurality of different residues, each containing ruthenium, of a precious metal preparation.

5. The method of claim 1, wherein the solid particles exhibit a particle size D10 in the range of 0.5 to 1 m and a particle size D50 in the range of 2 to 10 m.

6. The method of claim 1, wherein the weight ratio of the mixture to the molten potassium hydroxide in step (1) is from 1:2 to 1:5.

7. The method of claim 1, wherein in step (1) no further substances are used or added in addition to the mixture, the molten potassium hydroxide and the gaseous oxidizing agent.

8. The method of claim 1, wherein step (1) comprises producing the molten potassium hydroxide prior to the addition of the mixture into the molten potassium hydroxide.

9. The method of claim 8, wherein the molten potassium hydroxide has a temperature in the range of 400 to 800 C. during the addition of the mixture to the molten potassium hydroxide.

10. The method of claim 9, further comprising mixing a molten material, the molten material created upon complete addition of the mixture to the molten potassium hydroxide.

11. The method of claim 8, further comprising mixing a molten material, the molten material created upon complete addition of the mixture to the molten potassium hydroxide.

12. The method of claim 1, further comprising: (3) dissolving the solidified broken down material in water upon completion of step (2).

13. The method of claim 1, wherein the gaseous oxidizing agent is introduced below a surface of the molten potassium hydroxide using a gas introduction tube.

14. The method of claim 1, wherein the gaseous oxidizing agent is introduced into the molten potassium hydroxide in step (1) using a gassing agitator.

15. The method of claim 1, wherein the gaseous oxidizing agent is introduced into the molten potassium hydroxide in step (1) after addition of the mixture to the molten potassium hydroxide.

16. The method of claim 1, wherein the gaseous oxidizing agent is introduced into the molten potassium hydroxide in step (1) in an amount ranging from 200 to 600 liters of the gaseous oxidizing agent per kilogram of molten potassium hydroxide.

17. The method of claim 16, wherein the gaseous oxidizing agent is introduced into the molten potassium hydroxide in step (1) over a period of time ranging from 3 to 5 hours.

Description

EXAMPLES

Example 1

(1) 400 kg of potassium hydroxide were placed into a crucible and were melted at 550 C. 130 kg of an ore concentrate in the form of a mixture of solid particles (D10=0.47 m, D50=8.55 m; composition according to X-ray fluorescence (RFA), each in % by weight: 6% Ru, 26% Pt, 12% Pd, 4% Rh, 1% Ir, 3% Se, 3% Fe) were added by stirring for a time period of 3.5 hours. The temperature was then increased to 620 C. and was maintained for a time period of 5 hours under continuous stirring. 152 cubic meters of oxygen were meanwhile introduced into the melt by means of a stainless steel gas lance immersed into the melt. The melt was subsequently poured into melting vats. After the cool-down to 20 C., a total of 600 liters of water was added to the solidified melt and was suspended for 5 hours.

(2) The obtained aqueous suspension was allowed to settle and the excess aqueous solution obtained thereby was decanted and analyzed.

(3) The recovery rate for ruthenium was 98% (calculated from the ruthenium content of the aqueous solution with reference to the used mixture determined by means of inductively coupled plasma emission (ICP)).

Example 2

(4) 25 g of potassium hydroxide were melted in a crucible at 570 C. By stirring, a mixture of 10 g of Ru powder and 0.5 g of RuO.sub.2 powder were added in portions by stirring. Stirring was subsequently continued at 570 C. for 5 hours, accompanied by a four-hour introduction of a total of 12 liters of oxygen into the melt via a stainless steel gas introduction tube. Cool-down then took place. After the melt had cooled, the residue was dissolved in 150 ml of water and was filtrated subsequently. The dissolution residue was dried and weighed (0.01 g). The aqueous solution was analyzed.

(5) The recovery rate for the ruthenium was 98.79% (calculated from the ruthenium content of the aqueous solution with reference to the used mixture determined by means of inductively coupled plasma emission (ICP)).