Method for producing platinum

Details Method for producing platinum Method for producing platinum

2000-06-16

2001-11-13

King, Roy (Department: 1742)

Specialized metallurgical processes, compositions for use therei

Processes

Free metal or alloy reductant contains magnesium

C423S022000, C205S543000, C205S565000

Reexamination Certificate

active

06315811

ABSTRACT:

The invention relates to a method for the production of platinum.
It has long been known to produce platinum by reducing an aqueous solution of a hexachloroplatinate. A disadvantage of this method is the fact that the platinum sludge obtained has to be washed free of potassium ions by a number of washing operations, which for one thing manifests itself undesirably in the high consumption of the wash water and for another thing in the quality of the sponge which is degraded thereby.
From what has been stated, the problem is to eliminate the above disadvantages at least partially by means of a novel process. The problem lies especially in reducing the high water consumption to a minimum and thus at the same time improving the quality of the platinum sponge.
This problem is solved by the method of the invention according to claim
1
.
The core of the present invention is the fact that, before the actual reduction, an aqueous hexahalogenoplatinate solution is added through a cation exchanger, the cations present—potassium ions for example—are exchanged with H
+
. Furthermore, small amounts of impurities that might possibly be present are removed by the ion exchange process and the subsequent reduction to metallic platinum. In this manner a pure aqueous hexahalogenoplatinic acid solution free of metal ions is obtained, and then is reduced by a reducing agent at a temperature of T>+30° C. and a pH of 0 to 4, to precipitation, so that the resultant platinum sponge as such does not have to be washed free of metal ions.
It is advantageous, furthermore, if the platinum sponge product is washed, dried and heated to incandescence, since in this manner the last impurities are removed.
It is also advantageous if the solution after running through the cation exchanger is concentrated by evaporation, since the platinum obtained is more compact, can be better filtered and less wash water is used per kilogram of platinum sponge product.
Lastly, it proves to be advantageous to use hydrazine, ascorbic acid, formic acid or oxalic acid as reducing agents, since these substances have proven good in practice. However, other reducing agents are conceivable, such as hydrogen (under pressure), sugar, and formaldehyde, for example.
Advantageously, a solution of potassium hexahalogenoplatinate solution is used as the hexahalogenoplatinate solution, since this platinate can easily be isolated in preceding process steps.
Furthermore, a hexachloroplatinate solution is advantageous, since known separating processes are often produced in a hydrochloric acid medium and the hexachloroplatinate is the stable species in this medium.
Lastly, the reduction to platinum is advantageously performed at a temperature of +65° C. to +95° C. in order to obtain a finely divided platinum powder and prevent mirror coating or massive separation of platinum.


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