Method for platinum metal recovery from secondary raw materials

FIELD: noble metal hydrometallurgy.

SUBSTANCE: invention relates to method for acid leaching of platinum method from secondary raw materials, in particular from ceramic support coated with platinum metal film. Target metals are leached with mixture of hydrochloric acid and alkali hypochlorite at mass ratio of OCl^-/HCL = 0.22-0.25 and redox potential of 1350-1420 mV.

EFFECT: decreased leaching temperature, reduced cost, improved platinum metal yield.

2 ex

The invention relates to ferrous metallurgy and can be used in the production of platinum group metals.

Secondary raw materials containing metals of platinum group, is a material extremely heterogeneous both in composition and content of noble metals and materials basis.

The process of manufacturing thick-film resistors, monolithic capacitors, hybrid integrated circuits and the number of similar electronic products, as well as catalysts associated with drawing on a ceramic base (substrate) of the films of platinum group metals or resistive pastes based on them.

A method of processing catalysts [1] at a temperature 95-103° With a mixture containing hydrochloric acid (4-7 mol/l), hydrogen peroxide (1-4 mol/l) and dimethylformamide (0.5 to 3.0 mol/l).

Recovery of platinum from solutions produce products of hydrolytic cleavage of dimethylformamide at pH 3-4 and the temperature of 90-105° C. the Solution after washing the basics is directed to the recovery of platinum; after recovery of platinum dimethylformamide regenerate, and the solution after regeneration is directed to the treatment of the catalyst.

The disadvantages of this method - mnogostadiinost and use for the deposition of platinum metals expensive reagents.

The authors of the next method to extract the deposits of platinum from the platinum-containing catalysts based on aluminum oxide [2] proposed to gloriavale catalyst in dry form by blowing through the layer of material with chlorine at a temperature of 300-500° With or in suspension in a solution of hydrochloric acid at the boiling temperature of suspense solution.

The disadvantages of this method are associated with the environmental hazard of the chlorination process, caused by the release of toxic gases and waste water, high temperature reactions in the case of chlorination with gaseous chlorine, irretrievable loss of main parts, dissolving in concentrated hydrochloric acid in the case of liquid-phase chlorination. For separation of platinum from the solution required a multi-stage operation.

Also the known method [3] selection of platinum group metals, including platinum, from the surface of the catalyst based on oxides of silicon and aluminum, according to which a substrate is processed commodity sulfuric acid at 60-100° to the complete destruction of the substrate, the resulting slurry is cooled, diluted with water and filtered, and the residue is treated with Imperial vodka composition NGO₃:HCl:H₂O=1:3:4 at 100° to dissolve platinum. Then to the solution was added NaOH to provide a pH≈ 12, precipitated platinum by balikatan sodium and separate them from the solution. The degree of extraction of platinum is 84,2%.

The known method is characterized by a low degree of extraction of platinum group metals and may not be used for selection of platinum and iridium with the surface of ogneuporshchiki due to the complete destruction of the substrate. It is a complex technology and requires a signicant number of reagents (including expensive), a complex system of cleaning and ventilation air, because it is impossible to control the secretion of nitric oxide.

In the invention [4] catalyst mass on the basis of Al₂O₃is treated with a mixture of hydrochloric acid with a concentration of 20-35% and oxidant (hydrogen peroxide, hypochlorite, halogen and the like) in a ratio of 20:0,3-20:3. Then washed leached the basis of hydrochloric acid concentration of not less than 5%. Noble metals restore with hydrogen or hydrazine.

The known method is closest to the proposed composition of the processed material and, therefore, selected as a prototype.

The drawbacks of the invention involve the use for dissolution of platinum metals conc. hydrochloric acid and the large consumption of oxidant, and deposition from solutions of expensive reagents, such as gaseous N₂, hydrazine, borohydride and the like, with an excess of reducing agents and the production of large quantities of toxic wastewater requiring treatment.

The task, which was sent to the claimed invention, is to reduce the consumption of reagents, reducing the concentration of hydrochloric acid and oxidant, reducing production cost the spine processing, improving the extraction of platinum group metals and the elimination of redundant selection of active chlorine.

The problem is solved at the expense of achieving a technical result, which is to eliminate these drawbacks by eliminating from the process of dissolution of concentrated Hcl and excess oxidant.

This technical result is achieved in that in the method of recycling carried out the dissolution of platinum group metals in concentrated hydrochloric acid and oxidant. According to the invention dissolve lead a hydrochloric acid solution with a mass concentration of 120-180 g/l, and as the oxidant used solution of hypochlorites of alkali metals, when the mass ratio of the hypochlorite/hydrochloric acid, equal 0,22-0,25, redox potential (ORP), equal 1350-1420 mV and a temperature of 70° C (243 K).

The essence of the invention lies in the fact that when using hydrochloric acid and sodium hypochlorite alkali metals occur following dissolution reactions of platinum and palladium, which primarily interact hydrochloric acid and sodium hypochlorite with the formation of molecular chlorine:

(l)+2hcl→ 3l+H₂O+CL₂

The second stage involves the interaction of molecular chlorine in solution with valuable components having free is ing surface:

IU+2hcl+2l₂→H₂l₆

Me - platinum group metals

Comparative analysis of the proposed method with the prototype indicates the presence of essential features that distinguish it from the prototype that allows to make a conclusion on the conformity of the proposed technical solution the criterion of “Novelty”.

Analysis of similar technological solutions showed that the dissolution of noble metals (PGM) in hydrochloric acid in the presence of molecular chlorine is known, however, it applies for a different type of raw materials and the lack of it is used mainly chlorine gas, thereby increasing the environmental risk of the process and complexity of instrumentation.

Also there is a method of dissolving gold hydrochloric acid and chlorate of sodium, however, the application of sodium chlorate increases the cost of processing due to the high cost of sodium chlorate, whereas in the proposed method, the solution of alkali metal hypochlorite is a waste of chlorine.

Comparison of the proposed solution with the same is not obvious from the well-known technique, i.e., meets the criterion of “Inventive step”.

Examples of the proposed method.

1. Extraction of platinum and palladium produced from concentrate Kera is practical capacitors content, % platinum - 1,3 and palladium - 3,8 under the following conditions leaching: T:F=7:1, T° C=70; concentration, g/l Hcl=120-180 and NaClO=30-40. After leaching, the solution was filtered and directed to the stage of deposition of platinum and palladium in the form of salts of hexachlorostannate. Extraction was for palladium 98,7% and 95.2 percent for platinum and about 10% for substrate (Vato₃).

2. Under the same conditions leaching was tested product, representing a catalyst based on alumina containing 0.28% as platinum. The content valuable component in the cake hypochlorite leaching amounted to less than 0.01%, i.e. within the limits of detection that allows to speak about extracting more than 96%. The transition alumina in the solution amounted to 7%.

The claimed method differs from the known fact that improves the manufacturability of the process, excluded mnogostadiinost process, and the use of toxic and hazardous reagents. The use of waste electrochemical production of hypochlorites of alkali metals) leads to substantial savings and reduce the cost of the final product.

The claimed method allows you to select platinum and palladium in the finished product (hexachloroethane) both together and separate.

Sources of information

1. The method of extraction of platinum from spent catalysts: Pat 2103395 EN.

2. SU authorship, 139837, CL 22 In 1/08, 1961.

3. JP application No. 60-261233, CL 22 In 3/00, 1984.

4. JP application No. 57-169027, CL 22 In 11/04.

5. Metallurgy of noble metals (foreign experience). Meretukov M.A., Orlov A. M. - M.: metallurgy, 1990, 416 S.

The method of extracting platinum group metals from secondary raw materials, including leaching mixture of hydrochloric acid and hypochlorites of alkali metals with the dissolution of platinum and palladium, wherein the leaching is carried out at concentrations of hydrochloric acid 120-180 g/l, the mass ratio l^-/HCl=0,22-0,25, a temperature of 70°and redox potential 1350-1420 mV.