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INVENTION
Patent of the Russian Federation RU2111272
METHOD OF PLATINUM METAL ALLOCATION
The name of the inventor: Skorokhodov VI; Kremko EG; Volkova NA; Mastyugin SA; Swan AB; O. Goryaeva; Rychkov D.M.
The name of the patentee: Open Joint-Stock Company "Uralelectromed"
Address for correspondence:
Date of commencement of the patent: 1997.05.14
The invention can be used in the field of chemistry, metallurgy in the production of high purity silver and platinum metals. The starting silver-containing material with impurities of platinum metals is dissolved in nitric acid of concentration 150-200 g / dm 3 chemically or electrolytically. Sorption from it platinum metals anion exchanger based on copolymers of vinyl pyridine and divinylbenzene. The desorption of platinum group metals is carried out with a solution of ammonia of a concentration of 3 to 8 mol / dm 3 and then platinum metals are recovered from the eluate in one of the known ways: by electrolysis, precipitation of individual complex salts, isolation of insoluble compounds. The degree of separation of platinum metals from copper and silver is increased by a factor of 100, a concentrated eluate is obtained in platinum and palladium, practically free of copper and silver, and high-purity silver from materials containing both platinum metals and copper.
DESCRIPTION OF THE INVENTION
The invention relates to chemistry, in particular to the processing of silver materials containing both copper, gold and platinum group metals (PGMs). Such materials, for example the Dore alloy, are the raw materials for the refining of noble metals.
The claimed method for the isolation of platinum metals can be used in metallurgical and chemical industries and allows the isolation of platinum metals in the form of a concentrate, but also produces silver of high purity.
According to the methods known in the world for the separation of platinum metals from nitric acid solutions during the processing of silver-containing products, complete separation of platinum metals and silver is not achieved for a number of reasons:
- the concentration difference between silver and platinum metals is of the order of 100: 1;
- the close chemical properties of these metals, especially the tendency to complex formation;
- low selectivity of used reagents.
In some methods, complexing agents, for example, dimethylglyoxime, are used to extract platinum metals from solutions [1]. For the complete isolation of palladium, an excess of reagent is required: for every 10 mg of palladium, 25 ml of a 1% alcohol solution of dimethylglyoxime (palladium: dimethylglyoxime ratio = 1:25) is added.
This makes it possible to remove only palladium from the nitric acid solution, platinum is deposited by about 5%. Complete precipitation of palladium is achieved with an excess of dimethylglyoxime, but the residual content of the latter in a silver nitrate solution does not allow obtaining silver by known methods, for example, by electrolysis.
A method for the isolation of palladium from a silver electrolyte is known [2]. The method for purifying the silver electrolyte comprises passing silver-containing solutions after electrolysis with a silver concentration of 90 g / dm 3 ; Copper 1.4 g / dm 3 ; Palladium 0.16 g / dm 3 through a column filled with activated carbon with a chelated compound attached to its surface with an amine group. In the passing solution, the palladium content is reduced to <0.001 g / dm 3 . When eluting with solutions of nitric and hydrochloric acids, 4 fractions of the solution are obtained. The richest fraction contains 6.2 g / dm 3 of palladium and up to 0.01 g / dm 3 of silver.
Disadvantages of the method:
1. The eluate contains no more than 6.28 g / dm 3 of palladium (by the sum of the concentrations in 4 fractions).
2. The silver content in the eluate reaches 13.2 g / dm 3 .
3. The third fraction in silver content (0.22 g / dm 3 ) and palladium (6.2 g / dm 3 ) is suitable for obtaining a pure palladium product.
4. The possibility of sorption with activated charcoal of platinum is unknown.
Ionite - activated carbon with chelated compounds attached to its surface with amine group does not allow selective isolation of platinum metals from nitric acid solutions containing silver and copper.
The closest in technical essence to the claimed invention is the method for producing platinum metal compounds [3]. As a starting material, nitric acid solutions of electrochemical silver production with a high concentration of silver and copper and an insignificant concentration of platinum metals are used.
The compounds of platinum metals are isolated by sorption on an ion exchanger. As an ion exchanger, resins with chelating agents containing imidoacetic acid residues as active sites are used. The method comprises passing a nitric acid solution containing 190 g / dm 3 of silver, 35 g / dm 3 of copper and 1.3 g / dm 3 of platinum metals at a pH of 0.5-1.5 through an ion exchange column filled with an ion exchanger. Platinum metals are extracted from the ion exchanger bed by washing with a 2-5% ammonia solution containing 1-3 mol / dm 3 nitric or alkali metal sulfate salts or ammonium.
According to our experimental data, the method has the following drawbacks: (Tables 1 and 2)
1. Sorption on an ion exchanger containing aminocarboxylic groups leads to partial sorption of copper and silver cations. The maximum capacity of the ion exchanger is 4-5 g / dm 3 for silver, 10-15 g / dm 3 for copper, a significant amount of silver and copper passes into the eluate (up to 2.0-2.5 g / dm 3 ). Partition coefficient 3,5 
10 3 does not allow to obtain eluate containing only platinum metals.
2. Imidoacetic groupings in the structure of the ion exchanger cause the formation of strong chelate complexes with platinum metals, which complicate their subsequent desorption. Strong complexes form imidoacetic groups and with copper and silver.
3. Eluting agent - 5% ammonia solution with additions of 1-3 moles / dm 3 of alkali metal salts has a high salt background 
200-400 g / dm 3 .
4. The eluate containing, in addition to platinum and palladium, and copper and silver and a salt background of up to 400 g / dm 3 , requires additional operations to separate pure platinum and palladium.
It is an object of the present invention to increase the degree of separation of platinum metals from copper and silver and to obtain a platinum-concentrated and palladium-containing eluate.
This is achieved by the fact that a silver-containing material with impurities of platinum metals is dissolved in nitric acid concentrations of 150-200 g / dm 3 chemically or electrolytically. From the initial nitric solution containing silver and platinum group metals, platinum metals are sorbed by anion exchanger based on copolymers of vinyl pyridine and divinylbenzene, the desorption of platinum group metals is carried out with a solution of ammonia of concentration 3-8 mol / dm 3 and platinum metals are recovered from the eluate in one of the known ways: by electrolysis , Precipitation of individual complex salts, insoluble compounds.
A comparative analysis of the known technical solutions and the claimed invention allows us to conclude that the claimed invention is not known from the prior art and corresponds to the criterion of "Novelty."
From the prototype, the claimed method is characterized in that the sorption concentration of platinum metals is carried out on an anionite based on copolymers of vinyl pyridine and divinyl benzene, and the elution of platinum metals is carried out with a solution of ammonia of concentration 3-8 mol / dm 3 . The coefficients of separation of platinum metals from copper and silver calculated on the basis of experimental data confirm the higher selectivity of the anion exchanger based on copolymers of vinyl pyridine and divinyl benzene.
The data is summarized in Table. 1.
At the same maximum capacity for platinum metals of both anion exchangers, the maximum capacity of anionite by prototype for silver is an order of magnitude, and for copper it is 2 orders of magnitude higher than for anionite according to the claimed method. This important characteristic - the high selectivity of the anion exchanger according to the claimed method makes it possible to obtain eluant, concentrated in platinum metals and poor in copper and silver (see Table 2).
From Table. 2, the extraction of platinum metals from the anion exchanger into the eluate according to the claimed method is 15.6% higher than in the prototype, the content of platinum metals in the eluate is almost 2 times higher, and the concentration of silver and copper is several tens of times smaller in the eluate according to the claimed method .
The elution of platinum metals from the saturated anion exchanger was carried out by solutions of ammonia. The data are presented in Table. 3.
When an ammonia solution of 2.5 mol / dm 3 is passed through the anion exchanger, the content in the eluate of platinum and palladium reaches 4.29 and 35.0 g / dm 3, respectively. With an increase in the ammonia concentration above 8 mol / dm 3, the content of platinum and palladium increases to 4.5 and 38.2 g / dm 3, respectively. A further increase in the concentration of ammonia does not lead to a significant increase in the concentration of platinum metals in the eluate.
The essence of the claimed invention for a person skilled in the refining of noble metals of their multicomponent raw materials does not explicitly follow from the prior art and meets the criterion of the inventive level, since the claimed method for the isolation of platinum metals from silver-containing materials makes it possible to increase the separation coefficient of platinum metals from copper and silver In 100 times in comparison with the prototype, to increase the extraction of platinum metals in the eluate by 15-18% and to obtain a concentrate of platinum metals.
The method for the isolation of platinum metals has been tested experimentally on an industrial scale. The implementation of the method is illustrated by the following examples.
Example 1
The starting silver-containing material is dissolved in nitric acid concentrations of 150-180 g / l. 200 dm 3 of the obtained nitric acid solution containing (g / dm 3 ) of silver 123, palladium 0.256, platinum 0.08, copper 5.75, free acid 5.8 are passed through an anion exchange layer based on copolymers of vinyl pyridine and divinylbenzene VP-IP. The composition of the solution after sorption cleaning, g / dm 3 : silver 123.1, palladium 0.002, platinum 0.005, copper 5.73. After saturation of the anionite with platinum metals, 1 dm 3 ammonia solution of 3.0 mole / dm 3 concentration is passed through the anion exchange bed. The composition of the eluate, g / dm 3 : platinum 4.45, palladium 37.8, copper 0.01, silver 0.07 (Table 3), from which platinum metals are isolated by usual methods.
Passing a nitric acid solution through an anion exchanger layer based on copolymers of vinyl pyridine and divinyl benzene allows:
- Deeply clean the solution of platinum metals to obtain pure silver by known methods;
- to obtain a concentrated on platinum metals eluate, free of copper and silver;
- from the rich eluate (the sum of platinum metals> 40 g / dm 3 ) it is easy to isolate the concentrate of platinum metals by known methods.
Example 2
The isolation of the platinum metals is carried out as in Example 1, the desorption of the platinum metals leads to 1 dm 3 ammonia solution at a concentration of 8 mol / dm 3 . The degree of purification of the solution from platinum metals is the same as in Example 1: palladium to 0.002 g / dm 3 , and platinum to 0.005 g / dm 3 , the separation coefficient of platinum metals from silver and copper is about 10 5 . The eluate is rich in platinum and palladium (by the sum of metals> 40 g / dm 3 ), the concentrate of platinum metals is isolated from it by usual methods.
Example 3 (by prototype)
After 1 dm 3 anionite containing imidoacetic acid residues, 200 dm 3 of solution containing, g / dm 3 : silver 123.0, palladium 0.256, platinum 0.08, copper 5.75, free acid 9.8 are passed.
The composition of the solution after sorption cleaning, g / dm 3 : silver 122.0, palladium 0.002, platinum 0.005, copper 5.70. After saturation of the anionite with platinum metals, an eluent consisting of a 5% ammonia solution and 1 mole / dm 3 of sodium sulfate is passed through an anionite layer of 1 dm 3 . With the same degree of purification of the solution from platinum and palladium (2.83, 20.5, respectively), silver and copper are coprecipitated on the anion exchanger. In the eluate, the content of copper and silver is 2.5 and 2.4 g / dm 3, respectively. This is ten times higher than according to the claimed method (Cu 0.01 g / dm 3 , Ag 0.07 g / dm 3 ).
Comparison of the experimental data of two anion exchangers shows the advantages of the claimed method as compared to the prototype:
- on the degree of separation of platinum and palladium from copper and silver;
- a more concentrated platinum and palladium eluate, free of copper and silver.
Compared with the prototype, the claimed method of separation of platinum metals in the processing of silver-containing materials makes it possible to increase the degree of separation of platinum metals from copper and silver from nitric acid solutions by a factor of 100 and to obtain a 2-fold more concentrated platinum and palladium eluate free of copper and silver.
Positive results of testing the method in the experimental industrial conditions of OJSC "Uralelectromed" make it possible to consider the claimed method of isolation of platinum metals industrially applicable.
Advantages of industrial application of the claimed method: the possibility of obtaining high-purity silver from silver-containing solutions after their sorption purification from platinum and palladium on anionite based on vinyl pyridine and divinylbenzene and obtaining pure platinum and palladium from a platinum-metal-rich eluate free of copper and silver.
CLAIM
A method for separating platinum metals from silver-containing materials, including dissolving the starting material in nitric acid, sorption concentrating the platinum metals on the ion exchanger, desorbing them with an ammonia-containing solution, and subsequently recovering the concentrate of platinum metals from the eluate, characterized in that the sorption is carried out on an anionite based on copolymers of vinyl pyridine and divinylbenzene , And desorption - a solution of ammonia concentration of 3 - 8 mol / dm 3
print version
Date of publication 14.03.2007gg
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