RU2083704C1 - Method for production of metallic platinum - Google Patents

Abstract

FIELD: refining of precious metals. SUBSTANCE: method involves conversion of potassium chloroplatinate into potassium chloroplatinite. The process is carried out with the help of reduction agent, it is followed by extraction of metal platinum. To prepare insoluble Magnus salt solution of ammonium chloride in 20 % ammonia (having ratio of solid and liquid phases 1:10) is used. Then thus prepared product is affected by chemical reduction. EFFECT: improved efficiency of the method.

Description

 The invention relates to the metallurgy of non-ferrous metals, namely the refining of precious metals.

Almost all technological and analytical procedures for the separation and separation of platinum from solutions containing other noble, non-ferrous metals and other impurities are based on the precipitation of platinum in the form of sparingly soluble salts. These are primarily ammonium and potassium chloroplatinates in refining and cesium in the analysis. Despite the breadth of use of this technique, it has limitations on the degree of purification and is used in the initial stages of the process for primary separation of impurities from the bulk. The rotary application of such gravimetric cleaning is a rather laborious task related to the secondary dissolution of platinum obtained from primary chloroplatinate and the rotary performance of all necessary operations. However, even in the two-stage version, it is far from always possible to obtain platinum that satisfies the GOST purity conditions. The reason is isomorphic and nonisomorphic capture of impurities by finely dispersed crystals of chloroplatinate [1]. To obtain chemically pure and even spectrally pure platinum according to the method of I. I. Chernyaev, there is a known method for separating it from salts with a crystal lattice that is completely different from that of chloroplatinates [2] B in the first case, the Peyronediamine Pt (II) salt of the cis structure is used for this, and in the second, the Blomstrand salt (NH ₃ NO ₂ ) ₂ Cl ₂ Pt composition. The use of these nullvalent complexes with the molecular structure of crystals made it possible to obtain in one case platinum with a basic substance content of 99.9998, and in the other a spectrally pure metal.

The latter method is closest in its technical essence to the proposed one. Chernyaev’s method consists in carrying out the following operations: dissolving platinum in aqua regia, first producing platinum hydrochloric acid, and then its potassium salt, which is treated with potassium nitrite to form a solution from which a cis-configuration precipitate is obtained after adding a 20-ammonia solution (NH ₃ NO ₂ ) ₂ Pt. After filtration and washing, this salt is oxidized with gaseous chlorine to give the highly soluble Blomstrand salt. After several recrystallizations from the latter, spectrally pure platinum is obtained by its thermal decomposition.

 This method is not without drawbacks, namely the multi-stage process, the use of chlorination, a small yield of the target salt during its recrystallization, explosiveness during thermal decomposition to platinum black.

 The feedstock in the proposed method, a platinum concentrate obtained by processing deactivated platinum catalysts of the following typical material composition with impurities in the following ranges, wt. Cu 1 2; Ni 0.4 0.6; Cr 1.2 1.8; Si 0.2 0.3; Al 20 26. The amount of platinum concentrate 20 50 the rest is carbon, fluorine and moisture.

 After the aqua regia dissolution of the concentrate, distillation of nitrogen oxides and filtration from the insoluble residue, the resulting platinum hydrochloric acid is converted into potassium chloroplatinate, which is sent for further purification.

The essence of the proposed method is to obtain a complex polymer composition known in chemistry under the name "Magnus green salt" of the form [PtCl ₄ ] [Pt (NH ₃ ) ₄ ] ^o . This salt is practically insoluble in water and mineral acids and is isolated from the aqueous phase in the form of filamentous crystals of strictly stoichiometric composition. In its structure and chemical behavior, it does not have the selective ability to capture impurities of precious metals (excluding palladium). Thus, when platinum is precipitated in the form of Magnus salt, all contaminants of metallic and nonmetallic nature (except for palladium) remain in solution and do not crystallize, and pure platinum black is isolated from the filtered and washed salt by any known method.

To obtain the Magnus salt, the initial contaminated potassium or ammonium chloroplatinate salt is converted into the corresponding chloroplatinate by any convenient method (hydrazine salts or oxalates). A solution of the latter is used to synthesize Magnus salt either during processing with an ammonia solution or by mixing with a stoichiometrically specified amount of a solution of tetramine platinum (II) [Pt (NH ₃ ) ₄ ] ²⁺ .

 The choice of the scheme for producing Magnus salt is dictated by the level of impurities present in the original salt. In the case of a large number of metals (10 30), which give insoluble hydroxides, it is reasonable to first obtain tetraamine and, after filtration, from hydrates, send it to precipitate the salt. If the level of impurities of these elements does not exceed 1 2 then the Magnus salt can be isolated as an intermediate compound in the synthesis of tetraamine.

 To obtain Magnus salt using a solution of ammonia with ammonium chloride. The introduction of ammonium chloride significantly affects the depth of the reaction of substitution of chlorine ligands for ammonia molecules in accordance with the law of mass action, which allows you to control the degree of reaction, as well as to conduct this process during heating.

 In the case of excess ammonia, the resulting Magnus salt can dissolve due to conversion to tetraamine, which is extremely undesirable and leads to the transition of platinum into solution.

 The ratio of ammonium chloride in a 20-t ammonia solution Т Ж 1 10 was selected empirically to the specific reaction conditions: solution temperature, volume, time, mixing speed, etc.

 The process of producing platinum metal from Magnus salt can be carried out in two ways: by its thermal decomposition or chemical reduction in an aqueous medium. The first has a number of significant drawbacks: the use of crucibles for calcination, introducing pollution into platinum powder; metal loss due to thermolysis; a large amount of ammonium chloride and chlorine is released. Thermolysis of salt is accompanied by high costs of thermal energy and the complexity of the process.

 In the proposed process, chemical reduction is carried out in the pulp with a solution of hydrazine hydrate, which is used in the initial stage of the process of obtaining chloroplatinite.

 Partially platinum powder is restored in the form of mirror particles, which indicates their single crystal nature.

 Thus, the implementation of the proposed method provides for the production of high purity platinum.

 Example 1. In a platinum concentrate, the content of basic impurities is at the next level, wt. 0.01 0.03 Mg, Cu, Pb, Sb, Ni; 0.5 Si, Al, Sn, Fe.

To a sample of salt of 60 g in a glass of 1 liter add 100 ml of water and bring this pulp to a boil, then in parts (in 2 3 doses, bring 100 ml of a 9% solution of hydrazine hydrochloride. After 15 to 20 minutes of boiling, the reduction reaction ends, heating is stopped and adding 500 ml of cold water, allow the solution to settle, and then filter from the initial chloroplatinate and compounds of Pt (II) -Pt (IV) of unknown composition, green in color. The yield of chlorplatinite under these conditions is not lower than 90
The resulting solution of potassium chloroplatinite is heated to a temperature of 50-60 ^° C and 150 ml of a 20% solution of ammonia are gradually introduced, and 15 g of ammonium chloride are added. The reaction mixture was continued to warm until the solution became discolored and the Magnus [PtCl ₄ ] [Pt (NH ₃ ) ₄ ] composition was noticeably precipitated. The emerald green crystals separated from the solution are filtered off and washed on the filter with 100 ml of hydrochloric acid diluted 1 2. The residual content of platinum in the mother liquor does not exceed 0.07 g / l. The washed Magnus salt is transferred to a glass, doused with a 5-fold volume of water, the mixture is heated, and reduction to platinum is carried out with a 12% solution of hydrazine hydrate at pH 5-6, supported by a 10% solution of NaOH. The precipitate of metal platinum is defended, filtered and washed with distilled water.

 Obtained in this way, the metal plate according to atomic absorption and spectral analysis contains, by weight. FeO 0.01; Pb 0.008; Si <0.005; Sb <0.005; Sn <0.005; Cu <0.03; Al 0.005. A comparison of the results of the chemical composition of the obtained platinum mobile with the requirement of GOST N 14837-79 for platinum in powder allows us to conclude that it matches the brand no lower than PLAP-2.

 Example 2. The implementation of example 2 is carried out according to the conditions of example 1 to obtain potassium chloroplatinate. The resulting solution is divided into 2 equal volumes. To one of them, with heating, 20 g of ammonium chloride and 200 ml of a 20% solution of ammonia are added until a colorless or slightly yellow solution is obtained.

 The tetraamine Pt (II) solution is filtered off and drained with the remainder of chloroplatinite. During the subsequent heating, crystals of Magnus salt are released. Carrying out further operations to obtain platinum mobile according to the conditions of example 1.

Example 3. In an enameled reactor with a volume of 160 l, equipped with a mechanical stirrer with a controlled stirring speed of 60 120 rpm, add 15 kg of potassium chloroplatinate with a moisture content of about 30 pour 40 l of distilled water, include stirring and heated to a temperature of 70 80 ^o C. By when the desired temperature is reached, 25 l of a 20% solution of hydrazine chloride are introduced into the initial pulp of 200 ml; after the reduction reaction, the solution is filtered.

The resulting potassium chloroplatinate solution was heated to a temperature of 50-60 ^° C, and 37.5 L of a 20% ammonia solution was gradually added to which NH ₄ Cl was added.

 The reaction mixture is heated to isolate crystals of emerald green color, filtered and washed on the filter with 25 l of hydrochloric acid diluted with 1 2.

The washed Magnus salt is washed with a five-fold volume of water, heated to 80 ^° C, reduction to platinum black is carried out with a 12% solution of hydrazine hydrate at pH 5 6, supported by a 10% solution of NaOH to a residual platinum content of 3γ (μg / ml). The remainder of the platinum metal is defended, filtered and washed with distilled water.

Claims (1)

 A method of producing metal platinum, including the reduction of potassium chloroplatinate to potassium chloroplatinate, followed by treatment of the resulting potassium chloroplatinite solution with a reagent to isolate water insoluble platinum salt, characterized in that the treatment is carried out using a solution of ammonium chloride in 20% ammonia in mass the ratio of ammonium chloride and ammonia equal to 1 10, followed by treatment of the obtained insoluble salt of platinum with a reducing agent to release the metal.