RU2309999C2 - Method for extracting noble metals from concentrates - Google Patents

Abstract

FIELD: non-ferrous metallurgy, namely refining of noble metals.

SUBSTANCE: method comprises steps of heat treatment of charge including concentrate and reaction mixture containing aluminum powder and iron oxide at relation of concentrate mass to reaction mixture mass in range (1 : 1.1) - ( 1 : 1.4). Heat treatment is realized in inert gas medium. Refining of heat treated product is realized by leaching without separating product by metal and slag phase.

EFFECT: high degree of extracting metals of platinum group to chemically active forms.

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Description

The invention relates to the field of non-ferrous metallurgy, in particular the refining of precious metals (BM).

The first stage in BM refining technology is the opening of raw materials, i.e. their translation into soluble forms. The composition of BM includes metals of the platinum group (PGM). When opening the raw materials, insoluble residues are formed in which the most resistant PGMs accumulate. Among PGMs, the most resistant metals are the platinum satellite metals (SMEs): rhodium (Rh), iridium (Ir), ruthenium (Ru). Insoluble residues are usually subjected to pyrometallurgical enrichment, and the resulting target alloy is again sent for autopsy. In addition to PGM, non-precious elements are present in the composition of concentrates and intermediate products of refining production. The concentrates resulting from pyrometallurgical enrichment have different elemental composition. With a total content of SMEs (Rh, Ir, Ru) ≥5 wt.%, They are among the most resistant concentrates of refining production, while the maximum total SME content in such concentrates does not exceed, as a rule, 25 wt.%.

A known method of processing gold-containing concentrates by metallothermy method [1], including the preparation of a mixture consisting of a concentrate, fluxes, termite additives and a collector metal, initiating the reaction with an electric fuse and its subsequent flow in air, to obtain the metal phase enriched in the target component in the form of an ingot and slag refining of the enriched phase. The disadvantage of this method is: entanglement of part of the target component in the separated slag, which does not go to processing, and, as a result, low recovery of precious metal, which does not exceed 80-83%.

A known method for the extraction of precious metals from ores and concentrates [2], including mixing the source material with a reaction mixture containing aluminum powder, initiating ignition of the reaction mixture by using a fuse, heat treatment of the charge, separation of the metal phase enriched in precious metals from slag, refining enriched in metal phase. This method is adopted as a prototype.

The disadvantage of the prototype method is: the implementation of melting in the open air, leading to a partial loss of PGM as a result of the formation of volatile oxides, the formation of an oxide film on the surface of the PGM, which reduces their chemical activity [3], as well as the need to separate the enriched metal from the slag phase.

The technical result, the achievement of which the invention is directed, is to increase the extraction of PGMs in chemically active forms.

The achievement of the technical result is ensured by the fact that the initial BM concentrate is mixed with the reaction mixture containing aluminum powder and iron oxide, the concentrate and the reaction mixture are mixed at a ratio of the mass of the concentrate to the mass of the reaction mixture from (1: 1.1) to (1: 1, 4), initiate the ignition of the reaction mixture using a fuse, the heat treatment of the mixture is carried out in an inert gas, the heat treatment product is subjected to refining by leaching.

The essence of the proposed method is as follows. As a result of heat treatment of a mixture consisting of a concentrate and a reaction mixture (stoichiometric mixture of iron oxide with aluminum powder), various intermetallic compounds are formed between PGM and iron, which have a high degree of dissolution chemical activity. An inert medium during the heat treatment prevents the oxidation and loss of part of the PGM as a result of the formation of volatile oxides by them, and also eliminates the formation of an oxide film on the surface of the PGM, which reduces their chemical activity. Eliminates the need for separation and subsequent processing of slag, since the entire heat treatment product is sent to leaching.

Nonequilibrium intermetallic compounds of SMEs with iron have a low lattice energy, which ensures their increased chemical activity. Special experiments have shown that the maximum degree of extraction of Rh, Ir, Ru from the concentrate is achieved when the ratio in the charge of the mass of the concentrate to the mass of the reaction mixture is from (1: 1.1) to (1: 1.4). The completeness of opening with an increase in the quantity of the reaction mixture in the charge does not increase, and a decrease in the amount of the reaction mixture leads to a decrease in the specific thermal effect of the reaction and to a decrease in the completeness of opening.

The main advantages of the proposed technical solution for the method of extraction of precious metals from concentrates are:

- a high degree of PGM extraction;

- the lack of need for separation of the heat treatment product into metal and slag phases;

Examples

For opening, a concentrate of precious metals of the following composition was taken, shown in table 1.

Table 1 Element Pt Pd Rh Ir Ru Au  Wt% 7,186 11,228 5,291 5,328 10.553 2,021 Σ (Rh, Ir, Ru) = 21.172 wt.%.

Several samples of the concentrate weighing 10 g each were sewn with the reaction mixture at different weight ratios. A representative part of the charge was loaded into a crucible, rammed to a certain volume corresponding to the required bulk density, the crucible was placed in an inert argon gas medium or left in the open air, kept in an inert gas medium for 5-10 minutes, an electric valve initiated a reaction proceeding with the release of heat in the mode of self-propagating high-temperature synthesis, the crucible was cooled, extracted from argon medium, the product or the metal phase separated from slag was crushed and leached in aqua regia for 1.5 hours at a temperature of 90 ° C. The solution was filtered, the insoluble residue was washed with dilute hydrochloric acid, dried, weighed, and the residual content of the MSP was determined by spectral analysis. Wash water was combined with the mother liquor and analyzed for ICP content by induction coupled plasma (ICP).

The results of a series of experiments on the extraction of precious metals from the concentrate (K) after heat treatment of the mixture prepared by mixing the concentrate with the reaction mixture (PC) at various mass ratios: (K: PC) = (1: 0.67); (1: 1); (1: 1.22); (1: 1.5) are shown in table 2.

As can be seen from the above examples, the use of the proposed method allows to achieve high extraction of Rh, Ir, Ru from a concentrate of precious metals.

Information sources

1. Gostishchev V.V., Lebukhova N.V. Processing of gold-bearing concentrates by metallothermy method // Chemical technology. - 2005. - No. 2. - S. 28-31.

2. Patent 2078840. RF. The method of extraction of precious metals from ores and concentrates. Gostishchev V.V., Kovalev A.A., 05/10/97.

3. Ginzburg S.I., Yezerskaya N.A., Prokofieva I.V. et al. Analytical chemistry of platinum metals. M .: Nauka, 1972, p. 19.

table 2 Experience number K: PC ratio Heat treatment medium Separation of heat treatment products Recovery in solution, wt.% The output of insoluble residue, wt.% The output of slag, wt.% Rh Ir Ru Total (Rh, Ir, Ru) one 1: 0.67 Argon No 56.34 56.32 56.87 56.60 51.81 - 2 1: 1 Argon No 91.14 > 99 88.90 92.24 41.14 - 3 1: 1.22 Argon No 92.95 96.00 95.54 95.01 37.74 - four 1: 1.22 Argon Yes 84.27 79.86 80.21 81.14 19,20 28.00 5 1: 1.22 Air No 71.52 66.91 69.36 70.35 46.50 - 6 1: 1,5 Argon No 87.83 91.56 86.35 88.04 45.94 -

Claims (2)

1. The method of extraction of precious metals from concentrates, including the preparation of the mixture by mixing the concentrate with the reaction mixture containing aluminum powder, initiating ignition of the reaction mixture using a fuse and heat treatment of the mixture, characterized in that the reaction mixture further comprises iron oxide, mixing the concentrate and the reaction mixture is carried out at the ratio of the mass of the concentrate to the mass of the reaction mixture from (1: 1.1) to (1: 1.4), the heat treatment is carried out in an inert gas medium, the heat treatment product is tested leaching refining by leaching. 2. The method according to claim 1, characterized in that for the extraction of precious metals using concentrates with a total content of Rh, Ir, Ru from 5 to 25 wt.%.