RU2550064C2 - Processing method of copper anode slime - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy of non-ferrous and precious metals, namely to processing of slimes of electrolytic copper refining. A processing method of copper anode slime involves decoppering, saturation and leaching of selenium from decoppered slime or products of its saturation in an alkaline solution. Leaching of selenium is performed in a solution that contains a reducing agent, namely water-soluble organic or non-organic compounds providing a normal oxidation-reduction potential of the system in alkaline medium of more positive than -0.3 V in relation to a hydrogen electrode. With that, leaching is performed in a solution containing 50-200 g/l of sugar as a reducing agent and 20-100 g/l of alkaline at the temperature of 70-90°C.

EFFECT: increasing speed and limit degree of selenium leaching.

2 cl, 2 tbl, 1 ex

Description

The invention relates to the field of metallurgy of non-ferrous and noble metals, in particular to the processing of sludge from electrolytic refining of copper.

The complexity of the composition of the sludge, the diversity of chemical compounds and phases determine the presence of a wide range of technological schemes for processing in general and, in particular, methods for the extraction of precious metals, selenium and tellurium in the form of marketable products. At most enterprises, copper and nickel are sequentially removed from the sludge, selenium and tellurium are isolated with their release in the form of marketable products. In some cases, lead is extracted from the sludge by hydrometallurgical methods, but in any case, the main component of the pre-treated sludge is Ag ₂ Se silver selenide.

The final stage of sludge processing is smelting, the main task of which is to obtain a gold-silver alloy. Melting is accompanied by the formation of a large number of dust and gas products and slags. The turnover of precious metals in these products is a significant drawback of smelting (1. Metallurgy of precious metals: In 2 books. Book 1 / Yu.A. Kotlyar, MA Meretukov, LS Strizhko. - M.: MISIS, "Ore and Metals", 2005., - 432 pp. 2. Maslenitsky I.N., Chugaev L.G. Metallurgy of precious metals. - M .: Metallurgy, 1987. - 366 pp. 3. Meretukov M.A. ., Orlov AM Metallurgy of precious metals. Foreign experience. - M.: Metallurgy, 1990. - 416).

A supplement or alternative to smelting can be considered various hydrometallurgical technologies for processing sludge based on the use of sulfatizing, oxidizing, autoclave and electrochemical processes. In particular, to extract selenium and tellurium from sludges, nitric acid leaching, hydrochlorination, autoclave leaching in alkaline solutions are used (4. Belenky AM, Petrov GV, Baudouin A.Ya., Kukolevsky A.S. Nitric acid leaching of copper electrolyte sludges // Notes of the Mining Institute: New Technologies in Metallurgy, Chemistry, Enrichment and Ecology. - St. Petersburg, 2006. - T. 169. - S. 53-56; 5. Pat. 2215801 of the Russian Federation, IPK7 С22В 11/00. A method of obtaining selective concentrates of noble Metals / Graver T.N., Volkov L.V., Schneerson Y.M. et al .; publ. 10.11.2003). A distinctive feature of these methods is the oxidative nature of the effects of the reagents used on chalcogenides, while the oxidation products are selenite and selenate, tellurite and telluride ions.These processes are associated with the use of aggressive reagents and sophisticated equipment, they do not provide selectivity.

The known method, selected as a prototype and including leaching of selenium in an alkaline solution, while leaching of selenium is carried out in a solution containing a reducing agent, which is used electronegative metals, for example aluminum, zinc (6. SU 165309A, IPC C22B 61/00, from 11/23/1964).

The considered method is fundamentally different in the restorative nature of the processing of raw materials.

The method is based on the reaction proceeding in the volume of the reaction mass:

l, 5Ag ₂ Se + 4NaOH + Al = 3Ag + 1.5Na ₂ Se + NaAlO ₂ + 2H ₂ O

l, 5Ag ₂ Se + 4NaOH + Zn = 3Ag + 1.5Na ₂ Se + Zn (OH) ₂ + 2H ₂ O

as a result of which silver is reduced to metal and remains in powder form as part of a solid product, and selenium passes into a solution in the form of sodium selenide Na ₂ Se. Selenium is extracted from alkaline solutions by known methods to obtain a marketable product.

The advantages of the considered method are the “softness” of the modes, a sufficiently high speed and high extraction of selenium from the sludge. The main disadvantage of the prototype is the accumulation of aluminum (or zinc) in the solution and the need for disposal of such solutions. In addition, the interaction of alkaline solutions with cementing metals is likely to produce hydrogen:

NaOH + Al + H ₂ O = NaA1O ₂ + 1.5H ₂

This undesirable reaction leads to unproductive consumption of metals and the release of explosive gas.

The present invention addresses these drawbacks. The technical result is when replacing the reducing agent.

The technical result is achieved by using a method including decontamination, leaching of selenium from an decontaminated sludge or its enrichment product in an alkaline solution, characterized in that the leaching of selenium is carried out in a solution containing a reducing agent, which is used as a water-soluble organic or inorganic compounds that provide normal oxidation the reduction potential of the system in an alkaline medium is more positive than -0.3 V with respect to the hydrogen electrode. In particular, leaching of selenium is carried out in a solution containing 50-200 g / l of sugar, 20-100 g / l of alkali, at a temperature of 70-90 ° C.

The fundamental difference between the proposed method and the prototype is reduced to the re-treatment of the sludge with reagents, when used, hydrogen evolution and accumulation of undesirable products do not occur under the conditions of solution circulation. Thermodynamic analysis found that the main component of the decontaminated sludge - silver - can be reduced directly from the solid phase of selenide by various reducing agents. With a higher probability, the process proceeds in an alkaline medium in which selenium forms a highly soluble sodium selenide. Theoretically, solid-phase reduction is realized using hydrazine:

2Ag ₂ Se + N ₂ H ₄ + 4NaOH = 4Ag + 4H ₂ O + 2Na ₂ Se + N ₂ ; sodium sulfite:

Ag ₂ Se + 2NaOH + Na ₂ SO ₃ = 2Ag + Na ₂ Se + Na ₂ SO ₄ + H ₂ O; and some other reagents.

Calculations and laboratory studies have shown that this process requires a certain activation energy and, in practice, is realized in an alkaline medium when the redox potential of the system is reached, which is more positive than -0.35 V. This characteristic is determined, first of all, by the solubility product of silver selenide and depends on the nature of the resulting reaction products.

Calculations and practice have established that when using gaseous (propane, hydrogen) or solid (coal, flour) reducing agents, the process is impossible. Therefore, the choice is limited to water-soluble reagents.

When choosing a reducing agent, one should proceed from its reducing ability (potential), availability (cost), the possibility and complexity of processing the resulting products, environmental cleanliness and safety in use. In view of these considerations, sugar and its technical derivatives have significant advantages as a reducing agent in the proposed method. The process in this case is accompanied by the formation of water and carbon dioxide:

C ₁₂ H ₂₂ O ₁₁ + 24Ag ₂ Se + 48NaOH = 48Ag + 24Na ₂ Se + 12CO ₂ (g) + 35H ₂ O

The stoichiometric and practical consumption of sugar for the course of this reaction does not exceed 1 g per 15 g of silver selenide.

An increase in the sugar content in the solution from 50 to 200 g / l accelerates the reaction. At higher concentrations, the viscosity of the solutions increases and the process slows down. The alkali concentration has a positive effect in the range of 20-100 g / l. Heating the reaction mixture is favorable, but excessive heating leads to the release of toxic and aggressive vapors.

An example of the implementation of the proposed method can be the results of the following experiments.

Example

The selenium was leached from the debonded copper electrolysis slurry (UMMC) containing 29% Pb; 19% Ag; 7.5% Se. In other experiments, the oxidized phase (lead sulfate) was separated from chalcogenides and noble metals from decontaminated sludge by flotation. Selenium was leached from a flotation concentrate containing more than 80% silver selenide Ag ₂ Se.

In 100 ml of a solution of alkali NaOH (50 g / l) was added 10 g of sludge or flotation concentrate and solutions containing 10 g of various reducing agents. The reaction mixture was heated to a temperature of 80 ° C and leaching was carried out with stirring for 1 hour. During the process, the redox potential of the system was measured by a standard method using platinum and h.s. comparisons. At the end of the process, the solution was separated from the undissolved residue, the selenium content was determined in it, and the leaching rate was calculated. The results of the experiments are presented in table 1.

In the second series of experiments, reductive leaching of the sludge by sugar was carried out at various parameters for 15 minutes; while comparing the speed of the processes. Under the same conditions, the process was carried out for 1 hour, the selenium content was determined in the undissolved residue, and the degree of leaching of selenium was evaluated. The results of the experiments are shown in table 2. For comparison, an experiment was conducted according to the prototype method, while powdered aluminum and granular zinc were used as a reducing agent.

Comparative analysis of well-known technical solutions, including the method selected as a prototype, and the present invention allows to conclude that it is the totality of the claimed features ensures the achievement of the perceived technical result. The implementation of the proposed technical solution makes it possible to exclude the evolution of hydrogen during leaching of selenium and the need for disposal of aluminum (zinc) -containing solutions.

Claims (2)

1. A method of processing a copper-electrolyte sludge, including decontamination, enrichment and leaching of selenium from an de-ionized sludge or an enrichment product in an alkaline solution, the leaching of selenium is carried out in a solution containing a reducing agent, which is used as a water-soluble organic or inorganic compounds that provide normal oxidation the reduction potential of the system in an alkaline medium is more positive than -0.3 V with respect to the hydrogen electrode. 2. The method according to claim 1, characterized in that the leaching of selenium is carried out in a solution containing 50-200 g / l of sugar as a reducing agent and 20-100 g / l of alkali, at a temperature of 70-90 ° C.