RU2367691C1 - Method for processing of sulphide ores and pyrrhotine concentrate - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: method includes the leaching of non-ferrous metals with bacterial solution containing ions of trivalent iron with using of beforehand prepared bacterial solution of Acidithiobacillus ferrooxidans containing the ions of trivalent iron with content not less than 9 g/l and sulphuric acid. The latter is added at temperature 75-85C in amount providing the solution pH equal 1.3. Mineral raw material is sulphide copper-nickel ore or obtained from it pyrrhotine concentrate. The leaching is carried out during 60-48 hrs with mixing speed 400 rpm. ^ EFFECT: high degree of sulphide destruction, selective oxidation of pyrrhotine component, extraction enhancing of more than one metal, broadening of the processed products range, simplification of the process scheme. ^ 11 cl, 5 ex ^ .

Description

The invention relates to biotechnology, hydrometallurgy of non-ferrous rare and precious metals, more specifically, the invention relates to a new method for processing mineral raw materials containing metal sulfides, and can be used for leaching non-ferrous metals from ores and pyrrhotite concentrates, in particular from copper-nickel ores, which are refractory, or their concentrates.

There are various methods of processing sulfide ores: pyrometallurgical (Khudyakov I.F., Tikhonov V.N., Deev V.I., Naboyuchenko S.S. Metallurgy of copper, nickel and cobalt. - M .: Metallurgy. 1977, v.2 94 pp.), Flotation (Reznik I.D., Ermakov G.P., Shneerson, Ya.M. Nickel: in 3 volumes. Oxidized nickel ores. Characterization of ores. Pyrometallurgy and hydrometallurgy of oxidized nickel ores. - M. : Science and Technology. 2004. V. 2. 468 pp.), Hydrometallurgical (Gutin V.A. Isolation and processing of the Feinstein magnetic fraction is one of the ways to increase the extraction of precious metals c. Nonferrous metals. 1988. №12, p.28-29), biotechnology (Karavaiko GI Grudev S. (Ed.) Biogeotechnology metals. GKNT CIP. 1985. 435 pp.).

The disadvantages of the known pyrometallurgical methods for the processing of industrial products of copper-nickel production are high operating costs, multi-process flows, the formation of significant volumes of circulating products with a concentration of platinum metals in them. A disadvantage of the known flotation methods is the relatively low contrast of the flotation properties of the shared minerals - pentlandite and pyrrhotite - at the stage of their selection.

Environmentally friendly and more economical are biotechnological methods that are widely used and are constantly being improved. The basis of the bioleaching process is the bacterial oxidation of Fe ²⁺ to Fe ³⁺ , which serves as a powerful oxidizing agent for sulfide minerals and promotes the release of valuable metals (such as copper, nickel, cobalt, gold, etc.), as well as the oxidation of sulfur to sulfuric acid.

It is well known that microbial cultures can oxidize insoluble sulfides directly or indirectly. In direct oxidation, the destruction of the crystalline structure of a sulfide mineral occurs due to the action of the enzyme systems of living microorganisms. Indirect oxidation of sulfide minerals is associated with the action of Fe ³⁺ ions, which, in turn, is a product of the microbial (bacterial) oxidation of a compound of ferrous iron and iron-containing sulfide minerals.

Depending on the characteristics of the feedstock, one or another method of processing is selected. There is a method of heap bioleaching of sulfide ores, applicable for pan leaching (patent US 6207443 B1, 03/27/2001), which includes grinding products, flotation separation and two stages of biooxidation by the association of microorganisms with the oxidation of sulfides and the release of metals into solution. The disadvantages of the presented method are the multiplicity and complexity of the processing scheme (grinding, separation, separation into products, flotation, agglomeration), the density of the solid at the stage of bioleaching is not more than 4.5%, as well as the use of a complex association of microorganisms having different temperature optima for life, which complicates the technological parameters of the bioleaching process.

A known method of processing products containing metal sulfides (sulfides of nickel and copper) (patent CA 2282848, C22B 3/18), including the biological oxidation of mineral concentrates using thermophilic, moderately thermophilic bacteria and archaea. The specified biotechnology allows the extraction of metals from raw materials using the association of microorganisms that destroy metal-containing minerals, oxidizing sulfur of mineral sulfides to sulfuric acid and converting metals from minerals to solution. Leaching occurs during the cultivation of microorganisms. The disadvantages of this bacterial method of processing sulfide ores are the low leaching rate (vat leaching time is 80-120 hours), the need to aerate with an oxygen-containing gas and maintain certain technological conditions necessary for the life of microorganisms. For example, the high oxidative activity of mesophilic bacteria is observed when the solids content in the process of tank leaching is not more than 25%. In violation of the vital conditions of bacteria, despite their adaptability, the oxidative activity of microorganisms is significantly reduced, and the oxidation of sulfides is inhibited.

An increase in the processing speed of products containing metal sulfides is achieved in another known method due to the use of leaching using thermophilic bacteria at a temperature of 45-68 ° C (application WO 00717763, C22D 3/18, 30.11.2000). However, the method retains the disadvantages of the bacterial process - the duration, restrictions on temperature, acidity, concentration of substances, in addition, thermophilic bacteria can not withstand an increase in the solids content above 10%.

A known method of processing products containing metal sulfides (patent RU 2245380 C1, 10.21.2003). The method is devoid of the disadvantages of the above inventions. The method includes leaching the processed products in a sulfuric acid solution with a concentration of from 1.8 to 35 g / dm ³ , at a temperature of 0 to 150 ° C, in the presence of ferric ions more than 1 g / dm ³ . In the description of the invention, copper-nickel ores are processed under the condition of autoclave leaching at a pressure of 6 atm, a temperature of 145 ° C, a concentration of ferrous sulfate up to 8.5 g / l, and a solid phase content of up to 20%.

The disadvantages of this method of autoclave processing of products are: high temperature and pressure; high energy intensity; relatively low process selectivity due to harsh leaching conditions; significant yield of insoluble residue; obtaining a mixed solution containing copper and nickel; a complex scheme for the isolation of platinoids from a glandular precipitate in an autoclave; the release of only one metal in the solution.

The closest in technological essence of the claimed invention is a method for processing sulfide copper-zinc products (patent RU 2203336, C22D 3/18, 03/05/2002). The method is devoid of the disadvantages of the above inventions. Moderately thermophilic and mesophilic bacteria are used as bacteria. Leaching of processed products is carried out in two stages: the first stage is leaching at a temperature of 60 to 80 ° C, pH 1.6-1.7, ferric ion concentration of 8-12 g / l, dispersion of solid particles up to -44 microns and its content in the suspension is 25-40% until the accumulation of the sludge fraction (-10 μm) up to 40-60% by weight of the leachate product, from which the + 10 μm fraction is separated and returned to the first stage, and the second stage - re-leaching of the sludge fraction with ion regeneration ferric iron up to 12-15 g / l during aeration with air and return of solution with ferric iron in the first stage, carried out at 28-32 ° C. The disadvantages of the method are the limitations associated with the technological parameters of the process, the multi-stage leaching process and the need to use for processing products a complex hardware system for separating the solid phase by size.

The objective of the invention is to develop an environmentally friendly, cost-effective way to extract non-ferrous metals in a solution for a shorter period of time, to conduct the maximum selective oxidation of the main ore component - pyrrhotite, since the extraction of pyrrhotite from concentrates entering the smelting is an important task both from the point of view of minimizing emissions sulfur dioxide into the atmosphere, and from the point of view of reducing penetration at the metallurgical processing.

The problem is solved in that a method is developed for processing mineral raw materials containing metal sulfides, including leaching of non-ferrous metals with a bacterial solution containing ferric ions, different from the known one in that the leaching is carried out with a pre-prepared bacterial solution of Acidithiobacillus ferrooxidans containing at least 9 g / l of ions ferric iron and sulfuric acid, added in an amount sufficient to achieve a pH of a solution of pH 1.3, with a temperature of 75-85 ° C.

The bacterial solution is prepared on the mineral medium of Silverman and Lundgren with the addition of ferrous salts, and after the bacteria have completely oxidized ferrous iron to ferric, the temperature of the solution is raised to the temperature necessary for the process. In addition, the required amount of sulfuric acid is also added, that is, the conditions necessary for the leaching process are created.

To create a bacterial solution, in particular, Acidithiobacillus ferrooxidans bacteria isolated from samples of mineral raw materials, for example, from copper-nickel ore, are used. The leaching process, in particular, is in the range of 60-48 hours. In particular, sulfide copper-nickel ore or the pyrrhotite concentrate obtained from it can be used as mineral raw materials. Pyrrhotite concentrate, in particular, can be obtained by magnetic ore dressing. The leaching process is preferably carried out with stirring at a speed of 400 rpm. The ratio of the mineral feed to the leach solution is preferably 1: 5.

After completion of the leaching process, metals are isolated from the solution.

The solution after leaching of mineral raw materials is subjected to bacterial regeneration with the formation of ferric sulfate and replace it with a leaching solution.

In contrast to the known method, the leaching of mineral raw materials is carried out by the prepared bacterial solution in one stage according to a simplified scheme. A method for processing mineral raw materials containing metal sulfides includes leaching of non-ferrous metals with a bacterial solution containing ferric ions, characterized in that the leaching is carried out with a pre-prepared bacterial solution of Acidithiobacillus ferrooxidans containing at least 9 g / l of ferric ions and sulfuric acid added to an amount sufficient to achieve a pH of 1.3, with a temperature of 75-85 ° C. Leaching of mineral raw materials (sulfide ore or pyrrhotite concentrate) is carried out with stirring at a speed of 400 rpm, the ratio of mineral raw materials and leach solution is 1: 5. After leaching of mineral raw materials, non-ferrous metals are isolated from the solution, the solution is subjected to bacterial regeneration with the formation of ferric sulfate and the leaching solution is replaced by it

Thus, the stated conditions of the leaching process allow us to achieve a new technical result, which consists in a high degree of decomposition of sulfides, selective oxidation of the pyrrhotite component, an increase in the extraction of non-ferrous metals, an expansion of the spectrum of processed products and a reduction in the time of leaching, simplification of the processing scheme, also reduces energy consumption, reduction of expenses of expensive reagents, as well as costs of expensive equipment.

A feature of the mineralogical composition of sulfide minerals used to confirm the implementation of the leaching of metals, according to the claimed method is the high content of pyrrhotite, which includes non-ferrous metals in its crystal lattice. Thus, the pyrrhotite of copper-nickel ore from the Shanuch deposit contains up to 20% of all nickel. Thus, the complete oxidation of non-ferrous metals from ores requires the oxidation of pyrrhotite.

The mechanism of chemical oxidation of sulfide minerals on the example of pyrrhotite can be represented as follows:

1) FeS + 0.5O ₂ + H ₂ SO ₄ = FeSO ₄ + S ⁰ + H ₂ O

2) 2FeSO ₄ + 0.5O ₂ + H ₂ SO ₄ = Fe ₂ (SO ₄ ) ₃ + H ₂ O

3) FeS + Fe ₂ (SO ₄ ) ₃ → 3FeSO ₄ + S ⁰

Oxidation of pyrrhotite with oxygen in an acidic environment with the formation of transition salts of nickel, iron and elemental sulfur (1). The composition of the leach solution includes Fe ³⁺ sulfate, which is also an active oxidizing agent of many sulfide minerals. The reaction rate (2) is much lower than the reaction rate (3); therefore, the bulk of pyrrhotite is oxidized by ferric ions. When pyrrhotite is oxidized with ferric sulfate, ferrous sulfate is formed (3), which, when the leach solution is regenerated, is oxidized by bacteria again to the oxide form (4).

The preparation of a leach solution containing ferric iron and sulfuric acid was carried out as follows: first, a bacterial solution was prepared. A bacterial culture was grown using a nutrient medium containing salts of nitrogen, magnesium, chlorine, phosphorus, and iron (the aqueous mineral base of the standard Silverman and Lundgren culture medium for microorganism cultivation (Silverman MP, Lundgren DC Study on the chemoautotrophic iron bacterium Ferrobacillus ferrooxidans I. An improved medium and harvesting procedure for securing high cell yield // J. Bacteriol. 1959. V.77. No. 5. p.642-647) with the addition of ferrous salts. The acidity of the medium was adjusted to pH 1.6-1.8 with sulfuric acid Acidithiobacillus ferrooxidans bacteria in the ratio 1:10 (vol. m. Inoculum: the nutrient medium, respectively) Cultivation was carried out under optimum conditions for the microorganisms (28-30 ° C, pH 1,7; aeration and agitation) Culturing of bacteria led to the complete oxidation of ferrous iron, i.e. the translation into Fe ²⁺ Fe. ³⁺ to obtain a solution containing the required concentration of ferric iron (at least 9 g / l). After that, to obtain the leach solution necessary for the implementation of the leaching process, the pH of the solution was adjusted to 1.3 with sulfuric acid and the temperature of the resulting bacterial solution was raised to 75-85 ° C. Leaching with a prepared solution containing ferric ions in a dissolved state provides effective oxidation of metal sulfides at a temperature of 75-85 ° C and normal atmospheric pressure.

To maintain a high oxidizing potential of the system and the economical use of reagents during the leaching of sulfide-containing products, the replacement of the leach solution, in particular, if desired, is controlled by the value of ferric ions. A possible replacement of the leach solution is carried out with a decrease in the solution of ferric iron ions, which leads to a decrease in the redox potential. Maintaining the concentration of sulfide oxidizing agent - ferric ions - leads to an increase in the speed and depth of sulfide leaching and a decrease in the time of the process. In addition, the bacterial cell mass plays the role of surface-active substances, sorbing elemental sulfur on its surface (Karavayko G.I., Kuznetsov S.I., Golomzik A.I.The role of microorganisms in the leaching of metals from ores. - M.: Science . 1972. 248 S.), and thereby prevents the agglomeration of particles of the substrate, which also helps to accelerate the leaching process.

The proposed method has several advantages, which allows it to be used more widely along with other hydrometallurgical processes and makes it promising in the processing of mineral raw materials. Firstly, this process is fully controllable and controllable in comparison with heap and underground leaching processes. Secondly, it is used for finely ground products, which significantly accelerates the destruction of sulfide minerals. Thirdly, by creating certain leaching conditions, a high degree of selectivity can be achieved when extracting valuable components from complex mineral substrates. Fourth, the method does not require the use of special equipment, it can be carried out, for example, in acid-resistant vats and packs, providing the necessary mixing and aeration. And finally, this method is relatively low temperature, without harmful emissions into the atmosphere, with a closed water circulation. those. ecologically pure.

The method is confirmed by examples of leaching of complex complex ores, which are characterized by close mutual germination of minerals and the presence of atoms of other metals in the crystal lattice of minerals, for example, nickel in pyrrhotite, cobalt and copper in pentlandite, and gold in chalcopyrite. The metal content in the ore is: nickel - 5.9-6.2%, copper - 0.6-1.2%, cobalt - 0.14-0.25%, gold - up to 0.2 g / t, platinum - up to 0.4 g / t, palladium - 1.5 g / t, iridium - 0.3 g / t. The material composition of the ore determines the increased complexity of processing according to traditional technological schemes using the methods of magnetic, gravitational and flotation concentration and production of tailings. For leaching, copper-nickel sulfide ore and pyrrhotite concentrate obtained by magnetic ore processing at the Shanuch deposit were used. The yield of pyrrhotite concentrate is 48.9% of the ore with the content,%: 3.2 Ni, 0.04 Cu, 0.05 Co, 49.9 Fe, 39.4 S. The main amount of nickel in the concentrate is in pentlandite, which enters enrichment concentrate due to thin germination with pyrrhotite and a large number of sprouts. Nickel is also found in the crystal lattice of pyrrhotite - nickel-bearing pyrrhotite in an amount of up to 1.5%. The Shanuch deposit's pyrrhotite copper-nickel ore contains nickel, copper, cobalt, gold, silver, and platinum metals that are of interest for recovery. The main ore minerals are pyrrhotite Fe ₇ S ₈ , pentlandite (Fe, Ni) ₉ S ₈ , chalcopyrite CuFeS ₂ , pyrite FeS ₂ , minerals of the Violarite group FeNi ₂ S ₄ .

The process was monitored by changes in pH, Eh, and the concentration of metal ions (Ni ²⁺ , Cu ²⁺ , Fe ²⁺ , Fe ³⁺ ). Fe ³⁺ ions were determined spectrophotometrically after reaction with ammonium thiocyanate at a wavelength of 475 nm. The total amount of iron ions was determined after the conversion of Fe ²⁺ to the trivalent form by ammonium sulphate by the rhodanide method by the concentration of the rhodanide complex using a spectrophotometer (Reznikov A.A., Mulikovskaya E.P., Sokolov Yu.I. Methods of analysis of natural waters. - M. : Nedra, 1970). The concentration of copper and nickel was determined on an atomic absorption spectrophotometer (Perkin Elmer). After cessation of leaching, the pulp was directed to the separation of solid and liquid phases. A solid residue with a high content of elemental S ⁰ can be further directed to the stage of bacterial oxidation, which can be carried out by the association of chemolithotrophic thermophilic bacteria. At this stage, complete leaching (by 90-95%) of Ni, Cu, and Co can be achieved, as well as the opening of gold interspersed in sulfide minerals, which will allow it to be extracted almost completely by subsequent cyanidation. Non-ferrous metals are extracted from the liquid component of the pulp by conventional methods, the Fe ²⁺ solution ^is fed to bacterial regeneration with the formation of ferric sulfate Fe ₂ (SO ₄ ) ₃ .

The invention (can be illustrated) is illustrated by the following examples.

Example 1. Sulphide copper-Nickel ore of the Shanuch deposit, pre-crushed to 90% of the particle size class ± 44 μm, containing 6.2% Ni, 1.1% Cu and 0.16% Co, was mixed with a leach solution in the ratio of t: W = 1: 5. The ore leaching process was carried out at a temperature of 85 ° C, with mechanical stirring at a stirrer rotation speed of 400 rpm. Leaching time is 48 hours. Up to 80% Ni, 59% Cu and 75% Co. go into the solution from the ore.

Example 2. Sulfide copper-Nickel ore of the Shanuch deposit, pre-crushed to 70% particle size class -74 ± 44 μm, containing 6.2% Ni, 1.1% Cu and 0.16% Co was mixed with a bacterial solution in the ratio of: W = 1: 5. The ore leaching process was carried out at a temperature of 75 ° C, with mechanical stirring at a stirrer rotation speed of 400 rpm. Leaching time 60 h. Up to 75% Ni, 40% Cu and 60% Co. go into solution from the ore.

Example 3. Sulphide copper-nickel ore of the Shanuch deposit, pre-ground to 90% of the particle size class ± 44 μm, containing 6.2% Ni, 1.1% Cu and 0.16% Co was mixed with the prepared leach solution in the ratio t: w = 1: 5. The ore leaching process was carried out at a temperature of 75 ° C with mechanical stirring at a stirrer rotation speed of 400 rpm. Leaching time 60 h. Up to 78% Ni, 59% Cu and 71% Co. go into the solution from the ore.

Example 4. As a result of leaching of non-ferrous metals from a pyrrhotite concentrate, having a degree of grinding up to 90% of the class ± 44 μm, with a pulp density of t: w = 1: 5 with mechanical stirring at a speed of rotation of the mixer of 400 rpm and a temperature of 85 ° C, after 48 hours, the yield of metals in the solution was: Ni 70%, Cu 20%, Co 92%. The oxidation of pyrrhotite was 100% and 25% pentlandite + pyrrhotite in the intergrowths. The duration of the leaching process is 48 hours. In this case, only in the first 9 hours of the process, the Ni yield is 42.8%, which indicates the achievement of a high speed leaching process.

Example 5. When leaching a prepared solution of a pyrrhotite concentrate having a degree of grinding up to 90% of a class of ± 44 μm, with a pulp density of t: W = 1: 5 with mechanical stirring at a speed of rotation of the mixer of 400 rpm and a temperature of 75 ° C for 60 hours the yield of metals in the solution was 68% Ni, Cu 18%, Co 87%.

Thus, the proposed method for processing mineral raw materials allows non-ferrous metals to be leached from sulfide ore or pyrrhotite concentrate with a high yield of elements into solution in a relatively short period of time, and also to selectively separate the leach substrate with complete oxidation of the pyrrhotite component.

Claims (11)

1. A method of processing mineral raw materials containing metal sulfides, including leaching of non-ferrous metals with a bacterial solution containing ferric ions, characterized in that the leaching is carried out with a pre-prepared bacterial solution of Acidithiobacillus ferrooxidans containing at least 9 g / l of ferric ions and sulfuric acid, added in an amount sufficient to achieve a pH of 1.3, with a temperature of 75-85 ° C. 2. The method according to claim 1, characterized in that the bacterial solution is prepared on a silver and Lundgren mineral medium with the addition of ferrous salts and complete oxidation by bacteria Acidithiobacillus ferrooxidans. 3. The method according to claim 2, characterized in that the bacteria Acidithiobacillus ferrooxidans isolated from samples of mineral raw materials, for example from copper-Nickel ore. 4. The method according to claim 1, characterized in that the leaching is carried out for 60-48 hours 5. The method according to claim 1, characterized in that sulfide copper-nickel ore or a pyrrhotite concentrate obtained from it are used as mineral raw materials. 6. The method according to claim 5, characterized in that sulfide copper-nickel ore is used as a mineral raw material. 7. The method according to claim 5, characterized in that the raw material used is pyrrhotite concentrate obtained by magnetic ore beneficiation. 8. The method according to claim 1, characterized in that the leaching is carried out with stirring at a speed of 400 rpm./min 9. The method according to claim 1, characterized in that the ratio of mineral raw materials and leaching bacterial solution is 1: 5. 10. The method according to any one of claims 1 to 9, characterized in that after leaching from the solution non-ferrous metals are isolated. 11. The method according to claim 1, characterized in that the solution after leaching of mineral raw materials is subjected to bacterial regeneration with the formation of ferric sulfate and replace it with a leaching solution.