RU2560627C2 - Method of leaching of valuable components and rare-earth elements from cinder material - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to biohydrometallurgy, in particular to biotechnology of extraction of valuable components and rare-earth elements from coal combustion products - cinder material. The method of leaching of valuable components and rare-earth elements from cinder material includes preparation of a pulp in the bioreactor with the ratio of solid vs liquid phases (S:L) = 1:5, and the ratio of cinder material vs. element sulphur is 10-20:1. Then pH level of the pulp of concentrated sulphuric acid is brought to the values 2.0-3.0, nutritious salts are added to the pulp and the pulp is inoculated by adding of 10% of the culture liquid containing cenosis of acidophile chemolithotrophic microorganisms. Then the process of biooxidation of element sulphur by microorganisms is performed with mixing the pulp, aeration by air and at the temperature 44-46°C, followed by formation of sulphuric acid, decrease of pH level and leaching of valuable components and rare-earth elements.

EFFECT: decrease of consumption of reagent (sulphuric acid) for leaching of valuable components and rare-earth elements from cinder material and decrease of consumption of electric power for maintaining of temperature of reactionary mix.

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Description

The invention relates to the field of biohydrometallurgy, in particular to biotechnology for the extraction of valuable components and rare-earth elements from coal combustion products - ash and slag material.

At present, the problem of using waste from heat and power generation facilities, in particular ash and slag materials generated during the burning of coal, has not been resolved both in the world and in Russia. When coal is burned, solid waste is formed: fly ash and slag, which are transported to dumps, where they are stored and stored outdoors or under a layer of water. At present, billions of tons of ash and slag materials have accumulated in the world in dumps, which create great environmental tension in the regions of heat and power facilities, pose a threat to the environment and human health. As a result of wind erosion, ash particles enter the atmosphere and, settling, pollute the soil with toxic substances. Under the influence of acid precipitation, toxic substances migrate from dumps, leading to pollution of soils, groundwater, and surface waters. The equipment and operation of ash and slag dumps require significant costs, in addition, fertile lands are alienated under them.

From the point of view of rational environmental management, ash and slag materials are anthropogenic raw materials that can meet many of the needs of industry. Noble metals (gold, silver), trace elements (vanadium, gallium, strontium, zirconium, tin, barium, etc.) and rare-earth elements (scandium, yttrium, lanthanum, etc.) are of the greatest value.

From the foregoing, it follows that the development of energy and resource-saving integrated technologies for their utilization and extraction of valuable components is an urgent task.

The invention relates to the leaching of valuable components and rare earth elements from ash and slag material. The method includes preparing pulp in a bioreactor with a certain ratio of solid and liquid phases and a certain ratio of elemental sulfur and ash and slag material, adjusting the pulp pH with concentrated sulfuric acid to <3.0, inoculating the pulp with a culture fluid containing a community of acidophilic chemolithotrophic microorganisms, a biooxidation process elemental sulfur by microorganisms, accompanied by the formation of sulfuric acid and a decrease in pH, with intensive aeration and a certain temperature and is leached ue valuable components and the rare earth elements from fly ash-slag material.

The technical result of the invention is the development of scientific and technological solutions that provide: low-energy-intensive separation of valuable components from the waste of heat and power generation facilities; rational use of natural resources in the production of rare metals; reduction of the environmental load in the areas of heat and power generation facilities.

There are various methods for the extraction of valuable elements (including rare earths) from ash and slag materials, which consist in the chemical treatment of ash and slag materials after burning coal with various chemical reagents. The main method for processing ash and slag materials is opening them with acid reagents, which can be used mineral acids.

A known method of leaching of metals and rare earth elements (Y, La, Ce, Dy, etc.) from ash and slag dumps with solutions of nitric, sulfuric or hydrochloric acids in a concentration of from 50 to 300 g / l with a ratio of solid and liquid phases from 1: 3 to 1:10 and a temperature of 18 ° C to 90 ° C [Kuzmin V.I., Pashkov G.L., Kartseva N.V., Okhlopkov S.S. Kychkin V.R., Suleymanov A.M. The method of extraction of rare-earth metals and yttrium from coal and ash and slag waste from their combustion // RF Patent No. 2293134. Published 02/10/2007]. Ashes were leached with nitric acid at 90 ° C for 1 h. Rare earth elements were extracted from the solution with tributyl phosphate. Up to 80% of rare earth elements were recovered. The disadvantage of this method is the use of high concentrations of mineral acids, high energy costs and environmental hazard.

It is known to leach ash-slag materials with various concentrations of hydrochloric acid at various concentrations (0.68-6.5) M, in the temperature range up to 80 ° C, at different pulp densities [Kontseva AA, Mikhnev AD, Pashkov G.L., Kolmakova L.P. Extraction of scandium and yttrium from ash and slag waste // Journal of Applied Chemistry. 1995.V. 68. No. 7. S. 1075]. Under optimal conditions (3M HCl, 40 ° C, T: W = 1: 5) Sc was recovered at 84%, Y at 91%. It was possible to achieve concentrations of Sc - 84 mg / l, Y - 91 mg / l. The disadvantage of this method is the use of concentrated solutions of hydrochloric acid.

There is also a method of extracting rare and rare earth elements from lean ore containing pyrite in different solutions and in different modes [Sapsford DJ, Bowell RJ, Geroni JN, Penman KM, Dey M. Factors influencing the release rate of uranium, thorium, yttrium and rare earth elements from a low grade ore // Minerals Engineering. 2012. V. 39. P. 165-172]. Used different leaching times, the addition of 0.5 g / l Fe ₂ (SO ₄ ) ₃ ; Silverman and Lundgren's 9K medium was used as a solvent [Silverman MP, Lundgren DC Study on the chemoautotrophic iron bacterium Ferrobacillus ferrooxidans. An improved medium and harvesting procedure for securing high cell yield // J. Bacteriol. 1959. V. 77. No. 5. P. 642-647] without iron. Under optimal conditions (pH 3.5, 0.5 g / l Fe ³⁺ ), 58% U, 50% Th, 36% Y, and 45% rare earth elements were leached over 52 weeks. It has been shown that with the addition of nutrient salts, rare-earth elements from ore can “self-leach” due to the microbial oxidation of pyrite. This is the only patent known to us that mentions the role of microorganisms in leaching of rare-earth elements, but not from coal burning wastes, but from poor ore containing pyrite - an energy source for microorganisms.

A common disadvantage of the known processes for the extraction of rare earth elements from ash and slag materials is the high consumption of acids.

Another significant drawback of the known processes is the high energy costs of the process of leaching of rare earth elements at (80-90) ° C.

Closest to the proposed method for the extraction of rare-earth metals from ores and ash and slag waste is the method proposed in the patent Bashlykova TV, Zhivaeva AB [Bashlykova T.V., Zhivaeva A.B. A complex method of processing slag // RF Patent No. 2350666. Published October 20, 2008]. The invention relates to the processing of slag and ash and slag waste. A method of processing slag for the extraction of valuable components includes magnetic separation and gravity concentration to obtain concentrate and tailings. After enrichment, the tails are subjected to cavitation treatment and biohydrometallurgical redistribution, which ensures the extraction of valuable components present in the slag matrix. The treatment is carried out by growing bacteria to a concentration of (10 ³ -10 ⁵ ) cells in 1 ml, adding tails to the solution with bacteria with a ratio of T: W = 1: 5 and developing bacterial cultures to a concentration of 10 ⁷ cells in 1 ml. During processing, continuous aeration is carried out at an ambient temperature of (15-32) ° C. Valuable components are isolated from the resulting solution. The technical result is to increase the efficiency of processing slag and ash and slag waste. The disadvantage of this method is its unsuitability for the extraction of valuable metals from ash and slag waste (which is stated in the abstract), since they, unlike the ore processing example (Trepecha, Yugoslavia), do not contain an energy source for microorganisms as a result of oxidation which forms an acid leaching ash-slag material.

There are no patents for the development of scientific and technological solutions that provide low-energy-intensive separation of valuable components from coal combustion wastes using microorganisms as sulfuric acid generators. Such methods can ensure the rational use of natural resources in the production of rare metals and reduce environmental load in the areas of heat and power generation facilities.

The technical result of our method of leaching valuable components and rare-earth elements from ash and slag material is achieved by the fact that instead of concentrated acid solutions at a high processing temperature, the leaching process is carried out by sulfuric acid formed by a community of moderately thermophilic acid chemolithotrophic microorganisms during the oxidation of a cheap energy source - elemental sulfur at temperature not higher than 45 ° C. The method includes preparing pulp in a bioreactor with a certain ratio of solid and liquid phases and a certain ratio of elemental sulfur and ash and slag material; adjusting pulp pH with concentrated sulfuric acid to <3.0; inoculation of the pulp with a culture fluid containing a community of moderately thermophilic acidochemolithotrophic microorganisms; the process of biooxidation of elemental sulfur by microorganisms, accompanied by the formation of sulfuric acid and a decrease in pH, with intensive aeration and a certain temperature, and leaching of valuable components and rare earth elements from ash and slag material. The technical result of the invention is also the development of scientific and technological solutions that provide: low-energy-intensive extraction of valuable components from waste objects of heat and power generation; rational use of natural resources in the production of rare metals; reduction of environmental load in the areas of heat and power generation facilities.

The technical solution is illustrated by the following examples:

Example 1

Leaching of valuable components from ash and slag materials in the mode of the tank process in different temperature conditions: 28.40 or 45 ° C

The experiments were carried out in batch mode in reactors with a volume of 3.0 l with a pulp volume of 1.0 l in them with the following parameters: initial value of the pulp pH 1.60, pulp density 20% (T: G), aeration 5 min ^-1 , speed the rotation of the turbine mixer 500 min ^-1 , the ratio of ash and slag material and sulfur 20: 1, the amount of inoculum introduced 10% and the duration of bioleaching 10 days. Before pulp inoculation, ash and slag material was treated with sulfuric acid to bring the pH to the required level (1.60). The consumption of sulfuric acid was 51 kg / t. In the process of bioleaching valuable components and rare earth elements from ash and slag materials at 28 ° C, the mesophilic community of acidophilic chemolithotrophic microorganisms was used as an inoculum, while at 40 and 45 ° C, a moderately thermophilic community of acidophilic chemolithotrophic was used microorganisms.

The highest rate of decrease in pH, and hence the rate of oxidation of elemental sulfur, was observed during the process at a temperature of 45 ° C and the use of a moderately thermophilic microbial community of acidophilic chemolithotrophic microorganisms. So, the achieved pH value for 10 days of the process in this case was 1.15, while when carrying out the process at 28 and 40 ° C it was only 1.41 and 1.27, respectively. In addition, at 45 ° C there was a large number of microorganisms in the pulp (cell number / ml × 10 ⁸ ): 5.6, 5.0 and 4.8, and higher values of the redox potential: 817, 759 and 676 mV, respectively at 45, 40 and 28 ° C.

From the data presented in table 1, it can be seen that in the process at 45 ° C, the leaching rates of nickel, copper, and zinc reached 46.3, 46.0, and 64%, respectively. The temperature regime exerted the greatest influence on the bioleaching of scandium, yttrium, and lanthanum. The increase in the degree of their leaching with increasing temperature from 28 to 45 ° C was 2.25, 1.71, and 2.08 times, respectively. Extraction of a noble metal - silver - in all cases amounted to 100%.

Thus, the best of the studied was the bioleaching of valuable components and rare earth elements from ash and slag material at a temperature of 45 ° C, characterized by a more intense oxidation of elemental sulfur in the pulp and, as a consequence, a faster decrease in pH, as well as a greater recovery of valuable components (copper, nickel and zinc) and rare earth elements (scandium, yttrium and lanthanum).

Example 2

Leaching of valuable components from ash and slag materials in the regime of a tank process at various values of the initial pH: 3,0,2,6 or 2,0

The experiments were carried out in batch mode in reactors with a volume of 3.0 L with a volume of pulp in them of 1.0 L with the following parameters: temperature 45 ° C, pulp density 10% (T: G), aeration 5 min ^-1 , rotation speed of the turbine mixer 500 min ^-1 , the ratio of ash and slag material and sulfur is 10: 1, the amount of inoculum of a moderate thermophilic community of microorganisms is 10% and the bioleaching time is 10 days. Before inoculation of the pulp, ash and slag material was treated with sulfuric acid to bring the pH to the required level. The initial pH was set at 3.0, 2.6 and 2.0 by the addition of concentrated sulfuric acid. The consumption of sulfuric acid was 21 ± 3 kg / t for cases with an initial pH of 3.0 and 2.6, and in the case of an initial pH of 2.0-45 ± 1 kg / t.

The initial pH in the range 2.0–3.0 did not affect the sulfur-oxidizing activity of the moderately thermophilic community of acidophilic chemolithotrophic microorganisms during bioleaching of valuable metals and rare-earth elements from ash and slag material. The number of microorganisms was the same in all cases and amounted to 1.0 × 10 ⁹ cells / ml. The values of the redox potential naturally increased during bioleaching and reached 845-855 mV by the end of the process, which indicates the presence of ion elements in the medium in their higher valencies. A more active formation of sulfuric acid in the first four days of bioleaching was observed in the case with an initial pH of 2.0. Subsequently, the rates of formation of sulfuric acid by microorganisms were similar in all cases, with the final achieved pH value being 0.90-0.92, indicating a high sulfur-oxidizing activity of the moderately thermophilic community of acidophilic chemolithotrophic microorganisms. Thus, based on the fact that a long stay of ash and slag material under more acidic conditions will contribute to more efficient extraction of valuable metals and rare earth elements, a bioleaching regime with an initial pH of 2.0 is optimal.

Example 3

Leaching of valuable components from ash and slag materials in the regime of a tank process at various pulp densities: 33 or 10%

The experiments were carried out in batch mode in reactors with a volume of 3.0 l with a volume of pulp in them of 1.0 l with the following parameters: temperature 45 ° C, initial pH of the pulp 2.0, aeration 5 min ^-1 , rotation speed of the turbine mixer 500 min ^-1 , the ratio of ash-slag material and sulfur is 10: 1, the amount of the inoculum of the moderate thermophilic microbial community is 10% and the bioleaching time is 10 days. The pulp density was set at 10 and 33% solid in the liquid phase. Before pulp inoculation, ash and slag material was treated with sulfuric acid to bring the pH to the required level (2.0). At the same time, the consumption of sulfuric acid was independent of pulp density and amounted to 45 ± 1 kg / t.

A more effective decrease in pH was observed at a pulp density of 10%. The achieved final pH of the liquid phase was 0.90, while at a pulp density of 33% it was only 1.07. During the bioleaching of valuable components and rare earth elements from ash and slag material, both at pulp density of 10% and at 33%, high values of the redox potential were reached, reaching 855 and 805 mV by 10 days, which indicates oxidative conditions in the pulp. The number of microorganisms of the moderate thermophilic community of acidophilic chemolithotrophic microorganisms did not differ significantly in both cases and reached 1.0 × 10 ⁹ cells / ml in the active growth phase.

The degree of extraction of elements into the solution depending on the density of the pulp is given in table 2.

It can be seen from the presented data that the pulp density had a weak effect on the degree of extraction of valuable components (cobalt, nickel, copper, and zinc) into the solution. Moreover, the highest leaching values were obtained for copper and zinc (up to 54.3 and 57.3%, respectively). On the contrary, an increase in pulp density from 10 to 33% sharply reduced the efficiency of bioleaching of rare earth elements, including lanthanides. Thus, a decrease in the degree of extraction of scandium, yttrium, and lanthanum was 2.72, 1.98, and 2.0 times, respectively. The recovery of silver in both cases was 100%.

Thus, the best of the studied was the bioleaching of valuable metals and rare earth elements from ash and slag material at a pulp density of 10%, characterized by a more efficient oxidation of elemental sulfur in the pulp and, as a result, a large decrease in pH. Moreover, the extraction of rare-earth elements in the solution was the largest and amounted to 52.0, 52.6 and 59.5% for scandium, yttrium and lanthanum, respectively. In addition, 100% silver was leached.

Claims (7)

1. The method of leaching valuable components and rare earth elements from ash and slag material, including the preparation of pulp in a bioreactor with a ratio of solid and liquid phases (T: W) = 1: 5, the ratio of ash and slag material and elemental sulfur 10-20: 1, adjusting pulp pH with concentrated sulfuric acid to 2.0-3.0, adding nutrient salts to the pulp, inoculating the pulp with 10% culture fluid containing a community of acidophilic chemolithotrophic microorganisms, carrying out the process of elemental sulfur biooxidation ikroorganizmami while stirring the slurry, aeration and air at a temperature of 44-46 ° C, accompanied by the formation of sulfuric acid and decrease pH leaching of valuable components and the rare earth elements from a sol-slag material. 2. The method according to p. 1, characterized in that the composition of the nutrient salts added to the pulp for the life support of acidophilic chemolithotrophic microorganisms of the community includes (g / l): (NH ₄ ) ₂ SO ₄ -3,0, K ₂ HPO ₄ × 3H ₂ O-0.5, KCl-0.1, MgSO ₄ × 7H ₂ O-0.5. 3. The method according to p. 1, characterized in that the growth of the inoculum of microorganisms is carried out on a medium containing (g / l): (NH ₄ ) ₂ SO ₄ -3,0, K ₂ HPO ₄ × 3H ₂ O-0,5 , KCl-0.1, MgSO ₄ × 7H ₂ O-0.5, S ° -10, on a thermostatically controlled rocking chair at a speed of 200 rpm and 45 ° C. 4. The method according to p. 1, characterized in that the leaching is carried out by a selected community of moderately thermophilic acidophilic chemolithotrophic microorganisms with a high rate of oxidation of elemental sulfur, which includes strains of Acidithiobacillus caldus, A. thiooxidans, A. ferrooxidans, Sulfobacillus thermosulfidplosulfus thermosulfido . 5. The method according to p. 1, characterized in that the leaching is carried out with stirring of the pulp at a speed of 500 rpm 6. The method of claim. 1, characterized in that the leaching is carried out at an aeration from the air supply rate of 5 min ^-1. 7. The method according to any one of paragraphs. 1-6, characterized in that the valuable components in leaching are cobalt, nickel, copper, zinc, strontium, hafnium and silver.