CN113512652A - Method for extracting gallium metal from coal-series solid waste - Google Patents
Method for extracting gallium metal from coal-series solid waste Download PDFInfo
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- C22B58/00—Obtaining gallium or indium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
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- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
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Abstract
The invention discloses a method for extracting gallium metal from coal-series solid waste, and belongs to the technical field of metallurgy. Firstly, crushing coal-based solid waste to be treated, then obtaining leachate by adopting a nitric acid pressure leaching method, adding metastannic acid into the leachate to perform coprecipitation adsorption of iron and gallium, and sequentially washing and acid-washing the obtained coprecipitation slag for regeneration; and (3) carrying out ionic membrane enrichment on the pickling solution, adding alkali into the enrichment solution to remove iron, then carrying out a carbonation method twice to generate aluminum-gallium mixed salt, and finally carrying out alkali dissolution electrolysis to obtain high-purity gallium. The invention realizes that the total recovery rate of gallium is higher than 70 percent and the purity of the produced gallium is up to more than 99.9 percent by the synergistic combination of various process steps such as acid dissolution, coprecipitation and enrichment, alkali dissolution iron removal, step carbonation, alkali dissolution electrolysis and the like and related process parameters, and simultaneously, the process has the advantages of low energy consumption, low equipment requirement, good impurity removal effect, recyclable solvent and the like.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for extracting gallium metal from coal-series solid waste.
Background
Gallium is a metal element which is extremely important for the development of high-tech industries, is widely applied to the fields of semiconductors, solar cells, alloys, medicine, glass manufacturing, chemical engineering and the like, and has good market prospect. Gallium is commonly associated with aluminum, zinc and the like in minerals in the natural world, and sulfide ore of zinc and bauxite ore are important raw materials for extracting gallium. Currently, 90% of the world's gallium is obtained from byproducts of the alumina industry, which uses bauxite as a major raw material.
The coal-based solid waste comprises fly ash and coal gangue and comes from the mining, processing and utilizing processes of coal. China is a large country for coal production and consumption, generates a large amount of coal-based solid waste every year, occupies a large amount of land resources, and seriously pollutes the environment. Therefore, the disposal and high-value comprehensive utilization of the coal-based solid waste have important research significance. However, the economic value of the main component alumina is mainly considered in the utilization method of the fly ash and coal gangue at present, and other components are often disposed as impurities. In fact, a large amount of precious rare metals such as gallium, germanium and the like also exist in the fly ash and the coal gangue. Therefore, the method has good economic benefit for effectively recovering the rare metals from the coal-based solid waste.
The extraction method of crops in the prior art mainly comprises a solvent extraction method, an extraction resin method and a lime milk carbonation method. The most effective extractant adopted by the solvent extraction method is Kelex l00, but the synthesis difficulty is high, the price is high, and the application is limited. The main procedures of the extraction resin method comprise adsorption, leaching, lean resin transformation and electrolysis, and the prior reports of industrial production have been carried out, however, the price of the chelating resin or the ion exchange resin adopted in the process is higher, and if the concentration of crops in the circulating mother liquor is lower, higher production cost is caused, and further popularization is influenced. The lime milk carbonating method is to introduce carbon dioxide into the alumina carbon content mother liquor to complete carbonating decomposition, then to add lime milk to dealuminate, to reach the enrichment of crops, the process of the method is complex, and a large amount of crops are lost while calcium aluminate is formed. In addition, the electrolysis method has become the main method for producing gallium at present due to the advantages of high product purity, low production cost and energy consumption, less three-waste pollution and the like, and the obtained gallium with the purity of more than 99.99 percent has good feasibility in the subsequent crystal pulling purification method.
Chinese patent application CN101255504A discloses a process for extracting gallium from fly ash and coal gangue, which adopts an adsorption column adsorption method to extract gallium from gallium-containing aluminum chloride solution, wherein the gallium-containing aluminum chloride solution is prepared by mixing and calcining fly ash and sodium carbonate, soaking in water, separating carbon, and reacting with hydrochloric acid. CN85100163A discloses a method for extracting crops from decomposition liquid in alumina production, which is to introduce CO into mother liquid after separating aluminum hydroxide by carbonation decomposition2Completely carbonating and decomposing to deposit the crystal and aluminum in the form of amorphous hydrate, separating the deposit and removing most of Na2Adding lime milk into the precipitate for dealumination to obtain a solution rich in crops, and introducing CO2Dissolving the precipitate with sodium hydroxide, and adding sodium sulfide to remove heavy metals to obtain electrolyte containing 3.9g/L of crops; electrolyzing in an electrolytic bath with stainless steel as cathode and anode to obtain crop on the cathode, and treating with hydrochloric acid to obtain metal crop with purity of 99.99-99.999%. CN101284668A discloses a method for extracting silicon dioxide, aluminum oxide and gallium oxide from high-alumina fly ash, which comprises the steps of processing residues obtained after silicon oxide is extracted from fly ash to obtain gallium-containing sodium metaaluminate solution which is used as mother liquor for separating and enriching gallium, and then collecting the gallium-containing sodium metaaluminate solutionThe gallium is enriched by a fractional carbonation-sodium hydroxide dissolution method and a resin adsorption method. CN101130835A discloses a production method for extracting gallium, which takes intermediate carbon content mother liquor obtained in the process of producing alumina by fly ash as a raw material, and obtains gallium concentrate after reaction and complete carbonation with sodium bicarbonate. Moreover, Zhaoyei et al reported "experimental research on the separation of gallium from fly ash" (North China electric technology, 1998, No.1, 35-37 pages), and the research showed that the gallium-containing sodium metaaluminate solution obtained by sintering fly ash and limestone and leaching with sodium carbonate solution can be used as mother liquor for the separation and enrichment of gallium, and the extraction of gallium can be realized by a stepwise carbonation-sodium hydroxide dissolution method.
The reports of the prior art all adopt carbon content or seed precipitation mother liquor obtained in the process of extracting alumina from coal-based solid wastes as raw materials to separate and enrich gallium, namely the mother liquor for extracting gallium is alkaline gallium-containing sodium metaaluminate solution, and the methods have the problems of complex process, high gallium loss and the like.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a method for extracting metal gallium from coal-based solid waste, which comprises the working procedures of acid dissolution, coprecipitation adsorption and enrichment, alkali dissolution for removing iron, calcium and magnesium impurities, stepwise carbonation for removing aluminum, alkali dissolution for enriching gallium, electrolysis and the like, wherein the total recovery rate of the gallium is higher than 70 percent finally. The method has the advantages of low energy consumption, low equipment requirement, good impurity removal effect, recyclable solvent and the like.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for extracting metal gallium from coal-based solid waste comprises the following steps:
(1) crushing coal-based solid waste to be treated, and obtaining pickle liquor by adopting a nitric acid pressure leaching method;
(2) adding metastannic acid into the pickle liquor for coprecipitation reaction, filtering after full reaction to obtain iron-removed liquor and coprecipitation slag containing iron and gallium, washing the coprecipitation slag with water to remove most of aluminum, calcium and magnesium, and then pickling with nitric acid to recover iron and gallium to obtain absorbing liquor containing iron and gallium;
(3) carrying out nanofiltration membrane separation on the absorption liquid to obtain dilute nitric acid and enriched liquid containing iron and gallium, and returning the dilute nitric acid to the co-precipitation slag pickling process;
(4) adding a sodium hydroxide solution into the enrichment solution, and removing iron and a small amount of residual calcium and magnesium elements in the solution to obtain a gallium-containing sodium metaaluminate solution;
(5) introducing carbon dioxide into the gallium-containing sodium metaaluminate solution, controlling the pH value of the solution to precipitate aluminum and gallium in the solution step by step to obtain crude aluminum hydroxide and crude gallium hydroxide;
(6) and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium.
Further, the coal-based solid waste is crushed to the particle size of 0.02-0.1mm in the step (1).
Further, the mass concentration of the nitric acid solution in the nitric acid pressure leaching method in the step (1) is 10-50%, the heat preservation temperature is above 150 ℃, the heat preservation time is 0.5-5h, and the stirring speed is 700 r/min.
Further, the chemical element composition of the pickle liquor in the step (1) comprises: fe is 0.1-0.6 g/L; al is 45.6-78.9 g/L; si is 0.01-0.15 g/L; ca is 0.15-2.46 g/L; mg is 0.01-0.6 g/L; ga is 0.01-0.2 g/L.
Further, the pH value of the coprecipitation reaction in the step (2) is 0.5-3.0, the temperature is 20-80 ℃, the consumption of the metastannic acid is 1-10% of the mass of the pickle liquor, and the heat preservation time is 0.5-3 h. After iron and gallium are adsorbed by metastannic acid coprecipitation, the iron and gallium can be recycled by acid washing.
Further, in the step (2), the adsorption rate of iron in the metastannic acid coprecipitation reaction is 90-99%, and the adsorption rate of gallium is 70-80%; when the co-precipitation slag is washed by water, the washing-out rate of aluminum, calcium and magnesium is more than 90 percent, and the washing-out rate of iron and gallium is less than 5 percent; the elution rate of iron and gallium is more than 95 percent when the co-precipitation slag is subjected to acid washing.
Further, the liquid-solid ratio of the co-precipitation slag water washing in the step (2) is 3-10: 1; the liquid-solid ratio of the co-precipitation slag pickling is 3-10:1, and the mass concentration of the used nitric acid is 20-60%.
Further, the mass percentage of gallium in the enrichment solution in the step (3) is 0.05-0.5%.
Further, in the step (4), a sodium hydroxide solution is added into the enriched solution, the pH value of the solution is controlled to be 13-14, and the mass concentration of the sodium hydroxide solution is 30%. Adding a sodium hydroxide solution into the enrichment solution under stirring, controlling the pH value of the solution to enable aluminum nitrate, gallium nitrate and sodium hydroxide in the enrichment solution to react to generate sodium metaaluminate and sodium metagallate, forming precipitates of iron, calcium, magnesium and the like in the solution in the form of hydroxides, filtering, separating and washing to obtain the gallium-containing sodium metaaluminate solution.
Further, the step (5) specifically comprises:
primary carbon differentiation: directly introducing carbon dioxide gas into the gallium-containing sodium metaaluminate mother liquor for carbon differentiation, wherein the gas flow rate is 100-200ml/min, the uniformity of the reaction is ensured, the reaction temperature is controlled to be 60-80 ℃, the carbonation time is 1-5h, the pH value at the end point of the reaction is 9.5-11.3, most of aluminum generates aluminum hydroxide precipitate after the reaction, gallium is remained in the solution, and the mass ratio of gallium to aluminum in the filtrate after the aluminum hydroxide precipitate is separated is more than 1: 90, respectively;
secondary carbon differentiation: and (3) continuously introducing carbon dioxide gas into the filtrate, controlling the gas flow rate to be 150-250ml/min, controlling the reaction temperature to be 60-80 ℃, the carbon decomposition time to be 2-5h, controlling the pH value at the end of the reaction to be 8.5-8.9, precipitating all aluminum hydroxide and most gallium, filtering to obtain aluminum-gallium mixed salt precipitate, evaporating and crystallizing the obtained filtrate to separate sodium carbonate crystals, returning the gallium-containing liquid after separating the sodium carbonate to the step (4), wherein the mass ratio of gallium to aluminum in the aluminum-gallium mixed salt is more than 1: 50.
Further, the mass concentration of the sodium hydroxide solution in the step (6) is 15-30%.
Compared with the prior art, the technical scheme of the invention has the following technical advantages or positive effects:
(1) the method for extracting gallium disclosed by the invention is suitable for various gallium-containing coal-series solid wastes, and has wide raw material applicability;
(2) the invention adopts the nitric acid pressure leaching method to directly leach gallium from the raw materials, thereby ensuring that the leaching rate of gallium is up to more than 90 percent;
(3) the total recovery rate of gallium in the invention is higher than 70%, and the purity of gallium obtained by electrolysis is up to more than 99.9%;
(4) the process has the advantages of low energy consumption, low equipment requirement, good impurity removal effect, recyclable solvent and the like.
Drawings
Fig. 1 is a process flow diagram of the method for extracting gallium metal from coal-based solid waste according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.
[ example 1 ]
Crushing the coal-series solid waste to be treated to the granularity of 0.02mm, leaching the raw materials by adopting a nitric acid solution with the mass concentration of 10%, wherein the temperature of the leaching reaction is 160 ℃, the heat preservation time is 5h, and the stirring speed is 300 r/min.
And (3) coprecipitating the obtained pickle liquor by metastannic acid to adsorb iron and gallium, keeping the temperature at 20 ℃ and the content of metastannic acid at 2% for 1h, and filtering to obtain coprecipitation slag and iron-removed liquor.
The contents of iron, aluminum, calcium, magnesium and gallium in the solution before and after coprecipitation were measured, and the measurement results are shown in table 1.
TABLE 1 test results of the contents of substances before and after the coprecipitation of metastannic acid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Pickle liquor | 0.27 | 56.65 | 4.05 | 0.38 | 0.0062 |
| Liquid after iron removal | 0.012 | 54.36 | 3.81 | 0.34 | 0.0019 |
Washing the obtained coprecipitation slag with water, then washing with acid, eluting and regenerating, wherein the washing liquid solid ratio is 10:1, stirring and washing for 1 hour at normal temperature, and filtering to obtain washing slag and washing liquid; and (3) stirring and washing the washing slag at the liquid-solid ratio of 10:1 and the mass concentration of nitric acid of 30% for 1h at normal temperature, and filtering to obtain pickling slag and pickling solution.
The contents of iron, aluminum, calcium, magnesium and gallium in the water washing solution and the pickling solution were measured, and the measurement results are shown in table 2.
TABLE 2 test results of the content of substances in the co-precipitation sludge washing liquid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Water washing liquid | 0.047 | 7.81 | 0.92 | 0.56 | 0.001 |
| Pickling solution | 2.58 | 0.72 | 0.08 | 0.047 | 0.021 |
The pickle liquor was subjected to membrane filtration, here with a nanofiltration membrane, the solution composition after membrane filtration being shown in table 3.
TABLE 3 test results of the content of substances after the nanofiltration membrane treatment of the pickle water
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | Nitric acid (%) | |
| Fresh water | 0.0043 | 0.79 | 0.078 | 0.041 | 0.0002 | 15 |
| Concentrated solution | 26.5 | 8.2 | 0.94 | 0.46 | 0.48 | 4.1 |
At 65 ℃, carbon dioxide gas is introduced into 100ml of sodium metaaluminate mother liquor at the speed of 100ml/min, the pH value of the reaction end point is controlled to be 9.5, and the primary carbonation is finished by filtering. And (3) carrying out secondary carbonation on the solution after the aluminum hydroxide precipitate is separated by the primary carbonation, continuously introducing carbon dioxide gas at the temperature of 50 ℃ at the speed of 120ml/min, controlling the pH value at the end point of the reaction to be 8.5, and filtering to obtain the aluminum-gallium mixed salt precipitate. The weight ratio of gallium to aluminum in the aluminum-gallium mixed salt at this time was determined to be 1: 45.
and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium. The overall recovery of gallium was calculated to be 75.6%.
[ example 2 ]
Crushing the coal-series solid waste to be treated to the granularity of 0.05mm, leaching the raw material by using a nitric acid solution with the mass concentration of 20%, wherein the temperature of the leaching reaction is 170 ℃, the heat preservation time is 1.5h, and the stirring speed is 400 r/min.
And (3) coprecipitating the obtained pickle liquor by metastannic acid to adsorb iron and gallium, keeping the temperature at 30 ℃ and the content of metastannic acid at 3% for 1h, and filtering to obtain coprecipitation slag and iron-removed liquor.
The contents of iron, aluminum, calcium, magnesium and gallium in the solution before and after coprecipitation were measured, and the measurement results are shown in table 1.
TABLE 1 test results of the contents of substances before and after the coprecipitation of metastannic acid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Pickle liquor | 0.25 | 58.65 | 4.07 | 0.35 | 0.0068 |
| Liquid after iron removal | 0.008 | 58.36 | 3.41 | 0.30 | 0.0014 |
Washing the obtained coprecipitation slag with water, then washing with acid, eluting and regenerating, wherein the washing liquid solid ratio is 7:1, stirring and washing for 1 hour at normal temperature, and filtering to obtain washing slag and washing liquid; and (3) stirring and washing the washing slag at the liquid-solid ratio of 7:1 and the mass concentration of nitric acid of 35% for 1h at normal temperature, and filtering to obtain pickling slag and pickling solution.
The contents of iron, aluminum, calcium, magnesium and gallium in the water washing solution and the pickling solution were measured, and the measurement results are shown in table 2.
TABLE 2 test results of the content of substances in the co-precipitation sludge washing liquid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g-L) | Gallium (g/L) | |
| Water washing liquid | 0.042 | 7.91 | 0.98 | 0.58 | 0.001 |
| Pickling solution | 2.65 | 0.82 | 0.085 | 0.049 | 0.021 |
The pickle liquor was subjected to membrane filtration, here with a nanofiltration membrane, the solution composition after membrane filtration being shown in table 3.
TABLE 3 test results of the content of substances after the nanofiltration membrane treatment of the pickle water
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | Nitric acid (%) | |
| Fresh water | 0.0046 | 0.78 | 0.088 | 0.048 | 0.0003 | 12 |
| Concentrated solution | 24.5 | 8.5 | 0.95 | 0.43 | 0.28 | 4 |
At 65 ℃, carbon dioxide gas is introduced into 100ml of sodium metaaluminate mother liquor at the speed of 100ml/min, the pH value of the reaction end point is controlled to be 9.5, and the primary carbonation is finished by filtering. And (3) carrying out secondary carbonation on the solution after the aluminum hydroxide precipitate is separated by the primary carbonation, continuously introducing carbon dioxide gas at the temperature of 50 ℃ at the speed of 120ml/min, controlling the pH value at the end point of the reaction to be 8.5, and filtering to obtain the aluminum-gallium mixed salt precipitate. The weight ratio of gallium to aluminum in the aluminum-gallium mixed salt at this time was determined to be 1: 50.
and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium. The overall recovery of gallium was calculated to be 76.6%.
[ example 3 ]
Crushing the coal-series solid waste to be treated to the granularity of 0.07mm, leaching the raw material by adopting a nitric acid solution with the mass concentration of 30%, wherein the temperature of the leaching reaction is 200 ℃, the heat preservation time is 2.0h, and the stirring speed is 450 r/min.
And (3) coprecipitating the obtained pickle liquor by metastannic acid to adsorb iron and gallium, keeping the temperature at 60 ℃ and the content of metastannic acid at 10 percent for 1h, and filtering to obtain coprecipitation slag and iron-removed liquor.
The contents of iron, aluminum, calcium, magnesium and gallium in the solution before and after coprecipitation were measured, and the measurement results are shown in table 1.
TABLE 1 test results of the contents of substances before and after the coprecipitation of metastannic acid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Pickle liquor | 0.25 | 58.65 | 4.07 | 0.35 | 0.0068 |
| Liquid after iron removal | 0.008 | 58.36 | 3.41 | 0.30 | 0.0014 |
Washing the obtained coprecipitation slag with water, then washing with acid, eluting and regenerating, wherein the washing liquid solid ratio is 5:1, stirring and washing for 1 hour at normal temperature, and filtering to obtain washing slag and washing liquid; and (3) stirring and washing the washing slag at the normal temperature for 1h under the condition that the liquid-solid ratio is 5:1 and the mass concentration of the nitric acid is 40%, and filtering to obtain pickling slag and pickling solution.
The contents of iron, aluminum, calcium, magnesium and gallium in the water washing solution and the pickling solution were measured, and the measurement results are shown in table 2.
TABLE 2 test results of the content of substances in the co-precipitation sludge washing liquid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Water washing liquid | 0.072 | 8.61 | 0.99 | 0.78 | 0.003 |
| Pickling solution | 2.65 | 0.82 | 0.095 | 0.049 | 0.041 |
The pickle liquor was subjected to membrane filtration, here with a nanofiltration membrane, the solution composition after membrane filtration being shown in table 3.
TABLE 3 test results of the content of substances after the nanofiltration membrane treatment of the pickle water
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | Nitric acid (%) | |
| Fresh water | 0.0066 | 0.95 | 0.098 | 0.068 | 0.0006 | 18 |
| Concentrated solution | 27.5 | 8.5 | 0.93 | 0.48 | 0.58 | 5 |
At 65 ℃, carbon dioxide gas is introduced into 100ml of sodium metaaluminate mother liquor at the speed of 100ml/min, the pH value of the reaction end point is controlled to be 9.5, and the primary carbonation is finished by filtering. And (3) carrying out secondary carbonation on the solution after the aluminum hydroxide precipitate is separated by the primary carbonation, continuously introducing carbon dioxide gas at the temperature of 60 ℃ at the speed of 120ml/min, controlling the pH value at the end point of the reaction to be 8.5, and filtering to obtain the aluminum-gallium mixed salt precipitate. The weight ratio of gallium to aluminum in the aluminum-gallium mixed salt at this time was determined to be 1: 53.
and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium. The overall recovery of gallium was calculated to be 77.6%.
[ example 4 ]
Crushing the coal-series solid waste to be treated to the granularity of 0.1mm, leaching the raw material by adopting a nitric acid solution with the mass concentration of 50%, wherein the temperature of the leaching reaction is 210 ℃, the heat preservation time is 0.5h, and the stirring speed is 700 r/min.
And (3) coprecipitating the obtained pickle liquor by metastannic acid to adsorb iron and gallium, keeping the pH value of 1, the temperature of 80 ℃ and the content of metastannic acid of 10 percent for 1h, and filtering to obtain coprecipitation slag and iron-removed liquor.
The contents of iron, aluminum, calcium, magnesium and gallium in the solution before and after coprecipitation were measured, and the measurement results are shown in table 1.
TABLE 1 test results of the contents of substances before and after the coprecipitation of metastannic acid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Pickle liquor | 0.45 | 63.65 | 4.97 | 0.66 | 0.0083 |
| Liquid after iron removal | 0.014 | 62.67 | 3.83 | 0.56 | 0.0018 |
Washing the obtained coprecipitation slag with water, then washing with acid, eluting and regenerating, wherein the washing liquid solid ratio is 5:1, stirring and washing for 1 hour at normal temperature, and filtering to obtain washing slag and washing liquid; and (3) stirring and washing the washing slag at the liquid-solid ratio of 5:1 and the mass concentration of nitric acid of 60% for 1h at normal temperature, and filtering to obtain pickling slag and pickling solution.
The contents of iron, aluminum, calcium, magnesium and gallium in the water washing solution and the pickling solution were measured, and the measurement results are shown in table 2.
TABLE 2 test results of the content of substances in the co-precipitation sludge washing liquid
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | |
| Water washing liquid | 0.072 | 8.61 | 0.99 | 0.78 | 0.003 |
| Pickling solution | 2.65 | 0.82 | 0.095 | 0.049 | 0.041 |
The pickle liquor was subjected to membrane filtration, here with a nanofiltration membrane, the solution composition after membrane filtration being shown in table 3.
TABLE 3 test results of the content of substances after the nanofiltration membrane treatment of the pickle water
| Iron (g/L) | Aluminum (g/L) | Magnesium (g/L) | Calcium (g/L) | Gallium (g/L) | Nitric acid (%) | |
| Fresh water | 0.0066 | 0.95 | 0.098 | 0.068 | 0.0006 | 28 |
| Concentrated solution | 27.5 | 8.5 | 0.93 | 0.48 | 0.58 | 4.2 |
At 65 ℃, carbon dioxide gas is introduced into 100ml of sodium metaaluminate mother liquor at the speed of 100ml/min, the pH value of the reaction end point is controlled to be 9.5, and the primary carbonation is finished by filtering. And (3) carrying out secondary carbonation on the solution after the aluminum hydroxide precipitate is separated by the primary carbonation, continuously introducing carbon dioxide gas at the temperature of 50 ℃ at the speed of 120ml/min, controlling the pH value at the end point of the reaction to be 8.5, and filtering to obtain the aluminum-gallium mixed salt precipitate. The weight ratio of gallium to aluminum in the aluminum-gallium mixed salt at this time was determined to be 1: 56.
and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium. The overall recovery of gallium was calculated to be 77.9%.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for extracting gallium metal from coal-based solid waste is characterized by comprising the following steps:
(1) crushing coal-based solid waste to be treated, and obtaining pickle liquor by adopting a nitric acid pressure leaching method;
(2) adding metastannic acid into the pickle liquor for coprecipitation reaction, filtering after full reaction to obtain iron-removed liquor and coprecipitation slag containing iron and gallium, washing the coprecipitation slag with water to remove most of aluminum, calcium and magnesium, and then pickling with nitric acid to recover iron and gallium to obtain absorbing liquor containing iron and gallium;
(3) carrying out nanofiltration membrane separation on the absorption liquid to obtain dilute nitric acid and enriched liquid containing iron and gallium, and returning the dilute nitric acid to the co-precipitation slag pickling process;
(4) adding a sodium hydroxide solution into the enrichment solution, and removing iron and a small amount of residual calcium and magnesium elements in the solution to obtain a gallium-containing sodium metaaluminate solution;
(5) introducing carbon dioxide into the gallium-containing sodium metaaluminate solution, controlling the pH value of the solution to precipitate aluminum and gallium in the solution step by step to obtain crude aluminum hydroxide and crude gallium hydroxide;
(6) and adding the crude gallium hydroxide into a sodium hydroxide solution to obtain a gallium-containing alkali solution, and electrolyzing the gallium-containing alkali solution to obtain the metal gallium.
2. The method for extracting gallium metal from coal-based solid waste according to claim 1, wherein the coal-based solid waste is pulverized to a particle size of 0.02-0.1mm in step (1); in the nitric acid pressure leaching method, the mass concentration of the nitric acid solution is 10-50%, the heat preservation temperature is above 150 ℃, the heat preservation time is 0.5-5h, and the stirring speed is 300-700 r/min.
3. The method for extracting gallium metal from coal-based solid waste according to claim 1, wherein the chemical element composition of the pickle liquor in step (1) comprises: fe is 0.1-0.6 g/L; al is 45.6-78.9 g/L; si is 0.01-0.15 g/L; ca is 0.15-2.46 g/L; mg is 0.01-0.6 g/L; ga is 0.01-0.2 g/L.
4. The method for extracting gallium metal from coal-based solid waste as claimed in claim 1, wherein the pH value of the coprecipitation reaction in step (2) is 0.5-3.0, the temperature is 20-80 ℃, the usage amount of metastannic acid is 1-10% of the mass of the pickle liquor, and the heat preservation time is 0.5-3 h.
5. The method for extracting gallium metal from coal-based solid waste as claimed in claim 1, wherein in step (2), the iron adsorption rate is 90-99% and the gallium adsorption rate is 70-80% in the coprecipitation reaction of metastannic acid; when the co-precipitation slag is washed by water, the washing-out rate of aluminum, calcium and magnesium is more than 90 percent, and the washing-out rate of iron and gallium is less than 5 percent; the elution rate of iron and gallium is more than 95 percent when the co-precipitation slag is subjected to acid washing.
6. The method for extracting gallium metal from coal-based solid waste as claimed in claim 1, wherein the liquid-solid ratio of the co-precipitation slag washing in step (2) is 3-10: 1; the liquid-solid ratio of the co-precipitation slag pickling is 3-10:1, and the mass concentration of the used nitric acid is 20-60%.
7. The method for extracting gallium metal from coal-based solid waste according to claim 1, wherein the gallium content in the enrichment liquid in the step (3) is 0.05-0.5% by mass.
8. The method for extracting gallium metal from coal-based solid waste according to claim 1, wherein in the step (4), a sodium hydroxide solution is added into the enriched liquid, the pH of the solution is controlled to be 13-14, and the mass concentration of the sodium hydroxide solution is 30%.
9. The method for extracting gallium metal from coal-based solid waste according to claim 1, wherein the mass concentration of the sodium hydroxide solution in the step (6) is 15-30%.
10. The method for extracting gallium metal from coal-based solid waste according to any one of claims 1 to 9, wherein the step (5) specifically comprises:
primary carbon differentiation: directly introducing carbon dioxide gas into the gallium-containing sodium metaaluminate mother liquor for carbon differentiation, wherein the gas flow rate is 100-200ml/min, the uniformity of the reaction is ensured, the reaction temperature is controlled to be 60-80 ℃, the carbonation time is 1-5h, the pH value at the end point of the reaction is 9.5-11.3, most of aluminum generates aluminum hydroxide precipitate after the reaction, gallium is remained in the solution, and the mass ratio of gallium to aluminum in the filtrate after the aluminum hydroxide precipitate is separated is more than 1: 90, respectively;
secondary carbon differentiation: and (3) continuously introducing carbon dioxide gas into the filtrate, controlling the gas flow rate to be 150-250ml/min, controlling the reaction temperature to be 60-80 ℃, the carbon decomposition time to be 2-5h, controlling the pH value at the end of the reaction to be 8.5-8.9, precipitating all aluminum hydroxide and most gallium, filtering to obtain aluminum-gallium mixed salt precipitate, evaporating and crystallizing the obtained filtrate to separate sodium carbonate crystals, returning the gallium-containing liquid after separating the sodium carbonate to the step (4), wherein the mass ratio of gallium to aluminum in the aluminum-gallium mixed salt is more than 1: 50.
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