CN115976324A - Method for extracting aluminum-gallium-lithium system from coal gangue - Google Patents
Method for extracting aluminum-gallium-lithium system from coal gangue Download PDFInfo
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Abstract
The invention relates to a method for extracting an aluminum-gallium-lithium system from coal gangue, which comprises the following steps: leaching coal gangue and inorganic acid to obtain pickle liquor; passing the pickle liquor through ion exchange resin to obtain refined liquor, and eluting the ion exchange resin by using dilute hydrochloric acid to obtain eluent; concentrating and crystallizing the refined solution to obtain inorganic aluminum salt crystals and separating filtrate, and calcining the crystals; passing the eluent through a gallium extraction resin column, and eluting the gallium extraction resin by using dilute hydrochloric acid to obtain a second eluent; adding sodium hydroxide, then filtering, adding hydrochloric acid into the filtrate, then filtering to obtain gallium mud, adding a sodium hydroxide solution to form a gallium solution, and carrying out electrolysis treatment on the gallium solution; and spray roasting the separated filtrate to obtain a lithium-containing precipitate, reacting water with the lithium-containing precipitate to obtain a lithium-enriched solution, adding phosphate to obtain a second lithium-enriched solution, and adding carbonate to react.
Description
Technical Field
The invention relates to the technical field of coal gangue application, in particular to a method for extracting an aluminum-gallium-lithium system from coal gangue.
Background
Coal gangue is a solid waste in the coal processing process, and about 3000 million tons of coal per year is produced by taking a quasi-Georgi Dai open pit mine in Erdos city, inner Mongolia as an example, and the discharge amount of the coal gangue is up to about 1400 million tons per year. The combined coal yield of the two mines is about 7000 ten thousand tons, the discharge amount of the coal gangue is about 3500 ten thousand tons, the stockpiled coal gangue not only occupies land and pollutes the environment, but also when the temperature reaches the combustion point of combustible substances, the residual coal in the coal gangue stockpile can be spontaneously combusted, and potential safety hazards exist.
The main mineral components in the coal gangue in the quasi-Geer mining area are kaolinite and boehmite, and the main chemical component is Al 2 O 3 、SiO 2 And also contains a small amount of Fe 2 O 3 、TiO 2 、CaO、MgO、P 2 O 5 、K 2 O and Na 2 O, etc., wherein Al 2 O 3 35-40% of SiO 2 The content is 36-44%, and the ignition loss is 15-28%. The heat value of the rare earth coal gangue is relatively low, and if the coal gangue is directly combusted, the cost is higher. The results of chemical analysis of gangue minerals show that the alumina and silica in gangue mainly exist in the form of boehmite and kaolinite, have higher activity, and can be directly leached by acid and alkaliFurther improving the carbon content in the coal gangue and improving the heat value of the coal gangue. The content of trace elements gallium in the coal gangue in the mining area is about 98 g/ton, the content of lithium is about 359 g/ton, the total content of rare earth is about 0.09-0.12%, and in the process of producing alumina by an acid method, the valuable elements are enriched in waste water and can be extracted step by step.
Patent CN112897560A provides a method for preparing high-purity alumina from coal gangue, which comprises the steps of grinding the coal gangue, roasting at about 750 ℃, leaching with sulfuric acid, crystallizing ammonium alum, dissolving crystals, and salting out and crystallizing with hydrogen chloride for three times to prepare 99.95% of alumina.
Patent CN109516484B discloses a method for producing alumina by sintering calcium carbide slurry fly ash and coal gangue. The method comprises the working procedures of raw material preparation, clinker sintering, clinker dissolution, red mud separation and washing, red mud dealkalization, crude liquid desiliconization, seed crystal preparation, fine liquid carbonation decomposition, aluminum hydroxide separation and washing, aluminum hydroxide roasting, mother liquid evaporation and the like, and has the defects of long process flow, energy consumption, large residue of aluminum extraction residues and the like.
Patent CN113213482A discloses a method for extracting silicon and aluminum from coal gangue by plasma ball milling and vibratory fluidization calcination activation, which comprises the steps of firstly carrying out plasma ball milling treatment on a mixture of coal gangue and solid alkali to realize mechanical pre-activation, then carrying out calcination activation on the coal gangue in a manner of introducing air into solid coal gangue powder to realize solid fluidization, and then extracting by using acid. The alkali-added superfine grinding and roasting belongs to a high-energy-consumption process, and is not in accordance with the current energy utilization policy.
Patent CN113621794A discloses a method for extracting carbon and silica from coal gangue, which comprises activating pulverized coal gangue under supercritical water or subcritical water condition, separating the activated coal gangue into organic liquid phase and solid slag phase by separation equipment, and electrically separating the solid slag containing carbon and silica to obtain carbon and silica with high grade. The method has high cost, does not effectively utilize aluminum resources, and is not suitable for industrialization.
The method for extracting valuable elements from coal gangue in the prior art is not ideal, and cannot realize the synergistic extraction of the valuable elements, so that the method for extracting the valuable elements from coal gangue in the prior art needs to be improved.
Disclosure of Invention
The invention mainly aims to provide a method for extracting an aluminum-gallium-lithium system from coal gangue, so as to solve the technical problem that the synergistic extraction of valuable elements cannot be realized in the prior art.
To achieve the above object, according to one aspect of the present invention, there is provided a method for extracting an al-ga-li system from coal gangue, the method comprising the steps of:
step S1: mixing the coal gangue with inorganic acid and water, and then carrying out leaching reaction to obtain acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt;
step S2: separating the inorganic acid aluminum salt and the inorganic acid iron salt by passing the acid leaching solution through a cation exchange resin to obtain a refined solution containing the inorganic acid aluminum salt, and then carrying out first elution on the cation exchange resin by using dilute hydrochloric acid to obtain a first eluent containing gallium ions and iron ions;
and step S3: concentrating and crystallizing the refined liquid containing the inorganic acid aluminum salt, then carrying out solid-liquid separation to obtain inorganic aluminum salt crystals and a separation filtrate containing lithium, and calcining the inorganic aluminum salt crystals to obtain alumina;
and step S4: passing the first eluent through a gallium extraction resin column to enrich gallium, and performing second elution on the gallium extraction resin enriched with gallium by using dilute hydrochloric acid to obtain a second eluent containing gallium ions and iron ions;
step S5: adding sodium hydroxide into the second eluent, then carrying out first filtration treatment to obtain first filtrate, adding hydrochloric acid into the first filtrate, then carrying out second filtration treatment to obtain gallium mud, adding a sodium hydroxide solution into the gallium mud to form a gallium solution, and then carrying out electrolysis treatment on the gallium solution to extract gallium; and
step S6: and carrying out spray roasting on the separation filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate, then carrying out a reaction to obtain a first lithium-enriched liquid, adding phosphate into the first lithium-enriched liquid to carry out a reaction to obtain a second lithium-enriched liquid, and adding carbonate into the second lithium-enriched liquid to carry out a reaction to obtain lithium carbonate.
Further, in step S1, the inorganic acid includes hydrochloric acid or nitric acid, the inorganic acid aluminum salt includes aluminum chloride or aluminum nitrate, the inorganic acid iron salt includes ferric chloride or ferric nitrate, preferably, the mass ratio of the coal gangue to the inorganic acid is 1.5-5, the leaching temperature is 120-200 ℃, and the leaching time is 1-5 h.
Further, in step S2, the temperature is 60-80 ℃ and the speed is 2-3 times of the resin volume/h in the process of passing the pickle liquor through the cation exchange resin, preferably, in the first elution process, the concentration of dilute hydrochloric acid is 0.1-0.5 mol/L, and the volume of dilute hydrochloric acid is 1-3 times of the resin volume.
Further, in step S3, the evaporation temperature during the concentration and crystallization is 80 to 140 ℃, and the calcination temperature during the calcination is 750 to 1200 ℃.
Further, in step S4, during the process of passing the first eluent through the gallium extracting resin column, the temperature is 60 ℃ to 80 ℃, the speed is 1 to 2 times of the resin volume/h, preferably, during the second elution, the elution speed is 1 to 2 times of the resin volume/h, and the dosage of the dilute hydrochloric acid is 1 to 2 times of the resin volume.
Further, in step S6, in the spray roasting process, the roasting temperature is 450-900 ℃, and the roasting time is 1-5 min; preferably, in the reaction process after mixing water and the lithium-containing precipitate, the reaction temperature is 80-160 ℃, and the reaction time is 1-4 h; preferably, in the process of adding phosphate into the first lithium enrichment solution for reaction, the reaction temperature is 60-120 ℃, and the reaction time is 1-4 h; preferably, in the process of adding carbonate into the second lithium-enriched liquid for reaction, the reaction temperature is 60-120 ℃, the reaction time is 1-4 h, and preferably, the phosphate comprises sodium phosphate or potassium phosphate.
Further, in step S1, before mixing the coal gangue with the inorganic acid and water, the coal gangue is ground, and preferably, the grain size of the coal gangue after grinding is 50 to 300 meshes.
Further, in step S2, before passing the acid leaching solution through the cation exchange resin, an oxidant is added to the acid leaching solution to convert ferrous ions in the acid leaching solution into ferric ions, preferably, the oxidant is nitric acid, ozone, sodium hypochlorite or chlorine gas, and more preferably, the reaction temperature is 60 ℃ to 80 ℃.
Further, in step S4, before passing the first eluent through the gallium extracting resin column, the first eluent is heated and concentrated, preferably at a heating temperature of 90 ℃ to 150 ℃.
Further, in step S5, the concentration of the sodium hydroxide solution is 3 to 5mol/L, preferably, in step S5, after the gallium solution is electrolyzed to extract gallium, the extracted gallium is subjected to extraction and impurity removal by using acid and alkali in sequence to purify gallium, more preferably, the acid is hydrochloric acid, and the alkali is sodium hydroxide.
By applying the technical scheme of the invention, aluminum, gallium and lithium can be effectively extracted from the coal gangue, namely, an aluminum-gallium-lithium system can be effectively extracted from the coal gangue, so that the synergistic extraction of valuable elements can be realized.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the method for extracting valuable elements from coal gangue in the prior art cannot realize the synergistic extraction of valuable elements, and in order to solve the problem, the invention provides a method for extracting an aluminum-gallium-lithium system from coal gangue, which comprises the following steps:
step S1: mixing the coal gangue with inorganic acid and water, and then carrying out leaching reaction to obtain acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt;
step S2: separating the acid leaching solution from the inorganic acid aluminum salt and the inorganic acid iron salt through cation exchange resin to obtain refined solution containing the inorganic acid aluminum salt, and then carrying out first elution on the cation exchange resin by using dilute hydrochloric acid to obtain first eluent containing gallium ions and iron ions;
and step S3: concentrating and crystallizing the refined solution containing the inorganic acid aluminum salt, then carrying out solid-liquid separation to obtain inorganic aluminum salt crystals and a separation filtrate containing lithium, and calcining the inorganic aluminum salt crystals to obtain alumina;
and step S4: passing the first eluent through a gallium extraction resin column to enrich gallium, and performing second elution on the gallium extraction resin enriched with gallium by using dilute hydrochloric acid to obtain a second eluent containing gallium ions and iron ions;
step S5: adding sodium hydroxide into the second eluent, then carrying out first filtration treatment to obtain first filtrate, adding hydrochloric acid into the first filtrate, then carrying out second filtration treatment to obtain gallium mud, adding a sodium hydroxide solution into the gallium mud to form a gallium solution, and then carrying out electrolysis treatment on the gallium solution to extract gallium; and
step S6: spray roasting the separation filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate, then reacting to obtain a first lithium-enriched liquid, adding phosphate into the first lithium-enriched liquid to react to obtain a second lithium-enriched liquid, and adding carbonate into the second lithium-enriched liquid to react to obtain lithium carbonate.
The invention provides a method for extracting an aluminum-gallium-lithium system from coal gangue for the first time. The method adopts inorganic acid to directly leach coal gangue to prepare pickle liquor containing inorganic acid aluminum salt and inorganic acid iron salt, and prepares metallurgical-grade aluminum oxide by carrying out resin impurity removal and concentration crystallization on the pickle liquor; the first eluent after impurity removal is used for extracting gallium metal; and (3) the separation filtrate containing lithium is used for extracting lithium carbonate, so that the synergistic extraction of valuable elements is realized.
The method comprises the steps S1 to S6, wherein the step S1 comprises an inorganic acid leaching step, the step S2 comprises a resin impurity removal step, the step S3 comprises a concentration crystallization and high-temperature roasting step, the step S4 comprises a resin gallium enrichment step, the step S5 comprises a chemical impurity removal and electrolysis step, and the step S6 comprises a spray roasting step, a water leaching step, a deep impurity removal step and a lithium carbonate preparation step. The method can obtain the alumina with the purity of more than or equal to 99 percent, and the extraction rate of the alumina is more than or equal to 85 percent; 4N gallium with purity more than or equal to 99.99% is obtained, and the extraction rate of gallium is more than or equal to 98%; and obtaining the lithium carbonate with the purity of more than or equal to 99 percent, wherein the extraction rate of lithium is more than or equal to 85 percent.
By the method, aluminum, gallium and lithium can be effectively extracted from the coal gangue, namely, an aluminum-gallium-lithium system can be effectively extracted from the coal gangue, so that the synergistic extraction of valuable elements can be realized.
In order to better perform the leaching reaction of the coal gangue and the inorganic acid and to better leach valuable elements from the coal gangue, in step S1, the inorganic acid comprises hydrochloric acid or nitric acid, preferably hydrochloric acid; the inorganic acid aluminum salt includes aluminum chloride or aluminum nitrate, preferably includes aluminum chloride; the inorganic ferric salt comprises ferric chloride or ferric nitrate, and preferably comprises ferric chloride; preferably, the mass ratio of the coal gangue to the inorganic acid is 1.5-5, preferably 1; the leaching temperature is 120-200 ℃, and the optimal temperature is 140-160 ℃; the leaching time is 1 to 5 hours, preferably 2 to 2.5 hours. The stirring rate may be 60 to 200 revolutions per minute, preferably 150 to 180 revolutions per minute. Solid-liquid separation can be carried out after the leaching reaction to obtain a clarified pickle liquor containing inorganic acid aluminum salt and inorganic acid iron salt.
In a preferred embodiment of the present invention, in step S1, the coal gangue is mixed with hydrochloric acid and water according to a certain ratio and then subjected to leaching reaction at a certain temperature. After the leaching reaction, solid-liquid separation is carried out to obtain clear pickle liquor containing compounds such as aluminum chloride, ferric chloride and the like. The mass ratio of the coal gangue to the hydrochloric acid can be 1.5-5, the leaching temperature can be 120-200 ℃, and the leaching time can be 1-5 h. The stirring rate can be 60-200 r/min.
In order to remove impurities from the pickle liquor more fully and to separate the inorganic acid aluminum salt and the inorganic acid iron salt better, in step S2, the temperature is 60-80 ℃ and the speed is 2-3 times of the resin volume/h in the process of passing the pickle liquor through cation exchange resin. In order to more sufficiently elute the cation exchange resin subjected to ion exchange, it is preferable that the dilute hydrochloric acid concentration in the first elution is 0.1 to 0.5mol/L and the dilute hydrochloric acid volume is 1 to 3 times the resin volume. In step S2, the pickle liquor may be decontaminated using a cation exchange resin as known in the art. Preferably, the cation exchange resin is a quaternary ammonium type cation exchange resin.
In a preferred embodiment of the present invention, in step S2, the separation of the inorganic acid aluminum salt such as aluminum chloride and the inorganic acid iron salt such as ferric chloride is carried out by passing the pickle liquor through a cation exchange resin, preferably a quaternary ammonium type cation exchange resin, the temperature may be 60 to 80 ℃, the speed may be 2 to 3 times the volume of the resin per hour, the passing through the column may be either bottom-in-top-out or top-in-bottom-out, and the resin column may be a single column or a double column series connection. When the concentration of the resin inlet slurry is similar to that of the resin outlet slurry, dilute hydrochloric acid is adopted to carry out first elution on the cation exchange resin, the concentration of the dilute hydrochloric acid can be 0.1-0.5 mol/L, and the volume of the dilute hydrochloric acid can be 1-3 times of the volume of the resin.
In order to more favorably concentrate and crystallize the purified liquid containing the inorganic acid aluminum salt, the evaporation temperature in the concentration and crystallization process in step S3 is 80 to 140 ℃, preferably 80 to 120 ℃, and the calcination temperature in the calcination process is 750 to 1200 ℃, preferably 900 to 1150 ℃ in order to more sufficiently convert the inorganic acid aluminum salt crystals to alumina.
In a preferred embodiment of the present invention, in step S3, the purified liquid containing an inorganic aluminum salt such as aluminum chloride is concentrated by heating at an evaporation temperature of 80 to 140 ℃; the steam temperature is 100-180 ℃; the concentration of inorganic aluminum salt such as aluminum chloride is 40-60 wt.%, and the evaporation process can be triple-effect concurrent or countercurrent evaporation; cooling and crystallizing the concentrated solution, then carrying out solid-liquid separation to obtain inorganic aluminum salt crystals such as aluminum chloride crystals and a separation filtrate containing lithium, optionally returning the filtrate to the refined solution to continue concentrating and crystallizing, and discharging the filtrate from the system when the lithium in the filtrate reaches a certain concentration such as 400-500 mg/L for preparing lithium carbonate. Inorganic aluminum salt crystals, such as aluminum chloride crystals, are washed with a hydrochloric acid solution, and the hydrochloric acid wash is returned to the system for dosing. The concentration of the hydrochloric acid solution is 20 to 36 percent, and preferably 30 to 36 percent; the washing ratio is 1. The inorganic aluminum salt crystals, such as aluminum chloride crystals, are calcined to obtain alumina. The calcining temperature is 750-1200 ℃. And (4) recycling the calcined flue gas. The purity of the obtained alumina is more than or equal to 99 percent.
In order to extract gallium from the first eluent more effectively, in step S4, the temperature is 60-80 ℃ and the speed is 1-2 times of resin volume/h during the first eluent passes through the gallium extracting resin column, preferably, in the second eluent, the elution speed is 1-2 times of resin volume/h, and the dosage of dilute hydrochloric acid is 1-2 times of resin volume.
In a preferred embodiment of the present invention, in step S4, the first eluent is passed through a gallium-extracting resin column under the following conditions: the temperature is 60-80 ℃, the speed is 1-2 times of the volume of the resin per hour, the column passing mode is downward inlet and upward outlet or upward inlet and downward outlet, and the resin column can adopt a single column or double column series connection mode; when the concentration of gallium in the slurry at the inlet and outlet of the resin is similar or the same, dilute hydrochloric acid is adopted to elute the gallium-extracting resin, the elution speed is 1-2 times of the volume of the resin per hour, and the dosage of the dilute hydrochloric acid is 1-2 times of the volume of the resin. The concentration of gallium in the obtained second eluent is about 2-3 g/L.
In step S5, the second eluent is first chemically purified, and then the gallium solution is subjected to electrolytic treatment. Specifically, in step S5, sodium hydroxide is added to the second eluent to convert iron ions in the second eluent to Fe (OH) 3 Precipitating and converting gallium ions in the second eluate to GaO 2 - Then, first filtration treatment is performed to obtain a first filtrate, and hydrochloric acid is added to the first filtrate to cause GaO 2 - Conversion to Ga (OH) 3 The precipitate is then subjected to a second filtration treatment to obtainTo the gallium paste, adding a sodium hydroxide solution to the gallium paste to make Ga (OH) in the gallium paste 3 Conversion to GaO 2 - To form a gallium solution, which is then subjected to an electrolytic process to extract gallium.
The second eluent contains impurities such as iron, a small amount of sodium, calcium and the like besides gallium, and the main impurity ion in the second eluent is iron ion Fe 3+ . In a preferred embodiment of the invention, in step S5, sodium hydroxide (flake caustic) is added to the second eluent to a solution pH of 11 or more, preferably pH =12 to 13, to make the iron ion Fe 3+ Essentially total conversion to Fe (OH) 3 Precipitate is separated out to lead gallium ions Ga 3+ All converted to GaO 2 - Left in solution; after plate-frame filtration, hydrochloric acid was added to the filtrate to a pH of 5.5 to 6.0 to obtain GaO 2 - Conversion to Ga (OH) 3 Separating out the precipitate to obtain a gallium-rich precipitate; washing the gallium-rich precipitate with deionized water to neutrality, filtering with plate frame to obtain gallium mud, adding NaOH solution in the concentration of 3-5 mol/L to Ga (OH) 3 All converted into GaO 2 - (ii) a At the moment, the concentration of gallium can reach 25.3-30.7 g/L, and the concentration index of gallium in the electrolyte is completely met. Electrolyzing the gallium solution in an electrolytic bath to extract gallium; the electrolysis temperature is 35-45 ℃, and the current density is 180-200 A.m -2 The voltage is 9-12V.
In step S6, most of the aluminum impurities in the separation filtrate are converted into an alumina form by a spray roasting step, the water-insoluble alumina impurities are removed by a water leaching step to obtain a first lithium-enriched solution, the remaining aluminum ions, calcium ions and magnesium ions in the first lithium-enriched solution are reacted with phosphate to generate a water-insoluble precipitate by a deep impurity removal step to obtain a second lithium-enriched solution, and a carbonate is added to the second lithium-enriched solution to form a lithium carbonate precipitate.
In order to extract lithium efficiently, in step S6, in the spray roasting process, the roasting temperature is 450 ℃ to 900 ℃, preferably 600 ℃ to 850 ℃, and the roasting time is 1 to 5min, preferably 2 to 3min; preferably, in the reaction process after mixing water and the lithium-containing precipitate, the reaction temperature is 80-160 ℃, preferably 100-140 ℃, and the reaction time is 1-4 hours, preferably 1.5-3 hours; preferably, in the process of adding phosphate into the first lithium enrichment solution for reaction, the reaction temperature is 60-120 ℃, preferably 80-100 ℃, and the reaction time is 1-4 hours, preferably 2-4 hours; preferably, in the process of adding carbonate into the second lithium-enriched solution for reaction, the reaction temperature is 60-120 ℃, preferably 80-90 ℃, the reaction time is 1-4 hours, preferably 1-2 hours, and preferably, the phosphate comprises sodium phosphate or potassium phosphate. The phosphate is not limited to sodium or potassium phosphate, but both are used for economic and ready availability, and one skilled in the art can select a suitable phosphate as desired. The carbonate may be selected from potassium carbonate or sodium carbonate, which are readily available on the market.
Lithium carbonate may be prepared from the separated filtrate through step S6. In a preferred embodiment of the present invention, step S6 includes the steps of:
spray roasting: roasting the separated filtrate by adopting a spray roasting process to obtain a lithium-containing precipitate, wherein the roasting temperature is preferably 450-900 ℃, and the roasting time is preferably 1-5 min.
The water leaching process comprises the following steps: mixing water and a lithium-containing precipitate according to a certain proportion, reacting at a certain temperature, and filtering after the reaction is finished to obtain a first lithium enrichment solution with low impurity content, wherein the solid-to-liquid ratio is preferably 1; the reaction temperature is preferably 80-160 ℃; the reaction time is 1-4 h.
Deeply removing impurities: adding phosphate to the first lithium-enriched solution to precipitate aluminum, calcium and magnesium, and filtering to obtain a second lithium-enriched solution such as a mixed solution of lithium chloride and sodium chloride. The addition amount of phosphate such as sodium phosphate is 0.8 to 1.5 times of the theoretical calculation; the reaction temperature is 60-120 ℃; the reaction time is 1-4 h.
Preparing lithium carbonate: and adding an excess amount of carbonate such as sodium carbonate to the second lithium-enriched liquid such as a mixed liquid of lithium chloride and sodium chloride to precipitate lithium, and filtering, washing and drying the precipitate to prepare lithium carbonate. The addition amount of carbonate such as sodium carbonate is 1 to 2 times of the theoretical value; the reaction temperature is 60-120 ℃; the reaction time is 1-4 h. The drying temperature after filtration is 150 ℃ to 250 ℃, preferably 180 ℃ to 230 ℃.
In step S1, in order to increase the contact area between the coal gangue and the inorganic acid, the coal gangue is ground before being mixed with the inorganic acid and water. The granularity of the coal gangue after grinding treatment is 50-300 meshes, and preferably 100-300 meshes. The coal refuse may be subjected to a grinding process using grinding equipment known in the art, such as a mill.
In step S2, in order to remove impurities to the maximum extent, before passing the pickle liquor through a cation exchange resin, a ferrous oxidation step is performed, i.e. an oxidant is added to the pickle liquor to convert ferrous ions in the pickle liquor into ferric ions. The oxidizing agent may be nitric acid, ozone, sodium hypochlorite or chlorine, preferably ozone or chlorine. The reaction temperature may be 60 ℃ to 80 ℃, preferably 60 ℃ to 75 ℃. The air input of the ozone can be 1 to 3g/h, preferably 0.5 to 1.5g/h, and the flow can be 1 to 3L/min, preferably 1.5 to 2.5L/min.
In step S4, in order to increase the content of gallium in the first eluent, the first eluent is heated and concentrated before passing through the gallium extracting resin column, preferably at a heating temperature of 90 ℃ to 150 ℃, preferably 110 ℃ to 130 ℃.
In step S5, the concentration of the sodium hydroxide solution is 3 to 5mol/L for better chemical impurity removal. In order to improve the purity of the obtained gallium and obtain 4N gallium, in step S5, after the gallium solution is electrolyzed to extract gallium, the extracted gallium is subjected to extraction impurity removal by using acid and alkali in sequence to purify gallium, preferably, the acid is hydrochloric acid, and preferably, the alkali is sodium hydroxide.
Gallium extracted by electrolysis has a purity of 99.0-99.9% or higher, and may contain impurities such as Cu, pb, zn, al, in, ca, fe, sn, ni, etc., while some impurities In gallium are rapidly dissolved In acid or alkali at normal temperature. By utilizing the characteristic, the extracted gallium is extracted and purified by acid such as hydrochloric acid and alkali such as sodium hydroxide in sequence, the concentration of the hydrochloric acid and the sodium hydroxide is preferably 1-2 mol/L, so that 4N metal gallium with the purity of more than or equal to 99.99 percent is obtained; the extraction rate of gallium is more than or equal to 98 percent.
The method for extracting the aluminum-gallium-lithium system from the coal gangue can effectively extract aluminum, gallium and lithium from the coal gangue, namely, can effectively extract the aluminum-gallium-lithium system from the coal gangue, thereby realizing the synergistic extraction of valuable elements.
Specifically, the method for extracting the aluminum-gallium-lithium system from the coal gangue has the following advantages and positive effects:
(1) Firstly, a method for synergistically extracting an aluminum-gallium-lithium system from coal gangue is provided.
(2) The method provided by the invention is adopted to carry out synergistic extraction on the aluminum-gallium-lithium system in the coal gangue, so that higher extraction rate and higher purity can be obtained.
(3) The method synergistically extracts valuable elements in the coal gangue, achieves the effect of waste resource utilization, and plays a good demonstration role in improving the value of the coal gangue and resource utilization.
The following examples are provided to further illustrate the advantageous effects of the present invention.
Example 1
In this example, the solid material is analyzed industrially as shown in Table 1.
TABLE 1 solid sample composition (ω (B)/10) -2 )
(1) Production process of metallurgical-grade aluminum oxide
Grinding waste rocks: the coal gangue is ground in a grinder, and the granularity reaches 200 meshes.
Leaching with hydrochloric acid: the method comprises the following steps of mixing powdery coal gangue with hydrochloric acid and water (the mass ratio of the coal gangue to the hydrochloric acid is 1.5), and then carrying out leaching reaction at 140 ℃. After the leaching reaction, solid-liquid separation is carried out to obtain clear pickle liquor containing compounds such as aluminum chloride, ferric chloride and the like. The leaching time is 2h, and the stirring speed is 140 r/min.
Ferrous iron oxidation: and (3) introducing an ozone oxidant into the pickle liquor to convert ferrous ions in the pickle liquor into ferric ions. The ozone air input is 0.5g/h; the flow rate is 2L/min; the reaction temperature was 60 ℃.
Removing impurities by resin: and separating the aluminum chloride and the ferric chloride by passing the acid leaching solution through quaternary ammonium type cation exchange resin. The temperature is 80 ℃, the speed is 2 times of the volume of the resin per hour, and the column passing mode is bottom-in and top-out. When the concentrations of the resin inlet slurry and the resin outlet slurry are similar, eluting the resin by using dilute hydrochloric acid to obtain an iron-removing eluent, wherein the concentration of the dilute hydrochloric acid is 0.3mol/L, and the volume of the dilute hydrochloric acid is 2 times that of the resin; the content of gallium in the iron-removed eluent is 0.2g/L, the content of iron is 75g/L, and the iron-removed eluent is used for extracting gallium.
Concentration and crystallization: heating and concentrating the refined aluminum chloride solution, wherein the evaporation temperature is 120 ℃, the steam temperature is 140 ℃, the concentration of aluminum chloride is 50wt.%, and the evaporation process is a three-effect forward flow; and cooling and crystallizing the concentrated solution, then carrying out solid-liquid separation to obtain aluminum chloride crystals and filtrate, returning the filtrate to the refined solution for continuous concentration and crystallization, and discharging the solution out of the system when the lithium concentration in the filtrate reaches 500mg/L for preparing lithium carbonate. And (3) washing the aluminum chloride crystals by using a hydrochloric acid solution, and returning the hydrochloric acid washing solution to the system for batching. The concentration of the hydrochloric acid solution is 30%, and the washing ratio is 1.
And (3) high-temperature roasting: and calcining the aluminum chloride crystals to obtain the aluminum oxide. The calcination temperature was 1050 ℃. And (4) recycling the calcined flue gas. The purity of the obtained alumina was 99.2%, and the extraction rate of alumina was 85%.
(2) Process for extracting 4N gallium by taking iron-removing eluent as raw material
And (3) evaporation and concentration: the gallium content in the iron-removed eluent is about 0.2g/L, and the iron-removed eluent is heated, evaporated and concentrated until the gallium content is about 0.6g/L, and the heating temperature is 120 ℃.
Enriching gallium in resin: passing the concentrated iron-removed eluent through a gallium extraction resin column under the conditions: the temperature is 80 ℃, the speed is 2 times of the volume of the resin per hour, and the column passing mode is bottom-in and top-out. When the concentration of gallium in the resin inlet slurry and the resin outlet slurry is the same, 0.1mol/L diluted hydrochloric acid is adopted to elute the gallium extracting resin, the elution speed is 1 time of the volume/h of the resin, the dosage of the diluted hydrochloric acid is 1.5 times of the volume of the resin, and the concentration of gallium in the obtained gallium extracting eluent is about 3g/L.
Chemical impurity removal: the gallium-extracting eluent contains 45g/L of iron, a small amount of sodium, calcium and other impurities besides gallium. The main impurity ion in the gallium extraction eluent is Fe 3+ Adding sodium hydroxide into the gallium extracting eluent until the pH value of the solution is 12; after plate and frame filtration, 37% HCl was added to the solution to pH = 5.5-6.0 to get GaO 2 - Conversion to Ga (OH) 3 Separating out the precipitate to obtain a gallium-rich precipitate, wherein the gallium content is 22wt.%; washing the gallium-rich precipitate with deionized water to neutrality, filtering with plate frame to obtain gallium mud, adding a certain amount of NaOH solution with NaOH concentration of 4mol/L to Ga (OH) 3 All converted into GaO 2 - (ii) a At the moment, the concentration of gallium can reach 28.3g/L, and the concentration index of gallium in the electrolyte is completely met.
Electrolysis: electrolyzing the gallium solution in an electrolytic bath to extract crude gallium; the electrolysis temperature is 40 ℃, and the current density is 180 A.m -2 The voltage was 10V.
And (3) purifying crude gallium: the purity of the crude gallium can reach 99.0%, and the crude gallium contains impurities such as Cu, pb, zn, al, in, ca, fe, sn, ni and the like, and certain impurities In the gallium can be quickly dissolved In acid or alkali at normal temperature. By utilizing the characteristic, hydrochloric acid and sodium hydroxide are used for extracting and removing impurities from the crude gallium in sequence, wherein the concentration of the hydrochloric acid and the sodium hydroxide is 2mol/L, and 4N metal gallium with the purity of 99.99% is obtained; the gallium extraction rate was 98.2%.
(3) Process for preparing lithium carbonate from separated filtrate
Spray roasting: and roasting the separated filtrate by adopting a spray roasting process to obtain a lithium-containing precipitate. The roasting temperature is 450 ℃ and the roasting time is 1min.
The water leaching process comprises the following steps: mixing water and lithium-containing precipitate according to a certain proportion, reacting at a certain temperature, and filtering after the reaction is finished to obtain the lithium enrichment solution with low impurity content. The solid-liquid ratio is 1.
Deeply removing impurities: adding sodium phosphate to precipitate aluminum, calcium and magnesium, and filtering to obtain pure mixed solution of lithium chloride and sodium chloride. The addition amount of the sodium phosphate is 1.2 times of the theoretical calculation, the reaction temperature is 80 ℃, and the reaction time is 2 hours.
Preparing lithium carbonate: and adding excessive sodium carbonate into the pure mixed solution of the lithium chloride and the sodium chloride to precipitate the lithium, and filtering, washing and drying the precipitate to prepare the lithium carbonate. The addition of sodium carbonate is 1.5 times of theoretical value, the reaction temperature is 90 ℃, the reaction time is 2h, and the drying temperature after filtration is 200 ℃. The purity of the obtained lithium carbonate was 99.2%, and the lithium extraction rate was 90%.
Example 2
An aluminum-gallium-lithium system was extracted from coal gangue using substantially the same method as in example 1, except that: leaching by adopting nitric acid: mixing powdered coal gangue with nitric acid and water (the mass ratio of the coal gangue to the nitric acid is 1.5), and then carrying out leaching reaction at 140 ℃; and eliminates ferrous oxidation because nitric acid is oxidizing in nature. The other steps were identical to those in example 1. The method can obtain the alumina with the purity of 99.0 percent, and the extraction rate of the alumina is 85 percent; the extraction rates and product purities of gallium and lithium were the same as in example 1.
Example 3
(1) Production process of metallurgical-grade aluminum oxide
Grinding waste rocks: the coal gangue is ground in a grinder, and the granularity reaches 50 meshes.
Leaching with hydrochloric acid: the method comprises the following steps of mixing powdered coal gangue, hydrochloric acid and water (the mass ratio of the coal gangue to the hydrochloric acid is 1. After the leaching reaction, solid-liquid separation is carried out to obtain clear pickle liquor containing compounds such as aluminum chloride, ferric chloride and the like. The leaching time is 5h, and the stirring speed is 140 r/min.
Ferrous iron oxidation: and (3) introducing a nitric acid oxidant into the pickle liquor to convert ferrous ions in the pickle liquor into ferric ions. Nitrate radical NO 3 - Amount of Fe 2+ The molar ratio is 1/4; the reaction temperature was 80 ℃.
Removing impurities by resin: and separating the aluminum chloride and the ferric chloride by passing the acid leaching solution through quaternary ammonium type cation exchange resin. The temperature is 60 ℃, the speed is 2 times of the resin volume/h, and the column passing mode is bottom-in and top-out. When the concentrations of the resin inlet slurry and the resin outlet slurry are similar, eluting the resin by using dilute hydrochloric acid to obtain iron-removing eluent, wherein the concentration of the dilute hydrochloric acid is 0.1mol/L, and the volume of the dilute hydrochloric acid is 3 times that of the resin; the gallium content in the iron-removed eluent is 0.15g/L, the iron content is 50g/L, and the eluent is used for extracting gallium.
Concentration and crystallization: heating and concentrating the refined aluminum chloride solution, wherein the evaporation temperature is 80 ℃, the steam temperature is 140 ℃, the concentration of aluminum chloride is 50wt.%, and the evaporation process is a three-effect concurrent flow; and cooling and crystallizing the concentrated solution, then carrying out solid-liquid separation to obtain aluminum chloride crystals and filtrate, returning the filtrate to the refined solution for continuous concentration and crystallization, and discharging the filtrate out of the system when the concentration of lithium in the filtrate reaches 450mg/L for preparing lithium carbonate. And (3) washing the aluminum chloride crystals by using a hydrochloric acid solution, and returning the hydrochloric acid washing solution to the system for batching. The concentration of the hydrochloric acid solution is 30%, and the washing ratio is 1.
And (3) high-temperature roasting: and calcining the aluminum chloride crystals to obtain the aluminum oxide. The calcination temperature was 750 ℃. And recycling the calcined flue gas. The purity of the obtained alumina was 99.0%, and the extraction rate of alumina was 95%.
(2) Process for extracting 4N gallium by taking iron-removing eluent as raw material
And (3) evaporation and concentration: the gallium content in the iron-removed eluent is about 0.15g/L, and the iron-removed eluent is heated, evaporated and concentrated until the gallium content is about 0.6g/L, and the heating temperature is 90 ℃.
Enriching gallium in resin: passing the concentrated iron-removing eluent through a gallium extraction resin column, wherein the conditions are as follows: the temperature is 60 ℃, the speed is 1 time of the volume of the resin per hour, and the column passing mode is bottom-in and top-out. When the concentration of gallium in the resin inlet slurry and the resin outlet slurry is the same, 0.1mol/L diluted hydrochloric acid is adopted to elute the gallium extracting resin, the elution speed is 1 time of the volume/h of the resin, the dosage of the diluted hydrochloric acid is 1 time of the volume of the resin, and the concentration of gallium in the obtained gallium extracting eluent is about 4.5g/L.
Chemical impurity removal: the gallium-extracting eluent contains 45g/L of iron, a small amount of sodium, calcium and other impurities besides gallium. The main impurity ion in the gallium extraction eluent is Fe 3+ Adding sodium hydroxide into the gallium extracting eluent until the pH value of the solution is 12; after plate filtration, 37% was added to the solutionHCl to pH =5.5, make GaO 2 - Conversion to Ga (OH) 3 Separating out the precipitate to obtain a gallium-rich precipitate, wherein the gallium content is 22wt.%; washing the gallium-rich precipitate with deionized water to neutrality, filtering with plate frame to obtain gallium mud, adding a certain amount of NaOH solution with NaOH concentration of 4mol/L to Ga (OH) 3 All converted into GaO 2 - (ii) a At the moment, the concentration of gallium can reach 28.3g/L, and the concentration index of gallium in the electrolyte is completely met.
Electrolysis: electrolyzing the gallium solution in an electrolytic bath to extract crude gallium; the electrolysis temperature is 35 ℃, and the current density is 180 A.m -2 The voltage is 9V.
And (3) purifying crude gallium: the purity of the crude gallium can reach 99.0%, and the crude gallium contains impurities such as Cu, pb, zn, al, in, ca, fe, sn, ni and the like, and certain impurities In the gallium can be quickly dissolved In acid or alkali at normal temperature. By utilizing the characteristic, hydrochloric acid and sodium hydroxide are used for extracting and removing impurities from the crude gallium in sequence, wherein the concentration of the hydrochloric acid and the sodium hydroxide is 2mol/L, and 4N metal gallium with the purity of 99.99% is obtained; the gallium extraction rate was 98.0%.
(3) Process for preparing lithium carbonate from separated filtrate
Spray roasting: and roasting the separated filtrate by adopting a spray roasting process to obtain a lithium-containing precipitate. The roasting temperature is 500 ℃, and the roasting time is 2min.
The water leaching process comprises the following steps: mixing water and the lithium-containing precipitate according to a certain proportion, reacting at a certain temperature, and filtering after the reaction is finished to obtain the lithium enrichment solution with low impurity content. The solid-liquid ratio is 1.
Deeply removing impurities: adding sodium phosphate to precipitate aluminum, calcium and magnesium, and filtering to obtain pure mixed solution of lithium chloride and sodium chloride. The addition of sodium phosphate is 1.2 times of theoretical calculation, the reaction temperature is 100 ℃, and the reaction time is 1h.
Preparing lithium carbonate: and adding excessive sodium carbonate into the pure mixed solution of the lithium chloride and the sodium chloride to precipitate the lithium, and filtering, washing and drying the precipitate to prepare the lithium carbonate. The adding amount of the sodium carbonate is 1.5 times of the theoretical value, the reaction temperature is 60 ℃, the reaction time is 1h, and the drying temperature after filtration is 200 ℃. The purity of the obtained lithium carbonate was 99.0%, and the lithium extraction rate was 87%.
Example 4
(1) Production process of metallurgical-grade aluminum oxide
Grinding waste rocks: the coal gangue is ground in a grinder, and the granularity reaches 300 meshes.
Leaching with hydrochloric acid: the method comprises the following steps of mixing powdered coal gangue, hydrochloric acid and water (the mass ratio of the coal gangue to the hydrochloric acid is 1: 3.5), and then carrying out leaching reaction at 120 ℃. After the leaching reaction, solid-liquid separation is carried out to obtain clear pickle liquor containing compounds such as aluminum chloride, ferric chloride and the like. The leaching time is 1h, and the stirring speed is 140 r/min.
Ferrous iron oxidation: and (3) introducing a sodium hypochlorite oxidant into the acid leaching solution to convert ferrous ions in the acid leaching solution into ferric ions. Hypochlorite of ClO - Amount of ferrous iron 2+ The molar ratio is 1/1; the reaction temperature was 60 ℃.
Removing impurities by resin: and separating the aluminum chloride and the ferric chloride by passing the acid leaching solution through quaternary ammonium type cation exchange resin. The temperature is 80 ℃, the speed is 3 times of the volume of the resin per hour, and the column passing mode is bottom-in and top-out. When the concentrations of the resin inlet slurry and the resin outlet slurry are similar, eluting the resin by using dilute hydrochloric acid to obtain an iron-removing eluent, wherein the concentration of the dilute hydrochloric acid is 0.5mol/L, and the volume of the dilute hydrochloric acid is 1 time of that of the resin; the content of gallium in the iron-removed eluent is 0.4g/L, the content of iron is 150g/L, and the iron-removed eluent is used for extracting gallium.
Concentration and crystallization: heating and concentrating the refined aluminum chloride solution, wherein the evaporation temperature is 140 ℃, the steam temperature is 140 ℃, the concentration of aluminum chloride is 50wt.%, and the evaporation process is a three-effect concurrent flow; and cooling and crystallizing the concentrated solution, then carrying out solid-liquid separation to obtain aluminum chloride crystals and filtrate, returning the filtrate to the refined solution for continuous concentration and crystallization, and discharging the solution out of the system when the lithium concentration in the filtrate reaches 500mg/L for preparing lithium carbonate. And (3) washing the aluminum chloride crystals by using a hydrochloric acid solution, and returning the hydrochloric acid washing solution to the system for batching. The concentration of the hydrochloric acid solution is 30%, and the washing ratio is 1.
And (3) high-temperature roasting: and calcining the aluminum chloride crystals to obtain the aluminum oxide. The calcination temperature was 1200 ℃. And (4) recycling the calcined flue gas. The purity of the obtained alumina was 99.3%, and the extraction rate of alumina was 87%.
(2) Process for extracting 4N gallium by taking iron-removing eluent as raw material
And (3) evaporation and concentration: the gallium content in the iron-removed eluent is about 0.4g/L, and the iron-removed eluent is heated, evaporated and concentrated until the gallium content is about 0.6g/L, and the heating temperature is 150 ℃.
Enriching gallium in resin: passing the concentrated iron-removing eluent through a gallium extraction resin column, wherein the conditions are as follows: the temperature is 80 ℃, the speed is 2 times of the volume of the resin per hour, and the column passing mode is bottom-in and top-out. When the concentration of gallium in the resin inlet slurry and the resin outlet slurry is the same, 0.1mol/L diluted hydrochloric acid is adopted to elute the gallium extracting resin, the elution speed is 2 times of the volume/h of the resin, the dosage of the diluted hydrochloric acid is 2 times of the volume of the resin, and the concentration of gallium in the obtained gallium extracting eluent is about 2.2g/L.
Chemical impurity removal: the gallium-extracting eluent contains 45g/L of iron, a small amount of sodium, calcium and other impurities besides gallium. The main impurity ion in the gallium extraction eluent is Fe 3+ Adding sodium hydroxide into the gallium extracting eluent until the pH value of the solution is 12; after plate and frame filtration, 37% HCl was added to the solution to pH =6.0 to get GaO 2 - Conversion to Ga (OH) 3 Separating out the precipitate to obtain a gallium-rich precipitate, wherein the gallium content is 22wt.%; washing the gallium-rich precipitate with deionized water to neutrality, filtering with plate frame to obtain gallium mud, adding a certain amount of NaOH solution with NaOH concentration of 4mol/L to obtain Ga (OH) 3 All converted into GaO 2 - (ii) a At the moment, the concentration of gallium can reach 28.3g/L, and the concentration index of gallium in the electrolyte is completely met.
Electrolysis: electrolyzing the gallium solution in an electrolytic bath to extract crude gallium; the electrolysis temperature is 45 ℃, and the current density is 200 A.m -2 The voltage was 12V.
And (3) purifying crude gallium: the purity of the crude gallium can reach 99.0%, and the crude gallium contains impurities such as Cu, pb, zn, al, in, ca, fe, sn, ni and the like, and certain impurities In the gallium can be quickly dissolved In acid or alkali at normal temperature. By utilizing the characteristic, hydrochloric acid and sodium hydroxide are used for extracting and removing impurities from the crude gallium in sequence, wherein the concentration of the hydrochloric acid and the sodium hydroxide is 2mol/L, and 4N metal gallium with the purity of 99.99% is obtained; the gallium extraction rate was 98.0%.
(3) Process for preparing lithium carbonate from separated filtrate
Spray roasting: and roasting the separated filtrate by adopting a spray roasting process to obtain a lithium-containing precipitate. The roasting temperature is 900 ℃ and the roasting time is 5min.
The water leaching process comprises the following steps: mixing water and lithium-containing precipitate according to a certain proportion, reacting at a certain temperature, and filtering after the reaction is finished to obtain the lithium enrichment solution with low impurity content. The solid-liquid ratio is 1.
Deeply removing impurities: adding sodium phosphate to precipitate aluminum, calcium and magnesium, and filtering to obtain pure mixed solution of lithium chloride and sodium chloride. The addition of sodium phosphate is 1.2 times of theoretical calculation, the reaction temperature is 120 ℃, and the reaction time is 4 hours.
Preparing lithium carbonate: and adding excessive sodium carbonate into the pure mixed solution of the lithium chloride and the sodium chloride to precipitate the lithium, and filtering, washing and drying the precipitate to prepare the lithium carbonate. The addition of sodium carbonate is 1.5 times of theoretical value, the reaction temperature is 120 ℃, the reaction time is 4h, and the drying temperature after filtration is 200 ℃. The purity of the obtained lithium carbonate was 99.0%, and the lithium extraction rate was 85%.
Example 5
An aluminum-gallium-lithium system was extracted from coal gangue using substantially the same method as in example 1, except that: ferrous iron oxidation: and (3) introducing a chlorine oxidant into the pickle liquor to convert ferrous ions in the pickle liquor into ferric ions. Chlorine Cl 2 With ferrous iron Fe 2+ The molar ratio is 2/1; the reaction temperature was 60 ℃. The extraction rates and product purities of aluminum, gallium and lithium were the same as in example 1.
The invention provides a method for synergistically extracting an aluminum-gallium-lithium system from coal gangue for the first time. By applying the technical scheme of the invention, an aluminum-gallium-lithium system can be effectively extracted from coal gangue, so that the synergistic extraction of valuable elements can be realized. The method can obtain the alumina with the purity of more than or equal to 99 percent, and the extraction rate of the alumina is more than or equal to 85 percent; 4N gallium with purity more than or equal to 99.99% is obtained, and the extraction rate of gallium is more than or equal to 98%; and obtaining the lithium carbonate with the purity of more than or equal to 99 percent, wherein the extraction rate of lithium is more than or equal to 85 percent. Namely, the method of the invention is adopted to carry out the synergistic extraction of the aluminum-gallium-lithium system in the coal gangue, and higher extraction rate and higher purity can be obtained. The invention extracts valuable elements in the coal gangue, has the effect of waste resource utilization, and plays a good demonstration role in improving the value of the coal gangue and resource utilization.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A process for extracting an al-ga-li system from coal gangue, characterized in that it comprises the following steps:
step S1: mixing the coal gangue with inorganic acid and water, and then carrying out leaching reaction to obtain acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt;
step S2: separating the inorganic acid aluminum salt and the inorganic acid iron salt by passing the acid leaching solution through a cation exchange resin to obtain a refined solution containing the inorganic acid aluminum salt, and then carrying out first elution on the cation exchange resin by using dilute hydrochloric acid to obtain a first eluent containing gallium ions and iron ions;
and step S3: concentrating and crystallizing the refined liquid containing the inorganic acid aluminum salt, then carrying out solid-liquid separation to obtain inorganic aluminum salt crystals and a separation filtrate containing lithium, and calcining the inorganic aluminum salt crystals to obtain alumina;
and step S4: passing the first eluent through a gallium extraction resin column to enrich gallium, and performing second elution on the gallium extraction resin enriched with gallium by using dilute hydrochloric acid to obtain a second eluent containing gallium ions and iron ions;
step S5: adding sodium hydroxide into the second eluent, then carrying out first filtration treatment to obtain first filtrate, adding hydrochloric acid into the first filtrate, then carrying out second filtration treatment to obtain gallium mud, adding a sodium hydroxide solution into the gallium mud to form a gallium solution, and then carrying out electrolysis treatment on the gallium solution to extract gallium; and
step S6: and carrying out spray roasting on the separation filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate, then carrying out a reaction to obtain a first lithium-enriched liquid, adding phosphate into the first lithium-enriched liquid to carry out a reaction to obtain a second lithium-enriched liquid, and adding carbonate into the second lithium-enriched liquid to carry out a reaction to obtain lithium carbonate.
2. The method according to claim 1, wherein in step S1, the inorganic acid comprises hydrochloric acid or nitric acid, the inorganic acid aluminum salt comprises aluminum chloride or aluminum nitrate, the inorganic acid iron salt comprises ferric chloride or ferric nitrate, preferably the mass ratio of coal gangue to inorganic acid is 1.5-5, the leaching temperature is 120-200 ℃, and the leaching time is 1-5 h.
3. The method according to claim 1, characterized in that in step S2, the temperature is 60 ℃ to 80 ℃ and the velocity is 2 to 3 times the resin volume/h during the passage of the pickle liquor through the cation exchange resin, preferably in the first elution, the dilute hydrochloric acid concentration is 0.1 to 0.5mol/L and the dilute hydrochloric acid volume is 1 to 3 times the resin volume.
4. The method according to claim 1, wherein in step S3, the evaporation temperature during the concentration and crystallization is 80 to 140 ℃, and the calcination temperature during the calcination is 750 to 1200 ℃.
5. The method according to claim 1, wherein in step S4, the temperature is 60 ℃ to 80 ℃ and the speed is 1 to 2 times of the resin volume/h during the first elution process, preferably the elution speed is 1 to 2 times of the resin volume/h during the second elution process, and the dosage of the dilute hydrochloric acid is 1 to 2 times of the resin volume.
6. The method of claim 1, wherein in the step S6, in the spray roasting process, the roasting temperature is 450 to 900 ℃, and the roasting time is 1 to 5min; preferably, in the process of mixing water and the lithium-containing precipitate and then carrying out reaction, the reaction temperature is 80-160 ℃, and the reaction time is 1-4 h; preferably, in the process of adding phosphate into the first lithium enrichment solution for reaction, the reaction temperature is 60-120 ℃, and the reaction time is 1-4 h; preferably, in the process of adding carbonate into the second lithium-enriched liquid for reaction, the reaction temperature is 60-120 ℃, the reaction time is 1-4 h, and preferably, the phosphate comprises sodium phosphate or potassium phosphate.
7. The method according to claim 1, wherein in step S1, before mixing the coal gangue with the inorganic acid and water, the coal gangue is subjected to grinding treatment, preferably the coal gangue subjected to grinding treatment has a particle size of 50-300 mesh.
8. The method according to claim 1, characterised in that in step S2 an oxidising agent is added to the pickling liquor to convert ferrous ions in the pickling liquor to ferric ions, prior to passing the pickling liquor through the cation exchange resin, preferably the oxidising agent is nitric acid, ozone, sodium hypochlorite or chlorine gas, more preferably the reaction temperature is 60 ℃ to 80 ℃.
9. The method according to claim 1, wherein in step S4, the first eluate is subjected to a heating concentration treatment before passing through the gallium extracting resin column, preferably at a heating temperature of 90 ℃ to 150 ℃.
10. The method according to claim 1, wherein in step S5, the concentration of the sodium hydroxide solution is 3 to 5mol/L, preferably, in step S5, after the gallium solution is electrolyzed to extract gallium, the extracted gallium is subjected to extraction impurity removal by using acid and alkali sequentially to purify gallium, more preferably, the acid is hydrochloric acid, and the alkali is sodium hydroxide.
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