Method for extracting aluminum-gallium-lithium system from coal gangue

Abstract

The invention relates to a method for extracting an aluminum-gallium-lithium system from coal gangue. The method comprises the following steps: subjecting the coal gangue to a leaching reaction with an inorganic acid to obtain an acid leaching solution; passing the acid leaching solution through an ion exchange resin to obtain a refined solution, eluting the ion exchange resin with dilute hydrochloric acid to obtain an eluate; concentrating and crystallizing the refined solution to obtain inorganic acid aluminum salt crystals and a separation filtrate, and calcining the crystals; passing the eluate through a gallium extraction resin column, eluting the gallium extraction resin with dilute hydrochloric acid to obtain a second eluate; adding sodium hydroxide, then filtering, adding hydrochloric acid to the filtrate, then filtering to obtain gallium mud, adding sodium hydroxide solution to form a gallium solution, and electrolyzing the gallium solution; and spray-roasting the separation 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

[0001] The present invention relates to the technical field of coal gangue application, and in particular to a method for extracting an aluminum-gallium-lithium system from coal gangue. Background Art

[0002] Gangue is a solid waste produced during coal processing. For example, the Heidaigou open-pit mine in Zhungeer Banner, Ordos City, Inner Mongolia, produces approximately 30 million tons of coal annually, but emits approximately 14 million tons of gangue. The two mines combined produce approximately 70 million tons of coal, with gangue emissions reaching approximately 35 million tons. Stockpiled gangue not only occupies land and pollutes the environment, but also poses a safety hazard when the temperature reaches the combustion point of combustible materials, causing spontaneous combustion of the remaining coal in the gangue pile.

[0003] The primary mineral compositions of coal gangue from the Jungar mining area are kaolinite and boehmite. Its primary chemical components are Al2O3 and SiO2, with small amounts of Fe2O3, TiO2, CaO, MgO, P2O5, K2O, and Na2O. The Al2O3 content is 35-40%, the SiO2 content is 36-44%, and the loss on ignition is 15-28%. Rare earth coal gangue has a relatively low calorific value, making direct combustion of the gangue expensive. Mineralogical analysis of the gangue indicates that the aluminum oxide and silicon oxide in the gangue primarily exist in the form of boehmite and kaolinite, which are highly reactive and can be directly leached using acid or alkali methods to increase the carbon content and calorific value. The content of trace element gallium in the coal gangue of this mining area is about 98g / ton, the content of lithium is about 359g / ton, and the total amount of rare earth is about 0.09-0.12%. During the acid method of producing alumina, these valuable elements are enriched in the wastewater and can be extracted in steps.

[0004] Patent CN112897560A provides a method for preparing high-purity alumina from coal gangue. The method involves grinding the coal gangue, calcining it at approximately 750°C, leaching it with sulfuric acid, crystallizing it with ammonium alum, dissolving the crystals, and then salting it out with tertiary hydrochloride to produce 99.95% alumina. This method has disadvantages such as energy consumption during calcination, high environmental treatment costs due to the introduction of a large amount of ammonium salt during the reaction, high preparation costs for tertiary hydrochloride salting out crystallization, expensive analytical equipment, and low yield.

[0005] Patent CN109516484B discloses a method for producing alumina using the sintering process of calcium carbide mud, fly ash, and coal gangue. This method involves raw material preparation, clinker sintering, clinker dissolution, red mud separation and washing, red mud dealkalization, crude liquor desiliconization, seed crystal preparation, semen carbonation and decomposition, aluminum hydroxide separation and washing, aluminum hydroxide roasting, and mother liquor evaporation. However, it suffers from a lengthy process flow, high energy consumption, and significant residual aluminum extraction residue.

[0006] Patent CN113213482A discloses a method for extracting silicon and aluminum from activated coal gangue using plasma ball milling and vibratory fluidized bed calcination. The method involves plasma ball milling a mixture of the gangue and solid alkali for mechanical pre-activation. Air is then introduced into the solid gangue powder to achieve solid fluidization, calcining the activated material. Acid extraction is then performed. The addition of alkali for ultrafine grinding and calcination is energy-intensive and inconsistent with existing energy utilization policies.

[0007] Patent CN113621794A discloses a method for extracting carbon and silica from coal gangue. The crushed and ground coal gangue is activated in supercritical or subcritical water. The activated gangue is then separated into an organic liquid phase and a solid slag phase using a separation device. The solid slag containing carbon and silica is then electrostatically separated to produce high-quality carbon and silica. This method is costly and does not effectively utilize aluminum resources, making it unsuitable for industrialization.

[0008] The existing method for extracting valuable elements from coal gangue is not ideal and cannot achieve the coordinated extraction of valuable elements. Therefore, it is necessary to improve the existing method for extracting valuable elements from coal gangue. Summary of the Invention

[0009] The main purpose of the present invention is to provide a method for extracting an aluminum-gallium-lithium system from coal gangue, so as to solve the technical problem that the prior art cannot achieve the coordinated extraction of valuable elements.

[0010] To achieve the above object, according to one aspect of the present invention, the present invention provides a method for extracting an aluminum-gallium-lithium system from coal gangue, the method comprising the following steps:

[0011] Step S1: mixing coal gangue with inorganic acid and water and performing a leaching reaction to obtain an acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt;

[0012] Step S2: passing the acid leaching solution through a cation exchange resin to separate the inorganic acid aluminum salt and the inorganic acid iron salt to obtain a refined solution containing the inorganic acid aluminum salt, and then performing a first elution on the cation exchange resin with dilute hydrochloric acid to obtain a first eluate containing gallium ions and iron ions;

[0013] Step S3: concentrating and crystallizing the refined liquid containing the inorganic acid aluminum salt, and then performing solid-liquid separation to obtain inorganic acid aluminum salt crystals and a separated filtrate containing lithium, and calcining the inorganic acid aluminum salt crystals to obtain aluminum oxide;

[0014] Step S4: passing the first eluate through a gallium-extracting resin column to enrich gallium, and performing a second elution on the gallium-enriched gallium-extracting resin using dilute hydrochloric acid to obtain a second eluate containing gallium ions and iron ions;

[0015] Step S5: adding sodium hydroxide to the second eluate, then performing a first filtration process to obtain a first filtrate, adding hydrochloric acid to the first filtrate, then performing a second filtration process to obtain gallium sludge, adding sodium hydroxide solution to the gallium sludge to form a gallium solution, and then electrolyzing the gallium solution to extract gallium; and

[0016] Step S6: spray roasting the separated filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate and reacting to obtain a first lithium-rich solution, adding phosphate to the first lithium-rich solution to react to obtain a second lithium-rich solution, and adding carbonate to the second lithium-rich solution to react to obtain lithium carbonate.

[0017] Furthermore, in step S1, the inorganic acid includes hydrochloric acid or nitric acid, the inorganic acid aluminum salt includes aluminum chloride or aluminum nitrate, and the inorganic acid iron salt includes ferric chloride or ferric nitrate. Preferably, the mass ratio of coal gangue to inorganic acid is 1:1.5-5, the leaching temperature is 120°C-200°C, and the leaching time is 1-5h.

[0018] Furthermore, in step S2, during the process of passing the acid leaching solution through the cation exchange resin, the temperature is 60°C to 80°C, and the speed is 2 to 3 times the resin volume / h. Preferably, during the first elution process, the concentration of dilute hydrochloric acid is 0.1 to 0.5 mol / L, and the volume of dilute hydrochloric acid is 1 to 3 times the resin volume.

[0019] Furthermore, in step S3, the evaporation temperature during the concentration and crystallization process is 80°C to 140°C, and the calcination temperature during the calcination process is 750°C to 1200°C.

[0020] Furthermore, in step S4, during the process of passing the first eluent through the gallium extraction resin column, the temperature is 60° C. to 80° C., and the speed is 1 to 2 times the resin volume / h. Preferably, during the second elution process, the elution speed is 1 to 2 times the resin volume / h, and the amount of dilute hydrochloric acid used is 1 to 2 times the resin volume.

[0021] Furthermore, in step S6, during the spray roasting process, the roasting temperature is 450°C to 900°C, and the roasting time is 1 to 5 minutes; preferably, during the reaction process after mixing water with the lithium-containing precipitate, the reaction temperature is 80°C to 160°C, and the reaction time is 1 to 4 hours; preferably, during the reaction process of adding phosphate to the first lithium-rich solution, the reaction temperature is 60°C to 120°C, and the reaction time is 1 to 4 hours; preferably, during the reaction process of adding carbonate to the second lithium-rich solution, the reaction temperature is 60°C to 120°C, and the reaction time is 1 to 4 hours, and the phosphate preferably includes sodium phosphate or potassium phosphate.

[0022] Furthermore, in step S1, before the gangue is mixed with the inorganic acid and water, the gangue is first ground. Preferably, the particle size of the ground gangue is 50 to 300 meshes.

[0023] Furthermore, in step S2, before the acid leaching solution passes through the cation exchange resin, an oxidant is added to the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions. Preferably, the oxidant is nitric acid, ozone, sodium hypochlorite or chlorine, and more preferably the reaction temperature is 60°C to 80°C.

[0024] Furthermore, in step S4, before the first eluate passes through the gallium extraction resin column, the first eluate is first subjected to a heating and concentration treatment, preferably at a heating temperature of 90°C to 150°C.

[0025] Furthermore, in step S5, the concentration of the sodium hydroxide solution is 3 to 5 mol / L. Preferably, in step S5, after the gallium solution is electrolytically treated to extract gallium, the extracted gallium is extracted and impurities are removed using acid and alkali in sequence to purify the gallium. More preferably, the acid is hydrochloric acid and the alkali is sodium hydroxide.

[0026] By applying the technical solution of the present invention, aluminum, gallium and lithium can be effectively extracted from coal gangue, that is, the aluminum-gallium-lithium system can be effectively extracted from coal gangue, thereby realizing the coordinated extraction of valuable elements. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0028] As described in the background art, the existing methods for extracting valuable elements from coal gangue cannot achieve the coordinated extraction of valuable elements. To solve this problem, the present invention provides a method for extracting an aluminum-gallium-lithium system from coal gangue, which comprises the following steps:

[0029] Step S1: mixing coal gangue with inorganic acid and water and performing a leaching reaction to obtain an acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt;

[0030] Step S2: passing the acid leaching solution through a cation exchange resin to separate the inorganic acid aluminum salt and the inorganic acid iron salt to obtain a refined solution containing the inorganic acid aluminum salt, and then performing a first elution on the cation exchange resin with dilute hydrochloric acid to obtain a first eluate containing gallium ions and iron ions;

[0031] Step S3: concentrating and crystallizing the refined liquid containing the inorganic acid aluminum salt, and then performing solid-liquid separation to obtain inorganic acid aluminum salt crystals and a separated filtrate containing lithium, and calcining the inorganic acid aluminum salt crystals to obtain aluminum oxide;

[0032] Step S4: passing the first eluate through a gallium-extracting resin column to enrich gallium, and performing a second elution on the gallium-enriched gallium-extracting resin using dilute hydrochloric acid to obtain a second eluate containing gallium ions and iron ions;

[0033] Step S5: adding sodium hydroxide to the second eluate, then performing a first filtration process to obtain a first filtrate, adding hydrochloric acid to the first filtrate, then performing a second filtration process to obtain gallium sludge, adding sodium hydroxide solution to the gallium sludge to form a gallium solution, and then electrolyzing the gallium solution to extract gallium; and

[0034] Step S6: spray roasting the separated filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate and reacting to obtain a first lithium-rich solution, adding phosphate to the first lithium-rich solution to react to obtain a second lithium-rich solution, and adding carbonate to the second lithium-rich solution to react to obtain lithium carbonate.

[0035] This invention proposes, for the first time, a method for extracting an aluminum-gallium-lithium system from coal gangue. This method uses inorganic acid to directly leach the coal gangue to produce an acid leaching solution containing inorganic acid aluminum salts and inorganic acid iron salts. The acid leaching solution is then subjected to resin impurity removal and concentrated crystallization to produce metallurgical-grade alumina. The impurity-removed first eluate is used to extract metallic gallium, and the lithium-containing separation filtrate is used to extract lithium carbonate, achieving synergistic extraction of the valuable elements.

[0036] The method of the present invention includes steps S1 to S6, wherein step S1 includes an inorganic acid leaching step, step S2 includes a resin impurity removal step, step S3 includes a concentration crystallization and high-temperature roasting step, step S4 includes a resin gallium enrichment step, step S5 includes a chemical impurity removal and electrolysis step, and step S6 includes spray roasting, water leaching, deep impurity removal, and lithium carbonate preparation steps. The method of the present invention can produce alumina with a purity of ≥99% and an alumina extraction rate of ≥85%; 4N gallium with a purity of ≥99.99% and a gallium extraction rate of ≥98%; and lithium carbonate with a purity of ≥99% and a lithium extraction rate of ≥85%.

[0037] The method of the present application can effectively extract aluminum, gallium and lithium from coal gangue, that is, can effectively extract the aluminum-gallium-lithium system from coal gangue, thereby achieving the coordinated extraction of valuable elements.

[0038] To facilitate the leaching reaction between the gangue and the inorganic acid and to better leach valuable elements from the gangue, in step S1, the inorganic acid includes hydrochloric acid or nitric acid, preferably hydrochloric acid; the inorganic acid aluminum salt includes aluminum chloride or aluminum nitrate, preferably aluminum chloride; and the inorganic acid iron salt includes ferric chloride or ferric nitrate, preferably ferric chloride. The mass ratio of gangue to inorganic acid is preferably 1:1.5-5, preferably 1:2.5-3.5; the leaching temperature is 120°C-200°C, preferably 140°C-160°C; and the leaching time is 1-5 hours, preferably 2-2.5 hours. The stirring rate can be 60-200 rpm, preferably 150-180 rpm. After the leaching reaction, solid-liquid separation can be performed to obtain a clear acid leachate containing the inorganic acid aluminum salt and the inorganic acid iron salt.

[0039] In a preferred embodiment of the present invention, in step S1, coal gangue is mixed with hydrochloric acid and water in a certain proportion and then subjected to a leaching reaction at a certain temperature. After the leaching reaction, solid-liquid separation is performed to obtain a clear acid leachate containing compounds such as aluminum chloride and ferric chloride. The mass ratio of coal gangue to hydrochloric acid can be 1:1.5-5, the leaching temperature can be 120°C-200°C, and the leaching time can be 1-5 hours. The stirring rate can be 60-200 rpm.

[0040] To more thoroughly remove impurities from the pickling solution and better separate the inorganic acid aluminum salt from the inorganic acid iron salt, in step S2, the temperature during the passage of the pickling solution through the cation exchange resin is 60°C to 80°C, and the rate is 2 to 3 times the resin volume / h. To more thoroughly elute the cation exchange resin after ion exchange, the concentration of dilute hydrochloric acid in the first elution step is preferably 0.1 to 0.5 mol / L, and the volume of dilute hydrochloric acid is 1 to 3 times the resin volume. In step S2, the pickling solution can be removed from impurities using a cation exchange resin known in the art. Preferably, the cation exchange resin is a quaternary ammonium cation exchange resin.

[0041] In a preferred embodiment of the present invention, in step S2, the acid leaching solution is passed through a cation exchange resin, preferably a quaternary ammonium cation exchange resin, to separate inorganic acid aluminum salts such as aluminum chloride and inorganic acid iron salts such as ferric chloride. During the process of passing the acid leaching solution through the cation exchange resin, the temperature can be 60°C to 80°C, the speed can be 2 to 3 times the resin volume / h, the column flow mode can be bottom-in and top-out or top-in and bottom-out, and the resin column can be a single column or a double column in series. When the concentrations of the resin inlet and outlet slurries are similar, the cation exchange resin is first eluted with dilute hydrochloric acid, the concentration of the dilute hydrochloric acid can be 0.1 to 0.5 mol / L, and the volume of the dilute hydrochloric acid can be 1 to 3 times the resin volume.

[0042] In order to better concentrate and crystallize the refined liquid containing inorganic acid aluminum salt, in step S3, the evaporation temperature during the concentration and crystallization process is 80°C to 140°C, preferably 80°C to 120°C. In order to more fully and thoroughly convert the inorganic acid aluminum salt crystals into alumina, the calcination temperature during the calcination process is 750°C to 1200°C, preferably 900°C to 1150°C.

[0043] In a preferred embodiment of the present invention, in step S3, a refined liquid containing an inorganic acid aluminum salt, such as aluminum chloride, is heated and concentrated, with an evaporation temperature of 80°C to 140°C; a steam temperature of 100°C to 180°C; a concentration of the inorganic acid aluminum salt, such as aluminum chloride, of 40 to 60 wt.%, and the evaporation process can be a three-effect co-current or counter-current evaporation; the concentrated liquid is cooled and crystallized, and then solid-liquid separation is performed to obtain inorganic acid aluminum salt crystals, such as aluminum chloride crystals, and a separated filtrate containing lithium. The filtrate is optionally returned to the refined liquid for further concentration and crystallization. When the lithium in the filtrate reaches a certain concentration, such as 400 to 500 mg / L, it is discharged from the system and used to prepare lithium carbonate. The inorganic acid aluminum salt crystals, such as aluminum chloride crystals, are washed with a hydrochloric acid solution, and the hydrochloric acid washing solution is returned to the system for batching. The concentration of the hydrochloric acid solution is 20 to 36%, preferably 30 to 36%, and the washing ratio is 1:1 to 1:5, preferably 1:2 to 1:4. Alumina is obtained by calcining inorganic acid aluminum salt crystals, such as aluminum chloride crystals, at a calcination temperature of 750°C to 1200°C. The flue gas after calcination is recycled. The resulting alumina has a purity of greater than or equal to 99%.

[0044] In order to more efficiently extract gallium from the first eluate, in step S4, during the process of passing the first eluate through the gallium extraction resin column, the temperature is 60° C. to 80° C. and the speed is 1 to 2 times the resin volume / h. Preferably, during the second elution process, the elution speed is 1 to 2 times the resin volume / h, and the amount of dilute hydrochloric acid used is 1 to 2 times the resin volume.

[0045] In a preferred embodiment of the present invention, in step S4, the first eluate is passed through a gallium-extracting resin column under the following conditions: a temperature of 60°C to 80°C, an elution rate of 1 to 2 resin volumes per hour, a bottom-in, top-out or top-in, bottom-out pattern, and a single or dual resin column in series. When the gallium concentrations in the resin inlet and outlet slurries are similar or identical, the gallium-extracting resin is eluted with dilute hydrochloric acid at a rate of 1 to 2 resin volumes per hour, using 1 to 2 times the resin volume. The resulting second eluate has a gallium concentration of approximately 2 to 3 g / L.

[0046] In step S5, the second eluent is first subjected to chemical impurity removal, and then the gallium solution is electrolyzed. Specifically, in step S5, sodium hydroxide is added to the second eluent to convert the iron ions in the second eluent into Fe(OH)3 precipitates and the gallium ions in the second eluent into GaO2 - , then perform a first filtration process to obtain a first filtrate, to which hydrochloric acid is added to make GaO2 - The gallium sludge is converted into Ga(OH)3 precipitate, and then a second filtration process is performed to obtain gallium mud. Sodium hydroxide solution is added to the gallium mud to convert the Ga(OH)3 in the gallium mud into GaO2. - to form a gallium solution, which is then electrolytically treated to extract gallium.

[0047] In addition to gallium, the second eluent also contains iron, a small amount of sodium, calcium and other impurities. The main impurity ion in the second eluent is iron ion Fe 3+ In a preferred embodiment of the present invention, in step S5, sodium hydroxide (caustic soda) is added to the second eluent until the solution pH is ≥ 11, preferably pH = 12 to 13, so that the iron ions Fe 3+ Almost all of the gallium ions are converted into Fe(OH)3 precipitates, which makes the gallium ions Ga 3+ All converted into GaO2 - Remain in the solution; after plate and frame filtration, add hydrochloric acid to the filtrate to pH = 5.5-6.0 to make GaO2 - The gallium-rich precipitate is converted into Ga(OH)3 and precipitated to obtain a gallium-rich precipitate; the gallium-rich precipitate is washed with deionized water until neutral, and then filtered on a plate and frame to obtain gallium mud. A certain amount of NaOH solution is added to the gallium mud, and the NaOH concentration is preferably 3-5 mol / L to convert all Ga(OH)3 into GaO2 - At this time, the gallium concentration can reach 25.3-30.7 g / L, which fully meets the gallium concentration index in the electrolyte. The gallium solution is electrolyzed in an electrolytic cell to extract gallium; the electrolysis temperature is 35-45°C, and the current density is 180-200 A·m -2 , the voltage is 9~12V.

[0048] In step S6, most of the aluminum impurities in the separated filtrate are converted into aluminum oxide through a spray roasting step, and the water-insoluble aluminum oxide impurities are removed through a water leaching step to obtain a first lithium-rich solution. The remaining aluminum ions, calcium ions and magnesium ions in the first lithium-rich solution are reacted with phosphate to form a water-insoluble precipitate through a deep impurity removal step to obtain a second lithium-rich solution. Lithium carbonate precipitate is formed by adding carbonate to the second lithium-rich solution.

[0049] In order to efficiently extract lithium, in step S6, during the spray roasting process, the roasting temperature is 450°C to 900°C, preferably 600°C to 850°C, and the roasting time is 1 to 5 minutes, preferably 2 to 3 minutes; preferably, in the process of mixing water with the lithium-containing precipitate and reacting, the reaction temperature is 80°C to 160°C, preferably 100°C to 140°C, and the reaction time is 1 to 4 hours, preferably 1.5 to 3 hours; preferably, in the process of adding phosphate to the first lithium-rich solution and reacting, the reaction temperature is 60°C to 120°C, preferably 80°C to 100°C, and the reaction time is 1 to 4 hours, preferably 2 to 4 hours; preferably, in the process of adding carbonate to the second lithium-rich solution and reacting, the reaction temperature is 60°C to 120°C, preferably 80°C to 90°C, and the reaction time is 1 to 4 hours, preferably 1 to 2 hours, and the phosphate preferably includes sodium phosphate or potassium phosphate. The phosphate is not limited to sodium phosphate or potassium phosphate. These two phosphates are used for economic and readily available reasons. A person skilled in the art can select a suitable phosphate as needed. The carbonate can be selected from potassium carbonate or sodium carbonate that is readily available on the market.

[0050] Lithium carbonate can be prepared from the separated filtrate by step S6. In a preferred embodiment of the present invention, step S6 comprises the following steps:

[0051] Spray roasting: The separated filtrate is roasted by a spray roasting process to obtain a lithium-containing precipitate, preferably at a roasting temperature of 450° C. to 900° C. and for a roasting time of 1 to 5 minutes.

[0052] Water leaching process: After mixing water and lithium-containing precipitate in a certain proportion, react at a certain temperature. After the reaction is completed, filter to obtain a first lithium-enriched solution with low impurity content. The preferred solid-liquid ratio is 1:2.5 to 1:10, preferably 1:4 to 1:7; the preferred reaction temperature is 80°C to 160°C; and the reaction time is 1 to 4 hours.

[0053] Deep impurity removal: Phosphate is added to the first lithium-rich solution to precipitate aluminum, calcium, and magnesium. After filtration, a second lithium-rich solution, such as a mixture of lithium chloride and sodium chloride, is obtained. The amount of phosphate, such as sodium phosphate, added is 0.8 to 1.5 times the theoretical amount. The reaction temperature is 60°C to 120°C, and the reaction time is 1 to 4 hours.

[0054] Preparation of lithium carbonate: An excess amount of carbonate, such as sodium carbonate, is added to the second lithium-rich solution, such as a mixture of lithium chloride and sodium chloride, to precipitate lithium. The precipitate is filtered, washed, and dried to produce lithium carbonate. The amount of carbonate, such as sodium carbonate, added is 1 to 2 times the theoretical amount; the reaction temperature is 60°C to 120°C; and the reaction time is 1 to 4 hours. After filtration, the drying temperature is 150°C to 250°C, preferably 180°C to 230°C.

[0055] In step S1, to increase the contact area between the gangue and the inorganic acid, the gangue is ground before being mixed with the inorganic acid and water. The ground gangue has a particle size of 50 to 300 mesh, preferably 100 to 300 mesh. The gangue can be ground using grinding equipment known in the art, such as a mill.

[0056] In step S2, to maximize impurity removal, a ferrous oxidation step is performed before the acid extract passes through the cation exchange resin. Specifically, an oxidizing agent is added to the acid extract to convert the divalent iron ions in the acid extract into trivalent iron ions. The oxidizing agent can be nitric acid, ozone, sodium hypochlorite, or chlorine, preferably ozone or chlorine. The reaction temperature can be 60°C to 80°C, preferably 60°C to 75°C. The ozone inlet rate can be 1 to 3 g / h, preferably 0.5 to 1.5 g / h, and the flow rate can be 1 to 3 L / min, preferably 1.5 to 2.5 L / min.

[0057] In step S4, in order to increase the gallium content in the first eluate, the first eluate is first heated and concentrated before passing through the gallium extraction resin column. The heating temperature is preferably 90° C. to 150° C., more preferably 110° C. to 130° C.

[0058] In step S5, the concentration of the sodium hydroxide solution is 3 to 5 mol / L to better perform 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 extracted and impurities are removed using an acid and then a base to purify the gallium. Preferably, the acid is hydrochloric acid, and preferably, the base is sodium hydroxide.

[0059] Gallium extracted through electrolysis has a purity of 99.0% to 99.9% or higher. It may contain impurities such as Cu, Pb, Zn, Al, In, Ca, Fe, Sn, and Ni. However, some impurities in gallium dissolve rapidly in acid or alkali at room temperature. Taking advantage of this characteristic, the extracted gallium is extracted and removed with an acid such as hydrochloric acid and then an alkali such as sodium hydroxide. The concentrations of hydrochloric acid and sodium hydroxide are preferably 1 to 2 mol / L, resulting in 4N metallic gallium with a purity of ≥99.99% and a gallium extraction rate of ≥98%.

[0060] The method for extracting the aluminum-gallium-lithium system from coal gangue of the present invention can effectively extract aluminum, gallium and lithium from coal gangue, that is, can effectively extract the aluminum-gallium-lithium system from coal gangue, thereby realizing the coordinated extraction of valuable elements.

[0061] Specifically, the method for extracting aluminum-gallium-lithium system from coal gangue of the present invention has the following advantages and positive effects:

[0062] (1) A method for the synergistic extraction of aluminum-gallium-lithium system from coal gangue was proposed for the first time.

[0063] (2) The method of the present invention is used to synergistically extract the aluminum-gallium-lithium system from coal gangue, which can achieve a higher extraction rate and higher purity.

[0064] (3) The present invention extracts valuable elements from coal gangue in a coordinated manner, which achieves the effect of waste resource utilization and plays a good demonstration role in increasing the value of coal gangue and resource utilization.

[0065] The beneficial effects of the present invention will be further illustrated below with reference to the examples.

[0066] Example 1

[0067] In this example, the industrial analysis of the solid material is shown in Table 1.

[0068] Table 1 Solid sample composition (ω(B) / 10 -2 )

[0069]

[0070] (1) Metallurgical-grade alumina production process

[0071] Gangue grinding: Grind the gangue in a mill to a particle size of 200 mesh.

[0072] Hydrochloric acid leaching: Powdered gangue is mixed with hydrochloric acid and water (the mass ratio of gangue to hydrochloric acid is 1:1.5) and then leached at 140°C. After the leaching reaction, solid-liquid separation is performed to produce a clear acid leachate containing compounds such as aluminum chloride and ferric chloride. The leaching time is 2 hours, and the stirring rate is 140 rpm.

[0073] Ferrous oxidation: Ozone is introduced into the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions. The ozone inlet volume is 0.5 g / h, the flow rate is 2 L / min, and the reaction temperature is 60°C.

[0074] Resin Removal: The acid extract was passed through a quaternary ammonium cation exchange resin to separate aluminum chloride and ferric chloride. The temperature was 80°C, the flow rate was 2 times the resin volume / h, and the column flow was bottom-in, top-out. When the concentrations of the resin inlet and outlet slurries were similar, the resin was eluted with dilute hydrochloric acid to produce an iron-removing eluate. The dilute hydrochloric acid concentration was 0.3 mol / L, and the volume of dilute hydrochloric acid was 2 times the resin volume. The iron-removing eluate contained 0.2 g / L gallium and 75 g / L iron, which was then used for gallium extraction.

[0075] Concentration and Crystallization: The aluminum chloride refined liquid is heated and concentrated, with an evaporation temperature of 120°C, a steam temperature of 140°C, and an aluminum chloride concentration of 50 wt.%. The evaporation process is a three-effect, downstream process. The concentrated liquid is cooled and crystallized, followed by solid-liquid separation to produce aluminum chloride crystals and a filtrate. The filtrate is returned to the refined liquid for further concentration and crystallization. When the lithium concentration in the filtrate reaches 500 mg / L, it is discharged from the system and used to prepare lithium carbonate. The aluminum chloride crystals are washed with hydrochloric acid solution, and the hydrochloric acid washing liquid is returned to the system for batching. The hydrochloric acid solution concentration is 30%, and the washing ratio is 1:1.

[0076] High-temperature calcination: Aluminum chloride crystals are calcined to produce alumina. The calcination temperature is 1050°C. The flue gas after calcination is recycled. The resulting alumina has a purity of 99.2% and an alumina extraction rate of 85%.

[0077] (2) Process for extracting 4N gallium using iron removal eluate as raw material

[0078] Evaporation and concentration: The gallium content in the iron removal eluate is about 0.2 g / L, which is heated and evaporated to concentrate to a gallium content of about 0.6 g / L at a heating temperature of 120°C.

[0079] Gallium enrichment with resin: The concentrated, iron-removed eluate was passed through a gallium-extracting resin column at 80°C, at a rate of 2 resin volumes per hour, and in a bottom-in, top-out pattern. When the gallium concentrations in the resin inlet and outlet slurries were the same, the gallium-extracting resin was eluted with 0.1 mol / L dilute hydrochloric acid at a rate of 1 resin volume per hour, using 1.5 times the resin volume. The resulting gallium concentration in the gallium-extracting eluate was approximately 3 g / L.

[0080] Chemical impurity removal: In addition to gallium, the gallium extraction eluate also contains 45g / L iron, a small amount of sodium, calcium and other impurities. The main impurity ions in the gallium extraction eluate are Fe 3+ , add sodium hydroxide to the gallium extraction eluate until the solution pH is 12; after plate and frame filtration, add 37% HCl to the solution until the pH is 5.5-6.0, so that GaO2 - The precipitate was converted into Ga(OH)3 and precipitated to obtain a gallium-rich precipitate with a gallium content of 22 wt.%. The gallium-rich precipitate was washed with deionized water until neutral, and then filtered on a plate and frame to obtain gallium mud. A certain amount of NaOH solution was added to the gallium mud with a NaOH concentration of 4 mol / L to convert all Ga(OH)3 into GaO2. - At this time, the gallium concentration can reach 28.3g / L, which fully meets the gallium concentration index in the electrolyte.

[0081] Electrolysis: The gallium solution is electrolyzed in an electrolytic cell to extract crude gallium; the electrolysis temperature is 40°C and the current density is 180A·m -2 , the voltage is 10V.

[0082] Crude Gallium Purification: Crude gallium can reach a purity of 99.0%. It contains impurities such as Cu, Pb, Zn, Al, In, Ca, Fe, Sn, and Ni. However, some impurities in gallium dissolve rapidly in acid or alkali at room temperature. Taking advantage of this characteristic, the crude gallium is extracted and removed using hydrochloric acid and then sodium hydroxide at concentrations of 2 mol / L, yielding 4N metallic gallium with a purity of 99.99% and a gallium extraction yield of 98.2%.

[0083] (3) Process for preparing lithium carbonate from the separated filtrate

[0084] Spray calcination: The separated filtrate is calcined using a spray calcination process to obtain a lithium-containing precipitate at a temperature of 450°C and a calcination time of 1 minute.

[0085] Water leaching process: Water and lithium-containing precipitate are mixed in a certain proportion and reacted at a certain temperature. After the reaction is completed, it is filtered to obtain a lithium-enriched solution with low impurity content. The solid-liquid ratio is 1:5, the reaction temperature is 100°C, and the reaction time is 2 hours.

[0086] Deep impurity removal: Sodium phosphate is added to precipitate aluminum, calcium, and magnesium. After filtration, a pure mixture of lithium chloride and sodium chloride is obtained. The amount of sodium phosphate added is 1.2 times the theoretical amount. The reaction temperature is 80°C and the reaction time is 2 hours.

[0087] Preparation of lithium carbonate: An excess of sodium carbonate was added to the purified lithium chloride and sodium chloride mixture to precipitate lithium. The precipitate was filtered, washed, and dried to produce lithium carbonate. The amount of sodium carbonate added was 1.5 times the theoretical value. The reaction temperature was 90°C, the reaction time was 2 hours, and the drying temperature after filtration was 200°C. The resulting lithium carbonate had a purity of 99.2% and a lithium extraction yield of 90%.

[0088] Example 2

[0089] The aluminum-gallium-lithium system was extracted from coal gangue using a method essentially identical to that used in Example 1, with the following differences: nitric acid leaching was used: powdered coal gangue was mixed with nitric acid and water (the mass ratio of gangue to nitric acid was 1:1.5) and the leaching reaction was carried out at 140°C; and ferrous oxidation was omitted due to the inherent oxidizing properties of nitric acid. The remaining steps were consistent with those in Example 1. The method of the present invention yielded aluminum oxide with a purity of 99.0% and an aluminum oxide extraction yield of 85%. The gallium and lithium extraction yields and product purity were the same as in Example 1.

[0090] Example 3

[0091] (1) Metallurgical-grade alumina production process

[0092] Gangue grinding: Grind the gangue in a mill to a particle size of 50 mesh.

[0093] Hydrochloric acid leaching: Powdered gangue is mixed with hydrochloric acid and water (the mass ratio of gangue to hydrochloric acid is 1:5) and then leached at 200°C. After the leaching reaction, solid-liquid separation is performed to produce a clear acid leachate containing compounds such as aluminum chloride and ferric chloride. The leaching time is 5 hours, and the stirring rate is 140 rpm.

[0094] Ferrous oxidation: Add nitric acid oxidant into the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions. - Fe 2+ The molar ratio is 1 / 4; the reaction temperature is 80°C.

[0095] Resin Removal: The acid extract was passed through a quaternary ammonium cation exchange resin to separate aluminum chloride and ferric chloride. The temperature was 60°C, the flow rate was 2 times the resin volume / h, and the column flow was bottom-in, top-out. When the concentrations of the resin inlet and outlet slurries were similar, the resin was eluted with dilute hydrochloric acid to produce an iron-removing eluate. The dilute hydrochloric acid concentration was 0.1 mol / L, and the volume of dilute hydrochloric acid was 3 times the resin volume. The iron-removing eluate contained 0.15 g / L gallium and 50 g / L iron, and was used for gallium extraction.

[0096] Concentration and Crystallization: The aluminum chloride refined liquid is heated and concentrated, with an evaporation temperature of 80°C, a steam temperature of 140°C, and an aluminum chloride concentration of 50 wt.%. The evaporation process is a three-effect, downstream process. The concentrated liquid is cooled and crystallized, followed by solid-liquid separation to produce aluminum chloride crystals and a filtrate. The filtrate is returned to the refined liquid for further concentration and crystallization. When the lithium concentration in the filtrate reaches 450 mg / L, it is discharged from the system and used to prepare lithium carbonate. The aluminum chloride crystals are washed with hydrochloric acid solution, and the hydrochloric acid washing liquid is returned to the system for batching. The hydrochloric acid solution concentration is 30%, and the washing ratio is 1:1.

[0097] High-temperature calcination: Aluminum chloride crystals are calcined to produce alumina. The calcination temperature is 750°C. The flue gas after calcination is recycled. The resulting alumina has a purity of 99.0% and an alumina extraction rate of 95%.

[0098] (2) Process for extracting 4N gallium using iron removal eluate as raw material

[0099] Evaporation and concentration: The gallium content in the iron removal eluate is about 0.15 g / L, which is heated and evaporated to concentrate to a gallium content of about 0.6 g / L at a heating temperature of 90°C.

[0100] Gallium enrichment with resin: The concentrated, iron-removed eluate was passed through a gallium-extracting resin column at 60°C, at a rate of 1 resin volume / h, and in a bottom-in, top-out pattern. When the gallium concentrations in the resin inlet and outlet slurries were the same, the gallium-extracting resin was eluted with 0.1 mol / L dilute hydrochloric acid at a rate of 1 resin volume / h, using 100% dilute hydrochloric acid. The resulting gallium concentration in the gallium-extracting eluate was approximately 4.5 g / L.

[0101] Chemical impurity removal: In addition to gallium, the gallium extraction eluate also contains 45g / L iron, a small amount of sodium, calcium and other impurities. The main impurity ions in the gallium extraction eluate are Fe 3+ , add sodium hydroxide to the gallium extraction eluate until the solution pH is 12; after plate and frame filtration, add 37% HCl to the solution until the pH is 5.5, so that GaO2 - The precipitate was converted into Ga(OH)3 and precipitated to obtain a gallium-rich precipitate with a gallium content of 22 wt.%. The gallium-rich precipitate was washed with deionized water until neutral, and then filtered on a plate and frame to obtain gallium mud. A certain amount of NaOH solution was added to the gallium mud with a NaOH concentration of 4 mol / L to convert all Ga(OH)3 into GaO2. - At this time, the gallium concentration can reach 28.3g / L, which fully meets the gallium concentration index in the electrolyte.

[0102] Electrolysis: The gallium solution is electrolyzed in an electrolytic cell to extract crude gallium; the electrolysis temperature is 35°C and the current density is 180A·m -2 , the voltage is 9V.

[0103] Crude Gallium Purification: Crude gallium can reach a purity of 99.0%. It contains impurities such as Cu, Pb, Zn, Al, In, Ca, Fe, Sn, and Ni. However, some impurities in gallium dissolve rapidly in acid or alkali at room temperature. Taking advantage of this characteristic, the crude gallium is extracted and removed using hydrochloric acid and then sodium hydroxide at concentrations of 2 mol / L, yielding 4N metallic gallium with a purity of 99.99% and a gallium extraction yield of 98.0%.

[0104] (3) Process for preparing lithium carbonate from the separated filtrate

[0105] Spray calcination: The separated filtrate is calcined using a spray calcination process to obtain a lithium-containing precipitate at a temperature of 500°C and a calcination time of 2 minutes.

[0106] Water leaching process: Water and lithium-containing precipitate are mixed in a certain proportion and reacted at a certain temperature. After the reaction is completed, it is filtered to obtain a lithium-enriched solution with low impurity content. The solid-liquid ratio is 1:5, the reaction temperature is 100°C, and the reaction time is 2 hours.

[0107] Deep impurity removal: Sodium phosphate is added to precipitate aluminum, calcium, and magnesium. After filtration, a pure mixture of lithium chloride and sodium chloride is obtained. The amount of sodium phosphate added is 1.2 times the theoretical amount. The reaction temperature is 100°C and the reaction time is 1 hour.

[0108] Preparation of lithium carbonate: An excess of sodium carbonate was added to the purified lithium chloride and sodium chloride mixture to precipitate lithium. The precipitate was filtered, washed, and dried to produce lithium carbonate. The amount of sodium carbonate added was 1.5 times the theoretical value. The reaction temperature was 60°C, the reaction time was 1 hour, and the drying temperature after filtration was 200°C. The resulting lithium carbonate had a purity of 99.0% and a lithium extraction yield of 87%.

[0109] Example 4

[0110] (1) Metallurgical-grade alumina production process

[0111] Gangue grinding: Grind the gangue in a mill to a particle size of 300 mesh.

[0112] Hydrochloric acid leaching: Powdered gangue is mixed with hydrochloric acid and water (the mass ratio of gangue to hydrochloric acid is 1:3.5) and then leached at 120°C. After the leaching reaction, solid-liquid separation is performed to produce a clear acid leachate containing compounds such as aluminum chloride and ferric chloride. The leaching time is 1 hour, and the stirring rate is 140 rpm.

[0113] Ferrous oxidation: Sodium hypochlorite oxidant is introduced into the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions. - Fe 2+ The molar ratio was 1 / 1; the reaction temperature was 60°C.

[0114] Resin Removal: The acid extract was passed through a quaternary ammonium cation exchange resin to separate aluminum chloride and ferric chloride. The temperature was 80°C, the flow rate was 3 times the resin volume / h, and the column flow was bottom-in, top-out. When the concentrations of the resin inlet and outlet slurries were similar, the resin was eluted with dilute hydrochloric acid to produce an iron-removing eluate. The dilute hydrochloric acid concentration was 0.5 mol / L, and the volume of dilute hydrochloric acid was 1 times the resin volume. The iron-removing eluate contained 0.4 g / L gallium and 150 g / L iron, which was then used for gallium extraction.

[0115] Concentration and Crystallization: The aluminum chloride refined liquid is heated and concentrated to an evaporation temperature of 140°C, a steam temperature of 140°C, and an aluminum chloride concentration of 50 wt.%. The evaporation process is a three-effect, downstream process. The concentrated liquid is cooled and crystallized, followed by solid-liquid separation to obtain aluminum chloride crystals and a filtrate. The filtrate is returned to the refined liquid for further concentration and crystallization. When the lithium concentration in the filtrate reaches 500 mg / L, it is discharged from the system and used to prepare lithium carbonate. The aluminum chloride crystals are washed with hydrochloric acid solution, and the hydrochloric acid washing liquid is returned to the system for batching. The hydrochloric acid solution concentration is 30%, and the washing ratio is 1:1.

[0116] High-temperature calcination: Aluminum chloride crystals are calcined to produce alumina at a temperature of 1200°C. The flue gas from the calcination is recycled. The resulting alumina has a purity of 99.3% and an alumina extraction rate of 87%.

[0117] (2) Process for extracting 4N gallium using iron removal eluate as raw material

[0118] Evaporation and concentration: The gallium content in the iron removal eluate is about 0.4 g / L, which is heated and evaporated to concentrate to a gallium content of about 0.6 g / L at a heating temperature of 150°C.

[0119] Gallium enrichment with resin: The concentrated, iron-removed eluate was passed through a gallium-extracting resin column at 80°C, at a rate of 2 resin volumes per hour, and in a bottom-in, top-out pattern. When the gallium concentrations in the resin inlet and outlet slurries were the same, the gallium-extracting resin was eluted with 0.1 mol / L dilute hydrochloric acid at a rate of 2 resin volumes per hour, using a volume of dilute hydrochloric acid equal to 2 times the resin volume. The resulting gallium concentration in the gallium-extracting eluate was approximately 2.2 g / L.

[0120] Chemical impurity removal: In addition to gallium, the gallium extraction eluate also contains 45g / L iron, a small amount of sodium, calcium and other impurities. The main impurity ions in the gallium extraction eluate are Fe 3+ , add sodium hydroxide to the gallium extraction eluate until the solution pH is 12; after plate and frame filtration, add 37% HCl to the solution until the pH is 6.0, so that GaO2 - The precipitate was converted into Ga(OH)3 and precipitated to obtain a gallium-rich precipitate with a gallium content of 22 wt.%. The gallium-rich precipitate was washed with deionized water until neutral, and then filtered on a plate and frame to obtain gallium mud. A certain amount of NaOH solution was added to the gallium mud with a NaOH concentration of 4 mol / L to convert all Ga(OH)3 into GaO2. - At this time, the gallium concentration can reach 28.3g / L, which fully meets the gallium concentration index in the electrolyte.

[0121] Electrolysis: The gallium solution is electrolyzed in an electrolytic cell to extract crude gallium; the electrolysis temperature is 45°C and the current density is 200A·m -2 , the voltage is 12V.

[0122] Crude Gallium Purification: Crude gallium can reach a purity of 99.0%. It contains impurities such as Cu, Pb, Zn, Al, In, Ca, Fe, Sn, and Ni. However, some impurities in gallium dissolve rapidly in acid or alkali at room temperature. Taking advantage of this characteristic, the crude gallium is extracted and removed using hydrochloric acid and then sodium hydroxide at concentrations of 2 mol / L, yielding 4N metallic gallium with a purity of 99.99% and a gallium extraction yield of 98.0%.

[0123] (3) Process for preparing lithium carbonate from the separated filtrate

[0124] Spray calcination: The separated filtrate is calcined using a spray calcination process to obtain a lithium-containing precipitate at a temperature of 900°C and a calcination time of 5 minutes.

[0125] Water leaching process: Water and lithium-containing precipitate are mixed in a certain proportion and reacted at a certain temperature. After the reaction is completed, it is filtered to obtain a lithium-enriched solution with low impurity content. The solid-liquid ratio is 1:5, the reaction temperature is 160°C, and the reaction time is 4 hours.

[0126] Deep impurity removal: Sodium phosphate is added to precipitate aluminum, calcium, and magnesium. After filtration, a pure mixture of lithium chloride and sodium chloride is obtained. The amount of sodium phosphate added is 1.2 times the theoretical amount. The reaction temperature is 120°C and the reaction time is 4 hours.

[0127] Preparation of lithium carbonate: An excess of sodium carbonate was added to the purified lithium chloride and sodium chloride mixture to precipitate lithium. The precipitate was filtered, washed, and dried to produce lithium carbonate. The amount of sodium carbonate added was 1.5 times the theoretical value. The reaction temperature was 120°C, the reaction time was 4 hours, and the drying temperature after filtration was 200°C. The resulting lithium carbonate had a purity of 99.0% and a lithium extraction yield of 85%.

[0128] Example 5

[0129] The aluminum-gallium-lithium system was extracted from coal gangue using a method substantially the same as that in Example 1, except that: ferrous oxidation: chlorine oxidant was introduced into the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions. 2+ The molar ratio was 2 / 1 and the reaction temperature was 60° C. The extraction rates of aluminum, gallium and lithium and the product purity were the same as those in Example 1.

[0130] This invention proposes, for the first time, a method for the synergistic extraction of an aluminum-gallium-lithium system from coal gangue. Application of the present invention's technical solution enables the effective extraction of the aluminum-gallium-lithium system from coal gangue, thereby achieving the synergistic extraction of valuable elements. This method can produce aluminum oxide with a purity of ≥99% and an aluminum oxide extraction rate of ≥85%; 4N gallium with a purity of ≥99.99% and a gallium extraction rate of ≥98%; and lithium carbonate with a purity of ≥99% and a lithium extraction rate of ≥85%. In other words, the synergistic extraction of the aluminum-gallium-lithium system from coal gangue using the present method can achieve a high extraction rate and high purity. This invention extracts valuable elements from coal gangue, effectively utilizing waste resources and serving as a model for increasing the value of coal gangue and resource utilization.

[0131] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for extracting aluminum-gallium-lithium system from coal gangue, characterized in that: The method comprises the following steps: Step S1: mixing coal gangue with inorganic acid and water and performing a leaching reaction to obtain an acid leaching solution containing inorganic acid aluminum salt and inorganic acid iron salt; Step S2: passing the acid leaching solution through a cation exchange resin to separate the inorganic acid aluminum salt and the inorganic acid iron salt to obtain a refined solution containing the inorganic acid aluminum salt, and then performing a first elution on the cation exchange resin with dilute hydrochloric acid to obtain a first eluate containing gallium ions and iron ions; Step S3: concentrating and crystallizing the refined liquid containing the inorganic acid aluminum salt, and then performing solid-liquid separation to obtain inorganic acid aluminum salt crystals and a separated filtrate containing lithium, and calcining the inorganic acid aluminum salt crystals to obtain aluminum oxide; Step S4: passing the first eluate through a gallium-extracting resin column to enrich gallium, and performing a second elution on the gallium-enriched gallium-extracting resin using dilute hydrochloric acid to obtain a second eluate containing gallium ions and iron ions; Step S5: adding sodium hydroxide to the second eluate, then performing a first filtration process to obtain a first filtrate, adding hydrochloric acid to the first filtrate, then performing a second filtration process to obtain gallium sludge, adding sodium hydroxide solution to the gallium sludge to form a gallium solution, and then electrolyzing the gallium solution to extract gallium; and Step S6: spray roasting the separated filtrate to obtain a lithium-containing precipitate, mixing water with the lithium-containing precipitate and reacting to obtain a first lithium-rich solution, adding phosphate to the first lithium-rich solution and reacting to obtain a second lithium-rich solution, and adding carbonate to the second lithium-rich solution and reacting to obtain lithium carbonate. In step S2, during the process of passing the acid leaching solution through the cation exchange resin, the temperature is 60°C to 80°C, the speed is 2 to 3 times the resin volume / h, and during the first elution process, the concentration of dilute hydrochloric acid is 0.1 to 0.5 mol / L, and the volume of dilute hydrochloric acid is 1 to 3 times the resin volume.

2. The method according to claim 1, characterized in that In step S1 , the inorganic acid includes hydrochloric acid or nitric acid, the inorganic acid aluminum salt includes aluminum chloride or aluminum nitrate, and the inorganic acid iron salt includes ferric chloride or ferric nitrate.

3. The method according to claim 1, characterized in that In step S3, the evaporation temperature during the concentration and crystallization process is 80°C to 140°C, and the calcination temperature during the calcination process is 750°C to 1200°C.

4. The method according to claim 1, wherein In step S4, during the process of passing the first eluent through the gallium-extracting resin column, the temperature is 60° C. to 80° C., and the speed is 1 to 2 times the resin volume / h.

5. The method according to claim 1, characterized in that In step S6, during the spray roasting process, the roasting temperature is 450°C to 900°C, and the roasting time is 1 to 5 minutes.

6. The method according to claim 1, wherein In step S1 , the coal gangue is ground before being mixed with inorganic acid and water.

7. The method according to claim 1, characterized in that In step S2, before the acid leaching solution passes through a cation exchange resin, an oxidant is first added to the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions.

8. The method according to claim 1, characterized in that In step S4, before the first eluate passes through the gallium-extracting resin column, the first eluate is first subjected to a heating and concentration treatment.

9. The method according to claim 1, characterized in that In step S5, the concentration of the sodium hydroxide solution is 3-5 mol / L.

10. The method according to claim 1, characterized in that In step S1, the mass ratio of coal gangue to inorganic acid is 1:1.5-5, the leaching temperature is 120°C-200°C, and the leaching time is 1-5 hours.

11. The method according to claim 1, wherein In step S4, during the second elution process, the elution rate is 1 to 2 times the resin volume / h, and the amount of dilute hydrochloric acid used is 1 to 2 times the resin volume.

12. The method according to claim 1, characterized in that In step S6, during the reaction after mixing water and the lithium-containing precipitate, the reaction temperature is 80° C. to 160° C., and the reaction time is 1 to 4 hours.

13. The method according to claim 1, wherein In step S6, during the reaction of adding phosphate to the first lithium-rich solution, the reaction temperature is 60° C. to 120° C., and the reaction time is 1 to 4 hours.

14. The method according to claim 1, wherein In step S6, during the reaction of adding carbonate to the second lithium-rich solution, the reaction temperature is 60° C. to 120° C., and the reaction time is 1 to 4 hours.

15. The method according to claim 1, wherein The phosphate includes sodium phosphate or potassium phosphate.

16. The method according to claim 6, characterized in that The coal gangue has a particle size of 50 to 300 meshes after grinding.

17. The method according to claim 7, characterized in that The oxidant is nitric acid, ozone, sodium hypochlorite or chlorine.

18. The method according to claim 7, characterized in that In step S2, during the process of adding an oxidant to the acid leaching solution to convert the divalent iron ions in the acid leaching solution into trivalent iron ions, the reaction temperature is 60°C to 80°C.

19. The method according to claim 8, characterized in that In step S4, the heating temperature is 90°C to 150°C.

20. The method according to claim 1, wherein In step S5, after the gallium solution is electrolyzed to extract gallium, the extracted gallium is extracted and impurities are removed by using acid and alkali in sequence to purify the gallium.

21. The method according to claim 20, characterized in that In step S5, hydrochloric acid and sodium hydroxide are used to extract and remove impurities from the extracted gallium to purify the gallium.

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