Method for comprehensively recovering alkali metal from lithium-containing silicate ore

Abstract

The invention relates to the technical field of lithium-containing silicate ore treatment, and particularly discloses a method for comprehensively recovering alkali metal from lithium-containing silicate ore, which comprises the following steps: S1, mixing lepidolite with concentrated sulfuric acid and sulfate in sequence to obtain a mixture, and roasting the mixture to obtain clinker; s2, the clinker is subjected to plasma surface treatment and then mixed with water to form a mixture, the mixture is subjected to leaching treatment, and a leaching solution is obtained; and S3, a lithium precipitant is added into the leachate, so that lithium in the solution is precipitated out, and rubidium salt and cesium salt are obtained from the lithium-precipitated solution through an extraction-reverse extraction method. According to the method, the alkali metal is extracted by combining a sulfuric acid leaching method and a sulfate leaching method, in the leaching process, a large number of Li-F bonds on the surface of the lepidolite can be induced to be broken by utilizing interaction between plasma high-energy particles and the lepidolite to react, fluorine removal is achieved, and lithium loss is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of processing lithium-containing silicate ores, and more specifically, to a method for comprehensively recovering alkali metals from lithium-containing silicate ores. Background Art

[0002] Lithium-containing silicate ores are an important mineral resource, primarily including spodumene, lepidolite, ferroalite, petalite, and ferroalite. The first three minerals are the most important, and spodumene and lepidolite are rich in rare metals such as lithium, rubidium, and cesium. Lithium, rubidium, and cesium are all silvery-white, soft alkali metals with a wide range of uses. Lithium, as the metallic element with the smallest atomic diameter and lowest density, is used in batteries, heat-resistant glass, lubricants, refrigerants, and the nuclear industry. Rubidium and cesium have excellent photoelectric properties and are used in photomultiplier tubes, atomic clocks, photocells, infrared technology, and nuclear medicine.

[0003] At present, the methods for extracting alkali metal salts from lepidolite mainly include roasting and leaching. The leaching method is to leach the roasted lepidolite in a solution under high pressure or normal pressure, such as sulfuric acid leaching, sodium salt leaching, lime milk leaching, etc., to achieve the purpose of lithium extraction. In the relevant literature, "Research Progress on Lithium Extraction Process and Defluorination Technology of Lepidolite" by Yang Peidong, Dong Shuhao, et al. Mineral Protection and Utilization, 2022, 42(3): 15-23, it is pointed out that in the process of leaching lithium, the OH - Bound Li is more easily converted into soluble sulfate, but Li attached to F is difficult to dissolve by acidification, increasing the difficulty of lepidolite extraction. Furthermore, during the lithium extraction process, fluorine forms a capping layer of insoluble fluorine on the surface of the ore sample, and even coordinates and adsorbs lithium to form insoluble Li-F, causing lithium loss. In light of the aforementioned related technologies, exploring the removal of fluorine during the leaching process of lepidolite extraction is of great significance for improving lithium extraction efficiency and achieving clean and efficient utilization of lepidolite. Summary of the Invention

[0004] In order to improve the fluorine removal rate and the recovery rate of alkali metals during the lithium extraction process of lepidolite, the present application provides a method for comprehensively recovering alkali metals from lithium-containing silicate ores.

[0005] The present application provides a method for comprehensive recovery of alkali metals from lithium-containing silicate ores, which adopts the following technical solution: A method for comprehensively recovering alkali metals from lithium-containing silicate ores comprises the following steps: S1, sequentially mixing lepidolite with concentrated sulfuric acid and sulfate to obtain a mixture, and roasting the mixture to obtain a clinker; S2, mixing the plasma-treated clinker with water to form a mixture, and leaching the mixture to obtain a leachate; S3, adding a lithium precipitant to the leachate to precipitate lithium in the solution, and obtaining rubidium salt and cesium salt from the solution after lithium precipitation through extraction-stripping method.

[0006] By adopting the above technical solution, concentrated sulfuric acid is first used to corrode the lepidolite to increase the specific surface area and reaction active sites of the lepidolite; after the crystal transformation of the lepidolite after high-temperature roasting, the concentrated sulfuric acid and sulfate react with the lepidolite together to generate lithium sulfate that is easily soluble in water. At the same time, the associated rubidium and cesium are also converted into soluble sulfates for comprehensive utilization; the present application adopts a method combining sulfuric acid leaching and sulfate leaching, which not only alleviates the problem of corrosion of the equipment caused by the sulfuric acid method but also effectively reduces the probability of ring formation in the kiln during the sulfate method. More importantly, during the leaching process, the interaction between the plasma high-energy particles and the lepidolite is first used to react, which can induce a large number of Li-F bonds on the surface of the lepidolite to break, thereby achieving the removal of fluorine and avoiding lithium loss, thereby improving the extraction rate of alkali metals and the removal rate of fluorine.

[0007] Preferably, in S1, the lepidolite is pretreated before being mixed with concentrated sulfuric acid, specifically, the lepidolite is first crushed and then water vapor is introduced into the lepidolite for defluorination.

[0008] By adopting the above technical solution, the present application pre-treats the lepidolite by first crushing the lepidolite to increase its specific surface area, thereby increasing the contact area between water vapor and the lepidolite during the roasting process and reducing the activation energy of the chemical reaction; the water vapor reacts with the lepidolite to accelerate the defluorination reaction and make the dense structure of the lepidolite loose, making the interior of the ore more susceptible to contact and reaction with sulfate, thereby increasing the reactivity of the lepidolite and further improving the fluorine removal rate and alkali metal extraction rate.

[0009] Preferably, in S1, the sulfate is one or more of sodium sulfate, potassium sulfate, ferric sulfate, calcium sulfate, magnesium sulfate, and ferric sulfate, and more preferably is a mixture of calcium sulfate, sodium sulfate, and potassium sulfate in a mass ratio of (3-5): (2-4): 3.

[0010] By adopting the above technical solution, when mixed sulfates with different ratios are used to roast lepidolite, the use of mixed sulfates can improve the lithium leaching rate to a certain extent; at the same time, through comparison, it is found that increasing the use of potassium sulfate helps to improve the lithium leaching rate, but due to the high cost of potassium sulfate and the low melting point of sodium sulfate at high temperature, sintering is prone to occur under high-temperature calcination environment. Replacing part of the potassium sulfate with sodium sulfate and calcium sulfate can reduce the amount of potassium sulfate to 30%.

[0011] Preferably, in S1, a calcium compound is added while the lepidolite is mixed with the sulfate, and the calcium compound is one or more of calcium carbonate, calcium hydroxide, calcium oxide, and calcium sulfate; more preferably, calcium oxide.

[0012] By adopting the above technical solution, a small amount of hydrogen fluoride gas will be generated during the high-temperature roasting process to pollute the environment. Therefore, a small amount of calcium compound is added during roasting to absorb the generated hydrogen fluoride gas to prevent it from being discharged into the air and causing environmental pollution. Since calcium oxide has a high melting point, sintering and vitrification of the raw materials caused by the high-temperature heating process during the roasting process can be avoided.

[0013] Preferably, in S1, the mass ratio of the lepidolite, concentrated sulfuric acid, sulfate and calcium compound is 1: (0.2-0.3): (0.2-0.3): (0.05-0.1).

[0014] By adopting the above technical solution, an excess of concentrated sulfuric acid and sulfate is added relative to the lepidolite and calcium compound, so that the lithium contained in the lepidolite can be fully reacted and completely converted into lithium sulfate.

[0015] Preferably, in S1, the calcination temperature is 800-900°C and the calcination time is 45-60 minutes.

[0016] By adopting the above technical solution, since concentrated sulfuric acid in the present application first corrodes the lepidolite, many small pits are formed on the surface of the lepidolite, which increases the specific surface area of the lepidolite, improves the reactivity of the lepidolite, shortens the roasting reaction time, and saves energy consumption.

[0017] Preferably, in S2, the plasma treatment is specifically as follows: In S2, the plasma treatment is specifically as follows: placing the clinker in a plasma generating device, using nitrogen as a protective gas, and treating it at a power of 100-500W for 10 minutes.

[0018] By adopting the above technical solution, during the plasma surface treatment process, different process parameter settings will have different effects on the plasma surface treatment effect. This application improves the plasma treatment effect on clinker by optimizing the plasma's RF power, treatment time and protective gas, and further improves the defluorination effect of lithium mica.

[0019] Preferably, in S2, the mixed material is further subjected to ball milling treatment before the leaching treatment, the liquid-to-solid ratio of the ball milling treatment is (1-1.1):1, the ball milling time is 5-10 minutes, and the ball milling medium is steel balls.

[0020] By adopting the above technical solution, ball milling is beneficial to increasing the contact area between the leaching agent and the material during the leaching process, making the leaching reaction more complete.

[0021] Preferably, in S3, the lithium precipitant includes one or more of sodium carbonate, carbon dioxide, phosphoric acid, and sodium phosphate, and is more preferably sodium carbonate.

[0022] By adopting the above technical solution, sodium carbonate can convert lithium sulfate in the leachate into lithium carbonate to the maximum extent, thereby improving lithium precipitation efficiency and extraction rate and increasing metal recovery rate.

[0023] Preferably, in S3, the extractant used in the extraction-stripping method is 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP), and the stripping agent is one of sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, and carbon dioxide.

[0024] By adopting the above technical solution, the present application realizes the effective recovery of rubidium salt and cesium salt through a simple extraction-strip extraction method. Compared with the traditional precipitation method, ion exchange method, etc., it has the advantages of simple process and equipment, continuous operation of the production process, high separation efficiency, and low reagent consumption. By adding an organic extractant, it combines with the metal to form a metal organic compound, which is then dissolved in an organic solvent. Since rubidium and cesium have different binding abilities with the extractant, this enables the extractant to extract the metal in a certain order, thereby realizing the effective separation of rubidium and cesium. Then, through stripping, the rubidium metal organic compound and the cesium organic compound are transferred to the aqueous phase to obtain rubidium salt and cesium salt, respectively.

[0025] t-BAMBP has high extraction efficiency and good separation performance for rubidium and cesium. Its use in the separation and purification of rubidium and cesium from lithium extraction mother liquor from lepidolite has been systematically studied and the process is relatively mature. The process is simple, with high yield, low cost and good product quality.

[0026] In summary, this application has at least one of the following beneficial technical effects: 1. In the process of extracting alkali metals from lepidolite by leaching, the present invention utilizes the interaction between plasma high-energy particles and lepidolite to induce the cleavage of Li-F bonds on the lepidolite surface, thereby achieving the removal of fluorine and avoiding lithium loss. 2. The present application adopts a method combining sulfuric acid leaching and sulfate leaching, which not only makes up for the shortcomings of the two methods, but also adds concentrated sulfuric acid first to corrode the lepidolite, increasing its specific surface area and improving its reaction activity, thereby shortening the roasting time and saving energy consumption; 3. The present application pre-treats the lepidolite before mixing it with concentrated sulfuric acid, thereby increasing the reactivity of the lepidolite and reducing the chemical reactivity of the lepidolite with concentrated sulfuric acid. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to the examples. The raw materials involved in the present application can be obtained commercially.

[0028] Example 1 Raw materials: lepidolite, whose main chemical components are: 4.8wt%Li2O, 10.56wt%K2O, 0.59wt%Na2O, 24wt%Al2O3, 53.57wt%SiO2, 0.37wt%Fe2O3, 1.72wt%Rb2O, 0.3wt%Cs2O, and the balance is fluorine.

[0029] The method for comprehensively recovering alkali metals from lithium-containing silicate ores in this embodiment specifically comprises the following steps: (1) 1 kg of lepidolite was mixed with 0.2 kg of 98 wt% concentrated sulfuric acid, and then 0.09 kg of calcium sulfate, 0.12 kg of sodium sulfate and 0.09 kg of potassium sulfate were added and stirred to obtain a mixture. The mixture was placed in a muffle furnace and roasted at a temperature of 850 ° C for 50 min to obtain a clinker; (2) After the clinker is cooled, it is placed in the cavity of a plasma tube furnace, 50 cm away from the plasma generator, and then nitrogen gas with a flow rate of 50 ml / min is passed into the furnace as an induction gas for 10 minutes to remove the air in the tube; the vacuum pump is started to evacuate the cavity, and the flow rate of nitrogen is adjusted to 20-40 ml / min so that the vacuum degree in the cavity is within the range of 10-20 Pa and maintained for 30 minutes, and then the plasma excitation source is started and plasma induction treatment is performed at a power of 200 W for 10 minutes to obtain a mixture; water is added to the mixture and leaching is performed in a leaching tank at a leaching temperature of 60 ° C, a leaching stirring speed of 120 rpm, and a leaching time of 1 hour to obtain a leaching solution containing lithium, cesium and rubidium; (3) Since sodium carbonate and calcium ions in lithium mica will form a precipitate, and since carbonate is a weak acid radical, it is easy to hydrolyze in water to produce bicarbonate ions and hydroxide ions, thereby making the water alkaline. The iron ions and aluminum ions contained in lithium mica will undergo strong hydrolysis to produce insoluble metal hydroxides, affecting the purity of lithium carbonate. Therefore, impurity removal treatment is carried out first.

[0030] Specifically, sodium hydroxide solution is added to the leachate containing lithium, cesium and rubidium. When the pH value of the solution is controlled to be around 3, a reddish-brown precipitate, which is iron hydroxide, slowly precipitates out of the solution; sodium hydroxide solution is continued to be added dropwise. When the pH value is around 5, a white precipitate, which is aluminum hydroxide, begins to precipitate out; sodium hydroxide solution is continued to be added dropwise until the pH value of the solution reaches around 8. No more precipitate is generated, indicating that the iron ions and aluminum ions in the solution have been completely separated from the leachate. The iron ions and aluminum ions in the leachate can be removed by filtration. The obtained leachate containing lithium, cesium and rubidium contains a small amount of calcium ions. The leachate from which the iron ions and aluminum ions have been removed is further added with a sodium hydroxide solution until the pH reaches about 13, and is heated and concentrated to evaporate excess water vapor to increase the concentrations of lithium, cesium and rubidium in the solution. The calcium ions in the solution are accompanied by the precipitation of a small amount of white precipitate Ca(OH)2 during the heating and concentration process. After concentration, EDTA is added dropwise to the solution to remove the calcium ions, and the solution is filtered to obtain a solution containing a higher concentration of lithium, cesium and rubidium. At this time, the solution containing lithium, cesium and rubidium also contains a small amount of potassium salt and sodium salt. Taking advantage of the fact that the solubility of K2SO4 and Na2SO4 solutions changes greatly at different temperatures, the solution containing a higher concentration of lithium, cesium and rubidium is cooled to precipitate K2SO4 and Na2SO4 crystals. Specifically, the solution containing a higher concentration of lithium, cesium and rubidium is cooled to 0°C to precipitate potassium sulfate and sodium sulfate crystals, and then filtered to obtain a purified solution of lithium, rubidium and cesium with a higher concentration.

[0031] A saturated sodium carbonate solution is added to a purified solution containing lithium, rubidium, and cesium with a high concentration, and the solution is heated to 80°C for precipitation reaction to obtain lithium carbonate; the solution after lithium precipitation is subjected to extraction / stripping with an extractant (t-BAMBP), sulfonated kerosene and diethylbenzene as diluents, and hydrochloric acid as a stripping agent to obtain rubidium salt and cesium salt, specifically, the pH of the solution after lithium precipitation is adjusted to 11, a first organic solvent with a volume ratio of extractant to diluent of 2:1 is added to the solution after lithium precipitation for countercurrent extraction treatment, the extraction is performed for 5 minutes, and the ratio of the extracted organic phase to the aqueous phase is 2: 1. Obtain a cesium-loaded organic phase and a rubidium salt solution of the first extraction residual liquid, countercurrently wash the cesium-loaded organic phase with distilled water for 5 minutes, with a volume ratio of the aqueous phase to the organic phase of 1:10, to obtain a washed cesium-loaded organic phase and a first washing liquid; back-extract the washed cesium-loaded organic phase with hydrochloric acid for 5 minutes, with a ratio of the back-extracted organic phase to the water phase of 15:1, to obtain a cesium salt back-extraction solution and a first blank organic phase; concentrate the cesium salt back-extraction solution until crystals precipitate, cool to 25° C., and then perform solid-liquid separation to obtain a cesium salt. The pH of the first extraction residue was adjusted to 13, and the rubidium salt solution of the first extraction residue was added to the second organic solvent with a volume ratio of extractant to diluent of 3:2. The extraction was carried out for 5 minutes, and the ratio of the extracted organic phase to the water phase was 5:1 to obtain a rubidium-loaded organic phase and a second extraction residue. The rubidium-loaded organic phase was countercurrently washed with distilled water for 5 minutes, and the ratio of the organic phase to the water phase was 10:1 to obtain a washed rubidium-loaded organic phase and a second washing solution. The washed rubidium-loaded organic phase was back-extracted with hydrochloric acid for 5 minutes, and the ratio of the back-extracted organic phase to the water phase was 15:1 to obtain a rubidium salt back-extraction solution and a second blank organic phase. The rubidium salt back-extraction solution was concentrated until crystals precipitated, and after cooling to 25°C, solid-liquid separation was performed to obtain rubidium salt.

[0032] Example 2 This embodiment is basically the same as embodiment 1, except that: (1) 1 kg of lepidolite is crushed, ball-milled and sieved to 178 μm, and mixed uniformly to obtain primary raw ore powder, the primary raw ore powder is roasted for defluorination, 20 g of water vapor is introduced at a high temperature of 850°C for defluorination reaction for 80 minutes, gas-solid separation is performed to obtain fluorine-containing tail gas, HF is absorbed by sodium oxide, and the corresponding fluoride salt is obtained by drying and dehydrating, and then HF is prepared by treating with concentrated sulfuric acid; the obtained solid material is mixed uniformly with 0.2 kg of 98 wt% concentrated sulfuric acid, and then 0.09 kg of calcium sulfate, 0.12 kg of sodium sulfate and 0.09 kg of potassium sulfate are added and stirred to obtain a mixture, and the mixture is placed in a muffle furnace for roasting at a roasting temperature of 850°C for 50 minutes to obtain clinker.

[0033] Example 3 This embodiment is basically the same as embodiment 1, except that: (1) 1 kg of lepidolite is mixed evenly with 0.2 kg of 98 wt% concentrated sulfuric acid, and then 0.09 kg of calcium sulfate, 0.12 kg of sodium sulfate, 0.09 kg of potassium sulfate and 0.1 g of calcium oxide are added and stirred to obtain a mixture, and the mixture is placed in a muffle furnace for roasting at a temperature of 850 ° C. for 50 min to obtain a clinker.

[0034] Example 4 This embodiment is basically the same as embodiment 1, except that: (1) 1 kg of lepidolite is crushed, ball-milled and sieved to 178 μm, and mixed uniformly to obtain primary raw ore powder, the primary raw ore powder is roasted for defluorination, 20 g of water vapor is introduced at a high temperature of 850°C for defluorination reaction for 80 minutes, gas-solid separation is performed to obtain fluorine-containing tail gas, HF is absorbed by sodium oxide, and the corresponding fluoride salt is obtained by drying and dehydrating, and then HF is prepared by treating with concentrated sulfuric acid; the obtained solid material is mixed uniformly with 0.2 kg of 98 wt% concentrated sulfuric acid, and then 0.09 kg of calcium sulfate, 0.12 kg of sodium sulfate, 0.09 kg of potassium sulfate and 0.1 g of calcium oxide are added and stirred to obtain a mixture, and the mixture is placed in a muffle furnace for roasting at a temperature of 850°C for 50 minutes to obtain clinker.

[0035] Example 5 This embodiment is basically the same as embodiment 4, except that: (1) 1 kg of lepidolite is crushed, ball-milled and sieved to 178 μm, and mixed uniformly to obtain primary raw ore powder, the primary raw ore powder is roasted for defluorination, 20 g of water vapor is introduced at a high temperature of 850°C for defluorination reaction for 80 minutes, gas-solid separation is performed to obtain fluorine-containing tail gas, HF is absorbed by sodium oxide, and the corresponding fluoride salt is obtained by drying and dehydrating, and then HF is prepared by treating with concentrated sulfuric acid; the obtained solid material is mixed uniformly with 0.25 kg of 98 wt% concentrated sulfuric acid, and then 0.1 kg of calcium sulfate, 0.075 kg of sodium sulfate, 0.075 kg of potassium sulfate and 0.08 g of calcium oxide are added and stirred to obtain a mixture, and the mixture is placed in a muffle furnace for roasting at a temperature of 850°C for 50 minutes to obtain clinker.

[0036] Example 6 This embodiment is basically the same as embodiment 4, except that: (1) 1 kg of lepidolite is crushed, ball-milled and sieved to 178 μm, and mixed uniformly to obtain primary raw ore powder, the primary raw ore powder is roasted for defluorination, 20 g of water vapor is introduced at a high temperature of 850°C for defluorination reaction for 80 min, gas-solid separation is performed to obtain fluorine-containing tail gas, HF is absorbed by sodium oxide, and the corresponding fluoride salt is obtained by drying and dehydrating, and then HF is prepared by treating with concentrated sulfuric acid; the obtained solid material is mixed uniformly with 0.3 kg of 98 wt% concentrated sulfuric acid, and then 0.1 kg of calcium sulfate, 0.04 kg of sodium sulfate, 0.06 kg of potassium sulfate and 0.05 g of calcium oxide are added and stirred to obtain a mixture, and the mixture is placed in a muffle furnace for roasting at a temperature of 850°C for 50 min to obtain clinker.

[0037] Example 7 This embodiment is basically the same as embodiment 1, except that (2) the clinker is cooled and placed in the cavity of a plasma tube furnace, 50 cm away from the plasma generator, and then nitrogen gas with a flow rate of 50 ml / min is passed into the furnace as an induction gas for 10 minutes to remove the air in the tube; the vacuum pump is started to evacuate the cavity, and the flow rate of nitrogen is adjusted to 20-40 ml / min so that the vacuum degree in the cavity is within the range of 10-20 Pa and maintained for 30 minutes, and then, A plasma excitation source was started, and a plasma induction treatment was performed at a power of 200 W for 10 minutes to obtain a mixture. The mixture was mixed with water and ball milled with a liquid-to-solid ratio of 1.05:1 for 10 minutes using a steel ball with a diameter of 6 mm as the grinding medium to obtain a slurry with a fineness of 400 mesh. Water was added to the slurry, and leaching was performed in a leaching tank at a leaching temperature of 60° C., a leaching stirring speed of 120 rpm, and a leaching time of 1 hour to obtain a leaching solution containing lithium, cesium, and rubidium.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that step (2) is different, and the other steps are the same. Step (2) is specifically as follows: cooling the clinker and adding water, and leaching treatment is carried out in a leaching tank. The leaching temperature is 60°C, the leaching stirring speed is 120 rpm, and the leaching time is 1 hour to obtain a leachate containing lithium, cesium and rubidium.

[0039] Comparative Example 2 The difference between this comparative example and Example 2 is that step (2) is different, and the other steps are the same. Step (2) is specifically as follows: cooling the clinker and adding water, and leaching treatment is carried out in a leaching tank. The leaching temperature is 60°C, the leaching stirring speed is 120 rpm, and the leaching time is 1 hour to obtain a leachate containing lithium, cesium and rubidium.

[0040] Comparative Example 3 The difference between this comparative example and Example 3 is that step (2) is different, and the other steps are the same. Step (2) is specifically as follows: cooling the clinker and adding water, and leaching treatment is carried out in a leaching tank. The leaching temperature is 60°C, the leaching stirring speed is 120 rpm, and the leaching time is 1 hour to obtain a leachate containing lithium, cesium and rubidium.

[0041] Comparative Example 4 The difference between this comparative example and Example 4 is that step (2) is different, and the other steps are the same. Step (2) is specifically as follows: cooling the clinker and adding water, and leaching treatment is carried out in a leaching tank. The leaching temperature is 60°C, the leaching stirring speed is 120 rpm, and the leaching time is 1 hour to obtain a leachate containing lithium, cesium and rubidium.

[0042] Performance testing The masses of lithium, cesium, rubidium and fluorine were determined from the lithium-, cesium- and rubidium-containing leachates obtained in step (2) of Examples 1-7 and Comparative Examples 1-4. The extraction rates of lithium, cesium and rubidium and the removal rate of fluorine were calculated based on the ratios of the elements before and after extraction. The results are shown in Table 1.

[0043] Table 1 Performance test data of Examples 1-7 and Comparative Examples 1-4

[0044] Referring to Table 1, in combination with Examples 1-4 and Comparative Examples 1-4, it can be seen that the present application introduces plasma treatment during the leaching treatment, and the interaction between the plasma high-energy particles and the lepidolite reacts to induce the breakage of the Li-F bond on the surface of the lepidolite, thereby achieving the removal of fluorine and avoiding lithium loss, thereby improving the extraction rate of alkali metals and the removal rate of fluorine.

[0045] Referring to Table 1, in combination with Example 1 and Example 2, it can be seen that the present application pre-treats the lepidolite by first crushing the lepidolite to increase its specific surface area, increase the contact area between water vapor and lepidolite during the roasting process, and reduce the activation energy of the chemical reaction; and the water vapor reacts with the lepidolite to accelerate the defluorination reaction, and makes the dense structure of the lepidolite loose, making the interior of the ore more susceptible to contact and reaction with sulfate, thereby increasing the reactivity of the lepidolite and further improving the fluorine removal rate and the alkali metal extraction rate.

[0046] Referring to Table 1, in combination with Example 1 and Example 3, it can be seen that in the present application, calcium oxide is added while mixing lepidolite with sulfate. During the high-temperature roasting process, a small amount of hydrogen fluoride gas is generated to pollute the environment. Therefore, a small amount of calcium oxide is added during roasting to absorb the generated hydrogen fluoride gas, thereby further improving the fluorine removal rate and the alkali metal extraction rate.

[0047] With reference to Table 1, in combination with Example 1 and Example 4, it can be seen that the present application pre-treats the lepidolite, introduces calcium oxide during roasting, and uses plasma treatment on the clinker during leaching treatment, and sets a defluorination process in different steps. The three play different action mechanisms and can jointly improve the fluorine removal rate, reduce the adverse effects of fluorine on the extraction of alkali metals, and thus improve the extraction rate of alkali metals.

[0048] Referring to Table 1, in combination with Example 1 and Example 7, it can be seen that the present application adds water to the mixture and then ball mills it, so that water can penetrate between the particles, reducing the surface energy of the particle surface, thereby making the particles more easily broken up by the grinding medium, forming a more uniform suspension, which is beneficial to increase the contact area between the leaching agent and the material during the leaching process, making the leaching reaction more sufficient.

[0049] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for comprehensive recovery of alkali metals from lithium-containing silicate ores, characterized in that: The following steps are involved: S1, sequentially mixing lepidolite with concentrated sulfuric acid and sulfate to obtain a mixture, and roasting the mixture to obtain a clinker; S2, mixing the plasma-treated clinker with water to form a mixture, and leaching the mixture to obtain a leachate; S3, adding a lithium precipitant to the leachate to precipitate lithium in the solution, and obtaining rubidium salt and cesium salt from the solution after lithium precipitation through extraction-stripping method.

2. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, wherein: In S1, the lepidolite is pretreated before being mixed with concentrated sulfuric acid. Specifically, the lepidolite is first crushed and then water vapor is introduced to perform defluorination treatment.

3. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S1, the sulfate is one or more of sodium sulfate, potassium sulfate, iron sulfate, calcium sulfate, magnesium sulfate, and iron sulfate.

4. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, wherein: In S1, a calcium compound is added while the lepidolite is mixed with sulfate, and the calcium compound is one or more of calcium carbonate, calcium hydroxide, calcium oxide, and calcium sulfate.

5. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 4, characterized in that: In S1, the mass ratio of the lepidolite, concentrated sulfuric acid, sulfate and calcium compound is 1: (0.2-0.3): (0.2-0.3): (0.05-0.1).

6. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S1, the calcination temperature is 700-800° C. and the calcination time is 45-60 min.

7. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S2, the plasma treatment is specifically as follows: placing the clinker in a plasma generator, using nitrogen as a protective gas, and treating it at a power of 100-500W for 10 minutes.

8. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S2, the mixed material is further subjected to ball milling before the leaching treatment. The liquid-to-solid ratio of the ball milling treatment is (1-1.1):1, the ball milling time is 5-10 minutes, and the ball milling medium is steel balls.

9. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S3, the lithium precipitant includes one or more of sodium carbonate, carbon dioxide, phosphoric acid, and sodium phosphate.

10. The method for comprehensive recovery of alkali metals from lithium-containing silicate ores according to claim 1, characterized in that: In S3, the extractant used in the extraction-stripping method is 4-tert-butyl-2-(α-methylbenzyl)phenol, and the stripping agent is one of sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, and carbon dioxide.

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