Fluorine selective separating agent for lepidolite leaching solution as well as fluorine removal method and application of fluorine selective separating agent

Abstract

The invention provides a fluorine selective separating agent for lepidolite leachate and a fluorine removal method and application of the fluorine selective separating agent for the lepidolite leachate. A fluorine removal agent is prepared and obtained by mixing aluminum sulfate and lanthanum carbonate according to the weight part ratio of (1-3): 1; adjusting the pH value of the lepidolite roasting leaching solution to 3.5-4.5, and adding a fluorine removal agent according to 1-4g / L; stirring and reacting for 25-35 minutes at normal temperature, and carrying out suction filtration and solid-liquid separation to obtain fluorine-removed liquid and fluorine residues. According to the fluorine removal agent composed of the aluminum sulfate and the lanthanum carbonate, the fluorine removal effect is improved through cooperation of the aluminum salt and the lanthanum salt. According to the defluorination method, heating and heat preservation are not needed, and normal-temperature reaction is needed; the reaction time is about 0.5 h, so that the treatment time of the leachate in an impurity removal and purification section is saved, and the productivity is favorably improved; and the fluorine slag rate is 0.2-0.4%, so that the frequency of transferring slag in production is reduced, and the labor intensity of personnel is reduced. The method is simple in overall process, high in production efficiency, low in energy consumption, low in production cost and beneficial to application and popularization.

Description

Technical Field

[0001] This application relates to the technical field of chemical defluorination, and in particular to a fluorine selective separator for leaching solution of lepidolite, a defluorination method thereof, and an application thereof. Background Art

[0002] At present, the mainstream process for extracting lithium from lepidolite is the sulfate roasting method. However, the leaching solution obtained by treating lepidolite with the sulfate method has the characteristics of many impurity ions and high content. Moreover, during the process of preparing lithium carbonate from the lepidolite leaching solution, the main impurity elements calcium, magnesium, and fluorine will restrict the purity of the lithium carbonate product produced from the leaching solution, and will also affect the subsequent recovery of rubidium and cesium and the product purity. At the same time, during the production operation process, the high content of calcium and magnesium ions leads to serious scaling, and fluorine ions have certain corrosiveness to pipelines, towers, etc. All of these will greatly affect the production efficiency and increase the operating cost of the enterprise.

[0003] For example, a certain metal mine in Hunan produces lepidolite concentrate with a low lithium grade, containing 1.8 - 2% Li2O and about 5% F, which is a high-fluorine lepidolite ore. The mixed sulfate method is used for roasting to extract lithium, and the roasted ore is leached with water to obtain a leaching solution, in which the fluorine ion concentration is 50 - 500 ppm, and there is a problem of excessive fluorine content. If defluorination is not carried out and battery-grade lithium carbonate is directly produced, it will affect the quality and performance of the lithium carbonate product. At the same time, the accumulation of fluorine ions in the system is also not conducive to continuous and stable production, increasing the equipment maintenance cost.

[0004] In view of the problems of many impurity ions and high fluorine content in the existing lepidolite lithium extraction process, Patent CN 112176185A proposes a method for defluorinating lepidolite roasting leaching solution. A defluorinating agent is prepared by mixing aluminum sulfate, alumina, and silica in a mass ratio of 7 - 8:1 - 2.5:0.5. For every 1 m3 of leaching solution, 4 - 5 kg of the defluorinating agent is added, stirred evenly, kept at 30 - 50 °C for sufficient reaction, the pH is adjusted to 5.5 - 7.5, settled for 2 - 4 h, and filtered to obtain a filtrate with a reduced fluorine content. Although the above method for defluorinating lepidolite roasting leaching solution can effectively reduce the fluorine content in the lepidolite leaching solution, there are still the following problems: 1) Alumina is 3300 yuan / ton, activated alumina is 7600 yuan / ton, and silica is 2000 yuan / ton. 1 m 34-5 kg of defluorinating agent needs to be added to the liquid, and it needs to be kept at a temperature of 30-50 °C during the defluorination process, resulting in high energy consumption; 2) The reaction time is unknown during the defluorination process, and then sedimentation for 2-4 h is required, which greatly increases the time consumption of the purification and impurity removal process of the leaching solution of lepidolite roasting, reducing the production efficiency; 3) The removal rate of fluorine is 84.5-87.42%, and the defluorination effect is limited. Patent CN115872507A discloses a defluorinating agent for waste water from aluminum cans and its preparation method and usage method. The defluorinating agent includes the following components: aluminum sulfate, polyaluminum chloride, ferric chloride, lanthanum chloride; The present invention mainly removes fluoride in the waste water from aluminum can production by adsorption, ion exchange, precipitation, and flocculation. It uses Al 3+ 、Fe 2+ 、La 3+ in the defluorinating agent to react with F - in the waste water from aluminum can production to produce AlF3, FeF2, and LaF3 precipitates. It also adsorbs F 3+ in the waste water from aluminum can production through the charged aluminum hydroxide gel formed by the hydrolysis of Al - . However, there are problems such as low defluorination rate and large lithium loss. Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide a fluorine selective separator for lepidolite leaching solution and its defluorination method with simple process, high production efficiency, low energy consumption, and low production cost.

[0006] The first aspect of this application provides a defluorination method for a fluorine selective separator of lepidolite leaching solution, including the following steps: S1. Obtain a defluorinating agent by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 1-3:1; S2. Adjust the pH value of the lepidolite roasting leaching solution to 3.5-4.5, and add the defluorinating agent at 1-4 g / L; S3. Stir and react at room temperature for 25-35 min, then filter to separate the solid and liquid to obtain a defluorinated solution and fluorine slag.

[0007] In any embodiment, the mass ratio of aluminum sulfate to lanthanum carbonate is 1.8-2.5:1.

[0008] In any embodiment, the addition amount of the defluorinating agent in step S2 is 2.5-3 g / L.

[0009] In any embodiment, the stirring speed is 20-300 rpm; the stirring is carried out in sequence of rapid mixing, slow flocculation, and low-speed adsorption. The rapid mixing is carried out at 150-300 rpm for 1-3 min, the slow flocculation is carried out at 20-50 rpm for 15-28 min, and the low-speed adsorption is carried out at 40-70 rpm for 1-5 min.

[0010] In any embodiment, the fluorine content of the leaching solution of lepidolite is 180 - 230 mg / L.

[0011] The second aspect of the present application also provides a fluorine selective separator for lepidolite leaching solution, which consists of an aluminum salt and a lanthanum salt as a defluorinating agent.

[0012] In any embodiment, the mass ratio of the aluminum salt to the lanthanum salt is 1 - 3:1.

[0013] In any embodiment, the aluminum salt is at least one of aluminum carbonate and aluminum sulfate, and the lanthanum salt is at least one of lanthanum sulfate and lanthanum carbonate.

[0014] In any embodiment, the aluminum salt is aluminum sulfate and the lanthanum salt is lanthanum carbonate.

[0015] In any embodiment, the mass ratio of aluminum sulfate to lanthanum carbonate is 1.8 - 2.5:1.

[0016] The third aspect of the present application provides an application of a fluorine selective separator for lepidolite leaching solution and its defluorination method in the production of battery-grade lithium carbonate.

[0017] Advantages of the present invention: The defluorinating agent composed of aluminum sulfate and lanthanum carbonate in this application enhances the defluorination effect through the synergy of the aluminum salt and the lanthanum salt. The defluorination method of this application does not require heating and insulation, and can react at room temperature; the reaction time is about 0.5 h, which saves the treatment time of the leaching solution in the impurity removal and purification section, and is conducive to improving production capacity; and the lithium loss is small, the fluorine slag rate is 0.2% - 0.4%, which reduces the frequency of transferring slag in production and reduces the labor intensity of workers. The overall process of this application is simple, with high production efficiency, low energy consumption, and low production cost, which is conducive to popularization and application. Specific Embodiments

[0018] Hereinafter, embodiments of a fluorine selective separator for lepidolite leaching solution, its defluorination method and application, which specifically disclose the present application, will be described in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art.

[0019] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0020] If there is no special instruction, all implementation manners and optional implementation manners of this application can be combined with each other to form a new technical solution.

[0021] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0022] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0023] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can only include or comprise the listed components.

[0024] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0025] A method for removing fluorine from a fluorine-selective separation agent of a lepidolite leachate comprises the following steps: S1, preparing a defluorination agent by mixing aluminum sulfate and lanthanum carbonate in a ratio of 1-3 parts by weight; S2, the pH value of the calcined lepidolite solution is adjusted to 3.5-4.5 using sulfuric acid, and a defluoridant is added at 1-4 g / L; S3, stirring the reaction at room temperature for 25-35 minutes, filtering the solid and liquid to obtain defluorinated liquid and defluorinated residue.

[0026] The fluorine selective separation agent is a defluorination agent.

[0027] Al3(OH)4 produced by hydrolysis of aluminum sulfate Al2(SO4)3·17H2O 5+ 、Al7(OH) 17 4+ 、Al 13 O4(OH) 24 7+ High-valent cations such as F can be adsorbed by electrostatic action - , then form Al(OH)3(am) alum flowers to convert F - At the same time, F - And with Al 3+ The cations form complexes of AlF x (3-x) , entrained in Al(OH)3(am) and settled down. Lanthanum carbonate La2(CO3)3·8H2O has a porous structure and high specific surface area. Micropores and mesopores coexist, which is conducive to the diffusion and capture of fluoride ions. The specific surface area is also significantly higher than that of traditional adsorbent activated alumina, providing abundant adsorption sites. The hydroxyl and carbonate groups rich in the surface form stable complexes with fluoride ions through chemical adsorption.

[0028] Aluminum hydroxide gel generated by the hydrolysis of aluminum sulfate can - With Al 3+ The formed complex precipitated AlF3 flocculates into agglomerates through bridging, netting and other effects, promoting precipitation; - with La 3+ The formed LaF3 precipitate flocculates into agglomerates, which promotes precipitation and improves the fluorine removal effect of lanthanum carbonate.

[0029] The optimal pH range for the use of lanthanum carbonate is 4 - 6, and the higher the acidity, the faster lanthanum carbonate dissolves. Therefore, when adjusting the pH value of the solution to 4 (to partially dissolve lanthanum carbonate), the partially dissolved lanthanum carbonate can hydrolyze into lanthanum hydroxide, and the unhydrolyzed lanthanum carbonate has a porous structure and a high specific surface area, with the coexistence of micropores and mesopores, which is conducive to the diffusion and capture of fluoride ions. Aluminum sulfate hydrolyzes into aluminum hydroxide, and during the experiment, the pH value of the solution will fluctuate to about 6, while the optimal pH range for fluoride removal by aluminum sulfate is 5.5 - 6.5; when pH is less than 5, aluminum ions mainly exist in the free state and cannot effectively form aluminum hydroxide flocs, which will lead to a decrease in the ability to adsorb fluoride ions, and some aluminum ions form soluble complexes such as AlF 2+ and AlF 2+ , which will also reduce the fluoride removal efficiency; to make aluminum sulfate and lanthanum carbonate fit each other, therefore, it is preferable to adjust the pH value of the solution to 4 before adding the fluoride removal agent. First, experimental studies have found that starting from 4 for the reaction, the pH value can accurately fluctuate to about 6, achieving rapid and efficient fluoride removal. Second, under the condition of better fluoride removal effect, less acid can also save the cost of auxiliary materials.

[0030] In the initial stage of adding the fluoride removal agent in this application, the added lanthanum carbonate La2(CO3)3·8H2O has a porous structure and a high specific surface area, with the coexistence of micropores and mesopores, which is conducive to the diffusion and capture of fluoride ions. The free fluoride ions are captured in the micropores and mesopores of lanthanum carbonate, so that aluminum ions and lanthanum ions can quickly precipitate and remove fluoride ions; through the hydrolysis of aluminum sulfate Al2(SO4)3·17H2O to generate high-valent cations such as Al3(OH)4 5+ , Al7(OH) 17 4+ , Al 13 O4(OH) 24 7+ , etc., which can adsorb F - through electrostatic interaction, and then form Al(OH)3(am) flocs to sweep down F - , and F - forms complexes such as AlF 3+ with cations such as Al x (3-x) , which are incorporated in Al(OH)3(am) and settle down to remove most of the fluoride in the solution. At the same time, F - forms complexes with La 3+The formed LaF3 precipitate flocculates into clusters. The surface is rich in hydroxyl and carbonate groups, which form stable complexes with fluoride ions through chemical adsorption to promote precipitation. As the reaction progresses, the above-mentioned effect gradually decreases and further defluorination cannot be achieved. Finally, as the pH value increases and the fluoride concentration decreases, it is difficult to promote the dissolution of lanthanum carbonate. The porous structure and high specific surface area of the lanthanum carbonate precipitate itself, with the coexistence of micropores and mesopores, have abundant adsorption sites to further adsorb and remove low-concentration fluoride. During the previous reaction process, the porous structure and high specific surface area of lanthanum carbonate, with the coexistence of micropores and mesopores, are also conducive to the diffusion and capture of fluoride ions to achieve rapid and efficient defluorination.

[0031] In some embodiments, the mass ratio of aluminum sulfate to lanthanum carbonate is 1.8 - 2.5:1.

[0032] If the above ratio is high, the defluorination efficiency and effect will be reduced, and deep defluorination cannot be achieved. If the ratio is low, the cost will be high, the defluorination effect will be low under the same dosage, and the lithium loss rate will also increase.

[0033] In some embodiments, the dosage of the defluorinating agent in step S2 is 2.5 - 3 g / L.

[0034] In some embodiments, the stirring speed is 20 - 300 rpm. The stirring is carried out in sequence of rapid mixing, slow flocculation, and low-speed adsorption. The rapid mixing is at 150 - 300 rpm for 1 - 3 min, the slow flocculation is at 20 - 50 rpm for 15 - 28 min, and the low-speed adsorption is at 40 - 70 rpm for 1 - 5 min.

[0035] Rapid mixing (adding reagents) enables the rapid and uniform mixing of fluoride with the defluorinating agent (such as aluminum salts, calcium salts, etc.) to promote chemical reactions. Excessive rotation speed may cause the breakage of tiny flocs, while too low a speed may result in uneven mixing.

[0036] Slow flocculation (forming precipitate and flocs) promotes the growth of flocs for subsequent precipitation or filtration. Excessive rotation speed will break the flocs, while too low a speed may cause too fast precipitation.

[0037] Low-speed adsorption (pore adsorption of residual fluoride) increases the speed to a certain extent without destroying the previous flocs, enabling the separation of flocculated and precipitated substances from lanthanum carbonate, increasing the adsorption of residual trace fluoride ions by pores, and improving the defluorination rate. Excessive rotation speed will damage the flocs, while too low a speed cannot separate lanthanum carbonate, thus unable to adsorb residual fluoride.

[0038] In some embodiments, the fluoride content of the leaching solution of lepidolite after roasting is 180 - 230 mg / L.

[0039] The defluorinating agent of the present application has good defluorination effect under this fluorine content. In the case of too low fluorine content and too high fluorine concentration, due to the mutual synergistic effect between aluminum sulfate and lanthanum carbonate, it is difficult to achieve good defluorination effect, resulting in problems such as low defluorination rate, large lithium loss, and low efficiency.

[0040] The second aspect of the present application also provides a fluorine selective separator for leaching solution of lepidolite, which consists of aluminum salt and lanthanum salt as the defluorinating agent.

[0041] In some embodiments, the mass ratio of the aluminum salt to the lanthanum salt is 1-3:1.

[0042] In some embodiments, the aluminum salt is at least one of aluminum carbonate and aluminum sulfate, and the lanthanum salt is at least one of lanthanum sulfate and lanthanum carbonate.

[0043] The use of lanthanum carbonate reduces the dosage of the defluorinating agent, and a better proportion is found, so defluorination can be carried out with low cost and high efficiency. Lanthanum sulfate and lanthanum carbonate are used as high-efficiency deep defluorinating agents, with extremely strong adsorption capacity, wide pH application range, and strong selectivity for fluoride ions. In the present application, through the combined use of lanthanum salt and aluminum sulfate, aluminum sulfate can reduce the fluorine concentration, and then a small amount of the above lanthanum salt plays a role in deep treatment.

[0044] In some embodiments, the aluminum salt is aluminum sulfate and the lanthanum salt is lanthanum carbonate.

[0045] In some embodiments, the mass ratio of the aluminum sulfate to the lanthanum carbonate is 1.8-2.5:1.

[0046] Application of a fluorine selective separator for leaching solution of lepidolite and its defluorination method in the production of battery-grade lithium carbonate.

[0047] Examples Hereinafter, examples of the present application will be described. The examples described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those where specific technologies or conditions are not indicated in the examples, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0048] The situation of the leaching solution obtained by leaching multi-batch roasted clinker is shown in Table 1.

[0049] Table 1

[0050] Example 1 A defluorination method for a fluorine selective separator of leaching solution of lepidolite includes the following steps: S1. Configure the defluorinating agent, which is obtained by mixing aluminum sulfate and lanthanum carbonate according to 1:1 by weight; S2. Adjust the pH value of the leaching solution of lepidolite to 4 with sulfuric acid, and add a defluorinating agent at 1 g / L. S3. Rapidly mix and react at 200 rpm for 2 min at room temperature, slowly flocculate and react at 35 rpm for 28 min, slowly adsorb and react at 40 rpm for 1 min, and filter to separate the solid and liquid to obtain a defluorinated solution and fluorine slag.

[0051] The fluorine slag rate is 0.25%.

[0052] Example 2 A method for removing fluorine from a fluorine-selective separating agent for lepidolite leaching solution, comprising the following steps: S1. Prepare a defluorinating agent, obtained by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 2:1. S2. Adjust the pH value of the leaching solution of lepidolite to 4 with sulfuric acid, and add a defluorinating agent at 2 g / L. S3. Rapidly mix and react at 280 rpm for 2 min at room temperature, slowly flocculate and react at 30 rpm for 26 min, slowly adsorb and react at 60 rpm for 4 min, and filter to separate the solid and liquid to obtain a defluorinated solution and fluorine slag.

[0053] The fluorine slag rate is 0.3%.

[0054] Example 3 A method for removing fluorine from a fluorine-selective separating agent for lepidolite leaching solution, comprising the following steps: S1. Prepare a defluorinating agent, obtained by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 3:1. S2. Adjust the pH value of the leaching solution of lepidolite to 5 with sulfuric acid, and add a defluorinating agent at 2 g / L. S3. Rapidly mix and react at 300 rpm for 2.5 min at room temperature, slowly flocculate and react at 50 rpm for 28 min, slowly adsorb and react at 40 rpm for 4.5 min, and filter to separate the solid and liquid to obtain a defluorinated solution and fluorine slag.

[0055] The fluorine slag rate is 0.25%.

[0056] Example 4 A method for removing fluorine from a fluorine-selective separating agent for lepidolite leaching solution, comprising the following steps: S1. Prepare a defluorinating agent, obtained by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 2:1. S2. Adjust the pH value of the leaching solution of lepidolite to 4.5 with sulfuric acid, and add a defluorinating agent at 3 g / L. S3. Rapidly mix and react at 250 rpm for 1.5 min at room temperature, slowly flocculate and react at 50 rpm for 25 min, slowly adsorb and react at 40 rpm for 1.5 min, and filter to separate the solid and liquid to obtain a defluorinated solution and fluorine slag.

[0057] The fluorine residue rate is 0.35%.

[0058] Example 5 A method for removing fluorine from a fluorine-selective separation agent for a leaching solution of lepidolite, comprising the following steps: S1. Prepare a defluorinating agent, which is obtained by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 2:1; S2. Adjust the pH value of the roasted and leached solution of lepidolite to 4 with sulfuric acid, and add the defluorinating agent at 3 g / L; S3. Rapidly mix and react at 180 rpm for 2 min at room temperature, slowly flocculate and react at 40 rpm for 25 min, slowly adsorb and react at 50 rpm for 3 min, and perform suction filtration for solid-liquid separation to obtain a defluorinated solution and fluorine slag.

[0059] The fluorine residue rate is 0.4%.

[0060] Comparative Example 1 A method for removing fluorine from a roasted and leached solution of lepidolite, specifically: The leaching solution obtained by roasting and leaching lepidolite is added with a defluorinating agent in a proportion of adding 2-6 kg of defluorinating agent per 1 m of leaching solution, stirred evenly, kept at 30 °C, fully reacted, adjusted to pH 5.5, settled for 2 h, and then filtered to obtain a filtrate with reduced fluorine content for the preparation of battery-grade lithium carbonate, and the filter residue can be used as an auxiliary material for roasting. 3 Among them, the defluorinating agent is a mixture of aluminum sulfate, alumina, and silica. Among them, the mass ratio of aluminum sulfate, alumina, and silica in the mixture is 7.8:1.8:0.4.

[0061] The fluorine residue rate is 0.8%.

[0062] Comparative Example 2 S1. Weigh 60% of aluminum sulfate, 25% of polyaluminum chloride, 8.6% of ferric chloride, and 6.4% of lanthanum chloride in sequence by weight percentage, and fully mix and homogenize each component raw material to prepare a defluorinating agent; S2. Adjust the pH value of the roasted and leached solution of lepidolite to 7 with sulfuric acid to obtain a treated wastewater; S3. Add the defluorinating agent at 3 g / L, rapidly stir for 2 min, slowly stir for 5 min to obtain a treated solution, and let the treated solution stand for 30 min.

[0063] The fluorine residue rate is 1.5%.

[0064] Comparative Example 3 A method for removing fluorine from a leaching solution of lepidolite, comprising the following steps: S1. Use aluminum sulfate as the defluorinating agent; S2. Adjust the pH value of the leaching solution of lepidolite to 4 with sulfuric acid, and add a defluorinating agent at 4 g / L; S3. Stir and react at room temperature for 60 min, then perform suction filtration for solid-liquid separation to obtain a defluorinated solution and fluorinated slag.

[0065] The fluorinated slag rate is 1%.

[0066] Comparative Example 4 A method for defluorinating a leaching solution of lepidolite, comprising the following steps: S1. Use lanthanum carbonate as the defluorinating agent; S2. Adjust the pH value of the leaching solution of lepidolite to 4 with sulfuric acid, and add a defluorinating agent at 4 g / L; S3. Stir and react at room temperature for 30 min, then perform suction filtration for solid-liquid separation to obtain a defluorinated solution and fluorinated slag.

[0067] The fluorinated slag rate is 0.35%.

[0068] Comparative Example 5 A method for defluorinating a fluorine-selective separating agent for a leaching solution of lepidolite, comprising the following steps: S1. Prepare a defluorinating agent, which is obtained by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 2:1; S2. Adjust the pH value of the leaching solution of lepidolite to 4.5 with sulfuric acid, and add a defluorinating agent at 3 g / L; S3. React at 80 rpm at room temperature for 30 min, then perform suction filtration for solid-liquid separation to obtain a defluorinated solution and fluorinated slag.

[0069] The fluorinated slag rate is 0.35%.

[0070] Measure the F content and Li content in the leaching solution after defluorination in the above examples and comparative examples. Dry and weigh the defluorinated slag. The initial fluorine content in the leaching solution is 225.3 mg / L, and the initial lithium content is 9.88 g / L. The test data are shown in Table 2.

[0071] Table 2

[0072] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for removing fluorine from a fluorine selective separation agent for leaching solution of lepidolite, characterized in that, It includes the following steps: S1. Obtain a defluorinating agent by mixing aluminum sulfate and lanthanum carbonate in a weight ratio of 1 - 3:1; S2. Adjust the pH value of the leaching solution of lepidolite to 3.5 - 4.5, and add the defluorinating agent at 1 - 4 g / L; S3. Stir and react at room temperature for 25 - 35 min, and perform suction filtration for solid - liquid separation to obtain a defluorinated solution and fluorinated slag.

2. The defluorination method of the fluorine selective separator for leaching solution of lepidolite according to claim 1, characterized in that, The mass ratio of the aluminum sulfate to the lanthanum carbonate is 1.8 - 2.5:

1.

3. The defluorination method of the fluorine selective separator for a leaching solution of lepidolite according to claim 1, characterized in that, In step S2, the addition amount of the defluorinating agent is 2.5 - 3 g / L.

4. The defluorination method of the fluorine selective separator for leaching solution of lepidolite according to claim 1, characterized in that, The stirring speed is 20 - 300 rpm; the stirring is carried out in sequence of rapid mixing, slow flocculation and low - speed adsorption. The rapid mixing is carried out at 150 - 300 rpm for 1 - 3 min, the slow flocculation is carried out at 20 - 50 rpm for 15 - 28 min, and the low - speed adsorption is carried out at 40 - 70 rpm for 1 - 5 min.

5. The defluorination method of the fluorine selective separator for leaching solution of lepidolite according to claim 1, characterized in that, The fluorine content of the leaching solution of lepidolite is 180 - 230 mg / L.

6. A fluorine - selective separator for lepidolite leaching solution, which consists of an aluminum salt and a lanthanum salt as the defluorinating agent, and the mass ratio of the aluminum salt to the lanthanum salt is 1 - 3:

1.

7. The fluorine selective separator for leaching solution of lepidolite according to claim 6, characterized in that, The aluminum salt is at least one of aluminum carbonate and aluminum sulfate, and the lanthanum salt is at least one of lanthanum sulfate and lanthanum carbonate.

8. The fluorine selective separator for leaching solution of lepidolite according to claim 6 or 7, characterized in that, The aluminum salt is aluminum sulfate, and the lanthanum salt is lanthanum carbonate.

9. The fluorine selective separator for leaching solution of lepidolite according to claim 8, characterized in that, The mass ratio of the aluminum sulfate to the lanthanum carbonate is 1.8 - 2.5:

1.

10. The application of the defluorinating agent prepared by any one of claims 1 - 5 or obtained by any one of claims 6 - 9 in the production of battery - grade lithium carbonate.

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