A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction

Abstract

The present invention discloses a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction. The method is to adjust the pH of the solution containing lithium, sodium, and potassium to acidic, and then sequentially add jarosite seeds and an iron-based sodium and potassium remover to react, followed by solid-liquid separation to obtain sodium and potassium precipitates and a lithium solution. By adding jarosite seeds in the present invention, the temperature at which the sodium and potassium precipitation reaction occurs can be significantly reduced, the loss rate of lithium can be decreased, and energy consumption can be saved. The jarosite and potassium jarosite generated during the sodium and potassium removal process can be recycled as seeds, and can also be used as a potential substitute for building materials and a wastewater adsorption material, realizing the efficient selective separation of lithium, sodium, and potassium while also achieving the resource utilization of the precipitate. The technological process of the present invention is simple, environmentally friendly, helps to reduce the influence of impurity elements with similar properties on the product purity during the production of lithium salts from lithium ores, and helps to reduce the lithium loss rate.

Description

Technical Field

[0001] The present invention relates to a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution, and particularly to a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution, belonging to the field of deep purification of lithium resources. Background Art

[0002] Removing sodium and potassium from a lithium-containing sodium-potassium solution is mainly applied in the technical field of lithium salt material production and manufacturing.

[0003] Lithium carbonate and lithium hydroxide are two important products in the process of lithium resource extraction, and are also basic raw materials for the new energy industry. Lithium carbonate is the main cathode material in the production of lithium-ion batteries, while lithium hydroxide is an indispensable cathode material for the production of high-nickel ternary batteries of nickel cobalt manganese lithium type and nickel cobalt aluminum lithium type. The preparation of both has attracted much attention in the new energy industry.

[0004] Hydrometallurgy is the main technology for extracting lithium carbonate and lithium hydroxide from lithium ore. During the lithium extraction process, a large number of impurity ions (such as sodium, potassium, magnesium, aluminum, calcium, and iron, etc.) will enter the solution together with the extraction of lithium. Therefore, separating impurity ions from the lithium-containing solution has become the key to producing high-purity lithium products. However, sodium, potassium, and lithium all belong to the first main group elements and have similar chemical properties. It is difficult to selectively remove sodium and potassium from a lithium-sodium-potassium solution by traditional methods, which has become a technical bottleneck in the production of high-purity lithium products.

[0005] In the lithium carbonate production process, it is necessary to use an excessive amount of sodium carbonate as the precipitant for lithium ions in the solution. After precipitation, the sodium ion concentration in the supernatant is about 40 g / L, and due to the slight solubility of lithium carbonate, the supernatant also contains about 2 g / L of lithium ions; in addition, to prepare high-purity lithium carbonate, the lithium carbonate precipitate needs to be washed, and the washing water also contains lithium ions and sodium ions at the same time. Although freeze crystallization can partially separate sodium ions in the supernatant and washing solution, this method can never achieve complete separation of lithium and sodium, and it is easy to cause loss of lithium. It must be pointed out that when the sodium concentration is too high, it will also affect the quality of lithium salt products, resulting in excessive sodium ions in the lithium carbonate precipitate, which is not conducive to the production of battery-grade lithium carbonate. In addition to the difficulty of lithium-sodium separation, there is also a problem that potassium accumulates in the sodium-separating mother liquor during the production of lithium carbonate from lithium ore, affecting the carbonation precipitation of lithium. The difficult selective separation of lithium and potassium is another reason for lithium loss. After the mother liquor for lithium precipitation is crystallized by freezing to precipitate mirabilite, most of the sodium can be removed, but potassium remains in the solution and coexists with lithium; currently, industrial lithium carbonate production lines lack effective potassium removal processes, resulting in continuous enrichment of potassium in the mother liquor after freezing and separating sodium from the mother liquor for lithium precipitation, causing the sodium-separating mother liquor to have to be diluted and then returned to the production process; in particular, when potassium accumulates to a certain concentration in the sodium-separating mother liquor, some enterprises have to discharge the sodium-separating mother liquor, resulting in loss of lithium.

[0006] In the production process of lithium hydroxide, the lithium sulfate caustic freezing crystallization method is the most mature process applied in China. However, during the sulfuric acid leaching of lithium ore, the potassium content in the lithium extraction mother liquor is usually higher than 8 g / L. In particular, the potassium content is even often higher than the lithium content in the lithium extraction solution by the sulfuric acid method from lepidolite. The presence of potassium is very unfriendly to the evaporation crystallization of lithium hydroxide. In industry, in order to produce high-purity lithium hydroxide, multiple evaporation crystallizations have to be selected to gradually reduce the potassium content in the lithium salt product. However, the cycle process of evaporation crystallization, dissolution, and recrystallization will inevitably cause some lithium loss. In addition, due to the difficulty of achieving selective separation of lithium and potassium in the solution system, the problem of potassium affecting the production of high-purity lithium salts is particularly obvious in the "sulfuric acid potassium roasting" lithium extraction process from lepidolite. Therefore, solving the problem of selective separation of lithium, sodium, and potassium in the solution system can not only reduce lithium loss but also help simplify the process flow of the lithium hydroxide production line.

[0007] Chinese Patent CN 112408436 B relates to a method for converting sodium chloride into sodium sulfate and freezing out, however, this method requires ionization and has high energy consumption. During the freezing out process of sodium sulfate, part of the lithium will also be carried away, resulting in lithium loss. This method also cannot remove potassium in the solution and is more suitable for treating brine with a high sodium content. Chinese Patent CN 108517421B relates to a method for selectively adsorbing lithium by a lithium-sodium separation material. However, this method is complex in operation, including processes such as material preparation, lithium adsorption and desorption, and the cycle of selective separation and recovery of lithium and sodium is long. Chinese Patent CN 102010991B relates to a method for freezing out potassium in the form of potassium alum. However, the solubility of potassium alum is significantly affected by temperature, making it difficult to achieve complete separation of lithium and potassium. Chinese Patent CN 113387374 A relates to a method for removing impurities from a mixed solution of a mother liquor containing potassium in a lithium carbonate production line and a mother liquor rich in potassium in a first evaporation of a lithium hydroxide production line. However, this method has many problems such as adding sulfuric acid multiple times, repeatedly adding alkali to neutralize the solution, large reagent consumption, high energy consumption, and complex process. The removal rate of potassium in the solution is only 50%-80%, and there is no report on lithium loss, nor is the removal of sodium taken seriously. Chinese Patent CN 114231741 A relates to a method for removing potassium by phosphate metal complex ions. This method requires additional preparation of a potassium removal adsorbent precursor, and this potassium removal precursor also has a certain adsorption capacity for lithium, easily causing lithium loss. Patent CN108584993 A discloses a method for removing sodium and potassium ions during the production of lithium salts. This method can achieve better removal effects only at relatively high temperatures, and the rapid evaporation of water in the solution will occur under boiling conditions, requiring more water to wash the sodium and potassium precipitates to ensure a reduced entrainment loss of lithium, increasing energy consumption. In addition, the required pH range of this method is too narrow, increasing the difficulty of industrial implementation, and easily causing the sodium and potassium removal agents in the solution to be converted into hydroxide precipitates and unable to participate in the reaction of precipitating sodium and potassium, resulting in poor sodium and potassium removal effects. Summary of the Invention

[0008] Aiming at the problems of insufficient depth of sodium and potassium removal, low efficiency, and high purification temperature in the lithium-containing mother liquor during the extraction of existing lithium resources, the purpose of the present invention is to provide a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction, converting sodium and potassium into jarosite precipitates (sodium jarosite and potassium jarosite) with high stability, good crystal form, and low solubility, so as to achieve precise and efficient separation of lithium ions from sodium and potassium ions in the solution system. This method makes full use of the solution chemical environment of the lithium ore leaching solution and combines with jarosite seed induction, having the advantages of low reaction temperature, fast precipitation speed, high selectivity, easy solid-liquid separation, simple operation, environmental friendliness, low energy consumption, and low cost, which is of great significance for the production of high-purity lithium products.

[0009] To achieve the above technical objectives, the present invention provides a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction. The method involves adjusting the pH of the lithium-sodium-potassium solution to acidic, and then successively adding jarosite seeds and an iron-based sodium-potassium remover for reaction, followed by solid-liquid separation to obtain sodium-potassium precipitate and a lithium solution.

[0010] The key to this technical solution lies in the efficient selectivity of jarosite for lithium ions, sodium ions, and potassium ions during the nucleation process to capture sodium ions and potassium ions in the solution, and target-precipitate sodium and potassium as jarosite and potassium jarosite; the addition of jarosite seeds has a nucleation-stimulating effect, which can provide nucleation sites for the formation of jarosite or potassium jarosite, eliminate the induction period, reduce the activation energy for jarosite formation, thereby accelerating the precipitation of sodium ions and potassium ions, and significantly reducing the reaction temperature and expanding the reaction pH range; the technical solution of the present invention will not precipitate lithium in the solution, and the loss of lithium can also be prevented by washing the precipitate, making up for the deficiencies of existing lithium-sodium-potassium selective separation technologies, and achieving the precise and efficient target-precipitation separation of sodium ions and potassium ions from a lithium-sodium-potassium solution at a lower temperature.

[0011] As a preferred embodiment, the pH of the lithium-sodium-potassium solution is adjusted within the range of 1.0 - 3.0. The appropriate pH range can ensure that the added pyrite cinder releases iron ions and can effectively prevent the precipitation of iron ions.

[0012] As a preferred embodiment, the pH is adjusted using at least one of sulfuric acid, pyrite cinder, and lime. When the solution is a simulated lithium-sodium-potassium solution or a leaching solution of lithium mica sulfate, sulfuric acid can be preferably used to adjust the pH of the solution; when the solution is a sulfuric acid leaching solution of spodumene, pyrite cinder can be preferably used to adjust the pH of the solution.

[0013] As a preferred embodiment, the jarosite seeds include at least one of jarosite seeds and potassium jarosite seeds. The reaction for generating jarosite involves the formation of solid particles from a homogeneous solution. From a kinetic perspective, the occurrence of such reactions requires a long induction period, strict temperature and acidity requirements; the seeds added in the present invention can act as the initial nuclei, which is beneficial to eliminating the induction period for jarosite formation, helping to reduce the activation energy required for the iron reaction to occur, and thus significantly reducing the temperature required for jarosite formation.

[0014] As a preferred embodiment, the molar ratio of the jarosite seeds to the total amount of sodium and potassium in the lithium-sodium-potassium solution is 0.2 - 0.5∶1. If the dosage of the seeds is too low, it is difficult to increase the potassium precipitation rate, effectively reduce the temperature required for the potassium precipitation reaction, or expand the pH range suitable for potassium precipitation; while if the dosage of the seeds is too high, it will lead to a decrease in the liquid-solid ratio of the reaction system, which may not only increase the lithium loss rate but also significantly increase the amount of sodium-potassium precipitate.

[0015] As a preferred embodiment, the iron-based sodium and potassium remover comprises at least one of pyrite cinder, ferric sulfate, and ferrous sulfate + hydrogen peroxide. In the preferred sodium and potassium remover of the present invention, the ferric ions present in pyrite cinder and ferric sulfate and the ferrous ions present in ferrous sulfate are fully utilized to be converted into ferric sulfate in a sulfuric acid solution system, and then react with sodium ions and lithium ions in the solution to form jarosite and potassium jarosite.

[0016] As a preferred embodiment, after adding the iron-based sodium and potassium remover, the molar ratio of iron to sodium + potassium in the solution is controlled within the range of 4 to 6:1. A lower molar ratio will cause incomplete precipitation of sodium and potassium ions in the solution, especially incomplete precipitation of sodium ions. A higher molar ratio will result in too high a residual amount of iron in the solution after potassium precipitation, thereby affecting the purity of the lithium solution.

[0017] As a preferred embodiment, the reaction conditions are: temperature is 55 to 75 °C, time is 20 to 60 min, and pH is within the range of 1.0 to 3.0. The reaction conditions of the present invention are mild, and sodium ions and potassium ions in the solution can be rapidly precipitated at a lower temperature without affecting the content of lithium ions. Further preferably, the temperature is 65 to 75 °C.

[0018] As a preferred embodiment, the sodium and potassium precipitate is a mixture of jarosite and potassium jarosite, which can be recycled as iron alum crystal seeds.

[0019] The principle of the technical solution of the present invention is:

[0020] Iron alum compounds (MFe3(SO4)2(OH)6, M represents NH4 + , H3O + , Ag + and excluding Li +Alkali metal ions, etc. outside are substances with good stability and low solubility. Due to certain differences in the ionic radii of lithium, sodium, and potassium, in the acidic solution system of lithium, sodium, and potassium, by adding a certain amount of jarosite seeds, the nucleation rate of jarosite can be accelerated, the precipitation rates of sodium ions and potassium ions can be increased, and the addition of jarosite seeds can provide nucleation sites for jarosite, reduce the activation energy required for the reaction, and thus significantly reduce the reaction temperature and expand the pH range suitable for the jarosite reaction. Therefore, when the reaction temperature reaches above 55 °C and the pH is in the range of 1.0 - 3.0, potassium can quickly react with iron to form jarosite precipitate. After potassium is removed, sodium will react with iron to form natrojarosite precipitate, while lithium will never co-precipitate with iron. It should be noted that potassium is precipitated first, sodium is precipitated later, and lithium is not precipitated at all mainly due to the gradual decrease of their ionic radii. If no jarosite seeds are added, the reaction temperature will be almost close to the boiling point of the solution, which will greatly increase energy consumption, and the sodium and potassium precipitation reaction at a higher temperature will cause the water in the solution to evaporate quickly, and more water is required to wash the sodium and potassium precipitate to ensure the reduction of the entrainment loss of lithium. The technical solution of the present invention adding jarosite seeds to the lithium, sodium, and potassium solution not only significantly reduces the reaction temperature for precipitating sodium and potassium, but also helps to reduce the water consumption for washing the precipitate and the entrainment loss of lithium.

[0021] The main useful component of pyrite cinder in the present invention is iron(III) oxide, which can be used as both an iron source and a pH adjuster. The reaction of pyrite cinder providing an iron source is as follows:

[0022] Fe2O3 + 3H2SO4 = Fe2(SO4)3 + 3H2O

[0023] The reaction of ferrous sulfate + hydrogen peroxide providing an iron source is as follows:

[0024] 2FeSO4 + H2SO4 + H2O2 = Fe2(SO4)3 + 2H2O

[0025] The reaction of ferric iron precipitating sodium and potassium is as follows

[0026] 3Fe2(SO4)3 + X2SO4 + 12H2O = 2MFe3(SO4)2(OH)6(↓) + 6H2SO4 (X represents K / Na)

[0027] In addition, since the process of sodium and potassium precipitation is a sulfuric acid-producing process, it is necessary to dynamically add pyrite cinder during the reaction to control the pH within a suitable range.

[0028] The beneficial technical effects of the present invention:

[0029] 1) The efficient lithium extraction and impurity removal technical solution based on seed induction in a lithium-sodium-potassium solution system provided by the present invention has a strong selective precipitation effect on sodium ions and potassium ions during the sodium and potassium removal process. The introduction of jarosite seeds in the solution significantly reduces the precipitation temperature of sodium and potassium, saving energy consumption and reducing the lithium loss rate at the same time.

[0030] 2) When using pyrite cinder as a sodium and potassium remover in the present invention, it can not only provide an iron source but also act as a pH adjuster for the solution, which helps the comprehensive utilization of this type of industrial waste residue and has double environmental and economic benefits.

[0031] 3) The present invention can be used to treat lithium solutions with different sodium and potassium concentrations generated during the lithium extraction process from lithium ores, can be used to directly treat lithium ore leaching solutions, can also be used to remove sodium and potassium in the lithium-containing mother liquor after freezing and separating sodium during the production of lithium hydroxide, and can also be used to remove sodium and potassium in the supernatant and washing solution of lithium carbonate precipitation generated during the production of lithium carbonate. This lays a solid foundation for the production of battery-grade lithium hydroxide and lithium carbonate. The present invention can also provide important support for effectively and highly selectively removing sodium and potassium in salt lake brines and other similar solution systems.

[0032] 4) The jarosite and potassium jarosite generated during the implementation of the present invention are precipitates with good stability, low solubility, coarse particles, and rapid settling, which are conducive to solid-liquid separation and can be recycled as seeds for precipitating sodium and potassium; at the same time, the jarosite precipitate is also a potential substitute for building materials and an adsorbent for wastewater, which can partially replace the raw materials for cement, concrete, and ceramic production, and can also be used as an adsorbent for acidic mine wastewater to effectively reduce the content of harmful impurities such as arsenic in the wastewater. This not only realizes the efficient and selective separation of lithium, sodium, and potassium but also lays a foundation for the resource utilization of subsequent precipitates. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a process flow chart of a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction.

[0034] Figure 2 It is a natural sedimentation process diagram of the purified suspension in Example 3 of the present invention.

[0035] Figure 3 It is a jarosite precipitate diagram in Example 3 of the present invention.

[0036] Figure 4 It is an XRD diagram of the mixed precipitate of jarosite and potassium jarosite in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] The following further illustrates the specific implementation manners of the present invention through examples, but the specific implementation manners of the present invention are not limited to the following examples.

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] According to Figure 1 As shown, a method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction completes the process flows of Examples 1-5.

[0040] Example 1

[0041] Selectively remove sodium from the lithium-sodium simulated mixed solution. Set the lithium concentration and sodium concentration in the simulated solution to 8 g / L and 15 g / L respectively. Add 300 mL of the lithium-sodium simulated mixed solution to a 500 mL beaker, control the initial pH of the solution to 3.0 with sulfuric acid with a concentration of 98 wt%, and add jarosite as a sodium-precipitating seed according to a molar ratio of jarosite to sodium in the solution of 0.3:1; secondly, add a sodium-removing agent according to a molar ratio of iron to sodium in the solution of 4.5:1, fully oscillate and react at 65 or 75 °C for 50 min, and adjust the pH of the solution to 3.0 with sulfuric acid and pyrite cinder at the 5th, 10th, 20th, 30th, and 40th minutes of the reaction; then obtain jarosite precipitate and purified lithium-containing solution through solid-liquid separation. The lithium-sodium separation effect obtained in Example 1 is listed in Table 1.

[0042] As can be seen from Table 1, pyrite cinder, ferric sulfate, and ferrous sulfate + hydrogen peroxide can all effectively and selectively remove sodium. Even at a relatively low temperature (65 °C), sodium in the simulated solution can be effectively removed, and the loss rate of lithium is also very low, indicating that the present technical solution can accurately and efficiently achieve the selective separation of lithium and sodium in the solution system with low energy consumption.

[0043] Table 1 Variation of sodium removal rate and lithium loss rate in the simulated solution

[0044]

[0045] Example 2

[0046] The lithium-potassium simulated mixed solution selectively removes potassium. The lithium concentration and potassium concentration in the simulated solution are set to 8 g / L and 15 g / L respectively. Add 300 mL of the lithium-potassium simulated mixed solution to a 500 mL beaker, control the initial pH of the solution to 3.0 with sulfuric acid with a concentration of 98 wt%, and add jarosite as the potassium precipitation seed according to the molar ratio of jarosite to potassium in the solution being 0.3:1; secondly, add a potassium removal agent according to the molar ratio of iron to potassium in the solution being 4.5:1, and fully oscillate and react at 65 or 75 °C for 50 min. Use sulfuric acid and pyrite cinder to adjust the pH of the solution to 3.0 at the 5th, 10th, 20th, 30th, and 40th minutes of the reaction; then obtain jarosite precipitate and purified lithium-containing solution through solid-liquid separation. The lithium-potassium separation effect obtained in Example 2 is listed in Table 2.

[0047] Table 2 Variation of potassium removal rate and lithium loss rate in the simulated solution

[0048]

[0049] As can be seen from Table 2, pyrite cinder, ferric sulfate, and ferrous sulfate + hydrogen peroxide can all effectively and selectively remove potassium. Even at a relatively low temperature (65 °C), potassium in the simulated solution can be effectively removed, and the lithium loss rate is also very low, indicating that this technical solution can accurately and efficiently achieve the selective separation of lithium and potassium in the solution system with lower energy consumption.

[0050] Example 3

[0051] The lithium-sodium-potassium simulated mixed solution selectively removes sodium and potassium. The lithium concentration, sodium concentration, and potassium concentration in the simulated solution are set to 8 g / L, 15 g / L, and 15 g / L respectively. Add 300 mL of the lithium-sodium-potassium simulated mixed solution to a 500 mL beaker, control the initial pH of the solution to 3.0 with sulfuric acid with a concentration of 98 wt%, and add iron alum as the potassium precipitation seed according to the molar ratio of iron alum to the sum of sodium and potassium in the solution being 0.3:1 or 0 times, and the added iron alum is one or both of jarosite and jarosite; secondly, add ferric sulfate according to the molar ratio of iron to the sum of sodium and potassium in the solution being 4.5:1, and fully oscillate and react at 65 °C, 75 °C, or 95 °C for 50 min. Use sulfuric acid and lime to adjust the pH of the solution to 3.0 at the 5th, 10th, 20th, 30th, and 40th minutes of the reaction; then obtain iron alum precipitate and purified lithium-containing solution through solid-liquid separation. The lithium-sodium-potassium separation effect obtained in Example 3 is listed in Table 3.

[0052] From the analysis of the changes in lithium, sodium, and potassium in Table 3, when no seed crystal is added, a certain removal effect of sodium and potassium can be achieved at a relatively high temperature (95 °C); when ferric sulfate is added as a seed crystal, no matter which ferric sulfate seed crystal is used, sodium and potassium in the simulated solution can be very effectively removed at a relatively low reaction temperature (even at 65 °C), and the loss rate of lithium is also very low; compared with not adding a seed crystal and adding a seed crystal, the removal rate of sodium and potassium obtained at a higher temperature is even lower, and the loss rate of lithium is also significantly higher. In the absence of a seed crystal, the formation of ferric sulfate requires a long induction period and a high activation energy, resulting in the partial conversion of ferric ions in the solution into hydroxide precipitates under the condition of pH = 3.0 and thus unable to participate in the potassium precipitation reaction; while when a seed crystal is added, the induction period is directly omitted and the activation energy required for the formation of ferric sulfate is also reduced, which can effectively lower the reaction temperature and promote the rapid participation of ferric ions in the solution in the reaction of precipitating sodium and potassium. The results of Example 3 show that the technical solution using ferric sulfate seed crystals to induce the precipitation of sodium and potassium has significant advantages and can accurately and efficiently achieve the selective precipitation of sodium and potassium in the lithium-sodium-potassium solution system with low energy consumption.

[0053] Changes in the removal rate of sodium and potassium and the loss rate of lithium in the simulated solution in Table 3

[0054]

[0055] In addition, as Figure 2 shown, it is the natural sedimentation diagram of the suspension after removing sodium and potassium in Example 3, Figure 3 it is the ferric sulfate precipitation diagram in Example 3, Figure 4 it is the XRD diagram of the mixed precipitate of jarosite and potassium jarosite in Example 3. It can be seen through Figure 2 that the ferric sulfate precipitate is easy to sink rapidly in the solution, which is beneficial to achieving rapid solid-liquid separation in industry.

[0056] Example 4

[0057] Taking the leaching solution of a certain industrial lithium mica sulfate method rich in high-concentration lithium, sodium, and potassium as the treatment object, the lithium concentration, sodium concentration, and potassium concentration of this leaching solution are 8.60 g / L, 25.31 g / L, and 18.42 g / L respectively. Add 300 mL of the lithium mica sulfate method leaching solution to a 500 mL beaker, control the initial pH of the solution to 2.0 with 98 wt% sulfuric acid, and add jarosite as the potassium precipitation seed according to the molar ratio of jarosite to the sum of the molar numbers of sodium and potassium in the solution being 0.2:1 or 0 times. The added jarosite is one or both of sodium jarosite and potassium jarosite; secondly, add pyrite cinder according to the molar ratio of iron to the sum of the molar numbers of sodium and potassium in the solution being 6:1, and fully oscillate and react at 65, 75, or 95 °C for 50 min. Use sulfuric acid and pyrite cinder to adjust the pH of the solution to 2.0 at the 5th, 10th, 20th, 30th, and 40th minutes of the reaction; then obtain jarosite precipitate and purified lithium-containing solution through solid-liquid separation. The lithium-sodium-potassium separation effect obtained in Example 4 is listed in Table 4.

[0058] From the analysis of the changes in lithium, sodium, and potassium in Table 4, when no seed is added, a certain sodium and potassium removal effect can be achieved at a higher temperature (95 °C); when jarosite is added as a seed, no matter what kind of jarosite seed, it can very effectively remove sodium and potassium in the simulated solution at a lower reaction temperature (even at 65 °C), and the loss rate of lithium can be basically ignored; compared with not adding a seed and adding a seed, the sodium and potassium removal rate obtained at a higher temperature is lower, and the loss rate of lithium is also significantly higher, indicating that the present invention can accurately and efficiently achieve the selective precipitation of sodium and potassium in the lithium-sodium-potassium solution system with lower energy consumption, and has the potential for popularization and application in the lithium extraction industry from lithium mica.

[0059] Table 4 Changes in the sodium and potassium removal rates and lithium loss rate in the leaching solution of the lithium mica sulfate method

[0060]

[0061]

[0062] Example 5

[0063] Taking an industrial leaching solution of spodumene as the treatment object, the lithium concentration, sodium concentration, and potassium concentration of this leaching solution are 10.81 g / L, 0.92 g / L, and 0.87 g / L respectively. Add 300 mL of the spodumene sulfuric acid leaching solution to a 500 mL beaker, use pyrite cinder to control the initial pH of the solution to 2.0, and add jarosite as a potassium precipitation seed according to the molar ratio of jarosite to the sum of the molar numbers of sodium and potassium in the solution being 0.5:1 or 0 times; the added jarosite is one or both of jarosite and potassium jarosite; secondly, add pyrite cinder (including the molar number of iron already in the solution) according to the molar ratio of iron to the sum of the molar numbers of sodium and potassium in the solution being 6:1, and fully oscillate and react at 65, 75, or 95 °C for 20 min. Use sulfuric acid and pyrite cinder to adjust the pH of the solution to 2.0 at the 2nd, 5th, 10th, and 15th minutes of the reaction; then obtain jarosite precipitate and purified lithium-containing solution through solid-liquid separation. The lithium-sodium-potassium separation effect obtained in Example 5 is listed in Table 5.

[0064] From the analysis of the changes in lithium, sodium, and potassium in Table 5, when no seed crystal is added, a certain sodium and potassium removal effect can be achieved at a higher temperature (95 °C); when jarosite is added as a seed crystal, regardless of what kind of jarosite seed crystal, it can very effectively remove sodium and potassium in the simulated solution at a lower reaction temperature (even at 65 °C), and the loss rate of lithium can be basically ignored; compared with not adding a seed crystal and adding a seed crystal, the sodium and potassium removal rate obtained at a higher temperature is even lower, and the loss rate of lithium is also significantly higher, indicating that this technical solution can accurately and efficiently achieve the selective precipitation of sodium and potassium in the lithium-sodium-potassium solution system with lower energy consumption, and has the potential for popularization and application in the lithium extraction industry from spodumene.

[0065] Table 5 Changes in the sodium and potassium removal rates and lithium loss rate in the spodumene sulfuric acid leaching solution

[0066]

[0067]

[0068] Comparative Example 1

[0069] The method of Example 1 is used to remove sodium from the lithium-containing solution, with the difference that: jarosite is added as a sodium precipitation seed according to the molar ratio of jarosite to sodium in the solution being 0.05:1. The lithium-sodium separation effect obtained in Comparative Example 1 is listed in Table 6.

[0070] As can be seen from Table 6, at low temperatures, sodium cannot be effectively removed, and the lithium loss rate is also significantly higher, which is mainly attributed to the too low dosage of seed crystals. The too low seed crystals cannot provide enough nucleation sites for jarosite, resulting in the difficulty of the jarosite reaction under low-temperature conditions, and also unable to effectively promote the rapid participation of ferric ions in the solution in the reaction of precipitating sodium and potassium. Under the condition of pH = 3.0, a large amount of iron hydroxide precipitate forms, resulting in a significant increase in the entrainment loss rate of lithium. The comparison between Comparative Example 1 and Example 1 shows that only when the jarosite seed crystals are appropriate can the selective separation of lithium and sodium in the solution system be accurately and efficiently achieved with lower energy consumption.

[0071] Table 6 Variation of sodium removal rate and lithium loss rate in the simulated solution

[0072]

[0073] Comparative Example 2

[0074] The method of Example 1 was used to remove sodium from the lithium-containing solution, with the difference that: jarosite was added as the sodium-precipitating seed crystal according to the molar ratio of jarosite to sodium in the solution of 5:1. The lithium-sodium separation effect obtained in Comparative Example 2 is listed in Table 7.

[0075] As can be seen from Table 7, pyrite cinder, ferric sulfate, and ferrous sulfate + hydrogen peroxide can all effectively and selectively remove sodium. Even at a relatively low temperature (65 °C), sodium in the simulated solution can be effectively removed, indicating that the present technical solution can remove sodium ions in the lithium-containing solution with lower energy consumption. In addition, compared with Example 1, the lithium loss rate in Comparative Example 2 increased to a certain extent, which is mainly attributed to the too high dosage of jarosite seed crystals. The too high dosage of seed crystals caused the liquid-solid ratio of the reaction system to decrease, which would lead to partial entrainment loss of lithium in the precipitate. Although continuously washing the precipitate can reduce the lithium loss rate, this will increase the energy consumption. The results of Comparative Example 2 show that controlling the dosage of jarosite seed crystals within an appropriate range can achieve a higher sodium and potassium removal rate with a lower lithium loss rate.

[0076] Table 7 Variation of sodium removal rate and lithium loss rate in the simulated solution

[0077]

[0078] Comparative Example 3

[0079] The method of Example 2 was used to remove potassium from the lithium-containing solution, with the difference that: the potassium-removing agent was added according to the molar ratio of iron to potassium in the solution of 2:1. The lithium-potassium separation effect obtained in Comparative Example 3 is listed in Table 8.

[0080] As can be seen from Table 6, the potassium removal rate of Comparative Example 3 is seriously insufficient, which is mainly attributed to the too low dosage of the potassium remover. The too low dosage of the potassium remover cannot provide sufficient iron ions to ensure that the potassium in the solution is completely precipitated. When the iron ions in the solution are exhausted, the potassium precipitation reaction will stop. Therefore, in order to achieve an ideal potassium removal rate, it is necessary to control the dosage of the potassium remover within an appropriate range; in addition, the lithium loss rate in Comparative Example 3 is similar to that in Example 2 and is very low, indicating that this technical solution will not cause lithium loss.

[0081] Table 8 Variation of potassium removal rate and lithium loss rate in the simulated solution

[0082]

[0083] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art of this technology, the improvements and transformations obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction, characterized in that: After adjusting the pH of the solution containing lithium, sodium and potassium to acidic, ferric sulfate crystal seeds and an iron-based sodium and potassium remover are added successively for reaction, and then solid-liquid separation is carried out to obtain sodium and potassium precipitate and lithium solution; The pH of the solution containing lithium, sodium and potassium is adjusted within the range of 1.0 - 3.0; The ferric sulfate crystal seeds include at least one of jarosite crystal seeds and potassium jarosite crystal seeds; After adding the iron-based sodium and potassium remover, the molar ratio of iron to sodium + potassium in the solution is controlled within the range of 4 - 6:1; The reaction conditions are: temperature is 55 - 75 °C, time is 20 - 60 min, and pH is within the range of 1.0 - 3.

0.

2. A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction according to claim 1, characterized in that: The pH is adjusted by using at least one of sulfuric acid, pyrite cinder and lime; 3. A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction according to claim 2, characterized in that: The molar ratio of the ferric sulfate crystal seeds to the total amount of sodium and potassium in the lithium, sodium and potassium solution is 0.2 - 0.5:1; 4. A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction according to claim 1, characterized in that: The iron-based sodium and potassium remover includes at least one of pyrite cinder, ferric sulfate and ferrous sulfate + hydrogen peroxide; 5. A method for selectively removing sodium and potassium from a lithium-sodium-potassium solution based on seed induction according to claim 1, characterized in that: The sodium and potassium precipitate is a mixture of jarosite and potassium jarosite, which can be recycled as ferric sulfate crystal seeds.

Images