Method for recovering lithium precipitation mother liquor

Abstract

The present invention provides a method for recovering lithium precipitation mother liquor, which comprises step S1, firstly adsorbing the lithium precipitation mother liquor with lithium sodium resin and then resolving it with hydrochloric acid to obtain a first solution; step S2, mixing the first solution with potassium chloride to recover the lithium in the first solution. + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － The method comprises a quaternary salt-water system comprising: a first hydrated ...

Description

Technical Field

[0001] The present invention relates to the technical field of salt chemical industry, and in particular to a method for recovering lithium precipitation mother liquor. Background Art

[0002] Lithium is a strategically important resource, widely used in heat-resistant glass, ceramics, lithium grease lubricants, flux additives in iron, steel, and aluminum production, and batteries. In recent years, driven by the rise of the electric vehicle industry, lithium consumption as an energy storage material has steadily increased. China is the world's largest lithium consumer, accounting for 52% of global consumption. However, lithium supply is insufficient and the country is highly dependent on imports. Therefore, improving the utilization efficiency of lithium resources is of great practical significance. Li2CO3 is prepared by combining lithium extraction technologies such as adsorption, membrane, and solvent extraction with a concentration process to obtain a purified lithium-rich solution, which is then reacted with a sodium carbonate solution. However, during this process, up to 15% to 20% of the lithium is lost in the lithium precipitation mother liquor.

[0003] The lithium precipitation mother liquor is a complex multi-component brine system, in which the lithium concentration is relatively high (1.5-1.8 g / L) and contains a large amount of Na + (42~52g / L), CO3 2- (25~28g / L), K + (0.8~1.5g / L), B, Ca 2- 、SO4 2- A small amount of trace impurity ions, such as the pH value of the solution is 9 to 13. If the lithium precipitation mother liquor is directly returned to the circulation system, long-term use will cause B, Na + , Ca 2- 、CO3 2- Enrichment of trace impurity ions such as iodine.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The main purpose of this application is to provide a method for recovering lithium precipitation mother liquor, so as to solve the problem that the existing technology directly returns the lithium precipitation mother liquor to the circulation system, which leads to the long-term depletion of B and Na in the system. + , Ca 2- 、CO3 2- The enrichment of trace impurity ions such as chlorine and chlorine leads to a low recovery rate of lithium chloride, which is not conducive to the continuous production of lithium chloride.

[0006] In order to achieve the above object, according to one aspect of the present invention, a method for recovering lithium precipitation mother liquor is provided, which comprises the following steps: step S1, firstly adsorbing the lithium precipitation mother liquor with lithium sodium resin, and then decomposing it with hydrochloric acid to obtain a first solution; step S2, mixing the first solution with potassium chloride to make the lithium in the first solution +、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system to obtain a second solution; step S3, first evaporating and crystallizing the second solution to precipitate a first sodium chloride, and then performing solid-liquid separation to remove the first sodium chloride to obtain a third solution; step S4, freezing and crystallizing the third solution to precipitate a second sodium chloride and a small amount of potassium chloride, and then performing solid-liquid separation to remove the second sodium chloride and a small amount of potassium chloride to obtain a fourth solution; step S5, first evaporating and crystallizing the fourth solution to precipitate lithium chloride, and then performing solid-liquid separation to obtain a fifth solution and lithium chloride; wherein the fifth solution returns to step S4 and is mixed with the third solution and then continues to be frozen and crystallized.

[0007] Furthermore, the pH value of the lithium precipitation mother solution is 11-13, Li + :1.5~1.8g / L,Na + :42~50g / L,CO3 2- :25~28g / L,Cl - :75~79g / L,K + : 1.1~1.3g / L, B: 0.01%~1%g / L, SO4 2- :0.01%~1%g / L.

[0008] Furthermore, in step S1, the pH value of the first solution is 7 to 7.5, Li + :4~5g / L,Na + : 3-6 g / L, trace ions are independently <10 mg / L.

[0009] Furthermore, in step S2, the second solution component is Li + :4~5g / L,Na + :3~6g / L,K + : 0.2~0.9g / L, trace ions are independently <10mg / L.

[0010] Furthermore, in step S2, the purity of potassium chloride is ≥60%.

[0011] Furthermore, in step S3, the evaporation crystallization is reduced pressure evaporation crystallization, the pressure of the reduced pressure evaporation crystallization is -0.4 to -0.7 Bar, and the temperature is 77 to 82°C.

[0012] Furthermore, in the third solution, the mass concentration of LiCl is 38-42%, the mass concentration of NaCl is 0.019-0.025%, and the mass concentration of KCl is 0.08-0.14%.

[0013] Furthermore, in step S4, cooling treatment is first performed and then freezing crystallization is performed, the cooling temperature is 38-42°C, and the freezing crystallization temperature is 0-2°C.

[0014] Furthermore, in step S5, the temperature of evaporation crystallization is 110-120°C.

[0015] Furthermore, in step S3, B and Ca in the second solution 2+ Mg 2+ The concentration of each of the two solutions is independently ≤1 mg / L, and the concentration of B is ≤10 mg / L; if the mass concentration of B is greater than 10 mg / L, step S3 further comprises: removing boron by adsorption on the second solution using a methyl glucosamine resin, wherein the methyl glucosamine resin includes at least one of IRA743, S108, CRB01, BSR-1, and MK51; if Ca 2+ and / or Mg 2+ The mass concentration of the second solvent is greater than 1 mg / L, and step S2 includes adsorbing the second solvent with a chelating resin to remove Ca 2+ and Mg 2+ , wherein, the chelating resin, specific models include at least one of IRC747 / 748, S930 / 950, TP260, TP207 / 208, SIR300 / 500.

[0016] Furthermore, in step S1, the lithium precipitation mother liquor is first filtered so that the particle size of the solid particles in the lithium precipitation mother liquor is not greater than 0.02 μm, and then adsorption is performed; and / or, the lithium sodium resin is derived from the lithium sodium resin described in patent CN108421539A, and / or, the hydrochloric acid concentration is 3-8%.

[0017] The technical solution of the present application is applied to the recovery method of lithium precipitation mother liquor provided by the present application, wherein the first solution obtained by adsorption analysis of the lithium precipitation mother liquor is mixed with potassium chloride, and the lithium + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, and then sequentially remove sodium through evaporation crystallization and freezing crystallization, and finally evaporate to precipitate lithium chloride. Not only is the process simple, it constitutes a continuous cycle production process for preparing lithium chloride, and it will not cause B and Na in the system + , Ca 2- 、CO3 2- It can enrich trace impurity ions such as lithium chloride and improve the recovery rate of lithium chloride, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 A schematic diagram of a process for preparing lithium chloride from lithium precipitation mother liquor in one embodiment of the present application is shown;

[0020] Figure 2 Shows an embodiment of the present application Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system phase diagram;

[0021] Figure 3 Shows an embodiment of the present application Li + 、Na + , K + ∥Cl － - Schematic diagram of the local area method of the H2O quaternary water-salt system phase diagram. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As analyzed in the background technology of this application, the prior art evaporates and crystallizes the lithium precipitation mother liquor to remove sodium chloride to obtain a solution, and then directly returns the solution to the circulation system to evaporate and crystallize again with the lithium precipitation mother liquor. This will cause the B and Na in the system to increase in the long term. + , Ca 2- 、CO3 2- The enrichment of trace impurity ions such as ions leads to a low lithium recovery rate. In order to solve this problem, the present application provides a method for recovering lithium precipitation mother liquor.

[0024] In a typical embodiment of the present application, a method for recovering lithium precipitation mother liquor is provided, such as Figure 1 As shown, the preparation method includes the following steps: step S1, firstly adsorbing the lithium precipitation mother solution with lithium sodium resin, and then decomposing it with hydrochloric acid to obtain a first solution; step S2, mixing the first solution with potassium chloride, and adding Li + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl －-H2O quaternary water-salt system to obtain a second solution; step S3, first evaporating and crystallizing the second solution to precipitate a first sodium chloride, and then performing solid-liquid separation to remove the first sodium chloride to obtain a third solution; step S4, freezing and crystallizing the third solution to precipitate a second sodium chloride and a small amount of potassium chloride, and then performing solid-liquid separation to remove the second sodium chloride and a small amount of potassium chloride to obtain a fourth solution; step S5, evaporating and crystallizing the fourth solution to precipitate lithium chloride, and then performing solid-liquid separation to remove sodium to obtain a fifth solution and lithium chloride; wherein the fifth solution returns to step S4 and is mixed with the third solution and then continues to be frozen and crystallized.

[0025] The technical solution of the present application is applied to the recovery method of lithium precipitation mother liquor provided by the present application, wherein the first solution obtained by adsorption analysis of the lithium precipitation mother liquor is mixed with potassium chloride, and the lithium + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, and then sequentially remove sodium through evaporation crystallization and freezing crystallization, and finally evaporate to precipitate lithium chloride. Not only is the process simple, it constitutes a continuous cycle production process for preparing lithium chloride, and it will not cause B and Na in the system + , Ca 2- 、CO3 2- The enrichment of trace impurity ions such as lithium chloride and the recovery rate of lithium chloride are improved, which has broad application prospects. The lithium precipitation mother solution provided by this application is a multi-component complex brine system. The pH value of the lithium precipitation mother solution is preferably 11-13. + :1.5~1.8g / L,Na + :42~50g / L,CO3 2- :25~28g / L,Cl - :75~79g / L,K + : 1.1~1.3g / L, B: 0.01%~1%g / L, SO4 2- : 0.01% ~ 1% g / L, and the lithium precipitation mother solution also contains B, Ca 2- 、SO4 2- And other small amounts of trace impurity ions.

[0026] Typically but not limiting, in the lithium precipitation mother solution used in this application, Li + The mass concentration of Na is 1.5g / L, 1.6g / L, 1.7g / L, 1.8g / L or a range consisting of any two values; + The mass concentration of CO3 is 42g / L, 44g / L, 46g / L, 48g / L, 50g / L or a range consisting of any two values;2- The mass concentration of Cl is 25g / L, 26g / L, 27g / L, 28g / L or a range consisting of any two values; - The mass concentration of K is 75g / L, 76g / L, 77g / L, 78g / L, 79g / L or a range consisting of any two values; + The mass concentration of SO4 is 1.1g / L, 1.2g / L, 1.3g / L or a range of any two values, as well as B, SO4 2- Small amounts of trace impurity ions; pH value such as 11, 12, 13 or the range of values ​​composed of any two resins.

[0027] When the pH value of the lithium precipitation mother liquor is less than 11, the adsorption capacity of the lithium sodium resin for the lithium ions in the lithium precipitation mother liquor is weak, and a large amount of lithium ions are dissolved in the lithium precipitation mother liquor, resulting in a low recovery rate of lithium chloride. When the pH value of the lithium precipitation mother liquor is high, on the one hand, the adsorption capacity of the lithium sodium resin for sodium ions is enhanced, and the separation performance of lithium and sodium is poor. On the other hand, a large amount of hydrochloric acid needs to be added to ensure that the lithium ions adsorbed on the lithium sodium resin are decomposed, and the difficulty of decomposition increases. Within the above range, not only can the lithium ions in the lithium precipitation mother liquor be adsorbed on the lithium sodium resin to the maximum extent, but also the lithium ions adsorbed on the lithium sodium resin cannot be completely decomposed due to the increased difficulty of decomposition, which can effectively improve the lithium ion content in the first solution and the lithium sodium separation performance.

[0028] In the above step S1, in order to further improve the separation effect of lithium and sodium, the lithium sodium resin is preferably derived from the lithium sodium resin described in patent CN108421539A. The lithium sodium resin provided in the patent is an organic high molecular cross-linked polymer grafted with special functional groups, has a stable structure, and can selectively adsorb lithium ions in a high sodium environment, thereby achieving lithium and sodium separation performance. The lithium sodium resin can be washed and reused, saving preparation costs.

[0029] In some embodiments, the above-mentioned lithium sodium resin is loaded into a resin tower, and the lithium precipitate mother liquor is passed through the resin tower at a certain flow rate for adsorption. In order to avoid clogging the resin tower during the adsorption process and affecting the adsorption effect, the lithium precipitate mother liquor is adsorbed with the lithium sodium resin. Before the adsorption, the lithium precipitate mother liquor is filtered using a 0.02 micron precision filter, and then the filtrate is pumped into the lithium sodium resin tower for adsorption, and the lithium ion adsorption rate reaches more than 95%.

[0030] In step S1, after adsorption is completed, hydrochloric acid is used for analysis to obtain a first solution after analysis. The concentration of hydrochloric acid is not limited. In this application, a hydrochloric acid concentration of 3 to 8 wt% (the volume ratio of hydrochloric acid to lithium precipitation mother liquor is 1:2 to 1:1) is used. On the one hand, it can ensure that the loss of hydrochloric acid is small, the amount of water used for acid washing is reduced, and cost is saved; on the other hand, it can ensure that the lithium ion concentration after analysis is high, thereby reducing the subsequent evaporation and concentration costs, and the first solution is obtained after analysis.

[0031] In some embodiments, the pH value of the first solution is 7 to 7.5, and the Li + The mass concentration of Na is 4-5 g / L, + The mass concentration is 3-6 g / L and CO3 2- 、Cl - , K + , B, SO4 2- A small amount of trace impurity ions, the first solution forms Li + 、Na + ∥Cl － -H2O ternary water-salt system.

[0032] In the above step S2, in order to further improve the recovery rate of lithium chloride, it is preferred to mix the first solution with potassium chloride to + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, to obtain the second solution, in which the temperature, pressure and the concentration of each ion in the system will affect the water-salt system, and thus affect the solubility of various salts. + 、Na + , K + ∥Cl － The quaternary water-salt system (H2O) exists in chemical and phase equilibrium, enabling the production of lithium chloride, sodium chloride, and potassium chloride, respectively, by controlling process parameters. By varying temperature, pressure, and other conditions, the sodium chloride and potassium chloride in the second solution reach new chemical and phase equilibrium in the second solution. After the sodium chloride precipitates, the sodium chloride crystals are removed through solid-liquid separation, improving the quality of the lithium chloride. This process not only creates a continuous and stable cycle, but also avoids evaporating the entire solvent during the subsequent sodium ion removal process, reducing energy waste and further improving the recovery rate of lithium chloride.

[0033] In some embodiments, Li + 、Na + , K + ∥Cl－ Li in the quaternary water-salt system + The mass concentration of Na is 4-5 g / L, + The mass concentration of K is 3~6g / L, + The mass concentration is 0.08~0.14g / L and CO3 2- 、Cl - , K + , B, SO4 2- Small amounts of trace impurity ions are all less than 10 mg / mL.

[0034] In some embodiments, in order to further improve the quality of the recovered lithium chloride, the purity of potassium chloride is preferably ≥60%, and the potassium chloride is preferably Class I first-class or superior quality in the GB6549-2011 index to avoid the introduction of new impurities due to the addition of potassium chloride, which leads to poor quality of lithium chloride.

[0035] In order to further improve the quality of the recovered lithium chloride, in step S3, it is preferred that the Ca 2+ Mg 2+ Less than 1mg / L, the mass concentration of B also meets the concentration of B is ≤10mg / L, Ca 2+ The concentration is ≤1mg / L, Mg 2+ The concentration of B is ≤1mg / L. If the mass concentration of B in the second solution is higher than 10mg / L, methylglucosamine resin is used to remove B by adsorption, so that the mass concentration of B in the second solution is not higher than 10mg / L. If the mass concentration of Ca in the second solution is higher than 10mg / L, 2+ Mg 2+ If the concentration is higher than 1 mg / L, chelating resin is used to remove Ca in the second solution. 2+ Mg 2+ , so that Ca in the second solution 2+ Mg 2+ The mass concentration of Ca in the second solution is ≤1mg / L. 2+ Mg 2+ The mass concentration of B is within the above range, which can ensure that in the subsequent impurity removal process, the Ca 2+ Mg 2+ In some embodiments, the methylglucosamine resin and the chelating resin are not limited and can absorb B, Ca 2+ Mg 2+The methylglucosamine resin used in this application includes at least one of IRA743, S108, CRB01, BSR-1, and MK51, and the chelating resin includes at least one of IRC747 / 748, S930 / 950, TP260, TP207 / 208, and SIR300 / 500.

[0036] In some embodiments, the above step S3, such as Figure 2 and Figure 3 As shown, Li in the second solution + The concentration of Na is 4-5 g / L, + The concentration of K is 3-6 g / L. + When the concentration is 0.2~0.9g / L, the second solution system point A falls on Li + 、Na + , K + ∥Cl － In the NaCl crystal phase region in the H2O quaternary water-salt system phase diagram, using the vector law, evaporation and concentration are carried out to point B (the third solution system point). A large number of crystals are precipitated through evaporation and concentration. The crystals are mainly sodium chloride crystals and may also include a small amount of trace metal ions.

[0037] In order to further improve the efficiency of evaporation, concentration and crystallization, it is preferred to adopt the mode of reduced pressure evaporation and concentration. The equipment used for reduced pressure evaporation and concentration is not limited. It is a common equipment in this area. In some embodiments, the equipment adopted is a triple-effect evaporator. The second solution is passed into the triple-effect evaporator. The pressure of the reduced pressure evaporation and crystallization is -0.4~-0.7Bar, and the evaporation temperature is 77~82°C. After evaporation to a lithium chloride concentration of 38~42wt%, evaporation is stopped, and then solid-liquid separation is carried out to obtain the third solution and sodium chloride crystals. By changing the pressure and temperature, point A moves to point B, the solubility of sodium chloride is reduced, and sodium chloride crystals are precipitated, effectively improving the mass concentration of lithium chloride in the third solution.

[0038] In some embodiments, Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, such as Figure 2 and Figure 3As shown, if an excess of potassium chloride is added, the solution evaporates from point K to point L (point L is the saturation line of sodium chloride and potassium chloride), in this process sodium chloride precipitates, and the evaporation continues, and the solution evaporates from point L to point e (point e is the saturation point of sodium chloride, potassium chloride, and lithium chloride, also known as the three-phase saturation point). In this process, sodium chloride and potassium chloride co-precipitate. Therefore, potassium chloride cannot be added in excess, otherwise it will precipitate. If the amount of potassium chloride added is too little (to ensure that potassium ions are more than 20 times the amount of trace impurity ions), Ca 2+ Mg 2+ 、Li + 、Na + , K + ∥Cl － 、SO4 2- 、CO3 2- - One of the five-membered, six-membered, seven-membered, or eight-membered complex water-salt systems in H2O cannot form Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system phase diagram cannot constitute a continuous production cycle process.

[0039] In some embodiments, the mass concentration of LiCl in the third solution is 38-42%, the mass concentration of NaCl is 0.019-0.025%, and the mass concentration of KCl is 0.08-0.14%.

[0040] In the above step S4, the preparation process start-up phase is to freeze-crystallize the third solution, separate the solid and liquid to remove sodium, and obtain the fourth solution. Figure 3 As shown in Li + 、Na + , K + ∥Cl － In the quaternary salt-water phase diagram for the NH₂O system, quadrilateral abcd represents the 2°C lithium chloride crystallization zone. Point C (the brine mixture of the third and fifth solutions) is first cooled to point D and finally frozen to point F (the fourth solution point). Since line ab represents the co-saturated crystallization line for sodium chloride and potassium chloride, point F can only crystallize infinitely along line ab during the cooling process but cannot enter it, as this would cause lithium chloride and sodium chloride to co-crystallize and precipitate, reducing the lithium chloride yield. During this cooling process, all system points remain in the sodium chloride crystallization zone, resulting in the precipitation of only sodium chloride crystals. As the temperature decreases, the lithium chloride crystallization zone shrinks and the sodium chloride crystallization zone expands, achieving deep sodium removal from the third solution.

[0041] During the above-mentioned cooling process, each system point is always in the sodium chloride crystal phase region, thereby ensuring that only sodium chloride crystals are precipitated during the cooling process. If the fourth solution system point F is on the crystallization line ab or within the quadrilateral abcd, sodium chloride and potassium chloride will be crystallized together, resulting in a reduced yield of potassium chloride. If the fourth solution system point F is far away from the crystallization line ab, the amount of sodium chloride crystals precipitated is small, resulting in poor quality of potassium chloride.

[0042] In order to further improve the effect of sodium removal by freeze crystallization, it is preferred that in step S4, the brine solution of the third solution and the fifth solution is first cooled to 38-42°C before freeze crystallization. In some specific embodiments, the mixed solution of the third solution and the fifth solution and brine is first introduced into a cooling circulator by a forced circulation pump and cooled to 38-42°C, then introduced into a cooling crystallizer for cooling and sodium precipitation, then introduced into a cooling circulator by a forced circulation pump and frozen to 0-2°C, finally introduced into a freezing crystallizer for deep sodium removal, and finally solid-liquid separation is performed. The separated liquid is called the fourth solution.

[0043] In some embodiments, the above step S5 is as follows: Figure 3 As shown in Li + 、Na + , K + ∥Cl － In the quaternary water-salt system phase diagram of -H2O, quadrilateral efcg is the lithium chloride crystallization zone at 110℃, where line eg is the co-saturated crystallization line of sodium chloride and potassium chloride at 110℃. Potassium chloride crystals are obtained by temperature-raising evaporation and crystallization. As the temperature rises, the lithium chloride crystallization zone becomes larger and the sodium chloride crystallization zone becomes smaller. The system point F of the fourth solution is now in the lithium chloride crystallization zone. Evaporation continues to the fifth solution system point H. During the evaporation process, point H approaches line eg infinitely, causing lithium chloride crystallization and precipitation. Then, solid-liquid separation is performed to obtain lithium chloride and the fifth solution. If the fifth solution system point H is on the crystallization line eg or outside quadrilateral efcg, sodium chloride and potassium chloride will be crystallized together, resulting in poor quality of the obtained lithium chloride.

[0044] In some embodiments, the fourth solution is passed into a single-effect evaporator for evaporation and crystallization, and evaporated to a lithium chloride concentration of 52-55%. The solid-liquid separation and hot filtration are performed to obtain lithium chloride and a fifth solution. The mass concentration of LiCl in the fifth solution is 52-56%, the mass concentration of NaCl is 0.0018-0.0025%, and the mass concentration of KCl is 0.05-0.07%.

[0045] In order to further improve the quality of lithium chloride, the evaporation crystallization temperature is preferably 110-120°C. If the evaporation temperature is too low, the lithium chloride crystallization zone is smaller and the sodium chloride crystallization zone is larger, and the system point H of the fifth solution is in the lithium chloride crystallization zone, or sodium chloride and lithium chloride are precipitated simultaneously, resulting in the obtained crystals containing a large amount of sodium chloride, making the lithium chloride quality poor. Within the above range, the quality of lithium chloride can be effectively improved and the recovery rate of lithium chloride can be increased. At the same time, it is avoided to evaporate the entire solution to obtain lithium chloride crystals. The heat, condensed water and sodium chloride generated during the evaporation process can be reused, saving energy and reducing preparation costs.

[0046] In the present application, the fifth solution is returned to step S4 and mixed with the third solution to continue freezing crystallization, forming a continuous and stable circulation process, such as Figure 3 As shown in Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system phase diagram, the system point C of the mixture of the third solution and the fifth solution and brine is located in the sodium chloride crystal phase region of the phase diagram. The first freezing reaches the system point D, and the second freezing reaches the fourth solution system point F. The remaining process is the same as the above step S4 and is not repeated here. Through the above operation, the recovery rate of lithium chloride can be effectively improved, the preparation cost can be saved, and it is conducive to the recovery of lithium precipitation mother liquor for industrial large-scale production.

[0047] In some embodiments, in order to further reduce impurities attached to the surface of lithium chloride, the above step S5 further includes sequentially re-slurrying and washing the obtained lithium chloride and spray drying to obtain anhydrous potassium chloride product, and then packaging it. This application has at least the following advantages and beneficial effects:

[0048] First, after sodium chloride and lithium chloride in the lithium precipitation mother liquor are extracted and separated by lithium sodium resin, although a very small amount of potassium chloride is added, it constitutes a continuous circulation production process for producing anhydrous lithium chloride, and the product meets the product grade requirements after re-pulping and washing; second, the traditional lithium precipitation mother liquor recovery requires a large amount of hydrochloric acid acidification to remove carbonate ions, while the present invention can greatly reduce the amount of hydrochloric acid used, and the lithium sodium resin can be reused, saving a certain amount of cost. Third, there is no need to evaporate the entire solution, and the heat, condensed water and sodium chloride generated during the evaporation process can be reused; fourth, the overall lithium yield of the lithium precipitation mother liquor can reach more than 85%, and the recycling of lithium resources is realized; fifth, the present invention is a clean production process, and no toxic or harmful substances are generated during the process; sixth, the present invention is suitable for industrial large-scale production for lithium precipitation mother liquor recovery and has broad promotion significance.

[0049] The beneficial effects of the present application will be further illustrated below with reference to examples and comparative examples.

[0050] Example 1

[0051] This embodiment provides a lithium chloride product, and its preparation method comprises the following steps:

[0052] (1) The lithium precipitation mother liquor was filtered using a 0.02 micron precision filter, and the filtrate was pumped into a lithium sodium resin tower for adsorption. After the adsorption was completed, 5 wt% hydrochloric acid was used for analysis to obtain a first solution; wherein the pH of the lithium precipitation mother liquor was 13, Li + :5g / L,Na + :50g / L,CO3 2- :28g / L,Cl-:79g / L,K + :1.3g / L,B、SO4 2- The trace impurity ions were all less than 10 mg / mL; the pH of the first solution was 7.5, Li + :5g / L,Na + :6g / L, Ca 2+ and Mg 2+ The concentration of trace ions is less than 1 mg / L, and the concentration of other trace ions is less than 10 mg / L.

[0053] (2) Mix the first solution with potassium chloride. + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, in which Li + 、Na + , K + ∥Cl － In the quaternary salt-water system, Li + 5g / L, Na + 6g / L, K + The concentration of HCl was 0.9 g / L, and a second solution was obtained.

[0054] (3) The second solution is passed into a triple-effect evaporator to undergo reduced pressure evaporation and crystallization at a pressure of -0.5 Bar and an evaporation temperature of 80° C., so that sodium chloride crystals are precipitated. The sodium chloride crystals are then removed by solid-liquid separation to obtain a third solution.

[0055] (4) The third solution is introduced into a cooling circulator through a forced circulation pump and cooled to 40° C., and then introduced into a cooling crystallizer for cooling and crystallization at 0° C. to precipitate sodium chloride crystals, and finally solid-liquid separation is performed to obtain sodium chloride crystals and a fourth solution.

[0056] (5) The fourth solution is passed into a single-effect evaporator for evaporation and crystallization at an evaporation temperature of 115° C., and then solid-liquid separation is performed. After hot filtration, lithium chloride solid and a fifth solution are obtained; wherein the fifth solution is returned to step (3) and mixed with the second solution and then evaporated and crystallized under reduced pressure.

[0057] (6) The lithium chloride solid is sequentially subjected to re-slurry washing and spray drying, and then packaged to obtain a lithium chloride product.

[0058] Example 2

[0059] The difference between this embodiment and embodiment 1 is that in step (1), the pH of the lithium precipitation mother solution is 11.5, Li + :1.5g / L,Na + :42g / L,CO3 2- :25g / L,C l- :75g / L,K + :1.1g / L,B、SO4 2- ; The pH of the first solution is 7, Li + :4g / L,Na + : 3g / L, and other trace ions are less than 10mg / L. In step (2), by adjusting the amount of potassium chloride added, the content of each component in the second solution is Li + :4g / L,Na + :3g / L,K + :0.2g / L.

[0060] Example 3

[0061] The difference between this embodiment and embodiment 1 is that in step (2), the first solution is mixed with potassium chloride, and the amount of potassium chloride added is adjusted so that the content of each component in the second solution is Li + :4g / L,Na + :6g / L,K + :1.5g / L.

[0062] Example 4

[0063] The difference between this embodiment and embodiment 1 is that in step (2), the first solution is mixed with potassium chloride, and the amount of potassium chloride added is adjusted so that the content of each component in the second solution is Li + :4g / L,Na + :6g / L,K + :0.01g / L.

[0064] Comparative Example 1

[0065] This comparative example provides a lithium chloride product. The difference between its preparation method and that of Example 1 is that step (2) is omitted, and the first solution is directly passed into three small evaporators for reduced pressure evaporation and crystallization.

[0066] Test Example 1

[0067] The purity of the lithium chloride products prepared in the examples and comparative examples was tested, and the recovery of the lithium chloride products was calculated. The results are shown in Table 1 below.

[0068] (1) The test method for the purity of lithium chloride products is: GB / T 11064.

[0069] (2) The test method for the recovery rate of lithium chloride products is: the recovery rate of lithium chloride products = C 沉锂Li浓度 V 沉锂体积 *6.11 / (m 氯化锂质量* C 氯化锂产品纯度 ).

[0070] Table 1

[0071] Purity of lithium chloride product (%) Recovery rate of lithium chloride product (%) Example 1 99.52 88.35 Example 2 99.47 86.21 Example 3 66.23 (Unable to form a continuous process) 86.31 (Unable to form a continuous process) Example 4 99.32 (unable to form a continuous process) 54.72 (unable to form a continuous process) Comparative Example 1 99.02 (unable to form a continuous process) 52.25 (unable to form a continuous process)

[0072] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the method for preparing lithium chloride from lithium precipitated mother liquor provided by the present application comprises the following steps: mixing the first solution obtained by adsorption and decomposition of lithium precipitated mother liquor with potassium chloride, and then + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, and then sequentially through evaporation crystallization and freeze crystallization to remove sodium and finally evaporation to precipitate lithium chloride. Not only is the process simple, it constitutes a continuous cycle production process for preparing lithium chloride. There is no need to evaporate the entire lithium chloride solution to dryness, which can save a lot of energy and will not cause B and Na in the system. + , Ca 2- 、CO3 2- The enrichment of trace impurity ions such as lithium chloride and the like can improve the recovery rate of lithium chloride, which has broad application prospects. In Example 3, due to excessive potassium chloride added, potassium chloride precipitated during the evaporation process and could not form Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system, therefore cannot form a continuous production cycle process, resulting in a low recovery rate of lithium chloride products. In Example 4, too little potassium chloride is added, which will form Ca 2+ Mg2+ 、Li + 、Na + , K + ∥Cl － 、SO4 2- 、CO3 2- - One of the five-membered, six-membered, seven-membered, or eight-membered complex water-salt systems in H2O cannot form Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system phase diagram, can not form a continuous production cycle process, resulting in a low recovery rate of lithium chloride products. In Comparative Example 1, the system is Li + 、Na + ∥Cl － The H2O ternary water-salt system cannot form a continuous production cycle process, resulting in a low recovery rate of lithium chloride products.

[0073] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for recovering lithium precipitation mother liquor, characterized in that: The method comprises the following steps: Step S1, first adsorbing the lithium precipitated mother liquor with a lithium sodium resin, and then decomposing it with hydrochloric acid to obtain a first solution; Step S2, mixing the first solution with potassium chloride to make the Li + 、Na + ∥Cl － -H2O ternary water-salt system is converted to Li + 、Na + , K + ∥Cl － -H2O quaternary water-salt system to obtain a second solution; Step S3, evaporating and crystallizing the second solution to precipitate first sodium chloride, and then performing solid-liquid separation to remove the first sodium chloride to obtain a third solution; Step S4, freezing and crystallizing the third solution to precipitate a second sodium chloride and a small amount of potassium chloride, and then performing solid-liquid separation to remove the second sodium chloride and a small amount of potassium chloride to obtain a fourth solution; Step S5, first evaporating and crystallizing the fourth solution to precipitate lithium chloride, and then performing solid-liquid separation to obtain a fifth solution and lithium chloride; wherein the fifth solution returns to step S4 and is mixed with the third solution before continuing the freeze crystallization.

2. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: The pH value of the lithium precipitation mother solution is 11-13, Li + :1.5~1.8g / L,Na + :42~50g / L, CO3 2- :25~28 g / L,Cl - :75~79 g / L,K + :1.1~1.3 g / L, B: 0.01%~1%g / L, SO4 2- : 0.01%~1%g / L.

3. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: The step S1, The pH value of the first solution is 7-7.5, Li + :4~5g / L, Na + : 3~6g / L, trace ions are independently <10mg / L.

4. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: The step S2, The second solution component is Li + :4~5g / L, Na + :3~6g / L,K + : 0.2~0.9g / L, trace ions are independently <10mg / L.

5. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: In step S2, the purity of the potassium chloride is ≥60%.

6. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: In step S3, the evaporation crystallization is reduced pressure evaporation crystallization, the pressure of the reduced pressure evaporation crystallization is -0.4 to -0.7 Bar, and the temperature is 77 to 82°C.

7. The method for recovering lithium precipitated mother liquor according to claim 1, wherein: In the third solution, the mass concentration of LiCl is 38-42%, the mass concentration of NaCl is 0.019-0.025%, and the mass concentration of KCl is 0.08-0.14%.

8. The method for recovering lithium precipitation mother liquor according to claim 1, characterized in that: In step S4, cooling treatment is first performed and then freezing crystallization is performed. The cooling temperature is 38-42° C., and the freezing crystallization temperature is 0-2° C.

9. The method for recovering lithium precipitation mother liquor according to claim 1, characterized in that: In step S5, the temperature of the evaporation crystallization is 110-120°C.

10. The method for recovering lithium precipitation mother liquor according to claim 1, characterized in that: In step S3, the Ca in the second solution 2+ Mg 2+ The concentration of A is independently ≤1 mg / L, and the concentration of B is ≤10 mg / L; If the mass concentration of B is greater than 10 mg / L, step S3 further comprises: removing boron by adsorption on the second solution using a methyl glucosamine resin, wherein the methyl glucosamine resin includes at least one of IRA743, S108, CRB01, BSR-1, and MK51; If the Ca 2+ and / or Mg 2+ The mass concentration of the second solution is greater than 1 mg / L, and the step S2 includes adsorbing the second solution with a chelating resin to remove Ca 2+ and Mg 2+ , wherein the chelating resin, specific models include at least one of IRC747 / 748, S930 / 950, TP260, TP207 / 208, SIR300 / 500.

11. The method for recovering lithium precipitation mother liquor according to claim 1, characterized in that: In step S1, the lithium precipitation mother solution is first filtered to make the particle size of the solid particles in the lithium precipitation mother solution no larger than 0.02 μm, and then the adsorption is performed; And / or, the hydrochloric acid concentration is 3-8wt%.

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