Method for efficiently extracting high-specification battery-grade lithium carbonate

Abstract

The invention relates to a method for efficiently extracting high-specification battery-grade lithium carbonate, and belongs to the technical field of lithium carbonate preparation. The method comprises the following steps: pretreatment: mixing a lithium-containing solution raw material with liquid caustic soda; extraction: fully mixing the lithium-containing solution with a no-load extraction agent, and performing phase splitting; reverse extraction: conveying sulfuric acid with a certain concentration and a lithium-containing load oil phase through a centrifugal pump respectively, fully mixing in an extraction tank, and splitting phases; calcium and magnesium are removed from the strip liquor, specifically, the strip liquor is adsorbed through resin, calcium and magnesium in the strip liquor are adsorbed and removed, and the resin is recycled through acid-base regeneration and water washing after adsorption saturation; wastewater treatment: firstly recycling an organic extracting agent in a non-dissolved state from the water-phase raffinate in the extraction procedure through an oil separator, and then treating and regenerating through a macroporous resin adsorption tank; precipitating lithium: placing the prepared sodium carbonate solution in a beaker, stirring and heating, slowly dropwise adding the lithium sulfate solution, continuously reacting, and filtering; and washing and drying: filtering, and drying the lithium carbonate obtained after filtering.

Description

Technical Field

[0001] The present invention relates to the field of lithium carbonate preparation, and particularly to a method for efficiently extracting high-specification battery-grade lithium carbonate. Background Art

[0002] With the continuous update and iteration of lithium battery technology, the quality requirements of the cathode material for the upstream main raw material lithium carbonate are constantly upgraded, the requirements for impurity elements are getting higher and higher, and the enterprise standards are getting stricter. On the other hand, the price of lithium carbonate is gradually declining, which poses a huge test for production costs and quality.

[0003] Currently, in the process of producing battery-grade lithium carbonate from lithium sulfate solution in the market, the filtrate after lithium precipitation is called lithium precipitation mother liquor. When re-extracting the lithium in the lithium precipitation mother liquor to make lithium carbonate products, the following problems are likely to be encountered:

[0004] 1. The lithium metal content in the lithium precipitation mother liquor is still 2.5 g / L, and after evaporation and concentration, the contents of potassium, sodium, and sulfate are very high, resulting in the potassium and sulfate in the product being prone to exceed the standard, or being at the critical level between qualified and unqualified.

[0005] 2. Generally, after evaporation and concentration for desalination of the lithium precipitation mother liquor with a lithium content of 2.5 g / L, it is difficult for the lithium content to reach above 8 g / L. Otherwise, a large amount of lithium metal will be carried away by the precipitated salt, resulting in lithium loss. Due to the low lithium concentration, the production efficiency of the lithium precipitation process is very low, resulting in a large waste of auxiliary materials and steam energy consumption.

[0006] 3. The salt precipitated during the evaporation and concentration process entangles part of the lithium. According to statistics, the lithium loss rate is about 3%. After the concentrated lithium sulfate solution is completed, it needs to be decontaminated and pressure-filtered. At this time, the filter residue needs to take away part of the lithium, further causing lithium loss. Considering comprehensively, the lithium recovery rate is only 90%.

[0007] In view of the above problems, a method for efficiently extracting high-specification battery-grade lithium carbonate is needed. Summary of the Invention

[0008] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for efficiently extracting high-specification battery-grade lithium carbonate to solve the problems raised in the background art.

[0009] In order to achieve the above-mentioned invention purpose, the present invention provides a method for efficiently extracting high-specification battery-grade lithium carbonate, and the method includes the following steps:

[0010] Pretreatment: fully mixing the raw material of the lithium-containing solution with liquid alkali, and then adjusting the pH value of the mixed lithium-containing solution to 12 - 14;

[0011] Extraction: The lithium-containing solution after pH adjustment and the empty extractant are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. At this time, Li+ and H+ undergo ion exchange, and Li+ enters the extraction oil phase to go to the stripping section;

[0012] Stripping: Sulfuric acid with a certain concentration and the lithium-loaded oil phase are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. Li+ in the organic phase is stripped into the aqueous phase system. The high-lithium solution in the aqueous phase goes to the lithium precipitation system of the main device to prepare lithium carbonate products, while the empty organic phase after stripping returns to the extraction process of the previous step for repeated use, and the stripping solution enters the resin calcium and magnesium removal process;

[0013] Calcium and magnesium removal from the stripping solution: The stripping solution is adsorbed by resin to remove calcium and magnesium in the stripping solution. After the resin is saturated with adsorption, it is regenerated by acid and alkali and washed for recycling;

[0014] Wastewater treatment: The aqueous phase raffinate of the extraction process first passes through an oil separator to recover the non-dissolved organic extractant, then through a macroporous resin adsorption tank to adsorb and recover the dissolved organic extractant, and finally through an evaporator for concentration and desalination treatment. After the resin is saturated with adsorption, it is regenerated with pure water;

[0015] Lithium precipitation: A sodium carbonate solution with a prepared concentration of 300 g / L is placed in a beaker, stirred and heated to 95 °C, and then the high-concentration purified lithium sulfate solution adsorbed by the stripping solution in the above steps is slowly added dropwise to the beaker. After the addition is completed, the reaction continues for more than 30 min, and finally it is filtered;

[0016] Washing and drying: Wash at least twice with pure water according to a solid-liquid ratio of 1:3 and then filter. The lithium carbonate obtained after filtration is dried to obtain the finished product.

[0017] Further, the high-lithium solution in the stripping step includes lithium sulfate, and the lithium content is 28 g / L.

[0018] Further, the pH value of the lithium-containing solution raw material in the pretreatment step is 12.5, and the lithium content therein is 2746 ppm.

[0019] Further, the content of lithium carbonate in the obtained finished product after drying is 99.9%, and the water content is 0.09%.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This application adopts the method of extracting lithium by extraction. First, lithium is extracted to form a high-concentration lithium solution. The lithium content can be enriched to 25-30 g / L, and the lithium recovery rate is as high as 99%. The high-concentration lithium sulfate solution has a high lithium precipitation efficiency, and the impurities such as potassium, sodium, and sulfate radicals that are difficult to remove are greatly reduced. The product quality is good, and the content of all impurities is far lower than the battery-grade lithium carbonate level in the same industry. Brief Description of the Drawings

[0022] Figure 1 is a flow chart for preparing lithium carbonate in the prior art;

[0023] Figure 2 is a flow chart for preparing battery-grade lithium carbonate in the present invention. Detailed Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the invention. The embodiments of the present invention are described below with reference to the accompanying drawings.

[0025] Refer to Figure 1 , in the process of producing battery-grade lithium carbonate from lithium sulfate solution in the current market, the filtrate after lithium precipitation is called the lithium precipitation mother liquor. When the lithium in the lithium precipitation mother liquor is re-extracted to make a lithium carbonate product, the following problems are likely to be encountered:

[0026] 1. The lithium metal content in the lithium precipitation mother liquor is still 2.5 g / L, and after evaporation and concentration, the contents of potassium, sodium, and sulfate radicals are very high, resulting in the easy exceeding of potassium and sulfate radicals in the product, or at the critical level between qualified and unqualified.

[0027] 2. After the lithium precipitation mother liquor with a lithium content of 2.5 g / L is generally desalted by evaporation and concentration, it is difficult for the lithium content to reach more than 8 g / L. Otherwise, a large amount of lithium metal will be carried away by the precipitated salt, resulting in lithium loss. Due to the low lithium concentration, the production efficiency of the lithium precipitation process is very low, resulting in a large waste of auxiliary materials and steam energy consumption.

[0028] 3. The salt precipitated during the evaporation and concentration process entangles part of the lithium. According to statistics, the lithium loss rate is about 3%. After the lithium sulfate solution after concentration is completed, it needs to be filtered to remove impurities. At this time, the filter residue needs to carry away part of the lithium, further resulting in lithium loss. Considering comprehensively, the lithium recovery rate is only 90%.

[0029] To solve the above technical problems, the present application proposes a method for efficiently extracting high-specification battery-grade lithium carbonate. By adopting the method of lithium extraction by solvent extraction, lithium is first extracted to form a high-concentration lithium solution. Generally, the lithium content can be enriched to 25-30 g / L, and the lithium recovery rate is as high as 99%. The lithium precipitation efficiency of the high-concentration lithium sulfate solution is very high, and the impurities such as potassium, sodium, and sulfate radicals that are difficult to remove are significantly reduced, and the product quality is very good. The content of all impurities is far lower than the level of battery-grade lithium carbonate in the same industry.

[0030] Reference Figure 2 , a method for efficiently extracting high-specification battery-grade lithium carbonate, the method comprising the following steps:

[0031] Step 1: Pretreatment. The raw material of the lithium-containing solution is fully mixed with liquid caustic soda, and then the pH value of the mixed lithium-containing solution is adjusted to 12-14;

[0032] Specifically, the pH value of the lithium-containing solution can be adjusted to 13, and the raw material of the lithium-containing solution is pumped and fully mixed with liquid caustic soda in a pipeline mixer;

[0033] Step 2: Extraction. The lithium-containing solution after adjusting the pH value and the empty extractant are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. At this time, Li+ and H+ are ion-exchanged, and Li+ enters the extraction oil phase to go to the stripping section;

[0034] Specifically, the lithium-containing solution after adjusting the pH value and the empty extractant are each transported by a centrifugal pump, fully mixed in an extraction tank at a certain flow rate ratio and then phase-separated. At this time, through the ion exchange of Li+ and H+, Li+ enters the extraction oil phase to go to the stripping section, while most of the other ions still remain in the aqueous phase and go to the water treatment process as the raffinate;

[0035] Step 3: Stripping. Sulfuric acid with a certain concentration and the lithium-loaded oil phase are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. Li+ in the organic phase is stripped into the aqueous phase system, and the high-lithium solution in the aqueous phase goes to the lithium precipitation system of the main device to prepare lithium carbonate products, while the stripped empty organic phase returns to the extraction process of the previous step for repeated use, and the stripping solution enters the resin de-calcium and magnesium process;

[0036] The test results of the lithium sulfate solution after stripping are shown in the following table:

[0037] sample Ca (mg / L) K (mg / L) Li (mg / L) Na (mg / L) stock solution 169.4 31710 2746 116000 raffinate 25.94 22760 30.29 47360 stripping solution 189.1 107.2 28410 12320

[0038] Step 4: Removal of calcium and magnesium from the stripping solution. The stripping solution is adsorbed by resin to remove calcium and magnesium in the stripping solution. After the resin is saturated with adsorption, it is regenerated by acid and alkali and washed for recycling;

[0039] The test results of the lithium sulfate solution purified by resin adsorption are shown in the following table:

[0040]

[0041] Step 5: Wastewater treatment: The aqueous phase raffinate from the extraction process is first passed through a grease trap to recover the undissolved organic extractant, then passed through a macroporous resin adsorption tank to adsorb and recover the dissolved organic extractant, and finally passed through an evaporator for concentration and desalination. After the resin is saturated with adsorption, it is regenerated with pure water.

[0042] Step 6: Lithium precipitation: Place the prepared sodium carbonate solution with a concentration of 300g / L in a beaker, stir and heat to 95°C, then slowly add the high-concentration purified lithium sulfate solution adsorbed by the stripping solution in the above step to the beaker, continue to react for more than 30 minutes after the addition is completed, and finally filter;

[0043] Step 7: washing and drying. Wash with pure water at least twice according to a solid-liquid ratio of 1:3 and then filter. Dry the lithium carbonate obtained after filtration to obtain the finished product.

[0044] The indicators of the finished product are shown in the following table:

[0045]

[0046] The standard in the above table is the battery grade lithium carbonate standard, and the sample is the experimental sample prepared in this application. The units of Li2CO3 and H2O in the table are percentages, and the units of other elements such as Al, Ca, Mn, Cu, Fe, K, Mg, Na, Pb, SO4 2- , Zn, Cl-, Ni, and Si are in ppm. From the data in the above table, it can be seen that the various indicators of the finished product prepared by the method of the present application are almost close to those of high-purity lithium carbonate, which is far superior to the level of the same industry.

[0047] The technical solutions of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the above descriptions are merely for the purpose of explaining the solutions of the present invention and are not to be construed in any way as limiting the scope of protection of the invention. Based on the explanations herein, those skilled in the art can conceive of other specific embodiments of the present invention or equivalent replacements without inventive effort, and these will fall within the scope of protection of the present invention.

Claims

1. A method for efficiently extracting high-specification battery-grade lithium carbonate, characterized in that, The method comprises the following steps: Pretreatment: The lithium-containing solution raw material is fully mixed with liquid caustic soda, and then the pH value of the mixed lithium-containing solution is adjusted to 12 - 14; Extraction: The lithium-containing solution after pH adjustment and the empty extractant are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. At this time, Li⁺ and H⁺ undergo ion exchange, and Li⁺ enters the extraction oil phase to go to the stripping section; Stripping: Sulfuric acid with a certain concentration and the lithium-loaded oil phase are each transported by a centrifugal pump, fully mixed in an extraction tank and then phase-separated. Li⁺ in the organic phase is stripped into the aqueous phase system, and the high-lithium solution in the aqueous phase goes to the lithium precipitation system of the main device to prepare lithium carbonate products. The empty organic phase after stripping returns to the extraction process of the previous step for repeated use, and the stripping liquid enters the resin de-calcium and de-magnesium process; De-calcium and de-magnesium of the stripping liquid: The stripping liquid is adsorbed by resin to remove calcium and magnesium in the stripping liquid. After the resin is saturated with adsorption, it is regenerated by acid and alkali and washed for recycling; Wastewater treatment: The aqueous phase raffinate of the extraction process first passes through an oil separator to recover the non-dissolved organic extractant, then passes through a macroporous resin adsorption tank to adsorb and recover the dissolved organic extractant, and finally undergoes evaporation concentration and desalination treatment. After the resin is saturated with adsorption, it is regenerated with pure water; Lithium precipitation: A sodium carbonate solution with a concentration of 300 g / L prepared is placed in a beaker, stirred and heated to 95 °C, and then the highly concentrated purified lithium sulfate solution adsorbed by the stripping liquid in the above steps is slowly dropped into the beaker. After the dropping is completed, the reaction continues for more than 30 min, and finally filtration is carried out; Washing and drying: Wash with pure water according to a solid-liquid ratio of 1:3 at least twice and then filter. The lithium carbonate obtained after filtration is dried to obtain the finished product.

2. The method for efficiently extracting high-specification battery-grade lithium carbonate according to claim 1, wherein The high-lithium solution in the stripping step includes lithium sulfate, and the lithium content is 28 g / L.

3. The method for efficiently extracting high-specification battery-grade lithium carbonate according to claim 1, characterized in that, The pH value of the lithium-containing solution raw material in the pretreatment step is 12.5, and the lithium content is 2746 ppm.

4. The method for efficiently extracting high-specification battery-grade lithium carbonate according to claim 1, wherein The content of lithium carbonate in the obtained finished product after drying is 99.9%, and the water content is 0.09%.

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