Method for preparing lithium carbonate and anhydrous sodium sulphate by purifying and removing thallium from lepidolite leachate
By using Na-type cation exchange resin in the lithium mica leaching solution for alkaline thallium removal, combined with sodium carbonate precipitation and decarbonization evaporation processes, the problems of thallium leakage and impurity removal in the prior art were solved, and the preparation of high-efficiency and low-loss lithium carbonate and low-thallium Yuanming Powder was achieved.
Patent Information
- Application Number
- CN202510185834.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-06-06
AI Technical Summary
The existing lithium mica leaching liquid purification process has the risk of thallium leakage and enrichment, the lithium loss rate is high, and it is difficult to effectively remove impurities, affecting the quality of lithium carbonate.
The lithium mica leaching solution was removed under alkaline conditions by using Na-type cation exchange resin. By adjusting the pH value and controlling the operating parameters, combining sodium carbonate lithium precipitation and decarbonization evaporation technology, the thallium and other impurities were deeply removed, and high-purity lithium carbonate and low-thallium content Yuanming powder were prepared.
The effective removal of thallium in the lithium mica leaching liquid was achieved, with the removal rate reaching about 80%, reducing the lithium loss rate, improving the purity of lithium carbonate, meeting battery-grade requirements, and reducing the secondary pollution of thallium.
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Figure CN120097366A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of lithium carbonate production, and in particular to a method for preparing lithium carbonate and glauber's salt by purifying and removing thallium from lepidolite leachate. Background Art
[0002] In the preparation of lithium carbonate by the lithium mica sulfate method, lithium extraction requires high-temperature roasting and leaching. Thallium is a rare and dispersed heavy metal element. Thallium has both lithophilicity and sulfur-philicity and is widely present in ores such as mica and pyrite. The roasting and leaching process of lithium leads to the release of trace thallium in the ore, causing thallium pollution in water bodies, thallium pollution in soil, chronic thallium poisoning in humans and animals, etc. In addition to trace thallium elements, depending on the specific roasting and leaching processes, the lithium mica leachate also contains a large amount of metal impurities such as Fe, Al, Na, K, Ca, Mg, Mn, and non-metallic impurity elements such as Cl, F, and P. To obtain high-quality lithium carbonate, the lithium mica leachate needs to be purified and refined. It is very important to purify the lithium mica leachate to remove thallium and other impurities to prepare high-quality lithium carbonate and by-products, and to prevent thallium from enriching in the production system.
[0003] The extraction and purification processes for preparing lithium carbonate from lepidolite mainly include precipitation method, solvent extraction method, ion exchange method, etc. The inventors found in the implementation process that due to the differences in raw materials and lithium extraction processes, there are large differences in the raw material components in the lithium extraction leachate, the applicability of the existing technical methods is poor, there are risks of thallium leakage and enrichment, high lithium loss rate, or impact on the impurity content of the product, etc. The present invention aims to propose a method for preparing lithium carbonate and glauber salt by purifying lepidolite leachate to remove thallium. The method has a good purification effect on thallium in the system, and has high processing efficiency. The processing process is not easy to cause secondary pollution of thallium. The thallium content in the by-product glauber salt is low, and the prepared lithium carbonate can meet the battery grade requirements. Summary of the invention
[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for purifying thallium from a lepidolite leachate to prepare lithium carbonate and glauber salt. The method has a good purification effect on thallium in the system, and has high treatment efficiency. The treatment process is not easy to cause secondary pollution of thallium. The thallium content in the by-product glauber salt is low, and the prepared lithium carbonate can meet battery-grade requirements.
[0005] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides a method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt, comprising the following steps: S1: adjusting the pH of the lepidolite leachate to 9-12; S2: using Na type cation exchange resin to carry out adsorption and impurity removal purification to obtain lithium extraction purification liquid, and the resin after adsorption saturation is subjected to desorption treatment; S3: adding 1.05 to 1.1 times the theoretical amount of sodium carbonate to the purified lithium extraction liquid after impurities removal to precipitate lithium carbonate, separating to obtain filter residue and lithium precipitation mother liquor, and obtaining lithium carbonate after ball milling and pulp washing of the filter residue; S4: The obtained lithium precipitation mother liquor is decarbonized and evaporated to precipitate potassium-sodium mixed salt (which can be recovered as sulfate and returned to the lithium mica concentrate processing step), the remaining filtrate is frozen and crystallized, the precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt, and the frozen crystallized lithium-rich mother liquor is returned to S1.
[0006] Furthermore, the composition of the lepidolite leachate described in S1 includes: Li 2 O 10~13.5g / L, K 20~30g / L, Na5~15g / L, F 10~100mg / L, Tl 0.1~2mg / L, Ca 20~100mg / L, Mg 30~300mg / L, Cl 0.1~1g / L; The pH of the lepidolite leachate is 7 to 9; In S1, the pH is adjusted by using a sodium hydroxide solution with a concentration of 400 to 700 g / L.
[0007] Furthermore, the adsorption in S2 adopts static adsorption or dynamic adsorption of resin.
[0008] Furthermore, the specific method of static adsorption is to mix the lithium mica leachate with a pH of 9 to 12 with the Na-type cation exchange resin in a container, oscillate and adsorb on a constant temperature shaker at a speed of 160 r / min for 2 hours, and then let it stand; the mass volume ratio of the Na-type cation exchange resin to the lithium mica leachate is 1: (20 to 25) g / ml.
[0009] Furthermore, the specific method of dynamic adsorption is to fill the Na-type cation exchange resin in an exchange column, and pass the lithium mica leachate with a pH of 9 to 12 through the exchange column at a flow rate of 0.6 to 1.0 bv / h.
[0010] Furthermore, the desorption treatment method described in S2 is to wash the adsorption saturated resin with ultrapure water, and then desorb the washed resin with 9% sodium chloride solution, and the flow rate of the sodium chloride solution is 0.28 bv / h.
[0011] Furthermore, S2 also includes regenerating the Na-type cation exchange resin, soaking the desorbed resin in a 5% sodium chloride solution for 12 hours, washing with water until the washing liquid is clear and colorless, soaking it in a 3% sodium hydroxide solution for 24 hours, and washing with water until it is neutral for use.
[0012] Furthermore, the lithium deposition method described in S3 includes: S31: mixing the lithium extraction purification solution with a sodium carbonate solution, wherein the concentration of sodium carbonate is 200 to 300 g / L, and the sodium carbonate is 1.05 to 1.1 times the theoretical calculated amount, first adding 70 to 85% of the total amount of sodium carbonate required, heating to 90 to 95° C. for sufficient reaction, and filtering while hot to obtain a filtrate 1 and a filter residue 1; S32: Mix the filtrate 1 with the remaining sodium carbonate solution, concentrate by evaporation under reduced pressure to a Li content of 12 to 15 g / L, and filter while hot to obtain a lithium precipitation mother liquor and a filter residue 2.
[0013] Furthermore, the specific method of ball milling and slurry washing in S3 is to add 0.5 to 1.5 times the amount of water to the filter residue for ball milling, the ball-to-material ratio is 2 to 3:1, the ball milling speed is 30 to 80 r / min, and the ball milling time is 0.5 to 1 h; add 2 to 3 times the amount of water to the filter residue to the obtained ball milling slurry, heat it to 90 to 95°C, wash it at 50 to 100 r / min for 40 to 60 minutes, filter it while hot, wash it with water and dry it to obtain the lithium carbonate product.
[0014] Furthermore, the specific method of decarbonization evaporation in S4 is: adding concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 5-6 for decarbonization, and evaporating the decarbonization mother liquor to 40-50% of the original volume using MVR equipment.
[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts cation exchange resin to remove thallium from lepidolite leachate under alkaline conditions. By adjusting the pH of the lepidolite leachate, the cation exchange resin is selected and specific operating parameters are explored. The method has a deep purification degree of thallium in the lepidolite leachate, and the removal rate of thallium in the system reaches about 80%. The processing efficiency is high, and the adsorption saturated resin can realize the recovery of thallium through desorption operation, which is not easy to cause secondary pollution of thallium. After reaching adsorption equilibrium, the resin can be recycled after regeneration, and the operation cost is low, which is suitable for industrial promotion.
[0016] 2. The present invention uses Na-type cation exchange resin to remove thallium from the lepidolite leachate under alkaline conditions, and can deeply remove Ca and Mg in the lithium sulfate solution, thereby achieving the purpose of removing impurity ions at the same time. In the embodiment, the content of Ca can be reduced to below 5 mg / L, and the content of Mg can be reduced to below 1 mg / L. The treatment process Li 2 The loss rate of O is controlled within 1.5%.
[0017] 3. The lithium extraction purification liquid treated with Na-type cation exchange resin is subjected to lithium precipitation with sodium carbonate. A secondary lithium precipitation process is adopted and the amount of sodium carbonate is precisely controlled. The separated crude lithium carbonate is refined into crude sodium carbonate particles by ball milling, and then low-speed slurry washing is carried out with deionized water at high temperature. The above process and parameter control can effectively realize the separation of lithium carbonate and impurities and the removal of impurities. On the basis of ensuring that the yield can reach about 80%, it is ensured that the purity of the prepared lithium carbonate meets the battery grade requirements, and the contents of Na, K, Tl, Cl and F are low.
[0018] 4. After the present invention uses a cation exchange resin to remove thallium from the lepidolite leachate under alkaline conditions, the thallium content in the solution is significantly reduced, thereby stabilizing the thallium content in the self-produced potassium-sodium mixed salt and glauber salt in the later stage. The thallium content in the glauber salt in the embodiment of the present invention is stably reduced to less than 0.3ppm. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 The present invention is a process flow chart of a method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt. DETAILED DESCRIPTION
[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] The equipment and determination methods involved in the detection items in the following embodiments and comparative examples are shown in Table 1 below: Table 1: Test items, equipment and measurement methods
[0022] The lepidolite leaching solution used in the embodiments and comparative examples of the present invention is provided by Fengxin Times New Energy Materials Co., Ltd., and is obtained by sulfate process from lepidolite concentrate, and is composed of: 2 O 10.17g / L, K 23.17g / L, Na13.69g / L, F38.85mg / L, Tl 0.77mg / L, Ca 30.12mg / L, Mg 50.60mg / L, Cl0.46g / L, pH 8.57; The cation exchange resin used was purchased from Xi'an Lanxiao Technology New Materials Co., Ltd., model LSC-500B; The following is combined with specific embodiments Figure 1The scheme and effect of the present invention are further described. The methods described in the following specific implementation cases are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.
[0023] Example 1 The method for purifying and removing thallium from a lithium mica leachate is as follows: the pH values of the lithium mica leachate are adjusted to 9, 10, 11, and 12 respectively using sodium hydroxide with a concentration of 400 g / L, and the lithium mica leachate without pH adjustment is set as control 1. 12 g of Na-type cation exchange resin is weighed and placed in a 500 ml covered container, 250 ml of the lithium mica leachate is added thereto, and the mixture is placed on a shaker and shaken at 160 r / min for 2 h for adsorption. The concentrations of various substances in the lithium extraction purification solution are sampled and analyzed. The results are shown in Table 2.
[0024] The concentration of the purified lithium extraction liquid after the cation exchange column treatment was analyzed, and the results are shown in Table 1 below: Table 2: Concentration and removal rate of substances in lithium extraction purification solution after cation exchange treatment
[0025] Combining treatment groups 1 to 4 and control 1, it can be seen that under the condition of pH 9-11, the use of Na + The static adsorption of cation exchange resin can reduce Tl in the lepidolite leachate. Without pH adjustment, the removal rates of Tl, Ca and Mg are low. When the pH reaches 12, the removal rate of Tl decreases and the lithium loss rate is high. Under the condition of pH 10, the lithium loss rate is the lowest, the Tl removal rate is the highest, and it has a high removal effect of Ca and Mg.
[0026] Example 2 The method for purifying and removing thallium from lepidolite leachate specifically comprises the following steps: S1: The pH value of the lepidolite leachate is adjusted to 10 using a sodium hydroxide solution having a concentration of 400 g / L.
[0027] S2: The pretreated Na-type cation exchange resin is filled in an exchange column (diameter-to-height ratio is 1:5), and the pH-adjusted lithium mica leachate is added to the exchange column at flow rates of 0.6 bv / h, 0.8 bv / h, and 1 bv / h as treatment groups 5, 6, and 7, respectively, for adsorption and impurity removal to obtain lithium-extracting purified liquid, and the resin after adsorption saturation is desorbed.
[0028] Control 2 followed the method of treatment group 6, except that the pH of the lepidolite leachate was not adjusted; The concentration of the purified lithium extraction liquid after treatment with the cation exchange column was analyzed, and the results are shown in Table 3 below: Table 3: Concentration and removal rate of substances in lithium extraction purification solution after cation exchange treatment
[0029] Combining treatment groups 5, 6, and 7, it can be seen that treatment group 5 has a higher lithium loss at a flow rate of 0.6BV / h; treatment group 7 has a low Tl removal rate at a flow rate of 1BV / h; and at a flow rate of 0.8BV / h, the lithium loss rate is the lowest and the Tl removal rate is the highest, while it has a good Ca and Mg removal effect.
[0030] Combining treatment group 6 and control 2, it can be seen that control 2 did not undergo pH adjustment, and the removal rates of Tl, Ca, and Mg were lower, and lithium loss was greater.
[0031] The method of treatment group 6 was repeatedly used to carry out thallium removal experiments. The cation exchange resin was desorbed and regenerated and then recycled for 5 times. The following desorption and regeneration methods were used to desorb and regenerate the adsorption saturated resin. The desorption treatment method was as follows: the adsorption saturated resin was washed with ultrapure water, and then the washed resin was desorbed with 9% sodium chloride solution, and the flow rate of the sodium chloride solution was 0.28 bv / h; the regeneration method was as follows: the desorbed resin was soaked in 5% sodium chloride solution for 12 hours, washed with water until the washing liquid was clear and colorless, and then soaked in 3% sodium hydroxide for 24 hours, and washed with water until neutral for use.
[0032] The thallium removal effects for the 1st to 5th cycles were 83.0%, 82.8%, 82.5%, 81.7% and 80.9% respectively, all of which showed good thallium removal effects.
[0033] Example 3 The method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt specifically comprises the following steps: S1: The pH value of the lepidolite leachate is adjusted to 10 using a sodium hydroxide solution having a concentration of 400 g / L.
[0034] S2: The pretreated Na-type cation exchange resin is filled in the exchange column (diameter-to-height ratio is 1:5), and the pH-adjusted lithium mica leachate is added to the exchange column at a flow rate of 0.8 bv / h for adsorption and impurity removal to obtain lithium extraction purification liquid, and the resin after adsorption saturation is desorbed. The desorption treatment method is: after the adsorption saturation resin is washed with ultrapure water, the washed resin is desorbed with 9% sodium chloride solution, and the flow rate of the sodium chloride solution is 0.28 bv / h; the regeneration method is: the desorbed resin is soaked in 5% sodium chloride solution for 12 hours, washed with water until the washing liquid is clear and colorless, and then soaked in 3% sodium hydroxide for 24 hours, washed with water until neutral for use.
[0035] S3: According to the Li in the lithium extraction purification solution 2O concentration is used to calculate the theoretical amount of sodium carbonate M1 required for lithium precipitation, and the total amount of sodium carbonate M2 required is determined according to 1.1 times of the theoretical amount M1. A sodium carbonate solution with a concentration of 200g / L is prepared, and sodium carbonate M2×85% is added to the lithium extraction purification solution. The temperature is raised to 90℃ and stirred at 200r / min for 2h, and then filtered while hot to obtain filtrate 1 and residue 1; filtrate 1 is mixed with the remaining sodium carbonate solution, and concentrated under reduced pressure to a Li content of 15g / L, and filtered while hot to obtain lithium precipitation mother liquor and residue 2. The residue 1 and residue 2 are combined and added with 1 times the weight of deionized water, and transferred to a ball mill for ball milling, with a ball-to-material ratio of 2:1, a ball milling speed of 50r / min, and a ball milling time of 0.5h. Deionized water 2.5 times the weight of the residue is added to the obtained ball milled slurry, and the temperature is raised to 90℃, and the slurry is washed at 80r / min for 50min, and the lithium carbonate product is obtained by filtering while hot and washing with a small amount of deionized water and drying.
[0036] S4: Add concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 6 for decarbonization. The decarbonization mother liquor is evaporated to 50% of the original volume by MVR equipment to precipitate potassium-sodium mixed salt. The filtrate is frozen and crystallized at 0-5°C. The precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt. The frozen crystallized lithium-rich mother liquor is returned to S1.
[0037] Example 4 The method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt specifically comprises the following steps: The methods of S1 and S2 are the same as those of Example 3; S3: According to the Li in the lithium extraction purification solution 2 O concentration is used to calculate the theoretical amount of sodium carbonate M1 required for lithium precipitation, and the total amount of sodium carbonate M2 required is determined according to 1.05 times the theoretical amount M1. A sodium carbonate solution with a concentration of 280g / L is prepared, and M2×80% of sodium carbonate is added to the lithium extraction purification solution. The temperature is raised to 95℃ and stirred at 200r / min for 0.6h, and then filtered while hot to obtain filtrate 1 and residue 1; filtrate 1 is mixed with the remaining sodium carbonate solution, and concentrated under reduced pressure to a Li content of 15g / L, and filtered while hot to obtain lithium precipitation mother liquor and residue 2. The residue 1 and residue 2 are combined and added with 1.5 times the weight of deionized water, and transferred to a ball mill for ball milling, with a ball-to-material ratio of 3:1, a ball milling speed of 80r / min, and a ball milling time of 0.5h. Three times the amount of water of the residue is added to the obtained ball milled slurry, the temperature is raised to 95℃, and the slurry is washed at 100r / min for 40min, and the lithium carbonate product is obtained by filtering while hot and washing with a small amount of deionized water and drying.
[0038] S4: Add concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 6 for decarbonization. The decarbonization mother liquor is evaporated to 50% of the original volume by MVR equipment to precipitate potassium-sodium mixed salt. The filtrate is frozen and crystallized at 0-5°C. The precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt. The frozen crystallized lithium-rich mother liquor is returned to S1.
[0039] Example 5 The method for purifying and removing thallium from lithium mica leachate to prepare lithium carbonate and glauber salt is the same as in Example 3, except that the filter residue 1 and the filter residue 2 are combined, 0.5 times the weight of deionized water is added, and the mixture is transferred into a ball mill for ball milling, the ball-to-material ratio is 2:1, the ball milling speed is 30r / min, and the ball milling time is 1h. Three times the amount of water of the filter residue is added to the obtained ball mill slurry, the temperature is raised to 90°C, the slurry is washed at 50r / min for 60min, and the lithium carbonate product is obtained by filtering while hot, washing with a small amount of deionized water, and drying.
[0040] Comparative Example 1 The method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt is the same as that in Example 3, except that filter residue 1 and filter residue 2 are washed with 4 times the weight of deionized water at 90°C and 80 r / min for 50 min, filtered while hot, washed with a small amount of deionized water and dried to obtain the lithium carbonate product.
[0041] Comparative Example 2 The method for purifying and removing thallium from lithium mica leachate to prepare lithium carbonate and glauber salt is the same as in Example 3, except that the filter residue 1 and the filter residue 2 are combined and added with 1 times the weight of deionized water, and then transferred into a ball mill for ball milling, the ball-to-material ratio is 2:1, the ball milling speed is 50r / min, and the ball milling time is 0.5h. Deionized water 2.5 times the weight of the filter residue is added to the obtained ball mill slurry, the temperature is raised to 90°C, the slurry is washed at 300r / min for 50min, and the lithium carbonate product is obtained by filtering while hot and washing with a small amount of deionized water and drying.
[0042] Comparative Example 3 The method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt specifically comprises the following steps: S1: The pH value of the lepidolite leachate is adjusted to 10 using a sodium hydroxide solution having a concentration of 400 g / L.
[0043] S2: The pretreated Na-type cation exchange resin is filled in the exchange column (diameter-to-height ratio is 1:5), and the pH-adjusted lithium mica leachate is added to the exchange column at a flow rate of 0.8 bv / h for adsorption and impurity removal to obtain lithium extraction purification liquid, and the resin after adsorption saturation is desorbed. The desorption treatment method is: after the adsorption saturation resin is washed with ultrapure water, the washed resin is desorbed with 9% sodium chloride solution, and the flow rate of the sodium chloride solution is 0.28 bv / h; the regeneration method is: the desorbed resin is soaked in 5% sodium chloride solution for 12 hours, washed with water until the washing liquid is clear and colorless, and then soaked in 3% sodium hydroxide for 24 hours, washed with water until neutral for use.
[0044] S3: According to the Li in the lithium extraction purification solution 2O concentration is used to calculate the theoretical amount of sodium carbonate M1 required for lithium precipitation, and the total amount of sodium carbonate M2 required is determined according to 1.2 times the theoretical amount M1. A sodium carbonate solution with a concentration of 200g / L is prepared, and sodium carbonate M2 is added to the lithium extraction purification solution. After heating to 90°C and stirring at 200r / min for 2h, the mother liquor and filter residue are filtered while hot to obtain the lithium precipitation mother liquor and the filter residue. The filter residue is added with 1 times the weight of deionized water and transferred to a ball mill for ball milling. The ball-to-material ratio is 2:1, the ball milling speed is 50r / min, and the ball milling time is 0.5h. Deionized water 2.5 times the weight of the filter residue is added to the obtained ball mill slurry, heated to 90°C, and washed at 80r / min for 50min. The lithium carbonate product is obtained by filtering while hot and washing with a small amount of deionized water.
[0045] S4: Add concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 6 for decarbonization. The decarbonization mother liquor is evaporated to 50% of the original volume by MVR equipment to precipitate potassium-sodium mixed salt. The filtrate is frozen and crystallized at 0-5°C. The precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt. The frozen crystallized lithium-rich mother liquor is returned to S1.
[0046] Comparative Example 4 The method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt specifically comprises the following steps: S1: The pH value of the lepidolite leachate is adjusted to 10 using a sodium hydroxide solution having a concentration of 400 g / L.
[0047] S2: The pretreated Na-type cation exchange resin is filled in the exchange column (diameter-to-height ratio is 1:5), and the pH-adjusted lithium mica leachate is added to the exchange column at a flow rate of 0.8 bv / h for adsorption and impurity removal to obtain lithium extraction purification liquid, and the resin after adsorption saturation is desorbed. The desorption treatment method is: after the adsorption saturation resin is washed with ultrapure water, the washed resin is desorbed with 9% sodium chloride solution, and the flow rate of the sodium chloride solution is 0.28 bv / h; the regeneration method is: the desorbed resin is soaked in 5% sodium chloride solution for 12 hours, washed with water until the washing liquid is clear and colorless, and then soaked in 3% sodium hydroxide for 24 hours, washed with water until neutral for use.
[0048] S3: According to the Li in the lithium extraction purification solution 2O concentration is used to calculate the theoretical amount of sodium carbonate M1 required for lithium precipitation, and the total amount of sodium carbonate M2 required is determined according to 1.1 times the theoretical amount M1. A sodium carbonate solution with a concentration of 200g / L is prepared, and sodium carbonate M2 is added to the lithium extraction purification solution. After heating to 90°C and stirring at 200r / min for 2h, the mother liquor and filter residue are filtered while hot to obtain the lithium precipitation mother liquor and the filter residue. The filter residue is added with 1 times the weight of deionized water and transferred to a ball mill for ball milling. The ball-to-material ratio is 2:1, the ball milling speed is 50r / min, and the ball milling time is 0.5h. Deionized water 2.5 times the weight of the filter residue is added to the obtained ball mill slurry, heated to 90°C, and washed at 80r / min for 50min. The lithium carbonate product is obtained by filtering while hot and washing with a small amount of deionized water.
[0049] S4: Add concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 6 for decarbonization. The decarbonization mother liquor is evaporated to 50% of the original volume by MVR equipment to precipitate potassium-sodium mixed salt. The filtrate is frozen and crystallized at 0-5°C. The precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt. The frozen crystallized lithium-rich mother liquor is returned to S1.
[0050] The lithium carbonate prepared in Examples 3 to 5 and Comparative Examples 1 to 4 was tested, and the relevant test data results are shown in Table 4 below, wherein the single-step yield statistics S3 step yield data, the sodium sulfate prepared in Examples 3 to 4 and Comparative Examples 3 to 4 was tested, and the results are shown in Table 5 below: Table 4: Lithium carbonate related test data results
[0051] Table 5: Results of relevant test data of sodium sulphate
[0052] As shown in Table 4, in Examples 3, 4 and 5 of the present invention, after the filter residue 1 and the filter residue 2 are combined, deionized water is added for ball milling, and then deionized water is added for low-speed slurry washing at 90-95° C., and the weight ratio of deionized water to the filter residue is controlled. The purity of the obtained lithium carbonate is greater than 99.5%, the single-step yield is about 80%, and the contents of Na, K, Tl, F and Cl are relatively low; In combination with Example 3 and Comparative Example 1, Comparative Example 1 only uses deionized water for low-speed pulp washing, and the prepared lithium carbonate has significantly higher contents of Na, K, F, and Cl, and still has a trace amount of Tl remaining.
[0053] Combining Example 3 and Comparative Example 2, in Comparative Example 2, the ball mill slurry was added with deionized water and then subjected to high-speed slurry washing. The impurity contents of Na, K, F, and Cl in the prepared lithium carbonate were not reduced relative to those in Example 3, and a trace amount of Tl remained, and the single-step yield was low.
[0054] In combination with Example 3 and Comparative Example 3, 1.2 times of sodium carbonate was added to perform a precipitation in Comparative Example 3, and the prepared lithium carbonate had significantly higher contents of Na, K, F, and Cl, a trace amount of Tl remained, and the purity of lithium carbonate was low.
[0055] Combining Example 3 and Comparative Example 4, in Comparative Example 4, 1.1 times of sodium carbonate was added for one precipitation, and the contents of Na, K, F, and Cl were higher than those in Example 3, and there was still a trace amount of Tl remaining, the purity of lithium carbonate was low, and the single-step yield was low.
[0056] As can be seen from Table 5, in Examples 3 to 4 of the present invention, the glauber salt prepared in Comparative Example 3 has a Tl content of less than 0.3 ppm, a low F and Cl content, and a high purity. The glauber salt prepared in Comparative Example 4 has a high Tl content, a high F and Cl content, and a low purity.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents, which should all be included in the scope of the technical solution for protection of the present invention.
Claims
1. A method for purifying lepidolite leachate to remove thallium and prepare lithium carbonate and glauber salt, characterized in that: The following steps are involved: S1: adjusting the pH of the lepidolite leachate to 9-12; S2: using Na type cation exchange resin to carry out adsorption and impurity removal purification to obtain lithium extraction purification liquid, and the resin after adsorption saturation is subjected to desorption treatment; S3: adding 1.05 to 1.1 times the theoretical amount of sodium carbonate to the purified lithium extraction liquid after impurities removal to precipitate lithium carbonate, separating to obtain a filter residue and a lithium precipitation mother liquor, and ball milling and slurry washing the filter residue to obtain lithium carbonate; S4: The obtained lithium precipitation mother liquor is decarbonized and evaporated to precipitate potassium-sodium mixed salt, the remaining filtrate is frozen and crystallized, the precipitated sodium sulfate decahydrate is evaporated and dehydrated to obtain glauber salt, and the frozen crystallized lithium-rich mother liquor is returned to S1.
2. The method for purifying and removing thallium from a lepidolite leachate to prepare lithium carbonate and glauber salt according to claim 1, characterized in that: The composition of the lithium mica leachate in S1 includes: Li2O 10-13.5g / L, K 20-30g / L, Na 5-15g / L, F 10-100mg / L, Tl 0.1-2mg / L, Ca 20-100mg / L, Mg 30-300mg / L, Cl 0.1-1g / L; The pH of the lepidolite leachate is 7 to 9; In S1, the pH is adjusted by using a sodium hydroxide solution with a concentration of 400 to 700 g / L.
3. A method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 1, characterized in that: S2 The adsorption is carried out by static adsorption or dynamic adsorption of resin.
4. The method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 3, characterized in that: The specific method of static adsorption is to mix a lithium mica leachate with a pH of 9 to 12 with a Na-type cation exchange resin in a container, and then let it stand after oscillating and adsorbing on a constant temperature shaker at a speed of 160 r / min for 2 hours; the mass volume ratio of the Na-type cation exchange resin to the lithium mica leachate is 1: (20 to 25) g / ml.
5. The method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 3, characterized in that: The specific method of dynamic adsorption is to fill the Na type cation exchange resin in the exchange column, and pass the lithium mica leachate with pH value of 9 to 12 through the exchange column at a flow rate of 0.6 to 1.0 bv / h.
6. The method for purifying and removing thallium from a lepidolite leachate to prepare lithium carbonate and glauber salt according to claim 1, characterized in that: The desorption treatment method described in S2 is to wash the adsorption saturated resin with ultrapure water, and then desorb the washed resin with 9% sodium chloride solution, and the flow rate of the sodium chloride solution is 0.28 bv / h.
7. The method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 6, characterized in that: S2 also includes regenerating the Na-type cation exchange resin, soaking the desorbed resin in a 5% sodium chloride solution for 12 hours, washing with water until the washing liquid is clear and colorless, soaking it in a 3% sodium hydroxide solution for 24 hours, and washing with water until it is neutral for use.
8. The method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 1, characterized in that: The method for lithium deposition described in S3 comprises: S31: mixing the lithium extraction purification solution with a sodium carbonate solution, wherein the concentration of sodium carbonate is 200 to 300 g / L, and the sodium carbonate is 1.05 to 1.1 times the theoretical calculated amount, first adding 70 to 85% of the total amount of sodium carbonate required, heating to 90 to 95° C. for sufficient reaction, and filtering while hot to obtain a filtrate 1 and a filter residue 1; S32: Mix the filtrate 1 with the remaining sodium carbonate solution, concentrate by evaporation under reduced pressure to a Li content of 12 to 15 g / L, and filter while hot to obtain a lithium precipitation mother liquor and a filter residue 2.
9. A method for purifying and removing thallium from a lepidolite leachate to prepare lithium carbonate and glauber salt according to claim 1 or 8, characterized in that: The specific method of ball milling and slurry washing in S3 is to add 0.5 to 1.5 times the amount of water to the filter residue for ball milling, the ball-to-material ratio is 2 to 3:1, the ball milling speed is 30 to 80 r / min, and the ball milling time is 0.5 to 1 h; add 2 to 3 times the amount of water to the filter residue to the obtained ball milling slurry, heat it to 90 to 95°C, wash it at 50 to 100 r / min for 40 to 60 minutes, filter it while hot, wash it with water and dry it to obtain the lithium carbonate product.
10. The method for preparing lithium carbonate and sodium sulfate by purifying and removing thallium from a lepidolite leachate according to claim 1, characterized in that: The specific method of decarbonization evaporation in S4 is: adding concentrated sulfuric acid to the lithium precipitation mother liquor to adjust the pH to 5-6 for decarbonization, and evaporating the decarbonization mother liquor to 40-50% of the original volume by MVR equipment.