CN108862335B - A kind of method for preparing lithium carbonate with lithium phosphate - Google Patents
A kind of method for preparing lithium carbonate with lithium phosphate Download PDFInfo
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- CN108862335B CN108862335B CN201810804655.2A CN201810804655A CN108862335B CN 108862335 B CN108862335 B CN 108862335B CN 201810804655 A CN201810804655 A CN 201810804655A CN 108862335 B CN108862335 B CN 108862335B
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Abstract
The invention discloses a method for preparing lithium carbonate by using lithium phosphate, which comprises the following steps: dissolving lithium phosphate in acid to generate lithium dihydrogen phosphate and lithium salt; evaporating and separating out crystallized lithium salt; adding water to dissolve the lithium salt, adjusting the pH value to be alkalescent, and filtering to remove impurities to obtain a high-purity lithium salt solution; and adding sodium carbonate into the high-purity lithium salt solution, and filtering and washing to obtain lithium carbonate. According to the invention, the lithium salt and the phosphate radical are separated skillfully by utilizing the solubility difference between the lithium dihydrogen phosphate and other soluble lithium salts, high value-added raw materials are not used in the process, the lithium recovery rate reaches more than 98.5%, and sodium phosphate generated by waste liquid treatment can be provided for manufacturers producing lithium phosphate waste materials. The invention has the advantages of feasible process, high recovery rate, low treatment cost and basically closed process, and can obtain high-quality lithium carbonate products.
Description
Technical Field
The invention relates to the field of lithium carbonate preparation, and particularly relates to a method for preparing lithium carbonate from lithium phosphate.
Background
At present, lithium salt with low concentration or more soluble impurities is treated, and a method for producing lithium phosphate with extremely low solubility by adding sodium phosphate is most frequently adopted, so that the obtained lithium phosphate cannot be directly used as a raw material or a product and cannot be purified by a simple method, and in addition, the application range of the lithium phosphate is extremely narrow, so that the research on a process for converting the lithium phosphate into common lithium carbonate has very important significance in providing a more economic and effective method for lithium salt recovery.
The prior art reports that after lithium phosphate is dissolved, calcium is used for removing phosphate radicals, but the solubility of lithium phosphate is lower than that of calcium phosphate, and the lithium phosphate cannot be realized at all; after the lithium phosphate is dissolved, the lithium carbonate is directly precipitated by using sodium carbonate, but the solubility of the lithium carbonate is far higher than that of the lithium phosphate, so that the lithium phosphate is precipitated again. Therefore, no effective method for converting lithium phosphate into lithium carbonate exists at present.
Disclosure of Invention
The invention aims to provide a method for preparing lithium carbonate by using lithium phosphate, which solves the defects in the prior art.
The invention is realized by the following technical scheme:
a method for preparing lithium carbonate by using lithium phosphate comprises the following steps:
dissolving lithium phosphate in acid to generate lithium dihydrogen phosphate and lithium salt;
evaporating and separating out crystallized lithium salt;
step three, adding water to dissolve the lithium salt, adjusting the pH value to be alkalescent, and filtering to remove impurities to obtain a high-purity lithium salt solution;
and step four, adding sodium carbonate into the high-purity lithium salt solution, and filtering and washing to obtain lithium carbonate.
In the first step, the acid may be an inorganic acid, which may be selected from sulfuric acid, hydrochloric acid, nitric acid, etc., or an organic acid, which may be acetic acid, etc., preferably an inorganic acid, more preferably sulfuric acid. Furthermore, it should be ensured that after complete dissolution of the lithium phosphate, the solution pH is acidic.
Preferably, the evaporation and separation temperature in the second step is-20 ℃ to 30 ℃.
Preferably, the pH value is adjusted to 7.5-9 by sodium hydroxide after the lithium salt is dissolved in the third step.
As a preferred technical scheme, the washing liquid generated in the filtration washing step in the fourth step can be recycled for the dilution of acid in the first step, the dissolution of lithium salt in the third step or the dissolution of sodium carbonate in the fourth step.
As a further preferable technical scheme, the crystallization mother liquor separated in the second step and the mother liquor generated after the precipitation reaction in the fourth step are mixed, the pH value is adjusted to 7.5-9 by sodium hydroxide, and the lithium dihydrogen phosphate is converted into the lithium phosphate for recycling.
Lithium phosphate is almost insoluble in water, its solubility is only slightly greater than barium phosphate in all common phosphates, while barium is highly toxic and not economically feasible for large scale use, so the technical difficulty is how to remove phosphate.
The principle of the invention is that lithium phosphate is dissolved in dilute acid (sulfuric acid is taken as an example below) to generate a mixture of lithium dihydrogen phosphate and lithium sulfate (the reaction process is shown as a formula I), and because the solubility of lithium dihydrogen phosphate is higher, the solubility of lithium sulfate is lower, and the solubility of lithium sulfate is reduced along with the rise of temperature, the concentration and solubility difference of lithium dihydrogen phosphate and lithium sulfate are utilized to evaporate and separate crystalline lithium sulfate monohydrate (the solubility of other lithium salts such as lithium chloride, lithium nitrate and lithium acetate at the same temperature is lower than that of lithium dihydrogen phosphate, and the separation is carried out based on the same principle); dissolving the lithium sulfate, adjusting the pH value to be alkalescent by using sodium hydroxide, filtering to remove generated phosphate impurities, and precipitating and washing the lithium sulfate solution by using a common soda ash method to obtain lithium carbonate (the reaction process is shown as a formula II); and mixing the evaporated mother liquor with the mother liquor generated after the precipitation reaction for reaction, adjusting the pH value to be slightly alkaline by using sodium hydroxide, and converting lithium into lithium phosphate to return to the recovery process (the reaction process is shown as a formula III and a formula IV).
The basic reaction formula is as follows:
Li3PO4+H2SO4+H2O→LiH2PO4+Li2SO4(formula one)
Li2SO4+Na2CO3→Li2CO3↓+Na2SO4(formula II)
3LiH2PO4+6NaOH→Li3PO4↓+Na3PO4+6H2O (type three)
Li2SO4+LiH2PO4+NaOH→Li3PO4↓+Na2SO4+H2O (type four)
The invention utilizes the solubility of the lithium dihydrogen phosphate and the concentration and solubility difference between the lithium dihydrogen phosphate and other lithium salts, skillfully realizes the separation of other soluble lithium salts and phosphate radicals, high value-added raw materials are not used in the process, the lithium recovery rate reaches more than 98.5 percent, the sodium phosphate generated by the waste liquid treatment can be used for precipitating the lithium phosphate, and the sodium phosphate is provided for manufacturers for producing lithium phosphate waste materials. The invention has the advantages of feasible process, high recovery rate, low treatment cost and basically closed process, and can obtain the lithium carbonate product with better quality than the lithium carbonate product on the market.
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FIG. 1 is a process flow diagram of one embodiment of the present invention.
Detailed Description
The invention is illustrated below by means of specific examples, without being restricted thereto.
Example 1:
the whole process is shown in figure 1 and comprises the following steps:
1. washing crude lithium phosphate for later use, wherein the liquid-solid ratio is 3: 1;
2. adding sulfuric acid into an acid-resistant reaction kettle, and diluting to 20% concentration by using the washing liquid obtained in the step 6;
3. adding washed lithium phosphate to ensure that the pH value of the solution is acidic after the lithium phosphate is completely dissolved;
4. evaporating and concentrating the solution, crystallizing to obtain lithium sulfate monohydrate, wherein the liquid-solid separation temperature is-20-30 ℃, the lithium sulfate has low high-temperature solubility, and the lithium dihydrogen phosphate has high-temperature solubility, so that the lithium sulfate monohydrate is separated at a high temperature;
5. after the separated lithium sulfate is dissolved, the PH value is adjusted to be slightly alkaline (7.5-9) by using sodium hydroxide, lithium dihydrogen phosphate precipitated together with the lithium sulfate is precipitated into lithium phosphate, impurities such as calcium, magnesium and the like are also precipitated and removed together, and a pure lithium sulfate solution is obtained after filtration;
6. the lithium sulfate solution is precipitated as lithium carbonate with sodium carbonate, and the lithium carbonate product is obtained after washing (the washing liquid is used for preparing acid and dissolving sodium carbonate in the step 2).
7. And 6, mixing the mother liquor generated in the sodium carbonate precipitation process and the crystallization mother liquor generated in the step 4 for reaction, adding sodium hydroxide to adjust the pH to be slightly alkaline (7.5-9) if necessary, and precipitating lithium dihydrogen phosphate into lithium phosphate for recycling, wherein only waste liquor generated in the process of recovering the crystallization mother liquor is generated in the process, and in the solution, the lithium phosphate has extremely low solubility, so that the loss of the total lithium is less than 1%.
Example 2:
the whole process comprises the following steps:
1. washing crude lithium phosphate for standby, wherein the liquid-solid ratio is 10: 1;
2. adding hydrochloric acid into an acid-resistant reaction kettle, and diluting to 30% concentration by using the washing liquid obtained in the step 6;
3. adding washed lithium phosphate to ensure that the pH value of the solution is acidic after the lithium phosphate is completely dissolved;
4. evaporating and concentrating the solution, crystallizing to obtain lithium chloride, and performing liquid-solid separation at-20-30 ℃;
5. after the separated lithium chloride is dissolved, the PH value is adjusted to be slightly alkaline (7.5-9) by using sodium hydroxide, lithium dihydrogen phosphate precipitated together with the lithium chloride is precipitated into lithium phosphate, impurities such as calcium, magnesium and the like are also precipitated and removed together, and a pure lithium chloride solution is obtained after filtration;
6. the lithium chloride solution is precipitated as lithium carbonate with sodium carbonate and washed to give a lithium carbonate product (the washing solution is used to complex acid and dissolve sodium carbonate in step 2).
7. And 6, mixing the mother liquor generated in the sodium carbonate precipitation process and the crystallization mother liquor generated in the step 4 for reaction, adding sodium hydroxide to adjust the pH to be slightly alkaline (7.5-9) if necessary, and precipitating lithium dihydrogen phosphate into lithium phosphate for recycling, wherein only waste liquor generated in the process of recovering the crystallization mother liquor is generated in the process, and in the solution, the lithium phosphate has extremely low solubility, so that the loss of the total lithium is less than 1%.
Example 3:
the whole process comprises the following steps:
1. washing crude lithium phosphate for standby, wherein the liquid-solid ratio is 15: 1;
2. adding nitric acid into an acid-resistant reaction kettle, and diluting to 40% concentration by using the washing liquid obtained in the step 6;
3. adding washed lithium phosphate to ensure that the pH value of the solution is acidic after the lithium phosphate is completely dissolved;
4. evaporating and concentrating the solution, crystallizing to obtain lithium nitrate, and performing liquid-solid separation at the temperature of-20-30 ℃;
5. after the separated lithium nitrate is dissolved, the PH value is adjusted to be slightly alkaline (7.5-9) by using sodium hydroxide, lithium dihydrogen phosphate precipitated together with the lithium nitrate is precipitated into lithium phosphate, impurities such as calcium, magnesium and the like are also precipitated and removed together, and a pure lithium nitrate solution is obtained after filtration;
6. the lithium nitrate solution is precipitated as lithium carbonate with sodium carbonate, and the lithium carbonate product is obtained after washing (the washing liquid is used for preparing acid and dissolving sodium carbonate in the step 2).
7. And 6, mixing the mother liquor generated in the sodium carbonate precipitation process and the crystallization mother liquor generated in the step 4 for reaction, adding sodium hydroxide to adjust the pH to be slightly alkaline (7.5-9) if necessary, and precipitating lithium dihydrogen phosphate into lithium phosphate for recycling, wherein only waste liquor generated in the process of recovering the crystallization mother liquor is generated in the process, and in the solution, the lithium phosphate has extremely low solubility, so that the loss of the total lithium is less than 1%.
Example 4:
the whole process comprises the following steps:
1. washing crude lithium phosphate for standby, wherein the liquid-solid ratio is 20: 1;
2. adding acetic acid into an acid-resistant reaction kettle, and diluting to 50% concentration by using the washing liquid obtained in the step 6;
3. adding washed lithium phosphate to ensure that the pH value of the solution is acidic after the lithium phosphate is completely dissolved;
4. evaporating and concentrating the solution, crystallizing to obtain lithium acetate, and performing liquid-solid separation at the temperature of 0-30 ℃;
5. after the separated lithium acetate is dissolved, the PH value is adjusted to be slightly alkaline (7.5-9) by using sodium hydroxide, lithium dihydrogen phosphate precipitated together with the lithium acetate precipitates into lithium phosphate, impurities such as calcium, magnesium and the like are also precipitated and removed together, and a pure lithium acetate solution is obtained after filtration;
6. the lithium acetate solution is precipitated as lithium carbonate with sodium carbonate and washed to give a lithium carbonate product (the washing solution is used to complex acid and dissolve sodium carbonate in step 2).
7. And 6, mixing the mother liquor generated in the sodium carbonate precipitation process and the crystallization mother liquor generated in the step 4 for reaction, adding sodium hydroxide to adjust the pH to be slightly alkaline (7.5-9) if necessary, and precipitating lithium dihydrogen phosphate into lithium phosphate for recycling, wherein only waste liquor generated in the process of recovering the crystallization mother liquor is generated in the process, and in the solution, the lithium phosphate has extremely low solubility, so that the loss of the total lithium is less than 1%.
The invention does not use high value-added raw materials in the process, the recovery rate of lithium reaches more than 98.5 percent, and the sodium phosphate generated by the treatment of the waste liquid can be used for precipitating lithium phosphate and is provided for manufacturers producing lithium phosphate waste materials.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. A method for preparing lithium carbonate by using lithium phosphate is characterized by comprising the following steps:
dissolving lithium phosphate in acid to generate lithium dihydrogen phosphate and lithium salt;
evaporating and separating out crystallized lithium salt; in the second step, the evaporation and separation temperature is-20 ℃ to 30 ℃;
adding water to dissolve the lithium salt, adjusting the pH value to 7.5-9, and filtering to remove impurities to obtain a high-purity lithium salt solution;
adding sodium carbonate into the high-purity lithium salt solution, and filtering and washing to obtain lithium carbonate; the washing liquid generated in the filtration washing step in the fourth step can be recycled for the dilution of acid in the first step, the dissolution of lithium salt in the third step or the dissolution of sodium carbonate in the fourth step; and (4) mixing the crystallization mother liquor separated in the second step with the mother liquor generated after the precipitation reaction in the fourth step, adjusting the pH value to 7.5-9 by using sodium hydroxide, and converting the lithium dihydrogen phosphate into lithium phosphate for recycling.
2. The method of claim 1, wherein in step one, the acid is selected from an inorganic acid or an organic acid.
3. The method of claim 2, wherein the mineral acid is selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid.
4. The method of claim 2, wherein the organic acid is acetic acid.
5. The method of claim 1, wherein in step one, the acid is sulfuric acid.
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| CN110127731A (en) * | 2019-05-15 | 2019-08-16 | 上海中锂实业有限公司 | A method of battery-level lithium carbonate is directly prepared by lithium phosphate |
| CN110316747B (en) * | 2019-07-25 | 2022-03-11 | 湖南邦普循环科技有限公司 | Method for comprehensively recovering lithium and phosphorus from lithium phosphate |
| CN110759364A (en) * | 2019-11-13 | 2020-02-07 | 江西金辉锂业有限公司 | Method for preparing high-purity lithium carbonate by using crude lithium phosphate |
| CN113044820A (en) * | 2021-04-28 | 2021-06-29 | 四川思特瑞锂业有限公司 | Method for producing battery-grade lithium dihydrogen phosphate from crude lithium salt |
| CN114751432A (en) * | 2022-03-18 | 2022-07-15 | 瑜华科技(上海)有限公司 | Process method for preparing lithium hydroxide by using lithium phosphate |
| CN114906828B (en) * | 2022-06-28 | 2023-06-23 | 四川思特瑞锂业有限公司 | Method for treating lithium dihydrogen phosphate mother solution |
| US11973225B2 (en) * | 2022-10-04 | 2024-04-30 | Rivian Ip Holdings, Llc | Lithium metal phosphate electrode manufacturing |
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Denomination of invention: A method for preparing lithium carbonate from lithium phosphate Granted publication date: 20210423 Pledgee: Shanghai Bank Co.,Ltd. Fengxian Branch Pledgor: SHANGHAI CHINA LITHIUM INDUSTRIAL Co.,Ltd. Registration number: Y2025980014872 |