CN115448273A - Method for preparing lithium dihydrogen phosphate by using lepidolite as raw material - Google Patents

Method for preparing lithium dihydrogen phosphate by using lepidolite as raw material Download PDF

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CN115448273A
CN115448273A CN202211130865.0A CN202211130865A CN115448273A CN 115448273 A CN115448273 A CN 115448273A CN 202211130865 A CN202211130865 A CN 202211130865A CN 115448273 A CN115448273 A CN 115448273A
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lithium
dihydrogen phosphate
lithium dihydrogen
phosphate
lepidolite
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邓红云
朱强辉
段小勋
陈超凡
徐乐梅
袁璐
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Yichun Yinli New Energy Co ltd
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    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00Phosphorus; Compounds thereof
    • C01B25/16Oxyacids of phosphorus; Salts thereof
    • C01B25/26Phosphates
    • C01B25/30Alkali metal phosphates
    • C01B25/301Preparation from liquid orthophosphoric acid or from an acid solution or suspension of orthophosphates
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Abstract

The invention discloses a method for preparing lithium dihydrogen phosphate by taking lepidolite as a raw material, which comprises the following steps: mixing lepidolite and auxiliary materials in proportion to obtain a mixture; baking at 800 to 1000 ℃ to obtain clinker; cooling, fine grinding, extracting with water to obtain leached slurry, and solid-liquid separating to obtain lithium-containing bittern; adding alkali into lithium-containing brine to remove impurities to obtain a purified solution, and adding acid to obtain an acidizing solution; adding sodium phosphate into the acidizing fluid to obtain lithium phosphate precipitate; dissolving lithium phosphate in dilute phosphoric acid to obtain lithium dihydrogen phosphate solution; evaporating and crystallizing lithium dihydrogen phosphate liquid to obtain a crude product; dissolving the crude product in water, filtering to remove insoluble substances, removing magnetism, and evaporating to crystallize to obtain wet product; and drying and demagnetizing the wet product to obtain the product. The mother liquor and the by-products can be recycled, and the recovery rate of lithium is more than 80 percent; the method has the advantages of environmental friendliness, short process flow, low one-time investment and low production cost, effectively solves the pain point of the traditional process, is easy for industrial production, and has good economic and social benefits.

Description

Method for preparing lithium dihydrogen phosphate by using lepidolite as raw material
Technical Field
The invention belongs to the technical field of rare metal extraction and deep processing, and relates to a process method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material, in particular to a method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material.
Background
Lithium dihydrogen phosphate is mainly used as a raw material for producing lithium iron phosphate. The lithium iron phosphate is mainly used for power batteries, and has been rapidly developed in recent years, the momentum of the lithium iron phosphate exceeds that of ternary materials, and the lithium iron phosphate occupies more than 50% of the market share of positive electrode materials.
The process route for producing lithium iron phosphate mainly comprises the following steps:
(1) and (4) an iron process. The process route is mostly adopted by companies occupying 70 percent of the market share, including Hunan, hubei, guangdong, anhui and the like. The process comprises the steps of mixing ferric phosphate, lithium carbonate and glucose, and sintering the mixture into lithium iron phosphate in a protective atmosphere, wherein the glucose is used for converting Fe into Fe 2+ Reduction to Fe 2+ . Its advantages are high energy density and general cyclic performance.
(2) And (4) carrying out an iron oxide red process. The company Chongqing Terui and Xixin Gaoku are mainly used. The technological process is that lithium carbonate, ferric oxide, monoammonium phosphate and carbon source are mixed and sintered into lithium iron phosphate under protective atmosphere. The advantages are low production cost, but low energy density and cycle performance.
(3) And (4) ferrous oxalate process. The main use company is rich in new energy. The technological process is that lithium dihydrogen phosphate and ferrous oxalate are mixed with small amount of carbon source and sintered into lithium iron phosphate in protecting atmosphere. Its advantages are high energy density, high cyclic performance, low internal resistance and high cost.
Compared with other process routes, the process route of ferrous oxalate plus lithium dihydrogen phosphate has the advantages that the materials needing to be mixed are few in variety and easy to mix uniformly, and the performance of the produced product is more excellent; lithium dihydrogen phosphate provides both lithium and phosphorus sources, and the ferrous oxalate is Fe 2+ And contains a carbon source, unlike other iron sources, fe 3+ An increased amount of carbon source is also required for reduction to Fe 2+ And thus energy consumptionIs significantly reduced. The defect is that the production cost is higher, and the main reason for higher cost is that the traditional lithium dihydrogen phosphate is processed by adopting lithium hydroxide or lithium carbonate as raw materials, so that the cost of the lithium dihydrogen phosphate with equivalent lithium is higher than that of the lithium carbonate.
The traditional lithium dihydrogen phosphate production process is mainly prepared by the reaction of lithium hydroxide monohydrate (part of which is replaced by lithium carbonate for reducing the cost) and phosphoric acid, and the reaction equation taking lithium sulfate as a raw material is as follows:
Figure BDA0003849634450000011
Figure BDA0003849634450000012
LiOH·H 2 O+H 3 PO 4 =LiH 2 PO 4 +H 2 O
Li 2 CO 3 +2H 3 PO 4 =2LiHPO 4 +2H 2 O+CO 2
the process route is adopted by a preparation method of battery-grade lithium dihydrogen phosphate in Jianfeng lithium industry and battery-grade lithium dihydrogen phosphate prepared by the preparation method (CN 101638225B), a preparation method of battery-grade lithium dihydrogen phosphate in Tianqi lithium industry (CN 101269806B), a preparation method of battery-grade lithium dihydrogen phosphate in China general offshore oil company (CN 101702433B), a production method of lithium dihydrogen phosphate in Sichuan lithium (CN 101707782B), a preparation method of lithium dihydrogen phosphate in Shanghai lithium (CN 102030319B) and a preparation method of battery-grade lithium dihydrogen phosphate by recrystallized lithium hydroxide in Baijie Rui new material (CN 102442654R).
Biedi patent "a method for synthesizing lithium dihydrogen phosphate" (CN 101327919B), patent of boster new material "a method for preparing powdery lithium dihydrogen phosphate" (CN 702101660B), and patent of Zhengzhou institute of mineral exploitation (CN 104445128B) use organic solvent in the production process for removing impurities.
The main disadvantage of the above invention is the high manufacturing cost of lithium dihydrogen phosphate due to the long process flow and high cost of producing lithium hydroxide/lithium carbonate.
In another patent of Jianfeng lithium industry, namely a method for preparing battery-grade lithium dihydrogen phosphate by using high-purity lithium carbonate lithium precipitation mother liquor (CN 102351160B), the mother liquor for preparing high-purity lithium carbonate (the main component is lithium bicarbonate) is added with phosphoric acid and sodium phosphate to obtain a mixture of lithium phosphate and lithium dihydrogen phosphate, and then the phosphoric acid is added to generate the lithium dihydrogen phosphate, wherein the purity of the lithium carbonate mother liquor is required to be more than 99.9 percent.
Another patent of Tianqi lithium industry, namely a method for synthesizing lithium dihydrogen phosphate by freezing and separating out impurities (CN 113979413A), provides a novel process for synthesizing lithium dihydrogen phosphate, and lithium sulfate and sodium dihydrogen phosphate are mixed, frozen and separated out sodium sulfate to obtain lithium dihydrogen phosphate.
The reaction equation is as follows:
Figure BDA0003849634450000021
the process is simple and short in flow, but the process does not have a process of removing impurities, and the obtained product has poor quality.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the process method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material is provided, sulfate is used as an auxiliary material, and lithium is converted into soluble lithium by roasting the lepidolite; adding soda ash and sodium hydroxide to remove Ca 2+ 、Mg 2+ 、Fe 3+ 、Al 3+ 、Mn 2+ An isometalated cation; adding sodium phosphate to obtain lithium phosphate precipitate, and washing to separate a large amount of impurities Na, K, rb and Cs; dissolving lithium phosphate into lithium dihydrogen phosphate by adding dilute phosphoric acid; and recrystallizing the lithium dihydrogen phosphate for 1-2 times to obtain high-purity lithium dihydrogen phosphate, wherein the product can be used for manufacturing lithium iron phosphate.
Compared with the traditional lithium salt phosphoric acid conversion process, the method has the advantages that the acid-base consumption is low in the production process, and byproducts can be recycled or comprehensively utilized; the obtained product has stable quality; the process flow is short, the material consumption is low, the energy consumption is low, and the cost is low; simple process, strong practicability, few byproducts, high comprehensive benefit and easy realization of industrial production.
The technical scheme for preparing lithium dihydrogen phosphate by using lepidolite as a raw material comprises the following steps:
(1) And mixing the lepidolite with the auxiliary materials to obtain a mixture. The auxiliary materials are sodium potassium sulfate, calcium sulfate and calcium oxide, and the mass ratio of the auxiliary materials is lepidolite: sodium potassium sulfate: calcium sulfate: calcium oxide =100: (15-30): (15-30): (5-15);
(2) Carrying out roasting reaction on the mixture obtained in the step (1) at 800-1000 ℃ to obtain roasted clinker;
(3) Cooling the roasted clinker obtained in the step (2) to be below 100 ℃, wherein the solid-liquid weight ratio is 1: (0.6-1.5) adding water for leaching, and stirring to leach soluble lithium, sodium, potassium, rubidium and cesium salt to obtain leaching slurry;
(4) Carrying out solid-liquid separation on the leaching slurry obtained in the step (3) to obtain aluminosilicate solid filter residue and lithium-containing brine, and separately treating the aluminosilicate solid filter residue;
(5) Heating the lithium-containing brine obtained in the step (4) to 90-95 ℃, adding sodium hydroxide and sodium carbonate, controlling the pH to 10-12 3 2- Keeping the concentration at 0.5-1 g/L, stirring for 30min under heat preservation to obtain an alkalized liquid, and carrying out solid-liquid separation to obtain a purified liquid;
the partial reaction equation is as follows:
Ca 2+ +CO 3 2- =CaCO 3 ↓,
Mg 2+ +2OH - =Mg(OH) 2 ↓,
Mn2++2OH - +1/2O 2 =MnO 2 ↓,
Fe 3+ +3OH - =Fe(OH) 3 ↓,
Al 3+ +3OH - =Al(OH) 3 ↓,
(6) Purifying the purified liquid obtained in the step (5)Adding sulfuric acid or phosphoric acid, adjusting the pH value to 2-4 to enable OH - And CO 3 2- Is reacted to obtain acidified liquid; the main reaction equation is as follows:
CO 3 2- +2H + =H 2 O+CO 2 ↑,
OH - +H + =H 2 O;
(7) Heating the purified liquid obtained in the step (6) to 70-100 ℃, and according to the mol ratio of Li + :PO 4 3- Slowly adding sodium phosphate (0.95-1.05), stirring for reacting for 1h, filtering and washing to obtain lithium phosphate; returning the filtrate to the step (3) for leaching water after sodium is separated out; the reaction equation is as follows:
3Li + +PO 4 3- =Li 3 PO 4 ↓,
(8) Adding dilute phosphoric acid into the lithium phosphate obtained in the step (7) according to a molar ratio for dissolving, and controlling the concentration of lithium dihydrogen phosphate to be nearly saturated to obtain a primary solution of lithium dihydrogen phosphate; the reaction equation is as follows:
Li 3 PO 4 +2H 3 PO 4 =3LiH 2 PO 4
(9) Evaporating and concentrating the primary lithium dihydrogen phosphate solution obtained in the step (8) until crystallization happens, cooling to 10-45 ℃, performing solid-liquid separation to obtain a crude lithium dihydrogen phosphate product and a primary mother liquor, and returning the primary mother liquor to the step (8) for preparing diluted phosphoric acid;
(10) Adding water to dissolve the lithium dihydrogen phosphate crude product obtained in the step (9), and controlling the concentration of the lithium dihydrogen phosphate to be nearly saturated to obtain a lithium dihydrogen phosphate secondary solution;
(11) Filtering the lithium dihydrogen phosphate secondary solution obtained in the step (10) to remove insoluble substances; adsorbing magnetic foreign matters by using a demagnetizer; evaporating and concentrating the filtrate until crystallization happens, cooling to 10-45 ℃, performing solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother liquor, and returning the secondary mother liquor to the step (10) for dissolving water;
(12) Washing and step drying the wet lithium dihydrogen phosphate product obtained in the step (11); adsorbing magnetic foreign matters by using a demagnetizer; obtaining a lithium dihydrogen phosphate product;
(13) If the product index has higher requirements, the steps (10) to (11) can be repeated, and the evaporation and crystallization are carried out for 1 time.
The invention is mainly characterized in that:
1. the method for replacing lithium in aluminosilicate by adopting a sulfate high-temperature roasting method has the advantages of low cost, less slag and high yield;
compared with the traditional calcium oxide method and the sulfuric acid method, the sodium sulfate and potassium sulfate double salt is obtained from byproducts of the subsequent process, a part of double salt is recycled, and the redundant double salt is used for taking Rb and Cs out of the system. Only new calcium sulfate and calcium oxide need to be supplemented, the cost is low, the slag amount is less, the yield is high, and the industrial production is easy to realize.
2. The lithium ions are precipitated by adopting the phosphate, so that the precipitation efficiency is high;
the solubility of common lithium salts is shown in table 1.
Table 1 solubility of common lithium salts (g/100 mL):
Figure BDA0003849634450000041
* "/" indicates that no data was found.
As can be seen from Table 1, among the common lithium salts, the solubility of lithium phosphate is the lowest, and the lithium precipitation efficiency is the highest. When Li is in solution + The concentration, the same applies hereinafter) was 5g/L, the lithium deposition rate of lithium phosphate was 98.53% (20 ℃ C.), and the lithium deposition rate of lithium carbonate was only 46.21% (20 ℃ C.). The chemistry of lithium phosphate and lithium carbonate dictates that phosphate is an excellent lithium precipitating agent. Therefore, the low-concentration brine just leached can be used for precipitating lithium, and lithium precipitation can be carried out without concentrating the lithium sulfate brine as required in the production of lithium carbonate, so that the investment of concentration equipment such as MVR or triple-effect evaporators is saved.
3. The lithium ions are precipitated by phosphate, so that the separation effect is good;
the lepidolite contains potassium which is about 2 times of the lithium content, rubidium oxide of about 1 percent and cesium oxide of about 0.35 percent besides lithium, and has high industrial utilization value; during the roasting ion replacement process, part of potassium, rubidium and cesium are also converted into soluble salts, so that the obtained lithium-containing solution has poor purity and contains more Na, K, ca, rb and Cs; the lithium carbonate or lithium hydroxide prepared by the solution has lower product purity than lithium carbonate produced by spodumene, and the input yield of the same equipment is lower. According to the method, the lithium ions are precipitated by using the phosphate, na, K, ca, rb and Cs ions can be effectively separated, the purity of the obtained lithium phosphate is high, and the purity of the lithium phosphate is not obviously different from that of lithium phosphate produced by spodumene.
4. The method for separating impurities is ingenious;
in addition to Li ions, the lithium sulfate solution also contains a large amount of Na, K, rb and Cs and a small amount of Ca, mg, mn, fe and Al impurities. The invention makes ingenious use of: (1) under alkaline conditions, by adding OH - And CO 3 2- Make Ca 2+ 、Mg 2+ 、Mn 2+ 、Fe 3+ 、Al 3+ Precipitating with metal cation, and removing divalent metal cation (except Ca) in the solution by solid-liquid separation 2+ Incomplete precipitation); (2) residual calcium ions are further removed by filtering by utilizing the material property that lithium dihydrogen phosphate is acidic and calcium sulfate has low solubility in weak acid; (3) lithium dihydrogen phosphate has large solubility difference under different temperature conditions, and in the precipitation process, a small amount of sodium sulfate, potassium sulfate, rubidium sulfate and cesium sulfate can remain in solution due to salt effect on the thermodynamic principle, and lithium dihydrogen phosphate reaches or is superior to the indexes of battery-grade products through 1-2 times of recrystallization processes.
5. The auxiliary materials are simple and easy to obtain, and the by-products and the mother liquor are recycled;
the auxiliary materials of the invention, namely calcium sulfate and calcium oxide, are low in price; the auxiliary material of the sodium sulfate potassium double salt is a byproduct in the production process, can meet the production requirement and does not need to be purchased; each level of the mother liquor with low content of impurities returns to the previous process, so that the cyclic utilization of the mother liquor is realized.
6. The process flow is simple, the cost is low, and the industrial production is easy to realize;
valuable OH in the process of preparing lithium hydroxide or lithium carbonate from lithium sulfate and converting the lithium hydroxide or lithium carbonate into lithium dihydrogen phosphate - /CO 3 2- Reacting with acid to produceTo worthless H 2 O/CO 2 (ii) a In the process of converting lithium phosphate into lithium dihydrogen phosphate, no valuable substance is lost for dissolution reaction, so the cost is lower; the leaching solution does not need to be concentrated, and the flow is shorter; is easy to realize industrial production.
The invention has the beneficial effects that:
1. the lithium sulfate brine with low concentration and high impurity content can be prepared into lithium dihydrogen phosphate, the one-time investment is low, the process flow is short, and the industrial production is easy to realize;
2. the comprehensive yield is high. The solubility of lithium phosphate in common lithium salt is the lowest, so that the one-time lithium precipitation rate is high, the impurity removal efficiency is high, and the comprehensive yield is high;
3. the product is subjected to an evaporation recrystallization process, and has low impurity, high purity and Li/PO 4 3- The proportion is close to 1:1, and the method has great help for improving the cycle performance of the lithium iron phosphate product;
4. magnetic foreign matters are removed through a magnet, so that the safety performance of the lithium iron phosphate for producing the product is excellent;
5. the raw materials and auxiliary materials are common industrialized products, and are low in price and easy to purchase; short process flow, high impurity removal efficiency and easy realization of industrialization.
The present invention is described in further detail below by way of specific embodiments, but the present invention is not limited thereto, and those skilled in the art can make various changes and substitutions according to the present invention without departing from the spirit of the present invention, which falls within the scope of the appended claims.
Drawings
FIG. 1 is a flow chart of the process for producing lithium dihydrogen phosphate from lepidolite according to the present invention.
Detailed Description
The following are specific examples. The embodiment aims to prepare the battery-grade lithium dihydrogen phosphate, and the product index meets the requirements of YS/T967-2014 battery-grade lithium dihydrogen phosphate.
Example 1
(1) Weighing 5000g of lepidolite with the lithium oxide content of 2.50%, adding 1000g of calcium sulfate, 800g of sodium potassium sulfate double salt and 800g of calcium oxide, and uniformly mixing; roasting at 800 deg.C for 60min to obtain a roasted material; taking out, cooling to room temperature, finely grinding to 200 meshes and passing through 90%, adding 5000mL of water, stirring for 30min, and filtering to obtain leachate and filter residue;
TABLE 2 lepidolite data%
Li Na K Rb Cs
1.16 2.12 6.35 0.83 0.27
TABLE 3 leachate data, g/L
Li Na K Rb Cs Ca Mg Al Fe Mn
9.97 17.25 8.31 0.35 0.12 0.51 0.07 0.18 0.23 1.28
(2) Taking 3000mL of leachate obtained in step (1), heating to 90 ℃, adding NaOH to adjust the pH value to 11, and adding 4g of Na 2 CO 3 And preserving the heat for 30min, and filtering to obtain the purified liquid, wherein the data of the purified liquid are shown in a table 4.
TABLE 4 purification fluid data, g/L
Li Na K Rb Cs Ca Mg Al Fe Mn
9.98 18.26 8.43 0.35 0.12 0.021 ND ND ND ND
* "ND" indicates no detection (trace amount), the same applies below.
(3) Adding sulfuric acid into the purified solution to adjust pH to 3.5, heating to 70 deg.C to make CO 2 Is removed to obtain acidified liquid. According to mol ratio of Li: PO (PO) 4 3- 1.05 adding industrial grade Na 3 PO 4 Adding NaOH to adjust the pH value to 10-11, preserving the heat for 90min, and fully stirring and reacting for 80min to obtain the lithium precipitation slurry.
(4) And (4) carrying out solid-liquid separation on the lithium precipitation slurry obtained in the step (3), and washing to obtain lithium phosphate and a lithium precipitation mother solution.
TABLE 5 lithium phosphate data%
Figure BDA0003849634450000061
Figure BDA0003849634450000071
TABLE 6 mother liquor data
Li,g/L PO 4 3- ,g/L The rate of precipitation of lithium%
0.43 2.51 95.69
(5) Taking 150g (dry basis) of lithium phosphate obtained in the step (4), adding 500mL of water according to the molar ratio of Li 3 PO 4 :H 3 PO 4 =1:2 phosphoric acid was added and the final pH was controlled to 2.8 to obtain an aqueous lithium dihydrogen phosphate solution.
(6) Evaporating and concentrating the lithium dihydrogen phosphate solution obtained in the step (5) until crystals are separated out, and slowly cooling to 10 ℃. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate crude product and primary mother liquor.
TABLE 7 crude lithium dihydrogen phosphate data%
LiH 2 PO 4 Na K Rb Cs Ca SO 4 2-
99.03 0.021 0.006 0.001 0.001 0.006 0.056
(7) Adding purified water into the lithium dihydrogen phosphate crude product obtained in the step (6) according to the solid-liquid mass ratio of 1.8, heating to 80 ℃, adjusting the pH to 2.8, filtering, removing insoluble impurities, evaporating and concentrating until crystals are separated out, and slowly cooling to 45 ℃. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother solution.
(8) And (3) heating and drying the wet lithium dihydrogen phosphate product at the temperature of 50-70-90-110 ℃ in a step manner to obtain a lithium dihydrogen phosphate product.
TABLE 8 lithium dihydrogen phosphate product data%
LiH 2 PO 4 Li/PO 4 3- Na K Rb Cs
99.62 1.00 0.003 0.002 0.0001 0.0001
Ca Fe Pb SO 4 2- Cl - Water-insoluble substance
0.003 0.0005 0.0001 0.005 0.001 ND
As a result, the quality of the lithium dihydrogen phosphate product prepared by the present invention can be confirmed from the data in the table.
Example 2
(1) Weighing 10000g of lepidolite with the lithium oxide content of 3.55%, adding 2000g of calcium sulfate, 2500g of sodium potassium sulfate double salt and 500g of calcium oxide, and uniformly mixing; roasting at 950 deg.C for 60min to obtain a roasted material; taking out, cooling to room temperature, finely grinding to 200 meshes and passing through 90%, adding 10L of water, stirring for 30min, and filtering to obtain leachate and filter residue.
TABLE 9 lepidolite data%
Li Na K Rb Cs
1.65 3.22 8.29 0.98 0.33
TABLE 10 leachate data, g/L
Li Na K Rb Cs Ca Mg Al Fe Mn
14.52 19.88 9.81 0.44 0.15 0.52 0.06 0.13 0.20 0.99
(2) Taking 9L of the leaching solution obtained in the step (1), heating to 90 ℃, adding NaOH to adjust the pH value to 10, and adding 15g of Na 2 CO 3 Fully stirring and precipitating, keeping the temperature for 30min, and performing suction filtration to obtain a purified liquid, wherein the data of the purified liquid are shown in a table 4.
TABLE 11 purification fluid data, g/L
Li Na K Rb Cs Ca Mg Al Fe Mn
14.55 18.26 8.43 0.35 0.12 0.021 ND ND ND ND
(3) Adding phosphoric acid into the purified solution to adjust pH to 2.5, heating to 100 deg.C to make CO 2 Is removed to obtain acidified liquid. According to mol ratio of Li: PO (PO) 4 3- 1.01 adding industrial grade Na 3 PO 4 Adding NaOH to adjust the pH value to 12, preserving the heat for 120min, and fully stirring and reacting for 60min to obtain the lithium precipitation slurry.
(4) And (4) carrying out solid-liquid separation on the lithium precipitation slurry obtained in the step (3), and washing to obtain lithium phosphate and a lithium precipitation mother solution.
TABLE 12 lithium phosphate data%
Li 3 PO 4 Na K Rb Cs Ca SO 4 2-
97.66 0.32 0.026 0.004 0.002 0.022 0.93
TABLE 13 mother liquor data, g/L
Li PO 4 3- Rate of precipitation of lithium%
0.66 1.78 95.46
(5) Taking 600g (dry basis) of the lithium phosphate obtained in the step (4), adding 2000mL of water according to the molar ratio of Li 3 PO 4 :H 3 PO 4 =1:2 phosphoric acid was added and the final pH was controlled to 2.5 to obtain an aqueous lithium dihydrogen phosphate solution.
(6) Evaporating and concentrating the lithium dihydrogen phosphate solution obtained in the step (5) until crystals are separated out, and slowly cooling to 35 ℃. And carrying out solid-liquid separation to obtain a lithium dihydrogen phosphate crude product and a primary mother liquor.
TABLE 14 crude lithium dihydrogen phosphate data%
Figure BDA0003849634450000081
Figure BDA0003849634450000091
(7) Adding purified water into the lithium dihydrogen phosphate crude product obtained in the step (6) according to the solid-liquid mass ratio of 1.9, adjusting the pH value to 2.5, filtering, removing insoluble impurities, evaporating and concentrating until crystals are separated out, and slowly cooling to 16 ℃. Performing solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother solution; the wet lithium dihydrogen phosphate product is washed by a small amount of water, and the obtained washing water and the mother liquor are returned to the previous working procedure together.
(8) And (4) heating and drying the wet lithium dihydrogen phosphate product obtained in the step (7) at the temperature of 50-70-90-120 ℃ in a step manner to obtain a lithium dihydrogen phosphate product.
TABLE 15 lithium dihydrogen phosphate product data%
LiH 2 PO 4 Li/PO 4 3- Na K Rb Cs
99.95 1.02 0.001 0.0005 0.0001 0.0001
Ca Fe Pb SO 4 2- Cl - Water-insoluble substance
0.0025 0.0004 0.0001 0.003 0.0005 ND
Example 3
(1) Weighing 1000Kg of lepidolite with the lithium oxide content of 2.20 percent, adding 200Kg of calcium sulfate, 200Kg of sodium potassium sulfate double salt and 80Kg of calcium oxide, and uniformly mixing; roasting at 1000 deg.C for 90min to obtain a roasted material; taking out, cooling to room temperature, grinding to 200 mesh and 88%, adding 1000L water, heating to 75 deg.C, stirring for 90min, and filtering to obtain leachate and residue.
TABLE 16 lepidolite data%
Li Na K Rb Cs
1.01 1.46 5.47 0.76 0.23
TABLE 17 leachate data, g/L
Li Na K Rb Cs Ca Mg Al Fe Mn
8.38 11.66 6.74 0.28 0.07 0.58 0.09 0.16 0.20 1.07
(2) Taking 900L of the leaching solution obtained in the step (1), heating to 95 ℃, adding NaOH to adjust the pH value to 11, and adding 20KgNa 2 CO 3 Stirring for 30min under heat preservation, and performing solid-liquid separation to obtain purified liquid, wherein the data of the purified liquid are shown in Table 18.
TABLE 18 purification data, g/L
Li Na K Rb Cs Ca Mg Al Fe
8.39 12.39 6.81 0.28 0.07 0.020 ND ND ND
(3) Adding sulfuric acid into the purified solution to adjust pH to 2.8, heating to 85 deg.C to make CO 2 Is expelled, according to the molar ratio of Li: PO (PO) 4 3- 0.99 adding industrial grade Na 3 PO 4 Adding NaOH to adjust pHKeeping the temperature for 60min at 10 ℃, and fully stirring and reacting for 80min to obtain the lithium precipitation slurry.
(4) And (4) carrying out solid-liquid separation on the lithium precipitation slurry obtained in the step (3), and washing to obtain lithium phosphate and a lithium precipitation mother solution.
TABLE 19 lithium phosphate data%
Li 3 PO 4 Na K Rb Cs Ca SO 4 2-
97.89 0.42 0.015 0.006 0.002 0.038 1.97
Table 20 the mother liquor data are shown,
Li,g/L PO 4 3- ,g/L the rate of precipitation of lithium%
0.69 1.25 91.78
(5) Taking 40Kg of lithium phosphate obtained in the step (4) (dry basis), adding 120L of water according to the molar ratio of Li 3 PO 4 :H 3 PO 4 =1:2 phosphoric acid was added and the final pH was controlled to 2.8 to obtain an aqueous lithium dihydrogen phosphate solution.
(6) And (4) evaporating and concentrating the lithium dihydrogen phosphate solution obtained in the step (5) until crystals are separated out, and slowly cooling to 25 ℃. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate crude product and primary mother liquor.
TABLE 21 crude lithium dihydrogen phosphate data%
LiH 2 PO 4 Na K Rb Cs Ca SO 4 2-
98.11 0.067 0.0016 0.002 0.0007 0.009 0.219
(7) Adding purified water into the lithium dihydrogen phosphate crude product obtained in the step (6) according to the mass ratio of 1.7, heating to 90 ℃, adjusting the pH value to 2.5, filtering, removing insoluble impurities, adsorbing magnetic foreign matters by using a permanent magnet with the magnetic field intensity of 1200Gs, evaporating and concentrating until crystals are separated out, slowly cooling to 25 ℃, and adsorbing the magnetic foreign matters by using a magnetic rod with the magnetic field intensity of 8000 Gs. And carrying out solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother solution.
(8) And (3) carrying out step temperature rise drying on the wet lithium dihydrogen phosphate product at 50-70-90-130 ℃, and adsorbing magnetic foreign matters by using an electromagnet with the magnetic field intensity of 1800Gs to obtain the lithium dihydrogen phosphate product.
TABLE 22 lithium dihydrogen phosphate product data%
Figure BDA0003849634450000101
Figure BDA0003849634450000111
Example 4
(1) Same as example 3, step (1). Weighing 1000Kg of lepidolite with the lithium oxide content of 2.20 percent, adding 200Kg of calcium sulfate, 200Kg of sodium potassium sulfate double salt and 80Kg of calcium oxide, and uniformly mixing; roasting at 1000 deg.C for 90min to obtain a roasted material; taking out, cooling to room temperature, grinding to 200 mesh and 88%, adding 1000L water, heating to 75 deg.C, stirring for 90min, and filtering to obtain leachate and residue.
(2) Same as in step (2) of example 3. Taking 900L of the leaching solution obtained in the step (1), heating to 95 ℃, adding NaOH to adjust the pH value to 11, and adding 20KgNa 2 CO 3 Stirring for 30min under heat preservation, and performing solid-liquid separation to obtain purified liquid.
(3) Same as example 3, step (3). Adding sulfuric acid into the purified solution to adjust pH to 2.8, heating to 85 deg.C to make CO 2 Is expelled to obtain acidified liquid. According to mol ratio of Li: PO (PO) 4 3- 0.99 adding industrial grade Na 3 PO 4 Adding NaOH to adjust the pH value to 10, preserving the heat for 60min, and fully stirring and reacting for 80min to obtain the lithium precipitation slurry.
(4) Same as example 3, step (4). And (4) carrying out solid-liquid separation on the lithium precipitation slurry obtained in the step (3), and washing to obtain lithium phosphate and a lithium precipitation mother solution.
(5) Same as example 3, step (5). Taking 40Kg of lithium phosphate (calculated on a dry basis) obtained in the step (4), adding 120L of water, and adding Li according to the molar ratio 3 PO 4 :H 3 PO 4 =1:2 phosphoric acid was added and the final pH was controlled to 2.8 to obtain an aqueous lithium dihydrogen phosphate solution.
(6) Same as example 3, step (6). Evaporating and concentrating the lithium dihydrogen phosphate solution obtained in the step (5) until crystals are separated out, and slowly cooling to 22 ℃. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate crude product and primary mother liquor.
(7) Same as in step (7) of example 3. And (3) adding purified water into the lithium dihydrogen phosphate crude product obtained in the step (6) according to the solid-liquid mass ratio of 1:1, heating to 90 ℃, adjusting the pH to 2.5, filtering, removing insoluble impurities, evaporating and concentrating until crystals are separated out, slowly cooling to 40 ℃, and adsorbing magnetic foreign matters by using a magnetic rod of 8000 Gs. And carrying out solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother solution.
(8) Adding CaO into the lithium deposition mother liquor obtained in the step (4) according to the mol ratio to ensure that PO is 4 3- Formation of Ca 3 (PO 4 ) 2 Precipitating, and adjusting the pH value to 7.0 by using sulfuric acid to obtain phosphorus precipitation mother liquor.
TABLE 23 comparison of data before and after phosphorus deposition
Li,g/L PO 4 3- ,g/L The phosphorus deposition rate%
Before depositing phosphorus 0.69 1.25 /
After depositing phosphorus 0.69 0.05 96.00
(9) Taking part of the phosphorus precipitation mother liquor obtained in the step (8), evaporating and concentrating the phosphorus precipitation mother liquor to Na 2 SO 4 ·K 2 SO 4 The double salt is separated out, and the Na separated out by heat is continuously discharged 2 SO 4 ·K 2 SO 4 And (4) adding new phosphorus precipitation mother liquor continuously to the double salt solid, and continuously evaporating.
(10) When evaporating Li in mother liquor + When the concentration is close to 12g/L, evaporation is stopped, solid-liquid separation is carried out to obtain Na 2 SO 4 ·K 2 SO 4 Double salt solid and mother liquor of thermal sodium precipitation. Mixing the double salt solid and the double salt solid in the step (9) together, entering the step (11), returning the sodium thermal precipitation mother liquor to the step (3), and mixing the sodium thermal precipitation mother liquor and Na together with the acidizing fluid 3 PO 4 And (4) precipitating lithium through reaction.
TABLE 24 comparison of data before and after thermal analysis of double salts, g/L
Li Na K PO 4 3-
Before thermal precipitation of double salt 0.69 32.55 6.82 0.05
After heat precipitating double salt 11.52 47.86 34.61 1.01
(11) Na obtained in the steps (9) and (10) 2 SO 4 ·K 2 SO 4 And (3) drying the double salt, and returning to the step (1) to be used as a roasting auxiliary material.
(12) Returning the lithium precipitation mother liquor obtained in the step (4) to the step (3), and mixing with the acidification liquor and Na 3 PO 4 And (5) precipitating lithium through reaction.
(13) Returning the primary mother liquor obtained in the step (6) to the step (3), and mixing with the acidification liquid and Na 3 PO 4 And (5) precipitating lithium through reaction.
(14) And (5) returning the secondary mother liquor obtained in the step (7) to the step (5) for dissolving water, wherein the lithium dihydrogen phosphate solute is added into corresponding water according to a proportion.
Example 5
(1) Same as example 3, step (1). Weighing 1000Kg of lepidolite with the lithium oxide content of 2.20 percent, adding 200Kg of calcium sulfate, 200Kg of sodium potassium sulfate double salt and 80Kg of calcium oxide, and uniformly mixing; roasting at 1000 deg.C for 90min to obtain a roasted material; taking out, cooling to room temperature, fine grinding to 200 mesh and passing through 88%, adding 1000L water, heating to 75 deg.C, stirring for 90min, and filtering to obtain leachate and filter residue.
(2) Same as in step (2) of example 3. Taking 900L of the leaching solution obtained in the step (1), heating to 95 ℃, adding NaOH to adjust the pH value to 11, and adding 20KgNa 2 CO 3 Stirring for 30min under heat preservation, and performing solid-liquid separation to obtain purified liquid.
(3) Same as example 3, step (3). Adding sulfuric acid into the purified solution to adjust pH to 2.8, heating to 85 deg.C to make CO 2 Is removed to obtain acidified liquid. According to the mol ratio of Li: PO 4 3- 0.99 adding industrial grade Na 3 PO 4 Adding NaOH to adjust the pH value to 10, preserving the heat for 60min, and fully stirring and reacting for 80min to obtain the lithium precipitation slurry.
(4) Same as example 3, step (4). And (4) carrying out solid-liquid separation on the lithium precipitation slurry obtained in the step (3), and washing to obtain lithium phosphate and a lithium precipitation mother solution.
(5) Same as example 3, step (5). Taking 40Kg of lithium phosphate obtained in the step (4) (dry basis), adding 120L of water according to the molar ratio of Li 3 PO 4 :H 3 PO 4 =1:2 phosphoric acid was added and the final pH was controlled to 2.8 to obtain an aqueous lithium dihydrogen phosphate solution.
(6) Same as example 3, step (6). Evaporating and concentrating the lithium dihydrogen phosphate solution obtained in the step (5) until crystals are separated out, and slowly cooling to 15 ℃. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate crude product and primary mother liquor.
(7) Same as in step (7) of example 3. And (3) adding purified water into the lithium dihydrogen phosphate crude product obtained in the step (6) according to the solid-liquid mass ratio of 1.8, heating to 90 ℃, adjusting the pH to 2.5, filtering, removing insoluble impurities, evaporating and concentrating until crystals are separated out, slowly cooling to 12 ℃, and adsorbing magnetic foreign matters by using a magnetic bar of 8000 Gs. And performing solid-liquid separation to obtain a lithium dihydrogen phosphate wet product and a secondary mother solution.
(8) Cooling the lithium precipitation mother liquor obtained in the step (4) to 0 ℃ under stirring, and performing cold precipitation to obtain Na 2 SO 4 ·10H 2 O and K 2 SO 4 A solid mixture and a cold sodium separation mother liquor.
TABLE 25 comparison of data before and after cold-separation of double salts, g/L
Li Na K PO 4 3-
Before thermal precipitation of double salt 0.69 32.55 6.82 0.05
Before thermal precipitation of double salt 0.85 5.87 3.85 0.07
(9) Na obtained in the step (8) 2 SO 4 ·10H 2 O and K 2 SO 4 The mixed salt is dried and then returned to the step (1) to be used as a roasting auxiliary material.
(10) Returning the cold sodium separation mother liquor obtained in the step (8) to the step (3), and mixing the cold sodium separation mother liquor with the acidification liquid and Na 3 PO 4 And (4) precipitating lithium through reaction.
(11 same as example 4, step (12). The lithium precipitation mother liquor obtained in step (4) is returned to step (3), and together with the acidified solution, na is added 3 PO 4 And (5) precipitating lithium through reaction.
(12) Same as in (13) of example 4. Returning the primary mother liquor obtained in the step (6) to the step (3), and mixing with the acidification liquid and Na 3 PO 4 And (5) precipitating lithium through reaction.
(13) Same as example 4, step (14). And (5) returning the secondary mother liquor obtained in the step (7) to the step (5) for dissolving water, wherein the lithium dihydrogen phosphate solute is added into corresponding water according to a proportion.
Example 6
(1) And (5) adding 8L of water into 10Kg of lithium dihydrogen phosphate product obtained in the step (8) of the step (3), heating to 90 ℃ to ensure that the lithium dihydrogen phosphate solution reaches a saturated state, adding to obtain a three-time solution of lithium dihydrogen phosphate, and adjusting the pH value to 2.6.
(2) And (2) evaporating and concentrating the lithium dihydrogen phosphate tertiary solution obtained in the step (1) until crystals are separated out, cooling to 20 ℃, and carrying out solid-liquid separation to obtain a lithium dihydrogen phosphate wet product.
(3) And (3) carrying out stepped heating drying on the lithium dihydrogen phosphate wet product obtained in the step (2) to obtain a lithium dihydrogen phosphate product.
TABLE 26 lithium dihydrogen phosphate product data%
Figure BDA0003849634450000131
Figure BDA0003849634450000141
Description of the drawings: the quality of the product prepared by the method of the invention meets the quality requirement.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. All fall within the scope of the patent protection.

Claims (7)

1. A method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material is characterized by comprising the following steps:
(1) Mixing lepidolite with auxiliary materials to obtain a mixture;
(2) Compacting and roasting the mixture obtained in the step (1) to obtain roasted clinker;
(3) Cooling the roasted clinker obtained in the step (2) to be below 100 ℃, adding extraction water, and stirring to leach soluble lithium sodium potassium rubidium cesium salt to obtain leaching slurry;
the leaching slurry contains a mixed salt solution and solid aluminosilicate;
(4) Carrying out solid-liquid separation on the leaching slurry obtained in the step (3), wherein the obtained filter residue is aluminosilicate, the filtrate is lithium-containing brine containing lithium, sodium, potassium, rubidium and cesium, and the aluminosilicate filter residue is separately treated;
(5) Heating the lithium-containing brine obtained in the step (4) to 70-100 ℃, adding sodium carbonate and sodium hydroxide, and filtering to remove precipitates to obtain a purified solution;
(6) Heating the purified liquid obtained in the step (5) to 70-100 ℃, and slowly adding sodium phosphate to obtain lithium phosphate precipitate and lithium precipitation mother liquor; returning the lithium precipitation mother liquor to the step (3) for extracting water after sodium and potassium double salt precipitation;
(7) Washing the lithium phosphate obtained in the step (6), and adding dilute phosphoric acid according to a molar ratio to obtain a lithium dihydrogen phosphate solution;
(8) Filtering the lithium dihydrogen phosphate obtained in the step (7) to remove insoluble substances, so as to obtain purified lithium dihydrogen phosphate liquid;
(9) Evaporating and concentrating the lithium dihydrogen phosphate purified solution obtained in the step (8) until lithium dihydrogen phosphate is just separated out, cooling, filtering and washing to obtain a lithium dihydrogen phosphate crude product and an impurity-containing lithium dihydrogen phosphate mother solution; washing the crude product with water, and returning the washing water to the step (7) for preparing diluted phosphoric acid; the mother liquor returns to the step (7) for washing;
(10) Dissolving the lithium dihydrogen phosphate crude product obtained in the step (9) in water, and adsorbing magnetic foreign matters by using a demagnetizer;
evaporating and concentrating until lithium dihydrogen phosphate is just separated out, cooling, filtering and washing to obtain a lithium dihydrogen phosphate wet product and an impurity-containing lithium dihydrogen phosphate mother liquor; the mother liquor returns to the step (9) to be used as washing water;
(11) Washing and drying the wet lithium dihydrogen phosphate product obtained in the step (10), and adsorbing magnetic foreign matters by using a demagnetizer to obtain a lithium dihydrogen phosphate product;
the washing water is returned to the step (10) to be used as the dissolving water.
2. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, wherein: the auxiliary materials in the step (1) are a mixture of sodium potassium sulfate double salt, calcium sulfate and calcium oxide, and the mass ratio of the auxiliary materials is as follows: sodium potassium sulfate: calcium sulfate: calcium oxide =100: (15-30): (15-30): (5-15).
3. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, characterized in that: the roasting temperature of the step (2) is 800-1000 ℃.
4. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, characterized in that: in the step (6), the method for separating sodium is cold separation or hot separation.
5. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, wherein: in the step (7), the concentration of lithium dihydrogen phosphate is controlled to be nearly saturated.
6. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, characterized in that: in the step (11), the drying mode is step drying.
7. The method for preparing lithium dihydrogen phosphate by using lepidolite as a raw material according to claim 1, characterized in that: in the step (12) and the step (11), a demagnetizer is used for adsorbing magnetic foreign matters, and a permanent magnet or electromagnetic mode can be adopted, wherein the magnetic field intensity is not less than 6000Gs.
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CN111137908A (en) * 2019-12-27 2020-05-12 长沙市原鹏化工科技有限公司 System method for extracting lithium-containing brine from lepidolite and manufacturing lithium salt
CN113636579A (en) * 2021-09-10 2021-11-12 宜春银锂新能源有限责任公司 Process for preparing lithium carbonate by novel lepidolite sulfate roasting method

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