Full-chain integrated lithium recovery method

Abstract

The present disclosure provides a full-chain integrated lithium recovery method, the method comprises the following steps: (1) mixing a lithium-containing material from waste lithium batteries and a reducing agent and then roasting to obtain a roasted sand; (2) concentrating a high calcium chloride brine and then adding sodium dihydrogen phosphate to obtain dicalcium phosphate and a brine solution by solid-liquid separation; and (3) mixing the roasted sand and the brine solution to obtain transition slag calcium carbonate and a mixed solution by solid-liquid separation, mixing the mixed solution with an alkaline solution to adjust the pH, heating and stirring, and then performing solid-liquid separation to obtain a lithium phosphate precipitate and a recovery liquid. The method described in the present disclosure can extract lithium from high calcium chloride salt lake brine while recovering lithium from waste lithium-ion batteries, thus realizing the full-chain integrated recovery of lithium.

Description

A full-chain integrated method for lithium recovery Technical Field

[0001] The present invention relates to the field of resource recovery and relates to a full-chain integrated method for recovering lithium. Background Art

[0002] In recent years, lithium and its compounds have been widely used in many fields such as aerospace, electronic machinery, high-energy batteries, nuclear power generation, etc., and are one of the country's very valuable green resources and strategic mineral resources.

[0003] Lithium resources are primarily found in lithium ores and salt lakes. The cost of extracting lithium from salt lakes is lower than that from ore, making them a significant source of lithium resources. Currently, the more established methods for extracting lithium from salt lakes include precipitation, adsorption, membrane, and extraction. Precipitation is the most established and has a long history. The general process follows: brine → evaporation and concentration → boron removal → calcium and magnesium removal → lithium precipitation with sodium carbonate. While this method offers low production costs, it can only be used to process brines with low magnesium-to-lithium ratios and high lithium concentrations, resulting in low lithium recovery rates.

[0004] CN114906864A discloses a method for extracting lithium from high-calcium chloride salt lake brine. The method comprises: evaporating brine collected from a brine well in a pre-concentration tank under natural conditions to sequentially precipitate sodium chloride, potassium chloride and carnallite (KCl·MgCl2) until the calcium ion concentration of the brine reaches 11-13%; concentrating: further evaporating and concentrating the pre-concentrated brine in a concentration tank to precipitate calcium chloride crystals until the lithium ion concentration of the brine reaches 3-3.5%; extracting and removing boron: removing boron from the concentrated brine by an extraction process; removing calcium and magnesium: removing calcium and magnesium from the brine after boron removal by using sodium hydroxide and sodium carbonate; and lithium precipitation with sodium carbonate: continuously precipitating lithium from the solution after calcium and magnesium removal using sodium carbonate solution at a reaction temperature of 70-95°C. The slurry after lithium precipitation is centrifuged and washed. Finally, the washed lithium carbonate is dried and packaged to obtain a lithium carbonate product.

[0005] CN113998715A discloses a method for extracting lithium from a high-calcium lithium-containing raw material, comprising the following steps: (1) calcium precipitation: adding the calcium-containing and lithium-containing raw material into a reaction vessel, adding a calcium precipitant, stirring to produce calcium sulfate crystals, and separating the solid and liquid to obtain a decalcified lithium-containing mother liquor; (2) nanofiltration: passing the decalcified lithium-containing mother liquor obtained in step (1) through a nanofiltration system to further decalcify and remove other ions with a valence of ≥2 to obtain a lithium-containing filtrate; (3) evaporation concentration: concentrating the lithium-containing filtrate obtained in step (2) by evaporation to obtain a lithium-rich concentrated solution.

[0006] The above solution uses a precipitation method to treat high-calcium chloride brine. The resulting calcium chloride has strong water absorption, typically absorbing more than 50% of its own weight in water. Therefore, when calcium chloride crystallizes, it absorbs a large amount of brine with a high lithium concentration, resulting in a significant lithium loss rate of over 30%. Currently, there is no effective method for recovering lithium from high-calcium chloride brine.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of the present disclosure is to provide a full-chain integrated method for recovering lithium. The method disclosed in the present disclosure can extract lithium from high-calcium chloride salt lake brine while recovering lithium from waste lithium-ion batteries, thus realizing full-chain integrated recovery of lithium.

[0010] To achieve this disclosure purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for recycling lithium in an integrated manner, the method comprising the following steps:

[0012] (1) mixing lithium-containing materials from waste lithium batteries with a reducing agent and then roasting to obtain calcine;

[0013] (2) concentrating the high calcium chloride brine and adding sodium dihydrogen phosphate to separate the solid and liquid to obtain calcium phosphate salt and brine solution;

[0014] (3) Mixing the roasted sand and the brine solution, performing solid-liquid separation to obtain the transition slag calcium carbonate and the mixed solution, mixing the mixed solution with the alkaline solution to adjust the pH, heating and stirring, and performing solid-liquid separation to obtain the lithium phosphate precipitate and the recovered liquid.

[0015] The method described in the embodiment of the present disclosure does not limit the order of operations of step (1) and step (2), and step (1) can be performed first or step (2) can be performed first.

[0016] The disclosed embodiment adds sodium dihydrogen phosphate to the high-calcium chloride brine after evaporation and concentration, so that the highly hygroscopic calcium chloride crystallized in the salt lake brine is converted into non-hydroscopic calcium dihydrogen phosphate, thereby releasing the high-concentration brine absorbed by the calcium chloride, solving the problem of calcium chloride entraining in the high-concentration brine and causing a large amount of lithium loss. The obtained brine is mixed with roasted sand obtained by roasting the positive electrode material of the waste gas lithium battery. The residual calcium ions in the mixed solution A can be removed through precipitation conversion, and the lithium carbonate in the roasted sand is dissolved, so that the lithium in the roasted sand can be recovered, killing two birds with one stone, and finally obtaining lithium dihydrogen phosphate and lithium chloride solution. The pH and temperature are adjusted to finally obtain lithium carbonate precipitate and lithium chloride solution, realizing the full-chain integrated recovery of lithium.

[0017] In one embodiment, the reducing agent in step (1) includes any one of carbon monoxide, coke powder or carbon powder, or a combination of at least two of them.

[0018] In one embodiment, the calcination temperature is 500-1000°C, for example, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C.

[0019] In one embodiment, the calcination time is 2 to 4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0020] In one embodiment, the roasted sand in step (1) includes a transition metal element and lithium carbonate.

[0021] In one embodiment, the high calcium chloride brine in step (2) is concentrated to obtain calcium chloride crystals that have adsorbed a large amount of brine with a high lithium concentration.

[0022] In one embodiment, the concentration of brine adsorbed in the calcium chloride crystals is 25-35 g / L, for example, 25 g / L, 28 g / L, 30 g / L, 32 g / L or 35 g / L.

[0023] In one embodiment, the phosphorus source includes sodium dihydrogen phosphate.

[0024] In one embodiment, the molar ratio of the phosphorus source to the calcium chloride crystals in step (2) is (2-2.1):1, for example: 2:1, 2.02:1, 2.05:1, 2.08:1 or 2.1:1.

[0025] In one embodiment, the calcium phosphate salt in step (2) includes calcium phosphate and / or calcium hydrogen phosphate.

[0026] In one embodiment, the brine solution includes lithium chloride, lithium dihydrogen phosphate, sodium chloride and partially dissolved calcium dihydrogen phosphate.

[0027] The lithium recovery equations described in the embodiments of the present disclosure are as follows: CaCl2·2H2O+NaH2PO4==CaHPO4↓+2NaCl+2H2O+HCl 3CaCl2·2H2O+2NaH2PO4==Ca3(PO4)2↓+2NaCl+2H2O+4HCl Ca(H2PO4)2+Li2CO3==CaCO3↓+2LiH2PO4 3LiH2PO4+6OH - =Li3PO4+6H2O

[0028] In the recovery method described in the embodiment of the present disclosure, a phosphorus source (e.g., sodium dihydrogen phosphate) reacts with calcium chloride to form calcium hydrogen phosphate and / or calcium phosphate precipitate, and the calcium dihydrogen phosphate remaining in the solution dissolves and reacts with subsequently added lithium carbonate to form calcium carbonate precipitate, which is then removed by solid-liquid separation.

[0029] In one embodiment, the roasted sand and brine in step (3) are mixed and then stirred.

[0030] In one embodiment, the stirring time is 0.5 to 1 h, for example, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h.

[0031] In one embodiment, sodium dihydrogen phosphate is added to the mixed solution in step (3).

[0032] In the embodiment of the present disclosure, the addition of sodium dihydrogen phosphate in step (3) can make the lithium ions in the mixed solution completely precipitate into lithium phosphate to the greatest extent, reducing the residual lithium ions in the solution. If an excess of sodium dihydrogen phosphate is added in step (2), according to the solubility product formula, Excessive hydrogen phosphate content will cause the calcium ion concentration to decrease, resulting in insufficient calcium dihydrogen phosphate in the brine solution to react with the lithium phosphate in the roasted sand, making it impossible for the lithium carbonate to be completely dissolved, so there will not be enough calcium ions in the solution to dissolve in the water.

[0033] In one embodiment, the molar ratio of phosphorus element to lithium ion in the mixed solution after adding sodium dihydrogen phosphate is (3.05-3.15):1, for example: 3.05:1, 3.08:1, 3.1:1, 3.12:1 or 3.15:1.

[0034] In one embodiment, the alkaline solution in step (3) comprises aqueous ammonia.

[0035] In one embodiment, the molar concentration of the ammonia solution is 3 to 5 mol / L, for example, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L.

[0036] In one embodiment, the pH is 8-9, for example, 8, 8.2, 8.5, 8.8 or 9.

[0037] In one embodiment, the heating and stirring temperature in step (3) is 45-60°C, for example, 45°C, 48°C, 50°C, 55°C or 60°C.

[0038] In one embodiment, the heating and stirring time is 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes.

[0039] Compared with the prior art, the present disclosure has the following beneficial effects:

[0040] (1) The present invention adds sodium dihydrogen phosphate to the high-calcium chloride brine after evaporation and concentration, thereby converting the highly hygroscopic calcium chloride crystallized in the salt lake brine into non-hydroscopic calcium dihydrogen phosphate, thereby releasing the high-concentration brine absorbed by the calcium chloride, thereby solving the problem of calcium chloride entraining in the high-concentration brine and causing large amounts of lithium loss. Subsequently, solid-liquid separation is performed to obtain a calcium dihydrogen phosphate precipitate and a lithium-containing mixed solution.

[0041] (2) The present invention mixes the obtained lithium mixed solution with the roasted sand of the waste gas lithium battery positive electrode material to remove the residual calcium ions in the mixed solution A through precipitation conversion, and at the same time dissolves the lithium carbonate in the roasted sand, thereby recovering the lithium in the roasted sand, killing two birds with one stone.

[0042] (3) The lithium recovery rate of the method disclosed in the present invention reaches more than 90%, which greatly reduces the cost. DETAILED DESCRIPTION

[0043] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0044] The solubility products of the substances in the embodiments of the present disclosure are as shown in Table 1 below:

[0045] Table 1

[0046] Example 1

[0047] This embodiment provides a method for recycling lithium in an integrated manner, comprising the following steps:

[0048] (1) 1 kg of waste lithium-ion batteries was discharged, disassembled, crushed, and screened to obtain lithium-containing materials (average lithium content of 2%), followed by reduction roasting at 750° C. for 3 h in the presence of carbon monoxide to obtain roasted sand (nickel, cobalt, and manganese elements and approximately 105.8 g of lithium carbonate);

[0049] (2) placing high calcium chloride brine in an evaporation concentration tank, collecting 56.61 kg of calcium chloride crystals in the evaporation concentration tank and placing them in a container (at this time, a large amount of brine with a high lithium concentration (30 g / L) is adsorbed in the calcium chloride crystals, and the mass ratio of calcium chloride to brine is 2:1, so there are 37.74 kg of calcium chloride and 18.87 kg of brine); adding 81.60 kg of sodium dihydrogen phosphate to the container (the molar ratio of calcium chloride to sodium dihydrogen phosphate is 1:2, and according to the solubility, 1.45 mol of calcium dihydrogen phosphate will be dissolved in the solution, and this concentration of calcium dihydrogen phosphate will just dissolve 105.8 g of lithium carbonate), stirring for 30 minutes, at which time the solid is converted into calcium dihydrogen phosphate that does not absorb water, releasing the absorbed brine; at this time, the brine contains lithium chloride, lithium dihydrogen phosphate, sodium chloride and partially dissolved calcium dihydrogen phosphate; then the solid and liquid are separated, the solid is calcium dihydrogen phosphate, and the solution is sodium chloride, lithium chloride, lithium dihydrogen phosphate and calcium dihydrogen phosphate brine solution (Li in the brine solution + : 5861g, i.e. 87.73mol, requires 27.91mol hydrogen phosphate to completely form a precipitate. There are already 2.9mol hydrogen phosphate in the solution, so here you need to add 25.01mol hydrogen phosphate, i.e. 3kg of sodium dihydrogen phosphate);

[0050] (3) The calcined sand and brine solution were mixed and stirred for 0.8 h before solid-liquid separation to obtain a mixed solution containing sodium chloride, lithium dihydrogen phosphate, and lithium chloride, and transition slag calcium carbonate. Subsequently, 3.00 kg of sodium dihydrogen phosphate was added to the mixed solution, stirred evenly, and 4 mol / L ammonia water was added dropwise to adjust the solution pH to 8.5. The solution was stirred at 50°C for 30 min, and solid-liquid separation was performed to obtain lithium phosphate precipitate.

[0051] Example 2

[0052] This embodiment provides a method for recycling lithium in an integrated manner, comprising the following steps:

[0053] (1) 1 kg of waste lithium-ion batteries was discharged, disassembled, crushed, and screened to obtain lithium-containing material (average lithium content of 2%), followed by addition of carbon powder and reduction roasting at 500° C. for 4 h to obtain roasted sand (nickel, cobalt, manganese and approximately 105.8 g of lithium carbonate);

[0054] (2) High calcium chloride brine is placed in an evaporation concentration tank, and 56.61 kg of calcium chloride crystals are collected from the evaporation concentration tank and placed in a container (at this time, a large amount of brine with a high lithium concentration (25 g / L) is adsorbed in the calcium chloride crystals, and the mass ratio of calcium chloride to brine is 2:1, so there are 37.74 kg of calcium chloride and 18.87 kg of brine); 85.68 kg of sodium dihydrogen phosphate is added to the container (the molar ratio of calcium chloride to sodium dihydrogen phosphate is 1:2.1, and according to the solubility, 1.52 mol of calcium dihydrogen phosphate will dissolve in the solution, and this concentration of calcium dihydrogen phosphate will just dissolve 111.1 g of lithium carbonate), and stirred for 30 minutes. At this time, the solid is converted into calcium dihydrogen phosphate that does not absorb water, releasing the absorbed brine; at this time, the brine contains lithium chloride, lithium dihydrogen phosphate, sodium chloride and partially dissolved calcium dihydrogen phosphate; then the solid and liquid are separated, the solid is calcium dihydrogen phosphate, and the solution is sodium chloride, lithium chloride, lithium dihydrogen phosphate and calcium dihydrogen phosphate brine solution (Li in the brine solution + : 5861g, i.e. 87.73mol, requires 27.91mol hydrogen phosphate to completely form a precipitate. There are already 2.9mol hydrogen phosphate in the solution, so here you need to add 25.01mol hydrogen phosphate, i.e. 3kg of sodium dihydrogen phosphate);

[0055] (3) The calcined sand and brine solution were mixed and stirred for 0.8 h before solid-liquid separation to obtain a mixed solution containing sodium chloride, lithium dihydrogen phosphate, and lithium chloride, and transition slag calcium carbonate. Subsequently, 3.00 kg of sodium dihydrogen phosphate was added to the mixed solution, stirred evenly, and then 3 mol / L ammonia water was added dropwise to adjust the solution pH to 8. The solution was stirred at 45°C for 40 min, and solid-liquid separation was performed to obtain lithium phosphate precipitate.

[0056] Example 3

[0057] This embodiment provides a method for recycling lithium in an integrated manner, comprising the following steps:

[0058] (1) 0.3 kg of waste lithium-ion batteries were discharged, disassembled, crushed, and screened to obtain lithium-containing materials (average lithium content of 2%), followed by reduction roasting at 750° C. for 3 h in the presence of carbon monoxide to obtain roasted sand (nickel, cobalt, and manganese elements and approximately 31.74 g of lithium carbonate);

[0059] (2) Place high calcium chloride brine in an evaporation concentration tank, collect 56.61 kg of calcium chloride crystals in the evaporation concentration tank and place them in a container (at this time, a large amount of brine with a high lithium concentration (30 g / L) is adsorbed in the calcium chloride crystals, and the mass ratio of calcium chloride to brine is 2:1, so there are 37.74 kg (34 mol) of calcium chloride and 18.87 kg of brine); add 82.8 kg of sodium dihydrogen phosphate (69 mol) into the container (the molar ratio of calcium chloride to sodium dihydrogen phosphate is 1:2.03, according to the dissolution It is calculated that 0.41 mol of calcium dihydrogen phosphate (19 L of water solvent) will dissolve in the solution. This concentration of calcium dihydrogen phosphate will just dissolve 30.3 g of lithium carbonate (0.41 mol). After stirring for 30 minutes, the solid is converted into calcium dihydrogen phosphate that does not absorb water, releasing the absorbed brine. The brine now contains lithium chloride, lithium dihydrogen phosphate, sodium chloride and partially dissolved calcium dihydrogen phosphate. Then the solid and liquid are separated, the solid is calcium dihydrogen phosphate, and the solution is sodium chloride, lithium chloride, lithium dihydrogen phosphate and calcium dihydrogen phosphate brine solution.

[0060] (3) The calcined sand and brine solution were mixed and stirred for 0.8 h before solid-liquid separation to obtain a mixed solution containing sodium chloride, lithium dihydrogen phosphate, and lithium chloride, and transition slag calcium carbonate. 4 mol / L ammonia water was then added dropwise to the mixed solution to adjust the pH to 8.5. The solution was stirred at 50°C for 30 min, and solid-liquid separation was performed to obtain lithium phosphate precipitate.

[0061] Example 4

[0062] This embodiment provides a method for recycling lithium in an integrated manner, comprising the following steps:

[0063] (1) 1 kg of waste lithium-ion batteries was discharged, disassembled, crushed, and screened to obtain lithium-containing materials (average lithium content of 2%), followed by reduction roasting at 750° C. for 3 h in the presence of carbon monoxide to obtain roasted sand (nickel, cobalt, and manganese elements and approximately 105.8 g of lithium carbonate);

[0064] (2) High calcium chloride brine was placed in an evaporation concentration tank, and 56.61 kg of calcium chloride crystals were collected from the evaporation concentration tank and placed in a container (at this time, a large amount of brine with a high lithium concentration (30 g / L) was adsorbed in the calcium chloride crystals, and the mass ratio of calcium chloride to brine was 2:1, so there were 37.74 kg (34 mol) of calcium chloride and 18.87 kg of brine); 87.6 kg of sodium dihydrogen phosphate (73 mol) was added to the container (the molar ratio of calcium chloride to sodium dihydrogen phosphate was 1: 2.15, based on the solubility calculation, 0.127 mol of monocalcium phosphate will dissolve in the solution. This concentration of monocalcium phosphate will just dissolve 9.3 g of lithium carbonate). Stir for 30 minutes, at which point the solid transforms into monocalcium phosphate that does not absorb water, releasing the absorbed brine; the brine now contains lithium chloride, lithium dihydrogen phosphate, sodium chloride, and partially dissolved monocalcium phosphate; then the solid-liquid separation is performed, the solid is monocalcium phosphate, and the solution is sodium chloride, lithium chloride, lithium dihydrogen phosphate, and monocalcium phosphate brine solution;

[0065] (3) The calcined sand and brine solution were mixed and stirred for 0.8 h before solid-liquid separation to obtain a mixed solution containing sodium chloride, lithium dihydrogen phosphate, and lithium chloride, and transition slag calcium carbonate. Subsequently, 3.00 kg of sodium dihydrogen phosphate was added to the mixed solution, stirred evenly, and 4 mol / L ammonia water was added dropwise to adjust the solution pH to 8.5. The solution was stirred at 50°C for 30 min, and solid-liquid separation was performed to obtain lithium phosphate precipitate.

[0066] Example 5

[0067] The only difference between this embodiment and embodiment 1 is that the pH in step (3) is 7.5, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0068] Example 6

[0069] The only difference between this embodiment and embodiment 1 is that the pH in step (3) is 9.5, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and the embodiment is that the sodium dihydrogen phosphate in step (1) is replaced with sodium sulfate of the same amount of substance, and the other conditions and parameters are exactly the same as those in Example 1.

[0072] Performance testing:

[0073] The lithium recovery results of the methods described in Examples 1-6 are shown in Table 2:

[0074] Table 2

[0075] As can be seen from Table 2, the lithium recovery rate of the method disclosed in the present invention reaches more than 70%. By controlling the pH of step (3) and the timing of adding sodium dihydrogen phosphate, the lithium recovery rate reaches more than 90%, which greatly reduces the cost and realizes the recovery of lithium from waste lithium-ion batteries.

[0076] From the comparison between Example 1 and Example 3, it can be seen that the present disclosure does not add sodium dihydrogen phosphate in step (3), resulting in that the lithium ions in the mixed solution cannot be completely precipitated into lithium phosphate, and thus a large amount of lithium ions still remain in the solution.

[0077] By comparing Example 1 and Example 4, it can be seen that in the method disclosed herein, if an excess of sodium dihydrogen phosphate is added in step (2), according to the solubility product formula, Excessive hydrogen phosphate content will reduce the calcium ion concentration, resulting in insufficient calcium dihydrogen phosphate in the brine solution to react with the lithium phosphate in the roasted sand, making it impossible for the lithium carbonate to dissolve completely. As a result, there is insufficient calcium ion in the solution to dissolve in the water. Of course, the lithium recovery rate can be further improved by reducing the amount of roasting added or increasing the amount of brine introduced.

[0078] By comparing Example 1 with Examples 5-6, it can be seen that in the method described in the present disclosure, the pH of step (3) affects the lithium recovery rate. When the pH is controlled at 8-9, the lithium recovery rate is higher. If the pH is too low, the lithium phosphate cannot be completely precipitated. If the pH is too high, the recovery rate of lithium phosphate cannot be improved, but other cationic impurities may be precipitated.

[0079] A comparison of Example 1 and Comparative Example 1 shows that after adding sodium sulfate to react with calcium chloride to produce calcium sulfate in the comparative example, a large amount of brine remains in the calcium sulfate crystals due to the strong water absorption of calcium sulfate, resulting in a low lithium recovery rate. The present invention adds sodium dihydrogen phosphate to the high-calcium chloride brine after evaporation and concentration, converting the highly hygroscopic calcium chloride crystallized in the salt lake brine into non-hydrogen-absorbing calcium dihydrogen phosphate, thereby releasing the high-concentration brine absorbed by the calcium chloride, thereby solving the problem of calcium chloride entraining high-concentration brine and causing large amounts of lithium loss.

Claims

1. A method for recycling lithium in an integrated manner, the method comprising the following steps: (1) mixing lithium-containing materials from waste lithium batteries with a reducing agent and then roasting the mixture to obtain roasted sand; (2) After the high calcium chloride brine is concentrated, a phosphorus source is added to separate the solid and liquid to obtain calcium phosphate salt and brine solution; (3) Mixing roasted sand and brine solution, obtaining transition slag calcium carbonate and a mixed solution through solid-liquid separation, mixing the mixed solution with an alkaline solution to adjust the pH, heating and stirring, and then performing solid-liquid separation to obtain lithium phosphate precipitate and recovered liquid.

2. The method of claim 1, wherein: The reducing agent in step (1) includes any one of carbon monoxide, coke powder or carbon powder, or a combination of at least two of them.

3. The method according to claim 1 or 2, wherein: The calcination temperature is 500-1000°C; Optionally, the calcination time is 2 to 4 hours.

4. The method according to any one of claims 1 to 3, wherein: The roasted sand in step (1) comprises a transition metal element and lithium carbonate.

5. The method according to any one of claims 1 to 4, wherein: The high calcium chloride brine of step (2) is concentrated to obtain calcium chloride crystals that have absorbed a large amount of lithium-rich brine; Optionally, the concentration of brine adsorbed in the calcium chloride crystals is 25 to 35 g / L.

6. The method of claim 5, wherein: The phosphorus source includes sodium dihydrogen phosphate; Optionally, the molar ratio of the phosphorus source to calcium chloride crystals is (2-2.1):

1.

7. The method according to any one of claims 1 to 6, wherein: The brine solution in step (2) includes lithium chloride, lithium dihydrogen phosphate, sodium chloride and partially dissolved calcium dihydrogen phosphate.

8. The method according to any one of claims 1 to 7, wherein: The calcium phosphate salt includes calcium phosphate and / or calcium hydrogen phosphate.

9. The method according to any one of claims 1 to 8, wherein: Step (3) wherein the roasted sand and the brine are mixed and stirred; Optionally, the stirring time is 0.5 to 1 h.

10. The method according to any one of claims 1 to 9, wherein: Adding sodium dihydrogen phosphate to the mixed solution in step (3); Optionally, after adding sodium dihydrogen phosphate, the molar ratio of phosphorus element to lithium ion in the mixed solution is (3.05-3.15):

1.

11. The method according to any one of claims 1 to 10, wherein: The alkaline solution in step (3) includes aqueous ammonia.

12. The method of claim 11, wherein: The molar concentration of the ammonia water is 3-5 mol / L.

13. The method according to any one of claims 1 to 12, wherein: The pH of step (3) is 8-9.

14. The method according to any one of claims 1 to 13, wherein: The temperature of the heating and stirring in step (3) is 45-60°C.

15. The method according to any one of claims 1 to 14, wherein: The heating and stirring time in step (3) is 20 to 40 minutes.

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