Method for recovering lithium, phosphorus and aluminum in phosphorus-aluminum-lithium ore

Abstract

The invention discloses a method for recovering lithium, phosphorus and aluminum in phosphorus-aluminum-lithium ore. The method comprises the following steps: (1) mixing the phosphorus-aluminum-lithium ore with sulfuric acid and roasting; (2) the roasted material is leached, lithium carbonate is precipitated after impurities are removed from a leaching solution, and lithium recovery is completed; (3) adding water into the leaching residues, dissolving with concentrated sulfuric acid, filtering, adding ammonium sulfate for hydrolysis, cooling and crystallizing to obtain aluminum ammonium sulfate crystals and mother liquor, and completing the recovery of aluminum; and (4) extracting the mother liquor to obtain phosphoric acid and / or phosphate, thereby completing the recovery of phosphorus. According to the method, lithium, aluminum and phosphorus in phosphorus aluminum lithium can be independently recovered to prepare different products, the purity of the finally obtained product is remarkably improved, the recovery rate of lithium in the product reaches 95% or above, and the purity and the recovery rate of recovered aluminum ammonium sulfate and phosphate are both at a high level.

Description

Technical Field

[0001] The invention relates to the technical field of mineral processing, and in particular to a method for recovering lithium, phosphorus and aluminum resources from lithium aluminum phosphate ore. Background Art

[0002] Lithium ore is a key mineral that is vital to the country's economic development and national security, and is an indispensable mineral raw material for the development of the new energy industry. Lithium aluminum phosphate is a fluorophosphate containing lithium and aluminum, with a general chemical formula of LiAlPO4(F, OH). The theoretical content of lithium in lithium aluminum phosphate is 4.76% (Li2O: 10.2%), but the lithium content of most economic ores is 3.5%~4.4% (Li2O: 7.5%~9.5%). At present, there are three main routes for lithium extraction technology of lithium aluminum phosphate, the first is high-temperature roasting method with sulfuric acid; the second is high-temperature roasting method with inorganic salts; the third is alkaline dissolution method. These methods are only for lithium extraction, and P and Al in lithium aluminum phosphate also have high recovery value. The existing technology for recovering lithium, phosphorus and aluminum from phosphate-aluminum-lithium ore is shown in the patent "A method for comprehensive extraction of lithium, aluminum and phosphorus resources from phosphate-aluminum-lithium ore" (CN117070772A). This method is to extract lithium from phosphate-aluminum-lithium ore powder and aluminum sulfate by water leaching after high-temperature roasting, and then dissolving the slag with strong acid to obtain aluminum-phosphorus solution after lithium extraction, and neutralizing the solution with alkali to obtain aluminum phosphate product. However, this method adds aluminum sulfate, which brings a large amount of aluminum into the lithium sulfate solution, resulting in a large amount of slag and a large loss of lithium during the aluminum sulfate removal process. In addition, for the aluminum phosphate product recovered from the slag after lithium extraction, other metal elements in the ore will be brought into the product if it is simply prepared by acid dissolution and alkali neutralization, and a pure aluminum phosphate product cannot be obtained. Summary of the invention

[0003] The present invention provides a method for recovering lithium, aluminum and phosphorus from minerals, which is used to solve the technical problem of low purity of the recovered products in the prior art mentioned in the background technology.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore, comprising the following steps: (1) mixing the lithium aluminum phosphate ore with sulfuric acid and roasting to obtain a roasting material; (2) leaching the roasted material with water or a low-concentration lithium solution (a lithium sulfate solution with a concentration of 0.0 to 10 g / L) to obtain a leachate and a leachate residue, removing impurities from the leachate to precipitate lithium carbonate, thereby completing lithium recovery; (3) adding water to the leached residue to obtain a slurry, dissolving the slurry with concentrated sulfuric acid and filtering it, heating the filtrate and adding ammonium sulfate, cooling and crystallizing after the ammonium sulfate is dissolved to obtain ammonium aluminum sulfate crystals and mother liquor, thereby completing the recovery of aluminum; (4) Extracting the mother liquor to obtain phosphoric acid and / or phosphates, thereby completing the recovery of phosphorus.

[0005] The design idea of ​​the above technical solution is that in the phosphate-aluminum lithium ore, the molar amount of cationic aluminum is greater than that of anionic phosphate. The addition of aluminum sulfate in the existing conventional technology will result in excessive aluminum content in the lithium solution during lithium leaching, which is not conducive to the removal of impurities in the lithium solution. In addition, due to the presence of a large number of other metal ions in the ore, the purity of the product obtained by the conventional technology in recovering aluminum phosphate is not high. On the one hand, the present invention avoids the adverse effect of the aluminum content in the lithium solution on impurity removal by adding sulfuric acid for roasting. On the other hand, aluminum sulfate crystals are obtained by cooling and crystallizing, and then phosphoric acid is obtained by extraction, and aluminum and phosphorus are recovered separately. Lithium, aluminum, and phosphorus in phosphate-aluminum lithium can be separately recovered to make different products, thereby improving the purity of the final product obtained and solving the problems implied by the existing conventional technology.

[0006] As a further preferred embodiment of the above technical solution, in step (2), the low-concentration lithium solution is a lithium sulfate solution with a concentration of 0.0-10 g / L. In the present invention, water or washing water from washing lithium leaching slag is used as the leaching solution in the leaching process instead of dilute acid, thereby avoiding the problem of high impurities in the leached lithium sulfate solution caused by using dilute acid.

[0007] As a further preferred embodiment of the above technical solution, in step (3), the liquid-to-solid ratio of water to leached residue is 1:(1-3), the dissolution temperature is 50-90°C, and the dissolution time is 1-3h.

[0008] As a further preferred embodiment of the above technical solution, in step (3), the amount of concentrated sulfuric acid used is 0.8 to 1.2 times the amount of phosphate acid consumed in the leaching residue.

[0009] As a further preferred embodiment of the above technical solution, the amount of concentrated sulfuric acid used is 1.1 times the amount of phosphate acid consumed in the leaching residue.

[0010] As a further preferred embodiment of the above technical solution, in step (3), the filtrate is heated to 80° C. and ammonium sulfate is added, and the amount of ammonium sulfate added is 1 to 1.2 times the theoretical amount.

[0011] As a further preferred embodiment of the above technical solution, in step (3), the temperature of the cooling crystallization operation is -5~0°C.

[0012] As a further preferred embodiment of the above technical solution, in step (4), when extracting the mother liquor, the extractant is tributyl phosphate, and the stripping agent is pure water, ammonia water or sodium hydroxide solution.

[0013] As a further preferred embodiment of the above technical solution, in step (4), the raffinate obtained by extracting the mother liquor is returned to step (3) for use. This operation allows the aluminum and phosphorus that were not recovered in the first time to re-enter the system for circulation, thereby improving the recovery rate of aluminum and phosphorus.

[0014] As a further preferred embodiment of the above technical solution, in step (1), the phosphate aluminum lithium ore is ground to a particle size D90≤74 μm and then mixed with sulfuric acid and roasted.

[0015] As a further preferred embodiment of the above technical solution, in step (1), the mass ratio of the lithiatetrafluoroethylene ore to sulfuric acid is 1:(0.2-0.5).

[0016] As a further preferred embodiment of the above technical solution, in step (1), the mixed roasting operation of the phosphate aluminum lithium ore and sulfuric acid is divided into two roasting operations, the temperature of the first roasting stage is 180-300°C, and the insulation time is 1h; the temperature of the second roasting stage is 800-850°C, and the insulation time is 1h.

[0017] As a further preferred embodiment of the above technical solution, in step (2), the leaching temperature of the leaching operation is 60° C., and the leaching time is 0.5 to 2 hours; and the liquid-to-solid ratio of the water or low-concentration lithium solution to the roasting material is 1:(1 to 1.5).

[0018] As a further preferred embodiment of the above technical solution, in step (2), after the leaching operation is completed, the leached residue is washed several times with water or a low-concentration lithium solution at a liquid-to-solid ratio of 1:1.

[0019] The present invention has the following beneficial effects: The present invention can separately recover lithium, aluminum and phosphorus in lithium aluminum phosphate to prepare different products, and significantly improves the purity of the final product. The recovery rate of lithium in the product reaches more than 95%, and the purity and recovery rate of the recovered ammonium aluminum sulfate and phosphate are both at a relatively high level. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the embodiments thereof, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0021] Embodiment 1: The method for recovering lithium, phosphorus and aluminum from phosphate-aluminum-lithium ore with all components of the present embodiment comprises the following steps: (1) crushing, grinding and passing 200 g of lithium aluminum phosphate ore through a 200-mesh sieve to obtain lithium aluminum phosphate ore powder; (2) Mix the ground lithium aluminum phosphate ore powder and 60g of concentrated sulfuric acid, with the mass ratio of lithium aluminum phosphate ore powder to sulfuric acid being 1:0.3; (3) Roast the ore powder after mixing with acid in two stages. The first stage is calcined at 300°C for 1 hour, and the second stage is calcined at 800°C for 1 hour. (4) Lithium extraction by water leaching: the calcined material is added with water at a liquid-to-solid ratio of 1:1, and water is immersed at 60°C for 1 hour to obtain leaching residue and leaching solution; the leached residue is then washed twice with water at a liquid-to-solid ratio of 1:1 to obtain a high-concentration lithium sulfate solution and washing water, the high-concentration lithium solution is used to remove impurities and precipitate lithium carbonate, and the washing water is used as the bottom liquid for the next water leaching. In this process, the lithium leaching rate reaches 95%, and the mass proportion of lithium in the leaching residue after water washing is 0.15%; (5) Acid dissolution: Add 300g of water to 150g of leached residue for pulping, heat to 80°C, and then add 135g of concentrated sulfuric acid to dissolve. Keep warm for 2 hours and then filter. Wash the residue twice at a liquid-to-solid ratio of 1:1. The residue is waste residue, and the filtrate is a mixture of aluminum sulfate and phosphoric acid. In this process, the leaching rate of aluminum reaches 87%, and the leaching rate of phosphorus reaches 99.8%; (6) Recovery of aluminum: 300 ml of the filtrate was heated to 70 °C, and 50 g of ammonium sulfate was added. After dissolving, it was cooled and crystallized at 0 °C to obtain 343 g of ammonium aluminum sulfate crystals and 50 mL of phosphoric acid solution containing a small amount of aluminum sulfate (mother liquor). The recovery rate of aluminum in this process was 95%; (7) Phosphorus recovery: The mother liquor is extracted by a multi-stage countercurrent method. The extractant is tributyl phosphate. Pure water is used for stripping. The stripping liquid is phosphoric acid. The phosphorus extraction rate in this process reaches 81%. The raffinate is returned to step (5) for use.

[0022] In this embodiment, the detection of lithium aluminum phosphate ore raw materials is shown in Table 1: Table 1. Elemental composition of lithium aluminum ore of Example 1

[0023] Considering the leaching rate and recovery rate, the recovery rate of lithium reached 95%, the recovery rate of aluminum reached 82.6%, and the recovery rate of phosphorus reached 80.8% (the data given in Examples 1-3 are only the recovery rates of single recovery, and a higher recovery rate can be obtained if a cyclic recovery method is adopted).

[0024] Embodiment 2: The method for recovering lithium, phosphorus and aluminum from phosphate-aluminum-lithium ore with all components of the present embodiment comprises the following steps: (1) crushing, grinding and passing 1000 g of lithium aluminum phosphate ore through a 200-mesh sieve to obtain lithium aluminum phosphate ore powder; (2) Mix the ground lithium aluminum phosphate ore powder and 350 g of concentrated sulfuric acid, with the mass ratio of lithium aluminum phosphate ore powder to sulfuric acid being 1:0.35; (3) The ore powder mixed with acid is roasted in two stages. The first stage is at 180°C and kept warm for 1 hour. The second stage is at 800°C and kept warm for 1.5 hours. (4) Lithium extraction by water leaching: The calcined material was added with water at a liquid-to-solid ratio of 1:1, and the mixture was immersed in water at 60°C for 0.5 hours to obtain leached residue and leached liquid; the leached residue was then washed twice with water at a liquid-to-solid ratio of 1:1 to obtain a high-concentration lithium sulfate solution and washing water; the high-concentration lithium solution was used to remove impurities and precipitate lithium carbonate, and the washing water was used as the bottom liquid for the next leaching. In this process, the lithium leaching rate reached 96%, and the mass proportion of lithium in the leached residue after water washing was 0.13%; (5) Acid dissolution: Add 1300g of water to 900g of leached residue for pulping, heat to 80°C, and then add 850g of concentrated sulfuric acid to dissolve. Keep warm for 2 hours and then filter. Wash the residue twice at a liquid-to-solid ratio of 1:1. The residue is waste residue, and the filtrate is a mixture of aluminum sulfate and phosphoric acid. In this process, the leaching rate of aluminum reaches 85%, and the leaching rate of phosphorus reaches 98%; (6) Recovery of aluminum: 1800 ml of the filtrate was heated to 70°C, and 300 g of ammonium sulfate was added. After dissolving, the mixture was cooled and crystallized at -3°C to obtain 2000 g of ammonium aluminum sulfate crystals and 300 mL of phosphoric acid solution (mother liquor) containing a small amount of aluminum sulfate. The recovery rate of aluminum in this process was 92%; (7) Phosphorus recovery: The mother liquor is extracted by a multi-stage countercurrent method. The extractant is tributyl phosphate. Ammonia water is used for stripping. The stripping liquid is diammonium phosphate. The phosphorus extraction rate in this process reaches 83%. The raffinate is returned to step (5) for use.

[0025] In this embodiment, the detection of lithium aluminum phosphate ore raw materials is shown in Table 2: Table 2. Elemental composition of lithium aluminum ore of Example 2

[0026] Considering the comprehensive leaching rate and recovery rate, the lithium recovery rate reached 96%, the aluminum recovery rate reached 78%, and the phosphorus recovery rate reached 81%.

[0027] Embodiment 3: The method for recovering lithium, phosphorus and aluminum from phosphate-aluminum-lithium ore with all components of the present embodiment comprises the following steps: (1) crushing, grinding and passing 200 g of lithium aluminum phosphate ore through a 200-mesh sieve to obtain lithium aluminum phosphate ore powder; (2) Mix the ground lithium aluminum phosphate ore powder and 60g of concentrated sulfuric acid, with the mass ratio of lithium aluminum phosphate ore powder to sulfuric acid being 1:0.3; (3) Roast the ore powder after mixing with acid in two stages. The first stage is calcined at 250°C for 1 hour, and the second stage is calcined at 800°C for 1 hour. (4) Lithium extraction by water leaching: The calcined material was added with water at a liquid-to-solid ratio of 1:1.2, and water was immersed at 60°C for 1 hour to obtain leaching residue and leaching solution; the leached residue was then washed twice with water at a liquid-to-solid ratio of 1:1 to obtain a high-concentration lithium sulfate solution and washing water, and the high-concentration lithium solution was used to remove impurities and precipitate lithium carbonate, and the washing water was used as the bottom liquid for the next water leaching. In this process, the lithium leaching rate reached 92.3%, and the mass proportion of lithium in the leaching residue after water washing was 0.31%; (5) Acid dissolution: Add 300g of water to 140g of leached residue for pulping, heat to 80°C, and then add 175g of concentrated sulfuric acid to dissolve. Keep warm for 2 hours and then filter. Wash the residue twice at a liquid-to-solid ratio of 1:1. The residue is waste residue, and the filtrate is a mixture of aluminum sulfate and phosphoric acid. In this process, the leaching rate of aluminum reaches 86%, and the leaching rate of phosphorus reaches 99%; (6) Recovery of aluminum: 350 ml of the filtrate was heated to 80 °C, and 70 g of ammonium sulfate was added. After dissolving, it was cooled and crystallized at -5 °C to obtain 403 g of ammonium aluminum sulfate crystals and 65 mL of phosphoric acid solution containing a small amount of aluminum sulfate (mother liquor). The recovery rate of aluminum in this process was 86%; (7) Phosphorus recovery: The mother liquor is extracted by a multi-stage countercurrent method. The extractant is tributyl phosphate. Pure water is used for stripping. The stripping liquid is phosphoric acid. The phosphorus extraction rate in this process reaches 82%. The raffinate is returned to step (5) for use.

[0028] In this embodiment, the detection of lithium aluminum phosphate ore raw materials is shown in Table 3: Table 3. Elemental composition of lithium aluminum ore of Example 3

[0029] Considering the comprehensive leaching rate and recovery rate, the lithium recovery rate reached 92.3%, the aluminum recovery rate reached 74%, and the phosphorus recovery rate reached 81.2%.

[0030] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

[0031] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore, characterized in that: The following steps are involved: (1) mixing the lithium aluminum phosphate ore with sulfuric acid and roasting to obtain a roasting material; (2) leaching the roasted material with water or a low-concentration lithium solution to obtain a leaching solution and leaching residue, washing the leaching residue with water, removing impurities from the leaching solution and precipitating lithium carbonate to complete lithium recovery; (3) adding water to the washed leached residue to obtain a slurry, dissolving the slurry with concentrated sulfuric acid and filtering it, heating the filtrate and adding ammonium sulfate, cooling and crystallizing after the ammonium sulfate is dissolved to obtain ammonium aluminum sulfate crystals and mother liquor, thereby completing the recovery of aluminum; (4) Extracting the mother liquor to obtain phosphoric acid and / or phosphates, thereby completing the recovery of phosphorus.

2. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 1, characterized in that: In step (3), the liquid-to-solid ratio of water to leached residue is 1:(1-3), the dissolution temperature is 50-90° C., and the dissolution time is 1-3 h.

3. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 1, characterized in that: In step (3), the amount of concentrated sulfuric acid used is 0.8 to 1.2 times the amount of phosphate acid consumed in the leaching residue.

4. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 3, characterized in that: The amount of concentrated sulfuric acid used is 1.1 times the amount of phosphate consumed in the leaching residue.

5. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 1, characterized in that: In step (3), the filtrate is heated to 80° C. and ammonium sulfate is added, wherein the amount of ammonium sulfate added is 1 to 1.2 times the theoretical amount.

6. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 1, characterized in that: In step (3), the temperature of the cooling crystallization operation is -5~0°C.

7. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to any one of claims 1 to 6, characterized in that: In step (4), when the mother liquor is extracted, tributyl phosphate is selected as the extractant, and pure water, ammonia water or sodium hydroxide solution is selected as the stripping agent.

8. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 7, characterized in that: In step (4), the raffinate obtained by extracting the mother liquor is returned to step (3) for use.

9. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to any one of claims 1 to 6, characterized in that: In step (1), the phosphate aluminum lithium ore is ground to a particle size D90≤74 μm, and then mixed with sulfuric acid and roasted.

10. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to any one of claims 1 to 6, characterized in that: In step (1), the mass ratio of the lithium aluminum phosphate ore to sulfuric acid is 1: (0.2-0.5).

11. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to any one of claims 1 to 6, characterized in that: In step (1), the mixed roasting operation of the phosphate aluminum lithium ore and sulfuric acid is divided into two stages of roasting operation. In the first stage, the acidification stage has a temperature of 150°C to 300°C and a holding time of 1 hour; in the second stage, the roasting temperature is 800°C to 850°C and the holding time is 1 hour.

12. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to any one of claims 1 to 6, characterized in that: In step (2), the leaching temperature of the leaching operation is 60° C., and the leaching time is 0.5 to 2 hours; the liquid-to-solid ratio of the water or low-concentration lithium solution to the roasting material is 1:(1 to 1.5).

13. The method for recovering lithium, phosphorus and aluminum from lithium aluminum phosphate ore according to claim 12, characterized in that: In step (2), after the leaching operation is completed, the leached residue is washed several times with water or a low-concentration lithium solution at a liquid-to-solid ratio of 1:1.

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