Recycling method of lithium iron phosphate waste

Abstract

The invention provides a lithium iron phosphate waste material recovery method, which comprises: (1) slurrying a lithium iron phosphate waste material, and carrying out leaching treatment to obtain a leaching liquid and a leaching residue; (2) carrying out impurity removal treatment on the leaching solution to obtain an impurity removal solution, and carrying out lithium extraction treatment on the impurity removal solution to obtain an organic phase and a raffinate; (3) carrying out reverse extraction treatment on the organic phase to obtain reverse extraction liquid and an organic phase, and mixing the reverse extraction liquid with carbonate to obtain lithium carbonate; and (4) carrying out electrolytic treatment on the raffinate to obtain coarse electrolytic iron and an electrolytic barren solution, carrying out phosphorus precipitation-phosphorus extraction on the electrolytic barren solution to obtain phosphoric acid, and reducing the coarse electrolytic iron to obtain high-purity iron powder. According to the recycling method, iron and phosphorus in the lithium iron phosphate waste are recycled respectively, iron powder and phosphoric acid are obtained through recycling, meanwhile, residual lithium in the slag is recycled to obtain lithium carbonate, and recycling treatment of the lithium iron phosphate waste is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery and relates to a method for recovering lithium iron phosphate waste. Background Art

[0002] The waste lithium iron phosphate cathode material selective lithium extraction slag contains a large amount of iron and phosphorus, and its main component is iron phosphate. However, because it contains some impurities that are very easy to co-precipitate with iron, it is difficult to regenerate it into battery-grade iron phosphate, but abandoning it in landfill will cause a waste of resources. In addition, considering that a large number of companies have invested in iron phosphate production lines in recent years, the over-expansion has led to excess iron phosphate production capacity and difficulties in shipment. It is urgent to develop new processes and products to treat lithium iron phosphate waste and alleviate the pressure of terminal treatment of lithium iron phosphate waste.

[0003] CN118619311A discloses a method for recovering lithium from waste lithium iron phosphate batteries, including: obtaining lithium iron phosphate black powder from the waste lithium iron phosphate batteries; mixing the lithium iron phosphate black powder with an alkali material to obtain a roasted raw material; subjecting the roasted raw material to microwave roasting under anaerobic conditions to obtain a roasted clinker; mixing the roasted clinker with a leaching agent to perform a water leaching treatment to obtain a lithium-containing leaching solution; and subjecting the lithium-containing leaching solution to a crystallization treatment to obtain lithium hydroxide.

[0004] CN118598097A discloses a method for recovering waste lithium iron phosphate battery powder, which comprises: mixing the waste lithium iron phosphate battery powder with an acidic aqueous solution, filtering and washing to obtain a first solution; mixing the first solution with a first reducing agent, filtering and washing to obtain a second solution and copper powder; controlling the temperature of the second solution, mixing it with a first acid-base regulator and a second reducing agent, filtering and washing to obtain a third solution and a first aluminum slag; mixing the third solution with a phosphorus-iron ratio regulator, an oxidant, and a second acid-base regulator, filtering and washing to obtain hydrated iron phosphate.

[0005] In the above scheme for recycling lithium iron phosphate waste, only lithium or phosphorus and iron can be recovered separately. The operation steps are cumbersome and it is difficult to achieve simultaneous recovery, resulting in insufficient resource recovery and reduced practical value. Summary of the invention

[0006] The purpose of the present invention is to provide a method for recycling lithium iron phosphate waste. The recycling method of the present invention recycles the iron and phosphorus in the lithium iron phosphate waste into resources respectively, recovering iron powder and phosphoric acid, and at the same time recovers the residual lithium in the slag to obtain lithium carbonate, thereby realizing the resource disposal of lithium iron phosphate waste and alleviating environmental pressure.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for recycling lithium iron phosphate waste, the recycling method comprising the following steps:

[0009] (1) slurrying the lithium iron phosphate waste, mixing it with an acid solution and a reducing agent for leaching treatment to obtain a leachate and a leach residue;

[0010] (2) performing impurity removal treatment on the leachate to obtain an impurity-removing liquid, and performing lithium extraction treatment on the impurity-removing liquid to obtain a first organic phase and a raffinate;

[0011] (3) performing a first stripping treatment on the first organic phase to obtain a first stripping solution and a second organic phase, mixing the first stripping solution with a carbonate to obtain lithium carbonate, and performing a second stripping treatment on the second organic phase to obtain a second stripping solution and a regenerated extractant;

[0012] (4) The raffinate is used as the cathode liquid for electrolytic treatment to obtain crude electrolytic iron and electrolytic lean solution at the cathode, the electrolytic lean solution is mixed with a calcium source to obtain calcium phosphate slag, the calcium phosphate slag is mixed with sulfuric acid, and after reaction, solid-liquid separation is performed to obtain phosphoric acid, and the crude electrolytic iron is reduced to obtain high-purity electrolytic iron powder.

[0013] The present invention does not limit the operation order of step (3) and step (4), and step (3) can be performed first or step (4) can be performed first.

[0014] The present invention extracts and extracts lithium from lithium iron phosphate waste after leaching and impurity removal, and then extracts lithium to obtain an organic phase containing lithium and a raffinate containing iron and phosphorus, respectively. The organic phase is reversely extracted and then treated with lithium precipitation to obtain lithium carbonate. The raffinate is first electrolyzed to recover iron, and then the electrolytic lean solution obtained by electrolysis is treated with phosphorus precipitation and phosphorus extraction to recover phosphoric acid. The method of the present invention can achieve the synchronous recovery of various elements in lithium iron phosphate waste by reasonably matching the recovery order of various elements, reducing resource waste and alleviating environmental pressure.

[0015] Preferably, the acid solution in step (1) comprises hydrochloric acid.

[0016] Preferably, the molar ratio of chloride ions in the hydrochloric acid to iron ions in the lithium iron phosphate waste is (3-4.5):1, for example: 3:1, 3.6:1, 3.9:1, 4.2:1 or 4.5:1, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the reducing agent in step (1) comprises sodium metabisulfite and / or sodium thiosulfate.

[0018] Preferably, the leaching treatment in step (1) is followed by solid-liquid separation.

[0019] Preferably, the impurity remover in the impurity removal treatment in step (2) includes a first impurity remover and a second impurity remover.

[0020] Preferably, the first impurity remover comprises sodium sulfide and / or iron powder.

[0021] Preferably, the second impurity-removing agent comprises sodium fluoride.

[0022] Preferably, the impurity removal treatment in step (2) is followed by solid-liquid separation.

[0023] Preferably, the extractant for the lithium extraction treatment in step (2) includes tributyl phosphate (TBP).

[0024] Preferably, the mass concentration of the extractant is 50-80%, for example, 50%, 55%, 60%, 70% or 80%, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the ratio O / A of the lithium extraction treatment in step (2) is 1:(5-20), for example, 1:5, 1:8, 1:10, 1:15 or 1:20, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the stripping agent in the first stripping treatment in step (3) comprises hydrochloric acid.

[0027] Preferably, the concentration of the hydrochloric acid is 3 to 8 mol / L, for example, 3 mol / L, 5 mol / L, 6 mol / L, 7 mol / L or 8 mol / L, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the stripping phase ratio O / A of the first stripping treatment in step (3) is (2 to 10):1, for example: 2:1, 4:1, 6:1, 8:1 or 10:1, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the carbonate in step (3) comprises sodium carbonate.

[0030] Preferably, the molar ratio of the carbonate in step (3) to the lithium element in the first stripping solution is (0.75-1):1, for example: 0.75:1, 0.8:1, 0.9:1, 0.95:1 or 1:1, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the stripping agent of the second stripping treatment in step (3) comprises hydrochloric acid.

[0032] Preferably, the concentration of the hydrochloric acid is 0.01-1 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.4 mol / L or 1 mol / L, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the stripping phase ratio O / A of the second stripping treatment in step (3) is (2 to 10):1, for example: 2:1, 4:1, 6:1, 8:1 or 10:1, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the regenerated extractant in step (3) comprises tributyl phosphate.

[0035] Preferably, the pH of the raffinate in step (4) is adjusted to 3 to 5 before being used as the cathode liquid, for example: 3, 3.5, 4, 4.5 or 5, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the current density of the electrolytic treatment in step (4) is 500 to 5000 A / m 2 , for example: 500A / m 2 , 1000A / m 2 、2000A / m 2 、3000A / m 2 or 5000A / m 2 The present invention is not limited to the numerical values ​​listed, and other numerical values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the calcium source in step (4) comprises calcium hydroxide and / or calcium oxide.

[0038] Preferably, the electrolytic lean solution is subjected to impurity removal treatment before being mixed with the calcium source in step (4).

[0039] Preferably, in step (4), the electrolytic lean solution is mixed with the calcium source and then subjected to solid-liquid separation and water washing treatment.

[0040] Preferably, the amount of sulfuric acid in step (4) is 1.45 to 1.5 times the molar amount of phosphorus in the calcium phosphate slag, for example: 1.45 times, 1.46 times, 1.47 times, 1.48 times, 1.49 times, 1.5 times.

[0041] Preferably, the crude electrolytic iron is washed, crushed, sieved and dried before the reduction treatment in step (4).

[0042] Preferably, the reducing agent for the reduction treatment in step (4) comprises hydrogen.

[0043] Preferably, the temperature of the reduction treatment in step (4) is 750-1000°C, for example, 750°C, 800°C, 850°C, 900°C or 1000°C, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The recycling method of the present invention recycles the iron and phosphorus in the lithium iron phosphate waste into resources respectively, recovering iron powder and phosphoric acid, and at the same time recovers the residual lithium in the slag into lithium carbonate, thereby realizing the resource disposal of lithium iron phosphate waste and alleviating environmental pressure.

[0046] (2) Through the technical method of the present invention, the recovery rate of Fe in lithium iron phosphate waste can reach more than 90%, the recovery rates of Li and P can reach more than 95%, the purity of the recovered iron powder can reach more than 98.5%, and the purity of phosphoric acid can reach more than 80.5%. The operating parameters of each process have an important influence on the recovery rate of iron, lithium and phosphorus. Under the optimal parameter conditions, the recovery rate of Fe can reach more than 91%, the recovery rate of Li and P can reach more than 95%, the purity of the recovered iron powder can reach more than 99.1%, and the purity of phosphoric acid can reach more than 85.2%, which can effectively achieve waste reduction and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a process flow chart of the method for recycling lithium iron phosphate waste described in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0049] The lithium iron phosphate waste material of the present invention is obtained from the waste residue after selective lithium extraction from black powder of discarded lithium iron phosphate batteries.

[0050] Example 1

[0051] This embodiment provides a method for recycling lithium iron phosphate waste. The process flow chart of the recycling method is as follows: Figure 1 As shown, the recovery method comprises the following steps:

[0052] (1) adding water to the lithium iron phosphate waste to form a slurry, adding hydrochloric acid and sodium thiosulfate, wherein the molar ratio of chloride ions in the hydrochloric acid to iron elements in the lithium iron phosphate waste is 3.6:1, and performing a leaching treatment to obtain a leachate and a leached residue;

[0053] (2) adding sodium sulfide and sodium fluoride to the leachate (the amount of sodium sulfide and sodium fluoride is 3 times the theoretical amount required to remove impurities Cu and Al), performing solid-liquid separation after the reaction to obtain a decontamination liquid, and mixing the decontamination liquid with TBP having a mass concentration of 60% at a ratio of O / A=1:10 to perform extraction and lithium extraction treatment to obtain a first organic phase and a raffinate;

[0054] (3) According to the stripping ratio O / A of 5:1, the first organic phase was subjected to a first stripping treatment using 5 mol / L hydrochloric acid to obtain a first stripping solution and a second organic phase. The first stripping solution was mixed with sodium carbonate according to CO3 2- :Li + =0.9:1 molar ratio to obtain lithium carbonate, according to the stripping phase ratio O / A is 5:1, using 0.5 mol / L hydrochloric acid to perform a second stripping treatment on the second organic phase to obtain a second stripping solution and a regenerated extractant, and the second stripping solution is mixed with the impurity removal solution to perform the above step (2);

[0055] (4) The pH of the raffinate was adjusted to 4 and used as the cathode liquid at 1000 A / m 2 The electrolytic treatment is carried out at a current density of , and crude electrolytic iron and electrolytic lean solution are obtained at the cathode. The electrolytic lean solution is mixed with calcium hydroxide to obtain calcium phosphate slag, and the calcium phosphate slag is mixed with sulfuric acid to obtain phosphoric acid (the amount of sulfuric acid added is 1.48 times the molar amount of phosphorus in the calcium phosphate slag). The crude electrolytic iron is reduced with hydrogen at 900°C to obtain high-purity electrolytic iron powder.

[0056] Example 2

[0057] This embodiment provides a method for recycling lithium iron phosphate waste. The process flow chart of the recycling method is as follows: Figure 1 As shown, the recovery method comprises the following steps:

[0058] (1) adding water to the lithium iron phosphate waste to form a slurry, adding hydrochloric acid and sodium thiosulfate, wherein the molar ratio of chloride ions in the hydrochloric acid to iron elements in the lithium iron phosphate waste is 3:1, and performing a leaching treatment to obtain a leachate and a leached residue;

[0059] (2) adding sodium sulfide and sodium fluoride to the leachate (the amount of sodium sulfide and sodium fluoride is twice the theoretical amount required to remove impurities Cu and Al), separating the solid and liquid after the reaction to obtain a decontamination liquid, mixing the decontamination liquid with TBP having a mass concentration of 50% at a ratio of O / A=1:5 to perform extraction and lithium extraction treatment to obtain a first organic phase and a raffinate;

[0060] (3) According to the stripping phase O / A ratio of 2:1, the first organic phase was subjected to a first stripping treatment using 8 mol / L hydrochloric acid to obtain a first stripping solution and a second organic phase. The first stripping solution was mixed with sodium carbonate according to CO3 2-:Li + =0.75:1 molar ratio to obtain lithium carbonate, according to the stripping phase ratio O / A is 2:1, using 1 mol / L hydrochloric acid to perform a second stripping treatment on the second organic phase to obtain a second stripping solution and a regenerated extractant, and mixing the second stripping solution with the impurity removal solution to perform the above step (2);

[0061] (4) The pH of the raffinate was adjusted to 5 and used as the cathode liquid at 500 A / m 2 The electrolytic treatment is carried out at a current density of , and crude electrolytic iron and electrolytic lean solution are obtained at the cathode. The electrolytic lean solution is mixed with calcium hydroxide to obtain calcium phosphate slag, and the calcium phosphate slag is mixed with sulfuric acid to obtain phosphoric acid (the amount of sulfuric acid added is 1.45 times the molar amount of phosphorus in the calcium phosphate slag). The crude electrolytic iron is reduced with hydrogen at 750°C to obtain high-purity electrolytic iron powder.

[0062] Example 3

[0063] This embodiment provides a method for recycling lithium iron phosphate waste. The process flow chart of the recycling method is as follows: Figure 1 As shown, the recovery method comprises the following steps:

[0064] (1) adding water to the lithium iron phosphate waste to form a slurry, adding hydrochloric acid and sodium thiosulfate, wherein the molar ratio of chloride ions in the hydrochloric acid to iron elements in the lithium iron phosphate waste is 4.5:1, and performing a leaching treatment to obtain a leachate and a leached residue;

[0065] (2) adding sodium sulfide and sodium fluoride to the leachate (the amount of sodium sulfide and sodium fluoride is 5 times the theoretical amount required to remove impurities Cu and Al), separating the solid and liquid after the reaction to obtain a decontamination liquid, mixing the decontamination liquid with TBP having a mass concentration of 80% at a ratio of O / A=1:20 to perform extraction and lithium extraction treatment to obtain a first organic phase and a raffinate;

[0066] (3) According to the stripping phase O / A ratio of 10:1, the first organic phase was subjected to a first stripping treatment using 3 mol / L hydrochloric acid to obtain a first stripping solution and a second organic phase. The first stripping solution was mixed with sodium carbonate according to CO3 2- :Li + =1:1 molar ratio to obtain lithium carbonate, according to the stripping phase ratio O / A is 10:1, using 0.01 mol / L hydrochloric acid to perform a second stripping treatment on the second organic phase to obtain a second stripping solution and a regenerated extractant, and mixing the second stripping solution with the impurity removal solution to perform the above step (2);

[0067] (4) The pH of the raffinate was adjusted to 3 and used as the cathode liquid at 5000 A / m 2The electrolytic treatment is carried out at a current density of , and crude electrolytic iron and electrolytic lean solution are obtained at the cathode. The electrolytic lean solution is mixed with calcium hydroxide to obtain calcium phosphate slag, and the calcium phosphate slag is mixed with sulfuric acid to obtain phosphoric acid (the amount of sulfuric acid added is 1.5 times the molar amount of phosphorus in the calcium phosphate slag). The crude electrolytic iron is reduced with hydrogen at 1000°C to obtain high-purity electrolytic iron powder.

[0068] Example 4

[0069] The only difference between this embodiment and embodiment 1 is that the molar ratio of chloride ions in hydrochloric acid to iron elements in lithium iron phosphate waste used during leaching is 2:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0070] Example 5

[0071] The only difference between this embodiment and embodiment 1 is that the molar ratio of chloride ions in hydrochloric acid to iron elements in lithium iron phosphate waste used during leaching is 5:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0072] Example 6

[0073] The only difference between this embodiment and embodiment 1 is that the hydrochloric acid concentration in the first stripping treatment is 2 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0074] Example 7

[0075] The only difference between this embodiment and embodiment 1 is that the hydrochloric acid concentration in the first stripping treatment is 10 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0076] Example 8

[0077] The only difference between this embodiment and embodiment 1 is that the amount of sulfuric acid added in the phosphorus extraction process is 1.4 times the molar amount of phosphorus in the calcium phosphate slag, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0078] Example 9

[0079] The only difference between this embodiment and embodiment 1 is that the amount of sulfuric acid added in the phosphorus extraction process is 1.6 times the molar amount of phosphorus in the calcium phosphate slag, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0080] Comparative Example 1

[0081] The only difference between this comparative example and Example 1 is that no impurity removal treatment is performed, and other conditions and parameters are exactly the same as those in Example 1.

[0082] Comparative Example 2

[0083] The only difference between this comparative example and Example 1 is that no reduction purification treatment is performed, and other conditions and parameters are exactly the same as those in Example 1.

[0084] Performance Testing:

[0085] The raw material composition and the yield and composition of the product iron powder, phosphoric acid and lithium carbonate were detected by the national standard GB / T 30835-2014 determination method, and the recovery rate and purity of each element were calculated. The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088] As can be seen from Table 1, from Examples 1-9, the recovery rate of Fe from lithium iron phosphate waste in the present invention can reach more than 90%, the recovery rate of Li and P can reach more than 95%, the purity of the recovered iron powder can reach more than 98.5%, and the purity of phosphoric acid can reach more than 80.5%. The operating parameters of each process have an important influence on the recovery rate of iron, lithium and phosphorus. Under the preferred parameter conditions, the recovery rate of Fe can reach more than 91%, the recovery rate of Li and P can reach more than 95%, the purity of the recovered iron powder can reach more than 99.1%, and the purity of phosphoric acid can reach more than 85.2%.

[0089] By comparing Example 1 with Examples 4-5, it can be seen that in the method for recovering lithium iron phosphate waste of the present invention, the amount of hydrochloric acid used during leaching will affect the recovery effect. The amount of hydrochloric acid is controlled so that the molar ratio of chloride ion to iron is (3-4.5):1, and the recovery effect is better. If the amount of hydrochloric acid is too low, the recovery rates of Fe, Li, and P are significantly reduced. If the amount of hydrochloric acid is too high, the purity of the iron powder will be slightly reduced, and excessive acid will increase unnecessary costs.

[0090] By comparing Example 1 with Examples 6-7, it can be seen that in the method for recovering lithium iron phosphate waste described in the present invention, the hydrochloric acid concentration of the first stripping treatment will affect the recovery effect. When the hydrochloric acid concentration of the first stripping treatment is controlled within 3-8 mol / L, the recovery effect is better. If the hydrochloric acid concentration of the first stripping treatment is too low or too high, the recovery rate of lithium will decrease.

[0091] By comparing Example 1 with Examples 8-9, it can be seen that in the method for recovering lithium iron phosphate waste of the present invention, the amount of sulfuric acid added in the phosphorus extraction process will affect the recovery effect. The amount of sulfuric acid added is controlled to 1.45-1.5 times the molar amount of phosphorus in the calcium phosphate slag, and the recovery effect is better. If the amount of sulfuric acid is too low, the recovery rate of P is significantly reduced. If the amount of sulfuric acid is too high, the purity of the product phosphoric acid will decrease.

[0092] From the comparison between Example 1 and Comparative Example 1, it can be seen that the purity of iron powder and phosphoric acid can be effectively improved by removing impurities in the present invention.

[0093] From the comparison between Example 1 and Comparative Example 2, it can be seen that the present invention can effectively improve the purity of iron powder through reduction purification treatment, and obtain high-purity iron powder from coarse iron powder.

[0094] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling lithium iron phosphate waste, characterized in that: The recovery method comprises the following steps: (1) slurrying the lithium iron phosphate waste, mixing it with an acid solution and a reducing agent for leaching treatment to obtain a leachate and a leach residue; (2) performing impurity removal treatment on the leachate to obtain an impurity-removing liquid, and performing lithium extraction treatment on the impurity-removing liquid to obtain a first organic phase and a raffinate; (3) performing a first stripping treatment on the first organic phase to obtain a first stripping solution and a second organic phase, mixing the first stripping solution with a carbonate to obtain lithium carbonate, and performing a second stripping treatment on the second organic phase to obtain a second stripping solution and a regenerated extractant; (4) The raffinate is used as the cathode liquid for electrolytic treatment to obtain crude electrolytic iron and electrolytic lean liquid at the cathode, the electrolytic lean liquid is mixed with a calcium source to obtain calcium phosphate slag, the calcium phosphate slag is mixed with sulfuric acid, the solid and liquid are separated after the reaction to obtain phosphoric acid, and the crude electrolytic iron is reduced to obtain high-purity electrolytic iron powder.

2. The recycling method according to claim 1, characterized in that: The acid solution in step (1) comprises hydrochloric acid; Preferably, the molar ratio of chloride ions in the hydrochloric acid to iron ions in the lithium iron phosphate waste is (3-4.5):1; Preferably, the reducing agent in step (1) comprises sodium pyrosulfite and / or sodium thiosulfate; Preferably, the leaching treatment in step (1) is followed by solid-liquid separation.

3. The recovery method according to claim 1 or 2, characterized in that: The impurity remover in the impurity removal treatment in step (2) includes a first impurity remover and a second impurity remover; Preferably, the first impurity remover comprises sodium sulfide and / or iron powder; Preferably, the second impurity remover comprises sodium fluoride; Preferably, the impurity removal treatment in step (2) is followed by solid-liquid separation.

4. The recycling method according to any one of claims 1 to 3, characterized in that: The extractant for the lithium extraction treatment in step (2) comprises tributyl phosphate; Preferably, the mass concentration of the extractant is 50-80%; Preferably, the ratio of O / A in the lithium extraction treatment in step (2) is 1:(5-20).

5. The recycling method according to any one of claims 1 to 4, characterized in that: Step (3) The stripping agent of the first stripping treatment comprises hydrochloric acid; Preferably, the concentration of the hydrochloric acid is 3 to 8 mol / L; Preferably, in step (3), the stripping phase ratio O / A of the first stripping treatment is (2 to 10):

1.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The carbonate in step (3) comprises sodium carbonate; Preferably, the molar ratio of the carbonate in step (3) to the lithium element in the first stripping solution is (0.75-1):

1.

7. The recycling method according to any one of claims 1 to 6, characterized in that: Step (3) the stripping agent of the second stripping treatment comprises hydrochloric acid; Preferably, the concentration of the hydrochloric acid is 0.01 to 1 mol / L; Preferably, in step (3), the stripping phase ratio O / A of the second stripping treatment is (2-10):1; Preferably, the regenerated extractant in step (3) comprises tributyl phosphate.

8. The recycling method according to any one of claims 1 to 7, characterized in that: The pH of the raffinate in step (4) is adjusted to 3-5 before being used as the cathode liquid; Preferably, the current density of the electrolytic treatment in step (4) is 500 to 5000 A / m 2 .

9. The recycling method according to any one of claims 1 to 8, characterized in that: The calcium source in step (4) includes calcium hydroxide and / or calcium oxide; Preferably, the electrolytic lean solution is subjected to impurity removal treatment before mixing the electrolytic lean solution with the calcium source in step (4); Preferably, in step (4), the electrolytic lean solution is mixed with the calcium source and then solid-liquid separation and water washing are performed; Preferably, the amount of sulfuric acid used in step (4) is 1.45 to 1.5 times the molar amount of phosphorus in the calcium phosphate slag.

10. The recycling method according to any one of claims 1 to 9, characterized in that: Before the reduction treatment in step (4), the crude electrolytic iron is washed, crushed, sieved and dried; Preferably, the reducing agent for the reduction treatment in step (4) comprises hydrogen; Preferably, the temperature of the reduction treatment in step (4) is 750-1000°C.

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