Method for recovering iron phosphate by using lithium iron phosphate black powder and iron phosphate

Abstract

The invention discloses a method for recycling iron phosphate by using lithium iron phosphate black powder and iron phosphate, and relates to the technical field of waste lithium battery recycling, the method for recycling iron phosphate by using lithium iron phosphate black powder comprises the following steps: acid leaching: carrying out acid leaching on lithium iron phosphate black powder to obtain an acid leaching solution and graphite filter residues; precipitating, taking water as a base solution, adding the acid leaching solution and an oxidizing agent into the base solution in a parallel flow manner, and keeping the pH value of the reaction solution to be 0.3-1.0 and the temperature to be 90-100 DEG C, so as to obtain a reaction solution containing iron phosphate precipitate; and aging and post-processing to obtain the iron phosphate. According to the method, alkali liquor does not need to be added in the reaction process, salt by-products are avoided, impurity removal of the pickle liquor before preparation of iron phosphate is not needed, and the technological process is simplified. Meanwhile, compared with a process for recovering iron phosphate by an oxidation method, acid is not needed to dissolve the lithium extraction slag, and the consumption of the acid is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of waste lithium battery recycling, and in particular to a method for recycling iron phosphate by utilizing lithium iron phosphate black powder and the iron phosphate. Background Art

[0002] At present, the methods for recovering lithium iron phosphate and preparing iron phosphate can be divided into oxidation method and non-oxidation method. The oxidation method is to use acid and oxidant to leach lithium iron phosphate black powder once or multiple times to obtain lithium extraction slag and lithium-containing solution whose main components are iron phosphate and graphite. However, the impurity content of the iron phosphate obtained at this time is high, and it is usually necessary to remove impurities after acid dissolution, and adjust the iron-phosphorus ratio before precipitating iron phosphate. The acid consumption is large and the process flow is long. The non-oxidation method is to dissolve the lithium iron phosphate black powder with acid and remove impurities, add alkali solution and hydrogen peroxide to precipitate iron phosphate, and then add sodium carbonate to the iron precipitation mother liquor to prepare lithium carbonate. In the process of preparing iron phosphate by non-oxidation method, there are problems such as difficulty in removing impurities such as Cu and Al, which can easily affect product quality. In addition, the process of preparing iron phosphate by oxidation and non-oxidation method usually produces salt by-products, which increases the processing cost.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recovering iron phosphate using lithium iron phosphate black powder and iron phosphate. During the recovery process, there is no need to remove impurities from the lithium iron phosphate black powder leaching solution, the process flow is short, the lithium loss is small, and the impurity content is low.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for recovering iron phosphate using lithium iron phosphate black powder, comprising:

[0007] Acid leaching, acid leaching the lithium iron phosphate black powder to obtain an acid leaching solution and a graphite filter residue;

[0008] Precipitation, using water as the base liquid, adding the acid leaching solution and the oxidant to the base liquid in parallel and maintaining the pH of the reaction liquid at 0.3-1.0 and the temperature at 90° C.-100° C. to obtain a reaction liquid containing iron phosphate precipitation;

[0009] Aging, aging the reaction solution;

[0010] After post-treatment, filtering, washing and drying, iron phosphate is obtained.

[0011] In an optional embodiment, the lithium iron phosphate black powder is acid-leached with an inorganic acid;

[0012] Preferably, the inorganic acid comprises sulfuric acid and / or hydrochloric acid;

[0013] In an optional embodiment, the molar ratio of hydrogen ions in the inorganic acid used in the acid leaching step to iron in the lithium iron phosphate black powder is 2 to 4;

[0014] and / or, the acid leaching time is 1 h to 3 h;

[0015] And / or, the acid leaching step comprises adding an inorganic acid to a slurry containing lithium iron phosphate black powder and stirring the slurry, wherein the mass ratio of the lithium iron phosphate black powder to the liquid in the slurry is 1:3 to 1:5.

[0016] In an optional embodiment, before the acid leaching solution is added to the base liquid, the iron-phosphorus ratio of the acid leaching solution is adjusted to 0.96-1.

[0017] In an optional embodiment, in the precipitation step, the volume of the base liquid is 5 to 20 times that of the acid leaching liquid;

[0018] and / or, the flow rate of the acid leaching solution is the volume of the acid leaching solution / t, wherein the volume of the acid leaching solution is in units of L, and t = 1 to 3 h;

[0019] And / or, the oxidant is hydrogen peroxide with a concentration greater than 10wt%.

[0020] In an optional embodiment, in the precipitation step, the molar ratio of iron ions to hydrogen peroxide added to the base liquid in parallel is 1 to 3.

[0021] In an optional embodiment, the temperature of the aging step is 90° C. to 100° C., and the aging time is 2 h to 5 h.

[0022] In an optional embodiment, the washing includes: first rinsing the filter cake obtained by filtration, and then mixing the filter cake with water in a mass ratio of 1:10 to 1:30 and stirring to wash with water.

[0023] In an optional embodiment, the drying temperature is 200°C-700°C.

[0024] In a second aspect, the present invention provides an iron phosphate prepared by the method described in any one of the aforementioned embodiments.

[0025] The present invention has the following beneficial effects:

[0026] In the method for recovering iron phosphate using lithium iron phosphate black powder provided by the embodiment of the present invention, no alkali solution needs to be added during the reaction process, thus avoiding the generation of salt by-products, and no impurities need to be removed from the acid leaching solution before preparing iron phosphate, thus simplifying the process flow. At the same time, compared with the process of recovering iron phosphate by oxidation, no acid needs to be added to dissolve the lithium slag, which is conducive to reducing the amount of acid used. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a flow chart of the method for recovering iron phosphate using lithium iron phosphate black powder in Example 1. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0030] The present invention provides a method for recovering iron phosphate by using lithium iron phosphate black powder, comprising:

[0031] Acid leaching, acid leaching the lithium iron phosphate black powder to obtain an acid leaching solution and a graphite filter residue;

[0032] Precipitation, using water as the base liquid, adding the acid leaching solution and the oxidant to the base liquid in parallel and maintaining the pH of the reaction liquid at 0.3-1.0 and the temperature at 90° C.-100° C. to obtain a reaction liquid containing iron phosphate precipitation;

[0033] Aging, aging the reaction solution;

[0034] After post-treatment, filtering, washing and drying, iron phosphate is obtained.

[0035] In the embodiment of the present invention, the precipitation temperature of iron phosphate is 90°C to 100°C, specifically 90°C, 92°C, 94°C, 96°C, 98°C, 100°C or any value between 90°C and 100°C. Under this condition, the iron phosphate precipitated is iron phosphate dihydrate. In the embodiment of the present invention, the pH is also adjusted to 0.3 to 1.0 when precipitating iron phosphate, specifically 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any value between 0.3 and 1.0. Under this pH condition, iron phosphate is not easily dissolved by acid, and impurities such as Cu, Al, Ni, Co, and Mn will not precipitate, thereby achieving the goal of simplifying the process flow without the need for impurity removal.

[0036] In addition, the lithium iron phosphate black powder in the embodiment of the present invention is a mixed powder of positive and negative electrodes obtained after the waste lithium iron phosphate battery is discharged and crushed. In the embodiment of the present invention, the acid leaching solution and the oxidant are added to the base liquid in parallel to precipitate the iron phosphate. Compared with directly adding the oxidant to the acid leaching solution to precipitate the iron phosphate, it is more conducive to maintaining the stability of the pH of the reaction solution, and at the same time can reduce the entrainment of lithium in the iron phosphate, which is beneficial to reducing lithium loss and improving the purity of the iron phosphate.

[0037] In summary, in the method for recovering iron phosphate using lithium iron phosphate black powder provided by the embodiment of the present invention, no alkali solution needs to be added during the reaction process, thus avoiding the generation of salt by-products, and no impurities need to be removed from the acid leaching solution before preparing iron phosphate, thus simplifying the process flow. At the same time, compared with the process of recovering iron phosphate by oxidation, no acid needs to be added to dissolve the lithium slag, which is conducive to reducing the amount of acid used.

[0038] In an optional embodiment, the lithium iron phosphate black powder is acid-leached with an inorganic acid. Compared with an organic acid, the inorganic acid dissolves the lithium iron phosphate black powder faster, which is beneficial to improving production efficiency.

[0039] In an optional embodiment, the inorganic acid includes sulfuric acid and / or hydrochloric acid, and sulfuric acid, in particular, is more conducive to reducing iron loss and reducing corrosion to equipment than hydrochloric acid.

[0040] In an optional embodiment, the molar ratio of hydrogen ions in the inorganic acid used in the acid leaching step to iron in the lithium iron phosphate black powder is 2-4.

[0041] In an optional embodiment, the acid leaching time is 1 h to 3 h.

[0042] In an optional embodiment, the acid leaching step includes adding an inorganic acid to a slurry containing lithium iron phosphate black powder and stirring the slurry, wherein the mass ratio of the lithium iron phosphate black powder to the liquid in the slurry is 1:3 to 1:5.

[0043] Appropriate dosage of inorganic acid, acid leaching time, etc. are conducive to the full leaching of iron in lithium iron phosphate black powder.

[0044] In an optional embodiment, before the acid leaching solution is added to the base solution, the iron-phosphorus ratio of the acid leaching solution is adjusted to 0.96-1, and the prepared iron phosphate is used in the preparation of positive electrode materials, which is beneficial to improving the electrochemical properties of lithium iron phosphate positive electrode materials.

[0045] Specifically, when the iron-phosphorus ratio in the acid leaching solution is lower than the required iron-phosphorus ratio, it is necessary to add an iron source to the acid leaching solution, wherein the iron source may be ferrous sulfate, ferrous sulfate, ferrous chloride, ferric chloride, etc.; when the iron-phosphorus ratio in the acid leaching solution is higher than the required iron-phosphorus ratio, it is necessary to add a phosphorus source to the acid leaching solution, wherein the phosphorus source may be phosphoric acid.

[0046] In an optional embodiment, in the precipitation step, the volume of the base liquid is 5 to 20 times that of the acid leaching liquid, specifically, it can be 5, 8, 11, 14, 17, 20 or any value between 5 and 20.

[0047] A certain volume of base solution is beneficial to diluting the reaction solution, which in turn helps the ionization equilibrium to move toward the precipitation of iron phosphate.

[0048] In an optional embodiment, the flow rate of the acid leaching solution is the volume of the acid leaching solution / t, wherein the unit of the volume of the acid leaching solution is L, and t=1 to 3h;

[0049] In an optional embodiment, the oxidant is hydrogen peroxide with a concentration greater than 10 wt %.

[0050] The flow rate of the acid leaching solution and the concentration of hydrogen peroxide are conducive to regulating the pH, and the use of hydrogen peroxide as an oxidant can avoid the introduction of impurities.

[0051] In an optional embodiment, in the precipitation step, the molar ratio of iron ions to hydrogen peroxide added to the base liquid in parallel is 1 to 3.

[0052] In an optional embodiment, the temperature of the aging step is 90° C. to 100° C., and the aging time is 2 h to 5 h. These conditions are conducive to the formation of ferric phosphate dihydrate.

[0053] In an optional embodiment, the washing includes: first rinsing the filter cake obtained by filtration, and then mixing the filter cake with water in a mass ratio of 1:10 to 1:30 and stirring to wash with water.

[0054] In an optional embodiment, the drying temperature is 200°C-700°C.

[0055] In this embodiment, the purpose of drying is to remove free water and bound water in the ferric phosphate precipitate, wherein the bound water can only be removed from the dihydrate ferric phosphate at a temperature above 180°C, therefore, the drying temperature is selected to be above 200°C to minimize the residual bound water.

[0056] In addition, since a small amount of acid, such as hydrochloric acid and sulfuric acid, is also entrained in the iron phosphate precipitate, increasing the drying temperature is also beneficial to the decomposition or volatilization of the residual inorganic acid, which is in turn beneficial to the removal of the inorganic acid.

[0057] In a second aspect, the present invention provides an iron phosphate prepared by the method described in any one of the aforementioned embodiments.

[0058] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0059] Example 1

[0060] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, such as Figure 1 As shown, including:

[0061] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:3, and then press H + 98 wt % sulfuric acid was added at a molar ratio of 2 to Fe, and the mixture was stirred for 1 hour and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0062] 2. Take samples of the acid leaching solution for analysis, and based on the data of the sampled liquid, add phosphoric acid to adjust the iron-phosphorus ratio to 0.96.

[0063] 3. Add 5 times the volume of the acid leaching solution into the reactor as bottom water. After heating to 100°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom water at a flow rate of 1 L / h, and add 30 wt% hydrogen peroxide into the bottom water in parallel at a molar ratio of Fe to hydrogen peroxide of 1:3. The pH of the solution is controlled at 0.3-0.5 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0064] 4. The reaction solution was aged at 100°C for 2 h.

[0065] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0066] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0067] Example 2

[0068] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, comprising:

[0069] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:4, and then press H + 98 wt % sulfuric acid was added at a molar ratio of 3 to Fe, and the mixture was stirred for 2 hours and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0070] 2. Take samples of the acid leaching solution for analysis, and add ferrous sulfate based on the data of the sampled liquid to adjust the iron-phosphorus ratio to 0.98.

[0071] 3. Add 12 times the volume of water as the acid leaching solution into the reactor as bottom water. After the bottom liquid is heated to 95°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom liquid at a flow rate of 2L / h, and add 30wt% hydrogen peroxide into the bottom water in parallel at a molar ratio of Fe to hydrogen peroxide of 1:2. The pH value of the solution is controlled at 0.6-0.8 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0072] 4. The reaction solution was aged at 95°C for 3 h.

[0073] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0074] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0075] Example 3

[0076] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, comprising:

[0077] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:5, and then press H + 98 wt % sulfuric acid was added at a molar ratio of 4 to Fe, and the mixture was stirred for 3 hours and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0078] 2. Take samples of the acid leaching solution for analysis, and add ferric sulfate based on the data of the sampled liquid to adjust the iron-phosphorus ratio to 1.0.

[0079] 3. Add 20 times the volume of the acid leaching solution into the reactor as bottom water. After the bottom liquid is heated to 90°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom liquid at a flow rate of 5 L / h, and add 30 wt% hydrogen peroxide in parallel to the bottom water at a molar ratio of Fe to hydrogen peroxide of 1:1. The pH value of the solution is controlled at 0.7-1.0 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0080] 4. The above reaction solution was aged at 90°C for 5 hours.

[0081] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0082] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0083] Example 4

[0084] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, which is different from the first embodiment only in that sulfuric acid is replaced with hydrochloric acid with an equal molar amount of hydrogen ions. Specifically, it includes:

[0085] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:3, and then press H + 36 wt % hydrochloric acid was added at a molar ratio of 2 to Fe, and the mixture was stirred for 1 hour and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0086] 2. Take samples of the acid leaching solution for analysis, and based on the data of the sampled liquid, add phosphoric acid to adjust the iron-phosphorus ratio to 0.96.

[0087] 3. Add 5 times the volume of water of the acid leaching solution into the reactor as bottom water. After heating the bottom liquid to 100°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom water at a flow rate of 1L / h, and add 30wt% hydrogen peroxide into the bottom water in parallel at a molar ratio of Fe to hydrogen peroxide of 1:3. Control the pH of the solution at 0.3-0.5 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0088] 4. The reaction solution was aged at 100°C for 2 h.

[0089] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0090] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0091] Example 5

[0092] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, which is different from Embodiment 2 only in that sulfuric acid is replaced with hydrochloric acid with an equal molar amount of hydrogen ions. Specifically, it includes:

[0093] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:4, and then press H + 36 wt % hydrochloric acid was added at a molar ratio of 3 to Fe, and the mixture was stirred for 2 hours and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0094] 2. Take samples of the acid leaching solution for analysis, and add ferrous sulfate based on the data of the sampled liquid to adjust the iron-phosphorus ratio to 0.98.

[0095] 3. Add 12 times the volume of water as the acid leaching solution into the reactor as bottom water. After the bottom liquid is heated to 95°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom liquid at a flow rate of 2L / h, and add 30wt% hydrogen peroxide into the bottom water in parallel at a molar ratio of Fe to hydrogen peroxide of 1:2. The pH value of the solution is controlled at 0.6-0.8 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0096] 4. The reaction solution was aged at 95°C for 3 h.

[0097] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0098] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0099] Example 6

[0100] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, which is different from the embodiment 3 only in that sulfuric acid is replaced with hydrochloric acid with an equal molar amount of hydrogen ions. Specifically, it includes:

[0101] 1. Prepare 1 kg of lithium iron phosphate positive and negative electrode mixed powder into slurry at a solid-liquid mass ratio of 1:5, and then press H + 36 wt % hydrochloric acid was added at a molar ratio of 4 to Fe, and the mixture was stirred for 3 hours and then filtered to obtain a filter residue and an acid leaching solution whose main component was graphite.

[0102] 2. Take samples of the acid leaching solution for analysis, and add ferric sulfate based on the data of the sampled liquid to adjust the iron-phosphorus ratio to 1.0.

[0103] 3. Add 20 times the volume of the acid leaching solution into the reactor as bottom water. After the bottom liquid is heated to 90°C, add the acid leaching solution with adjusted iron-phosphorus ratio into the bottom liquid at a flow rate of 5 L / h, and add 30 wt% hydrogen peroxide in parallel to the bottom water at a molar ratio of Fe to hydrogen peroxide of 1:1. The pH value of the solution is controlled at 0.7-1.0 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0104] 4. The above reaction solution was aged at 90°C for 5 hours.

[0105] 5. The aged slurry is subjected to solid-liquid separation to obtain an iron phosphate filter cake and a filtrate. The filter cake is rinsed with water to remove entrained impurities, and then stirred and washed twice with 30 times the mass of water to obtain a washed iron phosphate precipitate.

[0106] 6. The washed iron phosphate precipitate is dried at 600°C to obtain battery-grade iron phosphate.

[0107] Example 7

[0108] This embodiment provides a method for recovering iron phosphate using lithium iron phosphate black powder, which is different from Embodiment 1 only in that, in step (6), the drying temperature is 100°C.

[0109] Comparative Example 1

[0110] This comparative example provides a method for recovering iron phosphate using lithium iron phosphate black powder, which differs from Example 1 only in that the bottom liquid temperature in step (3) is too low to 50°C.

[0111] Comparative Example 2

[0112] This comparative example provides a method for recovering iron phosphate using lithium iron phosphate black powder, which differs from Example 1 only in that in step (3), the pH value of the solution is controlled to be between 3 and 5 by adjusting the amount of hydrogen peroxide and leaching solution added.

[0113] Comparative Example 3

[0114] This comparative example provides a method for recovering iron phosphate using lithium iron phosphate black powder, which differs from Example 1 only in that in step (3), 30 wt % hydrogen peroxide is directly added to the acid leaching solution to adjust the solution pH to 0.3-0.5 to precipitate iron phosphate, and the precipitation temperature is 100°C.

[0115] Comparative Example 4

[0116] This comparative example provides a method for recovering iron phosphate using lithium iron phosphate black powder. The difference from Example 1 is that an oxidation method is used, and H is added simultaneously in step (1). + 98wt% sulfuric acid with a molar ratio of H2O2 / Fe of 2 and 30wt% hydrogen peroxide with a molar ratio of H2O2 / Fe of 1.5 were filtered and washed to obtain lithium extraction slag with the main components of iron phosphate and graphite. + The acid leaching solution is purified and the iron-phosphorus ratio is adjusted. The acid leaching solution is heated to 90°C, and ammonia water is added to adjust the pH to 2-3. Then, the solution is aged, washed and dried according to steps (4) to (6).

[0117] The iron phosphate products prepared in the above examples and comparative examples were tested, and the results are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] Note: ND means the content is below the detection limit.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recovering iron phosphate using lithium iron phosphate black powder, characterized in that: include: Acid leaching, acid leaching the lithium iron phosphate black powder to obtain an acid leaching solution and a graphite filter residue; Precipitation, using water as the base liquid, adding the acid leaching solution and the oxidant to the base liquid in parallel and maintaining the pH of the reaction liquid at 0.3-1.0 and the temperature at 90° C.-100° C. to obtain a reaction liquid containing iron phosphate precipitation; Aging, aging the reaction solution; After post-treatment, filtering, washing and drying, iron phosphate is obtained.

2. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: The lithium iron phosphate black powder is acid-leached with inorganic acid; Preferably, the inorganic acid comprises sulfuric acid and / or hydrochloric acid.

3. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 2, characterized in that: The molar ratio of hydrogen ions in the inorganic acid used in the acid leaching step to iron in the lithium iron phosphate black powder is 2 to 4; and / or, the acid leaching time is 1 h to 3 h; And / or, the acid leaching step comprises adding an inorganic acid to a slurry containing lithium iron phosphate black powder and stirring the slurry, wherein the mass ratio of the lithium iron phosphate black powder to the liquid in the slurry is 1:3 to 1:

5.

4. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: Before the acid leaching solution is added to the base solution, the iron-phosphorus ratio of the acid leaching solution is adjusted to 0.96-1.

5. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: In the precipitation step, the volume of the base solution is 5 to 20 times that of the acid leaching solution; and / or, the flow rate of the acid leaching solution is the volume of the acid leaching solution / t, wherein the volume of the acid leaching solution is in units of L, and t = 1 to 3 h; And / or, the oxidant is hydrogen peroxide with a concentration greater than 10wt%.

6. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: In the precipitation step, the molar ratio of iron ions to hydrogen peroxide is 1 to 3 and added to the base liquid in parallel.

7. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: The temperature of the aging step is 90° C. to 100° C., and the aging time is 2 h to 5 h.

8. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: The washing comprises: firstly rinsing the filter cake obtained by filtration, and then mixing the filter cake with water in a mass ratio of 1:10 to 1:30 and stirring to wash with water.

9. The method for recovering iron phosphate using lithium iron phosphate black powder according to claim 1, characterized in that: The drying temperature is 200℃-700℃.

10. An iron phosphate, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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