Method for preparing manganese iron phosphate by using waste phosphorus iron slag

Abstract

The application discloses a method for preparing manganese iron phosphate by using waste phosphorus iron slag, and comprises the following steps: S1, deionized water is added to the waste phosphorus iron slag, the temperature is increased to 40-90 DEG C, and the material is uniformly mixed by stirring for 10-30 min to obtain a slurry; S2, acid liquid is added to the slurry obtained in the step S1, after reaction, the leaching liquid is obtained by vacuum filtration, an oxidizing agent is added to the leaching liquid, and the manganese iron liquid is obtained after complete oxidation; S3, alkali liquid is added to the manganese iron liquid obtained in the step S2, the pH value is adjusted, a manganese source is added according to the corresponding iron and manganese substance amount ratio, after stirring and reaction for 0.5-2 h, a certain amount of phosphoric acid is added dropwise to the slurry, after reaction, filtration, washing and drying at 80-120 DEG C for 2-4 h are carried out, and the hydrated manganese iron phosphate is obtained; and S4, the hydrated manganese iron phosphate obtained in the step S3 is sintered in an air atmosphere, and the manganese iron phosphate is obtained; the application is favorable for further improving the material performance by promoting the uniform distribution of manganese and iron and reducing the particle size of the manganese iron phosphate.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery materials, and in particular to a method for preparing ferromanganese phosphate by utilizing waste ferrophosphorus slag. Background Art

[0002] With the rapid development of the new energy industry, sales of new energy vehicles have exploded. This has not only spurred extensive research and large-scale production of lithium-ion power batteries, but has also led to the generation and disposal of solid waste during the production and recycling of lithium-ion batteries. Furthermore, as social demands evolve, the low-voltage 3.4 V platform of lithium iron phosphate (LiFePO4) no longer meets the current market demand for high-energy-density batteries. Lithium iron manganese phosphate (LiFePO4), a high-voltage (4.1 V) phosphate material, not only offers the stability of LiFePO4 but also improves battery energy density. At equivalent specific capacity, LiFePO4 batteries boast an energy density over 20% higher than LiFePO4 batteries. Therefore, LiFePO4 is expected to become a new generation of high-energy-density power battery cathode materials, and its precursor, iron manganese phosphate (FeMnPO4), is garnering increasing attention.

[0003] The composition, structure, particle size, morphology, and other performance indicators of ferromanganese phosphate (FMP) play a crucial role in the electrochemical performance of the synthesized lithium iron manganese phosphate (LFP) material. However, the FMP products synthesized using most current technologies suffer from uneven distribution of manganese and iron phases, large and uneven particle size, resulting in poor rate performance of the prepared LFP cathode material, which seriously affects its rate performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing ferromanganese phosphate using waste ferrophosphorus slag, thereby reducing the emission of battery waste, improving its comprehensive utilization rate and solving the problem that the ferromanganese phosphate products prepared in the prior art have large particle size, resulting in reduced material performance.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing ferromanganese phosphate using waste ferrophosphorus slag comprises the following steps:

[0007] S1. Add deionized water to the waste ferrophosphorus slag, heat it to 40-90°C, and stir it for 10-30 minutes to mix the materials evenly to obtain a slurry;

[0008] S2. Add acid solution to the slurry obtained in step S1, heat to a constant temperature of 40-90° C., and stir to react for 1-5 hours. After the reaction is completed, obtain a leachate by vacuum filtration, add an oxidant to the leachate, and perform an oxidation reaction. After complete oxidation, obtain a ferrophosphorus liquid;

[0009] S3, adding alkali solution to the ferrophosphorus liquid obtained in step S2, adjusting the pH value, heating to a constant temperature of 30-80 ° C, adding a manganese source according to the corresponding ratio of the amount of iron and manganese substances, stirring and reacting for 0.5-2h, heating to 90-95 ° C, adding a certain amount of phosphoric acid to the slurry so that the ratio of the amount of phosphorus element to the total amount of iron and manganese elements is 1: (0.6~1.2), after completion of the dropwise addition, stirring and reacting at a constant temperature for 0.5-2.5h, after the reaction is completed, filtering, washing and drying at 80-120 ° C for 2-4h to obtain hydrated manganese ferrophosphate;

[0010] S4. Sintering the hydrated ferromanganese phosphate obtained in step S3 in an air atmosphere at a temperature of 300-400° C. for 2-4 hours to obtain ferromanganese phosphate.

[0011] Preferably, the waste ferrophosphorus slag in step S1 is a by-product of yellow phosphorus production or a waste slag from lithium extraction from waste lithium iron phosphate.

[0012] Preferably, the mass ratio of the waste ferrophosphorus slag to deionized water in step S1 is 1:2-1:5.

[0013] Preferably, the acid solution in step S2 is one or more combinations of sulfuric acid, hydrochloric acid and nitric acid.

[0014] Preferably, the oxidant in step S2 is one or more combinations of hydrogen peroxide and oxygen.

[0015] Preferably, the alkali solution in step S3 is at least one of sodium hydroxide solution or ammonia water, and the pH value is adjusted to 1.6-2.3.

[0016] Preferably, in step S3, the manganese source is one or more combinations of manganese oxyhydroxide, manganese hydroxide, trimanganese tetraoxide, manganese dioxide, and dimanganese trioxide.

[0017] Preferably, the manganese source is added in step S3 so that the ratio of the amounts of iron and manganese is any value between (0.2-0.8):(0.8-0.2).

[0018] Preferably, the manganese source is added in step S3 so that the ratio of the amounts of iron and manganese is one of 0.2:0.8, 0.3:0.7, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.7:0.3, and 0.8:0.2.

[0019] Preferably, the ratio of the amount of phosphorus element in step S3 to the total amount of iron and manganese elements is one of 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, and 1:1.2.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention uses waste ferrophosphorus slag as raw material to prepare ferrophosphate without aging, crystallization and drying steps. The obtained ferrophosphate precipitate is directly blended with a manganese source to synthesize ferromanganese phosphate, so that the ferrophosphate is uniformly dispersed in a solvent to form a suspension, and the ratio of the amount of phosphorus element to the total amount of iron and manganese elements is controlled in a coordinated manner, so that the particle size of the ferromanganese phosphate material is reduced and evenly distributed; further, by controlling the sintering temperature of the hydrated ferromanganese phosphate under an air atmosphere, the prepared ferromanganese phosphate has good crystallinity and purity. This process not only reduces the post-processing process of ferrophosphate, but also helps to increase the contact area between ferrophosphate and the manganese source, fully react, thereby promoting the uniform distribution of manganese and iron and reducing the particle size of ferromanganese phosphate, which is conducive to further improving material performance; the present invention uses waste ferrophosphorus slag to prepare ferromanganese phosphate, reduces the generation of waste in the preparation and recycling process of batteries, improves the comprehensive utilization rate of waste battery resources, and alleviates the pressure it brings to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The XRD patterns of Examples 1-3 and Comparative Example 1 are shown;

[0023] Figure 2 The SEM images of Examples 1-3 and Comparative Examples 1-3 are shown;

[0024] Figure 3 This is the XRD pattern of the lithium iron manganese phosphate positive electrode material prepared using the iron manganese phosphate obtained in Example 3 as a raw material;

[0025] Figure 4 The charge and discharge curves of button batteries using the lithium manganese iron phosphate positive electrode materials provided in Example 3 and Comparative Examples 2-3 of the present invention at 0.1C. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described in detail below with reference to the embodiments, but the protection scope is not limited thereto. Example 1

[0027] A method for preparing ferromanganese phosphate using waste ferrophosphorus slag, specifically comprising the following steps:

[0028] (1) Weigh 100 g of ferrophosphorus slag, a by-product of yellow phosphorus production, according to mass fractions, add 300 g of deionized water, heat to 60°C, and stir for 30 min to mix the materials evenly to obtain a slurry;

[0029] (2) adding hydrochloric acid to the slurry obtained in step S1, heating to a constant temperature of 60°C, stirring and reacting for 2 h, and after the reaction is completed, obtaining a leachate by vacuum filtration, adding hydrogen peroxide to the leachate to carry out an oxidation reaction, and obtaining a ferrophosphorus liquid after the oxidation is complete;

[0030] (3) Ammonia water was added to the ferrophosphorus solution obtained in step S2, and the pH value was adjusted to 2.0. The solution was heated to a constant temperature of 40°C, and manganese oxyhydroxide was added according to a certain ratio of the amount of iron and manganese substances of 0.4:0.6. After stirring for 1 hour, the solution was heated to 92°C, and phosphoric acid solution was added dropwise according to a ratio of the amount of phosphorus element to the total amount of iron and manganese elements of 1:1. After the addition was completed, the solution was stirred at a constant temperature for 1 hour. After the reaction was completed, the solution was filtered, washed, and dried at 90°C for 2 hours to obtain hydrated manganese ferrophosphate.

[0031] (4) The hydrated manganese ferrophosphate obtained in step S3 was sintered at 350°C for 2 h in air atmosphere to obtain manganese ferrophosphate. XRD and SEM characterization results were as follows: Figure 1 and Figure 2 shown. Example 2

[0032] A method for preparing ferromanganese phosphate using waste ferrophosphorus slag, specifically comprising the following steps:

[0033] (1) Weigh 200 g of waste lithium iron phosphate extraction waste residue according to mass fraction, add 500 g of deionized water, heat to 80°C, and stir for 30 min to mix the materials evenly to obtain a slurry;

[0034] (2) adding sulfuric acid to the slurry obtained in step S1, heating to a constant temperature of 80°C, stirring and reacting for 3 hours. After the reaction is completed, vacuum filtration is performed to obtain a leachate, and hydrogen peroxide is added to the leachate to carry out an oxidation reaction. After the oxidation is complete, a ferrophosphorus liquid is obtained;

[0035] (3) Add sodium hydroxide solution to the ferrophosphorus solution obtained in step S2, adjust the pH value to 1.8, heat to a constant temperature of 50°C, add manganese trioxide according to a certain ratio of the amount of iron and manganese substances of 0.5:0.5, stir and react for 1 hour, heat to 95°C, and start adding phosphoric acid solution dropwise according to the ratio of the amount of phosphorus element to the total amount of iron and manganese elements of 1:0.9. After the addition is completed, stir and react at a constant temperature for 1.5 hours. After the reaction is completed, filter, wash and dry at 100°C for 3 hours to obtain hydrated manganese ferrophosphate.

[0036] (4) The hydrated manganese ferrophosphate obtained in step S3 was sintered at 400°C for 2 h in air atmosphere to obtain manganese ferrophosphate. XRD and SEM characterization results were as follows: Figure 1 and Figure 2 shown. Example 3

[0037] A method for preparing ferromanganese phosphate using waste ferrophosphorus slag, specifically comprising the following steps:

[0038] (1) Weigh 100 g of waste lithium iron phosphate extraction waste residue according to mass fraction, add 300 g of deionized water, heat to 60°C, and stir for 30 min to mix the materials evenly to obtain a slurry;

[0039] (2) adding hydrochloric acid to the slurry obtained in step S1, heating to a constant temperature of 60°C, stirring and reacting for 2 h, and after the reaction is completed, obtaining a leachate by vacuum filtration, adding hydrogen peroxide to the leachate to carry out an oxidation reaction, and obtaining a ferrophosphorus liquid after the oxidation is complete;

[0040] (3) adding sodium hydroxide solution to the ferrophosphorus solution obtained in step S2, adjusting the pH value to 2.1, heating to a constant temperature of 40°C, adding manganese tetraoxide according to a certain ratio of the amount of iron and manganese substances of 0.3:0.7, stirring and reacting for 1.5 hours, heating to 95°C, and starting to dropwise add phosphoric acid solution according to a ratio of the amount of phosphorus element to the total amount of iron and manganese elements of 1:0.8. After the addition is completed, stirring and reacting at a constant temperature for 1.5 hours. After the reaction is completed, filtering, washing and drying at 120°C for 2 hours to obtain hydrated manganese ferrophosphate;

[0041] (4) The hydrated manganese ferrophosphate obtained in step S3 was sintered at 300°C for 3 h in air atmosphere to obtain manganese ferrophosphate. XRD and SEM characterization results were as follows: Figure 1 and Figure 2 shown.

[0042] Comparative Example 1:

[0043] (1) Weigh 100 g of waste lithium iron phosphate extraction waste residue according to mass fraction, add 300 g of deionized water, heat to 60°C, and stir for 30 min to mix the materials evenly to obtain a slurry;

[0044] (2) adding hydrochloric acid to the slurry obtained in step S1, heating to a constant temperature of 60°C, stirring and reacting for 2 h, and after the reaction is completed, obtaining a leachate by vacuum filtration, adding hydrogen peroxide to the leachate to carry out an oxidation reaction, and obtaining a ferrophosphorus liquid after the oxidation is complete;

[0045] (3) adding sodium hydroxide solution to the ferrophosphorus solution obtained in step S2, adjusting the pH value to 2.1, heating to a constant temperature of 40°C, adding manganese tetraoxide according to a certain ratio of the amount of iron and manganese substances of 0.3:0.7, stirring and reacting for 1.5 hours, heating to 95°C, and starting to dropwise add phosphoric acid solution according to a ratio of the amount of phosphorus element to the total amount of iron and manganese elements of 1:0.8. After the addition is completed, stirring and reacting at a constant temperature for 1.5 hours. After the reaction is completed, filtering, washing and drying at 120°C for 2 hours to obtain hydrated manganese ferrophosphate;

[0046] (4) The hydrated ferromanganese phosphate obtained in step S3 was sintered at 420°C for 2 h in an air atmosphere to obtain ferromanganese phosphate. XRD and SEM characterization results were as follows: Figure 1 and Figure 2 shown.

[0047] Comparative Example 2:

[0048] (1) Weigh 100 g of waste lithium iron phosphate extraction waste residue according to mass fraction, add 300 g of deionized water, heat to 60°C, and stir for 30 min to mix the materials evenly to obtain a slurry;

[0049] (2) adding hydrochloric acid to the slurry obtained in step S1, heating to a constant temperature of 60°C, stirring and reacting for 2 h, and after the reaction is completed, obtaining a leachate by vacuum filtration, adding hydrogen peroxide to the leachate to carry out an oxidation reaction, and obtaining a ferrophosphorus liquid after the oxidation is complete;

[0050] (3) adding sodium hydroxide solution to the ferrophosphorus solution obtained in step S2, adjusting the pH value to 2.1, heating to a constant temperature of 40°C, adding manganese tetraoxide according to a certain ratio of the amount of iron and manganese substances of 0.3:0.7, stirring and reacting for 1.5 hours, heating to 95°C, and starting to dropwise add phosphoric acid solution according to a ratio of the amount of phosphorus element to the total amount of iron and manganese elements of 1:1.5. After the addition is completed, stirring and reacting at a constant temperature for 1.5 hours. After the reaction is completed, filtering, washing and drying at 120°C for 2 hours to obtain hydrated manganese ferrophosphate;

[0051] (4) The hydrated ferromanganese phosphate obtained in step S3 was sintered at 350°C for 2 h in an air atmosphere to obtain ferromanganese phosphate. The ferromanganese phosphate was characterized by SEM. The results were as follows: Figure 2 shown.

[0052] Comparative Example 3:

[0053] The method of the present invention is not used to prepare ferromanganese phosphate using waste ferrophosphorus slag. The specific steps are derived from Example 3 in Patent Publication No.: CNCN118929612 A, as follows:

[0054] (1) According to the chemical formula Mn0.5Fe0.5PO4, add manganese sulfate and ferrous sulfate to a certain amount of pure water. Stir until the solution is clear and transparent. Then add phosphoric acid solution in an amount equal to the molar amount of manganese sulfate and ferrous sulfate and stir thoroughly. Then add an appropriate amount of pure water to the volume. The final result is a mixed solution A with a manganese sulfate concentration of 0.5 mol / L, a ferrous sulfate concentration of 0.5 mol / L, and a phosphoric acid concentration of 1 mol / L.

[0055] (2) Add diammonium hydrogen phosphate as a chelating agent to the mixed solution A at a ratio of phosphate ion molar amount: total iron and manganese metal ion molar amount = 1.5:1, and stir thoroughly. Then, add ammonium persulfate as an oxidant at a ratio of oxidant molar amount: total iron and manganese metal ion molar amount = 1.2:1, and continue stirring until the ammonium persulfate is completely dissolved. Filter the resulting solution and let it stand for 12 hours to obtain a mixed solution B.

[0056] (3) 20% volume of mixed solution B was used as the base liquid. Ammonia water was added to the base liquid as a pH regulator to adjust the pH of the base liquid to 5.0. After being fully stirred at a speed of 800 rpm, the temperature was raised to 90 °C and continued to stir and keep warm for 2 h to obtain a gray-green precursor slurry C.

[0057] (4) Using the gray-green precursor slurry C obtained in step (3) as the base liquid, slowly pump in the remaining 80% volume of the mixed solution B under stirring and heating conditions, and adjust the system pH to 3.0. During the reaction, the stirring speed is 800 rpm and the temperature is 95°C. After the feeding is completed, continue to keep warm for 2 h to obtain the precursor slurry D.

[0058] (5) The product obtained in step (4) was centrifuged, dried, and sieved to obtain a powder, wherein the drying temperature was 120°C and the drying time was 12 h; the powder was calcined and dehydrated at 450°C for 4 h and then naturally cooled in an air calcination atmosphere to obtain a ferromanganese phosphate material, which was characterized by SEM. The results are as follows: Figure 2 shown.

[0059] Test example:

[0060] The manganese iron phosphate prepared in Example 3 and Comparative Examples 2-3 was used as raw material to prepare lithium manganese iron phosphate positive electrode materials, and the preparation steps were as follows:

[0061] The lithium iron manganese phosphate precursor and lithium dihydrogen phosphate are mixed in a molar ratio of 1:1 and 8-15% of the finished product carbon source is added for wet grinding for 2 hours, and then spray drying is performed to obtain an intermediate product. The intermediate product is heat treated at 700°C for 8 hours under nitrogen protection to obtain a lithium iron manganese phosphate positive electrode material. Figure 3 This is an SEM image of the lithium manganese iron phosphate positive electrode material prepared using the manganese iron phosphate in Example 3.

[0062] Test example:

[0063] The lithium manganese iron phosphate obtained in Example 3 and Comparative Example 2-3 was prepared according to the following formula: active material: conductive carbon black: PVDF =

[0064] 90:5:5 dispersed in NMP solvent to prepare slurry, the slurry was coated on aluminum foil to make a pole piece, the pole piece was used as the positive electrode and the lithium sheet was used as the negative electrode to prepare a button battery, and the rate performance of the battery was tested. The test results are shown in Table 1. The first charge and discharge curve of the battery at 0.1C is as follows Figure 4 shown.

[0065] Experimental data and analysis:

[0066] Table 1 shows the discharge specific capacity and charge-discharge efficiency of button cells of lithium manganese iron phosphate positive electrode materials provided in Example 3 and Comparative Examples 2-3 at 0.1C, 0.2C and 1.0C;

[0067] Table 1

[0068]

[0069] 1. From Figure 1 It can be seen from the XRD patterns of Examples 1-3 and Comparative Example 1 that the XRD diffraction patterns of the ferromanganese phosphate prepared by sintering Examples 1-3 at 300-400°C are consistent with those of the standard card PDF#70-1555 (Fe 0.65 Mn 0.35 Comparisons with the main peaks of Example 1 and Comparative Example 1 show essentially identical peak positions and intensities, demonstrating the successful synthesis of highly crystalline ferromanganese phosphate using waste ferrophosphorus slag as raw material. The ferromanganese phosphate obtained in Example 3 exhibited the highest crystallinity and purity. However, after sintering at 420°C, the crystalline form of the ferromanganese phosphate prepared in Comparative Example 1 had significantly changed.

[0070] Further from Figure 2 It can be seen from the SEM images of Examples 1-3 and Comparative Example 1 that the surface morphology of the ferromanganese phosphate after sintering at 420°C has become a molten state, further illustrating that in order to ensure that the ferromanganese phosphate material provided by the present invention maintains its original crystal form after dehydration, it should be sintered in air at 300-400°C.

[0071] observe Figure 2 The SEM images of Examples 1-3 and Comparative Example 2 show that the ferromanganese phosphate prepared by the present invention consists of fine, spherical particles with a primary particle size distribution between 20 and 40 nm. However, in Comparative Example 2, due to the higher phosphorus content, the ratio of the phosphorus content to the total amount of iron and manganese content is 1:1.5, resulting in significant agglomeration of the primary particles of the ferromanganese phosphate material, forming irregular particles with a significantly non-uniform particle size distribution.

[0072] Further observation Figure 2 It can be seen from the SEM images of Examples 1-3 and Comparative Example 3 that the ferromanganese phosphate prepared in Comparative Example 3 according to the prior art is also composed of spherical particles, and its primary particle size is about 100 nm, which is significantly larger than the primary particle size of the ferromanganese phosphate material provided by the present invention. This shows that the ferromanganese phosphate material provided by the present invention can effectively improve the problem of large particle size of the ferromanganese phosphate product prepared in the prior art.

[0073] Combined with Table 1 and Figure 4 It can be seen that within the charge and discharge range of the operating voltage of 2.0 ~ 4.5 V, Example 3 shows better electrical performance than Comparative Examples 2-3, with an initial discharge specific capacity of 154.73 mAh / g and a charge and discharge efficiency of 98.02% at a 0.1C rate, which are 22.02% and 6.8% higher than the 0.1C discharge specific capacities of Comparative Examples 2 and 3, respectively. This indicates that the particle morphology and size of the ferromanganese phosphate material significantly affect the electrical properties of the prepared lithium ferromanganese phosphate positive electrode material, further illustrating that the ferromanganese phosphate product provided by the present invention is conducive to further improving the electrical properties of the material, and reduces the generation of waste during the preparation and recycling of the battery, thereby alleviating the pressure it brings to the environment.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing ferromanganese phosphate using waste ferrophosphorus slag, characterized in that: The following steps are included: S1. Add deionized water to the waste ferrophosphorus slag, heat it to 40-90°C, and stir it for 10-30 minutes to mix the materials evenly to obtain a slurry; S2. Add acid solution to the slurry obtained in step S1, heat to a constant temperature of 40-90° C., and stir to react for 1-5 hours. After the reaction is completed, obtain a leachate by vacuum filtration, add an oxidant to the leachate, and perform an oxidation reaction. After complete oxidation, obtain a ferrophosphorus liquid; S3, adding alkali solution to the ferrophosphorus liquid obtained in step S2, adjusting the pH value, heating to a constant temperature of 30-80 ° C, adding a manganese source according to the corresponding ratio of the amount of iron and manganese substances, stirring and reacting for 0.5-2h, heating to 90-95 ° C, adding a certain amount of phosphoric acid to the slurry so that the ratio of the amount of phosphorus element to the total amount of iron and manganese elements is 1: (0.6~1.2), after completion of the dropwise addition, stirring and reacting at a constant temperature for 0.5-2.5h, after the reaction is completed, filtering, washing and drying at 80-120 ° C for 2-4h to obtain hydrated manganese ferrophosphate; S4. Sintering the hydrated ferromanganese phosphate obtained in step S3 in an air atmosphere at a temperature of 300-400° C. for 2-4 hours to obtain ferromanganese phosphate.

2. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: The waste ferrophosphorus slag in step S1 is a by-product of yellow phosphorus production or a waste slag from lithium extraction from waste lithium iron phosphate.

3. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: The mass ratio of the waste ferrophosphorus slag and deionized water in step S1 is 1:2-1:

5.

4. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, wherein: The acid solution in step S2 is one or more combinations of sulfuric acid, hydrochloric acid and nitric acid.

5. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: The oxidant in step S2 is one or more combinations of hydrogen peroxide and oxygen.

6. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: The alkaline solution in step S3 is at least one of sodium hydroxide solution or ammonia water, and the pH value is adjusted to 1.6-2.

3.

7. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: In step S3, the manganese source is one or more combinations of manganese oxyhydroxide, manganese hydroxide, trimanganese tetraoxide, manganese dioxide, and dimanganese trioxide.

8. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: In step S3, a manganese source is added so that the ratio of the amounts of iron and manganese is any value between (0.2-0.8):(0.8-0.2).

9. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 8, characterized in that: In step S3, a manganese source is added so that the ratio of the amounts of iron and manganese is one of 0.2:0.8, 0.3:0.7, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.7:0.3, and 0.8:0.

2.

10. The method for preparing ferromanganese phosphate using waste ferrophosphorus slag according to claim 1, characterized in that: The ratio of the amount of phosphorus element in step S3 to the total amount of iron and manganese elements is one of 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, and 1:1.2.

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