Process for preparing battery-grade iron phosphate from recycled carbon coarse iron phosphate

Abstract

The present application relates to the technical field of iron phosphate preparation, in particular to a process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate. Specifically, the carbon-containing crude iron phosphate is ground into fine powder, and then deionized water is added to form a slurry, which is reacted in an alkaline environment to obtain carbon-containing iron hydroxide. The iron hydroxide is calcined in an inert atmosphere and then subjected to magnetic separation to obtain iron powder. The iron powder is dissolved in acid, and then passed through a membrane separator of a homogeneous cation exchange membrane to remove metal impurity ions. Sodium phosphate solution and hydrogen peroxide are added to obtain basic iron phosphate. The basic iron phosphate is aged with phosphoric acid, and then calcined to obtain anhydrous iron phosphate. The modified homogeneous cation exchange membrane has high selectivity and adsorption capacity. The metal impurity ions are removed from the iron phosphate solution by forming complexes with the metal impurity ions through coordination bonds. The method significantly improves the purity of the battery-grade iron phosphate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of iron phosphate preparation, and particularly relates to a process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate. BACKGROUND

[0002] At present, with the rapid development of the new energy industry, there are more and more waste lithium ion batteries. How to recover valuable metals in waste lithium ion batteries has become a research hotspot. Among them, the proportion of carbon-containing crude iron phosphate in waste lithium ion batteries does not meet the use requirements of battery-grade iron phosphate, and is stored as solid waste, which causes serious resource waste and environmental pollution.

[0003] Chinese patent application No. CN202310579184.0 discloses a method for recovering valuable metals in waste lithium cobaltate from carbon-containing crude iron phosphate after selective lithium extraction of lithium iron phosphate. Iron phosphate waste slag generated in the process of selective lithium extraction of lithium iron phosphate is prepared into a slurry, and then sodium hydroxide is added for reaction. Iron hydroxide and high-purity sodium phosphate are obtained through solid-liquid separation. The iron hydroxide is decomposed into iron powder by calcination, and the high-purity ferric oxide for coating is obtained by natural oxidation after impurity removal. After drying, the sodium phosphate is acidified by adding a theoretical amount of concentrated sulfuric acid, and then low-temperature freezing and solid-liquid separation are performed to obtain phosphoric acid and sodium sulfate decahydrate. That is, the iron in the iron phosphate is recovered and prepared into ferric oxide which can be used as a coating material, and the phosphorus is recovered and prepared into phosphoric acid. Then, the obtained phosphoric acid is used to recover metal cobalt and lithium from waste lithium cobaltate to prepare battery-grade lithium carbonate and bird droppings which have high economic value and can be used to make fertilizer.

[0004] The method for full-element combined recovery of waste phosphorus iron slag generated by selective lithium extraction of waste lithium iron phosphate and waste lithium cobaltate (Patent No. CN116581415A) uses the strong oxidizing property of trivalent cobalt ions in lithium cobaltate to oxidize divalent iron ions in lithium iron phosphate into trivalent iron ions, and uses the reducing property of ferrous ions in lithium iron phosphate to reduce trivalent cobalt ions in lithium cobaltate into divalent cobalt ions, so that the full-element combined recovery of lithium, cobalt, iron and phosphorus in waste lithium iron phosphate and waste lithium cobaltate can be completed without adding a reducing agent or an oxidizing agent.

[0005] However, the applicant believes that the above-mentioned disclosed technology is complex in the utilization process of carbon-containing crude iron phosphate in waste lithium ion batteries, and produces part of solid waste, which has a certain impact on the environment. SUMMARY

[0006] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate.

[0007] Another purpose of the present application is to provide battery-grade iron phosphate obtained by the above preparation method.

[0008] The application achieves the purpose by the following technical scheme.

[0009] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that the process comprises the following steps:

[0010] S1: 200-500 parts of carbon-containing crude iron phosphate are weighed by mass fraction, ground into fine powder, added into 3000-6000 parts of deionized water to form a slurry, and added into 145-285 parts of alkali liquor for reaction, with the reaction temperature being controlled, and the reaction being carried out for 1-3 hours, so as to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0011] S2: The carbon-containing iron hydroxide obtained in step S1 is calcined in an inert gas environment for 2-4 hours, 1-10 parts of carbon powder is added during the calcination, and the obtained mixture is subjected to magnetic separation to obtain iron powder;

[0012] S3: The iron powder obtained in step S2 is dissolved by adding acid to obtain a ferrous ion solution, the solution is subjected to membrane separation by using a membrane separator provided with a homogeneous cation exchange membrane to remove metal impurity ions, the filtrate is adjusted to neutral by using alkali liquor, and is introduced into a reaction kettle, and the sodium phosphate solution in step S1 and 600-1200 parts of hydrogen peroxide are added to the reaction kettle, so as to obtain alkaline iron phosphate by heating reaction;

[0013] S4: The alkaline iron phosphate obtained in step S3 is adjusted to a pH of 1-3 by using phosphoric acid, and is aged for 1-3 hours, and then is washed and dried by using deionized water, and is calcined in a calcination chamber for 1-3 hours, and is cooled to room temperature to obtain anhydrous iron phosphate.

[0014] In some embodiments of the application, the alkali liquor in step S1 is at least one selected from sodium hydroxide, strong potassium oxide and sodium bicarbonate.

[0015] In some embodiments of the application, the reaction temperature in step S1 is 80-110 DEG C.

[0016] In some embodiments of the application, the calcination temperature in step S2 is 600-900 DEG C, and the inert gas during the calcination is selected from nitrogen, argon or helium.

[0017] In some embodiments of the application, the total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.90-1:1.

[0018] In some embodiments of the application, the calcination temperature in step S4 is 450-850 DEG C.

[0019] In some embodiments of the application, the modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps:

[0020] A1 irradiation: 100-200 parts of homogeneous cation exchange membrane containing free radicals on the surface is obtained by UV irradiation according to weight parts;

[0021] A2 irradiation crosslinking grafting reaction: 3-7 parts of vinyl diphenyl phosphine, 0.01-0.3 parts of 3-dicyclohexyl ferrocenyl-2-butenoic acid, 0.5-2 parts of photoinitiator, 500-700 parts of DMF, 40-60℃ stirring for 50-100 minutes, then 50-100 parts of homogeneous cation exchange membrane containing free radicals is immersed in the above material, stirring at 60-70℃ for 2-5h, take out the homogeneous cation exchange membrane, dry, then irradiate again, dry, to obtain modified homogeneous cation exchange membrane with diphenyl phosphine and ferrocenyl group.

[0022] In some embodiments of the present application, the homogeneous cation exchange membrane is a commercially available product, such as YM-3 type homogeneous cation exchange membrane; CSE CMB CXP-S type homogeneous cation exchange membrane.

[0023] In some embodiments of the present application, the photoinitiator is 2-hydroxy-4”(2-hydroxyethoxy)-2-methyl propiophenone.

[0024] In some embodiments of the present application, the specified dose value range is 10-200kGy.

[0025] In some embodiments of the present application, the UV irradiation conditions in the A1 and A2 steps are: irradiation under 365nm UV light for 10-20min, and the environmental temperature of the film under irradiation is 15-30℃.

[0026] Modification mechanism of homogeneous cation exchange membrane:

[0027] Vinyl diphenyl phosphine, 3-dicyclohexyl ferrocenyl-2-butenoic acid, and the surface of the CMV membrane containing free radicals on the surface undergo photopolymerization to generate modified homogeneous cation exchange membrane with diphenyl phosphine and ferrocenyl group.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The modified homogeneous cation exchange membrane containing diphenyl phosphine and ferrocenyl group has high selectivity and adsorption capacity, and forms a complex with metal impurity ions through coordination bond, thereby removing metal impurity ions from the iron phosphate solution, thereby improving the purity of battery-grade iron phosphate. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with embodiments. If specific conditions are not indicated in the embodiments, conventional conditions or conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] Embodiment 1

[0033] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0034] S1: 200 g of carbon-containing crude iron phosphate is weighed and ground into fine powder, 3000 g of deionized water is added to prepare a slurry, 145 g of alkali solution is added for reaction, the reaction temperature is controlled, the reaction is carried out for 1 h, and filtration is performed to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0035] S2: The carbon-containing iron hydroxide obtained in step S1 is calcined in an inert gas environment for 2 h, 2 g of carbon powder is added during calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder;

[0036] S3: The iron powder obtained in step S2 is dissolved by adding acid to obtain a ferrous ion solution, which is subjected to membrane separation by a membrane separator equipped with a homogeneous cation exchange membrane to remove metal impurity ions, the filtrate is adjusted to neutral pH with alkali solution, and is introduced into a reaction kettle, 600 g of hydrogen peroxide and the sodium phosphate solution in step S1 are added, and the reaction is carried out at elevated temperature to obtain basic iron phosphate;

[0037] S4: The basic iron phosphate obtained in step S3 is adjusted to pH 1 with phosphoric acid, aged for 1 h, washed with deionized water, dried, calcined in a calcination chamber for 1 h, and cooled to room temperature to obtain anhydrous iron phosphate.

[0038] The alkali solution in step S1 is selected from sodium hydroxide.

[0039] The reaction temperature in step S1 is 80°C.

[0040] The calcination temperature in step S2 is 600°C, and the inert gas during calcination is selected from nitrogen.

[0041] The total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.90:1.

[0042] The calcination temperature in step S4 is 450°C.

[0043] The homogeneous cation exchange membrane modification method in step S3 comprises the following steps:

[0044] A1 irradiation: 100 g of homogeneous cation exchange membrane is irradiated by ultraviolet to obtain a homogeneous cation exchange membrane containing free radicals on the surface;

[0045] A2 irradiation crosslinking grafting reaction: 3 g of vinyl diphenyl phosphine, 0.1 g of 3-dicyclohexylferrocenyl-2-butenoic acid, and 0.5 g of a photoinitiator are added to a stirred tank, 500 g of DMF is stirred at 40°C for 50 minutes, then 50 g of the homogeneous cation exchange membrane containing free radicals is immersed in the above materials, and the reaction is stirred at 60°C for 2 h, the homogeneous cation exchange membrane is taken out, dried, and then subjected to secondary ultraviolet irradiation and drying to obtain a modified homogeneous cation exchange membrane containing diphenyl phosphine and ferrocenyl groups.

[0046] The homogeneous cation exchange membrane is a commercially available product, YM-3 type homogeneous cation exchange membrane.

[0047] The photoinitiator is 2-hydroxy-4”(2-hydroxyethoxy)-2-methyl propiophenone.

[0048] The specified dose value range is 50 kGy.

[0049] The ultraviolet irradiation conditions in steps A1 and A2 are as follows: irradiation under 365 nm ultraviolet light for 10 min, and the environmental temperature of the film under irradiation is 15°C.

[0050] According to the analysis and calculation, the purity of the prepared iron phosphate material in this example is 99.45%, and the impurity element content is 21 ppm.

[0051] Example 2

[0052] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0053] S1: 300 g of carbon-containing crude iron phosphate is ground into fine powder, 4000 g of deionized water is added to prepare a slurry, 175 g of alkali solution is added for reaction, the reaction temperature is controlled, and the reaction is carried out for 1 h to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0054] S2: The carbon-containing iron hydroxide in step S1 is calcined in an inert gas environment for 2 h, 4 g of carbon powder is added during calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder;

[0055] S3: dissolving the iron powder obtained in step S2 with acid to obtain ferrous ion solution, removing metal impurity ions through a membrane separator equipped with a homogeneous cation exchange membrane, adjusting the pH of the filtrate to neutral with lye, and then introducing the filtrate into a reaction kettle, adding the sodium phosphate solution in S1 and 800 g of hydrogen peroxide, and then heating to obtain basic ferric phosphate;

[0056] S4: adjusting the pH of the basic ferric phosphate obtained in step S3 to 2 with phosphoric acid, aging for 2 h, then washing with deionized water and drying, calcining in a calcining chamber for 2 h, and then obtaining anhydrous ferric phosphate after air cooling to room temperature.

[0057] The lye in step S1 is at least one selected from sodium hydroxide, strong potassium oxide, and sodium bicarbonate.

[0058] The reaction temperature in step S1 is 90°C.

[0059] The calcining temperature in step S2 is 700°C, and the inert gas during calcining is nitrogen.

[0060] The total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.95:1.

[0061] The calcining temperature in step S4 is 650°C.

[0062] The modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps:

[0063] A1 irradiation: obtaining a homogeneous cation exchange membrane containing free radicals on the surface by irradiating 145 g of the homogeneous cation exchange membrane with ultraviolet light;

[0064] A2 irradiation crosslinking grafting reaction: adding 4.5 g of vinyl diphenyl phosphine, 0.15 g of 3-dicyclohexyl ferrocenyl-2-butenoic acid, 1 g of a photoinitiator, and 580 g of DMF into a stirred tank, stirring at 45°C for 70 minutes, then immersing 70 g of the homogeneous cation exchange membrane containing free radicals into the above materials, stirring at 65°C for 3 h, taking out the homogeneous cation exchange membrane, air-drying, then irradiating again with ultraviolet light, and drying to obtain a modified homogeneous cation exchange membrane containing diphenyl phosphine and ferrocenyl groups.

[0065] The homogeneous cation exchange membrane is a commercially available product, and is a YM-3 type homogeneous cation exchange membrane.

[0066] The photoinitiator is 2-hydroxy-4”(2-hydroxyethoxy)-2-methyl propiophenone.

[0067] The specified dose value range is 100 kGy.

[0068] The ultraviolet irradiation conditions in steps A1 and A2 are: irradiating for 10 min under 365 nm ultraviolet light, and the environmental temperature of the film under irradiation is 30°C.

[0069] The purity of the prepared iron phosphate material in this example is 99.75%, and the impurity element content is 17 ppm.

[0070] Example 3

[0071] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0072] S1: 400 g of carbon-containing crude iron phosphate is weighed and ground into fine powder, 5000 g of deionized water is added to form a slurry, 235 g of alkali solution is added for reaction, the reaction temperature is controlled, and the reaction is carried out for 2 h to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0073] S2: The carbon-containing iron hydroxide obtained in step S1 is calcined in an inert gas environment for 3 h, 8 g of carbon powder is added during calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder;

[0074] S3: The iron powder obtained in step S2 is dissolved with acid to obtain a ferrous ion solution, which is subjected to membrane separation using a membrane separator equipped with a homogeneous cation exchange membrane to remove metal impurity ions, the filtrate is adjusted to neutral pH with alkali solution, and is introduced into a reaction kettle, 1000 g of sodium phosphate solution in S1 and 1000 g of hydrogen peroxide are added, and the reaction is carried out to obtain basic iron phosphate;

[0075] S4: The basic iron phosphate obtained in step S3 is adjusted to pH 2 with phosphoric acid, aged for 2 h, then washed with deionized water, dried, calcined in a calcination chamber for 2 h, and cooled to room temperature to obtain anhydrous iron phosphate.

[0076] The alkali solution in step S1 is selected from strong potassium oxide.

[0077] The reaction temperature in step S1 is 100°C.

[0078] The calcination temperature in step S2 is 800°C, and the inert gas used during calcination is selected from argon.

[0079] In step S3, the total iron to phosphorus molar ratio in the reaction kettle is controlled to be 0.95:1.

[0080] The calcination temperature in step S4 is 750°C.

[0081] The modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps:

[0082] A1 irradiation: 175 g of homogeneous cation exchange membrane is irradiated with ultraviolet light to obtain a homogeneous cation exchange membrane containing free radicals on the surface;

[0083] A2 irradiation crosslinking grafting reaction: 6 g of vinyl diphenyl phosphine, 0.25 g of 3-dicyclohexyl-2-butyne acid, 1.5 g of photoinitiator, 640 g of DMF, stirring for 85 min at 55℃, then 85 g of homogeneous cation exchange membrane containing free radicals is immersed in the above material, stirring for 3 h at 70℃, taking out the homogeneous cation exchange membrane, drying, and then irradiating twice under ultraviolet light, drying, to obtain a modified homogeneous cation exchange membrane with diphenyl phosphine and ferrocene groups.

[0084] The homogeneous cation exchange membrane is a commercially available product, which is a CSE CMB CXP-S type homogeneous cation exchange membrane.

[0085] The photoinitiator is 2-hydroxy-4”(2-hydroxyethoxy)-2-methyl propiophenone.

[0086] The specified dose value range is 150 kGy.

[0087] The ultraviolet irradiation conditions in the A1 and A2 steps are: irradiation under 365 nm ultraviolet light for 20 min, and the environmental temperature of the film under irradiation is 15℃.

[0088] After analysis and calculation, the purity of the iron phosphate material prepared in this example is 99.84%, and the impurity element content is 13 ppm.

[0089] Example 4

[0090] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0091] S1: 500 g of carbon-containing crude iron phosphate is ground into fine powder, 6000 g of deionized water is added to prepare a slurry, 285 g of alkali solution is added for reaction, the reaction temperature is controlled, and the reaction is carried out for 3 h to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0092] S2: The carbon-containing iron hydroxide in step S1 is calcined in an inert gas environment for 4 h, 10 g of carbon powder is added during calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder;

[0093] S3: The iron powder obtained in step S2 is dissolved by adding acid to obtain a ferrous ion solution, which is subjected to a membrane separator equipped with a homogeneous cation exchange membrane to remove metal impurity ions, the filtrate is adjusted to neutral pH with alkali solution, and is introduced into a reaction kettle, 1200 g of hydrogen peroxide and the sodium phosphate solution in S1 are added, and the reaction is carried out under heating to obtain basic iron phosphate;

[0094] S4: The basic iron phosphate obtained in step S3 is adjusted to pH 3 with phosphoric acid, aged for 3 h, then washed with deionized water and dried, calcined in a calcination chamber for 3 h, and cooled to room temperature to obtain anhydrous iron phosphate.

[0095] The alkali solution in step S1 is selected from sodium bicarbonate.

[0096] The reaction temperature in step S1 is 110°C.

[0097] The calcination temperature in step S2 is 900°C, and the inert gas during calcination is selected from helium.

[0098] In step S3, the total iron to phosphorus molar ratio in the reaction kettle is controlled to be 1:1.

[0099] The calcination temperature in step S4 is 850°C.

[0100] The homogeneous cation exchange membrane modification method in step S3 includes the following steps:

[0101] A1 irradiation: 200g of homogeneous cation exchange membrane is irradiated with ultraviolet light to obtain a homogeneous cation exchange membrane containing free radicals on the surface;

[0102] A2 irradiation crosslinking grafting reaction: 7g of vinyl diphenyl phosphine, 0.3g of 3-diferrocenyl-2-butenoic acid, 2g of a photoinitiator, 700g of DMF, and 60°C stirring for 100 minutes are added to a stirred tank, then 100g of the homogeneous cation exchange membrane containing free radicals is immersed in the above materials, and stirred at 70°C for 5h, the homogeneous cation exchange membrane is taken out, dried, and then subjected to secondary ultraviolet irradiation and drying to obtain a modified homogeneous cation exchange membrane with diphenyl phosphine and ferrocenyl groups.

[0103] The homogeneous cation exchange membrane is a commercially available product, which is a CSE CMB CXP-S type homogeneous cation exchange membrane.

[0104] The photoinitiator is 2-hydroxy-4”(2-hydroxyethoxy)-2-methyl propiophenone.

[0105] The specified dose value range is 200kGy.

[0106] The ultraviolet irradiation conditions in steps A1 and A2 are: irradiation under 365nm ultraviolet light for 20min, and the environmental temperature of the film under irradiation is 30°C.

[0107] According to the analysis and calculation, the purity of the prepared iron phosphate material in this example is 99.62%, and the impurity element content is 16ppm.

[0108] Comparative Example 1

[0109] A process for recovering carbon-containing crude iron phosphate to prepare battery-grade iron phosphate, characterized in that it comprises the following steps:

[0110] S1: 200g of carbon-containing crude iron phosphate was weighed and ground into fine powder, 3000g of deionized water was added to prepare a slurry, 145g of alkali solution was added for reaction, the reaction temperature was controlled, and the reaction was carried out for 1h, and then filtration was performed to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0111] S2: The carbon-containing iron hydroxide obtained in step S1 was calcined under an inert gas environment for 2h, 2g of carbon powder was added during calcination, and the obtained mixture was subjected to magnetic separation to obtain iron powder;

[0112] S3: The iron powder obtained in step S2 was dissolved by adding acid to obtain a ferrous ion solution, metal impurity ions were removed through a membrane separator equipped with a YM-3 type homogeneous cation exchange membrane, the filtrate was adjusted to neutral pH with alkali solution, and then introduced into a reaction kettle, 600g of hydrogen peroxide and the sodium phosphate solution in S1 were added, and the reaction was carried out under heating to obtain basic iron phosphate;

[0113] S4: The basic iron phosphate obtained in step S3 was adjusted to pH 1 with phosphoric acid, aged for 1h, then washed with deionized water and dried, calcined in a calcination chamber for 1h, and cooled to room temperature to obtain anhydrous iron phosphate.

[0114] The alkali solution in step S1 is selected from sodium hydroxide.

[0115] The reaction temperature in step S1 is 80℃.

[0116] The calcination temperature in step S2 is 600℃, and the inert gas used during calcination is selected from nitrogen.

[0117] In step S3, the total iron to phosphorus molar ratio in the reaction kettle is controlled to be 0.90:1.

[0118] The calcination temperature in step S4 is 450℃.

[0119] According to the analysis and calculation, the purity of the iron phosphate material prepared in this example is 94.80%, and the impurity element content is 114ppm.

[0120] Comparative Example 2

[0121] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0122] S1: 200g of carbon-containing crude iron phosphate was weighed and ground into fine powder, 3000g of deionized water was added to prepare a slurry, 145g of alkali solution was added for reaction, the reaction temperature was controlled, and the reaction was carried out for 1h, and then filtration was performed to obtain a sodium phosphate solution and carbon-containing iron hydroxide;

[0123] S2: The carbon-containing iron hydroxide obtained in step S1 was calcined under an inert gas environment for 2h, 2g of carbon powder was added during calcination, and the obtained mixture was subjected to magnetic separation to obtain iron powder;

[0124] S3: The iron powder obtained in step S2 is dissolved with acid to obtain a ferrous ion solution, which is passed through a membrane separator equipped with a homogeneous cation exchange membrane to remove metal impurity ions, and the filtrate is adjusted to neutral pH with lye and is introduced into a reaction kettle, and the sodium phosphate solution in S1 and 600 g of hydrogen peroxide are added, and the reaction is carried out at elevated temperature to obtain basic iron phosphate;

[0125] S4: The basic iron phosphate obtained in step S3 is adjusted to pH 1 with phosphoric acid, aged for 1 h, and then washed with deionized water, dried, and calcined in a muffle furnace for 1 h, and after air cooling to room temperature, anhydrous iron phosphate is obtained.

[0126] The lye in step S1 is selected from sodium hydroxide.

[0127] The reaction temperature in step S1 is 80°C.

[0128] The calcination temperature in step S2 is 600°C, and the inert gas during calcination is selected from nitrogen.

[0129] The total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.90:1.

[0130] The calcination temperature in step S4 is 450°C.

[0131] The modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps:

[0132] A1 irradiation: 100 g of a homogeneous cation exchange membrane is irradiated with ultraviolet light to obtain a homogeneous cation exchange membrane containing free radicals on the surface;

[0133] A2 irradiation crosslinking grafting reaction: 0.1 g of 3-dicyclohexylferrocenyl-2-butenoic acid, 0.5 g of a photoinitiator, 500 g of DMF, and 40°C stirring for 50 minutes are added to a stirred tank, then 50 g of the homogeneous cation exchange membrane containing free radicals is immersed in the above materials, and stirring is carried out at 60°C for 2 h, the homogeneous cation exchange membrane is taken out, dried, and then subjected to secondary ultraviolet irradiation, dried, to obtain a modified homogeneous cation exchange membrane with diphenylphosphine and ferrocenyl groups.

[0134] The homogeneous cation exchange membrane is a commercially available product, and is a YM-3 type homogeneous cation exchange membrane.

[0135] The photoinitiator is 2-hydroxy-4" (2-hydroxyethoxy) -2-methylbenzophenone.

[0136] The specified dose value range is 50 kGy.

[0137] The ultraviolet irradiation conditions in steps A1 and A2 are: irradiation for 10 min under 365 nm ultraviolet light, and the environmental temperature of the film under irradiation is 15°C.

[0138] The purity of the prepared iron phosphate material in this example is 96.95%, and the impurity element content is 56 ppm.

[0139] Comparative Example 3

[0140] A process for preparing battery-grade iron phosphate from carbon-containing crude iron phosphate, characterized in that it comprises the following steps:

[0141] S1: 200g of carbon-containing crude iron phosphate is weighed and ground into fine powder, 3000g of deionized water is added to form a slurry, 145g of alkali solution is added for reaction, the reaction temperature is controlled, and the reaction is carried out for 1h, and the sodium phosphate solution and carbon-containing iron hydroxide are obtained by filtration;

[0142] S2: The carbon-containing iron hydroxide obtained in step S1 is calcined in an inert gas environment for 2h, 2g of carbon powder is added during calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder;

[0143] S3: The iron powder obtained in step S2 is dissolved with acid to obtain a ferrous ion solution, which is subjected to membrane separation by a membrane separator equipped with a homogeneous cation exchange membrane to remove metal impurity ions, the filtrate is adjusted to neutral pH with alkali solution, and is introduced into a reaction kettle, 600g of sodium phosphate solution in S1 and 600g of hydrogen peroxide are added, and the reaction is carried out to obtain basic iron phosphate;

[0144] S4: The basic iron phosphate obtained in step S3 is adjusted to pH 1 with phosphoric acid, aged for 1h, then washed with deionized water and dried, calcined in a calcination chamber for 1h, and cooled to room temperature to obtain anhydrous iron phosphate.

[0145] The alkali solution in step S1 is selected from sodium hydroxide.

[0146] The reaction temperature in step S1 is 80°C.

[0147] The calcination temperature in step S2 is 600°C, and the inert gas during calcination is selected from nitrogen.

[0148] The total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.90:1.

[0149] The calcination temperature in step S4 is 450°C.

[0150] The modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps:

[0151] A1 irradiation: 100g of homogeneous cation exchange membrane is irradiated with ultraviolet light to obtain a homogeneous cation exchange membrane containing free radicals on the surface;

[0152] A2 irradiation crosslinking grafting reaction: 3g of vinyl diphenyl phosphine, 0.5g of photoinitiator, 500g of DMF were added into a stirred tank, stirred for 50 minutes at 40℃, then 50g of homogeneous cation exchange membrane containing free radicals was immersed in the above materials, stirred at 60℃ for 2h, the homogeneous cation exchange membrane was taken out, dried, then subjected to secondary ultraviolet irradiation, dried, to obtain a modified homogeneous cation exchange membrane with diphenyl phosphine and ferrocenyl groups.

[0153] The homogeneous cation exchange membrane is a commercially available product, YM-3 type homogeneous cation exchange membrane.

[0154] The photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0155] The specified dose value range is 50kGy.

[0156] The ultraviolet irradiation conditions in the A1 and A2 steps are: irradiation under 365nm ultraviolet light for 10min, the environmental temperature of the film under irradiation is 15℃.

[0157] Through analysis and calculation, the purity of the prepared iron phosphate material in this example is 97.32%, and the impurity element content is 45ppm.

[0158] The present application is described above through specific embodiments and examples, however these descriptions are only illustrative, and should not be understood as limiting the protection scope of the present application. Those skilled in the art can make various improvements, modifications or equivalent replacements to the technical solutions and embodiments of the present application without departing from the spirit and protection scope of the present application, and these should all fall within the protection scope of the present application.

Claims

1. A process for the preparation of battery grade iron phosphate from recycled carbon coarse iron phosphate, characterized in that, The method comprises the following steps: S1: 200-500 parts of carbon-containing crude iron phosphate are weighed by mass fraction, ground into fine powder, added into 3000-6000 parts of deionized water to form a slurry, and added into 145-285 parts of alkali liquor for reaction, with the reaction temperature being controlled, and the reaction being carried out for 1-3 hours, so as to obtain a sodium phosphate solution and carbon-containing iron hydroxide; S2: The carbon-containing iron hydroxide in step S1 is calcined in an inert gas environment for 2-4 hours, 1-10 parts of carbon powder is added during the calcination, and the calcined mixture is subjected to magnetic separation to obtain iron powder; S3: The iron powder obtained in step S2 is dissolved by adding acid to obtain a ferrous ion solution, metal impurity ions are removed through a membrane separator provided with a homogeneous cation exchange membrane, the filtrate is adjusted to neutral pH by adding alkali liquor, and is introduced into a reaction kettle, and the sodium phosphate solution in S1 and 600-1200 parts of hydrogen peroxide are added for reaction at elevated temperature to obtain basic iron phosphate; S4: The basic iron phosphate obtained in step S3 is adjusted to a pH of 1-3 by phosphoric acid, aged for 1-3 hours, washed with deionized water, dried, calcined in a calcination chamber for 1-3 hours, and cooled to room temperature to obtain anhydrous iron phosphate; The modification method of the homogeneous cation exchange membrane in step S3 comprises the following steps: A1 irradiation: 100-200 parts of homogeneous cation exchange membrane is irradiated by ultraviolet light to obtain homogeneous cation exchange membrane containing free radicals on the surface; A2 irradiation crosslinking grafting reaction: 3-7 parts of vinyl diphenyl phosphine, 0.01-0.3 parts of 3-dicyclohexyl ferrocenyl-2-butenoic acid, 0.5-2 parts of a photoinitiator, 500-700 parts of DMF, and 40-60℃ stirring for 50-100 minutes are added into a stirring kettle, then 50-100 parts of homogeneous cation exchange membrane containing free radicals is immersed in the above material, and stirring reaction is carried out at 60-70℃ for 2-5 hours, the homogeneous cation exchange membrane is taken out, dried, and then subjected to secondary ultraviolet irradiation and drying to obtain modified homogeneous cation exchange membrane containing diphenyl phosphine and ferrocenyl groups.

2. A process for the preparation of battery grade iron phosphate from recycled carbon coarse iron phosphate as claimed in claim 1 wherein, The alkali liquor in step S1 is at least one selected from sodium hydroxide, potassium hydroxide, and sodium bicarbonate.

3. A process for the preparation of battery grade iron phosphate from recycled carbon coarse iron phosphate as claimed in claim 1 wherein, The reaction temperature in step S1 is 80-110℃.

4. A process for the preparation of battery grade iron phosphate from recycled carbon coarse iron phosphate as claimed in claim 1 wherein, The calcination temperature in step S2 is 600-900℃, and the inert gas used in the calcination is selected from nitrogen, argon, or helium.

5. A process of recovering carbon crude ferric phosphate to prepare battery grade ferric phosphate as claimed in claim 1 wherein, The total iron to phosphorus molar ratio in the reaction kettle in step S3 is controlled to be 0.90-1:

1.

6. A process of recovering carbon crude ferric phosphate to prepare battery grade ferric phosphate as claimed in claim 1 wherein, The calcination temperature in step S4 is 450-850℃.

7. A process of recovering carbon crude ferric phosphate to prepare battery grade ferric phosphate as claimed in claim 1 wherein, The photoinitiator is 2-hydroxy-4”-(2-hydroxyethoxy)-2-methyl propiophenone.

8. A process of recovering carbon crude ferric phosphate to prepare battery grade ferric phosphate as claimed in claim 1, wherein, The ultraviolet irradiation conditions in steps A1 and A2 are: irradiation under 365nm ultraviolet light for 10-20 minutes, and the environmental temperature of the film under irradiation is 15-30℃.