CN116902937A - Preparation method of ferric phosphate - Google Patents

Preparation method of ferric phosphate Download PDF

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CN116902937A
CN116902937A CN202210878910.4A CN202210878910A CN116902937A CN 116902937 A CN116902937 A CN 116902937A CN 202210878910 A CN202210878910 A CN 202210878910A CN 116902937 A CN116902937 A CN 116902937A
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phosphate
filtrate
iron
acid
rare earth
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欧阳宇平
龚铽
禹斌华
吕广智
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Hunan Shengdian New Materials Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • C01B25/375—Phosphates of heavy metals of iron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Compounds Of Iron (AREA)

Abstract

The application relates to a preparation method of ferric phosphate, which comprises the following steps: carrying out acid dissolution on neodymium iron boron waste by adopting sulfuric acid solution with the mass percentage concentration of 5% -35%, so that the concentration of ferrous sulfate in the obtained acid-dissolved mixed solution is 50 g/L-350 g/L, and the pH value of the acid-dissolved mixed solution is 0.5-5; after adding the deoxidizer, carrying out solid-liquid separation after the first filtrate reacts with the first soluble phosphate, taking the second filtrate to react with the oxidizing agent in a mixing way, and obtaining the impurity elements in the ferric phosphate and the mole ratio of the iron element to the phosphorus element, which are in accordance with the requirements of the battery-level ferric phosphate, and the conversion rate is higher.

Description

Preparation method of ferric phosphate
Technical Field
The application relates to the field of lithium batteries, in particular to a preparation method of ferric phosphate.
Background
The lithium battery has the advantages of high energy ratio and safety, long cycle life, low manufacturing cost and the like, and is a clean green chemical energy source; while lithium iron phosphate is considered to be one of the ideal positive electrode materials for power cells.
Iron phosphate is an important precursor for preparing lithium iron phosphate cathode materials, and the content and the molar ratio of iron element and phosphorus element in the iron phosphate and the particle size influence the compaction density and the electrochemical performance of the lithium iron phosphate.
The volume magnetic energy of the rare earth NdFeB (NdFeB) permanent magnet is 240-440 kJ/m 3 Is a magnetic material with excellent comprehensive performance, is called as 'permanent magnet king', and is widely used in the fields of information technology, new energy automobiles, wind power generation, industrial motors and the like. In the production process, a large amount of defective products, leftover materials, slag, ultrafine powder, oil sludge and the like are generated, and after the equipment is worn out and retired, a large amount of NdFeB waste is also generated.
Neodymium iron boron is an alloy body, and comprises rare earth (such as praseodymium, neodymium, terbium, dysprosium, gadolinium, holmium, cerium, yttrium), iron, boron, copper, cobalt, aluminum and the like, wherein the content of each element in different neodymium iron boron wastes can fluctuate, and the iron content is about 60 percent and the rare earth metal content is about 30 percent. The neodymium iron boron waste is used as the raw material to prepare the ferric phosphate, so that the waste utilization can be realized.
The traditional method for preparing the ferric phosphate by utilizing the NdFeB waste material comprises the following steps: (1) dissolving: dissolving neodymium iron boron waste with hydrochloric acid to obtain ferrous chloride solution containing impurity ions; (2) removing impurities: precipitating rare earth ions in the ferrous chloride solution by oxalic acid, increasing the pH value of the solution by iron powder, and removing residual impurity ions by a hydrolysis method to achieve the aim of purifying ferrous sulfate; (3) preparing ferric phosphate: and oxidizing the purified ferrous chloride to prepare an iron phosphate product suitable for the lithium battery industry. However, the method prepares the ferric phosphate in a hydrochloric acid system, so that the iron element is difficult to be converted into the ferric phosphate, and the utilization rate of the iron in the raw materials is low; in the prepared ferric phosphate, the proportion of the iron element to the phosphorus element is too high, which is unfavorable for the electrochemical performance of the lithium iron phosphate.
Therefore, the preparation method of the iron phosphate, which takes neodymium iron boron waste as a raw material, has higher utilization rate of iron element, and the molar ratio of the iron element to the phosphorus element meets the requirements of battery-grade iron phosphate, has important significance.
Disclosure of Invention
Based on the method, the application provides the preparation method of the ferric phosphate, which takes neodymium iron boron waste as a raw material, has higher utilization rate of iron element, and the molar ratio of the iron element to the phosphorus element meets the requirement of battery-grade ferric phosphate.
The technical scheme for solving the technical problems is as follows.
A method for preparing ferric phosphate, comprising the following steps:
(1) Acid solution is adopted to carry out acid dissolution on the NdFeB waste material, so as to obtain acid-dissolved mixed solution; the acid solution is sulfuric acid solution with the mass percentage concentration of 5-35%, the concentration of ferrous sulfate in the acid solution mixed solution is 50-350 g/L, and the pH value of the acid solution mixed solution is 0.5-5;
(2) Mixing an deoxidizer with the acid solution mixed solution, and then carrying out solid-liquid separation to obtain a first filtrate;
(3) Mixing and reacting the first soluble phosphate with the first filtrate, and then carrying out solid-liquid separation to obtain a second filtrate;
(4) And mixing the second filtrate with an oxidant for reaction to prepare ferric phosphate.
In some embodiments, in the method for preparing iron phosphate, in the step (3), the molar ratio of the rare earth ions in the first filtrate to the first soluble phosphate is 1 (1-3).
In some embodiments, in the method for preparing iron phosphate, the pH of the reaction solution is 2 to 4 when the step (3) is mixed for reaction.
In some embodiments, the method of preparing ferric phosphate, in the step (3) mixing reaction, further comprises adding a flocculant.
In some of these embodiments, in the method of producing ferric phosphate, in step (4), fe in the second filtrate is controlled 2+ The concentration of the water-soluble phosphate is 10g/L to 100g/L, and then the water-soluble phosphate is mixed with the second soluble phosphate and the oxidant for reaction.
In some embodiments, in the method for preparing iron phosphate, in the step (4), the pH of the second filtrate is adjusted to 0.5-2 during the mixing reaction, and then the second filtrate is mixed with the second soluble phosphate and the oxidizing agent for reaction.
In some embodiments, the method for preparing ferric phosphate further comprises a step of adding a second soluble phosphate in the step (4) so that Fe in the reaction solution 2+ With soluble phosphorusThe mol ratio of the acid salt is 1 (2-5).
In some embodiments, the method for preparing ferric phosphate, in the step (4), the mixing reaction further comprises adding an organic dispersing agent.
In some embodiments, the method for preparing iron phosphate comprises adding at least one oxygen scavenger selected from the group consisting of ammonium sulfite, sodium sulfite, ammonium hypophosphite, sodium hypophosphite, ammonium phosphite, and sodium phosphite.
In some embodiments, the first soluble phosphate is selected from at least one of monoammonium phosphate, monosodium phosphate, diammonium phosphate, disodium phosphate, sodium phosphate, and ammonium phosphate.
Compared with the prior art, the preparation method of the iron phosphate has the following beneficial effects:
according to the preparation method of the ferric phosphate, the specific type of acid solution is adopted to carry out acid dissolution on the neodymium iron boron waste, and as the solubility difference between the rare earth sulfate and ferrous sulfate in water is larger and the solubility of the rare earth sulfate is smaller, the rare earth ions are easier to separate out rare earth sulfate crystals from sulfate radicals by controlling the mass percentage concentration of the sulfuric acid solution and the concentration of the ferrous sulfate in the acid-dissolved mixed solution, and ferrous ions are not crystallized to separate out and exist in the acid-dissolved mixed solution, so that the ferrous ions and the rare earth ions are primarily separated; by controlling the pH value of the acid-soluble mixed solution and mixing the deoxidizer with the acid-soluble mixed solution, ferrous ions are prevented from being oxidized into ferric ions, and the deoxidizer can reduce a small amount of oxidized ferric ions into ferrous ions, so that ferric phosphate precipitates generated by the subsequent reaction of ferric ions and phosphate radicals are prevented from settling together with rare earth phosphate; further, the phosphate radical can form rare earth phosphate and ferrous ion respectively, the solubility of the rare earth phosphate and ferrous phosphate in water is different, the rare earth ion is separated out of rare earth phosphate crystal, and ferrous ion exists in the second filtrate, so that ferrous ion and rare earth ion are further separated; meanwhile, the impurity elements such as aluminum, chromium, zinc and the like can generate phosphate precipitation and settle together with rare earth phosphate so as to be separated from ferrous ions; in the second filtrate obtained by twice separation, the content of metal elements other than ferrous ions is less, the second filtrate containing ferrous ions is mixed and reacted with second soluble phosphate and oxidant, and the mass percent of impurity elements, iron elements and phosphorus elements in the obtained ferric phosphate and the molar ratio of the iron elements to the phosphorus elements all meet the requirements of battery-level ferric phosphate, and the utilization rate of the iron elements is higher.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a process for preparing iron phosphate according to one embodiment of the present application;
FIG. 2 is an SEM image of the iron phosphate dihydrate produced in example 1;
FIG. 3 is an SEM image of the iron phosphate dihydrate produced in example 2;
FIG. 4 is an XRD diffraction spectrum analysis chart of iron phosphate obtained in example 2;
FIG. 5 is an SEM image of the iron phosphate dihydrate produced in example 3;
FIG. 6 is an SEM image of the iron phosphate dihydrate produced in example 4;
FIG. 7 is an SEM image of the iron phosphate dihydrate produced in example 5.
Detailed Description
The technical scheme of the application is further described in detail below with reference to specific embodiments. The present application may be embodied in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, 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 herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In the description of the present application, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
The weights of the relevant components mentioned in the description of the embodiments of the present application may refer not only to the specific contents of the components, but also to the proportional relationship between the weights of the components, so long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down within the scope of the disclosure of the embodiments of the present application. Specifically, the weight described in the specification of the embodiment of the present application may be mass units known in the chemical industry field such as μ g, mg, g, kg.
The technical staff of the application obtain that the traditional method for preparing the ferric phosphate by utilizing the NdFeB waste material has lower conversion rate of raw materials through a large number of experiments and analyses; and the reason why the ratio of the iron element to the phosphorus element is high in the prepared ferric phosphate is probably as follows:
dissolving neodymium iron boron waste by hydrochloric acid to obtain FeCl 2 When the ferric phosphate is synthesized in the acidic environment, the ferric phosphate can be dissolved due to the strong reducibility of the hydrochloric acid, which is unfavorable for the synthesis and conversion of the ferric phosphate, thereby reducing the conversion rate of raw materials to products; oxalic acid is used as a rare earth precipitant to recycle rare earth, and ferrous ions are easy to co-precipitate together when the oxalic acid precipitates the rare earth, so that the purity of rare earth oxalate is not good when iron is lost; excess oxalic acid is usually added to precipitate the rare earthAt this time, the concentration of the oxalic acid radical ions remained in the mother solution is high, the reducibility is strong, and the conversion of the ferric phosphate is also affected. The method adopts iron powder to raise the pH value of the solution so as to remove impurity ions in the ferrous solution, and the step needs to be operated in an anaerobic environment, otherwise, as the pH value is raised, the ferrous ions are easily oxidized into ferric high-iron, and ferric iron is hydrolyzed to generate ferric hydroxide, so that the conversion and the purity of ferric phosphate are not facilitated.
The technical staff of the application also try to recover the rare earth by a sulfuric acid double salt method and then recover iron, namely, after the neodymium iron boron waste is subjected to acid dissolution by adopting inorganic acid, sodium sulfate, sodium chloride or ammonium sulfate and other salts are added, the rare earth forms rare earth double salt precipitate, but the solubility of the repeated rare earth double salt is larger, so that a part of rare earth residues are in ferrous sulfate solution, further impurity removal is needed in the ferrous sulfate solution, and the difficulty of separating and purifying ferrous sulfate is increased.
Referring to fig. 1, an embodiment of the present application provides a method for preparing iron phosphate, which includes steps S10 to S40.
Step S10: acid solution is adopted to carry out acid dissolution on the NdFeB waste material, so as to obtain acid-dissolved mixed solution; wherein the acid solution is sulfuric acid solution with the mass percentage concentration of 5-35%, the concentration of ferrous sulfate in the acid solution mixed solution is 50-350 g/L, and the pH value of the acid solution mixed solution is 0.5-5.
The rare earth sulfate has the characteristic of small solubility, such as Pr in every 100g of water 2 (SO 4 ) 3 ·8H 2 O was dissolved in water at 40℃to 7.64g; nd 2 (SO 4 ) 3 ·8H 2 O is dissolved in water at 40 ℃ to 4.61g, and FeSO 4 The solubility in water at 40℃can reach 40.1g.
The solubility of ferrous sulfate and rare earth sulfate in water is different, sulfuric acid solution is adopted to carry out acid dissolution on neodymium iron boron waste, the mass percentage concentration of the sulfuric acid solution is controlled, and the concentration of ferrous sulfate in acid-soluble mixed solution is controlled, so that the rare earth sulfate is close to saturation, sulfate crystals are easier to separate out, iron ions cannot be crystallized, and ferrous ions and rare earth ions are primarily separated; and by controlling the pH value of the acid-soluble mixed solution, ferrous ions are prevented from being oxidized into ferric ions, so that ferric phosphate precipitates generated by the subsequent reaction of ferric ions and phosphate radicals are prevented from being settled together with rare earth phosphate.
It can be understood that the sulfuric acid solution with the mass percentage concentration of 5-35% can be directly mixed with the neodymium iron boron waste for acid dissolution, or a certain amount of water can be added into the neodymium iron boron waste first, then concentrated hydrochloric acid is slowly added, and the mass percentage concentration of sulfuric acid in the acid dissolution process is controlled to be 5-35%. When the second mode is used for adding sulfuric acid, the adding speed of sulfuric acid needs to be controlled so as to control the reaction speed not to be too high and prevent the overflow amount of hydrogen from overflowing to cause the overflow.
It is further understood that the mass percent concentration of sulfuric acid solution during acid dissolution includes, but is not limited to, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%; the concentration of ferrous sulfate in the acid-soluble mixed liquor includes, but is not limited to, 50g/L, 80g/L, 100g/L, 150g/L, 200g/L, 250g/L, 255g/L, 260g/L, 270g/L, 280g/L, 285g/L, 290g/L, 300g/L, 310g/L, 315g/L, 320g/L, 330g/L, 340g/L, 350g/L; the pH of the acid-soluble mixture includes, but is not limited to, 0.5, 0.6, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5.
It is also understood that the amount of sulfuric acid solution added can be controlled based on the concentration of ferrous sulfate in the acid solution mixture.
In some examples, in step S10, the mass percentage concentration of the sulfuric acid solution in the acid dissolution process is 15% -30%; optionally, the mass percentage concentration of the sulfuric acid solution is 20% -30%.
In some examples, in step S10, the pH of the acid-soluble mixed solution is 0.5 to 3.
In some examples, in step S10, the concentration of ferrous sulfate in the acid-soluble mixed solution is 250g/L to 330g/L.
By controlling the concentration of ferrous sulfate in the acid-soluble mixed solution, the rare earth sulfate is close to saturation, rare earth sulfate crystals are easier to separate out, and iron ions cannot crystallize; if the concentration of ferrous sulfate in the acid solution mixed solution is too low, correspondingly the concentration of rare earth ions is low, which is not beneficial to the crystallization of the rare earth ions into sulfate to be separated out; and too high a concentration of ferrous sulfate can result in the crystallization of ferrous ions as well.
It can be further understood that by controlling the concentration of ferrous sulfate in the acid-soluble mixed solution, the rare earth sulfate can be conveniently saturated, rare earth sulfate crystals are easier to separate out, and correspondingly, the concentration of rare earth ions in the acid-soluble mixed solution can be controlled; optionally, the concentration of rare earth ions in the acid-soluble mixed solution is 40 g/L-45 g/L.
It can be further understood that if the neodymium iron boron waste is the finished product waste disassembled on the retired motor, the neodymium iron boron waste is crushed, so that the acid dissolution speed can be accelerated.
In some examples, in step S10, the temperature of the acid dissolution is 60 ℃ to 105 ℃.
It is understood that the temperature of the acid dissolution includes, but is not limited to, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃.
Step S20: and (3) mixing the deoxidizer with the acid-soluble mixed solution obtained in the step (S10), and then carrying out solid-liquid separation to obtain a first filtrate.
The deoxidizer is mixed with the acid solution mixed solution, so that ferrous ions can be further ensured not to be oxidized; even if a small amount of ferrous ions are oxidized into ferrous ions, the addition of the deoxidizer can further reduce the ferrous ions into ferrous ions; thereby avoiding the subsequent ferric ions from reacting with phosphate to generate ferric phosphate precipitate and settling together with rare earth phosphate.
In some examples, in step S20, the oxygen scavenger is selected from at least one of ammonium sulfite, sodium sulfite, ammonium hypophosphite, sodium hypophosphite, ammonium phosphite, and sodium phosphite. Optionally, the deoxidizer is selected from at least one of ammonium sulfite and sodium sulfite.
In some examples, in step S20, the mass ratio of ferrous sulfate to deoxidizer in the acid-soluble mixed solution is 100 (0.04-0.1).
It is understood that the mass ratio of ferrous sulfate to deoxidizer in the acid-soluble mixed liquor includes, but is not limited to, 100:0.04, 100:0.05, 100:0.06, 100:0.07, 100:0.08, 100:0.09, 100:0.1.
In some examples, in step S20, after the deoxidizer is mixed with the acid solution mixture, the mixture is stirred and reacted for 0.5 to 1.5 hours, and then the mixture is left for 2 to 8 hours, and then solid-liquid separation is performed.
Step S30: and (3) mixing the first soluble phosphate with the first filtrate obtained in the step (S20) for reaction, and then performing solid-liquid separation to obtain a second filtrate.
Rare earth phosphate REPO 4 Or REPO 4 ·nH 2 The solubility of O (n=0.5-4) in water is also smaller, ferrous ions and rare earth ions in the NdFeB waste are preliminarily separated by adopting sulfuric acid, and then the rest rare earth ions are crystallized through second soluble phosphate to generate rare earth phosphate precipitate, so that the ferrous ions and the rare earth ions are further separated, and a ferrous sulfate solution with higher purity is obtained.
If the ferrous sulfate solution contains aluminum, chromium, zinc and other impurity elements, phosphate precipitate and rare earth phosphate precipitate are also generated to separate from ferrous ions.
In some examples, in step S30, the molar ratio of rare earth ions in the first filtrate to the first soluble phosphate is 1 (1-3).
It is understood that the molar ratio of rare earth ions to the first soluble phosphate in the first filtrate includes, but is not limited to, 1:1, 1:1.1, 1:1.5, 1:1.8, 1:2, 1:2.5, 1:2.8, 1:3.
It is further understood that unreacted soluble phosphate may be used to synthesize ferrous dihydrogen phosphate and further iron phosphate.
In some examples thereof, in step S30, the first soluble phosphate is selected from at least one of monoammonium phosphate, monosodium phosphate, diammonium phosphate, and disodium phosphate. Optionally, the first soluble phosphate is selected from at least one of monoammonium phosphate and monosodium phosphate.
In some examples, in step S30, the pH of the reaction solution is 2 to 4 during the mixing reaction.
In some examples, in step S30, at least one of sodium hydroxide, ammonia, or sodium carbonate may be used to adjust the pH.
And (3) by controlling the pH value of the reaction solution in the step S30, the rare earth ions and other non-iron impurity ions are promoted to be fully combined with phosphate to form phosphate precipitation, so that the ferrous sulfate solution is further purified.
In some examples, in step S30, the mixing reaction further includes adding a flocculant.
In some examples, in step S30, the flocculant is polyacrylamide.
In some examples, in step S30, the mass percentage of the flocculant to the rare earth ions in the first filtrate is 0.01% to 0.5%.
The addition of the flocculant can promote the growth of rare earth phosphate particles, improve the filterability of rare earth phosphate and reduce the inclusion loss of ferrous ions.
It can be understood that the first soluble phosphate, the first filtrate and the flocculating agent can be directly mixed for reaction, and further, the pH value is adjusted to be 2-4 after the first soluble phosphate, the first filtrate and the flocculating agent are mixed for reaction; the first soluble phosphate and the first filtrate are mixed to react, and then flocculant is added to react.
In some examples, in step S30, the temperature of the mixing reaction is 60-100 ℃ and the time is 1-6 h.
The impurity content requirements of the battery grade ferric phosphate production on the raw materials are as follows:
total mass of rare earth elements: the mass of iron element is less than 5.5 multiplied by 10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: iron Fe mass is less than 5 x 10 -5 。
Through detection, the impurities in the first filtrate meet the impurity content requirement of the battery grade ferric phosphate production on the raw materials.
It can be understood that the rare earth sulfate obtained after the solid-liquid separation in the step S20 and the rare earth phosphate obtained after the solid-liquid separation in the step S30 can be directly used as rare earth raw materials or used after conversion.
Step S40: and mixing the second filtrate with an oxidant for reaction to prepare the ferric phosphate.
It can be understood that in step S40, ferrous ions and the second soluble phosphate generate ferrous dihydrogen phosphate, ferrous dihydrogen phosphate and the oxidant react to generate ferric phosphate dihydrate, that is, the second filtrate, the second soluble phosphate and the oxidant react together to obtain a suspension containing ferric phosphate dihydrate solid particles, and the suspension is subjected to solid-liquid separation, washing, drying and high-temperature calcination to obtain ferric phosphate, wherein the reaction formula is as follows:
Fe 2+ +2NaH 2 PO 4 ＝Fe(H 2 PO 4 ) 2 +2Na +
2Fe(H 2 PO 4 ) 2 +H 2 O 2 ＝2FePO 4 ·2H 2 O↓+2H 3 PO 4
FePO 4 ·2H 2 O→FePO 4 。
in some examples, in step S40, the concentration of ferrous ions in the second filtrate is controlled to be 10g/L to 100g/L, and then the second filtrate is mixed with an oxidant for reaction.
It is understood that the concentration of ferric ion in the second filtrate includes, but is not limited to, 50g/L, 55g/L, 60g/L, 65g/L, 70g/L, 75g/L, 80g/L, 85g/L, 88g/L, 90g/L, 92g/L, 95g/L, 100g/L.
By controlling the concentration of ferrous ions in the second filtrate, the generated ferric phosphate is ensured to have fine basic particle size and excellent performance.
In some examples, in step S40, the pH of the second filtrate is adjusted to 0.5-2, and then mixed with the second soluble phosphate and the oxidizing agent for reaction.
It can be understood that in step S40, the pH value of the second filtrate is adjusted and controlled to ensure that phosphate is ionized into dihydrogen phosphate and generates ferrous dihydrogen phosphate with ferrous ion, thereby promoting the generation of ferric phosphate and improving the utilization rate of iron.
It is understood that the pH of the second filtrate in step S40 includes, but is not limited to, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.4, 2.5, 2.8, 3, 3.5, 3.8, 4.
In some examples, in step S40, a step of adding a second soluble phosphate is further included, so that the reaction solutionFe of (3) 2+ And H is 2 PO 4 - The molar ratio of (2) to (5) is 1.
It is understood that the second soluble phosphate may be added or not added as long as Fe in the reaction solution of step S40 2+ And H is 2 PO 4 - The molar ratio of (2) to (5) is 1. It is further understood that H in the reaction solution 2 PO 4 - The source of (a) may be all the first soluble phosphate, or may be both the first soluble phosphate and the second soluble phosphate. It can also be understood that Fe in the reaction solution of step S40 2+ And H is 2 PO 4 - Including but not limited to, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, 1:3.2, 1:3.4, 1:4, 1:4.5, 1:5.
In some examples thereof, in step S40, the second soluble phosphate is selected from at least one of monoammonium phosphate, monosodium phosphate, diammonium phosphate, and disodium phosphate. Optionally, the second soluble phosphate is selected from at least one of monoammonium phosphate and monosodium phosphate.
In some examples, in step S40, the oxidizing agent is selected from at least one of oxygen and hydrogen peroxide.
By adopting the oxidant, no new impurities are introduced.
In some examples, in step S40, the molar ratio of the oxidizing agent to ferrous ions in the second filtrate is (1-2): 1.
It is understood that the molar ratio of oxidizing agent to ferrous ions in the second filtrate includes, but is not limited to, 1:1, 1.1:1, 1.2:1, 1.5:1, 1.8:1, 2:1.
In some examples, in step S40, the mixing reaction further includes adding an organic dispersant.
In some examples, in step S40, the organic dispersant is selected from at least one of polyether, alkylpyridine, sodium alkylbenzenesulfonate, ethylenediamine tetraacetic acid (EDTA).
In some examples, in step S40, the mass percentage of the organic dispersant to the ferrous ions in the second filtrate is 0.01% to 0.2%.
And an organic dispersing agent is added, so that the granularity of the ferric phosphate dihydrate is controlled.
In some examples, in step S40, the reaction temperature is 80-100deg.C and the reaction time is 1-6 hours.
It is understood that the temperature of the reaction in step S40 includes, but is not limited to, 80 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃, 98 ℃, 100 ℃, and the time of the reaction includes, but is not limited to, 1h, 1.1h, 1.2h, 1.5h, 2h, 3h, 4h, 5h, 6h.
The reaction time in the step S40 can be determined according to the mole ratio of the phosphorus element to the iron element in the reaction solution in the step S40, the mole ratio of the phosphorus element to the iron element is high, the reaction time is short, and the granularity of the ferric phosphate dihydrate can be controlled, so that the granularity of the finally prepared ferric phosphate is controlled.
The solid ferric phosphate dihydrate particles obtained by the preparation method adopt a laser particle sizer to detect the particle size, the D50 is 0.8-2 mu m, the distribution is uniform, the solid ferric phosphate dihydrate particles belong to a super-micron-sized material, and the particle size characteristics of battery-sized ferric phosphate are met.
In the preparation method of the ferric phosphate, sulfuric acid is adopted instead of hydrochloric acid for acid dissolution, so that the problem that the hydrochloric acid can influence the subsequent conversion of the ferric phosphate is avoided, and the conversion rate of neodymium iron boron waste is effectively improved; and oxalic acid is not used for precipitating rare earth ions, so that the coprecipitation of ferrous oxalate is avoided, and the residual oxalic acid is not beneficial to the conversion of ferric phosphate in the subsequent ferric phosphate preparation process, so that the proportion of iron element and phosphorus element is higher, and the performance of ferric phosphate products is influenced; and the impurity is avoided being removed by improving the pH value hydrolysis method, the loss and waste of iron resources are reduced, and meanwhile, the technological process for preparing the ferric phosphate from the NdFeB waste is shortened to a great extent.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following examples of the method for producing iron phosphate according to the present application, it is to be understood that the method for producing iron phosphate according to the present application is not limited to the following examples.
Example 1
(1) Crushing 1 ton of NdFeB waste (containing 65.6% of iron, 30% of praseodymium and neodymium, 1.45% of other rare earth elements, 1% of boron, 0.3% of aluminum and the like) and placing in a PP reaction tankAdding a certain amount of water, slowly adding 98% concentrated sulfuric acid under stirring (70 r/min), controlling the acid adding speed to ensure that the sulfuric acid concentration in the PP reaction tank is 15%, supplementing water in the reaction process, and reacting at 80 ℃; stopping adding acid when the concentration of ferrous sulfate in the acid solution mixed solution is about 255g/L, regulating the pH value to 2.5 by using a small amount of NdFeB waste material, stopping the reaction, and filtering to obtain an acid solution with the total volume of about 7m 3 ；
(2) 700g of deoxidizer ammonium phosphite is added into the acid solution mixed solution obtained in the step (1), stirred and reacted for 1h, then the mixture is stood for 4h, and solid-liquid separation is carried out by adopting a water-ring type vacuum suction filtration mode, so as to obtain a first filtrate and rare earth sulfate precipitation;
(3) Detecting the concentration of rare earth ions in the first filtrate obtained in the step (2) to be 34.9g/L, wherein the volume of the first filtrate is 6.95m 3 Adding monoammonium phosphate according to the mol ratio of rare earth ions to monoammonium phosphate of 1:1.5, stirring and reacting for 1h, adjusting the pH value to be 2, adding a flocculating agent polyacrylamide solution with the mass percentage concentration of 0.02%, wherein the mass percentage of polyacrylamide to the rare earth ions in the first filtrate is 0.01%, and stirring and reacting for 4h at 90 ℃; performing solid-liquid separation by adopting plate-frame filter pressing to obtain ferrous sulfate purifying solution (second filtrate); through detection, the total mass RE of rare earth in the ferrous sulfate purifying solution is as follows: iron Fe mass ratio of 5.2×10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: fe mass of 3×10 -5 The method meets the impurity content requirement of battery grade ferric phosphate production on raw materials;
(4) Deionized water is added into the second filtrate to ensure that the ferrous ion concentration in the second filtrate is 60g/L, and ammonia water is used for regulating the pH value to be 1.5; according to Fe in the second filtrate 2+ And H is 2 PO 4 - Selectively adding ammonium dihydrogen phosphate at a molar ratio of 1:2, adding polyether organic dispersing agent according to the mass percent of the organic dispersing agent to ferrous ions in the second filtrate of 0.02%, adding oxidant hydrogen peroxide according to the molar ratio of the oxidant to ferrous ions in the second filtrate of 1.25:1, stirring and reacting for 2 hours at 90 ℃ to form white suspension containing ferric phosphate dihydrate solid particles, aging for 20 minutes, and performing solid-liquid separation, washing and dryingAfter dry and high temperature calcination, anhydrous ferric phosphate is obtained, and the conversion rate of the ferric into ferric phosphate is 99.5%.
SEM analysis shows that the obtained ferric phosphate dihydrate has fine granularity, spherical shape, D50 less than 1 μm and cell grade ferric phosphate granularity and microscopic morphology as shown in figure 2;
the obtained solid iron phosphate particles are measured by a laser particle sizer, and the D50 is 0.7 mu m and is uniformly distributed.
The rare earth element content of the obtained iron phosphate is shown in table 1, and other non-iron elements are shown in table 2.
TABLE 1
TABLE 2
Non-rare earth elements Aluminum Al Cu of copper Chromium Cr Nickel Ni Mn of Mn Titanium Ti Ca of calcium Mg of magnesium Cobalt Co
Content/ppm 4.5 1 1.4 17 4.3 1.2 14.7 21.2 14.7
Example 2
(1) Taking sulfuric acid solution with the mass percentage concentration of 20% and adding crushed neodymium iron boron waste slowly, controlling the reaction temperature to 90 ℃, stopping feeding when the concentration of ferrous sulfate in the sampled and tested acid solution mixed solution is 285g/L, adjusting the pH value to be 1.5 by using a small amount of neodymium iron boron waste or sulfuric acid, and standing for 6 hours;
(2) Adding 1720g of deoxidizer ammonium sulfite into the acid solution mixed solution in the step (1), stirring and reacting for 1h, standing for 4h, and performing solid-liquid separation in a water-ring vacuum suction filtration mode to obtain a first filtrate and rare earth sulfate precipitate;
(3) Adding monoammonium phosphate according to the mol ratio of rare earth ions to monoammonium phosphate in the first filtrate of 1:2, stirring and reacting for 1h, adjusting pH value to 4, adding a flocculating agent polyacrylamide solution with mass percent concentration of 0.05%, wherein the mass percent of polyacrylamide to the rare earth ions in the first filtrate of 0.03%, and stirring and reacting for 4h at 90 ℃; performing solid-liquid separation by adopting plate-frame filter pressing to obtain ferrous sulfate purifying solution (second filtrate); through detection, the total mass RE of rare earth in the ferrous sulfate purifying solution is as follows: iron Fe mass ratio of 4.3×10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: fe mass of 5×10 -5 The method meets the impurity content requirement of battery grade ferric phosphate production on raw materials;
(4) Deionized water is added into the second filtrate to ensure that the ferrous ion concentration in the second filtrate is 85g/L, and ammonia water is used for regulating the pH value to be 1.5; according to Fe in the second filtrate 2+ And H is 2 PO 4 - Selectively adding ammonium dihydrogen phosphate according to the molar ratio of 1:2, adding polyether organic dispersing agent according to the mass percentage of 0.02% of ferrous ions in the organic dispersing agent and the second filtrate, adding oxidant hydrogen peroxide according to the mass ratio of 1.25:1 of the oxidant to ferrous ions in the second filtrate, stirring and reacting for 2 hours at 95 ℃ to form white suspension containing solid particles of ferric phosphate dihydrate, aging for 20 minutes, and carrying out solid-liquid separation, washing, drying and high-temperature calcination to obtain anhydrous ferric phosphate. The concentration of iron ions in the ferric phosphate reaction mother liquor is 0.12g/L, and the conversion rate of converting iron into ferric phosphate is 99.3%.
As shown in a SEM (electron microscope) analysis chart as shown in figure 3, the obtained ferric phosphate dihydrate has fine granularity, is spherical, has D50 less than 1.5 mu m, and has the granularity and micro-morphology characteristics of battery grade ferric phosphate;
the obtained solid iron phosphate particles are measured by a laser particle sizer, and the D50 is 3.7 mu m and is uniformly distributed.
XRD diffraction spectrum analysis is shown in figure 4, and the obtained anhydrous ferric phosphate product has high purity.
The rare earth element content of the obtained iron phosphate is shown in Table 3, and the other non-iron elements are shown in Table 4.
TABLE 3 Table 3
TABLE 4 Table 4
Non-rare earth elements Aluminum Al Cu of copper Chromium Cr Nickel Ni Mn of Mn Titanium Ti Ca of calcium Mg of magnesium Cobalt Co
Content/ppm 5 4 1.2 11 3 1 18 20 14
Example 3
Substantially the same as in example 2, except that:
(1) The mass percentage concentration of sulfuric acid is 30%, the reaction temperature is 95 ℃, when the concentration of ferrous sulfate in the acid solution mixed solution reaches 315g/L, acid addition is stopped, and the pH value is adjusted to 2.5 by using NdFeB waste materials;
(3) Adding sodium dihydrogen phosphate according to the mol ratio of rare earth ions to sodium dihydrogen phosphate in the first filtrate of 1:1.5;
through the detection, the detection results show that,the total mass RE of rare earth in the obtained ferrous sulfate purification solution is as follows: iron Fe mass ratio of 3.2×10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: fe mass 3.2X10 -5 The method meets the impurity content requirement of battery grade ferric phosphate production on raw materials;
(4) Deionized water is added into the second filtrate to ensure that the ferrous ion concentration in the second filtrate is 90g/L, and the pH value is regulated to be 0.5 by sodium hydroxide; according to Fe in the second filtrate 2+ The molar ratio of the iron phosphate to the soluble phosphate is 1:2.5, ammonium phosphate is selectively added, the concentration of iron ions in the iron phosphate reaction mother liquor is 0.09g/L, and the conversion rate of converting iron into iron phosphate is 99.5%.
As shown in a SEM (electron microscope) analysis chart as shown in FIG. 5, the obtained ferric phosphate dihydrate has fine granularity, is spherical, has D50 less than 1.9 mu m, and has granularity and microscopic morphology characteristics of battery-grade ferric phosphate;
the obtained solid ferric phosphate particles are measured by a laser particle size analyzer, the D50 is 4.5 mu m, and the solid ferric phosphate particles are uniformly distributed;
the rare earth element content of the obtained iron phosphate is shown in Table 5, and the other non-iron elements are shown in Table 6.
TABLE 5
TABLE 6
Example 4
Substantially the same as in example 2, except that:
(1) Stopping adding acid when the concentration of ferrous sulfate in the acid solution mixed solution reaches 350g/L, and adjusting the pH value to 1.0;
(3) Adding sodium dihydrogen phosphate according to the mol ratio of rare earth ions to sodium dihydrogen phosphate in the first filtrate of 1:2.5;
and detecting to obtain the total mass RE of rare earth in the ferrous sulfate purification solution: iron Fe mass ratio of 5.2×10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: fe mass of 2X 10 -5 The method meets the impurity content requirement of battery grade ferric phosphate production on raw materials;
(4) Deionized water is added into the second filtrate to ensure that the ferrous ion concentration in the second filtrate is 50g/L, and the pH value is regulated to 1.5 by sodium hydroxide solution; according to Fe in the second filtrate 2+ Ammonium dihydrogen phosphate is selectively added in a molar ratio of 1:3 with respect to the soluble phosphate, the concentration of iron ions in the separated mother liquor is 0.9g/L, and the conversion rate of iron to ferric phosphate is 99.1%.
SEM analysis shows that the obtained ferric phosphate dihydrate has fine granularity, spherical shape, D50 smaller than 1.5 μm and battery grade ferric phosphate granularity and microscopic morphology as shown in FIG. 6;
the obtained solid iron phosphate particles are measured by a laser particle sizer, and the D50 is 2.5 mu m and is uniformly distributed.
The rare earth element content of the obtained iron phosphate is shown in Table 7, and the other non-iron elements are shown in Table 8.
TABLE 7
TABLE 8
Non-rare earth elements Aluminum Al Cu of copper Chromium Cr Nickel Ni Mn of Mn Titanium Ti Ca of calcium Mg of magnesium Cobalt Co
Content/ppm 2 1 1.9 10.3 1.2 1.5 10.2 23 13.5
Example 5
Substantially the same as in example 2, except that: in the step (4), deionized water is added into the second filtrate to ensure that the ferrous ion concentration in the second filtrate is 100g/L, and the pH value is regulated to 3.5 by sodium carbonate solution; according to Fe in the second filtrate 2+ Ammonium dihydrogen phosphate is selectively added in the molar ratio of 1:2.4 with the soluble phosphate, the concentration of iron ions in the ferric phosphate reaction mother solution is 0.04g/L, and the iron is converted into ferric phosphateThe conversion was 99.8%.
As shown in an SEM diagram of the obtained ferric phosphate dihydrate, as shown in fig. 7, the granularity is coarse, the agglomerated particles are more, the material activity is low, but the granularity and the microscopic morphology characteristics of the battery-grade ferric phosphate are still provided;
the obtained solid ferric phosphate particles show that the D50 is 4.5 mu m through the measurement of a laser particle size analyzer, and the distribution uniformity is reduced.
Example 6
Substantially the same as in example 2, except that: in the step (1), the acid addition is stopped when the concentration of ferrous sulfate in the sampling test acid solution mixed solution is 50 g/L.
Comparative example 1
(1) Acid-dissolving neodymium iron boron waste by adopting a hydrochloric acid solution with the mass percentage concentration of 20%, wherein the molar ratio of hydrochloric acid to neodymium iron boron waste is 2:1, the acid-dissolving temperature is 100 ℃, the acid-dissolving time is 2.5 hours, and the pH value of the acid-dissolving mixed solution is 0.5;
(2) Carrying out solid-liquid separation on the acid solution mixed solution obtained in the step (1), mixing filtrate and oxalic acid, wherein the molar ratio of oxalic acid to total rare earth in the filtrate is 1.15:1, and reacting for 35min at 90 ℃;
(3) Carrying out solid-liquid separation on the mixed solution obtained in the step (2), adding iron powder into filtrate to enable the pH value of the mixed solution to be 5, and hydrolyzing for 5 hours at 95 ℃;
(4) And (3) carrying out solid-liquid separation on the mixed solution obtained in the step (3) to ensure that the ferrous ion concentration in the filtrate is 100g/L, adding phosphoric acid and hydrogen peroxide for reaction to form white suspension containing solid particles of ferric phosphate dihydrate, and carrying out solid-liquid separation, washing, drying and high-temperature calcination to obtain anhydrous ferric phosphate, wherein the Fe/p (molar ratio) is higher, the rare earth content is higher and reaches 0.75%, and the conversion rate of converting iron into ferric phosphate (removing added iron powder) is 73.4%.
Comparative example 2
Substantially the same as in example 2, except that: in the step (1), a sulfuric acid solution with a mass percentage concentration of 55% was used in the comparative example 2. After the reaction stops and stands for 16 hours, a large amount of green ferrous sulfate and rare earth sulfate crystals are generated, which indicates that the ferrous sulfate and the rare earth form sulfate co-crystallization, the utilization rate of iron in the raw materials is reduced, and the conversion rate of converting iron into ferric phosphate is reduced to 70.2%. But the solution is subjected to subsequent treatment to obtain the iron phosphate product which is still battery grade iron phosphate.
Comparative example 3
Substantially the same as in example 2, except that: in the step (1), the feeding is stopped when the concentration of ferrous sulfate in the sampling test acid solution mixed solution is 10 g/L.
When phosphate precipitation is added for the first time, amorphous precipitate is generated, the dosage of flocculant is required to be increased, rare earth precipitate is difficult to filter, and the total mass RE of rare earth in ferrous sulfate purifying solution is detected: iron Fe mass ratio is 145 x 10 -5 Total mass of impurity metals such as Al, mn, cu, cr, zn: fe mass is 52×10 -5 The production of battery grade ferric phosphate is difficult to meet the requirement of impurity content in raw materials.
The conversion of iron to iron phosphate was 90.4%; the non-rare earth non-iron elements of the resulting iron phosphate are shown in table 9.
TABLE 9
Non-rare earth elements Aluminum Al Cu of copper Chromium Cr Nickel Ni Mn of Mn Titanium Ti Ca of calcium Mg of magnesium Cobalt Co
Content/ppm 16.5 6.4 11.9 13.11 12 21.1 60.18 102.1 52.1
Comparative example 4
Substantially the same as in example 2, except that: in the step (1), mixed acid of sulfuric acid and hydrochloric acid is adopted to carry out acid dissolution on neodymium iron boron waste, the mass ratio of the sulfuric acid to the hydrochloric acid is 1:1, the mass percentage concentration of the sulfuric acid is 15%, and the mass percentage concentration of the hydrochloric acid is 15%.
The obtained anhydrous ferric phosphate has high rare earth content which reaches 0.51 percent.
Comparative example 5
Substantially the same as in example 2, except that: and (3) directly carrying out solid-liquid separation without adding an deoxidizer in the step (2).
The conversion rate of iron into ferric phosphate is 85.4%, and the rare earth content of the obtained ferric phosphate reaches 0.23%.
Comparative example 6
Substantially the same as in example 2, except that: omitting the step (3) of mixing and reacting the first soluble phosphate with the first filtrate.
The rare earth content of the obtained anhydrous ferric phosphate is up to 35%, and the requirements of battery grade ferric phosphate are not met.
Some of the parameters in the preparation process of the iron phosphate of each example and comparative example are shown in table 10.
Table 10
The main component content and specific surface area of the iron phosphate prepared in each of the examples and comparative examples are shown in table 11; the requirements of the battery-grade ferric phosphate are as follows: the content of the phosphorus element in the ferric phosphate is 20.5-21%, the content of the iron element is 35-37%, the molar ratio of the iron to the phosphorus is 0.965-0.99, and the particle size of the ferric phosphate is less than 5 mu m.
TABLE 11
As can be seen from table 11, compared with the comparative example, the iron phosphate prepared in the example of the present application meets the technical requirements of battery grade iron phosphate; in comparative example 1, hydrochloric acid is adopted for acid dissolution, oxalic acid is adopted for rare earth precipitation and impurity removal, the Fe/p (molar ratio) of the obtained ferric phosphate is high, the conversion rate of the iron into the ferric phosphate is only 73.4%, the granularity is large, and the rare earth content is high; in comparative example 2, the concentration of the acid solution used in step (1) is higher, resulting in co-crystallization of ferrous sulfate and rare earth sulfate, thereby resulting in a greatly reduced conversion of iron to ferric phosphate and a larger particle size; comparative example 3, in which the concentration of ferrous sulfate is too low during acid dissolution, the granularity is large and the rare earth content is high; comparative example 4, using hydrochloric acid and sulfuric acid to dissolve the waste, the rare earth content of the iron phosphate product is slightly high, the granularity is large, and the conversion rate of iron into iron phosphate is low; in the process of the step (2) and the step (3), part of ferrous ions are oxidized into iron ions, and the iron ions and rare earth ions form phosphate together, so that the loss of the ferrous ions is caused, the conversion rate of iron is reduced, and in the subsequent preparation of ferric phosphate, the impurity content in the product is higher, and the rare earth content of the obtained ferric phosphate is higher; comparative example 6 does not perform the first step of phosphate precipitation of rare earth, and as a result, the rare earth content of the resulting iron phosphate is greatly exceeded the requirement of battery grade iron phosphate, since an important process for removing rare earth is omitted.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which facilitate a specific and detailed understanding of the technical solutions of the present application, but are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. It should be understood that, based on the technical solutions provided by the present application, those skilled in the art may obtain technical solutions through logical analysis, reasoning or limited experiments, which are all within the scope of protection of the appended claims. The scope of the patent is therefore intended to be covered by the appended claims, and the description and drawings may be interpreted as illustrative of the contents of the claims.

Claims (10)

1. The preparation method of the ferric phosphate is characterized by comprising the following steps of:
(1) Acid solution is adopted to carry out acid dissolution on the NdFeB waste material, so as to obtain acid-dissolved mixed solution; the acid solution is sulfuric acid solution with the mass percentage concentration of 5-35%, the concentration of ferrous sulfate in the acid solution mixed solution is 50-350 g/L, and the pH value of the acid solution mixed solution is 0.5-5;
(2) Mixing an deoxidizer with the acid solution mixed solution, and then carrying out solid-liquid separation to obtain a first filtrate;
(3) Mixing and reacting the first soluble phosphate with the first filtrate, and then carrying out solid-liquid separation to obtain a second filtrate;
(4) And mixing the second filtrate with an oxidant for reaction to prepare ferric phosphate.
2. The method of producing iron phosphate according to claim 1, wherein in step (3), the molar ratio of the rare earth ions in the first filtrate to the first soluble phosphate is 1 (1-3).
3. The method for producing iron phosphate according to claim 1, wherein the pH of the reaction solution is 2 to 4 during the mixing reaction in the step (3).
4. A method of producing iron phosphate according to any one of claims 1 to 3, further comprising adding a flocculant to the mixing reaction in step (3).
5. The method for producing iron phosphate according to claim 1, wherein in step (4), fe in the second filtrate is controlled 2+ The concentration of the water-soluble phosphate is 10g/L to 100g/L, and then the water-soluble phosphate is mixed with the second soluble phosphate and the oxidant for reaction.
6. The method according to claim 1, wherein the second filtrate is adjusted to a pH of 0.5 to 2 during the mixing reaction in step (4), and is mixed with the second soluble phosphate and the oxidizing agent.
7. The method for producing iron phosphate according to claim 1, further comprising the step of adding a second soluble phosphate in the step (4) so that Fe in the reaction solution 2+ And H is 2 PO 4 - The molar ratio of (2) to (5) is 1.
8. The method for producing iron phosphate according to any one of claims 1 to 3 and 5 to 7, wherein the mixing reaction in the step (4) further comprises adding an organic dispersant.
9. The method for producing iron phosphate according to any one of claims 1 to 3 and 5 to 7, wherein the deoxidizer is at least one selected from the group consisting of ammonium sulfite, sodium sulfite, ammonium hypophosphite, sodium hypophosphite, ammonium phosphite and sodium phosphite.
10. The method of producing iron phosphate according to any one of claims 1 to 3, 5 to 7, wherein the first soluble phosphate is at least one selected from monoammonium phosphate, monosodium phosphate, diammonium phosphate, disodium phosphate, sodium phosphate and ammonium phosphate.
CN202210878910.4A 2022-07-25 2022-07-25 Preparation method of ferric phosphate Pending CN116902937A (en)

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