Method for dephosphorizing ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron concentrate

Abstract

The present invention belongs to the field of lithium iron phosphate battery waste slag treatment, specifically relating to a method for dephosphorizing ferrophosphorus slag and recycling it to produce water-soluble phosphate fertilizer and iron concentrate. The ferrophosphorus slag dephosphorization method comprises: dephosphorizing the ferrophosphorus slag in a solution containing a dephosphorizing agent and an inhibitor, followed by solid-liquid separation to obtain a phosphorus-containing solution and dephosphorized ferrophosphorus slag. The dephosphorizing agent comprises components A, B, and C; component A is a compound of formula 1 (#imgabs0#); component B is a compound of formula 2 (#imgabs1#); and component C is a compound of formula 3 (#imgabs2#); and the inhibitor is at least one of sulfide, silicate, oxalate, and EDTA. The present invention innovatively utilizes a synergistic combination of components A, B, and C in a dephosphorizing agent and an inhibitor. This achieves synergy, effectively disrupting the stable iron phosphate crystal structure of the ferrophosphorus slag and achieving selective dephosphorization of the solid phase of the ferrophosphorus slag. This facilitates the simple resource utilization of phosphorus and iron.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of waste lithium-ion battery solid waste, and particularly relates to the field of decomposition and utilization of iron and phosphorus in ferrophosphorus slag. Background Art

[0002] Lithium iron phosphate (LiFePO4) has been widely used in electric vehicles, electric buses, communication base stations and other fields due to its advantages such as high specific capacity, excellent safety performance, long cycle life and low preparation cost.

[0003] Currently, the mainstream recycling technology for retired lithium iron phosphate battery cathode materials is the wet process for selective lithium recovery, a technology that has achieved industrialized operation. However, the lithium extraction process produces a large amount of ferrophosphorus slag, which has a complex composition and high impurity content, making resource recovery difficult.

[0004] The main existing process for ferrophosphorus slag is acid leaching and purification. For example, Chinese patent documents with publication numbers CN116425136A and CN111646447A both disclose methods for acid leaching and purifying ferrophosphorus slag to produce higher-purity ferric phosphate. Patent document WO2024178945A1 discloses a process for flotation and carbon removal of ferrophosphorus slag to obtain purified ferric phosphate.

[0005] Chinese patent publication CN115784187A discloses a method for preparing anhydrous ferric phosphate from iron-phosphorus slag. The method involves separating iron and phosphorus through alkaline leaching, where the iron enters the slag and the phosphorus enters the alkaline leaching solution. The iron slag is acid-dissolved to produce an iron-containing acid solution, which is then purified to produce a pure phosphorus-containing alkaline solution. The two solutions are then mixed to produce basic ferric phosphate, which is then aged, washed, dried, and calcined to produce anhydrous ferric phosphate. This method does not achieve deep dephosphorization of the iron slag obtained through alkaline leaching, and the steps are complex and costly.

[0006] In summary, although there are some existing technologies for treating ferrophosphorus slag, there are few existing technologies that can directly selectively dephosphorize ferrophosphorus slag (mainly iron phosphate) in the solid phase to achieve the decomposition of iron and phosphorus and their separate resource utilization. In addition, the existing processes have problems such as cumbersome procedures, high recycling costs, high risks of secondary pollution, or low added value of recycled products, and have not yet formed an economical and effective large-scale recycling and treatment method. Summary of the Invention

[0007] In view of the problem that the existing ferrophosphorus slag lacks a selective dephosphorization process, the first object of the present invention is to provide a ferrophosphorus slag dephosphorization method, which aims to directly selectively dephosphorize ferrophosphate solids and achieve selective decomposition and separation of iron and phosphorus.

[0008] The second object of the present invention is to provide a method for dephosphorizing the ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron ore concentrate.

[0009] To address the problem that the lattice stability of ferrophosphorus slag makes it difficult to achieve selective decomposition and separation of ferrophosphorus, the present invention provides the following improvement scheme:

[0010] A method for dephosphorizing ferrophosphorus slag, comprising dephosphorizing the ferrophosphorus slag in a solution containing a dephosphorizing agent and an inhibitor, followed by solid-liquid separation to obtain a phosphorus-containing solution and dephosphorized ferrophosphorus slag;

[0011] The dephosphorization agent comprises component A, component B and component C; wherein component A is a compound of formula 1; component B is a compound of formula 2; and component C is a compound of formula 3;

[0012] Formula 1;

[0013] Formula 2;

[0014] Formula 3;

[0015] Wherein, X is an alkyl group or a substituted alkyl group having a carbon number less than or equal to 4;

[0016] R1 and R2 are C1~C 20 Alkyl, C1~C 20 Oxyalkyl, C1~C 20 Substituted alkyl or C6~C 20 substituted phenyl;

[0017] R3 is H, Na, K, NH4 + or C1~C 20 Alkyl;

[0018] The substituents in the substituted alkyl and substituted phenyl groups include at least one of hydroxyl, amino, carboxyl, alkyl, and alkoxy;

[0019] In formula 2, M1 is Na, K or NH4 + ;

[0020] The inhibitor is at least one of sulfide, silicate, oxalate and EDTA.

[0021] In order to solve the problem that the crystal phase of solid ferrophosphorus slag is stable and difficult to selectively dephosphorize, the present invention innovatively adopts a dephosphorization agent and inhibitor that synergizes components A, B and C. This can achieve synergy and effectively break down the stable ferrophosphate crystal structure of the ferrophosphorus slag, thereby realizing selective dephosphorization of the solid phase of the ferrophosphorus slag. This is conducive to the simple resource utilization of phosphorus and iron. For example, high-quality phosphate fertilizer can be obtained. Not only that, it can also reduce the impact of phosphorus on the smelting of dephosphorized iron slag, which is conducive to obtaining zero-valent iron concentrate with a high recovery rate.

[0022] In the present invention, the ferrophosphorus slag is the slag from waste lithium iron phosphate positive electrode material after lithium extraction.

[0023] In the present invention, the combination of components A to C is one of the keys to collaboratively achieve selective dephosphorization of ferrophosphorus slag.

[0024] In the present invention, X in Formula 1 is preferably a substituted alkyl group, wherein the substituted alkyl group is a C1-C4 alkyl group with at least one of a hydroxyl group and a carboxyl group as a substituent. This preferred structure can be combined with other components to achieve enhanced synergy, further facilitating the selective separation of iron and phosphorus from ferrophosphorus slag.

[0025] Preferably, the formula 1 is at least one of formula 1A, formula 1B, and formula 1C;

[0026] Formula 1A;

[0027] Formula 1B;

[0028] Formula 1C.

[0029] In the present invention, in Formula 2, R1 is a C1-C4 alkyl group or a carboxylate group.

[0030] The formula 3 is formula 3A;

[0031] Formula 3A;

[0032] In formula 3A, R4 is H or C6~C 14 R5 is a C1~C4 alkyl group.

[0033] In the present invention, in the dephosphorization agent, the weight ratio of component A, component B and component C is 1-10:1-10:1-10; further, it can be 2-3:8-10:1-3.

[0034] In the present invention, the dephosphorization agent of Formulas 1 to 3 is combined with the inhibitor, which is beneficial to the selective decomposition of the lattice in the ferrophosphorus slag, the dephosphorization, and the selective recovery and utilization of phosphorus and iron.

[0035] In the inhibitor of the present invention, the silicate may be, for example, sodium silicate, ammonium silicate, etc. The oxalate may be, for example, sodium oxalate, ammonium oxalate, etc.

[0036] In the present invention, the weight ratio of ferrophosphorus slag, dephosphorizing agent and inhibitor is 1:0.5-15:0.5-10; further, it can be 1:8-10:1-2.

[0037] The temperature during the dephosphorization process of the present invention may be 70-125° C., and the time may be 5-10 hours.

[0038] The present invention also provides a method for dephosphorizing ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron concentrate, wherein the ferrophosphorus slag is treated by the ferrophosphorus slag dephosphorization method of the present invention to obtain a phosphorus-containing solution and dephosphorized ferrophosphorus slag;

[0039] The phosphorus-containing solution is subjected to impurity removal and crystallization treatment to obtain a water-soluble phosphate fertilizer;

[0040] The dephosphorized iron slag is smelted to obtain iron ore concentrate.

[0041] In the present invention, thanks to the combination of the dephosphorization agent and the inhibitor, the selective separation of iron and phosphorus in ferrophosphorus slag can be achieved, which not only can obtain high-quality phosphate fertilizer, but also can reduce the deterioration effect of phosphorus on smelting, which is beneficial to the quality and recovery rate of iron ore concentrate (zero-valent iron).

[0042] In the present invention, a phosphorus product can be obtained from a phosphorus-containing solution using existing methods. For example, as an alternative, the impurity removal step can be a conventional process step for removing aluminum ions and trivalent iron ions. For example, the impurity remover used in the impurity removal process includes at least one of polysilicic acid, hydroxyethylene diphosphate, and PAM. The amount of the impurity remover used can be 1 to 1.5 times the theoretical molar amount of impurities removed.

[0043] In the present invention, the selective dephosphorization process can effectively remove phosphorus from iron slag, which is conducive to obtaining zero-valent iron concentrate more simply and with higher recovery rate.

[0044] In the present invention, the steps of smelting the dephosphorized iron slag are: pelletizing the dephosphorized iron slag, mixing it with a flux, and smelting it; skimming the slag, cooling it, and then subjecting it to magnetic separation to obtain iron concentrate.

[0045] In the present invention, the smelting method of the dephosphorized iron slag may be a known method.

[0046] Beneficial effects

[0047] The present invention innovatively adopts the dephosphorization agent of the composition and the inhibitor to be used in combination for selective dephosphorization of ferrophosphorus slag, thereby realizing efficient resource utilization of phosphorus and iron in the ferrophosphorus slag.

[0048] The process of the present invention is short and can be used as a resource to obtain high-quality phosphorus products and iron concentrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the process roadmap of the present invention;

[0050] Figure 2 This is the XRD of the dephosphorized iron slag obtained in Example 1;

[0051] Figure 3 This is the XRD of the phosphate fertilizer obtained in Example 1;

[0052] Figure 4 This is the XRD of the iron ore concentrate obtained in Example 1. DETAILED DESCRIPTION

[0053] The present invention provides an optional method for preparing water-soluble phosphate fertilizer and iron concentrate based on ferrophosphorus slag, the flow diagram of which can be referred to as Figure 1 , the steps may include:

[0054] (1) Dephosphorization reaction: Stir the ferrophosphorus slag with the dephosphorization agent and inhibitor to react. After solid-liquid separation, phosphorus-containing solution and dephosphorized ferrophosphorus slag are obtained;

[0055] (2) impurity removal reaction: adding an impurity remover to the phosphorus-containing solution of step (1) to remove impurities and precipitate water-soluble phosphate fertilizer, filtering and separating the impurity solution and returning it to step (1) for recycling;

[0056] (3) Iron slag pelletization: Dephosphorized iron slag is mixed with a binder to form pellets, which are then pre-baked at high temperature.

[0057] (4) Electric arc furnace refining: The pellets are smelted with CaO-SiO2-Al2O3 flux under argon protection, and the slag is separated and magnetic separation is performed to obtain iron concentrate with an iron content of ≥96%.

[0058] The weight ratio of the dephosphorization agent component A, component B and component C is 1-10:1-10:1-10.

[0059] The weight ratio of ferrophosphorus slag, dephosphorization agent and inhibitor is 1:0.5~15:0.5~10.

[0060] The dephosphorization reaction is stirred at 70-125°C for 5-10 hours;

[0061] The inhibitor comprises at least one of sulfide, silicate, oxalate and EDTA complex.

[0062] The impurity remover comprises at least one of polysilicic acid, hydroxyethylene diphosphate and PAM.

[0063] The evaporation crystallization includes: evaporation concentration: evaporation at a temperature of 80-90°C and a vacuum degree of -0.07 to -0.09 MPa to a solution density of 1.30-1.35 g / cm³; cooling crystallization: cooling to 5-10°C at a rate of 2-3°C / min, with a crystal growth time of ≥30 min; centrifugal separation: using a horizontal spiral centrifuge at a speed of 2000-2500 rpm and a centrifugation time of 10-15 min;

[0064] The phosphorus residue in the dephosphorized iron slag in step (1) is ≤0.3%, and the iron recovery rate is ≥95%.

[0065] In step (2), the crystallization mother liquor is circulated for ≥6 times, and the impurities in the circulating liquid are solidified in the slag through the smelting step.

[0066] The binder comprises: bentonite: 6-10 wt%, particle size ≤75 μm, montmorillonite content ≥85%; starch: 1.5-2.5 wt%, selected from cassava starch or corn starch; sodium lignin sulfonate: 0.8-1.2 wt%, pH value 8.0-9.0.

[0067] Pelletizing process parameters include: pelletizing pressure of 10-15 MPa, holding time of 30-60 seconds; green pellet size of 8-15 mm, moisture content of 8-10%; calcination schedule: heating at 5-8°C / min to 800-900°C, holding for 40-60 minutes. The compressive strength of the pre-calcined pellets should be ≥250N / piece.

[0068] The composition of the flux in step (4) is CaO 50-65%, SiO2 25-35%, Al2O3 5-12%, and the basicity of the slag (CaO / SiO2) is controlled at 1.3-1.6;

[0069] The roasting reduction adopts: reducing gas composition: CO 65-75vol%, H2 25-35vol%.

[0070] In the present invention, in the dephosphorization agent for solid-phase dephosphorization of ferrophosphorus slag, the component A can be selected from at least one of the commercially available formulas 1A, 1B, and 1C.

[0071] The component B may optionally be of formula 2A ( ), Formula 2B ( ), Formula 2C ( ) at least one of .

[0072] The component C can be selected from the formula 3A1 .

[0073] The ferrophosphorus slag described in the present invention is the residue after conventional lithium extraction treatment of waste lithium iron phosphate positive electrode materials, and its main component is iron phosphate.

[0074] In the present invention, phosphate fertilizer can be recovered from the phosphorus-containing filtrate based on existing conventional means. For example, phosphate fertilizer with better purity can be prepared based on conventional impurity removal and crystallization means. The impurity remover can be any impurity remover in the industry that can remove Al. 3+ 、Fe 3+ The dosage is 1 to 1.5 times the theoretical amount of impurities removed.

[0075] In the present invention, the dephosphorized iron slag can be subjected to reduction, slagging, and magnetic separation processes using conventional smelting methods to obtain iron ore concentrate. During the smelting process, the pre-baking temperature can be 900-1100°C for 1-10 hours. The smelting temperature can be 1200-1500°C for 1-5 hours.

[0076] In the present invention, thanks to the dephosphorization means, the influence of phosphorus on smelting can be reduced, which is conducive to obtaining magnetic iron concentrate with high recovery.

[0077] Example 1

[0078] The dephosphorization agent includes component A, component B, and component C in a mass ratio of 3:10:1, wherein component A in this case is represented by formula 1B; component B is represented by formula 2A; and component C is represented by formula 3A1.

[0079] The inhibitor is sodium silicate.

[0080] Step 1:

[0081] Take ferrophosphorus slag (1 kg), dephosphorization agent and inhibitor in a weight ratio of 1:10:2, then disperse with water to make the ferrophosphorus slag content 50 g / L, and stir and react at 70 ° C for 6 hours. After solid-liquid separation, phosphorus-containing filtrate and dephosphorized ferrophosphorus slag (XRD see Figure 2 ), the phosphorus residual content of the dephosphorized iron slag was measured to be 0.25%, and the iron recovery rate was 96.5%.

[0082] Step 2:

[0083] Add impurity remover (hydroxyethylene diphosphate) to the phosphorus-containing filtrate to precipitate trisodium phosphate crystals (see XRD Figure 3 ), impurity Al 3+ ≤5ppm, Fe 3+ ≤30ppm. Crystallization mother liquor is recycled.

[0084] Step 3:

[0085] Dephosphorized iron slag is granulated with a binder (including bentonite, corn starch, and sodium lignin sulfonate in a weight ratio of 8:2:1; the binder is 11% of the weight of the dephosphorized iron slag), pressed into 12mm green balls, and pre-baked at 1000℃±30℃ for 2h to obtain a pellet with a compressive strength of 280N / piece. The pellets are smelted with a flux (the flux includes CaO, SiO2, and Al2O3 in a weight ratio of 60:30:10; the slag basicity (CaO / SiO2) is controlled at 1.4~1.5) in a CO / H2=70 / 30vol% atmosphere at 1300±50℃ for 1h. The smelted product is subjected to magnetic separation to obtain iron concentrate (XRD see Figure 4 ).

[0086] The final iron recovery rate in the iron concentrate was 92.8%, and the final iron concentrate contained TFe 96.8%, S 0.025%, and P 0.035%.

[0087] Example 2

[0088] Compared with Example 1, the only difference is that the dephosphorization agent includes component A, component B and component C in a weight ratio of 2:8:1, wherein component A in this case is formula 1B; component B is formula 2B; and component C is formula 3A1.

[0089] The inhibitor is ammonium oxalate,

[0090] Step 1:

[0091] 1 kg of ferrophosphorus slag was mixed with a dephosphorizing agent and an inhibitor in a weight ratio of 1:8:1 and stirred at 80°C for 5 hours. After solid-liquid separation, the residual phosphorus content of the dephosphorized slag was 0.35%, and the iron recovery rate was 97.8%.

[0092] Step 2: Add the impurity remover hydroxyethylene diphosphate to the phosphorus-containing filtrate to precipitate ammonium phosphate crystals and impurity Al 3+ ≤10ppm, Fe 3+ ≤20ppm. Crystallization mother liquor is recycled.

[0093] Step 3: The dephosphorized iron slag is pelletized with a binder (comprised of bentonite and sodium lignin sulfonate in a weight ratio of 12:2, with the binder comprising 14% of the dephosphorized iron slag weight). The pellets are pressed into 10mm green balls and pre-calcined at 950±30°C to achieve a compressive strength of 320N per pellet. The pellets are then smelted with a flux (comprised of CaO, SiO2, and Al2O3 in a weight ratio of 60:30:10; the slag basicity (CaO / SiO2) is controlled between 1.4 and 1.5) in an atmosphere of 70 / 30 vol% CO2 at 1250±50°C for 1.5 hours. The smelted product is then magnetically separated to produce an iron concentrate.

[0094] The final iron recovery rate in the iron concentrate was 93.3%; the iron concentrate contained TFe 95.2%, S 0.1%, and P 0.055%.

[0095] Example 3

[0096] Compared with Example 1, the only difference is that the dephosphorization agent includes component A, component B and component C in a weight ratio of 2:8:1, wherein component A in this case is formula 1A; component B is formula 2C; and component C is formula 3A1.

[0097] The inhibitor is sodium silicate,

[0098] Step 1:

[0099] 1 kg of ferrophosphorus slag was mixed with the dephosphorization agent and inhibitor sodium silicate at a solid-liquid ratio of 1:10:1 and stirred at 120°C for 8 hours. After solid-liquid separation, the residual phosphorus content of the dephosphorized slag was measured to be 0.44%, and the iron recovery rate was 98.8%.

[0100] Step 2:

[0101] Add impurity remover polysilicic acid to the phosphorus-containing filtrate to precipitate trisodium phosphate crystals, Fe 3+ ≤25ppm, total amount of other impurities ≤50ppm. Crystallization mother liquor is recycled.

[0102] Step 3:

[0103] Dephosphorized iron slag is pelletized with a binder (comprised of bentonite and sodium lignin sulfonate in a weight ratio of 12:2, with the binder comprising 14% of the dephosphorized iron slag weight), pressed into 10mm green balls, and pre-calcined at 980±30°C to yield a compressive strength of 320N per pellet. The pellets are then smelted with a flux (comprising CaO, SiO2, and Al2O3 in a weight ratio of 50:40:10; the slag basicity (CaO / SiO2) is controlled between 1.3 and 1.4) in an atmosphere of 60 / 40 vol% CO2 at 1300±50°C for 1 hour. The smelted product is then magnetically separated to produce an iron concentrate. The final iron concentrate has an iron recovery of 93.6%, and the final iron ore concentrate contains 97.2% TFe, 0.05% S, and 0.062% P.

[0104] Example 4

[0105] Compared with Example 3, the only difference is that the dephosphorizing agent uses the same weight of formula 1C ( ) as component A, and other operations and parameters are the same as those in Example 1.

[0106] After solid-liquid separation, the residual phosphorus content of the dephosphorized iron slag was measured to be 0.62%, and the iron recovery rate was 95.6%.

[0107] The final iron recovery rate in the iron concentrate was 93.1%; the final iron concentrate contained TFe 95.3%, S 0.08%, and P 0.098%.

[0108] Comparative Example 1

[0109] Compared with Example 1, the only difference is that the dephosphorization agent lacks component A, and the other components, total dosage and other operating conditions of the dephosphorization agent are the same as those of Example 1.

[0110] In step 1, the dephosphorized iron slag contains a large amount of iron phosphate crystals, and the residual phosphorus content is as high as 16.2%.

[0111] The final iron recovery rate in the iron concentrate was 86.3%.

[0112] Comparative Example 2

[0113] Compared with Example 1, the only difference is that the dephosphorizing agent lacks component B, and the other components, total dosage and other operating conditions of the dephosphorizing agent are the same as those of Example 1. Step 1 After solid-liquid separation, the residual phosphorus content of the iron slag was measured to be 15.12%.

[0114] The final iron recovery rate in the iron concentrate was 86.8%.

[0115] Comparative Example 3

[0116] Compared with Example 1, the only difference is that the dephosphorizing agent lacks component C. The other components, total dosage, and other operating conditions of the dephosphorizing agent are the same as those in Example 1. After solid-liquid separation in step 1, the residual phosphorus content in the iron slag was measured to be 15.31%. The final iron recovery rate in the iron concentrate was 86.1%.

[0117] Comparative Example 4

[0118] Compared with Example 1, the only difference is the lack of an inhibitor. Other operating conditions are the same as Example 1. After solid-liquid separation in step 1, the phosphorus residue in the iron slag was measured to be 1.21%. The final iron recovery rate in the iron concentrate was 72.1%.

[0119] Comparative Example 5

[0120] Compared with Example 1, the only difference is that the component A is replaced by an equal weight of sulfuric acid. The other operations and parameters are the same as those in Example 1. The results are:

[0121] In the dephosphorized iron slag after solid-liquid separation in step 1, the residual phosphorus content was 15.2%, and the iron yield was 82.3%.

[0122] Comparative Example 6

[0123] Compared with Example 1, the only difference is that the same weight Substituting component A, the other operations and parameters were the same as in Example 1, and the results were:

[0124] The residual phosphorus content in the dephosphorized iron slag after solid-liquid separation in step 1 was 16.6%. The final iron yield in the iron concentrate was 82.9%.

[0125] Comparative Example 7

[0126] Compared with Example 1, the only difference is that the same weight Substituting component C, the other operations and parameters were the same as in Example 1, and the results were:

[0127] The residual phosphorus content in the dephosphorized iron slag after solid-liquid separation in step 1 was 16.6%. The final iron yield in the iron concentrate was 86.7%.

[0128] In summary, the innovative use of the dephosphorization agent of the components and the inhibitor in combination for the selective dephosphorization of ferrophosphorus slag is conducive to obtaining high-quality phosphate fertilizer. Not only that, it can also effectively reduce the impact of phosphorus on the smelting of iron slag, which is conducive to the smelting of dephosphorized iron slag and can obtain elemental iron concentrate with a high yield.

Claims

1. A method for dephosphorizing ferrophosphorus slag, characterized in that: Dephosphorizing ferrophosphorus slag in a solution containing a dephosphorizing agent and an inhibitor, followed by solid-liquid separation to obtain a phosphorus-containing solution and dephosphorized ferrophosphorus slag; the ferrophosphorus slag is the slag from waste lithium iron phosphate positive electrode material after lithium extraction; The dephosphorization agent comprises component A, component B and component C; wherein component A is a compound of formula 1, wherein the formula 1 is at least one of formula 1A, formula 1B, and formula 1C; the component B is a compound of formula 2; the component C is a compound of formula 3, wherein the formula 3 is formula 3A; Formula 1A Formula 1B Formula 1C; Formula 2 In formula 2, R1 is a C1~C4 alkyl group, and M1 is Na, K or NH4 + ; Formula 3A In formula 3A, R4 is H or C6~C 14 R5 is a C1~C4 alkyl group; In the dephosphorization agent, the weight ratio of component A, component B and component C is 2-3:8-10:1-3; The inhibitor is at least one of silicate and oxalate; wherein the silicate includes at least one of sodium silicate and ammonium silicate; the oxalate includes at least one of sodium oxalate and ammonium oxalate; The weight ratio of ferrophosphorus slag, dephosphorization agent and inhibitor is 1:8~10:1~2.

2. A method for dephosphorizing ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron ore concentrate, characterized in that: The ferrophosphorus slag is subjected to a stirring treatment using the ferrophosphorus slag dephosphorization method according to claim 1 to obtain a phosphorus-containing solution and dephosphorized ferrophosphorus slag; The phosphorus-containing solution is subjected to impurity removal and crystallization treatment to obtain a water-soluble phosphate fertilizer; The dephosphorized iron slag is smelted and magnetically separated to obtain iron concentrate.

3. The method for dephosphorizing ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron ore concentrate according to claim 2, characterized in that: The impurity remover selected in the impurity removal process includes at least one of polysilicic acid, hydroxyethylene diphosphate and PAM.

4. The method for dephosphorizing ferrophosphorus slag and recycling it to prepare water-soluble phosphate fertilizer and iron ore concentrate according to claim 3, characterized in that: The steps of smelting dephosphorized iron slag are as follows: pelletizing the dephosphorized iron slag and mixing it with flux for smelting treatment, cooling it after slagging, and then subjecting it to magnetic separation treatment to obtain iron ore concentrate; the atmosphere in the smelting treatment stage is a reducing gas, which is composed of CO 65~75vol% and H2 25~35vol%.

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