Method for recycling phosphorus resources in iron phosphate mother liquor by disodium hydrogen phosphate process

Abstract

The invention discloses a method for recycling phosphorus resources in disodium hydrogen phosphate process iron phosphate mother liquor, which comprises the following steps: enabling the disodium hydrogen phosphate process iron phosphate mother liquor to flow into an oxidation reaction kettle through a mother liquor inlet pipe, then enabling phosphoric acid to flow into the oxidation reaction kettle through a phosphoric acid inlet pipe, adjusting the pH value in the oxidation reaction kettle to be 1-1.5, then respectively adding a ferrous sulfate solution and hydrogen peroxide through a ferrous solution inlet pipe and a hydrogen peroxide inlet pipe, synthesizing a crude iron phosphate solution in the oxidation reaction kettle, discharging the crude iron phosphate solution into a first filter through a first discharge pipe, filtering, and applying a crude iron phosphate filter cake to an aging step (an aging kettle); after filtration, first filtrate is discharged into a neutralization adjusting kettle through a first filtrate pipe, and a sodium hydroxide solution is added into the neutralization adjusting kettle through an alkali liquor inlet pipe, so that the pH value in the neutralization adjusting kettle is controlled to be 7-8; a PAM solution is added through a PAM inlet pipe, other metal impurities are removed through precipitation, supernate is used for recovering sodium sulfate in a sodium sulfate recovery process, and the content of impurity metal ions is extremely low.

Description

Technical Field

[0001] This invention belongs to the field of iron phosphate production technology, specifically relating to a method for recovering and reusing phosphorus resources from iron phosphate mother liquor produced by the disodium hydrogen phosphate method. Background Technology

[0002] Iron phosphate is the core precursor for preparing lithium iron phosphate, a cathode battery material. The synthesized lithium iron phosphate has safety and long cycle life, and is widely used in electric vehicles, energy storage systems, etc.

[0003] There are various production processes for iron phosphate, including six main methods: sodium method, ammonium method, iron powder method, fertilizer phosphoric acid method, iron oxide red method, and dicalcium phosphate method.

[0004] Our company synthesizes ferric phosphate using disodium hydrogen phosphate, a byproduct of our glyphosate production, as the phosphorus source. It is added dropwise with ferrous sulfate and hydrogen peroxide to initially produce crude ferric phosphate. After pressure filtration, the crude ferric phosphate yields a filter cake and a crude mother liquor. The filter cake is then further aged with phosphoric acid to adjust the pH of the reaction system to approximately 2, and the resulting product is synthesized as ferric phosphate. The aging mother liquor is reused.

[0005] The crude mother liquor contains: phosphorus 220–580 mg / L, iron ion 50–130 mg / L, sodium ion 22300–51400 mg / L, magnesium ion 130–150 mg / L, sulfate ion 46540–107230 mg / L, manganese ion 80–110 mg / L, and calcium ion 13–45 mg / L. The mother liquor must be treated before being discharged. The phosphorus content in the crude mother liquor is approximately 0.5% to 1% of the total phosphorus content. If it is disposed of as waste, the amount to be treated is large, the wastewater treatment cost is high, and it does not conform to the concept of green and pollution-free industrial production.

[0006] Based on the above reasons and adhering to the principle of reducing waste and pollution at the source, our company has developed a new pretreatment method, which involves recovering a large amount of phosphorus source from the mother liquor. The recovered phosphorus source is then reused in the synthesis of iron phosphate, thereby greatly increasing the utilization rate of phosphorus and reducing the emission of phosphorus resources. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of the prior art and provide a method for recovering and reusing phosphorus resources from the mother liquor of ferric phosphate produced by the disodium hydrogen phosphate method. The mother liquor of ferric phosphate produced by the disodium hydrogen phosphate method flows into an oxidation reactor through a mother liquor inlet pipe. Subsequently, phosphoric acid flows into the oxidation reactor through a phosphoric acid inlet pipe. The pH value in the oxidation reactor is adjusted to 1-1.5. Then, ferrous sulfate solution and hydrogen peroxide are added through ferrous solution inlet pipe and hydrogen peroxide inlet pipe, respectively. A crude ferric phosphate solution is synthesized in the oxidation reactor. The crude ferric phosphate solution is discharged into a first filter through a first outlet pipe. After filtration, the crude ferric phosphate filter cake is used in the aging step (aging kettle). The first filtrate after filtration is discharged into the neutralization and adjustment kettle through the first filtrate tube. Sodium hydroxide solution is added to the neutralization and adjustment kettle through the alkali inlet tube to control the pH in the neutralization and adjustment kettle at 7-8. Then, PAM solution is added through the PAM inlet tube to precipitate and remove other metal impurities. The supernatant is used in the sodium sulfate recovery process to recover sodium sulfate. The content of impurity metal ions is extremely low. This invention can achieve a phosphorus recovery rate of over 95% in the mother liquor and a total phosphorus utilization rate of 99.9% in the synthesis of ferric phosphate.

[0008] This invention is achieved through the following technical solution: A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method includes the following steps: Step 1: Place the disodium hydrogen phosphate mother liquor, ferrous sulfate, and hydrogen peroxide into an oxidation reactor for oxidation reaction; Step 2: After the oxidation reaction is completed, the reaction solution is subjected to the first pressure filtration. The first filtrate obtained from the first pressure filtration flows into the neutralization vessel. Step 3: Add 20%–30% sodium hydroxide solution to the neutralization vessel to adjust the pH, then add PAM solution to precipitate. The supernatant obtained from the precipitation is used in the sodium sulfate recovery process to recover sodium sulfate.

[0009] Preferably, in step one, sulfuric acid is added to the oxidation reactor to control the pH value of the oxidation reactor at 1 to 1.5.

[0010] Preferably, the phosphorus content of the mother liquor of the disodium hydrogen phosphate method is determined by reacting it with quinomolybdate to form a yellow quinoline phosphomolybdate precipitate.

[0011] Preferably, in step one, the molar ratio of phosphorus, ferrous sulfate and hydrogen peroxide in the disodium hydrogen phosphate method ferric phosphate mother liquor is 1:(1.2-1.5):(1.05-1.2). Preferably, in step one, the oxidation reaction temperature is 10–40°C and the oxidation reaction time is 1–4 hours.

[0012] Preferably, in step two, the first pressure filtration uses a 5-10 μm filter membrane and a pressure of 0.8-1.6 MPa.

[0013] Preferably, in step two, the crude ferric phosphate filter cake obtained from the first pressure filtration is reused in step one.

[0014] Preferably, in step two, sodium hydroxide solution is added to the neutralization vessel to control the pH value of the oxidation vessel at 7-8.

[0015] Preferably, in step three, the amount of PAM solution added is 0.1% to 0.3% of the mass of the first filtrate.

[0016] Preferably, in step three, the concentration of the PAM solution is 0.1% to 0.5%.

[0017] Preferably, in step three, after adding sulfuric acid solution to the neutralization vessel, the mixture is stirred for 30 to 60 minutes at a speed of 100 to 300 r / min; the sedimentation time is 2 to 6 hours.

[0018] Preferably, in step three, the precipitate obtained from precipitation is subjected to a second pressure filtration, and the second filtrate obtained from the second pressure filtration is sent to a multi-effect evaporator to evaporate and recover sodium sulfate. The evaporation and recovery temperature is 25~40℃, and the pressure is -0.095~-0.09MPa, with continuous evaporation. The second filter cake obtained from the second pressure filtration is used for sludge solid waste treatment. The second pressure filtration uses a 5~10μm filter membrane and the pressure is 0.8~1.6MPa.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: I. This invention provides a method for recovering and reusing phosphorus resources from ferric phosphate mother liquor produced by the disodium hydrogen phosphate method. The disodium hydrogen phosphate mother liquor flows into an oxidation reactor through a mother liquor inlet pipe. Subsequently, phosphoric acid flows into the oxidation reactor through a phosphoric acid inlet pipe. The pH value in the oxidation reactor is adjusted to 1-1.5. Then, ferrous sulfate solution and hydrogen peroxide are added through ferrous solution inlet pipe and hydrogen peroxide inlet pipe, respectively. A crude ferric phosphate solution is synthesized in the oxidation reactor. The crude ferric phosphate solution is discharged into a first filter through a first outlet pipe. After filtration, the crude ferric phosphate solution is... The ferric sulfate filter cake is used in the aging step (aging kettle). After filtration, the first filtrate is discharged into the neutralization and adjustment kettle through the first filtrate pipe. Sodium hydroxide solution is added to the neutralization and adjustment kettle through the alkali inlet pipe to control the pH of the neutralization and adjustment kettle at 7-8. Then, PAM solution is added through the PAM inlet pipe to precipitate and remove other metal impurities. The supernatant is used in the sodium sulfate recovery process to recover sodium sulfate. The content of impurity metal ions is extremely low. This invention can achieve a phosphorus recovery rate of over 95% in the mother liquor and a total phosphorus utilization rate of 99.9% in the synthesis of ferric phosphate.

[0020] II. The present invention provides a method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method. The phosphorus content in the supernatant is ≤0.5mg / L. The supernatant is used in the sodium sulfate recovery process to recover sodium sulfate. The content of impurity metal ions is extremely low.

[0021] Third, this invention provides a method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method. This method reduces phosphorus emissions and treatment volume in wastewater. For every 10,000 tons of ferric phosphate, 80-90 tons of ferric phosphate can be recovered, corresponding to 18-20 tons of phosphorus, while simultaneously reducing the associated waste phosphorus treatment costs. The water recovered through multi-effect evaporation is reused in the production cycle. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0023] Example 1 A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method includes the following steps: A. At 10℃, add 1300g of ferric phosphate mother liquor (phosphorus content 0.056%) to a 2000mL four-necked flask. While stirring, add 27g of 20% ferrous sulfate solution and 4.6g of 27.5% hydrogen peroxide dropwise. Stir for 2 hours to fully oxidize the mixture. Filter to obtain 6.3g of wet filter cake and 1331g of primary liquid for the next step of neutralization.

[0024] B. At 10℃, add the above-obtained mother liquor into a 2000mL four-necked flask, add 6.8g of 30% sodium hydroxide dropwise until the pH value is 7 under stirring, add 1.3g of 0.1% PAM solution dropwise, stir for 1h, let it settle naturally, and filter the resulting solid sludge for solid waste treatment.

[0025] C. Vacuum concentrate the filtered solution to recover sodium sulfate. The concentrated water is reused in the upstream ferric phosphate synthesis. Sodium sulfate is then tested.

[0026] Example 2 A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method includes the following steps: Step 1: At 10℃, 2000 kg of disodium hydrogen phosphate mother liquor (0.056% phosphorus content), 6.56 kg (1.2 eq) of 20% ferrous sulfate, and 1.94 kg (1.05 eq) of 27.5% hydrogen peroxide were placed into an oxidation reactor for oxidation reaction. Step 2: After the oxidation reaction is completed, the reaction solution is subjected to the first pressure filtration. The first filtrate obtained from the first pressure filtration flows into the neutralization vessel. Step 3: Add 20% sodium hydroxide solution to the neutralization vessel to adjust the pH, then add 0.1% PAM solution by weight of the mother liquor to precipitate. The supernatant obtained from the precipitation is used in the sodium sulfate recovery process to recover sodium sulfate.

[0027] In step one, sulfuric acid is added to the oxidation reactor to control the pH value of the oxidation reactor at 1.

[0028] The phosphorus content of the mother liquor obtained by the disodium hydrogen phosphate method is determined by reacting it with quinomolybdate to form a yellow quinoline phosphomolybdate precipitate.

[0029] In step one, the molar ratio of phosphorus, ferrous sulfate, and hydrogen peroxide in the disodium hydrogen phosphate mother liquor is 1:1.5:1.05. In step one, the oxidation reaction temperature is 10°C and the oxidation reaction time is 2 hours.

[0030] In step two, the first pressure filtration uses a 5μm filter membrane at a pressure of 0.8MPa.

[0031] In step two, the crude ferric phosphate filter cake obtained from the first pressure filtration is reused in step one.

[0032] In step two, sodium hydroxide solution is added to the neutralization vessel to control the pH value of the oxidation vessel at 7.

[0033] In step three, the amount of PAM solution added is 0.1% of the mass of the first filtrate.

[0034] In step three, the concentration of the PAM solution is 0.5%.

[0035] In step three, PAM solution is added to the neutralization vessel and stirred for 30 minutes at a speed of 300 r / min; the precipitation time is 2 hours.

[0036] In step three, the precipitate obtained from precipitation is subjected to a second pressure filtration. The second filtrate obtained from the second pressure filtration is sent to a multi-effect evaporator to evaporate and recover sodium sulfate. The evaporation and recovery temperature is 35℃ and the pressure is -0.095MPa, and the evaporation is continuous. The second filter cake obtained from the second pressure filtration is used for sludge solid waste treatment. The second pressure filtration uses a 5μm filter membrane and the pressure is 1.6MPa.

[0037] Example 3 A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method includes the following steps: Step 1: At 25℃, 2000 kg of disodium hydrogen phosphate mother liquor, 7.14 kg (1.3 eq) of 20% ferrous sulfate and 2.03 kg (1.1 eq) of 27.5% hydrogen peroxide were placed into an oxidation reactor for oxidation reaction. Step 2: After the oxidation reaction is completed, the reaction solution is subjected to the first pressure filtration. The first filtrate obtained from the first pressure filtration flows into the neutralization vessel. Step 3: Add 25% sodium hydroxide solution to the neutralization vessel to adjust the pH, then add PAM solution to precipitate. The supernatant obtained from the precipitation is used in the sodium sulfate recovery process to recover sodium sulfate.

[0038] In step one, sulfuric acid is added to the oxidation reactor to control the pH value of the oxidation reactor at 1.25.

[0039] The phosphorus content of the mother liquor obtained by the disodium hydrogen phosphate method is determined by reacting it with quinomolybdate to form a yellow quinoline phosphomolybdate precipitate.

[0040] In step one, the molar ratio of phosphorus, ferrous sulfate, and hydrogen peroxide in the disodium hydrogen phosphate mother liquor is 1:1.5:1.05. In step one, the oxidation reaction temperature is 25°C and the oxidation reaction time is 2 hours.

[0041] In step two, the first pressure filtration uses a 7μm filter membrane at a pressure of 1.2MPa.

[0042] In step two, the crude ferric phosphate filter cake obtained from the first pressure filtration is reused in step one.

[0043] In step two, sodium hydroxide solution is added to the neutralization vessel to control the pH value of the oxidation vessel at 7.5.

[0044] In step three, the amount of PAM solution added is 0.2% of the mass of the first filtrate.

[0045] In step three, the concentration of the PAM solution is 0.3%.

[0046] Preferably, in step three, after adding PAM solution to the neutralization vessel, the mixture is stirred for 45 minutes at a stirring speed of 200 r / min; the precipitation time is 4 hours.

[0047] In step three, the precipitate obtained from precipitation is subjected to a second pressure filtration. The second filtrate obtained from the second pressure filtration is sent to a multi-effect evaporator to evaporate and recover sodium sulfate. The evaporation and recovery temperature is 38℃ and the pressure is -0.092MPa, and the evaporation is continuous. The second filter cake obtained from the second pressure filtration is used for sludge solid waste treatment. The second pressure filtration uses a 7μm filter membrane and the pressure is 1.2MPa.

[0048] Example 4 A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method includes the following steps: Step 1: Place the disodium hydrogen phosphate mother liquor, ferrous sulfate, and hydrogen peroxide into an oxidation reactor for oxidation reaction; Step 2: After the oxidation reaction is completed, the reaction solution is subjected to the first pressure filtration. The first filtrate obtained from the first pressure filtration flows into the neutralization vessel. Step 3: Add 30% sodium hydroxide solution to the neutralization vessel to adjust the pH, then add PAM solution to precipitate. The supernatant obtained from the precipitation is used in the sodium sulfate recovery process to recover sodium sulfate.

[0049] In step one, sulfuric acid is added to the oxidation reactor to control the pH value of the oxidation reactor at 1.5.

[0050] The phosphorus content of the mother liquor obtained by the disodium hydrogen phosphate method is determined by reacting it with quinomolybdate to form a yellow quinoline phosphomolybdate precipitate.

[0051] In step one, the molar ratio of phosphorus, ferrous sulfate, and hydrogen peroxide in the mother liquor of ferric phosphate produced by the disodium hydrogen phosphate method is 1:1.5:1.2. In step one, the oxidation reaction temperature is 40°C and the oxidation reaction time is 1 hour.

[0052] In step two, the first pressure filtration uses a 10μm filter membrane at a pressure of 0.8MPa.

[0053] In step two, the crude ferric phosphate filter cake obtained from the first pressure filtration is reused in step one.

[0054] In step two, sodium hydroxide solution is added to the neutralization vessel to control the pH value of the oxidation vessel at 8.

[0055] In step three, the amount of PAM solution added is 0.3% of the mass of the first filtrate.

[0056] In step three, the concentration of the PAM solution is 0.1%.

[0057] In step three, sulfuric acid solution is added to the neutralization vessel and stirred for 60 minutes at a speed of 100 r / min; the precipitation time is 6 hours.

[0058] In step three, the precipitate obtained from precipitation is subjected to a second pressure filtration. The second filtrate obtained from the second pressure filtration is sent to a multi-effect evaporator to evaporate and recover sodium sulfate. The evaporation and recovery temperature is 40℃ and the pressure is -0.09MPa, and the evaporation is continuous. The second filter cake obtained from the second pressure filtration is used for sludge solid waste treatment. The second pressure filtration uses a 10μm filter membrane and the pressure is 0.8MPa.

[0059] Comparative Example 1 The difference between this comparative example and Example 2 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.2:1; in step two, the pH value is controlled to 5 after adding sodium hydroxide solution to the neutralization vessel.

[0060] Comparative Example 2 The differences between this comparative example and Example 4 are as follows: in step one, the oxidation temperature is 10°C; in step three, the amount of PAM added is 0.1%; in step three, the sodium sulfate evaporation and recovery temperature is 35°C, and the vacuum degree is -0.095MPa.

[0061] Comparative Example 3 The difference between this comparative example and Example 2 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.8:1.1; in step two, the pH value is controlled to 9 after adding sodium hydroxide solution to the neutralization vessel.

[0062] Comparative Example 4 The difference between this comparative example and Example 2 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.5:1; in step two, the pH value is controlled to 9 after adding sodium hydroxide solution to the neutralization vessel.

[0063] Comparative Example 5 The difference between this comparative example and Example 3 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.8:1.05; in step two, the pH value is controlled to 5 after adding sodium hydroxide solution to the neutralization vessel.

[0064] Comparative Example 6 The difference between this comparative example and Example 3 is that in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.2:1.1.

[0065] Comparative Example 7 The difference between this comparative example and Example 3 is that in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.8:1.

[0066] Comparative Example 8 The difference between this comparative example and Example 4 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.2:1.05; in step two, the pH value is controlled to 9 after adding sodium hydroxide solution to the neutralization vessel.

[0067] Comparative Example 9 The difference between this comparative example and Example 4 is that: in step one, the feed ratio (total phosphorus in mother liquor: ferrous sulfate: hydrogen peroxide) is 1:1.5:1.1; in step two, the pH value is controlled to 5 after adding sodium hydroxide solution to the neutralization vessel.

[0068] Total phosphorus recovery rate in mother liquor = (mother liquor mass * total phosphorus content - secondary filtrate * total phosphorus content) / (mother liquor mass * total phosphorus content) * 100%.

[0069] Sodium sulfate purity test method: According to GB / T6009-2014, the purity of sodium sulfate is determined by gravimetric method using silver nitrate and sulfate precipitation.

[0070] The total phosphorus utilization rate in the synthesis of iron phosphate = (dosage of disodium hydrogen phosphate solution * total phosphorus content + dosage of phosphoric acid * total phosphorus content - secondary filtrate * total phosphorus content) / (dosage of disodium hydrogen phosphate solution * total phosphorus content + dosage of phosphoric acid * total phosphorus content) * 100%.

[0071] Examples 1-4 and Comparative Examples 1-9

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method, characterized in that, Includes the following steps: Step 1: Place the disodium hydrogen phosphate mother liquor, ferrous sulfate, and hydrogen peroxide into an oxidation reactor for oxidation reaction; Step 2: After the oxidation reaction is completed, the reaction solution is subjected to the first pressure filtration. The first filtrate obtained from the first pressure filtration flows into the neutralization vessel. Step 3: Add 20%–30% sodium hydroxide solution to the neutralization vessel to adjust the pH, then add PAM solution to precipitate. The supernatant obtained from the precipitation is used in the sodium sulfate recovery process to recover sodium sulfate.

2. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 1, characterized in that: In step one, sulfuric acid is added to the oxidation reactor to control the pH value of the oxidation reactor at 1 to 1.

5.

3. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 2, characterized in that: The phosphorus content of the mother liquor of the disodium hydrogen phosphate method is determined by reacting it with quinomolybdate to form a yellow quinoline phosphomolybdate precipitate.

4. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 3, characterized in that: In step one, the molar ratio of phosphorus, ferrous sulfate and hydrogen peroxide in the disodium hydrogen phosphate method ferric phosphate mother liquor is 1:(1.2~1.5):(1.05~1.2).

5. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 4, characterized in that: In step one, the oxidation reaction temperature is 10–40°C, and the oxidation reaction time is 1–4 hours.

6. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 5, characterized in that: In step two, the first pressure filtration uses a 5-10 μm filter membrane and a pressure of 0.8-1.6 MPa.

7. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 6, characterized in that: In step two, the crude ferric phosphate filter cake obtained from the first pressure filtration is reused in step one.

8. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 7, characterized in that: In step two, sodium hydroxide solution is added to the neutralization vessel to control the pH value of the oxidation vessel at 7-8.

9. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 8, characterized in that: In step three, the amount of PAM solution added is 0.1% to 0.3% of the mass of the first filtrate.

10. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 9, characterized in that: In step three, the concentration of the PAM solution is 0.1% to 0.5%.

11. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 10, characterized in that: In step three, sulfuric acid solution is added to the neutralization vessel and stirred for 30 to 60 minutes at a speed of 100 to 300 r / min; the precipitation time is 2 to 6 hours.

12. The method for recovering and reusing phosphorus resources from ferric phosphate mother liquor using the disodium hydrogen phosphate method according to claim 11, characterized in that: In step three, the precipitate obtained from precipitation is subjected to a second pressure filtration. The second filtrate obtained from the second pressure filtration is sent to a multi-effect evaporator to evaporate and recover sodium sulfate. The evaporation temperature during recovery is 25~40℃, and the pressure is -0.095~-0.09MPa, with continuous evaporation. The second filter cake obtained from the second pressure filtration is used for sludge solid waste treatment. The second pressure filtration uses a 5~10μm filter membrane and the pressure is 0.8~1.6MPa.

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