A method for reverse osmosis membrane filtration of iron phosphate acid wastewater based on reducing agent treatment

Abstract

The application discloses a kind of based on reducing agent processing iron phosphate acid wastewater reverse osmosis membrane filtration method, comprising the following steps: S1.pretreatment: respectively to iron phosphate wash water and iron phosphate filtrate addition reducing agent, make trivalent iron in system is reduced to divalent iron;S2.wash water membrane treatment: after reduction treatment, iron phosphate wash water is carried out atmospheric pressure reverse osmosis treatment, obtains first reverse osmosis concentrated liquid and first reverse osmosis product water;S3.filtrate membrane treatment: first reverse osmosis concentrated liquid and after reduction treatment, iron phosphate filtrate is mixed, and is carried out high pressure reverse osmosis treatment, obtains second reverse osmosis concentrated liquid and second reverse osmosis product water;S4.phosphorus recovery: second reverse osmosis concentrated liquid is added to oxidizing agent, and pH is adjusted, so that iron phosphate is settled.The application first uses reducing agent to reduce trivalent iron in wastewater into strong solubility divalent iron, reduce membrane pollution risk, then again combine reverse osmosis technology to realize the purification and resource of wastewater.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and specifically relates to a reverse osmosis membrane filtration method for ferric phosphate acid wastewater treated with a reducing agent. Background Technology

[0002] Acidic wastewater from iron phosphate is commonly found in industries such as lithium battery material production and phosphate chemicals. A typical iron phosphate preparation process involves using ferrous sulfate, hydrogen peroxide, and phosphoric acid as main raw materials, followed by a series of steps including solution preparation, oxidation precipitation, aging and washing, drying, and crushing, ultimately yielding the iron phosphate product.

[0003] In this process, because the iron phosphate crystals formed by oxidation precipitation are relatively small, they are often aged for a long time to promote crystal growth before being subjected to pressure filtration and washing, producing a filter cake and filtrate. Industrially, to save water, the washing process is often carried out in stages. For the filter cake, lower-quality water is used for washing until a certain conductivity level is reached, then the water is replaced with higher-quality water for washing, continuing until the conductivity meets the requirements for the finished product. This washing process generates a large amount of wash water.

[0004] The filtrate and wash water mentioned above are both acidic wastewater containing ferric phosphate, characterized by strong acidity (pH < 3) and high concentrations of phosphate (PO43-) and ferric ions. Traditional treatment methods include neutralization precipitation, reverse osmosis, and chemical oxidation / reduction, but these methods have the following problems:

[0005] Neutralization precipitation requires the addition of large amounts of alkaline agents (such as calcium hydroxide), resulting in excessive sludge production, high costs, and the inability to recover phosphates; direct reverse osmosis (RO) treatment, however, leads to Fe... 3+ Ferric hydroxide colloids easily form on the membrane surface, fouling the membrane pores and causing a sharp drop in membrane flux and a short operating cycle; the wastewater is highly acidic, and conventional treatment methods cannot simultaneously achieve the goals of acid regulation and iron ion removal. Summary of the Invention

[0006] The purpose of this invention is to provide a reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment, in order to overcome the shortcomings of the prior art.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A reverse osmosis membrane filtration method for ferric phosphate acidic wastewater treated with a reducing agent, wherein the ferric phosphate acidic wastewater includes ferric phosphate washing water and ferric phosphate filtrate, the method comprising the following steps:

[0009] S1. Pretreatment: A reducing agent is added to the ferric phosphate washing water and the ferric phosphate filtrate respectively to reduce the trivalent iron in the system to divalent iron;

[0010] S2. Wash water membrane treatment: The reduced iron phosphate wash water is subjected to atmospheric pressure reverse osmosis treatment to obtain the first reverse osmosis concentrate and the first reverse osmosis permeate;

[0011] S3. Filtrate membrane treatment: The first reverse osmosis concentrate and the reduced iron phosphate filtrate are mixed and subjected to high-pressure reverse osmosis treatment to obtain the second reverse osmosis concentrate and the second reverse osmosis permeate.

[0012] S4. Phosphorus recovery: Add oxidant to the second reverse osmosis concentrate and adjust the pH to cause ferric phosphate to precipitate. After solid-liquid separation, ferric phosphate is recovered.

[0013] Preferably, the phosphorus content in the ferric phosphate washing water is 50-250 ppm, the Fe content is 100-500 ppm, the sulfate content is 3-10 g / L, and the pH is 2-4.

[0014] The ferric phosphate filtrate contains 100–500 ppm phosphorus, 200–900 ppm Fe, 40–60 g / L sulfate, and has a pH of 2–4.

[0015] Preferably, the reducing agent in step S1 is at least one selected from sodium sulfite, ferrous sulfate, sodium thiosulfate, or ascorbic acid.

[0016] Preferably, the amount of reducing agent added in step S1 is such that the redox potential in the system is adjusted to -100 eV to -200 eV.

[0017] Preferably, the atmospheric pressure reverse osmosis treatment in step S2 adopts multi-stage reverse osmosis. The first-stage reverse osmosis concentrate enters the second-stage reverse osmosis, and the second-stage reverse osmosis concentrate is the first reverse osmosis concentrate. It is mixed with the reduced iron phosphate filtrate for high-pressure reverse osmosis treatment.

[0018] The permeate from the two reverse osmosis stages is combined and returned to the ferric phosphate production process for use as wash water.

[0019] Preferably, the parameters of the first-stage reverse osmosis permeate are controlled as follows: pH 2-4, phosphorus content 1-10 ppm, and Fe content 2-25 ppm; the parameters of the first-stage reverse osmosis concentrate are controlled as follows: pH 2-4, phosphorus content 350-2500 ppm, and Fe content 1200-8000 ppm.

[0020] The permeate parameters for the second-stage reverse osmosis system are pH 2–4, phosphorus content 10–50 ppm, and Fe content 15–90 ppm; the concentrate parameters for the second-stage reverse osmosis system are pH 2–4, phosphorus content 900–5000 ppm, and Fe content 3000–16000 ppm.

[0021] Preferably, the high-pressure reverse osmosis pressure is 4–8 MPa;

[0022] After the reverse osmosis concentrate and the reduced iron phosphate filtrate are mixed in step S3, the pH of the system is 2-4, the phosphorus content is 400-5000 ppm, and the Fe content is 900-9000 ppm.

[0023] The parameters for high-pressure reverse osmosis permeate are controlled as follows: pH 2-4, phosphorus content 8-50 ppm, and Fe content 15-90 ppm; the parameters for high-pressure reverse osmosis concentrate are controlled as follows: pH 2-4, phosphorus content 1400-15000 ppm, and Fe content 3300-27000 ppm.

[0024] The high-pressure reverse osmosis permeate is recycled to step S2 for further reverse osmosis treatment.

[0025] Preferably, the amount of oxidant added in step S4 is to adjust the redox potential of the system to 100-250 eV.

[0026] Preferably, in step S4, the pH is adjusted to 1.5–3.

[0027] Preferably, the liquid after solid-liquid separation in step S4 is adjusted to pH 6-9 before being discharged in compliance with standards.

[0028] This application first uses a reducing agent to reduce ferric iron in wastewater to ferrous iron, which is highly soluble, thereby reducing the risk of membrane fouling. Then, it combines reverse osmosis technology to purify and recycle the wastewater, while also achieving efficient recovery and utilization of ferric phosphate in the wastewater. Detailed Implementation

[0029] This application provides a reverse osmosis membrane filtration method for ferric phosphate acid wastewater treated with a reducing agent, comprising the following steps:

[0030] S1. Pretreatment: First, add a reducing agent to the ferric phosphate washing water and ferric phosphate filtrate respectively to reduce the trivalent iron in the system to divalent iron;

[0031] S2. Wash water membrane treatment: The reduced iron phosphate wash water is subjected to atmospheric pressure reverse osmosis treatment to obtain the first reverse osmosis concentrate and the first reverse osmosis permeate;

[0032] S3. Filtrate membrane treatment: The first reverse osmosis concentrate and the reduced iron phosphate filtrate are mixed and subjected to high-pressure reverse osmosis treatment to obtain the second reverse osmosis concentrate and the second reverse osmosis permeate.

[0033] S4. Phosphorus recovery: Add oxidant to the second reverse osmosis concentrate and adjust the pH to cause ferric phosphate to precipitate. After solid-liquid separation, ferric phosphate is recovered.

[0034] Ferric phosphate wash water and ferric phosphate filtrate are acidic wastewaters generated during ferric phosphate production. Ferric phosphate filtrate is the mother liquor of the reaction system produced by direct pressure filtration after oxidation precipitation, while ferric phosphate wash water is the wash water produced by washing the filter cake after pressure filtration.

[0035] The conductivity of ferric phosphate filtrate and wash water differs significantly due to the different contents of sodium sulfate and iron ions. The filtrate contains 100–500 ppm phosphorus, 200–900 ppm Fe, 40–60 g / L sulfate, and has a pH of 2–4. The wash water contains 50–250 ppm phosphorus, 100–500 ppm Fe, 3–10 g / L sulfate, and has a pH of 2–4. The salt content (mainly sodium sulfate) differs greatly between the two. This application addresses this issue by subjecting the ferric phosphate wash water with lower salt content to atmospheric pressure reverse osmosis treatment. The resulting first reverse osmosis concentrate has a higher salt content and is then combined with the ferric phosphate filtrate with higher salt content for high-pressure reverse osmosis treatment. High-pressure treatment is used to improve the reverse osmosis effect. If atmospheric pressure reverse osmosis is used for both, the water production rate will be significantly reduced, or even no water will be produced.

[0036] This application first reduces the ferric iron in the ferric phosphate acid wastewater to ferrous iron before reverse osmosis treatment. Ferrous iron is more soluble than ferric iron and is less likely to form precipitates that foul the membrane pores during reverse osmosis treatment. Therefore, it can effectively reduce the risk of membrane fouling.

[0037] After sequential treatment by atmospheric pressure reverse osmosis and high-pressure reverse osmosis, most of the phosphorus and iron in the waste liquid are concentrated in the high-pressure reverse osmosis concentrate. Then, an oxidant is added to re-oxidize the highly soluble ferrous iron (Fe2+) to the less soluble ferric iron (Fe3+). By adjusting the pH of the system, effective sedimentation of ferric phosphate is promoted, thus achieving ferric phosphate recovery. The recovered ferric phosphate has high purity and low impurity content, and can be directly mixed with ferric phosphate produced on the ferric phosphate production line for subsequent processes.

[0038] Therefore, this application first uses a reducing agent to reduce the ferric iron in the wastewater to the highly soluble ferrous iron, thereby reducing the risk of membrane fouling. Then, it combines reverse osmosis technology to achieve wastewater purification and resource utilization, while simultaneously realizing the efficient recovery and utilization of ferric phosphate in the wastewater.

[0039] The reducing agent in step S1 includes, but is not limited to, at least one of sodium sulfite, ferrous sulfate, sodium thiosulfate, or ascorbic acid.

[0040] The amount of reducing agent added is to adjust the redox potential in the system to -100 eV to -200 eV. Within this range, ferric iron can be completely reduced and ferrous iron can be effectively prevented from being oxidized again by air.

[0041] Preferably, step S2 reverse osmosis treatment employs multi-stage reverse osmosis, which can fully concentrate and separate ferric phosphate. More preferably, it involves two-stage reverse osmosis. The concentrate from the first-stage reverse osmosis enters the second-stage reverse osmosis, and the concentrate from the second-stage reverse osmosis becomes the concentrate from the first-stage reverse osmosis. This concentrate is then mixed with the reduced ferric phosphate filtrate and subjected to high-pressure reverse osmosis treatment. The permeate from both stages of reverse osmosis is of good quality and, after merging, can be returned to the ferric phosphate pre-process as wash water (for aging and washing).

[0042] Preferably, the parameters of the first-stage reverse osmosis permeate are controlled as follows: pH 2-4, phosphorus content 1-10 ppm, and Fe content 2-25 ppm; the parameters of the first-stage reverse osmosis concentrate are controlled as follows: pH 2-4, phosphorus content 350-2500 ppm, and Fe content 1200-8000 ppm.

[0043] The permeate parameters for the second-stage reverse osmosis system are pH 2–4, phosphorus content 10–50 ppm, and Fe content 15–90 ppm; the concentrate parameters for the second-stage reverse osmosis system are pH 2–4, phosphorus content 900–5000 ppm, and Fe content 3000–16000 ppm.

[0044] Preferably, the high-pressure reverse osmosis pressure in step S3 is 4 to 8 MPa. This pressure fluctuates depending on the conductivity of the feed water. The higher the conductivity of the feed water, the greater the pressure required. However, under stable operating conditions, the pressure is generally stable at 4 to 5 MPa.

[0045] After mixing the reverse osmosis concentrate and the reduced-treated ferric phosphate filtrate, the system has a pH of 2–4, a phosphorus content of 400–5000 ppm, and an Fe content of 900–9000 ppm. The controlled parameters for the high-pressure reverse osmosis permeate are: pH 2–4, phosphorus content 8–50 ppm, and Fe content 15–90 ppm; the controlled parameters for the high-pressure reverse osmosis concentrate are: pH 2–4, phosphorus content 1400–15000 ppm, and Fe content 3300–27000 ppm.

[0046] The high-pressure reverse osmosis permeate is recycled to step S2 for further reverse osmosis treatment, allowing the iron phosphate in the permeate to be further concentrated and separated.

[0047] As reverse osmosis continues, the concentration of ferric phosphate in the concentrate gradually increases, and the concentration and separation efficiency gradually decreases. By controlling the parameters of atmospheric pressure reverse osmosis and high pressure reverse osmosis, a balance can be achieved between concentration and separation efficiency and concentration and separation degree.

[0048] Preferably, in step S4, the amount of oxidant added is such that the redox potential of the system is controlled to be 100–250 eV. Within this range, ferrous iron can be completely oxidized to ferric iron. The oxidant can be air, oxygen, hydrogen peroxide, etc.

[0049] Preferably, in step S4, the pH is adjusted to 1.5–3 to promote the precipitation of ferric phosphate, while ferric hydroxide does not precipitate, ensuring that the impurity content in the ferric phosphate meets the requirements. Sodium hydroxide, potassium hydroxide, etc., are preferred pH adjusters.

[0050] Preferably, the liquid after solid-liquid separation in step S4 is adjusted to pH 6-9 before being discharged in compliance with standards. The pH adjuster is preferably a calcium-containing alkaline substance.

[0051] Example 1

[0052] 1. Take ferric phosphate wash water. The parameters of the ferric phosphate wash water are: pH 2.9, phosphorus content (as P) 234 ppm, Fe content 498 ppm, sulfate 5 g / L; adjust the ORP (oxidation-reduction potential) index of the system to -154 eV using sodium sulfite; enter the wash water atmospheric pressure reverse osmosis membrane treatment system, where the parameters of the first-stage reverse osmosis permeate are controlled as follows: pH 2.9, phosphorus content (as P) 11.70 ppm, Fe content 24.9 ppm; parameters of the first-stage reverse osmosis concentrate are: pH 2.9, phosphorus content (as P) 835 ppm, Fe content 1700 ppm; parameters of the second-stage reverse osmosis permeate are: pH 2.9, phosphorus content (as P) 42 ppm, Fe content 89 ppm; parameters of the second-stage reverse osmosis concentrate are: pH 2.9, phosphorus content (as P) 2034 ppm, Fe content 4298 ppm.

[0053] 2. Take the ferric phosphate filtrate. The ferric phosphate filtrate has the following parameters: pH 2.9, phosphorus content (as P) 200 ppm, Fe content 450 ppm, and sulfate content 48 g / L. Adjust the ORP index of the system to -167 eV using sodium sulfite. Mix it with the wash water and secondary reverse osmosis concentrate. The mixed water has the following parameters: pH 2.9, phosphorus content (as P) 437 ppm, and Fe content 952 ppm. It is then treated by a high-pressure reverse osmosis membrane at a pressure of 6 MPa. The parameters of the permeate are controlled as follows: pH 2.9, phosphorus content (as P) 8.8 ppm, and Fe content 19 ppm. The parameters of the concentrate are: pH 2.9, phosphorus content (as P) 1600 ppm, and Fe content 3498 ppm.

[0054] 3. An oxidant was added to the high-pressure reverse osmosis concentrate system until the system ORP reached 220 eV. The pH was adjusted to 2.8 using NaOH, and solid-liquid separation was performed by pressure filtration to recover ferric phosphate. The recovered ferric phosphate contained 35.9% iron and 20.1% phosphorus, with an iron-to-phosphorus ratio of 0.996. The impurity content is shown in Table 1.

[0055] Table 1

[0056] Al(％) Ca(%) Cu(%) Mg(%) Mn(%) Na(%) Water(%) Zn(%) S(％) 0.003 0.003 0.001 0.003 0.003 0.006 0.007 0.003 0.006

[0057] 4. The liquid obtained after solid-liquid separation is neutralized with calcium carbide sludge until the pH is 7.5. The tested neutralized water has a COD of 35 ppm, an ammonia nitrogen of 3.6 ppm, a total nitrogen of 11.3 ppm, and a total phosphorus of 0.2 ppm, which meets the discharge standards and is discharged.

[0058] Example 2

[0059] 1. Take ferric phosphate wash water. The parameters of the ferric phosphate wash water are: pH 2.2, phosphorus content (as P) 104 ppm, Fe content 357 ppm, sulfate 8 g / L; adjust the ORP index of the system to -165 eV using sodium sulfite; enter the wash water atmospheric pressure reverse osmosis membrane treatment system. The parameters of the first-stage reverse osmosis permeate are: pH 2.2, phosphorus content (as P) 5.2 ppm, Fe content 17.85 ppm; the parameters of the first-stage reverse osmosis concentrate are: pH 2.2, phosphorus content (as P) 371 ppm, Fe content 1273.8 ppm; the parameters of the second-stage reverse osmosis permeate are: pH 2.2, phosphorus content (as P) 18.6 ppm, Fe content 63.7 ppm; the parameters of the second-stage reverse osmosis concentrate are: pH 2.2, phosphorus content (as P) 900 ppm, Fe content 3089 ppm.

[0060] 2. Take the ferric phosphate filtrate. The ferric phosphate filtrate has the following parameters: pH 2.9, phosphorus content (as P) 334 ppm, Fe content 679 ppm, and sulfate content 45 g / L. Adjust the ORP index of the system using sodium sulfite to -167 eV. Mix it with the wash water and secondary reverse osmosis concentrate. The mixed water has the following parameters: pH 2.2, phosphorus content (as P) 407.6 ppm, and Fe content 992.6 ppm. Enter high-pressure reverse osmosis treatment at a pressure of 6 MPa. The product water has the following parameters: pH 2.2, phosphorus content (as P) 8.1 ppm, and Fe content 19 ppm. The high-pressure reverse osmosis concentrate has the following parameters: pH 2.9, phosphorus content (as P) 1487 ppm, and Fe content 3622 ppm.

[0061] 3. Add oxidant to the high-pressure reverse osmosis concentrate system until the system ORP is 240 eV. Adjust the pH to 2.8 using NaOH. Perform solid-liquid separation by pressure filtration to recover ferric phosphate. The recovered ferric phosphate contains 36.2% iron and 20.08% phosphorus, with an iron-to-phosphorus ratio of 1.0. The impurity content is shown in Table 2.

[0062] Table 2

[0063] Al(％) Ca(%) Cu(%) Mg(%) Mn(%) Na(%) Water(%) Zn(%) S(％) 0.002 0.004 0.001 0.002 0.006 0.005 0.007 0.003 0.005

[0064] 4. The liquid obtained after solid-liquid separation is neutralized with calcium carbide sludge until the pH is 7.5. The tested neutralized water has a COD of 32 ppm, an ammonia nitrogen of 3.1 ppm, a total nitrogen of 12.3 ppm, and a total phosphorus of 0.33 ppm, which meets the discharge standards and is discharged.

[0065] Comparative Example 1

[0066] 1. Take ferric phosphate wastewater with the following parameters: pH 2.2, phosphorus content (as P) 200ppm, Fe content 492ppm, sulfate 7g / L; enter the reverse osmosis membrane treatment system, run for about 12 hours, the operating pressure continuously rises, the permeate flux continuously decreases until the pressure limit is reached, causing the system to shut down.

[0067] Comparative Example 2

[0068] 1. Take ferric phosphate wastewater with the following parameters: pH 2.2, phosphorus content (as P) 200 ppm, Fe content 492 ppm, sulfate 7 g / L; add hydrogen peroxide for oxidation, and add NaOH to adjust the pH to 2.5. After precipitation, perform solid-liquid separation, and the liquid enters the reverse osmosis membrane system for treatment.

[0069] 2. As membrane concentration proceeds, the membrane system pressure gradually increases and the membrane flux gradually decreases. The system is shut down and washed. If the flux does not increase significantly after washing, the membrane system can be considered to be clogged.

[0070] 3. After removing and disassembling the blocked membrane system, some iron phosphate solids remained in the ash after burning. This can be attributed to the blockage caused by the gradual increase in the concentration of the concentrate side during the membrane concentration process, which led to the precipitation of iron phosphate.

[0071] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A reverse osmosis membrane filtration method for ferric phosphate acidic wastewater treated with a reducing agent, wherein the ferric phosphate acidic wastewater comprises ferric phosphate washing water and ferric phosphate filtrate, characterized in that, Includes the following steps: S1. Pretreatment: A reducing agent is added to both the ferric phosphate wash water and the ferric phosphate filtrate to reduce ferric iron to ferrous iron. The amount of reducing agent added is such that the redox potential in the system is adjusted to -100 eV to -200 eV, ensuring complete reduction of ferric iron and preventing ferrous iron from being oxidized again by air. The ferric phosphate wash water contains 50-250 ppm phosphorus, 100-500 ppm Fe, 3-10 g / L sulfate, and has a pH of 2-4. The ferric phosphate filtrate contains 100-500 ppm phosphorus, 200-900 ppm Fe, 40-60 g / L sulfate, and has a pH of 2-4. S2. Wash water membrane treatment: The reduced iron phosphate wash water is subjected to atmospheric pressure reverse osmosis treatment to obtain the first reverse osmosis concentrate and the first reverse osmosis permeate; S3. Filtrate membrane treatment: The first reverse osmosis concentrate and the reduced iron phosphate filtrate are mixed and subjected to high-pressure reverse osmosis treatment to obtain the second reverse osmosis concentrate and the second reverse osmosis permeate. S4. Phosphorus recovery: Add the second reverse osmosis concentrate to an oxidant, the amount of which is used to adjust the redox potential of the system to 100~250 eV and the pH to 1.5~3, so that ferric phosphate precipitates. After solid-liquid separation, ferric phosphate is recovered.

2. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 1, characterized in that, The reducing agent in step S1 is at least one selected from sodium sulfite, sodium thiosulfate, or ascorbic acid.

3. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 1, characterized in that, The atmospheric pressure reverse osmosis treatment in step S2 adopts multi-stage reverse osmosis. The first-stage reverse osmosis concentrate enters the second-stage reverse osmosis, and the second-stage reverse osmosis concentrate is the first-stage reverse osmosis concentrate. It is mixed with the reduced iron phosphate filtrate for high-pressure reverse osmosis treatment. The permeate from the two reverse osmosis stages is combined and returned to the ferric phosphate production process for use as wash water.

4. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 3, characterized in that, The parameters of the first-stage reverse osmosis permeate are controlled as follows: pH 2-4, phosphorus content 1-10 ppm, and Fe content 2-25 ppm; the parameters of the first-stage reverse osmosis concentrate are controlled as follows: pH 2-4, phosphorus content 350-2500 ppm, and Fe content 1200-8000 ppm. The permeate parameters for the secondary reverse osmosis system are pH 2-4, phosphorus content 10-50 ppm, and Fe content 15-90 ppm; the concentrate parameters for the secondary reverse osmosis system are pH 2-4, phosphorus content 900-5000 ppm, and Fe content 3000-16000 ppm.

5. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 1, characterized in that, The high-pressure reverse osmosis pressure is 4~8 MPa.

6. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 5, characterized in that, In step S3, after mixing the first reverse osmosis concentrate and the reduced iron phosphate filtrate, the system has a pH of 2-4, a phosphorus content of 400-5000 ppm, and an Fe content of 900-9000 ppm. The parameters of the second reverse osmosis permeate are controlled as follows: pH 2~4, phosphorus content 8~50ppm, and Fe content 15~90ppm; the parameters of the second reverse osmosis concentrate are controlled as follows: pH 2~4, phosphorus content 1400~15000ppm, and Fe content 3300~27000ppm. The second reverse osmosis permeate is recycled to step S2 for further reverse osmosis treatment.

7. The reverse osmosis membrane filtration method for ferric phosphate acid wastewater based on reducing agent treatment as described in claim 1, characterized in that, After solid-liquid separation in step S4, the pH of the liquid is adjusted to 6-9 before being discharged in compliance with standards.