Method for recovering phosphorus from iron phosphate waste residues

Abstract

The invention relates to the technical field of iron phosphate production waste recovery, in particular to a method for recovering phosphorus from iron phosphate waste residues. The method for recycling phosphorus from the iron phosphate waste residues comprises the following steps that the iron phosphate waste residues, rutile mother liquor and a hydrochloric acid solution are subjected to acid leaching, and after solid-liquid separation, a high-salt solution and a solid product are obtained. According to the method for recycling phosphorus from the iron phosphate waste residues, the iron phosphate waste residues are subjected to acid leaching reaction through the rutile mother liquor and the hydrochloric acid solution by utilizing a chemical method, the recycling cost of the iron phosphate waste residues and the loss of phosphorus can be reduced, and a solid product with the phosphorus content being larger than or equal to 25 wt% is obtained in terms of P2O5; the solid product can be sold as a commercial phosphate fertilizer.

Description

Technical Field

[0001] This invention relates to the field of waste recycling technology in ferric phosphate production, and in particular to a method for recovering phosphorus from ferric phosphate waste residue. Background Technology

[0002] With the booming development of China's new energy industry, the demand for green, environmentally friendly, and relatively safe lithium iron phosphate batteries is increasing daily. To further reduce costs and expand production capacity, large-scale and continuous process technologies are being applied. During the production of lithium iron phosphate materials, a large amount of low-phosphorus waste residue is generated due to factors such as material fluctuations. This waste residue is mainly composed of lithium iron phosphate, but also contains large amounts of manganese, magnesium, calcium, silicon, and other elements. However, current treatment methods mostly involve landfilling or simple incineration, resulting in resource waste and environmental pollution. Therefore, developing an efficient and environmentally friendly method for phosphorus extraction from waste residue has significant economic and social implications.

[0003] Currently, the main methods for recovering phosphorus from waste residue include the following: 1. Chemical extraction: Phosphorus is extracted or separated from waste residue using chemical solvents or acid-base reactions; commonly used reagents include sulfuric acid and hydrochloric acid. 2. Physical methods: Phosphorus in waste residue is separated from other components through physical separation techniques such as flotation and magnetic separation, thereby improving the phosphorus recovery rate. This method is usually used in combination with chemical methods to improve recovery efficiency. 3. Thermal treatment: The waste residue is incinerated or calcined at high temperatures to convert phosphorus into volatile compounds, which are then condensed and collected. This method requires control of temperature and atmosphere to prevent the generation of harmful gases. 4. Biological methods: The metabolic activity of microorganisms degrades organic matter in waste residue, while simultaneously promoting the dissolution and release of phosphorus. This method has the advantages of being environmentally friendly and sustainable, but it has high requirements for reaction conditions and the selection of microorganisms.

[0004] In view of this, this invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering phosphorus from ferric phosphate waste residue. By using rutile mother liquor and hydrochloric acid solution to treat the ferric phosphate waste residue, the recovery cost of ferric phosphate waste residue can be reduced and phosphorus loss can be minimized.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a method for recovering phosphorus from ferric phosphate waste, comprising the following steps: The ferric phosphate residue, rutile mother liquor, and hydrochloric acid solution were subjected to acid leaching, followed by solid-liquid separation to obtain a high-salt solution and a solid product.

[0007] Furthermore, the mass ratio of the rutile mother liquor to the hydrochloric acid solution is 1:(2~5).

[0008] Furthermore, the pH of the acid leaching is 4.0 to 6.7.

[0009] Furthermore, the acid leaching temperature is 10~40℃.

[0010] Furthermore, the acid leaching time is 45-90 minutes.

[0011] Further, the ferric phosphate waste residue is dried, crushed and screened in sequence to obtain powder residue; the powder residue and water are pulped to obtain slurry; the slurry, rutile mother liquor and hydrochloric acid solution are acid leached, and after solid-liquid separation, a high-salt solution and solid product are obtained.

[0012] Furthermore, the phosphorus content in the slag, calculated as P2O5, is 5wt%~15wt%.

[0013] Furthermore, the solid content of the slurry is 20wt%~50wt%.

[0014] Furthermore, the phosphorus content in the solid product, calculated as P2O5, is ≥25wt%.

[0015] Furthermore, the phosphorus content in the high-salt solution is <50 ppm, calculated as P2O5.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention discloses a method for recovering phosphorus from ferric phosphate waste. This method utilizes a chemical approach, employing rutile mother liquor and hydrochloric acid solution to perform an acid leaching reaction on the ferric phosphate waste. This reduces the recovery cost of the ferric phosphate waste and the loss of phosphorus. Based on P2O5, a solid product with a phosphorus content ≥25wt% is obtained. The solid product includes elements such as P, Fe, Ca, Mg, Mn, Si, and S, meeting the phosphorus content requirements of commonly used calcium magnesium phosphate fertilizers, and can be sold as a commercial phosphate fertilizer. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of the method for recovering phosphorus from ferric phosphate waste according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0020] The following is a detailed description of a method for recovering phosphorus from ferric phosphate waste according to the present invention.

[0021] See Figure 1 This invention provides a method for recovering phosphorus from ferric phosphate waste, comprising the following steps: The ferric phosphate residue, rutile mother liquor, and hydrochloric acid solution were subjected to acid leaching, followed by solid-liquid separation to obtain a high-salt solution and a solid product.

[0022] Ferric phosphate production waste residue is a low-phosphorus sludge formed after the filtrate and wash water produced during the production of ferric phosphate materials are treated. Its components include ferric phosphate (FePO4), and also contain one or more of the following elements: manganese (Mn), magnesium (Mg), calcium (Ca), silicon (Si), and sulfur (S).

[0023] Rutile mother liquor is a large amount of acidic mixed solution produced during the artificial production of rutile using the hydrochloric acid method. It contains a variety of complex metal chlorides and some unreacted hydrochloric acid.

[0024] The present invention discloses a method for recovering phosphorus from ferric phosphate waste. This method utilizes a chemical process, employing rutile mother liquor and hydrochloric acid solution to treat the ferric phosphate waste through an acid leaching reaction. This method can utilize a portion of the unreacted hydrochloric acid in the rutile mother liquor to replace the finished hydrochloric acid, reducing recovery costs. Simultaneously, complex metal elements in the mother liquor can combine with phosphate ions to form precipitates (such as calcium, iron, aluminum, etc.), further reducing the recovery cost of ferric phosphate waste and phosphorus loss. A solid product with a phosphorus content ≥25wt% (based on P2O5) is obtained. The solid product includes elements such as P, Fe, Ca, Mg, Mn, Si, and S, meeting the phosphorus content requirements of commonly used calcium magnesium phosphate fertilizers, and can be sold as a commercial phosphate fertilizer.

[0025] This invention uses hydrochloric acid, which is beneficial for the recovery of phosphorus from ferric phosphate waste. Compared with other acid solutions, such as sulfuric acid solution, ferric phosphate waste contains more calcium and magnesium elements, and the introduction of more sulfate ions will increase the amount of precipitate.

[0026] In some embodiments of the present invention, the rutile mother liquor is purified acidic rutile mother liquor. The purified acidic rutile mother liquor is a mixed acidic solution containing at least one of metal ions, sulfuric acid, and hydrochloric acid; for example, the main components of the purified acidic rutile mother liquor are residual dilute hydrochloric acid and sulfates of iron, calcium, and manganese; the pH of the purified acidic rutile mother liquor is 0.9; the metal ions in the purified acidic rutile mother liquor include iron (concentration of 29 g / L), calcium (concentration of 0.17 g / L), and manganese (concentration of 0.61 g / L).

[0027] In some embodiments of the present invention, the concentration of the hydrochloric acid solution is 20 wt%.

[0028] In some embodiments of the present invention, the mass ratio of rutile mother liquor to hydrochloric acid solution is 1:(2~5); typically, but not limitingly, for example, the mass ratio of rutile mother liquor to hydrochloric acid solution can be 1:2, 1:3, 1:4, 1:5 or any combination thereof; preferably, the mass ratio of rutile mother liquor to hydrochloric acid solution is 1:3.

[0029] In some embodiments of the invention, the pH of the acid leaching is 4.0 to 6.7; typically, but not limitingly, for example, the pH of the acid leaching can be a range of 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.7 or any combination thereof; preferably, the pH of the acid leaching is 4.7.

[0030] In some embodiments of the present invention, the acid leaching temperature is 10~40°C; typically, but not limitingly, for example, the acid leaching temperature can be a range of 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or any combination thereof; preferably, the acid leaching temperature is 35°C.

[0031] In some embodiments of the present invention, the pickling time is 45 to 90 minutes; typically, but not limitingly, for example, the pickling time can be 45 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes or any range between two of these; preferably, the pickling time is 45 minutes.

[0032] The present invention performs an acid leaching reaction under the above conditions. Due to the exothermic neutralization reaction of acid and alkali, the reaction temperature can be maintained at 30~45℃, reducing additional heating energy consumption; at the same time, the phosphate structure is relatively stable at this temperature and pH and does not easily enter the liquid phase, thereby reducing the phosphorus loss rate.

[0033] In some embodiments of the present invention, the ferric phosphate waste residue is dried, crushed and screened in sequence to obtain powder residue; the powder residue and water are pulped to obtain slurry; the slurry, rutile mother liquor and hydrochloric acid solution are acid leached, and after solid-liquid separation, a high-salt solution and solid product are obtained.

[0034] In some embodiments of the invention, drying includes natural air drying.

[0035] In some embodiments of the present invention, the ferric phosphate waste residue is successively subjected to natural drying, crushing and sieving to obtain powder residue and foreign magnetic slag; the powder residue and water are pulped; and the foreign magnetic slag is discharged externally.

[0036] This invention removes most of the moisture through drying; and removes foreign matter and magnetic slag through crushing and sieving.

[0037] In some embodiments of the present invention, the phosphorus content in the slag powder is 5wt% to 15wt% based on P2O5; typically, but not limitingly, the phosphorus content in the slag powder can be a range of 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt% or any combination thereof based on P2O5; preferably, the phosphorus content in the slag powder is 7wt% to 15wt% based on P2O5.

[0038] In some embodiments of the present invention, pulping includes: stirring powder residue and water at 10~40°C to form a slurry; preferably, stirring powder residue and water at 35°C.

[0039] In some embodiments of the present invention, the solid content of the slurry is 20wt% to 50wt%; typically, but not limitingly, for example, the solid content of the slurry can be a range of 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt% or any combination thereof; preferably, the solid content of the slurry is 50wt%.

[0040] In some embodiments of the present invention, the method for recovering phosphorus from ferric phosphate residue specifically includes the following steps: S1. After drying, crushing and sieving the collected ferric phosphate waste residue, powder residue is obtained; the phosphorus content in the powder residue is 5wt%~15wt% based on P2O5. S2. The above-mentioned powder residue is stirred with water at 10~40℃ to form a slurry; the solid content of the slurry is 20wt%~50wt%; S3. Mix the purified acidic rutile mother liquor with a 20wt% hydrochloric acid solution at a ratio of 1:(2~5) to obtain a mixed acid solution. S4. Add mixed acid to the slurry to adjust the pH of the system to 4.0~6.7, stir at 10~40℃, and carry out the acid leaching reaction. Then, perform solid-liquid separation to obtain a high-salt solution and solid product.

[0041] In some embodiments of the present invention, the phosphorus content in the solid product is ≥25wt% based on P2O5; preferably, the phosphorus content in the solid product is 25wt%~27wt% based on P2O5.

[0042] In some embodiments of the present invention, the phosphorus content in the high-salt solution is <50 ppm, calculated as P2O5.

[0043] In some embodiments of the present invention, the high-salt solution is subjected to water treatment.

[0044] In some embodiments of the present invention, solid-liquid separation includes filtration.

[0045] In some embodiments of the present invention, after solid-liquid separation, a high-salt solution and a filter cake are obtained; the filter cake is washed to obtain a solid product; preferably, the washing includes water washing; the wash water can be reused and mixed with primary water for the pulping process.

[0046] In some embodiments of the present invention, the solid product is dried and pulverized in sequence to obtain phosphate fertilizer.

[0047] The solid product contains elements such as P, Fe, Ca, Mg, Mn, Si, and S, which meet the phosphorus content requirements of commonly used calcium magnesium phosphate fertilizers. After drying and pulverizing, the solid product can be sold as a commercial phosphate fertilizer.

[0048] Example 1 The method for recovering phosphorus from ferric phosphate waste provided in this embodiment includes the following steps: S1. After naturally drying, crushing, and sieving the collected ferric phosphate residue, powder residue is obtained; the phosphorus content (calculated as P2O5) in the powder residue is 9.6 wt%. S2. Add the above powder residue and water to a mixing container and stir at 35°C to form a slurry; the solid content of the slurry is 50 wt%. S3. The purified acidic rutile mother liquor is mixed with a 20wt% hydrochloric acid solution at a mass ratio of 1:3 to obtain a mixed acid solution. The main components of the purified acidic rutile mother liquor are residual dilute hydrochloric acid and sulfates of iron, calcium, and manganese. The pH of the purified acidic rutile mother liquor is 0.9. The concentration of iron ions in the purified acidic rutile mother liquor is 29 g / L, the concentration of calcium ions is 0.17 g / L, and the concentration of manganese ions is 0.61 g / L. S4. Add mixed acid to the slurry to adjust the pH of the system to 5.5, carry out acid leaching reaction at 35℃ for 45 min, then filter to obtain a high salt solution and filter cake. Wash the filter cake with water to obtain a solid product.

[0049] Example 2 The method for recovering phosphorus from ferric phosphate waste provided in this embodiment includes the following steps: S1. The collected ferric phosphate waste residue is naturally dried, crushed, and sieved to obtain powder residue; the phosphorus content (calculated as P2O5) in the powder residue is 7.4 wt%. S2. Add the above powder residue and water to a mixing container and stir at 35°C to form a slurry; the solid content of the slurry is 50 wt%. S3. The purified acidic rutile mother liquor is mixed with a 20wt% hydrochloric acid solution at a mass ratio of 1:3 to obtain a mixed acid solution. The main components of the purified acidic rutile mother liquor are residual dilute hydrochloric acid and sulfates of iron, calcium, and manganese. The pH of the purified acidic rutile mother liquor is 0.9. The concentration of iron ions in the purified acidic rutile mother liquor is 29 g / L, the concentration of calcium ions is 0.17 g / L, and the concentration of manganese ions is 0.61 g / L. S4. Add mixed acid to the slurry to adjust the pH of the system to 4.7, stir at 35℃ for 45 minutes to carry out acid leaching reaction, then filter to obtain a high salt solution and filter cake. Wash the filter cake with water to obtain a solid product.

[0050] Example 3 S1. After naturally drying, crushing, and sieving the collected ferric phosphate residue, powder residue is obtained; the phosphorus content (calculated as P2O5) in the powder residue is 13.2 wt%. S2. Add the above powder residue and water to a mixing container and stir at 35°C to form a slurry; the solid content of the slurry is 50 wt%. S3. The purified acidic rutile mother liquor is mixed with a 20wt% hydrochloric acid solution at a mass ratio of 1:3 to obtain a mixed acid solution. The main components of the purified acidic rutile mother liquor are residual dilute hydrochloric acid and sulfates of iron, calcium, and manganese. The pH of the purified acidic rutile mother liquor is 0.9. The concentration of iron ions in the purified acidic rutile mother liquor is 29 g / L, the concentration of calcium ions is 0.17 g / L, and the concentration of manganese ions is 0.61 g / L. S4. Add mixed acid to the slurry to adjust the pH of the system to 4.7, stir at 35℃ for 45 minutes to carry out acid leaching reaction, then filter to obtain a high salt solution and filter cake. Wash the filter cake with water to obtain a solid product.

[0051] Example 4 The method for recovering phosphorus from ferric phosphate waste provided in this embodiment is the same as in Embodiment 1, except that in step S3, the mass ratio of the purified acidic rutile mother liquor to the 20wt% hydrochloric acid solution is 1:4.

[0052] Example 5 The method for recovering phosphorus from ferric phosphate waste provided in this embodiment is the same as that in embodiment 1, except that in step S4, a mixed acid solution is added to the slurry to adjust the pH of the system to 4.7, and the acid leaching reaction is carried out by stirring at 25°C for 45 minutes.

[0053] Example 6 The method for recovering phosphorus from ferric phosphate waste provided in this embodiment is the same as in embodiment 1, except that in step S4, a mixed acid solution is added to the slurry to adjust the pH of the system to 4.7, and the acid leaching reaction is carried out by stirring at 50°C for 45 minutes.

[0054] Comparative Example 1 The method for recovering phosphorus from ferric phosphate residue provided in this comparative example includes the following steps: S1. After naturally drying, crushing, and sieving the collected ferric phosphate residue, powder residue is obtained; the phosphorus content (calculated as P2O5) in the powder residue is 9.6 wt%. S2. Add the above powder residue and water to a mixing container and stir at 35°C to form a slurry; the solid content of the slurry is 50 wt%. S3. Add a 20wt% hydrochloric acid solution to the slurry to adjust the pH of the system to 4.7. Stir at 35℃ for 45 minutes to carry out the acid leaching reaction. Then filter to obtain a high-salt solution and filter cake. Wash the filter cake with water to obtain a solid product.

[0055] Comparative Example 2 The method for recovering phosphorus from ferric phosphate waste provided in this comparative example refers to Example 1, except that in step S3, the mass ratio of the purified acidic rutile mother liquor to the 20wt% hydrochloric acid solution is 1:1.

[0056] Test case The phosphorus content in the solid products of Examples 1-6 and Comparative Examples 1-2, as well as the phosphorus content in the high-salt solutions, are shown in Table 1.

[0057] Table 1

[0058] As can be seen from Table 1, the method for recovering phosphorus from ferric phosphate waste of the present invention utilizes rutile mother liquor and hydrochloric acid solution to treat ferric phosphate waste, which can reduce the recovery cost of ferric phosphate waste and reduce phosphorus loss.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering phosphorus from ferric phosphate waste residue, characterized in that, Includes the following steps: The ferric phosphate residue, rutile mother liquor, and hydrochloric acid solution were subjected to acid leaching, followed by solid-liquid separation to obtain a high-salt solution and a solid product.

2. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The mass ratio of the rutile mother liquor to the hydrochloric acid solution is 1:(2~5).

3. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The pH of the acid leaching is 4.0~6.

7.

4. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The acid leaching temperature is 10~40℃.

5. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The acid leaching time is 45-90 minutes.

6. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The ferric phosphate waste residue is successively dried, crushed and screened to obtain powder residue; the powder residue and water are pulped to obtain slurry; the slurry, rutile mother liquor and hydrochloric acid solution are acid leached, and after solid-liquid separation, a high-salt solution and solid product are obtained.

7. The method for recovering phosphorus from ferric phosphate waste according to claim 6, characterized in that, The phosphorus content in the slag is 5wt%~15wt% based on P2O5.

8. The method for recovering phosphorus from ferric phosphate waste according to claim 6, characterized in that, The solid content of the slurry is 20wt%~50wt%.

9. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The phosphorus content in the solid product is ≥25wt% based on P2O5.

10. The method for recovering phosphorus from ferric phosphate waste according to claim 1, characterized in that, The phosphorus content in the high-salt solution is <50 ppm, calculated as P2O5.

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