A method for preparing iron phosphate from red mud

Abstract

The application discloses a method for preparing iron phosphate from red mud, which comprises the following steps: A, after drying, grinding and sieving, the red mud is stirred and leached with high-concentration strong acid under high-temperature conditions to obtain an acid leaching solution containing iron, aluminum and sodium; B, cationic resin is added to the acid leaching solution for ion exchange, and solid-liquid separation is performed to obtain resin adsorbing aluminum ions and filtrate a; C, desorption is performed on the resin to release aluminum ions from the resin, and filtration is performed to obtain a desorption solution and desorbed resin, and the desorption solution is subjected to polymerization to prepare aluminum sulfate; D, the filtrate a is cooled and crystallized to obtain a crystallization product sodium salt and filtrate b; E, the content of iron ions in the filtrate b is detected, a phosphorus-containing solution is added to the filtrate b, pH is adjusted, and homogeneous precipitation reaction is performed, and filtration is performed to obtain a precipitate which is iron phosphate, and the filtrate is adjusted to have a pH of 1.0-2.5 and then is sent back to the step A to be used as high-concentration strong acid for recycling.

Description

A method for preparing ferric phosphate from red mud Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization technology, specifically to a method for preparing ferric phosphate from red mud. Background Technology

[0002] Red mud is a highly alkaline, reddish solid waste generated during alumina production. Producing one ton of alumina generates 1.5-2.5 tons of red mud. In 2018, the global red mud stockpile reached 460 million tons, and it is increasing at a rate of approximately 200 million tons per year. Given its complex composition, large specific surface area, strong alkalinity, and large quantity, red mud has long been a problem hindering alumina production and the development of alumina plants. The composition of red mud varies depending on the source of bauxite. For high-iron red mud, there are relatively mature processes for recovering the iron components, but the economic benefits are not significant.

[0003] In recent years, with the booming development of the new energy field, the utilization rate of lithium iron phosphate batteries has shown a continuous upward trend. As an important precursor for the cathode material of lithium iron phosphate batteries, iron phosphate has enormous economic potential and significant market value and development prospects. Using the iron component in high-iron red mud as the iron source for preparing iron phosphate aligns with the mainstream trend of green environmental protection. Patent CN113620268A discloses an extraction-back-extraction method for preparing iron phosphate, in which red mud is leached with high-concentration hydrochloric acid, an organic phase containing an anionic extractant is added to the hydrochloric acid leachate for extraction, followed by back-extraction to prepare iron phosphate. This method is relatively complex, and the cost of iron extraction through extraction-back-extraction is high. Patent CN115818604A discloses a method for preparing iron phosphate from red mud iron extraction solution by sulfite reduction. This method involves mixing red mud with iron phosphate slurry filtrate mother liquor or sulfuric acid, slurrying and filtering to obtain pretreated red mud, then mixing the red mud with concentrated sulfuric acid, heating and stirring to obtain a slurry. After adjusting the pH of the slurry, a reducing agent is added to obtain a ferrous sulfate solution, which is then used to prepare ferric phosphate. This method involves multiple complex chemical reactions and operational steps, and the addition of the reducing agent generates sulfur dioxide, leading to some pollution.

[0004] The main difficulty in preparing iron phosphate from red mud by acid leaching lies in the low efficiency of low-concentration acid leaching and the complex composition of the leaching solution. Elements such as iron, aluminum, and sodium in red mud will dissolve in the solution during the acid leaching process, forming a complex system containing multiple metal ions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing ferric phosphate from red mud. This method uses red mud as raw material and performs high-temperature acid leaching with high-concentration sulfuric acid, which can fully leach out and recover the iron, aluminum and sodium elements.

[0006] To solve the above technical problems, the present invention adopts the following technical solution:

[0007] The method for preparing ferric phosphate from red mud includes the following steps:

[0008] A. After drying, grinding and sieving the red mud, it is leached with a high-concentration strong acid under high temperature conditions to obtain an acid leaching solution containing iron, aluminum and sodium.

[0009] B. Add a cation exchange resin selective for aluminum ions to the acid leaching solution for ion exchange, and separate the solid and liquid to obtain the resin that adsorbs aluminum ions and filtrate a.

[0010] C. Desorb the resin to release aluminum ions from the resin, filter to obtain desorbed solution and desorbed resin, and then perform a polymerization reaction on the desorbed solution to obtain aluminum sulfate.

[0011] D. Cool and crystallize filtrate a to obtain sodium salt crystallization product and filtrate b;

[0012] E. Detect the iron ion content in filtrate b, add a phosphorus-containing solution to filtrate b, adjust the pH to 1.0-2.5, carry out a homogeneous precipitation reaction, filter, and obtain ferric phosphate as the precipitate. After adjusting the pH to 1.0-2.5, the filtrate is returned to step A for recycling as a high-concentration strong acid.

[0013] The iron ion content in filtrate b can be detected using various existing methods, such as:

[0014] (1) Transfer 2 mL of filtrate b to a 250 mL Erlenmeyer flask, add 5 mL of hydrochloric acid, and heat to near boiling. While hot, add stannous chloride solution dropwise while shaking the Erlenmeyer flask until the solution color changes from brownish-yellow to light yellow.

[0015] (2) Add 4 to 5 drops of sodium tungstate indicator solution, and add titanium trichloride solution dropwise while shaking until the solution turns light blue. Immediately cool with running water, add 50 ml of water, and titrate with potassium dichromate standard solution until the blue color just fades (usually 1 to 2 drops, without recording the reading). Dilute with water to 100 mL, add 10 mL of sulfuric acid-phosphoric acid mixed solution, 3 to 4 drops of sodium diphenylamine sulfonate indicator solution, and titrate with potassium dichromate standard solution until a stable purple-red color (not disappearing for 30 seconds) is reached as the endpoint.

[0016] (3) Calculation of results:

[0017] Iron content is expressed as the mass fraction of iron (Fe), w, in percentage (%), and is calculated using the formula:

[0018]

[0019] In the formula:

[0020] V—The volume of potassium dichromate standard titration solution consumed in the titration of the leachate, in mL.

[0021] V0—The volume of potassium dichromate standard titration solution consumed in the titration of the blank sample, in mL.

[0022] V1—Total volume of leachate, in mL

[0023] V2—Sampling volume, in mL

[0024] c—The accurate value of the concentration of the potassium dichromate standard titration solution, in mol / L.

[0025] m—mass of the original sample, in grams.

[0026] 19.75% — Fe content of the sample.

[0027] In step A, the high-concentration strong acid is sulfuric acid with a concentration of 6-14 mol / L.

[0028] In step A, the high temperature is 60-120℃ and the reaction time is 1-4h.

[0029] In step B, the cationic resin is D001 resin, S957 resin, or S950 resin.

[0030] The Chinese name of D001 resin is: styrene-divinylbenzene copolymer sulfonic acid group cation exchange resin;

[0031] The Chinese name for S957 resin is: sulfonic acid-based / phosphonic acid-based cation exchange resin;

[0032] The Chinese name for S950 resin is: aminophosphonic acid cation exchange resin.

[0033] In step B, the reaction conditions for ion exchange of the cation exchange resin are: reaction temperature of 10-60℃, reaction time of 1-4h, and solid-liquid ratio of resin to solution of 0.2-0.8:1.

[0034] In step C, the conditions for desorbing the resin are as follows: adding 1-4 mol / L of dilute sulfuric acid at a solid-liquid ratio of 1:2-8, the reaction temperature is 10-90℃, and the reaction time is 1-4 h.

[0035] In step C, the polymerization reaction is carried out in the desorption solution under the following conditions: reaction temperature of 50-100℃ and reaction time of 1-6h.

[0036] In step D, the cooling crystallization temperature is -10℃ to 10℃.

[0037] In step E, the phosphorus-containing solution is one or a mixture of more than one of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate.

[0038] In step E, the conditions for the homogeneous precipitation reaction are: a molar ratio of iron to phosphorus-containing solution of 1:0.8-2, a reaction temperature of 50-100℃, and a reaction time of 2-8h.

[0039] The present invention has the following advantages:

[0040] The method of the present invention uses red mud as raw material and high-temperature acid leaching with high-concentration sulfuric acid, which can fully leach out and recycle the iron, aluminum and sodium elements.

[0041] This invention involves adding resin to red mud acid leaching solution to adsorb aluminum ions and conduct an ion exchange reaction. After desorption, the resin is regenerated, and the desorbed solution undergoes a polymerization reaction to produce aluminum sulfate. The acid leaching solution after aluminum separation is cooled and crystallized to obtain sodium sulfate. Adding a phosphorus source to the remaining crystallization solution yields ferric phosphate. This process achieves high-value utilization of iron, aluminum, and sodium elements in red mud.

[0042] The filtrate produced during the preparation of ferric phosphate in this invention is mainly composed of sulfuric acid, which can be recycled, reducing the raw material consumption of the entire process and lowering costs. Attached Figure Description

[0043] Figure 1 is a diagram of the ferric phosphate product obtained in Example 4 of the present invention;

[0044] Figure 2 is an XRD phase analysis diagram of the iron phosphate product obtained in Example 4 of the present invention;

[0045] Figure 3 is a diagram of the aluminum sulfate product obtained in Example 4 of the present invention;

[0046] Figure 4 is a diagram of the sodium sulfate product obtained in Example 4 of the present invention. Detailed Implementation

[0047] To facilitate a better understanding of the present invention, the following examples are provided. These examples fall within the scope of protection of the present invention, but do not limit the scope of protection of the present invention.

[0048] Example 1

[0049] A method for preparing ferric phosphate from red mud includes the following steps:

[0050] A. After drying, grinding and sieving the red mud, it is leached with 6 mol / L sulfuric acid at 60℃ with stirring for 1 hour to obtain an acid leaching solution containing iron, aluminum and sodium.

[0051] B. Add D001 cation exchange resin to the acid leaching solution for ion exchange. The reaction conditions for ion exchange are: reaction temperature of 10℃, reaction time of 1h, and solid-liquid ratio of resin to solution of 0.2:1. Then, separate the solid and liquid to obtain resin adsorbed with aluminum ions and filtrate a.

[0052] C. Desorb the resin to release aluminum ions from the resin, filter to obtain desorbed solution and desorbed resin, and then perform a polymerization reaction on the desorbed solution to obtain aluminum sulfate.

[0053] The conditions for desorbing the resin are as follows: add 1 mol / L dilute sulfuric acid at a solid-liquid ratio of 1:2, the reaction temperature is 10℃, and the reaction time is 1 h.

[0054] The polymerization reaction was carried out in the desorption solution under the following conditions: reaction temperature 50℃ and reaction time 1h.

[0055] D. Cool the filtrate a at -10℃ to 10℃ to crystallize it, and obtain the crystallized sodium salt and filtrate b.

[0056] E. Detect the iron ion content in filtrate b, add one or more of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate to filtrate b, adjust the pH to 1.0, carry out a homogeneous precipitation reaction, filter, and obtain ferric phosphate as the precipitate. After adjusting the pH to 1.0, the filtrate is sent back to step A for recycling as a high-concentration strong acid.

[0057] The conditions for the homogeneous precipitation reaction were: a molar ratio of iron to phosphorus-containing solution of 1:0.8, a reaction temperature of 50℃, and a reaction time of 2h.

[0058] Example 2

[0059] A method for preparing ferric phosphate from red mud includes the following steps:

[0060] A. After drying, grinding and sieving the red mud, it is leached with 14 mol / L sulfuric acid at 120℃ with stirring for 4 hours to obtain an acid leaching solution containing iron, aluminum and sodium.

[0061] B. Add S957 cation exchange resin to the acid leaching solution for ion exchange. The reaction conditions for ion exchange are: reaction temperature of 60℃, reaction time of 4h, and solid-liquid ratio of resin to solution of 0.8:1. Then, separate the solid and liquid to obtain resin adsorbed with aluminum ions and filtrate a.

[0062] C. Desorb the resin to release aluminum ions from the resin, filter to obtain desorbed solution and desorbed resin, and then perform a polymerization reaction on the desorbed solution to obtain aluminum sulfate.

[0063] The conditions for desorbing the resin were as follows: 4 mol / L dilute sulfuric acid was added at a solid-liquid ratio of 1:8, the reaction temperature was 90℃, and the reaction time was 4 h.

[0064] The polymerization reaction was carried out in the desorption solution under the following conditions: reaction temperature 100℃ and reaction time 6h.

[0065] D. Cool the filtrate a at 10°C to crystallize, and obtain the crystallized sodium salt and filtrate b.

[0066] E. Detect the iron ion content in filtrate b, add one or more of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate to filtrate b, adjust the pH to 2.5, carry out a homogeneous precipitation reaction, filter, and obtain ferric phosphate as the precipitate. After adjusting the pH to 2.5, the filtrate is sent back to step A for recycling as a high-concentration strong acid.

[0067] The conditions for the homogeneous precipitation reaction were: a molar ratio of iron to phosphorus-containing solution of 1:2, a reaction temperature of 100℃, and a reaction time of 8h.

[0068] Example 3

[0069] A method for preparing ferric phosphate from red mud includes the following steps:

[0070] A. After drying, grinding and sieving the red mud, it is leached with 8 mol / L sulfuric acid at 100℃ with stirring for 2 hours to obtain an acid leaching solution containing iron, aluminum and sodium.

[0071] B. Add S950 cation exchange resin to the acid leaching solution for ion exchange. The reaction conditions for ion exchange are: reaction temperature of 40℃, reaction time of 3h, and solid-liquid ratio of resin to solution of 0.5:1. Then, separate the solid and liquid to obtain resin adsorbing aluminum ions and filtrate a.

[0072] C. Desorb the resin to release aluminum ions from the resin, filter to obtain desorbed solution and desorbed resin, and then perform a polymerization reaction on the desorbed solution to obtain aluminum sulfate.

[0073] The conditions for desorbing the resin are as follows: add 2 mol / L dilute sulfuric acid at a solid-liquid ratio of 1:5, the reaction temperature is 50℃, and the reaction time is 3h.

[0074] The polymerization reaction was carried out in the desorption solution under the following conditions: reaction temperature 70℃ and reaction time 4h.

[0075] D. Cool the filtrate a at -10℃ to 10℃ to crystallize it, and obtain the crystallized sodium salt and filtrate b.

[0076] E. Detect the iron ion content in filtrate b, add one or more of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate to filtrate b, adjust the pH to 1.5, carry out a homogeneous precipitation reaction, filter, and obtain ferric phosphate as the precipitate. After adjusting the pH to 1.5, the filtrate is sent back to step A for recycling as a high-concentration strong acid.

[0077] The conditions for the homogeneous precipitation reaction were: a molar ratio of iron to phosphorus-containing solution of 1:1.2, a reaction temperature of 70℃, and a reaction time of 6h.

[0078] Example 4

[0079] The method for preparing ferric phosphate from red mud is as follows:

[0080] A. Dry 20g of red mud, grind it, and sieve it through a 100-mesh sieve. Then, leach the red mud with 6mol / L sulfuric acid. The acid leaching reaction conditions are: reaction temperature 90℃, reaction time 1h. The reaction yields an acid leaching solution containing iron, aluminum, and sodium.

[0081] B. D001 resin with a solid-liquid ratio of 0.5:1 was added to the acid leaching solution for an ion exchange reaction. After reacting at room temperature (25℃) for 2 hours, solid-liquid separation was performed to obtain resin that had adsorbed aluminum ions from the solution and filtrate a. The resin was then subjected to a desorption reaction by adding 4 mol / L dilute sulfuric acid at a solid-liquid ratio of 1:6 at 60℃ for 1 hour. The desorbed solution was then subjected to a polymerization reaction under the following conditions: reaction temperature 80℃ for 2 hours.

[0082] C. Cool filtrate a at 0℃ to crystallize, obtaining sodium sulfate crystallization product and filtrate b;

[0083] D. Add 0.5 mol / L phosphoric acid to filtrate b, adjust the pH to 2 with alkali solution, the iron-phosphorus feed ratio is 1:1.2, the reaction temperature is 80℃, and the reaction time is 4h to carry out homogeneous precipitation of iron phosphate; after the reaction is completed, add acid to the filtered liquid to adjust the pH, and then send it back to step A for use.

[0084] The method for detecting the iron ion content in filtrate b is as follows:

[0085] (1) Transfer 2 mL of filtrate b to a 250 mL Erlenmeyer flask, add 5 mL of hydrochloric acid, and heat to near boiling. While hot, add stannous chloride solution dropwise while shaking the Erlenmeyer flask until the solution color changes from brownish-yellow to light yellow.

[0086] (2) Add 4 to 5 drops of sodium tungstate indicator solution, and add titanium trichloride solution dropwise while shaking until the solution turns light blue. Immediately cool with running water, add 50 ml of water, and titrate with potassium dichromate standard solution until the blue color just fades (usually 1 to 2 drops, without recording the reading). Dilute with water to 100 mL, add 10 mL of sulfuric acid-phosphoric acid mixed solution, 3 to 4 drops of sodium diphenylamine sulfonate indicator solution, and titrate with potassium dichromate standard solution until a stable purple-red color (not disappearing for 30 seconds) is reached as the endpoint.

[0087] (3) Calculation of results:

[0088] Iron content is expressed as the mass fraction of iron (Fe), w, in percentage (%), and is calculated using the formula:

[0089]

[0090] In the formula:

[0091] V—The volume of potassium dichromate standard titration solution consumed in the titration of the leachate, in mL.

[0092] V0—The volume of potassium dichromate standard titration solution consumed in the titration of the blank sample, in mL.

[0093] V1—Total volume of leachate, in mL

[0094] V2—Sampling volume, in mL

[0095] c—The accurate value of the concentration of the potassium dichromate standard titration solution, in mol / L.

[0096] m—mass of the original sample, in grams.

[0097] 19.75% — Fe content of the sample.

[0098] In this embodiment, the iron leaching rate reaches 65%, and the iron-to-phosphorus ratio of the obtained iron phosphate product is 0.78.

[0099] Example 5

[0100] A method for preparing ferric phosphate from red mud includes the following steps:

[0101] A. Dry 20g of red mud, grind it, and sieve it through a 100-mesh sieve. Then, leach the red mud in 9mol / L sulfuric acid. The acid leaching reaction conditions are: reaction temperature 100℃, reaction time 1.5h. The reaction yields an acid leaching solution containing iron, aluminum, and sodium.

[0102] B. An ion exchange reaction was initiated by adding S957 resin at a solid-liquid ratio of 0.5:1 to the acid leaching solution. After reacting at room temperature (25℃) for 2 hours, solid-liquid separation was performed to obtain resin that had adsorbed a certain amount of aluminum ions from the solution and filtrate a. The resin was then subjected to a desorption reaction by adding 4 mol / L dilute sulfuric acid at a solid-liquid ratio of 1:6 at a reaction temperature of 60℃ for 1 hour. The desorbed solution was then subjected to a polymerization reaction under the following conditions: reaction temperature 80℃ for 2 hours.

[0103] C. Cool filtrate a at 0℃ to crystallize, obtaining sodium sulfate crystallization product and filtrate b;

[0104] D. Add 0.5 mol / L phosphoric acid to filtrate b, adjust the pH to 2 with alkali solution, the iron-phosphorus feed ratio is 1:1.4, the reaction temperature is 90℃, and the reaction time is 4h to carry out homogeneous precipitation of iron phosphate; after the reaction is completed, add acid to the filtered liquid to adjust the pH, and then send it back to step A for use.

[0105] The method for detecting the iron ion content in filtrate b is as follows:

[0106] (1) Transfer 2 mL of filtrate b to a 250 mL Erlenmeyer flask, add 5 mL of hydrochloric acid, and heat to near boiling. While hot, add stannous chloride solution dropwise while shaking the Erlenmeyer flask until the solution color changes from brownish-yellow to light yellow.

[0107] (2) Add 4 to 5 drops of sodium tungstate indicator solution, and add titanium trichloride solution dropwise while shaking until the solution turns light blue. Immediately cool with running water, add 50 ml of water, and titrate with potassium dichromate standard solution until the blue color just fades (usually 1 to 2 drops, without recording the reading). Dilute with water to 100 mL, add 10 mL of sulfuric acid-phosphoric acid mixed solution, 3 to 4 drops of sodium diphenylamine sulfonate indicator solution, and titrate with potassium dichromate standard solution until a stable purple-red color (not disappearing for 30 seconds) is reached as the endpoint.

[0108] (3) Calculation of results:

[0109] Iron content is expressed as the mass fraction of iron (Fe), w, in percentage (%), and is calculated using the formula:

[0110]

[0111] In the formula:

[0112] V—The volume of potassium dichromate standard titration solution consumed in the titration of the leachate, in mL.

[0113] V0—The volume of potassium dichromate standard titration solution consumed in the titration of the blank sample, in mL.

[0114] V1—Total volume of leachate, in mL

[0115] V2—Sampling volume, in mL

[0116] c—The accurate value of the concentration of the potassium dichromate standard titration solution, in mol / L.

[0117] m—mass of the original sample, in grams.

[0118] 19.75% — Fe content of the sample.

[0119] In this embodiment, the iron leaching rate reaches 85%, and the iron-to-phosphorus ratio of the obtained iron phosphate product is 1.05.

[0120] Example 6

[0121] A method for preparing ferric phosphate from red mud includes the following steps:

[0122] A. Dry 20g of red mud, grind it, and sieve it through a 100-mesh sieve. Then, leach the red mud into 10mol / L sulfuric acid. The acid leaching reaction conditions are: reaction temperature 100℃, reaction time 1.5h. The reaction yields an acid leaching solution containing iron, aluminum, and sodium.

[0123] B. An ion exchange reaction was initiated by adding S950 resin at a solid-liquid ratio of 0.5:1 to the acid leaching solution. After reacting at room temperature (25℃) for 2 hours, solid-liquid separation was performed to obtain resin that had adsorbed a certain amount of aluminum ions from the solution and filtrate a. The resin was then subjected to a desorption reaction by adding 4 mol / L dilute sulfuric acid at a solid-liquid ratio of 1:6 at a reaction temperature of 60℃ for 1 hour. The desorbed solution was then subjected to a polymerization reaction under the following conditions: reaction temperature 80℃ for 2 hours.

[0124] C. Cool filtrate a at 0℃ to crystallize, obtaining sodium sulfate crystallization product and filtrate b;

[0125] D. Add 0.5 mol / L phosphoric acid to filtrate b, adjust the pH to 2 with alkali solution, the iron-phosphorus feed ratio is 1:1.4, the reaction temperature is 90℃, and the reaction time is 4h to carry out homogeneous precipitation of iron phosphate; after the reaction is completed, add acid to the filtered liquid to adjust the pH, and then send it back to step A for use.

[0126] The method for detecting the iron ion content in filtrate b is as follows:

[0127] (1) Transfer 2 mL of filtrate b to a 250 mL Erlenmeyer flask, add 5 mL of hydrochloric acid, and heat to near boiling. While hot, add stannous chloride solution dropwise while shaking the Erlenmeyer flask until the solution color changes from brownish-yellow to light yellow.

[0128] (2) Add 4 to 5 drops of sodium tungstate indicator solution, and add titanium trichloride solution dropwise while shaking until the solution turns light blue. Immediately cool with running water, add 50 ml of water, and titrate with potassium dichromate standard solution until the blue color just fades (usually 1 to 2 drops, without recording the reading). Dilute with water to 100 mL, add 10 mL of sulfuric acid-phosphoric acid mixed solution, 3 to 4 drops of sodium diphenylamine sulfonate indicator solution, and titrate with potassium dichromate standard solution until a stable purple-red color (not disappearing for 30 seconds) is reached as the endpoint.

[0129] (3) Calculation of results:

[0130] Iron content is expressed as the mass fraction of iron (Fe), w, in percentage (%), and is calculated using the formula:

[0131]

[0132] In the formula:

[0133] V—The volume of potassium dichromate standard titration solution consumed in the titration of the leachate, in mL.

[0134] V0—The volume of potassium dichromate standard titration solution consumed in the titration of the blank sample, in mL.

[0135] V1—Total volume of leachate, in mL

[0136] V2—Sampling volume, in mL

[0137] c—The accurate value of the concentration of the potassium dichromate standard titration solution, in mol / L.

[0138] m—mass of the original sample, in grams.

[0139] 19.75% — Fe content of the sample.

[0140] In this embodiment, the iron leaching rate reaches 80%, and the iron-to-phosphorus ratio of the obtained iron phosphate product is 0.89.

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 4 is that a low-concentration acid leaching method was used to extract the red mud.

[0143] This comparative processing method includes the following steps:

[0144] A. Dry 20g of red mud, grind it, and sieve it through a 100-mesh sieve. Then, leach the red mud with 2mol / L sulfuric acid. The acid leaching reaction conditions are: reaction temperature 90℃, reaction time 1h. The reaction yields an acid leaching solution containing iron, aluminum, and sodium.

[0145] B. The concentration of aluminum ions in the acid leaching solution was measured to be 2.3 g / L. The ion exchange efficiency after adding resin was very low, and the desorption solution failed to produce aluminum sulfate product.

[0146] The iron leaching rate in this embodiment was 28% as tested. The results indicate that high acidity has a significant impact on leaching, and iron enrichment and subsequent steps can only be carried out under high acid conditions.

[0147] Comparative Example 2

[0148] The main difference between this comparative example and Example 1 is that the ion exchange reaction conditions in step B are such that the ratio of ion exchange resin added is 0.1:1.

[0149] In this invention, the optimal solid-liquid ratio of resin to solution in the ion exchange reaction is (0.2-0.8):1. In the comparative example, as the amount of ion exchange resin added decreases, the amount of aluminum ions in the desorption solution also decreases. The aluminum ions remaining in the subsequent solution affect the purity of ferric phosphate, manifested as an increase in the impurity content in the product. When the solid-liquid ratio exceeds 0.8:1, the adsorption effect of ion exchange resin on aluminum ions no longer increases, indicating that the adsorption capacity of the ion exchange resin has reached saturation. Even if the amount of ion exchange resin added continues to increase, it is impossible to adsorb more aluminum ions. This further verifies the importance of optimizing the solid-liquid ratio and the crucial role of ensuring sufficient ion exchange resin dosage in guaranteeing product purity.

[0150] Comparative Example 3

[0151] The main difference between this comparative example and Example 2 is that in step B, the polymerization reaction of the desorption liquid was carried out at a room temperature of 25°C. After 2 hours of reaction, no white precipitate was produced in the solution. Further extending the reaction time did not produce any precipitate.

[0152] This result indicates that the polymerization reaction may be more efficient at high temperatures compared to room temperature conditions. Therefore, temperature is one of the key factors affecting the efficiency of aluminum sulfate polymerization, and high temperature conditions help to increase the reaction rate and the yield of aluminum sulfate.

[0153] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing ferric phosphate from red mud, characterized in that, Includes the following steps: A. After drying, grinding, and sieving the red mud, it is leached with a high-concentration strong acid under high temperature conditions to obtain an acid leaching solution containing iron, aluminum, and sodium; B. A cation exchange resin selectively targeting aluminum ions is added to the acid leaching solution for ion exchange, and solid-liquid separation is performed to obtain resin adsorbing aluminum ions and filtrate a; the cation exchange resin is D001 resin, S957 resin, or S950 resin; C. The resin is desorbed to release aluminum ions from the resin, filtered, and desorbed solution and desorbed resin are obtained. The desorbed solution is subjected to a polymerization reaction to obtain aluminum sulfate. D. Cool and crystallize filtrate a to obtain sodium salt crystallization product and filtrate b; E. Detect the iron ion content in filtrate b, add phosphorus-containing solution to filtrate b, adjust the pH to 1.0-2.5, carry out homogeneous precipitation reaction, filter, and obtain precipitate as iron phosphate. After adjusting the pH to 1.0-2.5, the filtrate is returned to step A for recycling as a high-concentration strong acid.

2. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step A, the high-concentration strong acid is sulfuric acid with a concentration of 6-14 mol / L.

3. The method for preparing ferric phosphate from red mud according to claim 2, characterized in that: In step A, the high temperature is 60-120℃ and the reaction time is 1-4h.

4. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step B, the reaction conditions for ion exchange of the cation exchange resin are: reaction temperature of 10-60℃, reaction time of 1-4h, and solid-liquid ratio of resin to solution of 0.2-0.8:

1.

5. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step C, the conditions for desorbing the resin are as follows: adding 1-4 mol / L of dilute sulfuric acid at a solid-liquid ratio of 1:2-8, the reaction temperature is 10-90℃, and the reaction time is 1-4h.

6. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step C, the polymerization reaction is carried out in the desorption solution under the following conditions: reaction temperature of 50-100℃ and reaction time of 1-6h.

7. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step D, the cooling crystallization temperature is -10℃ to 10℃.

8. The method for preparing ferric phosphate from red mud according to claim 1, characterized in that: In step E, the phosphorus-containing solution is one or a mixture of more than one of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate.

9. The method for preparing ferric phosphate from red mud according to claim 8, characterized in that: In step E, the conditions for the homogeneous precipitation reaction are: a molar ratio of iron to phosphorus-containing solution of 1:0.8-2, a reaction temperature of 50-100℃, and a reaction time of 2-8h.

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