Method for using red mud to efficiently prepare ferrous phosphate dihydrate

Abstract

Disclosed is a method for using red mud to efficiently prepare ferrous phosphate dihydrate, comprising: mixing red mud and an acid solution to carry out an acid leaching reaction to obtain a red mud leachate; adding a reducing agent into the red mud leachate to carry out a reduction or comproportionation reaction to obtain a reaction solution; selectively adding an organic solvent into the reaction solution, and using an organic phase to extract impurities to respectively obtain a mixed organic solution and a target object solution; and adding an oxidizing agent and a phosphorus source into the target object solution to carry out an oxidation reaction and a homogeneous precipitation reaction, and cleaning and drying a precipitation product to obtain ferrous phosphate dihydrate.

Description

A method for efficiently preparing ferric phosphate dihydrate using red mud CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese patent application No. 202410163925.1 filed on February 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the technical field of ferric phosphate preparation, and in particular to a method for efficiently preparing ferric phosphate dihydrate by utilizing red mud. Background Art

[0003] Red mud is rich in iron, and iron is the main elemental component of red mud. Therefore, iron is one of the metal elements in red mud with recycling value. The iron minerals in red mud are mainly iron ores such as hematite and goethite. This type of iron ore has poor magnetic separation properties, and the use of strong magnetic separation and magnetic roasting methods has the characteristics of large investment and high energy consumption, resulting in magnetic separation technology being limited by capital costs. However, in the future, as the output of alumina production companies using high-iron bauxite as raw material gradually increases, the proportion of alumina production using high-iron bauxite as raw material will approach 50%, which will lead to a continuous increase in the proportion of high-iron red mud production. Therefore, how to efficiently separate or extract iron-containing targets from red mud is a key issue for the efficient and rapid preparation of iron phosphate from red mud.

[0004] Iron phosphate was initially used in ceramic glass, agriculture, steel, and surface passivation. However, with the deepening of research, lithium iron phosphate batteries have become its most important downstream application. Demand for lithium iron phosphate batteries has surged, especially with the development of new energy vehicles. As one of the emerging precursors for new energy materials, iron phosphate is a key precursor material for the preparation of lithium iron phosphate. Due to the rapid growth in demand for lithium iron phosphate, the preparation of iron phosphate has also attracted considerable attention.

[0005] Since the main elements in high-iron red mud are iron, aluminum, calcium, magnesium and silicon, the separation principle of the currently disclosed technology for preparing ferric phosphate dihydrate using red mud is to introduce a variety of additives during the precipitation process to remove impurities and precipitate impurities to achieve solid-liquid separation. The preparation process is complicated and lacks consideration for the purity and quality of the ferric phosphate; or, without considering the separation of other elements, all leached elements in the acid leaching solution are directly separated by extraction for future use. Summary of the Invention

[0006] This article discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. By utilizing one or more embodiments of the present disclosure, technical problems such as long preparation process time and complex additives in the related art of preparing ferric phosphate dihydrate using red mud are solved.

[0007] Disclosed herein is a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising: mixing red mud and acid solution to perform an acid leaching reaction to obtain a red mud leachate; adding a reducing agent to the red mud leachate to perform a reduction reaction or a neutralization reaction to obtain a reaction solution; selectively adding an organic solvent to the reaction solution to perform an organic phase extraction reaction of impurities to respectively obtain a mixed organic solution and a target solution; and adding an oxidant and a phosphorus source to the target solution to perform an oxidation reaction and a homogeneous precipitation reaction to obtain a precipitated product, and washing and drying the precipitated product to obtain ferric phosphate dihydrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0010] FIG1 shows a flow chart of a method for efficiently preparing ferric phosphate dihydrate using red mud according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0012] Various embodiments of the present disclosure may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the present disclosure; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0013] In this disclosure, unless otherwise stated, terms including "including" and "comprising" mean "including but not limited to". In this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this document, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0014] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased from the market or prepared by existing methods.

[0015] In a first aspect, this article discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0016] mixing red mud and acid solution to perform acid leaching reaction to obtain red mud leachate;

[0017] adding a reducing agent to the red mud leachate to perform a reduction reaction or a neutralization reaction to obtain a reaction solution;

[0018] Selectively adding an organic solvent to the reaction solution to extract impurities from the organic phase to obtain a mixed organic solution and a target solution; and

[0019] An oxidant and a phosphorus source are added to the target solution to carry out an oxidation reaction and a homogeneous precipitation reaction to obtain a precipitated product. The precipitated product is washed and dried to obtain ferric phosphate dihydrate.

[0020] In the above embodiment, no exogenous substances such as a variety of impurity removers, separators and metal scavengers are added. Instead, the target substance is separated from the acid leaching solution and subsequently synthesized by utilizing the properties of different metal chlorides themselves and the principle of different solubility in specific organic solvents. This reduces the addition of exogenous substances, shortens the process flow, and realizes the high-value utilization of red mud.

[0021] It should be noted that in the above embodiment, the purpose of adding a reducing agent to the red mud leachate is to reduce the ferric ions in the red mud leachate to ferrous ions. During this reaction, the ferric ions are reduced, and this reaction process can be referred to as a reduction reaction. If the reducing agent used is elemental iron, then during this reaction, the ferric ions in the red mud leachate are reduced to ferrous ions, and the reducing agent elemental iron is oxidized to ferrous ions. The ferric ions and the elemental iron return to the same valence, and this reaction process can also be referred to as a neutralization reaction.

[0022] As an optional embodiment, the acid solution is concentrated hydrochloric acid, and the acid leaching reaction is achieved through a pressurized and heated process.

[0023] In the above embodiment, the progress of the acid leaching reaction can be accelerated by increasing pressure and temperature, so that the metal components in the red mud can be quickly dissolved in the concentrated hydrochloric acid.

[0024] In the above embodiment, the concentrated hydrochloric acid is hydrochloric acid with a mass fraction of hydrogen chloride exceeding 20%. Alternatively, the concentrated hydrochloric acid in the above embodiment can be commercially available concentrated hydrochloric acid, which may have a concentration of 36% to 38%.

[0025] As an optional embodiment, the acid solution is concentrated hydrochloric acid, and the leaching time of the acid leaching reaction is 2 hours to 3 hours.

[0026] As an optional embodiment, the mass concentration of the concentrated hydrochloric acid is 1.0 mol / L to 6.0 mol / L.

[0027] In the above embodiment, the concentration of concentrated hydrochloric acid is controlled to be between 1.0 mol / L and 6.0 mol / L because concentrated hydrochloric acid within this concentration range is conducive to the sufficient leaching of the valuable element iron in red mud. The disadvantage of excessively high concentrated hydrochloric acid concentration is that it is highly hazardous, expensive, and results in excessive impurities in the red mud leachate. The disadvantage of too low a concentrated hydrochloric acid concentration is that it is not conducive to the sufficient leaching of the valuable element iron.

[0028] As an optional embodiment, the molar ratio of iron ions to reducing agent in the red mud leachate is 1:(0.1-1.0.)

[0029] In the above embodiment, the specific value of the molar ratio of iron ions to reducing agent in the red mud leachate is not specified. For example, the molar ratio of iron ions to reducing agent in the red mud leachate can be set to 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 and 1:1.

[0030] In the above embodiment, the molar ratio of iron ions to reducing agent in the red mud leachate is controlled to 1: (0.1-1.0) because this molar ratio range facilitates the complete reaction of the reducing agent and avoids wasting resources. If the molar ratio of iron ions to reducing agent in the red mud leachate is too low, i.e., if too much reducing agent is added, unnecessary impurities are easily generated during the reduction reaction. If the molar ratio of iron ions to reducing agent in the red mud leachate is too high, i.e., if insufficient reducing agent is added, the yield of the target product will be relatively low, i.e., the iron ions in the red mud leachate cannot be completely reduced.

[0031] As an optional embodiment, the reducing agent includes at least one of elemental iron, zinc powder, sulfurous acid, thiosulfate and elemental copper.

[0032] In the above embodiments, the reducing agent first reacts with the ferric ions to generate ferrous ions. If the amount of reducing agent used is excessive, exceeding the amount required to reduce the ferric ions to ferrous ions, the newly generated ferrous ions may be further reduced to elemental iron, affecting the reaction and yield of subsequent steps. Therefore, the amount of reducing agent used should be lower than the amount required to reduce the ferric ions to ferrous ions.

[0033] As an optional embodiment, the reducing agent is elemental iron.

[0034] In the above embodiment, elemental iron is used because it is not only green and safe, but also has a certain degree of reducibility, capable of completely reacting with trivalent iron ions, and the products of elemental iron oxidation and trivalent ion reduction are integrated. In addition, elemental iron has a moderate metallic activity and generally does not react with ions such as K, Ca, Na, Mg, and Al, thereby reducing the generation of impurities.

[0035] As an optional embodiment, the organic solvent is selected from at least one of diethyl ether, acetone, butanone and methyl isobutyl ketone.

[0036] In the above embodiment, the chlorides including calcium chloride and magnesium chloride in the reaction solution can be dissolved in any one of the above organic solvents of diethyl ether, acetone, butanone and methyl isobutyl ketone, while the ferrous chloride in the reaction solution is difficult to dissolve in any one of the above organic solvents of diethyl ether, acetone, butanone and methyl isobutyl ketone. Therefore, the ferrous chloride can be separated from the other chlorides by virtue of the different solubilities of ferrous chloride and other chlorides such as calcium chloride and magnesium chloride in the organic solvent.

[0037] As an optional embodiment, the selective addition of an organic solvent to the reaction liquid to perform an organic phase impurity extraction reaction includes: adding the organic solvent to the reaction liquid, stirring the organic solvent and the reaction liquid, allowing the organic solvent and the reaction liquid to be fully mixed and then standing, separating the organic phase, and repeating the above steps 3 to 5 times.

[0038] In the above embodiment, by repeatedly extracting the reaction solution with an organic solvent 3 to 5 times, chlorides other than ferrous chloride in the reaction solution can be extracted from the reaction solution into the organic phase, thereby reducing the content of other chlorides in the target solution, improving the purity of the target solution, and further improving the purity and quality of the finally obtained ferric phosphate dihydrate.

[0039] As an optional embodiment, the oxidant includes at least one of hydrogen peroxide, ammonium persulfate, oxygen, peroxydisulfate and Thiobacillus ferrooxidans.

[0040] As an optional embodiment, the oxidant is hydrogen peroxide.

[0041] In the above embodiment, hydrogen peroxide was selected as the oxidant due to its readily available, low cost, lack of toxic substances and pollutants, no negative impact on the reaction system, and environmental friendliness. Other oxidants, such as Thiobacillus ferrooxidans, can also achieve the desired effect. However, industrial applications present challenges such as high acquisition costs, long cultivation times, and difficulty in large-scale application.

[0042] As an optional embodiment, the phosphorus source is an aqueous solution containing at least one of phosphoric acid, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, and potassium phosphate.

[0043] As an optional embodiment, the temperature of the oxidation reaction is 20°C to 95°C.

[0044] In the above embodiment, the specific value of the temperature of the oxidation reaction is not limited. For example, the temperature of the oxidation reaction can be set to 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 95°C.

[0045] In the above embodiment, controlling the oxidation reaction temperature to 20° C. to 95° C. is beneficial for accelerating the oxidation reaction. If the oxidation reaction temperature is too low, the oxidation reaction may be slow or non-reactive, resulting in insufficient oxidation of ferrous ions and a reduced yield of ferric phosphate dihydrate in the generated precipitate. If the oxidation reaction temperature is too high, the reaction may be intensified, which is not conducive to the safe reaction of the system and may easily cause splashing hazards.

[0046] As an optional embodiment, the pH during the homogeneous precipitation reaction is 2.0 to 6.7.

[0047] In the above embodiment, the specific pH value during the homogeneous precipitation reaction is not limited. For example, the pH value during the homogeneous precipitation reaction can be set to 2.0, 3.0, 4.0, 5.0, 6.0, or 6.7.

[0048] In the above embodiment, the reason for controlling the pH during the homogeneous precipitation reaction to be 2.0 to -6.7 is that the precipitation conditions of ferric phosphate dihydrate are acidic. If the pH during the homogeneous precipitation reaction is too high, ferric phosphate dihydrate will not easily form a precipitate. If the pH during the homogeneous precipitation reaction is too low, ferric phosphate dihydrate will be unstable in the system.

[0049] As an optional embodiment, the molar ratio of the oxidant to the phosphorus source is 3:1.

[0050] The present disclosure will be further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the present disclosure only and are not intended to limit the scope of the present disclosure. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with industry standards. If no corresponding industry standards are available, the methods were performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0051] The chemical composition of the red mud used in the following examples and comparative examples is shown in Table 1:

[0052] Table 1 Main components of red mud / ω%

[0053] Example 1

[0054] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0055] Red mud and acid are mixed in a specific ratio to form a slurry. A leaching reaction is carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Elemental iron is then added to the red mud leachate as a reducing agent to initiate a neutralization reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of the elemental iron as a reducing agent to the iron ions in the red mud leachate is 1:1. Acetone, an organic solvent, is then added to the reaction solution, stirred, and allowed to stand to extract impurities from the organic phase and separate them from the target product, resulting in a mixed organic solution and a target product solution. Hydrogen peroxide as an oxidant and phosphoric acid as a phosphorus source are added to the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is controlled at 90°C, and the pH during the homogeneous precipitation reaction is maintained at 2.8. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0056] Example 2

[0057] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0058] Red mud and acid are mixed in a specific ratio to form a slurry. A leaching reaction is carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Sulfite is then added to the red mud leachate as a reducing agent to initiate a reduction reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of sulfurite to iron ions in the red mud leachate is 0.5:1. Ether is then added to the reaction solution as an organic solvent, stirred, and allowed to stand to extract impurities from the target product through the organic phase, resulting in a mixed organic solution and a target product solution. Ammonium persulfate as an oxidant and phosphoric acid as a phosphorus source are then added to the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is controlled at 90°C, and the pH during the homogeneous precipitation reaction is maintained at 3.6. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0059] Example 3

[0060] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0061] Red mud and acid are mixed in a specific ratio to form a slurry. A leaching reaction is carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Zinc powder is then added to the red mud leachate as a reducing agent to initiate a reduction reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of zinc powder to iron ions in the red mud leachate is 0.7:1. Butanone is then added to the reaction solution as an organic solvent, stirred, and allowed to stand to extract impurities from the target product through the organic phase, resulting in a mixed organic solution and a target product solution. Thiobacillus ferrooxidans as an oxidant and phosphoric acid as a phosphorus source are added to the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is maintained at 60°C, and the pH during the homogeneous precipitation reaction is maintained at 4.4. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0062] Example 4

[0063] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0064] Red mud and acid are mixed in a specific ratio to form a slurry. The leaching reaction is then carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Thiosulfate, a reducing agent, is then added to the red mud leachate to initiate a reduction reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of the reducing agent, thiosulfate, to the iron ions in the red mud leachate is 0.9:1. Acetone, an organic solvent, is then added to the reaction solution, stirred, and allowed to stand to extract impurities from the organic phase and separate them from the target product, resulting in a mixed organic solution and a target product solution. Hydrogen peroxide as an oxidant and phosphoric acid as a phosphorus source are then added to the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is maintained at 40°C, and the pH during the homogeneous precipitation reaction is maintained at 5.2. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0065] Example 5

[0066] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0067] Red mud and acid are mixed in a specific ratio to form a slurry. A leaching reaction is carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Elemental copper is then added to the red mud leachate as a reducing agent to initiate a reduction reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of the elemental copper as a reducing agent to the iron ions in the red mud leachate is 0.1:1. Methyl isobutyl ketone (MIBK) is then added to the reaction solution, stirred, and allowed to stand to extract impurities from the target product through the organic phase, resulting in a mixed organic solution and a target product solution. Peroxydisulfate (Oxidant) and phosphoric acid (Phosphoric Acid) as a phosphorus source are then added to the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is maintained at 20°C, and the pH during the homogeneous precipitation reaction is maintained at 6.7. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0068] Example 6

[0069] This embodiment discloses a method for efficiently preparing ferric phosphate dihydrate using red mud, comprising:

[0070] Red mud and acid are mixed in a specific ratio to form a slurry. A leaching reaction is carried out under pressure and temperature. The product of the leaching reaction is subjected to solid-liquid separation, resulting in a red mud leachate. Elemental iron is then added to the red mud leachate as a reducing agent to initiate a neutralization reaction. After completion of the reaction, a reaction solution is obtained in which the molar ratio of the elemental iron as a reducing agent to the iron ions in the red mud leachate is 0.8:1. Acetone, an organic solvent, is then added to the reaction solution, stirred, and allowed to stand to extract impurities from the target product through the organic phase, resulting in a mixed organic solution and a target product solution. Oxygen as an oxidant and phosphoric acid as a phosphorus source are then introduced into the target product solution to carry out an oxidation reaction and a homogeneous precipitation reaction. The oxidation reaction temperature is maintained at 30°C, and the pH during the homogeneous precipitation reaction is maintained at 3. The reaction product is filtered to obtain a precipitate. The precipitate is then washed and dried to obtain ferric phosphate dihydrate.

[0071] Comparative Example 1

[0072] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 1 is that no reducing agent is added, and thus no product is obtained.

[0073] Comparative Example 2

[0074] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 1 is that no selective organic solvent is added, and thus no product is obtained.

[0075] Comparative Example 3

[0076] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 1 is that no oxidant is added, and thus no product is obtained.

[0077] Comparative Example 4

[0078] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 3 is that the molar ratio of zinc powder as a reducing agent to iron ions in the red mud leachate solution is increased to 1.5:1, and the obtained product does not meet the standards and contains a large amount of impurities.

[0079] Comparative Example 5

[0080] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 5 is that the temperature of the oxidation reaction is controlled at 10° C., and no product is obtained.

[0081] Comparative Example 6

[0082] This comparative example discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. The difference between this comparative example and Example 1 is that the pH of the homogeneous precipitation reaction is controlled to 8, and no ferric phosphate dihydrate product is obtained.

[0083] The effects of Examples 1-6 and Comparative Examples 1-6 are shown in Table 2 below:

[0084] Table 2 Effects of Examples 1-6 and Comparative Examples 1-6

[0085] It can be seen from Comparative Examples 1-3 in Table 2 that in the method for preparing ferric phosphate dihydrate disclosed herein, a reducing agent, a selective organic solvent and an oxidizing agent are necessary. The lack of any one of them will result in an incomplete process and the final ferric phosphate dihydrate product cannot be obtained.

[0086] It can be seen from Comparative Example 4 that when the molar ratio of the reducing agent to the iron ion is too high, other impurities will be reduced, affecting the quality of the ferric phosphate dihydrate product.

[0087] It can be seen from Comparative Example 5 that during the oxidation reaction, when the temperature of the oxidation reaction is low, the oxidation reaction will be slow or terminated, and no oxidation product can be obtained, which ultimately leads to the inability to obtain the final ferric phosphate dihydrate product.

[0088] It can be seen from Comparative Example 6 that when performing a homogeneous precipitation reaction, controlling the pH is a key factor in obtaining and precipitating the ferric phosphate dihydrate product. The ferric phosphate dihydrate product is generated in the solution. If the pH precipitation conditions are not met, the precipitate cannot be precipitated and the ferric phosphate dihydrate product cannot be obtained.

[0089] The above technical solution provided by the present disclosure has the following advantages compared with the related art:

[0090] This article discloses a method for efficiently preparing ferric phosphate dihydrate using red mud. This method does not require the addition of a variety of exogenous substances such as impurity removers, separators, and metal capture agents. Instead, the target substance is separated from the acid leaching solution and subsequently synthesized based on the characteristics of different metal chlorides themselves and the principle of different solubility in specific organic solvents, thereby reducing the addition of exogenous components, shortening the process flow, and achieving high-value utilization of red mud. The above is only a specific embodiment of the present disclosure, which enables those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for efficiently preparing ferric phosphate dihydrate using red mud, comprising: mixing red mud and acid solution to perform acid leaching reaction to obtain red mud leachate; adding a reducing agent to the red mud leachate to perform a reduction reaction or a neutralization reaction to obtain a reaction solution; Selectively adding an organic solvent to the reaction solution to extract impurities from the organic phase to obtain a mixed organic solution and a target solution; and An oxidant and a phosphorus source are added to the target solution to carry out an oxidation reaction and a homogeneous precipitation reaction to obtain a precipitated product. The precipitated product is washed and dried to obtain ferric phosphate dihydrate.

2. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The acid solution is concentrated hydrochloric acid, and the leaching time of the acid leaching reaction is 2 hours to 3 hours.

3. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The molar ratio of iron ions to reducing agent in the red mud leachate is 1:(0.1-1.0).

4. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1 or 3, wherein: The reducing agent includes at least one of elemental iron, sulfurous acid, zinc powder, thiosulfate and elemental copper.

5. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The organic solvent is selected from at least one of ether, acetone, butanone and methyl isobutyl ketone.

6. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The selective addition of an organic solvent to the reaction solution to perform an organic phase impurity extraction reaction comprises: The organic solvent is added to the reaction solution, and the organic solvent and the reaction solution are stirred to fully mix, and then allowed to stand, and the organic phase is separated. The above steps are repeated 3 to 5 times.

7. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The oxidant includes at least one of hydrogen peroxide, ammonium persulfate, oxygen, peroxydisulfate and Thiobacillus ferrooxidans.

8. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The phosphorus source is an aqueous solution containing at least one of phosphoric acid, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, and potassium phosphate.

9. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The temperature of the oxidation reaction is 20°C to 95°C.

10. The method for efficiently preparing ferric phosphate dihydrate using red mud according to claim 1, wherein: The pH value during the homogeneous precipitation reaction is 2.0 to 6.7.

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