Iron-manganese oxide as well as preparation method and application thereof

Abstract

The invention discloses an iron and manganese oxide as well as a preparation method and application thereof. The method comprises the following steps: 1) dispersing soluble permanganate and phosphate in water, adding hexadecyl trimethyl ammonium bromide, stirring to prepare a mixed solution, and adding a sulfuric acid aqueous solution for acidification to obtain an acidified mixed solution; 2) adding polyvinylpyrrolidone or citric acid into the acidified mixed solution, and sequentially adding a ferrite solution and an aluminum sulfate solution to react to obtain a colloidal solution; 3) adding an alkali solution into the colloidal solution to adjust the pH value to 7.2-7.8, and reacting at normal temperature for 1-5 hours; 4) after the reaction, standing and aging for 1h, and repeatedly centrifugally washing with deionized water; and 5) carrying out vacuum drying after solid-liquid separation to obtain the iron-manganese oxide. By optimizing the raw material ratio and process parameters, the prepared iron and manganese oxide has the advantages of high specific surface area, controllable crystal form and good dispersity, and can be widely applied to the fields of water body heavy metal adsorption, organic pollutant catalytic degradation and the like.

Description

Technical Field

[0001] This invention relates to the field of iron-manganese oxide preparation technology, specifically to an iron-manganese oxide, its preparation method, and its application. Background Technology

[0002] Iron-manganese oxides are a class of inorganic composite functional materials that combine the properties of both iron and manganese oxides. Their surfaces are rich in active sites such as hydroxyl groups and oxygen vacancies, and they possess excellent redox, adsorption, and catalytic properties, making them valuable for applications in environmental remediation, energy storage, and sensors. Currently, the main methods for preparing iron-manganese oxides include co-precipitation, hydrothermal methods, sol-gel methods, and redox methods. Among these, co-precipitation is a commonly used industrial method due to its simplicity and low equipment requirements; however, traditional co-precipitation methods have the following significant drawbacks:

[0003] The products exhibit severe agglomeration and low specific surface area. Traditional processes lack effective dispersion control methods, leading to rapid aggregation of iron and manganese ions during precipitation, forming agglomerated particles with uneven particle sizes. This results in a product specific surface area typically below 50 m² / g, significantly reducing the number of surface active sites and limiting adsorption and catalytic performance. For example, in existing technologies, directly mixing ferrous salts with permanganate solutions can easily trigger "bumpy oxidation" due to excessively high local concentrations, producing iron and manganese oxide particle agglomerates with particle sizes reaching the micrometer level, which is insufficient for high-precision applications.

[0004] The controllability of crystal form and morphology is poor. The performance of iron-manganese oxides is closely related to their crystal form and morphology (e.g., the catalytic activity of α-MnO2 is significantly higher than that of β-MnO2, and the adsorption capacity of nanosheet structures is better than that of particulate structures). However, traditional methods lack targeted crystal form guidance and morphology control techniques, making it impossible to customize product structures according to specific application requirements. For example, existing schemes do not introduce crystal form guiding agents (such as aluminum sulfate), and the products are mostly amorphous or mixed crystal forms, making it difficult to adapt to the high-performance requirements of specific scenarios. Summary of the Invention

[0005] This invention belongs to the field of iron-manganese oxide preparation technology, specifically relating to an iron-manganese oxide, its preparation method, and its applications. Addressing the problems in existing iron-manganese oxide preparation processes, such as easy product agglomeration, low specific surface area, poor controllability of crystal form and properties, poor reproducibility due to ambiguous process parameters, and the need for improved safety and environmental protection, this invention provides a stable, safe, and environmentally friendly method for preparing iron-manganese oxides with high specific surface area, high activity, and controllable crystal form by optimizing raw material ratios, improving process steps, and introducing synergistic dispersants and crystal-directing agents. This method effectively solves the defects of traditional preparation methods by precisely controlling key parameters such as the molar ratio of soluble permanganate to phosphate, the proportion of dispersant, and reaction conditions. The prepared iron-manganese oxide exhibits excellent performance in adsorption, catalysis, and energy storage, making it suitable for industrial production and widespread application.

[0006] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a method for preparing iron-manganese oxide, comprising the following steps: Step 1) Disperse soluble permanganate and phosphate in water, then add hexadecyltrimethylammonium bromide, stir until homogeneous to prepare a mixed solution, then add acid solution to acidify, and obtain an acidified mixed solution; Step 2) First, add 0.1%~0.5% (by mass) of polyvinylpyrrolidone or citric acid to the acidified mixed solution, then add ferrous salt solution and aluminum sulfate solution in sequence to react and obtain a colloidal solution; Step 3) Add the alkaline solution to the colloidal solution to adjust the pH of the system to 7.2-7.8, and react at room temperature for 1-5 hours; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. Step 5) After washing, solid-liquid separation is performed, and the mixture is vacuum dried at 60℃~80℃ for 8~10h to obtain iron-manganese oxide.

[0007] Furthermore, the molar ratio of the soluble permanganate to the phosphate is 1:0.3 to 0.8; the molar ratio of the soluble permanganate to the ferrous salt in the ferrous salt solution is 1:1 to 5.

[0008] Furthermore, the soluble permanganate in step 1) is at least one of sodium permanganate, potassium permanganate, and calcium permanganate; Furthermore, the phosphate mentioned in step 1) is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; Furthermore, the acid solution in step 1) is a sulfuric acid aqueous solution with a mass fraction of 20% to 30%.

[0009] Furthermore, in step 1), the volume ratio of the mixed solution to the acid solution is 1:0.001 to 0.020.

[0010] Furthermore, in step 2), the ferrous salt in the ferrous salt solution is at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0011] Furthermore, the reaction described in step 2) is carried out at 45℃~50℃ for 20min~40min.

[0012] Furthermore, the mass fraction of the hexadecyltrimethylammonium bromide is 0.2-0.5%.

[0013] Furthermore, the concentration of the aluminum sulfate solution is 0.05 mol / L.

[0014] Secondly, the present invention provides an iron-manganese oxide prepared by the above method.

[0015] Thirdly, an application of the iron-manganese oxide prepared by the above method in the fields of adsorption or catalysis is provided.

[0016] The present invention has the following beneficial effects: 1. The present invention utilizes the synergistic dispersion effect of hexadecyltrimethylammonium bromide and polyvinylpyrrolidone (or citric acid), combined with the crystal-guiding function of aluminum sulfate, to prepare iron-manganese oxides with a large specific surface area. 2. The prepared iron-manganese oxides can be controlled into nanosheets or rods as needed, and are suitable for multiple scenarios such as heavy metal removal in water, degradation of organic pollutants in industrial wastewater, and battery electrode materials; 3. The preparation method provided by this invention is simple and easy to operate, suitable for large-scale mass production, and has good application prospects. Detailed Implementation

[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be noted that these embodiments are only for explaining the invention and are not intended to limit the scope of protection of the invention. Conventional modifications and adjustments made based on the technical solutions provided by this invention without departing from the technical concept of this invention are all within the scope of protection of this invention. In the following embodiments, all raw materials used are commercially available analytical grade reagents. Operations not specifically described are performed according to conventional laboratory methods. The testing instruments and methods have been specified in the previous technical solutions and will not be repeated here.

[0018] In a first aspect, the present invention provides a method for preparing iron-manganese oxide, comprising the following steps: Step 1) Disperse soluble permanganate and phosphate in water, then add hexadecyltrimethylammonium bromide, stir until homogeneous to prepare a mixed solution, then add acid solution to acidify, and obtain an acidified mixed solution; Step 2) First, add 0.1%~0.5% (by mass) of polyvinylpyrrolidone or citric acid to the acidified mixed solution, then add ferrous salt solution and aluminum sulfate solution in sequence to react and obtain a colloidal solution; Step 3) Add the alkaline solution to the colloidal solution to adjust the pH of the system to 7.2-7.8, and react at room temperature for 1-5 hours; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. Step 5) After washing, solid-liquid separation is performed, and the mixture is vacuum dried at 60℃~80℃ for 8~10h to obtain iron-manganese oxide.

[0019] Furthermore, the molar ratio of the soluble permanganate to the phosphate is 1:0.3 to 0.8; Furthermore, the molar ratio of ferrous salt in the soluble permanganate and ferrous salt solutions is 1:1 to 5.

[0020] Furthermore, the soluble permanganate in step 1) is at least one of sodium permanganate, potassium permanganate, and calcium permanganate; Furthermore, the phosphate mentioned in step 1) is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

[0021] Furthermore, the acid solution in step 1) is a sulfuric acid aqueous solution with a mass fraction of 20% to 30%.

[0022] Furthermore, in step 1), the volume ratio of the mixed solution to the acid solution is 1:0.001 to 0.020.

[0023] Furthermore, in step 2), the ferrous salt in the ferrous salt solution is at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0024] Furthermore, the reaction described in step 2) is carried out at 45℃~50℃ for 20min~40min.

[0025] Furthermore, the mass fraction of the hexadecyltrimethylammonium bromide is 0.2-0.5%.

[0026] Furthermore, the concentration of the aluminum sulfate solution is 0.05 mol / L.

[0027] Secondly, the present invention provides an iron-manganese oxide prepared by the above method.

[0028] Thirdly, an application of the iron-manganese oxide prepared by the above method in the fields of adsorption or catalysis is provided.

[0029] The following provides specific embodiments of the present invention.

[0030] Example 1 Preparation of iron-manganese oxides: Step 1) Disperse soluble sodium permanganate (0.1 mol) and potassium dihydrogen phosphate (0.03 mol) in water, then add 0.2% hexadecyltrimethylammonium bromide by mass of the resulting mixed solution, stir at 600 rpm to prepare a mixed solution, then add 20% sulfuric acid aqueous solution for acidification (mixed solution to acid volume ratio 1:0.001) to obtain an acidified mixed solution; Step 2) First, add 0.4% (by mass) of polyvinylpyrrolidone to the acidified mixed solution, then add 0.1 mol of ferrous sulfate (molar ratio of 1:1 to permanganate) and 5 mL of 0.05 mol / L aluminum sulfate solution in sequence, and react at 45 °C for 20 min to obtain a colloidal solution. Step 3) Add sodium hydroxide alkaline solution to the colloidal solution to adjust the pH of the system to 7.2, and react at room temperature for 1 hour; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. Step 5) After washing, perform solid-liquid separation (8000 rpm × 5 min), wash 3 times, and vacuum dry at 60℃ for 10 h to obtain iron-manganese oxide.

[0031] Example 2 Preparation of iron-manganese oxides: Step 1) Disperse soluble potassium permanganate (0.1 mol) and disodium hydrogen phosphate (0.055 mol) in water, then add 0.35% hexadecyltrimethylammonium bromide by mass of the resulting mixed solution, stir at 600 rpm to prepare a mixed solution, then add 25% sulfuric acid aqueous solution for acidification (mixed solution to acid volume ratio 1:0.01) to obtain an acidified mixed solution; Step 2) First, add 0.875% citric acid by mass of the acidified mixed solution to the mixed solution, then add 0.3 mol ferrous chloride and 10 mL of 0.05 mol / L aluminum sulfate solution in sequence, and react at 47℃ for 30 min to obtain a colloidal solution; Step 3) Add sodium hydroxide alkaline solution to the colloidal solution to adjust the pH of the system to 7.8, and react at room temperature for 3 hours; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. Step 5) After washing, perform solid-liquid separation (8000 rpm × 5 min), wash 3 times, and vacuum dry at 60℃ for 10 h to obtain iron-manganese oxide.

[0032] Example 3 Preparation of iron-manganese oxides: Step 1) Disperse soluble calcium permanganate (0.1 mol) and dipotassium hydrogen phosphate (0.08 mol) in water, then add 0.5% hexadecyltrimethylammonium bromide by mass of the resulting mixed solution, stir at 600 rpm to prepare a mixed solution, then add 30% sulfuric acid aqueous solution for acidification (mixed solution to acid volume ratio 1:0.02) to obtain an acidified mixed solution; Step 2) First, add 1.5% citric acid by mass of the acidified mixed solution to the mixed solution, then add 0.3 mol ferrous nitrate (molar ratio of 1:5 with permanganate) and 15 mL of 0.05 mol / L aluminum sulfate solution in sequence, and react at 50℃ for 40 min to obtain a colloidal solution; Step 3) Add sodium hydroxide alkaline solution to the colloidal solution to adjust the pH of the system to 7.8, and react at room temperature for 5 hours; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. Step 5) After washing, perform solid-liquid separation (8000 rpm × 5 min), wash 3 times, and vacuum dry at 60℃ for 10 h to obtain iron-manganese oxide.

[0033] Comparative Example 1 Preparation of iron-manganese oxides: Step 1) Disperse soluble potassium permanganate (0.1 mol) and disodium hydrogen phosphate (0.055 mol) in water, stir at 600 rpm to prepare a mixed solution, and then add 25% sulfuric acid aqueous solution for acidification (mixed solution to acid volume ratio 1:0.01) to obtain an acidified mixed solution; Step 2) Add ferrous chloride (0.3 mol) sequentially to the acidified mixed solution to react and obtain a suspension; Step 3) Add sodium hydroxide alkaline solution to the suspension to adjust the pH of the system to 7.8, and react at room temperature for 3 hours; Step 4) After the reaction is complete, let the system stand for 1 hour to obtain a precipitate (non-colloidal). Wash the precipitate repeatedly by centrifugation with deionized water. Step 5) After washing, perform solid-liquid separation (8000 rpm × 5 min), wash 3 times, and vacuum dry at 60℃ for 10 h to obtain brown iron-manganese oxide solid.

[0034] Performance testing Table 1 Performance Test Results As can be seen from the table above, the specific surface area of ​​the iron-manganese oxides prepared in the embodiments of the present invention is much higher than that of Comparative Example 1. This is directly attributed to the effective inhibition of particle agglomeration by the surfactant and dispersant, resulting in a rich nanoscale porous structure. Furthermore, by adjusting the process parameters, the embodiments can obtain different morphologies such as porous microspheres (Example 1), nanosheets (Example 2), and nanospheres (Example 3), while Comparative Example 1 only contains irregular large agglomerates, making its application more difficult. The PDI values ​​of Examples 1-3 are all close to or better than 0.2, indicating that they are well dispersed in the liquid phase and can fully expose active sites. In contrast, the PDI of Comparative Example 1 is as high as 0.45, indicating severe agglomeration. For the two heavy metal ions, Pb²⁺ and Cu²⁺, the adsorption capacity of the iron-manganese oxides obtained in the embodiments of the present invention is much higher than that of Comparative Example 1. After five adsorption-desorption cycles, the capacity retention rate of the iron-manganese oxides in the embodiments of the present invention is significantly higher than that of Comparative Example 1, proving that the iron-manganese oxides prepared by the method of the present invention have excellent structural stability and reusability. Reaction rate constant (k) The k-value of the iron-manganese oxide in this invention is 5 to 7 times that of the comparative example 1. This quantitatively demonstrates the significant improvement in catalytic efficiency from a kinetic perspective. In the test of catalytic degradation of phenol and methyl orange, the degradation rate of the iron-manganese oxide in this invention is much higher than that in the comparative example 1.

Claims

1. A method for producing an iron-manganese oxide, characterized by, Includes the following steps: 0) Disperse soluble permanganate and phosphate in water, then add hexadecyltrimethylammonium bromide, stir until homogeneous to prepare a mixed solution, then add acid solution to acidify, to obtain an acidified mixed solution; 1) First, add 0.1%~0.5% of polyvinylpyrrolidone or citric acid by mass of the acidified mixed solution to the mixed solution, and then add ferrous salt solution and aluminum sulfate solution in sequence to react and obtain colloidal solution; 2) Add the alkaline solution to the colloidal solution to adjust the pH of the system to 7.2-7.8, and react at room temperature for 1-5 hours; 3) After the reaction is complete, let the system stand for 1 hour to obtain a stable iron-manganese oxide colloid, and then wash it repeatedly by centrifugation with deionized water. 4) After washing, solid-liquid separation is performed, and the mixture is vacuum dried at 60℃~80℃ for 8~10h to obtain iron-manganese oxide.

2. The method for preparing iron-manganese oxide according to claim 1, characterized in that, The molar ratio of the soluble permanganate to the phosphate is 1:0.3 to 0.8; the molar ratio of the soluble permanganate to the ferrous salt in the ferrous salt solution is 1:1 to 5.

3. The method for preparing iron-manganese oxide according to claim 1, characterized in that, The soluble permanganate in step 1) is at least one of sodium permanganate, potassium permanganate, and calcium permanganate; the phosphate in step 1) is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

4. The method for preparing iron-manganese oxide according to claim 1, characterized in that, Step 1) The acid solution is a sulfuric acid aqueous solution with a mass fraction of 20%~30%.

5. The method for preparing iron-manganese oxide according to claim 1, characterized in that, The volume ratio of the mixed solution and the acid solution in step 1) is 1:0.001 to 0.

020.

6. The method for preparing iron-manganese oxide according to claim 1, characterized in that, Step 2) The ferrous salt in the ferrous salt solution is at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate.

7. The method for preparing iron-manganese oxide according to claim 1, characterized in that, The reaction described in step 2) is carried out at 45℃~50℃ for 20min~40min.

8. The method for preparing iron-manganese oxide according to claim 1, characterized in that, The mass fraction of the hexadecyltrimethylammonium bromide is 0.2-0.5%; the concentration of the aluminum sulfate solution is 0.05 mol / L.

9. An iron-manganese oxide prepared by the method according to any one of claims 1-8.

10. An application of an iron-manganese oxide prepared by the method according to any one of claims 1-8 in the field of adsorption or catalysis.

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