Production method of high-efficiency and environment-friendly high-purity ferric oxide powder

Abstract

The invention belongs to the technical field of preparation of iron oxide powder, and particularly relates to a production method of high-efficiency and environment-friendly high-purity iron oxide powder, which comprises the following steps: preparing soluble iron salt into an aqueous solution, adding a dispersing agent into the aqueous solution, and uniformly stirring; carrying out atomization treatment on the obtained solution through a pressure type atomizer or an airflow type atomizer; the atomized liquid drops enter a high-temperature reaction furnace, and air or oxygen is introduced into the high-temperature reaction furnace at the same time until atomization is finished; a product obtained after reaction enters a cyclone separator along with airflow for preliminary separation, and then fine collection is performed through a bag-type dust collector; and washing the collected ferric oxide crude product with deionized water for multiple times to remove impurity ions left on the surface, and drying. The method has the advantages of compact process flow, high reaction speed and controllable product performance. And the reaction contact area is increased through the atomization process, so that the oxidation reaction is rapidly carried out, the problem of non-uniform particle size distribution or easy agglomeration of the product in the traditional method is avoided, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of iron oxide powder preparation technology, and in particular relates to a method for producing high-efficiency, environmentally friendly, and high-purity iron oxide powder. Background Technology

[0002] Iron oxide, as an important inorganic material, has wide applications in many fields such as pigments, coatings, electronics, and magnetic materials. In the pigment field, iron oxide, with its rich colors (such as iron oxide red, iron oxide yellow, and iron oxide black), is widely used in coloring architectural coatings, inks, and plastics, giving products beautiful and long-lasting colors. In the fields of electronics and magnetic materials, iron oxide is a key raw material for the preparation of soft magnetic ferrites. Soft magnetic ferrites are widely used in electronic components such as transformers and inductors, playing an important role in the miniaturization and efficiency of electronic devices.

[0003] Currently, the main methods for preparing iron oxide are divided into dry methods, wet methods, and gas-phase methods. The solid-phase dry method, such as the traditional calcination method, involves directly calcining and decomposing iron-containing raw materials (such as iron ore and iron salts) at high temperatures to convert them into iron oxide. However, this method typically involves reaction temperatures exceeding 1000℃, resulting in enormous energy consumption and difficulty in precisely controlling the particle size and morphology of the product, easily leading to uneven particle size distribution and hindering its application in high-end fields. While the gas-phase method can produce high-purity, uniformly sized iron oxide, the equipment is expensive, the production process is complex, the yield is low, and the cost remains high, limiting its large-scale industrial application.

[0004] Wet processes, also known as liquid-phase processes, include sol-gel methods, air oxidation methods, hydrolysis methods, and precipitation methods. The sol-gel method requires large amounts of organic reagents, resulting in high costs and the generation of organic pollutants during preparation, placing significant pressure on the environment. Furthermore, its complex post-processing makes large-scale production difficult. Air oxidation methods are slow, have long production cycles, and are inefficient, failing to meet growing market demands. Hydrolysis methods require stringent reaction conditions, and the products are prone to agglomeration, necessitating cumbersome post-processing to improve dispersibility. While precipitation methods are relatively simple to operate, the product purity is often low, with a high impurity content, affecting product performance and application range.

[0005] Some existing patented technologies for the preparation of iron oxide also have shortcomings. For example, patent publication number CN115992373A discloses a method for preparing titanium-iron alloy materials, which involves spray pyrolysis to prepare composite oxide powder containing iron oxide and titanium oxide. However, its focus is on the preparation of titanium-iron alloys, and it is not specifically targeted at the efficient and high-purity preparation of pure iron oxide. Patent publication number CN118908289A proposes a method for preparing high-performance iron oxide for soft magnetic ferrites, which prepares iron oxide through steps such as mixed leaching of industrial hydrochloric acid and raw ore powder and flash roasting. However, it still has problems such as complex process and high equipment requirements.

[0006] In conclusion, developing an efficient, environmentally friendly method for producing iron oxide that allows for precise control of product performance is of great significance. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a highly efficient, environmentally friendly, and high-purity iron oxide powder production method. This method employs solution atomization oxidation to achieve efficient and green preparation of iron oxide while reducing energy consumption. By adjusting the solution concentration, atomization parameters, and reaction temperature, the particle size and purity of the iron oxide can be precisely controlled.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for producing high-efficiency, environmentally friendly, and high-purity iron oxide powder includes the following steps:

[0010] 1) Prepare an aqueous solution of soluble iron salt with a concentration of 0.5-3 mol / L, add a dispersant to the aqueous solution, and stir until homogeneous;

[0011] 2) The solution obtained in step 1) is atomized by a pressure nebulizer or an airflow nebulizer into tiny droplets with an average particle size of 10 to 100 μm.

[0012] 3) The atomized droplets enter a high-temperature reactor at a temperature of 800–1200°C, while air or oxygen is simultaneously introduced into the reactor until atomization is complete; the ferrous ions in the droplets are rapidly oxidized, undergoing the following main reactions:

[0013] 4Fe 2+ +O2 + 2H2O = 4Fe 3+ +4OH - ;

[0014] Iron oxide is formed in crystalline form through processes such as solid-state reaction, crystal growth, and sintering.

[0015] 4) The product after the reaction in step 3) enters the cyclone separator with the airflow for preliminary separation, and then is finely collected by the bag filter. The collected crude iron oxide product is washed multiple times with deionized water to remove residual impurity ions on the surface, and then dried at 80-120℃ to obtain a high-purity iron oxide product.

[0016] In step 1), the amount of dispersant added is 0.5% to 3% of the mass of the soluble iron salt.

[0017] The soluble iron salt is ferrous sulfate or ferrous chloride.

[0018] The dispersant is polyvinylpyrrolidone or sodium polyacrylate.

[0019] The working pressure of the pressure atomizer is controlled at 1 to 5 MPa, and the compressed air pressure of the airflow atomizer is 0.3 to 1 MPa.

[0020] In step 3), the air flow rate is 5L / min to 10L / min; the oxygen flow rate is 2L / min to 4L / min.

[0021] In step 4), the crude iron oxide product is washed with deionized water 2 to 4 times.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. High-efficiency production: The atomization process greatly increases the reaction contact area, enabling the oxidation reaction to proceed rapidly and significantly improving production efficiency. Compared with the traditional liquid phase method, the production cycle is significantly shortened. The process flow of this invention is compact and the reaction speed is fast, solving the problems of long production cycles, complex processes, low efficiency, or cumbersome post-processing in wet processes (such as air oxidation and sol-gel methods).

[0024] 2. Controllable product performance: By adjusting the solution concentration, atomization parameters and reaction temperature, as well as precisely controlling the raw materials, adding dispersants and subsequent washing steps, the impurity content can be reduced, and the particle size and purity of iron oxide can be precisely controlled.

[0025] 3. Environmentally friendly and energy-saving: The entire production process produces no harmful gas emissions. Rapid and efficient conversion is achieved within a relatively controllable temperature range (800~1200℃), reducing energy consumption.

[0026] 4. This invention employs solution atomization technology to process the reaction precursor into uniformly sized micro-droplets (10-100μm), and combines this with a relatively controllable temperature range (800-1200℃) for high-temperature oxidation reaction, thereby achieving better control over the particle size and morphology of the final iron oxide product and avoiding the problems of uneven particle size distribution or easy agglomeration in traditional methods. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Example 1:

[0029] A method for producing high-efficiency, environmentally friendly, and high-purity iron oxide powder includes the following steps:

[0030] 1. Raw material preparation: Prepare 1L of 1mol / L aqueous solution of ferrous sulfate (FeSO4·7H2O), add 7g of polyvinylpyrrolidone (PVP) as a dispersant, stir and dissolve for 30min to ensure that the dispersant is fully dispersed in the solution and to ensure the uniformity of subsequent atomization and reaction.

[0031] 2. Solution atomization: A pressure atomizer is used, with the working pressure set at 2 MPa, to atomize the solution. Under this pressure, the solution is sprayed at high speed and broken into tiny droplets with an average particle size of 10–100 μm, which greatly increases the specific surface area of ​​the reaction.

[0032] 3. Oxidation reaction: The atomized droplets enter a reactor at 900℃, while air is simultaneously introduced into the high-temperature reactor at a rate of 8L / min until atomization ends. Ferrous ions are rapidly oxidized, undergoing the following main reactions:

[0033] 4Fe 2+ +O2 + 2H2O = 4Fe 3+ +4OH - ;

[0034] Iron oxide is formed in crystalline form through processes such as solid-state reaction, crystal growth, and sintering.

[0035] 4. Product Collection and Post-processing: The reaction products are carried by the airflow into a cyclone separator for preliminary separation, where larger particles are separated. Then, they are finely collected using a bag filter. The resulting crude iron oxide product is washed three times with deionized water to remove residual impurity ions, and then dried at 100℃ for 12 hours to obtain orange-red α-Fe₂O₃ powder. The purity was measured to be 99.2%, and the average particle size was 50 nm.

[0036] Example 2:

[0037] A method for producing high-efficiency, environmentally friendly, and high-purity iron oxide powder includes the following steps:

[0038] 1. Raw material preparation: Prepare 1L of 2mol / L ferrous chloride (FeCl2) aqueous solution, add 10g of sodium polyacrylate dispersant, and stir thoroughly.

[0039] 2. Solution atomization: An airflow atomizer with compressed air pressure of 0.5 MPa is used to atomize the solution. The high-speed impact of the airflow disperses the solution into uniform tiny droplets, creating conditions for a rapid oxidation reaction.

[0040] 3. Oxidation reaction: The atomized droplets are fed into a 1000℃ reactor, and oxygen is introduced into the high-temperature reactor at a rate of 3L / min until the atomization ends. The high temperature and high purity of the oxygen make the reaction more complete, the oxidation reaction rate is faster, and the generated iron oxide crystals are more regular.

[0041] 4. Product Collection and Post-processing: After collection by a cyclone separator and a bag filter, the product was washed three times with deionized water and dried at 120℃ for 8 hours. The obtained iron oxide powder was analyzed to be α-Fe₂O₃ with a purity of 99.5% and an average particle size of 30 nm. This product exhibited good magnetic properties in magnetic material application tests and is suitable for preparing high-performance magnetic recording media.

[0042] Example 3:

[0043] A method for producing high-efficiency, environmentally friendly, and high-purity iron oxide powder includes the following steps:

[0044] 1. Raw material preparation: Prepare 2 L of 0.5 mol / L ferrous sulfate (FeSO4·7H2O) aqueous solution, add 30 g of polyvinyl alcohol (PVA) as a dispersant, and stir for 45 min. Lower concentration solutions help prepare finer and more uniform iron oxide particles, and PVA can improve the dispersion performance and stability of the solution.

[0045] 2. Solution atomization: A pressure atomizer is used, with the working pressure controlled at 1MPa, to atomize the solution into tiny droplets with an average particle size of about 80μm, ensuring the efficient progress of the reaction.

[0046] 3. Oxidation reaction: The atomized droplets enter a reactor at 800°C, and oxygen is simultaneously introduced into the high-temperature reactor at a rate of 4L / min until atomization ends.

[0047] 4. Product Collection and Post-processing: The reaction product was collected sequentially by a cyclone separator and a bag filter, washed four times with deionized water, and dried at 80℃ for 15 h to obtain α-Fe₂O₃ with a purity of 99.3% and an average particle size of 20 nm. This product exhibits high activity in the catalytic field and can be used as a catalyst for some organic synthesis reactions.

[0048] Comparative Example 1

[0049] Iron oxide was prepared using a traditional precipitation method, following conventional procedures. Ferrous sulfate solution was mixed with sodium hydroxide solution to form ferrous hydroxide precipitate, which was then oxidized to ferric hydroxide by air purging. Finally, the precipitate was filtered, washed, and calcined to obtain iron oxide. Compared to Example 1, this method has a longer production cycle, requiring 4–6 days from raw material reaction to final product, while Example 1 only requires 2–3 hours. The product has a wide particle size distribution; under scanning electron microscopy, the particle sizes are inconsistent, affecting its performance in high-end applications, with a purity of only 97%.

[0050] The present invention features a compact process flow and fast reaction speed, which solves the problems of long production cycle, complex process, low efficiency or cumbersome post-processing in wet processes (such as air oxidation method and sol-gel method).

Claims

1. A method for producing high-efficiency, environmentally friendly, high-purity iron oxide powder, characterized by, The method comprises the following steps: 1) taking a soluble iron salt to prepare an aqueous solution with a concentration of 0.5-3 mol / L, adding a dispersing agent to the aqueous solution, the amount of the dispersing agent being 0.5%-3% of the mass of the soluble iron salt, and stirring uniformly; 2) subjecting the solution obtained in step 1) to atomization treatment by a pressure atomizer or an air flow atomizer to form microdroplets with an average particle size of 10-100 μm; 3) introducing the atomized droplets into a high-temperature reaction furnace, the temperature of the reaction furnace being 800-1200 ℃, and simultaneously introducing air or oxygen into the high-temperature reaction furnace until the atomization is completed; 4) subjecting the product after the reaction in step 3) to preliminary separation in a cyclone separator and then fine collection by a bag-type dust collector; The collected crude iron oxide product is washed with deionized water for multiple times to remove residual impurity ions on the surface, and then dried at 80-120 ℃ to obtain a high-purity iron oxide product.

2. The method according to claim 1, wherein the method is characterized by, The soluble iron salt is ferrous sulfate or ferrous chloride.

3. The method according to claim 1, wherein the method is characterized by, The dispersing agent is polyvinylpyrrolidone or sodium polyacrylate.

4. The method according to claim 1, wherein the method is characterized by, The working pressure of the pressure atomizer is controlled at 1-5 MPa, and the compressed air pressure of the air flow atomizer is 0.3-1 MPa.

5. The method according to claim 1, wherein the method is characterized by, In step 3), the air flow rate is 5 L / min-10 L / min, and the oxygen flow rate is 2 L / min-4 L / min.

6. The method of producing high efficiency, environmentally friendly high purity iron oxide powder according to claim 1, characterized by, In step 4), the crude iron oxide product is washed with deionized water for 2-4 times.