A method for preparing manganese ferrite for soft magnets by a liquid-phase method

Abstract

The present invention belongs to the technical field of manganese tetraoxide preparation, and discloses a method for preparing manganese tetraoxide for soft magnets by a liquid-phase method. In the present invention, ammonia water, absolute ethanol, and a surfactant are mixed to obtain an alkaline solution; a manganese sulfate solution is added to the alkaline solution for a precipitation reaction; at the same time, ammonia water is added dropwise to control the pH value; when the median particle size of the generated precipitate is 5-10 μm, the addition of ammonia water is stopped, and the reaction is continued for a certain time to obtain a manganese hydroxide precipitate; a sodium hydroxide solution is added to the suspension obtained by mixing the manganese hydroxide precipitate with water, and air is introduced for a liquid-phase oxidation reaction. The surfactant in the present invention can regulate the morphology of the manganese hydroxide generated by precipitation, and the absolute ethanol can prevent the aggregation of manganese hydroxide, making the product closer to a spherical shape with a uniform particle size distribution. Moreover, by controlling the pH value of the system during the precipitation process and the feeding order of the reactants, the generation of basic manganese sulfate is avoided, and the purity of the product manganese tetraoxide is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of manganese tetraoxide preparation, and in particular to a method for preparing manganese tetraoxide for soft magnets by a liquid phase method. Background Art

[0002] Manganese tetraoxide is mainly used in the electronics industry and is one of the important raw materials for producing soft magnetic materials such as manganese-zinc ferrite. Soft magnetic materials have a narrow remanence induction curve and can be magnetized repeatedly. At the same time, their direct current resistivity is very high, which can avoid eddy current losses. It can be used as magnetic cores, disks and tapes for storing information in electronic computers, transformers for telephones and high-quality inductors, flyback transformers for televisions, magnetic heads for magnetic recording, inductors, magnetic amplifiers, saturable inductors, antenna rods, etc. With the development of electronic information technology, the demand for soft magnetic materials is huge, and correspondingly, the demand for manganese tetraoxide, one of its preparation raw materials, is also gradually increasing.

[0003] Currently, methods for preparing manganese tetraoxide include liquid phase method, roasting method, reduction method, oxidation method, electrolysis method, etc. The above methods have relatively high requirements for the purity of raw materials, and impurities such as magnesium, calcium, and additive elements are likely to exist in the prepared manganese tetraoxide, which cannot meet the requirements of high-purity manganese tetraoxide. For example, the synthesis method of electrolytic manganese powder requires the process of electrolytic manganese, which is prone to introducing impurities, and the purity of the prepared manganese tetraoxide is also related to the purity of the manganese powder. Currently, the method that has received more attention is the liquid phase method, which mainly uses manganese sulfate as the precursor solution, adds alkali to convert manganese ions into Mn(OH)2 precipitate, and then obtains manganese tetraoxide through air oxidation. However, this method has low product yield, long preparation time, and uneven particle size, and cannot meet the requirements of high-performance manganese tetraoxide.

[0004] Therefore, how to develop a synthesis method of manganese tetraoxide with low production cost, simple process, and controllable morphology of manganese tetraoxide is an urgent problem to be solved at present. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing manganese tetraoxide for soft magnets by a liquid phase method, so as to solve the above problems existing in the existing methods for preparing manganese tetraoxide.

[0006] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing manganese tetraoxide for soft magnets by a liquid phase method, comprising the following steps:

[0008] Mix ammonia water, absolute ethanol, and a surfactant to obtain an alkali solution;

[0009] Add a manganese sulfate solution to an alkali solution to carry out a precipitation reaction; during the precipitation reaction, dropwise add ammonia water to control the pH value to be 10 - 10.5; when the median particle size of the precipitate produced by the precipitation reaction is 5 - 10 μm, stop dropwise adding ammonia water, continue the reaction for a certain period of time and then filter to obtain manganese hydroxide precipitate;

[0010] Mix the manganese hydroxide precipitate with water to obtain a suspension; add a sodium hydroxide solution to the suspension to control the pH value of the suspension to be 10 - 11, and then introduce air to carry out a liquid-phase oxidation reaction; after the liquid-phase oxidation reaction ends, filter, wash, and dry the generated precipitate to obtain manganese tetraoxide for soft magnetic materials.

[0011] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the mass-volume ratio of the ammonia water, absolute ethanol, and surfactant is 3 - 6 mL: 1 - 2 mL: 0.05 - 0.2 g; the concentration of the ammonia water is 1 - 10 g / L; the surfactant is one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and sodium dodecyl sulfate.

[0012] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the volume ratio of the alkali solution to the manganese sulfate solution is 1 - 3: 2 - 11; the concentration of the manganese sulfate solution is 0.1 - 5 mol / L.

[0013] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the specific method of adding the manganese sulfate solution to the alkali solution is dropwise addition.

[0014] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, stirring is also included during the precipitation reaction; the rotation speed of the stirring is 200 - 800 rpm.

[0015] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the time for the continued reaction is 30 - 240 min.

[0016] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the mass ratio of the manganese hydroxide precipitate to water is 1 - 2: 3 - 8.

[0017] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the flow rate of the introduced air is 0.1 - 3 L / min.

[0018] Preferably, in the above method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, the temperature of the liquid-phase oxidation reaction is 40 - 80 °C; the time of the liquid-phase oxidation reaction is 3 - 10 h.

[0019] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) In the present invention, a surfactant and absolute ethanol are added to the alkaline solution. After the alkaline solution reacts with manganese sulfate, the surfactant can control the morphology of the precipitated manganese hydroxide, and absolute ethanol can prevent the aggregation of manganese hydroxide, making the manganese hydroxide closer to spherical after oxidation, with a uniform particle size distribution, enabling the morphology control of manganese tetroxide prepared by the liquid phase method. Moreover, the presence of the surfactant can further increase the specific surface area of manganese tetroxide.

[0021] (2) The present invention uses the liquid phase method to prepare manganese tetroxide. By controlling the pH value of the system and the feeding order of the reactants during the precipitation process, the generation of manganese basic sulfate during the reaction is avoided, improving the purity of the product manganese tetroxide, which can meet the requirements of soft magnetic materials for high-performance manganese tetroxide. At the same time, in the liquid phase oxidation reaction, the manganese hydroxide precipitate is oxidized in the form of a suspension, also avoiding the generation of manganese basic sulfate and reducing the sulfur content of manganese tetroxide.

[0022] (3) The preparation method of the present invention is simple, the reaction conditions are mild, the reaction process is controllable, and it is suitable for large-scale industrial production. Detailed Embodiments

[0023] The present invention provides a method for preparing manganese tetroxide for soft magnetic materials by the liquid phase method, comprising the following steps:

[0024] Mix ammonia water, absolute ethanol, and a surfactant to obtain an alkaline solution;

[0025] Add a manganese sulfate solution to the alkaline solution for a precipitation reaction; during the precipitation reaction, add ammonia water dropwise to control the pH value to 10 - 10.5; when the median particle size of the precipitate generated by the precipitation reaction is 5 - 10 μm, stop adding ammonia water, continue the reaction for a certain time, and then filter to obtain a manganese hydroxide precipitate;

[0026] Mix the manganese hydroxide precipitate with water to obtain a suspension; add a sodium hydroxide solution to the suspension to control the pH value of the suspension to 10 - 11, and then introduce air for a liquid phase oxidation reaction; after the liquid phase oxidation reaction is completed, filter, wash, and dry the generated precipitate to obtain manganese tetroxide for soft magnetic materials.

[0027] In the present invention, the mass-volume ratio of the ammonia water, absolute ethanol, and surfactant is preferably 3 - 6 mL: 1 - 2 mL: 0.05 - 0.2 g, more preferably 3.3 - 5.4 mL: 1.2 - 1.9 mL: 0.09 - 0.16 g, and even more preferably 4.6 mL: 1.6 mL: 0.13 g.

[0028] In the present invention, the concentration of the ammonia water is preferably 1 to 10 g / L, more preferably 3 to 8 g / L, and still more preferably 7 g / L.

[0029] In the present invention, the surfactant is preferably one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and sodium dodecyl sulfate, more preferably cetyltrimethylammonium chloride.

[0030] In the present invention, the volume ratio of the alkali solution to the manganese sulfate solution is preferably 1 to 3:2 to 11, more preferably 1.2 to 2.7:4 to 10, and still more preferably 2:7.

[0031] In the present invention, the concentration of the manganese sulfate solution is preferably 0.1 to 5 mol / L, more preferably 0.7 to 4 mol / L, and still more preferably 3.6 mol / L.

[0032] In the present invention, the specific method of adding the manganese sulfate solution to the alkali solution is preferably dropwise addition.

[0033] In the present invention, the temperature of the precipitation reaction is preferably 25 to 70 °C, more preferably 35 to 60 °C, and still more preferably 45 °C.

[0034] In the present invention, stirring is also included during the precipitation reaction; the rotation speed of the stirring is preferably 200 to 800 rpm, more preferably 280 to 710 rpm, and still more preferably 550 rpm.

[0035] In the present invention, the concentration of the ammonia water added dropwise during the precipitation reaction is preferably 5 to 15 g / L, more preferably 7 to 12 g / L, and still more preferably 9 g / L.

[0036] In the present invention, the time for the continued reaction is preferably 30 to 240 min, more preferably 50 to 160 min, and still more preferably 140 min.

[0037] In the present invention, the mass ratio of the manganese hydroxide precipitate to water is preferably 1 to 2:3 to 8, more preferably 1.3 to 1.8:3.8 to 6.5, and still more preferably 1.6:5.1.

[0038] In the present invention, the concentration of the sodium hydroxide solution is preferably 1 to 5 mol / L, more preferably 1.7 to 4.2 mol / L, and still more preferably 2.8 mol / L.

[0039] In the present invention, the flow rate of the introduced air is preferably 0.1 to 3 L / min, more preferably 0.6 to 2.3 L / min, and still more preferably 1.6 L / min.

[0040] In the present invention, the temperature of the liquid-phase oxidation reaction is preferably 40 to 80 °C, more preferably 46 to 70 °C, and even more preferably 55 °C; the time of the liquid-phase oxidation reaction is preferably 3 to 10 h, more preferably 5 to 8 h, and even more preferably 7 h.

[0041] In the present invention, the washing is preferably carried out by washing with water 3 to 5 times.

[0042] In the present invention, the drying temperature is preferably 80 to 120 °C, more preferably 85 to 110 °C, and even more preferably 100 °C; the drying time is preferably 6 to 12 h, more preferably 8 to 11 h, and even more preferably 9 h.

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1

[0045] This example provides a method for preparing manganese tetraoxide for soft magnets by a liquid-phase method, which includes the following steps:

[0046] (1) Mix ammonia water at 3 g / L, absolute ethanol, and cetyltrimethylammonium bromide in a mass-to-volume ratio of 5 mL: 1 mL: 0.12 g to obtain an alkaline solution.

[0047] (2) Dropwise add a 2 mol / L manganese sulfate solution to the alkaline solution. The volume ratio of the alkaline solution to the manganese sulfate solution is 1:5. Carry out a precipitation reaction under stirring at 30 °C and 700 rpm; at the same time, dropwise add ammonia water with a concentration of 8 g / L during the precipitation reaction to control the pH value of the precipitation reaction system to 10.0 to 10.1; during the precipitation reaction, take samples to measure the median particle size of the generated precipitate. When the median particle size of the precipitate is 7 μm, stop dropping ammonia water, and continue to react for 30 min under stirring and then filter to obtain manganese hydroxide precipitate.

[0048] (3) Mix the manganese hydroxide precipitate and deionized water in a mass ratio of 1:6 to obtain a suspension; add a 2 mol / L sodium hydroxide solution to the suspension to control the pH value of the suspension to 10.5, and then introduce air at a flow rate of 2 L / min and carry out a liquid-phase oxidation reaction at 60 °C for 5 h; after the liquid-phase oxidation reaction is completed, filter the generated precipitate in sequence, wash it with water 3 times, and dry it at 90 °C for 8 h to obtain manganese tetraoxide for soft magnets.

[0049] The Mn content in the prepared manganese tetraoxide is 71.64%, the S content is 0.02%, the particle size of the manganese tetraoxide is 7.4 μm, and the BET is 12.3 m 2 / g, and the apparent density is 0.65 g / cm 3 .

[0050] Example 2

[0051] This example provides a method for preparing manganese tetraoxide for soft magnets by a liquid-phase method, which includes the following steps:

[0052] (1) Mix 8 g / L ammonia water, absolute ethanol, and cetyltrimethylammonium chloride in a mass-to-volume ratio of 5 mL: 2 mL: 0.08 g to obtain an alkaline solution;

[0053] (2) Dropwise add 1 mol / L manganese sulfate solution to the alkaline solution. The volume ratio of the alkaline solution to the manganese sulfate solution is 1:3. Perform a precipitation reaction while stirring at 25 °C and 500 rpm; at the same time, dropwise add 10 g / L ammonia water during the precipitation reaction to control the pH value of the precipitation reaction system to be 10.0 - 10.1; during the precipitation reaction, take samples to measure the median particle size of the generated precipitate. When the median particle size of the precipitate is 5 μm, stop dropping ammonia water, continue to react for 40 min under stirring conditions, and then filter to obtain manganese hydroxide precipitate;

[0054] (3) Mix the manganese hydroxide precipitate and deionized water in a mass ratio of 2:3 to obtain a suspension; add 4 mol / L sodium hydroxide solution to the suspension to control the pH value of the suspension to be 10.7, then introduce air at a flow rate of 1.2 L / min, and perform a liquid-phase oxidation reaction at 40 °C for 8 h; after the liquid-phase oxidation reaction is completed, filter the generated precipitate in sequence, wash it with water 3 times, and dry it at 80 °C for 8 h to obtain manganese tetraoxide for soft magnets.

[0055] The Mn content in the prepared manganese tetraoxide is 71.23%, the S content is 0.05%, the particle size of the manganese tetraoxide is 5.6 μm, and the BET is 10.6 m 2 / g, and the apparent density is 0.67 g / cm 3 .

[0056] Example 3

[0057] This example provides a method for preparing manganese tetraoxide for soft magnets by a liquid-phase method, which includes the following steps:

[0058] (1) Mix 3 g / L ammonia water, absolute ethanol, and cetyltrimethylammonium bromide in a mass-to-volume ratio of 4 mL: 1 mL: 0.13 g to obtain an alkaline solution;

[0059] (2) Add a 4 mol / L manganese sulfate solution dropwise to the alkaline solution. The volume ratio of the alkaline solution to the manganese sulfate solution is 2.5:7. Conduct a precipitation reaction under stirring at 50 °C and 600 rpm. At the same time, during the precipitation reaction, add ammonia water with a concentration of 5 g / L dropwise, and control the pH value of the precipitation reaction system to be 10.3 - 10.4. During the precipitation reaction, take samples to measure the median particle size of the generated precipitate. When the median particle size of the precipitate is 8 μm, stop adding ammonia water, continue to react for 60 min under stirring, and then filter to obtain manganese hydroxide precipitate;

[0060] (3) Mix the manganese hydroxide precipitate with deionized water at a mass ratio of 1:6 to obtain a suspension. Add a 3 mol / L sodium hydroxide solution to the suspension, control the pH value of the suspension to be 10.5, and then introduce air at a flow rate of 0.8 L / min. Conduct a liquid-phase oxidation reaction at 50 °C for 6 h. After the liquid-phase oxidation reaction is completed, filter the generated precipitate successively, wash it 5 times with water, and dry it at 100 °C for 8 h to obtain manganese tetraoxide for soft magnetic materials.

[0061] The Mn content in the manganese tetraoxide prepared above is 71.48%, the S content is 0.04%, the particle size of the manganese tetraoxide is 8.8 μm, and the BET is 11.7 m 2 / g, and the apparent density is 0.71 g / cm 3 .

[0062] Example 4

[0063] This example provides a method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method, including the following steps:

[0064] (1) Mix 8 g / L ammonia water, absolute ethanol, and sodium dodecyl sulfate according to a mass-volume ratio of 6 mL:1 mL:0.18 g to obtain an alkaline solution;

[0065] (2) Add a 3 mol / L manganese sulfate solution dropwise to the alkaline solution. The volume ratio of the alkaline solution to the manganese sulfate solution is 3:8. Conduct a precipitation reaction under stirring at 40 °C and 800 rpm. At the same time, during the precipitation reaction, add ammonia water with a concentration of 6 g / L dropwise, and control the pH value of the precipitation reaction system to be 10.4 - 10.5. During the precipitation reaction, take samples to measure the median particle size of the generated precipitate. When the median particle size of the precipitate is 9 μm, stop adding ammonia water, continue to react for 80 min under stirring, and then filter to obtain manganese hydroxide precipitate;

[0066] (3) Mix the manganese hydroxide precipitate and deionized water at a mass ratio of 1.3:7 to obtain a suspension; add a 4 mol / L sodium hydroxide solution to the suspension, control the pH value of the suspension to be 11, then introduce air at a flow rate of 2 L / min, and carry out a liquid-phase oxidation reaction at 70 °C for 4 h; after the liquid-phase oxidation reaction is completed, filter the generated precipitate successively, wash it with water 3 times, and dry it at 100 °C for 10 h to obtain manganese tetroxide for soft magnets.

[0067] The Mn content in the manganese tetroxide prepared above is 71.19%, the S content is 0.06%, the particle size of the manganese tetroxide is 9.7 μm, and the BET is 10.9 m 2 / g, and the loose bulk density is 0.74 g / cm 3 .

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing manganese tetroxide for soft magnets by a liquid-phase method. Specifically, refer to Example 1. The difference is that an alkali solution is added to the manganese sulfate solution in step (2).

[0070] The Mn content in the manganese tetroxide prepared above is 69.52%, the S content is 0.13%, the particle size of the manganese tetroxide is 7.1 μm, and the BET is 11.9 m 2 / g, and the loose bulk density is 0.82 g / cm 3 .

[0071] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing manganese tetraoxide for soft magnets by a liquid-phase method, characterized in that, It includes the following steps: Mix ammonia water, absolute ethanol, and surfactant to obtain an alkaline solution; Add a manganese sulfate solution to the alkaline solution for a precipitation reaction; during the precipitation reaction, dropwise add ammonia water to control the pH value at 10 - 10.5; when the median particle size of the precipitate generated by the precipitation reaction is 5 - 10 μm, stop dropwise adding ammonia water, continue the reaction for a certain period of time, and then filter to obtain manganese hydroxide precipitate; Mix the manganese hydroxide precipitate with water to obtain a suspension; add a sodium hydroxide solution to the suspension to control the pH value of the suspension at 10 - 11, and then introduce air for a liquid-phase oxidation reaction; after the liquid-phase oxidation reaction ends, filter, wash, and dry the generated precipitate to obtain manganese tetraoxide for soft magnets; The mass-volume ratio of the ammonia water, absolute ethanol, and surfactant is 3 - 6 mL: 1 - 2 mL: 0.05 - 0.2 g; the concentration of the ammonia water is 1 - 10 g / L; the surfactant is one or several of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and sodium dodecyl sulfate; The flow rate of the introduced air is 0.1 - 3 L / min.

2. The method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method according to claim 1, characterized in that, The volume ratio of the alkaline solution to the manganese sulfate solution is 1 - 3: 2 - 11; the concentration of the manganese sulfate solution is 0.1 - 5 mol / L.

3. The method for preparing manganese tetroxide for soft magnetic materials by a liquid phase method according to claim 1, characterized in that, The specific method of adding the manganese sulfate solution to the alkaline solution is dropwise addition.

4. The method for preparing manganese tetroxide for soft magnetic materials by a liquid-phase method according to claim 1 or 3, characterized in that, Stirring is also included during the precipitation reaction; the rotation speed of the stirring is 200 - 800 rpm.

5. The method for preparing manganese tetraoxide for soft magnetic materials by a liquid-phase method according to claim 4, characterized in that, The time for the continued reaction is 30 - 240 min.

6. The method for preparing manganese tetraoxide for soft magnetic materials by a liquid phase method according to claim 1 or 3, characterized in that, The mass ratio of the manganese hydroxide precipitate to water is 1 - 2: 3 - 8.

7. A method for preparing manganese tetroxide for soft magnetic materials by a liquid-phase method according to claim 1 or 3, characterized in that, The temperature of the liquid-phase oxidation reaction is 40 - 80 °C; the time of the liquid-phase oxidation reaction is 3 - 10 h.