Method for improving activity of heavy magnesium oxide

Abstract

The invention relates to a method for improving the activity of heavy magnesium oxide. According to the method, through the fine process steps of secondary cold water stirring, secondary time and temperature adjustment drying, primary calcination and the like, the activity of the heavy magnesium oxide is remarkably improved under the condition that the bulk density, the granularity and the crystal structure of the heavy magnesium oxide are not affected, and the active CAA value is increased from 500 seconds or above to 10 seconds to 185 seconds. In the whole preparation process, through reasonable selection of raw materials and accurate control of reaction conditions, high activity and excellent filling performance of magnesium oxide are realized, and finally, a high-performance magnesium oxide product suitable for various industrial applications is obtained. The method has the characteristics of simple process, environmental protection, high efficiency and low energy consumption, is especially suitable for large-scale production, and has wide application prospects in cobalt precipitation, sewage treatment and other industrial fields.

Description

Technical Field

[0001] The invention relates to a method for preparing heavy magnesium oxide, in particular to a method for improving the activity of heavy magnesium oxide. Background Art

[0002] Heavy magnesium oxide has a large bulk density, dense particles, generally in spherical and granular form, good wear resistance, and flame retardant and heat insulating properties, so heavy magnesium oxide is widely used in brake pads and friction materials. In addition, heavy magnesium oxide also has certain application value in some electrical components, flame retardant and heat insulating agents and ceramic materials. However, due to its large particle size and small specific surface area, heavy magnesium oxide often has low activity, and its CAA value is often above 500s, and some are even higher, which often limits its application and development. Magnesium oxide also plays a great role in sewage treatment, water purification and environmental protection. Light magnesium oxide generally has a large specific volume, low density, high activity, but poor filling performance; heavy magnesium oxide has good filling performance, but poor activity and poor treatment effect, so the development of high-activity heavy magnesium oxide with good filling and high activity is very important. Summary of the invention

[0003] The present invention provides a method for improving the activity of heavy magnesium oxide. By adopting fine process steps such as secondary cold water stirring, secondary time and temperature adjustment drying and primary calcination, the activity of heavy magnesium oxide is significantly improved without affecting the bulk density, particle size and crystal structure of the heavy magnesium oxide. The whole preparation process realizes the high activity and excellent filling performance of magnesium oxide through reasonable selection of raw materials and precise control of reaction conditions, and finally obtains a high-performance magnesium oxide product suitable for various industrial applications.

[0004] The technical solution adopted by the present invention is:

[0005] A method for improving the activity of heavy magnesium oxide comprises the following steps:

[0006] (a) preparing a dispersant: mixing a liquid dispersant with pure water in a volume ratio of 1:10-100, and stirring at low temperature for at least 15 minutes;

[0007] (b) adding 0.05% to 1% of calcium oxide by mass of pure water to the dispersant obtained in step (a), and stirring at low temperature for 5 to 10 minutes to form a weak alkaline environment and promote the attachment of calcium oxide to the surface of magnesium oxide particles;

[0008] (c) adding 10% to 60% of heavy magnesium oxide by mass of pure water to the solution obtained in step (b), stirring at room temperature for 20 to 60 minutes to form a uniform slurry;

[0009] (d) filtering the slurry obtained in step (c) to control the moisture content of the filter cake to be between 50% and 600%;

[0010] (e) drying the filter cake obtained in step (d) at a constant temperature of 100-150° C. for 2-6 hours;

[0011] (f) grinding the material block obtained in step (e) for 10-30 minutes to obtain a uniform powder;

[0012] (g) adding 1-10 parts of pure water to the powder obtained in step (f) according to the mass ratio of magnesium oxide powder, and stirring at room temperature for 10-40 minutes to form a slurry;

[0013] (h) treating the slurry obtained in step (g) at a constant temperature of 100-200° C. for 2-5 hours, and then calcining at 400-1000° C. for 1.5-8.5 hours;

[0014] (i) cooling the powder obtained in step (h) and then grinding it to obtain high-activity heavy magnesium oxide.

[0015] The liquid dispersant in step (a) includes anhydrous ethanol, propanol, methanol, acetone, and ethyl acetate.

[0016] Preferably, the liquid dispersant in step (a) is anhydrous ethanol.

[0017] The stirring temperature in step (a) is 0-5°C.

[0018] The stirring temperature in step (b) is 0-5°C.

[0019] Preferably, in step (d), the moisture content of the filter cake is controlled at 600%.

[0020] Preferably, the drying temperature in step (e) is 120° C. and the drying time is 4 hours.

[0021] Preferably, the calcination conditions in step (h) are: time is 2 hours, temperature is 500°C.

[0022] Preferably, the grinding in step (i) is carried out using a ball mill for a grinding time of 0.5-2 hours.

[0023] The heavy magnesium oxide product prepared by the above method has an activity value CAA between 10 seconds and 185 seconds, has excellent filling performance, and is suitable for industrial applications such as cobalt precipitation, sewage treatment, and water purification.

[0024] Key process steps and principles:

[0025] Optimization of the dispersion process: The present invention first uses ethanol and water as dispersants to fully mix the magnesium oxide powder and the additives under low temperature conditions. Through the secondary cold water stirring process, it is ensured that the magnesium oxide particles can be evenly dispersed, providing a good physical basis for subsequent reactions and improving the uniformity and effectiveness of the overall reaction.

[0026] Formation of a weak alkaline environment: Adding calcium oxide to the dispersion creates a weak alkaline environment, which causes calcium ions to adhere to the surface of magnesium oxide particles. The purpose of this step is to improve the surface activity of magnesium oxide, lay the foundation for the smooth progress of the subsequent calcination process, and ensure that the activity is improved while maintaining the structural integrity of the material.

[0027] Precise drying and calcination control: Through the secondary drying step of adjusting time and temperature, the magnesium oxide is first dried at a lower temperature to promote the formation of magnesium hydroxide, and then dried thoroughly at a higher temperature. This process not only controls the hydration reaction of magnesium oxide, but also prepares for calcination. In the calcination step, the temperature and time are precisely controlled to make the magnesium oxide highly active without destroying the crystal structure.

[0028] Refining treatment of grinding and sieving: After calcination, the magnesium oxide is ground and sieved to ensure that the particle size of the powder is uniform, and finally a magnesium oxide powder with a high specific surface area is obtained. This step not only improves the fluidity and filling performance of the powder, but also further improves the reaction efficiency of the product in the application.

[0029] The beneficial effects of the present invention include:

[0030] Improving the activity of magnesium oxide without destroying its crystal structure: Under the premise of maintaining the stability of the magnesium oxide crystal structure, the activity of magnesium oxide is significantly improved by optimizing the process parameters and reaction conditions, greatly improving its reaction efficiency in various applications.

[0031] Good dispersibility and volatility: Using ethanol and water as dispersants not only improves the dispersibility of magnesium oxide powder, but also ensures that the dispersant can evaporate quickly during the subsequent drying process, reducing residues and simplifying post-processing steps.

[0032] Precise control of activity value, simple and efficient process: By controlling the reaction process, the activity value of magnesium oxide can be accurately adjusted. The preparation process is simple, involving few reaction steps, with the characteristics of low energy consumption and high yield, and is suitable for large-scale production.

[0033] Green and environmentally friendly raw materials: The use of non-toxic and harmless raw materials not only ensures the safety of the product, but also meets the requirements of green environmental protection. It is particularly suitable for the production of medical or food-grade magnesium oxide, broadening the application range of the product.

[0034] Uniform particles, good fluidity and filling properties: The prepared magnesium oxide powder has uniform particles and excellent fluidity and filling properties, which makes the material have better processing and use performance in various industrial applications.

[0035] Wide application and mass production potential: The high-activity magnesium oxide prepared by the present invention can be widely used in the fields of cobalt precipitation, sewage treatment, water purification, etc., and the process is simple and efficient, with the potential for large-scale mass production, and has significant market value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 To obtain the morphology of highly active heavy magnesium oxide at a magnification of 7000 times;

[0037] Figure 2 This is the morphology of the highly active heavy magnesium oxide at a magnification of 20,500 times. DETAILED DESCRIPTION

[0038] Example:

[0039] 1. Material preparation:

[0040] Heavy magnesium oxide powder is used as a raw material, and anhydrous ethanol and calcium oxide are added in proportion.

[0041] The moisture content of the filter cake ranged from 50% to 600% to investigate the effect of different moisture contents on the final activity of magnesium oxide.

[0042] 2. Mixing and Hydration:

[0043] Add 1-5L of anhydrous ethanol into a stainless steel container, followed by 50-100L of pure water, and stir at 0-5°C for at least 15 minutes.

[0044] Add 0.05-0.5kg of calcium oxide to the dispersion and stir again at 0-5°C for 5-10 minutes to generate a weakly alkaline environment. Calcium ions can adhere to the surface of magnesium oxide particles to enhance reactivity and activity.

[0045] 3. Formation of slurry:

[0046] Add 10-30 kg of heavy magnesium oxide to the above mixed solution and stir at room temperature for 20-60 minutes to form a uniform slurry.

[0047] 4. Vacuum filtration:

[0048] The slurry is placed in a vacuum filtration device, the pressure of which is usually controlled within a negative pressure range of 0.05 to 0.1 MPa, and the moisture content of the filter cake is controlled between 50% and 600%.

[0049] According to the experimental design, the moisture content of the filter cake was graded to evaluate its effect on the activity of the final product.

[0050] 5. Drying process:

[0051] The filter cake is placed in a stainless steel container and dried in an oven at 100-150°C for 2.0-6.0 hours. The purpose of the first drying is to evaporate most of the water in the filter cake and initially form magnesium hydroxide.

[0052] According to the experiment, the first drying conversion rate of the filter cake increased from 33.32% (50% moisture content) to 82.55% (600% moisture content), indicating that the higher the moisture content, the more obvious the drying effect.

[0053] 6. Rehydration and secondary drying:

[0054] After grinding the material block that has been dried for the first time for 10-30 minutes, 1-10 parts of pure water are added again and stirred for 10-40 minutes to make the magnesium oxide particles further hydrated and uniform.

[0055] After the material blocks are stirred again, they are dried for the second time. The second drying is completed in an oven, and the temperature and time are the same as or slightly higher than the first drying. The conversion rate of the second drying is significantly improved, ranging from 85.32% (50% moisture content) to 98.38% (600% moisture content).

[0056] 7. Calcination process:

[0057] The dried material blocks were calcined at 500° C. and 1000° C., with calcination times of 2 hours and 7 hours, respectively, to test the activity (CAA value) of magnesium oxide under different calcination conditions.

[0058] The results show that when the moisture content of the filter cake is 600%, the CAA value of the magnesium oxide obtained by calcining at 500℃ for 2 hours is 10 seconds, reaching the highest activity. With the change of calcination temperature and time, the activity of magnesium oxide gradually decreases. After calcining at 1000℃ for 7 hours, the CAA value is 81 seconds, the lowest activity.

[0059] 8. Product performance evaluation:

[0060] The experimental results are shown in Table 1:

[0061] 1) Relationship between filter cake moisture content and drying conversion rate

[0062] First drying conversion rate: As the moisture content of the filter cake increases, the conversion rate of the first drying also increases. It gradually increases from 33.32% at 50% moisture content to 82.55% at 600% moisture content. This shows that as the moisture content increases, more water is removed during the first drying process, forming more magnesium hydroxide.

[0063] Second drying conversion rate: The conversion rate of the second drying increased significantly in the early stage (50% to 100% moisture content), from 85.32% to 98.16%, and then stabilized after the moisture content reached 400%, approaching 98%. This shows that the second drying process further completed the removal and conversion of moisture, but after a certain moisture content, the influence of moisture decreased and the conversion efficiency tended to saturation.

[0064] 2) Effect of different moisture content on calcination process (active CAA value)

[0065] Calcination at 500℃ for 2 hours: Under the condition of calcination at 500℃ for 2 hours, as the moisture content of the filter cake increases, the activity of magnesium oxide (i.e., CAA value) increases significantly, from 53s at a moisture content of 50% to 10s at a moisture content of 600%. This indicates that a higher moisture content leads to a significant increase in the activity of magnesium oxide.

[0066] Calcination at 500℃ for 7 hours: After the calcination time was extended to 7 hours, the active CAA value generally decreased, but compared with 2 hours, the effect of increased moisture content was still significant, and the activity of magnesium oxide increased from 95s to 26s. This means that a higher moisture content helps to improve the activity of magnesium oxide, and too long calcination time will reduce the activity of magnesium oxide.

[0067] Calcination at 1000℃ for 7 hours: At a higher calcination temperature (1000℃), the activity of magnesium oxide further decreased, but increased with the increase of water content, and finally increased from 185s at 50% water content to 81s at 600%. This once again shows that a higher water content helps to improve the activity of magnesium oxide, and too long calcination time will reduce the activity of magnesium oxide.

[0068] 3) Summary of experimental results

[0069] The moisture content has a significant effect on the activity of magnesium oxide: under the condition of calcination at 500°C for 2 hours, the activity of magnesium oxide increases with the increase of moisture content. The activity value at a moisture content of 600% is the lowest, which is 10 seconds, which fully meets the high activity requirements.

[0070] Effect of temperature and calcination time on the activity of magnesium oxide: Under the conditions of calcination at 500℃ for 7 hours and 1000℃ for 7 hours, the activity of magnesium oxide decreased, indicating that high temperature and long time calcination has an adverse effect on the activity.

[0071] Stability of drying conversion rate: The second drying conversion rate tends to be stable at high moisture content (400% and above), indicating that the effect of moisture on the conversion at this stage gradually weakens.

[0072] 9. Conclusion:

[0073] By optimizing the degree of hydration and calcination conditions, the activity of magnesium oxide can be effectively controlled, making it suitable for industrial applications such as cobalt precipitation and sewage treatment.

[0074] The optimal conditions are that the moisture content of the filter cake is 600% and calcination at 500°C for 2 hours can obtain high-activity heavy magnesium oxide with a CAA value of less than 15 seconds. Figure 1 To obtain the morphology of highly active heavy magnesium oxide at a magnification of 7000 times; Figure 2 This is the morphology of the highly active heavy magnesium oxide at a magnification of 20500 times. Figure 1 and Figure 2 It can be seen that there are many holes on its surface and the specific surface area is large, so the activity is high.

[0075] Table 1

[0076]

[0077] The experimental results in Table 1 show that the activity of magnesium oxide can be controlled by controlling the degree of hydration and calcination conditions.

[0078] Application significance: In order to obtain highly active heavy magnesium oxide, the initial moisture content of the filter cake should be controlled and calcined at an appropriate temperature and time. High moisture content and long calcination time have important application value in production and can significantly improve the activity of the product.

[0079] Technical advantages: By precisely controlling the degree of hydration and calcination conditions, the present invention can effectively adjust the activity of the product. Compared with chemical synthesis methods, the process flow is simple, the required equipment is simpler, and through reasonable process design, the automation and continuous production of the entire production line can be achieved. At present, the African market has a huge demand for high-activity magnesium oxide used in cobalt precipitation processes. The heavy high-activity magnesium oxide prepared by the present invention is fully suitable for this industry, and the market prospects are very optimistic. In addition, since the raw materials used contain low levels of impurities such as heavy metals, and only a small amount of additives such as calcium oxide and anhydrous ethanol are used, and no other impurities are introduced, the process of the present invention is fully suitable for the production of pharmaceutical or food grade heavy magnesium oxide.

Claims

1. A method for improving the activity of heavy magnesium oxide, characterized in that: The method comprises the following steps: (a) preparing a dispersant: mixing a liquid dispersant with pure water in a volume ratio of 1:10-100, and stirring at low temperature for at least 15 minutes; (b) adding 0.05% to 1% of calcium oxide by mass of pure water to the dispersant obtained in step (a), and stirring at low temperature for 5 to 10 minutes to form a weak alkaline environment and promote the attachment of calcium oxide to the surface of magnesium oxide particles; (c) adding 10% to 60% of heavy magnesium oxide by mass of pure water to the solution obtained in step (b), stirring at room temperature for 20 to 60 minutes to form a uniform slurry; (d) filtering the slurry obtained in step (c) to control the moisture content of the filter cake to be between 50% and 600%; (e) drying the filter cake obtained in step (d) at a constant temperature of 100-150° C. for 2-6 hours; (f) grinding the material block obtained in step (e) for 10-30 minutes to obtain a uniform powder; (g) adding 1-10 parts of pure water to the powder obtained in step (f) according to the mass ratio of magnesium oxide powder, and stirring at room temperature for 10-40 minutes to form a slurry; (h) treating the slurry obtained in step (g) at a constant temperature of 100-200° C. for 2-5 hours, and then calcining at 400-1000° C. for 1.5-8.5 hours; (i) cooling the powder obtained in step (h) and then grinding it to obtain high-activity heavy magnesium oxide.

2. The method according to claim 1, characterized in that The liquid dispersant in step (a) includes anhydrous ethanol, propanol, methanol, acetone, and ethyl acetate.

3. The method according to claim 2, characterized in that The liquid dispersant in step (a) is anhydrous ethanol.

4. The method according to claim 1, characterized in that The stirring temperature in step (a) is 0-5°C.

5. The method according to claim 1, characterized in that The stirring temperature in step (b) is 0-5°C.

6. The method according to claim 1, characterized in that In step (d), the moisture content of the filter cake is controlled at 600%.

7. The method according to claim 1, characterized in that The drying temperature in step (e) is 120° C. and the drying time is 4 hours.

8. The method according to claim 1, characterized in that The calcination conditions in step (h) are: time is 2 hours and temperature is 500°C.

9. A heavy magnesium oxide product prepared by the method according to any one of claims 1 to 8, characterized in that: The activity value CAA of the magnesium oxide product is between 10 seconds and 185 seconds.

10. Application of the heavy magnesium oxide product according to claim 9 in cobalt precipitation, sewage treatment and water purification.

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