Preparation method of ozone catalyst and application thereof

Abstract

The application relates to the technical field of organic wastewater treatment, in particular to a preparation method and application of an ozone catalyst, and the preparation method and application of the ozone catalyst, the method comprising the following steps: (1) ball milling, (2) melting and (3) staged cooling; the catalyst can promote the reaction between ozone molecules and refractory organic matters, effectively reduces the refractory COD in water, improves the COD removal rate, improves the ozone utilization rate, and achieves the purpose of improving the sewage treatment efficiency.

Description

[Technical Field]

[0001] This invention relates to the field of organic wastewater treatment technology, and in particular to a method for preparing an ozone catalyst and its application. [Background Technology]

[0002] With the gradual improvement of environmental protection policies and technologies, the requirements for wastewater discharge standards have become more stringent, and the treatment technologies for organic wastewater such as coal chemical wastewater, aquaculture wastewater, printing and dyeing wastewater, medical wastewater, and landfill leachate have also been greatly improved.

[0003] Ozone, as an excellent strong oxidant, generates hydroxyl radicals during the oxidation of organic matter, which possess extremely strong electron-acquiring (oxidizing) capabilities. With an oxidation potential of 2.8 eV, second only to fluorine, it enables the oxidation, decomposition, and mineralization of organic matter, achieving harmless treatment. While ozone is a commonly used advanced oxidant, its low utilization rate leads to high costs for treating organic wastewater, limiting its widespread application. To improve ozone utilization efficiency, research and application of heterogeneous ozone catalysts have rapidly developed in recent years. Catalyst supports include activated alumina spheres, ceramsite, and activated carbon.

[0004] Among them, ozone catalysts supported by activated alumina spheres have higher production and application costs and a smaller application range; ozone catalysts supported by ceramsite have relatively poor mechanical strength, which affects their service life; ozone catalysts supported by activated carbon have a large specific surface area, but there is a risk of combustion and explosion during the use of high-concentration ozone.

[0005] Therefore, obtaining a highly efficient and low-cost ozone catalyst is an urgent problem to be solved in this application. [Summary of the Invention]

[0006] In view of the above, it is necessary to provide a method for preparing an ozone catalyst and its application. This method is simple to operate, low in cost, and the obtained ozone catalyst can be effectively applied in wastewater treatment.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing an ozone catalyst, the method comprising the following steps:

[0009] (1) Ball milling: The ceramsite, waste glass slag, steel slag and alumina powder are mixed in a mass ratio of 6-12:5-9:3-5:1-2 and ball milled to obtain a mixture;

[0010] (2) Melting: The mixture is melted at high temperature to obtain a melt. Coconut shell powder is added to the melt, then the temperature is lowered to 600-800℃, and titanium dioxide is added. The mixture is stirred and reacted for 30-50 minutes to obtain a molten mixture.

[0011] (3) Segmented cooling: The molten mixture obtained in step (2) is cooled in segments to obtain the ozone catalyst.

[0012] Furthermore, in step (2), the mass ratio of the melt, coconut shell powder, and titanium dioxide is 10-15:2-4:1-2.

[0013] Furthermore, the melting in step (2) is achieved by heating to 1000-1200°C at a heating rate of 10-15°C / min.

[0014] Furthermore, before adding the coconut shell powder in step (2), the following treatment is performed: the coconut shell powder is hydrothermally reacted at 120-140℃ for 55-70 minutes, cooled to room temperature, and then dried at 100-110℃. The dried material is then heated to 500-700℃ in a vacuum furnace under gas protection for 30-50 minutes, cooled to room temperature, washed with deionized water and dried, and then ground until it passes through an 80-100 mesh sieve.

[0015] Furthermore, the vacuum furnace is a vacuum tube furnace, and the protective gas is nitrogen.

[0016] Furthermore, the segmented cooling in step (3) is as follows: first, the temperature is reduced to 300-400℃ at a cooling rate of 25-35℃ / min, then the temperature is reduced to 80-150℃ at a cooling rate of 10-15℃ / min, and finally the temperature is reduced to 25-30℃ at a cooling rate of 15-20℃ / min.

[0017] The ozone catalyst described in this application is used in wastewater treatment, specifically to catalyze the oxidation reaction of ozone during the process of wastewater treatment using ozone.

[0018] The present invention has at least the following beneficial effects:

[0019] 1. This application addresses the problem that ozone molecules react selectively with organic matter, resulting in incomplete reactions and low utilization rates, thus failing to completely degrade all organic pollutants in wastewater. It proposes a highly efficient ozone catalyst using ceramsite as the main carrier. Through a series of treatments, the poor mechanical strength of ozone catalysts using ceramsite as the carrier is resolved. The catalyst of this application can promote the reaction of ozone molecules with difficult-to-react organic matter, effectively reducing recalcitrant COD in water, improving COD removal rate, increasing ozone utilization rate, and ultimately improving wastewater treatment efficiency.

[0020] 2. In this application, after melting the carrier raw material, treated coconut shell powder is added. The coconut shell powder generates a large amount of gas inside after hydrothermal carbonization, forming loose and porous hydrothermal carbon in a confined space. Then, high-temperature carbonization is carried out. During the treatment process, the specific surface area and number of pores of the material are increased, and a porous hierarchical material with micropores, mesopores and macropores coexisting is obtained. This can effectively increase the catalyst activity and reaction contact sites, and improve the catalytic activity of ozone. Then, titanium dioxide is added to make it have better catalytic performance. The preparation method of this application also helps to attach titanium dioxide to the carrier raw material.

[0021] 3. This application employs a segmented, gradual cooling method to cool the product. First, the product is cooled at a rate of 25-35℃ / min, which maintains the catalyst strength at a high level. Then, the product is cooled at a rate of 10-15℃ / min to avoid stress deformation. Finally, the product is cooled to room temperature at a rate of 15-20℃ / min. The catalyst obtained by this segmented, gradual cooling method has a long service life, maintains good catalytic performance, and has high strength.

Detailed Implementation Methods

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Example 1:

[0024] This embodiment provides a method for preparing an ozone catalyst, the method comprising the following steps:

[0025] (1) Ball milling: The ceramsite, waste glass slag, steel slag and alumina powder are mixed in a mass ratio of 6:5:3:1 and ball milled to obtain a mixture;

[0026] (2) Melting: The mixture is melted at high temperature to obtain a melt. Coconut shell powder is added to the melt, and then the temperature is lowered to 600-800℃. Titanium dioxide is then added and stirred for 30 minutes to obtain a molten mixture. The mass ratio of the melt, coconut shell powder and titanium dioxide in step (2) is 10:2:1. The melting in step (2) is carried out by heating to 1000℃ at a heating rate of 10℃ / min. Before adding the coconut shell powder in step (2), the following treatment is performed: the coconut shell powder is hydrothermally reacted at 120℃ for 55 minutes, cooled to room temperature, and then dried at 100℃. The dried material is placed in a vacuum furnace and heated to 500℃ under gas protection for 30 minutes. After cooling to room temperature, it is washed with deionized water and dried, and then ground until it passes through an 80-mesh sieve. The vacuum furnace is a vacuum tube furnace, and the protective gas is nitrogen.

[0027] (3) Segmented cooling: The molten mixture obtained in step (2) is cooled in segments to obtain the ozone catalyst; the segmented cooling in step (3) is as follows: first, the temperature is lowered to 300°C at a cooling rate of 25°C / min, then the temperature is lowered to 80°C at a cooling rate of 10°C / min, and finally the temperature is lowered to 25°C at a cooling rate of 15°C / min.

[0028] Example 2:

[0029] This embodiment provides a method for preparing an ozone catalyst, the method comprising the following steps:

[0030] (1) Ball milling: The ceramsite, waste glass slag, steel slag and alumina powder are mixed in a mass ratio of 8:7:4:2 and ball milled to obtain a mixture;

[0031] (2) Melting: The mixture is melted at high temperature to obtain a melt. Coconut shell powder is added to the melt, then the temperature is lowered to 700℃, and titanium dioxide is added. The mixture is stirred and reacted for 40 minutes to obtain a molten mixture. The mass ratio of the melt, coconut shell powder and titanium dioxide in step (2) is 12:3:2. The melting in step (2) is carried out by heating to 1100℃ at a heating rate of 12℃ / min. Before adding the coconut shell powder in step (2), the following treatment is performed: the coconut shell powder is hydrothermally reacted at 130℃ for 62 minutes, cooled to room temperature, and then dried at 105℃. The dried material is placed in a vacuum furnace, heated to 600℃ under gas protection, reacted for 40 minutes, cooled to room temperature, washed with deionized water and dried, and ground until it passes through a 90-mesh sieve. The vacuum furnace is a vacuum tube furnace, and the protective gas is nitrogen.

[0032] (3) Segmented cooling: The molten mixture obtained in step (2) is cooled in segments to obtain the ozone catalyst; the segmented cooling in step (3) is as follows: first, the temperature is lowered to 350°C at a cooling rate of 30°C / min, then the temperature is lowered to 120°C at a cooling rate of 12°C / min, and finally the temperature is lowered to 27°C at a cooling rate of 17°C / min.

[0033] Example 3:

[0034] This embodiment provides a method for preparing an ozone catalyst, the method comprising the following steps:

[0035] (1) Ball milling: The ceramsite, waste glass slag, steel slag and alumina powder are mixed in a mass ratio of 12:9:5:2 and ball milled to obtain a mixture;

[0036] (2) Melting: The mixture is melted at high temperature to obtain a melt. Coconut shell powder is added to the melt, then the temperature is lowered to 800℃, and titanium dioxide is added. The mixture is stirred and reacted for 50 minutes to obtain a molten mixture. The mass ratio of the melt, coconut shell powder and titanium dioxide in step (2) is 15:4:2. The melting in step (2) is carried out by heating to 1200℃ at a heating rate of 15℃ / min. Before adding the coconut shell powder in step (2), the following treatment is performed: the coconut shell powder is hydrothermally reacted at 140℃ for 70 minutes, cooled to room temperature, and then dried at 110℃. The dried material is placed in a vacuum furnace, heated to 700℃ under gas protection, reacted for 50 minutes, cooled to room temperature, washed with deionized water and dried, and ground until it passes through a 100-mesh sieve. The vacuum furnace is a vacuum tube furnace, and the protective gas is nitrogen.

[0037] (3) Segmented cooling: The molten mixture obtained in step (2) is cooled in segments to obtain the ozone catalyst; the segmented cooling in step (3) is as follows: first, the temperature is lowered to 400°C at a cooling rate of 35°C / min, then the temperature is lowered to 150°C at a cooling rate of 15°C / min, and finally the temperature is lowered to 30°C at a cooling rate of 20°C / min.

[0038] Experimental example:

[0039] To demonstrate the effectiveness of this application, the applicant conducted relevant experiments;

[0040] The obtained catalyst was added to a water treatment facility to treat the effluent from a municipal wastewater treatment plant. The reaction conditions were: the catalyst loading amount was 10% of the effective volume of the water treatment facility, and the water flow rate was 3 m³ / s. 3 The system operates at room temperature and atmospheric pressure. After heterogeneous catalytic ozone oxidation treatment, the COD values ​​of the water before and after treatment are measured to calculate the COD removal rate.

[0041] The catalysts in each group are as follows:

[0042] Group 1: The catalyst described in Example 2;

[0043] Group 2: Remove the coconut shell powder, otherwise the process is the same as Group 1;

[0044] Group 3: Remove the coconut shell powder, otherwise the method is the same as Group 1;

[0045] Group 4: Remove the segmented cooling and directly cool down to 27℃ at a cooling rate of 30℃ / min. Other methods are the same as Group 1.

[0046] Group 5: Remove the segmented cooling and directly cool to 27℃ at a cooling rate of 12℃ / min. Other methods are the same as Group 1.

[0047] Group 6: The segmented cooling process is as follows: First, the temperature is reduced to 350℃ at a cooling rate of 30℃ / min, then reduced to 120℃ at a cooling rate of 17℃ / min, and finally reduced to 27℃ at a cooling rate of 12℃ / min.

[0048] The COD removal rates of the above-mentioned catalysts after catalytic ozone oxidation are shown in Table 1:

[0049] Table 1 COD removal rate for each group

[0050]

[0051] As shown in Table 1, the catalyst obtained according to the method of this application exhibits good catalytic activity, indicating that the catalyst of this application can effectively improve the utilization rate of ozone. The second group, which did not undergo coconut shell powder treatment, showed a deterioration in catalytic effect, possibly due to a decrease in the number of pores leading to a reduction in the contact sites between the catalytic activity and the reaction, thus resulting in decreased catalytic activity. The third group, after removing the coconut shell powder, showed a significant decrease in COD removal rate, indicating that the coconut shell powder has a positive effect on catalytic activity. The fourth group, by removing the segmented cooling and directly cooling at a relatively rapid rate, experienced stress deformation, significantly reducing the catalytic effect of the catalyst. The sixth group, by simply changing the cooling rate, showed an unexpected decrease in catalytic effect.

[0052] In addition, the applicant further tested the strength of the catalysts in each group. The test method was as follows: 150mm*150mm test blocks were cut from the catalysts obtained from each group, and the axial and transverse compressive strengths were tested using a pressure testing machine. The data are recorded as shown in Table 2.

[0053] Table 2. Strength of each catalyst group

[0054]

[0055] As shown in Table 2, the catalyst prepared by the method of this application has high strength, which solves the problem of low strength of current ceramic-supported catalysts. In contrast, in the fifth group in Table 1, although the catalytic effect is good, its strength is low.

[0056] Since the catalyst is mass-produced, the applicant continued to test the catalytic effect of the catalyst after storage for a period of time. The test method was the same as the first test mentioned above, testing the catalytic effect after storage for 3 months and 6 months. The results are recorded in Table 3:

[0057] Table 3 COD removal rate for each group

[0058]

[0059] As shown in Table 3, the catalyst prepared by the method of this application can maintain good catalytic activity after being stored for a period of time.

[0060] The various embodiments of this invention are described in detail, but they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for preparing an ozone catalyst, characterized in that, The method includes the following steps: (1) Ball milling: The ceramsite, waste glass slag, steel slag and alumina powder are mixed in a mass ratio of 6-12:5-9:3-5:1-2 and ball milled to obtain a mixture; (2) Melting: The mixture is melted at high temperature to obtain a melt. Coconut shell powder is added to the melt, and then the temperature is lowered to 600-800℃. Titanium dioxide is then added and the mixture is stirred for 30-50 minutes to obtain a molten mixture. (3) Segmented cooling: The molten mixture obtained in step (2) is cooled in segments to obtain the ozone catalyst; Before adding the coconut shell powder in step (2), the following treatment is performed: the coconut shell powder is hydrothermally reacted at 120-140℃ for 55-70 minutes, cooled to room temperature, and then dried at 100-110℃. The dried material is then heated to 500-700℃ in a vacuum furnace under gas protection and reacted for 30-50 minutes. After cooling to room temperature, it is washed with deionized water and dried, and then ground until it passes through an 80-100 mesh sieve. The segmented cooling in step (3) is as follows: first, the temperature is lowered to 300-400℃ at a cooling rate of 25-35℃ / min, then lowered to 80-150℃ at a cooling rate of 10-15℃ / min, and finally lowered to 25-30℃ at a cooling rate of 15-20℃ / min.

2. The method according to claim 1, characterized in that, In step (2), the mass ratio of the melt, coconut shell powder and titanium dioxide is 10-15:2-4:1-2.

3. The method according to claim 1, characterized in that, The melting in step (2) is achieved by heating to 1000-1200℃ at a heating rate of 10-15℃ / min.

4. The method according to claim 1, characterized in that, The vacuum furnace is a vacuum tube furnace, and the gas used for protection is nitrogen.

5. The application of the ozone catalyst prepared by the method according to any one of claims 1-4, characterized in that, The ozone catalyst is used in wastewater treatment, specifically to catalyze the oxidation reaction of ozone.

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