Ozone catalyst loaded with metal oxide and application thereof

Abstract

The invention relates to the field of environmental protection, and particularly discloses a metal oxide-loaded ozone catalyst and application thereof, by loading a metal oxide on a catalyst carrier, the material cost can be greatly reduced, the oxidation reaction efficiency can be improved through the synergistic effect between the carrier and active components, and meanwhile, the high activity of the catalyst is kept. Specifically, the service life of the catalyst can be effectively prolonged by using the porous ceramic as the carrier, and meanwhile, the COD removal effect can be effectively improved and the catalytic performance can be improved by using the characteristics of the metal oxide.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and in particular to an ozone catalyst loaded with a metal oxide and application thereof. Background Art

[0002] Wastewater contains large amounts of COD, SS, and other pollutants. Common wastewater treatment methods include physical treatment, chemical treatment, and biological treatment. Physical treatment uses physical forces to separate and recover insoluble suspended pollutants (including oil films and droplets) in wastewater. For example, traditional activated carbon adsorption uses activated carbon to adsorb substances that are toxic and harmful to microorganisms and ultimately collect them with the sludge. Regular cleaning of saturated activated carbon and spent activated carbon can persist in wastewater, making activated carbon adsorption expensive. Chemical treatment involves adding chemicals to wastewater, using chemical reactions to separate and recover certain pollutants or convert them into harmless substances. Common methods include chemical precipitation, coagulation, neutralization, and redox (including electrolysis). While chemical treatment offers good results, it is costly and requires the addition of chemicals during the treatment process, which can easily lead to secondary pollution. Biological treatment utilizes the metabolic capacity of microorganisms to decompose and oxidize dissolved or colloidal organic matter in wastewater into stable inorganic substances, thereby purifying the wastewater. However, biological treatment is not suitable for treating high-concentration organic wastewater, especially organic wastewater containing phenols, aldehydes, and large or high molecules that cannot be degraded by microorganisms.

[0003] At present, there is a lack of economical and effective treatment technology for treating wastewater containing difficult-to-degrade COD, SS, etc. The wastewater treatment technology using ozone for catalytic oxidation has become one of the key technologies for removing highly stable and difficult-to-degrade organic matter such as COD and SS in wastewater due to its advantages of cleanliness, pollution-free, high oxidation efficiency and simple operation.

[0004] The types and methods of loading metal oxides are diverse, which is also an important difficulty in the wastewater treatment method that directly affects the ozone-loading synergistic reaction. How to improve the treatment effect is also an important research direction at present. Summary of the Invention

[0005] The purpose of the present invention is to provide an ozone catalyst loaded with metal oxides and its application, which utilizes the advantages of the hydroxyl functional groups and oxygen vacancies of the metal oxides and the faster electron transfer rate to improve the treatment effect of sewage.

[0006] To achieve the above object, the present invention provides the following technical solutions: A metal oxide-loaded ozone catalyst and its application, comprising a carrier; the carrier is a ceramsite structure, specifically a ceramsite structure with a multi-level pore structure; the carrier content is metal oxide; The preparation method of the metal oxide-loaded ozone catalyst specifically comprises the following steps: Step 1: Take a sufficient amount of 3-5 mm uniform ceramsite as a carrier, wash it repeatedly with pure water, and then dry it in an oven at 100 ° C. Use 0.1 mol / L sodium hydroxide and hydrochloric acid for ultrasonic cleaning for 1 hour respectively, take out the ceramsite and use pure water ultrasonic cleaning and rinse until the pH is neutral, and then dry it to obtain the pretreated bioceramsite; Step 2: Place the pretreated ceramsite in a beaker and add the metal sol solution to completely immerse it. To enhance the coating effect, perform ultrasonic immersion for 60 minutes, then dry at 60°C and calcine at 400°C. Repeat the coating-drying-calcination process many times until a significant color change is observed on the ceramsite, and it becomes light yellow and the coating does not fall off due to being too thick. The Al2O3 / ceramsite catalyst is considered to be completed.

[0007] Step 3: Prepare 250 mL of a 5% by mass nitrate solution as the precursor of the active ingredient and place it in a conical flask. Place the coated ceramsite in the nitrate solution and ultrasonically immerse it for 2 hours. After drying in an oven at 60°C, calcinate it in a muffle furnace. After aging in air, the ceramsite can be used for ozone oxidation.

[0008] As a further embodiment of the present invention, the metal oxide is a transition metal oxide.

[0009] As a further embodiment of the present invention, the metal oxide is a combination oxide of any two or more of iron, manganese, copper or cobalt, or an oxide of any one of the metal oxides.

[0010] As a further solution of the present invention: in step 2, in the calcination step, the calcination time is 2h-4.5h.

[0011] More specifically, as a further solution of the present invention: in step 2, in the calcination step, the calcination time is 2.5h-4h.

[0012] As a further solution of the present invention: in step 2, in the calcination step, the calcination temperature is 300°C-450°C.

[0013] As a more optimal technical solution: in step 2, in the calcination step, the calcination temperature is 350°C-400°C.

[0014] As a further solution of the present invention: the diameter of the carrier is 3-5 mm.

[0015] As a further solution of the present invention: the metal sol solution in step 2 is an aluminum sol solution.

[0016] Loading metal oxides on catalyst supports can not only significantly reduce material costs, but also improve the efficiency of the oxidation reaction through the synergistic effect between the support and the active components, while maintaining the high activity of the catalyst. Taking bioceramic granules as an example, this type of support forms a rich multi-level pore structure through high-temperature sintering. The pores are evenly distributed and have low density. It has good permeability to gases and liquids, and is corrosion-resistant, high-temperature resistant, and structurally stable. Compared with powder catalysts that are prone to agglomeration and loss, the advantages of ceramic granule-based catalysts are: their through-pores can provide sufficient active sites to promote the generation of free radicals, thereby improving ozone utilization; by optimizing the filling method, the catalyst loss caused by fluid scouring can be alleviated; and ceramic granules have high mechanical strength and a long service life, making them easier to replace and manage in industrial reactors, and more feasible in engineering applications.

[0017] Beneficial effects of the present invention: Compared with the prior art, the technical solution disclosed in the present invention can not only improve the high activity of the catalyst, but also improve the ozone utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 In order to study the effects of different metal loadings on COD removal in simulated wastewater, the aim was to compare the COD removal effects of various metal oxide combinations and determine the optimal metal oxide combination.

[0020] Figure 2 The purpose of this study is to compare the effects of different calcination times on COD removal in simulated wastewater and determine the optimal calcination time.

[0021] Figure 3 The purpose of this study is to investigate the effects of different calcination temperatures on COD removal in simulated wastewater, compare the effects of calcination temperature on COD removal, and determine the optimal calcination temperature. DETAILED DESCRIPTION

[0022] The technical solutions of this application will be described clearly and completely below, in conjunction with the accompanying drawings. It should be understood that the described embodiments represent only some, and not all, embodiments of this application. The components of this application, generally described and illustrated in the drawings herein, can be designed and arranged in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but rather merely represents selected embodiments of this application. All other embodiments derived by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used solely to distinguish descriptions and are not to be construed as indicating or implying relative importance.

[0023] A metal oxide-loaded ozone catalyst is prepared in three main steps. A sufficient amount of 3-5 mm uniform ceramsite (clay ceramsite was used in this experiment) is used as a carrier. After repeated washing with pure water, it is dried in an oven at 100°C. Ultrasonic cleaning is performed with 0.1 mol / L sodium hydroxide and hydrochloric acid for 1 hour each. The ceramsite is then removed and ultrasonically cleaned and rinsed with pure water until the pH is neutral, followed by drying to obtain the pretreated bioceramsite.

[0024] The pretreated ceramsite was placed in a beaker and aluminum sol solution was added to completely immerse it. To enhance the coating effect, ultrasonic immersion was performed for 60 minutes. Then, it was dried at 60°C and calcined at 400°C. The coating-drying-calcination process was repeated many times until an obvious color change was observed on the ceramsite, and it became light yellow and the coating did not fall off due to being too thick. The Al2O3 / ceramsite catalyst was considered to be completed.

[0025] Prepare 250 mL of a 5% by mass nitrate solution as the active ingredient precursor and place it in an Erlenmeyer flask. Place the coated ceramsite in the nitrate solution and ultrasonically immerse it for 2 hours. Dry it in an oven at 60°C and calcine it in a muffle furnace. After aging in air, the ceramsite is ready for ozone oxidation.

[0026] In this experiment, a certain amount of metal elements was loaded on the biological ceramsite carrier by the impregnation and roasting method, and phenol was used to simulate sewage as the degradation object to investigate the influence of preparation conditions on the activity of the catalyst, and to screen out catalysts with higher activity.

[0027] The main research conditions and design scheme are shown in Table 1: Table 1: The optimal solution obtained by setting different experimental variables and levels:

[0028] like Figure 1 As shown in this study, two of the transition metals iron (Fe), manganese (Mn), copper (Cu), and cobalt (Co) were loaded onto ceramsite as active components. After calcination at 400°C for 3.5 hours, all components existed as oxides. A 120-minute degradation experiment was conducted under simulated wastewater conditions with an ozone flow rate of 0.2 L / min, a concentration of 20 mg / L, and an initial pH of 7.2, and the catalytic performance of each catalyst was compared. The COD removal performance of various metal-modified catalysts in simulated wastewater was analyzed. It can be seen that after 120 minutes of reaction, the COD removal rate of the blank ceramsite support (19.36%) did not significantly improve compared to the removal rate of ozone oxidation alone (18.69%). This is because the ceramsite is primarily composed of SiO2, which has fewer surface functional groups, making it less conducive to catalytic reaction.

[0029] After loading the metal active components Fe-Mn-Al2O3 / ceramic, Fe-Cu-Al2O3 / ceramic, CuMn-Al2O3 / ceramic, and Co-Mn-Al2O3 / ceramic, the COD removal effects were improved to varying degrees, from 19.36% to 52.78%, 46.90%, 45.39%, and 39.54%, respectively. This is mainly due to the different rates and yields of -OH produced by different types of active metals catalyzing ozone molecules, resulting in certain differences in removal rates. Among them, the Fe-Mn loaded catalyst showed the highest catalytic activity. It has been reported in the literature that Fe and Mn oxides have multiple valence states. After being successfully loaded on the surface and interior of the ceramic carrier, they are in the form of metal Fe 3+ 、Fe 2+ 、Mn 3+ and Mn 2+ It exists in the form of oxides and has more abundant hydroxyl functional groups and oxygen vacancies, and the electron transfer rate is faster. When ozone is introduced, ozone contacts it and obtains electrons to produce strong oxidizing intermediates, which promotes the decomposition of ozone, thereby improving the oxidation capacity of phenol. In addition, the advantages of iron and manganese as active components include: ① Fe and Mn are low in price, environmentally friendly, and easy to obtain; ② Fe and Mn oxides have multiple valence states, and redox electron pairs (such as Fe 2+ / Fe 3+ 、Mn 2+ / Mn 3+ / Mn 4+ ) can enhance the decomposition of ozone; ③ The introduction of Fe and Mn can generate new active sites and greatly improve the conductivity; ④ The rich pores of ceramsite and the effect of aluminum sol can effectively inhibit the leaching of metal ions by fixing Fe and Mn oxides on ceramsite, thereby improving the stability of the material.

[0030] like Figure 2 As shown in the figure: High-temperature calcination is a key step in catalyst activation. Only through this process can the catalyst obtain the required activity. During the calcination process, the salt substances introduced into the carrier during the impregnation stage will be converted into catalytically active oxides. This process is accompanied by the formation and distribution of catalyst grains, and the generation of active grains is a gradual and slow process. If the calcination time is insufficient, it will lead to insufficient decomposition of salts and oxides, impurities and moisture residues, and will also affect the mechanical strength of the catalyst, reducing its industrial application value and reuse rate. However, too long calcination time is also unfavorable, which may cause the collapse of the carrier pore structure and deactivation of the catalyst. Therefore, it is crucial to choose the right calcination time. In this experiment, Fe-Mn-Al2O3 / ceramsite catalyst was prepared at a calcination temperature of 400°C, the reaction ozone concentration was 20 mg / L, and the initial pH of the solution was 7.2. The effect of calcination conditions on catalyst performance is shown in Figure 2. Figure 2 and Figure 3 As shown, both calcination time and temperature have a certain impact on COD removal efficiency. When the calcination time was 2.5 hours, the COD removal efficiency was 38.53%. This was primarily due to the incomplete decomposition of metal nitrates into highly active oxide crystals due to the short calcination time, resulting in insufficient active sites. When the calcination time was increased from 3 hours to 3.5 hours, the COD removal efficiency increased from 44.91% to 53.38%. At this point, the metal salts on the catalyst surface completely decomposed into oxide crystals, demonstrating high activity. When the calcination time was extended to 4 hours, the removal efficiency decreased by 2.31%, which is closely related to the masking of active sites and pore collapse caused by high-temperature sintering. Compared to the catalyst prepared with a calcination time of 3.5 hours, although the final degradation results of the catalyst prepared with a 4-hour calcination were similar, the degradation effect showed a downward trend throughout the reaction, and the degradation efficiency was lower than that of the catalyst prepared with a 3.5-hour calcination time. Based on the balance between economic efficiency and degradation efficiency, a 3.5-hour calcination time was selected as the optimal one.

[0031] like Figure 3As shown, calcination temperature also has a certain impact on the catalytic activity of the catalyst. When the calcination temperature is too low, the metal salts cannot completely decompose into oxides. When the calcination temperature is too high, the catalyst surface sintering occurs, reducing the number of active sites and adsorption sites. Calcination temperature is a key parameter for regulating catalyst activity. Experiments show that under the conditions of a fixed calcination time of 3 hours, an ozone flow rate of 0.2 L / min, an ozone concentration of 20 mg / L, and an initial pH of 7.2, the COD removal rate of the catalyst increases first and then decreases with increasing calcination temperature (300-450°C). As the temperature increases from 300°C to 400°C, the metal hydroxides gradually decompose into crystalline oxides (MnO2 and Fe2O3), increasing the density of active sites and boosting the COD removal rate from 45.24% to 52.78%. Among them, when the temperature rises to 350℃, oxides have been initially generated and the removal rate rises to 48.64%; at 400℃, oxides have been generated and evenly distributed on the carrier surface, and the activity reaches the highest; but when the temperature further rises to 450℃, the high-temperature sintering effect causes the carrier pores to collapse and the oxide particles to agglomerate, the exposed area of ​​the active sites is sharply reduced, and the COD removal rate drops.

[0032] In summary, the use of the catalyst disclosed in this application can effectively improve the efficiency of sewage treatment, increase the utilization rate of the catalyst, reduce catalyst loss, and improve ozone utilization.

[0033] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A metal oxide-loaded ozone catalyst, characterized in that: The ozone catalyst includes a carrier; The carrier is a ceramsite structure; specifically, a ceramsite structure with a multi-level pore structure; The carrier content is a metal oxide; The preparation method of the metal oxide-loaded ozone catalyst specifically comprises the following steps: Step 1, carrier preparation: take a sufficient amount of ceramsite as a carrier, wash it repeatedly with pure water and then dry it in an oven, ultrasonically clean it with sodium hydroxide and hydrochloric acid respectively, take out the ceramsite, ultrasonically clean it with pure water and then rinse it until the pH is neutral, and then dry it to obtain pretreated bioceramsite; Step 2, preparation of ceramsite catalyst: put the pretreated ceramsite into a beaker, add the metal sol solution to completely immerse it, and perform ultrasonic impregnation to enhance the coating effect. Then, dry and calcine in sequence, and repeat the coating-drying-calcination process many times until a significant color change is observed on the ceramsite, and it becomes light yellow and the coating does not fall off due to being too thick. The ceramsite catalyst is considered to be completed; Step 3: Catalyst activation: prepare a nitrate solution as a precursor of the active ingredient and place it in a container for later use; place the coated ceramsite in the nitrate solution, ultrasonically impregnate it, dry it in an oven, and then calcine it in a muffle furnace. After aging the calcined ceramsite in air, it can be put into ozone oxidation for use.

2. The metal oxide-supported ozone catalyst according to claim 1, characterized in that: The metal oxide is a transition metal oxide.

3. The metal oxide-supported ozone catalyst according to claim 1 or 2, characterized in that: The metal oxide is a combination oxide of any two or more of iron, manganese, copper or cobalt, or an oxide of any one of the metal oxides.

4. The metal oxide-supported ozone catalyst according to claim 1, wherein: In step 2, the calcination step, the calcination time is 2h-4.5h.

5. The metal oxide-supported ozone catalyst according to claim 4, characterized in that: In step 2, the calcination step, the calcination time is 2.5h-4h.

6. The metal oxide-supported ozone catalyst according to claim 1, wherein: In step 2, the calcination step, the calcination temperature is 300°C-450°C.

7. The metal oxide-supported ozone catalyst according to claim 6, characterized in that: In step 2, the calcination step, the calcination temperature is 350°C-400°C.

8. The metal oxide-supported ozone catalyst according to claim 1, characterized in that: The carrier has a diameter of 3-5 mm.

9. The metal oxide-supported ozone catalyst according to claim 1, characterized in that: The metal sol solution in step 2 is an aluminum sol solution.

10. Use of the metal oxide-loaded ozone catalyst according to any one of claims 1 to 9 in sewage treatment.

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