Metal oxide supported ozone catalyst and use thereof

Abstract

This invention relates to the field of environmental protection, specifically disclosing an ozone catalyst supported on a metal oxide and its application. Loading metal oxides onto a catalyst support not only significantly reduces material costs but also enhances oxidation reaction efficiency through the synergistic effect between the support and the active component, while maintaining high catalyst activity. Specifically, using porous ceramics as a support effectively extends the catalyst's lifespan, and the properties of metal oxides effectively improve COD removal and catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of environmental protection, specifically to an ozone catalyst supported on metal oxides and its application. Background Technology

[0002] Wastewater contains high levels of COD and SS (suspended solids). Common wastewater treatment methods include physical, chemical, and biological treatment. Physical treatment separates and recovers insoluble suspended pollutants (including oil films and droplets) from wastewater through physical processes. For example, traditional activated carbon adsorption uses activated carbon to adsorb substances toxic to microorganisms, which are then collected along with sludge. Regular cleaning of saturated activated carbon and the continued presence of degraded activated carbon in the wastewater make this method costly. Chemical treatment involves adding chemicals to the wastewater to separate and recover certain pollutants or convert them into harmless substances through chemical reactions. Common methods include chemical precipitation, coagulation, neutralization, and oxidation-reduction (including electrolysis). Chemical treatment is effective but expensive, and the need to add chemicals during the process can easily lead to secondary pollution from residual chemicals. Biological treatment utilizes the metabolic functions of microorganisms to decompose and oxidize dissolved or colloidal organic matter in wastewater into stable inorganic substances, thus purifying the wastewater. However, biological treatment methods are not suitable for treating high-concentration organic wastewater, especially organic wastewater containing phenols, aldehydes, and large or high-molecular-weight organic wastewater that cannot be degraded by microorganisms.

[0003] Currently, there is a lack of economical and effective treatment technologies for wastewater containing recalcitrant COD and SS. However, wastewater treatment technology using ozone for catalytic oxidation has become one of the key technologies for removing highly stable and recalcitrant organic matter such as COD and SS from wastewater due to its advantages such as being clean and pollution-free, having high oxidation efficiency, and being simple to operate.

[0004] The variety of types and methods of loading metal oxides is a significant challenge that directly affects wastewater treatment methods involving ozone-loaded synergistic reactions. Improving treatment efficiency is also an important research direction at present. Summary of the Invention

[0005] The purpose of this invention is to provide an ozone catalyst supported on metal oxides and its application, which utilizes the advantages of faster electron transfer rates of the hydroxyl functional groups and oxygen vacancies of metal oxides to improve the treatment effect of wastewater.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An ozone catalyst supported on a metal oxide and its application therein, comprising a support; the support is a ceramic particle structure; specifically, a ceramic particle structure having a hierarchical porous structure; the contents of the support are metal oxides;

[0008] The method for preparing the ozone catalyst supported on metal oxides specifically includes the following steps:

[0009] Step 1: Take a sufficient amount of 3-5mm uniform ceramsite as a carrier, wash it repeatedly with pure water, dry it in an oven at 100℃, and ultrasonically clean it with 0.1mol / L sodium hydroxide and hydrochloric acid for 1h respectively. Take out the ceramsite, ultrasonically clean it with pure water and rinse it until the pH is neutral, and then dry it to obtain the pretreated biological ceramsite.

[0010] Step 2: Place the pretreated ceramsite into a beaker, add metal sol solution to completely immerse it, and to enhance the coating effect, perform ultrasonic impregnation for 60 minutes. Then, perform drying at 60℃ and calcination at 400℃ in sequence. Repeat the coating-drying-calcination process multiple times until a significant color change can be observed on the ceramsite, which is light yellow and the coating does not peel off due to excessive thickness. At this point, the Al2O3 / ceramsite catalyst is considered complete.

[0011] Step 3: Prepare 250 mL of a 5% (w / w) nitrate solution as a precursor for the active ingredient and place it in an Erlenmeyer flask for later use. Place the coated ceramsite in the aforementioned nitrate solution and ultrasonically impregnate for 2 hours. After drying in an oven at 60°C, calcine it in a muffle furnace. The calcined ceramsite can then be used for ozone oxidation after air aging.

[0012] As a further aspect of the present invention, the metal oxide is a transition metal oxide.

[0013] As a further embodiment of the present invention: the metal oxide is any combination oxide of any two or more of iron, manganese, copper or cobalt, or an oxide of any one of them.

[0014] As a further embodiment of the present invention: in step two, the calcination time is 2h-4.5h.

[0015] More specifically, as a further aspect of the present invention: in step two, the calcination time is 2.5h-4h.

[0016] As a further aspect of the present invention: in step two, the calcination temperature is 300℃-450℃.

[0017] As a better technical solution: In step two, the calcination temperature is 350℃-400℃.

[0018] As a further aspect of the present invention, the diameter of the carrier is 3-5 mm.

[0019] As a further aspect of the present invention: the metal sol solution in step two is an aluminum sol solution.

[0020] Loading metal oxides onto catalyst supports not only significantly reduces material costs but also enhances oxidation reaction efficiency through synergistic effects between the support and active components, while maintaining high catalyst activity. Taking bio-ceramic particles as an example, this support, sintered at high temperatures, forms a rich hierarchical porous structure with uniform pore distribution and low density, exhibiting good permeability to gases and liquids, while also possessing corrosion resistance, high-temperature resistance, and structural stability. Compared to powdered catalysts prone to agglomeration and loss, ceramic-based catalysts offer advantages such as: their interconnected channels provide ample active sites to promote free radical generation, thereby improving ozone utilization; optimized loading methods can mitigate catalyst loss caused by fluid scouring; and ceramic particles have high mechanical strength and long service life, facilitating replacement and management in industrial reactors, thus demonstrating greater feasibility in engineering applications.

[0021] The beneficial effects of the present invention are as follows: 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. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 To investigate the effects of different metal loadings on COD removal efficiency in simulated wastewater, this study aims to compare the effects of various metal oxide combinations on COD removal and determine the optimal metal oxide combination.

[0024] Figure 2 To investigate the effect of different calcination times on COD removal efficiency in simulated wastewater, this study aims to compare the effects of calcination time on COD removal efficiency and determine the optimal calcination time.

[0025] Figure 3 To investigate the effect of different calcination temperatures on COD removal efficiency in simulated wastewater, this study aims to compare the effects of calcination temperature on COD removal efficiency and determine the optimal calcination temperature. Detailed Implementation

[0026] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be designed and arranged in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained 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 in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] An ozone catalyst supported on metal oxides was prepared in three main steps. Sufficient 3-5 mm uniform ceramsite (clay ceramsite was used in this experiment) was taken as a support, repeatedly washed with pure water, and then dried in an oven at 100℃. It was then ultrasonically cleaned for 1 hour each with 0.1 mol / L sodium hydroxide and hydrochloric acid. The ceramsite was then removed, ultrasonically cleaned and rinsed with pure water until the pH was neutral, and then dried to obtain pretreated bio-ceramsite.

[0028] The pretreated ceramsite was placed in a beaker and aluminum sol solution was added to completely immerse it. To enhance the coating effect, ultrasonic impregnation was performed for 60 minutes. Then, the ceramsite was dried at 60°C and calcined at 400°C. The coating-drying-calcining process was repeated multiple times until a significant color change was observed on the ceramsite, which turned light yellow and the coating did not peel off due to excessive thickness. At this point, the Al2O3 / ceramsite catalyst was considered complete.

[0029] A 250 mL (w / w) nitrate solution with a nitrate content of 5% was prepared as a precursor for the active ingredient and placed in an Erlenmeyer flask for later use. The coated ceramsite was then placed in the nitrate solution and ultrasonically impregnated for 2 hours. After drying in an oven at 60°C, it was calcined in a muffle furnace. The calcined ceramsite was then aged in air before being put into use for ozone oxidation.

[0030] This experiment investigated the effect of preparation conditions on catalyst activity by loading a certain amount of metal elements onto a bio-ceramic support using an impregnation-calcination method, and using phenol to simulate wastewater as the degradation target, and screened out catalysts with higher activity.

[0031] The main research conditions and design scheme are shown in Table 1:

[0032] Table 1: Obtaining the optimal solution through different experimental variables and level settings:

[0033]

[0034] like Figure 1 As shown, this experiment selected two of the transition metals iron (Fe), manganese (Mn), copper (Cu), and cobalt (Co) as active components and loaded them onto ceramsite. After calcination at 400℃ for 3.5 hours, all components existed in oxide form. A degradation experiment was conducted for 120 minutes under simulated wastewater conditions with an ozone flow rate of 0.2 L / min, a concentration of 20 mg / L, and an initial solution 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 also analyzed. It can be seen that after 120 minutes of reaction, compared with the removal rate of ozone oxidation alone (18.69%), the COD removal rate of the blank ceramsite carrier (19.36%) did not significantly increase. This is because the ceramsite is mainly composed of SiO2 with few surface functional groups, which is not conducive to the catalytic reaction.

[0035] After loading the active metal components Fe-Mn-Al2O3 / ceramsite, Fe-Cu-Al2O3 / ceramsite, CuMn-Al2O3 / ceramsite, and Co-Mn-Al2O3 / ceramsite, the COD removal efficiency was improved to varying degrees, increasing 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 generated from ozone molecules by different types of active metals, leading to certain differences in removal rates. Among them, the Fe-Mn supported catalyst exhibited the highest catalytic activity. Literature reports that Fe and Mn oxides have multiple valence states; after successful loading onto the surface and interior of the ceramsite support, they exist as metallic Fe... 3+ Fe 2+ Mn 3+ and Mn 2+ Existing in oxide form, and possessing more hydroxyl functional groups and oxygen vacancies, the electron transfer rate is faster. When ozone is introduced, the ozone gains electrons upon contact with the oxide, producing a highly oxidizing intermediate, promoting ozone decomposition, and thus enhancing the oxidation capacity of phenol. Furthermore, the advantages of iron and manganese as active components include: ① Fe and Mn are inexpensive, environmentally friendly, and readily available; 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+ The recycling of 100% of the material can enhance ozone decomposition; the introduction of Fe and Mn can generate new active sites and greatly improve conductivity; the rich pores of the ceramsite and the role of alumina sol can effectively inhibit the leaching of metal ions by fixing Fe and Mn oxides on the ceramsite, thereby improving the stability of the material.

[0036] like Figure 2 As shown, high-temperature calcination is a crucial step in catalyst activation; only through this process can the catalyst acquire the desired activity. During calcination, the salts introduced into the support during the impregnation stage are transformed into catalytically active oxides. This process is accompanied by the formation and distribution of catalyst grains, and the formation of active grains is a gradual and slow process. Insufficient calcination time leads to incomplete decomposition of salts and oxides, leaving impurities and moisture residues, and also affects the mechanical strength of the catalyst, reducing its industrial application value and reusability. However, excessively long calcination times are also detrimental, potentially causing the collapse of the support's pore structure and catalyst deactivation. Therefore, selecting an appropriate calcination time is crucial. In this experiment, Fe-Mn-Al2O3 / ceramsite catalyst was prepared at a calcination temperature of 400℃, with a reaction ozone concentration of 20 mg / L and an initial solution pH of 7.2. The effect of calcination conditions on catalyst performance is shown below. Figure 2 and Figure 3 As shown, both calcination time and temperature have a certain impact on COD removal rate. When the calcination time is 2.5 h, the COD removal rate is 38.53%, mainly because the calcination time is too short, and the process of metal nitrates gradually decomposing into highly active oxide crystals is not complete, resulting in insufficient active sites. When the calcination time is increased from 3 h to 3.5 h, the COD removal rate increases from 44.91% to 53.38%, at which point the metal salts on the catalyst surface are completely decomposed into oxide crystals, exhibiting high activity. When the calcination time is further extended to 4 h, the removal rate decreases by 2.31%, which is closely related to the masking of active sites and pore collapse caused by high-temperature sintering. Compared with the calcination time of 3.5 h, although the final degradation result of the catalyst calcined for 4 h is similar, the degradation effect shows a downward trend from the perspective of the entire reaction process, and the degradation efficiency is lower than that of the catalyst prepared by calcination for 3.5 h. Based on the balance between economy and degradation efficiency, 3.5 h was selected as the optimal calcination time.

[0037] 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 salt cannot be completely decomposed into oxides; when the calcination temperature is too high, the catalyst surface will sinter, thus reducing the active sites and adsorption sites. Calcination temperature is a key parameter for controlling catalyst activity. Experiments show that under the conditions of a fixed calcination time of 3 h, ozone flow rate of 0.2 L / min, ozone concentration of 20 mg / L, and initial pH of 7.2, the COD removal rate of the catalyst first increases and then decreases with increasing calcination temperature (300-450℃). When the temperature rises from 300℃ to 400℃, the metal hydroxide gradually decomposes into crystalline oxides (MnO2, Fe2O3), the density of active sites increases, and the COD removal rate increases from 45.24% to 52.78%. Among them, when the temperature rises to 350℃, oxides have been initially generated, and the removal rate increases to 48.64%; at 400℃, oxides have been generated and are evenly distributed on the surface of the carrier, and the activity reaches its highest level; however, when the temperature rises further to 450℃, the high-temperature sintering effect causes the carrier pores to collapse, oxide particles to agglomerate, the exposed area of ​​active sites to decrease sharply, and the COD removal rate drops.

[0038] In summary, using the catalyst disclosed in this application can effectively improve the efficiency of wastewater treatment, increase the utilization rate of the catalyst, reduce catalyst loss, and improve ozone utilization.

[0039] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An ozone catalyst supported on a metal oxide, characterized in that: The ozone catalyst includes a support; the support is a ceramic particle structure; specifically, it is a ceramic particle structure with a hierarchical porous structure; the contents of the support are metal oxides; more specifically, the metal oxides are transition metal oxides; the method for preparing the ozone catalyst supported on metal oxides specifically includes the following steps: Step 1: Carrier preparation: Take a sufficient amount of ceramsite as a carrier, wash it repeatedly with pure water and dry it in an oven. Clean it with sodium hydroxide and hydrochloric acid by ultrasound. Take out the ceramsite, clean it with pure water by ultrasound and rinse it. After rinsing until the pH is neutral, dry it to obtain pretreated bioceramsite. Step 2: Preparation of Ceramsite Catalyst: The pretreated ceramsite is placed in a beaker, and a metal sol solution is added to completely submerge it. To enhance the coating effect, ultrasonic impregnation is performed. Then, drying and calcination are carried out sequentially, and the coating-drying-calcination process is repeated multiple times until a significant color change is observed on the ceramsite, turning pale yellow, and the coating does not peel off due to excessive thickness. The ceramsite catalyst is then considered complete. In the calcination step, the calcination time is 2-4.5 hours; the calcination temperature is 300℃-450℃; the metal sol solution is an aluminum sol solution. Step 3, Catalyst Activation: Prepare a nitrate solution as a precursor for the active ingredient and place it in a container for later use; place the coated ceramsite in the above nitrate solution, ultrasonically impregnate it, dry it in an oven, and then calcine it in a muffle furnace. After calcination, the ceramsite can be used for ozone oxidation after aging in air.

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

3. The ozone catalyst supported on metal oxides according to claim 1, characterized in that: In step two, the calcination time is 2.5h-4h.

4. The ozone catalyst supported on a metal oxide according to claim 1, characterized in that: In step two, the calcination temperature is 350℃-400℃.

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

6. The application of an ozone catalyst supported on metal oxides as described in any one of claims 1 to 5 in wastewater treatment.

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