Multi-site ozone catalyst and its preparation method and application

Abstract

The present invention provides a multi-site ozone catalyst and a preparation method and application thereof, which belongs to the technical field of sewage treatment. The multi-site ozone catalyst preparation method comprises: adding a carbon-nitrogen precursor to water, and oxygenating the precursor through hydrothermal treatment to obtain an oxygen-doped precursor; then mixing the oxygen-doped precursor with a transition metal salt in an organic solvent, so that the transition metal salt is distributed on the surface of the oxygen-doped precursor to obtain a catalyst precursor; finally, calcining the catalyst precursor twice to form transition metal sites, nitrogen sites and oxygen sites on the surface of the catalyst precursor to obtain a multi-site ozone catalyst. Wherein, the nitrogen site is pyrrole nitrogen and / or pyridine nitrogen, the oxygen site is hydroxyl oxygen, and the transition metal site is a transition metal atom.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a multi-site ozone catalyst and a preparation method and application thereof. Background Art

[0002] Refractory organic pollutants are a prominent problem in water pollution control, and their harm has gradually increased with economic and industrial development. Some refractory organic pollutants are not only chemically stable and difficult to be biodegraded in the natural environment, but also toxic, with carcinogenic and teratogenic effects on organisms, seriously affecting human health. Therefore, it is imperative to reasonably and effectively treat refractory organic pollutants.

[0003] Ozone catalytic oxidation technology is an efficient and economical advanced oxidation technology for water treatment. It relies on the strong oxidizing and non-selective hydroxyl radicals produced by its catalysis to achieve rapid removal of difficult-to-degrade organic matter in water bodies. The core of this technology is the selection of ozone catalysts.

[0004] Common ozone catalysts include metal catalysts, heterogeneous catalysts and other types. However, due to the continuous development of economy and industry, the types of water pollutants have become more complex, and single-site catalysts have the risk of poisoning and failure, thereby reducing the efficiency of pollutant removal. Therefore, it is of far-reaching practical significance to find an ozone catalyst with high catalytic activity that can maintain efficient catalytic action in complex water bodies. Summary of the invention

[0005] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a method for preparing a multi-site ozone catalyst, the preparation method comprising: firstly, adding a carbon-nitrogen precursor to water, and then doping the carbon-nitrogen precursor with oxygen by hydrothermal treatment to obtain an oxygen-doped precursor; then, mixing the oxygen-doped precursor with a transition metal salt in an organic solvent, so that the transition metal salt is distributed on the surface of the oxygen-doped precursor, and obtaining a catalyst precursor; finally, calcining the catalyst precursor twice to form transition metal sites, nitrogen sites and oxygen sites on the surface of the catalyst precursor, and obtaining a multi-site ozone catalyst. Wherein, in the multi-site ozone catalyst, the nitrogen site is pyrrole nitrogen and / or pyridinic nitrogen, the oxygen site is hydroxyl oxygen, and the transition metal site is a transition metal atom.

[0006] According to an embodiment of the present invention, the two calcinations include: first calcining the catalyst precursor to fix the transition metal sites; and then second calcining the catalyst precursor after the first calcination to form nitrogen sites and oxygen sites and expose them on the surface of the multi-site ozone catalyst. The second calcination temperature of the second calcination is greater than the first calcination temperature of the first calcination.

[0007] According to an embodiment of the present invention, in the first calcination, the first calcination temperature is 350-500°C, the first calcination time is 1.5-5h, and the first calcination heating rate is 5-15°C / min; in the second calcination, the second calcination temperature is 700-900°C, the second calcination time is 1.5-5h, and the second calcination heating rate is 5-15°C / min.

[0008] According to an embodiment of the present invention, in the hydrothermal treatment, the reaction temperature is 150-200° C., and the insulation time is 6-24 h.

[0009] According to an embodiment of the present invention, the carbon-nitrogen precursor includes at least one of melamine, dicyandiamide and urea.

[0010] According to an embodiment of the present invention, the transition metal salt includes at least one of ferric chloride, manganese chloride, nickel chloride, cupric chloride, cobalt chloride, ferric nitrate, manganese nitrate, nickel nitrate, copper nitrate, cobalt nitrate, ferric acetate, manganese acetate, nickel acetate, copper acetate, and cobalt acetate; and the organic solvent includes ethanol.

[0011] According to an embodiment of the present invention, the mass ratio of the oxygen-doped precursor to the transition metal salt is 1:(0.1-1).

[0012] According to an embodiment of the present invention, the oxygen-doped precursor and the transition metal salt are mixed in an organic solvent by stirring, and the stirring time is 12-48 hours.

[0013] In another aspect of the present invention, a multi-site ozone catalyst obtained by the above-mentioned preparation method is provided. The multi-site ozone catalyst uses a carbon-based material as a carrier, and the surface of the carbon-based material exposes oxygen sites, nitrogen sites and transition metal sites with ozone catalytic activity.

[0014] In another aspect of the present invention, the application of the aforementioned multi-site ozone catalyst in sewage treatment is proposed.

[0015] According to the embodiment of the present invention, the present invention first uses water as a medium to dope oxygen into a carbon-nitrogen precursor through a hydrothermal reaction; then, through the self-assembly effect of a transition metal salt solution, the loading of the transition metal salt on the surface of the oxygen-doped precursor is achieved; further, through two calcination reactions, the conversion of the catalytic site is achieved and fixed on the surface of the carbon material, thereby obtaining a multi-site ozone catalyst. The preparation process is safe and non-toxic, and efficiently realizes the formation and coordination of transition metal sites, nitrogen sites, and oxygen sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0017] Figure 1The flowchart of the preparation method of the multi-site ozone catalyst in the embodiment of the present invention is shown;

[0018] Figure 2 The X-ray photoelectron spectroscopy (XPS) of the 1s electrons of carbon in the multi-site ozone catalysts prepared in Example 1 and Example 3 of the present invention is shown;

[0019] Figure 3 The X-ray diffraction patterns of the multi-site ozone catalysts prepared in Example 1 and Example 4 of the present invention are shown;

[0020] Figure 4 The degradation rate curve of oxalic acid degradation by Examples 1-4 of the present invention and the mixed catalyst is shown;

[0021] Figure 5 The degradation rate curves of oxalic acid degradation in Example 1 and Examples 5-9 of the present invention are shown. DETAILED DESCRIPTION

[0022] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0023] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0024] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. If the full text involves descriptions such as "first", "second", etc., the descriptions such as "first", "second", etc. are only used to distinguish similar objects, and cannot be understood as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data described by "first", "second", etc. can be interchangeable under appropriate circumstances.

[0027] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] In the process of realizing the concept of the present invention, it was found that common active sites of ozone catalysts include surface hydroxyl groups, pyridinic nitrogen, pyrrolic nitrogen and transition metal sites, which correspond to different catalytic pathways. The present invention integrates multiple catalytic active sites onto the same carrier to achieve multi-site synergistic catalysis.

[0029] Figure 1 The flowchart of the preparation of the multi-site ozone catalyst in the embodiment of the present invention is shown.

[0030] Specifically, according to an embodiment of one aspect of the present invention, a method for preparing a multi-site ozone catalyst is provided, such as Figure 1 As shown, the preparation method includes the following steps S101-S103.

[0031] Step S101: adding a carbon-nitrogen precursor into water, and performing a hydrothermal treatment to dope the carbon-nitrogen precursor with oxygen to obtain an oxygen-doped precursor.

[0032] Step S102: mixing the oxygen-doped precursor and the transition metal salt in an organic solvent so that the transition metal salt is distributed on the surface of the oxygen-doped precursor to obtain a catalyst precursor.

[0033] Step S103: calcining the catalyst precursor twice to form transition metal sites, nitrogen sites and oxygen sites on the surface of the catalyst precursor to obtain a multi-site ozone catalyst, wherein the nitrogen site in the multi-site ozone catalyst is pyrrolic nitrogen and / or pyridinic nitrogen, the oxygen site is hydroxyl oxygen, and the transition metal site is a transition metal atom.

[0034] According to the embodiments of the present invention, the present invention first uses water as a medium to dope oxygen into a carbon-nitrogen precursor through a hydrothermal reaction; then, through the self-assembly effect of a transition metal salt solution, the loading of the transition metal salt on the surface of the oxygen-doped precursor is achieved; further, through two calcination reactions, the conversion of the catalytic site is achieved and fixed on the surface of the carbon material, thereby obtaining a multi-site ozone catalyst. The preparation process of the present invention is safe and non-toxic, and efficiently realizes the formation and coordination of transition metal sites, nitrogen sites and oxygen sites.

[0035] In some specific embodiments, step S101 further includes, after the oxygen-doped precursor is cooled, washing, filtering and drying it with pure water.

[0036] In some specific embodiments, step S103 further includes filtering and washing the catalyst precursor after the first calcination to remove the transition metal salt that is not combined with the oxygen-doped precursor.

[0037] According to an embodiment of the present invention, in step S103, the two calcinations include: first calcining the catalyst precursor to fix the transition metal sites; and then second calcining the catalyst precursor after the first calcination to form nitrogen sites and oxygen sites and expose them on the surface of the multi-site ozone catalyst. The second calcination temperature of the second calcination is greater than the first calcination temperature of the first calcination.

[0038] According to an embodiment of the present invention, the purpose of the first calcination is, on the one hand, to decompose the residual solvent on the surface of the catalyst precursor; on the other hand, the catalyst precursor is thermally polymerized by calcination to form a graphite phase carbon nitride structure, so that the transition metal site is in the form of an atom, and the nitrogen and oxygen atoms in the catalyst precursor are coordinated and bonded, thereby fixing the transition metal site. The purpose of the second calcination is to decompose and carbonize the graphite phase carbon nitride matrix structure formed after the first calcination, thereby forming a carbon-based material matrix. This transformation is beneficial to the exposure of the active sites (transition metal sites, nitrogen sites and oxygen sites) inside the carbon-based material to the surface of the multi-site ozone catalyst through polymer polycondensation, thereby improving the catalytic ozone activity of the multi-site ozone catalyst; on the other hand, the graphitization degree of the carbon-based material is higher, so that the multi-site ozone catalyst has better stability in the strong oxidizing environment of ozone, and ensures the long-lasting catalytic activity of the multi-site ozone catalyst in wastewater treatment.

[0039] According to an embodiment of the present invention, in the first calcination, the first calcination temperature is 350-500°C, for example, 350°C, 370°C, 390°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, etc., the first calcination time is 1.5-5h, for example, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc., the first calcination heating rate is 5-15°C / min, for example, 5°C / min, 7°C / min, 9°C / min, 11°C / min, 13°C / min, 15°C / min, etc.; In the second calcination, the second calcination temperature is 700-900°C, for example, it can be 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, etc., the second calcination time is 1.5-5h, for example, it can be selected from 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc., the second calcination heating rate is 5-15°C / min, for example, it can be 5°C / min, 7°C / min, 9°C / min, 11°C / min, 13°C / min, 15°C / min, etc.

[0040] According to an embodiment of the present invention, the first calcination temperature is in the range of 350-500°C so that the carbon and nitrogen compounds in the oxygen-doped precursor are converted into graphite phase carbon nitride, and the transition metal sites are fixed at the same time. Too high a temperature will make the transition metal temperature fixation unstable, thereby reducing the stability and catalytic efficiency of the multi-site ozone catalyst. The second calcination temperature is in the range of 700-900°C so that the graphite phase carbon nitride formed by the first calcination is converted into a carbon-based material. Within this range, the catalytic effect of the multi-site ozone catalyst increases with the increase of the second calcination temperature. At the same time, the heating rate during the calcination process also affects the catalytic efficiency of the multi-site ozone catalyst. Specifically, the catalytic effect of the multi-site ozone catalyst increases with the increase of the heating rate.

[0041] According to an embodiment of the present invention, in the hydrothermal treatment of step S101, the reaction temperature is 150-200°C, for example, it can be selected as 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the insulation time is 6-24h, for example, it can be selected as 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, etc.

[0042] According to an embodiment of the present invention, during the hydrothermal process, under the influence of high temperature (greater than 100°C) and high pressure (greater than standard pressure), some CN bonds in the carbon-nitrogen precursor are broken, and the oxygen atoms in the water are bonded to the carbon in the carbon-nitrogen precursor, thereby achieving oxygen doping. The advantage of this process is that the hydrothermal solvent is changed from a traditional organic solvent to water, which improves the process safety and reduces the production cost.

[0043] According to an embodiment of the present invention, the carbon-nitrogen precursor includes at least one of melamine, dicyandiamide and urea.

[0044] According to the embodiment of the present invention, melamine, dicyandiamide and urea are rich in a large number of CN bonds, and thus can provide a large number of oxygen atom incorporation connection sites during the hydrothermal process.

[0045] According to an embodiment of the present invention, the transition metal salt includes at least one of ferric chloride, manganese chloride, nickel chloride, cupric chloride, cobalt chloride, ferric nitrate, manganese nitrate, nickel nitrate, copper nitrate, cobalt nitrate, ferric acetate, manganese acetate, nickel acetate, copper acetate, and cobalt acetate; and the organic solvent includes ethanol.

[0046] According to an embodiment of the present invention, the mass ratio of the oxygen-doped precursor to the transition metal salt is 1:(0.1-1), for example, it can be selected as 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:0.9, 1:1, etc.

[0047] According to an embodiment of the present invention, in step S102, the oxygen-doped precursor and the transition metal salt are mixed in an organic solvent by stirring, and the stirring time is 12-48 hours.

[0048] According to an embodiment of the present invention, after the oxygen-doped precursor and the transition metal salt are mixed in an organic solvent, the transition metal salt is self-assembled and distributed on the surface of the oxygen-doped precursor in the form of a metal salt, and is connected in the form of non-covalent bonds to form an ordered catalyst precursor; wherein, stirring makes the distribution of the metal salt more uniform.

[0049] Specifically, in another aspect of the present invention, a multi-site ozone catalyst obtained by the above-mentioned preparation method is proposed. The multi-site ozone catalyst uses a carbon-based material as a carrier, and the surface of the carbon-based material exposes oxygen sites, nitrogen sites and transition metal sites with ozone catalytic activity.

[0050] According to an embodiment of the present invention, the present invention uses a carbon-based material as a carrier, and introduces oxygen sites, nitrogen sites and transition metal sites on its surface. Among them, through the synergistic effect of the three, the catalytic ozone activity is jointly improved. Specifically: the oxygen site provides surface hydroxyl groups to catalyze ozone while also providing electrons for the transition metal site, thereby synergistically improving the transition metal catalytic activity; nitrogen sites, such as pyrrole nitrogen, pyridine nitrogen, etc., as catalytic ozone sites, and due to the electrophilicity of the nitrogen site, it can provide a bonding effect with the transition metal site to fix the transition metal site, thereby reducing the leaching rate of the multi-site ozone catalyst and improving the stability of the multi-site ozone catalyst; in addition to its own catalytic ozone activity, the transition metal site can also transfer electrons with the oxygen site and the nitrogen site to improve the catalytic efficiency.

[0051] Specifically, in another aspect of the present invention, the application of the aforementioned multi-site ozone catalyst in sewage treatment is proposed.

[0052] According to an embodiment of the present invention, multiple catalytic sites can catalyze ozone to produce hydroxyl radicals, which have the advantages of strong oxidizing properties and non-selectivity, and can quickly remove difficult-to-degrade organic pollutants in complex water bodies, such as oxalic acid, thereby solving the problems of single sites, easy poisoning and poor stability of existing ozone catalysts, and meeting the treatment needs of difficult-to-degrade organic pollutants in complex water bodies.

[0053] It should be noted that the embodiments described below are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0054] Example 1

[0055] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0056] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0057] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0058] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace. The temperature was raised to 850°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-Co.

[0059] Example 2

[0060] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0061] The dried oxygen-doped precursor was placed in a tube furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalytic material.

[0062] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace, and heated to 850°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN.

[0063] Example 3

[0064] Weigh 1g of melamine and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of 1g of melamine to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0065] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0066] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace, and heated to 850°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as CN-Co.

[0067] Example 4

[0068] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0069] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0070] The dried catalyst precursor was placed in a tube furnace, heated to 500°C at a heating rate of 10°C / min, and calcined for 2 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-1-Co.

[0071] Example 5

[0072] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0073] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate and copper acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate and copper acetate is 1:0.05:0.05. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0074] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0075] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace, and heated to 850°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, recorded as OCN-Co-Cu.

[0076] Example 6

[0077] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0078] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0079] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0080] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace. The temperature was raised to 750°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-Co-750.

[0081] Example 7

[0082] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0083] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0084] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0085] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace. The temperature was raised to 800°C at a heating rate of 10°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-Co-800.

[0086] Example 8

[0087] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0088] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0089] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0090] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace. The temperature was raised to 850°C at a heating rate of 5°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-Co-5.

[0091] Example 9

[0092] Add 1g of melamine as a carbon-nitrogen precursor to 60ml of water, stir thoroughly, and transfer to a 100ml hydrothermal kettle, and heat at 180°C for 18h to perform a hydrothermal reaction to obtain an oxygen-doped precursor. After the reaction is cooled, the oxygen-doped precursor is filtered and washed with pure water, and dried for later use.

[0093] Weigh 1g of oxygen-doped precursor and disperse it in 20ml of ethanol solution. After fully dispersing, add cobalt acetate to obtain a self-organized mixed solution. The mass ratio of oxygen-doped precursor to cobalt acetate is 1:0.1. Stir at room temperature for 36h, then centrifuge the self-organized mixed solution to obtain a catalyst precursor.

[0094] The dried catalyst precursor was placed in a tubular furnace, heated to 500° C. at a heating rate of 10° C. / min, and subjected to a first calcination treatment for 2 h to obtain a primary catalyst.

[0095] The primary catalyst was filtered, washed, dried, and placed in a tubular furnace. The temperature was raised to 850°C at a heating rate of 15°C / min for a second calcination treatment for 3 hours to obtain a multi-site ozone catalyst, which was recorded as OCN-Co-15.

[0096] Performance Testing

[0097] Catalysts prepared in Examples 1-9 and a mixed catalyst (the mixed catalyst includes the OCN catalyst prepared in Example 2 and the CN-Co-1 prepared in Example 3 mixed in a mass ratio of 1:1, denoted as OCN-CN-Co-mixed) were used to treat water pollutants using catalytic ozone technology.

[0098] The operation of catalytic ozone technology to treat difficult-to-degrade organic pollutants in water is as follows:

[0099] The degradation environment was an ozone atmosphere with a concentration of 0.15 g / L, and oxalic acid was selected as the difficult-to-degrade organic pollutant with a concentration of 100 mg / L. During the degradation process, the dosage of the multi-site ozone catalyst was 0.1 g / L, and the treatment time was 30 min.

[0100] Figure 2 The X-ray photoelectron spectra (XPS) of 1s electrons of carbon in the multi-site ozone catalysts prepared in Examples 1 and 3 of the present invention are shown.

[0101] like Figure 2 As shown, the results show that after the hydrothermal oxygen doping process, the XPS C1s spectrum of OCN-Co splits the characteristic peak of the CO bond, while the non-hydrothermal material CN-Co has no such characteristic peak, indicating that the hydrothermal method can achieve oxygen doping of the carbon-nitrogen precursor.

[0102] Figure 3 The X-ray diffraction patterns of the multi-site ozone catalysts prepared in Example 1 and Example 4 of the present invention are shown.

[0103] like Figure 3 As shown, the results show that the structure of the material OCN-1-Co after the first calcination is still based on graphite phase carbon nitride (there are characteristic peaks of graphite phase carbon nitride), while after the second high-temperature calcination, Figure 3 The characteristic peak of graphite phase carbon nitride disappears, indicating that the material transforms from graphitized carbon nitride to carbon material, which is significantly different from the graphite phase carbon nitride matrix.

[0104] Figure 4 The degradation rate curves of oxalic acid degradation by Examples 1-4 of the present invention and the mixed catalyst are shown.

[0105] like Figure 4 As shown, the treatment effect of ozone atmosphere alone on oxalic acid is not good; in the OCN catalyst experimental group and the CN-Co catalyst experimental group, the oxalic acid degradation efficiency is improved to varying degrees; the oxalic acid degradation efficiency of the OCN-Co experimental group is significantly improved, and its catalytic effect is significantly higher than that of the OCN and CN-Co catalysts. This shows that the OCN-Co multi-site ozone catalyst has excellent catalytic ozone activity and can achieve rapid removal of difficult-to-degrade organic matter in water.

[0106] In addition, the treatment effect of OCN-Co catalyst is better than that of mixed catalyst, which further confirms that there is a synergistic effect among oxygen sites, nitrogen sites and transition metal sites in OCN-Co material, which significantly improves the catalytic activity and realizes efficient treatment of pollutants.

[0107] Figure 5 The degradation rate curve of oxalic acid degradation by the catalyst in Example 1 and Examples 5-9 of the present invention is shown.

[0108] Depend on Figure 5 It can be seen that the treatment effect of the double transition metal catalyst OCN-Co-Cu is slightly lower than that of the OCN-Co material, but it also proves that it has a higher catalytic ozone activity.

[0109] Furthermore, the treatment effects of the catalysts prepared by different calcination procedures showed that the treatment effect of the catalysts improved with the increase of calcination temperature, among which the material prepared at 850°C had the highest catalytic ozone activity. The treatment effects of the materials prepared by different heating rates showed that the multi-site ozone catalysts prepared at 10°C / min and 15°C / min had the best catalytic effect.

[0110] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multi-site ozone catalyst, characterized in that: The preparation method comprises: Adding a carbon-nitrogen precursor into water, and performing a hydrothermal treatment to dope the carbon-nitrogen precursor with oxygen to obtain an oxygen-doped precursor; Mixing the oxygen-doped precursor and a transition metal salt in an organic solvent so that the transition metal salt is distributed on the surface of the oxygen-doped precursor to obtain a catalyst precursor; calcining the catalyst precursor twice to form transition metal sites, nitrogen sites and oxygen sites on the surface of the catalyst precursor to obtain a multi-site ozone catalyst; Wherein, the nitrogen site is pyrrolic nitrogen and / or pyridinic nitrogen, the oxygen site is hydroxyl oxygen, and the transition metal site is a transition metal atom.

2. The preparation method according to claim 1, characterized in that: The two calcinations include: calcining the catalyst precursor for the first time to fix the transition metal sites; calcining the catalyst precursor after the first calcination for a second time to achieve the formation of the nitrogen site and the oxygen site and the exposure of the nitrogen site and the oxygen site on the surface of the multi-site ozone catalyst; Wherein, the second calcination temperature of the second calcination is greater than the first calcination temperature of the first calcination.

3. The preparation method according to claim 2, characterized in that: In the first calcination, the first calcination temperature is 350-500° C., the first calcination time is 1.5-5 h, and the first calcination heating rate is 5-15° C. / min; In the second calcination, the second calcination temperature is 700-900° C., the second calcination time is 1.5-5 h, and the second calcination heating rate is 5-15° C. / min.

4. The preparation method according to claim 1, characterized in that: In the hydrothermal treatment, the reaction temperature is 150-200° C. and the insulation time is 6-24 hours.

5. The preparation method according to claim 1, characterized in that: The carbon-nitrogen precursor includes at least one of melamine, dicyandiamide and urea.

6. The preparation method according to claim 1, characterized in that: The transition metal salt includes at least one of ferric chloride, manganese chloride, nickel chloride, cupric chloride, cobalt chloride, ferric nitrate, manganese nitrate, nickel nitrate, copper nitrate, cobalt nitrate, ferric acetate, manganese acetate, nickel acetate, copper acetate, and cobalt acetate; The organic solvent includes ethanol.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the oxygen-doped precursor to the transition metal salt is 1:(0.1-1).

8. The preparation method according to claim 1, characterized in that: The oxygen-doped precursor and the transition metal salt are mixed in the organic solvent by stirring, and the stirring time is 12-48 hours.

9. A multi-site ozone catalyst obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The multi-site ozone catalyst uses a carbon-based material as a carrier, and the surface of the carbon-based material exposes oxygen sites, nitrogen sites and transition metal sites with ozone catalytic activity.

10. Use of the multi-site ozone catalyst as claimed in claim 9 in sewage treatment.

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