A sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst, its preparation method and its application

Abstract

The application discloses a kind of sulfur-modified mesoporous carbon confined loading Fe3O4 heterogeneous catalyst, preparation method and application, belong to sewage treatment technical field.The catalyst includes: carbon carrier, with the mesoporous channel of pore size 3-4nm, sulfur element is doped in the carbon carrier;And active component: Fe3O4 in the mesoporous channel of the carbon carrier distribution.This application with hard template with uniform mesoporous structure as foundation, utilize its mesoporous characteristics to make metal salt and organic matter pyrolysis under confined condition, obtain sulfur-modified mesoporous carbon material, sulfur doping can cause mesoporous carbon structural defect influence carbon layer structure electron arrangement, carbon layer structure defect is further regulated by charge transmission between Fe3O4 and the content of Fe3O4 oxygen vacancy confined therein, effectively promote iron oxide surface iron valence state cycle, to improve oxidation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and more specifically, relates to a sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, iron-based heterogeneous catalysts have been widely used in advanced oxidation processes due to their wide applicability, low cost, and lack of iron sludge generation. The application of iron oxides such as hematite, goethite, and magnetite in heterogeneous Fenton oxidation has garnered increasing attention. However, in practical applications, iron oxide particles tend to agglomerate, leading to insufficient exposure of active sites. Furthermore, the slow iron cycling on their surface severely limits the efficient and stable use of the catalyst in the Fenton oxidation process. In addition, traditional iron-based heterogeneous Fenton oxidation primarily generates non-selective free radicals, which are easily interfered with by inorganic anions and readily degradable dissolved organic matter when dealing with multi-polluting chemical wastewater, resulting in a decrease in the removal efficiency of characteristic pollutants in the water. Therefore, developing highly efficient, stable iron oxide catalysts with strong anti-interference capabilities is of great significance for the application of iron-based heterogeneous catalysts in practical wastewater treatment.

[0003] To improve the surface active sites of iron oxides, iron oxide particles are generally loaded onto a carrier. Common carriers include graphene oxide and porous carbon materials. These carriers utilize a large specific surface area to disperse iron oxides and reduce their agglomeration. However, when the content of iron oxides is high, it is difficult to avoid agglomeration of the dispersed iron oxides. Furthermore, the conversion efficiency of Fe(III) to Fe(II) in heterogeneous reaction systems is low, and the problem of low surface iron recycling efficiency cannot be effectively improved by increasing the dispersibility of iron oxides.

[0004] Therefore, there is an urgent need to develop an iron oxide catalyst with high surface iron recycling efficiency. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the problems of insufficient exposure of metal active sites and low surface iron recycling efficiency in existing iron oxide catalysts during heterogeneous Fenton oxidation, the first aspect of this invention provides a sulfur-modified mesoporous carbon-confined supported Fe3O4 catalyst.

[0007] The second aspect provides a method for preparing the above-mentioned sulfur-modified mesoporous carbon-confined supported Fe3O4 catalyst;

[0008] The third aspect provides the application of the aforementioned sulfur-modified mesoporous carbon-confined supported Fe3O4 catalyst.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A first aspect of the present invention provides a sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst, comprising:

[0012] A carbon support having mesoporous channels with a pore size of 3-4 nm, in which sulfur is doped;

[0013] Active component: Fe3O4 distributed in the mesoporous channels of the carbon support.

[0014] Based on the elemental ratio, the weight ratio of sulfur to carbon is (0.01-2.36):(70.25-90.45), preferably (0.1-0.84):(70.25-90.45); the weight ratio of Fe3O4 to carbon support is (5.25-32.75):(70.25-90.45).

[0015] The heterogeneous catalyst has an oxygen vacancy concentration of 33.93%-58.25% by mole fraction.

[0016] When the heterogeneous catalyst was analyzed by Raman spectroscopy, carbon defect I was observed. D / I G The ratio is 2.80~3.32.

[0017] In any embodiment of the first aspect of the invention, the sulfur element is doped into the carbon support by CSC bonding.

[0018] According to any embodiment of the first aspect of the present invention, the Fe3O4 is a nanoflower structure distributed in the mesoporous channels of a carbon support, and the particle size of the Fe3O4 is 100-150 nm.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst, comprising the following steps:

[0020] S1. Ingredients: Dissolve raw materials containing carbon source, sulfur source and iron source in dispersion medium to prepare precursor solution;

[0021] S2, Vacuum induction: The precursor solution obtained in step S1 is mixed evenly with the template agent under vacuum conditions and then dried;

[0022] S3. Pyrolysis: The material obtained in step S2 is calcined under the protection of an inert gas.

[0023] S4. Remove the template agent to obtain a mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst.

[0024] In any embodiment of the second aspect of the present invention, in step S1, the carbon source can be any substance with two or more phenolic hydroxyl groups, which utilizes the reduction reaction between phenolic hydroxyl groups and ferric iron to form ferrous iron, so that the substances are linked by ferric bonds, preferably phenolphthalein;

[0025] The preferred sulfur source is sodium poly(p-styrene sulfonate). During the pyrolysis of the polymer, the sulfonic acid groups are released more slowly, which can ensure that the sulfur atoms are more uniformly doped in the carbon layer.

[0026] The preferred iron source is ferric chloride. In addition, ferric nitrate and ferric sulfate can also be used to provide the iron source.

[0027] According to any embodiment of the second aspect of the present invention, in step S1, the weight ratio of the carbon source, sulfur source and iron source is (10-100):(1-200):(5-30).

[0028] According to any embodiment of the second aspect of the present invention, in step S1, the dispersion medium is a mixed solution of deionized water and ethanol, wherein the volume ratio of deionized water to ethanol can be any ratio to achieve the dissolution of the raw materials, for example (0-10):(0-10); preferably (1-5):(5-10), more preferably (1-3):(5-7), and more preferably, the volume ratio of deionized water to ethanol is 1:6.

[0029] According to any embodiment of the second aspect of the present invention, in step S2, the template agent is a template agent with a uniform mesoporous structure, preferably a hard template agent, such as SiO2 or Al2O3 with a uniform mesoporous structure, and the amount of template agent added is satisfied by mass ratio as follows: the weight ratio of carbon source, sulfur source, iron source and template agent is (10-100):(1-200):(5-30):(200-800).

[0030] According to any embodiment of the second aspect of the present invention, in step S2, the precursor solution obtained in step S1 is mixed with the template agent under vacuum conditions and shaken evenly. After ultrasonically vibrating the mixture for 10-30 min, it is dried at 30-80°C for 10-15 h. By mixing the precursor solution with the template agent under vacuum conditions, the precursor solution enters the mesoporous channels of the template agent.

[0031] In any embodiment of the second aspect of the present invention, in step S3, the inert gas is argon, and other inert gases such as nitrogen and helium may also be used as protective gases.

[0032] According to any embodiment of the second aspect of the present invention, in step S3, the calcination temperature is 600-1000℃, preferably 650℃-950℃, the calcination holding time is 2-5h, and the heating rate is 2-5℃ / min.

[0033] According to any embodiment of the second aspect of the present invention, in step S4, the template agent is removed, and the material obtained in step S3 is etched using an alkaline solution. Preferably, when SiO2 is used as the hard template agent, the material obtained in step S3 is dispersed in a 1-5 mol / L sodium hydroxide solution, stirred in a water bath at 50-80°C for 5-20 h, then the mixture is rinsed with deionized water until pH=7, and then dried at 30-80°C.

[0034] In any embodiment of the second aspect of the present invention, in step S4, when Al2O3 is used as a hard template agent, its removal method refers to the removal method of SiO2.

[0035] A third aspect of the present invention provides an application of a sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst, as described in the first aspect of the present invention, for treating electron-rich pollutants.

[0036] According to any embodiment of the third aspect of the present invention, the electron-rich pollutant is a sulfonamide organic compound or a phenolic organic compound.

[0037] The sulfonamides mentioned can be sulfamethoxazole, or sulfadiazine, sulfisoxazole, sulfadiazine, sulfasalazine, sulfasalazine, and other sulfonamide pollutants.

[0038] The phenols can be phenol, or electron-rich phenolic pollutants such as chlorophenol, bromophenol, and bisphenol A.

[0039] This catalyst is particularly suitable for treating electron-rich pollutants in complex organic wastewater systems.

[0040] Alternatively, in one possible implementation of the third aspect, the initial catalyst dosage is 0.1-1 g / L, and the persulfate dosage is 0.06-1 g / L.

[0041] This method prepares a catalyst using mesoporous silica as a template. The oxygen vacancy content in Fe3O4 nanoflowers is simultaneously controlled through the mesoporous confinement effect and in-situ sulfur doping, forming a heterogeneous catalyst with mesoporous carbon-confined Fe3O4. On one hand, the dispersion of Fe3O4 by sulfur-modified mesoporous carbon promotes the exposure of its surface active sites, effectively solving the problem of mutual coverage of active sites. Simultaneously, the oxygen vacancies formed by the mesoporous confinement effectively promote the valence state cycling of iron, enabling electron transfer between the catalyst, oxidant, and contaminants. On the other hand, sulfur doping on the mesoporous carbon creates structural defects, affecting the electron configuration of the carbon layer structure. These defects further regulate the oxygen vacancy content confined within the Fe3O4 through charge transport with Fe3O4, enhancing the catalyst's surface activity. Through the synergistic effect of sulfur modification and oxygen vacancies, pollutants are degraded via a non-radical pathway of direct electron transfer during the induced persulfate activation process, unaffected by ions in water and dissolved organic matter, thus improving the catalyst's resistance to environmental interference.

[0042] 3. Beneficial effects

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] Firstly, the sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst provided by this invention:

[0045] (1) When Fe3O4 is loaded on sulfur-modified mesoporous carbon materials, the confined environment of mesoporous carbon can promote the generation of low-valence iron and oxygen vacancies. Sulfur doping will cause defects in the mesoporous carbon structure, affecting the electronic arrangement of the carbon layer structure. The defects in the carbon layer structure further regulate the content of oxygen vacancies in Fe3O4 through charge transport between Fe3O4 and Fe3O4, effectively promoting the cycling of iron valence states on the surface of iron oxides, thereby promoting oxidation efficiency.

[0046] (2) Fe3O4 forms a nanoflower structure in the mesoporous channels of the carbon support, which prevents Fe3O4 from agglomerating. Fe3O4 is evenly distributed in the mesoporous channels of the carbon material, exposing more active sites.

[0047] Secondly, the preparation method of the sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst provided by the present invention:

[0048] (1) Based on a hard template agent with mesoporous channels, the metal salt and organic matter are pyrolyzed under confined conditions using its mesoporous properties to obtain sulfur-modified mesoporous carbon materials. The confined environment can promote the generation of low-valence iron and oxygen vacancies. Sulfur doping will cause defects in the mesoporous carbon structure. The carbon defects further regulate the content of oxygen vacancies in the confined Fe3O4 through charge transport with Fe3O4, effectively promoting the cycling of iron valence state on the surface of iron oxide, thereby promoting oxidation efficiency.

[0049] (2) By controlling the oxygen vacancies in Fe3O4 through calcination temperature and sulfur doping, the iron valence state on the surface of iron oxides can be effectively promoted, thereby improving oxidation efficiency.

[0050] Thirdly, the application of the sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst provided by this invention:

[0051] (1) The prepared catalyst was applied to the degradation of electron-rich pollutants by persulfate. The synergistic catalytic effect of sulfur modification and oxygen vacancies was utilized to effectively regulate the direct electron transfer process of oxygen vacancies, thereby effectively ensuring the overall activity and long-term stable use of the catalyst.

[0052] (2) The prepared catalyst was applied to the degradation of water pollutants by persulfate, especially multi-pollutant chemical wastewater. The non-radical pathway that mediates the direct electron transfer reaction from persulfate to pollutants was used to degrade the pollutants. It was not affected by other pollutants and ions, and effectively improved the degradation efficiency of characteristic pollutants under the interference of various organic substances and anions.

[0053] (3) The mesoporous confinement space formed inside the catalyst is used to effectively enrich pollutants, thereby ensuring efficient electron transfer. Attached Figure Description

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0055] Figure 1 TEM images of Fe3O4@SMC prepared in Example 1, (a) 200 nm, (b) 100 nm;

[0056] Figure 2 The image shows the EDS characterization of Fe3O4@SMC prepared in Example 1, where (a) green represents C, (b) red represents Fe, (c) purple represents O, and (d) yellow represents S.

[0057] Figure 3 The XRD patterns of Fe3O4@SMC prepared in Example 1, Fe3O4@SC prepared in Comparative Example 1, Fe3O4@MC prepared in Comparative Example 2, SMC prepared in Comparative Example 3, and Fe3O4 prepared in Comparative Example 4 are shown.

[0058] Figure 4The BET adsorption curves are for Fe3O4@SMC prepared in Example 1, Fe3O4@SC prepared in Comparative Example 1, Fe3O4@MC prepared in Comparative Example 2, SMC prepared in Comparative Example 3, and Fe3O4 prepared in Comparative Example 4.

[0059] Figure 5 EPR spectra of Fe3O4@SMC prepared in Example 1, Fe3O4@SC prepared in Comparative Example 1, Fe3O4@MC prepared in Comparative Example 2, and Fe3O4 prepared in Comparative Example 4.

[0060] Figure 6 XPS plots (a) and Raman plots (b) of the sulfur source catalysts with different contents in Examples 1-5 are shown, where I D / I G D - Peak and G - Peak intensity ratio, D - Peaks represent lattice defects, I D / I G值 The larger the carbon atom, the more defects the carbon crystal has; O surf For surface oxygen, O ads To adsorb oxygen, O latt It is lattice oxygen;

[0061] Figure 7 XPS (a) and Raman (b) plots of catalysts from Examples 1, 5, 6-8 at different calcination temperatures.

[0062] Figure 8 The degradation effect of Fe3O4@SMC prepared in Example 1 on different pollutants in organic wastewater is shown in the figure. SMX is sulfamethoxazole, NB is nitrobenzene, BA is benzoic acid, and ATZ is atrazine.

[0063] Figure 9 Examples 1-5 illustrate the degradation effects of Fe3O4@SMC with different sulfur contents on sulfamethoxazole.

[0064] Figure 10 To investigate the degradation effects of different quenchers on sulfamethoxazole, FFA was tert-butanol, TBA was furfuryl alcohol, MeOH was methanol, and K2Cr2O7 was potassium dichromate.

[0065] Figure 11 The degradation effects of Fe3O4@SMC prepared in Example 1, Fe3O4@SC prepared in Comparative Example 1, Fe3O4@MC prepared in Comparative Example 2, and SMC prepared in Comparative Example 3 on sulfamethoxazole are shown.

[0066] Figure 12The degradation effect of Fe3O4@SMC obtained by different calcination temperatures on sulfamethoxazole is shown in Examples 1, 6-8 and Comparative Example 5.

[0067] Figure 13 The cycling effect of Fe3O4@SMC prepared in Example 1 on sulfamethoxazole;

[0068] Figure 14 The degradation effect of Fe3O4@SMC prepared in Example 1 on sulfamethoxazole under different pH conditions;

[0069] Figure 15 The degradation effect of Fe3O4@SMC prepared in Example 1 on sulfamethoxazole under different ion interference conditions is shown. Detailed Implementation

[0070] This disclosure will be more readily understood by referring to the following description, taken in conjunction with the accompanying drawings and examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0071] It should also be understood that, for clarity, certain features of this disclosure may be described herein in the context of individual embodiments, but may also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for brevity, various features of this disclosure described in the context of individual embodiments may also be provided individually or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure may also be considered an independent embodiment in itself.

[0072] Unless otherwise stated, it should be understood that each individual element in the list and each combination of individual elements in the list will be interpreted as a distinct embodiment. For example, when an item is described using the inductive terms “...and / or ...", the description should be understood to include any one of the associated listed items and all combinations thereof.

[0073] Generally, the use of the term "about" indicates an approximation that can vary depending on the desired characteristics obtained from the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, those skilled in the art will be able to interpret a degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about." In other cases, a gradient within a range of values ​​can be used to determine the range of differences allowed by the term "about." Furthermore, all ranges in this disclosure are inclusive and composable, and references to values ​​described within a range include every value within that range.

[0074] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0075] Unless otherwise specified, all materials used in this invention are commercially available products.

[0076] [1] A method for preparing a sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst

[0077] The preparation method includes the following steps:

[0078] S1. Ingredients: Dissolve raw materials containing carbon source, sulfur source and iron source in dispersion medium to prepare precursor solution;

[0079] S2, Vacuum induction: The precursor solution obtained in step S1 is mixed evenly with the template agent under vacuum conditions and then dried;

[0080] S3. Pyrolysis: The material obtained in step S2 is calcined under the protection of an inert gas.

[0081] S4. Remove the template agent to obtain a mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst.

[0082] In step S1, the carbon source can be any substance with two or more phenolic hydroxyl groups. It utilizes the reduction reaction between phenolic hydroxyl groups and ferric iron to form ferrous iron, so that the substances are linked by ferric bonds. Phenolphthalein is preferred.

[0083] The preferred sulfur source is sodium poly(p-styrene sulfonate). During the pyrolysis of the polymer, the sulfonic acid groups are released more slowly, which can ensure that the sulfur atoms are more uniformly doped in the carbon layer.

[0084] The preferred iron source is ferric chloride. In addition, ferric nitrate and ferric sulfate can also be used to provide the iron source.

[0085] The weight ratio of the carbon source, sulfur source and iron source is (10-100):(1-200):(5-30).

[0086] The dispersion medium is a mixed solution of deionized water and ethanol. Other dispersion media capable of dissolving carbon, sulfur, and iron sources are also applicable. The volume ratio of deionized water to ethanol can be any ratio to achieve the dissolution of the raw materials. Deionized water is beneficial for the dissolution of inorganic salts, while ethanol is beneficial for the dissolution of organic salts. In practice, the ratio can be further selected according to the type of raw materials. For example, the volume ratio of deionized water to ethanol is (0-10):(0-10); preferably (1-5):(5-10), more preferably (1-3):(5-7), and even more preferably, the volume ratio of deionized water to ethanol is 1:6. Preferably, the volume ratio of deionized water to ethanol is 1:6. Preferably, 0.1-1g of phenolphthalein, 0.01-0.2g of sodium poly(p-styrene sulfonate), and 0.05-0.3g of ferric chloride hexahydrate are dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0087] The sulfur doping amount affects the oxygen vacancy content of Fe3O4, which in turn affects the iron valence state cycle on the iron oxide surface. Generally speaking, the sulfur doping amount is positively correlated with the oxygen vacancy content of Fe3O4. As the sulfur doping amount increases, the degree of carbon defect of sulfur doping increases, resulting in an increase in the oxygen vacancy content. Conversely, as the sulfur doping amount decreases, the oxygen vacancy content decreases. Preferably, the weight ratio of sulfur doping amount to Fe3O4 is (0.01-2.36):(5.25-32.75), and more preferably (0.1-0.84):(5.25-32.75).

[0088] In step S2, the template agent is a template agent with a uniform mesoporous structure, preferably a hard template agent, such as SiO2 or Al2O3 with a uniform mesoporous structure. The carbon support prepared using a hard template agent with a uniform mesoporous structure also has uniformly distributed mesoporous channels. The confined space provided by the mesoporous channels is conducive to the generation of more low-valence iron and oxygen vacancies. Under confined conditions, the growth of iron(III) oxide crystals is affected by the spatial confinement of the carbon structure, which hinders the epitaxial growth of the crystal and leads to the mismatch of the original lattice. This, in turn, causes the generation of more oxygen vacancies in the iron(III) oxide epitaxial layer. The formation of oxygen vacancies regulates the iron electron structure coordinated with them to generate more low-valence iron, thereby facilitating the generation of more low-valence iron and oxygen vacancies. In addition, the confined space of the mesoporous channels can disperse iron(III) oxide to form nanoflowers and prevent agglomeration.

[0089] The precursor solution obtained in step S1 is mixed with the template agent under vacuum and shaken well. The mixture is then ultrasonically vibrated for 10-30 minutes and dried at 30-80°C for 10-15 hours.

[0090] The amount of template agent added is in the following mass ratio: the weight ratio of carbon source, sulfur source, iron source and SiO2 is (10-100): (1-200): (5-30): (200-800).

[0091] In step S3, the inert gas is argon. Other inert gases, such as nitrogen and helium, can also be used as protective gases.

[0092] The calcination temperature is 600-1000℃, the calcination holding time is 2-5h, and the heating rate is 2-5℃ / min.

[0093] As mentioned above, calcination temperature affects the oxygen vacancy content of Fe3O4. As the calcination temperature increases, the degree of carbon defect in sulfur doping first increases and then decreases, which in turn leads to an increase and then a decrease in the oxygen vacancy content.

[0094] The oxygen vacancy content of Fe3O4 can be jointly regulated by calcination temperature and sulfur doping. The principle is that calcination temperature and sulfur doping will cause defects in the mesoporous carbon structure, affecting the electronic arrangement of the carbon layer structure. The defects in the carbon layer structure further regulate the oxygen vacancy content of Fe3O4 confined within it through charge transport between the carbon layer structure and Fe3O4.

[0095] In step S4, the template agent is removed. When SiO2 is used as the hard template agent, the material obtained in step S3 is dispersed in a 1-5 mol / L sodium hydroxide solution and stirred in a water bath at 50-80°C for 5-20 hours. The mixture is then rinsed with deionized water until pH=7 and then dried at 30-80°C.

[0096] When Al2O3 is used as a hard template agent, the removal method can refer to the removal method of SiO2.

[0097] [2] A sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst

[0098] Its structure includes:

[0099] A carbon support having mesoporous channels with a pore size of 3-4 nm, in which sulfur is doped;

[0100] Active component: Fe3O4 distributed in the mesoporous channels of the carbon support.

[0101] Based on the elemental ratios, the weight ratio of sulfur to carbon is (0.1-0.84):(70.25-90.45); the weight ratio of Fe3O4 to carbon support is (5.25-32.75):(70.25-90.45).

[0102] The sulfur element is doped into the carbon support by CSC bonding.

[0103] The Fe3O4 has a nanoflower structure and is distributed in the mesoporous channels of the carbon support. The particle size of the Fe3O4 is 100-150 nm.

[0104] Among them, Fe3O4 grows into nanoflower structures in the mesoporous channels of the carbon support, which is conducive to the dispersion of Fe3O4, avoids particle agglomeration, and exposes more oxygen vacancies, promotes the cycling of iron valence states on the surface of iron oxide, thereby improving oxidation efficiency.

[0105] [3] Application of a sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst

[0106] The above-mentioned sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst was applied to the treatment of electron-rich pollutants, and is particularly suitable for the treatment of electron-rich pollutants in complex organic wastewater.

[0107] The electron-rich pollutants are sulfonamide organic compounds and phenolic organic compounds.

[0108] The sulfonamides mentioned can be sulfamethoxazole, or sulfadiazine, sulfisoxazole, sulfadiazine, sulfasalazine, sulfasalazine, and other sulfonamide pollutants.

[0109] The phenols can be phenol, or electron-rich phenolic pollutants such as chlorophenol, bromophenol, and bisphenol A.

[0110] The complex organic wastewater also contains electron-deficient pollutants, such as nitrobenzene, benzoic acid, and atrazine, which often appear as interfering substances in the organic wastewater during treatment.

[0111] The catalyst of this application has a good catalytic effect on pollutants, especially electron-rich pollutants such as sulfamethoxazole. Electron-rich pollutants are low-ionization-potential pollutants, which are the minimum energy required for an atom or molecule to lose an electron during ionization. The lower the ionization potential, the easier it is to donate electrons, so the direct electron transfer process is stronger. Conversely, they are ionization-potential pollutants, i.e., electron-deficient pollutants.

[0112] The organic wastewater used in this embodiment is production wastewater from a chemical plant. The concentrations of nitrobenzene, benzoic acid, and atrazine are 50-80 mg / L, the concentration of sulfamethoxazole is 5-10 mg / L, the pH of the wastewater is 5-8, and the main pollutants are organic compounds such as sulfamethoxazole, nitrobenzene, benzoic acid, and atrazine.

[0113] The initial catalyst dosage was 0.1-1 g / L, and the persulfate dosage was 0.06-1 g / L.

[0114] Example 1

[0115] A method for preparing a sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst includes the following steps:

[0116] S1. Ingredients: Dissolve 0.5g of phenolphthalein, 0.2g of sodium poly(p-styrene sulfonate) (Aladdin, CAS: 25704-18-1, average molecular weight approximately 70,000), and 0.1g of ferric chloride hexahydrate in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0117] S2, Vacuum induction: The precursor solution obtained in step S1 is mixed with 0.5g of mesoporous SiO2 under vacuum conditions and shaken well. The mixture is then ultrasonically vibrated for 20min and dried at 70℃ for 12h.

[0118] S3. Pyrolysis: The material obtained in step S2 is placed in a tube furnace with argon gas and heated to 850°C at a rate of 5°C / min, and held at that temperature for 4 hours.

[0119] S4. Removal of template agent: The material obtained in step S2 is dispersed in a 2 mol / L sodium hydroxide solution and stirred in a 70°C water bath for 10 h. The mixture is then washed with deionized water until the pH is neutral and dried at 70°C to obtain a mesoporous carbon-confined Fe3O4 heterogeneous catalyst, denoted as Fe3O4@SMC.

[0120] The characterization of the mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst prepared in Example 1 is as follows: Figure 1-5 As shown, Figure 1 TEM images of Fe3O4@SMC show that the prepared Fe3O4@SMC uses sulfur-modified mesoporous carbon as a support, with Fe3O4 nanoflowers loaded on the mesoporous carbon, and the Fe3O4 cluster size is 100-150 nm.

[0121] Figure 2 EDS results showed that all elements were uniformly dispersed in the prepared Fe3O4@SMC, ​​indicating that sulfur and Fe3O4 were uniformly dispersed on the mesoporous carbon. According to the EDS surface scan results, the weight ratio of sulfur to carbon was 0.84:87.99; the weight ratio of Fe3O4 to carbon support was 11.17:87.99.

[0122] Figure 3 XRD results showed that in the prepared Fe3O4@SMC, ​​iron was loaded onto sulfur-modified mesoporous carbon in the form of Fe3O4 crystals.

[0123] Figure 4 BET results show that under SiO2 hard template conditions, mesoporous carbon structures are formed by utilizing its mesoporous properties. After sulfur doping and Fe3O4 loading, the catalyst still maintains a certain mesoporous structure.

[0124] Figure 5 EPR results show that sulfur doping can increase the oxygen vacancy density of the catalyst.

[0125] Comparative Example 1

[0126] The Fenton-like catalyst prepared in Comparative Example 1 was kept under the same conditions as in Example 1, except that no hard template agent, mesoporous SiO2, was added. The steps were as follows:

[0127] 0.5 g of phenolphthalein, 0.2 g of sodium poly(p-styrene sulfonate), and 0.1 g of ferric chloride hexahydrate were dissolved in a mixed solution of deionized water and ethanol. After thorough stirring, the precursor solution was dried directly at 70 °C for 2 h and then pyrolyzed. All other conditions were the same as in Example 1. The resulting catalyst was a sulfur-modified carbon-supported Fe3O4 heterogeneous catalyst without mesoporous channels, named Fe3O4@SC.

[0128] Comparative Example 2

[0129] The Fenton-like catalyst prepared in Comparative Example 2 was kept under the same conditions as in Example 1, except that the sulfur source sodium poly(p-styrene sulfonate) was not added, and the steps were as follows:

[0130] 0.5 g of phenolphthalein and 0.1 g of ferric chloride hexahydrate were dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution. All other conditions were the same as in Example 1. The resulting catalyst was a non-sulfur-doped mesoporous carbon-confined Fe3O4 heterogeneous catalyst, named Fe3O4@MC.

[0131] Comparative Example 3

[0132] The catalyst prepared in Comparative Example 3 was consistent with that in Example 1, except that ferric chloride hexahydrate, an iron source, was not added. The steps were as follows:

[0133] 0.5 g of phenolphthalein and 0.2 g of sodium poly(p-styrene sulfonate) were dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution. Other conditions were the same as in Example 1. The resulting catalyst was a sulfur-modified mesoporous carbon heterogeneous catalyst, named SMC.

[0134] Comparative Example 4

[0135] The Fe3O4 catalyst prepared in Comparative Example 4 was consistent with that in Example 1, except that the sulfur source sodium poly(p-phenylene sulfonate) and the hard template agent mesoporous SiO2 were not added. The steps were as follows:

[0136] 0.1 g of ferric chloride hexahydrate was dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution. Other conditions were the same as in Example 1. The resulting catalyst was Fe3O4 catalyst, named Fe3O4.

[0137] Example 2

[0138] The method in this embodiment is basically the same as that in Example 1, except that the sulfur content is different and the amount of sodium poly(p-styrene sulfonate) added is 25 mg. That is, in step S1, 0.5 g of phenolphthalein, 0.025 g of sodium poly(p-styrene sulfonate) and 0.1 g of ferric chloride hexahydrate are dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0139] Example 3

[0140] The method in this embodiment is basically the same as that in Example 1, except that the sulfur content is different and the amount of sodium poly(p-styrene sulfonate) added is 50 mg. That is, in step S1, 0.5 g of phenolphthalein, 0.05 g of sodium poly(p-styrene sulfonate) and 0.1 g of ferric chloride hexahydrate are dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0141] Example 4

[0142] The method in this embodiment is basically the same as that in Example 1, except that the sulfur content is different and the amount of sodium poly(p-styrene sulfonate) added is 75 mg. That is, in step S1, 0.5 g of phenolphthalein, 0.075 g of sodium poly(p-styrene sulfonate) and 0.1 g of ferric chloride hexahydrate are dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0143] Example 5

[0144] The method in this embodiment is basically the same as that in Example 1, except that the sulfur content is different and the amount of sodium poly(p-styrene sulfonate) added is 100 mg. That is, in step S1, 0.5 g of phenolphthalein, 0.1 g of sodium poly(p-styrene sulfonate) and 0.1 g of ferric chloride hexahydrate are dissolved in a mixed solution of deionized water and ethanol to prepare a precursor solution.

[0145] Figure 6 (a) XPS results show that with the increase of sodium poly(p-styrene sulfonate) content, the oxygen vacancy concentration gradually increases, and its oxygen vacancy concentration varies according to the adsorption oxygen O. ads The ratio of surface oxygen to total oxygen is calculated, where total oxygen is the surface oxygen (O₂). surf Adsorbed oxygen O ads and lattice oxygen O latt With the addition of sodium poly(p-styrene sulfonate) content, the oxygen vacancy concentration increased from 33.93% to 58.25%, indicating that sulfur doping can effectively improve the oxygen vacancy density of the catalyst.

[0146] Figure 6 (b) Raman results show that with the increase of sodium poly(p-styrene sulfonate) content, the catalyst's I...D / I G Gradually increase, I D / I G The range increased from 2.80 to 3.32, indicating an increase in the degree of carbon defect, which in turn indicates an increase in oxygen vacancy content.

[0147] Comparative Example 5

[0148] The method of this comparative example is basically the same as that of Example 1, except that the calcination temperature is different. The calcination temperature is 550°C, that is, the material obtained in step S2 is placed in a tube furnace with argon gas and calcined at a heating rate of 5°C / min for 4 hours at 550°C.

[0149] Example 6

[0150] The method in this embodiment is basically the same as that in embodiment 1, except that the calcination temperature is different. The calcination temperature is 650°C, that is, the material obtained in step S2 is placed in a tube furnace with argon gas and calcined at a heating rate of 5°C / min for 4 hours at 650°C.

[0151] Example 7

[0152] The method in this embodiment is basically the same as that in embodiment 1, except that the calcination temperature is different. The calcination temperature is 750°C, that is, the material obtained in step S2 is placed in a tube furnace with argon gas and calcined at a heating rate of 5°C / min for 4 hours at 750°C.

[0153] Example 8

[0154] The method in this embodiment is basically the same as that in embodiment 1, except that the calcination temperature is different. The calcination temperature is 950°C, that is, the material obtained in step S2 is placed in a tube furnace with argon gas and calcined at a heating rate of 5°C / min for 4 hours at 950°C.

[0155] Figure 7 (a) XPS results show that as the calcination temperature increases from 550℃ to 950℃, the oxygen vacancy concentration first increases and then decreases; Figure 7 (b) Raman results show that as temperature increases, I D / I G The fact that the carbon defect first increases and then decreases indicates that as the calcination temperature increases, the carbon defect first increases and then decreases. Carbon defects are generally vacancies formed by the absence or deviation of carbon atoms from their normal positions, which in turn indicates that the oxygen vacancy content increases and then decreases.

[0156] Example 9

[0157] Application of the sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst prepared in Example 1.

[0158] In this embodiment, the organic wastewater to be treated is production wastewater from a chemical plant. The pollutants include sulfamethoxazole, nitrobenzene, benzoic acid, and atrazine. The concentrations of nitrobenzene, benzoic acid, and atrazine are 50 mg / L, the concentration of sulfamethoxazole is 5 mg / L, and the pH of the wastewater is 7.6.

[0159] In Example 1, the dosage of Fe3O4@SMC prepared was 0.1 g / L, the dosage of persulfate was 5 mmol / L, and the total treatment time of the oxidation system was 15 min.

[0160] The changes in the removal rate of sulfonamide compounds in wastewater are as follows: Figure 8 As shown, the results indicate that with the addition of persulfate, sulfamethoxazole undergoes a rapid reaction phase, degrading 80% within 7 minutes and 95% within 15 minutes. This is because when using mesoporous SiO2 as a template to prepare the catalyst, the mesoporous confinement effect induces the formation of sulfur-modified mesoporous carbon. The dispersion effect of sulfur-modified mesoporous carbon on Fe3O4 nanoflowers promotes the exposure of active sites on the Fe3O4 surface; oxygen vacancies can promote the cycling of iron valence states; S doping causes structural defects in the mesoporous carbon, affecting the electron configuration of the carbon layer structure. These structural defects further regulate the content of oxygen vacancies in the confined Fe3O4 through charge transport with Fe3O4, improving the catalyst's anti-interference ability. Through the synergistic effect of sulfur modification and oxygen vacancies, pollutants are degraded via a non-radical pathway of direct electron transfer during the persulfate activation process. The mesoporous confinement space formed by the catalyst is conducive to the effective enrichment of pollutants, improving the degradation efficiency. Furthermore, due to... Figure 8 It can be seen that the removal rates of nitrobenzene, benzoic acid, and atrazine within 15 minutes were 12%, 17%, and 9%, respectively, which indicates that the catalyst of the present invention has a significant selective degradation effect on characteristic pollutants when treating organic wastewater with complex components.

[0161] The catalysts with different sulfur contents obtained in Examples 1-5 were used in the treatment of organic wastewater, and the changes in the removal rate of sulfamethoxazole were as follows: Figure 9 As shown. Figure 9 In addition, as the amount of sulfur doping increases, the degree of defect in the mesoporous carbon structure increases, which in turn promotes the formation of oxygen vacancies and low-valent iron, thereby further improving the catalytic effect.

[0162] Example 10

[0163] In this embodiment, the catalyst prepared in Example 1 was used to conduct free radical quenching experiments. 0.05 mM furfuryl alcohol (FFA), 500 mM tert-butanol (TAB), 500 mM methanol (MeOH) and 5 mM potassium dichromate (K2Cr2O7) were added to the reaction system to study the reaction mechanism of the mesoporous carbon-confined Fe3O4 heterogeneous catalyst.

[0164] Potassium dichromate is used to inhibit direct electron transfer processes; furfuryl alcohol is commonly used to quench singlet oxygen; tert-butanol is used to quench hydroxyl radicals; methanol is used to quench sulfate and hydroxyl radicals; and the removal rate of sulfamethoxazole in wastewater is as follows: Figure 10 The results showed that after adding potassium dichromate, only 5% of sulfamethoxazole was removed within 15 minutes, significantly inhibiting its degradation. This indicates that the degradation of organic matter mainly occurs through direct electron transfer. The addition of furfuryl alcohol reduced the concentration of sulfamethoxazole in the organic wastewater by 96%, indicating the generation of a small amount of singlet oxygen. However, the degradation rates of sulfamethoxazole remained around 99% after the addition of tert-butanol and methanol, indicating low yields of hydroxyl and sulfate radicals. This further proves that the mesoporous carbon-confined Fe3O4 heterogeneous catalyst prepared in this invention primarily degrades pollutants through a non-radical pathway of direct electron transfer.

[0165] Comparative Example 6

[0166] The catalysts obtained in Comparative Examples 1-4 were used to treat organic wastewater. The organic wastewater to be treated in these comparative examples was consistent with that in Example 9. The changes in the removal rate of sulfamethoxazole were as follows: Figure 11 The results showed that without mesoporous SiO2 as a template, the catalyst achieved a 70% degradation rate of sulfamethoxazole. This is because the mesoporous nature of SiO2 allows for the pyrolysis of metal salts and organic matter under confined conditions. Further alkaline etching to prepare sulfur-modified mesoporous carbon ensures the uniform dispersion of Fe3O4 nanoflowers on the carbon material. The mesoporous confinement effect induces sulfur modification and the formation of oxygen vacancies on Fe3O4, thereby promoting direct electron transfer. Without sulfur doping, the catalyst only achieved a 52% degradation rate of sulfamethoxazole. This is attributed to the fact that sulfur doping causes structural defects in the mesoporous carbon, affecting the electron configuration of the carbon layer structure. These structural defects further regulate the content of confined Fe3O4 oxygen vacancies through charge transport with Fe3O4, enhancing the surface activity of the catalyst. Without oxygen vacancies, the degradation rate of sulfamethoxazole was only 49%. This is because the oxygen vacancies formed by the mesoporous confinement effectively promote the valence state cycling of iron. The synergistic effect of sulfur modification and oxygen vacancies in the induction of persulfate activation degrades pollutants via a non-radical pathway of direct electron transfer.

[0167] Comparative Example 7

[0168] The catalysts obtained from Examples 6-8 and Comparative Example 5, treated at different calcination temperatures, were used in the treatment of organic wastewater. In this comparative example, the organic wastewater to be treated was consistent with that in Example 9. The change in the removal rate of sulfamethoxazole is as follows: Figure 12 As shown, the degradation efficiency of SMX first increases and then decreases with the increase of calcination temperature. This may be because increasing the temperature will increase the defect degree of mesoporous carbon, thereby increasing the content of oxygen vacancies and low-valent iron, thus improving the catalytic effect. However, excessively high temperature will cause the mesoporous carbon structure to collapse, affecting the oxygen vacancy content, thereby causing the catalyst to lose its active sites.

[0169] Example 11

[0170] The stability of the sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst Fe3O4@SMC prepared in Example 1 was studied. Five consecutive degradations of SMX were performed under the same conditions as in Example 9, and the experimental results are as follows: Figure 13 As shown, the removal rate of sulfamethoxazole decreased slightly after five cycles, with removal rates of 95%, 91%, 88%, 84%, and 80% after each cycle, respectively, indicating that the catalyst has high cycle stability and can be used for long-term purposes. Furthermore, after the fifth cycle, calcining the catalyst at 850°C for 4 hours under argon atmosphere resulted in the catalyst's catalytic effect returning to the initial level, further demonstrating the stability of the catalyst prepared in this invention.

[0171] Example 12

[0172] The remaining conditions in this embodiment are the same as in Example 9, except that the pH of the wastewater is adjusted to 2, 3, 4, 5, 6, 7, 8, 9, and 10. A control degradation experiment is conducted on Fe3O4@SMC prepared in Example 1, Fe3O4@SC prepared in Comparative Example 1, Fe3O4@MC prepared in Comparative Example 2, and SMC prepared in Comparative Example 3.

[0173] The ability of catalysts to treat organic wastewater under different pH conditions, such as Figure 14 As shown, compared with Fe3O4@SC, Fe3O4@MC and SMC, Fe3O4@SMC has a degradation efficiency of over 92% for sulfamethoxazole over a wider pH range, indicating that the catalyst has a stable catalytic effect. The possible reason is that the higher oxygen vacancies increase the content of low-valence iron, which enhances the direct electron transfer, thus enabling the catalyst to have a good catalytic effect over a wider pH range.

[0174] Example 13

[0175] The remaining conditions in this embodiment are the same as in Example 9, except that 50 mM SO4 is added to the sulfamethoxazole wastewater. 2- NO3- Cl - HCO3 - Ions were used to conduct degradation experiments on sulfamethoxazole to study the catalyst's ability to resist ion interference.

[0176] The ability of the catalyst to degrade sulfamethoxazole under different anion interference conditions, such as Figure 15 As shown, the SO4 content in the system within 15 minutes 2- NO3 - Cl - CO3 2- PO4 3- The effect of HA on the degradation efficiency of sulfamethoxazole is negligible, indicating that the mesoporous carbon-confined Fe3O4 heterogeneous catalyst provided by this invention has a good resistance to ion interference. This is because the mesoporous carbon-confined Fe3O4 heterogeneous catalyst provided by this invention mainly degrades sulfamethoxazole through a non-radical pathway of electron transfer reaction, thereby improving the catalyst's resistance to environmental interference.

[0177] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0178] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst, characterized in that, include: Carbon support, which has mesoporous channels with a pore size of 3-4 nm; Sulfur element is doped into the carbon support and forms CSC bonds with the carbon support; Active component: Fe3O4 distributed in the mesoporous channels of the carbon support; The weight ratio of sulfur to carbon is (0.01-2.36):(70.25-90.45). The heterogeneous catalyst has an oxygen vacancy concentration of 33.93%-58.25% by mole fraction.

2. The sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst according to claim 1, characterized in that, The weight ratio of Fe3O4 to carbon support is (5.25-32.75):(70.25-90.45).

3. The sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst according to claim 2, characterized in that, When the heterogeneous catalyst was analyzed by Raman spectroscopy, carbon defect I was observed. D / I G The ratio is 2.80~3.

32.

4. The preparation method of the sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst as described in claim 1, characterized in that, Including the following raw materials: Carbon source, sulfur source, and iron source; Includes the following steps: S1. Ingredients: Dissolve raw materials containing carbon source, sulfur source and iron source in dispersion medium to prepare precursor solution; S2, Vacuum induction: The precursor solution obtained in step S1 is mixed evenly with the template agent under vacuum conditions and then dried; S3. Pyrolysis: The material obtained in step S2 is calcined under the protection of an inert gas. S4. Remove the template agent to obtain a sulfur-modified mesoporous carbon-confined supported Fe3O4 heterogeneous catalyst. In step S2, the template agent is a hard template agent with a uniform mesoporous structure.

5. The preparation method according to claim 4, characterized in that, In step S1, the weight ratio of the carbon source, sulfur source and iron source is (10-100):(1-200):(5-30).

6. The preparation method according to claim 4, characterized in that, In step S2, the amount of template agent added is in the following mass ratio: the weight ratio of carbon source, sulfur source, iron source and template agent is (10-100):(1-200):(5-30):(200-800).

7. The preparation method according to claim 4, characterized in that, In step S3, the calcination temperature is 600-1000℃, the calcination holding time is 2-5h, and the heating rate is 2-5℃ / min.

8. The preparation method according to claim 4, characterized in that, In step S4, the material obtained in step S3 is etched using an alkaline solution.

9. The application of a sulfur-modified mesoporous carbon-confined Fe3O4 heterogeneous catalyst as described in any one of claims 1-3, or a heterogeneous catalyst prepared by the method described in any one of claims 4-8, characterized in that, Used for persulfate degradation of electron-rich pollutants.

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