Preparation method and application of iron-doped nitrogen-oxygen-rich graphene monatomic catalyst

Abstract

The invention provides a preparation method and application of an iron-doped nitrogen-oxygen-rich graphene monatomic catalyst, and the preparation raw materials comprise, by weight of iron ions, 0.056-0.532 parts of an iron source, 0.2-10 parts of urea, 1-12 parts of dicyandiamide and 0.5-12 parts of precursor silkworm excrement. The iron source is selected from at least one of ferric trichloride hexahydrate, ferric nitrate, ferric sulfate, ferrous chloride tetrahydrate and ferrous chloride dihydrate. According to the iron-doped nitrogen-oxygen-enriched graphene monatomic catalyst disclosed by the invention, pollutants in water can be efficiently removed through a self-purification process under a normal-temperature neutral condition in a reaction process.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and particularly relates to a preparation method and application of an iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst. Background Art

[0002] In the past few decades, the substantial increase in global antibiotic consumption has led to their frequent detection in various aquatic environments, posing an inestimable potential threat to human health and the ecosystem. To remove these pollutants, many technologies have been developed, such as Fenton oxidation, UV photolysis, PMS activation, and ferrate oxidation. However, these treatment processes are often accompanied by a large amount of energy consumption, which hinders their large-scale application in natural and industrial water matrices. In addition, the ubiquitous dissolved organic carbon (DOC) in water bodies can greatly inhibit the destruction of antibiotics and promote the formation of harmful by-products, making the remediation of antibiotic pollution in actual water bodies face more severe challenges. Therefore, it is urgent to break through the traditional concept and develop a new type of water treatment technology with high efficiency and low energy consumption.

[0003] Single-atom site catalysts (SACs) have been proven to have broad prospects in the rapid removal of water pollutants, but currently have disadvantages such as high oxidant consumption and poor activity. In recent years, scholars have found that cation-π interactions can promote the generation of an electric field by regulating the charge rearrangement between metal ions and the π system or the coordination of surface pollutants. In addition, the strength of cation-π interactions depends on the type of cation and the nature of the π system, indicating that the involved neighboring environment can regulate the strength of the electric field to change the electronic state of SACs. Therefore, graphene-based SACs are expected to break through the limitations of the current single-atom catalytic system and achieve the spontaneous and rapid mineralization of antibiotics under environmental conditions. However, the high cost and cumbersome synthesis process of graphene are still problems to be solved. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the purpose of the present invention is to provide a preparation method and application of an iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst, and solve the above problems.

[0005] Research shows that feces contain a large amount of organic matter, which can serve as a graphene-like precursor in the catalyst preparation process. Therefore, using feces as a raw material to prepare a catalyst may be an innovative strategy that can not only solve the actual feces treatment problem but also achieve low-energy and high-efficiency water treatment. For this reason, we propose a preparation method and application of an iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0007] Iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst, the preparation raw materials include 0.056 - 0.532 parts of iron source by weight of iron ions, 0.2 - 10 parts of urea by weight, 1 - 12 parts of dicyandiamide, and 0.5 - 12 parts of precursor silkworm excrement;

[0008] The iron source is selected from at least one of ferric chloride hexahydrate, ferric nitrate, ferric sulfate, ferrous chloride tetrahydrate, and ferrous chloride dihydrate.

[0009] Preferably, the addition amount of the urea is 1 part;

[0010] The addition amount of the dicyandiamide is 6 parts;

[0011] The addition amount of the precursor silkworm excrement is 4.5 parts.

[0012] Preferably, it includes the following steps:

[0013] S1: Add the dicyandiamide, the urea, and the precursor silkworm excrement into water and stir evenly to form dispersion liquid A;

[0014] S2: Add the iron source into the dispersion liquid A and stir evenly to form dispersion liquid B;

[0015] S3: Place the dispersion liquid B in an oven and let it stand and dry to obtain solid particles A;

[0016] S4: Place the solid particles A in a tube furnace and calcine them under an N2 atmosphere, and obtain solid product A after natural cooling;

[0017] S5: Wash the solid product A with water, place it in an oven to dry, and obtain the iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst FeSA-N,O-GO.

[0018] Preferably, in S1, the addition amount of water in the dispersion liquid A is 35 parts by weight, and the stirring time is 0.5 - 3 h.

[0019] Preferably, the stirring time in S2 is 0.5 - 6 h.

[0020] Preferably, the drying temperature in S3 is 60 - 150 °C, and the drying time is 12 - 72 h.

[0021] Preferably, the calcination temperature in S4 is 450 - 1000 °C, the calcination time is 1 - 5 h, and the heating rate is 2 - 15 °C / min.

[0022] Preferably, the drying temperature in S5 is 60 - 120 °C, and the drying time is 6 - 36 h.

[0023] Preferably, the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst is used for catalytic degradation of antibiotic organic pollutants through a self-purification process.

[0024] Preferably, the antibiotic organic pollutants are selected from one or more of ciprofloxacin (CIP), tetracycline (TC), norfloxacin (NFX), and oxytetracycline (OTC).

[0025] The present invention also provides an iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst prepared by the above method, which has high-spin and low-spin single-atom Fe sites and a graphene-like N,O-GO π system. In its structure, the single-atom Fe and the graphene-like structure are connected by Fe−O−C and Fe−N−C chemical coordination bonds. Based on this special structural property, the π electrons on N,O-GO are activated and migrate through these chemical bond bridges to concentrate around the single-atom Fe species, forming a high-electron-density region, while a low-electron-density region is formed near N,O-GO, thus forming a stable electric field with a field strength of 146 mV on the Fe SA -N,O-GO surface. During the reaction process, the synergistic coordination of DOC-antibiotic-H2O at the high-spin single-atom Fe sites and N,O-GO sites causes strong surface charge rearrangement, generating greater electric field energy, resulting in continuous oxidation of the adsorption groups of the antibiotic and homolytic cleavage of adjacent chemical bonds until complete mineralization. During the entire reaction process, the generated organic free radicals can continuously charge and supply energy to the catalyst, thereby achieving low-energy and highly efficient purification of sewage, especially complex sewage.

[0026] Compared with the prior art, the present invention provides a preparation method and application of an iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst, having the following beneficial effects:

[0027] First, the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst of the present invention can achieve efficient removal of pollutants in water through a self-purification process under normal temperature and neutral conditions during the reaction process.

[0028] Second, compared with the usual sewage oxidation treatment means, the catalyst of the present invention can effectively overcome the adverse effects of natural organic carbon (DOC) in water on the pollutant removal process.

[0029] Third, the catalyst of the present invention uses surface substance coordination to cause strong surface charge rearrangement, which can generate strong electric field energy. It can mineralize and remove pollutants by utilizing the electrons of pollutants only with the assistance of weak electron acceptors (such as O2, Fe 3+ etc.) without external energy assistance, effectively overcoming the problem of excessive energy consumption in current sewage treatment.

[0030] Fourth, the catalyst of the present invention has good adaptability and stability during the process of removing organic pollutants.

[0031] 5. The catalyst of the present invention belongs to a supported particulate catalyst, which is convenient for separation from water and can be recycled by recovery. Description of the Drawings

[0032] Figure 1 SEM image of Fe SA -N,O-GO prepared in the example;

[0033] Figure 2 HAADF-STEM of Fe SA -N,O-GO prepared in the example;

[0034] Figure 3 Mössbauer spectrum of Fe SA -N,O-GO prepared in the example;

[0035] Figure 4 Degradation curves of Fe SA -N,O-GO prepared in the example for CIP, TC, OTC and NFX;

[0036] Figure 5 TOC removal diagram of Fe SA -N,O-GO prepared in the example for CIP, TC, OTC and NFX;

[0037] Figure 6 Degradation curves of Fe SA -N,O-GO prepared in the example for CIP in urban sewage and drinking water source water;

[0038] Figure 7 Degradation curves of Fe SA -N,O-GO prepared in the example for SMX;

[0039] Figure 8 Repeated experiment activity evaluation diagram of Fe SA -N,O-GO prepared in the example. Detailed Embodiments

[0040] The following details the embodiments of the present invention. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0041] Please refer to Figure 1-6 , Example

[0042] A synthesis method of Fe SA -N,O-GO includes the following steps:

[0043] (1) Add 1 g of urea, 6 g of dicyandiamide, and 4.5 g of the precursor silkworm excrement to 35 ml of water and stir magnetically for 1 h to form dispersion A;

[0044] (2) Add 00.0060 mol of ferric chloride hexahydrate to dispersion A and stir magnetically for 1 h to form dispersion B;

[0045] (3) Place dispersion B in an oven at 100 °C and let it stand and dry for 24 h to obtain solid particles A;

[0046] (4) Place solid particles A in a tubular furnace and calcine under an N2 atmosphere. The heating rate of calcination is 5 °C / min. Heat up to 700 °C and hold for 2 h, and then cool naturally to obtain solid product A;

[0047] (5) Wash solid product A three times with water, place it in an oven at 60 °C and bake for 24 h to obtain the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst Fe SA -N,O-GO of the present invention.

[0048] The Fe SA -N,O-GO prepared in the example was characterized as follows:

[0049] Figure 1 、 Figure 2 and Figure 3 are the SEM image, HAADF-STEM image, and Mössbauer spectrum of the Fe SA -N,O-GO prepared in the example, respectively. It can be seen from the figure that Fe SA -N,O-GO has a honeycomb-like porous structure with a pore size of 0.1 - 8 μm. The isolated bright spots on the surface of the entire Fe SA -N,O-GO indicate that the ingenious complexation of Fe with the nitrogen-rich oxygen-containing graphene structure promotes the formation of abundant iron atom sites on the catalyst surface. Through Mössbauer spectrum analysis, the iron species in Fe SA -N,O-GO exist in the form of high-spin state Fe II and Fe III as well as low-spin state Fe II .

[0050] Table 1 Fitting results of the Fe-edge EXAFS oscillation values of Fe SA -N,O-GO

[0051]

[0052] Table 1 is for Fe SA-Numerical fitting results of the Fe-edge EXAFS oscillations of Fe-N,O-GO. Apparently, the coordination number of the central Fe atom is 4, with two O and two N atoms directly connected in the first coordination layer, and on average 1.8 C atoms directly connected in the second coordination layer. The results confirm the SA symmetry-breaking configuration of Fe-N,O-GO, which effectively improves the interfacial electron transfer ability and structural stability of the catalyst. Therefore, on the surface of Fe SA -N,O-GO, single-atom Fe undergoes strong Fe-π interactions with the delocalized π orbitals perpendicular to the aromatic ring plane in the graphene-like N,O-GO support through Fe—O—C and Fe—N—C bond bridges.

[0053] Application experiments:

[0054] Put 0.03 g of the Fe-N,O-GO sample prepared in the example into 50 mL of a pollutant solution with a concentration of 10 mg / L. Under neutral reaction conditions, keep the temperature at 35 °C constant, and start the degradation reaction with continuous magnetic stirring. Take samples at different time points and detect the concentration of pollutants in them. SA Figures SA , SA , SA , SA , SA are the degradation curve graphs of different pollutants, TOC removal curve graphs, catalytic degradation curve graphs of different pollutants in actual sewage, and repeated experiment activity evaluation graphs of Fe-N,O-GO in the examples under neutral conditions. It can be seen from Figures Figure 4 and Figure 5 that under the condition of no external energy assistance, the air-saturated suspension of Fe-N,O-GO can completely remove 100% of CIP, TC, OTC, and NFX through the self-purification process within 90 minutes, and the corresponding TOC removal rates are also as high as 72.3%, 79.3%, 79.7%, and 65.2% respectively, indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes (

[0055] Figure 4 , Figure 5 , Figure 6 and Figure 7 are the degradation curve graphs of different pollutants, TOC removal curve graphs, catalytic degradation curve graphs of different pollutants in actual sewage, and repeated experiment activity evaluation graphs of Fe-N,O-GO in the examples under neutral conditions. It can be seen from Figures Figure 4 and Figure 5 that under the condition of no external energy assistance, the air-saturated suspension of Fe-N,O-GO can completely remove 100% of CIP, TC, OTC, and NFX through the self-purification process within 90 minutes, and the corresponding TOC removal rates are also as high as 72.3%, 79.3%, 79.7%, and 65.2% respectively, indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( SA ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( Figure 4 and Figure 5 ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( SA ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( SA ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( SA ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( Figure 6 ), indicating that Fe-N,O-GO has good catalytic performance for the treatment of organic pollutants in water. It is worth noting that in the air-saturated suspension of urban sewage (MW) or drinking water source water (RDW) of Fe-N,O-GO, 100% of CIP can be removed within only 60 minutes ( SA- In the MW treated by the -N,O-GO system for 20 minutes, the degradation rate of CIP was faster than that in the original MW, indicating that the multi-component intermediates generated by DOC degradation greatly promoted the degradation of CIP, which was completely different from the usual oxidation process. Within 120 minutes, the removal rate of sulfamethoxazole (SMX) was only 10%. In the presence of 5 mg / L of CIP and DOC, the removal rates of SMX were significantly increased to 74.1% and 89.3%( Figure 7 ), confirming that Fe SA -N,O-GO is a promising catalyst for treating sewage with complex pollution at low energy consumption. As can be seen from Figure 8 , after 6 consecutive runs, the removal rate of CIP by Fe SA -N,O-GO still remained above 99.9%, and the iron release amount was only 0.04 mg / L after consecutive reactions, indicating that Fe SA -N,O-GO has good stability.

[0056] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. Iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst, characterized in that, The preparation raw materials include 0.056 - 0.532 parts of iron source by weight of iron ions, 0.2 - 10 parts of urea by weight, 1 - 12 parts of dicyandiamide, and 0.5 - 12 parts of precursor silkworm excrement; The iron source is selected from at least one of ferric chloride hexahydrate, ferric nitrate, ferric sulfate, ferrous chloride tetrahydrate, and ferrous chloride dihydrate.

2. The iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 1, wherein The addition amount of the urea is 1 part; The addition amount of the dicyandiamide is 6 parts; The addition amount of the precursor silkworm excrement is 4.5 parts.

3. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 1, characterized in that, It includes the following steps: S1: Add the dicyandiamide, the urea, and the precursor silkworm excrement into water and stir evenly to form dispersion liquid A; S2: Add the iron source into the dispersion liquid A and stir evenly to form dispersion liquid B; S3: Place the dispersion liquid B in an oven and let it stand for drying to obtain solid particles A; S4: Place the solid particles A in a tubular furnace and calcine under an N2 atmosphere, and obtain solid product A after natural cooling; S5: Wash the solid product A, place it in an oven for drying, and obtain the iron-doped nitrogen- and oxygen-rich graphene single-atom catalyst Fe SA -N,O-GO.

4. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 3, characterized in that, In the S1, the addition amount of water in the dispersion liquid A is 35 parts by weight, and the stirring time is 0.5 - 3 h.

5. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 3, characterized in that, The stirring time in the S2 is 0.5 - 6 h.

6. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 3, wherein, The drying temperature in the S3 is 60 - 150 °C, and the drying time is 12 - 72 h.

7. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 3, characterized in that, The calcination temperature in the S4 is 450 - 1000 °C, the calcination time is 1 - 5 h, and the heating rate is 2 - 15 °C / min.

8. The preparation method of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 3, wherein, The drying temperature in the S5 is 60 - 120 °C, and the drying time is 6 - 36 h.

9. Application of the iron-doped nitrogen-rich oxygen-containing graphene single-atom catalyst according to claim 1 in catalytic degradation of antibiotic organic pollutants through a self-purification process.

10. The application according to claim 9, wherein The antibiotic organic pollutants are selected from one or more of ciprofloxacin (CIP), tetracycline (TC), norfloxacin (NFX), and oxytetracycline (OTC).

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