Preparation methods and applications of iron-doped nitrogen- and oxygen-rich graphene single-atom catalysts

Abstract

This invention provides a method for preparing and applying an iron-doped nitrogen-oxygen-rich graphene single-atom catalyst. The raw materials include 0.056-0.532 parts by weight of an iron source, 0.2-10 parts by weight of urea, 1-12 parts by weight of dicyandiamide, and 0.5-12 parts by weight of 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. The iron-doped nitrogen-oxygen-rich graphene single-atom catalyst of this invention can achieve highly efficient removal of pollutants from water through a self-purification process under neutral conditions at room temperature during the reaction.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sewage treatment, and particularly relates to a preparation method and application of an iron-doped nitrogen-rich oxygen-containing graphene monatomic catalyst. BACKGROUND

[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 immeasurable potential threat to human health and ecosystems. To remove these pollutants, a number of techniques have been developed, such as Fenton oxidation, UV photolysis, PMS activation, and ferrate oxidation. However, these treatment processes are often accompanied by substantial 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 byproducts, making the remediation of antibiotic pollution in actual water bodies face even more severe challenges. Therefore, it is urgent to break through the traditional concept and develop new water treatment technologies that are efficient and low in energy consumption.

[0003] Monatomic site catalysts (SACs) have been proven to have broad prospects in rapidly removing water pollutants, but there are currently shortcomings such as high consumption of oxidants and poor activity. In recent years, scholars have found that cation-pi interactions can promote the generation of electric fields by adjusting the charge rearrangement between metal ions and pi systems or the coordination of surface pollutants. In addition, the strength of cation-pi interactions depends on the type of cations and the properties of pi systems, indicating that the adjacent environment involved can adjust 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 current monatomic catalytic systems and achieve the spontaneous and rapid mineralization of antibiotics under environmental conditions. However, the high cost and cumbersome synthesis process of graphene still remain a problem to be solved. SUMMARY

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

[0005] Studies have shown 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 both solve the problem of actual feces disposal and achieve low-energy and efficient water treatment. For this reason, we propose a preparation method and application of an iron-doped nitrogen-rich oxygen-containing graphene monatomic catalyst.

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

[0007] The iron-doped nitrogen-rich oxygen-based graphene monatomic catalyst is prepared from 0.056-0.532 parts of iron source, 0.2-10 parts of urea, 1-12 parts of dicyandiamide and 0.5-12 parts of precursor silkworm sand by weight of iron ions.

[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 urea is added in an amount of 1 part;

[0010] The dicyandiamide is added in an amount of 6 parts;

[0011] The precursor silkworm sand is added in an amount of 4.5 parts.

[0012] Preferably, the following steps are included:

[0013] S1: adding the dicyandiamide, the urea and the precursor silkworm sand into water and stirring to form a dispersion A;

[0014] S2: adding the iron source into the dispersion A and stirring to form a dispersion B;

[0015] S3: placing the dispersion B in an oven for standing and drying to obtain a solid particle A;

[0016] S4: placing the solid particle A in a tube furnace for calcination under N2 atmosphere, and obtaining a solid product A after natural cooling;

[0017] S5: washing the solid product A with water, placing it in an oven for drying, and obtaining an iron-doped nitrogen-rich oxygen-based graphene monatomic catalyst FeSA-N,O-GO.

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

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

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

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

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

[0023] Preferably, the application of the iron-doped nitrogen-rich oxygen-like graphene monatomic catalyst to 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 application also provides an iron-doped nitrogen-rich oxygen-like graphene monatomic catalyst prepared according to the above method, having high-spin and low-spin monatomic Fe sites and a graphene-like N, O-GO π system, wherein the monatomic Fe and the graphene-like structure are connected through Fe-O-C and Fe-N-C chemical coordination bonds in the structure. Based on this special structural characteristic, the π electrons on the N, O-GO are activated and migrate and concentrate on the periphery of the monatomic Fe species through these chemical bond bridges, forming an electron high-density region, while an electron low-density region is formed near the N, O-GO, so that the Fe SA A stable electric field with a field strength of 146 mV is formed on the surface of the N, O-GO. During the reaction, the synergistic coordination of the DOC-antibiotic-H2O at the high-spin monatomic Fe sites and the N, O-GO sites causes a strong surface charge rearrangement, generating greater electric field energy, causing the continuous oxidation of the adsorption groups of the antibiotic and the homolytic cleavage of the adjacent chemical bonds, until complete mineralization. During the entire reaction process, the generated organic free radicals can continuously charge the catalyst to provide energy, thereby achieving low-energy efficient purification of wastewater, especially complex wastewater.

[0026] Compared with the prior art, the present application provides a preparation method and application of an iron-doped nitrogen-rich oxygen-like graphene monatomic catalyst, which has the following beneficial effects:

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

[0028] Secondly, compared with conventional wastewater oxidation treatment methods, the catalyst of the present application can effectively overcome the adverse effects of natural organic carbon (DOC) in water on the pollutant removal process.

[0029] Thirdly, the catalyst of the present application utilizes surface material coordination to cause a strong surface charge rearrangement, which can generate strong electric field energy, and only with the assistance of weak electron acceptors (such as O2, Fe 3+ etc.) can achieve the mineralization and removal of pollutants using the electrons of the pollutants without external energy assistance, effectively overcoming the problem of excessive energy consumption in current wastewater treatment.

[0030] Fourthly, the catalyst of the present application has good adaptability and stability in the process of removing organic pollutants.

[0031] V. The catalyst of this invention is a supported particulate catalyst, which is easy to separate from water and recycle. Attached Figure Description

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

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

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

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

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

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

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

[0039] Figure 8 Fe prepared for the example SA -N,O-GO repeated experimental activity evaluation diagram. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below. The embodiments described below are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the embodiments described below.

[0041] Please see Figures 1-6 , Example

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

[0043] (1) 1 g urea, 6 g dicyandiamide and 4.5 g silkworm chrysalis precursor were added into 35 ml water and magnetically stirred for 1 h to form dispersion liquid A;

[0044] (2) 0.0060 mol of iron trichloride hexahydrate was added into dispersion liquid A and magnetically stirred for 1 h to form dispersion liquid B;

[0045] (3) Dispersion liquid B was placed in a 100℃ oven and statically baked for 24 h to obtain solid particles A;

[0046] (4) Solid particles A were placed in a tube furnace and baked under N2 atmosphere, the baking heating rate was 5℃ / min, the temperature was raised to 700℃ and kept for 2 h, and after natural cooling, solid product A was obtained;

[0047] (5) Solid product A was washed with water for three times, and placed in a 60℃ oven and baked for 24 h to obtain the iron-doped nitrogen-rich oxygen-containing graphene monatomic catalyst Fe SA -N,O-GO of the present application.

[0048] The structure of Fe SA -N,O-GO prepared in the example was characterized.

[0049] Figure 1 、 Figure 2 and Figure 3 are respectively SEM, HAADF-STEM and Mossbauer spectra of Fe SA -N,O-GO prepared in the example. As can be seen from the figures, Fe SA -N,O-GO has a honeycomb-like porous structure, and the pore size is 0.1-8 um. The isolated bright spots on the surface of Fe SA -N,O-GO indicate that the ingenious complexation of Fe and nitrogen-rich oxygen-containing graphene structure promotes the formation of abundant iron atomic sites on the surface of the catalyst. Through Mossbauer spectrum analysis, the iron species in Fe SA -N,O-GO exists in the form of high-spin Fe II and Fe III and low-spin Fe II .

[0050] Table 1 is the fitting results of Fe SA EXAFS oscillation values of Fe

[0051]

[0052] Table 1 is the fitting results of Fe SAFe EXAFS oscillation numerical fitting results of 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 shell, and an average of 1.8 C atoms directly connected in the second coordination shell. The results confirm that Fe SA the symmetry breaking configuration of N, O-GO, which effectively improves the interface electron transfer capability and structural stability of the catalyst. Therefore, in the Fe SA On the surface of N, O-GO, single-atom Fe bridges with the delocalized π orbitals in the graphenelike N, O-GO support perpendicular to the aromatic ring plane through Fe—O—C and Fe—N—C bonds, resulting in strong Fe-π interactions.

[0053] Application experiments:

[0054] 0.03 g of Fe SA -N,O-GO prepared in the example was placed in 50 mL of a pollutant solution with a concentration of 10 mg / L, and the degradation reaction was started under constant magnetic stirring at a constant temperature of 35°C under neutral reaction conditions. Samples were taken at different time points and the concentration of pollutants was detected.

[0055] Figure 4 , Figure 5 , Figure 6 and Figure 7 are the degradation curves of different pollutants, TOC removal curves, catalytic degradation curves of different pollutants in actual wastewater, and repeated experiment activity evaluation curves of Fe SA -N,O-GO under neutral conditions. From Figure 4 and Figure 5 , it can be seen that under the condition of no external energy assistance, Fe SA -N,O-GO air-saturated suspension can completely remove 100% of CIP, TC, OTC, and NFX through self-purification within 90 minutes, with corresponding TOC removal rates of up to 72.3%, 79.3%, 79.7%, and 65.2%, respectively, indicating that Fe SA -N,O-GO has good catalytic performance for organic pollutants in water. Notably, in the Fe SA -N,O-GO air-saturated municipal wastewater (MW) or drinking water source water (RDW) suspension, 100% CIP removal Figure 6 ) can be achieved within 60 minutes, which is about 1.9 times and 1.5 times faster than the reaction rate in the ultrapure water suspension system, respectively. In addition, after Fe SAThe degradation rate of CIP in the presence of DOC is faster than that in the original MW, which indicates that the multi-component intermediates produced by the degradation of DOC greatly promote the degradation of CIP, which is completely different from the general oxidation process. Within 120 minutes, the removal rate of sulfamethoxazole (SMX) is only 10%, but in the presence of 5 mg / L of CIP and DOC, the removal rate of SMX is significantly increased to 74.1% and 89.3%, Figure 7 respectively, which confirms that Fe SA -N,O-GO is a promising catalyst for the treatment of low-energy composite contaminated wastewater. From the above results, it can be seen that after 6 times of continuous operation, the removal rate of CIP by Fe Figure 8 -N,O-GO still remains above 99.9%, and the release amount of iron is only 0.04 mg / L after continuous reaction, which indicates that Fe SA -N,O-GO has good stability. SA -N,O-GO has good stability.

[0056] The above detailed the preferred embodiments of the present application. It should be understood that those skilled in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the existing technology according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. Iron-doped nitrogen-rich oxygenated graphenes single-atom catalysts, 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 cocoon precursor; The iron source is selected from at least one of ferric chloride hexahydrate, ferric nitrate, ferric sulfate, ferrous chloride tetrahydrate and ferrous chloride dihydrate; The preparation method of the iron-doped nitrogen-rich oxygen-based graphene monatomic catalyst comprises the following steps: S1: the dicyandiamide, the urea and the cocoon precursor are added into water and stirred uniformly to form a dispersion A; S2: the iron source is added into the dispersion A and stirred uniformly to form a dispersion B; S3: the dispersion B is placed in an oven and left to dry to obtain a solid particle A; S4: the solid particle A is placed in a tube furnace and calcined under N2 atmosphere, and the solid product A is obtained after natural cooling; S5: the solid product A is washed with water, dried in an oven, and an iron-doped nitrogen-rich oxygen-based graphene monatomic catalyst FeSA-N,O-GO is obtained.

2. The iron-doped nitrogen-oxide graphene monolayer catalyst of claim 1, wherein, The added amount of the urea is 1 part; The added amount of the dicyandiamide is 6 parts; The added amount of the cocoon precursor is 4.5 parts. 3.The iron-doped nitrogen-enriched oxygen graphite monatomic catalyst of claim 1, wherein, The added amount of water in the dispersion A in S1 is 35 parts by weight, and the stirring time is 0.5-3h. 4.The iron-doped nitrogen-enriched oxygen graphite monatomic catalyst of claim 1, wherein, The stirring time in S2 is 0.5-6h.

5. The iron-doped nitrogen-oxide graphene monolayer catalyst of claim 1, wherein, The drying temperature in S3 is 60-150℃, and the drying time is 12-72h. 6.The iron-doped nitrogen-enriched oxygen graphite monatomic catalyst of claim 1, wherein, The calcination temperature in S4 is 450-1000℃, the calcination time is 1-5h, and the heating rate is 2-15℃ / min. 7.The iron-doped nitrogen-enriched oxygen graphite monatomic catalyst of claim 1, wherein, The drying temperature in S5 is 60-120℃, and the drying time is 6-36h.

8. The application of the iron-doped nitrogen-rich oxygen-based graphene monatomic catalyst according to claim 1 to catalytic degradation of antibiotic organic pollutants through a self-purification process.

9. Use according to claim 8, characterized in that, The antibiotic organic pollutants are selected from one or more of ciprofloxacin, tetracycline, norfloxacin and terramycin.

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