Iron single-atom catalyst with controllable sulfur content and coordination mode and application thereof

Abstract

The application discloses a kind of iron monatomic catalysts with controllable sulfur content and coordination mode and its preparation method and application, nitrogen-allyl thiourea and thiocyanic acid are respectively used as sulfur-containing organic ligand and sulfur-containing supramolecular precursor, chelate with iron ion, and use the hydrogen bond interaction between melamine and cyanuric acid, complete supramolecular self-assembly process;And high-temperature pyrolysis is carried out under argon atmosphere, and iron monatomic catalysts with controllable sulfur content and coordination mode can be prepared.The application also includes the application of iron monatomic catalysts with controllable sulfur content and coordination mode in removing organic pollutants such as p-chlorophenol and antibiotics in water.Iron monatomic catalysts with controllable sulfur content and coordination mode can improve the activation efficiency of persulfate, the content and selectivity of active oxygen species generated, and achieve efficient degradation of p-chlorophenol under different anion-cation, humic acid and pH conditions, while having good recycling performance.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to an iron single-atom catalyst with controllable sulfur content and coordination mode and its applications. Background Technology

[0002] Advanced oxidation technologies for the in-situ generation of reactive oxygen species (ROS) from persulfate (PMS) activated by transition metals have developed rapidly. However, traditional transition metal catalysts suffer from problems such as low atom utilization, low PMS activation efficiency, and easy dissolution of metal ions. Iron single-atom catalysts (FeSAC) are a novel, environmentally friendly, highly active, and atom-utilized catalyst. FeSAC can generate ROS by activating PMS, effectively removing p-chlorophenols and antibiotics. However, due to the weak interaction between the support and metal atoms and the diverse types of anchoring sites, FeSAC suffers from low metal loading, diverse coordination configurations, and low yield and selectivity of ROS generation from activated PMS. Compared to nitrogen atoms, sulfur atoms exhibit a larger covalent radius and lower electronegativity. By controlling the coordination configuration between sulfur atoms and the active iron atom, the Fe-N... X The delocalization effect generated by the electronic structure of the active center enhances the catalytic activity and selectivity of Fe SAC. However, the coordinated S atoms in Fe SAC obtained by current "top-down" and "bottom-up" methods exhibit random distribution, resulting in unsatisfactory controllability of the Fe atom content and coordination configuration in the active center. We found that by increasing the Fe atom loading and controlling the coordination configuration between Fe and S atoms, we can optimize the binding energy and reaction pathway for PMS to generate ROS, thereby improving the activation efficiency of Fe SAC for PMS and the yield and selectivity of ROS. Therefore, developing a method for preparing an iron single-atom catalyst with controllable sulfur content and coordination mode holds promise for achieving green and efficient removal of organic pollutants from water and reducing the cost of wastewater treatment. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing an iron single-atom catalyst with controllable sulfur content and coordination mode, and its applications.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] In a first aspect, the present invention provides a method for preparing an iron single-atom catalyst with controllable sulfur content and coordination mode, wherein the iron single-atom catalyst with controllable sulfur content and coordination mode is prepared by the following steps:

[0006] S1: melamine is dissolved in deionized water to obtain a melamine solution; cyanuric acid is dissolved in deionized water to obtain a cyanuric acid solution; ferrous acetate is dissolved in deionized water to obtain a ferrous acetate solution; the molar ratio of the melamine, cyanuric acid and ferrous acetate is 1:0.2-0.8:0.8-0.2;

[0007] S2: nitrogen-allyl thiourea is added to the ferrous acetate solution and stirred to obtain solution A; the molar ratio of the nitrogen-allyl thiourea and ferrous acetate is 1:0.1-0.5;

[0008] S3: solution A is added to the cyanuric acid solution and stirred to obtain a precipitate, which is mixed with the melamine solution to obtain a precursor, which is washed and dried to obtain the precursor;

[0009] S4: the precursor obtained in step S3 is heated to 550-650℃ under an argon atmosphere, and after being kept for 3-6h, it is cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is denoted as Fe1S / CN.

[0010] In a second aspect, the present application further provides a preparation method of an iron single-atom catalyst with controllable sulfur content and coordination mode, which is prepared by the following steps:

[0011] S1: melamine is dissolved in deionized water to obtain a melamine solution; cyanuric acid is dissolved in deionized water to obtain a cyanuric acid solution; thiocyanic acid is dissolved in deionized water to obtain a thiocyanic acid solution; ferric citrate is dissolved in deionized water to obtain a ferric citrate solution; the molar ratio of the melamine, cyanuric acid, thiocyanic acid and ferric citrate is 1:0.2-0.8:0.6-0.1:0.2-0.1;

[0012] S2: the ferric citrate solution, the cyanuric acid solution and the thiocyanic acid solution are mixed, stirred and mixed with the melamine solution to obtain a precipitate, which is washed and dried to obtain a precursor;

[0013] S3: the precursor obtained in step S2 is heated to 550-650℃ under an argon atmosphere, and after being kept for 3-6h, it is cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is denoted as Fe1 / SCN.

[0014] In a third aspect, the application further provides an application of the iron monatomic catalyst with controllable sulfur content and coordination mode in removing organic pollutants in water, comprising the following steps: adding the iron monatomic catalyst with controllable sulfur content and coordination mode and peroxymonosulfate into water, the water temperature is 15-35 DEG C, stirring for 5-10 min to complete the removal of organic pollutants in water; the addition amount of the iron monatomic catalyst with controllable sulfur content and coordination mode is 0.1-1 g / L; the addition amount of the peroxymonosulfate is 0-500 micromol / L; and the concentration of the organic pollutants is 0-100 micromol / L.

[0015] Further, the organic pollutants are p-chlorophenol or antibiotics.

[0016] The application has the following beneficial effects:

[0017] (1) By adjusting the type, addition amount and addition sequence of the sulfur-containing organic ligand, the controllable preparation of the iron monatomic catalyst with controllable sulfur content and coordination mode is realized, and the activation PMS efficiency, the content of generated ROS and the selectivity of ROS components of the iron monatomic catalyst with controllable sulfur content and coordination mode are precisely controlled;

[0018] (2) By the hydrogen bond assembly supermolecule fixation strategy, the iron monatomic catalyst with controllable sulfur content and coordination mode with high iron atom loading is prepared, and the degradation ability of the iron monatomic catalyst with controllable sulfur content and coordination mode for activating PMS to p-chlorophenol and antibiotics is enhanced;

[0019] (3) The iron monatomic catalyst with controllable sulfur content and coordination mode can realize the efficient degradation of p-chlorophenol and antibiotics under different anions and cations, humic acid and pH conditions, and has good periodicity. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a flow chart of the preparation method of the iron monatomic catalyst with controllable sulfur content and coordination mode;

[0021] Figure 2 It is an X-ray diffraction pattern of the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 and the graphite phase carbon nitride prepared in Comparative Example 2;

[0022] Figure 3 It is a Fourier infrared spectrum of the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 and the graphite phase carbon nitride prepared in Comparative Example 2;

[0023] Figure 4 It is a spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscope and element distribution map of the iron monatomic catalyst prepared in Example 1;

[0024] Figure 5 High-angle annular dark-field scanning transmission electron microscopy and elemental mapping of the iron monatomic catalyst prepared for Example 5 with spherical aberration correction;

[0025] Figure 6 High-angle annular dark-field scanning transmission electron microscopy and elemental mapping of the iron monatomic catalyst prepared for Comparative Example 1 with spherical aberration correction;

[0026] Figure 7 X-ray photoelectron spectroscopy of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1, wherein, Figure 7 (a) C 1s spectra of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1, Figure 7 (b) N 1s spectra of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1, Figure 7 (c) Fe 2p spectra of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1, Figure 7 (d) S 2p spectra of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1;

[0027] Figure 8 Fe K-edge X-ray absorption near-edge structure spectroscopy and Fourier-transformed R-space X-ray extended-edge absorption fine-structure spectroscopy of the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1, wherein, Figure 8 (a) Fe K-edge X-ray absorption near-edge structure spectroscopy, Figure 8 (b) Fourier-transformed R-space X-ray extended-edge absorption fine-structure spectroscopy;

[0028] Figure 9 Degradation curves and degradation rate comparison of p-chlorophenol by the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1 activated with PMS, wherein, Figure 9 (a) Degradation curves of p-chlorophenol by the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1 activated with PMS, Figure 9 (b) Degradation rate comparison of p-chlorophenol by the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1 activated with PMS;

[0029] Figure 10 Quencher capture experiment comparison of p-chlorophenol degradation by the iron monatomic catalysts prepared for Example 1, Example 5, and Comparative Example 1 activated with PMS;

[0030] Figure 11The concentration change of PMS and the utilization rate of PMS in the process of activating PMS by the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol are compared in the following figure, wherein, Figure 11 (a) is a diagram of the concentration change of PMS in the process of activating PMS by the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol, Figure 11 (b) is a comparison diagram of the utilization rate of PMS in the process of activating PMS by the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol;

[0031] Figure 12 The correlation between the degradation rate of p-chlorophenol by PMS activated by the iron monatomic catalyst prepared in Example 1 to Example 8 and Comparative Example 1 and the molar ratio of iron to sulfur is shown in the following figure;

[0032] Figure 13 The correlation between the degradation rate of p-chlorophenol by PMS activated by the iron monatomic catalyst prepared in Example 1 to Example 8 and Comparative Example 1 and the type of oxygen-containing active species is shown in the following figure;

[0033] Figure 14 The effect of anion and cation species on the process of activating PMS by the iron monatomic catalyst to degrade p-chlorophenol is shown in the following figure, wherein, Figure 14 (a) is a diagram of the effect of anion and cation species on the process of activating PMS by the iron monatomic catalyst prepared in Example 1 to degrade p-chlorophenol, Figure 14 (b) is a diagram of the effect of anion and cation species on the process of activating PMS by the iron monatomic catalyst prepared in Example 5 to degrade p-chlorophenol;

[0034] Figure 15 The effect of humic acid concentration on the process of activating PMS by the iron monatomic catalyst prepared in Example 1 and Example 5 to degrade p-chlorophenol is shown in the following figure;

[0035] Figure 16 The effect of different pH ranges on the process of activating PMS by the iron monatomic catalyst prepared in Example 1 and Example 5 to degrade p-chlorophenol is shown in the following figure;

[0036] Figure 17 The effect of different water qualities on the process of activating PMS by the iron monatomic catalyst prepared in Example 1 to degrade p-chlorophenol is shown in the following figure;

[0037] Figure 18 The cycle number and iron ion leaching rate in the process of activating PMS by the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol are shown in the following figure, wherein, Figure 18 (a) is a diagram of the cycle number in the process of activating PMS by the iron monatomic catalyst prepared in Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol, Figure 18(b) Iron ion leaching rate graph of the process of activating PMS by the iron single-atom catalyst prepared for Example 1, Example 5 and Comparative Example 1 to degrade p-chlorophenol;

[0038] Figure 19 Comparison graph of degradation rates of different antibiotics by the iron single-atom catalyst prepared for Example 1, Example 5 and Comparative Example 1 to activate PMS. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, rather than all examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0040] In the following examples, the experimental methods are described, and if not specifically stated, they are all conventional methods; the reagents and materials, if not specifically stated, can be obtained commercially.

[0041] The present application provides an iron single-atom catalyst with controllable sulfur content and coordination mode. One kind of iron single-atom catalyst with controllable sulfur content and coordination mode is prepared by adjusting the dosage of nitrogen-allyl thiourea, denoted as Fe1S / CN, and the coordination mode is short-range coordination, such as Example 1, Example 2, Example 3 and Example 4. Another kind of iron single-atom catalyst with controllable sulfur content and coordination mode is prepared by adjusting the dosage and order of trithiocyanic acid, denoted as Fe1 / SCN, and the coordination mode is long-range coordination, such as Example 5, Example 6, Example 7 and Example 8.

[0042] Example 1: Iron single-atom catalyst with controllable sulfur content and coordination mode (0.21-Fe1S / CN) is prepared by the following steps:

[0043] S1: 1.0 grams of melamine and 0.8 grams of trithionic acid are weighed and dissolved in 200 milliliters of deionized water to obtain a melamine solution and a trithionic acid solution, respectively;

[0044] S2: 0.2 grams of ferrous acetate is weighed and dissolved in 90 milliliters of deionized water to obtain a ferrous acetate solution;

[0045] S3: 0.19 grams of nitrogen-allyl thiourea is weighed and added to the ferrous acetate solution, and stirred at room temperature for 6 minutes to obtain solution A;

[0046] S4: After the solution A is added to the cyanic acid solution at room temperature and stirred for 6 min, the precipitate is obtained by mixing with the melamine solution, and is washed with deionized water and ethanol alternately for 3 times; and is dried in a blast drying oven at 60 DEG C for 12 h to obtain a precursor;

[0047] S5: The precursor obtained in step S4 is heated to 600 DEG C at a temperature increasing rate of 2.5 DEG C / min under an argon atmosphere, and is cooled to room temperature after being kept for 4 h to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is recorded as 0.21-Fe1S / CN.

[0048] The measured sulfur-iron molar ratio of the iron single-atom catalyst with controllable sulfur content and coordination mode prepared in Example 1 is 0.21, and the coordination mode is short-range coordination, so it is recorded as 0.21-Fe1S / CN.

[0049] Example 2: An iron single-atom catalyst (0.28-Fe1S / CN) with controllable sulfur content and coordination mode is prepared by the following steps:

[0050] S1: 1.0 g of melamine and 0.6 g of cyanic acid are weighed and dissolved in 200 ml of deionized water to obtain a melamine solution and a cyanic acid solution;

[0051] S2: 0.2 g of ferrous acetate is weighed and dissolved in 90 ml of deionized water to obtain a ferrous acetate solution;

[0052] S3: 0.37 g of nitrogen-allyl thiourea is weighed and added to the ferrous acetate solution, and is stirred at room temperature for 6 min to obtain a solution A;

[0053] S4: After the solution A is added to the cyanic acid solution at room temperature and stirred for 6 min, the precipitate is obtained by mixing with the melamine solution, and is washed with deionized water and ethanol alternately for 3 times; and is dried in a blast drying oven at 60 DEG C for 12 h to obtain a precursor;

[0054] S5: The precursor obtained in step S4 is heated to 600 DEG C at a temperature increasing rate of 2.5 DEG C / min under an argon atmosphere, and is cooled to room temperature after being kept for 4 h to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is recorded as 0.28-Fe1S / CN.

[0055] The measured sulfur-iron molar ratio of the iron single-atom catalyst with controllable sulfur content and coordination mode prepared in Example 2 is 0.28, and the coordination mode is short-range coordination, so it is recorded as 0.28-Fe1S / CN.

[0056] Example 3: An iron single-atom catalyst (0.35-Fe1S / CN) with controllable sulfur content and coordination mode is prepared by the following steps:

[0057] S1: 1.0 grams of melamine and 0.4 grams of cyanuric acid were weighed and added to 200 milliliters of deionized water to dissolve to obtain a melamine solution and a cyanuric acid solution;

[0058] S2: 0.2 grams of ferrous acetate was weighed and added to 90 milliliters of deionized water to dissolve to obtain a ferrous acetate solution;

[0059] S3: 0.56 grams of nitrogen-allyl thiourea was weighed and added to the ferrous acetate solution, and stirred at room temperature for 6 min to obtain solution A;

[0060] S4: Solution A was added to the cyanuric acid solution at room temperature, stirred for 6 min, then mixed with the melamine solution to obtain a precipitate, and washed with deionized water and ethanol alternately for 3 times; placed in a blast drying oven at 60°C for 12 h to obtain a precursor;

[0061] S5: The precursor obtained in step S4 was heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and kept for 4 h, then cooled to room temperature to obtain a sulfur content and coordination mode controllable iron monatomic catalyst, denoted as 0.35-Fe1S / CN.

[0062] The actual sulfur to iron molar ratio of the sulfur content and coordination mode controllable iron monatomic catalyst prepared in Example 3 was 0.35, and the coordination mode was short-range coordination, so it was denoted as 0.35-Fe1S / CN.

[0063] Example 4: A sulfur content and coordination mode controllable iron monatomic catalyst (0.44-Fe1S / CN) was prepared by the following steps:

[0064] S1: 1.0 grams of melamine and 0.2 grams of cyanuric acid were weighed and added to 200 milliliters of deionized water to dissolve to obtain a melamine solution and a cyanuric acid solution;

[0065] S2: 0.2 grams of ferrous acetate was weighed and added to 90 milliliters of deionized water to dissolve to obtain a ferrous acetate solution;

[0066] S3: 0.74 grams of nitrogen-allyl thiourea was weighed and added to the ferrous acetate solution, and stirred at room temperature for 6 min to obtain solution A;

[0067] S4: Solution A was added to the cyanuric acid solution at room temperature, stirred for 6 min, then mixed with the melamine solution to obtain a precipitate, and washed with deionized water and ethanol alternately for 3 times; placed in a blast drying oven at 60°C for 12 h to obtain a precursor;

[0068] S5: The precursor obtained in step S4 was heated to 600℃ at a temperature increasing rate of 2.5℃ / min under an argon atmosphere, and after being kept at 600℃ for 4h, it was cooled to room temperature to obtain the single-atom iron catalyst with controllable sulfur content and coordination mode, which is denoted as 0.44-Fe1S / CN.

[0069] The single-atom iron catalyst with controllable sulfur content and coordination mode prepared in Example 4 has a measured sulfur-to-iron molar ratio of 0.44, and the coordination mode is short-range coordination, so it is denoted as 0.44-Fe1S / CN.

[0070] The single-atom iron catalyst with controllable sulfur content and coordination mode (0.20-Fe1 / SCN) prepared in Example 5 is prepared by the following steps:

[0071] S1: 1.0 grams of melamine, 0.83 grams of cyanuric acid, and 0.14 grams of thiocyanuric acid were weighed and dissolved in 200 milliliters of deionized water to obtain a melamine solution, a cyanuric acid solution, and a thiocyanuric acid solution, respectively;

[0072] S2: 0.2 grams of ferric citrate was weighed and dissolved in 90 milliliters of deionized water to obtain a ferric citrate solution;

[0073] S3: The ferric citrate solution in step S2 was mixed with the cyanuric acid solution and the thiocyanuric acid solution at room temperature, and after stirring for 6 minutes, it was mixed with the melamine solution to obtain a precipitate, which was washed with deionized water and ethanol alternately for 3 times. It was dried in a blast drying oven at 60℃ for 12h to obtain a precursor;

[0074] S4: The precursor obtained in step S3 was heated to 600℃ at a temperature increasing rate of 2.5℃ / min under an argon atmosphere, and after being kept at 600℃ for 4h, it was cooled to room temperature to obtain the single-atom iron catalyst with controllable sulfur content and coordination mode, which is denoted as 0.20-Fe1 / SCN.

[0075] The single-atom iron catalyst with controllable sulfur content and coordination mode prepared in Example 5 has a measured sulfur-to-iron molar ratio of 0.2, and the coordination mode is long-range coordination, so it is denoted as 0.20-Fe1 / SCN.

[0076] The single-atom iron catalyst with controllable sulfur content and coordination mode (0.29-Fe1 / SCN) prepared in Example 6 is prepared by the following steps:

[0077] S1: 1.0 grams of melamine, 0.62 grams of cyanuric acid, and 0.28 grams of thiocyanuric acid were weighed and dissolved in 200 milliliters of deionized water to obtain a melamine solution, a cyanuric acid solution, and a thiocyanuric acid solution, respectively;

[0078] S2: 0.2 grams of ferric citrate was weighed and dissolved in 90 milliliters of deionized water to obtain a ferric citrate solution;

[0079] S3: The ferric citrate solution in step S2 is mixed with the cyanuric acid solution and the thiocyanuric acid solution at room temperature, and after stirring for 6 min, the precipitate is obtained by mixing with the melamine solution, and is washed with deionized water and ethanol alternately for 3 times; and is dried in a blast drying oven at 60°C for 12 h to obtain a precursor;

[0080] S4: The precursor obtained in step S3 is heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and after holding for 4 h, it is cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is recorded as 0.29-Fe1 / SCN.

[0081] The measured sulfur-iron molar ratio of the iron single-atom catalyst with controllable sulfur content and coordination mode prepared in Example 6 is 0.29, and the coordination mode is long-range coordination, so it is recorded as 0.29-Fe1 / SCN.

[0082] Example 7: An iron single-atom catalyst (0.36-Fe1 / SCN) with controllable sulfur content and coordination mode is prepared by the following steps:

[0083] S1: 1.0 g of melamine, 0.41 g of cyanuric acid and 0.42 g of thiocyanuric acid are weighed and dissolved in 200 ml of deionized water to obtain a melamine solution, a cyanuric acid solution and a thiocyanuric acid solution, respectively;

[0084] S2: 0.2 g of ferric citrate is weighed and dissolved in 90 ml of deionized water to obtain a ferric citrate solution;

[0085] S3: The ferric citrate solution in step S2 is mixed with the cyanuric acid solution and the thiocyanuric acid solution at room temperature, and after stirring for 6 min, the precipitate is obtained by mixing with the melamine solution, and is washed with deionized water and ethanol alternately for 3 times; and is dried in a blast drying oven at 60°C for 12 h to obtain a precursor;

[0086] S4: The precursor obtained in step S3 is heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and after holding for 4 h, it is cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, which is recorded as 0.36-Fe1 / SCN.

[0087] The measured sulfur-iron molar ratio of the iron single-atom catalyst with controllable sulfur content and coordination mode prepared in Example 7 is 0.36, and the coordination mode is long-range coordination, so it is recorded as 0.36-Fe1 / SCN.

[0088] Example 8: An iron single-atom catalyst (0.42-Fe1 / SCN) with controllable sulfur content and coordination mode is prepared by the following steps:

[0089] S1: 1.0 grams of melamine, 0.21 grams of cyanuric acid and 0.56 grams of thiocyanuric acid were weighed and added to 200 milliliters of deionized water to dissolve to obtain a melamine solution, a cyanuric acid solution and a thiocyanuric acid solution;

[0090] S2: 0.2 grams of ferric citrate was weighed and added to 90 milliliters of deionized water to dissolve to obtain a ferric citrate solution;

[0091] S3: The ferric citrate solution in step S2 was mixed with the cyanuric acid solution and the thiocyanuric acid solution at room temperature, stirred for 6 min, then mixed with the melamine solution to obtain a precipitate, and washed with deionized water and ethanol alternately for 3 times; placed in a blast drying oven at 60°C for 12h to obtain a precursor;

[0092] S4: The precursor obtained in step S3 was heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and kept for 4h, then cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, denoted as 0.42-Fe1 / SCN.

[0093] The actual sulfur-iron molar ratio of the iron single-atom catalyst with controllable sulfur content and coordination mode prepared in Example 8 was 0.42, and the coordination mode was long-range coordination, so it was denoted as 0.42-Fe1 / SCN.

[0094] Preparation of a nitrogen coordination controllable high loading iron single-atom catalyst (Fe1 / CN)

[0095] S1: 1.0 grams of melamine and 0.8 grams of cyanuric acid were weighed and added to 200 milliliters of deionized water to dissolve to obtain a melamine solution and a cyanuric acid solution;

[0096] S2: 0.2 grams of ferric citrate was weighed and added to 90 milliliters of deionized water to dissolve to obtain a ferric citrate solution;

[0097] S3: The ferric citrate solution in step S2 was mixed with the cyanuric acid solution and stirred for 6 min, then mixed with the melamine solution to obtain a precipitate, and washed with deionized water and ethanol alternately for 3 times; placed in a blast drying oven at 60°C for 12h to obtain a precursor;

[0098] S4: The precursor obtained in step S3 was heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and kept for 4h, then cooled to room temperature to obtain an iron single-atom catalyst with controllable sulfur content and coordination mode, denoted as 0.42-Fe1 / SCN.

[0099] The measured iron content of the iron monatomic catalyst prepared in Comparative Example 1 is 9wt%, which is close to the iron atom loading of the iron monatomic catalysts prepared in Examples 1 and 5. In order to facilitate the comparison of the differences in catalytic activity and selectivity, the iron monatomic catalyst is denoted as Fe1 / CN.

[0100] Preparation of a graphite phase carbon nitride in Comparative Example 2

[0101] S1: 1.0 grams of melamine and 1.0 grams of cyanuric acid were weighed and dissolved in 200 milliliters of deionized water to obtain a melamine solution and a cyanuric acid solution, respectively;

[0102] S2: The melamine solution and the cyanuric acid solution were mixed at room temperature and stirred uniformly for 6 minutes, then the precipitate was obtained by mixing the melamine solution, and washed with deionized water and ethanol alternately for 3 times. The precipitate was dried in a blast drying oven at 60°C for 12 hours to obtain a precursor;

[0103] S3: The precursor obtained in step S2 was heated to 600°C at a heating rate of 2.5°C / min under an argon atmosphere, and cooled to room temperature after holding for 4 hours to obtain a graphite phase carbon nitride, denoted as CN.

[0104] A flow chart of the preparation method of an iron monatomic catalyst with controllable sulfur content and coordination mode is shown in Figure 1 The coordination ability between iron and oxygen is stronger than that between sulfur and oxygen. Therefore, we chose a nitrogen-allyl thiourea containing only nitrogen and sulfur as the sulfur-containing organic ligand to complete the complexation process between sulfur and iron ions, and used thiocyanuric acid as a supramolecular assembly precursor to introduce remote sulfur by substitution between the terminal nitrogen and sulfur atoms in the heptazine ring. Then, the supramolecular precursors with controllable short-range and long-range sulfur coordination were obtained by hydrogen bonding assembly of melamine and cyanuric acid molecules, respectively, and the iron monatomic catalysts with controllable short-range and long-range sulfur coordination were prepared by pyrolysis at 600°C under an argon atmosphere, denoted as Fe1S / CN and Fe1 / SCN, respectively. As a comparison, an iron monatomic catalyst (Fe1 / CN) and a graphite phase carbon nitride (CN) lacking sulfur were synthesized by the same method.

[0105] Figure 2 X-ray diffraction patterns of the iron monatomic catalysts prepared in Examples 1, 5 and Comparative Example 1, and the graphite phase carbon nitride prepared in Comparative Example 2; Figure 3 Fourier transform infrared spectra of the iron monatomic catalysts prepared in Examples 1, 5 and Comparative Example 1, and the graphite phase carbon nitride prepared in Comparative Example 2. From Figure 2 and Figure 3As can be seen from Table 1, Fe1S / CN, Fe1 / SCN, Fe1 / CN and CN all show similar diffraction patterns and stretching vibration patterns; indicating that the introduction of sulfur and iron source only changes the conjugated structure of CN without affecting the crystallization process of CN. Compared with CN, the introduction of iron and remote sulfur atoms has little effect on the distance between the top carbon and the bottom nitrogen in the seven-membered ring of CN and the interlayer distance. From Figure 2 As can be seen from Table 1, Fe1S / CN, Fe1 / SCN, Fe1 / CN and CN all show similar diffraction patterns and stretching vibration patterns; indicating that the introduction of sulfur and iron source only changes the conjugated structure of CN without affecting the crystallization process of CN. Compared with CN, the introduction of iron and remote sulfur atoms has little effect on the distance between the top carbon and the bottom nitrogen in the seven-membered ring of CN and the interlayer distance. From

[0106] The structure and morphology of the iron single-atom catalysts prepared in Example 1, Example 5 and Comparative Example 1 were analyzed by high-angle annular dark field scanning transmission electron microscopy with spherical aberration correction, and the high-angle annular dark field (HAADF) scanning transmission electron microscopy image and element distribution map of the iron single-atom catalyst (Fe1S / CN) prepared in Example 1 are shown in FIG. 1A and FIG. 1B, respectively; the high-angle annular dark field (HAADF) scanning transmission electron microscopy image and element distribution map of the iron single-atom catalyst (Fe1 / SCN) prepared in Example 2 are shown in FIG. 2A and FIG. 2B, respectively; and the high-angle annular dark field (HAADF) scanning transmission electron microscopy image and element distribution map of the iron single-atom catalyst (Fe1 / CN) prepared in Comparative Example 1 are shown in FIG. 3A and FIG. 3B, respectively. Figure 4 Figure 5 Figure 6 Fe1 / CN, Fe1S / CN and Fe1 / SCN not only retain the same sheet structure as CN, but also do not detect any iron-containing nanoparticles (such as iron or iron sulfide), which is consistent with the test structure of the X-ray diffraction analysis. In addition, the corresponding element distribution images show that the C, N, Fe and S elements in Fe1S / CN and Fe1 / SCN are uniform, and S is missing in Fe1 / CN. From Figure 4 to Figure 6 As can be seen from Table 1, Fe1S / CN, Fe1 / SCN, Fe1 / CN and CN all show similar diffraction patterns and stretching vibration patterns; indicating that the introduction of sulfur and iron source only changes the conjugated structure of CN without affecting the crystallization process of CN. Compared with CN, the introduction of iron and remote sulfur atoms has little effect on the distance between the top carbon and the bottom nitrogen in the seven-membered ring of CN and the interlayer distance. From

[0107] Table 1: Test results of inductively coupled plasma emission spectrometer

[0108] ​​

[0109] The chemical composition and elemental states of the iron single-atom catalysts prepared in Examples 1, 5, and Comparative Example 1 were studied using X-ray photoelectron spectroscopy. Figure 7 As shown, the high-resolution C1s and N1s spectra of Fe1 / CN and Fe1 / SCN show little change in the binding energies of C1s and N1s, indicating that there is no interaction force between long-range sulfur and iron atoms. However, the N1s peak of Fe1S / CN can be deconvolved into two discrete characteristic peaks at 398.3 and 399.8 eV, which is attributed to sp... 2 Hybridized nitrogen atoms (NC=N) and tertiary nitrogen atoms (N-(C)3). With the coordination of short-range sulfur with iron atoms, their binding energies shift to lower values, indicating that introducing sulfur atoms, which have a lower electronegativity than nitrogen, can regulate the valence state of iron and the coordination configuration between iron and nitrogen atoms. Furthermore, the Fe 2p spectrum shows that Fe1S / CN has a higher Fe content than Fe1 / CN and Fe1 / SCN. 2+ Compared to Fe1 / CN and Fe1 / SCN, the S2p spectrum of Fe1S / CN shows a new characteristic peak at 163.6 eV corresponding to Fe-S coordination. These results further demonstrate the controllable design of the coordination mode between iron and sulfur atoms in Fe1S / CN and Fe1 / SCN.

[0110] The coordination configuration and electronic states of iron atoms in the iron single-atom catalysts prepared in Examples 1, 5, and Comparative Example 1 were further investigated using analytical techniques such as X-ray absorption near-edge structure and extended X-ray absorption fine structure. Figure 8 As shown. Figure 8 As shown in (a), a comparative analysis of FeO, Fe2O3, Fe3O4, and Fe foil reveals that the absorption edges and transition energies of Fe1S / CN, Fe1 / SCN, and Fe1 / CN are all located between the FeO and Fe2O3 reference values, indicating that the average valence state of the iron center is at the Fe... 2+ and Fe 3+ This is due to the strong interaction between iron atoms and CN. For example... Figure 8 As shown in (b), after performing Fourier transform processing on the extended X-ray absorption fine structure, it was found that Fe1 / CN and Fe1 / SCN... A distinct characteristic peak appears at [position name], which is a result of iron-nitrogen coordination scattering. Due to the potential contribution of the iron-sulfur bond, the dominant peak of Fe1S / CN shifts to [position name]. The absence of obvious iron-iron characteristic peaks corresponding to the iron foil indicates that iron atoms in Fe1S / CN are coordinated with nitrogen and sulfur atoms, which is consistent with the XPS spectrum results.

[0111] Application Example 1

[0112] Take 0.025 g of the iron single-atom catalyst prepared in Examples 1, 5, and Comparative Example 1 and place them in three 80 mL beakers containing 50 mL of deionized water. Then, add a saturated aqueous solution of p-chlorophenol (4-CP) to each beaker to make the initial concentration of 4-CP 100 μmol / L. The three beakers containing the iron single-atom catalyst and 4-CP are ultrasonically dispersed while maintaining continuous stirring. When the adsorption reaction reaches equilibrium, a saturated solution of persulfate (PMS) is added to each of the three beakers to make the initial concentration of PMS 500 μmol / L. Simultaneously, timing was initiated during the addition of saturated PMS solution. Using a clean syringe, samples were taken at 0, 0.5, 1, 1.5, 2, 2.5, 3, 5, and 10 minutes. The samples were then filtered through a 0.22 μm filter into ampoules containing 10% methanol (v / v). The concentration of 4-CP in the solution was detected by high-performance liquid chromatography (HPLC), and the concentration of PMS was determined by ultraviolet spectrophotometry (UV spectrophotometry). The 4-CP concentration change curve during the degradation reaction is shown below. Figure 9 As shown.

[0113] from Figure 9 As can be seen, compared to the iron single-atom catalyst (Fe1 / SCN) prepared in Example 5 and the iron single-atom catalyst (Fe1 / CN) prepared in Comparative Example 1, the iron single-atom catalyst (Fe1S / CN) prepared in Example 1 can completely degrade 4-CP in the solution after activating PMS. And for... Figure 9 (a) The degradation curve of Fe1S / CN was fitted with first-order kinetics, and the degradation rate was found to be 1.85 min. -1 The values ​​were 8 times that of Fe1 / CN and 13 times that of Fe1 / SCN, respectively. These results suggest that Fe1S / CN, Fe1 / SCN, and Fe1 / CN activate PMS to produce various oxygen-containing reactive species (ROS), which then degrade 4-CP.

[0114] To clarify the contribution of various ROS generated in these reaction systems to the degradation of 4-CP, a quenching analysis experiment was designed. Compared to the control group without any quenching agent, the addition of methanol, tert-butanol, and nitroblue tetrazolium to the Fe1S / CN / PMS / 4-CP reaction showed a slight inhibitory effect on the degradation of 4-CP, such as... Figure 10As shown in the figure. The addition of methyl phenyl sulfoxide and sodium azide significantly inhibited the degradation of 4-CP. In the Fe1 / SCN / PMS reaction system, the addition of methanol, tert-butanol, nitroblue tetrazolium, methyl phenyl sulfoxide, and sodium azide all inhibited the degradation of 4-CP. However, for the Fe1 / CN / PMS reaction system, only sodium azide significantly inhibited the degradation of 4-CP. The above experimental results indicate that various oxygen-containing reactive species generated by Fe1S / CN-activated PMS are in singlet oxygen (… 1 O2) and high-priced iron (Fe) VI =O) as the main component, the contribution rates (DC) to 4-CP degradation were found to be 65% and 35%, respectively, as shown in 9(b). Fe1 / CN activated PMS only produced 1 O2, Fe1 / SCN activation of PMS will produce 1 O2, Fe VI =O and other free radicals (such as ·OH, ·SO4) - O2 - (etc.). Simultaneously, changes in PMS concentration in each control group were detected, such as... Figure 11 (a) and Figure 11 As shown in (b), the PMS utilization rate of Fe1S / CN reached 36%, which is 3 times and 4.5 times higher than that of Fe1 / CN and Fe1 / SCN, respectively. This result indicates that Fe IV The generation of =O is beneficial for improving the utilization rate of PMS, while the generation of free radicals reduces the utilization rate of PMS. Therefore, with 1 O2 and Fe VI =O-based Fe1S / CN significantly improves the utilization efficiency of PMS and the rate of 4-CP degradation.

[0115] To reveal the influence of S atom content and coordination mode on the activation of PMS by iron single-atom catalysts... 1 O2 and Fe VI The effect of O was investigated by using the iron single-atom catalysts prepared in Examples 1 to 8 and Comparative Example 1 to activate PMS for the degradation of 4-CP. Figure 12 As shown, it was found that when the S / Fe molar ratio in Fe1 / SCN increased from 0.21 to 0.44, the degradation rate increased from 0.14 to 0.21, indicating a linear positive correlation between the S / Fe molar ratio and the degradation rate. However, when the S / Fe molar ratio in Fe1S / CN increased from 0.20 to 0.42, the degradation rate decreased from 1.85 to 0.98, indicating a negative correlation between the S / Fe molar ratio and the degradation rate. Figure 13 As shown, simultaneously, in each reaction system 1 O2, Fe VI The amount of O generated was measured and analyzed, and it was observed that near-range S atoms not only promote the formation of Fe, but also... VIthe generation of =O, and can significantly improve 1 the amount of O2 generation, with 1 O2 / Fe VI the increase of =O, the degradation rate of Fe1S / CN linearly increases. Although remote S atoms can increase the generation of =O VI of =O and reduce 1 O2 / Fe VI =O, but still produce some free radicals, thereby improving the degradation rate of Fe1 / SCN. It is shown that the content and coordination mode of S can regulate the generation of Fe SAC activated PMS 1 O2 and Fe VI =O, thereby affecting the utilization of PMS.

[0116] Application Example 2

[0117] In actual water bodies, anions and cations and natural organic matter are ubiquitous, and the pH value of water bodies varies greatly.

[0118] Take 0.025 g of the iron single-atom catalyst prepared in Example 1 and place it in 9 80 mL beakers containing 50 mL of deionized water, then add SO3 - , HCO3 - , F - , Cl - , Ca 2+ , Mg + , K + or Na + to the beakers, respectively, and finally one beaker without adding any anions and cations as a control group, adjust the pH to 5.6, and then perform the experiment of activating PMS to degrade 4-CP under the same experimental parameters as in Application Example 1, and the experimental results are shown in Figure 14 (a).

[0119] Take 0.025 g of the iron single-atom catalyst prepared in Example 5 and place it in 9 80 mL beakers containing 50 mL of deionized water, then add SO3 - , HCO3 - , F - , Cl - , Ca 2+ , Mg + , K + or Na + to the beakers, respectively, and finally one beaker without adding any anions and cations as a control group, adjust the pH to 5.6, and then perform the experiment of activating PMS to degrade 4-CP under the same experimental parameters as in Application Example 1, and the experimental results are shown in Figure 14 (b).

[0120] respectively, 10, 30 or 50 ppm of humic acid was added into the beaker, and the pH was adjusted to 5.6, then the experiment of degrading 4-CP by activating PMS was carried out under the same experimental parameters as in Application Example 1; 0.025 g of the iron monatomic catalyst prepared in Example 5 was placed in four 80 mL beakers containing 50 mL of deionized water, 10, 30 or 50 ppm of humic acid was added into the beaker, and the pH was adjusted to 5.6, then the experiment of degrading 4-CP by activating PMS was carried out under the same experimental parameters as in Application Example 1, and the experimental results are shown in Figure 15 .

[0121] From Figure 14 (a) and Figure 15 , it can be seen that Fe1S / CN still maintains the ability to rapidly degrade 4-CP for different anions and different contents of humic acid. From Figure 14 (b) and Figure 15 , it can be seen that Fe1 / SCN activates PMS to generate a large amount of free radicals, which are easily quenched by anions and humic acid in the solution, so that the degradation effect of 4-CP changes greatly.

[0122] As shown in Figure 16 , when the pH in the water body is adjusted to the range of 3.5 to 10.6, it is found that the main Fe1S / CN generated is 1 O2and Fe VI =O, which is not affected by the pH in the water, and maintains the degradation rate of 4-CP of about 100%; while the free radicals are easily disturbed by the pH in the solution, so that the degradation efficiency of 4-CP by the main large amount of free radicals Fe1 / SCN decreases obviously with the increase of pH.

[0123] In addition, the actual water body (such as surface water and groundwater) is selected to carry out the experiment of degrading 4-CP by Fe1S / CN, as shown in Figure 17 . It is observed that the degradation ability of Fe1S / CN for 4-CP is not affected by the water body, and 4-CP can be completely degraded within 5 minutes.

[0124] In order to verify the stability of the iron monatomic catalysts prepared in Example 1, Example 5 and Comparative Example 1, periodic experiment verification was carried out, and the experimental results are shown in Figure 18 . From Figure 18 (a), it can be found that the stability of Fe1S / CN and Fe1 / CN is good, while Fe1 / SCN generates more ROS species, causing poor cycle performance in multiple degradation reactions. From Figure 18The Fe leaching rates of Fe1S / CN, Fe1 / SCN and Fe1 / CN in (b) are all below 5%. Therefore, the cost can be reduced by recycling the catalyst in the chlorophenol wastewater treatment application.

[0125] Application Example 3

[0126] Sulfamethoxazole, tetracycline, ciprofloxacin, chloramphenicol, flumequine, etc. are widely used in pharmaceutical factories and livestock industry for the prevention and treatment of bacterial infections. Their molecular structures contain amino, chlorine and fluorine functional groups, and they are representatives of antibiotics.

[0127] 0.025 g of the iron monatomic catalyst (Fe1S / CN) prepared in Example 1 was placed in five 80 mL beakers containing 50 mL of deionized water, and saturated aqueous solutions of sulfamethoxazole, tetracycline, ciprofloxacin, chloramphenicol or flumequine were added to each beaker to give an initial concentration of 100 μmol / L. 0.025 g of the iron monatomic catalyst (Fe1 / SCN) prepared in Example 5 was placed in five 80 mL beakers containing 50 mL of deionized water, and saturated aqueous solutions of sulfamethoxazole, tetracycline, ciprofloxacin, chloramphenicol or flumequine were added to each beaker to give an initial concentration of 100 μmol / L. 0.025 g of the iron monatomic catalyst (Fe1 / CN) prepared in Comparative Example 1 was placed in five 80 mL beakers containing 50 mL of deionized water, and saturated aqueous solutions of sulfamethoxazole, tetracycline, ciprofloxacin, chloramphenicol or flumequine were added to each beaker to give an initial concentration of 100 μmol / L. Then, the experiments of degrading 4-CP by activating PMS were carried out under the same experimental parameters as in Application Example 1, and the 4-CP concentration change curves during the degradation reaction are shown in Figure 19

[0128] From the degradation effects of different antibiotics, it can be seen that Fe1S / CN exhibits excellent degradation rate (0.01-0.64 min -1 ), which indicates that high content of 1 O2and Fe VI =O can attack the amino, chlorine and fluorine functional groups, and 1 O2generates Fe1 / SCN with high selectivity and Fe1 / CN generates a large amount of free radicals, and the degradation rates of antibiotics with different structures are not the same. For ciprofloxacin and chloramphenicol, the degradation rates of Fe1 / SCN are 0.35 and 0.07 min -1 , respectively, which are faster than those of Fe1 / CN; and for sulfamethoxazole, tetracycline and flumequine, the degradation rates of Fe1 / CN are 0.03, 0.04 and 0.003 min -1 ​The above experimental results show that the Fe1S / CN prepared in Example 1 has a certain universal degradation capacity for different antibiotics. This provides a scientific basis for promoting its application in the green and efficient treatment of antibiotic wastewater.

[0129] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An iron single-atom catalyst with controllable sulfur content and coordination mode, characterized in that, The sulfur content and coordination mode controllable iron monatomic catalyst is prepared by the following steps: S1: melamine is dissolved in deionized water to obtain a melamine solution; cyanuric acid is dissolved in deionized water to obtain a cyanuric acid solution; ferrous acetate is dissolved in deionized water to obtain a ferrous acetate solution; the molar ratio of the melamine, cyanuric acid and ferrous acetate is 1:0.2-0.8:0.8-0.2; S2: nitrogen-allyl thiourea is added to the ferrous acetate solution and stirred uniformly to obtain solution A; the molar ratio of the nitrogen-allyl thiourea and ferrous acetate is 1:0.1-0.5; S3: solution A is added to the cyanuric acid solution and stirred uniformly, then mixed with the melamine solution to obtain a precipitate, and washed and dried to obtain a precursor; S4: the precursor obtained in step S3 is heated to 550-650°C under an argon atmosphere, incubated for 3-6 h and cooled to room temperature to obtain the sulfur content and coordination mode controllable iron monatomic catalyst, denoted as Fe1S / CN.

2. An iron single-atom catalyst with controllable sulfur content and coordination mode, characterized in that, The sulfur content and coordination mode controllable iron monatomic catalyst is prepared by the following steps: S1: melamine is dissolved in deionized water to obtain a melamine solution; cyanuric acid is dissolved in deionized water to obtain a cyanuric acid solution; thiocyanic acid is dissolved in deionized water to obtain a thiocyanic acid solution; ferric citrate is dissolved in deionized water to obtain a ferric citrate solution; the molar ratio of the melamine, cyanuric acid, thiocyanic acid and ferric citrate is 1:0.2-0.8:0.6-0.1:0.2-0.1; S2: the ferric citrate solution, cyanuric acid solution and thiocyanic acid solution are mixed, stirred uniformly and mixed with the melamine solution to obtain a precipitate, and washed and dried to obtain a precursor; S3: the precursor obtained in step S2 is heated to 550-650°C under an argon atmosphere, incubated for 3-6 h and cooled to room temperature to obtain the sulfur content and coordination mode controllable iron monatomic catalyst, denoted as Fe1 / SCN.

3. Use of the iron single-atom catalyst with controllable sulfur content and coordination mode according to claim 1 or 2 for removing organic pollutants in water bodies, characterized in that, The method comprises the following steps: The sulfur content and coordination mode controllable iron monatomic catalyst and peroxymonosulfate are added to water, the water temperature is 15-35°C, and the removal of organic pollutants in the water body is completed by stirring for 5-10 min; the addition amount of the sulfur content and coordination mode controllable iron monatomic catalyst is 0.1-1 g / L; the addition amount of the peroxymonosulfate is 0-500 μmol / L, and the addition amount of the peroxymonosulfate is not 0; the concentration of the organic pollutants is 0-100 μmol / L, and the concentration of the organic pollutants is not 0.

4. Use according to claim 3, characterised in that, The organic pollutants are p-chlorophenol or antibiotics.

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