A sulfur-modified iron-nitrogen-carbon catalyst and preparation and application thereof

Abstract

A sulfur-modified iron-nitrogen-carbon catalyst and its preparation and application. The present application relates to a preparation method of a series of sulfur-doped iron-nitrogen-carbon catalysts with high catalytic activity obtained by changing the addition amount of thiourea in the catalyst synthesis process and its application. Even under the water quality conditions containing a series of high-concentration inorganic anion humic acid, the catalyst can still achieve high-efficiency degradation of hydroxybenzoic acid. The sulfur atom doping plays a very important role in improving the activity of the main catalytically active site Fe-N4 activated persulfate, forming a catalytic reaction system dominated by singlet oxygen active groups, and realizing selective degradation of organic pollutants with different molecular structures, not only meeting the requirements of high catalytic activity, high stability and high adaptability of the catalyst, but also providing an effective preparation method for improving the catalytic activity of the traditional Fe-N4 structure site, which has good prospects in the application field of degrading organic wastewater containing a large amount of complex matrix.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation and application, and particularly relates to a sulfur-doped iron-nitrogen-carbon catalyst with high activity and high resistance and a preparation method thereof. BACKGROUND

[0002] As a new type of advanced oxidation technology, PMS-AOPs have been widely studied in recent years. In the activation process, it can produce sulfate radicals with stronger oxidation ability than hydroxyl radicals, longer survival time and selective singlet oxygen, which are favored by people. Iron-based nanocatalysts have the characteristics of low price, environmental friendliness and superior activity, and have become an ideal catalyst material for activating persulfate. Single-atom iron-based catalysts with atomic distribution on nitrogen-doped carbon carriers have gradually attracted the attention of researchers. Because of its high atom utilization rate, unsaturated coordination structure and strong metal-support interaction, it can overcome the disadvantage of uneven metal sites and often exhibit high catalytic activity in heterogeneous catalytic reactions. In addition, single-atom iron-based catalysts inherit the advantages of homogeneous and heterogeneous catalysts, and their simple catalytic structure can also be used as a model catalyst for studying catalytic reactions, so they are also ideal research models in the study of catalytic mechanism. Among them, Fe-NC structure shows great potential in environmental remediation, and has become a hot spot for the study of many single-atom catalysts.

[0003] Heteroatom modification is considered to be an effective strategy for single-atom catalysts to improve the activation efficiency of PMS. Nitrogen-doped carbon substrates are generally considered to be ideal materials for anchoring transition metal atoms. By doping heteroatoms with different electronegativity and atomic radius, it may break the stereotype of traditional symmetrical structure, introduce additional carbon defects in the second coordination shell, and thus produce asymmetric geometry and electronic state distribution through long-range interaction. In addition, heteroatom modification can introduce new active sites in Csp 2Spin charge is generated on the lattice and effectively replaces C / N groups. Although heteroatom modification has broad application prospects in various catalytic systems such as oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), lithium-sulfur battery, etc., there are few studies on the precise position, number, modification structure of heteroatom modification and peroxide activation pathway, especially in the PMS-AOPs system. Therefore, by using thiourea as a sulfur source, the S atom is first modified into the metal organic ligand precursor by hydrothermal method, and then the sulfur-modified iron-nitrogen-carbon site (Fe-N4C) is prepared by one-step calcination, and it has good prospects for being used in Fenton-like reaction to degrade organic pollutants. SUMMARY

[0004] The purpose of the present application is to provide a Fenton-like catalyst with high activity and high resistance, and a preparation method thereof. The sulfur-modified metal organic ligand structure is synthesized by hydrothermal method using thiourea as a sulfur source, and then a stable sulfur-modified iron-nitrogen-carbon catalyst is generated by nitrogen calcination.

[0005] It is found that the catalyst generates non-radical active groups dominated by singlet oxygen by activating potassium monopersulfate, and exhibits superior degradation activity on p-hydroxybenzoic acid (HBA). When the addition amount of thiourea is 48 mg, the Fe-NS2C catalyst exhibits the best catalytic activity. The main components of Fe-NS2C are sulfur-doped graphite carbon, nitrogen-doped graphite carbon, and sulfur-modified Fe-N4 structural units, and the sulfur-modified Fe-N4 is the main catalytic active site. It is worth mentioning that the non-radical degradation path dominated by singlet oxygen in the process of degrading p-hydroxybenzoic acid in the Fenton-like reaction system makes it can still maintain superior catalytic activity under complex conditions such as high concentration of different ions, high concentration of humic acid, different pH and other water quality, and the catalyst structure is stable, and the performance decay is not serious after several cycles, and there is no large metal filter out, and it has certain practical application value.

[0006] The present application is realized by the following technical means:

[0007] Catalyst preparation

[0008] 1) using a hydrothermal method to prepare a metal organic ligand precursor: 140 mg FeCl2 4H2O, 24-96 mg (preferably 40-50 mg, more preferably 46-50 mg) thiourea, 1.2-2.0 g (preferably 1.5-1.7 g) ZnCl2 are sequentially added to 120 mL of formamide, stirred for 30-60 min, then transferred to a hydrothermal reactor, placed in an oven at 180°C for 10-15 h (preferably 11-13 h), after the reaction is completed, cooled to room temperature, open the hydrothermal reactor, centrifugal separation to obtain a yellow solid precipitate, washed with deionized water 3 times, then dried in an oven at 60-80°C (preferably 60-70°C) to obtain a yellow powder.

[0009] 2) The dried metal organic ligand precursor powder is ground in a crucible for 10-30 min (preferably 15-20 min), 200-400 mg of the powder is placed in a porcelain boat, calcined at 900-1000°C (preferably 850-950°C) in a nitrogen atmosphere for 1-4 h (preferably 2-3 h), the heating rate from room temperature to the calcination temperature is 3-8°C / min (preferably 4-6°C / min), after calcination, naturally cooled to room temperature, the catalyst is removed, 100-300 mg of the catalyst is placed in 200 mL of a 0.5-2 M (preferably 1-1.5 M) sulfuric acid solution, acid washed at 70-90°C (preferably 75-85°C) for 12-36 h (preferably 16-24 h), after acid washing, the acid washed catalyst is washed with water until the pH of the washing liquid stabilizes at 6-7, dried in a 60°C oven to obtain a sulfur-modified iron-nitrogen-carbon catalyst;

[0010] The application of the catalyst in a Fenton-like reaction for catalyzing the oxidative degradation of organic pollutants by an oxidant.

[0011] The oxidant is one or more of potassium hydrogen persulfate, hydrogen peroxide or potassium peroxodisulfate;

[0012] The reaction substrate (pollutant) is one or both of a 100-200 μM p-hydroxybenzoic acid, phenol solution, the catalyst concentration in the solution is 50-500 mg / L (preferably 100-450 mg / L), the oxidant concentration is 0.5-6 mM (preferably 1-4 mM), and the pH is 2-10.6.

[0013] The reaction device for the Fenton-like degradation of pollutants is a dark reaction box, which maintains dark conditions, and a temperature control stirrer and a reaction container are placed in the box;

[0014] The catalyst can realize efficient degradation of model pollutants, i.e., hydroxybenzoic acid, in a reactor; the catalyst can attack organic pollutants by non-radical species (singlet oxygen) under conditions containing humic acid and various ions, so as to realize degradation of the organic pollutants.

[0015] In the reaction solution for degrading pollutants by Fenton-like reaction, the concentration of one or more than two of bicarbonate ions, carbonate ions, sulfate ions, perchlorate ions and chloride ions should be < 20 mM (preferably 0 mM-10 mM), or the concentration of humic acid should be < 20 mg / L (preferably 0 mg / L-10 mg / L).

[0016] In the reaction solution for degrading pollutants by Fenton-like reaction, the pH range of the reaction solution should be controlled in 2-10.6 (preferably 3-9).

[0017] In the reaction process for degrading pollutants by Fenton-like reaction, the reaction time should be greater than or equal to 5 min (preferably greater than or equal to 15 min).

[0018] The preparation method of the catalyst is simple and easy to implement, and the prepared catalyst has high activity (the removal rate of HBA can reach 93.9% within 7 min) and high environmental matrix tolerance (high concentrations of anions and high concentrations of humic acid have little effect on the degradation process). The catalyst of the present application still maintains high catalytic degradation activity of HBA even in water containing high concentrations of humic acid and a series of high concentrations of anions. The sulfur atom doping plays a very important role in improving the activity of the main catalytic active site Fe-N4 for activating persulfate. The sulfur-modified Fe-N4 structure site unit serves as the main catalytic active site, realizes efficient activation of potassium hydrogen persulfate, forms a non-radical dominant reaction system mainly with singlet oxygen, and can selectively degrade pollutants of different properties. The catalyst not only has high catalytic activity, but also has high activity, high stability, high selectivity and high adaptability. The preparation method of the catalyst is simple, environmentally friendly and cost controllable, and has good application prospect in the field of degrading organic wastewater containing complex matrix. The present application uses thiourea as a sulfur source and nitrogen-doped carbon material as a single-atom iron anchoring site to form a sulfur-modified iron-nitrogen-carbon catalyst. The catalyst directly generates singlet oxygen and exhibits excellent catalytic activity in the Fenton-like degradation reaction of HBA. The catalyst is simple to prepare, has high activity and high environmental matrix tolerance, and has not been reported in the previous Fenton-like reaction field. It has good application prospect in the field of treating refractory organic wastewater containing complex matrix. DETAILED DESCRIPTION

[0019] Examples 1-38

[0020] 1. Investigate the influence of the change of thiourea and ferrous chloride dosage on the activity of the catalyst

[0021] Example 4

[0022] 1) Preparation of metal organic ligand precursor by hydrothermal method:

[0023] 150mg FeCl 2· 4H2O, 48mg thiourea, 1.6g ZnCl2 were added into 120mL formamide in turn, stirred for 30min, then transferred into a hydrothermal reactor, placed in an oven at 180℃ for 12h, after the reaction was completed, cooled to room temperature, opened the hydrothermal reactor, centrifuged to obtain yellow solid precipitate, washed with deionized water for 3 times, then dried in an oven at 60℃ to obtain yellow powder.

[0024] 2) Preparation of sulfur-modified iron-nitrogen-carbon catalyst

[0025] The dried metal organic ligand precursor powder was ground in a crucible for 20min, 300mg powder was placed in a porcelain boat, calcined at 900℃ under nitrogen atmosphere for 2h, the heating rate from room temperature to calcination temperature was 5℃ / min, after calcination, naturally cooled to room temperature, the catalyst was taken out, 200mg catalyst was placed in 200mL 1M sulfuric acid solution, acid washed in an 80℃ water bath for 24h, after acid washing, the acid washed catalyst was washed with water until the pH of the washing liquid was stable between 6-7, dried in an oven at 60℃ to obtain sulfur-modified iron-nitrogen-carbon catalyst Fe-NS3C(48mg thiourea).

[0026] Examples 1, 2, 3, 5, 6, 7 The processes and conditions are the same as Example 4, except that the different amounts of thiourea are added (annotated in parentheses after the name), according to the different amounts of thiourea added, respectively named Fe-NC(0mg thiourea), Fe-NS1N(24mg thiourea), Fe-NS2C(36mg thiourea), Fe-NS4C(60mg thiourea), Fe-NS5C(72mg thiourea), Fe-NS6C(84mg thiourea).

[0027] Examples 8, 9 The processes and conditions are the same as Example 4, except that the different amounts of FeCl 2· 4H2O are added (annotated in parentheses after the name), according to the different amounts of FeCl 2· 4H2O added, respectively named HFe-NS3C(200mg FeCl 2· 4H2O), LFe-NS3C(100mg FeCl 2· 4H2O).

[0028] The sulfur-modified iron-nitrogen-carbon catalysts are microscopically two-dimensional sheet layer stacking structures, and the composition is sulfur-doped graphite carbon nitride loaded with iron single atom, and has no magnetism. According to the change of the amount of thiourea added, the catalysts with different sulfur contents have the following specific characteristics: the specific surface area of Fe-NC is 46.91 m 2 / g, the main component is a sheet layer graphite carbon loaded with iron single atom sites, no sulfur element is found in the graphite layer catalyst material, the iron content is 2.72wt%, the nitrogen-carbon molar ratio is 0.105, the sheet layer graphene diameter is 200-950nm, the average diameter is 450nm, the sheet layer thickness is between 2nm-65nm, and the active component in the Fe-NC catalyst is Fe-N4 site. The sulfur-modified iron-nitrogen-carbon catalyst has a unique catalytic structure, and the S element and the C element in the sulfur-modified iron-nitrogen-carbon catalyst form a C-S bond, the C-S bond interacts with the single atom catalytic structure of Fe-N4, and effectively regulates the electronic distribution state of the central metal iron atom of Fe-N4. The specific surface area of Fe-NS1C is 52.72 m 2 / g, the main component is a sulfur-doped graphite carbon nitride loaded with iron single atom site, the mass fraction of sulfur element in the catalyst material is 6.14wt%, the iron content is 3.18wt%, the nitrogen-carbon molar ratio is 0.109, the sheet layer graphene diameter is 100-900nm, the average diameter is 420nm, and the sheet layer thickness is between 2nm-60nm. The specific surface area of Fe-NS2C is 64.47 m 2 / g, the main component is a sulfur-doped graphite carbon nitride loaded with iron single atom site, the mass fraction of sulfur element in the catalyst material is 8.16wt%, the iron content is 3.22wt%, the nitrogen-carbon molar ratio is 0.115, the sheet layer graphene diameter is 100-850nm, the average diameter is 400nm, and the sheet layer thickness is between 2nm-58nm. The specific surface area of Fe-NS3C is 76.49 m 2 / g, the main component is a sulfur-doped graphite carbon nitride loaded with iron single atom site, the mass fraction of sulfur element in the catalyst material is 10.14wt%, the iron content is 3.04wt%, the nitrogen-carbon molar ratio is 0.117, the sheet layer graphene diameter is 100-800nm, the average diameter is 300nm, and the sheet layer thickness is between 1nm-50nm. The specific surface area of Fe-NS4C is 69.25 m 2 / g, the main component is a sulfur-doped graphite carbon nitride loaded with iron single atom site, the mass fraction of sulfur element in the catalyst material is 12.22wt%, the iron content is 2.85wt%, the nitrogen-carbon molar ratio is 0.121, the sheet layer graphene diameter is 100-850nm, the average diameter is 350nm, and the sheet layer thickness is between 2nm-55nm. The specific surface area of Fe-NS5C is 67.33 m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron single-atom sites, the mass fraction of sulfur in the catalytic material is 13.28wt%, the iron content is 3.12wt%, the nitrogen-carbon molar ratio is 0.119, the flake graphene diameter is 100-880nm, the average diameter is 380nm, and the flake thickness is between 2nm-58nm. The specific surface area of Fe-NS6C is: 66.31m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron single-atom sites, the mass fraction of sulfur in the catalytic material is 15.42wt%, the iron content is 2.53wt%, the nitrogen-carbon molar ratio is 0.123, the flake graphene diameter is 100-850nm, the average diameter is 400nm, and the flake thickness is between 2nm-60nm.

[0029] By changing the amount of ferrous chloride in the metal organic ligand precursor, a series of sulfur-modified iron-nitrogen-carbon catalysts are obtained, which are microscopically two-dimensional flake stacking structures. The main structural characteristics are as follows: the specific surface area of LFe-NS3C is: 77.36m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron single-atom sites, the mass fraction of sulfur in the catalytic material is 11.38wt%, the iron content is 2.04wt%, the nitrogen-carbon molar ratio is 0.103, the flake graphene diameter is 100-800nm, the average diameter is 300nm, and the flake thickness is between 1nm-50nm. The specific surface area of HFe-NS3C is: 63.36m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron single-atom sites and graphite carbon layer wrapped iron nanoparticles, the iron nanoparticle diameter size is 2nm-120nm, the wrapped graphite carbon layer number is 5-25 layers, and the wrapped layer thickness is 1-50nm. Due to the formation of iron nanoparticles by some iron atoms, the number of single-atom Fe sites is reduced, and the interaction between C-S bond and Fe-N4 single-atom catalytic structure is weakened. The mass fraction of sulfur in the catalytic material is 10.87wt%, the iron content is 4.52wt%, the nitrogen-carbon molar ratio is 0.106, the flake graphene diameter is 100-850nm, the average diameter is 340nm, and the flake thickness is between 1nm-50nm.

[0030] In the experiment investigating the activity of iron, nitrogen, and carbon prepared with different amounts of thiourea and ferrous chloride, the Fenton-like potassium persulfate oxidation experiment, using p-hydroxybenzoic acid as a model pollutant, was used as a probe reaction. The first-order reaction rate constant k was used as the evaluation index of the catalytic reaction efficiency. k represents the rate of reaction in the Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the HBA concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained through linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The reaction substrate is 50 mL of 2 mM HBA solution. The final concentration of the sulfur-modified iron-nitrogen-carbon catalyst (or Fe-NC) is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the reaction pH is the pH of the reaction solution before initiation (adjusted using 0.1 M NaOH and 0.1 M HCl solutions). At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher, and the mixture was thoroughly mixed to quench the reaction. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column (Table 1). For Example 4, Fe-NS3C achieved a HBA removal rate of 87.91% at 5 min and 96.24% at 10 min.

[0031] Table 1 Effect of different composite ratios on catalyst activity

[0032]

[0033]

[0034] Table 1 shows that the sulfur-modified iron-nitrogen-carbon catalyst prepared with different amounts of thiourea has a crucial impact on the reaction. As shown in Table 1, both excessive and insufficient thiourea additions are detrimental to the reaction. The Fe-NS3C catalyst with the optimal thiourea addition ratio (i.e., the sulfur-modified iron-nitrogen-carbon catalyst synthesized with 48 mg of thiourea) can achieve a large-scale degradation of pollutants in a short time, exhibiting the best catalytic degradation activity. Similarly, excessive or insufficient addition of ferrous chloride is also detrimental to the reaction. Excessive addition of ferrous chloride leads to the formation of iron particles, which is not conducive to the formation of single-atom iron sites and reduces the utilization efficiency of active sites. Insufficient addition of ferrous chloride results in insufficient iron catalytic sites, which cannot effectively promote the reaction.

[0035] 2. Investigate the effect of different reaction conditions on catalyst activity.

[0036] In the test of catalyst activity under different reaction conditions, the reaction rate constant k is used as the evaluation index of catalytic reaction efficiency. k represents the rate of reaction in a Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the p-hydroxybenzoic acid (HBA) concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The reaction substrate is 50 mL of 2 mM HBA solution, and the Fe-NS3C catalyst concentration is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the reaction pH is the pH of the reaction solution before initiation (adjusted using 0.1 M NaOH and 0.1 M HCl solutions). At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min respectively), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher, mixed thoroughly, and the reaction was quenched. The concentration of HBA was analyzed and detected by liquid chromatography equipped with a C18 column.

[0037] The reaction pH was fixed by adjusting the pH of the reaction system with 0.1M NaOH solution and 0.1M HC1 solution before the reaction was started. The 100 μΜ HBA solution with different pH was prepared as follows: 5 mL of 1 mM HBA solution with high concentration was added to 45 mL of deionized water, mixed well, and the reaction pH was adjusted by titration of 0.1M NaOH solution and 0.1M HC1 solution. The pH of the solution after titration was measured in real time by pH meter, and 50 mL of HBA solution with different buffer pH (reaction substrate) was obtained after the pH was stable.

[0038] In addition, the PMS concentration, catalyst concentration and HBA concentration in the reaction system were controlled by changing the concentration of PMS (0.25 mM, 0.5 mM, 1.0 mM, 2.0 mM), the concentration of catalyst Fe-NS3C (50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L) and the concentration of HBA solution (1 mM, 2 mM, 4 mM, 10 mM) respectively. The reaction device was a dark reaction box, which was kept in the dark. A temperature-controlled stirrer and a 150 mL beaker were placed in the box, and the reaction temperature was controlled at 25°C. 1 mL of reaction solution was taken at fixed intervals of reaction time (the sampling time points were 0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, 20 min, respectively), and 0.5 mL of 0.2M sodium sulfite was added to the sample as a reaction quencher, mixed well, and then quenched. The reaction was analyzed online by high performance liquid chromatography equipped with a C18 column.

[0039] Table 2 Effect of different reaction conditions on the activity of the catalyst

[0040]

[0041]

[0042] As can be seen from Table 2, Fe-NS3C can efficiently degrade organic pollutants in a wide pH range. Compared with acidic and alkaline reaction conditions, the weakly acidic environment with pH = 5.1 has the best catalytic activity. The catalytic performance gradually deteriorates with the increase of HBA concentration, gradually increases and then weakens with the increase of PMS concentration, and first becomes better and then gradually tends to be stable with the increase of catalyst concentration. This is because when too much catalyst is added, the number of catalytic sites is no longer a factor that restricts the speed of the reaction. At this time, the effect of adding more catalyst on the reaction rate can be ignored.

[0043] 3. Investigate the effect of different ions on the catalyst reactivity.

[0044] In the activity tests of catalysts with different ion pairs, the degradation reaction of p-hydroxybenzoic acid was used as the probe reaction, and the reaction rate constant k was used as the evaluation index of catalytic reaction efficiency. k represents the rate of reaction in a Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the HBA concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, -lnC / C0 is plotted on the ordinate, and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The reaction substrate is 50 mL of 2 mM HBA solution. The final concentration of the Fe-NS3C catalyst is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the pH is the same as the pH of the reaction solution before initiation. Water quality conditions were altered by adding different ionic salts to the reaction system. The added ionic salts were sodium chloride, sodium bicarbonate, and sodium sulfate (NaCl, NaHCO3, Na2SO4, Na2CO3, Na2HPO4, NaNO3). The concentration of the ionic salts in the reaction system was uniformly controlled at 10 mmol / L. 1 mL of the reaction solution was taken at fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min). 0.5 mL of 0.2 M sodium sulfite was added to the taken samples as a reaction quencher, and the mixture was thoroughly mixed to quench the reaction. The concentration of bisphenol A was analyzed using liquid chromatography equipped with a C18 column.

[0045] Table 3 Effect of different reaction conditions on catalyst activity

[0046]

[0047] Cl - Chloride ions; HCO3- - : Bicarbonate ion; SO4 2- Sulfate ion; HPO4 2- : Hydrogen phosphate ion; CO3 2-： carbonate ion; NO3 - nitrate ions

[0048] As shown in Table 3, the addition of all ions did not significantly inhibit the reactivity. In addition, the addition of some ions interacted with PMS in the reaction system to generate other active groups, which actually promoted the reaction. This is mainly because the active groups in the reaction system are not free radicals that are easily affected by ions, but rather active components mainly composed of non-free radicals play an important role in the degradation of HBA.

[0049] 4. Investigate the catalytic performance of sulfur-modified iron-nitrogen-carbon catalysts for different pollutants.

[0050] In the activity tests of sulfur-modified iron-nitrogen-carbon catalysts for different pollutants, the main pollutants selected were five major organic pollutants: p-hydroxybenzoic acid, benzoic acid, phenol, and nitrobenzene. The degradation reactions of these pollutants were used as probe reactions, and the reaction rate constant k was used as the evaluation index of the catalytic reaction efficiency. k represents the rate of reaction in a Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the p-hydroxybenzoic acid concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The final concentration of the Fe-NS3C catalyst is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the reaction pH is the same as the pH of the reaction solution before initiation. The reaction substrate was 50 mL of 100 μM solution containing different contaminants. 0.5 mL of 100 mM potassium persulfate (PMS) solution was added to the reaction solution containing 150 mg / L catalyst to initiate the reaction. At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher. After thorough mixing, the reaction was quenched. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column.

[0051] Table 4 Effect of different reaction conditions on catalyst activity

[0052]

[0053] As shown in Table 4, Fe-NS3C exhibits significant degradation selectivity for different pollutants. It has high degradation efficiency for pollutants with strong electron-donating ability (phenol and p-hydroxybenzoic acid), while its degradation activity is limited for pollutants containing electron-withdrawing groups (nitrobenzene and benzoic acid).

[0054] 5. Investigate the effect of different concentrations of humic acid on the catalyst's reactivity.

[0055] In the activity tests of catalysts with different ion pairs, the potassium persulfate oxidation reaction of p-hydroxybenzoic acid was used as a probe reaction, and the reaction rate constant k was used as an evaluation index of the catalytic reaction efficiency. k represents the rate of reaction in a Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the HBA concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The concentration of the Fe-NS3C catalyst is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the reaction pH is the same as the pH of the reaction solution before initiation. The reaction substrate was 50 mL of a 2 mM solution containing HBA. Water quality conditions were altered by adding different concentrations of humic acid to the reaction system, with concentrations controlled at 1 mg / L, 5 mg / L, 10 mg / L, 15 mg / L, and 20 mg / L. 0.5 mL of a 100 mM potassium persulfate (PMS) solution was added to the reaction solution containing 150 mg / L catalyst to initiate the reaction. At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher. After thorough mixing, the reaction was quenched. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column.

[0056] Table 5 Effect of different reaction conditions on catalyst activity

[0057]

[0058] As shown in Table 5, the addition of different concentrations of humic acid (1 mg / L, 5 mg / L, 10 mg / L, 15 mg / L and 20 mg / L) did not have a significant adverse effect on the degradation of HBA by Fe-NS3C. However, it should be noted that as the concentration of humic acid increases, the inhibition of the reaction first increases and then decreases, indicating that the catalyst can resist the influence of humic acid to a certain extent during the degradation of pollutants and has a certain tolerance to wastewater containing humic acid.

[0059] 6. Investigate the effect of different oxidants on the catalyst reactivity.

[0060] In the activity tests of different oxidants on the catalyst, the potassium persulfate oxidation reaction of p-hydroxybenzoic acid was used as the probe reaction, and the reaction rate constant k was used as the evaluation index of the catalytic reaction efficiency. k represents the rate of reaction in the Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the HBA concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The concentration of the Fe-NS3C catalyst is 150 mg / L. The reaction is initiated by adding 0.5 mL of a 100 mM solution of potassium persulfate (PMS), hydrogen peroxide (H2O2), and potassium persulfate (PDS). The reaction temperature is 25 °C, and the pH is the same as the pH of the reaction solution before the reaction is initiated. The reaction substrate was 50 mL of a 2 mM solution containing HBA. 0.5 mL of 100 mM potassium persulfate (PMS), hydrogen peroxide (H2O2), or potassium persulfate (PDS) solution was added to the reaction solution containing 150 mg / L catalyst to initiate the reaction. At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher. After thorough mixing, the reaction was quenched. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column.

[0061] Table 6. Effects of different reaction conditions on catalyst activity

[0062]

[0063] From Table 6, it can be seen that the addition of different types of oxidants has a significant effect on the degradation of HBA by Fe-NS3C, in which PMS as an oxidant for the degradation of HBA exhibits the most superior activity, while the activation ability of Fe-NS3C for H2O2 is limited, with the lowest catalytic reaction efficiency, but it is worth noting that the three different oxidants exhibit a certain degradation capacity for HBA under the action of Fe-NS3C.

[0064] 5. Investigation of the comparison of the reaction activity of the sulfur-modified iron-nitrogen-carbon catalysts prepared by Fe-NS3C catalyst and different sulfur sources, different hydrothermal solvents, commercial Fe2O3 and Fe3O4 catalysts

[0065] Comparative Example 1:

[0066] 1) Preparation of metal organic ligand precursor by hydrothermal method:

[0067] 150 mg of FeCl2 4H2O, 48 mg of thioacetamide or sodium sulfide, and 1.6 g of ZnCl2 were sequentially added to 120 mL of formamide, stirred for 30 min, then transferred to a hydrothermal reactor, placed in an oven at 180°C for 12 h, and after the reaction was completed, cooled to room temperature, opened the hydrothermal reactor, centrifuged to obtain a yellow solid precipitate, washed with deionized water for 3 times, and dried in a 60°C oven to obtain a yellow powder.

[0068] 2) Preparation of sulfur-modified iron-nitrogen-carbon catalyst

[0069] The dried metal organic ligand precursor powder was ground in a crucible for 20 min, 300 mg of the powder was placed in a porcelain boat, calcined at 900°C under nitrogen atmosphere for 2 h, the heating rate from room temperature to calcination temperature was 5°C / min, and after calcination, the catalyst was naturally cooled to room temperature, 200 mg of the catalyst was placed in 200 mL of 1M sulfuric acid solution, and acid washed in an 80°C water bath for 24 h, after acid washing, the acid washed catalyst was washed with water until the pH of the washing liquid was stable between 6-7, and dried in a 60°C oven to obtain a sulfur-modified iron-nitrogen-carbon catalyst prepared with thioacetamide as a sulfur source, named Fe-NCS2. A sulfur-modified iron-nitrogen-carbon catalyst prepared with sodium sulfide as a sulfur source was named Fe-NCS3.

[0070] Fe-NCS2 and Fe-NCS3 are both iron-nitrogen-carbon catalysts obtained by calcination of metal-based organic ligand precursors, and thus exhibit two-dimensional sheet structure in microcosm, only the diameters of the two-dimensional sheet structure are slightly different: for Fe-NCS2, the diameter of the sheet structure ranges from 200 nm to 600 nm, with an average diameter of 230 nm, the sheet thickness is between 1 nm and 42 nm, and the specific surface area is relatively large, 68.26 m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron monatomic, and it has no magnetism, the mass fraction of sulfur in the catalytic material is 6.14wt%, the iron content is 2.18wt%, and the molar ratio of nitrogen to carbon is 0.102. For Fe-NCS3, the diameter of the sheet structure ranges from 150 nm to 650 nm, with an average diameter of 320 nm, the sheet thickness is between 2 nm and 50 nm, and the specific surface area is relatively large, 58.72 m 2 / g, the main component is sulfur-doped graphite carbon nitride loaded with iron monatomic, and it has no magnetism, the mass fraction of sulfur in the catalytic material is 4.14wt%, the iron content is 1.84wt%, and the molar ratio of nitrogen to carbon is 0.107.

[0071] Comparative Example 2:

[0072] 2) Preparation of metal organic ligand precursor by hydrothermal method:

[0073] 150 mg of FeCl 2· 4H2O, 48 mg of thiourea, and 1.6 g of ZnCl2 were sequentially added to 120 mL or 1M of glucose solution or 1M of chitosan solution, stirred for 30 min, then transferred to a hydrothermal reactor, placed in an oven at 180°C for 12 h, and after the reaction was completed, cooled to room temperature, opened the hydrothermal reactor, and centrifuged to obtain a yellow solid precipitate, washed with deionized water for 3 times, and dried in an oven at 60°C to obtain a yellow powder.

[0074] 2) Preparation of sulfur-modified iron-nitrogen-carbon catalyst

[0075] The dried metal organic ligand precursor powder was ground in a crucible for 20 min, 300 mg of the powder was placed in a porcelain boat, calcined at 900°C under a nitrogen atmosphere for 2 h, the heating rate from room temperature to the calcination temperature was 5°C / min, and the calcined catalyst was naturally cooled to room temperature. Then, 200 mg of the catalyst was placed in a 200 mL 1M sulfuric acid solution, and acid washing was performed in an 80°C water bath for 24 h. After acid washing, the acid-washed catalyst was washed with water until the pH of the washing liquid was stable at 6-7, and then dried in a 60°C oven to obtain a sulfur-modified iron-nitrogen-carbon catalyst prepared by using a 1M glucose solution as a hydrothermal solvent, which was named G-Fe-NS3C. A sulfur-modified iron-nitrogen-carbon catalyst prepared by using a 1M chitosan solution as a hydrothermal solvent was named C-Fe-NS3C.

[0076] Due to the difference in the selected hydrothermal solvent in the synthesis of the metal organic ligand precursor, the carbon source in the synthesis of the iron-nitrogen-carbon catalyst is different, and thus the structure of the catalyst is greatly different. For G-Fe-NS3C, a micron-level carbon sphere structure is present in the microstructure, the diameter of the carbon sphere is 500 nm-2 μm, the average diameter is 800 nm, the specific surface area is 57.56 m 2 / g, and the main components are sulfur-doped graphite-nitrogen-carbon loaded with iron monatomic and iron metal particles, the iron metal particles are embedded on the surface of the carbon sphere, the diameter is 25 nm-150 nm, the average diameter is 56 nm, the mass percentage of the iron metal particles is 87 wt%, and the mass percentage of the sulfur-doped graphite-nitrogen-carbon loaded with iron monatomic is 13 wt%. For C-Fe-NS3C, a micron-level carbon sphere structure is present in the microstructure, the diameter of the carbon sphere is 800 nm-2.5 μm, the average diameter is 1.2 μm, the specific surface area is 46.52 m 2 / g, and the main components are sulfur-doped graphite-nitrogen-carbon loaded with iron monatomic and iron metal particles, the iron metal particles are embedded on the surface of the carbon sphere, the diameter is 32 nm-165 nm, the average diameter is 72 nm, the mass percentage of the iron metal particles is 95 wt%, and the mass percentage of the sulfur-doped graphite-nitrogen-carbon loaded with iron monatomic is 5 wt%.

[0077] Comparative Example 3:

[0078] Commercially purchased nano Fe2O3 and Fe3O4 catalysts (both purchased from Sinopharm Group)

[0079] The commercially purchased Fe2O3 and Fe3O4 catalysts both have magnetism.

[0080] In the comparative analysis of the reaction activities of Fe-NS2C catalyst, sulfur-modified iron-nitrogen-carbon catalyst prepared using thioacetamide as the sulfur source, and commercial Fe2O3 and Fe3O4 catalysts, the degradation reaction of HBA was used as a probe reaction, and the reaction rate constant k was used as the evaluation index of catalytic reaction efficiency. k represents the rate of reaction in a Fenton-like reaction, and the first-order reaction rate equation is: k t = -ln C / C0, where C is the HBA concentration at sampling time t, C0 is the p-hydroxybenzoic acid concentration in the solution at the start of the reaction, t is the reaction time, and k t To represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The final concentrations of the catalysts—nano-Fe2O3, Fe3O4, Fe-NS2C, and Fe-NCS2—are 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the pH is the same as the pH of the reaction solution before initiation. The reaction substrate was 50 mL of a 2 mM HBA-containing contaminant solution. 0.5 mL of a 100 mM potassium persulfate (PMS) solution was added to the reaction solution containing 0.15 g / L catalyst to initiate the reaction. At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher. After thorough mixing, the reaction was quenched. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column.

[0081] Table 7. Effects of different synthesis methods of iron, nitrogen, and carbon on catalyst activity.

[0082]

[0083] As can be seen from Table 7, compared with the sulfur-modified iron-nitrogen-carbon catalyst prepared by using thioacetamide / sodium sulfide as a sulfur source, the sulfur-modified iron-nitrogen-carbon catalyst prepared by using thiourea as a sulfur source exhibits the optimal catalytic performance, which is mainly related to the physical and chemical properties of thiourea and thioacetamide. Meanwhile, the iron-nitrogen-carbon catalyst prepared by using 1M glucose solution and 1M chitosan solution has a reduced utilization rate of iron sites in the reaction due to the generation of iron particles, and the activity is obviously lower than that of the sulfur-doped iron monatomic catalyst synthesized by using formamide. In addition, compared with the commercial Fe2O3 and Fe3O4 catalysts, the sulfur-modified iron-nitrogen-carbon catalyst has a more outstanding reaction efficiency, indicating that the catalyst prepared by this simple method has a very promising application prospect.

[0084] 6. Investigation of the influence of changes in the synthesis conditions on the performance of the catalyst

[0085] 1) Preparation of metal organic ligand precursor by hydrothermal method:

[0086] 150 mg of FeCl 2· 4H2O, 48 mg of thiourea, and 1.6 g of ZnCl2 were sequentially added to 120 mL of formamide, stirred for 30 min, and then transferred to a hydrothermal reactor, which was placed in an oven at 180°C for 12 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature, opened, and the yellow solid precipitate was separated by centrifugation. After being washed with deionized water for 3 times, the yellow powder was dried in an oven at 60°C.

[0087] 2) The dried metal organic ligand precursor powder was ground in a crucible for 20 min, 300 mg of the powder was placed in a porcelain boat, and calcination was carried out at 900-1000°C (900°C, 950°C, 1000°C) under a nitrogen atmosphere for 1-4 h (1 h, 2 h, 4 h). The heating rate from room temperature to the calcination temperature was 5°C / min. After the calcination was completed, the catalyst was naturally cooled to room temperature, and 200 mg of the catalyst was placed in 200 mL of 0.5-2M (0.5M, 2M) sulfuric acid solution and acid-washed at 80°C for 12-36 h (12 h, 36 h). After the acid-washing was completed, the acid-washed catalyst was washed with water until the pH of the washing liquid was stable at 6-7, and then dried to obtain a sulfur-doped iron-nitrogen-carbon catalyst.

[0088] In the test of the activity of the catalysts prepared under different synthesis conditions, the oxidation reaction of p-hydroxybenzoic acid by potassium monopersulfate was used as a probe reaction, and the reaction rate constant k was used as an evaluation index of the catalytic reaction efficiency. k represents the speed of the reaction rate in the Fenton-like reaction, and the formula of the first-order reaction rate equation is: k = -ln C / C0, C is the concentration of HBA at sampling time t, C0 is the concentration of HBA in the solution at the beginning of the reaction, t is the reaction time, and k t = -ln C / C0, C is the concentration of HBA at sampling time t, C0 is the concentration of HBA in the solution at the beginning of the reaction, t is the reaction time, and k tTo represent the degree of pollutant degradation at time t, we plot -ln C / C0 on the ordinate and the corresponding time t on the abscissa. ， The slope obtained by linear fitting is the first-order reaction rate constant, where k is a constant. A larger k indicates a faster reaction rate and better activity. The reaction apparatus is a dark reaction chamber, maintained in complete darkness. A temperature-controlled stirrer and a 100 mL beaker are placed inside. The catalyst concentration is 150 mg / L. The reaction is initiated by adding 0.5 mL of 100 mM potassium persulfate (PMS) solution. The reaction temperature is 25 °C, and the reaction pH is the same as the pH of the reaction solution before initiation. The reaction substrate was 50 mL of a 100 μM solution containing HBA. 0.5 mL of a 100 mM potassium persulfate (PMS) solution was added to the reaction solution containing 150 mg / L catalyst to initiate the reaction. At fixed reaction intervals (0 min, 0.5 min, 1 min, 2 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, and 20 min), 0.5 mL of 0.2 M sodium sulfite was added to the sample as a reaction quencher. After thorough mixing, the reaction was quenched. The concentration of HBA was analyzed using liquid chromatography equipped with a C18 column.

[0089] Table 8. Effects of changes in synthesis conditions on catalyst performance

[0090]

[0091]

[0092] Table 8 shows that changes in synthesis conditions during the synthesis process have a certain impact on the performance of the catalyst. For calcination temperature, both excessively high and excessively low calcination temperatures have a negative impact on catalytic activity. Simultaneously, shortening the calcination time makes it difficult for the iron-nitrogen-carbon catalyst to be fully calcined, leading to a decrease in catalytic activity, which is detrimental to the formation of active sites. By changing the concentration of the sulfuric acid solution and the acid washing time, it can be seen that sufficient acid washing is essential for high catalytic activity. This is mainly because sufficient acid washing can remove any metal particles that may be present, maximizing the opportunity for single-atom catalytic sites in the catalyst to participate in the reaction.

Claims

1. Application of sulfur-doped iron-nitrogen-carbon catalyst in Fenton-like reaction of oxidative degradation of organic pollutants by catalytic oxidant, characterized in that: 1) a metal organic ligand precursor is prepared by hydrothermal method: 100-200 mg FeCl2·4H2O, 24-96 mg thiourea, 1.2-2.0 g ZnCl2 are added into 120 mL formamide, stirred uniformly, reacted at 160-200℃ for 10-15 h, solid-liquid separation, the solid precipitate is dried to obtain a solid product; 2) the solid product obtained in step 1) is calcined at 900-1000℃ in a nitrogen atmosphere for 1-4 h, taken out to obtain a calcined product, 100-300 mg of the calcined product is soaked in 200 mL of 0.5-2M sulfuric acid solution for acid washing, after acid washing, the acid-washed catalyst is washed with water until the pH of the washing liquid stabilizes at 6-7, dried to obtain a sulfur-doped iron-nitrogen-carbon catalyst. The specific process is as follows: 2) the dried metal organic ligand precursor powder is ground in a crucible for 10-30 min, 200-400 mg of the powder is placed in a porcelain boat, calcined at 900-1000℃ in a nitrogen atmosphere for 1-4 h, the heating rate from room temperature to calcination temperature is 3-8℃ / min, after calcination, it is naturally cooled to room temperature, taken out to obtain a calcined product, 100-300 mg of the calcined product is placed in 200 mL of 0.5-2M sulfuric acid solution for acid washing at 70-90℃ for 12-36 h, after acid washing, the acid-washed catalyst is washed with water until the pH of the washing liquid stabilizes at 6-7, dried to obtain a sulfur-doped iron-nitrogen-carbon catalyst.

3. The application according to claim 1, characterized in that:

2. Use of a catalyst according to claim 1, characterized in that:

4. The application of the catalyst according to claim 1, characterized in that: 1) Preparation of metal organic ligand precursor using hydrothermal method: 100-200 mg FeCl 2• 4H2O, 24-96 mg thiourea, 1.2-2.0 g ZnCl2were added into 120 mL formamide, stirred uniformly for 30-60 min, then transferred into a hydrothermal reactor, reacted at 160-200 °C for 10-15 h, after the reaction was completed, cooled to room temperature, opened the hydrothermal reactor, centrifuged to obtain a solid precipitate, washed with water, and dried in an oven at 60-80 °C to obtain a powder; The oxidant is one or more of potassium hydrogen persulfate, hydrogen peroxide or potassium peroxodisulfate; The reaction substrate is one or more of 100-200 µM p-hydroxybenzoic acid, bisphenol A, phenol, the concentration of the catalyst in the solution is 50-500 mg / L, the concentration of the oxidant is 0.5-6 mM, and the pH is 2-10.

6. The sulfur-doped iron-nitrogen-carbon catalyst has a two-dimensional sheet structure in microstructure, the surface diameter of the sheet structure is distributed in the range of 100 nm-900 nm, the average diameter is 300 nm-450 nm, the sheet thickness is 1 nm-65 nm, and the specific surface area is 46.91-76.49 m 2 / g; the composition is sulfur-doped graphite-nitrogen-carbon loaded with iron monatomic, and the catalyst has no magnetism.

5. The application according to claim 1, characterized in that: The reaction device for Fenton-like degradation of pollutants is a dark reaction box, which maintains dark conditions, and a temperature-controlled stirrer and a reaction container are placed in the box; The catalyst can achieve high-efficiency degradation of model pollutant p-hydroxybenzoic acid in the reactor; the catalyst can attack organic pollutants by non-free radical species under conditions containing humic acid and various ions to achieve degradation of organic pollutants.

6. The application according to claim 1, characterized in that: In the reaction solution for Fenton-like degradation of pollutants, the concentration of one or more of bicarbonate ions, carbonate ions, sulfate ions, perchlorate ions and chloride ions should be < 20 mM, or the concentration of humic acid should be < 20 mg / L.

7. The application of the catalyst according to claim 1, characterized in that: ​ ​ ​ The pH of the reaction solution in the Fenton-like degradation of pollutants should be controlled in the range of 2-10.

6.

8. Use of a catalyst according to claim 1, characterized in that: The reaction time in the Fenton-like degradation of pollutants should be greater than or equal to 5 min.

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