Preparation method and application of heptasulfurized iron loaded biochar catalyst

Abstract

The invention discloses a preparation method and application of a biochar catalyst loaded with iron octasulfide, and belongs to the technical field of sewage treatment. The preparation method of the catalyst is: biochar raw material, ferric chloride hexahydrate, and thiourea are completely dissolved in ethylene glycol, and an iron octasulfide-loaded biomass precursor is obtained by a solvent thermal method, and an iron octasulfide-loaded biochar catalyst is obtained after a pyrolysis method, and the catalyst and peroxymonosulfate are added to a water body containing antibiotics, and the antibiotics in the water body are removed by a non-free radical pathway mainly based on singlet oxygen. The catalyst preparation method of the invention is simple, has high efficiency in removing antibiotics, has a wide range of pH and temperature applications, has a large specific surface area, is easy to recycle, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a preparation method and application of a heptaferrous octasulfide-loaded biochar catalyst. Background Art

[0002] The production of antibiotics will generate a large amount of wastewater, which contains much higher concentrations of organic pollutants than urban wastewater. In addition, after taking antibiotics, the antibiotics cannot be completely absorbed by the human body, and 90% of the antibiotics are excreted through urine and feces. When antibiotics enter the water body, even at low concentrations, they may increase the drug resistance of microorganisms and even destroy aquatic ecosystems, ultimately posing a potential threat to human health. Therefore, there is an urgent need to develop an efficient and environmentally friendly technology for treating antibiotic pollution.

[0003] Permonosulfate-based advanced oxidation processes (PMS-AOPs) have attracted widespread attention due to their system stability, simple operation, wide applicability, economy and environmental friendliness. Compared with other advanced oxidation processes, PMS-AOPs are based on activated permonosulfate to remove organic pollutants through multiple pathways, such as sulfate radicals, hydroxyl radical-dominated radical pathways and non-radical pathways with singlet oxygen, high-valent metal oxygen species, etc. Methods for activating PMS include transition metals, ultrasound, ultraviolet rays and heat. Among them, transition metal activation of PMS has become a relatively efficient method due to its simple operation and the lack of external energy.

[0004] As a transition metal-based material, iron octasulfide has high electrical conductivity, abundant redox sites, and thermal stability. The unsaturated sulfur species it contains can promote the 3+ To Fe 2+ In addition, the particle agglomeration problem caused by the strong metallic magnetism inherent in transition metals and the environmental problems caused by metal ion leaching are the focus of attention in practical applications.

[0005] Carbon-based materials have been proven to be good carrier materials for solving the above problems. Biochar (BC) is a carbon-based material produced by pyrolysis of waste biomass under anaerobic conditions. BC has attracted widespread attention due to its simple preparation process, wide source of raw materials, environmental friendliness, large specific surface area, and rich functional groups, but its application is limited by its low catalytic ability.

[0006] Therefore, providing a stable, efficient and environmentally friendly Fenton-like catalyst to activate peroxymonosulfate to treat antibiotics in wastewater is a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a preparation method and application of an iron octasulfide-loaded biochar catalyst. The prepared catalyst can overcome the shortcomings of iron octasulfide, such as reduced catalytic efficiency due to metal particle agglomeration and environmental problems caused by metal ion leaching, as well as low biochar activation ability and poor stability. The iron octasulfide-loaded biochar catalyst can achieve efficient removal of antibiotics in sewage by activating permonosulfate, dominated by non-free radicals mainly composed of singlet oxygen.

[0008] It should be noted that the present invention can directly load iron octasulfide on biochar through a simple hydrothermal method and calcination method, overcoming the shortcomings of the complex preparation process of previous Fenton-like catalysts and providing technical support for the future development of the combination of metal-based catalysts and non-metallic materials.

[0009] In addition, in the prepared iron octasulfide-loaded biochar catalyst, the iron octasulfide is randomly distributed on the biochar surface in granular form, which can expose more active sites and improve its catalytic ability, while effectively reducing the environmental hazards caused by metal ion leaching.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] A technical purpose of the present invention is to provide a method for preparing a biochar catalyst supported by iron octasulfide, the steps of which are as follows:

[0012] 1) washing the collected sycamore leaves, drying and dehydrating them, grinding and screening them to obtain leaf-based biochar raw materials;

[0013] 2) adding the leaf-based biochar raw material, ferric chloride hexahydrate, and thiourea into ethylene glycol, and stirring thoroughly to obtain a mixed solution;

[0014] 3) transferring the mixed solution to a reactor to react by a solvothermal method, and after the reaction is completed, washing the solid product by centrifugation, drying and dehydrating to obtain a heptasulfide-loaded biochar precursor;

[0015] 4) The iron octasulfide-loaded biochar precursor is subjected to a pyrolysis method to obtain an iron octasulfide-loaded biochar catalyst.

[0016] Furthermore, in step 2), the mass ratio of the iron element in the ferric chloride hexahydrate to the biochar raw material is 1:5 to 1:20.

[0017] Furthermore, in the step 2), the molar ratio of the iron element in the ferric chloride hexahydrate to the sulfur element in the thiourea is 1:1 to 1:2.

[0018] Furthermore, the conditions of the solvothermal method in step 3) are: reaction temperature is 180-200° C., and reaction time is 8-12 h.

[0019] Furthermore, the conditions for centrifugal washing of the solid product in step 3) are: a centrifugal rate of 5000 to 10000 r / min, and washing solvents of ethanol and water.

[0020] Furthermore, the drying and dehydration conditions in step 3) are: the dehydration temperature is 60 to 80° C., and the dehydration time is 12 to 24 hours.

[0021] Furthermore, the conditions of the pyrolysis method in step 4) are: the protective gas is nitrogen, the heating rate is 3-5°C / min, the pyrolysis temperature is 600-900°C, and the pyrolysis holding time is 2-3h.

[0022] Another technical purpose of the present invention is to provide an application of a heptasulfide iron-loaded biochar catalyst in activating peroxymonosulfate to remove antibiotics.

[0023] By adding the prepared catalyst and peroxymonosulfate into simulated organic wastewater containing antibiotics for reaction, efficient removal of the antibiotics can be achieved.

[0024] Wherein, the antibiotic is doxycycline, the catalyst dosage is 0.1 g / L to 0.4 g / L, and the peroxymonosulfate concentration is 0.5 mmol / L to 3 mmol / L;

[0025] Moreover, the pH value of the reaction system is 1 to 13, and the temperature of the reaction system is 15° C. to 35° C.;

[0026] Quenching agents include ethanol, tert-butyl alcohol, furfuryl alcohol, and methyl phenyl sulfoxide.

[0027] It can be seen from the above technical solution that, compared with the prior art, the preparation method and application of a heptasulfurized iron loaded biochar catalyst provided by the present invention have the following excellent effects:

[0028] 1) The preparation method of the present invention has the advantages of simple process flow, low cost, etc., and realizes the resource utilization of waste biomass.

[0029] 2) The iron octasulfide-loaded biochar catalyst prepared by the present invention has metal nanoparticles randomly dispersed on its surface, which can expose more active sites. In addition, the prepared catalyst also inherits the large specific surface area of ​​biochar and can effectively reduce the environmental damage caused by metal ion leaching.

[0030] 3) The antibiotic removal process of the present invention is less affected by water temperature and has a wide pH application range. 96.7% of antibiotic removal can be achieved after 30 minutes of reaction. The antibiotic removal process follows a non-free radical pathway based mainly on singlet oxygen and is less affected by the external environment, so it is suitable for the treatment of antibiotics in various occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0032] Figure 1 The removal rate of DOX by peroxymonosulfate activated by catalysts with different iron ratios prepared in Examples 1 to 5;

[0033] Figure 2 This is a scanning electron microscope image of the catalyst prepared in Example 1;

[0034] Figure 3 is the X-ray diffraction pattern of the catalyst prepared in Example 1;

[0035] Figure 4 The removal rate of DOX by peroxymonosulfate activated by catalysts prepared in Example 1 and Examples 6 to 8 at different pyrolysis temperatures is shown;

[0036] Figure 5 The peroxymonosulfate consumption diagram of the catalysts prepared in Example 1 and Examples 6 to 8 at different pyrolysis temperatures during the activation of peroxymonosulfate to remove DOX;

[0037] Figure 6 The adsorption-desorption isotherm diagram of the catalyst prepared in Example 1;

[0038] Figure 7 This is the X-ray photoelectron spectrum of the catalyst prepared in Example 1.

[0039] Figure 8 Graph showing the effect of catalyst dosage on the activation of peroxymonosulfate to remove DOX by the catalyst prepared in Example 1;

[0040] Fig. 9 Graph showing the effect of peroxymonosulfate concentration on the activation of the catalyst prepared in Example 1 to remove DOX by peroxymonosulfate;

[0041] Fig.10 This is a graph showing the effect of the initial pH value of the reaction system on the activation of the catalyst prepared in Example 1 to remove DOX by peroxymonosulfate;

[0042] Fig.11 Graph showing the effect of reaction system temperature on the activation of peroxymonosulfate to remove DOX by the catalyst prepared in Example 1;

[0043] Fig.12This is a diagram of the quenching experiment of the catalyst prepared in Example 1 to activate peroxymonosulfate to remove DOX. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0046] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] Example 1

[0050] A method for preparing a heptasulfurized iron-supported biochar catalyst, comprising the following steps:

[0051] The collected sycamore leaves were soaked and washed with deionized water, then dried at 60-80°C for 12-24h, and the biochar raw materials were obtained by grinding and sieving;

[0052] According to the mass ratio of iron in ferric chloride hexahydrate to biochar raw material being 1:10, and the molar ratio of iron in ferric chloride hexahydrate to sulfur in thiourea being 1:1-1:2, the biochar raw material, ferric chloride hexahydrate and thiourea were added to 60 mL of ethylene glycol, and fully stirred to obtain a mixed solution, which was transferred to a 100 mL reactor, and reacted at 180° C. for 12 h by a solvothermal method. After the reaction was completed, the solid product was centrifuged and washed with deionized water and ethanol, respectively, and dried and dehydrated at 60-80° C. to obtain a heptasulfide-loaded biochar precursor;

[0053] The iron octasulfide-loaded biochar precursor was placed in a quartz boat and then transferred to a tubular furnace. N2 was introduced into the tubular furnace to expel the air. Then, in a nitrogen atmosphere, the temperature was increased to 800°C at a heating rate of 3 to 5°C / min and maintained for 2 to 3 hours for pyrolysis, and finally the iron octasulfide-loaded biochar catalyst Fe7S8-0.1@BC-800 was obtained.

[0054] Example 2

[0055] Same as Example 1, except that ferric chloride hexahydrate is not added to obtain BC-800

[0056] Example 3

[0057] Same as Example 1, except that no biochar raw material was added to obtain Fe7S8-800

[0058] Example 4

[0059] Same as Example 1, except that the mass ratio of iron in ferric chloride hexahydrate to biochar raw material is 1:20 to obtain Fe7S8-0.05@BC-800

[0060] Example 5

[0061] Same as Example 1, except that the mass ratio of iron in ferric chloride hexahydrate to biochar raw material is 1:5, and Fe7S8-0.2@BC-800 is obtained.

[0062] The removal rate of doxycycline (DOX) in water by the products of Examples 1 to 5 was tested, and the testing method was as follows:

[0063] A 250 mL conical flask was selected as the reaction flask, and 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared. The pH of the sewage was not adjusted (the pH of the sewage was 6.0 at this time), and 0.3 g / L of the catalyst prepared in Examples 1 to 5 and 1 mmol / L of permonosulfate were added to the reaction flask, respectively. The reaction was carried out by stirring in a constant temperature shaking shaker at 180 r / min at 25°C. The residual concentration of DOX was measured at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, and the removal rate of DOX was calculated.

[0064] The calculation results are as follows Figure 1 As shown. Figure 1 It can be seen that the removal rate of DOX by iron octasulfide and biochar alone is low. After combining the two, the removal rate shows a significant improvement, reaching 96.7% after 30 minutes of reaction. In addition, with the increase of the proportion of iron, the removal rate of DOX shows a trend of first increasing and then decreasing.

[0065] Figure 2 This is a scanning electron microscope image of the iron octasulfide-loaded biochar catalyst prepared in Example 1. Figure 2 As shown in FIG. 1 , the iron octasulfide nanoparticles are randomly dispersed on the surface of the biochar, indicating that the iron octasulfide-loaded biochar catalyst was successfully prepared. In addition, the X-ray diffraction pattern of the iron octasulfide-loaded biochar catalyst prepared in Example 1 is shown in FIG. Figure 3 As shown in the figure, the catalyst of Example 1 exhibits obvious characteristic peaks at 30.0°, 33.5°, 34.0°, 43.3°, and 53.3°, corresponding to the (200), (114), (203), (213), and (220) crystal planes of iron octasulfide, respectively.

[0066] Example 6

[0067] The same as Example 1, except that the temperature of the tube furnace is raised to 600° C. to prepare the iron octasulfide-loaded biochar catalyst Fe7S8-0.1@BC-600.

[0068] Example 7

[0069] The same as Example 1, except that the temperature of the tube furnace is raised to 700° C. to prepare the iron octasulfide-loaded biochar catalyst Fe7S8-0.1@BC-700.

[0070] Example 8

[0071] The same as Example 1, except that the temperature of the tube furnace is raised to 900° C. to prepare the iron octasulfide-loaded biochar catalyst Fe7S8-0.1@BC-900.

[0072] The removal rate of doxycycline (DOX) in water by the products of Example 1 and Examples 6 to 8 was tested, and the testing method was as follows:

[0073] A 250 mL conical flask was selected as the reaction flask, and 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared. The pH of the sewage was not adjusted (the pH of the sewage was 6.0 at this time), and 0.3 g / L of the catalyst prepared in Examples 6 to 8 and 1 mmol / L of permonosulfate were added to the reaction flask, respectively. The mixture was fully stirred in a constant temperature shaking shaker at 180 r / min at 25°C for reaction. The residual concentration of DOX was determined at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, respectively, and the removal rate of DOX was calculated. At the same time, the residual concentration value of permonosulfate in the sewage was determined.

[0074] The calculation results are as follows Figure 4 As shown. Figure 4 It can be seen that with the increase of pyrolysis temperature, the removal rate of DOX increased significantly, reaching a maximum removal rate of 96.7% at 800 ° C. As the pyrolysis temperature further increased to 900 ° C, the degradation efficiency decreased slightly.

[0075] The residual concentration of peroxymonosulfate during the reaction is Figure 5 As shown, it can be seen that the prepared iron octasulfide-loaded biochar catalyst effectively overcomes the shortcomings of low utilization rate of peroxymonosulfate by traditional catalysts and maximizes resource utilization.

[0076] Figure 6 The adsorption-desorption isotherm diagram of the iron octasulfide-supported biochar catalyst prepared in Example 1 shows that the prepared catalyst has a large specific surface area. The elemental analysis of the iron octasulfide-supported biochar catalyst is as follows: Figure 7 shown.

[0077] Example 9

[0078] Four treatment groups were set up with the iron octasulfide-loaded biochar catalyst prepared in Example 1: a 250 mL conical flask was selected as the reaction bottle, and 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared. The pH of the sewage was not adjusted (the pH of the sewage was 6.0 at this time), and catalysts of 0.1 g / L (treatment group 1), 0.2 g / L (treatment group 2), 0.3 g / L (treatment group 3), 0.4 g / L (treatment group 4) and 1 mmol / L of permonosulfate were added to the four reaction systems, respectively. The mixture was fully stirred in a constant temperature shaking shaker at 180 r / min at 25 ° C for reaction, and the residual concentration of DOX was measured at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, and the removal rate of DOX was calculated.

[0079] The calculation results are as follows Figure 8 As shown. Figure 8 It can be seen that as the catalyst dosage increases from 0.1g / L to 0.3g / L, the removal rate of DOX increases significantly, reaching a maximum removal rate of 96.7% at 0.3g / L, indicating that as the catalyst dosage increases, the catalyst can provide more active sites during the reaction and produce a large number of active species, thereby improving the DOX removal rate. When the catalyst dosage is further increased to 0.4g / L, the removal rate of DOX increases slightly, indicating that the active sites provided by the catalyst are excessive and cannot be fully utilized during the reaction. The above analysis results show that in practical applications, the catalyst dosage can be adjusted according to the actual situation of local sewage and the requirements of treatment efficiency, so as to achieve the purpose of efficient removal of organic pollutants.

[0080] Example 10

[0081] Four treatment groups were set up with the iron octasulfide-loaded biochar catalyst prepared in Example 1: a 250 mL conical flask was selected as the reaction bottle, and 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared. The pH of the sewage was not adjusted (the pH of the sewage was 6.0 at this time), and 0.5 mmol / L (treatment group 1), 1.0 mmol / L (treatment group 2), 2.0 mmol / L (treatment group 3), 3.0 mmol / L (treatment group 4) of peroxymonosulfate and 0.3 g / L of catalyst were added to the four reaction systems, respectively, and the mixture was fully stirred in a constant temperature shaking shaker at 180 r / min at 25 ° C for reaction. The residual concentration of DOX was measured at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, and the removal rate of DOX was calculated.

[0082] The calculation results are as follows Fig. 9 As shown. Fig. 9 It can be seen that with the increase of permonosulfate concentration, the removal rate of DOX continues to increase and can reach a high level, indicating that in practical applications, the concentration of permonosulfate can be adjusted according to the actual situation of local sewage and the requirements of treatment efficiency to achieve the purpose of controlling costs and improving removal efficiency.

[0083] Embodiment 11

[0084] Eight treatment groups were set up with the iron octasulfide-loaded biochar catalyst prepared in Example 1: a 250 mL conical flask was selected as the reaction bottle, and 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared, and the initial pH of the sewage was adjusted to: 1 (treatment group 1), 3 (treatment group 2), 5 (treatment group 3), 6 (treatment group 4), 7 (treatment group 5), 9 (treatment group 6), 11 (treatment group 7), 13 (treatment group 8), respectively, 0.3 g / L catalyst and 1 mmol / L permonosulfate were added to the reaction bottles, respectively, and the reaction was fully stirred in a constant temperature shaking shaker at 180 r / min at 25 ° C. The residual concentration of DOX was measured at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, and the removal rate of DOX was calculated.

[0085] The calculation results are as follows Fig.10 As shown. Fig.10 It can be seen that, except for pH values ​​of 1 and 13, the DOX removal rate reached more than 90% under other pH conditions, indicating that in practical applications, the system has strong adaptability to the pH values ​​of sewage under different environments and can efficiently treat antibiotics in various types of sewage.

[0086] Example 12

[0087] Three treatment groups were set up with the iron octasulfide-loaded biochar catalyst prepared in Example 1: a 250 mL conical flask was selected as the reaction flask, 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared, the sewage pH was not adjusted (the sewage pH was 6.0 at this time), 0.3 g / L of catalyst and 1 mmol / L of permonosulfate were added to the reaction flask, the reaction temperature was adjusted to 15°C (treatment group 1), 25°C (treatment group 2) and 35°C (treatment group 3), respectively, the reaction was fully stirred in a constant temperature shaking shaker at 180 r / min for reaction, the residual concentration of DOX was measured at 1 min, 2 min, 5 min, 10 min, 20 min, and 30 min of the reaction, and the removal rate of DOX was calculated.

[0088] The calculation results are as follows Fig.11 As shown. Fig.11 It can be seen that under different reaction temperatures, the DOX removal rate reached more than 95% in a short time, indicating that the system has strong adaptability to different temperatures and can efficiently treat actual sewage at 15°C to 35°C.

[0089] Embodiment 13

[0090] Four treatment groups and one untreated group were set up with the iron octasulfide-loaded biochar catalyst prepared in Example 1 for quenching experiments: a 250 mL conical flask was selected as a reaction bottle, 100 mL of simulated organic sewage with an initial DOX concentration of 20 mg / L was prepared, the pH of the sewage was not adjusted (the pH of the sewage was 6.0 at this time), 0.3 g / L of catalyst and 1 mmol / L of permonosulfate were added to the reaction bottle, and 100 mmol / L of ethanol was added as a quencher for sulfate radicals and hydroxyl radicals (treatment group 1), 100mmol / L tert-butanol as a quencher of hydroxyl radicals (treatment group 2), 50mmol / L furfuryl alcohol as a quencher of singlet oxygen (treatment group 3) and 50mmol / L methyl phenyl sulfoxide as a quencher of high-valent iron species (treatment group 4), the mixture was fully stirred in a constant temperature shaking shaker at 180r / min for reaction, and the residual concentration of DOX was measured at 1min, 2min, 5min, 10min, 20min and 30min of reaction, and the removal rate of DOX was calculated.

[0091] The calculation results are as follows Fig.12 As shown. Fig.12 It can be seen that after adding ethanol and tert-butyl alcohol, the inhibitory effect on DOX removal is negligible, indicating that sulfate radicals and hydroxyl radicals play a small role in the reaction process. After adding furfuryl alcohol and methyl phenyl sulfoxide, DOX removal was inhibited by 44.7% and 13.1%, respectively, indicating that the non-radical pathway dominated by singlet oxygen plays the most important role in DOX removal. The non-radical pathway is less affected by changes in external conditions and can treat antibiotics in actual sewage in various situations.

[0092] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An application of a biochar catalyst loaded with iron octasulfide in the activation of peroxymonosulfate to remove antibiotics, characterized in that: The antibiotic is doxycycline; The preparation method of the iron octasulfide-loaded biochar catalyst comprises the following steps: 1) washing, drying, dehydrating, grinding and screening the collected sycamore leaves to obtain leaf-based biochar raw materials; 2) adding the leaf-based biochar raw material, ferric chloride hexahydrate and thiourea into ethylene glycol and stirring thoroughly to obtain a mixed solution; 3) The mixed solution is transferred to a reactor to react by a solvothermal method. After the reaction is completed, the solid product is washed by centrifugation and dried to obtain a heptasulfide-loaded biochar precursor; 4) The iron octasulfide-loaded biochar precursor is subjected to pyrolysis to obtain the iron octasulfide-loaded biochar catalyst; In step 2), the mass ratio of the iron element in the ferric chloride hexahydrate to the biochar raw material is 1:5-1:20, and the molar ratio of the iron element in the ferric chloride hexahydrate to the sulfur element in thiourea is 1:1-1:

2.

2. The use according to claim 1, characterized in that: In step 3), the conditions of the solvothermal method are as follows: The reaction temperature is 180-200°C and the reaction time is 8-12h.

3. The use according to claim 1, characterized in that: The drying and dehydration conditions in step 3) are as follows: The dehydration temperature is 60-80℃, and the dehydration time is 12-24h.

4. The use according to claim 1, characterized in that: The pyrolysis conditions in step 4) are as follows: The protective gas is nitrogen, the heating rate is 3-5°C / min, the pyrolysis temperature is 600-900°C, and the pyrolysis holding time is 2-3h.

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