A CuFeS2@FeS2 composite Fenton-type catalyst and its preparation method and application

Abstract

The present invention discloses a CuFeS2@FeS2 composite Fenton-type catalyst and its preparation method and application. The present invention utilizes natural pyrite without the need for further forming process and its own good adsorption of copper ions, and embeds the Cu element into the pyrite lattice through a citrate impregnation-anaerobic calcination process to form a CuFeS2@FeS2 composite Fenton-type catalyst with a heterogeneous structure. The catalyst of the present invention can activate peroxymonosulfate and hydrogen peroxide to produce active oxygen species, thereby achieving rapid degradation and mineralization of different types of organic pollutants such as sodium dodecylbenzenesulfonate, tetracycline hydrochloride, rhodamine B and other common surfactants, antibiotics, dyes and other organic pollutants in water bodies. The present invention uses pyrite, which has huge reserves in nature, as raw material, and prepares a granular catalyst with good catalytic performance through a simple impregnation-calcination process. The method has the advantages of strong feasibility, low cost, and easy industrial preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of environmentally friendly functional materials and catalytic materials, and in particular to a CuFeS2@FeS2 composite Fenton-type catalyst and a preparation method and application thereof. Background Art

[0002] Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) can generate more abundant reactive oxygen species (ROS), including sulfate radicals (SO4 ·- ), hydroxyl radicals (·OH), superoxide radicals (·O2 - ) and non-radical forms of singlet oxygen ( 1 O2), the high reactivity of these active oxygen species enables them to undergo rapid chain reactions with most organic pollutants in water, non-selectively oxidizing these harmful substances into CO2, H2O or mineral salts, thereby achieving rapid degradation of different types of organic pollutants in water without causing secondary pollution.

[0003] Typically, PMS and H₂O₂ are difficult to decompose directly to produce ROS. They require external energy or catalyst activation to achieve rapid mineralization of pollutants. Currently, methods for activating PMS and H₂O₂ include UV activation, microwave activation, alkali activation, thermal activation, homogeneous catalyst activation based on transition metal ions, and heterogeneous catalyst activation based on transition metal oxides. UV, microwave, alkali, and thermal activation all require continuous energy input, resulting in high processing costs and harsh reaction conditions, making them difficult to commercialize. Homogeneous catalyst activation, on the other hand, produces large amounts of sludge and poses the risk of secondary heavy metal pollution. Heterogeneous catalysts, such as transition metal oxides, offer superior performance and lower costs compared to these methods, making them the most promising approach for industrial application. However, current heterogeneous catalysts are primarily synthetic, often with complex preparation processes and high costs, a major obstacle to their industrial application. Furthermore, reported catalysts are generally powdered, making efficient separation from water difficult. In practice, wastewater treatment processes would significantly improve efficiency if fixed-bed or fluidized-bed systems with continuous water inflow were used, requiring macroscopic, granular catalysts.

[0004] Iron is the most common, inexpensive, readily available, and non-toxic metallic element. Natural pyrite is one of the most abundant metal sulfides on Earth, possessing a well-preserved crystal structure and environmentally friendly properties. Currently, pyrite is primarily used to produce sulfuric acid and sulfur, resulting in a low overall utilization rate. The iron in pyrite can activate PMS and H₂O₂ to generate a large number of free radicals, degrading organic pollutants. Its use in advanced oxidation catalysts can significantly increase the value of pyrite. Furthermore, natural pyrite is inherently macroscopic, requiring no further forming, reducing the cost of converting powders into granules for traditional synthetic catalysts. However, natural pyrite particles are dense, have a low specific surface area, and exhibit few exposed active sites. This results in a slow Fe(III)→Fe(II) conversion process during catalysis, resulting in poor catalytic activity and low oxidant utilization in actual pollutant degradation processes. Therefore, modification of natural pyrite is necessary to increase the number of active sites and enhance its catalytic performance. Summary of the Invention

[0005] In view of the above-mentioned shortcomings, the present invention provides a CuFeS2@FeS2 composite Fenton-like catalyst, its preparation method and application. The present invention utilizes the characteristics of natural pyrite particles, such as the fact that they do not require further shaping and their own characteristic functional groups have good adsorption properties for copper ions. After simple crushing, the Cu ions are impregnated and adsorbed, and then further calcined in the absence of oxygen to embed the Cu ions into the pyrite lattice. At the same time, combined with the etching of the pyrite surface by citric acid and the pore expansion effect during the calcination process, the pyrite is prepared into a CuFeS2@FeS2 composite Fenton-like catalyst with a heterogeneous structure. Compared with natural pyrite, the composite material has a larger specific surface area and more exposed active sites. The incorporation of Cu enhances the redox cycle of Fe(II) / Fe(III), greatly improving the catalyst's utilization rate of the oxidant. Compared with the heterogeneous Fenton-like catalysts prepared by chemical synthesis that have been reported so far, the preparation cost is significantly lower. This technological invention helps to realize the high-value utilization of pyrite resources, provides favorable assistance in the field of water organic pollutant treatment, and provides an innovative technical solution for the industrial application of advanced oxidation technology based on PMS / H2O2.

[0006] In order to achieve the above object, the present invention provides a method for preparing a CuFeS2@FeS2 composite Fenton-type catalyst, comprising the following steps:

[0007] S1. Crushing, sieving, washing, and drying natural pyrite in sequence to obtain natural pyrite particles; placing copper salt and citric acid in water and stirring to obtain a mixed solution;

[0008] S2, adding the natural pyrite particles to the mixed solution, subjecting the mixed solution to vacuum impregnation treatment, evaporating part of the water, and then subjecting the mixed solution to vacuum impregnation, repeating the evaporation-vacuum impregnation treatment to obtain a precursor;

[0009] S3. After filtering and drying the precursor, calcining it under an inert atmosphere, and then washing it with water, a granular CuFeS2@FeS2 composite Fenton-like catalyst is obtained.

[0010] It should be noted that the purpose of water washing in step S3 is to remove surface impurities and unstable substances.

[0011] Furthermore, in step S1, the purity of the natural pyrite is above 95%, and the average particle size of the natural pyrite is 1 to 6 mm.

[0012] Furthermore, natural pyrite is not limited to its origin and its purity is above 98%.

[0013] Furthermore, the average particle size of the natural pyrite is 2 to 4 mm.

[0014] Furthermore, in step S1, the molar ratio of copper salt to citric acid in the mixed solution is 1:1 to 1:4; the copper salt is one or both of copper nitrate and copper sulfate; and the citric acid and the copper salt are both industrial grade.

[0015] Furthermore, in step S2, the molar ratio of the iron element in the natural pyrite particles to the copper salt and citric acid in the mixed solution is 25:2:2 to 25:5:20.

[0016] Furthermore, in step S2, the molar ratio of the iron element in the natural pyrite particles to the copper salt and citric acid in the mixed solution is 25:2:2 to 25:4:16.

[0017] Furthermore, in step S2, the vacuum impregnation treatment is performed for 4 to 8 hours, the drying temperature used for the evaporation is 60 to 80° C., and the evaporation-vacuum impregnation treatment is repeated 1 to 4 times.

[0018] Furthermore, the evaporation-vacuum impregnation treatment is repeated 1 to 3 times.

[0019] Furthermore, in step S3, the inert atmosphere includes any one of nitrogen and argon.

[0020] Furthermore, in step S3, the heating rate of the calcination treatment is 3-10°C / min, the temperature of the calcination treatment is 350-450°C, and the holding time of the calcination treatment is 60-120min.

[0021] Furthermore, in step S3, the temperature of the calcination treatment is 400-450° C., and the holding time of the calcination treatment is 60-90 minutes.

[0022] Based on the same inventive concept, the present invention also provides a CuFeS2@FeS2 composite Fenton-type catalyst prepared by the above preparation method.

[0023] Based on the same inventive concept, the present invention also provides the application of the CuFeS2@FeS2 composite Fenton catalyst prepared by the above preparation method in the treatment of organic wastewater, wherein the CuFeS2@FeS2 composite Fenton catalyst degrades organic pollutants in wastewater based on catalytic activation of an oxidant; wherein the oxidant includes at least one of hydrogen peroxide and peroxymonosulfate.

[0024] Furthermore, the organic pollutants include any one of surfactants, antibiotics, and dyes commonly found in water bodies; the surfactant includes sodium dodecylbenzenesulfonate; the antibiotic includes tetracycline hydrochloride; and the dye includes rhodamine B.

[0025] Beneficial effects of the present invention:

[0026] (1) Obvious raw material advantages: The present invention uses natural pyrite as the main raw material, which is abundant in nature and inexpensive. By modifying natural pyrite to prepare the CuFeS2@FeS2 composite catalyst, natural resources are fully utilized and the production cost of the catalyst is reduced. In addition, the copper salt and citric acid raw materials used in the preparation process are relatively common and easy to obtain. Compared with other synthetic catalysts, the composite catalyst of the present invention has obvious advantages in cost, which makes it possible to be used on a large scale in organic wastewater treatment. At the same time, this method also provides a new way to high-value utilization of natural pyrite, with good economic and environmental benefits.

[0027] (2) Good stability and recyclability: The pyrite-derived CuFeS2@FeS2 composite catalyst has a macroscopic granular structure and good stability. During the wastewater treatment process, the catalyst particles are not easily broken or dissolved, and can maintain their structural integrity and catalytic activity. At the same time, the granular catalyst can be recovered and reused by simple sedimentation, filtration or centrifugation. This not only reduces the loss of catalyst and reduces the cost of wastewater treatment, but also avoids secondary pollution of the catalyst to the environment. After multiple recycling and use, the composite catalyst can still maintain a high catalytic activity and has good reusability.

[0028] (3) Excellent catalytic performance: The granular CuFeS2@FeS2 composite Fenton-like catalyst derived from natural pyrite of the present invention exhibits excellent catalytic performance in Fenton-like reactions. The present invention utilizes the good adsorption of Cu ions by pyrite, the etching of the pyrite surface by citrate, and the pore expansion effect during calcination to adsorb a large amount of Cu ions on the pyrite surface. Cu is embedded in the pyrite lattice by calcination, forming a honeycomb porous structure on the pyrite surface. The active sites of the catalyst are exposed, and the synergistic effect of Cu and Fe elements accelerates the redox cycle of Cu(I) / Cu(II) and Fe(II) / Fe(III). It can efficiently activate oxidants such as hydrogen peroxide and persulfate, and produce highly oxidizing active oxygen species such as hydroxyl radicals and sulfate radicals. These active oxygen species can quickly degrade various difficult-to-degrade organic pollutants in wastewater, such as surfactant molecules in washing wastewater, antibiotic molecules in aquaculture wastewater, and dye molecules in printing and dyeing wastewater.

[0029] In summary, this patent uses natural pyrite, which is commonly found in nature, as raw material, and performs a simple modification treatment on it to form a granular CuFeS2@FeS2 composite Fenton-like catalyst with a heterogeneous structure. Compared with natural pyrite, this catalyst has a larger specific surface area and more exposed active sites. The incorporation of Cu enhances the redox cycle of Fe(Ⅱ) / Fe(Ⅲ), thereby greatly improving the utilization rate of the oxidant and the production of active oxygen species, and enhancing the catalytic degradation effect. Compared with the heterogeneous Fenton-like catalysts prepared by synthetic means that have been reported so far, the preparation cost is lower, the stability is better, and the recycling is more convenient. This technical invention helps to realize the high-value utilization of natural pyrite resources, provides favorable assistance to the field of water organic pollutant treatment, and provides an innovative technical solution for the industrial application of advanced oxidation technology based on PMS / H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 X-ray diffraction patterns of the granular CuFeS2@FeS2 composite catalyst of Example 1 of the present invention and the natural pyrite particles of Comparative Example 1;

[0031] Figure 2 These are scanning electron microscope images of the granular CuFeS2@FeS2 composite catalyst of Example 1 of the present invention and the natural pyrite particles of Comparative Example 1; wherein, (a) is the natural pyrite particles of Comparative Example 1; (b) is the granular CuFeS2@FeS2 composite catalyst of Example 1. DETAILED DESCRIPTION

[0032] To make the present invention easier to understand, the present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by professional and technical personnel in this field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.

[0033] The comparative examples and examples of the present invention use natural pyrite from different regions of my country as raw materials, the purity of which is shown in Table 1. The copper salt used in the examples is one or a combination of copper nitrate and copper sulfate, and the citric acid and copper salt are both industrial grade.

[0034] Table 1:

[0035]

[0036] The organic pollutant degradation experiments of the various embodiments and comparative examples of the present invention are all completed using a continuous catalytic degradation experimental device. The main body of the device is a cylindrical fixed bed, which is filled with quartz sand as an inert filler on the top and bottom, and a catalyst particle bed of a determined height in the middle; a constant flow peristaltic pump is used to transport organic polluted wastewater (containing oxidant) with a concentration of C0 to the fixed bed for catalytic degradation reaction, and the effluent after passing through the fixed bed reactor is collected to detect changes in pollutant concentration. The temperature of the fixed bed and the wastewater is controlled separately by a temperature control device to ensure the accuracy and stability of the experimental data. After the set experimental time, the concentration of organic pollutants in the effluent (C t The catalytic performance was evaluated by the degradation rate (Equation 1).

[0037] Degradation rate = (C0-C t ) / C0×100% Formula (1)

[0038] Example 1

[0039] The natural pyrite used in this embodiment is produced in Gansu and has a purity of 98%. Industrial-grade copper nitrate trihydrate and industrial-grade citric acid monohydrate are used. The specific implementation process includes:

[0040] (1) The natural pyrite is crushed, and the crushed pyrite particles are sieved to screen out pyrite particles with a particle size of 3±1 mm. The sieved pyrite particles are placed in ultrapure water for washing to remove surface impurities, and then placed in an oven for drying.

[0041] (2) Copper nitrate trihydrate and citric acid monohydrate are placed in a beaker filled with ultrapure water and stirred thoroughly to dissolve them to form a mixed solution. The molar ratio of copper salt to citric acid in the mixed solution is 1:2.

[0042] (3) natural pyrite particles are added to the mixed solution, wherein the molar ratio of the iron element in the natural pyrite particles to the copper salt and citric acid is 25:2:4, and then vacuum impregnation is performed for 5 hours. The impregnated solution is placed in an oven at 60°C, and after evaporating part of the water, vacuum impregnation is performed again; the evaporation-vacuum impregnation step is repeated once to obtain a precursor.

[0043] (4) The precursor was filtered, dried, and placed in a tube furnace. It was calcined in an inert atmosphere at a heating rate of 5°C / min within a calcination temperature range of 400°C for 60 minutes. It was then taken out and washed in ultrapure water to remove surface impurities and unstable substances to obtain a granular CuFeS2@FeS2 composite Fenton-like catalyst. The granular CuFeS2@FeS2 composite Fenton-like catalyst was analyzed by X-ray diffraction and scanning electron microscopy. The results are as follows: Figures 1-2 shown.

[0044] Two equal portions of granular CuFeS2@FeS2 composite catalyst were loaded into two fixed beds. Tetracycline hydrochloride was the target pollutant (at a concentration of 30 mg / L), and PMS and H2O2 were added to the two tetracycline hydrochloride solutions. M is defined as the ratio of the mass of the treated wastewater to the mass of the catalyst used. With PMS as the oxidant, when M was 100, the degradation rate of tetracycline hydrochloride was 91%, and when M was 2000, the degradation rate remained at 79%. With H2O2 as the oxidant, when M was 100, the degradation rate of tetracycline hydrochloride was 88%, and when M was 2000, the degradation rate remained at 74%. See Table 2 for details. The CuFeS2@FeS2 composite catalyst can activate both PMS and H2O2, demonstrating excellent degradation performance for tetracycline hydrochloride and long-term catalytic stability.

[0045] Example 2

[0046] The natural pyrite used in this embodiment is produced in Anhui Province and has a purity of 96%. Industrial-grade copper sulfate pentahydrate and industrial-grade citric acid monohydrate are used. The specific implementation process includes:

[0047] (1) The natural pyrite is crushed, and the crushed pyrite particles are sieved to screen out pyrite particles with a particle size of 5±1 mm. The sieved pyrite particles are placed in ultrapure water for washing to remove surface impurities, and then placed in an oven for drying.

[0048] (2) Copper sulfate pentahydrate and citric acid monohydrate are placed in a beaker filled with ultrapure water and stirred thoroughly to dissolve them to form a mixed solution. The molar ratio of copper salt to citric acid in the mixed solution is 1:3.

[0049] (3) natural pyrite particles are added to the mixed solution, wherein the molar ratio of iron element to copper salt and citric acid in the natural pyrite particles is 25:4:16, and then vacuum impregnation is performed for 6 hours. The impregnated solution is placed in an oven at 60°C, and after evaporating part of the water, vacuum impregnation is performed again; the evaporation-vacuum impregnation step is repeated 3 times to obtain a precursor.

[0050] (4) The precursor was filtered, dried, and placed in a tube furnace. It was calcined in an inert atmosphere at a heating rate of 10°C / min within a calcination temperature range of 450°C for 90 minutes. It was then taken out and washed in ultrapure water to remove surface impurities and unstable substances to obtain a granular CuFeS2@FeS2 composite Fenton-like catalyst.

[0051] Two equal amounts of granular CuFeS2@FeS2 composite catalyst were taken and filled into two fixed beds. Sodium dodecylbenzene sulfonate was used as the target pollutant (concentration of 40 mg / L), and PMS and H2O2 were added to the two sodium dodecylbenzene sulfonate solutions respectively. M is defined as the ratio of the mass of the treated wastewater to the mass of the catalyst used. Using PMS as the oxidant, when M is 100, the degradation rate of sodium dodecylbenzene sulfonate is 84%, and when M is 2000, the degradation rate still retains 72%. Using H2O2 as the oxidant, when M is 100, the degradation rate of sodium dodecylbenzene sulfonate is 81%, and when M is 2000, the degradation rate still retains 69%, see Table 2 for details. The CuFeS2@FeS2 composite catalyst can activate both PMS and H2O2, and has excellent degradation performance for sodium dodecylbenzene sulfonate and long-term catalytic stability.

[0052] Example 3

[0053] The natural pyrite used in this embodiment is produced in Guangdong and has a purity of 95%. Industrial-grade copper nitrate trihydrate and industrial-grade citric acid monohydrate are used. The specific implementation process includes:

[0054] (1) The natural pyrite is crushed, and the crushed pyrite particles are sieved to screen out pyrite particles with a particle size of 6±1 mm. The sieved pyrite particles are placed in ultrapure water for washing to remove surface impurities, and then placed in an oven for drying.

[0055] (2) Copper nitrate trihydrate and citric acid monohydrate were placed in a beaker filled with ultrapure water and stirred thoroughly to dissolve them to form a mixed solution. The molar ratio of copper salt to citric acid in the mixed solution was 1:1.5.

[0056] (3) natural pyrite particles were added to the mixed solution, wherein the molar ratio of iron element to copper salt and citric acid in the natural pyrite particles was 25:3:4.5, and then vacuum impregnation was performed for 7 hours. The impregnated solution was placed in an oven at 80°C, and after evaporating part of the water, vacuum impregnation was performed again. The evaporation-vacuum impregnation step was repeated twice to obtain a precursor.

[0057] (4) The precursor was filtered, dried, and placed in a tube furnace. It was calcined in an inert atmosphere at a heating rate of 5°C / min within a calcination temperature range of 350°C for 120 min. It was taken out and washed in ultrapure water to remove surface impurities and unstable substances to obtain a granular CuFeS2@FeS2 composite Fenton-like catalyst.

[0058] Two equal portions of granular CuFeS2@FeS2 composite catalyst were filled into two fixed beds. Rhodamine B was the target pollutant (at a concentration of 20 mg / L), and PMS and H2O2 were added to the two Rhodamine B solutions. M is defined as the ratio of the mass of the treated wastewater to the mass of the catalyst used. With PMS as the oxidant, when M was 100, the degradation rate of Rhodamine B was 98%, and when M was 2000, the degradation rate remained at 86%. With H2O2 as the oxidant, when M was 100, the degradation rate of the catalyst tetracycline hydrochloride was 96%, and when M was 2000, the degradation rate remained at 80%, as shown in Table 2. The CuFeS2@FeS2 composite catalyst can activate both PMS and H2O2, demonstrating excellent Rhodamine B degradation performance and long-term catalytic stability.

[0059] Comparative Example 1

[0060] The natural pyrite used in this comparative example is produced in Gansu and has a purity of 98%. The specific implementation process includes:

[0061] First, the natural pyrite was crushed and sieved, and the pyrite particles with a particle size of 3±1 mm were screened and washed with ultrapure water to remove surface impurities and unstable components, and then dried in an oven to obtain pyrite particles for later use. The pyrite particles were subjected to X-ray diffraction and scanning electron microscopy analysis, and the results were as follows: Figures 1-2 As shown. The catalytic degradation process is the same as in Example 1. M is defined as the ratio of the mass of the treated wastewater to the mass of the catalyst used. Taking PMS as the oxidant, when M is 100, the degradation rate of tetracycline hydrochloride is 59%, and when M is 2000, the degradation rate is reduced to 34%. Taking H2O2 as the oxidant, when M is 100, the degradation rate of tetracycline hydrochloride is 54%, and when M is 2000, the degradation rate is reduced to 32%, see Table 2 for details. Natural pyrite can activate both PMS and H2O2, but the catalytic degradation performance of pyrite on tetracycline hydrochloride is poor.

[0062] Comparative Example 2

[0063] The natural pyrite used in this comparative example is produced in Gansu and has a purity of 98.00%. Industrial-grade copper nitrate trihydrate and industrial-grade citric acid monohydrate are used. The specific implementation process includes:

[0064] (1) The natural pyrite is crushed, and the crushed pyrite particles are sieved to screen out pyrite particles with a particle size of 3±1 mm. The sieved pyrite particles are placed in ultrapure water for washing to remove surface impurities, and then placed in an oven for drying.

[0065] (2) Copper nitrate trihydrate and citric acid monohydrate are placed in a beaker filled with ultrapure water and stirred thoroughly to dissolve them to form a mixed solution. The molar ratio of copper salt to citric acid in the mixed solution is 1:2.

[0066] (3) adding natural pyrite particles to the mixed solution, wherein the molar ratio of the iron element in the natural pyrite particles to the copper salt and citric acid is 25:2:4, and then vacuum impregnation is performed for 5 hours without repeated impregnation to obtain a precursor.

[0067] (4) The precursor was filtered, dried, and placed in a tube furnace. It was calcined in an inert atmosphere at a heating rate of 5°C / min within a calcination temperature range of 400°C for 60 min. The precursor was taken out and washed in ultrapure water to remove surface impurities and unstable substances to obtain a granular CuFeS2@FeS2 composite Fenton-like catalyst.

[0068] Two equal portions of granular CuFeS2@FeS2 composite catalyst were loaded into two fixed beds. Tetracycline hydrochloride was the target pollutant (at a concentration of 30 mg / L), and PMS and H2O2 were added to the two tetracycline hydrochloride solutions. M is defined as the ratio of the mass of the treated wastewater to the mass of the catalyst used. With PMS as the oxidant, when M was 100, the degradation rate of tetracycline hydrochloride was 76%, and when M was 2000, the degradation rate dropped to 60%. With H2O2 as the oxidant, when M was 100, the degradation rate of tetracycline hydrochloride was 72%, and when M was 2000, the degradation rate dropped to 54%. See Table 2 for details. The CuFeS2@FeS2 composite catalyst activated both PMS and H2O2. However, due to only a single impregnation, the Cu loading was low, resulting in a moderate degradation effect on tetracycline hydrochloride.

[0069] Table 2:

[0070]

[0071]

[0072] Result analysis:

[0073] Table 2 above is a comparison of the performance of the Fenton-like catalysts in various comparative examples and examples for catalyzing the degradation of organic matter using PMS / H2O2.

[0074] Comparative Example 1 uses unmodified natural pyrite particles as PMS and H2O2 catalysts, and conducts catalytic degradation experiments with tetracycline hydrochloride as the target pollutant to evaluate its catalytic performance. It can be seen that natural pyrite can activate PMS and H2O2, but its catalytic degradation performance and cyclic stability for pollutants are relatively poor. In Example 1, when the granular CuFeS2@FeS2 composite catalyst is M=100, with PMS and H2O2 as oxidants, the degradation rates of tetracycline hydrochloride are 91% and 88% respectively. When M=2000, the degradation rates of tetracycline hydrochloride are 79% and 74% respectively, which are significantly higher than the effect of Comparative Example 1. The CuFeS2@FeS2 composite catalyst of Example 1 of the present application has a higher utilization rate of PMS and H2O2 than Comparative Example 1, and has stronger catalytic performance and cyclic stability.

[0075] Comparative Example 2 is a granular CuFeS2@FeS2 composite catalyst prepared by calcining after a single impregnation. Due to the limited adsorption performance of pyrite for Cu ions, the Cu element loading in the catalyst is relatively small, and the catalytic degradation performance is significantly worse than that of Example 1. In Example 1, after heating after impregnation and evaporating some of the water, the Cu ion concentration is further improved. Repeating the vacuum impregnation step can continue to adsorb Cu ions, greatly improving the Cu element loading. However, the repeated impregnation step should not be too many. Too many impregnation times will cause the loading layer to be too dense, resulting in the inner layer active sites being covered, and it is impossible to achieve a good catalytic effect.

[0076] Depend on Figure 1 and Figure 2 It can be seen that after modification, peaks of FeS2 and CuFeS2 appeared on the surface of the granular CuFeS2@FeS2 composite catalyst of the present application, and a honeycomb structure appeared on the surface of the catalyst, which increased the number of active sites, making it easier for the oxidant to be adsorbed on the catalyst surface and further decomposed into a large number of active oxygen species, thereby achieving rapid degradation of organic pollutants; while in Comparative Example 1, the surface of natural pyrite was dense and smooth, with few active sites exposed, less contact between the active sites and the oxidant, and poor catalytic performance.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a CuFeS2@FeS2 composite Fenton-type catalyst, characterized in that: The following steps are involved: S1. Crushing, sieving, washing, and drying natural pyrite in sequence to obtain natural pyrite particles; placing copper salt and citric acid in water and stirring to obtain a mixed solution; S2, adding the natural pyrite particles to the mixed solution, subjecting the mixed solution to vacuum impregnation treatment, evaporating part of the water, and then subjecting the mixed solution to vacuum impregnation, repeating the evaporation-vacuum impregnation treatment to obtain a precursor; S3. After filtering and drying the precursor, calcining it under an inert atmosphere, and then washing it with water, a granular CuFeS2@FeS2 composite Fenton-like catalyst is obtained.

2. The preparation method of the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, characterized in that In step S1, the purity of the natural pyrite is above 95%, and the average particle size of the natural pyrite is 1 to 6 mm.

3. The preparation method of the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, characterized in that In step S1, the molar ratio of the copper salt to the citric acid in the mixed solution is 1:1 to 1:4; the copper salt is one or both of copper nitrate and copper sulfate; and the citric acid and the copper salt are both industrial grade.

4. The preparation method of the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, characterized in that In step S2, the molar ratio of the iron element in the natural pyrite particles to the copper salt and citric acid in the mixed solution is 25:2:2 to 25:5:

20.

5. The preparation method of the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, characterized in that In step S2, the vacuum impregnation treatment lasts for 4 to 8 hours, the evaporation temperature is 60 to 80°C, and the evaporation-vacuum impregnation treatment is repeated 1 to 4 times.

6. The method for preparing the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, wherein In step S3, the inert atmosphere includes any one of nitrogen and argon.

7. The preparation method of the CuFeS2@FeS2 composite Fenton-type catalyst according to claim 1, characterized in that In step S3, the heating rate of the calcination treatment is 3-10°C / min, the temperature of the calcination treatment is 350-450°C, and the holding time of the calcination treatment is 60-120min.

8. A CuFeS2@FeS2 composite Fenton-type catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the CuFeS2@FeS2 composite Fenton catalyst prepared by the preparation method according to any one of claims 1 to 7 or the CuFeS2@FeS2 composite Fenton catalyst according to claim 8 in sewage treatment, characterized in that: The CuFeS2@FeS2 composite Fenton-like catalyst degrades organic pollutants in wastewater based on catalytic activation of an oxidant; wherein the oxidant includes at least one of hydrogen peroxide and peroxymonosulfate.

10. The use according to claim 9, characterized in that The organic pollutants include any one of surfactants, antibiotics, and dyes commonly found in water bodies; the surfactant includes sodium dodecylbenzenesulfonate; the antibiotic includes tetracycline hydrochloride; and the dye includes rhodamine B.

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