Zsm-5 molecular sieve confined ferrous sulfide composite catalyst, and preparation method and application thereof

Abstract

The application relates to a ZSM-5 molecular sieve confined ferrous disulfide composite catalyst and a preparation method and application thereof, and belongs to the field of advanced oxidation technology. The preparation method comprises the following steps: performing calcination pretreatment on ZSM-5 molecular sieve, dispersing the pretreated ZSM-5 molecular sieve into a non-polar solvent to obtain a mixed solution; adding an aqueous solution containing an iron salt into the mixed solution, stirring, and drying to obtain a molecular sieve loaded with iron; mixing and grinding the molecular sieve loaded with iron with thiourea according to a molar ratio of 2-5:1 of the thiourea and the iron salt to obtain catalyst precursor powder; and performing calcination, washing and drying on the catalyst precursor powder to obtain the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst. The catalyst prepared by the preparation method can adapt to a relatively wide pH range, shows high removal capacity for phenolic pollutants, has excellent cycle stability, can still maintain extremely high degradation efficiency after multiple cycles, and has good engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of advanced oxidation technology, specifically to a ZSM-5 molecular sieve-confined ferrous disulfide composite catalyst, its preparation method, and its application. Background Technology

[0002] Phenolic pollutants, typical organic pollutants in the aquatic environment, originate from wastewater discharges from chemical industries such as oil refining, gasification, pharmaceuticals, and papermaking, posing a serious threat to aquatic environments. Phenolic pollutants exhibit strong biotoxicity; high concentrations of phenolic compounds can rapidly penetrate biomembranes, interfere with mitochondrial respiratory chain function, inhibit key enzyme activity, and induce neurotoxicity, liver and kidney damage, among other biotoxic effects. Typical phenolic pollutants, such as phenol and 2,4-dichlorophenol, have been included in the "Priority Control Pollutants in Water" blacklist. Because most phenolic pollutants contain electrophilic substituents, they are more difficult to degrade, leading to their accumulation and migration in the environment. Therefore, achieving efficient and deep degradation of phenolic pollutants has become one of the key challenges in solving phenolic water pollution.

[0003] Even after biological treatment, the concentration of some recalcitrant phenolic pollutants remains high, causing the effluent quality to fail to meet discharge standards. This could lead to serious ecological damage from their discharge, necessitating advanced treatment. Commonly used advanced treatment technologies include coagulation sedimentation, adsorption, membrane separation, and advanced oxidation processes. While coagulation sedimentation, adsorption, and membrane separation are effective, they still have limitations such as high treatment costs and the potential for secondary pollution. Advanced oxidation technologies, characterized by strong oxidation capacity and non-selectivity, can degrade organic pollutants in wastewater into CO2, H2O, and other compounds.

[0004] The Fenton advanced oxidation system, as a typical process in advanced oxidation technology, has advantages such as simple process, environmental friendliness, and no secondary pollution. However, its narrow pH range and easy deactivation of catalyst active components limit its application in practical scenarios. Summary of the Invention

[0005] (a) Purpose of the invention The purpose of this invention is to overcome the limitations of traditional Fenton oxidation and provide a ZSM-5 molecular sieve-confined ferrous disulfide composite catalyst, its preparation method, and its application. The catalyst prepared by this method can adapt to a wide pH range, exhibits high efficiency in removing phenolic pollutants, and has excellent cycle stability, maintaining extremely high degradation efficiency even after multiple cycles, thus showing good prospects for engineering applications.

[0006] (II) Technical Solution To address the above problems, this invention provides a method for preparing a ZSM-5 molecular sieve-confined ferrous disulfide composite catalyst, comprising the following steps: Step 1: Calcine the ZSM-5 molecular sieve to obtain a pretreated ZSM-5 molecular sieve; Step 2: Disperse the pretreated ZSM-5 molecular sieve described in Step 1 into a nonpolar solvent to obtain a mixed solution; Step 3: Add the aqueous solution containing iron salt dropwise to the mixed solution described in Step 2, stir, and dry to obtain the iron-loaded molecular sieve; Step 4: Mix and grind the iron-loaded molecular sieve with thiourea according to the molar ratio of thiourea to iron salt in step 3 of 2-5:1 to obtain catalyst precursor powder. The molar amount of iron salt is calculated based on the molar amount of iron ions added in step 3, and the molar amount of thiourea is calculated based on its own molar amount. Step 5: The catalyst precursor powder is calcined, washed, and dried to obtain the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst.

[0007] This invention achieves uniform distribution of iron salts within the slit channels of ZSM-5 molecular sieves by leveraging the synergistic effect of the nonpolar solvent-polar solution interface and the capillary force of the molecular sieve channels. Subsequently, by controlling the amounts of thiourea and iron salts, the iron-containing molecular sieves and thiourea are uniformly mixed through grinding. During the subsequent calcination process, the thiourea decomposes in situ upon heating, and the resulting highly active sulfur-containing species diffuse into the channels, undergoing an in-situ sulfidation reaction with the previously anchored iron salts to form uniformly sized and highly dispersed ferrous disulfide active sites.

[0008] This preparation method effectively inhibits the migration and aggregation of active components during heat treatment, successfully constructing ferrous disulfide active sites stably anchored within the molecular sieve. Its highly dispersed structural characteristics provide abundant interfacial reaction centers, significantly shortening electron transport paths, effectively improving interfacial electron transfer efficiency, and accelerating the valence state regeneration of iron species.

[0009] Under the synergistic effect of the confined structure and highly dispersed properties, the catalyst can efficiently activate hydrogen peroxide over a wide pH range of 3-9, producing •OH, 1 O2 and O2 •- It can synergistically attack various reactive oxygen species, including typical phenolic organic pollutants such as phenol, catechol, and hydroquinone, as well as typical antibacterial drugs such as acyclovir and sulfadiazine, demonstrating broad-spectrum, high-efficiency, and stable catalytic degradation performance.

[0010] This catalyst exhibits excellent cycle stability and maintains extremely high degradation efficiency even after multiple cycles.

[0011] Specifically, the silicon-aluminum ratio of the ZSM-5 molecular sieve in step 1 is 20-38; The specific conditions for calcination include: The calcination temperature is 450-550 ℃; The heating rate is 5-10 ℃ / min; The calcination time is 1.5-3 h.

[0012] Furthermore, prior to the calcination described in step 1, the process also includes: ZSM-5 molecular sieve was placed in an alkaline aqueous solution and etched by stirring at 60-90℃ for 1.5-2.5 h, wherein the solid-liquid mass ratio of ZSM-5 molecular sieve to alkaline aqueous solution was 1:45-55, and the stirring rate was 400-600 rpm. The concentration of the aqueous solution of the alkali is 0.1-0.3 mol / L; The alkali is selected from at least one of sodium hydroxide and potassium hydroxide.

[0013] Specifically, the nonpolar solvent mentioned in step 2 is an alkane organic solvent, selected from at least one of n-hexane, cyclohexane, or petroleum ether; The content of the pretreated ZSM-5 molecular sieve in the mixed solution is 0.03-0.06 g / ml.

[0014] Specifically, the iron salt mentioned in step 3 is selected from at least one of ferric nitrate, ferric sulfate, and ferric chloride; The molar concentration of iron ions in the aqueous solution containing iron salts is 0.8-1.4 mmol / mL; Preferably, the molar content of iron ions in the aqueous solution containing iron salt is 1.0-1.2 mmol / mL.

[0015] When the total metal molar content in the iron salt solution is within the preferred range, highly dispersed iron species can be formed in the pore structure of the pretreated ZSM-5 molecular sieve. These iron species are transformed into highly dispersed ferrous disulfide active sites during subsequent sulfidation, effectively improving interfacial electron transfer efficiency and accelerating the valence state regeneration of iron species, thereby significantly enhancing the catalytic degradation performance of phenolic pollutants.

[0016] The amount of the aqueous solution containing iron salt added is 0.1-0.2 times the volume of the nonpolar solvent; The stirring speed in step 3 is 250-350 rpm.

[0017] Specifically, the grinding conditions described in step 4 include: The grinding time is 5-15 minutes; The ground particles can pass through a 200-mesh sieve.

[0018] Preferably, in step 4, the thiourea and the iron salt in step 3 are mixed and ground in a molar ratio of 2-3:1 to ensure that the organic pollutants (including phenol, catechol, hydroquinone, bisphenol A, sulfadiazine, and acyclovir, etc.) in the wastewater (pH in the range of 3-9) can be removed at a rate of over 90% within 60 minutes, and the pollutant removal rate can still reach over 90% after the catalyst is reused 5 times.

[0019] Specifically, the specific conditions for calcination described in step 4 include: The calcination is carried out in two stages under an inert atmosphere. The first stage calcination temperature is 250-400 ℃ Heating rate 3-5 ℃ / min The calcination time is 0.5-1.5 h; The second stage calcination temperature is 450-600 ℃. Heating rate 3-5 ℃ / min The calcination time is 1.5-3 h.

[0020] To ensure that the removal rate of phenol in wastewater reaches more than 85%; In the embodiments of the present invention, the inert atmosphere is either a nitrogen atmosphere or a rare gas atmosphere, wherein the rare gas atmosphere is selected from at least one of argon, helium, and neon.

[0021] More preferably, the specific conditions for calcination in step 4 include: a first-stage calcination temperature of 300-350 ℃ and a second-stage calcination temperature of 500-550 ℃, to ensure that the pH of the wastewater is in the range of 3-9, and that the removal rate of pollutants (including phenol, catechol, hydroquinone, bisphenol A, sulfadiazine, and acyclovir, etc.) can reach more than 90% within 60 min, and that the pollutant removal rate can still reach more than 90% after the catalyst is reused 5 times.

[0022] In a specific embodiment of the present invention, a method for preparing a ZSM-5 molecular sieve-confined ferrous disulfide composite catalyst comprises the following steps: Step 1: Mix ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 20-38 with an aqueous solution of 0.1-0.3 mol / L alkali at a solid-liquid mass ratio of 1:45-55. Etch the mixture by magnetic stirring in a water bath at 60-90 ℃ for 1.5-2.5 h. Then, raise the temperature from room temperature to 450-550 ℃ at a rate of 5-10 ℃ / min and calcine at this temperature for 1.5-3 h to stabilize the molecular sieve structure. Step 2: Disperse 0.3 g of ZSM-5 molecular sieve pretreated in Step 1 in a nonpolar alkane organic solvent and sonicate for 20-30 min; Step 3: Dissolve the iron salt in ultrapure water and stir for 15-20 min to prepare an iron salt aqueous solution. The total amount of metal ions in the iron salt aqueous solution (in terms of the number of moles of iron ions) is 0.8-1.4 mmol / mL. Step 4: Add the iron salt aqueous solution obtained in Step 3 dropwise to the non-polar solvent containing ZSM-5 molecular sieve obtained in Step 2. Use capillary action to allow the iron component to penetrate into the molecular sieve channels. The amount of iron salt aqueous solution added is 0.1-0.2 times the volume of the non-polar solvent. Stir for 1.5-3 h at a stirring rate of 250-350 rpm. After recovering the non-polar solvent, dry in an oven or water bath at 60-80℃ for 5-7 h. Step 5: Mix and grind the iron-loaded molecular sieve obtained in Step 4 with thiourea for 5-15 minutes until no obvious agglomeration is observed and it can pass through a 200-mesh sieve. The molar ratio of the amount of thiourea added to the amount of iron ions loaded in the molecular sieve (based on the actual number of iron ions added in Step 4) is 2-5:1. The resulting powder is ready for use. Step 6: Place the powder obtained in Step 5 in a tube furnace and calcine it for 0.5-1.5 h at a rate of 3-5 ℃ / min under a nitrogen atmosphere, then calcine it for 1.5-3 h at a rate of 3-5 ℃ / min to 450-600 ℃. After cooling, wash it with 0.1 mol / L sulfuric acid and pure water, and then vacuum dry it to obtain the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst, denoted as FeS2@MZSM-5.

[0023] The composite catalyst can be used to catalyze the activation of hydrogen peroxide, and efficiently degrade phenol-containing recalcitrant organic pollutant wastewater within a pH range of 3-9. In addition, it also shows good degradation effects on typical phenolic organic pollutants such as hydroquinone, hydroquinone, and bisphenol A, as well as pollutants such as acyclovir and sulfadiazine.

[0024] In another aspect, the present invention provides a ZSM-5 molecular sieve confined ferrous disulfide composite catalyst prepared by any of the methods described above.

[0025] In another aspect, the present invention provides the application of the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst prepared by the method described in any of the above-mentioned methods in the degradation of organic pollutants in water by activated hydrogen peroxide.

[0026] Specifically, the organic pollutant is at least one of typical phenolic organic pollutants, endocrine disruptors, and typical antibacterial drugs, preferably at least one of phenol, hydroquinone, catechol, vanillin, and bisphenol A.

[0027] Specifically, the dosage of the composite catalyst is 10-50 mg / L, the pH value is 3-9, and the hydrogen peroxide concentration is 1-2.5 mM.

[0028] Preferably, the dosage of the composite catalyst is 20-40 mg / L and the hydrogen peroxide concentration is 1-2 mM to ensure that phenol in the wastewater can be 100% removed within 60 min.

[0029] Compared with the prior art, the present invention has the following superior effects: This invention employs a strategy combining a dual-solvent method with mechanical grinding. By leveraging the synergistic effect of the non-polar solvent-polar solution interface and the capillary force of the molecular sieve channels, uniform distribution of iron species within the slit channels of the ZSM-5 molecular sieve is achieved. Subsequently, the iron-containing molecular sieve is uniformly mixed with thiourea through grinding. During the subsequent calcination process, the thiourea undergoes in-situ thermal decomposition, and the resulting highly active sulfur-containing species diffuse into the channels, undergoing an in-situ sulfidation reaction with the previously anchored iron species to form uniformly sized and highly dispersed ferrous disulfide active sites.

[0030] This preparation method effectively inhibits the migration and aggregation of active components during heat treatment, successfully constructing ferrous disulfide active sites stably anchored within the molecular sieve. Its highly dispersed structural characteristics provide abundant interfacial reaction centers, significantly shortening electron transport paths, effectively improving interfacial electron transfer efficiency, and accelerating the valence state regeneration of iron species.

[0031] Under the synergistic effect of the confined structure and highly dispersed properties, the catalyst can efficiently activate hydrogen peroxide over a wide pH range of 3-9, producing •OH, 1 O2 and O2 •- It can synergistically attack various reactive oxygen species, including typical phenolic organic pollutants such as phenol, catechol, and hydroquinone, as well as typical antibacterial drugs such as acyclovir and sulfadiazine, demonstrating broad-spectrum, high-efficiency, and stable catalytic degradation performance.

[0032] This catalyst exhibits excellent cycle stability and maintains extremely high degradation efficiency even after multiple cycles. Attached Figure Description

[0033] Figure 1 The images are scanning electron microscope (SEM) images of the FeS2@MZSM-5 catalysts prepared in Comparative Examples 1-2 and Example 1 of this invention, where a is Comparative Example 1, b is Comparative Example 2, and c is Example 1. Figure 2 The images shown are transmission electron microscope (TEM) images and X-ray energy dispersive spectroscopy (XEDS) images of the composite catalyst FeS2@MZSM-5 prepared in Example 1 of this invention. In the images, a is the TEM image of Al, b and f are XEDS images of different elements, b is Al, c is Fe, d is O, e is S, and f is Si. Figure 3 X-ray diffraction patterns of the pretreated ZSM-5 molecular sieve prepared in Comparative Example 1 of this invention, the catalyst FeS2@MZSM-5 prepared in Example 1, and FeS2. Figure 4 The degradation effect of p-phenol wastewater in Example 1 and Comparative Examples 1-2 of this invention is shown in the figure. Figure 5 The following are the degradation effect diagrams of phenol wastewater in Examples 2-4 of this invention; Figure 6 The degradation effect of phenol wastewater in Examples 5-7 and Comparative Examples 3 and 4 of the present invention is shown in the figure. Figure 7 The following are diagrams illustrating the degradation effect of phenol wastewater in Examples 8-11 of this invention; Figure 8 The following are application examples 2-6 of this invention, showing the degradation effect on phenol wastewater; Figure 9 Example 7 illustrates the cyclic degradation performance of phenol in this invention. Figure 10 This demonstrates the universality of the application examples 8-12 in degrading other pollutants; Figure 11 This is a comparison chart showing the degradation effects of p-phenol wastewater in Example 1 and Comparative Example 5 of the present invention; Figure 12 The cumulative concentration of each reactive oxygen species generated by FeS2@MZSM-5 provided in Example 1 of this invention over 60 minutes. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The raw materials and reagents used in the embodiments and comparative examples of this invention are all conventional commercially available products; The wastewater mentioned in each embodiment of the present invention is simulated wastewater prepared by mixing the target pollutant with ultrapure water; The activation reaction of hydrogen peroxide was carried out at room temperature (25 ℃) in a constant temperature water bath shaker. The pH value of the wastewater was adjusted by using 0.1 mol / L sulfuric acid and 0.1 mol / L sodium hydroxide. Ultrapure water was used for water preparation.

[0036] The grinding equipment used in all embodiments of the present invention is a mortar with an inner diameter of 110 mm purchased from Licheng Technology Co., Ltd.

[0037] Example 1 (1) ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25 was mixed with 0.2 mol / L sodium hydroxide aqueous solution at a solid-liquid mass ratio of 1:50 and etched by magnetic stirring in an 80 ℃ water bath for 2 h. Then, the temperature was increased from room temperature to 550 ℃ at a rate of 5 ℃ / min and calcined for 2 h to stabilize the molecular sieve structure, thus obtaining the pretreated ZSM-5 molecular sieve; (2) Weigh 0.3 g of ZSM-5 molecular sieve pretreated in step (1), place it in a beaker containing 5 mL of non-polar alkane organic solvent n-hexane, and sonicate for 30 min to fully disperse it in the hydrophobic solvent to obtain a mixed solution; (3) Dissolve 6 mmol of ferric nitrate nonahydrate (in molar amounts of iron ions) in 5 mL of ultrapure water and stir for 20 min until completely dissolved and mixed evenly to obtain an aqueous solution of iron salt; (4) Add the iron salt aqueous solution obtained in step (3) to the mixed solution containing ZSM-5 molecular sieve obtained in step (2) dropwise, with an addition amount of 1 ml. After the addition is complete, stir for 2 h at a stirring rate of 300 rpm. After recovering n-hexane, dry in an oven at 60-80 ℃ for 6 h to obtain the iron-loaded molecular sieve. (5) Mix and grind the iron-loaded molecular sieve obtained in step (4) with thiourea (2.4 mmol) for 10 min until no obvious agglomeration is observed and it can pass through a 200-mesh sieve. The molar ratio of the amount of thiourea added to the amount of iron ions loaded in the molecular sieve (based on the actual amount of iron ions added in step (4)) is 2:1. The resulting powder is ready for use. (6) The powder obtained in step (5) is placed in a tube furnace and heated to 350 °C at a rate of 5 °C / min under a nitrogen atmosphere with a gas flow rate of 1 L / min. It is then calcined for 1 h and then heated to 550 °C at a rate of 5 °C / min. After cooling, it is washed with 0.1 mol / L sulfuric acid and pure water. After washing, it is vacuum dried to obtain the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst, denoted as FeS2@MZSM-5.

[0038] Examples 2 and 3 The catalyst preparation process in Examples 2 and 3 is the same as that in Example 1, except that the alkaline etching concentrations of ZSM-5 molecular sieve are 0.1 mol / L and 0.3 mol / L, respectively.

[0039] Example 4 The catalyst preparation process was the same as in Example 1, except that alkaline etching was not performed.

[0040] Examples 5-7 The catalyst preparation process in Examples 5-7 is the same as that in Example 1, except that the molar ratio of the amount of thiourea added to the iron ions loaded in the molecular sieve in Examples 5-7 (based on the actual number of iron ions added in step (4)) is 3:1, 4:1 and 5:1 respectively, and the calcination temperature in the first stage in step 6 is 300 °C.

[0041] Examples 8-10 The catalyst preparation process in Examples 8-10 is basically the same as that in Example 1, except that the calcination temperatures in the first stage of step 6 in Examples 8-10 are 250 ℃, 300 ℃, and 400 ℃, respectively.

[0042] Example 11 The catalyst preparation process in Example 11 is basically the same as that in Examples 8-10, except that the first stage of calcination is omitted in Example 11, and calcination is only carried out in the second stage for 3 hours.

[0043] Comparative Example 1 Compared with Example 1, steps (2) to (6) were omitted in Comparative Example 1, and only ZSM-5 molecular sieve was pretreated as a blank control.

[0044] Comparative Example 2 Compared with Example 1, step (2) was omitted in the preparation process of Comparative Example 2.

[0045] Comparative Example 3 The catalyst preparation process of Comparative Example 3 is the same as that of Examples 5-7, except that the molar ratio of the added thiourea to the iron ions loaded in the molecular sieve in Comparative Example 3 is 1:1.

[0046] Comparative Example 4 The catalyst preparation process of Comparative Example 4 was the same as that of Examples 4-7, except that the amount of thiourea added in Comparative Example 4 was 0 mmol.

[0047] Comparative Example 5 The catalyst preparation process in this comparative example is the same as that in Example 1, except that metallic iron was not added.

[0048] The products provided in each embodiment and comparative example were characterized, with Example 1, Comparative Examples 1 and 2 as typical representatives. Other embodiments all have the same or similar morphological features as Example 1. Specific characterization results are referred to [reference needed]. Figure 1-3 : Depend on Figure 3 As can be seen from the X-ray diffraction pattern, the catalyst prepared in Example 1 not only completely retained the characteristic diffraction peaks consistent with those in Comparative Example 1, proving that the framework structure of the molecular sieve was not destroyed during the preparation process; at the same time, the characteristic diffraction peaks consistent with pure phase FeS2 clearly appeared in the spectrum of Example 1, confirming that ferrous disulfide phase was indeed generated in the catalyst system.

[0049] Secondly, combining Figure 1 Morphological comparison and analysis were performed on the scanning electron microscope images. Figure 1 a and Figure 1 b shows that the catalyst in Example 1 maintained the original regular crystal morphology of the molecular sieve, and the outer surface of the crystal was relatively clean. No obvious large particles or agglomerates of ferrous disulfide were observed, indicating that ferrous disulfide existed in the narrow pores of the molecular sieve nanoscale bulk. For comparison, Figure 1 In the scanning electron microscope image of Comparative Example 2 shown in c, a large number of attached particles and significant agglomeration can be clearly observed on the outer surface of the crystal. This comparison intuitively confirms that under unconfined conditions, the active component is very likely to macroscopically aggregate on the outer surface of the support.

[0050] Finally, further integration Figure 2 The EDS elemental distribution map shows that the active component exhibits a uniform distribution throughout the entire molecular sieve particle region of Example 1, without localized enrichment. In summary... Figures 1 to 3 The characterization results fully demonstrate that, compared with the unrestricted comparative example 2, Example 1 of the present invention successfully achieved the confined loading of active components on molecular sieves.

[0051] Application Example 1 The catalysts obtained in each embodiment and comparative example were used to activate hydrogen peroxide to degrade phenol wastewater, specifically including: Test 1: The FeS2@MZSM-5 catalyst prepared in the above steps of Example 1 was used to activate hydrogen peroxide to degrade phenol wastewater, specifically including: FeS2@MZSM-5 catalyst and hydrogen peroxide were added to 100 mL of phenol wastewater with an initial concentration of 10 mg / L to obtain a reaction mixture. The catalyst dosage in the mixture was 40 mg / L, the hydrogen peroxide concentration was 2 mM, and the initial pH of 100 mL of phenol wastewater with an initial concentration of 10 mg / L was 6.86. The reaction was carried out at room temperature (25 °C).

[0052] Test 2: The conditions were basically the same as those in Test 1, except that the catalysts were replaced with those in Comparative Examples 1, 2 and 5, respectively.

[0053] Test 3: The conditions were basically the same as those in Test 1, except that the catalyst was replaced with the catalyst provided in Examples 2-11, and the catalyst dosage in the mixed system was 30 mg / L, and the hydrogen peroxide concentration was 1 mM.

[0054] Application Example 2-6 The phenol removal effect of the catalyst prepared in Example 1 at different pH values: In Application Examples 2-6, the FeS2@MZSM-5 catalyst was used to activate hydrogen peroxide to degrade phenol wastewater, which was basically the same as Test 1 in Application Example 1. The difference was that the initial pH of 100 mL of phenol wastewater with an initial concentration of 10 mg / L was adjusted to 3, 5, 7, 9, and 11, respectively, in Examples 2-6.

[0055] Application Example 7 The FeS2@MZSM-5 catalyst provided in Example 1 was used to activate hydrogen peroxide to degrade wastewater, which was basically the same as Test 1 in Application Example 1. The difference was that in Application Example 7, after each reaction was completed, the catalyst was separated and recovered from the reaction system, cleaned and dried, and then put back into the next reaction. The above steps were repeated five times to examine the reusability of the catalyst.

[0056] Application Example 8-12 The FeS2@MZSM-5 catalyst provided in Example 1 was used to activate hydrogen peroxide to degrade wastewater in essentially the same way as Test 1 in Application Example 1, except that the target pollutants in Application Examples 8-12 were catechol, hydroquinone, bisphenol A, sulfadiazine, and acyclovir, respectively. Under the conditions of a catalyst dosage of 40 mg / L and a hydrogen peroxide concentration of 2 mM, 100 mL of wastewater with a target pollutant concentration of 10 mg / L was treated.

[0057] See the test results for each application example. Figure 4-11 Specifically, it includes: like Figure 4 As shown, after reacting for 40 minutes, the catalyst corresponding to Example 1 achieved a 100% removal rate of phenol, while under the same conditions, see [reference needed]. Figure 4 and Figure 11 The removal rates of Comparative Examples 1 and 5 were almost 0, and the removal rate of Comparative Example 2 was less than 50%.

[0058] like Figure 5As shown, the phenol removal rate in Example 4 was about 80%, while in Examples 2-3, the phenol removal rate was over 90%. Alkali etching of the molecular sieve significantly improved the phenol removal rate.

[0059] like Figure 6 As shown, the phenol removal rate of Comparative Example 3 was only about 10%, while the phenol removal rates of Examples 5-7 were all above 80%; the phenol removal rate of Comparative Example 4 was only about 10%, while the removal rates of Examples 5-7, especially Examples 5 and 6, were above 90%.

[0060] like Figure 7 As shown, the phenol removal efficiency of Example 11 is about 80%, while the phenol removal rates of Examples 8-10 are all greater than 90%, especially Example 9, which has a removal rate of about 100%. This is because during the first stage of calcination, thiourea decomposes in situ under heat, and the generated highly active sulfur-containing species diffuse into the pores and undergo in-situ sulfidation reaction with the previously anchored iron species to form uniform and highly dispersed ferrous disulfide active sites. The second stage of calcination further consolidates the structural stability of the ferrous disulfide active sites, thus improving the removal rate of the target pollutant.

[0061] like Figure 8 As shown, the catalyst maintained a 100% removal rate of phenol over a wide pH range of 3-9 within 60 min.

[0062] The results are as follows Figure 9 As shown, the FeS2@MZSM-5 catalyst provided in Example 1 achieved a phenol removal rate of 98% after 60 min of reaction in five cycles.

[0063] The results are as follows Figure 10 As shown, within 60 min, the FeS2@MZSM-5 catalyst provided in Example 1 achieved a 100% removal rate for catechol, hydroquinone, and bisphenol A, and a removal rate of over 98% for acyclovir and sulfadiazine.

[0064] The FeS2@MZSM-5 composite catalyst prepared in Example 1 was used to catalyze hydrogen peroxide treatment of benzoic acid, nitrotetrazole blue chloride, and 1,3-diphenylisobenzofuran to investigate the cumulative concentration of active species generated by FeS2@MZSM-5.

[0065] The method for determining the cumulative formation of •OH is as follows: Benzoic acid is used as a probe molecule, and the concentration of benzoic acid is controlled at 1 mmol / L. •OH is captured by oxidizing benzoic acid to p-hydroxybenzoic acid. High-performance liquid chromatography (HPLC) is used to quantitatively analyze the generated p-hydroxybenzoic acid at a detection wavelength of 255 nm. Based on the conversion relationship: c(•OH) = 5.8 × c(p-hydroxybenzoic acid), the cumulative formation of •OH is calculated.

[0066] O2 •- The method for determining the cumulative amount is as follows: using nitroblue tetrazolium as a probe molecule, the concentration of nitroblue tetrazolium is controlled at 1 mmol / L, and the cumulative amount is determined by the reaction of nitroblue tetrazolium with O2. •- The reaction captures O2 •- The absorbance of nitroblue tetrazolium was measured at 259 nm using a spectrophotometer and quantitatively analyzed. Based on the conversion relationship: c(O2) •- O2 is calculated as 4 × c(nitroblue tetrazolium) = 4 × c(nitroblue tetrazolium). •- The cumulative amount generated.

[0067] 1 The method for determining O2 concentration is as follows: using 1,3-diphenylisobenzofuran as a probe molecule, controlling the DPBF concentration at 1 mmol / L, and utilizing the reaction of 1,3-diphenylisobenzofuran with... 1 O2 is captured by a degradation reaction at a 1:1 molar ratio. 1 O2. The absorbance of 1,3-diphenylisobenzofuran was measured at a wavelength of 410 nm using a spectrophotometer and quantitatively analyzed. According to the conversion relationship: c( 1 O2)=1×c(1,3-diphenylisobenzofuran), calculated to obtain 1 The cumulative amount of O2 generated.

[0068] Experimental results are as follows Figure 12 As shown, the FeS2@MZSM-5 catalyst catalyzes the production of a large amount of hydrogen peroxide. •OH, and a small amount 1 O2 and O2 •- .

[0069] By employing thiourea as the sulfiding agent, it is first uniformly mixed with iron-pretreated molecular sieves through grinding. In the subsequent calcination process, the thiourea melts upon heating and decomposes in situ, releasing highly active sulfur-containing species. These sulfur species diffuse into the molecular sieve, undergoing an in-situ sulfidation reaction with the iron species previously anchored within the slit channels, generating ferrous disulfide active sites. This in-situ sulfidation process, combined with the spatial confinement effect of the molecular sieve channels, results in uniform and highly dispersed ferrous disulfide, which is stably anchored within the channels. This highly dispersed confined structure endows the catalyst with abundant interfacial reaction centers, significantly shortening the electron transport path, effectively enhancing interfacial electron transfer efficiency, and accelerating the valence state regeneration of iron species, thereby greatly improving the catalyst's intrinsic activity and structural stability. Under this synergistic effect of structural regulation, the catalyst exhibits highly efficient and stable catalytic degradation performance for pollutants such as phenol over a wide pH range.

[0070] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a ZSM-5 molecular sieve-confined ferrous disulfide composite catalyst, characterized in that, Includes the following steps: Step 1: Calcine the ZSM-5 molecular sieve to obtain a pretreated ZSM-5 molecular sieve; Step 2: Disperse the pretreated ZSM-5 molecular sieve described in Step 1 into a nonpolar solvent to obtain a mixed solution; Step 3: Add the aqueous solution containing iron salt dropwise to the mixed solution described in Step 2, stir, and dry to obtain the iron-loaded molecular sieve; Step 4: Mix and grind the iron-loaded molecular sieve with thiourea according to the molar ratio of thiourea to iron salt in step 3 of 2-5:1 to obtain catalyst precursor powder. The molar amount of iron salt is calculated based on the molar amount of iron ions added in step 3, and the molar amount of thiourea is calculated based on its own molar amount. Step 5: The catalyst precursor powder is calcined, washed, and dried to obtain the ZSM-5 molecular sieve confined ferrous disulfide composite catalyst.

2. The preparation method according to claim 1, characterized in that, The silica-alumina ratio of the ZSM-5 molecular sieve mentioned in step 1 is 20-38; The specific conditions for calcination include: The calcination temperature is 450-550 ℃; The heating rate is 5-10 ℃ / min; The calcination time is 1.5-3 h.

3. The preparation method according to claim 1 or 2, characterized in that, Before the calcination described in step 1, the process also includes: ZSM-5 molecular sieve was placed in an alkaline aqueous solution and etched by stirring at 60-90 °C for 1.5-2.5 h, wherein the solid-liquid mass ratio of ZSM-5 molecular sieve to alkaline aqueous solution was 1:45-55, and the stirring rate was 400-600 rpm. The concentration of the aqueous solution of the alkali is 0.1-0.3 mol / L; The alkali is selected from at least one of sodium hydroxide and potassium hydroxide.

4. The preparation method according to claim 1, characterized in that, The nonpolar solvent mentioned in step 2 is an alkane organic solvent, selected from at least one of n-hexane, cyclohexane, or petroleum ether; The content of the pretreated ZSM-5 molecular sieve in the mixed solution is 0.03-0.06 g / ml.

5. The preparation method according to claim 1, characterized in that, The iron salt mentioned in step 3 is selected from at least one of ferric nitrate, ferric sulfate, and ferric chloride; The molar concentration of iron ions in the aqueous solution containing iron salts is 0.8-1.4 mmol / mL; The amount of the aqueous solution containing iron salt added is 0.1-0.2 times the volume of the nonpolar solvent; The stirring speed in step 3 is 250-350 rpm.

6. The preparation method according to claim 1, characterized in that, The specific grinding conditions described in step 4 include: The grinding time is 5-15 minutes; The ground particles can pass through a 200-mesh sieve.

7. The preparation method according to claim 1, characterized in that, The specific conditions for calcination described in step 4 include: The calcination is carried out in two stages under an inert atmosphere. The first stage calcination temperature is 250-400 ℃ Heating rate 3-5 ℃ / min The calcination time is 0.5-1.5 h; The second stage calcination temperature is 450-600 ℃. Heating rate 3-5 ℃ / min The calcination time is 1.5-3 h.

8. The ZSM-5 molecular sieve confined ferrous disulfide composite catalyst prepared by the method according to any one of claims 1-7.

9. The application of the composite catalyst prepared by the method according to any one of claims 1-7 in the degradation of organic pollutants in water by activated hydrogen peroxide.

10. The application according to claim 9, characterized in that, The dosage of the composite catalyst is 10-50 mg / L, the pH of the reaction system is 3-9, and the hydrogen peroxide concentration is 1-2.5 mM.

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