Preparation method and application of a Fe3S4-derived catalyst

Abstract

The present invention discloses a preparation method of an Fe3S4-derived catalyst. In this method, ferric chloride hexahydrate and 1,4-benzenedicarboxylic acid are added to N,N-dimethylformamide, and the reaction is carried out at 97-102 °C for 118-120 h. After solid-liquid separation, the solid is washed successively with N,N-dimethylformamide and acetone, and then dried under vacuum to obtain the MIL68-(Fe) catalyst. The MIL-68(Fe) catalyst and thioacetamide are placed in absolute ethanol, ultrasonicated at 25-40 °C for 25-35 min, and then reacted at 110-150 °C for 14-18 h. After cooling to room temperature and centrifuging, the solid is washed successively with absolute ethanol and deionized water, and then dried under vacuum to obtain the Fe3S4-derived catalyst. The catalyst of the present invention has excellent degradation effect in activating oxidants to degrade the dye Rhodamine B, and the degradation efficiency can reach 100%. The catalyst has certain magnetism and can be separated by an external magnet in an aqueous solution, which solves the problem of difficult recovery.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of an Fe3S4-derived catalyst, belonging to the technical field of water purification materials. Background Art

[0002] Water pollution caused by organic pollutants has always been a serious problem in industrial fields such as coatings, textiles, leather, papermaking, cosmetics, and chemical processing. These organic pollutants are highly toxic and colored, posing a major threat to the water ecosystem and human health. Therefore, there is an urgent need for an efficient, rapid, and safe method to remove organic dye pollutants from wastewater.

[0003] Previous studies have shown that traditional water treatment methods, such as adsorption, biological treatment, and membrane filtration, can effectively remove dye pollutants from wastewater. However, these technologies are usually inefficient and prone to generating secondary pollutants. Traditional advanced oxidation treatment technologies mainly rely on homogeneous activation such as light energy, thermal energy, or transition metals, usually requiring additional energy input, and some transition metal centers have certain toxicity, prone to metal ion leaching problems during activation, causing secondary pollution to the environment. Advanced oxidation processes (AOPs) can be activated by catalysts to generate substances with strong oxidation activity, mineralizing organic pollutants into low-toxic and harmless small molecules, carbon dioxide, and water, and have received great attention, being considered a particularly efficient technology for degrading organic pollutants in the water environment. Therefore, developing environmentally friendly and highly efficient catalysts is one of the current research hotspots.

[0004] Metal-organic frameworks (MOFs), due to their large surface area, rich active sites, and adjustable structures, can be used as precursors to prepare different catalyst materials, and have become a promising catalyst. The transition metal centers in MOFs can serve as reaction active sites; currently, there are no reports on the research or patents of using MIL-68(Fe) to prepare Fe3S4 for advanced oxidation technology to generate free radicals to degrade organic pollutants in wastewater. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a preparation method of an Fe3S4-derived catalyst, aiming to solve problems such as insufficient active sites of some heterogeneous catalysts, the need for additional energy input during the actual catalytic process, low efficiency in degrading rhodamine B dye in wastewater, difficult catalyst recovery, high price and easy to cause secondary pollution, and large consumption of oxidants; the Fe3S4-derived catalyst prepared by the present invention has extremely high degradation efficiency for RhB, simple catalyst recovery, does not require additional energy consumption, and will not cause secondary pollution.

[0006] The preparation method of the Fe3S4-derived catalyst of the present invention is as follows:

[0007] (1) Add ferric chloride hexahydrate and 1,4-benzenedicarboxylic acid to N,N-dimethylformamide, react at 97 - 102 °C for 118 - 120 h, perform solid-liquid separation, wash the solid successively with N,N-dimethylformamide and acetone, and dry it under vacuum to obtain the MIL-68(Fe) catalyst;

[0008] The mass ratio of the ferric chloride hexahydrate to the 1,4-benzenedicarboxylic acid is 1:1 - 3;

[0009] (2) Place the MIL-68(Fe) catalyst and thioacetamide in absolute ethanol, ultrasonicate at 25 - 40 °C for 25 - 35 min, then react at 108 - 113 °C for 14 - 18 h, cool to room temperature, after centrifugation, wash the solid successively with absolute ethanol and deionized water, and dry it under vacuum to obtain the Fe3S4-derived catalyst;

[0010] The mass ratio of the MIL-68(Fe) catalyst to the thioacetamide is 1:3 - 5.

[0011] The ultrasonic power is 50 - 150 W.

[0012] Another object of the present invention is to apply the Fe3S4-derived catalyst prepared by the above method to the degradation of the dye Rhodamine B in water, and add persulfate (PMS), persulfate (PDS), hydrogen peroxide or peracetic acid (PAA) during the degradation.

[0013] The beneficial effects of the present invention are:

[0014] (1) The present invention uses a non-toxic iron-based metal-organic framework (MIL-68(Fe)) as a template, and through ligand exchange with thioacetamide, the prepared derived Fe3S4 catalyst is layered, has a larger specific surface area. The larger specific surface area and layered structure can significantly shorten the distance of free radical diffusion, provide more active sites for the conversion of organic pollutants, and greatly improve the interaction between organic pollutants and the catalyst;

[0015] (2) Accelerating the conversion of Fe(III) to Fe(II) and increasing the number of persistent unsaturated Fe sites are the keys to improving the performance of Fe-MOFs. The present invention uses thioacetamide as the S source, and introducing unsaturated S atoms as electron donors is beneficial for Fe 3+ / Fe 2+ cycle;

[0016] (3) The catalyst derived from MIL-68(Fe) as a precursor in the present invention has super strong magnetism and can also be recovered by an external magnet in water, solving the problem of difficult catalyst recovery;

[0017] (4) The preparation method of the present invention is simple, easy to operate, and the catalyst is environmentally friendly. The catalyst has extremely high activation effects on different oxidants in advanced oxidation technologies, such as peroxymonosulfate, persulfate, hydrogen peroxide, etc.; that is, it has excellent degradation performance for Rhodamine B. In the Fe3S4 / PDS system, the degradation efficiency can reach 100% in 5 minutes; in the Fe3S4 / PMS system, the degradation efficiency can reach 94% in 5 minutes; in the Fe3S4 / H2O2 system, the degradation efficiency can reach 88% in 5 minutes. It has high application potential in the repair of dye wastewater. Description of the Drawings

[0018] Figure 1 It is the hysteresis loop (VSM) diagram of the Fe3S4-derived catalyst;

[0019] Figure 2 It is the scanning electron microscope (SEM) diagram of the Fe3S4-derived catalyst;

[0020] Figure 3 It is the scanning electron microscope (SEM) diagram of the template-free Fe3S4 catalyst;

[0021] Figure 4 It is the X-ray diffraction (XRD) diagram of the Fe3S4-derived catalyst;

[0022] Figure 5 It is the N2 adsorption-desorption isotherm diagram of the Fe3S4-derived catalyst;

[0023] Figure 6 It is the thermogravimetric (TGA) diagram of the Fe3S4-derived catalyst;

[0024] Figure 7 It is the activation effect of the Fe3S4-derived catalyst on different oxidants in water;

[0025] Figure 8 It is the degradation result of Rhodamine B by different dosages of the Fe3S4-derived catalyst in water;

[0026] Figure 9 It is the degradation effect of Rhodamine B by different dosages of PDS in water;

[0027] Figure 10 It is the schematic diagram of the degradation results of Rhodamine B by different catalysts. In the figure, Fe3S4 is the Fe3S4-derived catalyst

[0028] Figure 11 It is the degradation effect of the Fe3S4-derived catalyst on Rhodamine B at different pH values in water;

[0029] Figure 12Influence diagram of Fe3S4-derived catalyst on the degradation of Rhodamine B at different humic acid concentrations in water bodies. Detailed implementation manners

[0030] The present invention will be further described in detail below in conjunction with the specific implementation manners, but the protection scope of the present invention is not limited to the content described. Example 1

[0031] 1. The preparation method of the present Fe3S4-derived catalyst is as follows:

[0032] (1) Add 1.351 g of ferric chloride hexahydrate and 1.66 g of 1,4-benzenedicarboxylic acid to 60 mL of N,N-dimethylformamide, react at 100 °C for 120 h, perform solid-liquid separation, wash the solid successively with N,N-dimethylformamide and acetone, and dry it under vacuum at 100 °C to obtain the MIL-68(Fe) catalyst;

[0033] (2) Place 0.5 g of MIL-68(Fe) and 2 g of thioacetamide in 80 mL of absolute ethanol, ultrasonicate at 30 °C and 50 W for 30 min, then place it at 110 °C to react for 16 h and cool to room temperature. After centrifugation, wash the solid successively with absolute ethanol and deionized water, and dry it under vacuum at 60 °C to obtain the Fe3S4-derived catalyst;

[0034] Detect the saturation magnetization value of the Fe3S4-derived catalyst prepared in this example through a hysteresis loop test. The result is 28.9 emu / g, which has strong magnetism and can be recovered by an external magnet in water bodies, solving the problem of difficult catalyst recovery. The hysteresis loop diagram is shown in Figure 1 .

[0035] At the same time, refer to the method in "Zhang, J., et al., Humic acid promoted activation of peroxymonosulfate by Fe(3)S(4) for degradation of 2,4,6-trichlorophenol : An experimental and theoretical study. J Hazard Mater, 2022. 434: p. 128913." to prepare a template-free Fe3S4 catalyst as a control;

[0036] The scanning electron microscope images of the Fe3S4-derived catalyst and the template-free Fe3S4 catalyst prepared in this example are shown in Figure 2 , Figure 3 , from Figure 2It can be seen that the morphology of Fe3S4 is layered and composed of nanosheets, while the surface of the template-free Fe3S4 catalyst is smooth; due to the layered structure being conducive to shortening the ion diffusion distance and providing more active sites for the conversion of oxidants, the interaction between the Fe3S4-derived catalyst and the oxidant is significantly improved, thereby enhancing the degradation efficiency of RhB.

[0037] The XRD pattern of the Fe3S4-derived catalyst prepared in this example is shown in Figure 4 , from Figure 4 it can be seen that the precursor MIL-68(Fe) and the derived Fe3S4 catalyst have good crystallinity, and the main peak position of the prepared Fe3S4 catalyst is consistent with the standard card No. 16-173, indicating the successful preparation of the derived material.

[0038] The N2 adsorption-desorption isotherm diagram of the Fe3S4-derived catalyst in this example is shown in Figure 5 , the specific surface area of MIL-68(Fe) is about 301 m 2 / g, which is similar to the literature reports; the Fe3S4-derived catalyst has a larger specific surface area and a larger average pore diameter, which is conducive to the exposure of active sites.

[0039] The thermogravimetric diagram of the Fe3S4-derived catalyst in this example is shown in Figure 6 , from Figure 6 it can be seen that the thermal stability of MIL-68(Fe) can reach 384 °C, and the thermal stability of Fe3S4 after derivation is greatly improved, reaching 527 °C, indicating that the thermal stability of the derived material is higher than that of the precursor MOFs material.

[0040] 2. Performance test of the Fe3S4-derived catalyst prepared in this example for activating persulfate to degrade rhodamine B in water: According to the dosing ratio of 0.15 g / L, the Fe3S4-derived catalyst was put into 50 mL of rhodamine B solution with a concentration of 15 mg / L, and rapidly stirred at 600 rpm for 30 min to reach the adsorption-desorption equilibrium. PDS and PMS 、 H2O2 were respectively added at a ratio of 0.4 mmol / L. At certain intervals during the reaction, the reaction solution was taken and filtered through a 0.22 μm filter head to obtain the clear liquid, and the amount of remaining rhodamine B in the clear liquid was measured by an ultraviolet spectrophotometer;

[0041] The results are shown in Figure 7 , from Figure 7 it can be seen that the degradation efficiency of rhodamine B in the three oxidation systems can reach more than 88% within 5 min, indicating that the catalyst has a good activation effect on different oxidants. In the presence of persulfate (PDS), the Fe3S4-derived catalyst in this example has an excellent degradation effect on rhodamine B (5 min, 100%), and the Fe3S4-derived catalyst in water has a good activation effect on different oxidants.

[0042] 3. Add Fe3S4-derived catalyst to the rhodamine B solution at 15 mg / L in proportions of 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, and 0.25 g / L, and add PDS. The other conditions are the same as in step 2. The results are shown in Figure 8 , from Figure 8 it can be seen that when the catalyst dosage is 0.15 g / L, the degradation rate of rhodamine B at 5 min is 100%;

[0043] 4. Add Fe3S4-derived catalyst to the rhodamine B solution at 15 mg / L in a proportion of 0.15 g / L, and detect the degradation effect of different dosages of PDS on rhodamine B. The results are shown in Figure 9 , from Figure 9 it can be seen that when the PDS addition amount is 0.2 mmol / L, the degradation rate of rhodamine B at 5 min is 98.1%; when the PDS addition amount is 0.4 mmol / L, the degradation rate of rhodamine B at 5 min is 100%; when the PDS addition amount is 0.6 mmol / L, the degradation rate of rhodamine B at 5 min is 98.6%; when the PDS addition amount is 0.8 mmol / L, the degradation rate of rhodamine B at 5 min is 98.9%; when the PDS addition amount is 1 mmol / L, the degradation rate of rhodamine B at 5 min is 98.9%;

[0044] 5. Add PDS, Fe3S4-derived catalyst, Fe3S4-derived catalyst + PDS, MIL-68(Fe) catalyst + PDS, and template-free Fe3S4 catalyst + PDS to the rhodamine B solution at 15 mg / L respectively, and set a blank control without adding a catalyst. The PDS addition amount is 0.4 mmol / L, and the other catalysts are added in a proportion of 0.15 g / L;

[0045] The results of the degradation of rhodamine B are shown in Figure 10 , as can be seen from the figure, the Fe3S4-derived catalyst prepared in this example has a significantly higher catalytic degradation effect on rhodamine B than other reagents.

[0046] 6. Degradation experiment of the rhodamine B solution at 15 mg / L with different pH values (2 - 10) using the Fe3S4-derived catalyst (0.15 g / L), with the PDS addition amount being 0.4 mmol / L and the other conditions the same as in step 2. The results are shown in Figure 11 , from Figure 11 it can be seen that it still has a good degradation effect on rhodamine B within the pH range of 2 - 10, indicating that the pH application range of this derived catalyst is relatively wide.

[0047] 7. Humic acid widely exists in nature as a natural organic substance, and its impact on degradation cannot be ignored. The degradation of 15 mg / L rhodamine B solution containing different concentrations of humic acid (0 - 40 mg / L) by the Fe3S4-derived catalyst was carried out with a PDS addition amount of 0.4 mmol / L. The results are shown in Figure 12 , Figure 12 It can be seen that in the rhodamine B solution containing different concentrations of humic acid, humic acid has little effect on the activation of persulfate by the catalyst to degrade rhodamine B. Example 2

[0048] (1) 1 g of ferric chloride hexahydrate and 2 g of 1,4-benzenedicarboxylic acid were added to 60 mL of N,N-dimethylformamide and reacted at 97 °C for 120 h. After solid-liquid separation, the solid was washed successively with N,N-dimethylformamide and acetone and dried under vacuum at 100 °C to obtain the MIL-68(Fe) catalyst;

[0049] (2) 0.6 g of MIL-68(Fe) and 2 g of thioacetamide were placed in 80 mL of absolute ethanol. After ultrasonic treatment at 25 °C and 70 W for 30 min, the mixture was reacted at 130 °C for 16 h and cooled to room temperature. After centrifugation, the solid was washed successively with absolute ethanol and deionized water and dried under vacuum at 60 °C to obtain the Fe3S4-derived catalyst;

[0050] (3) The Fe3S4-derived catalyst prepared in this example was used for the performance test of activating PDS to degrade rhodamine B in water

[0051] According to the addition ratio of 0.15 g / L, the Fe3S4-derived catalyst was put into 50 mL of rhodamine B solution with a concentration of 15 mg / L, and rapidly stirred at 600 rpm for 30 min to reach the adsorption-desorption equilibrium. Then PDS (0.4 mM) was added. The reaction solution was filtered through a 0.22 μm filter head to obtain the clear liquid, and the amount of remaining rhodamine B in the clear liquid was measured by an ultraviolet spectrophotometer; the degradation efficiency of RhB at 5 min was 97.3%. Example 3

[0052] (1) 1 g of ferric chloride hexahydrate and 3 g of 1,4-benzenedicarboxylic acid were added to 60 mL of N,N-dimethylformamide and reacted at 97 °C for 120 h. After solid-liquid separation, the solid was washed successively with N,N-dimethylformamide and acetone and dried under vacuum at 100 °C to obtain the MIL-68(Fe) catalyst;

[0053] (2) 0.4 g of MIL-68(Fe) and 2 g of thioacetamide were placed in 80 mL of absolute ethanol. After ultrasonic treatment at 35 °C and 70 W for 30 min, the mixture was reacted at 150 °C for 16 h and then cooled to room temperature. After centrifugation, the solid was washed successively with absolute ethanol and deionized water and dried in vacuo at 60 °C to obtain the Fe3S4-derived catalyst.

[0054] (3) Performance test of the Fe3S4-derived catalyst prepared in this example for activating persulfate to degrade rhodamine B in water

[0055] According to the addition ratio of 0.15 g / L, the Fe3S4-derived catalyst was put into a 50 mL rhodamine B solution with a concentration of 15 mg / L and stirred rapidly at 600 rpm for 30 min to reach the adsorption-desorption equilibrium. Then PDS (0.4 mM) was added. The reaction solution was filtered through a 0.22 μm filter head to obtain the clear liquid, and the amount of remaining rhodamine B in the clear liquid was measured by an ultraviolet spectrophotometer; the degradation efficiency of RhB was 91.5% at 5 min.

Claims

1. Application of an Fe3S4-derived catalyst in degrading dye Rhodamine B, and the preparation method of the Fe3S4-derived catalyst is as follows: (1) Add ferric chloride hexahydrate and 1,4-terephthalic acid into N,N-dimethylformamide, react at 97-102 °C for 118-120 h, perform solid-liquid separation, wash the solid successively with N,N-dimethylformamide and acetone, and dry in vacuum to obtain the MIL-68(Fe) catalyst; (2) Place the MIL-68(Fe) catalyst and thioacetamide in absolute ethanol, ultrasonicate at 25-40 °C for 25-35 min, then react at 110-150 °C for 14-18 h, cool to room temperature, after centrifugation, wash the solid successively with absolute ethanol and deionized water, and dry in vacuum to obtain the Fe3S4-derived catalyst; Add monopersulfate, dipersulfate, hydrogen peroxide or peracetic acid during the process of degrading dye Rhodamine B.

2. The application according to claim 1, characterized in that: The mass ratio of ferric chloride hexahydrate to 1,4-terephthalic acid is 1:1-3.

3. The application according to claim 1, characterized in that: The mass ratio of the MIL-68(Fe) catalyst to thioacetamide is 1:3-5.

4. The application according to claim 1, characterized in that: The ultrasonic power in step (2) is 50~150 W.

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