Heterogeneous iron-based catalysts with singlet oxygen as the main active species, methods of preparation and use

Abstract

This invention discloses a heterogeneous iron-based catalyst with singlet oxygen as the main active material, its preparation method, and its application, belonging to the field of catalyst material technology. Graphene is dispersed in water to prepare a graphene suspension; a nitrogen source and an iron source are added to the graphene suspension, mixed evenly, and then subjected to a hydrothermal reaction. The reactants are washed and dried; the dried material is then carbonized at high temperature under a nitrogen atmosphere to obtain a heterogeneous iron-based catalyst with singlet oxygen as the main active material. The heterogeneous iron-based catalyst prepared by this invention produces [a specific active material] during the catalytic process. 1 O2 is the main active oxygen substance in the non-radical oxidation process, which has a high pollutant degradation efficiency and is not easily affected by coexisting ions in water and different water matrices. It has wide applications in the treatment of actual water bodies.

Description

Technical Field

[0001] This invention belongs to the field of catalyst materials technology, specifically relating to a heterogeneous iron-based catalyst with singlet oxygen as the main active material, its preparation method, and its application. Background Technology

[0002] Compared with traditional advanced oxidation technologies, persulfate (PS)-based advanced oxidation technologies (PS-AOPs) have attracted widespread attention due to their advantages such as high stability, long transport distance, and low cost. PS can be activated using external energy sources (such as ultraviolet irradiation, heat, ultrasound, and electricity), but this method suffers from high energy requirements, high equipment costs, and poor equipment durability. Heterogeneous catalyst activation, on the other hand, is characterized by high efficiency, mild reaction conditions, and no need for external energy input; therefore, catalyst-based activation methods are increasingly being used in PS-AOPs. Currently, iron-based catalysts are a research hotspot in heterogeneous catalytic persulfate removal of tetracycline (TC) from water due to their Fenton-like activity and low cost.

[0003] In natural water bodies, inorganic ions and natural organic matter (NOM) are ubiquitous and have a significant impact on PS-AOPs. Compared to free radicals, non-radical oxidation exhibits high selectivity and resistance to interference, including singlet oxygen (…). 1 O2), high-valence metals, and surface-bound oxidizing complexes allow for the selective oxidation of electron-rich pollutants, thus utilizing oxidants more efficiently than radical reaction systems and playing a crucial role in pollutant degradation. Furthermore, they are unaffected by coexisting ions and different aqueous matrices. Therefore, there is growing interest in the preferential generation of non-radical catalysts.

[0004] Patent CN116422360A discloses a heterogeneous cobalt-based catalyst, its preparation method, and its application. Zinc nitrate and cobalt nitrate are weighed and dissolved in methanol to obtain solution A. 2-methylimidazole is weighed and dissolved in methanol to obtain solution B. Solutions A and B are then mixed and allowed to stand at 20-40°C for 12-72 hours to obtain a suspension. The solvent in the suspension is removed, and the suspension is washed three times with methanol. The resulting product, after drying, is the catalyst precursor. The catalyst precursor is calcined and then reduced to obtain the final Co-C / N catalyst. However, this catalyst leaches Co during the activation of persulfate (PDS) to degrade pollutants. 2+ Toxic Co 2+ It will cause pollution to the water body again.

[0005] Patent CN116809081A provides a heterogeneous iron-based catalyst and its preparation method and application, the main steps include: under stirring, NH4Fe(SO4)2 solution is added dropwise into tungsten disulfide ethanol suspension, stirring reaction at 50~90°C for 2~10 hours, wherein the molar ratio of NH4Fe(SO4)2 to WS2 is (1~4):1, and the heterogeneous iron-based catalyst FeOOH@WS2 is prepared by filtering, washing and drying. The main active substance in the process of activating PDS to degrade pollutants by the heterogeneous iron-based catalyst is SO4 ·- The active substance is easily disturbed by coexisting ions in water and different water matrices, which is limited in actual water application. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a heterogeneous iron-based catalyst with singlet oxygen as the main active substance and a preparation method and application thereof, so that the catalytic process produces a non-radical oxidation process with O2 as the main active oxygen substance, which has high pollutant degradation efficiency and is not easily disturbed by coexisting ions in water and different water matrices, and has wide application in actual water treatment. 1 The active substance is easily disturbed by coexisting ions in water and different water matrices, which is limited in actual water application.

[0007] The present application is realized by the following technical solutions:

[0008] A preparation method of a heterogeneous iron-based catalyst with singlet oxygen as the main active substance, comprising the following steps:

[0009] (1) Graphene is dispersed in water to prepare a graphene suspension;

[0010] (2) A nitrogen source and an iron source are added to the graphene suspension, and after mixing uniformly, a hydrothermal reaction is carried out, and the reaction product is washed and dried;

[0011] (3) The dried material in step (2) is carbonized at high temperature under a nitrogen atmosphere to obtain a heterogeneous iron-based catalyst with singlet oxygen as the main active substance.

[0012] Further, in step (1), the concentration of graphene in the graphene suspension is 1-4 mg / L.

[0013] Further, in step (2), the mass ratio of graphene, iron source and nitrogen source is 1:1~3:1~10:2:40.

[0014] Further, in step (2), the nitrogen source is one of urea, ammonium nitrate and ammonia water, and the iron source is ferrous sulfate or ferrous ammonium sulfate.

[0015] Further, in step (2), the hydrothermal reaction conditions are as follows: the reaction temperature is 140-180°C, and the reaction time is 8-14h.

[0016] Furthermore, the conditions for high-temperature carbonization in step (3) are: high-temperature carbonization temperature of 650-750℃ and high-temperature carbonization time of 2-3h.

[0017] Furthermore, the drying in step (2) is vacuum freeze drying; the heating rate in step (3) is 3-5℃ / min, and the cooling rate is 3-5℃ / min.

[0018] In this invention, the heterogeneous iron-based catalyst prepared by the above preparation method uses singlet oxygen as the main active material.

[0019] In this invention, the heterogeneous iron-based catalyst with singlet oxygen as the main active substance is applied in the catalytic degradation of water pollutants.

[0020] Furthermore, the water pollutant is tetracycline.

[0021] Furthermore, in order to achieve higher economic benefits, the FexOy / NG in the water body is separated, recovered, washed, and dried after the degradation reaction is completed to obtain reusable FexOy / NG material. During the washing process, deionized water and ethanol are used to wash the material repeatedly 3-5 times.

[0022] Beneficial effects

[0023] This invention modulates the active sites on the catalyst surface, and the prepared catalyst generates [a specific chemical / property] during the catalytic process. 1 O2 is the main active oxygen substance in the non-radical oxidation process, which has a high pollutant degradation efficiency and is not easily affected by coexisting ions in water and different water matrices. It has wide applications in the treatment of actual water bodies. Attached Figure Description

[0024] Figure 1 The X-ray diffraction pattern of the heterogeneous iron-based catalyst prepared in Example 1, with singlet oxygen as the main active material;

[0025] Figure 2 Scanning electron microscope image of the heterogeneous iron-based catalyst prepared in Example 1, with singlet oxygen as the main active material;

[0026] Figure 3 EPR diagram of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active material;

[0027] Figure 4 This is a diagram showing the catalytic degradation of a heterogeneous iron-based catalyst with singlet oxygen as the main active substance. Detailed Implementation

[0028] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0029] Example 1

[0030] (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it by ultrasonic vibration in a water bath to obtain a graphene suspension of 2 mg / L.

[0031] (2) 600 mg of urea and 120 mg of ferrous sulfate were added to the graphene suspension as iron source and nitrogen source respectively. The mixture was stirred magnetically for 5 hours to make it evenly mixed. The solution in the beaker was placed in the polytetrafluoroethylene reactor and reacted at 180°C for 10 hours. The reactants were soaked in deionized water and the water was changed every 12 hours to remove excess raw materials from the material. The material was then vacuum freeze-dried for 48 hours.

[0032] (3) The material dried in step (2) is placed in a tube furnace and carbonized at 700℃ for 2 hours under a nitrogen atmosphere, with a heating rate of 5℃ / min and a cooling rate of 5℃ / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG) with singlet oxygen as the main active material. 700℃ ).

[0033] Example 2

[0034] (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it by ultrasonic vibration in a water bath to obtain a graphene suspension of 2 mg / L.

[0035] (2) 600 mg of urea and 120 mg of ferrous sulfate were added to the graphene suspension in sequence as iron source and nitrogen source, respectively. The mixture was stirred magnetically for 5 hours to make it uniform. The solution in the beaker was placed in the polytetrafluoroethylene reactor and reacted at 160°C for 14 hours. The reactants were soaked in deionized water and the water was changed every 12 hours to remove excess raw materials from the material. The material was then vacuum freeze-dried for 48 hours.

[0036] (3) The material dried in step (2) is placed in a tube furnace and carbonized at 650°C for 3 hours under a nitrogen atmosphere, with a heating rate of 5°C / min and a cooling rate of 5°C / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG) with singlet oxygen as the main active material. 650℃ ).

[0037] Example 3

[0038] (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it by ultrasonic vibration in a water bath to obtain a graphene suspension of 2 mg / L.

[0039] (2) 1200 mg of urea and 120 mg of ferrous sulfate were added to the graphene suspension as iron and nitrogen sources, respectively. The mixture was stirred magnetically for 5 hours to make it uniform. The solution in the beaker was placed in the polytetrafluoroethylene reactor and reacted at 180°C for 8 hours. The reactants were soaked in deionized water and the water was changed every 12 hours to remove excess raw materials from the material. The material was then vacuum freeze-dried for 48 hours.

[0040] (3) The material dried in step (2) is placed in a tube furnace and carbonized at 750°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min and a cooling rate of 5°C / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG) with singlet oxygen as the main active material. 750℃ ).

[0041] Comparative Example 1

[0042] (1) rGO 700℃ Preparation: 60 mg of graphene (rGO) was weighed into a beaker, and 30 ml of deionized water was added. The mixture was ultrasonically dispersed in a water bath to obtain a 2 mg / L graphene suspension. Similar to Example 1, to minimize interference, magnetic stirring was used for 5 hours. The solution in the beaker was then placed in a polytetrafluoroethylene reactor and reacted at 180°C for 10 hours. The reactants were immersed in deionized water, with the water changed every 12 hours to remove excess raw materials. The material was then vacuum freeze-dried for 48 hours. The dried material was placed in a tube furnace and carbonized at 700°C for 2 hours under a nitrogen atmosphere, with a heating rate of 5°C / min and a cooling rate of 5°C / min, to obtain the heterogeneous catalyst (rGO). 700℃ ).

[0043] (2) NG 700℃ Preparation: 60 mg of graphene (rGo) was weighed into a beaker, and 30 ml of deionized water was added. The mixture was ultrasonically dispersed in a water bath to obtain a 2 mg / L graphene suspension. 600 mg of urea was added to the graphene suspension as a nitrogen source, and the mixture was magnetically stirred for 5 hours to ensure homogeneity. The solution in the beaker was placed in a polytetrafluoroethylene reactor and reacted at 180 °C for 10 hours. The reactants were immersed in deionized water, with the water changed every 12 hours to remove excess raw materials. The reactants were then vacuum freeze-dried for 48 hours. The dried material was placed in a tube furnace and carbonized at 700 °C for 2 hours under a nitrogen atmosphere, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain a heterogeneous catalyst (rGo). 700℃ ).

[0044] (3) FexOy / G700℃ Preparation: 60 mg of graphene (rGo) was weighed into a beaker, and 30 ml of deionized water was added. The mixture was ultrasonically dispersed in a water bath to obtain a 2 mg / L graphene suspension. 120 mg of ferrous sulfate was added to the graphene suspension as an iron source, and the mixture was magnetically stirred for 5 hours to ensure homogeneity. The solution in the beaker was placed in a polytetrafluoroethylene reactor and reacted at 180 °C for 10 hours. The reactants were immersed in deionized water, with the water changed every 12 hours to remove excess raw materials. The mixture was then vacuum freeze-dried for 48 hours. The dried material was placed in a tube furnace and carbonized at 700 °C for 2 hours under a nitrogen atmosphere, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain a heterogeneous catalyst (FexOy / G). 700℃ ).

[0045] Performance characterization:

[0046] (1) The crystal properties and phase structure of the catalyst material were analyzed using X-ray diffraction (XRD). The X-ray diffraction pattern of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active material is shown below. Figure 1 As shown, its intensity is in good agreement with the magnetite structure of JCPDS No. 88-0866. The diffraction peaks at the crystal planes of Fe3O4 nanoparticles (111), (220), (311), (222), (400), (422), (511), (440), and (533) are 18.43°, 30.22°, 35.63°, 37.14°, 43.25°, 53.65°, 57.13°, and 62.76°, respectively.

[0047] (2) The microstructure of the catalyst material was characterized using scanning electron microscopy (SEM). The SEM image of the heterogeneous iron-based catalyst prepared in Example 1, with singlet oxygen as the main active material, is shown below. Figure 2 As shown, by Figure 2 It is known that graphene oxide has a sheet-like porous structure, which is beneficial for providing a large specific surface area and active anchor points. Small spherical particles are distributed on the sheet-like surface of graphene, indicating that iron oxide has been successfully doped into graphene. Moreover, doping with N will lead to an increase in the amount of Fe oxide doped and a decrease in volume.

[0048] (3) Determination of ·OH and SO4 by EPR experiment ·- O2 ·- and 1 O2, using DMPO (100 mmol / L) as a spin trapping agent, captures OH and SO4 in the solution. ·- and O2 ·- Free radicals, captured using TEMP (10 mmol / L) 1O2, the EPR diagram of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active material is shown below. Figure 3 As shown in the figure, DMPO-HO (strength ratio 1:2:2:1), DMPO-SO4 (strength ratio 1:1:1:1:1:1), DMPO-O2 (strength ratio 1:1:1:1) and TEMP- are present. 1 The four spectral lines of O2 (intensity ratio of 1:1:1), among which TEMP- 1 The intensity of the O2 spectral peak is significantly higher than that of the other three, indicating that the heterogeneous iron-based catalyst + PDS system, with singlet oxygen as the main active material, contains a large amount of [missing information - likely a chemical component]. 1 O2 is generated, and 1 The content of O2 is much higher than that of OH and SO4. ·- and O2 ·- .

[0049] (4) Catalytic degradation activity:

[0050] Six 40 mg / L tetracycline solutions were prepared, and their initial absorbance was measured. The solutions were then stirred at a constant speed on a magnetic stirrer. PDS and FexOy / NG were added to each solution respectively. 700℃ rGO 700℃ NG 700℃ FexOy / G 700℃ and FexOy / NG 700℃ First, adsorption was allowed to reach adsorption equilibrium for 30 minutes. Then, oxidant PDS was added to all solutions except PDS for catalytic degradation experiments at a concentration of 3 mmol / L. The mixture was stirred continuously for 90 minutes, and the absorbance of the six solutions was measured at intervals.

[0051] The heterogeneous iron-based catalyst (FexOy / NG) prepared in Example 1 with singlet oxygen as the main active material 700℃ ), rGO 700℃ NG 700℃ FexOy / G 700℃ The degradation diagram of tetracycline by catalysis is shown below. Figure 4 As shown, by Figure 4 It can be seen that, with only FexOy / NG... 700℃ Under these conditions, the removal efficiency of the catalyst material for pollutant TC only reached 56.73% after 2 hours, and essentially reached adsorption equilibrium after 30 minutes. When only PDS was added, the TC concentration hardly changed; however, the removal rate of TC significantly improved after the catalyst was added, and the FexOy / NG ratio... 700℃ Its adsorption and catalytic effects are comparable to those of the other three catalysts (rGO). 700℃ NG 700℃FexOy / G 700℃ To be better, NG 700℃ This is because agglomeration occurs during carbonization, resulting in a reduced specific surface area and fewer exposed active sites on the catalyst material, leading to poor adsorption and catalytic performance. (FexOy / G) 700℃ Both their adsorption and catalytic abilities are slightly lower than those of FexOy / NG. 700℃ This indicates that N doping can effectively improve the adsorption and catalytic performance of the catalyst.

Claims

1. A method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active material, characterized in that, Includes the following steps: (1) Graphene is dispersed in water to prepare a graphene suspension; (2) Add nitrogen source and iron source to graphene suspension, mix evenly and carry out hydrothermal reaction, wash the reactants and freeze dry them in vacuum; (3) The material dried in step (2) is carbonized at high temperature for 2-3 hours under nitrogen atmosphere and temperature of 650-750℃ to obtain a heterogeneous iron-based catalyst with singlet oxygen as the main active substance; wherein the heating rate is 3-5℃ / min and the cooling rate is 3-5℃ / min. The heterogeneous iron-based catalyst has a plate-like porous structure, and small spherical iron oxide particles are distributed on the plate-like surface.

2. The method for preparing the heterogeneous iron-based catalyst with singlet oxygen as the main active material according to claim 1, characterized in that, In step (2), the mass ratio of graphene, iron source and nitrogen source is 1:2:10 or 1:2:

20.

3. The method for preparing the heterogeneous iron-based catalyst with singlet oxygen as the main active material according to claim 1, characterized in that, In step (2), the nitrogen source is one of urea, ammonium nitrate, or ammonia water, and the iron source is ferrous sulfate or ferrous ammonium sulfate.

4. The method for preparing the heterogeneous iron-based catalyst with singlet oxygen as the main active material according to claim 1, characterized in that, The conditions for the hydrothermal reaction in step (2) are: reaction temperature of 140-180℃ and reaction time of 8-14h.

5. A heterogeneous iron-based catalyst prepared by the preparation method according to any one of claims 1 to 4, with singlet oxygen as the main active substance.

6. The application of the heterogeneous iron-based catalyst of claim 5, which uses singlet oxygen as the main active substance, in the catalytic degradation of water pollutants.

7. The application according to claim 6, characterized in that, The water pollutant mentioned is tetracycline.

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