Heterogeneous iron-based catalyst taking singlet oxygen as main active substance as well as preparation method and application of heterogeneous iron-based catalyst

Abstract

The invention discloses a heterogeneous iron-based catalyst taking singlet oxygen as a main active substance as well as a preparation method and application thereof, and belongs to the technical field of catalyst materials. Dispersing graphene in water to prepare a graphene suspension; adding a nitrogen source and an iron source into the graphene suspension, uniformly mixing, carrying out hydrothermal reaction, and washing and drying a reactant; and carrying out high-temperature carbonization on the dried material in a nitrogen atmosphere to obtain the heterogeneous iron-based catalyst taking singlet oxygen as a main active substance. The heterogeneous iron-based catalyst prepared by the invention generates a non-free radical oxidation process taking < 1 > O2 as a main active oxygen substance in a catalysis process, has relatively high pollutant degradation efficiency, is not easily interfered by coexisting ions in water and different water matrixes, and has wide application in actual water treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst materials, and in particular relates to a heterogeneous iron-based catalyst with singlet oxygen as a main active substance, a preparation method and an application thereof. Background Art

[0002] Compared with traditional advanced oxidation technologies, persulfate (PS)-based advanced oxidation technologies (PS-AOPs) have the advantages of high stability, long transmission distance, and low cost, and have attracted widespread attention. PS can be activated by external energy (such as ultraviolet irradiation, heat, ultrasound, and electricity), but this method has the problems of high energy requirements, high equipment costs, and poor equipment durability. Heterogeneous catalyst activation has the characteristics of high efficiency, mild reaction conditions, and no need for external energy. Therefore, catalyst-based activation methods are increasingly being used in PS-AOPs. At present, iron-based catalysts are the research hotspot for heterogeneous catalytic persulfate removal of tetracycline (TC) in water bodies due to their Fenton-like activity, low cost, and easy availability.

[0003] In natural water bodies, inorganic ions and natural organic matter (NOM) are ubiquitous and have a great impact on PS-AOPs. Compared with free radicals, non-radical oxidation has high selectivity and anti-interference ability, including singlet oxygen ( 1 O2), high-valent metals, and surface-bound oxidative complexes, which allow for the selective oxidation of electron-rich pollutants, thus utilizing oxidants more efficiently than free radical reaction systems, play a vital role in pollutant degradation and are not interfered by coexisting ions and different water matrices. Therefore, there is a growing interest in catalysts that preferentially generate non-radicals.

[0004] Patent CN116422360A provides a heterogeneous cobalt-based catalyst and its preparation method and application. Zinc nitrate and cobalt nitrate are weighed and dissolved in methanol solvent to obtain solution A. 2-methylimidazole is weighed and dissolved in methanol to obtain solution B. Then, solution A and solution B are mixed and allowed to stand for 12-72 hours at a temperature of 20-40°C to obtain a suspension. The solvent of the suspension is removed and washed three times with methanol. The product obtained is dried to obtain a catalyst precursor. The catalyst precursor is calcined and then reduced to obtain a Co-C / N catalyst product. However, the catalyst will leach Co in the process of activating peroxydisulfate (PDS) to degrade pollutants. 2+ , the toxic Co 2+ Will cause pollution to the water bodies again.

[0005] Patent CN116809081A provides a heterogeneous iron-based catalyst and its preparation method and application. The main steps include: adding NH4Fe(SO4)2 solution dropwise to tungsten disulfide ethanol suspension under stirring, stirring and reacting at 50-90°C for 2-10 hours, wherein the molar ratio of NH4Fe(SO4)2 to WS2 is (1-4):1, filtering, washing and drying to obtain the heterogeneous iron-based catalyst FeOOH@WS2. The main active substance in the process of heterogeneous iron-based catalyst activation PDS degradation of pollutants is SO4 ·- , this active substance is easily interfered by coexisting ions in water and different water matrices, and is easily restricted in actual water applications. Summary of the invention

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

[0007] The present invention is achieved through the following technical solutions: A method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active substance comprises the following steps: (1) Graphene is dispersed in water to prepare a graphene suspension; (2) adding a nitrogen source and an iron source to the graphene suspension, mixing them evenly, performing a hydrothermal reaction, and washing and drying the reactants; (3) The material after drying in step (2) is carbonized at high temperature in a nitrogen atmosphere to obtain a heterogeneous iron-based catalyst with singlet oxygen as the main active substance.

[0008] Furthermore, the concentration of graphene in the graphene suspension in step (1) is 1-4 mg / L.

[0009] Furthermore, in step (2), the mass ratio of graphene, iron source and nitrogen source is 1:1~3:1~10:2:40.

[0010] Furthermore, in step (2), the nitrogen source is one of urea, ammonium nitrate and ammonia water, and the iron source is ferrous sulfate or ammonium ferrous sulfate.

[0011] Furthermore, the conditions of the hydrothermal reaction in step (2) are: reaction temperature is 140-180° C., and reaction time is 8-14 h.

[0012] Furthermore, the high temperature carbonization conditions in step (3) are as follows: the high temperature carbonization temperature is 650-750°C, and the high temperature carbonization time is 2-3h.

[0013] Furthermore, the drying in step (2) is vacuum freeze drying; and the heating rate in step (3) is 3-5°C / min, and the cooling rate is 3-5°C / min.

[0014] In the present invention, the heterogeneous iron-based catalyst with singlet oxygen as the main active substance is prepared by the above-mentioned preparation method.

[0015] In the present invention, the above-mentioned heterogeneous iron-based catalyst with singlet oxygen as the main active substance is used in catalytic degradation of water pollutants.

[0016] Furthermore, the water pollutant is tetracycline.

[0017] Furthermore, in order to achieve higher economic benefits, after the degradation reaction is completed, the FexOy / NG in the water body is separated, recovered, cleaned and dried to obtain reusable FexOy / NG materials. Deionized water and ethanol are used for repeated cleaning for 3-5 times.

[0018] Beneficial Effects The present invention regulates the active sites on the catalyst surface, and the prepared catalyst produces 1 The non-radical oxidation process in which O2 is the main active oxygen species has a high pollutant degradation efficiency and is not easily interfered by coexisting ions in water and different water matrices. It is widely used in the treatment of actual water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The X-ray diffraction spectrum of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active substance; Figure 2 This is a scanning electron microscope image of a heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active substance; Figure 3 The EPR diagram of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active substance; Figure 4 This is a diagram of the catalytic degradation of a heterogeneous iron-based catalyst with singlet oxygen as the main active species. DETAILED DESCRIPTION

[0020] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0021] Example 1 (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it in a water bath by ultrasonic vibration to obtain a 2 mg / L graphene suspension; (2) Add 600 mg of urea and 120 mg of ferrous sulfate as the iron source and nitrogen source to the graphene suspension in sequence, stir magnetically for 5 h to mix them evenly, put the solution in the beaker into a polytetrafluoroethylene reactor, react at 180 ° C for 10 h, soak the reactants in deionized water, change the water every 12 hours, remove the excess raw materials in the material, and perform vacuum freeze drying for 48 h; (3) The dried material in step (2) was placed in a tubular furnace and carbonized at 700°C for 2 h under a nitrogen atmosphere, wherein the heating rate was 5°C / min and the cooling rate was 5°C / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG 700℃ ).

[0022] Example 2 (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it in a water bath by ultrasonic vibration to obtain a 2 mg / L graphene suspension; (2) Add 600 mg of urea and 120 mg of ferrous sulfate as the iron source and nitrogen source to the graphene suspension in sequence, stir magnetically for 5 h to mix them evenly, put the solution in the beaker into a polytetrafluoroethylene reactor, react at 160 ° C for 14 h, soak the reactants in deionized water, change the water every 12 hours, remove the excess raw materials in the material, and perform vacuum freeze drying for 48 h; (3) The dried material in step (2) was placed in a tubular furnace and carbonized at 650°C for 3 h under a nitrogen atmosphere, wherein the heating rate was 5°C / min and the cooling rate was 5°C / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG 650℃ ).

[0023] Example 3 (1) Weigh 60 mg of graphene (rGo) into a beaker, add 30 mL of deionized water, and disperse it in a water bath by ultrasonic vibration to obtain a 2 mg / L graphene suspension; (2) 1200 mg of urea and 120 mg of ferrous sulfate were added to the graphene suspension as the iron source and nitrogen source, respectively, and the mixture was mixed by magnetic stirring for 5 h. The solution in the beaker was placed in a polytetrafluoroethylene reactor and reacted at 180 °C for 8 h. The reactants were immersed in deionized water, and the water was changed every 12 hours. Excess raw materials in the material were removed, and vacuum freeze-dried for 48 h. (3) The dried material in step (2) was placed in a tubular furnace and carbonized at 750°C for 2 h under a nitrogen atmosphere, wherein the heating rate was 5°C / min and the cooling rate was 5°C / min, to obtain a heterogeneous iron-based catalyst (FexOy / NG 750℃ ).

[0024] Comparative Example 1 (1) rGO 700℃ Preparation: weigh 60 mg of graphene (rGO) in a beaker, add 30 ml of deionized water, and disperse it in a water bath with ultrasonic vibration to obtain a 2 mg / L graphene suspension; as in Example 1, in order to reduce the impact, magnetic stirring is also used for 5 hours, the solution in the beaker is placed in a polytetrafluoroethylene reactor, and reacted at 180°C for 10 hours, the reactants are immersed in deionized water, the water is changed every 12 hours, the excess raw materials in the material are removed, and vacuum freeze-dried for 48 hours; the dried material is placed in a tubular furnace and carbonized at 700°C for 2 hours under a nitrogen atmosphere, wherein the heating rate is 5°C / min and the cooling rate is 5°C / min, to obtain a heterogeneous catalyst (rGO 700℃ ).

[0025] (2) NG 700℃ Preparation: weigh 60 mg of graphene (rGo) in a beaker, add 30 ml of deionized water, and disperse it in a water bath with ultrasonic vibration to obtain a 2 mg / L graphene suspension; add 600 mg of urea as a nitrogen source to the graphene suspension, use magnetic stirring for 5 hours to mix it evenly, put the solution in the beaker into a polytetrafluoroethylene reactor, react at 180°C for 10 hours, soak the reactants in deionized water, change the water every 12 hours, remove the excess raw materials in the material, and perform vacuum freeze drying for 48 hours; put the dried material into a tubular furnace and carbonize it 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 (NG 700℃ ).

[0026] (3) FexOy / G 700℃Preparation: 60 mg of graphene (rGo) was weighed into a beaker, 30 ml of deionized water was added, and the graphene suspension was dispersed by ultrasonic vibration 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 magnetic stirring was used for 5 hours to mix it evenly. 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, and the water was changed every 12 hours. The excess raw materials in the material were removed and vacuum freeze-dried for 48 hours; the dried material was placed in a tubular furnace and carbonized at 700°C for 2 hours under a nitrogen atmosphere, wherein the heating rate was 5°C / min and the cooling rate was 5°C / min, to obtain a heterogeneous catalyst (FexOy / G 700℃ ).

[0027] Performance characterization: (1) The crystal properties and phase structure of the catalyst material were analyzed by X-ray diffraction (XRD). The X-ray diffraction spectrum of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active substance is shown in Figure 1 As shown, the intensity is consistent with the magnetite structure of JCPDS No. 88-0866. The diffraction peaks at the (111), (220), (311), (222), (400), (422), (511), (440) and (533) Fe3O4 nanoparticle planes are 18.43°, 30.22°, 35.63°, 37.14°, 43.25°, 53.65°, 57.13° and 62.76°, respectively.

[0028] (2) The microstructure of the catalyst material was characterized by scanning electron microscopy (SEM). The SEM image of the heterogeneous iron-based catalyst prepared in Example 1 with singlet oxygen as the main active substance is as follows: Figure 2 As shown by Figure 2 It can be seen that graphene oxide has a flaky porous structure, which is conducive to providing a larger specific surface area and active anchor points. Small spherical particles are distributed on the flaky surface of graphene, indicating that iron oxide is successfully doped on graphene, and doping with N will lead to an increase in the doping amount of Fe oxide and a decrease in volume.

[0029] (3) Determination of OH and SO4 by EPR experiment ·- 、O2 ·- and 1 O2, DMPO (100mmol / L) was used as a spin trap to capture OH and SO4 in the solution ·- and O2 ·- Free radicals, captured using TEMP (10mmol / L) 1 O2, the EPR pattern of the heterogeneous iron-based catalyst with singlet oxygen as the main active substance prepared in Example 1 is as follows Figure 3As shown in the figure, there are DMPO-HO (intensity ratio of 1:2:2:1), DMPO-SO4 (intensity ratio of 1:1:1:1:1:1), DMPO-O2 (intensity ratio of 1:1:1:1) and TEMP- 1 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 there are a large number of 1 O2 is generated, and 1 The content of O2 is much higher than that of OH and SO4 ·- and O2 ·- .

[0030] (4) Catalytic degradation activity: Prepare 6 portions of 40 mg / L tetracycline solution, detect their initial absorbance respectively, then place them on a magnetic stirrer for uniform stirring, add PDS, FexOy / NG 700℃ , rGO 700℃ NG 700℃ 、FexOy / G 700℃ and FexOy / NG 700℃ First, adsorption was carried out for 30 minutes to reach adsorption equilibrium, and then the oxidant PDS was added to the solution except PDS for catalytic degradation experiment. The concentration was 3mmol / L, and stirring was continued for 90 minutes. The absorbance of 6 solutions was detected at intervals.

[0031] The heterogeneous iron-based catalyst (FexOy / NG 700℃ )、rGO 700℃ NG 700℃ 、FexOy / G 700℃ The degradation diagram of tetracycline catalytic degradation is shown in Figure 4 As shown by Figure 4 It can be seen that only FexOy / NG 700℃ In the case of , the removal efficiency of the catalyst material for the pollutant TC only reached 56.73% after 2 hours, and basically reached adsorption equilibrium after 30 minutes. When only PDS was added, the concentration of TC hardly changed. When the catalyst was added, the removal rate of TC was significantly improved, and FexOy / NG 700℃ The adsorption and catalytic effects of rGO 700℃ NG 700℃ 、FexOy / G 700℃ ) to be better, NG 700℃This is because agglomeration occurs during the carbonization process, which results in a reduction in the specific surface area of ​​the catalyst material and fewer active sites exposed on the surface, resulting in poor adsorption and catalytic effects. 700℃ The adsorption and catalytic abilities of FexOy / NG are slightly lower than those of 700℃ , which 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 substance, characterized in that: The following steps are involved: (1) Graphene is dispersed in water to prepare a graphene suspension; (2) adding a nitrogen source and an iron source to the graphene suspension, mixing them evenly, performing a hydrothermal reaction, and washing and drying the reactants; (3) The material after drying in step (2) is carbonized at high temperature in a nitrogen atmosphere to obtain a heterogeneous iron-based catalyst with singlet oxygen as the main active substance.

2. The method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active substance according to claim 1, characterized in that: The concentration of graphene in the graphene suspension in step (1) is 1-4 mg / L.

3. The method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active substance according to claim 1, characterized in that: In step (2), the mass ratio of graphene, iron source and nitrogen source is 1:1~3:1~10:2:

40.

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

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

6. The method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active substance according to claim 1, characterized in that: The conditions for high temperature carbonization in step (3) are: high temperature carbonization temperature is 650-750°C, and high temperature carbonization time is 2-3h.

7. The method for preparing a heterogeneous iron-based catalyst with singlet oxygen as the main active substance according to claim 1, characterized in that: The drying in step (2) is vacuum freeze drying; the heating rate in step (3) is 3-5°C / min, and the cooling rate is 3-5°C / min.

8. A heterogeneous iron-based catalyst with singlet oxygen as the main active substance prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the heterogeneous iron-based catalyst with singlet oxygen as the main active substance as claimed in claim 8 in catalytic degradation of water pollutants.

10. The use according to claim 9, characterized in that: The water pollutant is tetracycline.

Images