Biochar-based catalyst with Fe-Mn double-atom active center as well as preparation method and application of biochar-based catalyst

Abstract

The invention discloses a biochar-based catalyst with an Fe-Mn double-atom active center as well as a preparation method and application of the biochar-based catalyst, and belongs to the technical field of catalyst materials. Dispersing the corn straw powder in water to prepare a straw powder suspension; adding a chelating agent, an iron source, a manganese source and a zinc source into the straw powder suspension, uniformly mixing, standing, and washing and drying the mixture; and uniformly mixing the dried material with a nitrogen source, and carrying out high-temperature carbonization on the mixture in a nitrogen atmosphere to obtain the charcoal-based catalyst with the Fe-Mn double-atom active center. The Fe-Mn double-atom catalyst prepared by the invention generates free radical and non-free radical oxidation processes taking < 1 > O2, O2 and IO3 as main active oxygen substances 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 present invention belongs to the technical field of catalyst materials, and particularly relates to a biochar-based catalyst with Fe-Mn dual-atom active centers, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, advanced oxidation processes have been considered very effective methods for treating complex organic matters. The advanced oxidation technology based on periodate (PI) has attracted increasing attention due to its high stability, strong oxidation potential, safe transportation and storage, and preferential use in some cases. However, the oxidation ability of PI alone (standard redox potential is 1.60 V) is quite limited. The activity of PI can be effectively improved by methods such as carbonaceous materials, freezing, ultraviolet (UV) light, ultrasound, and transition metal oxides. Among them, the carbonaceous material - biochar is considered a promising catalytic material due to its high specific surface area, rich functional groups, and excellent electrical conductivity. Single-metal catalysts have problems such as poor stability, low activity, and the need for higher reaction conditions. Compared with single-metal catalysts, dual-atom active centers have advantages such as high atomic utilization rate and unique electronic properties. The synergistic effect between dual-metal active centers can make up for the deficiencies of single-atom catalysts, so they have been widely studied in pollutant remediation. At present, iron-manganese dual-metal-based catalysts have become a research hotspot for removing oxytetracycline (OTC) in water in heterogeneous catalysis due to their high activity, low cost, and easy availability.

[0003] In natural waters, inorganic ions and natural organic matter (NOM) are commonly present and have a great influence on PI-AOPs. PI-based AOPs can generate various transient reactive substances, such as iodate radicals (IO3•), hydroxyl radicals (•OH), superoxide anion radicals (O2• − ), and singlet oxygen ( 1 1O2). The dual-pathway synergistic degradation of pollutants by free radicals and non-free radicals has stronger adaptability, higher selectivity, and anti-interference ability than the single pathway of free radicals or non-free radicals. In the actual process of degrading water pollutants, this technology is not easily affected by coexisting ions and water matrices. Therefore, designing and developing new energy-saving, widely applicable, and highly efficient dual-metal-based catalytic systems for pollutant degradation has broad application prospects.

[0004] Patent CN119524894A provides a bimetallic-based catalyst for the hydrogenation synthesis of 2-methoxy-4-methylphenol from vanillin, its preparation method and application. Weigh and dissolve soluble cobalt salt and soluble iron salt in water to obtain an active component precursor solution. Add molybdenum carbide to the active component precursor solution for impregnation treatment to obtain a catalyst precursor. First, calcine the catalyst precursor in an inert atmosphere and a reducing atmosphere in sequence, and then cool it in an inert atmosphere to obtain the target bimetallic-based catalyst. However, Co will leach out during the actual use of this catalyst. 2+ The toxic Co 2+ will pollute the water body again.

[0005] Patent CN116809081A provides a heterogeneous iron-based catalyst, its preparation method and application. The main steps include: under stirring, dropwise add the NH4Fe(SO4)2 solution into the tungsten disulfide ethanol suspension, and stir and react at 50 - 90 °C for 2 - 10 hours, where the molar ratio of NH4Fe(SO4)2 to WS2 is (1 - 4):1. Filter, wash, and dry it to obtain the heterogeneous iron-based catalyst FeOOH@WS2. The main active substance during the process of the heterogeneous iron-based catalyst activating PDS to degrade pollutants is SO4• - This active substance is easily interfered by coexisting ions and different water matrices in water, and is easily restricted in the actual water body application. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention provides a biochar-based catalyst with Fe-Mn dual-atom active centers, its preparation method and application. This catalyst improves the degradation efficiency of pollutants through the synergistic oxidation of free radical and non-free radical pathways, is not easily interfered by coexisting ions and different water matrices in water, and has broad application potential in actual water treatment.

[0007] The present invention is realized through the following technical solutions:

[0008] A preparation method of a biochar-based catalyst with Fe-Mn dual-atom active centers, comprising the following steps:

[0009] (1) Disperse corn straw powder in water to prepare a straw powder suspension;

[0010] (2) Add a chelating agent, an iron source, a manganese source, and a zinc source to the corn straw powder suspension, mix evenly and then let it stand, wash and dry the mixture;

[0011] (3) Mix the material dried in step (2) evenly with a nitrogen source, and carbonize the mixture at high temperature in a nitrogen atmosphere to obtain a biochar-based catalyst with Fe-Mn dual-atom active centers.

[0012] Further, the concentration of corn straw powder in the straw powder suspension in step (1) is 4 - 40 g / L.

[0013] Further, in step (2), the mass ratio of corn straw powder, chelating agent, iron source, manganese source and zinc source is 4:7:7 - 8:5 - 6:8 - 9.

[0014] Further, the chelating agent in step (2) is disodium ethylenediaminetetraacetate, the iron source is ferric nitrate, the manganese source is manganese chloride, and the zinc source is zinc sulfate.

[0015] Further, the nitrogen source in step (3) is melamine, the mass ratio of the dry material to the nitrogen source is 1:5, and the conditions for high - temperature carbonization are: the reaction temperature is 500 - 900 °C, and the high - temperature carbonization time is 2 - 3 h.

[0016] Further, in step (3), the heating rate is 3 - 5 °C / min, and the cooling rate is 3 - 5 °C / min.

[0017] In the present invention, the biochar - based catalyst with Fe - Mn dual - atom active centers prepared by the above - mentioned preparation method.

[0018] In the present invention, the application of the above - mentioned biochar - based catalyst with Fe - Mn dual - atom active centers in the catalytic degradation of water pollutants.

[0019] Further, the water pollutant is oxytetracycline.

[0020] Further, in order to achieve higher economic benefits, after the degradation reaction, the Fe - Mn - NDAC in the water body is separated, recovered, washed and dried to obtain the reusable Fe - Mn - NDAC material, and it is washed 3 - 5 times repeatedly with deionized water and ethanol during washing. Beneficial effects

[0021] The present invention regulates the active sites on the surface of the catalyst. The prepared catalyst improves the degradation efficiency of pollutants through the synergistic oxidation of free - radical and non - free - radical pathways, and is not easily interfered by co - existing ions and different water matrices in water, and has a wide application in the treatment of actual water bodies. Description of the drawings

[0022] Figure 1 It is the X - ray diffraction pattern of the biochar - based catalyst with Fe - Mn dual - atom active centers prepared in Example 1;

[0023] Figure 2 It is the scanning electron micrograph of the biochar - based catalyst with Fe - Mn dual - atom active centers prepared in Example 1;

[0024] Figure 3Scanning electron microscopy energy spectrum diagram of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1;

[0025] Figure 4 Quenching experiment diagram and EPR diagram of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1;

[0026] Figure 5 Catalytic degradation diagram of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1.

[0027] Figure 6 Actual water body catalytic degradation diagram of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1. Specific implementation plan

[0028] The above content of the present invention will be further described in detail through the following examples. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention. Example 1

[0029] (1) Weigh 4.0 g of corn straw powder into a beaker, add 100 mL of deionized water, add 2.0 g of EDTA to the water, and stir for 5 min to obtain a 40 g / L corn straw powder suspension;

[0030] (2) Add 11.3 g of iron nitrate, 5.5 g of manganese chloride, and 8.1 g of zinc sulfate as iron source, manganese source, and zinc source to the corn straw powder suspension in sequence, stir magnetically for 1 h to mix evenly, let it stand overnight, and wash and dry for 8 h;

[0031] (3) Mix the material dried in step (2) with melamine in a mass ratio of 1:5. Put the mixed sample into a muffle furnace and carbonize it at 500 °C for 1 h under a nitrogen atmosphere, then raise the temperature to 900 °C and carbonize it for 1 h. The heating rate is 5 °C / min, and the cooling rate is 5 °C / min to obtain a biochar-based catalyst with Fe-Mn dual-atom active centers (Fe-Mn-NDAC 900℃ ). Example 2

[0032] (1) Weigh 4.0 g of corn straw powder into a beaker, add 100 mL of deionized water, add 2.0 g of EDTA to the water, and stir for 5 min to obtain a 40 g / L corn straw powder suspension;

[0033] (2) 11.3 g of iron nitrate, 5.5 g of manganese chloride, and 8.1 g of zinc sulfate were successively added to the corn straw powder suspension as iron source, manganese source, and zinc source, and magnetically stirred for 1 h to mix evenly, then left standing overnight, followed by washing and drying for 8 h;

[0034] (3) The material dried in step (2) was mixed with melamine at a mass ratio of 1:5. The mixed sample was placed in a muffle furnace and carbonized at 500 °C for 1 h under a nitrogen atmosphere, then heated to 850 °C and carbonized for 1 h, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain a biochar-based catalyst with Fe-Mn dual-atom active centers (Fe-Mn-NSAC 850℃ ) Example 3

[0035] (1) 4.0 g of corn straw powder was weighed into a beaker, 100 mL of deionized water was added, and 2.0 g of EDTA was added to the water. After stirring for 5 min, a 40 g / L corn straw powder suspension was obtained;

[0036] (2) 11.3 g of iron nitrate, 5.5 g of manganese chloride, and 8.1 g of zinc sulfate were successively added to the corn straw powder suspension as iron source, manganese source, and zinc source, and magnetically stirred for 1 h to mix evenly, then left standing overnight, followed by washing and drying for 8 h;

[0037] (3) The material dried in step (2) was mixed with melamine at a mass ratio of 1:5. The mixed sample was placed in a muffle furnace and carbonized at 500 °C for 1 h under a nitrogen atmosphere, then heated to 800 °C and carbonized for 1 h, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain a biochar-based catalyst with Fe-Mn dual-atom active centers (Fe-Mn-NSAC 800℃ ) Comparative Example 1

[0038] (1) Preparation of Fe-NSAC: 4.0 g of corn straw powder was weighed into a beaker, 100 mL of deionized water was added, and 2.0 g of disodium ethylenediaminetetraacetate (EDTA) was added to the water. After stirring for 5 min, a 40 g / L corn straw powder suspension was obtained; 11.3 g of iron nitrate and 8.1 g of zinc sulfate were successively added to the corn straw powder suspension as iron source and zinc source, and magnetically stirred for 1 h to mix evenly, then left standing overnight, followed by washing and drying for 8 h; the dried material was mixed with melamine at a mass ratio of 1:5. The mixed material was placed in a muffle furnace and carbonized at 500 °C for 1 h under a nitrogen atmosphere, then heated to 900 °C and carbonized for 1 h, with a heating rate of 5 °C / min and a cooling rate of 5 °C / min, to obtain an iron single-atom biochar-based catalyst (Fe-NSAC). Comparative Example 2

[0039] (2)Preparation of Mn-NSAC: Weigh 4.0 g of corn straw powder into a beaker, add 100 mL of deionized water, and add 2.0 g of disodium ethylenediaminetetraacetate (EDTA) to the water. Stir for 5 min to obtain a 40 g / L corn straw powder suspension. Then, add 5.5 g of manganese chloride and 8.1 g of zinc sulfate to the corn straw powder suspension as the manganese source and zinc source respectively. Stir magnetically for 1 h to mix evenly, let it stand overnight, and then wash and dry for 8 h. Mix the dried material with melamine at a mass ratio of 1:5. Put the mixed material into a muffle furnace and carbonize it at 500 °C for 1 h under a nitrogen atmosphere, then raise the temperature to 900 °C and carbonize for 1 h. The heating rate is 5 °C / min and the cooling rate is 5 °C / min to obtain a manganese single-atom biochar-based catalyst (Mn-NSAC). Comparative Example 3

[0040] (3)Preparation of BC: Weigh 4.0 g of corn straw powder into a beaker, add 100 mL of deionized water, and stir for 5 min to obtain a 40 g / L corn straw powder suspension. Add 8.1 g of zinc sulfate to the corn straw powder suspension as the zinc source. Stir magnetically for 1 h to mix evenly, let it stand overnight, and then wash and dry for 8 h. Put the dried material into a muffle furnace and carbonize it at 500 °C for 1 h under a nitrogen atmosphere, then raise the temperature to 900 °C and carbonize for 1 h. The heating rate is 5 °C / min and the cooling rate is 5 °C / min to obtain a biochar-based catalyst (BC). Performance Characterization:

[0041] (1)The crystal properties and phase structure of the catalyst materials were analyzed by X-ray diffraction (XRD). The X-ray diffraction pattern of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1 is as Figure 1 shown. Its intensity is in good agreement with the silica structure of PDF#98-000-0369. The diffraction peaks at the crystal planes of (100), (011), (110), (102), (200), (112), (013), (121), and (122) of SiO2 nanoparticles are 20.86°, 26.64°, 36.55°, 39.47°, 42.45°, 50.14°, 55.33°, 59.96°, and 67.75° respectively. No obvious aggregated peaks of Fe (such as Fe2O3, Fe3O4, FeOOH) or Mn oxides are observed in the figure, indicating that the Fe and Mn metal elements in the catalyst exist in the form of single atoms.

[0042] (2)The microstructure of the catalyst materials was characterized by scanning electron microscopy (SEM). The scanning electron micrograph of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1 is as Figure 2As shown, the catalyst presents a wrinkled porous structure, which is beneficial to providing a large specific surface area and active anchor points, providing stable internal conditions for the doping of metal elements.

[0043] (3) The elemental distribution on the surface of the catalyst material was characterized by scanning electron microscopy energy dispersive spectrometer (EDS). The scanning electron microscopy energy spectrum of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1 is as Figure 3 shown. The elements C, O, Si, N, Fe, and Mn are evenly distributed on the surface of the catalyst, confirming the existence of Fe and Mn single atoms on the N-doped carbon surface layer, which is mainly attributed to the isolation of Zn elements and the doping of N elements.

[0044] (4) The active substances generated in the system were determined by radical quenching experiments and EPR experiments. Using DMPO (100 mmol / L) as a spin trap to capture O2• - and •OH radicals in the solution, and using TEMP (100 mmol / L) to capture 1 O2. The quenching experiment diagram and EPR diagram of the biochar-based catalyst with Fe-Mn dual-atom active centers prepared in Example 1 are as Figure 4 shown. According to the quenching experiment diagram, it can be seen that there are radical (O2• − and IO3•) and non-radical ( 1 O2) pathways in Fe-Mn-NDAC. The EPR test results show that the spectral lines show three spectral lines of DMPO-X (intensity ratio of 1:2:1:2:1:2:1), DMPO-O2• - (intensity ratio of 1:1:1:1) and TEMP- 1 O2 (intensity ratio of 1:1:1). Among them, the intensity peaks of the DMPO-O2• - and TEMP- 1 O2 spectral lines are relatively obvious. However, no spectral line of •OH radicals is generated, indicating that there are a large number of O2• − and 1 O2 generated in the biochar-based catalyst + PI system with Fe-Mn dual-atom active centers, and 1 the content of O2 is roughly the same as the content of O2• − , IO3• and •OH radicals.

[0045] (5)Catalytic degradation activity: Prepare 6 portions of 20 mg / L oxytetracycline solution, and measure their initial absorbance respectively. Then place them on a magnetic stirrer for uniform stirring, and add PI, BC, Fe-NSAC, Mn-NSAC, and Fe-Mn-NDAC to them respectively. First, conduct adsorption for 30 min to reach adsorption equilibrium. In addition to the solution already containing PI, add the oxidant PI to the remaining solutions to conduct catalytic degradation experiments with a concentration of 2 mmol / L, and continue stirring for 90 min. Measure the absorbance of the 6 portions of solution at regular intervals.

[0046] The degradation diagrams of the biochar-based catalysts (Fe-Mn-NDAC), PI, BC, Fe-NSAC, and Mn-NSAC with Fe-Mn dual-atom active centers prepared in Example 1 for the catalytic degradation of oxytetracycline are as Figure 5 shown. In the case of only Fe-Mn-NDAC, the removal efficiency of the catalyst material for the pollutant OTC only reached 43.7% after 120 min, and basically reached adsorption equilibrium after 30 min. When only PI was added, the concentration of OTC hardly changed. When the catalyst was added, the removal rate of OTC increased significantly, and the adsorption and catalytic effects of Fe-Mn-NDAC were better than those of the other three catalysts (BC, Fe-NSAC, and Mn-NSAC). Compared with single-atom active centers, the synergistic effect between dual-atom active centers can promote the degradation of pollutants. Since BC was not modified, its adsorption and catalytic performance was significantly lower than that of the other three materials. The adsorption and catalytic ability of Fe-NSAC was slightly higher than that of Mn-NSAC, indicating that the catalytic effect of iron active centers was better than that of manganese active centers.

Claims

1. A biochar-based catalyst with Fe-Mn dual-atom active centers, a preparation method thereof, and applications thereof, characterized in that, It includes the following steps: (1) Corn straw powder is dispersed in water to prepare a straw powder suspension; (2) Chelating agent, iron source, manganese source and zinc source are added to the straw powder suspension, and after mixing evenly, it is left standing. The mixture is washed and dried; (3) The material dried in step (2) is mixed evenly with the nitrogen source, and the mixture is carbonized at high temperature in a nitrogen atmosphere to obtain a biochar-based catalyst with Fe-Mn dual-atom active centers.

2. The biochar-based catalyst with Fe-Mn dual-atom active centers and the preparation method according to claim 1, characterized in that In step (1), the concentration of corn straw powder in the straw powder suspension is 10 - 40 g / L.

3. The biochar-based catalyst with Fe-Mn dual-atom active centers and the preparation method according to claim 1, characterized in that, In step (2), the mass ratio of corn straw powder, chelating agent, iron source, manganese source and zinc source is 4:2:11 - 12:5 - 6:8 - 9.

4. The preparation method of the biochar-based catalyst with Fe-Mn dual-atom active centers according to claim 1, characterized in that, The chelating agent in step (2) is disodium ethylenediaminetetraacetate (EDTA), the iron source is iron nitrate, the manganese source is manganese chloride, and the zinc source is zinc sulfate.

5. The preparation method of the biochar-based catalyst with Fe-Mn dual-atom active centers according to claim 1, characterized in that, The nitrogen source in step (3) is melamine, and the mass ratio of the dried material to the nitrogen source is 1:

5. The conditions for high-temperature carbonization are: the reaction temperature is 500 - 900 °C, and the high-temperature carbonization time is 2 - 3 h.

6. The preparation method of the biochar-based catalyst with Fe-Mn dual-atom active centers according to claim 1, wherein, In step (3), the heating rate is 3 - 5 °C / min, and the cooling rate is 3 - 5 °C / min.

7. A biochar-based catalyst with Fe-Mn dual-atom active centers prepared by the preparation method according to any one of claims 1 - 6.

8. Application of the biochar-based catalyst with Fe-Mn dual-atom active centers according to claim 7 in catalytic degradation of water pollutants.

9. The application according to claim 8, characterized in that, The water pollutant is oxytetracycline.

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