Biochar-based composite catalyst as well as preparation method and application thereof

Abstract

The invention relates to a biochar-based composite catalyst and a preparation method and application thereof, and belongs to the technical field of environmental catalysis, and the preparation method comprises the following steps: (1) washing a waste biochar precursor, calcining, cooling, and grinding to obtain a biochar matrix; (2) mixing and stirring the obtained charcoal matrix and KOH in water, and then drying to obtain a mixed precursor; (3) calcining the obtained mixed precursor to obtain a biochar material B; (4) adding cobalt nitrate, aluminum nitrate and urea into water, stirring and dissolving to obtain a mixed solution; (5) adding the obtained biochar material B into the mixed solution, uniformly mixing, and drying to obtain a composite precursor; and (6) calcining the obtained composite precursor to obtain the biochar-based composite catalyst. The catalyst prepared by the invention has rich pore structures and active sites, can efficiently catalyze persulfate, enhances the electron transfer ability, and significantly improves the catalytic activity of pollutant degradation.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis technology, and in particular to a biochar-based composite catalyst, its preparation method, and its application. Background Technology

[0002] Persulfate advanced oxidation technology is a highly efficient water treatment process based on the degradation of organic pollutants by sulfate free radicals. It is generally believed that bimetallic oxides, due to the synergistic effect of their bimetallic components, can significantly activate persulfate to generate free radicals, exhibiting superior catalytic performance compared to single-metal oxides.

[0003] However, nanoscale bimetallic oxide particles face two major challenges in practical applications: First, poor cycle stability. During continuous catalytic reactions and recovery processes, nanoparticles are prone to aggregation and loss, leading to a rapid decline in catalytic activity. Second, the problem of metal ion leaching. Especially in acidic or neutral aquatic environments, the leaching of active cobalt ions not only causes secondary pollution but also deactivates the catalyst itself, severely limiting its large-scale application prospects.

[0004] To address the aforementioned issues, bimetallic oxides can be loaded onto porous supports. However, traditional physical mixing or simple impregnation methods often suffer from weak bonding and unstable loading, failing to effectively suppress the shedding and leaching of active components during the reaction process. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems in the prior art and to provide a biochar-based composite catalyst with high catalytic activity, good stability and low metal leaching rate, as well as its preparation method and application.

[0006] In this invention, during the high-temperature calcination process, KOH not only acts as a classic activator to etch biochar, creating a rich porous structure, but more importantly, it serves as an effective "binder" to build a robust chemical bridge between the metal oxide and the biochar framework. This strong interfacial coupling firmly "anchors" the active sites to the carbon substrate, thereby significantly enhancing the structural stability of the prepared composite material, greatly reducing the leaching of metal ions, and ultimately obtaining a composite functional material with both high catalytic activity and excellent cycle life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a biochar-based composite catalyst includes the following steps:

[0009] (1) Wash the waste biochar precursor, calcine it at 500~600℃, cool it and grind it to obtain the biochar matrix;

[0010] (2) The biochar matrix obtained in step (1) is mixed with KOH in water and stirred, and then dried to obtain a mixed precursor;

[0011] (3) The mixed precursor obtained in step (2) is calcined at 500~600℃ to obtain biochar material B;

[0012] (4) Add cobalt nitrate, aluminum nitrate and urea to water in a molar ratio of (2~4.5):(1.5~2.5):(10~15), stir to dissolve, and obtain a mixed solution;

[0013] (5) Add the biochar material B obtained in step (3) to the mixed solution in step (4), mix evenly, let it stand, observe that the upper liquid is a transparent clear liquid, and then dry it to obtain the composite precursor.

[0014] (6) The composite precursor obtained in step (5) is calcined at 600~800℃ to obtain the biochar-based composite catalyst.

[0015] In step (1), the heating rate of calcination is 10~20℃ / min, and the calcination time is 1~2h.

[0016] In step (2), the mass ratio of the biochar matrix to KOH is 1:0.8~1.2.

[0017] In step (2), the stirring time is 20~28h.

[0018] In step (3), the heating rate of calcination is 10~20℃ / min, and the calcination time is 1~2h.

[0019] In step (6), the heating rate of calcination is 5~15℃ / min, and the calcination time is 1~3h.

[0020] A biochar-based composite catalyst was prepared using the method described above in this invention.

[0021] The aforementioned biochar-based composite catalyst is used to treat organic polluted water.

[0022] Specifically, a catalytic system is constructed using a persulfate and a biochar-based composite catalyst, which activates the persulfate to degrade organic pollutants in the water.

[0023] The persulfate is a permonosulfate, such as potassium peroxymonosulfate.

[0024] The organic pollutants include at least one of acetaminophen, cyclohexanone, carbamazepine, metronidazole, naproxen, ciprofloxacin, and rhodamine B.

[0025] The waste biochar precursors include peanut shells, straw, wood, leaves, etc.

[0026] In this invention, a prolonged stirring process of 20–28 hours is employed to promote the full dispersion and introduction of KOH into the biochar material. Subsequently, calcination at 500–600°C yields a KOH-activated biochar support rich in potassium species on its surface. This support is then composited with a cobalt- and aluminum-containing precursor and calcined in air at 600–800°C. This process facilitates stable interfacial interactions between KOH-derived potassium species and the CoAl bimetallic oxide, thereby achieving synergistic construction and obtaining excellent catalytic performance.

[0027] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0028] 1. This invention utilizes KOH as a key "binder-activator" to form a strong chemical bond between the CoAl bimetallic oxide and the biochar support through interaction with biochar and metal salts at high temperature. This significantly enhances the stability of the active components and effectively inhibits the leaching of metal ions such as cobalt during the reaction process.

[0029] 2. The biochar-based composite catalyst prepared by this invention has abundant pore structure and huge specific surface area, providing sufficient active sites for catalytic reaction. It can efficiently activate persulfate to generate sulfate free radicals and exhibit excellent degradation efficiency for a variety of organic pollutants.

[0030] 3. The catalyst prepared by this invention has good reusability and stability, and can still maintain high catalytic activity after multiple cycles, thus reducing the operating cost in practical applications.

[0031] 4. This invention uses waste peanut shells as raw materials, realizing the resource utilization of waste. The preparation process is green and economical, and meets the requirements of sustainable development. Attached Figure Description

[0032] Figure 1 The image shows a scanning electron microscope image of the biochar-based composite catalyst prepared in Example 1.

[0033] Figure 2 The N2 adsorption curve of the biochar-based composite catalyst prepared in Example 1 is shown.

[0034] Figure 3 The image shows the pore size distribution of the biochar-based composite catalyst prepared in Example 1.

[0035] Figure 4 The effects of different systems on the treatment of APAP in water in Example 2 are shown.

[0036] Figure 5 The effect of the materials prepared in Comparative Examples 1-2 in Example 2 on the treatment of APAP in water.

[0037] Figure 6 This illustrates the effect of recycling the CAB catalyst five times in Example 3 to treat APAP in water.

[0038] Figure 7 This is a graph showing the cobalt metal ion leaching data of APAP treated in water after the CAB catalyst was recycled 5 times in Example 3.

[0039] Figure 8 This illustrates the effect of the CAB catalyst on cyclohexanone treatment in Example 3.

[0040] Figure 9 These are photographs of experimental phenomena observed during the synthesis process of Example 1 and Comparative Example 3. Detailed Implementation

[0041] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] This embodiment describes a method for preparing a biochar-based composite catalyst, comprising the following steps:

[0044] (1) Wash the peanut shells, place them in a muffle furnace, heat them to 600°C at a heating rate of 15°C / min, calcine for 1 hour, cool and grind to obtain biochar matrix.

[0045] (2) The biochar matrix obtained in step (1) and KOH are placed in a beaker at a mass ratio of 1:1. Deionized water is added and stirred for 24 hours. The mixture is then dried in an oven at 85°C to obtain a mixed precursor.

[0046] (3) The mixed precursor obtained in step (2) is placed in a muffle furnace and heated to 550°C at a heating rate of 15°C / min. After calcination for 1 hour, it is cooled and ground to obtain biochar material B.

[0047] (4) Add 4.5mM cobalt nitrate, 1.5mM aluminum nitrate and 13.5mM urea to 90mL of deionized water and stir magnetically until completely dissolved to obtain a homogeneous mixed solution.

[0048] (5) Add the biochar material B obtained in step (3) to the mixed solution in step (4), stir magnetically for 2 hours to mix thoroughly, let it stand, and observe that the upper liquid is a clear liquid (see Figure 9 (See attached left side of the image). The composite precursor was dried in an oven at 60°C to obtain a dry composite precursor.

[0049] (6) The composite precursor obtained in step (5) is placed in a muffle furnace and heated to 800°C at a heating rate of 10°C / min. After calcination for 2 hours and cooling, the biochar-based composite catalyst is obtained, denoted as CAB.

[0050] like Figure 1 As shown, the prepared biochar-based composite catalyst exhibits a porous structure on its surface, with uniformly distributed particles and no obvious agglomeration. Figure 2 and Figure 3 It is known that the material has a specific surface area of ​​396.1244 m² / g and an average adsorption porosity of 2.1026 nm. Therefore, the biochar-based composite catalyst prepared in this invention facilitates the dispersion of active components and the mass transfer of reactants, thereby improving catalytic performance.

[0051] Comparative Example 1

[0052] Except for replacing the KOH used in Example 1 with an equal mass of KHCO3, all other steps were exactly the same as in Example 1. The resulting material was denoted as CAB–KHCO3.

[0053] Comparative Example 2

[0054] Except for replacing KOH with an equal mass of NaOH, all other steps are exactly the same as in Example 1. The resulting material is denoted as CAB–NaOH.

[0055] Comparative Example 3

[0056] Comparative Example 3 describes a method for preparing a biochar-based composite catalyst, comprising the following steps:

[0057] (1) Wash the peanut shells, place them in a muffle furnace, heat them to 600°C at a heating rate of 15°C / min, calcine for 1 hour, cool and grind to obtain biochar matrix.

[0058] (2) The biochar matrix obtained in step (1) and KOH are placed in a beaker at a mass ratio of 1:1. Deionized water is added and stirred for 24 hours. The mixture is then dried in an oven at 85°C to obtain a mixed precursor.

[0059] (3) The mixed precursor obtained in step (2) is placed in a muffle furnace and heated to 550°C at a heating rate of 15°C / min. After calcination for 1 hour, it is cooled and ground to obtain biochar material B.

[0060] (4) The obtained biochar material B was washed with ethanol and deionized water until neutral and dried in an oven at 60°C.

[0061] (5) Add 4.5mM cobalt nitrate, 1.5mM aluminum nitrate and 13.5mM urea to 90mL of deionized water and stir magnetically until completely dissolved to obtain a homogeneous mixed solution.

[0062] (6) Add the biochar material B obtained in step (4) to the mixed solution in step (5), stir magnetically for 2 hours to mix it thoroughly, and let it stand.

[0063] During the experiment, it was found that ( Figure 9 (See attached right-hand side of the figure). In Comparative Example 3, the metal salt solution consistently maintained the intrinsic color of cobalt nitrate, and no obvious metal ion deposition or adsorption was observed, indicating that Co... 2+ And Al 3+ Ions mainly exist in a dissolved state, making it difficult to effectively load them onto the surface of the neutralized biochar support, ultimately failing to obtain structurally stable biochar-based CoAl composite catalytic materials.

[0064] Example 2

[0065] The experiment was conducted in the following groups:

[0066] PMS group: Under normal temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate to a concentration of 1.0 mM. The treatment effect was detected by high-performance liquid chromatography at different time points. Figure 4 As shown, the degradation efficiency of APAP after 15 minutes is less than 16%.

[0067] B / PMS group: Under normal temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate and biochar material B obtained in step (3) of Example 1, to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected by high performance liquid chromatography at different time points; Figure 4 As shown, the degradation efficiency of APAP after 15 minutes was 16%.

[0068] CAB / PMS group: Under normal temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate and the biochar-based composite catalyst CAB prepared in step (6) of Example 1 to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected by high performance liquid chromatography at different time points. Figure 4 As shown, APAP's degradation efficiency was 100% after 15 minutes.

[0069] CAB–KHCO3 / PMS group: Under room temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate and CAB–KHCO3 prepared in Comparative Example 1 to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected by high performance liquid chromatography at different time points. Figure 5 As shown, the degradation efficiency of APAP after 15 minutes was 72.78%.

[0070] CAB–NaOH / PMS group: Under room temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate and CAB–NaOH prepared in Comparative Example 2 to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected by high performance liquid chromatography at different time points. Figure 5 As shown, the degradation efficiency of APAP after 15 min was 51.87%.

[0071] Figure 4 The removal efficiency of APAP in water by different systems was demonstrated. It can be seen that the degradation efficiency of PMS alone is low, while the removal rate of APAP is significantly improved when the biochar-based composite catalyst prepared in this invention is used in conjunction with PMS. This indicates that the catalyst of this invention has excellent performance in activating PMS to degrade organic pollutants.

[0072] Figure 5 The removal effects of different alkaline substances on APAP in water were demonstrated. It can be seen that KOH showed the best degradation effect, indicating that KOH has a significant effect on CoAl-oxide catalysts supported on biochar.

[0073] Example 3

[0074] Under ambient temperature and neutral pH conditions, 100 mL of an aqueous solution containing 10 mg / L APAP was added to the reactor, followed by the addition of potassium persulfate and the biochar-based composite catalyst CAB obtained in Example 1 to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected by high-performance liquid chromatography at different time points. After each reaction, the catalyst was recovered by high-speed centrifugation, washed three times alternately with deionized water and ethanol, and dried in a vacuum drying oven at 60 °C for 8 h for the next cycle. This process was repeated for a total of 5 cycles.

[0075] like Figure 6As shown, after five cycles of recycling, the degradation efficiency of APAP decreased from 100% to 98%, indicating that the CAB catalyst still maintains high catalytic activity. Therefore, the CAB / PMS system has advantages such as excellent catalytic effect, good stability, and convenient recovery, and has great practical application value.

[0076] Example 4

[0077] Take 1 mL of the solution after each reaction in Example 3 and obtain the leaching data of cobalt metal ions by ICP-MS; as Figure 7 As shown, after 5 cycles of Co 2+ The leaching levels all met the limit of 1.0 mg / L set by GB3838-2002 "Environmental Quality Standard for Surface Water". Therefore, the CAB / PMS system effectively inhibited the leaching of cobalt metal ions during the reaction process.

[0078] Example 5

[0079] The experiment was conducted in the following groups:

[0080] CAB / PMS group: Under normal temperature and neutral pH conditions, 100 mL of an aqueous solution containing 5 mg / L cyclohexanone was added to the reactor, followed by the addition of potassium persulfate and CAB prepared in step (6) of Example 1 to concentrations of 1.0 mM and 20 mg / L, respectively. The treatment effect was detected at different time points using a UV-Vis spectrophotometer. Figure 8 As shown, the degradation efficiency of cyclohexanone was 100% after 5 minutes.

[0081] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a biochar-based composite catalyst, characterized in that, Includes the following steps: (1) Wash the waste biochar precursor, calcine it at 500~600℃, cool it and grind it to obtain the biochar matrix; (2) The biochar matrix obtained in step (1) is mixed with KOH in water and stirred, and then dried to obtain a mixed precursor; (3) The mixed precursor obtained in step (2) is calcined at 500~600℃ to obtain biochar material B; (4) Add cobalt nitrate, aluminum nitrate and urea to water in a molar ratio of (2~4.5):(1.5~2.5):(10~15), stir to dissolve, and obtain a mixed solution; (5) Add the biochar material B obtained in step (3) to the mixed solution in step (4), mix evenly, let it stand, observe that the upper liquid is a transparent clear liquid, and then dry it to obtain the composite precursor; (6) The composite precursor obtained in step (5) is calcined at 600~800℃ to obtain the biochar-based composite catalyst.

2. The method for preparing a biochar-based composite catalyst as described in claim 1, characterized in that: In step (1), the calcination time is 1~2 hours.

3. The method for preparing a biochar-based composite catalyst as described in claim 1, characterized in that: In step (2), the mass ratio of the biochar matrix to KOH is 1:0.8~1.

2.

4. The method for preparing a biochar-based composite catalyst as described in claim 1, characterized in that: In step (2), the stirring time is 20~28h.

5. The method for preparing a biochar-based composite catalyst as described in claim 1, characterized in that: In step (3), the calcination time is 1~2 hours.

6. The method for preparing a biochar-based composite catalyst as described in claim 1, characterized in that: In step (6), the calcination time is 1~3h.

7. A biochar-based composite catalyst, characterized in that: It is prepared by any one of the preparation methods of claims 1 to 6.

8. The application of the biochar-based composite catalyst according to claim 7, characterized in that: Used for treating organic polluted water.

9. The application as described in claim 8, characterized in that: A catalytic system is constructed using a persulfate and biochar-based composite catalyst, which activates the persulfate to degrade organic pollutants in water.

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