Modified biochar supported CoNiFe-LDH catalyst, preparation method and application thereof

Abstract

This invention discloses a modified biochar-supported CoNiFe-LDH catalyst, its preparation method, and an application, relating to the technical field of catalytic materials. Using corn stalk biochar as raw material, the biochar is modified through sequential calcination, acid washing, alkali activation, and recalcination to improve its specific surface area and surface activity. The modified biochar is further introduced into a mixed metal salt solution composed of cobalt nitrate hexahydrate, nickel chloride hexahydrate, and ferric nitrate nonahydrate. A mixed alkaline solution composed of sodium hydroxide and sodium carbonate is added dropwise, and under heating and aging conditions, in-situ growth of CoNiFe-LDH is achieved on the surface of the modified biochar, yielding a modified biochar-supported CoNiFe-LDH composite material. This method is simple, highly controllable, and produces a composite material with stable structure and uniform loading. The biochar and CoNiFe-LDH exhibit a good synergistic effect, making it suitable for catalysis, adsorption, and energy conversion.

Description

Technical Field

[0001] This invention relates to the technical field of catalytic materials, specifically a modified bio-carbon supported CoNiFe-LDH catalyst, its preparation method, and its application. Background Technology

[0002] With the global energy structure shifting towards cleaner and lower-carbon energy, and the accelerating pace of industrialization and urbanization, efficient energy conversion and environmental pollution control have become key issues hindering sustainable social development. In fields such as electrochemical energy conversion, renewable energy utilization, and industrial wastewater treatment, critical reactions like the oxygen evolution reaction (OER), electrocatalytic oxidation, and advanced oxidation processes generally suffer from slow reaction kinetics and high energy consumption. The performance of the catalyst directly determines the efficiency and economic viability of these reactions. Against this backdrop, developing catalytic materials with high catalytic activity, good conductivity, strong structural stability, and controllable cost has become a research hotspot in the fields of new energy and environmental catalysis.

[0003] While traditional noble metal catalysts possess high catalytic activity, their high cost and limited resources make them unsuitable for large-scale applications. Therefore, non-noble metal catalytic materials, represented by transition metals such as Co, Ni, and Fe, have gradually gained attention. Layered double hydroxides (LDHs) have shown promising applications in electrocatalysis and environmental catalysis due to their tunable composition and abundant active sites. However, existing LDH materials generally suffer from poor conductivity and limited electron transport, and their layered structures are prone to stacking, resulting in low specific surface area and active site utilization. Under long-term reaction or strong oxidation conditions, LDH structural stability is insufficient, leading to performance degradation and limiting their practical applications.

[0004] Biochar materials have gradually become ideal catalyst support materials due to their wide availability, low cost, rich pore structure, and good electrical conductivity. However, existing biochar supports have limited surface functional groups and weak binding forces with LDH active components, making it difficult to achieve uniform loading and stable dispersion of LDH, thus limiting the improvement in catalytic performance.

[0005] Therefore, it is necessary to develop a modified bio-carbon supported CoNiFe-LDH (K-BC / LDH) catalyst with stable structure, excellent conductivity, abundant active sites, and controllable preparation method to overcome the shortcomings of existing technologies and expand its application in energy conversion and environmental catalysis. Summary of the Invention

[0006] To address the aforementioned problems, specifically those raised in the background section, this invention proposes a modified bio-carbon supported CoNiFe-LDH catalyst, its preparation method, and its applications. The specific technical solution is as follows: A method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst, the method comprising the following steps: Corn stalk biochar was calcined, the calcined product was acid-washed and washed with deionized water until neutral, the washed product was dried, ground and sieved, added to potassium hydroxide solution and stirred, filtered and dried, and then placed in a nickel crucible for high-temperature calcination. After calcination, it was washed with deionized water until neutral and dried to obtain modified biochar. A mixed metal salt solution was prepared using cobalt nitrate hexahydrate, nickel chloride hexahydrate, and ferric nitrate nonahydrate as raw materials. The modified biochar from the above steps was added to the solution. Sodium hydroxide and sodium carbonate were mixed to form a mixed alkaline solution. This mixed alkaline solution was slowly added dropwise to the mixed metal salt solution. The mixture was heated and aged. The precipitate was filtered and washed with deionized water until neutral. Then, it was washed with anhydrous ethanol. The product was dried, ground, and sieved to obtain the modified biochar-supported CoNiFe-LDH catalyst.

[0007] Furthermore, the corn stalk biochar calcination process specifically involves placing corn stalks, preferably washed and dried, in a tube furnace under an inert gas atmosphere and calcining them at 400-600℃ for 1-3 hours, preferably 2-3 hours, to form an initial biochar skeleton structure.

[0008] Furthermore, in the pickling step, a hydrochloric acid solution with a mass fraction of 0.5%-5% is used for pickling to remove ash and inorganic impurities from the biochar. After pickling, the biochar is repeatedly washed with deionized water until the washing solution is neutral, and then dried, ground, and passed through a 100-mesh sieve at 50-70°C.

[0009] Furthermore, in the alkaline activation step, the acid-washed biochar is added to potassium hydroxide with a mass fraction of 0.5%-5%, and reacted under mechanical stirring for 18-28 hours, preferably 20-24 hours. After the reaction is completed, the biochar is separated into solid and liquid phases and dried at 90-120°C to obtain pretreated biochar.

[0010] Furthermore, in the high-temperature calcination step, the pretreated biochar is placed in a nickel crucible and heated in a tube furnace at a heating rate of 2-10℃ / min, preferably 5℃ / min, to 600-800℃ and calcined for 1-3 hours, preferably 2 hours. After calcination, the biochar is cooled to room temperature, washed with deionized water until the washing solution is neutral, and then dried to obtain modified biochar.

[0011] Furthermore, the mixed metal salt solution is prepared by cobalt nitrate hexahydrate, nickel chloride hexahydrate, and ferric nitrate nonahydrate in a cobalt:nickel:iron molar ratio of (1-10):(0.5-5):1.

[0012] Furthermore, the CO3 in the mixed alkaline solution 2- with Fe 3+ The ratio is 2:1, OH - With CO3 2- The ratio was 3.2:1. The mixed alkaline solution was slowly added dropwise to the mixed metal salt solution under stirring conditions, and the pH of the reaction system was adjusted to 10.5 using 1 mol / L sodium hydroxide solution.

[0013] Furthermore, the above reaction steps were stirred at 60°C for 1 hour, dried at 60-90°C for 12-16 hours, ground and passed through a 100-mesh sieve to obtain CoNiFe-LDH.

[0014] Furthermore, the modified biochar is added to a mixed metal salt solution, such that the mass ratio of modified biochar to CoNiFe-LDH is 1:1, and the same co-precipitation process as that used to prepare CoNiFe-LDH is employed to load the CoNiFe-LDH onto the surface of the biochar through in-situ growth, thereby obtaining a modified biochar-supported CoNiFe-LDH catalyst.

[0015] A modified bio-carbon supported CoNiFe-LDH catalyst, wherein the catalyst is prepared according to any of the methods described above.

[0016] Application of a modified bio-carbon supported CoNiFe-LDH catalyst as described above in the catalytic ozone oxidation degradation of organic pollutants in water.

[0017] Furthermore, the organic pollutants include, but are not limited to, at least one of the following categories: organics in pharmaceuticals and personal care products, endocrine disruptors, organics in pesticides and herbicides, dyes and colored organics, aromatic organic compounds, and nitrogen- and / or sulfur-containing organics.

[0018] Furthermore, the organic substances in the category of pharmaceuticals and personal care products include antiepileptic drugs, antibiotics, hormonal drugs, and their metabolites.

[0019] The beneficial technical effects of this invention are as follows: This invention employs a multi-step synergistic modification process involving calcination, acid washing, alkali activation, and subsequent high-temperature calcination of corn stalk biochar. This process effectively removes ash impurities, significantly improves the pore structure and surface chemical properties of the biochar, increases the specific surface area and the number of active sites, thereby enhancing the biochar's load-bearing capacity and structural stability as a carrier for functional materials. This invention introduces modified biochar into a multi-metal salt co-precipitation system and uses a slow dropwise addition of a mixed alkaline solution to allow CoNiFe layered multi-metal hydroxides to nucleate and grow in situ on the surface of the modified biochar. This effectively inhibits the aggregation of LDH and enhances the synergistic effect among Co, Ni, and Fe multi-metals, thereby improving the structural stability and comprehensive application performance of the modified biochar-supported CoNiFe-LDH composite material.

[0020] Through five cycles of experiments, the degradation efficiency of CBZ did not decrease significantly, demonstrating the good stability of the catalyst. Furthermore, the use of biochar not only reduces the addition of metals and the dissolution of metal ions, inhibiting the aggregation of LDH, but also promotes the reuse of waste biomass materials, making it more low-carbon and environmentally friendly. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of a modified biocarbon-supported CoNiFe-LDH catalyst from Example 1; Figure 2 This is a scanning electron microscope image of the unmodified catalyst CoNiFe-LDH in Example 1; Figure 3 The optimal XRD pattern for the modified biocarbon supported catalyst K-BC / LDH in Example 1 is shown. Figure 4 Figure 1 shows the cyclic performance test results of the catalyst-catalyzed sampling of micro-nanobubbles for the degradation of carbamazepine. Detailed Implementation

[0022] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] Step 1, Preparation of biochar (BC): The surface of the corn stalks was washed, dried, and then calcined in a tube furnace at 500°C for two hours. After cooling, the product was washed with an appropriate amount of 1mol / L hydrochloric acid solution to remove ash impurities. After acid washing, the product was repeatedly washed with deionized water until the washing solution was neutral. The washed product was then dried at 60°C, ground, and passed through a 100-mesh sieve.

[0024] 5g of biochar was placed in 100mL of 1mol / L potassium hydroxide solution and mechanically stirred for 24h. The resulting reactants were filtered, and the solid product was dried at 105℃ to obtain pretreated biochar.

[0025] The dried pretreated biochar was placed in a nickel crucible and calcined in a tube furnace at 700 degrees Celsius for two hours at a heating rate of 5 degrees Celsius per minute. After the temperature dropped to room temperature, the product was removed, washed with deionized water until neutral, and then dried to obtain modified biochar (K-BC).

[0026] Step 2, Preparation of CoNiFe-LDH: Will Co(No 3)2 A metal solution was obtained by adding 6H2O, NiCl2·6H2O, and Fe(NO3)2·9H2O to 200 ml of deionized water in a molar ratio of 2:1:1.

[0027] Prepare 200 ml of a mixed alkaline solution consisting of NaOH and Na₂CO₃, wherein CO₃²⁻… 2- with Fe 3+ The ratio is 2:1, OH - With CO3 2- The ratio of the two alkaline solutions was 3.2:1. Under vigorous stirring, the above mixed alkaline solution was slowly added dropwise to the above mixed metal salt solution. The pH was adjusted to 10.5 with 1 mol / L NaOH solution, and the mixture was stirred continuously at 60°C for 1 h. The reaction system was then heated in an 80°C water bath and aged for 6 h to promote the formation and crystallization of the precipitate. After the reaction was completed, the system was subjected to solid-liquid separation, the precipitate was collected, and washed with deionized water until neutral. Then, it was washed with anhydrous ethanol to improve dispersibility. The obtained product was dried at 70°C for 12 h, ground, and passed through a 100-mesh sieve to obtain CoNiFe-LDH.

[0028] Step 3, Preparation of K-BC / LDH: Add 4g of K-BC to the mixed metal solution (the mass ratio of modified biochar to LDH is 1:1), and follow the same steps as for LDH preparation to obtain K-BC / LDH.

[0029] XRD analysis revealed that the characteristic diffraction peaks of CoNiFe-LDH appeared in the modified bio-carbon-supported CoNiFe-LDH composite material described in Example 1, while the characteristic diffraction peaks of bio-carbon were retained in the low-angle region, indicating that CoNiFe-LDH was successfully loaded onto the surface of modified bio-carbon and its crystal structure was not significantly damaged.

[0030] SEM analysis revealed that the modified biochar exhibited a porous structure, with CoNiFe-LDH uniformly distributed on the surface of the modified biochar in a lamellar morphology, forming a loose layered composite structure. This indicates that CoNiFe-LDH achieved a relatively uniform loading on the surface of the modified biochar.

[0031] To demonstrate the catalytic performance of the K-BC / LDH catalyst prepared according to the above steps, the catalysts obtained in steps 1, 2, and 3 were tested for their effectiveness in catalyzing the degradation of carbamazepine, an organic pollutant in water, using ozone micro-nanobubbles. Specifically, 3 L of a 50 mg / L carbamazepine solution (CBZ) was prepared. The experiment was conducted under the following conditions: ozone concentration of 40 mg / L, gas-liquid ratio of 1:30, and a dosage of 0.5 g / L for CoNiFeLDH, K-BC, and K-BC / LDH catalysts. The reaction was carried out for 10 minutes, with water samples taken every minute. The samples were filtered through a 0.45 μm filter membrane, and the carbamazepine concentration was measured using high-performance liquid chromatography (HPLC) to indirectly demonstrate the catalytic activity of the three catalysts. Unless otherwise specified, all degradation experiments were conducted at room temperature.

[0032] 1. Ozone micro-nano bubbles can catalyze the degradation of CBZ by 81.6% within 8 minutes.

[0033] 2. CoNiFe-LDH can catalyze the degradation of CBZ by ozone micro-nano bubbles to 96.1% in 8 min.

[0034] 3. K-BC can catalyze the degradation of CBZ by ozone micro-nano bubbles to 89.6% within 8 minutes.

[0035] 4. K-BC / LDH can catalyze the degradation of CBZ by ozone micro-nano bubbles to 99% within 8 minutes.

[0036] 5. In the experiment, the actual LDH content was only half of that in step 2, indicating that the LDH aggregation phenomenon was weakened after loading, the active sites were fully exposed, and the catalytic activity was stronger.

[0037] 6. Test results of the catalytic ozone micro-nano bubble degradation carbamazepine cycle performance are as follows: Figure 4 As shown, after five cycles, each lasting ten minutes, the initial catalyst achieved a carbamazepine removal rate of over 98%. After five cycles of recovery / reuse, 94-98% of the initial catalytic activity was retained, demonstrating the catalyst's good stability.

[0038] Comparative Example 1 The process of Example 1 is the same as that of Example 1, except that CoNiFe-LDH is used instead of K-BC / LDH obtained in step 3.

[0039] The morphology and microstructure of the catalysts prepared in Example 1 and Comparative Example 1 were analyzed: The morphology of the samples from Example 1 and Comparative Example 1 was observed using a scanning electron microscope (SEM), and the results are as follows: Figure 1 , Figure 2As shown in the figure, compared to the catalyst in Example 1, which exhibits a relatively loose lamellar and porous structure, pure CoNiFe-LDH mainly presents a lamellar or lamellar stacked structure, with obvious agglomeration in local areas. The lamellars are arranged more densely, resulting in a relatively compact structure.

[0040] Further X-ray diffraction (XRD) was used to analyze the crystal structure of the comparative sample, and the results are as follows: Figure 3 As shown in the figure, the comparative sample exhibits typical characteristic diffraction peaks of CoNiFe-LDH, indicating that the material successfully formed a layered bimetallic hydroxide structure. However, compared to the K-BC / LDH composite catalyst supported by modified biocarbon in Example 1, its diffraction peaks are more intense and sharper, indicating a relatively larger grain size and a certain degree of stacking in the structure.

[0041] Table 1. Data on specific surface area, pore volume, and average pore size of the catalysts in the examples and comparative examples. Table 1 shows that the modified biochar-supported catalyst has a higher specific surface area, significantly larger than that of the unmodified catalyst. This indicates that the modification process effectively improves the surface structure of the material, facilitating the exposure of more catalytic active sites. Furthermore, the total pore volume data in Table 1 shows that the modified biochar-supported catalyst has a larger pore volume, indicating a well-developed pore structure that promotes mass transfer and diffusion of reactants and products within the catalyst during the reaction. Further analysis of the average pore size data reveals that the catalyst's pore structure is primarily mesoporous. This pore size range facilitates the entry of molecular-sized reactants into the pores in liquid or gas phase reaction systems, thereby improving the utilization efficiency of the active components. In summary, the results of specific surface area, pore volume, and pore size distribution demonstrate that the modification of the biochar support maintains structural stability while creating a hierarchical pore structure. This structural feature contributes to the uniform dispersion of the metal active components on the support surface and provides a favorable structural basis for the catalytic reaction.

[0042] Comparative Example 2 In this embodiment, the molar ratio of hydroxide ions to biochar is OH. - The biochar was modified with an alkali ratio of BC = 1.5:1, and the remaining preparation steps were the same as in Example 1 to obtain modified biochar. CoNiFe-LDH was further loaded on its surface by in-situ co-precipitation to obtain K-BC / LDH composite catalyst.

[0043] This catalyst was used to catalytically degrade carbamazepine in an ozone micro / nano bubble system. Under the same reaction conditions, the catalyst exhibited high catalytic activity. The degradation rate reached approximately 95% at a reaction time of 8 min, demonstrating high catalytic activity and reaction stability. The carbamazepine removal rate steadily increased with increasing reaction time, showing excellent ozone catalytic degradation performance.

[0044] Comparative Example 3 In this embodiment, the conditions for the first calcination are kept unchanged, only the time for the second calcination is changed to 3 hours, and the remaining preparation steps are the same as step 1 of Example 1.

[0045] In degradation performance testing, the catalyst prepared under these conditions achieved a degradation rate of approximately 95% for the target pollutant within 8 minutes. Compared to samples with shorter or longer calcination times, this catalyst maintained high degradation efficiency while exhibiting a more stable reaction process, demonstrating a good balance between structural stability and catalytic performance.

[0046] Comparative Example 4 In this embodiment, the secondary calcination temperature is controlled at 600 °C, and the remaining preparation steps are the same as in Example 1.

[0047] Catalytic degradation experiments showed that, under the same reaction conditions, the catalyst could achieve a degradation rate of approximately 96% for the target pollutant within 8 minutes. The results indicate that appropriately increasing the secondary calcination temperature is beneficial for improving the material's structural stability and maintaining high catalytic degradation activity.

[0048] Comparative Example 5 In this embodiment, the mass ratio of modified biochar to layered double hydroxide was adjusted to KBC:CoNiFe-LDH = 0.5:1, and the remaining preparation steps were the same as in Example 1.

[0049] In the degradation experiment, the catalyst achieved a degradation rate of 96.8% for the target pollutant within 8 minutes.

[0050] Comparative Example 6 In this embodiment, the mass ratio of modified biochar to layered double hydroxide was adjusted to KBC:CoNiFe-LDH = 1.5:1, and the remaining preparation steps were the same as in Example 1. In the degradation experiment, the catalyst achieved a degradation rate of 95.4% for the target pollutant within 8 minutes.

[0051] Examples 1, 5, and 6 show that the amount of CoNiFe-LDH added has a certain impact on catalytic performance. If the CoNiFe-LDH loading on biochar is too low, the biochar content increases, reducing the LDH content and the number of active sites. When the CoNiFe-LDH content is too high, catalyst agglomeration is not well resolved, and the degradation efficiency of carbamazepine by catalytic ozone micro-nanobubbles decreases.

[0052] Although the invention has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0053] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those processes, articles, or apparatus / devices.

[0054] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst, characterized in that: The method includes the following steps: Corn stalk biochar was calcined, and the calcined product was acid-washed to remove ash and washed with deionized water until neutral. The washed product was dried, ground and sieved, then added to potassium hydroxide solution and stirred, filtered and dried. The product was then placed in a nickel crucible and calcined at high temperature. After calcination, it was washed with deionized water until neutral and dried to obtain modified biochar. A mixed metal salt solution was prepared using cobalt nitrate hexahydrate, nickel chloride hexahydrate, and ferric nitrate nonahydrate as raw materials. The modified biochar from the above steps was added to the solution. Sodium hydroxide and sodium carbonate were mixed to form a mixed alkaline solution. This mixed alkaline solution was slowly added dropwise to the mixed metal salt solution. The mixture was heated and aged. The precipitate was filtered and washed with deionized water until neutral. Then, it was washed with anhydrous ethanol. The product was dried, ground, and sieved to obtain the modified biochar-supported CoNiFe-LDH catalyst.

2. The method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst according to claim 1, characterized in that: The corn stalk biochar calcination process specifically involves calcination under an inert gas atmosphere.

3. The method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst according to claim 1, characterized in that: In the pickling step, a hydrochloric acid solution with a mass fraction of 1%-2% is used for pickling; in the step of adding potassium hydroxide solution, a potassium hydroxide solution with a mass fraction of 0.5%-5% is used.

4. The method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst according to claim 1, characterized in that: In the high-temperature calcination step, the calcination temperature is specifically 600-800℃, and in the aging reaction step, the aging time is 6-8h.

5. The method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst according to claim 1, characterized in that: In the mixed metal salt solution, the molar ratio of cobalt, nickel, and iron is (1-10):(0.5-5):1, and the mixed alkaline solution contains CO3. 2- with Fe 3+ The ratio is 2:1, OH - With CO3 2- The ratio is 3:1 to 4:

1.

6. The method for preparing a modified bio-carbon supported CoNiFe-LDH catalyst according to claim 1, characterized in that: The CoNiFe-LDH was loaded onto the surface of biochar via in-situ growth.

7. A modified biocarbon-supported CoNiFe-LDH catalyst, characterized in that: The catalyst is a catalyst prepared according to any one of the methods described in claims 1-7.

8. The application of the modified bio-carbon supported CoNiFe-LDH catalyst as described in claim 7 in the catalytic ozone oxidation degradation of organic pollutants in water.

9. The application of the modified bio-carbon supported CoNiFe-LDH catalyst according to claim 8, characterized in that: The organic pollutants include, but are not limited to, at least one of the following: organics in pharmaceuticals and personal care products, endocrine disruptors, organics in pesticides and herbicides, dyes and colored organics, aromatic organic compounds, and nitrogen- and / or sulfur-containing organics.

10. The application of the modified biocarbon-supported CoNiFe-LDH catalyst according to claim 9, characterized in that: The organic substances in the category of drugs and personal care products include antiepileptic drugs, antibiotics, hormone drugs and their metabolites.

Images