Biochar-based multi-metal modified composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of environmental governance, in particular to a charcoal-based multi-metal modified composite material and a preparation method and application thereof. The preparation method provided by the invention comprises the following steps: pyrolyzing biomass to obtain pre-carbonized biochar; and then the pre-carbonized biochar is soaked in an aqueous solution containing Cu < 2 + >, Co < 2 + > and Zn < 2 + >, separated and dried, and the biochar-based multi-metal modified composite material is obtained through roasting. The prepared multi-metal modified composite material can solve the problems that in an existing catalytic oxidation technology, catalyst preparation materials are high in price, preparation and reaction conditions are harsh and the like, the catalytic oxidation capacity on volatile organic compounds under the low-temperature working condition is improved, and the high industrial application value is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental governance, and particularly relates to a biochar-based multi-metal modified composite material and a preparation method and application thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) can undergo photochemical reactions with nitrogen oxides in the atmosphere, and as important precursors of ozone and fine particulate matter (PM 2.5 ), VOCs seriously threaten and harm the environment and human health. VOCs exist widely in the use of raw and auxiliary materials and the production process of products, and most of them are toxic to humans and organisms. Especially for the key industries of atmospheric pollution control such as pharmaceutical and chemical industries, the VOCs emission is large, the concentration is low, and the composition is complex, so it is very important to control VOCs emission by using scientific and reasonable technology. At present, the end treatment technology of VOCs in the pharmaceutical and chemical industries mainly includes condensation, absorption, adsorption, catalytic combustion, photocatalytic degradation and other technologies. Among the many end control technologies, catalytic oxidation technology has high degradation efficiency and less secondary pollution, and is considered as an effective VOCs removal technology.

[0003] As the core of catalytic oxidation technology, the development of high-efficiency and low-cost catalysts under low energy consumption (especially at low reaction temperature) is the key to industrial application. The catalysts mainly face three challenges of low activity, poor stability and poor high-temperature resistance under low temperature conditions. The low activity of the catalysts under low temperature leads to slow reaction rate and difficulty in meeting the conversion efficiency standard. The catalysts are usually composed of active substances, carriers and cocatalysts. Researchers found that the low-temperature activity of the catalysts can be enhanced by means of element substitution, carrier optimization, structure (crystal form) morphology control and other means. The active component of the catalyst is an important part of the catalytic oxidation technology, and the introduction of metal elements into the carrier can increase the active sites, reduce the reaction window temperature and ensure the performance of the catalyst. With the progress of technology, transition metals have gradually replaced precious metals which are expensive and have limited natural production, and become a hot research direction of catalysts in catalytic oxidation technology. The carrier is also an important component of the high-cost catalyst. The specific surface area of biochar is large, contains various functional groups, and the preparation process is simple and low in cost, so the biochar can be used as a high-quality carrier to realize the uniform dispersion of the active component of the catalyst and improve the heat energy distribution in the reaction process, reduce the sintering and deactivation of the active sites, and improve the overall thermal stability of the catalyst. However, the physicochemical properties of biochar are affected by factors such as raw material type and preparation method, which further affects the efficacy of the biochar as a catalyst carrier. SUMMARY

[0004] To address the aforementioned technical problems, this invention provides a biochar-based multimetal modified composite material, its preparation method, and its applications. The biochar-based multimetal modified composite material provided by this invention is suitable for the catalytic oxidation of VOCs under low-temperature conditions. Compared with existing catalytic oxidation materials, it can significantly improve catalytic oxidation efficiency. Furthermore, the biochar-based multimetal modified composite material of this invention can reduce preparation costs, and the preparation method is simple, highly operable, and has high industrial application value.

[0005] In a first aspect, the present invention provides a method for preparing a biochar-based multimetal-modified composite material, comprising the following steps: S1. Pyrolyze biomass to obtain pre-carbonized biochar; S2, The pre-carbonized biochar is then placed in a Cu-containing environment. 2+ Co 2+ and Zn 2+ The precursor material is obtained by impregnation in an aqueous solution, separation of the solid, and drying. S3. The precursor material is calcined to obtain a biochar-based multimetal modified composite material.

[0006] Biochar exhibits superior performance in terms of specific surface area, active sites, cost, and raw material availability, making it a significant advantage for catalysts prepared using biochar as a support for controlling VOC emissions. Compared to activated carbon, biochar has lower energy requirements. The interconnected network of micropores and mesopores in biochar provides abundant and dispersed active sites, which is beneficial for the degradation of VOCs such as toluene. Furthermore, biochar has the ability to reduce the oxidation state of metals in the dispersion system, thereby enhancing the dispersion activity of the central metal.

[0007] This invention optimizes the potential of biochar as a support and its metal doping modification ability by controlling parameters such as pre-carbonization and multi-metal co-impregnation, thus preparing biochar as a support for Cu. 2+ Co 2+ and Zn 2+ Biochar-based multimetal-modified composite materials with co-doped active centers. The materials prepared by the method described in this application exhibit significantly improved structural stability and catalytic oxidation capacity for VOCs under low-temperature conditions.

[0008] In some embodiments of the present invention, the preparation method further includes drying, pulverizing and sieving the biomass before pyrolysis.

[0009] In some embodiments of the present invention, the biomass source includes agricultural waste, which includes any one or more of straw, fruit shells, and tobacco stalks.

[0010] In some embodiments of the present invention, the pyrolysis temperature is 690-710℃, for example 690℃, 695℃, 700℃, 705℃, 710℃, etc.

[0011] In some embodiments of the present invention, the pyrolysis time is 110-125 min, for example 110 min, 115 min, 120 min, 125 min, etc.

[0012] The pre-carbonization step of this invention helps optimize the structure and crystallinity of biochar, thereby improving the stability of the resulting biochar carrier. Before pre-carbonization, the surface of blank biochar is rough and uneven; after pre-carbonization, the surface of the biochar has fewer impurities, which is beneficial for the uniform loading of multiple metals.

[0013] In some embodiments of the present invention, the Cu 2+ The source is one or more of copper nitrate, copper sulfate and copper chloride, preferably copper nitrate.

[0014] In some embodiments of the present invention, the Co 2+ The source is one or more of cobalt nitrate, cobalt sulfate and cobalt chloride, preferably cobalt nitrate.

[0015] In some embodiments of the present invention, the Zn 2+ The source is one or more of zinc nitrate, zinc sulfate, and zinc chloride, preferably zinc nitrate.

[0016] In some embodiments of the present invention, the Cu 2+ and the Co 2+ The mass ratio is (2-7):(3-8), for example 1:1, 1:2, 1:4, 2:1, 2:3, 7:3, etc., preferably 1:2.

[0017] In some embodiments of the present invention, the Cu 2+ and the Co 2+ The total mass and the Zn 2+ The mass ratio is 10:(3-8), for example 10:3, 10:7, 5:3, 2:1, 5:4, etc., preferably 5:3.

[0018] In some embodiments of the present invention, the Cu 2+ Co 2+ and Zn 2+ The ratio of the total mass to the mass of the biochar is 13-18:100, for example, 13:100, 14:100, 15:100, 16:100, 17:100, 18:100, etc.

[0019] In some embodiments of the present invention, the impregnation is carried out under constant temperature and vibration conditions.

[0020] In some embodiments of the present invention, the temperature of the isothermal oscillation is 18-25°C, such as 18°C, 20°C, 22°C, 25°C, etc.

[0021] In some embodiments of the present invention, the isothermal oscillation time is 10-12 h, for example 10 h, 11 h, 12 h, etc.

[0022] This invention synthesizes different Cu using an impregnation method. 2+ Co 2+ and Zn 2+ A biochar-based multimetal modified composite material with a mass ratio of [specific component] is used to enhance the stability and heat resistance of the catalyst, resulting in excellent catalytic oxidation performance under low-temperature conditions.

[0023] In some embodiments of the present invention, the drying temperature is 55-65°C, for example 55°C, 58°C, 60°C, 62°C, 65°C, etc.

[0024] In some embodiments of the present invention, the drying time is 10-12 h, for example 10 h, 11 h, 12 h, etc.

[0025] In some embodiments of the present invention, the roasting is carried out in a tube furnace under an argon atmosphere.

[0026] In some embodiments of the present invention, the calcination temperature is 700-1000℃, for example 700℃, 800℃, 900℃, 1000℃, preferably 700℃.

[0027] The calcination temperature conditions of this invention are beneficial for the structural optimization of the modified composite material and its effective combination with the three metal ions. Under low calcination temperature conditions, the pore structure of the material cannot be effectively constructed, and the combination effect of the three metal ions with activated carbon is poor; if the calcination temperature is too high, the activity of the three metal ions is affected, resulting in unnecessary weight loss of the material.

[0028] In some embodiments of the present invention, the calcination time is 2-3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, etc.

[0029] In some embodiments of the present invention, the heating rate of the calcination is 4-7℃ / min, for example 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, etc.

[0030] The programmed temperature conditions of this invention are beneficial for the uniform dispersion and active release of the three metal ions attached to the biochar. If the temperature rises too quickly, it is not conducive to the uniform dispersion and active release of the three metal ions and biochar, and the metal activity on the material surface is significantly affected; if the temperature rises too slowly, the porosity of the material decreases and the specific surface area is lower, which also affects the catalytic oxidation effect of the material under low-temperature conditions, and will lead to an increase in the calcination process time and a significant increase in the material preparation cost.

[0031] In a second aspect, the present invention provides a biochar-based multimetal modified composite material prepared by the preparation method described in the first aspect.

[0032] This invention disperses Cu, Co, and Zn—metals with similar ionic radii but distinct chemical properties—into a single biochar material through metal doping. Compared to single-metal materials, the resulting biochar-based multi-metal modified composite material exhibits a multi-metal synergistic coordination effect, endowing the material with abundant reaction sites. This enhances the material's catalytic oxidation performance and thermal stability under low-temperature conditions, while also offering greater component controllability, more diverse structures, and simplified preparation conditions. Co exhibits higher reactivity than Cu, and the two metals work synergistically in structure establishment and reaction processes. For cost considerations, this invention uses Co to partially replace Cu to strengthen the material's reactivity. Zn, being a member of the same group as Cu, effectively optimizes the pore structure and increases the material's specific surface area after volatilization at high temperatures.

[0033] Thirdly, the present invention provides an application of the biochar-based multimetal modified composite material as described in the second aspect in the catalytic oxidation of volatile organic compounds.

[0034] The biochar-based multimetallic modified composite material provided by this invention has a maximum specific surface area of ​​356.72 m². 2 / g, maximum total pore volume 0.2342 cm³ 2 / g, suitable for the catalytic oxidation of VOCs (including but not limited to toluene, phenol and tetrahydrofuran) under low temperature conditions up to 240℃, solving the problem of low catalytic efficiency of VOCs under low temperature conditions.

[0035] Fourthly, the present invention provides a method for catalytic oxidation of volatile organic compounds, the method comprising catalytic oxidation of volatile organic compounds using the biochar-based multimetal modified composite material described in the second aspect under reaction conditions of 240-270°C.

[0036] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: The preparation method provided by this invention is simple, low-cost, and highly operable. The biochar-based multi-metal modified composite material prepared by this invention is suitable for the catalytic oxidation degradation of volatile organic waste gas at low temperatures down to 240℃. The material's structural stability is improved, the degradation effect is significant, and it is easy to industrialize. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 XPS image of the biochar-based multimetal modified composite material of Example 1 of the present invention; Figure 2 XPS image of the biochar-based multimetal modified composite material of Example 5 of the present invention; Figure 3 XPS image of the biochar-based multimetal modified composite material of Comparative Example 1 of this invention; Figure 4 XPS image of the biochar-based multimetal modified composite material of Comparative Example 4 of this invention; Figure 5 This is a SEM image of the biochar-based multimetal modified composite material of Example 1 of the present invention; Figure 6 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 4-7 of the present invention at different temperatures; Figure 7 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 8-9 of the present invention at different temperatures; Figure 8 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 10-11 of the present invention at different temperatures; Figure 9 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Example 1 and Comparative Examples 1-6 at different temperatures. Figure 10 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Example 1 and Comparative Example 7 at different temperatures. Detailed Implementation

[0040] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0042] Example 1 This embodiment provides a biochar-based multimetal-modified composite material, the preparation method of which is as follows: S1. Crush 3g of dry wheat straw, filter it through a 40-mesh sieve, put it into a covered crucible, and then pyrolyze the crushed wheat straw at 700℃ for 120 min to obtain pre-carbonized wheat straw. S2. Prepare aqueous solutions of copper nitrate (Cu(NO3)2·3H2O), cobalt nitrate (Co(NO3)2·6H2O), and Zn(NO3)2·6H2O) respectively. Mix the three solutions to obtain a doped metal solution. The doped metal solution contains Cu... 2+ The weight percentage is 3.33 wt%, Co 2 + The weight percentage of Zn is 6.66 wt%. 2+ The weight percentage of Cu is 6 wt%. 2+ Co 2+ and Zn 2+ The total mass was 0.48 g. The pre-carbonized wheat straw was placed in 20 mL of a prepared metal-doped solution and shaken at 20 °C for 12 h, and then dried at 60 °C for 12 h to obtain the precursor material. S3. Place the dried precursor material in a tube furnace under argon atmosphere protection at 5°C / min. -1 The heating rate was increased to 700℃ and sintered for 2 hours to form a powdered biochar-based multimetal modified composite material with catalytic oxidation of VOCs.

[0043] Example 2 This embodiment provides a biochar-based multimetal-modified composite material, the preparation method of which is as follows: S1. Crush 3g of dry wheat straw, filter it through a 40-mesh sieve, put it into a covered crucible, and then pyrolyze the crushed wheat straw at 710℃ for 110 min to obtain pre-carbonized wheat straw. S2. Prepare aqueous solutions of copper nitrate (Cu(NO3)2·3H2O), cobalt nitrate (Co(NO3)2·6H2O), and Zn(NO3)2·6H2O) respectively. Mix the three solutions to obtain a doped metal solution. The Cu in the doped metal solution... 2+ 2wt% by weight, Co 2+ The total weight percentage is 8 wt%, Zn 2+ The weight percentage of Cu is 3 wt%. 2+ Co 2+ and Zn 2+ The total mass was 0.39 g. The pre-carbonized wheat straw was placed in 20 mL of a prepared metal-doped solution and shaken at 22 °C for 10 h, and then dried at 65 °C for 10 h to obtain the precursor material. S3. Place the dried precursor material in a tube furnace under argon atmosphere protection at 5°C / min. -1 The heating rate was increased to 900℃ and sintered for 3 hours to form a powdered biochar-based multimetal modified composite material with catalytic oxidation of VOCs.

[0044] Example 3 This embodiment provides a biochar-based multimetal-modified composite material, the preparation method of which is as follows: S1. Crush 3g of dry wheat straw, filter it through a 40-mesh sieve, put it into a covered crucible, and then pyrolyze the crushed wheat straw at a high temperature of 690℃ to obtain pre-carbonized wheat straw. S2. Prepare aqueous solutions of copper nitrate (Cu(NO3)2·3H2O), cobalt nitrate (Co(NO3)2·6H2O), and Zn(NO3)2·6H2O) respectively. Mix the three solutions to obtain a doped metal solution. The Cu in the doped metal solution... 2+ The weight percentage is 6.66 wt%, Co 2+ The total weight percentage is 3.33 wt%, Zn 2+ The weight percentage of Cu is 8 wt%. 2+ Co 2+ and Zn 2+ The total mass was 0.54 g. The pre-carbonized wheat straw was placed in 20 mL of a prepared metal-doped solution and shaken at 22 °C for 10 h, and then dried at 55 °C for 10 h to obtain the precursor material. S3. Place the dried precursor material in a tube furnace under argon atmosphere protection at 5°C / min. -1 The heating rate was increased to 800℃ and sintered for 3 hours to form a powdered biochar-based multimetal modified composite material with catalytic oxidation of VOCs.

[0045] Examples 4-5 This embodiment provides a biochar-based multimetal modified composite material. The difference between its preparation method and that of Example 1 is that the firing temperature in step S3 is 850℃ (Example 4) and 1000℃ (Example 5), respectively.

[0046] Examples 6-7 This embodiment provides a biochar-based multimetal modified composite material. The difference between its preparation method and that of Example 1 is that the firing temperature in step S3 is 500℃ (Example 6) and 1200℃ (Example 7), respectively.

[0047] Examples 8-9 This embodiment provides a biochar-based multimetal modified composite material. The difference between its preparation method and that of Example 1 is that the heating rate in step S3 is 4℃ / min (Example 8) and 7℃ / min (Example 9), respectively.

[0048] Example 10 This embodiment provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 lies in the fact that, in step S2, the Cu in the doping metal solution... 2+ The weight percentage is 3.33 wt%, Co 2+ The weight percentage of Zn is 6.66 wt%. 2+ The weight percentage is 1 wt%.

[0049] Example 11 This embodiment provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 lies in the fact that, in step S2, the Cu in the doping metal solution... 2+ The weight percentage is 3.33 wt%, Co 2+ The weight percentage of Zn is 6.66 wt%. 2+ The weight percentage is 10 wt%.

[0050] Comparative Example 1 This comparative example provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 is that only Cu is added in step S2. 2+ and Co 2+ The weight percentage is the same as in Example 1.

[0051] Comparative Example 2 This comparative example provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 is that only Co is added in step S2. 2+ and Zn 2+ And Co in the doped metal solution 2+The weight percentage of Zn is 10 wt%. 2+ The weight percentage is 6 wt%.

[0052] Comparative Example 3 This comparative example provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 is that only Zn is added in step S2. 2+ and Cu 2+ Cu in doped metal solution 2+ The weight percentage of Zn is 10 wt%. 2+ The weight percentage is 6 wt%.

[0053] Comparative Example 4 This comparative example provides a biochar-based metal-modified composite material. The difference between its preparation method and that of Example 1 is that the doped metal solution in step S2 contains only Cu. 2+ Its weight percentage is 10 wt%.

[0054] Comparative Example 5 This comparative example provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 is that the doped metal solution in step S2 contains only Co. 2+ Its weight percentage is 10 wt%.

[0055] Comparative Example 6 This comparative example provides a biochar-based multimetal-modified composite material. The difference between its preparation method and that of Example 1 is that the doped metal solution in step S2 contains only Zn. 2+ Its weight percentage is 6 wt%.

[0056] Comparative Example 7 This comparative example provides a biochar-based multimetal modified composite material, the preparation method of which differs from the preparation method of Example 1 in that it does not have a pre-carbonization step.

[0057] Performance Test 1 1. XPS tests were performed on the biochar-based multimetal modified composite materials prepared in the examples and comparative examples.

[0058] It can be observed that the XPS patterns of the biochar-based multimetal modified composite materials prepared in Examples 1-11 are similar. Specifically, the XPS patterns of the biochar-based multimetal modified composite materials prepared in Examples 1 and 5 are shown below. Figure 1 and Figure 2 As shown, the XPS results of the biochar-based multimetal modified composite materials prepared in Comparative Examples 1 and 4 are as follows: Figure 3 and Figure 4 As shown.

[0059] Depend on Figure 1 It can be seen that Cu 2p In the spectrum, Cu is represented by Cu 0 (931.9 eV), Cu 1+ Cu 2+ The presence of a mixed form, with this valence distribution, favors Cu's participation in electron transfer during catalytic oxidation reactions. Co 2p In the spectrum, Co from Example 1 2+ Comparative Example 5 ( Figure 2 ) more than 5.23%, Co 2+ The presence of Zn helps maintain the reactive oxygen vacancies on the catalyst surface. 2p The spectrum shows distinct absorption peaks at 1021.3 eV and 1044.0 eV, confirming the successful loading of Cu, Co, and Zn onto the biochar surface. Furthermore, from O... 1s As shown in the spectrum, the proportion of coordinated unsaturated oxygen (O2, corresponding to active defect sites) is significantly higher than that of comparative example 1. Figure 3 This indicates that the introduction of Zn promotes the generation and retention of active oxygen species on the catalyst surface, reducing the Co content at high temperatures. 2+ To Co 0 The transformation thus retains more Co related to catalytic activity. 2+ This provides sufficient oxidation sites for the catalytic oxidation reaction of target organic pollutants.

[0060] Depend on Figure 3 It can be seen that Co in Comparative Example 1 2p The spectrum contains three pairs of characteristic peaks, and Co is calculated through peak segmentation. 0 9.43%, Co 2+ 54.92%, Co 3+ The proportion of 35.64% indicates highly dispersed amorphous Co. 2+ and Co 3+ This catalyst is compared to Comparative Example 4 ( Figure 4 This is a key factor contributing to superior catalytic performance. Furthermore, the introduction of Co did not significantly affect the form of Cu, indicating that the introduction of Co can provide more active sites for the catalytic oxidation of organic pollutants.

[0061] Depend on Figure 4 It can be seen that Cu in Comparative Example 4 2p In the spectrum, Cu at 932.7 eV 2p 3 / 2 And Cu at 952.5 eV 2p 1 / 2 The main peak proves that Cu in the catalyst 0 or Cu 1+The presence of Cu, and the relatively weak peaks at 934.9 eV and 954.6 eV with a binding energy difference of 19.7 eV, further confirm the presence of Cu. 2+ The presence of Cu indicates that the surface of Comparative Example 4 is mainly composed of Cu. 0 Cu 1+ Cu 2+ It exists in mixed forms.

[0062] Depend on Figures 1-4 It can be seen that the biochar-based multimetal modified composite material prepared in Example 1 of the present invention has characteristic peaks of Cu, Co and Zn. The peak positions are basically similar to those of Comparative Example 1 and Comparative Example 4, but the intensity of some characteristic peaks changes and the cell parameters are basically the same. This is because the electron densities of Cu, Co and Zn are almost the same, and the metal atoms are randomly distributed in the same position in the lattice with a relative Cu / Co / Zn ratio. This indicates that the appropriate amount of Cu, Co and Zn in the examples of the present invention are randomly distributed in the same position in the lattice with a relative ratio. This not only regulates the content of active oxygen species, stabilizes the valence state distribution of Co and optimizes the electronic environment of Cu, but also enriches the elemental composition and surface active site system of the catalyst by introducing Zn, which significantly improves the catalytic oxidation performance of Example 1.

[0063] 2. SEM tests were performed on the biochar-based multimetal modified composite materials prepared in the examples and comparative examples. The SEM image of the biochar-based multimetal modified composite material prepared in Example 1 is shown below. Figure 5 As shown.

[0064] Depend on Figure 5 It can be observed that the surface of biochar is uniformly loaded with small spheres of about 250 nm. Combined with the analysis and test results such as XPS, it can be determined that most of the Cu, Co and a small part of the Zn elements are highly dispersed on the surface of biochar in an amorphous state.

[0065] Performance Test 2 (1) Specific surface area detection The specific surface area of ​​the biochar-based multimetal modified composite materials in the examples and comparative examples was measured using the following methods: The specific surface area and porosity were determined using an ASAP 2460 fully automated specific surface area and porosity analyzer manufactured by Micromeritics Instruments, Inc., USA.

[0066] The test results of specific surface area, total pore volume, micropore volume and average pore size of biochar-based multimetal modified composite materials are shown in Table 1: Table 1

[0067] As shown in Table 1, the biochar-based multimetal modified composite material prepared in the embodiments of the present invention has a significantly increased specific surface area and a significantly improved catalytic oxidation efficiency compared with the comparative example.

[0068] (2) Detection of toluene's catalytic oxidation degradation ability The inlet and outlet gas concentrations of the reactor were detected online using an Agilent Technologies A7820 gas chromatograph to calculate the toluene reaction rate.

[0069] Toluene reaction rate calculation:

[0070] Where r is the reaction rate, mg‧g -1 ‧s -1 Q represents the flow rate of toluene, in mL·s. -1 C in The concentration of toluene at the inlet is in mg·mL. -1 W represents the mass of the catalyst, in g; η represents the toluene conversion rate, in percent.

[0071] The catalytic reaction rates of the biochar-based multimetal modified composite materials in the examples and comparative examples at different temperatures are shown in Table 2 and... Figures 6-10 As shown, where, Figure 6 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 4-7 at different temperatures; Figure 7 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 8-9 at different temperatures; Figure 8 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Examples 1 and 10-11 at different temperatures; Figure 9 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Example 1 and Comparative Examples 1-6 at different temperatures. Figure 10 This is a comparison of the catalytic reaction rates of the biochar-based multimetal modified composite materials of Example 1 and Comparative Example 7 at different temperatures.

[0072] The results in Table 2 are shown below: Table 2

[0073] As shown in Table 2, the catalytic oxidation rate of toluene by the biochar-based multimetal modified composite material prepared in this invention is significantly increased under low temperature reaction conditions. This indicates that the catalytic ability of the biochar-based multimetal modified composite material prepared in this invention is significantly improved under low temperature reaction conditions, and it is suitable for the catalytic oxidation degradation of volatile organic waste gas at low temperatures down to 240℃.

[0074] A comparison of Examples 1 and 4-7 reveals that both excessively high and excessively low calcination temperatures in step S3 can lead to a decrease in the catalytic reaction rate of the prepared multi-metal modified composite material.

[0075] A comparison of Examples 1 and 8-9 reveals that the heating rate during calcination in step S3 is 5°C / min. -1 When the time is right, the catalytic reaction rate of the prepared multi-metal modified composite material is optimal.

[0076] A comparison of Examples 1 and 10-11 reveals that the biochar-based multimetal modified composite material prepared in Example 11 exhibits a 47% reduction in catalytic reaction rate at 240°C compared to Example 1 due to excessive Zn loading; while the biochar-based multimetal modified composite material prepared in Example 10 exhibits a 19% reduction in catalytic reaction rate at 240°C compared to Example 1 due to insufficient Zn loading.

[0077] A comparison of Example 1 and Comparative Examples 1-6 reveals that when the doped metal ions contain only Cu... 2+ Co 2+ and Zn 2+ When any two of the following conditions are met, the catalytic reaction rate of the prepared biochar-based multimetal modified composite material decreases, especially when the doped metal ions contain only Cu. 2+ Co 2+ and Zn 2+ When any one of the following conditions is met, the catalytic reaction rate of the prepared biochar-based multimetal modified composite material is the lowest.

[0078] A comparison between Example 1 and Comparative Example 7 reveals that, under catalytic reaction temperatures of 240°C, 250°C, 260°C, and 270°C, the catalytic oxidation rate of toluene by the biochar-based multimetal modified composite material of Example 1 is significantly higher than that of the non-precarbonized material.

[0079] In summary, the biochar-based multimetal modified composite material prepared in this invention is produced by obtaining pre-carbonized biochar through biomass pyrolysis, and then processing the pre-carbonized biochar in a process containing Cu. 2+ Co 2+ and Zn 2+ The biochar-based multi-metal modified composite material was obtained by immersion and separation in an aqueous solution and drying, followed by calcination. This enhanced the structural stability of the material and improved the catalytic oxidation effect of the multi-metal modified composite material on volatile organic compounds under low-temperature reaction conditions. Furthermore, the preparation method of this invention is simple, highly operable, and has high industrial application value.

[0080] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0081] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of preparing a biochar-based multi-metal modified composite material, characterized in that, The method comprises the following steps: S1, pyrolyzing biomass to obtain pre-carbonized biochar; S2, impregnating the pre-carbonized biochar in an aqueous solution containing Cu 2+ , Co 2+ , and Zn 2+ , separating the solid and drying to obtain a precursor material; S3, calcining the precursor material to obtain a biochar-based multi-metal modified composite material.

2. The production method according to claim 1, characterized by, The preparation method further comprises the operations of drying, crushing and sieving the biomass before the pyrolysis; And / or, the biomass source comprises agricultural waste, which comprises any one or more of straw, fruit shell and tobacco stem.

3. The production method according to claim 1 or 2, characterized by, The pyrolysis temperature is 690-710℃; And / or, the pyrolysis time is 110-125 min.

4. The method of claim 1, wherein, The Cu 2+ is derived from one or more of copper nitrate, copper sulfate and copper chloride, preferably copper nitrate; and / or, the Co 2+ is derived from one or more of cobalt nitrate, cobalt sulfate and cobalt chloride, preferably cobalt nitrate; and / or, the Zn 2+ is derived from one or more of zinc nitrate, zinc sulfate and zinc chloride, preferably zinc nitrate.

5. The preparation method according to claim 1, characterized in that, the mass ratio of the Cu 2+ and the Co 2+ is (2-7):(3-8), preferably 1:2; and / or the Cu 2+ and the Co 2+ total mass is in the range of 10:(3-8), preferably 5:3, relative to the mass of the Zn 2+ and / or the Cu and / or, the Cu 2+ , Co 2+ , and Zn 2+ total mass of the Cu, Co, and Zn to the mass of the biochar is 13-18:

100.

6. The method of claim 1, wherein, The impregnation is carried out under constant temperature oscillation conditions; Preferably, the constant temperature oscillation temperature is 18-25℃; Preferably, the constant temperature oscillation time is 10-12 h; And / or, the drying temperature is 55-65℃, And / or, the drying time is 10-12 h.

7. The preparation method according to claim 1, characterized in that, The calcination is carried out in a tube furnace under an argon atmosphere; And / or, the calcination temperature is 700-1000℃; And / or, the calcination time is 2-3 h; And / or, the calcination heating rate is 4-7℃ / min.

8. A biochar-based multi-metal modified composite material prepared by the preparation method of any one of claims 1-7.

9. Use of the biochar-based multi-metal modified composite material of claim 8 in catalytic oxidation of volatile organic compounds.

10. A method of catalytic oxidation of volatile organic compounds, characterized by, The method comprises catalytic oxidation of volatile organic compounds at a reaction condition of 240-270℃ using the biochar-based multi-metal modified composite material of claim 8.

Images