Carbon-coal composite functional material, and preparation method and application thereof

Abstract

The application discloses a carbon-coal composite functional material and a preparation method and application thereof. The preparation method of the carbon-coal composite functional material comprises the following steps: 1) pulverizing and sieving lignite and straw; 2) pyrolyzing the straw obtained in the step 1) under an inert atmosphere to obtain a straw biochar material; 3) washing the straw biochar material obtained in the step 2) to neutral with deionized water, air-drying and crushing; and 4) mixing the straw biochar material obtained in the step 3) with the lignite obtained in the step 1) and pyrolyzing under low temperature and oxygen, so that the carbon-coal composite functional material is obtained. The carbon-coal composite functional material is applied to adsorb substances containing NH3 / NH4 + . The modified carbon-coal composite material has the advantages of large specific surface area, dense pore, high humic acid content and rich oxygen-containing functional groups, and has remarkable effects on absorbing NH4 + .

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and relates to a carbon-coal composite functional material, its preparation method and application. Background Technology

[0002] Biochar is a carbon-rich material with a complex microstructure, unique physicochemical properties, and high aromaticity, produced by the thermochemical transformation of various organic waste materials under anaerobic or oxygen-deficient conditions. Biochar prepared from agricultural and forestry biomass waste such as straw and sawdust has become an ideal new type of high-efficiency adsorbent due to its advantages such as large specific surface area, well-developed micropores, and high surface charge density. It is widely used in wastewater treatment, ecological restoration, and environmental protection, and shows great promise in soil improvement, carbon sequestration, and pollutant adsorption and degradation. The combustion of biomass, fossil fuels, pharmaceutical production, and livestock manure treatment all lead to the emission of large amounts of ammonia, which poses a significant threat to human health, animal welfare, and the ecological environment. Existing research has shown that biochar has good adsorption effects on malodorous gases such as ammonia, hydrogen sulfide, and volatile organic compounds. Its mechanism of action is mainly closely related to the specific surface area, microporous structure, and functional group content of biochar. During the preparation of biochar, as the pyrolysis temperature increases, the pore structure of biochar becomes more abundant and the specific surface area becomes larger. However, the number of oxygen-containing functional groups, especially acidic functional groups, on the surface decreases, leading to a reduction in its ability to react with NH3 / NH4+. + The adsorption effect weakens. In practical applications, the adsorption of NH3 / NH4 relies solely on the physical structural properties of biochar. + The adsorption stability is insufficient, therefore, research is needed on combining biochar with suitable functional materials to improve adsorption stability. Lignite is a weakly acidic carbonaceous material with few pores and a small specific surface area, resulting in weak physical adsorption capacity for pollutants. However, its surface contains abundant active groups such as carboxyl, quinone, carbonyl, and methoxy groups, as well as humic acid macromolecules. The functional groups carried on the surface of lignite can interact with NH3 / NH4+. + A chemical reaction occurs to achieve the firm fixation of nitrogen. Therefore, exploring a composite functional material that combines the complementary properties of biochar and lignite, and constructing a highly efficient functional system, is of great significance for solving the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide a coal-biochar composite functional material, its preparation method, and its application. This invention utilizes a mixture of lignite and biochar to prepare the composite functional material, which allows the performance advantages of biochar and lignite to complement each other, thereby improving the utilization value of these two materials.

[0004] This invention provides a method for preparing a biochar and lignite-modified biochar-coal composite functional material. Using agricultural and forestry biomass waste and lignite as raw materials, the biochar and lignite are mixed and modified by low-temperature aerobic pyrolysis to obtain the biochar-coal composite functional material. This composite material exhibits good biocompatibility and complementary performance advantages, overcoming the limitations of single materials. It provides a theoretical basis for the creation of biochar-lignite composite functional materials, achieving efficient utilization of biochar and lignite and reducing pollutants.

[0005] To achieve the above objectives, the present invention provides a method for preparing a coal-carbon composite functional material, comprising the following steps: 1) crushing and sieving lignite and agricultural and forestry biomass waste respectively;

[0006] 2) The agricultural and forestry biomass waste obtained in step 1) is pyrolyzed under an inert atmosphere to obtain biochar material;

[0007] 3) The biochar material is washed with deionized water until neutral, then air-dried and crushed;

[0008] 4) Mix the biochar material treated in step 3) with the lignite treated in step 1) and perform low-temperature aerobic pyrolysis to obtain the biochar-coal composite functional material.

[0009] In this invention, in step 1), the agricultural and forestry biomass waste needs to be air-dried in advance, and the lignite needs to have its pH, sulfur content, and humic acid content measured to ensure that the above raw materials are of qualified quality.

[0010] In the above preparation method, the agricultural and forestry biomass waste is at least one of rice straw, corn straw, wheat straw, soybean straw, rice straw, and tree branches and wood chips;

[0011] The particle size of the lignite sieved can be 0.2–0.5 mm;

[0012] The particle size of the agricultural and forestry biomass waste sieved can be 1-2 mm;

[0013] The biochar material can be sieved to a particle size of 0.2-0.5 mm to ensure uniform mixing with the lignite.

[0014] In the above preparation method, the pyrolysis process is as follows: the agricultural and forestry biomass waste obtained in step 1) is placed in a tubular furnace through which the inert gas is passed, and the temperature is raised to 550-650°C at a rate of 5-10°C / min, and pyrolyzed for 1-2 hours to obtain the biochar material; specifically, the heating rate can be 10°C / min, the pyrolysis temperature can be 600°C, and the pyrolysis time can be 2 hours.

[0015] The inert gas includes nitrogen.

[0016] In this invention, the biochar material prepared by pyrolysis in step 2) is alkaline. If it is directly blended with the lignite in the future, it will affect the content of acidic functional groups in the lignite. Therefore, the biochar material needs to be cleaned in step 3).

[0017] In the above preparation method, in step 4), the mass ratio of the biochar material to the lignite can be 1:0.5 to 2, specifically 1:1, 1:0.5 to 1, or 1:1 to 2.

[0018] In the above preparation method, in step 4), the temperature is raised to 175-250°C at a heating rate of 5-10°C / min before the low-temperature pyrolysis is carried out; specifically, the heating rate can be 10°C / min.

[0019] The conditions for the low-temperature pyrolysis are as follows: pyrolysis is performed under aerobic conditions, with a temperature of 175–250℃ (specifically 225℃, 175–225℃, or 225–250℃) and a time of 0.5–2h (specifically 2h or 1–2h).

[0020] In the above preparation method, step 4) further includes crushing and sieving after low-temperature pyrolysis; wherein the sieved particle size can be 0.2-0.5 mm to facilitate mixing with NH4. + The adsorption reaction occurs through full contact.

[0021] The present invention also provides a carbon-coal composite functional material prepared by the above preparation method.

[0022] The carbon-coal composite functional material of the present invention is used for adsorbing NH3 / NH4. + In the substance.

[0023] In this invention, the coal-carbon composite functional material can be applied to wastewater treatment, ecological restoration, environmental protection, biomass combustion, fossil fuel combustion, pharmaceutical production, and livestock manure treatment, as well as other applications involving or producing NH3 / NH4. + In the materials containing pollutants.

[0024] The present invention further provides a method for removing NH4 from solution using the above-mentioned carbon-coal composite functional material. + The method includes the following steps:

[0025] The coal-carbon composite functional material is added to a substance containing NH4. + The solution is reacted and then filtered to remove NH4 from the solution. + .

[0026] In the above method, the NH4-containing + NH4 in solution + The concentration can be 0.001–0.02 mol / L;

[0027] The reaction temperature is room temperature, and the reaction time can be 20 to 24 hours, specifically 24 hours.

[0028] The filtration uses a nylon filter, and the pore size of its filter membrane can be 0.4 to 0.5 μm, specifically 0.45 μm.

[0029] The present invention has the following beneficial effects:

[0030] 1. This invention uses agricultural and forestry biomass waste (specifically rice straw) and lignite as raw materials, mixes them evenly in an appropriate ratio, and prepares a modified coal composite material with large specific surface area, dense pores, high humic acid content, and rich oxygen-containing functional groups by low-temperature pyrolysis under aerobic conditions.

[0031] 2. The biochar and lignite-modified biochar-coal composite functional materials prepared by this method are micron-sized. Specifically, the modified biochar-coal composite functional material prepared from rice straw and lignite at a 1:1 ratio, 225℃, and 2h has a pore size of approximately 0.6–1.8 μm and a micropore area of ​​approximately 0.3–1.7 μm². 2 It has abundant pores, a relatively uniform distribution, and a strong adsorption and loading capacity for NH4. + It has a synergistic reduction effect, realizing the synergistic effect of straw and lignite, harmless treatment and resource utilization.

[0032] 3. The biochar and lignite-modified biochar-coal composite functional material of the present invention has no negative impact on the adsorption performance of biochar due to lignite. In a specific example, biochar material and lignite are compounded in a 1:1 ratio for NH4 absorption. + Significant effects, particularly on NH4 + The adsorption rate reached 20.81%. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the biochar material prepared in Example 1 of the present invention, wherein... Figure 1 Images (a)-(c) are scanning images obtained under electron microscopes with magnifications of ×10μm, ×1μm, and ×500nm, respectively.

[0034] Figure 2 Here is a scanning electron microscope image of the lignite material prepared in Example 1 of this invention, wherein... Figure 2 Images (a)-(c) are scanning images obtained under electron microscopes with magnifications of ×10μm, ×1μm, and ×500nm, respectively.

[0035] Figure 3 This is a scanning electron microscope (SEM) image of the modified coal-carbon composite functional material prepared in Example 1 of this invention, wherein... Figure 3Images (a)-(c) are scanning images obtained under electron microscopes with magnifications of ×10μm, ×1μm, and ×500nm, respectively.

[0036] Figure 4 The modified carbon-coal composite functional material prepared in Example 1 of this invention adsorbs NH4. + Scanning electron microscope images, in which Figure 4 Images (a)-(c) are scanning images obtained under electron microscopes with magnifications of ×10μm, ×1μm, and ×500nm, respectively. Detailed Implementation

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0038] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0039] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and tables, through specific embodiments.

[0040] Example 1

[0041] The method for preparing the carbon-coal composite functional material provided in this embodiment includes the following steps:

[0042] (1) A certain amount of dried, chopped, and sieved rice straw (1.0–2.0 mm) was placed in a tube furnace and heated to 600°C at a rate of 10°C / min under nitrogen protection. The mixture was pyrolyzed for 2 hours, then washed with deionized water. The resulting product was dried in an oven to obtain rice straw biochar. Figure 1 The image shown is a scanning electron microscope (SEM) image of the prepared rice straw biochar. The prepared biochar has a large number of pores and a rich microporous structure on its surface. The pore size of the prepared biochar material is 1.0–3.0 μm, and the micropore area is 0.7–2.5 μm². 2 .like Figure 2 The image shown is a scanning electron microscope (SEM) image of lignite. The surface porosity of lignite is much smaller than that of straw biochar, and the pore structure is poor, with pore sizes ranging from 0.5 to 1.5 μm and micropore areas of 0.5–1.5 μm. 2 .

[0043] (2) Biochar material was composite-modified with lignite in a 1:1 ratio. 40g of rice straw biochar and 40g of lignite were weighed, mixed evenly, and transferred to a forced-air drying oven for low-temperature pyrolysis at 225℃ for 2 hours under aerobic conditions. After the reaction, the material was cooled to room temperature (25℃) to obtain a dry, blocky biochar-lignite composite functional material. This material was then crushed in an airtight sealed bag and passed through a 60-mesh sieve to obtain powdered biochar-lignite modified biochar-lignite composite functional material, such as… Figure 3The images show scanning electron microscope (SEM) images of biochar and lignite-modified coal-carbon composite functional materials. As can be seen from the images, the prepared coal-carbon composite material has a rough surface, abundant binding sites for easy adsorption and adhesion, and a large number of irregularly shaped micropores. Compared with biochar materials, the pores are more densely packed, and the complex micropore surface structure is evident, likely due to the large number of functional group binding sites generated during low-temperature aerobic pyrolysis. The pore size of the prepared material ranges from 0.6 to 1.8 μm, and the micropore area is approximately 0.3 to 1.7 μm². 2 .

[0044] (3) Using biochar and lignite-modified coal composite functional materials for NH4 adsorption + ,like Figure 4 To improve the adsorption of NH4 by modified coal-carbon composite functional materials + The subsequent scanning electron microscope image shows that the prepared adsorbed NH4 + The composite material after the process showed a significant change in surface pores, transforming from an irregular shape to a regular elliptical shape, thus improving its ability to adsorb NH4. + The pore size of the subsequent material is 0.3–1.0 μm, and the micropore area is approximately 0.2–0.9 μm². 2 Compared to before adsorption, the pore size and micropore area of ​​the material were reduced, the material's structural roughness decreased, and particulate matter was attached to the surface, proving that NH4... + It undergoes an adsorption reaction with modified coal-carbon composite functional materials.

[0045] (4) Table 1 shows the comparison of the adsorption of NH4 by biochar, lignite, biochar-coal composite functional materials, and biochar-coal composite functional materials. + Subsequent elemental changes in each material, followed by composite modification, resulted in a coal-carbon composite functional material and an adsorbent for NH4. + The sulfur (S) content gradually decreased after the reaction, proving that low-temperature pyrolysis and adsorption reactions facilitated S removal. The N, C, H, and O contents of the modified coal-carbon composite material were essentially the median of those of the biochar and lignite materials, demonstrating good compatibility between the two materials during the low-temperature aerobic pyrolysis modification process. The biochar and lignite-modified coal-carbon composite material exhibited good adsorption of NH4. + The significant increase in N and H content afterwards proves that NH4 + Successfully attached to biochar and lignite modified coal composite functional materials.

[0046] Table 1. Adsorption of NH3 by biochar, lignite, biochar-coal composite functional materials, and biochar-coal composite functional materials. 4+ Elemental analysis

[0047]

[0048] Example 2

[0049] This embodiment is based on embodiment 1, except that in step (2), the biochar and lignite are changed to a single biochar.

[0050] Example 3 This example is based on Example 1, except that in step (2), biochar and lignite are changed to lignite alone.

[0051] Example 4

[0052] This embodiment is based on embodiment 1, except that the rice straw biochar in step (1) is replaced with corn straw biochar.

[0053] Example 5

[0054] This embodiment is based on embodiment 1, with the temperature of the low-temperature decomposition in step (3) adjusted to 175°C.

[0055] Example 6

[0056] This embodiment is based on embodiment 1, with the temperature of the low-temperature decomposition in step (3) adjusted to 200°C.

[0057] Example 7

[0058] This embodiment is based on embodiment 1, with the temperature of the low-temperature decomposition in step (3) adjusted to 250°C.

[0059] Example 8

[0060] This embodiment is based on embodiment 1, except that the ratio of straw biochar to lignite in step (3) is changed from 1:1 to 1:2.

[0061] Example 9

[0062] This embodiment is based on embodiment 1, except that the ratio of straw biochar to lignite in step (3) is changed from 1:1 to 2:1.

[0063] Example 10

[0064] This embodiment is based on embodiment 1, but the low-temperature pyrolysis in step (3) is adjusted from 2h to 0.5h.

[0065] Example 11

[0066] This embodiment is based on embodiment 1, but the low-temperature pyrolysis in step (3) is adjusted from 2h to 1h.

[0067] Example 12

[0068] This embodiment is based on embodiment 1, but the low-temperature pyrolysis in step (3) is adjusted from 2h to 1.5h.

[0069] Example 13

[0070] The materials prepared in Examples 1-12 above were used to remove NH3 / NH4. + The solution is as follows:

[0071] Adsorption of NH4 + Experiment: The functional materials prepared in Examples 1-12 were added to conical flasks containing NH4Cl solutions of the same concentration, and the effect of the modified carbon-coal composite functional materials on NH4Cl was measured. + Adsorption capacity. The solution was placed in a constant-temperature shaker at 100 rpm for 24 hours. After filtration through a 0.45 μm nylon filter, the remaining NH4+ in the solution was measured. + The concentration of NH4. The materials prepared in Examples 1-12 have a certain effect on NH4. + The adsorption effect is shown in Table 2.

[0072] Table 2. Effects of various materials on NH4 under different conditions. + Adsorption results

[0073]

[0074] The analysis of the above adsorption effects fully demonstrates that the biochar and lignite-modified biochar-coal composite functional material improves the adsorption capacity of the single material for NH4. + Regarding the adsorption effect, under the same conditions and considering only the effect of pyrolysis time, the differences in adsorption effects after pyrolysis for 1 h, 1.5 h, and 2 h are small. Considering time costs, no further studies on longer pyrolysis times were conducted. The optimal preparation process conditions obtained in this invention are a biochar to lignite composite ratio of 1:1, a low-temperature pyrolysis temperature of 225℃, and a reaction time of 2 h.

[0075] The biochar and lignite-modified coal composite functional material prepared by this invention has the characteristics of abundant pores, complex microporous structure, rough surface, and easy contact adsorption, which makes up for the shortcomings of biochar, such as few oxygen-containing functional groups, and lignite, such as fewer pores and smooth surface. The biochar and lignite-modified coal composite functional material uses biochar and lignite as raw materials, which are abundant and readily available, and promotes the resource utilization of agricultural and forestry biomass waste and lignite.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Use of carbon-coal composite functional material in the preparation of adsorbent for substances containing NH3 / NH4 + . The preparation method of the carbon coal composite functional material comprises the following steps: 1) pulverizing and sieving lignite and forestry and agricultural biomass waste respectively; the forestry and agricultural biomass waste is rice straw; 2) pyrolyzing the forestry and agricultural biomass waste obtained in step 1) under inert atmosphere to obtain a biochar material; 3) washing the biochar material with deionized water until neutral, then air-drying and crushing; 4) mixing the biochar material obtained in step 3) with the lignite obtained in step 1) and pyrolyzing under low temperature and in the presence of oxygen to obtain the carbon coal composite functional material; The mass ratio of the biochar material to the lignite is 1:1; The pyrolyzing under low temperature and in the presence of oxygen is performed after the temperature is raised to 225 DEG C at a temperature raising rate of 5-10 DEG C / min; The pyrolyzing under low temperature and in the presence of oxygen is performed under the following conditions: pyrolyzing under the presence of oxygen, temperature is 225 DEG C, and time is 0.5-2 h.

2. Use according to claim 1, characterized in that, The particle size of the lignite after sieving is 0.2-0.5 mm; The particle size of the forestry and agricultural biomass waste after sieving is 1.0-2.0 mm; The particle size of the biochar material after sieving is 0.2-0.5 mm.

3. Use according to claim 1 or 2, characterized in that, The pyrolyzing is performed as follows: the forestry and agricultural biomass waste obtained in step 1) is put into a pipe furnace filled with the inert gas, the temperature is raised to 550-650 DEG C at a temperature raising rate of 5-10 DEG C / min, and pyrolyzing is performed for 1-2 h to obtain the biochar material; The inert gas comprises nitrogen.

4. Use according to claim 1 or 2, characterized in that, The pyrolyzing under low temperature and in the presence of oxygen in step 4) further comprises the steps of crushing and sieving; the particle size after sieving is 0.2-0.5 mm.

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