Pyrrhotite coupled biochar material and preparation method thereof

Abstract

The invention relates to the technical field of biochar materials, in particular to a pyrrhotite coupled biochar material and a preparation method thereof. Comprising the following components in percentage by weight: 20-30% of nitrogen-oxygen doped carbon skeleton modified charcoal, 8-15% of attapulgite, 21-28% of pyrrhotite and the balance of methyl methacrylate, the preparation method of the nitrogen-oxygen-doped carbon skeleton modified biochar comprises the following steps: S1, dissolving transition metal salt and an imidazole compound in a solvent, uniformly mixing, and carrying out co-pyrolysis to obtain a precursor; s2, crushing a biomass material, performing carbonization treatment, and performing acid pickling to obtain a biochar material; and S3, mixing and grinding the precursor, the biochar material and an activator, and carrying out an activation reaction in ammonia and oxygen atmospheres to obtain the nitrogen-doped carbon skeleton modified biochar.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biochar materials, more particularly, it relates to a magnetite pyrite coupled biochar material and a preparation method thereof. BACKGROUND

[0002] Magnetic (magnetic pyrite) coupled biochar materials are a new type of functional composite material that has attracted much attention in recent years. Due to its unique magnetic properties, high specific surface area, porous structure and rich surface functional groups, it is widely used in environmental remediation, wastewater treatment, pollutant removal and other fields.

[0003] The preparation of magnetite pyrite coupled biochar materials usually includes the combination of magnetite pyrite (FeS), biochar and surface modification technology, and the core goal is to optimize the magnetic properties, adsorption performance and chemical reaction activity of the material. Biochar is usually derived from agricultural biomass (such as sawdust, sawdust, crop straw, rice husk, etc.) by pyrolysis; magnetite pyrite can be obtained by natural mineral extraction or chemical synthesis (such as iron sulfide precipitation).

[0004] In the current preparation technology, magnetite pyrite coupled biochar materials, especially when modified biochar and attapulgite are introduced, although they show good application prospects in environmental remediation (such as heavy metal adsorption, organic pollutant degradation), catalysis, energy storage and other fields, there are still some technical defects or challenges. Although the modification process can improve the specific surface area and active sites of the biochar, some functional groups (such as -COOH, -OH) are prone to desorption or decomposition in complex water environments, resulting in performance degradation. Attapulgite is a natural one-dimensional nanorod silicate mineral, which is prone to aggregation in aqueous or composite systems due to hydrogen bonding or van der Waals forces, reducing its effective specific surface area and reaction activity. When modified biochar, magnetite pyrite and attapulgite are physically mixed, the interface interaction (such as chemical bonding, electron transfer) is insufficient, which is prone to component peeling during use, affecting the structural integrity and cycle stability. SUMMARY

[0005] The present application provides a magnetite pyrite coupled biochar material and a preparation method thereof. The nitrogen and oxygen doped in the prepared magnetite pyrite coupled biochar material improves the surface active sites, attapulgite provides high specific surface area and ion exchange, magnetite pyrite contributes to magnetic separation and redox, and methyl methacrylate ensures structural stability, forming a synergistic effect of high specific surface area, rich functional groups, magnetic recyclability and mechanical robustness.

[0006] In a first aspect, the present application provides a magnetite pyrite coupled biochar material, comprising the following weight percentage components: 20-30% nitrogen and oxygen doped carbon skeleton modified biochar, 8-15% attapulgite, 21-28% magnetite pyrite, and the balance is methyl methacrylate; The preparation method of the nitrogen-oxygen doped carbon skeleton modified biochar comprises the following steps: S1, dissolving a transition metal salt and an imidazole compound in a solvent, uniformly mixing, and then co-pyrolyzing to obtain a precursor; S2, crushing and carbonizing a biomass material, and then acid washing to obtain a biochar material; S3, mixing and grinding the precursor, the biochar material, and an activating agent, and performing an activation reaction in an ammonia and oxygen atmosphere to obtain a nitrogen-doped carbon skeleton modified biochar.

[0007] Preferably, the transition metal salt is at least one of a halide salt, a nitrate salt, an acetate salt, and a phosphate salt.

[0008] Preferably, the transition metal is at least one of Zn, Co, Ni, Cu, Mn, Cr, V, Ce, Ag, Mo, and W.

[0009] Preferably, the imidazole compound is at least one of 2-methyl imidazole, 4-methyl imidazole, 2-ethyl imidazole, 2-phenyl imidazole, and 1-ethyl-3-methyl imidazolium salt.

[0010] Preferably, the solvent is at least one of methanol, ethanol, DMA, DEF, and NMP; the biomass material is at least one of coconut shell, bamboo, sugarcane, and rice husk; and the activating agent is at least one of sulfuric acid, oxalic acid, sodium carbonate, and sodium hydroxide.

[0011] Preferably, the co-pyrolysis temperature is 600-900℃, and the time is 4-5h.

[0012] Preferably, the activation reaction temperature is 1500-2500℃, the temperature rising rate is 5-25℃ / min, and the activation time is 6-7h.

[0013] Preferably, the molar ratio of the precursor, the biochar material, and the activating agent is 2-5:1-3:1.

[0014] In a second aspect, the application provides a preparation method of a pyrrhotite coupled biochar material, comprising the following steps: (1) drying nitrogen-oxygen doped carbon skeleton modified biochar, attapulgite, pyrrhotite, and methyl methacrylate, and then mixing under constant temperature stirring in an ultrasonic wave; (2) performing mold forming to obtain a pyrrhotite coupled biochar material.

[0015] In a third aspect, the application provides an application of a pyrrhotite coupled biochar material, and the pyrrhotite coupled biochar material is applied as an adsorption material in sewage treatment.

[0016] In summary, the present application has the following beneficial effects: The nitrogen and oxygen doped in the pyrrhotite coupled biochar material in the present application improves the surface active sites, the attapulgite provides high specific surface area and ion exchange, the pyrrhotite contributes to magnetic separation and redox, and the methyl methacrylate ensures structural stability, forming a synergistic effect of high specific surface area, rich functional groups, magnetic recyclability and mechanical robustness. The pyrolysis process can produce nitrogen source during the cracking of the imidazole ring, and the metal ions can quickly coordinate with the nitrogen source to directly generate M-N-C type active centers, thereby eliminating the need for subsequent nitrogen doping or high-temperature nitriding steps. The co-pyrolysis process can realize uniform mixing of raw materials, in-situ generation of metal-nitrogen coordination sites, metal atomic dispersion, and construction of high specific surface area porous structure in one heat treatment.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the protection scope of the present application. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below in conjunction with examples, and it is particularly pointed out that: in the following examples, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following examples can be obtained from ordinary market sales unless otherwise specified.

[0019] The inventors found that in the current preparation technology, the uneven distribution of pyrrhotite particles on the surface of biochar would lead to unstable performance. The pyrrhotite particles on the surface of biochar are prone to agglomeration, which leads to a decrease in specific surface area and blockage of pores, thereby weakening the availability of adsorption sites.

[0020] In view of the above problems, the present application provides a pyrrhotite coupled biochar material, which comprises the following weight percentage components: 20-30% nitrogen and oxygen doped carbon skeleton modified biochar, 8-15% attapulgite, 21-28% pyrrhotite, and the balance is methyl methacrylate; The preparation method of the nitrogen and oxygen doped carbon skeleton modified biochar comprises the following steps: S1, dissolving a transition metal salt and an imidazole compound in a solvent, uniformly mixing, and then co-pyrolyzing to obtain a precursor; S2, crushing and carbonizing the biomass material, then acid washing to obtain a biochar material; S3, mixing and grinding the precursor with the biochar material and an activating agent, and performing an activation reaction in an ammonia and oxygen atmosphere to obtain a nitrogen doped carbon skeleton modified biochar.

[0021] In some embodiments, the nitrogen-oxygen co-doped porous biochar has a significant specific surface area increase, providing a large space for adsorption sites. Further, with the introduction of a large number of polar groups such as carboxyl, hydroxyl, amine groups, N and O heteroatoms provide a large number of functional groups, enhancing the electrostatic adsorption and coordination ability to organic pollutants and metal ions. Further, the electrical conductivity and catalytic activity are improved, nitrogen doping can increase the electronic density and defect sites of carbon materials, significantly improve the electrical conductivity and redox performance, making it perform better in electrochemical degradation and catalytic reaction. Further, it has the ability of multifunctional adsorption and degradation. In the advanced oxidation system of ozone, persulfate, etc., N-C biochar can efficiently catalyze the generation of active oxygen, and improve the degradation rate of organic pollutants such as drug residues.

[0022] In some embodiments, the attapulgite has a natural high specific surface area and microporous structure. After compounding with biochar, the attapulgite converts the layered structure of biochar into a loose porous network, significantly increases the pore volume and pore size distribution of the material, and improves the slow-release of nutrients and the capture efficiency of pollutants. It can be further used in nutrient slow-release and soil improvement. Attapulgite-biochar composite material can realize long-term and stable release of nitrogen and phosphorus, significantly improve fertilizer utilization rate and reduce environmental loss. It also has ion exchange and adsorption selectivity. The silicon-aluminum layer structure of attapulgite itself provides strong ion exchange sites, further enhancing the fixation effect of heavy metals such as Cd and Zn.

[0023] In some embodiments, the pyrrhotite has the characteristics of magnetic separation. Pyrrhotite endows the composite material with strong magnetic response. Using an external magnetic field, fast solid-liquid separation can be achieved, reducing the cost of post-processing. It also has redox activity. FeS2 can produce active sulfide and Fe 2+ / Fe 3+ in the presence of oxygen, realizing synergistic adsorption, reduction precipitation and chemical complexation of heavy metal ions, phosphorus and organic pollutants such as TCE and Cr(VI), with a removal efficiency significantly higher than that of single biochar or single pyrite. It also has a uniform dispersion structure. In the FeS2@BC composite material prepared by ball milling, pyrite particles are uniformly distributed on the surface of the carbon skeleton, preventing agglomeration and improving the accessibility of active sites. It also has the advantages of low cost and environmental friendliness. Pyrite is abundant and has low mining cost. Combined with biochar, it realizes cost control and environmental friendliness of the material.

[0024] In some embodiments, methyl methacrylate (PMMA) is used as a polymer binder, which forms a continuous polymer matrix in the composite material, firmly binding FeS2, attapulgite and doped biochar, and significantly improving the overall mechanical strength and structural integrity. It can prevent particles from falling off and leaking in the composite material, and the polymer network encapsulation can inhibit the wear and tear of metal mineral particles during use, ensuring the long-term stability and safety of magnetic particles. It can also adjust the hydrophilic and hydrophobic properties. The hydrophobic properties of PMMA provide a waterproof layer for the material, reducing the excessive swelling of the carbon skeleton in water, maintaining the stability of the pore structure, and thus improving the adsorption cycle life. Further improve the processability, through free radical polymerization or in-situ polymerization, PMMA can be uniformly poured at low temperature, which is convenient for large-scale preparation of shaped blocks, particles or films, and is suitable for practical engineering applications.

[0025] In some embodiments, the advantages of multifunctional adsorption and catalysis are achieved, nitrogen and oxygen doping improves the surface active site, attapulgite provides high specific surface area and ion exchange, and pyrrhotite contributes to magnetic separation and redox. PMMA guarantees the structural stability, forming a synergistic effect of high specific surface area, rich functional groups, magnetic recyclability and mechanical firmness. It can be quickly separated by magnetic field, and the magnetism of pyrrhotite enables the material to be quickly recycled after water treatment, reducing the risk of secondary pollution. Further, it can release nutrients and pollutants efficiently, and the pore network of attapulgite-biochar can release nutrients slowly, while simultaneously removing various pollutants such as heavy metals, phosphorus and dyes. It is also environmentally friendly and cost-effective, as the raw materials are derived from waste biomass, natural minerals and low-cost pyrite, and the preparation process (ball milling or one-step method) is simple, meeting the requirements of green and sustainable development.

[0026] In some embodiments, the temperature of co-pyrolysis is 600-900℃, which can be one of 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃ or a range value of any two of them. The time is 4-5h, which can be one of 4h, 4.5h, 5h or a range value of any two of them. Co-pyrolysis enables metal ions and imidazole ligands to decompose and interact simultaneously in the same pyrolysis environment, forming metal-imidazole coordination complexes, avoiding the risk of metal precipitation or agglomeration in the later stage. The co-pyrolysis process can realize uniform mixing of raw materials, in-situ generation of metal-nitrogen coordination sites, metal atomic dispersion and construction of high specific surface area porous structure in one heat treatment.

[0027] In some embodiments, the temperature of the activation reaction is 1500-2500 °C, which can be one of 1500 °C, 1600 °C, 1700 °C, 1800 °C, 1900 °C, 2000 °C, 2100 °C, 2200 °C, 2300 °C, 2400 °C, 2500 °C or a range value of any two of them. The heating rate is 5-25 °C / min, which can be one of 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min or a range value of any two of them. The activation time is 6-7 h, which can be one of 6 h, 6.5 h, 7 h or a range value of any two of them.

[0028] In some embodiments, the precursor is prepared: 0.5 mol Zn(NO3)2·6H2O and 1.0 mol 2-methylimidazole are dissolved in 200 mL ethanol, stirred for 30 min. Rotary evaporation to dryness to obtain a solid precursor. In a tube furnace, 5 °C / min -1 Ramp to 400 °C, hold for 2 h under argon protection.

[0029] In some embodiments, the biochar is prepared: 100 g of rice husk is crushed to <250 µm, dried at 105 °C for 12 h. In a tube furnace, 10 °C / min -1 Ramp to 750 °C, hold for 1.5 h. Soak in 6 M HCl for 12 h, wash to neutral, dry to obtain BC.

[0030] In some embodiments, the activation and doping: 10 g of the precursor, 30 g of BC and 20 g of KOH are ball-milled for 30 min. The mixture is loaded into a quartz tube, 200 mL / min -1 and O2 240 mL / min -1 , 5 °C / min -1 Ramp to 1600 °C, hold for 1 h. After cooling, wash with deionized water to pH = 7, dry at 125 °C for 12 h.

[0031] The specific surface area of the N, O-doped carbon skeleton modified biochar is 1500 m 2 g -1 , the N content is 5 wt%.

[0032] Embodiment Embodiment 1 A pyrrhotite-coupled biochar material, comprising the following weight percentage components: 20% N, O-doped carbon skeleton modified biochar, 8% attapulgite, 21% pyrrhotite, and the balance is methyl methacrylate.

[0033] A method for preparing a pyrrhotite-coupled biochar material, comprising the following steps: (1) After drying the nitrogen-oxygen doped carbon skeleton modified biochar, attapulgite, pyrrhotite and methyl methacrylate, the drying temperature is 80℃, the drying time is 12h, and the constant temperature stirring mixing is carried out in the ultrasonic wave bath of 40kHz, 300W, the temperature is set to 25℃ (constant temperature water bath), and the ultrasonic wave is 1h; (2) The mold pressing is carried out, the pressure is 10MPa, the temperature is 150℃, and the heat preservation is 1h. The pyrrhotite coupled biochar material is obtained.

[0034] Example 2 A pyrrhotite coupled biochar material comprises the following weight percentage components: 25% nitrogen-oxygen doped carbon skeleton modified biochar, 12% attapulgite, 25% pyrrhotite, and the balance is methyl methacrylate.

[0035] A preparation method of a pyrrhotite coupled biochar material comprises the following steps: (1) After drying the nitrogen-oxygen doped carbon skeleton modified biochar, attapulgite, pyrrhotite and methyl methacrylate, the drying temperature is 80℃, the drying time is 12h, and the constant temperature stirring mixing is carried out in the ultrasonic wave bath of 40kHz, 300W, the temperature is set to 25℃ (constant temperature water bath), and the ultrasonic wave is 1h; (2) The mold pressing is carried out, the pressure is 10MPa, the temperature is 150℃, and the heat preservation is 1h. The pyrrhotite coupled biochar material is obtained.

[0036] Example 3 A pyrrhotite coupled biochar material comprises the following weight percentage components: 30% nitrogen-oxygen doped carbon skeleton modified biochar, 15% attapulgite, 28% pyrrhotite, and the balance is methyl methacrylate.

[0037] A preparation method of a pyrrhotite coupled biochar material comprises the following steps: (1) After drying the nitrogen-oxygen doped carbon skeleton modified biochar, attapulgite, pyrrhotite and methyl methacrylate, the drying temperature is 80℃, the drying time is 12h, and the constant temperature stirring mixing is carried out in the ultrasonic wave bath of 40kHz, 300W, the temperature is set to 25℃ (constant temperature water bath), and the ultrasonic wave is 1h; (2) The mold pressing is carried out, the pressure is 10MPa, the temperature is 150℃, and the heat preservation is 1h. The pyrrhotite coupled biochar material is obtained.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that attapulgite is not added.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that nitrogen-oxygen doped carbon skeleton modified biochar is not added.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that the nitrogen- oxygen doped carbon skeleton modified biochar is replaced by ordinary biochar.

[0041] Table 1 Performance test results

[0042] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A pyrrhotite-coupled biochar material, characterized in that, Includes the following components by weight percentage: 20-30% nitrogen-oxygen doped carbon skeleton modified biochar, 8-15% attapulgite, 21-28% pyrrhotite, balance methyl methacrylate; The method for preparing the nitrogen-oxygen-doped carbon framework modified biochar includes the following steps: S1. Dissolve the transition metal salt and imidazole compound in a solvent, mix them evenly, and then perform co-pyrolysis to obtain the precursor; S2. After crushing the biomass material, carbonize it and then acid wash it to obtain biochar material; S3. The precursor is mixed and ground with the biochar material and activator, and activated in an atmosphere of ammonia and oxygen to obtain nitrogen-doped carbon framework modified biochar.

2. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The transition metal salt is selected from at least one of halides, nitrates, acetates, and phosphates.

3. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The transition metal is selected from at least one of Zn, Co, Ni, Cu, Mn, Cr, V, Ce, Ag, Mo, and W.

4. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The imidazole compound is selected from at least one of 2-methylimidazolium, 4-methylimidazolium, 2-ethylimidazolium, 2-phenylimidazolium, and 1-ethyl-3-methylimidazolium salt.

5. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The solvent is selected from at least one of methanol, ethanol, DMA, DEF, and NMP; the biomass material is selected from at least one of coconut shell, bamboo, sugarcane, and rice husk; and the activator is selected from at least one of sulfuric acid, oxalic acid, sodium carbonate, and sodium hydroxide.

6. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The co-pyrolysis temperature is 600-900℃, and the time is 4-5h.

7. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The activation reaction is carried out at a temperature of 1500-2500℃, a heating rate of 5-25℃ / min, and an activation time of 6-7h.

8. The pyrrhotite-coupled biochar material according to claim 1, characterized in that, The molar ratio of the precursor to biochar material and activator is 2-5:1-3:

1.

9. The method for preparing pyrrhotite-coupled biochar material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) After drying the nitrogen-oxygen-doped carbon skeleton modified biochar, attapulgite, pyrrhotite and methyl methacrylate, they were mixed by constant temperature stirring in an ultrasonic environment. (2) Molding is performed to obtain pyrrhotite coupled biochar material.

10. The application of the pyrrhotite-coupled biochar material according to any one of claims 1-8, characterized in that, The application of the pyrrhotite-coupled biochar material as an adsorbent in wastewater treatment.

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