A preparation method of wool-based nitrogen-doped magnetic biochar material

Abstract

The present invention discloses a method for preparing a wool-based nitrogen-doped magnetic biochar material. First, the wool after impurities and scales are immersed in a ferric chloride solution for coordination reaction to obtain a wool / iron complex; then melamine, a metal salt and the wool / iron complex are added to deionized water, sealed to form a closed environment, and then shaken to evenly disperse the metal salt and melamine on the surface of the wool; after being taken out and dried to anhydrous, a mixture of metal salt / melamine / wool is obtained; then the mixture is placed in an oxygen-free environment for carbonization, and the metal salt and impurities in the product are removed; after drying, a wool-based nitrogen-doped magnetic biochar material is obtained. The present invention uses wool to prepare a magnetic biochar material loaded with magnetic nanoparticles. The material has excellent adsorption and adsorption-catalytic effects on complex mixed dye liquors, achieving catalytic-adsorption synergistic integration, and has superparamagnetism. Solid-liquid separation and recovery can be achieved by setting an external magnetic field.

Description

Technical Field

[0001] The invention belongs to the field of adsorption materials and relates to magnetic biochar materials, in particular to a method for preparing a wool-based nitrogen-doped magnetic biochar material. Background Art

[0002] The sources of chemical pollutants in textile printing and dyeing wastewater are diverse, ranging from chemical fiber materials, spinning slurries, dyes, and chemicals to laundry wastewater, mercerizing wastewater, and post-combing wastewater. Generally speaking, this type of industrial wastewater is characterized by severe pollution, a wide variety of substances, strong alkalinity, high toxicity, and high color. Therefore, research on the treatment of printing and dyeing wastewater is particularly important.

[0003] At present, the commonly used printing and dyeing wastewater treatment technologies at home and abroad are: (1) Physical membrane separation method: This method has the advantages of low reaction temperature requirements, good selectivity for separation targets, material separation at the molecular level, low mass transfer energy consumption, and strong adaptability. The disadvantages are, for example, poor membrane strength, short service life, and easy contamination of the membrane during industrial reactions, which affects the separation efficiency. (2) Photocatalytic method: This method has good decolorization effect, no large amount of sludge is produced, good sterilization effect, and low operating costs, but the high one-time investment cost and installation difficulties are problems that need to be solved urgently. (3) Adsorption method: This method uses the adsorption capacity of porous solid substances to remove certain pollutants, suspended matter, colloids and dissolved organic matter in sewage. It is simple, efficient, easy to operate, low-cost, does not require the addition of any chemicals, has no secondary pollution and controllable adsorption capacity, can produce good economic and environmental benefits, and has broad development and application prospects.

[0004] Element doping is a method of replacing carbon atoms in the carbon lattice with other heteroatoms (such as N, B, P, S, etc.), which essentially changes the crystal structure of the carbon material and thus changes its surface energy state and chemical activity. Nitrogen has similar chemical properties to carbon and is easier to combine with. When nitrogen atoms are doped into the interior of the carbon material, the nitrogen atoms can replace the carbon atoms in the carbon material, and the extra electron of the nitrogen atom can be sp 2 The π electrons in the hybridized carbon skeleton provide electrons, which not only enhances the carbon n - It can not only improve the conductivity of the carbon material, but also enhance the hydrophilicity and surface activity of the carbon material by improving the surface structure, so that the nitrogen-doped carbon material has better physical and chemical properties.

[0005] Molten salt synthesis is a novel synthesis method that has emerged in recent years. It typically uses one or more low-melting-point salts as the reaction medium. The reactants have a certain solubility in the molten salt, allowing the reaction to proceed at the atomic level. After the reaction is complete, the salts are dissolved in a suitable solvent and filtered and washed to obtain the synthesized product. Molten salt is an ionic medium with high ionic conductivity, a wide electrochemical window, and strong dissolving power.

[0006] Currently, researchers primarily focus on cellulose as a precursor for biochar production. However, biochar produced from cellulose biomass undergoes severe pyrolysis and polycondensation during high-temperature pyrolysis, leading to partial pore blockage. Furthermore, cellulose biochar exhibits poor mechanical strength, electrical conductivity, and chemical stability. Compared to cellulose biochar, protein biochar offers a more stable structure. Proteins are also rich in heteroatoms such as nitrogen and sulfur, which enhance the adsorption and catalytic properties of biochar. Protein molecules contain a variety of functional groups, which enhance the chemical activity of these groups. Furthermore, proteins have a low carbon-to-nitrogen ratio, resulting in fewer volatiles during pyrolysis, thus minimizing pollution. Wool is a common natural protein fiber with a rich elemental composition. In addition to carbon, it also contains significant amounts of nitrogen and sulfur. However, there are currently no reports on using wool as a precursor to produce biochar that overcomes the limitations of existing biochar. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a wool-based nitrogen-doped magnetic biochar material.

[0008] The technical solution of the present invention to solve the technical problem is to provide a method for preparing a wool-based nitrogen-doped magnetic biochar material, characterized in that the method comprises the following steps:

[0009] Step 1, removing impurities from the wool to obtain the removed wool;

[0010] Step 2: removing the scale layer on the surface of the wool after the impurities are removed in step 1 to obtain descaled wool;

[0011] Step 3, immersing the descaled wool in step 2 in a ferric chloride solution to carry out a coordination reaction, taking out the wool after the reaction is completed, and drying to remove moisture to obtain a wool / iron complex;

[0012] Step 4: adding melamine, metal salt and wool / iron complex to deionized water, sealing to form a closed environment, and then shaking to evenly disperse the metal salt and melamine on the surface of the wool; then taking out and drying until there is no water to obtain a metal salt / melamine / wool mixture;

[0013] Step 5: Carbonize the mixture in an oxygen-free environment to obtain initial biochar; filter and wash the initial biochar with deionized water to remove metal salts and impurities in the product; and dry to obtain a wool-based nitrogen-doped magnetic biochar material.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention uses wool to prepare magnetic biochar materials loaded with magnetic nanoparticles, which solves the problem that traditional biochar does not have universal adsorption and is difficult to separate and recover. It has excellent adsorption effect on complex mixed dye solutions and has adsorption catalytic effect on dye solution treatment, achieving catalytic adsorption synergistic integration. It also has superparamagnetism and can achieve solid-liquid separation and recovery by setting an external magnetic field.

[0016] (2) Biochar has good adsorption properties for waste dye liquor and is universally applicable to the adsorption of various dye liquors.

[0017] Taking into account the multi-element nature of wool itself, it is easy to form element-doped biochar in the later stage. In order to improve the practical application performance of the biochar, the molten salt synthesis method was selected as the carbonization method. Metal salts such as potassium chloride and zinc chloride were added during the carbonization process. The etching effect of the metal salts achieved a biochar surface structure with high specific surface area and developed pore size distribution. At the same time, the ionic conductivity of the metal salts was used to give the biochar good electrochemical properties.

[0018] For wool, a nitrogen-rich precursor, the present invention performs subsequent nitrogen doping on the basis of nitrogen enrichment, which can improve the performance of the prepared biochar. The biochar has a developed porous structure and rich oxygen-containing functional groups, which can achieve strong adsorption with dye molecules through electrostatic forces, π-π forces, hydrogen bonds and other forces. Experiments show that biochar has a good adsorption effect on acid dyes, basic dyes, reactive dyes, direct dyes, etc., and can effectively remove dye pollutants in wastewater. Wool-based nitrogen-doped magnetic biochar has strong dispersibility and universal adsorption, and is suitable for a variety of dye solution adsorption environments. It has a short processing time for a single type of simulated dye solution and low temperature requirements. It also has a good waste liquid treatment effect for complex mixed simulated dye solutions and can process complex types of simulated dye solutions in a relatively short time.

[0019] (3) Due to the multifunctionality of wool itself, wool itself has abundant ligands to complex with metal ions, making it easy to form metal-nonmetal doped biochar during the carbonization process, which greatly improves the performance of biochar.

[0020] (4) Loading metal oxides on biochar can have both catalytic and adsorption effects.

[0021] Biochar has high electrical conductivity and chemical stability, making it an excellent carrier material. Metal oxides are loaded onto its surface, and their magnetic properties enhance the composite's dispersibility and permeability in the dye solution, facilitating full contact and interaction with the dye molecules. Furthermore, the metal oxides' catalytic activity (which exhibits a Fenton-like catalytic effect) can be harnessed to oxidatively degrade organic dye molecules by generating free radicals and other reactive species, thus promoting dye degradation. Furthermore, biochar itself retains its dye adsorption capacity, achieving an integrated "catalysis-adsorption" effect. This composite component approach helps improve dye removal efficiency.

[0022] (5) It has strong superparamagnetism, optimizes the processing process, and is easy to quickly recycle and reuse.

[0023] The low-temperature liquid phase method is used to introduce magnetic materials into biochar, which has excellent magnetic separation and adsorption characteristics. An external magnetic field is used to effectively separate and recycle the suspension after the adsorption reaction, so as to realize the resource utilization of waste wool. Even if it is used repeatedly, it can maintain a relatively high adsorption effect and will not cause secondary pollution to the water quality during use. By utilizing the magnetic responsiveness of biochar, an external magnetic field can be used to achieve solid-liquid separation and quickly and efficiently recycle the used biochar. This avoids the cumbersome operation and secondary pollution of traditional separation methods such as filtration and centrifugation. The magnetic response characteristics make it possible to design a continuous fluidized bed reactor to achieve continuous recycling of biochar and improve processing efficiency. Under the action of the magnetic field, the magnetic biochar can be induced to form an orderly arrangement or highly concentrated area in the reactor, optimizing the reaction process.

[0024] (6) The magnetic biochar material prepared by the method of the present invention has the characteristics of larger specific surface area, developed pore structure, rich functional groups, better stability, good solid-liquid separation effect, high adsorption capacity for heavy metals and organic pollutants, and reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the wool after impurity removal prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron micrograph of the wool / iron complex prepared in Example 1 of the present invention;

[0027] Figure 3 This is a scanning electron microscope image of the initial biochar prepared in Example 1 of the present invention;

[0028] Figure 4 This is an adsorption / desorption curve of the biochar material prepared in Example 1 of the present invention;

[0029] Figure 5This is a water-washed pore size distribution diagram of the biochar material prepared in Example 1 of the present invention;

[0030] Figure 6 This is a scanning electron microscope image of the biochar material prepared in Example 1 of the present invention magnified 3000 times;

[0031] Figure 7 This is a scanning electron microscope image of the biochar material prepared in Example 1 of the present invention magnified 10,000 times;

[0032] Figure 8 This is a diagram showing the effect of treating dye solutions with different initial concentrations with the biochar material prepared in Example 1 of the present invention;

[0033] Figure 9 This is a diagram showing the effects of the biochar material prepared in Example 1 of the present invention treating dye liquor of the same concentration at different temperatures. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention and do not limit the scope of protection of the present invention.

[0035] The present invention provides a method for preparing a wool-based nitrogen-doped magnetic biochar material (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0036] Step 1, removing impurities from the wool to obtain the removed wool;

[0037] Preferably, step 1 specifically comprises: placing the wool in anhydrous ethanol and stirring at a low speed to remove impurities on the wool; after taking out, repeatedly rinsing with distilled water until the residual anhydrous ethanol is completely removed; and then drying to remove moisture to obtain the wool after impurity removal;

[0038] Preferably, in step 1, the ratio of the volume of anhydrous ethanol to the mass of wool is 30-50 mL:1 g.

[0039] Preferably, in step 1, the low-speed stirring process is: a frequency of 80-100 Hz, a rotation speed of 80-100 rpm, and stirring for 30-50 minutes. In this embodiment, the stirring is carried out in a constant temperature water bath oscillator.

[0040] Preferably, in step 1, the wool after impurities removal is placed in a packaging bag to keep the wool clean and stored for future use.

[0041] Preferably, in step 1, the drying process is: drying in an environment of 80-100° C. for 120-140 minutes. In this embodiment, the drying environment is a forced air drying oven.

[0042] Step 2: removing the scale layer on the surface of the wool after the impurities are removed in step 1 to obtain descaled wool;

[0043] Preferably, step 2 specifically comprises: adding NaHSO3 to a urea solution to prepare a NaHSO3 / urea solution; then placing the wool after the impurities removal in step 1 in the NaHSO3 / urea solution to react and remove the scale layer on the surface of the wool; then taking out the wool, washing it with deionized water to remove residual NaHSO3 / urea; then drying to remove moisture, to obtain the descaled wool;

[0044] Preferably, in step 2, the concentration of the urea solution is 1-1.5 mol / L; the ratio of the volume of the urea solution to the mass of NaHSO3 is 20-30 mL:1 g (preferably 25 mL:1 g).

[0045] Preferably, in step 2, the ratio of the mass of the wool after impurity removal to the volume of the NaHSO3 / urea solution is 1 g:150-250 mL (preferably 1 g:200 mL).

[0046] Preferably, in step 2, the reaction process is: reaction temperature is 80-90° C., and reaction time is 2-2.5 h. In this embodiment, the reaction is carried out in a constant temperature water bath oscillator with a frequency of 100-120 Hz and a rotation speed of 80-100 rpm.

[0047] Preferably, in step 2, the drying process is: drying in an environment at 60° C. to 80° C. for 120 to 140 minutes. In this embodiment, the environment is an oven.

[0048] Step 3, immersing the descaled wool in step 2 in a ferric chloride solution to carry out a coordination reaction, taking out the wool after the reaction is completed, and drying to remove moisture to obtain a wool / iron complex;

[0049] Preferably, in step 3, the concentration of the ferric chloride solution is 0.2-0.5 mol / L; the ratio of the volume of the ferric chloride solution to the mass of the descaled wool is 80-120 mL:1 g (preferably 100 mL:1 g).

[0050] Preferably, in step 3, the coordination reaction process is: stirring the reaction at room temperature for 8 to 9 hours; the stirring parameters are: frequency of 100 to 120 Hz and rotation speed of 80 to 100 rpm. In this embodiment, the stirring is carried out in a constant temperature water bath oscillator.

[0051] Preferably, in step 3, the drying process is: temperature is 50° C. to 80° C., and time is 1 to 2 hours.

[0052] Step 4: adding melamine, metal salt, and wool / iron complex to deionized water, sealing with plastic wrap to form a closed environment to prevent water from volatilizing and carrying away the metal salt during shaking, and then shaking to evenly disperse the metal salt and melamine on the surface of the wool; then removing the mixture and drying it until it is free of water to obtain a metal salt / melamine / wool mixture;

[0053] Preferably, in step 4, the mass ratio of the wool / iron complex to melamine is 1:1-5, and the mass ratio of the wool / iron complex to the metal salt is 1:10-30; and the amount of deionized water is excessive enough to immerse the added substances.

[0054] Preferably, in step 4, the metal salt is a mixture of KCl and ZnCl2, and the mass ratio of KCl to ZnCl2 is 1:1 to 1.5.

[0055] Preferably, in step 4, the shaking process is: frequency of 100-120 Hz, rotation speed of 80-100 rpm, temperature of 80-100° C., and time of 6-8 hours. In this embodiment, the shaking is performed in a constant temperature water bath shaker.

[0056] Preferably, in step 4, the drying process is: drying in an environment of 100-120° C. for 4-6 hours until no water is present. In this embodiment, the drying environment is a forced air drying oven.

[0057] Step 5: Place the mixture in a high-temperature reactor (preferably a tubular furnace) in an oxygen-free environment for carbonization to obtain initial biochar; after cooling to room temperature, repeatedly filter and wash the initial biochar with deionized water to remove metal salts in the product and surface impurities; after drying, obtain a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material).

[0058] Preferably, in step 5, the oxygen-free environment is a nitrogen environment or an inert gas environment, and the inert gas is argon or helium.

[0059] Preferably, in step 5, the carbonization process is: a heating rate of 5 to 10 K / min, a temperature of 700 to 800° C., and a time of 1.5 to 2 h.

[0060] Preferably, in step 5, the drying process is: drying temperature is 80-90° C., and drying time is 4-5 hours. In this embodiment, the drying environment is a vacuum drying oven.

[0061] The present invention also provides a wool-based nitrogen-doped magnetic biochar material prepared by the method for preparing the wool-based nitrogen-doped magnetic biochar material.

[0062] The present invention also provides an application of the wool-based nitrogen-doped magnetic biochar material, characterized in that the wool-based nitrogen-doped magnetic biochar material is applied to the treatment of printing and dyeing wastewater and the adsorption and removal of pollutants.

[0063] Research on the actual performance and wastewater treatment of biochar materials: The prepared biochar material was put into a simulated dye solution for treatment. It has a significant treatment effect on methylene blue (MB), a small molecular weight, alkaline dye solution. The treatment temperature requirement is low and the time required for complete adsorption is short. For the treatment of large molecular weight reactive dye solutions, taking Reactive Brilliant Red K-2BP as an example, the treatment effect on weakly alkaline dye solutions is also good, but the temperature requirement is high and the time required for complete adsorption is long. For complex dye solutions mixed with multiple types, taking a mixed dye solution of non-ionic and ionic types as an example, it can have a significant adsorption effect in a relatively short time. While improving the adsorption treatment capacity, it also solves the problem of small size of biochar and difficulty in rapid sedimentation to a certain extent, making it easier to recycle.

[0064] Example 1:

[0065] (1) 1 g of waste wool was placed in anhydrous ethanol and stirred in a constant temperature water bath oscillator for 30 min to remove impurities on the wool; after taking it out, it was repeatedly rinsed with distilled water; then it was dried in a blast drying oven at 100°C for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0066] (2) Add 8 g of NaHSO3 to 200 mL of 1 mol / L urea solution to prepare a NaHSO3 / urea solution; then place the wool after impurity removal in the NaHSO3 / urea solution and oscillate it in a constant temperature water bath at a frequency of 50 Hz and a reaction temperature of 80°C for 2 h to remove the scale layer on the wool surface; then take out the wool and wash it with deionized water to remove the residual NaHSO3 / urea; then dry it in a 60°C oven for 120 min to remove moisture, thereby obtaining the descaled wool;

[0067] (3) Immersing the descaled wool in 100 mL of 0.2 mol / L ferric chloride solution and stirring at room temperature for 8 h for coordination reaction, taking it out after the reaction is completed, and vacuum drying it at 50°C for 1 h to remove moisture to obtain a wool / iron complex;

[0068] (4) Add a mixture of melamine, KCl and ZnCl2 metal salt and wool / iron complex into 50 mL of deionized water, with the mass ratio of wool / iron complex: melamine: KCl-ZnCl2 being 1:1:10, and the mass ratio of KCl to ZnCl2 being 1:1. Seal with plastic wrap to form a closed environment, and then place in a constant temperature water bath oscillator at 80°C for 6 hours to evenly disperse the metal salt and melamine on the surface of the wool; then take out and place in a 120°C forced air drying oven to dry for 4 hours until there is no moisture, to obtain a mixture of metal salt / melamine / wool;

[0069] (5) The mixture was placed in a tubular furnace under an inert atmosphere for carbonization at a heating rate of 5 K / min to 700 °C and maintained for 120 min to obtain initial biochar; after cooling to room temperature, the initial biochar was repeatedly filtered and washed with deionized water to remove metal salts and surface impurities in the product; after drying in a vacuum drying oven at 80 °C, a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material) was obtained.

[0070] The biochar material was added to a methylene blue solution with an initial concentration of 70 mg / L and subjected to an adsorption reaction at 40°C for 40 minutes. The results showed that the biochar material had a maximum adsorption capacity of 135.18 mg / g of methylene blue and a removal rate of 96.56%, demonstrating excellent adsorption performance.

[0071] Depend on Figure 1 It can be seen that there are a large number of scale layers on the surface of wool.

[0072] Depend on Figure 2 It can be seen that through the descaling process, the scale layer on the surface of the wool is well removed, so that a large amount of ferric chloride substance is attached to the surface of the wool, and a large amount of magnetic precursors are successfully introduced on the surface of the wool.

[0073] Depend on Figure 3 It can be seen that the carbonization process causes many particles to appear on the surface of the initial biochar, indicating that the magnetic precursor undergoes a thermal reduction process during the pyrolysis process and becomes metal oxide particles loaded on the biochar surface.

[0074] Depend on Figure 4 It can be seen that the specific surface area of ​​the prepared biochar material is 296.34m 2 / g.

[0075] Depend on Figure 5 It can be seen that the pore size distribution of the prepared biochar material is mainly between 2.9 and 4 nm, and is mainly mesopores.

[0076] Depend on Figure 6It can be seen that after water washing, the metal oxides are still successfully retained on the surface of biochar. Since the metal oxides are loaded on the surface of biochar, its catalytic performance is improved. At the same time, the prepared biochar material has strong magnetism, which improves its recyclability.

[0077] Depend on Figure 7 It can be seen that although the metal oxides are loaded on the surface of biochar, the surface of the prepared biochar material still has abundant pores, high porosity, uniform pore size distribution, high specific surface area, and exhibits good adsorption performance.

[0078] Depend on Figure 8 It can be seen that at 40 °C, the biochar material has a higher equilibrium adsorption capacity (135.18 mg / g) when treating 80 mg / L dye solution, indicating that this type of material is suitable for treating medium and high concentration dye solutions.

[0079] Depend on Figure 9 It can be seen that the biochar material was tested for adsorption of 70 mg / L dye solution at different temperatures, and the equilibrium adsorption amount did not increase continuously with the increase of temperature, indicating that the biochar material is not dependent on temperature and can achieve good adsorption effect at medium and low temperatures.

[0080] Table 1 shows the EDS analysis of the initial biochar obtained in step (5), and Table 2 shows the EDS analysis of the wool-based nitrogen-doped magnetic biochar material obtained in step (5).

[0081] Table 1

[0082]

[0083]

[0084] Table 2

[0085] element Line Type wt% wt% Sigma at% C K-line system 30.32 0.48 55.25 N K-line system 4.37 0.27 6.84 O K-line system 7.25 0.12 9.92 S K-line system 0.20 0.03 0.14 Cl K-line system 20.85 0.19 12.87 K K-line system 9.73 0.12 5.45 Fe L line series 7.08 0.30 2.78 Zn L line series 20.18 0.20 6.76 Total 100.00 100.00

[0086] Analysis of the data in Table 1 shows that compared to the elements contained in wool (original wool contains C, N, O, and S), the initial biochar contains increased Cl, K, Fe, and Zn, indicating that the wool was doped with elements and carbonized using the molten salt method to produce a material containing magnetic elements and metal salts. A comparison of the data in Tables 1 and 2 shows that the initial biochar was treated with deionized water to remove most of the metal salt solution, significantly reducing the K, Cl, and Zn content and increasing the Fe and N content, indicating the successful preparation of wool-based nitrogen-doped magnetic biochar.

[0087] Example 2:

[0088] (1) 1 g of waste wool was placed in anhydrous ethanol and stirred in a constant temperature water bath oscillator for 30 min to remove impurities on the wool; after taking it out, it was repeatedly rinsed with distilled water; then it was dried in a blast drying oven at 100°C for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0089] (2) Add 8 g of NaHSO3 to 200 mL of 1 mol / L urea solution to prepare a NaHSO3 / urea solution; then place the wool after impurity removal in the NaHSO3 / urea solution and oscillate it in a constant temperature water bath at a frequency of 50 Hz and a reaction temperature of 80°C for 2 h to remove the scale layer on the wool surface; then take out the wool and wash it with deionized water to remove the residual NaHSO3 / urea; then dry it in a 60°C oven for 120 min to remove moisture, thereby obtaining the descaled wool;

[0090] (3) Immersing the descaled wool in 100 mL of 0.2 mol / L ferric chloride solution and stirring at room temperature for 8 h for coordination reaction, taking it out after the reaction is completed, and vacuum drying it at 50°C for 2 h to remove moisture to obtain a wool / iron complex;

[0091] (4) Add a mixture of melamine, KCl and ZnCl2 metal salt and wool / iron complex into 50 mL of deionized water, with the mass ratio of wool / iron complex: melamine: KCl-ZnCl2 being 1:1.5:10, and the mass ratio of KCl to ZnCl2 being 1:1. Seal with plastic wrap to form a closed environment, and then place in a constant temperature water bath oscillator at 80°C for 6 hours to evenly disperse the metal salt and melamine on the surface of the wool; then take out and place in a 120°C forced air drying oven to dry for 4 hours until there is no moisture, to obtain a mixture of metal salt / melamine / wool;

[0092] (5) The mixture was placed in a tubular furnace under an inert atmosphere for carbonization at a heating rate of 5 K / min to 700 °C and maintained for 120 min to obtain initial biochar; after cooling to room temperature, the initial biochar was repeatedly filtered and washed with deionized water to remove metal salts and surface impurities in the product; after drying in a vacuum drying oven at 80 °C, a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material) was obtained.

[0093] The biochar was added to a methylene blue solution with an initial concentration of 80 mg / L and subjected to an adsorption reaction at 25°C for one hour. The results showed that the biochar had a maximum adsorption capacity of 72.4 mg / g for methylene blue and a removal rate of 64.5%, demonstrating excellent adsorption performance.

[0094] Example 3:

[0095] (1) 1 g of waste wool was placed in anhydrous ethanol and stirred in a constant temperature water bath oscillator for 30 min to remove impurities on the wool; after taking it out, it was repeatedly rinsed with distilled water; then it was dried in a blast drying oven at 100°C for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0096] (2) Add 8 g of NaHSO3 to 200 mL of 1 mol / L urea solution to prepare a NaHSO3 / urea solution; then place the wool after impurity removal in the NaHSO3 / urea solution and oscillate it in a constant temperature water bath at a frequency of 50 Hz and a reaction temperature of 80°C for 2 h to remove the scale layer on the wool surface; then take out the wool and wash it with deionized water to remove the residual NaHSO3 / urea; then dry it in a 60°C oven for 120 min to remove moisture, thereby obtaining the descaled wool;

[0097] (3) Immersing the descaled wool in 100 mL of 0.2 mol / L ferric chloride solution and stirring at room temperature for 8 h for coordination reaction, taking it out after the reaction is completed, and vacuum drying it at 50°C for 1 h to remove moisture to obtain a wool / iron complex;

[0098] (4) Add a mixture of melamine, KCl and ZnCl2 metal salt and wool / iron complex into 50 mL of deionized water, wherein the mass ratio of wool / iron complex: melamine: KCl-ZnCl2 is 1:1:20, and the mass ratio of KCl to ZnCl2 is 1:1. Seal with plastic wrap to form a closed environment, and then place in a constant temperature water bath oscillator at 80°C for 6 hours to evenly disperse the metal salt and melamine on the surface of the wool; then take out and place in a 120°C forced air drying oven to dry for 4 hours until there is no moisture, to obtain a mixture of metal salt / melamine / wool;

[0099] (5) The mixture was placed in a tubular furnace under an inert atmosphere for carbonization at a heating rate of 5 K / min to 700 °C and maintained for 120 min to obtain initial biochar; after cooling to room temperature, the initial biochar was repeatedly filtered and washed with deionized water to remove metal salts and surface impurities in the product; after drying in a vacuum drying oven at 80 °C, a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material) was obtained.

[0100] The biochar was added to a methylene blue solution with an initial concentration of 100 mg / L and subjected to an adsorption reaction at 35°C for one hour. The results showed that the biochar had a maximum adsorption capacity of 85.2 mg / g of methylene blue and a removal rate of 71.0%, demonstrating excellent adsorption performance.

[0101] Example 4:

[0102] (1) 1 g of waste wool was placed in anhydrous ethanol and stirred in a constant temperature water bath oscillator for 30 min to remove impurities on the wool; after taking it out, it was repeatedly rinsed with distilled water; then it was dried in a blast drying oven at 100°C for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0103] (2) Add 8 g of NaHSO3 to 200 mL of 1 mol / L urea solution to prepare a NaHSO3 / urea solution; then place the wool after impurity removal in the NaHSO3 / urea solution and oscillate it in a constant temperature water bath at a frequency of 50 Hz and a reaction temperature of 80°C for 2 h to remove the scale layer on the wool surface; then take out the wool and wash it with deionized water to remove the residual NaHSO3 / urea; then dry it in a 60°C oven for 120 min to remove moisture, thereby obtaining the descaled wool;

[0104] (3) Immersing the descaled wool in 100 mL of 0.2 mol / L ferric chloride solution and stirring at room temperature for 8 h for coordination reaction, taking it out after the reaction is completed, and vacuum drying it at 50°C for 1 h to remove moisture to obtain a wool / iron complex;

[0105] (4) Add a mixture of melamine, KCl and ZnCl2 metal salt and wool / iron complex into 50 mL of deionized water, with the mass ratio of wool / iron complex: melamine: KCl-ZnCl2 being 1:1:30, and the mass ratio of KCl to ZnCl2 being 1:1. Seal with plastic wrap to form a closed environment, and then place in a constant temperature water bath oscillator at 80°C for 6 hours to evenly disperse the metal salt and melamine on the surface of the wool; then take out and place in a 120°C forced air drying oven to dry for 4 hours until there is no moisture, to obtain a mixture of metal salt / melamine / wool;

[0106] (5) The mixture was placed in a tubular furnace under an inert atmosphere for carbonization at a heating rate of 10 K / min to 800 °C and maintained for 90 min to obtain initial biochar; after cooling to room temperature, the initial biochar was repeatedly filtered and washed with deionized water to remove metal salts and surface impurities in the product; after drying in a vacuum drying oven at 80 °C, a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material) was obtained.

[0107] The biochar was added to a methylene blue solution with an initial concentration of 70 mg / L and subjected to an adsorption reaction at 25°C for one hour. The results showed that the biochar had a maximum adsorption capacity of 68.6 mg / g of methylene blue and a removal rate of 68.9%, demonstrating excellent adsorption performance.

[0108] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing wool-based nitrogen-doped magnetic biochar material, characterized in that: The method comprises the following steps: Step 1, removing impurities from the wool to obtain the removed wool; Step 2: Add NaHSO3 to the urea solution to prepare a NaHSO3 / urea solution; then place the wool after the impurities are removed in step 1 in the NaHSO3 / urea solution to react and remove the scale layer on the surface of the wool; then take out the wool and wash it with deionized water to remove the residual NaHSO3 / urea; then dry it to remove the moisture to obtain the descaled wool; Step 3, immersing the descaled wool in step 2 in a ferric chloride solution to carry out a coordination reaction, taking out the wool after the reaction is completed, and drying to remove moisture to obtain a wool / iron complex; Step 4: adding melamine, metal salt, and wool / iron complex to deionized water, sealing to form a closed environment, and then shaking to evenly disperse the metal salt and melamine on the surface of the wool; then removing and drying to anhydrous to obtain a metal salt / melamine / wool mixture; the metal salt is a mixture of KCl and ZnCl2; Step 5: Carbonize the mixture in an oxygen-free environment to obtain initial biochar; filter and wash the initial biochar with deionized water to remove metal salts and impurities in the product; and dry to obtain a wool-based nitrogen-doped magnetic biochar material.

2. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: Step 1 specifically comprises: placing the wool in anhydrous ethanol and stirring at a low speed to remove impurities on the wool; taking out the wool and repeatedly rinsing it with distilled water until the residual anhydrous ethanol is completely removed; and then drying to remove moisture to obtain the wool after impurity removal.

3. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 2, characterized in that: In step 1, the ratio of the volume of anhydrous ethanol to the mass of wool is 30-50 mL:1 g; The low-speed stirring process is: frequency 80~100Hz, speed 80~100rpm, stirring for 30~50min; The drying process is: drying in an environment of 80~100℃ for 120~140min.

4. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 2, the concentration of the urea solution is 1-1.5 mol / L; the volume ratio of the urea solution to the mass of NaHSO3 is 20-30 mL:1 g; The ratio of the mass of the wool after cleaning to the volume of the NaHSO3 / urea solution is 1g:150~250mL; The reaction process is as follows: reaction temperature is 80-90°C, reaction time is 2-2.5h; The drying process is: drying in an environment of 60℃~80℃ for 120~140min.

5. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 3, the concentration of the ferric chloride solution is 0.2-0.5 mol / L; the ratio of the volume of the ferric chloride solution to the mass of the descaled wool is 80-120 mL:1 g; The coordination reaction process is: stirring reaction at room temperature for 8 to 9 hours; the stirring parameters are: frequency of 100 to 120 Hz, speed of 80 to 100 rpm; The drying process is: temperature is 50℃~80℃, time is 1~2h.

6. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 4, the mass ratio of the wool / iron complex to melamine is 1:1-5, and the mass ratio of the wool / iron complex to the metal salt is 1:10-30; The mass ratio of KCl to ZnCl2 is 1:1~1.

5.

7. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 4, the shaking process is: frequency of 100-120 Hz, speed of 80-100 rpm, temperature of 80-100°C, and time of 6-8 hours; The drying process is: drying in an environment of 100~120℃ for 4~6h until there is no water.

8. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 5, the oxygen-free environment is a nitrogen environment, an argon environment, or a helium environment; The drying process is: drying temperature is 80~90℃, and drying time is 4~5h.

9. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: In step 5, the carbonization process is: a heating rate of 5-10 K / min, a temperature of 700-800° C., and a time of 1.5-2 h.

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