Preparation method of wool-based nitrogen-doped magnetic biochar material

Abstract

The invention discloses a preparation method of a wool-based nitrogen-doped magnetic biochar material, which comprises the following steps: firstly, impregnating impurity-removed and scale-removed wool in a ferric chloride solution for coordination reaction to obtain a wool / iron complex; adding melamine, metal salt and the wool / iron complex into deionized water, sealing to form a closed environment, and then vibrating to uniformly disperse the metal salt and melamine on the surface of the wool; taking out and drying until no water exists to obtain a metal salt / melamine / wool mixture; carbonizing the mixture in an oxygen-free environment, and removing metal salt and impurities in the product; and drying to obtain the wool-based nitrogen-doped magnetic biochar material. The magnetic biochar material loaded with magnetic nanoparticles is prepared from wool, has excellent adsorption effect and adsorption catalysis effect on complex mixed dye liquor, achieves catalysis and adsorption synergistic integration, has superparamagnetism, and can realize solid-liquid separation and recovery 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 polluting chemicals in textile printing and dyeing wastewater are very wide, ranging from chemical fiber materials, spinning slurry, dyes, chemicals, etc., to specified laundry wastewater, mercerizing wastewater, post-combing wastewater, etc. In general, this kind of industrial wastewater has the characteristics of serious pollution, many varieties, strong alkalinity, strong toxicity and high color. Therefore, the treatment research 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 and short service life. During the industrial reaction process, the membrane is easily contaminated, thus affecting the separation efficiency. (2) Photocatalytic method: This method has good decolorization effect, no large amount of sludge is generated, good sterilization effect, and low operating cost, but the high one-time investment cost and difficult installation are problems that need to be solved urgently. (3) Adsorption method: This method is a method that 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 agents, 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, thereby changing 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 donate 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 new type of synthesis method that has emerged in recent years. Usually one or several low-melting-point salts are used as reaction media. The reactants have a certain solubility in the molten salt, so that the reaction proceeds at the atomic level. After the reaction is completed, the salts are dissolved in a suitable solvent, and the synthetic product can be obtained after filtering and washing. Molten salt is an ionic medium melt with high ionic conductivity, a wide electrochemical window and strong solubility.

[0006] At present, most researchers choose cellulose as the precursor of biochar. However, biochar prepared from cellulose biomass materials will undergo severe pyrolysis and polycondensation during high-temperature pyrolysis, resulting in partial pore blockage. At the same time, the mechanical strength, conductivity and chemical stability of cellulose biomass char are poor. Compared with cellulose biochar, protein biochar has a stable structure. At the same time, most proteins are rich in heteroatoms such as nitrogen and sulfur, which is conducive to improving the adsorption and catalytic properties of biochar. Protein molecular structure contains a variety of functional groups, and biochar has better functional group chemical activity. At the same time, the carbon-nitrogen ratio of protein is relatively low, and less volatiles are produced during pyrolysis, reducing pollution. Wool is a common natural protein fiber with rich elemental composition. In addition to carbon, it also contains a large amount of nitrogen and sulfur. At present, there is no report on the preparation of biochar using wool as a precursor to overcome the shortcomings of existing biochar. Summary of the invention

[0007] In view of the deficiencies in the prior art, the technical problem that the present invention intends to solve 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 wool to obtain the wool after impurities removal;

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

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

[0012] Step 4, adding melamine, metal salt and wool / iron complex into 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 to be free of water to obtain a mixture of metal salt / melamine / wool;

[0013] Step 5: placing the mixture in an oxygen-free environment for carbonization to obtain initial biochar; filtering and washing the initial biochar with deionized water to remove metal salts and impurities in the product; and drying 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, and 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 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 make the performance of the prepared biochar better. The biochar has a developed porous structure and rich oxygen-containing functional groups, and 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, greatly improving 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 and can be used as an excellent carrier material. Metal oxides are loaded on its surface, and magnetism can promote the dispersibility and permeability of the composite material in the dye solution, which is conducive to full contact and action on the dye molecules; at the same time, the catalytic activity of metal oxides (with Fenton-like catalytic effect) can be used to oxidize and degrade organic dye molecules by generating active species such as free radicals; promote the degradation reaction of dyes; at the same time, biochar itself still has the ability to adsorb dyes, so it can achieve the integrated effect of "catalysis-adsorption". This component composite method helps to improve the efficiency of dye removal.

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

[0023] The magnetic material is introduced into the biochar by the low-temperature liquid phase method, which has excellent magnetic separation and adsorption characteristics. The external magnetic field is used to effectively separate and recycle the suspension after the adsorption reaction 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 a highly concentrated area in the reactor to optimize 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 microscope image 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 is an adsorption / desorption curve diagram 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 obtained in Example 1 of the present invention magnified 3000 times;

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

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

[0033] Fig. 9 This is a diagram showing the effect of the biochar material prepared in Example 1 of the present invention being treated with dye solution 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 in detail and do not limit the protection scope 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 wool to obtain the wool after impurities removal;

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

[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: frequency of 80-100 Hz, rotation speed of 80-100 rpm, stirring for 30-50 min. In this embodiment, it is carried out in a constant temperature water bath oscillator.

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

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

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

[0043] Preferably, step 2 specifically comprises: adding NaHSO 3 Add to urea solution to make NaHSO 3 / urea solution; then place the wool after impurities removal in step 1 in NaHSO 3 / urea solution to remove the scale layer on the wool surface; then the wool is taken out and washed with deionized water to remove the residual NaHSO 3 / urea; then drying to remove moisture and obtain descaled wool;

[0044] Preferably, in step 2, the concentration of the urea solution is 1 to 1.5 mol / L; the volume of the urea solution is about 1 to 1.5 mol / L. 3 The mass ratio is 20-30 mL:1 g (preferably 25 mL:1 g).

[0045] Preferably, in step 2, the mass of the wool after impurity removal is equal to that of NaHSO 3 The volume ratio of the urea solution is 1 g: 150-250 mL (preferably 1 g: 200 mL).

[0046] Preferably, in step 2, the reaction process is: the reaction temperature is 80-90° C., and the 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 of 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 for coordination reaction, taking out after the reaction is completed, drying to remove moisture, and obtaining 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, speed of 80 to 100 rpm. In this embodiment, the stirring is performed 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 into deionized water, sealing with plastic wrap to form a closed environment to prevent water from volatilizing and taking away the metal salt under shaking, 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 mixture of metal salt / melamine / wool;

[0053] Preferably, in step 4, the mass ratio of wool / iron complex to melamine is 1:1-5, and the mass ratio of wool / iron complex to 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 KCl and ZnCl 2 A mixture of KCl and ZnCl 2 The mass ratio is 1:1~1.5.

[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 h. 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 there is no water. In this embodiment, the drying environment is a blast drying oven.

[0057] Step 5, placing 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, the initial biochar is repeatedly filtered and washed with deionized water to remove metal salts in the product and surface impurities; after drying, a wool-based nitrogen-doped magnetic biochar material (referred to as biochar material) is obtained.

[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: the drying temperature is 80-90° C., and the 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] Study on the actual performance and wastewater treatment of biochar materials: The prepared biochar materials were placed in a simulated dye solution for treatment. It had a significant treatment effect on methylene blue (MB), a small molecular weight, alkaline dye solution, with a low treatment temperature requirement and a short time required for complete adsorption. For the treatment of large molecular weight active dye solutions, taking active brilliant red K-2BP as an example, the treatment effect on weakly alkaline dye solutions was also good, but the temperature requirement was high and the time required for complete adsorption was long. For complex dye solutions mixed with multiple types, taking a mixed dye solution of non-ionic and ionic as an example, it can have a significant adsorption effect in a relatively short time. While improving the adsorption treatment capacity, it can also solve the problem of small volume of biochar and difficulty in rapid sedimentation to a certain extent, making it easier to recycle.

[0064] Embodiment 1:

[0065] (1) 1 g of waste wool is 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 is repeatedly rinsed with distilled water; then it is dried in a 100°C forced air drying oven for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0066] (2) 8 g of NaHSO 3 Add to 200mL of 1mol / L urea solution to make NaHSO 3 / urea solution; then place the cleaned wool in NaHSO 3 / urea solution, in a constant temperature water bath oscillator, the frequency is 50 Hz, the reaction temperature is 80 ° C, and the time is 2 h to remove the scale layer on the surface of the wool; then the wool is taken out and washed with deionized water to remove the residual NaHSO 3 / urea; then dried in an oven at 60°C for 120 min to remove moisture, obtaining 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 out after the reaction is completed, and vacuum drying at 50° C. for 1 h to remove moisture to obtain a wool / iron complex;

[0068] (4) Melamine, KCl and ZnCl 2 A mixture of metal salts and wool / iron complex was added to 50 mL of deionized water. Wool / iron complex: melamine: KCl-ZnCl 2 The mass ratio of KCl and ZnCl is 1:1:10. 2The mass ratio of the wool and the metal salt is 1:1, and the wool is sealed with plastic wrap to form a closed environment, and then placed 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 taken out, placed in a 120°C forced air drying oven for 4 hours to dry 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 in the product and impurities on the surface; 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] After testing, the biochar material was added to a methylene blue solution with an initial concentration of 70 mg / L and adsorbed at 40°C for 40 minutes. The results showed that the maximum adsorption capacity of the biochar material for methylene blue was 135.18 mg / g, and the removal rate was 96.56%, showing 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 the scale layer on the surface of the wool is well removed through the descaling process, 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 results in the presence of many particles 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 surface of the biochar.

[0074] Depend on Figure 4 It can be seen that the specific surface area of ​​the prepared biochar material is 296.34 m 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, with mesopores being the main component.

[0076] Depend on Figure 6 It can be seen that after washing with water, 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 7It 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 treated with 80 mg / L dye solution has a higher equilibrium adsorption capacity (135.18 mg / g), indicating that this type of material is suitable for the treatment of medium and high concentration dye solutions.

[0079] Depend on Fig. 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 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 is the EDS analysis of the initial biochar obtained in step (5), and Table 2 is 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 7.08 0.30 2.78 Zn L Line 20.18 0.20 6.76 Total 100.00 100.00

[0086] Analysis of the data in Table 1 shows that compared with the elements contained in wool (the elements of the original wool contain C, N, O, and S), the initial biochar has increased Cl, K, Fe, and Zn elements, indicating that wool has been doped with elements and carbonized by the molten salt method to prepare materials containing magnetic elements and metal salt elements. Comparative analysis of the data in Tables 1 and 2 shows that most of the metal salt solution has been removed from the initial biochar after deionized water treatment, the content of K, Cl, and Zn elements has been significantly reduced, and the content of Fe and N elements has increased, indicating that wool-based nitrogen-doped magnetic biochar materials have been successfully prepared.

[0087] Embodiment 2:

[0088] (1) 1 g of waste wool is 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 is repeatedly rinsed with distilled water; then it is dried in a 100°C forced air drying oven for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0089] (2) 8 g of NaHSO 3 Add to 200mL of 1mol / L urea solution to make NaHSO3 / urea solution; then place the cleaned wool in NaHSO 3 / urea solution, in a constant temperature water bath oscillator, the frequency is 50 Hz, the reaction temperature is 80 ° C, and the time is 2 h to remove the scale layer on the surface of the wool; then the wool is taken out and washed with deionized water to remove the residual NaHSO 3 / urea; then dried in an oven at 60°C for 120 min to remove moisture, obtaining 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 out after the reaction is completed, and vacuum drying at 50° C. for 2 h to remove moisture to obtain a wool / iron complex;

[0091] (4) Melamine, KCl and ZnCl 2 A mixture of metal salts and wool / iron complex was added to 50 mL of deionized water. Wool / iron complex: melamine: KCl-ZnCl 2 The mass ratio of KCl and ZnCl is 1:1.5:10. 2 The mass ratio of the wool and the metal salt is 1:1, and the wool is sealed with plastic wrap to form a closed environment, and then placed 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 taken out, placed in a 120°C forced air drying oven for 4 hours to dry 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 in the product and impurities on the surface; 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] After testing, the biochar material was added to a methylene blue solution with an initial concentration of 80 mg / L and adsorbed at 25°C for 1 hour. The results showed that the maximum adsorption capacity of the biochar material for methylene blue was 72.4 mg / g, and the removal rate was 64.5%, showing excellent adsorption performance.

[0094] Embodiment 3:

[0095] (1) 1 g of waste wool is 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 is repeatedly rinsed with distilled water; then it is dried in a 100°C forced air drying oven for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0096] (2) 8 g of NaHSO 3 Add to 200mL of 1mol / L urea solution to make NaHSO 3 / urea solution; then place the cleaned wool in NaHSO 3 / urea solution, in a constant temperature water bath oscillator, the frequency is 50 Hz, the reaction temperature is 80 ° C, and the time is 2 h to remove the scale layer on the surface of the wool; then the wool is taken out and washed with deionized water to remove the residual NaHSO 3 / urea; then dried in an oven at 60°C for 120 min to remove moisture, obtaining 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 out after the reaction is completed, and vacuum drying at 50° C. for 1 h to remove moisture to obtain a wool / iron complex;

[0098] (4) Melamine, KCl and ZnCl 2 A mixture of metal salts and wool / iron complex was added to 50 mL of deionized water. Wool / iron complex: melamine: KCl-ZnCl 2 The mass ratio of KCl and ZnCl is 1:1:20. 2 The mass ratio of the wool and the metal salt is 1:1, and the wool is sealed with plastic wrap to form a closed environment, and then placed 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 taken out, placed in a 120°C forced air drying oven for 4 hours to dry 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 in the product and impurities on the surface; 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] After testing, the biochar material was added to a methylene blue solution with an initial concentration of 100 mg / L and adsorbed at 35°C for 1 hour. The results showed that the maximum adsorption capacity of the biochar material for methylene blue was 85.2 mg / g, and the removal rate was 71.0%, showing excellent adsorption performance.

[0101] Embodiment 4:

[0102] (1) 1 g of waste wool is 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 is repeatedly rinsed with distilled water; then it is dried in a 100°C forced air drying oven for 120 min to remove moisture, thereby obtaining the wool after impurity removal;

[0103] (2) 8 g of NaHSO 3 Add to 200mL of 1mol / L urea solution to make NaHSO 3 / urea solution; then place the cleaned wool in NaHSO 3 / urea solution, in a constant temperature water bath oscillator, the frequency is 50 Hz, the reaction temperature is 80 ° C, and the time is 2 h to remove the scale layer on the surface of the wool; then the wool is taken out and washed with deionized water to remove the residual NaHSO 3 / urea; then dried in an oven at 60°C for 120 min to remove moisture, obtaining 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 out after the reaction is completed, and vacuum drying at 50° C. for 1 h to remove moisture to obtain a wool / iron complex;

[0105] (4) Melamine, KCl and ZnCl 2 A mixture of metal salts and wool / iron complex was added to 50 mL of deionized water. Wool / iron complex: melamine: KCl-ZnCl 2 The mass ratio of KCl and ZnCl is 1:1:30. 2 The mass ratio of the wool and the metal salt is 1:1, and the wool is sealed with plastic wrap to form a closed environment, and then placed 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 taken out, placed in a 120°C forced air drying oven for 4 hours to dry 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, where it was 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] After testing, the biochar material was added to a methylene blue solution with an initial concentration of 70 mg / L and adsorbed at 25°C for 1 hour. The results showed that the maximum adsorption capacity of the biochar material for methylene blue was 68.6 mg / g, and the removal rate was 68.9%, showing 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 wool to obtain the wool after the impurities are removed; Step 2, removing the scale layer on the surface of the wool after the impurities are removed in step 1, to obtain descaled wool; Step 3, immersing the descaled wool in step 2 in a ferric chloride solution for coordination reaction, taking out after the reaction is completed, drying to remove moisture, and obtaining a wool / iron complex; Step 4, adding melamine, metal salt and wool / iron complex into 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 to be free of water to obtain a mixture of metal salt / melamine / wool; Step 5: placing the mixture in an oxygen-free environment for carbonization to obtain initial biochar; filtering and washing the initial biochar with deionized water to remove metal salts and impurities in the product; and drying 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 includes: placing the wool in anhydrous ethanol and stirring at a low speed to remove impurities on the wool; taking out and repeatedly rinsing with distilled water until the residual anhydrous ethanol is completely removed; and then drying to remove moisture to obtain the wool after impurities are removed.

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 process of low-speed stirring is: frequency of 80-100 Hz, rotation speed of 80-100 rpm, stirring for 30-50 minutes. The drying process is: drying in an environment of 80-100°C for 120-140 minutes.

4. The method for preparing the wool-based nitrogen-doped magnetic biochar material according to claim 1, characterized in that: Step 2 specifically comprises: adding NaHSO3 to the urea solution to prepare a NaHSO3 / urea solution; The wool after impurity removal in step 1 is then placed in a NaHSO3 / urea solution to react and remove the scale layer on the wool surface; the wool is then taken out and washed with deionized water to remove residual NaHSO3 / urea; and then dried to remove moisture to obtain descaled wool.

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

6. 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.

7. 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 metal salt is a mixture of KCl and ZnCl2, and the mass ratio of KCl to ZnCl2 is 1:1-1.

5.

8. 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 is 100-120 Hz, speed is 80-100 rpm, temperature is 80-100° C., and time is 6-8 h; The drying process is: drying in an environment of 100-120°C for 4-6 hours until there is no water.

9. 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 or an inert gas environment, and the inert gas is argon or helium; The drying process is: drying temperature is 80-90°C and drying time is 4-5h.

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

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