A magnetic biomass carbon nanopolymer material for adsorbing heavy metals and a preparation method thereof

Abstract

The present invention provides a magnetic biomass carbon nanocomposite material for adsorbing heavy metals and a preparation method thereof, belonging to the technical field of adsorption materials. The method specifically includes the following steps: S1. Mix the biomass carbon nanomaterial with ultrapure water and perform ultrasonic dispersion, then add ferric chloride hexahydrate, ferrous chloride tetrahydrate and sodium citrate dihydrate and stir to dissolve to obtain a mixed solution; S2. Adjust the pH of the mixed solution at a constant temperature, perform a constant temperature reaction, cool, perform magnetic separation, and wash to obtain a magnetic biomass carbon nanomaterial; S3. Add the nanomaterial and potassium persulfate to the aqueous phase A, and then dropwise add the oil phase B while stirring and perform a first reaction and a second reaction at a constant temperature, and then perform solid-liquid separation with a magnet to obtain a black solid powder; S4. Crush the black solid powder and wash it with hot water, and then remove the residual suspension with ethanol and ethanol-acetic acid solution respectively, and then successively filter, wash and dry to obtain the product, which has the characteristics of large specific surface area, high selectivity and adsorption capacity, fast adsorption rate and good recycling performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedicine, and particularly relates to a magnetic biomass carbon nanopolymer material for adsorbing heavy metals and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization and the acceleration of urbanization, a large amount of untreated or inadequately treated industrial wastewater discharges, agricultural drainage containing heavy metals, urban sewage, and leachate from landfills have further exacerbated the heavy metal pollution in the water environment. Therefore, it is of great significance to study the technology for removing heavy metal ions in water to reduce their harmful effects on the environmental ecology.

[0003] At present, common methods for removing heavy metal ions in wastewater include adsorption, electrochemical precipitation, membrane separation, and ion exchange, etc. Among them, the adsorption method is easy to operate, has high treatment efficiency, and is economical and practical, and is considered a promising treatment technology. Biomass carbon is a solid carbonaceous material prepared by pyrolyzing biomass at high temperature. It has a large specific surface area and well-developed porosity, and has been widely studied in the field of heavy metal ion adsorption. However, biomass carbon can only physically adsorb metal ions relying on its own large specific surface energy, with low adsorption capacity and removal rate, and it is not easy to separate biomass carbon from water, which is prone to cause secondary pollution of the water environment, thus limiting the application of biomass carbon. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a magnetic biomass carbon nanopolymer material for adsorbing heavy metals and a preparation method thereof. The prepared magnetic biomass carbon nanopolymer material has the characteristics of large specific surface area, high selectivity and adsorption capacity, fast adsorption rate, and good recycling performance.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a magnetic biomass carbon nanopolymer material for adsorbing heavy metals, comprising the following steps:

[0007] S1. Mix the biomass carbon nanomaterial with ultrapure water and perform ultrasonic dispersion, then add ferric chloride hexahydrate, ferrous chloride tetrahydrate, and sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0008] S2. Heat the mixed solution and sequentially adjust the pH, perform a constant-temperature reaction, cool, perform magnetic separation, and wash at a constant temperature to obtain a magnetic biomass carbon nanomaterial;

[0009] S3. Add magnetic biochar nanomaterials and potassium persulfate to the aqueous phase A, and then slowly add the oil phase B drop by drop while stirring and carry out the first reaction at a constant temperature; after the reaction is completed, raise the temperature to carry out the second reaction, and after the reaction is completed, use a magnet for solid-liquid separation to obtain a black solid powder;

[0010] S4. Crush the black solid powder and wash it several times with hot water, then use ethanol and ethanol-acetic acid solution respectively to remove the residual suspension emulsion by Soxhlet extraction, and then filter, wash and dry in sequence to obtain magnetic biochar nanocomposite materials;

[0011] The preparation method of the aqueous phase A is as follows: mix polyvinyl alcohol and ultrapure water, carry out constant temperature stirring until completely dissolved, and then add sodium dodecyl sulfate and sodium sulfite, and obtain the aqueous phase A after sufficient stirring;

[0012] The preparation method of the oil phase B is as follows: mix toluene, 2-thiophenecarboxaldehyde, acrylamide, ethylene glycol dimethacrylate and ammonium persulfate, and ultrasonically dissolve at a constant temperature to obtain the oil phase B.

[0013] Preferably, the preparation method of the biochar nanomaterials is as follows:

[0014] The dried biomass is subjected to high-temperature carbonization to obtain biochar nanomaterials;

[0015] The biomass is one of pineapple, begonia flower, rhododendron, kapok, Chinese redbud, mimosa, reed flower; the high-temperature carbonization temperature is 600-1000 °C, and the high-temperature carbonization time is 1-4 h.

[0016] Preferably, the mass-volume ratio of the biochar, ultrapure water, ferric chloride hexahydrate, ferrous chloride tetrahydrate, and sodium citrate dihydrate in the S1 is 0.1-1 g: 20-100 mL: 0.1-1 g: 0.05-0.5 g: 0.05-0.5 g.

[0017] Preferably, the heating temperature in the S2 is 40-90 °C;

[0018] Adjust the pH value to 9-13, and the pH regulator is 25% ammonia water;

[0019] The constant temperature reaction time is 0.5-12 h.

[0020] Preferably, the mass-volume ratio of the aqueous phase A, magnetic biochar nanomaterials, potassium persulfate, and oil phase B in the S3 is: 100-400 mL: 0.4-4 g: 0.02-0.2 g: 3-6.5 mL.

[0021] Preferably, the stirring rate in the S3 is 300-800 r / min;

[0022] The temperature of the first reaction is 30 - 70 °C, and the time of the first reaction is 0.5 - 10 h;

[0023] The temperature of the second reaction is 60 - 95 °C, and the time of the second reaction is 2 - 24 h.

[0024] Preferably, in S4, the volume ratio of ethanol to acetic acid is 1 - 10:1 - 10, and the Soxhlet extraction time is 5 - 48 h.

[0025] Preferably, in the preparation method of the aqueous phase A, the mass - volume ratio of polyvinyl alcohol, ultrapure water, sodium dodecyl sulfate, and sodium sulfite is: 0.3 - 5 g:50 - 500 mL:1 - 8 g:0.5 - 6 g.

[0026] The constant temperature is 55 - 95 °C;

[0027] The stirring rate is 300 - 800 r / min, and the stirring time is 0.5 - 3 h.

[0028] Preferably, in the preparation method of the oil phase B, the volume - mass ratio of toluene, 2 - thiophenecarboxaldehyde, acrylamide, ethylene glycol dimethacrylate, and ammonium persulfate is 0.5 - 5 mL:0.2 - 4 mL:0.1 - 2.0 g:0.2 - 4 mL:0.02 - 0.2 g;

[0029] The constant temperature is 40 - 80 °C.

[0030] In a second aspect, the present invention provides a magnetic biomass carbon nanocomposite material for adsorbing heavy metals, which is prepared by the above - mentioned preparation method.

[0031] It has at least the following beneficial technical effects:

[0032] (1) The present invention magnetically functionalizes the biomass carbon, and rapid solid - liquid separation can be achieved by applying an external magnetic field.

[0033] (2) The polymer synthesized by using 2 - thiophenecarboxaldehyde and acrylamide as functional monomers in the present invention has a large number of nitrogen, oxygen, and sulfur functional groups, and has a strong coordination ability with metal ions, improving the adsorption performance for heavy metal ions.

[0034] (3) The adsorbent described in the present invention has a large specific surface area, high selectivity, high adsorption capacity, fast adsorption rate, and good recycling performance. Description of the Drawings

[0035] Figure 1 It is the scanning electron micrograph of the magnetic biomass carbon polymer material in Example 1;

[0036] Figure 2Infrared light images of different materials, where: (a) is biomass carbon, (b) is magnetic biomass carbon, and (c) is the magnetic biomass carbon polymer material of Example 1;

[0037] Figure 3 Influence diagram of adsorption time on adsorption capacity of the magnetic biomass carbon polymer material of Example 1;

[0038] Figure 4 Influence diagram of initial concentration of heavy metal ions on adsorption capacity of the magnetic biomass carbon polymer material of Example 1;

[0039] Figure 5 Influence diagram of number of recycling times on adsorption rate of the magnetic biomass carbon polymer material of Example 1. Detailed implementation manners

[0040] The present invention provides a preparation method of a magnetic biomass carbon nanopolymer material for adsorbing heavy metals, comprising the following steps:

[0041] S1. Mix the biomass carbon nanomaterial with ultrapure water and perform ultrasonic dispersion, then add ferric chloride hexahydrate, ferrous chloride tetrahydrate and sodium citrate dihydrate and stir to dissolve to obtain a mixed solution.

[0042] In this step, the mass-volume ratio of biomass carbon, ultrapure water, ferric chloride hexahydrate, ferrous chloride tetrahydrate, and sodium citrate dihydrate is 0.1~1 g: 20~100 mL: 0.1~1 g: 0.05~0.5 g: 0.05~0.5 g; further preferably 0.5 g: 40 mL: 0.35 g: 0.185 g: 0.139 g. The present invention magnetically functionalizes the biomass carbon, endows the biomass carbon with new magnetic properties, and can realize rapid solid-liquid separation through an external magnetic field, avoiding the cumbersome and time-consuming traditional filtration or centrifugation methods, facilitating industrial production and improving efficiency.

[0043] S2. Heat the mixed solution and sequentially adjust the pH, carry out a constant-temperature reaction, cool, perform magnetic separation, and wash at a constant temperature to obtain a magnetic biomass carbon nanomaterial;

[0044] In this step, the heating temperature is 40~90 °C; the pH value is adjusted to 9~13, and the pH regulator is 25% ammonia water; the constant-temperature reaction time is 0.5~12 h.

[0045] S3. Add the magnetic biomass carbon nanomaterial and potassium persulfate to the aqueous phase A, and then dropwise add the oil phase B while stirring and carry out a first reaction at a constant temperature; after the reaction is completed, raise the temperature to carry out a second reaction, and after the reaction is completed, perform solid-liquid separation with a magnet to obtain a black solid powder;

[0046] In this step, the mass-volume ratio of aqueous phase A, magnetic biomass carbon nanomaterial, potassium persulfate, and oil phase B is: 100~400 mL: 0.4~4 g: 0.02~0.2 g: 3~6.5 mL.

[0047] The stirring rate is 300~800 r / min;

[0048] The temperature of the first reaction is 30~70 °C, and the time of the first reaction is 0.5~10 h;

[0049] The temperature of the second reaction is 60~95 °C, and the time of the second reaction is 2~24 h;

[0050] In the present invention, by adopting the suspension polymerization method, magnetic biomass carbon is used as the matrix, 2-thiophenecarboxaldehyde and acrylamide are used as functional monomers, and ethylene glycol dimethacrylate is used as the cross-linking agent to prepare magnetic biomass carbon polymers. Among them, by utilizing the stabilizing agent effect of magnetic biomass carbon during the suspension polymerization process, magnetic carbon nanopolymers with uniform particle size distribution, good dispersibility and stability are prepared; the polymers synthesized by using 2-thiophenecarboxaldehyde and acrylamide as functional monomers have a large number of nitrogen, oxygen and sulfur functional groups, and strong coordination ability for metal ions, which improves the adsorption performance for heavy metal ions.

[0051] The preparation method of the aqueous phase A is: mixing polyvinyl alcohol and ultrapure water, carrying out constant-temperature stirring until completely dissolved, and then adding sodium dodecyl sulfate and sodium sulfite, and obtaining the aqueous phase A after sufficient stirring;

[0052] In the preparation method of the aqueous phase A, the mass-volume ratio of polyvinyl alcohol, ultrapure water, sodium dodecyl sulfate, and sodium sulfite is: 0.3~5 g: 50~500 mL: 1-8 g: 0.5~6 g.

[0053] In the present invention, the aqueous phase serves as the continuous phase, providing a dispersion medium for the oil phase, enabling the oil phase to be uniformly dispersed in water in the form of tiny droplets, which helps to improve the stability of the emulsion.

[0054] The constant temperature is 55~95 °C;

[0055] The stirring rate is 300~800 r / min, and the stirring time is 0.5~3 h.

[0056] The preparation method of the oil phase B is: mixing toluene, 2-thiophenecarboxaldehyde, acrylamide, ethylene glycol dimethacrylate and ammonium persulfate, and ultrasonic dissolving at a constant temperature to obtain the oil phase B.

[0057] In the preparation method of the oil phase B, the volume-mass ratio of toluene, 2-thiophenecarboxaldehyde, acrylamide, ethylene glycol dimethacrylate, and ammonium persulfate is 0.5 - 5 mL : 0.2 - 4 mL : 0.1 - 2.0 g : 0.2 - 4 mL : 0.02 - 0.2 g;

[0058] The constant temperature is 40 - 80 °C.

[0059] In the present invention, the oil phase is used as the dispersed phase, which can improve the solubility of the functional monomer and the cross-linking agent and promote the polymerization reaction. At the same time, the oil phase can also be used as a pore-forming agent. The product is washed with hot water and subjected to Soxhlet extraction with ethanol and ethanol-acetic acid solution to remove the residual suspension, and finally a porous polymer is obtained.

[0060] S4. Crush the black solid powder and wash it several times with hot water, then remove the residual suspension by Soxhlet extraction with ethanol and ethanol-acetic acid solution respectively, and then obtain the magnetic biomass carbon nanopolymer material through filtration, washing, and drying in sequence;

[0061] In this step, the temperature of the hot water is preferably 50 - 80 °C, and the number of washing times is 5 times; the black solid powder is first subjected to Soxhlet extraction with ethanol to remove the residual suspension, and then subjected to Soxhlet extraction with ethanol-acetic acid solution to remove the residual suspension. Removing the suspension twice successively is more thorough, and the purity of the obtained product is higher.

[0062] Among them, the volume ratio of ethanol to acetic acid is 1 - 10 : 1 - 10, and the Soxhlet extraction time is 5 - 48 h.

[0063] The technical solution of the present invention will be further described below through the drawings and examples.

[0064] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs.

[0065] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the gist or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed by the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0066] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment contains only an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered by the protection scope of the present invention.

[0067] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention / invention.

[0068] Example 1

[0069] This example provides a preparation method of a magnetic biomass carbon nanocomposite material for adsorbing heavy metals:

[0070] S1. Carbonize the dried rhododendron at 700 °C for 2 h under nitrogen protection to obtain a biomass carbon nanomaterial;

[0071] S2. Mix 0.5 g of the biomass carbon nanomaterial with 40 mL of ultrapure water and perform ultrasonic dispersion, then add 0.35 g of ferric chloride hexahydrate, 0.185 g of ferrous chloride tetrahydrate, and 0.139 g of sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0072] S3. After heating the mixed solution to 70 °C, adjust the pH to 11 with 25% ammonia water, stir the reaction at a constant temperature for 3 h, then cool to room temperature, use a magnet for solid-liquid separation to collect the solid product, wash it with ultrapure water until neutral, and dry it in vacuo at 60 °C for 12 h to obtain a magnetic biomass carbon nanomaterial;

[0073] S4. Prepare an aqueous phase A solution: Mix 1.0 g of polyvinyl alcohol and 200 mL of ultrapure water, stir at a stirring rate of 500 r / min at 90 °C until completely dissolved, then add 4.0 g of sodium dodecyl sulfate solution and 2.0 g of sodium sulfite, stir for 30 min, and then lower the temperature to 45 °C;

[0074] Prepare an oil phase B solution: Mix 2.5 mL of toluene, 1.2 mL of 2-thiophenecarboxaldehyde, 0.57 g of acrylamide, 1.0 mL of ethylene glycol dimethacrylate, and 0.04 g of ammonium persulfate, and dissolve it by ultrasonic wave at 60 °C;

[0075] Add 1.0 g of magnetic biochar nanomaterial and 0.04 potassium persulfate to aqueous phase A at 45 °C, and then dropwise add 5.4 mL of oil phase B at a stirring rate of 500 r / min for reaction for 1 h; after the reaction is completed, raise the temperature to 85 °C for polymerization reaction for 16 h, and after the reaction is completed, use a magnet for solid-liquid separation to obtain a black solid.

[0076] S5. After grinding the collected black solid, wash it 5 times with hot water at 60 °C, and then perform Soxhlet extraction with ethanol and ethanol-acetic acid solution (volume ratio 9:1) for 24 h respectively to remove the residual suspension, filter and collect the product, wash it several times with ultrapure water, and dry it in vacuum at 60 °C for 12 h to obtain the magnetic biochar nanopolymer material.

[0077] Example 2

[0078] This example provides a preparation method of a magnetic biochar nanopolymer material for adsorbing heavy metals:

[0079] S1. Carbonize the dried kapok at 700 °C for 2 h under nitrogen protection to obtain biochar nanomaterial;

[0080] S2. Mix 0.5 g of biochar nanomaterial with 40 mL of ultrapure water and perform ultrasonic dispersion, then add 0.20 g of ferric chloride hexahydrate, 0.25 g of ferrous chloride tetrahydrate and 0.139 g of sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0081] S3. After heating the mixed solution to 70 °C, adjust the pH to 11 with 25% ammonia water, stir the reaction at a constant temperature for 3 h, then cool to room temperature, use a magnet for solid-liquid separation to collect the solid product, wash it with ultrapure water until neutral, and dry it in vacuum at 60 °C for 12 h to obtain magnetic biochar nanomaterial;

[0082] S4. Prepare aqueous phase A solution: Mix 0.8 g of polyvinyl alcohol and 200 mL of ultrapure water, stir at a stirring rate of 500 r / min at 90 °C until completely dissolved, then add 2.0 g of sodium dodecyl sulfate solution and 2.0 g of sodium sulfite, stir for 30 min and then lower the temperature to 45 °C;

[0083] Prepare oil phase B solution: Mix 2.5 mL of toluene, 1.2 mL of 2-thiophenecarboxaldehyde, 0.57 g of acrylamide, 1.0 mL of ethylene glycol dimethacrylate and 0.04 g of ammonium persulfate, and dissolve it by ultrasonic wave at 60 °C;

[0084] Add 1.0 g of magnetic biochar nanomaterial and 0.04 potassium persulfate to the above aqueous phase A at 45 °C, and then dropwise add 5.0 mL of oil phase B at a stirring rate of 500 r / min for reaction for 1 h; after the reaction is completed, raise the temperature to 85 °C for polymerization reaction for 16 h, and after the reaction is completed, use a magnet for solid-liquid separation to obtain a black solid.

[0085] S5. After crushing the collected black solid, wash it 5 times with hot water at 50 °C, then perform Soxhlet extraction with ethanol and ethanol-acetic acid solution (volume ratio 9:1) for 24 h respectively to remove the residual suspension, filter and collect the product, wash it several times with ultrapure water, and dry it in vacuum at 60 °C for 12 h to obtain the magnetic biochar nanopolymer material.

[0086] Example 3

[0087] This example provides a preparation method of a magnetic biochar nanopolymer material for adsorbing heavy metals:

[0088] S1. Carbonize the dried rhododendron at 800 °C for 2 h under nitrogen protection to obtain biochar nanomaterial;

[0089] S2. Mix 0.5 g of biochar nanomaterial with 40 mL of ultrapure water and perform ultrasonic dispersion, then add 0.35 g of ferric chloride hexahydrate, 0.185 g of ferrous chloride tetrahydrate and 0.10 g of sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0090] S3. After heating the mixed solution to 60 °C, adjust the pH to 10 with 25% ammonia water, stir and react at a constant temperature for 3 h, then cool to room temperature, use a magnet for solid-liquid separation to collect the solid product, wash it with ultrapure water until neutral, and dry it in vacuum at 60 °C for 12 h to obtain magnetic biochar nanomaterial;

[0091] S4. Prepare aqueous phase A solution: Mix 1.0 g of polyvinyl alcohol and 200 mL of ultrapure water, stir at a stirring rate of 500 r / min at 90 °C until completely dissolved, then add 4.0 g of sodium dodecyl sulfate solution and 2.0 g of sodium sulfite, stir for 30 min and then lower the temperature to 45 °C;

[0092] Prepare oil phase B solution: Mix 3.0 mL of toluene, 1.0 mL of 2-thiophenecarboxaldehyde, 0.57 g of acrylamide, 1.0 mL of ethylene glycol dimethacrylate and 0.04 g of ammonium persulfate, and dissolve it by ultrasonic wave at 60 °C;

[0093] Add 1.0 g of magnetic biochar nanomaterial and 0.04 potassium persulfate to the above aqueous phase A at 45 °C, and then dropwise add 5.4 mL of oil phase B at a stirring rate of 500 r / min for reaction for 1 h; after the reaction is completed, raise the temperature to 70 °C for polymerization reaction for 8 h, and use a magnet for solid-liquid separation after the reaction is completed to obtain a black solid.

[0094] S5. After crushing the collected black solid, wash it 5 times with hot water at 80 °C, then perform Soxhlet extraction for 24 h with ethanol and ethanol-acetic acid solution (volume ratio 8:2) respectively to remove the residual suspension, filter and collect the product, wash it several times with ultrapure water, and dry it in vacuum at 60 °C for 12 h to obtain the magnetic biochar nanopolymer material.

[0095] Example 4

[0096] This example provides a preparation method of a magnetic biochar nanopolymer material for adsorbing heavy metals:

[0097] S1. Carbonize the dried Chinese redbud flowers at 700 °C for 2 h under nitrogen protection to obtain biochar nanomaterial;

[0098] S2. Mix 0.1 g of biochar nanomaterial with 20 mL of ultrapure water and perform ultrasonic dispersion, then add 0.1 g of ferric chloride hexahydrate, 0.05 g of ferrous chloride tetrahydrate and 0.05 g of sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0099] S3. After heating the mixed solution to 40 °C, adjust the pH to 9 with 25% ammonia water, stir the reaction at a constant temperature for 0.5 h, then cool to room temperature, use a magnet for solid-liquid separation to collect the solid product, wash it with ultrapure water until neutral, and dry it in vacuum at 60 °C for 12 h to obtain magnetic biochar nanomaterial;

[0100] S4. Prepare aqueous phase A solution: Mix 0.3 g of polyvinyl alcohol and 50 mL of ultrapure water, stir at a stirring rate of 300 r / min at 55 °C until completely dissolved, then add 1.0 g of sodium dodecyl sulfate solution and 0.5 g of sodium sulfite, stir for 30 min and then lower the temperature to 30 °C;

[0101] Prepare oil phase B solution: Mix 0.5 mL of toluene, 0.2 mL of 2-thiophenecarboxaldehyde, 0.1 g of acrylamide, 0.2 mL of ethylene glycol dimethacrylate and 0.02 g of ammonium persulfate, and dissolve it by ultrasonic wave at 40 °C;

[0102] Add 0.4 g of magnetic biochar nanomaterial and 0.02 potassium persulfate to aqueous phase A at 30 °C, and then dropwise add 3 mL of oil phase B at a stirring rate of 500 r / min for reaction for 1 h; after the reaction is completed, raise the temperature to 60 °C for polymerization reaction for 2 h, and perform solid-liquid separation with a magnet after the reaction is completed to obtain a black solid.

[0103] S5. After crushing the collected black solid, wash it 5 times with hot water at 60 °C, then perform Soxhlet extraction with ethanol and ethanol-acetic acid solution (volume ratio 1:1) for 24 h respectively to remove the residual suspension, filter and collect the product, wash it several times with ultrapure water, and vacuum dry it at 60 °C for 12 h to obtain the magnetic biochar nanopolymer material.

[0104] Example 5

[0105] This example provides a preparation method of a magnetic biochar nanopolymer material for adsorbing heavy metals:

[0106] S1. Carbonize the dried reed flowers at 700 °C for 2 h under nitrogen protection to obtain biochar nanomaterial;

[0107] S2. Mix 1 g of biochar nanomaterial with 100 mL of ultrapure water and perform ultrasonic dispersion, then add 1 g of ferric chloride hexahydrate, 0.5 g of ferrous chloride tetrahydrate and 0.5 g of sodium citrate dihydrate and stir to dissolve to obtain a mixed solution;

[0108] S3. After heating the mixed solution to 90 °C, adjust the pH to 13 with 25% ammonia water, stir and react at a constant temperature for 12 h, then cool to room temperature, perform solid-liquid separation with a magnet to collect the solid product, wash it with ultrapure water until neutral, and vacuum dry it at 60 °C for 12 h to obtain the magnetic biochar nanomaterial;

[0109] S4. Prepare aqueous phase A solution: Mix 5 g of polyvinyl alcohol and 500 mL of ultrapure water, stir at a stirring rate of 800 r / min at 95 °C until completely dissolved, then add 8.0 g of sodium dodecyl sulfate solution and 6 g of sodium sulfite, stir for 3 h and then lower the temperature to 70 °C;

[0110] Prepare oil phase B solution: Mix 5 mL of toluene, 4 mL of 2-thiophenecarboxaldehyde, 2.0 g of acrylamide, 4 mL of ethylene glycol dimethacrylate and 0.2 g of ammonium persulfate, and ultrasonically dissolve at 80 °C;

[0111] Add 4 g of magnetic biochar nanomaterials and 0.2 potassium persulfate to aqueous phase A at 70 °C, and then dropwise add 6.5 mL of oil phase B at a stirring rate of 800 r / min for reaction for 10 h; after the reaction is completed, raise the temperature to 95 °C for polymerization reaction for 24 h. After the reaction is completed, perform solid-liquid separation with a magnet to obtain a black solid.

[0112] S5. After grinding the collected black solid, wash it 5 times with hot water at 60 °C, and then perform Soxhlet extraction with ethanol and ethanol-acetic acid solution (volume ratio 1:10) for 24 h respectively to remove the residual suspension. Filter and collect the product, wash it several times with ultrapure water, and dry it in vacuum at 60 °C for 12 h to obtain magnetic biochar nanocomposite polymer materials.

[0113] Comparative Example 1

[0114] In this comparative example, magnetic biochar nanomaterials were obtained according to steps S1-S3 of Example 1. Then, 1.0 g of magnetic biochar nanomaterials was mixed with 1.2 mL of 2-thiophenecarboxaldehyde, 0.57 g of acrylamide, 1.0 mL of ethylene glycol dimethacrylate, and 50 mL of ultrapure water. After ultrasonic dissolution, it was heated to 85 °C for polymerization reaction for 16 h. After the reaction was completed, solid-liquid separation was performed with a magnet to obtain a black solid, which was washed 5 times with ethanol and ultrapure water respectively, and dried in vacuum at 60 °C for 12 h to obtain magnetic biochar nanocomposite polymer materials.

[0115] Comparative Example 2

[0116] In this comparative example, magnetic biochar nanomaterials were obtained according to steps S1-S3 of Example 1.

[0117] Experimental Example 1

[0118] Characterize the magnetic biochar nanocomposite polymer materials prepared in Example 1:

[0119] 1. Scanning electron microscopy characterization

[0120] Characterize the magnetic biochar nanocomposite polymer materials prepared in Example 1 by scanning electron microscopy. The characterization results are shown in the appendix Figure 1 . It can be clearly observed from Figure 1 that the material is in the form of irregular stacked particle flowers, with a rough surface, good dispersibility, and a large number of voids between the particles. This multi-void structure is conducive to accelerating mass transfer.

[0121] 2. Infrared spectroscopy characterization

[0122] Characterize the magnetic biochar nanocomposite polymer materials prepared in Example 1 by infrared spectroscopy. The characterization results are as shown in the appendix Figure 2 . The biochar spectrum (appendix Figure 2a) The broad peak at 3300 cm -1 is the -OH stretching vibration peak, and the peak at 1638 cm -1 is attributed to the stretching vibration peak of C=O; from the spectra of the magnetic biochar in Figure 2 b and the magnetic biochar nanopolymer material in Figure 2 c, the Fe-O characteristic peak at 567 - 580 cm -1 can be observed, indicating that magnetite is embedded in the biochar and polymer. In addition, in the spectra of the magnetic biochar nanopolymer material (attached Figure 2 c) The broad peak at 1088 cm -1 is attributed to the stretching vibration peaks of C-O-C, C-S, and O-H. The peak at 1394 cm -1 is attributed to the characteristic absorption peak of CH 2 . The strong broad peak at 1628 cm −1 is attributed to the stretching vibrations of -NH 2 , -C=C, -C=N, -C=O. The peak at 3183 cm -1 is the stretching vibration peak of -CH=C on the thiophene ring. The strong absorption peak in the range of 3300 - 3550 cm −1 is the stretching vibration peak of -OH and -NH 2 . The above results confirm that cross-linking reactions occurred between thiophene formaldehyde and acrylamide as bifunctional monomers and ethylene glycol dimethacrylate, indicating the successful synthesis of the magnetic biochar nanopolymer material.

[0123] 3. Study on dynamic adsorption performance

[0124] Disperse 15 mg of the magnetic biochar nanopolymer adsorbent prepared in Example 1 in 10 mL of a mixed solution (pH 6.0) of Zn 2+ , Cd 2+ and Pb 2+ with a concentration of 400 mg / L. At 25 °C, oscillate and adsorb at a constant temperature with a rotation speed of 100 r / min for 0 - 60 min, and perform solid-liquid separation with a magnet. Use graphite furnace atomic absorption spectrometry to measure the content of metal ions in the solution, and calculate the adsorption amount of the adsorbent for metal ions according to the following formula (1) Q .

[0125] (1)

[0126] Where: c 0 and c t are the initial concentration and the concentration at the adsorption t time of the metal ions in the solution, respectively, in mg / L; vis the solution volume, mL; m is the weight of the adsorbent, g.

[0127] With the adsorption time t as the abscissa and the adsorption capacity Q as the ordinate, the adsorption kinetic curve of the adsorbent for metal ions was plotted, and the results are shown in Appendix Figure 3 . As can be seen from the figure, when the adsorption time is 20 min, the adsorption of the adsorbent for Zn 2+ , Cd 2+ and Pb 2+ tends to saturation, and the maximum adsorption capacities are 240.0, 204.6 and 139.6 mg / g, respectively. The pseudo-first-order kinetic model and the pseudo-second-order kinetic model were used to fit the kinetic data. The results show that the correlation coefficient ( R 2 greater than 0.999) of the pseudo-second-order kinetic model is much larger than that of the pseudo-first-order kinetic model. Moreover, the equilibrium adsorption capacities of Zn 2+ , Cd 2+ , Pb 2+ obtained from the fitting curve of the pseudo-second-order kinetic model are 246.3, 209.2, 144.9 mg / g, which are very close to the actual measured Zn 2+ , Cd 2+ , Pb 2+ adsorption capacities (240.0, 204.6 and 139.6 mg / g), indicating that the adsorption behavior of the adsorbent for Zn 2+ , Cd 2+ and Pb 2+ conforms to the pseudo-second-order kinetic model, and during the adsorption process, the adsorption rate is mainly controlled by chemical interactions.

[0128] Study on static adsorption performance Disperse 15 mg of the magnetic biomass carbon nanopolymer adsorbent prepared in Example 1 in 10 mL of a mixed solution of Zn 2+ , Cd 2+ and Pb 2+ with a concentration of 50 - 1000 mg / L (pH 6.0), adsorb for 1 h at 25 °C and 100 r / min, and separate the solid and liquid with a magnet. The content of metal ions in the solution after adsorption equilibrium was determined by graphite furnace atomic absorption spectrometry, and then the adsorption amount of the adsorbent for metal ions was calculated. Figure 4 is the influence diagram of the initial concentration of metal ions on the adsorption amount. As Figure 4 can be seen, when the initial concentration increases to 600 mg / L, the adsorption tends to saturation. The adsorption isotherms of the three metal ions on the adsorbent were fitted by the Langmuir and Freundlich models. The results show that the correlation coefficient of the linear equation fitting of the Langmuir modelR 2 The values are higher than those fitted by the linear equation of the Freundlich model, indicating that the Langmuir adsorption isotherm is more suitable for describing the adsorption behavior of Zn 2+ , Cd 2+ and Pb 2+ on the magnetic biochar nanocomposite adsorbent. Therefore, it can be inferred that the adsorption behavior is monolayer type, which includes physical and chemical adsorption mechanisms. In addition, the maximum adsorption capacities of Zn 2+ , Cd 2+ and Pb 2+ calculated from the Langmuir adsorption model are 349.65, 256.41 and 180.83 mg / g respectively, which are close to the experimental values of 343.3, 250.7 and 177.6 mg / g.

[0129] The static adsorption experiments were used to determine the maximum adsorption capacities of the adsorption materials obtained in Examples 2-5 and Comparative Examples 1-2 for Zn 2+ , Cd 2+ and Pb 2+ . The results are shown in Table 1.

[0130]

[0131] Recyclability: 15 mg of the magnetic biochar nanocomposite adsorbent prepared in Example 1 was dispersed in 10 mL of a mixed solution (pH 6.0) of Zn 2+ , Cd 2+ and Pb 2+ with a concentration of 300 mg / L, adsorbed at 25 °C and 100 r / min for 1 h, and the solid-liquid separation was carried out with a magnet to measure the adsorption capacity. The separated adsorbent was eluted with 200 mL of an EDTA solution with a concentration of 0.1 mol / L for 30 min for metal ions, and repeated 2 times. It was washed several times with ultrapure water, dried and reused. The results are as Figure 5 shown. After 6 adsorption-desorption cycles, the adsorption amounts of the adsorbent for Zn 2+ , Cd 2+ and Pb 2+ still reached more than 81% of the initial value, indicating that the adsorbent has good reusability.

[0132] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for preparing a magnetic biomass carbon nanopolymer material for adsorbing heavy metals, characterized in that: The following steps are involved: S1. After mixing the biomass carbon nanomaterial with ultrapure water and performing ultrasonic dispersion, ferric chloride hexahydrate, ferrous chloride tetrahydrate and sodium citrate dihydrate are added and stirred to dissolve to obtain a mixed solution; S2. heating the mixed solution and sequentially adjusting the pH, reacting at a constant temperature, cooling, magnetically separating, and washing to obtain a magnetic biomass carbon nanomaterial; S3. Add magnetic biomass carbon nanomaterials and potassium persulfate to the aqueous phase A, and then add the oil phase B dropwise while stirring to carry out a first reaction at a constant temperature; after the reaction is completed, increase the temperature to carry out a second reaction, and after the reaction is completed, use a magnet to separate the solid and liquid to obtain a black solid powder; S4. The black solid powder is crushed and washed with hot water several times, and then the residual suspension is removed by Soxhlet extraction with ethanol and ethanol-acetic acid solution respectively, and then filtered, washed and dried in sequence to obtain a magnetic biomass carbon nanopolymer material; The preparation method of the aqueous phase A is as follows: polyvinyl alcohol and ultrapure water are mixed, stirred at a constant temperature until they are completely dissolved, and then sodium lauryl sulfate and sodium sulfite are added, and the aqueous phase A is obtained after sufficient stirring; The preparation method of the oil phase B is as follows: toluene, 2-thiophene carboxaldehyde, acrylamide, ethylene glycol dimethacrylate and ammonium persulfate are mixed, and the oil phase B is obtained by ultrasonically dissolving the mixture at a constant temperature.

2. The preparation method according to claim 1, characterized in that: The preparation method of the biomass carbon nanomaterial is: The dried biomass is carbonized at high temperature to obtain biomass carbon nanomaterials; The biomass is one of yellow flower pineapple, crabapple flower, azalea, kapok flower, bauhinia flower, red cherry flower and reed flower; the high temperature carbonization temperature is 600-1000° C., and the high temperature carbonization time is 1-4 hours.

3. The preparation method according to claim 1, characterized in that: The mass volume ratio of the biochar, ultrapure water, ferric chloride hexahydrate, ferrous chloride tetrahydrate, and sodium citrate dihydrate in the S1 is 0.1-1 g: 20-100 mL: 0.1-1 g: 0.05-0.5 g: 0.05-0.5 g.

4. The preparation method according to claim 1, characterized in that: The heating temperature in S2 is 40-90° C.; Adjust the pH value to 9-13, and the pH adjuster is 25% ammonia water; The constant temperature reaction time is 0.5 to 12 hours.

5. The preparation method according to claim 1, characterized in that: The mass volume ratio of the water phase A, the magnetic biomass carbon nanomaterial, potassium persulfate and the oil phase B in the S3 is: 100-400 mL: 0.4-4 g: 0.02-0.2 g: 3-6.5 mL.

6. The preparation method according to claim 1, characterized in that: The stirring rate in S3 is 300-800 r / min; The temperature of the first reaction is 30-70°C, and the time of the first reaction is 0.5-10h; The temperature of the second reaction is 60 to 95° C., and the time of the second reaction is 2 to 24 hours.

7. The preparation method according to claim 1, characterized in that: The volume ratio of ethanol to acetic acid in S4 is 1-10:1-10, and the Soxhlet extraction time is 5-48 hours.

8. The preparation method according to claim 1, characterized in that: In the preparation method of the aqueous phase A, the mass volume ratio of polyvinyl alcohol, ultrapure water, sodium lauryl sulfate and sodium sulfite is: 0.3-5 g: 50-500 mL: 1-8 g: 0.5-6 g; The constant temperature is 55-95°C; The stirring rate is 300-800 r / min, and the stirring time is 0.5-3 h.

9. The preparation method according to claim 1, characterized in that: In the preparation method of the oil phase B, the volume mass ratio of toluene, 2-thiophenecarboxaldehyde, acrylamide, ethylene glycol dimethacrylate, and ammonium persulfate is 0.5-5 mL: 0.2-4 mL: 0.1-2.0 g: 0.2-4 mL: 0.02-0.2 g; The constant temperature is 40-80°C.

10. A magnetic biomass carbon nanopolymer material for adsorbing heavy metals, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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