CN106378093B - Preparation method and application of magnetic hollow graphene-based composite microsphere material - Google Patents

Preparation method and application of magnetic hollow graphene-based composite microsphere material Download PDF

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CN106378093B
CN106378093B CN201610984633.XA CN201610984633A CN106378093B CN 106378093 B CN106378093 B CN 106378093B CN 201610984633 A CN201610984633 A CN 201610984633A CN 106378093 B CN106378093 B CN 106378093B
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刘玉荣
张进
刘碧桃
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Chongqing University of Arts and Sciences
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Abstract

The invention discloses a preparation method and application of a magnetic hollow graphene-based composite microsphere material. The preparation method adopts polymer microspheres with positive charges as a template, and obtains the magnetic hollow graphene-based composite microsphere material through a high-temperature heat treatment one-step method. The preparation method is simple and easy to implement, has no environmental pollution, is easy to realize industrial production, and the prepared magnetic hollow graphene-based composite microspheres have high specific surface area and developed pore structures and can carry out efficient and rapid adsorption separation on dye molecules. The magnetic hollow graphene-based composite microsphere material prepared by the invention has wide application prospect in the aspect of treating dye wastewater.

Description

Preparation method and application of magnetic hollow graphene-based composite microsphere material
Technical Field
The invention belongs to the technical field of novel carbon materials, and particularly relates to a preparation method and application of a magnetic hollow graphene-based composite microsphere material.
Background
With the rapid development of industrial technology, organic synthetic dyes are widely used in the fields of textile, printing and dyeing, papermaking, printing, food, cosmetics and the like, and simultaneously, a large amount of dye wastewater is also generated. The dye wastewater has the characteristics of large discharge amount, high chroma, complex components, higher Chemical Oxygen Demand (COD) value, large toxicity and the like. The discharge of a large amount of dye wastewater has caused serious water pollution and ecological damage. Therefore, people pay high attention to how to effectively treat the dye wastewater.
The existing methods for treating dye wastewater mainly comprise a chemical method, a biological method, an adsorption method and the like. Chemical methods require the addition of chemical reagents to the water body, which is highly susceptible to secondary pollution and difficult to completely eliminate dye contaminants. The biological method has the advantages of long period, complex process flow, strict operation and high elimination efficiency which is greatly influenced by water temperature, pH value and the like. The adsorption method has the advantages of simple process, low equipment investment, low cost, no environmental pollution, obvious adsorption treatment effect and the like, and thus the adsorption method is widely concerned. The key to influence the adsorption efficiency is the adsorption material, so the development of the cheap and efficient adsorption material is very important. The porous carbon material has the characteristics of high specific surface area, developed pore structure, simple synthesis steps, economy, high efficiency, stable physical and chemical properties, excellent adsorption performance and the like, and is the first choice of the adsorption material. Common carbon material adsorbents include activated carbon, mesoporous carbon, carbon nanotubes, graphene and the like.
Graphene is a novel carbon material emerging in recent years and is sp2The thickness of the periodic honeycomb lattice structure of the two-dimensional monoatomic layer consisting of hybridized carbon six-membered rings is only 0.335 nm. Graphene has many unique advantages over conventional carbon materials, such as high theoretical specific surface area (2600 m)2The catalyst has excellent thermal conductivity, good chemical stability, excellent mechanical property and the like, shows good application prospect in the aspect of replacing the traditional adsorbent, and has good adsorption performance on heavy metal ions, dye molecules, oil products and the like. However, since the particle size of graphene is small, the graphene cannot be separated and recovered by the conventional industrial filtration and centrifugation means, and thus, the graphene adsorbing the pollutants may cause serious secondary pollution. In addition, due to pi-pi bond interaction between adjacent sheets, graphene is prone to serious aggregation or accumulation, so that the effective specific surface area of graphene is reduced, and the adsorption capacity of graphene is reduced. These problems severely limit the practical application of graphene in the field of adsorption.
The magnetic separation technology is adopted to realize the high-efficiency and rapid separation of the adsorbent. Therefore, the development of the magnetic graphene composite material has important significance for improving the separation efficiency of the graphene-based adsorption material and reducing secondary pollution and cost after adsorption. The preparation method of the magnetic graphene composite material mainly comprises a chemical coprecipitation method, a hydrothermal method, a solvothermal method and a chemical reduction method. The magnetic graphene composite material prepared by the methods is single in appearance and relatively easy to aggregate or accumulate. Most of the reported magnetic graphene composite materials are solid structures, and the specific surface area of the magnetic graphene composite materials is relatively small, so that the adsorption performance of the magnetic graphene composite materials is influenced to a great extent. Compared with a graphene adsorption material with a solid structure, the graphene adsorption material with a hollow structure has the advantages of high specific surface area, large internal space, rich pores, good thermal stability, low density and the like, and has important scientific research value and special application prospect in the adsorption field. The high specific surface area creates conditions for capturing a large amount of adsorbates in the solution, and the unique cavity structure and the developed pore structure provide a channel for the rapid transmission of the adsorbates, so that the adsorption efficiency of the material on pollutants is greatly improved. Therefore, the construction of the graphene material with the hollow structure is one of effective ways for reducing the agglomeration degree of the graphene and improving the adsorption performance of the graphene.
The hollow carbon sphere material with controllable appearance and higher directionality can be obtained by adopting a template method, and the currently adopted hard template agent mainly comprises SiO2Microspheres, Polystyrene (PS) microspheres, Polymethylmethacrylate (PMMA) microspheres, and the like. By means of SiO2When the microspheres are used as templates, a layer of polymer is embedded on the surface of the microspheres by a vapor deposition method or a hydrothermal method, then a carbon shell is formed by carbonization, and finally the silicon template is removed by sodium hydroxide or hydrofluoric acid to obtain the hollow carbon spheres. The process has more synthesis steps, relatively complex operation and longer synthesis period. In addition, the template inevitably needs to be removed by sodium hydroxide or hydrofluoric acid or the like during the preparation process, which not only pollutes the environment but also increases the cost. When PS or PMMA microspheres are used as templates, the templates can be removed by adopting specific solvent dissolution or high-temperature roasting to synthesize the hollow carbon spheres. However, the surface of the adopted PS or PMMA microsphere template agent is inert, so that graphene is easy to agglomerate, and the synthesized graphene microsphere with a hollow structure has the problems of poor controllability, poor dispersibility, low adsorption performance, difficult separation and recovery and the like. Therefore, the development of a feasible efficient preparation process of the graphene microspheres with the hollow structures has very important theoretical value and practical significance.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method and application of a magnetic hollow graphene-based composite microsphere material, aiming at solving the technical problems of poor controllability and dispersibility, low adsorption performance of products, difficult recovery and separation and the like in the preparation process of the currently produced hollow graphene microsphere material.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: magnetic propertyThe preparation method of the hollow graphene-based composite microsphere material is characterized in that a proper template agent and a self-assembly strategy are selected, and the controllable preparation of the magnetic hollow graphene-based composite microsphere material is realized through a high-temperature heat treatment one-step method, wherein the preparation mechanism schematic diagram is shown in fig. 1. Firstly, adding polymer microsphere dispersion liquid with positive surface charge to Graphene Oxide (GO) with negative surface charge-) In the dispersion, polymer microspheres coated by graphene oxide are formed through electrostatic self-assembly, a proper amount of metal salt solution is added into the obtained mixed dispersion, and metal ions (M) with positive charges are fully adsorbed through electrostatic interactionx+) And then removing the polymer microsphere template agent by a high-temperature heat treatment one-step method, simultaneously converting the adsorbed metal ions into magnetic nano particles, and reducing the graphene oxide component into graphene so as to obtain the magnetic hollow graphene-based composite microsphere material.
The method specifically comprises the following steps:
s1: and adding the polymer microsphere dispersion liquid into the graphene oxide dispersion liquid, and magnetically stirring for 2-5 hours to obtain a mixed dispersion liquid.
S2: adding metal salt into the mixed dispersion liquid obtained in the step S1, continuing to magnetically stir for 12-24 hours, and filtering to obtain a solid product; washing and drying the solid product, placing the solid product in a protective gas atmosphere, heating to 500-900 ℃, and roasting at high temperature for 2-5 h; and naturally cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere material.
In step S1, the mass ratio of the graphene oxide to the polymer microspheres in the mixed dispersion liquid is 1: (5-15), the graphene oxide can completely and effectively coat the polymer microspheres according to the proportion.
The mass ratio of the metal salt added in the step S2 to the graphene oxide in the mixed dispersion liquid is (1-30): 1; the proportion is beneficial to the uniform dispersion of the obtained magnetic metal substances in the graphene in the product, and the graphene substances are not stacked or aggregated. The metal salt is a salt containing iron, cobalt, nickel or manganese.
The concentration of the graphene oxide dispersion liquid in the step S1 is 1-10 mg/mL, an improved Hummers method can be adopted for preparing graphene oxide, and the preparation steps are as follows:
a: under the ice-water bath condition, adding concentrated sulfuric acid with the mass fraction of 95-98% into a mixture of sodium nitrate and graphite powder, and stirring for reaction for 10-60 min;
b: adding potassium permanganate, and continuing to react for 12-48 h, wherein the temperature is kept to be less than or equal to 20 ℃ in the reaction process;
c: adding deionized water as a diluent, and stirring for reaction for 30min to obtain a reaction solution; heating to 98 ℃ and preserving the temperature for 48 hours until the color of the reaction solution is changed from black to brown yellow;
d: dropwise adding 35% hydrogen peroxide into the brown yellow reaction solution, and continuously reacting for 30min to change the brown yellow reaction solution into a bright yellow reaction solution;
e: filtering the bright yellow reaction solution, washing the filtered solid substance by using an HCl solution with the mass fraction of 5-10% and deionized water, and drying at room temperature to constant weight to obtain graphene oxide;
f: and at room temperature, adding graphene oxide into deionized water, and performing ultrasonic stirring to form a graphene oxide dispersion liquid.
Wherein: the ratio of the graphite powder to the sodium nitrate to the concentrated sulfuric acid to the potassium permanganate to the diluent to the hydrogen peroxide is (0.5-5.5 g): (0.5-5.5 g): (90-300 ml): (5-25 g): (25-350 ml): (50-100 ml), and the proportion is beneficial to obtaining the graphene oxide product with large specific surface area and moderate size and layer number.
The polymer microsphere dispersion liquid in the step S1 is polymethyl methacrylate (PMMA) microsphere dispersion liquid with positive charges on the surface, the concentration of the polymer microsphere dispersion liquid is 1-15 wt%, a free radical initiator with positive charges is selected, namely azobisisobutylamidine hydrochloride (AMPMDHC) is used for initiating Methyl Methacrylate (MMA) monomer polymerization, and monodisperse PMMA microspheres with positive charges on the surface are synthesized through an emulsifier-free emulsion polymerization method, wherein the preparation steps are as follows: mixing MMA with water to obtain an MMA solution, and stirring for 30-60 min under a protective gas atmosphere; raising the reaction temperature to 50-70 ℃, adding AMPMDHC and water, and carrying out polymerization reaction for 1-6 h at the temperature of 60-80 ℃ to obtain PMMA microsphere dispersion liquid with positive charges on the surface; wherein the mass ratio of MMA to AMPMDHC is 1: (0.001-0.002).
The polymer microsphere dispersion liquid in the step S1 may also be a Polystyrene (PS) microsphere dispersion liquid with a positive surface charge at a concentration of 1-15 wt%, and the preparation steps are as follows:
(1) styrene, polyvinylpyrrolidone, 2' -azobisisobutylamidine dihydrochloride and water are mixed according to the ratio of the dosage (6-10 g): (1-1.5 g): (0.2-0.3 g): (100-200 ml) are sequentially added into a reaction vessel, stirred for 30-60 min under the protective gas atmosphere, and then heated to 50-80 ℃ to carry out polymerization reaction for 12-48 h;
(2) centrifuging, cleaning and filtering by using ethanol and deionized water in sequence to obtain PS microspheres with positive charges on the surfaces; then water is used as solvent to prepare PS microsphere dispersion liquid.
The protective gas involved in the above step is typically nitrogen or argon.
The heating rate in the high-temperature roasting process is 0.5-10 ℃/min, and the flow rate of the protective gas is 50-150 mL/min. The selected heating rate is beneficial to the complete and thorough implementation of the high-temperature cracking reaction in the high-temperature heat treatment process, and the selected flow rate of the protective gas is beneficial to protecting the hollow structure, the microporous structure and the like of the product generated after the high-temperature cracking.
The magnetic hollow graphene-based composite microsphere prepared by the invention has the height of 900-2000 m2Specific surface area per gram, total pore volume of 0.35-0.6 cm3The volume of the micropores is 0.22-0.4 cm3/g。
The magnetic hollow graphene-based composite microsphere material prepared by the method is applied to dye wastewater treatment. The magnetic hollow graphene-based composite microsphere material prepared by the invention has good adsorption performance on dye molecules such as acid blue 92, orange II, malachite green, rhodamine B, methylene blue and the like.
Compared with the prior art, the invention has the following beneficial effects:
1. the graphene microsphere prepared by the method is of a hollow structure and large in specific surface area. Most of the graphene microspheres reported at present are solid structures, and the graphene microsphere material prepared by the invention is a hollow structure, so that the specific surface area of graphene can be increased to the maximum extent, and the saturated adsorption capacity of the graphene can be increased; the unique cavity structure and the developed pore structure provide a channel for the rapid transmission of adsorbate, thereby greatly improving the adsorption efficiency of the material to pollutants.
2. The dispersibility is good, and the controllability is strong. The conventional polymer microsphere template agents such as PS microspheres or PMMA microspheres are usually inert on the surface, so that the synthesized graphene microspheres with hollow structures have the defects of poor controllability, poor dispersibility, difficult separation and recovery and the like. According to the invention, PS microspheres or PMMA microspheres with positive charges on the surface are used as a template agent, and graphene oxide with negative charges is self-assembled on the surface of the template agent, so that the components in a dispersion liquid are uniformly dispersed, the self-assembly strategy can effectively avoid the aggregation or accumulation phenomenon of graphene, and the obtained graphene microspheres with hollow structures have uniform size and shape controllability and good monodispersity.
3. The synthetic method is environment-friendly and efficient. The formation of the magnetic nanoparticles, the reduction of the graphene oxide component and the removal of the template agent are realized in one step by a high-temperature heat treatment method, so that the reduction of graphene by using a toxic reducing agent (such as hydrazine hydrate, sodium borohydride and the like) is avoided, and the method has the advantages of high efficiency, low cost, environmental friendliness, safety and the like.
4. The adsorption effect is good. The polymer microsphere template and the oxygen-containing functional group of the graphene oxide generate a large amount of gas in the high-temperature decomposition process, so that the obtained graphene composite microsphere material has a rich three-dimensional porous skeleton structure, the obtained product has a high specific surface area, and adsorption sites are increased, so that the adsorption speed and the adsorption capacity of the graphene composite microsphere material are improved.
5. Convenient desorption and recovery. The magnetic hollow graphene-based composite microsphere obtained by the invention has unique magnetic responsiveness, can be efficiently and quickly separated by an external magnetic field, does not need traditional operations such as filtration, centrifugation and the like, has no secondary pollution, greatly simplifies the preparation process flow, effectively reduces the preparation cost, and solves the practical application problem that the adsorption material is difficult to separate. The magnetic hollow graphene-based composite microsphere material prepared by the invention has the advantages of strong adsorption performance, easiness in separation and recovery, no secondary pollution and the like.
6. Low cost and easy popularization. The preparation method is simple, easy to operate, low in cost and easy for large-scale production.
Drawings
FIG. 1 is a schematic diagram of a preparation mechanism of a magnetic hollow graphene-based composite microsphere material;
FIG. 2 is a scanning electron microscope image of PMMA microspheres with positive charges on the surface prepared in the first example;
FIG. 3 shows PMMA prepared in the first example+/GO-Scanning electron microscope images of the composite microspheres;
fig. 4 is a scanning electron microscope image of the magnetic hollow graphene-based composite microsphere prepared in the first example.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example one
The magnetic hollow graphene-based composite microsphere material is prepared in the following way, and an adsorption experiment is carried out by applying the microsphere material.
1. Preparation of graphene oxide
The graphene oxide is prepared by adopting an improved Hummers method, and the process flow is as follows: assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of concentrated sulfuric acid with the mass percent of 95%, and reacting in the ice-water bath for 30 min; then, 15g of potassium permanganate is added, the reaction temperature is controlled not to exceed 20 ℃, and the reaction is continued for 12 hours; and adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of the graphene oxide. Dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; and filtering, washing and drying to obtain a graphene oxide product. And (3) preparing graphene oxide into 2mg/ml GO dispersion liquid by taking water as a solvent.
2. Preparation of polymethyl methacrylate (PMMA) microsphere template with positive charges on surface
A free radical initiator with positive charges, namely azobisisobutylamidine hydrochloride (AMPMDHC), is selected to initiate Methyl Methacrylate (MMA) monomer polymerization, and the monodisperse PMMA microspheres with the positive charges on the surfaces are synthesized by a soap-free emulsion polymerization method. The specific process flow is as follows: adding 10g of MMA and 165ml of water into a 250ml reactor, stirring for 30min under the protection of nitrogen gas, raising the reaction temperature to 70 ℃, adding 0.015g of AMPMDHC and 5ml of water, and carrying out polymerization reaction for 6h at the temperature of 70 ℃ to obtain a PMMA microsphere dispersion liquid with 10wt% of positive surface charge. The scanning electron microscope image of the obtained PMMA microspheres is shown in FIG. 2, and it can be seen from the image that the PMMA microsphere material has very uniform particle size, the average particle size is about 200 nm, good monodispersity and no aggregation or accumulation phenomenon.
3. Preparation of magnetic hollow graphene-based composite microsphere material
Adding 10wt% of PMMA microsphere dispersion liquid with positive charges on the surface into 2mg/ml graphene oxide dispersion liquid, and magnetically stirring for 2 hours to enable PMMA microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, so as to obtain PMMA+/GO-Compounding the microspheres, and adding 2.5mmol of FeSO4 · 7H2And (3) continuing magnetically stirring the O solution for 20 hours, filtering and drying, calcining the product at 700 ℃ for 3 hours in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere material. In which PMMA prepared in this example+/GO-The scanning electron microscope image of the composite microsphere is shown in FIG. 3, from which it can be seen that the surface of the microsphere is tightly coated with a film-like substance, which indicates that the graphene oxide component is successfully assembled on the surface of the PMMA microsphere, and PMMA+/GO-The composite microspheres also have good monodispersity, and no aggregation or accumulation phenomenon occurs in the self-assembly process. The scanning electron microscope image of the obtained magnetic hollow graphene-based composite microsphere material is shown in FIG. 4, from which it can be seen that the composite microsphere material hasThe regular three-dimensional macroporous structure with the size of about 200 nm is mainly the three-dimensional macroporous structure generated after the PMMA template is removed in the high-temperature roasting process.
4. Adsorption of magnetic hollow graphene-based composite microsphere material to dye molecules
The specific surface area of the magnetic hollow graphene-based composite microsphere material prepared by the embodiment is 987m2Per g, total pore volume of 0.56cm3Per g, pore volume of the micropores is 0.36cm3And/g, has good adsorption performance on dye molecules. After adsorbing the dye, the adsorbent can be rapidly separated by an external magnetic field. Table 1 shows the adsorption performance of the magnetic hollow graphene-based composite microsphere prepared in this embodiment on dye molecules, and it can be seen from the table that the prepared magnetic hollow graphene-based composite microsphere has a high-efficient adsorption effect on dye molecules, and the adsorbent has magnetism, and can realize high-efficient and rapid magnetic separation, thereby avoiding secondary pollution, indicating that the regenerability is good, and the removal rates of acid blue 92, orange yellow ii, malachite green, rhodamine B and methylene blue after 10 cycles are all above 75%.
Table 1 adsorption performance of magnetic hollow graphene-based composite microsphere material prepared in example 1 on dye molecules
Number of cycles Number of Acid blue 92 removal Percentage (%) Orange II removal Percentage (%) Malachite green removal Percentage (%) Rhodamine B removal Percentage (%) Methylene blue removal Percentage (%)
1 99 99 99 99 98
2 98 98 98 98 97
3 97 97 97 97 96
4 96 96 96 96 95
5 95 95 95 95 94
6 93 93 94 92 91
7 91 91 92 89 88
8 88 88 88 87 86
9 85 84 84 83 82
10 80 79 79 76 75
Example two
The magnetic hollow graphene-based composite microsphere material is prepared in the following way, and an adsorption experiment is carried out by applying the microsphere material.
1. Preparation of graphene oxide
The graphene oxide is prepared by adopting an improved Hummers method, and the process flow is as follows: assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of 98% concentrated sulfuric acid by mass, and reacting in the ice-water bath for 60 min; then, 15g of potassium permanganate is added, the reaction temperature is controlled not to exceed 20 ℃, and the reaction is continued for 24 hours; and adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of the graphene oxide. Dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; and filtering, washing and drying to obtain a graphene oxide product. And (3) preparing graphene oxide into 1mg/ml GO dispersion liquid by taking water as a solvent.
2. Preparation of Polystyrene (PS) microsphere template agent with positive charges on surface
Sequentially adding 8g of styrene, 1.2g of polyvinylpyrrolidone, 0.25g of 2, 2' -azobisisobutylamidine dihydrochloride and 150mL of water into a reaction container, stirring for 60min under the protection of nitrogen gas, heating to 70 ℃, carrying out thermal polymerization for 24h, sequentially centrifuging with ethanol and deionized water, cleaning and filtering to obtain the PS microspheres with positive charges on the surfaces. Using water as a solvent, and preparing the PS microspheres into a PS microsphere dispersion liquid with the concentration of 10 wt%.
3. Preparation of magnetic hollow graphene-based composite microsphere material
Adding 8wt% of PS microsphere dispersion liquid with positive charges on the surface into 1mg/ml graphene oxide dispersion liquid, stirring for 2 hours by magnetic force to enable PS microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, and then adding 0.56g of FeSO4 · 7H2And (3) continuing magnetically stirring the O solution for 20 hours, filtering and drying, calcining the product at 750 ℃ for 3 hours in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere.
(4) Adsorption of magnetic hollow graphene-based composite microsphere material to dye molecules
The specific surface area of the magnetic hollow graphene-based composite microsphere material prepared by the embodiment is 992m2Per g, total pore volume of 0.55cm3Per g, pore volume of the micropores was 0.34cm3And/g, has good adsorption performance on dye molecules. After adsorbing the dye, the adsorbent can be rapidly separated by an external magnetic field. Table 2 shows the adsorption performance of the magnetic hollow graphene-based composite microsphere prepared in this embodiment on dye molecules, and it can be seen from the table that the prepared magnetic hollow graphene-based composite microsphere has a high-efficient adsorption effect on dye molecules, and the magnetic property of the adsorbent can realize high-efficient and rapid magnetic separation, thereby avoiding secondary pollution, indicating that the regenerability is good, and the removal rates of acid blue 92, orange yellow ii, malachite green, rhodamine B and methylene blue after 10 cycles are all over 75%.
Table 2 adsorption performance of magnetic hollow graphene-based composite microsphere material prepared in example 2 on dye molecules
Number of cycles Number of Acid blue 92 removal Percentage (%) Orange II removal Percentage (%) Malachite green removal Percentage (%) Rhodamine B removal Percentage (%) Methylene blue removal Percentage (%)
1 99 99 99 98 97
2 98 98 98 97 96
3 97 98 98 97 95
4 95 95 96 96 93
5 93 94 94 93 92
6 90 91 92 89 88
7 87 86 87 86 85
8 84 83 84 83 82
9 81 79 78 78 77
10 77 75 75 75 75
EXAMPLE III
The magnetic hollow graphene-based composite microsphere material is prepared in the following way, and an adsorption experiment is carried out by applying the microsphere material.
1. Preparation of graphene oxide
The graphene oxide is prepared by adopting an improved Hummers method, and the process flow is as follows: assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of 98% concentrated sulfuric acid by mass, and reacting in the ice-water bath for 60 min; then, adding 15g of potassium permanganate, controlling the reaction temperature not to exceed 20 ℃, and continuing to react for 36 hours; and adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of the graphene oxide. Dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; and filtering, washing and drying to obtain a graphene oxide product. And (3) preparing graphene oxide into 2mg/ml GO dispersion liquid by taking water as a solvent.
2. Preparation of PMMA microsphere template agent with positive charges on surface
Selecting a positively charged free radical initiator AMPMDHC to initiate MMA monomer polymerization, and synthesizing the monodisperse PMMA microspheres with positive charges on the surfaces by a soap-free emulsion polymerization method. The specific process flow is as follows: adding 10g of MMA and 115ml of water into a 250ml reactor, stirring for 60min under the protection of nitrogen gas, raising the reaction temperature to 70 ℃, adding 0.015g of AMPMDHC and 5ml of water, and carrying out polymerization reaction for 3h at the temperature of 70 ℃ to obtain a PMMA microsphere dispersion liquid with a 15wt% concentration and a positive surface charge.
3. Preparation of magnetic hollow graphene-based composite microsphere material
Adding 15wt% of PMMA microsphere dispersion liquid with positive charges on the surface into 1mg/ml graphene oxide dispersion liquid, magnetically stirring for 3 hours to enable PMMA microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, and then adding 0.27g FeCl3 · 6H2And (3) continuing magnetically stirring the O solution for 18h, filtering and drying, calcining the product at 800 ℃ for 2.5h in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere.
4. Adsorption of magnetic hollow graphene-based composite microsphere material to dye molecules
The specific surface area of the magnetic hollow graphene-based composite microsphere material prepared in the embodiment is 942m2Per g, total pore volume of 0.52cm3Per g, pore volume of the micropores was 0.29cm3And/g, has good adsorption performance on dye molecules. After adsorbing the dye, the adsorbent can be rapidly separated by an external magnetic field. Table 3 shows the adsorption performance of the magnetic hollow graphene-based composite microsphere prepared in this embodiment on dye molecules, and it can be seen from the table that the prepared magnetic hollow graphene-based composite microsphere has a high-efficient adsorption effect on dye molecules, and the adsorbent has magnetism, and can realize high-efficient and rapid magnetic separation, thereby avoiding secondary pollution, indicating that the regenerability is good, and the removal rates of acid blue 92, orange ii, malachite green, rhodamine B and methylene blue after 10 cycles are all above 75%.
Table 3 adsorption performance of magnetic hollow graphene-based composite microsphere material prepared in example 3 on dye molecules
Number of cycles Number of Acid blue 92 removal Percentage (%) Orange II removal Percentage (%) Malachite green removal Percentage (%) Rhodamine B removal Percentage (%) Methylene blue removal Percentage (%)
1 99 99 99 99 98
2 98 98 98 98 98
3 97 97 97 97 97
4 95 95 96 95 96
5 94 94 95 94 95
6 92 92 93 92 93
7 90 90 91 90 90
8 88 88 88 88 87
9 85 84 84 84 84
10 81 80 81 77 76
Example four
The magnetic hollow graphene-based composite microsphere material is prepared in the following way, and an adsorption experiment is carried out by applying the microsphere material.
1. Preparation of graphene oxide
The graphene oxide is prepared by adopting an improved Hummers method, and the process flow is as follows: assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of concentrated sulfuric acid with the mass percent of 95%, and reacting in the ice-water bath for 40 min; then, 15g of potassium permanganate is added, the reaction temperature is controlled not to exceed 20 ℃, and the reaction is continued for 48 hours; and adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of the graphene oxide. Dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; and filtering, washing and drying to obtain a graphene oxide product. And (3) preparing graphene oxide into 1mg/ml GO dispersion liquid by taking water as a solvent.
2. Preparation of PS microsphere template agent with positive charges on surface
Sequentially adding 10g of styrene, 1.5g of polyvinylpyrrolidone, 0.3g of 2, 2' -azobisisobutylamidine dihydrochloride and 180mL of water into a reaction container, stirring for 60min under the protection of nitrogen gas, heating to 65 ℃, carrying out thermal polymerization for 48h, sequentially centrifuging with ethanol and deionized water, cleaning and filtering to obtain the PS microspheres with positive charges on the surfaces. Using water as a solvent, and preparing the PS microspheres into a PS microsphere dispersion liquid with the concentration of 15 wt%.
3. Preparation of magnetic hollow graphene-based composite microsphere material
Adding 15wt% of PS microsphere dispersion liquid with positive charges on the surface into 1mg/ml graphene oxide dispersion liquid, stirring for 2 hours by magnetic force to enable PS microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, and then adding 0.2g FeCl3 · 6H2And (3) continuing magnetically stirring the O solution for 20 hours, filtering and drying, calcining the product at 750 ℃ for 3 hours in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere.
4. Adsorption of magnetic hollow graphene-based composite microsphere material to dye molecules
The specific surface area of the magnetic hollow graphene-based composite microsphere material prepared by the embodiment is 915m2Per g, total pore volume of 0.55cm3Per g, pore volume of the micropores was 0.31cm3And/g, has good adsorption performance on dye molecules. After adsorbing the dye, the adsorbent can be rapidly separated by an external magnetic field. Table 4 shows the adsorption performance of the magnetic hollow graphene-based composite microsphere prepared in this example to dye molecules, which can be seen from the tableTherefore, the prepared magnetic hollow graphene-based composite microsphere has an efficient adsorption effect on dye molecules, the adsorbent has magnetism, efficient and rapid magnetic separation can be realized, secondary pollution is avoided, the regenerability is good, and the removal rate of acid blue 92, orange II, malachite green, rhodamine B and methylene blue after 10 times of circulation is over 70%.
Table 4 adsorption performance of magnetic hollow graphene-based composite microsphere material prepared in example 4 on dye molecules
Number of cycles Number of Acid blue 92 removal Percentage (%) Orange II removal Percentage (%) Malachite green removal Percentage (%) Rhodamine B removal Percentage (%) Methylene blue removal Percentage (%)
1 99 99 99 99 98
2 98 98 98 98 97
3 97 97 97 97 96
4 95 95 96 95 94
5 93 93 94 93 92
6 90 90 91 90 89
7 86 86 88 86 85
8 83 83 85 82 81
9 81 80 81 78 77
10 77 76 77 74 73
The above examples of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.

Claims (3)

1. A preparation method of a magnetic hollow graphene-based composite microsphere material is characterized by comprising the following steps:
1) preparation of graphene oxide
Assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of concentrated sulfuric acid with the mass percent of 95%, and reacting in the ice-water bath for 30 min; then, 15g of potassium permanganate is added, the reaction temperature is controlled not to exceed 20 ℃, and the reaction is continued for 12 hours; adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of graphene oxide; dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; filtering, washing and drying to obtain a graphene oxide product;
preparing graphene oxide into 2mg/ml GO dispersion liquid by taking water as a solvent;
2) preparation of polymethyl methacrylate (PMMA) microsphere template with positive charges on surface
Adding 10g of MMA and 165ml of water into a 250ml reactor, stirring for 30min under the protection of nitrogen gas, raising the reaction temperature to 70 ℃, adding 0.015g of AMPMDHC and 5ml of water, and carrying out polymerization reaction for 6h at the temperature of 70 ℃ to obtain PMMA microsphere dispersion liquid with 10wt% of positive charge on the surface;
3) preparation of magnetic hollow graphene-based composite microsphere material
Adding 10wt% of PMMA microsphere dispersion liquid with positive charges on the surface into 2mg/ml graphene oxide dispersion liquid, and magnetically stirring for 2 hours to enable PMMA microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, so as to obtain PMMA+/GO-Compounding the microspheres, and adding 2.5mmol of FeSO4 · 7H2And (3) continuing magnetically stirring the O solution for 20 hours, filtering and drying, calcining the product at 700 ℃ for 3 hours in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere material.
2. A preparation method of a magnetic hollow graphene-based composite microsphere material is characterized by comprising the following steps:
1) preparation of graphene oxide
Assembling a reactor in an ice-water bath, adding 1g of expanded graphite powder and 2.5g of sodium nitrate into a reaction bottle under the stirring condition, adding 150ml of 98% concentrated sulfuric acid by mass, and reacting in the ice-water bath for 60 min; then, 15g of potassium permanganate is added, the reaction temperature is controlled not to exceed 20 ℃, and the reaction is continued for 24 hours; adding 150ml of deionized water for dilution, stirring for reaction for 30min, heating to 98 ℃, preserving heat for 48h, and changing the color of the solution from black to brown yellow to obtain a crude product of graphene oxide; dropwise adding 50ml of 35% hydrogen peroxide into the crude product to reduce the residual oxidant, and continuing to react for 30min after the dropwise adding is finished, so that the solution becomes bright yellow; filtering, washing and drying to obtain a graphene oxide product;
preparing graphene oxide into 1mg/ml GO dispersion liquid by taking water as a solvent;
2) preparation of Polystyrene (PS) microsphere template agent with positive charges on surface
Sequentially adding 8g of styrene, 1.2g of polyvinylpyrrolidone, 0.25g of 2, 2' -azobisisobutylamidine dihydrochloride and 150mL of water into a reaction container, stirring for 60min under the protection of nitrogen gas, heating to 70 ℃, carrying out thermal polymerization for 24h, sequentially centrifuging, cleaning and filtering by using ethanol and deionized water to obtain PS microspheres with positive charges on the surfaces;
preparing the PS microspheres into PS microsphere dispersion liquid with the concentration of 10wt% by taking water as a solvent;
3) preparation of magnetic hollow graphene-based composite microsphere material
Adding 8wt% of PS microsphere dispersion liquid with positive charges on the surface into 1mg/ml graphene oxide dispersion liquid, stirring for 2 hours by magnetic force to enable PS microspheres and graphene oxide to be self-assembled into uniform dispersion liquid through electrostatic interaction, and then adding 0.56g of FeSO4 ·7H2And (3) continuing magnetically stirring the O solution for 20 hours, filtering and drying, calcining the product at 750 ℃ for 3 hours in an inert gas atmosphere, and cooling to room temperature to obtain the magnetic hollow graphene-based composite microsphere.
3. The application of the magnetic hollow graphene-based composite microsphere material prepared according to the claim 1 or 2 in dye wastewater treatment.
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