CN103182294B - Method for preparing magnetic mesoporous carbon nanoparticles with high adsorption property for dyes under acidic condition - Google Patents

Abstract

The invention discloses a method for preparing magnetic mesoporous carbon nanospheres with high adsorption performance for dyes under acidic conditions, which relates to a preparation method for magnetic mesoporous carbon materials with a core-shell structure. The invention aims to solve the problems of small pore diameter and low specific surface area of the core-shell structure magnetic mesoporous carbon prepared by the existing alkaline condition path method. The present invention synthesizes the core-shell structure magnetic mesoporous silica material with magnetic _Fe3O4 as the inner core, dense _SiO2 layer as the middle layer, and mesoporous _SiO2 layer as the outer _layer under acidic conditions and solvent volatilization self-assembly method, and then It is a hard template, and sucrose is filled into the mesoporous channel, and the _SiO2 layer is removed after carbonization to obtain a magnetic mesoporous carbon material with a core-shell structure. The magnetic mesoporous carbon nanospheres of the present invention have large mesoporous diameters (3.4nm and 11.1nm), high specific surface area (971.3m ² /g) and large pore volume (1.42cm ³ /g), magnetic The saturation is 1.73emu/g.

Description

Method for preparing magnetic mesoporous carbon nanospheres with high adsorption performance for dyes under acidic conditions

technical field

The invention relates to a preparation method of a magnetic mesoporous carbon material with a core-shell structure.

Background technique

Core-shell magnetic mesoporous carbon is a nanomaterial with magnetic Fe ₃ O ₄ as the core and a carbon layer with high specific surface area, large pore volume, and large mesoporous pore size as the shell. It is used in electrochemistry, catalysis, It has a wide range of applications in sewage treatment, biomedicine and other fields. Its core Fe ₃ O ₄ has superparamagnetism, which enables it to be separated quickly and directionally under the action of an external magnetic field; the outer mesoporous carbon layer has a fast and efficient separation effect on pollutants in water. The magnetic mesoporous carbon material prepared by combining the magnetic core and the mesoporous carbon layer can be used in wastewater treatment, biomedicine, electrochemistry, catalysis and other fields. At present, the synthesis of magnetic mesoporous materials with core-shell structure generally adopts alkaline conditions to prepare MCM-41 mesoporous silicon layer first, and then use it as a hard template to further fill carbon sources to obtain mesoporous carbon materials. Due to the small pore size and low surface area of the mesoporous silicon layer acting as a hard template, the synthesized mesoporous carbon material has a small mesopore size and low surface area, which limits its application in the fields of macromolecular pollutants and biomacromolecular adsorption. wide application.

Contents of the invention

The purpose of the present invention is to solve the problem of small pore size and low specific surface area of magnetic mesoporous carbon with core-shell structure prepared by the existing alkaline condition route method, and to provide a magnetic mesoporous carbon nanometer with high adsorption performance for dyes prepared under acidic conditions. microsphere method.

The method for preparing the magnetic mesoporous carbon nanospheres with high adsorption performance to dyes under acidic conditions of the present invention is carried out according to the following steps:

A. Preparation of magnetic Fe ₃ O ₄ nanoparticles: 1. Weigh 1 to 2 parts of iron source in parts by weight, add it into 40 to 60 parts by weight of reducing agent under magnetic stirring and mix evenly to obtain a mixed solution 2. Add 2 to 3 parts by weight of the precipitant and 0.8 to 1.0 parts by weight of polyethylene glycol into the mixed solution obtained in step 1 under stirring conditions, and mix evenly to obtain a mixed solution; 3. Transfer the mixed solution in step 2 into the reaction kettle, heated to 200°C for crystallization for 8 hours, cooled to room temperature, washed with distilled water and absolute ethanol for 6 times, and dried in an oven at 60°C for 12 hours to obtain Fe ₃ O ₄ nanoparticles;

B. Preparation of Fe ₃ O ₄ nSiO ₂ : 4. Take 0.1 parts by weight of Fe ₃ O ₄ nanoparticles prepared in step A, disperse them in the mixed solution, and ultrasonically treat them for 15 minutes; The ₃ O ₄ nanoparticles were separated under the action of an external magnetic field, the solid phase was collected, washed three times with distilled water and absolute ethanol successively, and then 80 to 100 parts by weight of absolute ethanol, 20 parts by weight of distilled water and 1 part by weight of concentrated ammonia were added. Stir at room temperature for 60 minutes to obtain a uniform mixed solution; 6. To the uniform mixed solution obtained in step 5, add 0.6 parts by weight of silicon source dropwise at a rate of 0.1 drops/second, and then mechanically stir at a speed of 800 to 1000 rpm 12h; separate under the action of an external magnetic field, collect the solid phase, wash with distilled water and absolute ethanol for 6 times, and dry in an oven at a temperature of 60°C for 12h to obtain Fe ₃ O ₄ nSiO ₂ ; wherein, step 4 The mixed solution is prepared by 30-40 parts by weight of absolute ethanol and 5-8 parts by weight of 0.2M hydrochloric acid solution;

C. Preparation of Fe ₃ O ₄ nSiO ₂ mSiO ₂ : 7. Disperse the Fe ₃ O ₄ nSiO ₂ obtained in step B in the mixed solution, and ultrasonicate for 15 minutes; 8. Stir and mix the solution after ultrasonic treatment in step 7, add After 0.02 parts by weight of polyvinylpyrrolidone, stir for 2 hours to obtain a mixed solution; 9. Dissolve 1 part by weight of surfactant in 10 to 15 parts by weight of absolute ethanol and stir until clarified, then add it to the mixed solution in step 8. Stir for 2 hours to obtain a solution; 10. Add 0.8 parts by weight of silicon source to the solution in step 9, stir at room temperature for 2 days, and then dry it; 11. Grind the dried product of step 10 and transfer it to the reaction kettle, add 20 parts by weight of distilled water was placed in an oven at 100°C for crystallization for 24 hours, and after the solid phase was magnetically separated, it was dried in an oven at a temperature of 60°C for 12 hours; 12. Transfer the dried product obtained in step 11 into a tube furnace , under N ₂ atmosphere, calcined at 550°C for 5-6 hours, then cooled to room temperature and ground to obtain Fe ₃ O ₄ nSiO ₂ mSiO ₂ ; wherein, the mixed solution described in step 7 is made of 20 ~30 parts by weight of absolute ethanol and 5 parts by weight of hydrochloric acid solution with a concentration of 0.2M;

D. Preparation of magnetic mesoporous carbon Fe ₃ O ₄ mC: 13. Add Fe ₃ O ₄ nSiO ₂ mSiO ₂ obtained in step 12 into the mixture, stir evenly, dry in an oven at 80°C for 4 hours, and then heat up to 160°C, stand for 12 hours to obtain a solid; 14. Grind the solid obtained in step 13, then add it to the mixed solution, repeat step 13 once to obtain a solid; 15. mix the solid obtained in step 14 Put the material into a tube furnace, and carbonize it at 900°C for 5 to 6 hours under _N2 atmosphere; 20% NaOH solution, mechanically stirred for 8 hours to obtain a solid phase; then washed the solid phase with distilled water until neutral, then separated under the action of an external magnetic field, collected the solid phase, and placed it at 60°C Oven drying, the dried product is magnetic mesoporous carbon Fe ₃ O ₄ mC; wherein, the mixed liquid described in step 13 is made of 5 parts by weight of distilled water, 0.025-0.030 parts by weight of concentrated sulfuric acid and 0.75-1.00 parts by weight of carbon source Obtained; the mixed solution described in step 14 is prepared from 3 parts by weight of distilled water, 0.01 to 0.02 parts by weight of concentrated sulfuric acid and 0.4 parts by weight of carbon source.

The present invention comprises following beneficial effect:

The present invention adopts acidic conditions and _solvent volatilization self-assembly method to synthesize magnetic _Fe3O4 as the core, dense _SiO2 layer as the middle layer, and mesoporous _SiO2 layer as the outer layer of magnetic mesoporous silica material with core-shell structure, marked as Fe ₃ O ₄ nSiO ₂ mSiO ₂ . Then Fe ₃ O ₄ nSiO ₂ mSiO ₂ is used as a hard template, sucrose and other carbon sources are filled into the mesoporous channels, and the SiO ₂ layer is removed after carbonization to obtain a magnetic mesoporous carbon material with a core-shell structure.

The invention adopts an acidic condition and a solvent volatilization self-assembly method to synthesize a magnetic mesoporous carbon material with a core-shell structure. The obtained material has larger pore size (3.4nm, 11.1nm), higher specific surface area (971.3m ² /g) and larger pore volume (1.42cm ³ /g) than the material synthesized by the alkaline route, and the magnetic saturation is 1.73emu/g. The carbon sphere has fast and high adsorption capacity for the cationic dye rhodamine B and the anionic dye methyl orange MO, and the material after adsorbing the dye can be quickly separated under the action of an external magnetic field. After washing with ethanol, the dye is dissolved in ethanol, The adsorbent can re-adsorb the dye after being magnetically separated and dried, and the adsorption capacity changes little after repeated use several times. Among them, solvent volatilization self-assembly: a method in which surface-active block polymers are self-assembled in a solution induced by solvent volatilization.

Description of drawings

Fig. 1 is the synthesis roadmap of the core-shell magnetic mesoporous carbon with high adsorption performance for dyes in test 1;

Figure 2 is the small-angle XRD diffraction pattern of the core-shell magnetic mesoporous carbon material Fe ₃ O ₄ mC in Experiment 1;

Figure 3 is the wide-angle XRD diffraction pattern of the core-shell magnetic mesoporous carbon material Fe ₃ O ₄ mC in Experiment 1;

Figure 4 is the N ₂ adsorption-desorption isotherm diagram of the core-shell structure magnetic mesoporous carbon material Fe ₃ O ₄ mC in Test 1. Among them, ◆ represents the desorption curve, and ■ represents the adsorption curve;

Figure 5 is the pore size distribution diagram of the core-shell structure magnetic mesoporous carbon material Fe ₃ O ₄ mC in Experiment 1;

Fig. 6 is the IR diagram of the magnetic mesoporous carbon material Fe ₃ O ₄ mC with core-shell structure in Experiment 1;

Fig. 7 is the MH curve of the magnetic mesoporous carbon material Fe ₃ O ₄ mC with core-shell structure in Experiment 1;

Fig. 8 is the UV absorption spectrum of Rhodamine B adsorbed on the core-shell magnetic mesoporous carbon material Fe ₃ O ₄ mC in Experiment 1; where a is the UV absorption curve at 0 minutes, b is the UV absorption curve at 5 minutes, and c is the UV absorption curve at 10 minutes. Absorption curve, d is the 20-minute UV absorption curve, e is the 30-minute UV absorption curve;

Figure 9 is a schematic diagram of the adsorption-desorption dye and adsorbent separation process of Fe ₃ O ₄ mC magnetic mesoporous carbon material with core-shell structure in Experiment 1;

Figure 10 is a cycle test diagram of the adsorption performance of rhodamine B by the core-shell magnetic mesoporous carbon material Fe ₃ O ₄ mC in Experiment 1;

Figure 11 is the UV absorption spectrum of methyl orange adsorbed by the core-shell magnetic mesoporous carbon material Fe ₃ O ₄ mC in Test 1; where a is the 0-minute UV absorption curve, b is the 5-minute UV absorption curve, and c is the 10-minute UV absorption curve. Absorption curve, d is the UV absorption curve for 20 minutes, e is the UV absorption curve for 30 minutes, f is the UV absorption curve for 40 minutes, g is the UV absorption curve for 50 minutes, h is the UV absorption curve for 60 minutes, i is the UV absorption curve for 120 minutes .

Detailed ways

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Embodiment 1: A method for preparing a magnetic mesoporous carbon material with a core-shell structure under acidic conditions in this embodiment is carried out according to the following steps:

A. Preparation of magnetic Fe ₃ O ₄ nanoparticles: 1. Weigh 1 to 2 parts of iron source in parts by weight, add it into 40 to 60 parts by weight of reducing agent under magnetic stirring and mix evenly to obtain a mixed solution 2. Add 2 to 3 parts by weight of the precipitant and 0.8 to 1.0 parts by weight of polyethylene glycol into the mixed solution obtained in step 1 under stirring conditions, and mix evenly to obtain a mixed solution; 3. Transfer the mixed solution in step 2 into the reaction kettle, heated to 200°C for crystallization for 8 hours, cooled to room temperature, washed with distilled water and absolute ethanol for 6 times, and dried in an oven at 60°C for 12 hours to obtain Fe ₃ O ₄ nanoparticles;

B. Preparation of Fe ₃ O ₄ nSiO ₂ : 4. Take 0.1 parts by weight of Fe ₃ O ₄ nanoparticles prepared in step A, disperse them in the mixed solution, and ultrasonically treat them for 15 minutes; The ₃ O ₄ nanoparticles were separated under the action of an external magnetic field, the solid phase was collected, washed three times with distilled water and absolute ethanol successively, and then 80 to 100 parts by weight of absolute ethanol, 20 parts by weight of distilled water and 1 part by weight of concentrated ammonia were added. Stir at room temperature for 60 minutes to obtain a uniform mixed solution; 6. To the uniform mixed solution obtained in step 5, add 0.6 parts by weight of silicon source dropwise at a rate of 0.1 drops/second, and then mechanically stir at a speed of 800 to 1000 rpm 12h; separate under the action of an external magnetic field, collect the solid phase, wash with distilled water and absolute ethanol for 6 times, and dry in an oven at a temperature of 60°C for 12h to obtain Fe ₃ O ₄ nSiO ₂ ; wherein, step 4 The mixed solution is prepared by 30-40 parts by weight of absolute ethanol and 5-8 parts by weight of 0.2M hydrochloric acid solution;

C. Preparation of Fe ₃ O ₄ nSiO ₂ mSiO ₂ : 7. Disperse the Fe ₃ O ₄ nSiO ₂ obtained in step B in the mixed solution, and ultrasonicate for 15 minutes; 8. Stir and mix the solution after ultrasonic treatment in step 7, add After 0.02 parts by weight of polyvinylpyrrolidone, stir for 2 hours to obtain a mixed solution; 9. Dissolve 1 part by weight of surfactant in 10 to 15 parts by weight of absolute ethanol and stir until clarified, then add it to the mixed solution in step 8. Stir for 2 hours to obtain a solution; 10. Add 0.8 parts by weight of silicon source to the solution in step 9, stir at room temperature for 2 days, and then dry it; 11. Grind the dried product of step 10 and transfer it to the reaction kettle, add 20 parts by weight of distilled water was placed in an oven at 100°C for crystallization for 24 hours, and after the solid phase was magnetically separated, it was dried in an oven at a temperature of 60°C for 12 hours; 12. Transfer the dried product obtained in step 11 into a tube furnace , under N ₂ atmosphere, calcined at 550°C for 5-6 hours, then cooled to room temperature and ground to obtain Fe ₃ O ₄ nSiO ₂ mSiO ₂ ; wherein, the mixed solution described in step 7 is made of 20 ~30 parts by weight of absolute ethanol and 5 parts by weight of hydrochloric acid solution with a concentration of 0.2M;

D. Preparation of magnetic mesoporous carbon Fe ₃ O ₄ mC: 13. Add Fe ₃ O ₄ nSiO ₂ mSiO ₂ obtained in step 12 into the mixture, stir evenly, dry in an oven at 80°C for 4 hours, and then heat up to 160°C, stand for 12 hours to obtain a solid; 14. Grind the solid obtained in step 13, then add it to the mixed solution, repeat step 13 once to obtain a solid; 15. mix the solid obtained in step 14 Put the material into a tube furnace, and carbonize it at 900°C for 5 to 6 hours under _N2 atmosphere; 20% NaOH solution, mechanically stirred for 8 hours to obtain a solid phase; then washed the solid phase with distilled water until neutral, then separated under the action of an external magnetic field, collected the solid phase, and placed it at 60°C Oven drying, the dried product is magnetic mesoporous carbon Fe ₃ O ₄ mC; wherein, the mixed liquid described in step 13 is made of 5 parts by weight of distilled water, 0.025-0.030 parts by weight of concentrated sulfuric acid and 0.75-1.00 parts by weight of carbon source Obtained; the mixed solution described in step 14 is prepared from 3 parts by weight of distilled water, 0.01 to 0.02 parts by weight of concentrated sulfuric acid and 0.4 parts by weight of carbon source.

The beneficial effects of this embodiment are:

In this embodiment, a magnetic mesoporous silicon material with a core-shell structure is synthesized by solvent volatilization and self-assembly method under acidic conditions, with magnetic Fe ₃ O ₄ as the core, dense SiO ₂ layer as the middle layer, and mesoporous SiO ₂ layer as the outer layer, marked as Fe ₃ O ₄ nSiO ₂ mSiO ₂ . Then Fe ₃ O ₄ nSiO ₂ mSiO ₂ is used as a hard template, sucrose is filled into the mesoporous channels, and the SiO ₂ layer is removed after carbonization to obtain a magnetic mesoporous carbon material with a core-shell structure.

In this embodiment, the core-shell magnetic mesoporous carbon material is synthesized by self-assembly under acidic conditions and solvent volatilization. Compared with the carbon material synthesized by the alkaline route, the obtained material has a larger pore size: 3.4nm and 11.1nm, a higher specific surface area: 971.3m ² /g and a larger pore volume: 1.42cm ³ /g, and a magnetic saturation of 1.73emu /g. The carbon spheres prepared by this method have fast and high adsorption capacity for the cationic dye rhodamine B and the anionic dye methyl orange MO, and the material after adsorbing the dye can be quickly separated under the action of an external magnetic field. After washing with ethanol, the adsorbent After magnetic separation and drying, the dye can be re-adsorbed several times with little change in the adsorption amount.

Embodiment 2: This embodiment differs from Embodiment 1 in that: the iron source in step A is FeCl ₃ ·6H ₂ O or Fe(NO ₃ ) ₃ ·9H ₂ O. Others are the same as in the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the reducing agent described in step A is ethylene glycol or ammonia water. Others are the same as in the first or second embodiment.

Embodiment 4: This embodiment differs from Embodiment 1 to Embodiment 3 in that the precipitating agent described in step A is sodium acetate or sodium hydroxide. Others are the same as those in the first to third specific embodiments.

Embodiment 5: This embodiment is different from Embodiment 1 to Embodiment 4 in that the silicon source described in Step B and Step C is tetraethyl orthosilicate. Others are the same as one of the specific embodiments 1 to 4.

Specific embodiment six: This embodiment is different from one of specific embodiments one to five in that: the surfactant described in step C is polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer P123 (molecular formula is EO20PO70EO20) or F127 (molecular formula EO106PO70EO106). Others are the same as one of the specific embodiments 1 to 5.

Embodiment 7: This embodiment is different from Embodiment 1 to Embodiment 6 in that: the carbon source described in step D is sucrose or phenolic resin. Others are the same as one of the specific embodiments 1 to 6.

Verify beneficial effect of the present invention by following test:

The preparation method of the core-shell magnetic mesoporous carbon material with high adsorption performance to the dye in this test is carried out according to the following steps:

(1) Preparation of magnetic Fe ₃ O ₄ nanoparticles

1. Dissolve 1.08g of FeCl ₃ 6H ₂ O in 40mL of ethylene glycol under the condition of magnetic stirring, then add 2.88g of sodium acetate and 0.8g of polyethylene glycol, stir and mix at room temperature for 4h, turn to Put it into the reaction kettle and heat it to 200°C for crystallization for 8 hours; 2. After the crystallization in step 1, cool to room temperature to obtain black particles, wash them with distilled water and absolute ethanol for 6 times, and dry them in an oven at 60°C 12h to obtain magnetic Fe ₃ O ₄ nanoparticles;

(2) Preparation of Fe ₃ O ₄ nSiO ₂

3. Take 0.1 g of the magnetic _Fe3O4 nanoparticles prepared in step 2, disperse them in the mixed solution, and disperse _them ultrasonically for 15 minutes under the condition that the ultrasonic frequency is 40KHz; After being separated under the action of an external magnetic field with a permanent magnet, wash with distilled water and absolute ethanol three times respectively, transfer to a 250mL three-necked round bottom flask, then add 80mL absolute ethanol, 20mL distilled water and 1mL concentrated ammonia water, and stir at room temperature for 60min to obtain Homogeneous mixed solution; 5. Add 0.6mL tetraethyl orthosilicate (TEOS) dropwise to the homogeneous mixed solution obtained in step 4 at a speed of 0.1 drop/second, then mechanically stir at a speed of 1000rpm for 12h, and apply an external magnetic field Separation under high temperature, the obtained black product was washed 6 times with distilled water and absolute ethanol successively, and dried in an oven at a temperature of 60°C for 12h to obtain Fe ₃ O ₄ nSiO ₂ ; wherein, the mixed solution described in step 3 was obtained from 20mL of Prepared with water ethanol and 5mL of 0.2M hydrochloric acid solution;

(3) Preparation of Fe ₃ O ₄ nSiO ₂ mSiO ₂

6. Disperse the obtained Fe ₃ O ₄ nSiO ₂ in the mixed solution, ultrasonically disperse for 15 minutes, and mechanically stir to make the dispersion uniform; add 0.01g of polyvinylpyrrolidone (PVP) and continue to stir for 2 hours to obtain a mixed solution; 7. Mix 1g of P123 was dissolved in 10mL of absolute ethanol, stirred until clarified and added to the mixture obtained in step 6. After stirring at room temperature for 2 hours, 0.8mL of TEOS was added dropwise at a rate of 0.1 drop/second. Stir the volatile solvent, and after stirring for 2 days, a sticky solid phase is obtained; 8. After drying the sticky solid phase obtained in step 7 in an oven at a temperature of 60°C for 12 hours, grind it and transfer it to a 30mL reaction kettle, Add 15mL of distilled water and place it in an oven at 100°C for crystallization for 24 hours; 9. After magnetically separating the crystallized product in step 8, dry it in an oven at a temperature of 60°C for 12 hours; transfer the obtained gray product into a tube furnace , calcined for 6 hours under N ₂ atmosphere at a temperature of 550°C to remove the template agent, cooled to room temperature and ground to obtain Fe ₃ O ₄ nSiO ₂ mSiO ₂ ; wherein, the mixed solution described in step 6 was obtained from 20 mL of anhydrous Prepared with ethanol and 5mL of 0.2M hydrochloric acid solution;

(4) Preparation of magnetic mesoporous carbon Fe ₃ O ₄ mC

10. Add Fe ₃ O ₄ nSiO ₂ mSiO ₂ obtained in step 9 into the mixture containing 5mL distilled water, 0.025mL concentrated sulfuric acid and 0.75g sucrose, stir well, put the suspension in an oven at 80°C to evaporate the solvent for 4h Then heat up to 160°C and stand for 12 hours to obtain a solid; 11. Grind the solid in step 10, add it again to the mixture containing 3mL distilled water, 0.01mL concentrated sulfuric acid and 0.4g sucrose, stir well, and place the suspension in Evaporate the solvent in an oven at 80°C for 4 hours, then raise the temperature to 160°C, and place it for 12 hours to obtain a black substance; 12. Put the black substance obtained in step 11 into a tube furnace, and carbonize it at 900°C for 6 hours under _N2 atmosphere 13. After pulverizing 0.4 g of the black substance after carbonization in step 12, place it in 50 mL of 20% NaOH solution by mass percentage, and mechanically stir for 8 hours to obtain a solid phase; wash the solid phase with distilled water several times to Neutral, and then separated under the action of an external magnetic field, the product was collected and dried in an oven at 60°C. The obtained black dry product was magnetic mesoporous carbon Fe ₃ O ₄ mC.

The core-shell structure magnetic mesoporous carbon material obtained in this test is detected as follows:

1. XRD small angle and wide angle detection

XRD diffraction detection was carried out on the core-shell magnetic mesoporous carbon material obtained in this experiment, and the results are shown in Figure 2 and Figure 3 . It can be seen from Figure 2 that the shell layer of the core-shell magnetic mesoporous carbon material has a typical two-dimensional hexagonal structure channel, but its (100) diffraction peak is broadened, and the (110) and (200) diffraction peaks disappear. It is caused by long-term high-temperature carbonization and subsequent NaOH strong alkali solution etching that destroys the ordered mesoporous structure.

It can be seen from Figure 3 that a broad peak appears at 20-28° in 2θ, corresponding to the composition of amorphous carbon in the structure. The diffraction peaks appearing at 2θ of 30.1°, 35.61°, 43.04°, 53.7°, 57.20°, and 63.19° correspond to (220), (311), (400), (422) of Fe ₃ O ₄ , respectively. The (511), (440) crystal planes are diffracted, thus well demonstrating the existence of the face-centered cubic spinel structure Fe ₃ O ₄ . At 2θ=43.50°, the (101) diffraction peak of graphitic carbon overlaps with the (400) diffraction peak of Fe ₃ O ₄ , so a broadened peak appears here.

2. Nitrogen adsorption-desorption isotherm test

N ₂ adsorption-desorption detection was performed on the magnetic mesoporous carbon material with core-shell structure obtained in this experiment, and the results are shown in Figure 4. The nitrogen adsorption-desorption curve presents a sudden jump at P/P ₀ =0.4-0.8, which belongs to the typical IV isotherm, and the H1-type hysteresis loop indicates the existence of a uniform pore mesoporous structure. The BET ratio of the Fe ₃ O ₄ mC material The surface area is as high as 971.3m ² /g. , the peaks at 3.4nm and 11.1nm in the pore size distribution diagram (Figure 5) correspond to the mesoporous pore size of the outer mesoporous carbon layer and the cavity size produced after etching away the inner silicon dioxide, respectively. The large specific surface area, large pore size, and large pore volume (1.42cm ³ /g) make Fe ₃ O ₄ mC materials have a faster adsorption rate and larger adsorption capacity when adsorbing macromolecular dyes.

3. IR detection

IR detection was carried out on the magnetic mesoporous carbon material with core-shell structure obtained in this test, and the results are shown in Figure 6. At 570cm ^-1 is the Fe-O stretching vibration peak, indicating the existence of Fe ₃ O ₄ . At 1390 and 2950cm ^-1 are saturated CH bond stretching vibration peaks. The ν(C=C) absorption peak appears at 1565cm ^-1 , and the ν(CH ₂ -O-CH ₂ ) absorption peak appears at 1162 and 1080cm ^-1 .

4. M-H detection

The magnetic saturation of the magnetic mesoporous carbon with core-shell structure obtained in this test was tested, and the results are shown in Figure 7. The magnetic saturation of magnetic mesoporous carbon nanospheres is 1.73emu/g, which is sufficient for magnetic separation. There is no hysteresis loop in the curve, which indicates that the prepared magnetic mesoporous carbon Fe ₃ O ₄ mC sample is superparamagnetic. Nanomaterials with superparamagnetic characteristics can quickly respond to external magnetic fields, and when the external magnetic field disappears, they can be redispersed in the solution, which is very beneficial for the subsequent recovery and regeneration of adsorbents in practical applications.

5. Detection of the adsorption performance of the dye Rhodamine B

The cationic dye Rhodamine B adsorption performance test is carried out as follows: 10mg of adsorbent is added to 100mL of 20PPM Rhodamine B solution, and adsorbed in a vibrating bed. After a certain time interval, after separation by an external magnetic field, a small amount of supernatant is taken. The adsorption effect was measured by ultraviolet spectroscopy, and the results are shown in Figure 8. For Fe ₃ O ₄ mC adsorbent, within 5 minutes, 82.24% of Rhodamine B was adsorbed, and within 30 minutes, the adsorption reached 99.45%, the adsorption was basically completed, and the adsorption amount reached 198.9mgg ^-1 . The reasons for the rapid adsorption and high adsorption capacity are mainly due to the high specific surface area and large pore size and pore volume of mesoporous materials.

For adsorbents, their regeneration and recycling performance is crucial for practical applications. The operating steps of the cycle experiment (as shown in Figure 9) are: (1) prepare a certain amount of Rhodamine B solution with known concentration; (2) add Fe ₃ O ₄ mC to water to absorb dye; (3) separate the adsorbent under the action of external magnetic field (4) Wash the adsorbent several times with a small amount of absolute ethanol to desorb the dye in ethanol, and then reuse the adsorbent after magnetic separation and drying. The cycle regeneration performance test of the adsorbent is shown in Figure 10. It can be seen from the adsorption amount of the five cycles that the obtained Fe ₃ O ₄ mC has an adsorption amount of 176.2 mg/g after five cycles, ranking first in the adsorption amount. 88.6% of the adsorption capacity at the first use. It can be seen that Fe ₃ O ₄ mC, as the adsorbent of rhodamine B, is stable in nature and has good recycling performance.

6. Detection of the adsorption performance of the dye methyl orange

The test of the adsorption performance of the anionic dye methyl orange is carried out as follows: 10mg of adsorbent is added to 100mL of 20PPM methyl orange solution, and the adsorption is carried out in a vibrating bed. After a certain time interval, the supernatant is taken after separation by an external magnetic field A small amount, the adsorption effect was measured by ultraviolet spectroscopy, and the results are shown in Figure 11. Within 5 minutes, 72.87% of methyl orange was adsorbed; after 40 minutes, the adsorption reached 95.18%, and after 120 minutes, 97.68% of methyl orange was adsorbed. It was 195.4 mg/g. Due to the high specific surface area and large pore volume of this mesoporous carbon material, it exhibits fast and high adsorption capacity for methyl orange dye.

In summary, combined with the test results shown in Figures 2 to 11, it can be known that this test has successfully prepared a core-shell magnetic mesoporous carbon material with high adsorption performance for dyes under acidic conditions, which is expected to be used in sewage treatment, biological There are a wide range of applications in fields such as medicine, catalysis and energy.

Claims (4)

1. under acid condition, prepare method dyestuff to the magnetic mesoporous carbon nanometer micro ball of high absorption property, it is characterized in that its preparation method carries out according to following steps:

A, magnetic Fe ₃o ₄the preparation of nano particle: one, take by weight 1～2 part of source of iron, join under the condition of magnetic agitation in 40～60 weight portion reducing agents and be uniformly mixed, obtain mixed solution; Two, the precipitating reagent of 2～3 weight portions and 0.8～1.0 weight portion polyethylene glycol are joined under stirring condition in the mixed solution that step 1 obtains, after mixing, obtain mixed liquid; Three, mixed step 2 liquid being transferred in reactor, being heated to, after 200 DEG C of crystallization 8h, be cooled to room temperature, successively with distilled water with absolute ethyl alcohol is each cleans 6 times, is dry 12h in the baking oven of 60 DEG C in temperature, obtains Fe ₃o ₄nano particle;

B, Fe ₃o ₄@nSiO ₂preparation: the Fe that four, gets 0.1 weight portion that steps A makes ₃o ₄nano particle, is scattered in mixed liquor, ultrasonic processing 15min; Five, by ultrasonic step 4 Fe after treatment ₃o ₄under the effect of nano particle outside magnetic field, separate, collect solid formation, respectively wash 3 times with distilled water and absolute ethyl alcohol successively, then add 80～100 weight portion absolute ethyl alcohols, 20 weight portion distilled water and 1 weight portion concentrated ammonia liquor, under room temperature, stir 60min, obtain even mixed liquor; Six,, in the even mixed liquor obtaining to step 5, drip 0.6 weight portion silicon source with the speed of 0.1 drop/sec, under the condition that is then 800～1000rpm at rotating speed, mechanical agitation 12h; Under outside magnetic field effect, separating, collect solid formation, respectively clean 6 times successively with distilled water and absolute ethyl alcohol, is to be dried after 12h in 60 DEG C of baking ovens in temperature, obtains Fe ₃o ₄@nSiO ₂; Wherein, the mixed liquor described in step 4 is that 0.2M hydrochloric acid solution makes by the concentration of 30～40 weight portion absolute ethyl alcohols and 5～8 weight portions;

C, Fe ₃o ₄@nSiO ₂@mSiO ₂preparation: seven, by step B gained Fe ₃o ₄@nSiO ₂be scattered in mixed liquor ultrasonic processing 15min; Eight, the ultrasonic solution after treatment of step 7 is stirred and evenly mixed, add after 0.02 weight account polyethylene pyrrolidones, stir 2h, obtain mixed liquor; Nine, the absolute ethyl alcohol and stirring that the surfactant of 1 weight portion is dissolved in to 10～15 weight portions adds in the mixed liquor of step 8 to clarification, under room temperature, stirs 2h, obtains solution; Ten, in the solution of step 9, add 0.8 weight portion silicon source, under room temperature, stir after 2d, dry; 11, step 10 is dried to product grinding and proceed in reactor, add the distilled water of 15～20 weight portions, be placed in 100 DEG C of baking oven crystallization 24h, Magnetic Isolation goes out after solid formation, is dry 12h in 60 DEG C of baking ovens in temperature; 12, dry step 11 gained thing is proceeded in tube furnace, at N ₂under atmosphere, temperature is to calcine 5～6h under 550 DEG C of conditions, is then cooled to after room temperature grinding, obtains Fe ₃o ₄@nSiO ₂@mSiO ₂; Wherein, the mixed liquor described in step 7 is to be 0.2M by absolute ethyl alcohol and the 5 weight portion concentration of 20～30 weight portions hydrochloric acid solution is made;

D, magnetic mesoporous carbon Fe ₃o ₄the preparation of@mC: 13, by step 12 gained Fe ₃o ₄@nSiO ₂@mSiO ₂add in mixed liquid, after stirring, be placed in 80 DEG C of baking ovens and dry after 4h, be warming up to 160 DEG C, place 12h, obtain solid; 14, the solid of step 13 is ground, then add in mixed liquor, repeating step 13 operation 1 time, obtains decorating film; 15, step 14 gained decorating film is put into tube furnace, at N ₂under atmosphere, carbonization 5～6h under 900 DEG C of conditions; 16, get product after the carbonization of step 15 0.4～0.5 weight portion and grind and be placed in the NaOH solution that the quality percentage composition of 50～60 weight portions is 20%, mechanical agitation 8h, obtains solid formation; Then extremely neutral with distillation washing solid formation, then separate under outside magnetic field effect, collect solid formation, be placed in 60 DEG C of oven dryings, desciccate is magnetic mesoporous carbon Fe ₃o ₄@mC; Wherein, the mixed liquid described in step 13 is the distilled water by 5 weight portions, and 0.025～0.030 weight portion concentrated sulfuric acid and 0.75～1.00 weight portion carbon source make; Mixed liquor described in step 14 is by 3 weight portion distilled water, and 0.01～0.02 weight portion concentrated sulfuric acid and 0.4 weight portion carbon source make; Wherein, the reducing agent described in steps A is ethylene glycol or ammoniacal liquor; Precipitating reagent described in steps A is sodium acetate or NaOH; Carbon source described in step D is sucrose or phenolic resins.

2. method dyestuff to the magnetic mesoporous carbon nanometer micro ball of high absorption property of preparing under acid condition according to claim 1, is characterized in that the source of iron described in steps A is FeCl ₃6H ₂o or Fe (NO ₃) ₃9H ₂o.

3. method dyestuff to the magnetic mesoporous carbon nanometer micro ball of high absorption property of preparing under acid condition according to claim 1, is characterized in that the silicon source described in step B and step C is tetraethyl orthosilicate.

4. method dyestuff to the magnetic mesoporous carbon nanometer micro ball of high absorption property of preparing under acid condition according to claim 1, is characterized in that the surfactant described in step C is polyoxyethylene-poly-oxypropylene polyoxyethylene triblock copolymer P123 or F127.