TRANSITION METAL-DOPED CARBON MICROSPHERE, PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

Abstract

Disclosed are a transition metal-doped carbon microsphere, a preparation method therefor and an application thereof. The transition metal-doped carbon sphere has a uniform solid porous structure, and the transition metal is uniformly distributed inside the carbon sphere. The preparation method comprises that a carbon microsphere uniformly doped with manganese, vanadium, molybdenum and tungsten is prepared by means of a one-step hydrothermal method, is mixed with potassium oxalate, and is roasted in a protective atmosphere to obtain an activated metal-doped carbon sphere. The doped transition metal elements remain uniformly dispersed after being roasted, and do not agglomerate. The transition metal-doped carbon microsphere obtained has the following characteristics: it exhibits good adsorption properties for heavy metal ions Cr(VI), with the maximum adsorption amount being 660.7 mg/g; it can achieve advanced removal of Cr(VI) from the wastewater of which the initial Cr(VI) concentration is lower than 200 mg/L, with the residual Cr(VI) concentration after adsorption being lower than 0.05 mg/L; and it shows good application prospect in the treatment of wastewater containing heavy metal.

Claims

1. A method for preparing transition metal-doped carbon spheres, characterized in that the method comprises the following steps: mixing sucrose, transition metal salts and persulfate in water, then transferring the obtained mixed liquid into a hydrothermal kettle, and then carrying out a hydrothermal reaction at 180° C. for 4 h; cooling, washing, separating, and then drying the reaction products to obtain carbon microspheres; then mixing the carbon microspheres with potassium oxalate, and heating the mixture to a temperature of 600° C. to 800° C. to roast in a protective atmosphere for 1-3 h, thereby obtaining the carbon spheres doped with transition metals.

2. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: the transition metal salts include at least one of potassium permanganate, sodium orthovanadate, sodium molybdate dihydrate, and sodium tungstate dihydrate; and the persulfate is ammonium persulfate.

3. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: the addition amount of sucrose is 4 parts by mass, the addition amount of transition metal salts is 1-4 parts by mass, and the addition amount of persulfate is 1-5 parts by mass.

4. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: the addition amount of carbon microspheres is 1 part by mass, and the addition amount of potassium oxalate is 1-4 parts by mass.

5. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: in the roasting, the temperature is raised to a range of 600° C. to 800° C. at a heating rate of 1° C./min to 5° C./min.

6. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: the roasting is carried out at 700° C. for 2 h.

7. The method for preparing transition metal-doped carbon spheres according to claim 1, characterized in that: the roasting is carried out in a protective atmosphere of nitrogen or inert gas.

8. A transition metal-doped carbon sphere prepared by the method according to claim 1.

9. An application of the metal-doped carbon sphere according to claim 8 in adsorption of Cr(VI) in wastewater.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows SEM photos of the Mn-doped carbon sphere (Mn-CS) and control sample (Mn—C) prepared in Example 1.

[0034] FIG. 2 shows SEM photos of Mn-ACS obtained from Mn-CS in Example 2 after the high-temperature activation with potassium oxalate.

[0035] FIG. 3 is an element distribution diagram of Mn-CS and Mn-ACS in Example 2, in which A: Mn-CS; B: sections of broken Mn-CS; C: Mn-ACS; and D: sections of broken Mn-ACS.

[0036] FIG. 4 shows the adsorption amount of Mn-ACS in Example 2 on solutions with different initial Cr(VI) concentrations, and the residual Cr(VI) concentrations.

[0037] FIG. 5 shows SEM photos of the V-doped carbon sphere (V-CS) and control sample (V-C) prepared in Example 3.

[0038] FIG. 6 shows SEM photos of the Mo-doped carbon sphere (Mo-CS) and control sample (Mo-C) prepared in Example 4.

[0039] FIG. 7 shows SEM photos of the W-doped carbon sphere (W-CS) and control sample (W-C) prepared in Example 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be further described below in detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto. Process parameters not specified can be determined with reference to conventional technology.

[0041] The materials involved in the following examples are commercially available. The dosage of each component is calculated in parts by mass and volume (g/mL).

Example 1

[0042] This example relates to the preparation of Mn-doped carbon spheres (Mn-CS), the preparation of Mn-doped carbon materials (Mn—C) as a control sample, and the preparation of Mn-ACS through the non-destructive activation of Mn-CS with potassium oxalate.

[0043] The preparation of Mn-CS was as follows: Dissolving 4 parts by mass of sucrose, 1 part by mass of KMnO.sub.4, and 3 parts by mass of APS (ammonium persulfate) in 40 parts by volume of water, then transferring the obtained mixed liquid into a stainless-steel hydrothermal kettle lined with polytetrafluoroethylene and placing the kettle in a hot air oven, and then heating up to 180° C. and reacting at this temperature for 4 h; filtering the obtained reaction solution to obtain a filter cake, then washing the filter cake respectively with water and ethanol for three times, and finally drying the filter cake in a hot air oven at 80° C. for 8 h, thereby obtaining Mn-CS with a manganese content of 0.89 wt %.

[0044] The control sample Mn—C was prepared by the same method as above without the addition of APS. A control sample CS was prepared by the same method as above without the addition of KMnO.sub.4 and APS.

[0045] FIG. 1 shows SEM photos of Mn-CS and Mn—C for comparison, in which Mn-CS appeared as smooth spheres and Mn—C as fused flakes.

[0046] The preparation of Mn-ACS was as follows: Taking 1 part by mass of the Mn-CS sample, mixing it with 3 parts by mass of potassium oxalate uniformly, transferring the obtained mixture into a ceramic boat, placing the boat in a tubular furnace, introducing nitrogen to replace the air in the furnace, then adjusting the nitrogen flow to 30 mL/min, raising the temperature to 600° C. at a heating rate of 3° C./min to roast for 2 h, and then naturally cooling to room temperature; then washing the black powder obtained from the roasting with water until a neutral filter cake was obtained, and finally drying the filter cake in a hot air oven at 110° C. for 6 h, thereby obtaining the Mn-doped activated carbon spheres Mn-ACS. By the same method, CS was activated to prepare a control sample ACS. The SEM photos of Mn-ACS are shown in FIG. 2, indicating that Mn-ACS maintained smooth and spherical after the activation.

[0047] 100 mg of Mn-ACS and 100 mg of ACS were respectively added into two beakers respectively containing 100 mL of a Cr(VI) solution (800 mg/L, pH=1-2), and then the beakers were shaken in a rotary shaker at 25° C. at a rotational speed of 180 rpm for 5 h for an adsorption experiment. The adsorption amount of Mn-ACS for Cr(VI) was 272.8 mg/g, while the adsorption amount of undoped activated carbon spheres ACS for Cr(VI) was only 96.2 mg/g.

Example 2

[0048] This example relates to the preparation of Mn-doped carbon spheres (Mn-CS), and the preparation of Mn-ACS through the non-destructive activation of Mn-CS with potassium oxalate.

[0049] The preparation of Mn-CS was as follows: Dissolving 4 parts by mass of sucrose, 4 part by mass of KMnO.sub.4, and 5 parts by mass of APS in 40 parts by volume of water, then transferring the obtained mixed liquid into a stainless-steel hydrothermal kettle lined with polytetrafluoroethylene and placing the kettle in a hot air oven, and then heating up to 180° C. and reacting at this temperature for 4 h; filtering the obtained reaction solution to obtain a filter cake, then washing the filter cake respectively with water and ethanol for three times, and finally drying the filter cake in a hot air oven at 80° C. for 8 h, thereby obtaining Mn-CS with a manganese content of 2.31 wt %.

[0050] The preparation of Mn-ACS was as follows: Taking 1 part by mass of the Mn-CS sample, mixing it with 3 parts by mass of potassium oxalate uniformly, transferring the obtained mixture into a ceramic boat, placing the boat in a tubular furnace, introducing nitrogen to replace the air in the furnace, then adjusting the nitrogen flow to 30 mL/min, raising the temperature to 800° C. at a heating rate of 3° C./min to roast for 2 h, and then naturally cooling to room temperature; then washing the black powder obtained from the roasting with water until a neutral filtrate was obtained, and finally drying the obtained filter cake in a hot air oven at 110° C. for 6 h, thereby obtaining the Mn-doped activated carbon spheres Mn-ACS.

[0051] The corresponding element distribution diagrams of Mn-CS and Mn-ACS are shown in FIGS. 3 and 4, which indicate that the Mn atoms were uniformly distributed in the carbon spheres, and the roasting did not cause non-obvious aggregation of the Mn atoms.

[0052] By the same method as in Example 1, the obtained Mn-ACS was tested for Cr(VI) adsorption, showing that the maximum adsorption amount of Mn-ACS for Cr(VI) was 660.7 mg/g. 100 mg of Mn-ACS was respectively added into six beakers respectively containing 100 mL of a Cr(VI) solution (respectively at a concentration of 0, 50, 100, 150, 250 and 300 mg/L, pH=2), and then the beakers were shaken in a rotary shaker at 25° C. at a rotational speed of 180 rpm for 5 h for an adsorption experiment. The measured adsorption amount and the concentration of residual Cr(VI) in the solution are shown in FIG. 5; in the solution with the initial Cr(VI) concentration lower than 200 mg/L, the residual Cr(VI) concentration of the solution after adsorption was lower than 0.05 mg/L (the allowable Cr(VI) concentration in drinking water according to GB 5749-2006).

Example 3

[0053] This example relates to the preparation of V-doped carbon spheres (V-CS), the preparation of V-doped carbon materials (V-C) as a control sample, and the preparation of V-ACS through the non-destructive activation of V-CS with potassium oxalate.

[0054] The preparation of V-CS was as follows: Dissolving 4 parts by mass of sucrose, 1 part by mass of Na.sub.3VO.sub.4, and 3 parts by mass of APS in 40 parts by volume of water, then transferring the obtained mixed solution into a stainless-steel hydrothermal kettle lined with polytetrafluoroethylene and placing the kettle in a hot air oven, and then heating up to 180° C. and reacting at this temperature for 4 h; filtering the obtained reaction solution to obtain a filter cake, then washing the filter cake respectively with water and ethanol for three times, and finally drying the filter cake in a hot air oven at 80° C. for 8 h, thereby obtaining V-CS with a vanadium content of 2.59 wt %.

[0055] The control sample V-C was prepared by the same method as above without the addition of APS. FIG. 5 shows SEM photos of V-CS and V-C for comparison, in which V-CS appeared as smooth spheres and V-C as fused irregular blocks.

[0056] The preparation of V-ACS was as follows: Taking 1 part by mass of the V-CS sample, mixing it with 3 parts by mass of potassium oxalate uniformly, transferring the obtained mixture into a ceramic boat, placing the boat in a tubular furnace, introducing nitrogen to replace the air in the furnace, then adjusting the nitrogen flow to 30 mL/min, raising the temperature to 700° C. at a heating rate of 3° C./min to roast for 2 h, and then naturally cooling to room temperature; then washing the black powder obtained from the roasting with water until a neutral filter cake was obtained, and finally drying the filter cake in a hot air oven at 110° C. for 6 h, thereby obtaining the V-doped activated carbon spheres V-ACS.

[0057] 100 mg of V-ACS was added into a beaker containing 100 mL of a Cr(VI) solution (500 mg/L, pH=1-2), and then the beaker was shaken in a rotary shaker at 25° C. at a rotational speed of 180 rpm for 5 h for an adsorption experiment. The adsorption amount of V-ACS for Cr(VI) was 193.4 mg/g.

Example 4

[0058] This example relates to the preparation of Mo-doped carbon spheres (Mo-CS), the preparation of Mo-doped carbon materials (Mo-C) as a control sample, and the preparation of Mo-ACS through the non-destructive activation of Mo-CS with potassium oxalate.

[0059] The preparation of Mo-CS was as follows: Dissolving 4 parts by mass of sucrose, 1 part by mass of Na.sub.2MoO.sub.4.Math.2H.sub.2O, and 3 parts by mass of APS in 40 parts by volume of water, then transferring the obtained mixed liquid into a stainless-steel hydrothermal kettle lined with polytetrafluoroethylene and placing the kettle in a hot air oven, and then heating up to 180° C. and reacting at this temperature for 4 h; filtering the obtained reaction solution to obtain a filter cake, then washing the filter cake respectively with water and ethanol for three times, and finally drying the filter cake in a hot air oven at 80° C. for 8 h, thereby obtaining Mo-CS with a molybdenum content of 10.62 wt %.

[0060] The control sample Mo-C was prepared by the same method as above without the addition of APS. FIG. 6 shows SEM photos of Mo-CS and Mo-C for comparison, in which Mo-CS appeared as smooth spheres and Mo-C as fused irregular slag, some molybdenum oxide particles being wrapped on the spheres, the remaining molybdenum oxides being mixed in the carbon materials in the form of chips.

[0061] The preparation of Mo-ACS was as follows: Taking 1 part by mass of the Mo-CS sample, mixing it with 3 parts by mass of potassium oxalate uniformly, transferring the obtained mixture into a ceramic boat, placing the boat in a tubular furnace, introducing nitrogen to replace the air in the furnace, then adjusting the nitrogen flow to 30 mL/min, raising the temperature to 800° C. at a heating rate of 3° C./min to roast for 2 h, and then naturally cooling to room temperature; then washing the black powder obtained from the roasting with water until a neutral filtrate was obtained, and finally drying the obtained filter cake in a hot air oven at 110° C. for 6 h, thereby obtaining the Mo-doped activated carbon spheres Mo-ACS.

[0062] According to the method in Example 3, the adsorption amount of Mo-ACS for Cr(VI) was 191.7 mg/g.

Example 5

[0063] This example relates to the preparation of W-doped carbon spheres (W-CS), the preparation of W-doped carbon materials (W-C) as a control sample, and the preparation of W-ACS through the non-destructive activation of W-CS with potassium oxalate.

[0064] The preparation of W-CS was as follows: Dissolving 4 parts by mass of sucrose, 1 part by mass of Na.sub.2WO.sub.4.Math.2H.sub.2O, and 3 parts by mass of APS in 40 parts by volume of water, then transferring the obtained mixed liquid into a stainless-steel hydrothermal kettle lined with polytetrafluoroethylene and placing the kettle in a hot air oven, and then heating up to 180° C. and reacting at this temperature for 4 h; filtering the obtained reaction solution to obtain a filter cake, then washing the filter cake respectively with water and ethanol for three times, and finally drying the filter cake in a hot air oven at 80° C. for 8 h, thereby obtaining W-CS with a tungsten content of 3.31 wt %.

[0065] The control sample W-C was prepared by the same method as above without the addition of APS. FIG. 7 shows SEM photos of W-CS and W-C for comparison, in which W-CS appeared as smooth spheres, and W-C appeared as fused blocks where tungsten oxides of large particles (granular and rod-shaped) could be seen.

[0066] The preparation of W-ACS was as follows: Taking 1 part by mass of the W-CS sample, mixing it with 3 parts by mass of potassium oxalate uniformly, transferring the obtained mixture into a ceramic boat, placing the boat in a tubular furnace, introducing nitrogen to replace the air in the furnace, then adjusting the nitrogen flow to 30 mL/min, raising the temperature to 800° C. at a heating rate of 3° C./min to roast for 2 h, and then naturally cooling to room temperature; then washing the black powder obtained from the roasting with water until a neutral filtrate was obtained, and finally drying the obtained filter cake in a hot air oven at 110° C. for 6 h, thereby obtaining the W-doped activated carbon spheres W-ACS.

[0067] According to the method in Example 3, the adsorption amount of W-ACS for Cr(VI) was 160.4 mg/g.

[0068] In the above examples, the concentration of the heavy metal ion Cr(VI) was detected by the diphenylcarbazide spectrophotometry, and the UVmini-1240 UV-VIS spectrophotometer used was from Shimadzu, Japan; the content of transition metal dopants was determined by the inductively coupled plasma-atomic emission spectrometry, and the Prodigy7 full-spectrum direct-reading plasma emission spectrometer used was from Leeman Labs Inc., USA; and the surface microstructure of samples was detected by JSM-IT300 scanning electron microscope produced by Japan Electronics Co., Ltd.

[0069] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited thereto, and any other alterations, modifications, replacements, combinations and simplifications made without departing from the spirit and principle of the present invention shall all be equivalent substitutions and included in the scope of protection of the present invention.