CN110433789B - Method for preparing photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide - Google Patents
Method for preparing photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide Download PDFInfo
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- CN110433789B CN110433789B CN201910700898.6A CN201910700898A CN110433789B CN 110433789 B CN110433789 B CN 110433789B CN 201910700898 A CN201910700898 A CN 201910700898A CN 110433789 B CN110433789 B CN 110433789B
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- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 title claims abstract description 180
- 239000011787 zinc oxide Substances 0.000 title claims abstract description 92
- 240000003826 Eichhornia crassipes Species 0.000 title claims abstract description 46
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 43
- 239000002131 composite material Substances 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title abstract description 19
- 241000169203 Eichhornia Species 0.000 claims abstract description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000001035 drying Methods 0.000 claims abstract description 16
- 238000004140 cleaning Methods 0.000 claims abstract description 10
- 238000001354 calcination Methods 0.000 claims abstract description 9
- 239000003610 charcoal Substances 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 239000011701 zinc Substances 0.000 claims abstract description 7
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 6
- 235000015097 nutrients Nutrition 0.000 claims description 17
- 241000196324 Embryophyta Species 0.000 claims description 16
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- 229960002180 tetracycline Drugs 0.000 claims description 12
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- 235000019364 tetracycline Nutrition 0.000 claims description 12
- 150000003522 tetracyclines Chemical class 0.000 claims description 12
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- 239000002245 particle Substances 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 238000007873 sieving Methods 0.000 claims description 8
- 238000012258 culturing Methods 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 6
- 230000007935 neutral effect Effects 0.000 claims description 6
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- 239000000463 material Substances 0.000 description 20
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 11
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
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- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 4
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- 238000005054 agglomeration Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
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Images
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/06—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of zinc, cadmium or mercury
-
- B01J35/39—
-
- B01J35/394—
-
- B01J35/61—
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/40—Monitoring or fighting invasive species
Abstract
The invention relates to a method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide, which comprises the following specific steps of: 1) Cleaning water hyacinth growing in a natural lake, putting the cleaned water hyacinth into a culture solution containing nano zinc oxide for culture, taking out the water hyacinth after 15 to 45 days of culture, cleaning the water hyacinth, drying and crushing the water hyacinth for later use; 2) Calcining the crushed eichhornia crassipes in an inert atmosphere, and cooling and then processing to obtain the nano zinc oxide-charcoal photocatalytic composite material. The invention takes the eichhornia crassipes as a charcoal source, and the eichhornia crassipes as a foreign species is abused in many eutrophic water areas in recent years to cause disasters.
Description
Technical Field
The invention belongs to the technical field of photocatalytic materials, and particularly relates to a method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide.
Background
The tetracycline antibiotics are cheap, so the dosage of the tetracycline antibiotics is huge in China. After being used, tetracycline enters a municipal pipe network in a mode of excrement and then is discharged into a sewage treatment plant, and most of the sewage treatment plants do not have a treatment process for tetracycline antibiotics at present. Therefore, the tetracycline can flow into natural water areas along with the effluent of sewage plants, and pollute the water environment.
The nano zinc oxide is used as a photocatalyst due to the characteristics of small particle size, large specific surface area, high chemical activity and the like. Under the irradiation of ultraviolet light, the nano zinc oxide is excited to generate free radicals with high oxidizability, and the free radicals can react with complex organic matters which are difficult to degrade, so that the purpose of degrading and removing the organic matters is achieved. However, the nano zinc oxide is easy to agglomerate, and the nano effect and the photocatalytic effect of the agglomerated nano zinc oxide are obviously reduced, so that the application of the nano zinc oxide is greatly limited.
The biochar is a solid material generated by pyrolyzing a biomass material under the conditions of limited oxygen (or no oxygen) and relatively low temperature (generally less than 700 ℃), and has the characteristics of high refractoriness, stability, porosity, high aromaticity, carbon enrichment and the like. Because the raw materials for preparing the biochar are different, the surface functional groups and the electrochemical performance are limited in the preparation process, and the ideal effect on removing pollutants is difficult to achieve. However, biochar has a large specific surface area, a regular pore size distribution, a developed void structure, and stable physicochemical properties, and is a material having excellent performance from the viewpoint of a matrix material. If the biochar is used as a substrate, the aggregation effect among the nano particles can be greatly reduced by dispersing the nano zinc oxide on the surface of the biochar, and the semiconductor bandwidth of the nano zinc oxide is properly reduced, so that the modified biochar has an adsorption effect and a remarkable photocatalytic effect. However, the current mode of combining the nano zinc oxide and the biochar is to carry out artificial loading through some physical or chemical means, and the loading modes are complex in steps and complex in operation, so that the consumption of experimental materials and reagents is increased, and the experimental cost is invisibly increased.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide aiming at the defects in the prior art. The nano zinc oxide enters the plant body of the water hyacinth and is tightly combined with the plant, after the water hyacinth is fired into the biochar, the nano zinc oxide is uniformly dispersed on the surface of the biochar, the bandwidth of a semiconductor of the nano zinc oxide is effectively reduced and is easier to be excited by an ultraviolet lamp, and the obtained biochar composite material can be efficiently degraded by tetracycline under the irradiation of a low-pressure ultraviolet lamp.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the method for preparing the photocatalytic biochar composite material by utilizing the eichhornia crassipes accumulated nano zinc oxide comprises the following specific steps:
1) Cleaning water hyacinth growing in a natural lake, putting the cleaned water hyacinth into a culture solution containing nano zinc oxide for culture, taking out the water hyacinth after culturing for 15 to 45 days, cleaning the water hyacinth, drying and crushing the water hyacinth for later use;
2) Calcining the crushed eichhornia crassipes in an inert atmosphere, and cooling and then processing to obtain the nano zinc oxide-charcoal photocatalytic composite material.
According to the scheme, the fresh weight of a single plant of the eichhornia crassipes in the step 1) is 20-30 g.
According to the scheme, the particle size of the nano zinc oxide is 20-40nm.
According to the scheme, the preparation method of the culture solution containing the nano zinc oxide in the step 1) comprises the following steps: adding nano zinc oxide into water, uniformly dispersing by ultrasonic to obtain a nano zinc oxide solution, mixing the obtained nano zinc oxide solution with a nutrient solution, and diluting by adding distilled water to obtain a culture solution containing nano zinc oxide.
According to the scheme, the concentration of the nano zinc oxide in the culture solution containing the nano zinc oxide is 100-400 mg/L.
According to the scheme, the culture solution is a Hoagland nutrient solution, and the volume ratio of the Hoagland nutrient solution to the culture solution containing nano zinc oxide is 1:100 to 200.
According to the scheme, the drying conditions in the step 1) are as follows: baking for 12-36 h at 60-100 ℃.
According to the scheme, the particle size of the crushed eichhornia crassipes in the step 1) is smaller than 1mm.
According to the scheme, the calcining temperature in the step 2) is 550-600 ℃, and the calcining time is 2-3 h.
According to the scheme, the post-treatment in the step 2) comprises the following steps: grinding, washing until pH value is neutral, drying, and sieving.
According to the scheme, the drying conditions in the step 2) are as follows: baking at 105 ℃ for 12h.
According to the scheme, the step 2) of sieving is to pass through a 80-mesh sieve.
The invention also comprises the photocatalytic biochar composite material prepared by the method, and the loading capacity of the nano zinc oxide in the composite material is 16.71-90.16 mg/g.
The invention also comprises the application of the photocatalytic biochar composite material in the aspect of photocatalytic degradation of organic pollutants.
According to the scheme, the organic pollutant is tetracycline.
The invention also comprises the application of the method for preparing the photocatalytic biochar composite material by utilizing the eichhornia crassipes accumulated nano zinc oxide in removing nano material pollutants in water.
The invention has the beneficial effects that:
1) The invention takes the water hyacinth as the source of the charcoal, and the water hyacinth as a foreign species floods in a plurality of eutrophic water areas in recent years to cause disasters, so the invention changes waste into valuable and realizes the resource utilization of the water hyacinth;
2) The invention utilizes the natural absorption of the nano zinc oxide in the water solution by the eichhornia crassipes, omits a complex artificial loading mode, effectively disperses in the eichhornia crassipes after the nano zinc oxide enters the plant body, and is combined with the cell wall, cell sap, vacuole and the like of the plant, and the nano zinc oxide is tightly combined with the internal structures of the plant cell wall, phloem, xylem and the like, and can also be combined with saccharides and proteins in the plant body, thereby realizing the effective attachment of the nano zinc oxide in the eichhornia crassipes plant body, avoiding the inactivation problem of zinc oxide calcination agglomeration and agglomeration, finally converting the eichhornia crassipes plant absorbed with the nano zinc oxide into a biochar composite material with a photocatalytic effect under the condition of high temperature and limited oxygen, the nano zinc oxide is more tightly combined with a biochar matrix, the particle diameter of the nano zinc oxide is maintained, and the nano zinc oxide is uniformly dispersed on the biochar surface;
3) The method can properly reduce the forbidden bandwidth of the nano zinc oxide semiconductor, so that the material is easier to be excited by an ultraviolet lamp, and the photocatalytic effect of the material is improved;
4) After the biological carbon composite material is used for adsorbing and removing nano material pollutants in a water body, the biological carbon composite material can be fired into a biological carbon material and is continuously recycled, so that the hazard of the nano material to the water body environment is reduced.
Drawings
FIG. 1 is an SEM image of a photocatalytic biochar composite material obtained in example 3 of the present invention;
FIG. 2 is a photograph showing Eichhornia crassipes grown in the culture solution of example 3, the culture solution of comparative example 3, and the culture solution of comparative example 4 for 15 days, respectively;
FIG. 3 is a semiconductor forbidden bandwidth diagram of the photocatalytic biochar composite material and nano-zinc oxide obtained in examples 1-3;
FIG. 4 is a graph showing the degradation rate of tetracycline by the photocatalytic biochar composite materials obtained in examples 1-4 and the biochar material prepared in comparative example 4.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings.
The particle size of the nano zinc oxide used in the embodiment of the invention is 20-40nm.
Example 1
A method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide comprises the following specific steps:
(1) Taking water hyacinth which grows in a natural lake and has the fresh weight of 20-30 g and the consistent growth vigor, washing the water hyacinth with distilled water for later use, preparing a Hoagland nutrient solution and a nano zinc oxide solution (crushing the water hyacinth by an ultrasonic crusher for 1 h), mixing 5mL of the nutrient solution with the nano zinc oxide solution after ultrasonic crushing for 1h, adding distilled water to prepare 1L of a culture solution (wherein the concentration of the nano zinc oxide is 100 mg/L), placing the water hyacinth in the culture solution and culturing the water hyacinth under laboratory conditions, wherein the laboratory conditions are that the water hyacinth is illuminated for 12h in the daytime, the illumination intensity is 12000Lux, the water hyacinth is placed in the dark for 12h at night, and the day and night temperatures are 24 ℃ and 22 ℃ respectively;
(2) Taking out the water hyacinth and cleaning after the water hyacinth is cultured for 15 days, drying for 12 hours at the temperature of 105 ℃, and crushing to obtain powder with the particle size of less than 1mm for later use;
(3) Placing the crushed eichhornia crassipes in nitrogen, heating to 600 ℃ at the speed of 12 ℃/min, preserving heat for 2 hours, cooling to room temperature, taking out and firing to obtain eichhornia crassipes biochar, and grinding;
(4) And washing the ground biochar until the pH value is neutral, drying, and sieving by a 80-mesh sieve to obtain the photocatalytic biochar composite material accumulated with the nano zinc oxide.
Comparative example 1
A photocatalytic biochar composite material is prepared by a method similar to that in example 1, except that zinc chloride with equal mass is used for replacing nano zinc oxide to prepare a culture solution, and the concentration of the zinc chloride in the culture solution is 100mg/L.
Example 2
A method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide comprises the following specific steps:
(1) Taking water hyacinth which grows in a natural lake and has the fresh weight of 20-30 g and the consistent growth vigor, washing the water hyacinth with distilled water for later use, preparing a Hoagland nutrient solution and a nano zinc oxide solution (crushing the water hyacinth by an ultrasonic crusher for 1 h), mixing 5mL of the nutrient solution with the nano zinc oxide solution after ultrasonic crushing for 1h, adding distilled water to prepare 1L of a culture solution (wherein the concentration of the nano zinc oxide is 200 mg/L), placing the water hyacinth in the culture solution and culturing the water hyacinth under laboratory conditions, wherein the laboratory conditions are that the water hyacinth is illuminated for 12h in the daytime, the illumination intensity is 12000Lux, the water hyacinth is placed in the dark for 12h at night, and the day and night temperatures are 24 ℃ and 22 ℃ respectively;
(2) Taking out the water hyacinth and cleaning after the water hyacinth is cultured for 15 days, drying for 12 hours at the temperature of 105 ℃, and crushing to obtain powder with the particle size of less than 1mm for later use;
(3) Placing the crushed eichhornia crassipes in nitrogen, heating to 600 ℃ at the speed of 12 ℃/min, preserving heat for 2 hours, cooling to room temperature, taking out and firing to obtain eichhornia crassipes biochar, and grinding;
(4) And washing the ground biochar until the pH value is neutral, drying, and sieving by a 80-mesh sieve to obtain the photocatalytic biochar composite material accumulating the nano zinc oxide.
Comparative example 2
A photocatalytic biochar composite material is prepared by a method similar to that in example 2, except that zinc chloride with equal mass is used for replacing nano zinc oxide to prepare a culture solution, and the concentration of the zinc chloride in the culture solution is 200mg/L.
Example 3
A method for preparing a photocatalytic biochar composite material by utilizing eichhornia crassipes accumulated nano zinc oxide comprises the following specific steps:
(1) Taking water hyacinth which grows in a natural lake and has the fresh weight of 20-30 g and the consistent growth vigor, washing the water hyacinth with distilled water for later use, preparing a Hoagland nutrient solution and a nano zinc oxide solution (crushing the water hyacinth by an ultrasonic crusher for 1 h), mixing 5mL of the nutrient solution with the nano zinc oxide solution after ultrasonic crushing for 1h, adding distilled water to prepare 1L of a culture solution (wherein the concentration of the nano zinc oxide is 400 mg/L), placing the water hyacinth in the culture solution and culturing the water hyacinth under laboratory conditions, wherein the laboratory conditions are that the water hyacinth is illuminated for 12h in the daytime, the illumination intensity is 12000Lux, the water hyacinth is placed in the dark for 12h at night, and the day and night temperatures are 24 ℃ and 22 ℃ respectively;
(2) Taking out the water hyacinth and cleaning after the water hyacinth is cultured for 15 days, drying for 12 hours at the temperature of 105 ℃, and crushing to obtain powder with the particle size of less than 1mm for later use;
(3) Placing the crushed eichhornia crassipes in nitrogen, heating to 600 ℃ at the speed of 12 ℃/min, preserving heat for 2 hours, cooling to room temperature, taking out and firing to obtain eichhornia crassipes biochar, and grinding;
(4) And washing the ground biochar until the pH value is neutral, drying, and sieving by a 80-mesh sieve to obtain the photocatalytic biochar composite material accumulated with the nano zinc oxide.
As shown in fig. 1, a SEM image obtained by scanning electron microscope observation of the photocatalytic biochar composite material obtained in this example is shown, and the nano zinc oxide can be observed to be uniformly dispersed on the surface of the biochar material without agglomeration at a magnification of 5000.
Comparative example 3
A photocatalytic biochar composite material is prepared by a method similar to that in example 3, except that zinc chloride with equal mass is used for replacing nano zinc oxide to prepare a culture solution, and the concentration of the zinc chloride in the culture solution is 400mg/L.
Comparative example 4
A method for preparing a photocatalytic biochar material by using eichhornia crassipes comprises the following steps:
(1) Taking water hyacinth which grows in a natural lake and has the fresh weight of 20-30 g and the consistent growth vigor, washing the water hyacinth with distilled water for later use, preparing Hoagland nutrient solution, preparing 5mL of nutrient solution and distilled water into 1L of solution, placing the water hyacinth in the solution containing the nutrient solution and culturing the water hyacinth under the laboratory condition, wherein the laboratory condition is that the water hyacinth is illuminated for 12 hours in the daytime, the illumination intensity is 12000Lux, the darkness is 12 hours, and the day and night temperature is 24 ℃ and 22 ℃ respectively;
(2) Taking out cultured Eichhornia crassipes (mart.) Gaertn after 15 days, cleaning, baking at 105 deg.C for 12 hr, and pulverizing to particle size less than 1 mm;
(3) Placing the crushed eichhornia crassipes in nitrogen, heating to 600 ℃ at the speed of 12 ℃/min, keeping for 2h, cooling to room temperature, taking out the baked eichhornia crassipes biochar, and grinding;
(4) And washing the ground biochar until the pH value is neutral, drying, and sieving by a 80-mesh sieve to obtain the eichhornia crassipes biochar material.
The same growth of Eichhornia crassipes was cultured in example 3 (400 NPs) and comparative example 3 (400 Zn), respectively 2+ ) The photo of the culture solution of (1) is shown in fig. 2 after 15 days of growth, and the leaves of Eichhornia crassipes grown in the culture solution of (4) which does not contain zinc oxide or zinc ions and only contains nutrient solution are yellow, while the leaves of Eichhornia crassipes grown in the culture solution of (3) for 15 days are all withered and yellow and die completely.
Since the nano zinc oxide in the obtained charcoal cannot be directly and quantitatively tested, the content of the nano zinc oxide in the composite material of the eichhornia crassipes biochar prepared in examples 1 to 3 and the content of the nano zinc oxide in the eichhornia crassipes biochar prepared in comparative examples 1 to 4 are roughly expressed by performing an ICP-OES test, and the results are shown in Table 1.
TABLE 1 Zinc content in biochar materials obtained in examples 1-3 and comparative example 1
As can be seen from Table 1, the difference of the zinc content in the obtained biochar material is large when the nano zinc oxide and the zinc chloride solution with the same concentration are used for culture. In general, the Eichhornia crassipes plant has a better absorption effect on the nano zinc oxide, and the obtained biochar material has higher zinc content, probably because the toxicity of zinc ions on plants is higher than that of the nano zinc oxide, especially on the roots of the plants, the toxic effect is not beneficial to the adsorption of the roots of the plants on the zinc ions, and is also not beneficial to the transfer and transportation of the zinc ions in the plants.
In order to visually inspect the photocatalytic performance of the accumulated nano-zinc oxide eichhornia crassipes biochar composite material prepared in the embodiment of the invention, the photocatalytic biochar composite material obtained in the embodiment 1-3 and a nano-zinc oxide material are subjected to an ultraviolet-visible diffuse reflection test, the obtained data are processed by a Tauc plot method, and the obtained semiconductor forbidden band width diagram is shown in fig. 3. As can be seen from fig. 3, the forbidden bandwidth of the nano zinc oxide in the photocatalytic biochar composite material obtained in examples 1-3 is respectively reduced from original 3.17eV to 3.15 eV, 3.02 eV and 3.08eV, and the forbidden bandwidth of the nano zinc oxide composite material obtained in example 2 is the lowest by the natural adsorption and calcination method of the nano zinc oxide through eichhornia crassipes. The reduction of the forbidden band width is beneficial to the excitation of the photocatalytic material and the exertion of the photocatalytic effect. By combining the results obtained in table 1, the plant culture by using 200mg/L of nano zinc oxide is more beneficial to the adsorption of the plant on the nano zinc oxide and the improvement of the photocatalytic effect of the nano zinc oxide material.
Example 4
The eichhornia crassipes is placed in the culture solution of the example 2 for continuous culture, when the culture time is 45 days, the stems and leaves of eichhornia crassipes plants are all yellow-black, the plants are necrotic, and the adsorption of nano zinc oxide can not be carried out any more, and the relative content of the prepared charcoal material nano zinc oxide is 90.16mg/g.
In order to investigate the degradation effect of the accumulated nano zinc oxide eichhornia crassipes biochar composite material prepared by the embodiment of the invention on pollutants, a tetracycline degradation test is carried out, and the specific operations are as follows: 0.2g of the biochar materials prepared in examples 1-4 and comparative example 4 were respectively put into 1L of tetracycline solution with a concentration of 50mg/L, the pH value was adjusted to =7 with 0.1mol/L of sodium hydroxide, the mixture was put into a magnetic stirrer, the rotation speed was kept at 200rpm, the mixture was adsorbed for 30min in the dark, and then the mixture was irradiated under a 30W ultraviolet lamp for 4.5h, and the degradation effect on tetracycline was shown in FIG. 4. As can be seen from FIG. 4, when the concentration of the nano-zinc oxide solution in the culture solution is increased from 100mg/L to 200mg/L, the degradation rate of tetracycline is also increased. After the irradiation of a 30W ultraviolet lamp for 4.5h, the catalytic degradation rate of the biochar material in example 2 reaches 65.79% (when the nano zinc oxide solution is 200 mg/L), but when the concentration of the nano zinc oxide is increased to 400mg/L, the degradation rate of the obtained photocatalytic biochar composite material on tetracycline is reduced. Example 4 the biochar material has the best degradation effect on tetracycline, and the degradation rate of 5h is 85.13%.
The invention and the embodiments have been described in detail, but modifications and improvements without departing from the spirit of the invention are within the scope of the invention.
Claims (4)
1. The application of the photocatalytic biochar composite material in the aspect of photocatalytic degradation of organic pollutants is characterized in that the preparation method of the photocatalytic biochar composite material comprises the following specific steps:
1) Cleaning water hyacinth growing in a natural lake with distilled water, and culturing in a culture solution containing nano zinc oxide, wherein the preparation method of the culture solution containing nano zinc oxide comprises the following steps: adding nano zinc oxide into water, wherein the particle size of the nano zinc oxide is 20 to 40nm, performing ultrasonic dispersion uniformly to obtain a nano zinc oxide solution, mixing the obtained nano zinc oxide solution with a nutrient solution, and adding distilled water to dilute the solution to obtain a culture solution containing the nano zinc oxide, wherein the concentration of the nano zinc oxide in the culture solution containing the nano zinc oxide is 200mg/L, the nutrient solution is a Hoagland nutrient solution, and the volume ratio of the Hoagland nutrient solution to the culture solution containing the nano zinc oxide is 1: culturing for 15 to 45 days at the temperature of 100 to 200 ℃, taking out the eichhornia crassipes, cleaning, drying and crushing for later use;
2) Calcining the crushed eichhornia crassipes in an inert atmosphere, and cooling and then treating to obtain a nano zinc oxide-charcoal photocatalytic composite material;
the organic contaminant is tetracycline.
2. The application of the photocatalytic biochar composite material in photocatalytic degradation of organic pollutants as claimed in claim 1, wherein the fresh weight of each eichhornia crassipes single plant in step 1) is 20 to 30g.
3. The application of the photocatalytic biochar composite material in photocatalytic degradation of organic pollutants as claimed in claim 1, wherein the calcination temperature in the step 2) is 550-600 ℃, and the calcination time is 2-3h.
4. The application of the photocatalytic biochar composite material in the aspect of photocatalytic degradation of organic pollutants according to claim 1, is characterized in that the post-treatment in the step 2) is as follows: grinding, washing until the pH value is neutral, drying and sieving; step 2) the drying conditions are as follows: drying at 105 ℃ for 12h; and 2) sieving by using a 80-mesh sieve.
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