CN115445647A - Carbon nitride composite photocatalyst, preparation method thereof and treatment method of herbicide wastewater - Google Patents
Carbon nitride composite photocatalyst, preparation method thereof and treatment method of herbicide wastewater Download PDFInfo
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- CN115445647A CN115445647A CN202210999934.5A CN202210999934A CN115445647A CN 115445647 A CN115445647 A CN 115445647A CN 202210999934 A CN202210999934 A CN 202210999934A CN 115445647 A CN115445647 A CN 115445647A
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- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 title claims abstract description 185
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- 239000002131 composite material Substances 0.000 title claims abstract description 123
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- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 84
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- 230000007812 deficiency Effects 0.000 claims abstract description 29
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical group [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims abstract description 24
- 125000004437 phosphorous atom Chemical group 0.000 claims abstract description 23
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 20
- MXWJVTOOROXGIU-UHFFFAOYSA-N atrazine Chemical group CCNC1=NC(Cl)=NC(NC(C)C)=N1 MXWJVTOOROXGIU-UHFFFAOYSA-N 0.000 claims description 41
- 239000002243 precursor Substances 0.000 claims description 37
- 239000000203 mixture Substances 0.000 claims description 22
- 238000013032 photocatalytic reaction Methods 0.000 claims description 19
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- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 claims description 5
- 238000001179 sorption measurement Methods 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 4
- 230000007717 exclusion Effects 0.000 claims description 3
- 230000002950 deficient Effects 0.000 claims description 2
- RYCLIXPGLDDLTM-UHFFFAOYSA-J tetrapotassium;phosphonato phosphate Chemical compound [K+].[K+].[K+].[K+].[O-]P([O-])(=O)OP([O-])([O-])=O RYCLIXPGLDDLTM-UHFFFAOYSA-J 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
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- 239000000463 material Substances 0.000 description 32
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- 230000000052 comparative effect Effects 0.000 description 18
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- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
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- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- OWYWGLHRNBIFJP-UHFFFAOYSA-N Ipazine Chemical group CCN(CC)C1=NC(Cl)=NC(NC(C)C)=N1 OWYWGLHRNBIFJP-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
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- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000010916 herbicide waste Substances 0.000 description 1
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Images
Classifications
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- B01J35/39—
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
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- B01J35/40—
-
- 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
- C02F2101/306—Pesticides
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
-
- 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
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Abstract
The invention relates to a functional composite photocatalyst, and discloses a carbon nitride composite photocatalyst, a preparation method thereof and a treatment method of herbicide wastewater. The carbon nitride composite photocatalyst comprises a graphene carbon nitride nanosheet catalyst containing cyano groups and nitrogen deficiency sites, and phosphorus atoms and potassium atoms doped in the catalyst. The carbon nitride composite photocatalyst has the advantages of high photocatalytic activity, good photocatalytic stability, wide photoresponse range, high removal rate of herbicides and good reusability.
Description
Technical Field
The invention relates to a functional composite photocatalyst, and in particular relates to a carbon nitride composite photocatalyst as well as a preparation method and application thereof. In addition, the invention also relates to a method for treating the herbicide wastewater.
Background
In recent years, photocatalytic technology has been rapidly developed, and in particular, semiconductor-based photocatalytic degradation technology for the removal of environmental pollutants has received much attention from researchers. The photocatalytic reaction mainly occurs on the surface of the photocatalyst, so that the property of the photocatalyst determines whether the photocatalyst has good photocatalytic performance. Therefore, designing and preparing high-efficiency semiconductor photocatalytic materials become the focus of research in the field of environmental photocatalysis at present.
Non-metallic graphite phase carbon nitride has attracted a great deal of attention in the selection and application of materials. However, the forbidden band width of the graphite-phase carbon nitride is 2.7eV, so that the absorption range of the graphite-phase carbon nitride is limited to illumination within 460nm, the photoresponse range is small, sunlight cannot be fully utilized, the catalytic degradation effect of the graphite-phase carbon nitride material on pollutants in the environment cannot be improved, and the unmodulated graphite-phase carbon nitride cannot achieve a satisfactory photocatalytic effect.
Therefore, the obtained graphite-phase carbon nitride nanosheet composite photocatalyst has high photocatalytic activity, good photocatalytic stability and wide photoresponse range, and has important significance for improving the catalytic degradation effect of graphite-phase carbon nitride on pollutants.
Disclosure of Invention
The invention aims to solve the problem that the catalytic degradation effect of a graphite-phase carbon nitride material needs to be improved in the prior art, and provides a carbon nitride composite photocatalyst, a preparation method thereof and a herbicide wastewater treatment method.
In order to achieve the above object, one aspect of the present invention provides a carbon nitride composite photocatalyst, including a graphene carbon nitride nanosheet catalyst containing a cyano group and a nitrogen deficiency, and phosphorus atoms and potassium atoms doped in the catalyst.
Preferably, the graphene carbon nitride nanosheet catalyst containing cyano groups and nitrogen deficiency sites comprises graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites, the phosphorus atom being decorated on the graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites.
Further preferably, the graphene carbon nitride nanosheets containing cyano groups and nitrogen vacancies are provided with at least two sheets, the potassium atoms being intercalated between the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen vacancies.
Preferably, the total content of the phosphorus atom and the potassium atom in the carbon nitride composite photocatalyst is 0.1 to 7 mass%.
Preferably, the graphite phase carbon nitride nanoplatelets containing cyano and nitrogen deficiency sites are in the form of porous platelets.
Further preferably, the thickness of the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites is 1-3nm.
The second aspect of the invention provides a preparation method of a carbon nitride composite photocatalyst, which comprises the following steps:
(1) Mixing and grinding urea and monopotassium phosphate to obtain a precursor mixture;
(2) Carrying out thermal polycondensation reaction on the precursor mixture to obtain a carbon nitride composite photocatalyst precursor;
(3) And calcining the carbon nitride composite photocatalyst precursor to obtain the carbon nitride composite photocatalyst.
Preferably, the mass ratio of the urea to the potassium diphosphate is 10000.
Preferably, in step (2), the conditions of the thermal polycondensation reaction include: the temperature is 500-600 ℃, and the time is 3-5h.
Preferably, in step (3), the calcination is carried out under oxygen exclusion conditions, and the calcination conditions include: the temperature is 450-550 ℃ and the time is 1.5-2.5h.
The third aspect of the invention provides a carbon nitride composite photocatalyst provided by the first aspect and application of the carbon nitride composite photocatalyst prepared by the preparation method provided by the second aspect in treatment of herbicide wastewater.
The fourth aspect of the present invention provides a method for treating herbicide wastewater, comprising the steps of:
(1) Under the condition of keeping out of the sun, mixing and adsorbing the carbon nitride composite photocatalyst provided by the first aspect and/or the prepared carbon nitride composite photocatalyst provided by the second aspect with the herbicide wastewater to obtain a mixed solution;
(2) And carrying out photocatalytic reaction on the mixed solution under the condition of visible light.
Preferably, in the step (1), the mass ratio of the carbon nitride composite photocatalyst to the herbicide is 40-120.
Further preferably, the herbicide is atrazine.
More preferably, the adsorption time is 25-35min.
Preferably, in the step (2), the wavelength λ of the visible light is more than 420nm, and the time of the photocatalytic reaction is 50-70min.
Through the technical scheme, the invention has the beneficial effects that:
(1) According to the carbon nitride composite photocatalyst provided by the invention, the cyano group is taken as a strong negative group, the original charge balance can be broken through by introducing the cyano group into the catalyst material, and the generated potential difference not only can provide power for the transfer of a photon-generated carrier, but also can enable the photon-generated carrier to move directionally, so that the photocatalytic performance of the catalyst material is improved. The uncoordinated electrons on the nitrogen deficiency position can enhance the adsorption of the catalyst material on oxygen and a target, and also can greatly improve the photosensitivity of the catalyst material, thereby improving the photocatalytic performance of the material. Phosphorus atoms and potassium atoms doped in the graphene carbon nitride nanosheet catalyst can effectively improve the absorption and utilization of the catalyst material on light energy, so that the photocatalytic performance of the material is further improved. The carbon nitride composite photocatalyst has the advantages of high photocatalyst activity, wide photoresponse range, stable photocatalytic performance, good reusability and the like.
(2) The phosphorus atoms are doped into the graphite-phase carbon nitride nanosheets by replacing corner carbon and gulf carbon in the graphite-phase carbon nitride framework, so that the absorption and utilization of the catalyst material on light energy can be effectively improved, and the phosphorus atoms can be used as new active sites, so that the photocatalytic performance of the catalyst material is improved.
(3) The potassium atoms are intercalated between the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency positions, so that the conductivity of the catalyst material can be effectively improved, and the interlayer spacing can be changed, so that the effective transfer of photo-generated carriers of the catalyst material is improved, and the catalyst activity of the catalyst material can be further improved.
(4) The carbon nitride composite photocatalyst provided by the invention is in a porous flaky shape containing the cyano-group and nitrogen-deficient graphite-phase carbon nitride nanosheet, and the porous structure can not only improve the contact area between the catalyst material and a target object, but also enable light rays to be reflected and refracted for multiple times in the catalyst material, so that the photocatalytic performance of the catalyst material is improved.
(5) The preparation method provided by the invention introduces phosphorus atoms, potassium atoms, cyano groups and nitrogen vacancies into graphite-phase carbon nitride through thermal polycondensation to prepare the ultrathin porous structured photocatalytic material, and the preparation method is simple in preparation process, simple and convenient to operate and low in cost.
(6) The method for treating the herbicide wastewater provided by the invention utilizes the carbon nitride composite photocatalyst to carry out photocatalytic reaction on the herbicide wastewater, has the advantages of simple application method, low cost, high removal rate of the herbicide and the like, can realize effective degradation of the herbicide in the wastewater, and has a good application prospect. Taking atrazine as an example, the removal rate of atrazine by the carbon nitride composite photocatalyst can reach 83.5% within 60min, which is about 5.8 times of that of graphite-phase carbon nitride nanosheets (14.3%), so that the photocatalytic efficiency is remarkably improved, and the carbon nitride composite photocatalyst has higher catalytic efficiency and better removal effect; in addition, after five times of circulating treatment, the photocatalytic removal rate of the carbon nitride composite photocatalyst is not obviously reduced, the removal rate can still reach 81%, and good photocatalytic stability and recycling performance are shown.
Drawings
Fig. 1 is a transmission electron microscope image of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and a carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1, wherein a is a transmission electron microscope image of PKCN, and b is a transmission electron microscope image of BCN;
FIG. 2 is XRD patterns of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and a carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1;
FIG. 3 is an atomic force microscope scan of a carbonized carbon composite Photocatalyst (PKCN) prepared in example 1 of the present invention;
FIG. 4 is a UV-visible spectrum diffuse reflectance graph of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and a carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1;
FIG. 5 is a Fourier infrared spectrum of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and a carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1;
FIG. 6 is an XPS map of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention;
FIG. 7 shows paramagnetic resonance spectra of a carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and a carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1;
fig. 8 is a schematic diagram showing the relationship between the concentration of atrazine during photocatalytic degradation in the visible light region (λ >420 nm) between the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and the carbon nitride nanosheet catalyst (BCN) prepared in comparative example 1, as a function of photocatalytic time;
fig. 9 is a schematic diagram showing the relationship between the concentration of atrazine during photocatalytic degradation in the visible light region (λ >420 nm) between the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 of the present invention and the carbon nitride nanosheet catalyst (BCN) prepared in comparative example 2, as a function of photocatalytic time;
fig. 10 is a graph showing the effect of the removal rate of the composite carbon nitride Photocatalyst (PKCN) prepared in example 1 of the present invention in the recycling of atrazine-containing wastewater.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a carbon nitride composite photocatalyst, which comprises a graphene carbon nitride nanosheet catalyst containing a cyano group and a nitrogen deficiency position, and a phosphorus atom and a potassium atom which are doped in the catalyst.
The carbon nitride composite photocatalyst provided by the invention is a graphite-phase carbon nitride nanosheet catalyst which is doped with phosphorus and potassium and contains cyano and nitrogen vacancy, the cyano is used as a strong negative group, the cyano is introduced into the catalyst material to break the original charge balance, and the generated potential difference not only can provide power for the transfer of a photo-generated carrier, but also can enable the photo-generated carrier to move directionally, so that the photocatalytic performance of the catalyst material is improved. The uncoordinated electrons on the nitrogen vacancy can enhance the adsorption of the catalyst material on oxygen and a target, and can also greatly improve the photosensitivity of the catalyst material, thereby improving the photocatalytic performance of the material. Phosphorus atoms and potassium atoms doped in the graphene carbon nitride nanosheet catalyst can effectively improve the absorption and utilization of the catalyst material on light energy, so that the photocatalytic performance of the material is further improved. The carbon nitride composite photocatalyst has the advantages of high photocatalyst activity, wide photoresponse range, stable photocatalytic performance, good reusability and the like.
Preferably, the graphene carbon nitride nanosheet catalyst containing cyano groups and nitrogen deficiency sites comprises graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites, and the phosphorus atom is modified on the graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites. In the research process, the inventor finds that phosphorus atoms can effectively improve the absorption and utilization of the catalyst material on light energy and can be used as a new active site by substituting corner carbon and bay carbon in a graphite-phase carbon nitride framework and doping the corner carbon and the bay carbon into a graphite-phase carbon nitride nanosheet, so that the photocatalytic performance of the catalyst material is improved.
Wherein the angular carbon is carbon at the corner of the carbon nitride heptazine ring; the gulf carbon is the carbon connecting two adjacent carbonitride heptazine rings.
Preferably, the graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites are provided with at least two sheets, and the potassium atoms are intercalated between the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites. The inventor finds out through calculation that potassium atoms are intercalated between the graphite-phase carbon nitride nanosheets containing the cyano groups and the nitrogen deficiency positions in a layered manner, and the intercalation of the potassium atoms between the graphite-phase carbon nitride nanosheets containing the cyano groups and the nitrogen deficiency positions not only can effectively improve the conductivity of the catalyst material, but also can change the interlayer spacing so as to improve the effective transfer of photo-generated carriers of the catalyst material.
Preferably, the total content of the phosphorus atom and the potassium atom in the carbon nitride composite photocatalyst is 0.1 to 7 mass%, and the ratio may specifically be 0.1 mass%, 1 mass%, 2 mass%, 3 mass%, 4 mass%, 5 mass%, 6 mass%, 7 mass%, or any value between the two values. The total content of the phosphorus atom and the potassium atom in the carbon nitride composite photocatalyst is more preferably 1.5 to 4% by mass. In the research process, the inventors find that under the condition of the above ratio, the absorption and utilization of the light energy by the carbon nitride composite photocatalyst can be further improved, and the photocatalytic activity of the carbon nitride composite photocatalyst can also be further improved.
In order to further improve the photocatalytic activity of the carbon nitride composite photocatalyst, the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites are preferably in the form of porous platelets. From the viewpoint of further improving the photocatalytic activity of the carbon nitride composite photocatalyst, preferably, the thickness of the graphite-phase carbon nitride nanosheet containing cyano groups and nitrogen deficiency is 1 to 3nm.
The second aspect of the invention provides a preparation method of a carbon nitride composite photocatalyst, which comprises the following steps:
(1) Mixing and grinding urea and potassium dihydrogen phosphate to obtain a precursor mixture;
(2) Carrying out thermal polycondensation reaction on the precursor mixture to obtain a carbon nitride composite photocatalyst precursor;
(3) And calcining the carbon nitride composite photocatalyst precursor to obtain the carbon nitride composite photocatalyst.
According to the preparation method provided by the invention, the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency positions and having a porous structure can be prepared in a thermal polycondensation reaction and calcination mode, potassium atoms can be intercalated between the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency positions, and phosphorus atoms are doped into the graphite-phase carbon nitride nanosheets by replacing corner carbon and bay carbon in a graphite-phase carbon nitride framework, so that the photocatalyst activity, the photocatalytic stability and the reusability of the carbon nitride composite photocatalyst can be effectively improved.
According to the invention, the grinding can be mechanical grinding or manual grinding, and the grinding time can be determined by a person skilled in the art according to actual conditions. Preferably, the conditions of the milling include: the time is 5-20min. The urea and the monopotassium phosphate can be uniformly mixed, the original crystal structures of the urea and the monopotassium phosphate can be damaged in the grinding process, the structures are further improved, and the catalytic activity of the prepared carbon nitride composite photocatalyst can be improved.
According to the invention, the mass ratio between the urea and the monopotassium phosphate is greater than or equal to 50. In order to further improve the catalytic activity of the prepared carbon nitride composite photocatalyst, the mass ratio of the urea to the potassium phosphate is 10000.
In order to further improve the photocatalytic activity of the prepared carbon nitride composite photocatalyst, preferably, in step (2), the conditions of the thermal polycondensation reaction include: the temperature is 500-600 deg.C, specifically 500 deg.C, 520 deg.C, 540 deg.C, 560 deg.C, 580 deg.C, 600 deg.C, or any value therebetween, and the time is 3-5h, specifically 3h, 3.5h, 4h, 4.5h, 5h, or any value therebetween. In the invention, in the thermal polycondensation reaction, the heating rate is 1-3 ℃/min.
Preferably, in step (3), the calcination is carried out under exclusion of oxygen, and the calcination conditions include: the temperature is 450-550 ℃, specifically 450 ℃, 470 ℃, 490 ℃, 510 ℃, 530 ℃, 550 ℃, or any value between the two values, and the time is 1.5-2.5h, specifically 1.5h, 1.7h, 1.9h, 2.1h, 2.3h, 2.5h, or any value between the two values. In the research process, the inventor finds that the calcination under the conditions can further improve the catalytic activity of the carbon nitride composite photocatalyst. In the invention, the heating rate is 3-8 ℃/min during the calcination.
The oxygen-isolating condition can be achieved by introducing an inert gas into the reaction vessel, wherein the inert gas can be nitrogen, argon, helium or the like which does not react with oxygen at high temperature, and nitrogen is preferred.
The third aspect of the invention provides a carbon nitride composite photocatalyst provided by the first aspect and application of the carbon nitride composite photocatalyst prepared by the preparation method provided by the second aspect in treatment of herbicide wastewater. The carbon nitride composite photocatalyst provided by the invention can carry out photocatalytic reaction on herbicide wastewater, realizes efficient degradation and removal of the herbicide in the wastewater, and has the advantages of stable photocatalytic performance, good reusability, simple application method, low cost and the like.
According to the present invention, the herbicide-containing wastewater is a wastewater containing a herbicide.
The fourth aspect of the present invention provides a method for treating herbicide wastewater, comprising the steps of:
(1) Under the condition of keeping out of the sun, mixing and adsorbing the carbon nitride composite photocatalyst provided by the first aspect and/or the prepared carbon nitride composite photocatalyst provided by the second aspect with the herbicide wastewater to obtain a mixed solution;
(2) And carrying out photocatalytic reaction on the mixed solution under the condition of visible light.
The inventor finds that the provided carbon nitride composite photocatalyst has higher removal rate on herbicides, and is low in cost and simple in method.
According to the invention, the dosage of the herbicide and the carbon nitride composite photocatalyst in the wastewater is not particularly limited, and the herbicide can be degraded and removed by applying the carbon nitride composite photocatalyst and performing photocatalysis. Preferably, in the step (1), the mass ratio of the carbon nitride composite photocatalyst to the herbicide is 40-120. Further preferably, the concentration of the herbicide in the herbicide wastewater can be adjusted to 1-15mg/L by water, and the addition amount of the carbon nitride composite photocatalyst in the wastewater is 0.2-1 g/L.
Preferably, the herbicide is atrazine. The composite photocatalyst has a better atrazine removing effect.
According to the invention, the adsorption time is preferably 15-25min, and specifically may be 15min, 17min, 19min, 21min, 23min, 25min, or any value between the two values.
According to the invention, in order to further improve the efficiency of treating the herbicide wastewater, preferably, in the step (2), the wavelength λ of the visible light is more than 420nm, and a xenon lamp can be particularly used as a light source of the visible light; the conditions of the photocatalytic reaction include: the temperature is 5-40 deg.C, specifically 5 deg.C, 10 deg.C, 15 deg.C, 20 deg.C, 25 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, or any value between the above two values; the time is 50-70min, specifically 50min, 55min, 60min, 65min, 70min, or any value between the above two values.
According to a particularly preferred embodiment of the present invention, there is provided a method for treating herbicide waste water, comprising the steps of:
(1) Mixing and grinding urea and monopotassium phosphate according to a mass ratio of 10000-40 for 5-20min to obtain a precursor mixture;
(2) Placing the precursor mixture obtained in the step (1) in a muffle furnace, heating the precursor mixture from room temperature to 500-600 ℃ at the heating rate of 1-3 ℃/min, sintering the precursor mixture for 3-5h, and cooling the sintered precursor mixture to obtain a carbon nitride composite photocatalyst precursor;
(3) Placing the precursor of the carbon nitride composite photocatalyst obtained in the step (2) in a tube furnace, heating to 450-550 ℃ from room temperature at a heating rate of 3-8 ℃/min for sintering for 1.5-2.5h in a nitrogen atmosphere, and cooling to obtain the carbon nitride composite Photocatalyst (PKCN);
(4) Adding the carbon nitride composite photocatalyst obtained in the step (3) into atrazine wastewater with the initial concentration of 5-15mg/L in a dark environment (the mass ratio of the carbon nitride composite photocatalyst to the atrazine is 40-120: 1), and adsorbing for 15-25min to obtain a mixed solution;
(5) And (3) under the condition of visible light (the wavelength lambda is more than 420 nm), placing the mixed solution obtained in the step (4) into a photocatalytic reaction device, and reacting for 50-70min.
In the preferred embodiment, atrazine has a higher removal rate.
The present invention will be described in detail below by way of examples.
In the following examples, the concentration of atrazine was measured by hplc (mobile phase methanol: water =70, flow rate 1mL/min column temperature 30 ℃, monitoring wavelength 227 nm. The high performance liquid chromatograph is purchased from Agilent company, and the instrument model is 1290Infinity II; the transmission electron microscope is purchased from Saimer Fei company, and the instrument model is TalosF200x; fourier Infrared Spectroscopy was purchased from Thermo Scientific, USA, with an instrument model of Nicolet iS20; the paramagnetic resonance spectrometer is purchased from Bruker company of Germany, and the model of the instrument is EMXplus-6/1; the XRD analyzer is purchased from Bruker, and the model of the analyzer is D8 advance; the ultraviolet-visible spectrum diffuse reflection analyzer is purchased from Hitachi, and the model of the analyzer is U-4100; the light source system of visible light is PLS-SXE 300D xenon lamp, which is purchased from Beijing Pofely science and technology Co., ltd; x-ray photoelectron spectroscopy was purchased from Sammerfei, inc. under the instrument model Thermo Fisher ESCALB Xi +. Atomic force microscopy was purchased from Bruker, germany, under the instrument model Dimension Icon.
In the following examples, unless otherwise specified, the raw materials and equipment used were all conventional commercial products, wherein urea and potassium dihydrogen phosphate were purchased from national drug group, herbicide wastewater used was self-prepared atrazine solution as simulated wastewater, and atrazine was purchased from mclin corporation as product number a821828.
In the following examples, unless otherwise specified, the data obtained are the average of three or more replicates at room temperature of 25. + -. 5 ℃.
Example 1
(1) Mixing and grinding urea and potassium dihydrogen phosphate according to a mass ratio of 10000;
(2) Placing the precursor mixture obtained in the step (1) in a crucible, then placing the crucible in a muffle furnace, heating the mixture from room temperature to 550 ℃ at the heating rate of 2 ℃/min, sintering the mixture for 4 hours, and cooling the mixture to obtain a carbon nitride composite photocatalyst precursor;
(3) Placing the precursor of the carbon nitride composite photocatalyst obtained in the step (2) in a tube furnace, heating the precursor from room temperature to 500 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, sintering the precursor for 2 hours, and cooling the precursor to obtain the carbon nitride composite Photocatalyst (PKCN);
performing element analysis on the carbon nitride composite photocatalyst by using X-ray photoelectron spectroscopy (XPS), and obtaining that the content of potassium atoms in the carbon nitride composite photocatalyst is 1 mass% and the content of phosphorus atoms in the carbon nitride composite photocatalyst is 0.7 mass% as shown in figure 2; and (3) analyzing the thickness of the carbon nitride composite photocatalyst by using an atomic force microscope, wherein the average thickness of the graphite-phase carbon nitride nanosheet containing cyano-groups and nitrogen deficiency sites is 2nm as shown in fig. 3.
Example 2
(1) Mixing and grinding urea and potassium dihydrogen phosphate according to a mass ratio of 10000;
(2) Placing the precursor mixture obtained in the step (1) in a crucible, then placing the crucible in a muffle furnace, heating the crucible to 500 ℃ from room temperature at the heating rate of 1 ℃/min, sintering the crucible for 5 hours, and cooling the crucible to obtain a carbon nitride composite photocatalyst precursor;
(3) Placing the carbon nitride composite photocatalyst precursor obtained in the step (2) in a tube furnace, heating from room temperature to 450 ℃ at a heating rate of 3 ℃/min in a nitrogen atmosphere, sintering for 2.5h, and cooling to obtain a carbon nitride composite Photocatalyst (PKCN);
performing element analysis on the carbon nitride composite photocatalyst by adopting X-ray photoelectron spectroscopy (XPS), and obtaining that the content of potassium atoms in the carbon nitride composite photocatalyst is 0.6 mass percent and the content of phosphorus atoms in the carbon nitride composite photocatalyst is 0.3 mass percent.
Example 3
(1) Mixing and grinding urea and monopotassium phosphate according to a mass ratio of 10000;
(2) Placing the precursor mixture obtained in the step (1) in a crucible, then placing the crucible in a muffle furnace, heating the crucible to 600 ℃ from room temperature at the heating rate of 3 ℃/min, sintering the crucible for 3 hours, and cooling the crucible to obtain a carbon nitride composite photocatalyst precursor;
(3) Placing the precursor of the carbon nitride composite photocatalyst obtained in the step (2) in a tube furnace, heating to 550 ℃ from room temperature at the heating rate of 8 ℃/min in the nitrogen atmosphere, sintering for 1.5h, and cooling to obtain the carbon nitride composite Photocatalyst (PKCN);
performing element analysis on the carbon nitride composite photocatalyst by adopting X-ray photoelectron spectroscopy (XPS), and obtaining that the content of potassium atoms in the carbon nitride composite photocatalyst is 3.8 mass% and the content of phosphorus atoms in the carbon nitride composite photocatalyst is 2.5 mass%.
Comparative example 1
(1) Grinding 10g of urea for 10min to obtain a precursor mixture;
(2) Placing the precursor mixture obtained in the step (1) in a crucible, then placing the crucible in a muffle furnace, heating the crucible to 550 ℃ from room temperature at the heating rate of 2 ℃/min, sintering the crucible for 4 hours, and cooling the crucible to obtain a carbon nitride composite photocatalyst precursor;
(3) And (3) placing the carbon nitride composite photocatalyst precursor obtained in the step (2) in a tube furnace, heating to 500 ℃ from room temperature at the heating rate of 5 ℃/min in the nitrogen atmosphere, sintering for 2h, and cooling to obtain the carbon nitride nanosheet photocatalyst (BCN).
Comparative example 2
(1) Adding 10g of urea and 10mg of potassium phosphate into a 50mL crucible containing 20mL of deionized water, mixing, and uniformly dispersing to obtain a photocatalyst precursor;
(2) Recrystallizing the photocatalyst precursor in an oven at 60 ℃ to obtain a recrystallized product;
(3) And (3) heating the recrystallized product in a muffle furnace at the temperature rise rate of 2 ℃/min to 550 ℃ for 4h, and obtaining the interlayer-doped potassium phosphate-like graphene carbon nitride photocatalyst with the addition of 10mg of potassium phosphate after the heat treatment is finished.
Test example 1
The carbon nitride composite Photocatalyst (PKCN) prepared in example 1 and the carbon nitride nanosheet photocatalyst (BCN) prepared in comparative example 1 were analyzed by a projection electron microscope (TEM), respectively, and the results are shown in fig. 1. As can be seen from fig. 1, the PKCN prepared in example 1 is in the form of a porous sheet with twisted edges; while the BCN prepared in the comparative example 1 is a blocky smooth sheet, which shows that the appearance of the material is changed by adding the monopotassium phosphate.
Test example 2
XRD analyses were performed on the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 and the carbon nitride nanosheet photocatalyst (BCN) prepared in comparative example 1, respectively, and the results are shown in fig. 2. As can be seen from fig. 2, the BCN prepared in comparative example 1 shows a typical diffraction peak of carbon nitride, while PKCN shows a similar diffraction peak to that of BCN, indicating that the addition of monopotassium phosphate does not change the crystal structure of graphite-phase carbon nitride nanosheets, which is of great significance for maintaining the excellent photocatalytic performance of the composite photocatalyst. Furthermore, it was found that the intensity of the characteristic peaks was reduced, which was mainly associated with the introduction of potassium atoms, phosphorus atoms and cyano and nitrogen vacancies.
Test example 3
Ultraviolet-visible spectrum diffuse reflection (UV-VIS) analysis was performed on the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 and the carbon nitride nanosheet photocatalyst (BCN) prepared in comparative example 1, respectively, and the results are shown in fig. 4. As can be seen from fig. 4, the light absorption boundary of BCN is around 440nm, and the absorption intensity is weak in the visible light band; the light absorption boundary of PKCN is obviously red-shifted, about 470nm and the absorption intensity in a visible light wave band is obviously increased. Thus showing that the PKCN has better visible light corresponding capability and absorption intensity.
Test example 4
Fourier infrared spectroscopy (FT-IR) analysis was performed on the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 and the carbon nitride nanosheet photocatalyst (BCN) prepared in comparative example 1, respectively, and the results are shown in fig. 5. As can be seen from fig. 5, PKCN exhibits a map similar to that of BCN. But at 2170cm -1 The PKCN shows a new peak, which is a characteristic peak of a cyano group and represents the generation of the cyano group.
Test example 5
XPS characterization is performed on the carbon nitride composite Photocatalyst (PKCN) prepared in example 1, as shown in FIG. 6, wherein the electron binding energy of Pd is 133.4eV, which corresponds to the electron binding energy of N-P, and indicates that the position of P is coordinated with nitrogen, and indicates that the P atom is modified on the graphene carbon nitride nanosheet containing the cyano group and the nitrogen vacancy.
Test example 6
Paramagnetic resonance spectrometer (EPR) analysis was performed on the carbon nitride composite Photocatalyst (PKCN) prepared in example 1 and the carbon nitride nanosheet photocatalyst (BCN) prepared in comparative example 1, respectively, and the results are shown in fig. 7. As can be seen from fig. 7, PKCN exhibits a stronger signal, and a g-factor of 2.004 indicates that there is a vacancy and is a nitrogen vacancy in PKCN.
Test example 7
(1) Weighing 40mg of PKCN prepared in the embodiment 1, adding the PKCN into 50mL of atrazine wastewater with the initial concentration of 10mg/L in a dark environment, adsorbing for 30min, and placing the mixture into a photocatalytic reaction device;
(2) And (3) performing a photocatalytic reaction for 60min in a visible light region (lambda is more than 420 nm) by using a 300W xenon lamp as a light source to finish the treatment of the atrazine in the wastewater.
Sampling at the photocatalytic reaction time t of 0min, 15min, 30min, 45min and 60min, filtering with a filter membrane of 0.22 mu m, and detecting the concentration of atrazine in the solution. Analyzing and measuring the atrazine concentration by a high performance liquid chromatograph, combining a standard curve to obtain the atrazine concentration C corresponding to different illumination times according to a formula (D = (C) 0 -C)/C 0 X 100% where C 0 Initial concentration of atrazine) was calculated, and the results are shown in fig. 8, in which the atrazine removal rate D was calculated for different light irradiation times.
In addition, 40mg of PKCN prepared in example 1 and BCN prepared in comparative example 1 were weighed, respectively, and the above atrazine wastewater treatment procedure was repeated, to obtain the atrazine removal rate of the two photocatalysts from the wastewater at different illumination times, respectively, and the results are shown in fig. 8.
As can be seen from fig. 8, the removal rate of atrazine by PKCN in 60min can reach 83.5%, which is about 5.8 times of BCN (14.3%), and the photocatalytic efficiency is significantly improved, i.e., the composite photocatalyst of the present invention has faster catalytic efficiency and better removal effect. Therefore, the carbon nitride composite photocatalyst has higher photocatalytic activity than BCN.
Test example 8
(1) Weighing 40mg of PKCN prepared in the embodiment 1, adding the PKCN into 50mL of atrazine wastewater with the initial concentration of 10mg/L in a dark environment, adsorbing for 30min, and placing the mixture into a photocatalytic reaction device;
(2) And (3) performing a photocatalytic reaction for 60min in a visible light region (lambda is more than 420 nm) by using a 300W xenon lamp as a light source to finish the treatment of the atrazine in the wastewater.
Sampling at the photocatalytic reaction time t of 0min, 15min, 30min, 45min and 60min, filtering with a 0.22-micron filter membrane, and detecting the concentration of atrazine in the solution. Analyzing and measuring the atrazine concentration by a high performance liquid chromatograph, combining a standard curve to obtain the atrazine concentration C corresponding to different illumination times, and obtaining the atrazine concentration C according to a formula (D = (C) 0 -C)/C 0 X 100% where C 0 Initial concentration for atrazine) calculation of different illuminationsThe results of the atrazine removal rate D with respect to time are shown in fig. 9.
In addition, 40mg of the PKCN prepared in example 1 and the graphene-like carbon nitride photocatalyst with interlayer doped potassium phosphate prepared in comparative example 2 were weighed, respectively, and the above atrazine wastewater treatment procedure was repeated, so as to obtain the atrazine removal rate of the two photocatalysts on the wastewater at different illumination times, respectively, and the results are shown in fig. 9.
As can be seen from fig. 9, the removal rate of atrazine by the PKCN in 60min can reach 83.5%, which is about 2.57 times that of the graphene-like carbon nitride photocatalyst (32.4%) doped with potassium phosphate between layers, and the photocatalytic efficiency is significantly improved, i.e., the composite photocatalyst of the present invention has faster catalytic efficiency and better removal effect. Therefore, the carbon nitride composite photocatalyst has higher photocatalytic activity than the graphene-like carbon nitride photocatalyst doped with potassium phosphate between layers.
Test example 9
(1) The reaction solution after the photocatalytic reaction in test example 7 was subjected to centrifugal separation, and the carbon nitride composite photocatalyst was collected, then washed with water and ethanol alternately for 2 times, and dried in an oven at 60 ℃ for 12 hours to obtain a regenerated carbon nitride composite photocatalyst (APKCN).
(2) Weighing 2mg of the regenerated carbon nitride composite photocatalyst prepared in the step (1), adding the regenerated carbon nitride composite photocatalyst into 50mL of atrazine wastewater with the initial concentration of 10mg/L in a dark environment, adsorbing for 30min, and placing the mixture in a photocatalytic reaction device.
(3) A300W xenon lamp is used as a light source, and the photocatalytic reaction is carried out for 60min in a visible light region (lambda is more than 420 nm).
(4) Repeating the steps (1) - (3) 4 times.
After each circulation test is finished, measuring the concentration of the atrazine in the reaction solution, combining a standard curve to obtain the concentration C of the atrazine corresponding to each circulation test, and obtaining the concentration C according to a formula (D = (C) 0 -C)/C 0 X 100% where C 0 As the initial concentration of atrazine) the atrazine removal rate D corresponding to each cycle test was calculated, and the results are shown in fig. 10. As can be seen from FIG. 10, in the 5 th photocatalytic experiment, the present inventionThe photocatalytic removal rate of the carbon nitride composite photocatalyst is not obviously reduced, and the removal rate can still reach 80 percent, which shows that the composite photocatalyst has good photocatalytic stability and reutilization property.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. The carbon nitride composite photocatalyst is characterized by comprising a graphene carbon nitride nanosheet catalyst containing cyano groups and nitrogen deficiency sites, and phosphorus atoms and potassium atoms doped in the catalyst.
2. The carbon nitride composite photocatalyst according to claim 1, wherein the graphene carbon nitride nanosheet catalyst containing cyano groups and nitrogen deficiency sites comprises graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites, the phosphorus atom being modified on the graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites;
preferably, the graphene carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites are provided with at least two sheets, and the potassium atoms are intercalated between the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites.
3. The carbon nitride composite photocatalyst according to claim 1 or 2, wherein the total content of the phosphorus atom and the potassium atom in the carbon nitride composite photocatalyst is 0.1 to 7% by mass.
4. The carbon nitride composite photocatalyst according to claim 1 or 2, wherein the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficiency sites are in the form of porous platelets;
preferably, the thickness of the graphite-phase carbon nitride nanosheets containing cyano groups and nitrogen deficient sites is from 1 to 3nm.
5. A preparation method of a carbon nitride composite photocatalyst is characterized by comprising the following steps:
(1) Mixing and grinding urea and potassium dihydrogen phosphate to obtain a precursor mixture;
(2) Carrying out thermal polycondensation reaction on the precursor mixture to obtain a carbon nitride composite photocatalyst precursor;
(3) And calcining the carbon nitride composite photocatalyst precursor to obtain the carbon nitride composite photocatalyst.
6. The method according to claim 5, wherein the mass ratio of urea to potassium diphosphate is 10000.
7. The production method according to claim 5 or 6, wherein in step (2), the conditions of the thermal polycondensation reaction include: the temperature is 500-600 ℃, and the time is 3-5h;
in step (3), the calcination is carried out under oxygen exclusion conditions, and the calcination conditions include: the temperature is 450-550 ℃, and the time is 1.5-2.5h.
8. Use of the carbon nitride composite photocatalyst according to any one of claims 1 to 4 and the preparation method according to any one of claims 5 to 7 in treatment of herbicide wastewater.
9. A method for treating herbicide wastewater is characterized by comprising the following steps:
s1, mixing and adsorbing the carbon nitride composite photocatalyst of any one of claims 1 to 4 and/or the carbon nitride composite photocatalyst prepared by the preparation method of any one of claims 5 to 7 with the herbicide wastewater under a dark condition to obtain a mixed solution II;
and S2, carrying out photocatalytic reaction on the mixed liquid II obtained in the step S1 under the condition of visible light.
10. The treatment method according to claim 9, wherein in step S1, the weight ratio of the carbon nitride composite photocatalyst to the herbicide is 40 to 120;
preferably, the herbicide is atrazine;
preferably, the adsorption time is 25-35min;
preferably, in step S2, the wavelength λ of the visible light is >420nm, and the conditions of the photocatalytic reaction include: the time is 50-70min.
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