CN115445646A - Carbon nitride composite photocatalyst and preparation method and application thereof - Google Patents
Carbon nitride composite photocatalyst and preparation method and application thereof Download PDFInfo
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- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 title claims abstract description 262
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 124
- 239000002131 composite material Substances 0.000 title claims abstract description 113
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
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- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 71
- MXWJVTOOROXGIU-UHFFFAOYSA-N atrazine Chemical compound CCNC1=NC(Cl)=NC(NC(C)C)=N1 MXWJVTOOROXGIU-UHFFFAOYSA-N 0.000 claims abstract description 67
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- 238000000034 method Methods 0.000 claims abstract description 25
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- HDMGAZBPFLDBCX-UHFFFAOYSA-M potassium;sulfooxy sulfate Chemical compound [K+].OS(=O)(=O)OOS([O-])(=O)=O HDMGAZBPFLDBCX-UHFFFAOYSA-M 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
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- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 3
- 238000001179 sorption measurement Methods 0.000 claims description 3
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
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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
- 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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- 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
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/722—Oxidation by peroxides
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- 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
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
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- 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
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- C02F2101/38—Organic compounds containing nitrogen
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- C02F2305/10—Photocatalysts
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Abstract
The invention relates to a functional composite photocatalyst technology, and discloses a carbon nitride composite photocatalyst, and a preparation method and application thereof. The carbon nitride composite photocatalyst consists of common carbon nitride and nitrogen-rich carbon nitride, and is of a porous lamellar structure, and a homojunction is formed between the common carbon nitride and the nitrogen-rich carbon nitride, wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 . The preparation method comprises the following steps: grinding and mixing common carbon nitride and 3-amino-1, 2, 4-triazole to obtain mixed powder; feeding the mixed powder intoLine calcination I. The method for treating the pesticide wastewater comprises the following steps: under the condition of keeping out of the sun, mixing and adsorbing the carbon nitride composite photocatalyst and the pesticide wastewater to obtain a mixed solution; and under the condition of visible light, mixing the mixed solution with persulfate, and carrying out photocatalytic reaction. The photocatalyst has high photocatalytic activity, good photocatalytic stability and good reusability, and can effectively degrade atrazine in wastewater.
Description
Technical Field
The invention relates to a functional composite photocatalyst technology, in particular to a carbon nitride composite photocatalyst, a preparation method of the carbon nitride composite photocatalyst and application of the carbon nitride composite photocatalyst.
Background
In recent years, as advanced oxidation technology has matured, the technology is widely used for removing pollutants from water. The advanced oxidation process based on photocatalytic activation of persulfate has attracted people's attention and is considered as a purification technology for quickly and effectively removing the organic pollutants which are difficult to degrade in water. Compared with the traditional advanced oxidation technology based on hydroxyl free radicals, the method has higher reaction stability and wider adaptability to the sewage quality. Photocatalytic activation of persulfate advanced oxidation technology to exert its strong oxidizing property, a photocatalyst having high photocatalytic activity is required to activate persulfate. However, most semiconductor photocatalysts are limited by factors such as high electron-hole recombination rate, and the like, and the photocatalytic effect of the semiconductor photocatalysts cannot meet the actual requirement. Therefore, it is necessary to design a photocatalyst with high photocatalytic activity and good photocatalytic stability, which can be applied to the persulfate advanced oxidation technology.
The non-metal carbon nitride as a novel semiconductor photocatalyst has a strong conjugated structure, semiconductor properties and photocatalytic performance, can absorb visible light to generate photo-generated electrons to activate persulfate, and is an ideal PMS activator. However, carbon nitride has a wide band gap and low efficiency of separating photo-generated electrons and holes, which greatly hinders its photocatalytic performance. Therefore, the carbon nitride composite photocatalyst with high photocatalytic activity and good photocatalytic stability is obtained, and has very important significance for expanding the application range of the photocatalytic technology.
Disclosure of Invention
The invention aims to solve the problems of wider carbon nitride band gap, low separation efficiency of photo-generated electron holes and great obstruction to the photocatalytic performance in the prior art, and provides a carbon nitride composite photocatalyst, a preparation method and application thereof.
In order to achieve the above object, a first aspect of the present invention provides a carbon nitride composite photocatalyst, which is composed of common carbon nitride and nitrogen-rich carbon nitride, and has a porous lamellar structure, and a homojunction is formed between the common carbon nitride and the nitrogen-rich carbon nitride, wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
Preferably, the weight ratio of the nitrogen-enriched carbon nitride to the common carbon nitride is 1.
The second aspect of the invention provides a preparation method of a carbon nitride composite photocatalyst, which comprises the following steps:
s1, grinding and mixing common carbon nitride and 3-amino-1, 2, 4-triazole to obtain mixed powder;
s2, calcining I is carried out on the mixed powder obtained in the step S1, so as to obtain a carbon nitride composite photocatalyst consisting of common carbon nitride and nitrogen-rich carbon nitride, wherein a homojunction is formed between the common carbon nitride and the nitrogen-rich carbon nitride, and the carbon nitride composite photocatalyst is in a porous lamellar structure;
wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
Preferably, the weight ratio of the nitrogen-enriched carbon nitride to the common carbon nitride is 1.
Preferably, the weight ratio of the 3-amino-1, 2, 4-triazole to the common carbon nitride is 1.
Preferably, the ordinary carbon nitride is prepared by calcining II urea.
Preferably, the conditions of calcining II include: the calcining heating rate is 1-3 ℃/min, the temperature is 500-600 ℃, and the time is 3-5h.
Preferably, in step S2, the conditions for calcining I include: the calcining heating rate is 1-3 ℃/min, the temperature is 500-600 ℃, and the time is 3-5h.
The third aspect of the invention provides the carbon nitride composite photocatalyst and the application of the carbon nitride composite photocatalyst prepared by the preparation method in pesticide wastewater treatment.
Preferably, the pesticide in the pesticide wastewater is atrazine.
The fourth aspect of the present invention provides a method for treating pesticide wastewater, comprising the steps of:
(1) Under the condition of keeping out of the sun, mixing and adsorbing the carbon nitride composite photocatalyst or the carbon nitride composite photocatalyst prepared by the preparation method with the pesticide wastewater to obtain a mixed solution;
(2) And (2) under the condition of visible light, mixing the mixed solution obtained in the step (1) with persulfate, and carrying out photocatalytic reaction.
Preferably, the pesticide in the pesticide wastewater is atrazine.
Preferably, the initial concentration of the pesticide in the pesticide wastewater is 2-10mg/L; the weight ratio of the pesticide in the pesticide wastewater, the carbon nitride composite photocatalyst and the persulfate is 1:20-80:4-20, more preferably 1:35-45:6-12.
Preferably, in the step (1), the adsorption time is 15-25min; in the step (2), the wavelength lambda of the visible light is more than 420nm, and the conditions of the photocatalytic reaction comprise: the temperature is 5-40 ℃, the pH is 3-9, the rotating speed is 500-700rpm, and the time is 1-2h; the persulfate is at least one selected from potassium hydrogen persulfate, sodium hydrogen persulfate, potassium persulfate and sodium persulfate.
Through the technical scheme, the invention has the beneficial effects that:
(1) In the carbon nitride composite photocatalyst provided by the invention, the special triazole unit rich in nitrogen and carbon nitride can promote light absorption, and the band gap of the nitrogen and carbon nitride is narrower than that of the carbon nitride, so that rapid electron transfer is realized; the surface of the nitrogen-rich carbon nitride is distorted, so that the time for transferring photogenerated electron and hole between the nitrogen-rich carbon nitride and common carbon nitride is shortened, and the recombination of the nitrogen-rich carbon nitride and the common carbon nitride is favorably prevented. The carbon nitride composite photocatalyst is of a porous lamellar structure, has a larger contact area and more reaction sites, and can better synergistically degrade pesticide wastewater together with persulfate; in addition, a heterogeneous interface of a homojunction structure formed by the nitrogen-rich carbon nitride and the common carbon nitride can better promote the separation of the photo-generated electron hole pairs and improve the photocatalytic capability. In addition, due to pi-pi interaction in the carbon nitride composite photocatalyst, photo-generated charge separation is facilitated, and the photocatalytic capacity is improved. Therefore, the carbon nitride composite photocatalyst provided by the invention has the advantages of large photoresponse range, high photocatalytic activity and the like, can be widely used for photocatalytic degradation of pollutants in the environment as a novel photocatalyst, and has a good application prospect.
(2) According to the preparation method of the carbon nitride composite photocatalyst, the common carbon nitride and the nitrogen-rich carbon nitride are combined together by a method of matching grinding mixing and thermal polycondensation, so that the two are combined tightly, the material stability is good, and the repeatability is high; further, a two-step thermal polycondensation method is adopted, urea is subjected to polycondensation reaction through high-temperature heating to generate common carbon nitride, and then the common carbon nitride is stripped by using a nitrogen-rich carbon nitride precursor 3-amino-1, 2, 4-triazole through the thermal polycondensation method to form the carbon nitride homojunction photocatalyst without using any solvent; therefore, the preparation method provided by the invention has the advantages of simple process, simple and convenient operation, low cost and the like, and the prepared composite photocatalyst has good stability.
(3) According to the method for treating pesticide wastewater, the carbon nitride composite photocatalyst is used for treating pesticide wastewater, and the advantages of stable photocatalytic performance, good reusability and the like of the carbon nitride composite photocatalyst are utilized, so that effective degradation of atrazine in pesticide wastewater is realized, and the method has the advantages of simple application method, low treatment cost, high atrazine removal rate and the like, and has high practical value and good application prospect.
Drawings
FIG. 1 shows a composite photocatalyst of carbon nitride (AT-CN) obtained in example 1 and ordinary carbon nitride C obtained in comparative example 1 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 The local high-resolution transmission electron microscope picture (a) is C 3 N 4 And (b) is C 3 N 5 And (c) is AT-CN;
FIG. 2 shows a composite photocatalyst of carbon nitride (AT-CN) obtained in example 1 and ordinary carbon nitride C obtained in comparative example 1 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 XRD analysis pattern of (a);
FIG. 3 shows a composite photocatalyst of carbon nitride (AT-CN) obtained in example 1 and ordinary carbon nitride C obtained in comparative example 1 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 Ultraviolet-visible spectrum diffuse reflectance analysis chart of (1);
FIG. 4 shows AT-CN and C in test example 2 3 N 4 、C 3 N 5 A relation schematic diagram of the atrazine concentration changing with time in the process of degrading the activated persulfate;
FIG. 5 is a graph showing the effect of the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 on the cyclic degradation of atrazine;
FIG. 6 is C 3 N 5 And C 3 N 4 Carbon nitride composite photocatalyst formed by different mass ratios, common carbon nitride C obtained in comparative example 1 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 Histogram of atrazine removal effect in wastewater;
FIG. 7 is a graph showing the effect of the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 on the degradation of atrazine under different atrazine concentrations;
FIG. 8 is a graph showing the effect of the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 on atrazine degradation under different pH conditions.
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 consists of common carbon nitride and nitrogen-rich carbon nitride and is in a porous lamellar structure, wherein homojunctions are formed between the common carbon nitride and the nitrogen-rich carbon nitride, and the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
The inventors of the present invention found in the course of their research that ordinary carbon nitride (C) 3 N 4 ) With nitrogen-rich carbon nitride (C) 3 N 5 ) A homojunction structure is formed between the two to lead photo-generated electrons to rapidly pass through C 3 N 4 Transfer to C 3 N 5 While holes are drawn from C 3 N 5 Migration to C 3 N 4 Above, at C 3 N 4 And C 3 N 5 Holes and electrons are respectively gathered, so that the recombination of a photo-generated electron hole pair is efficiently prevented, the vertical migration distance of charge carriers can be shortened by the ultrathin nanosheet structure of the carbon nitride composite photocatalyst, the charge transmission is accelerated, the recombination of the photo-generated electrons and the holes is inhibited, and the persulfate is rapidly activated to carry out an oxidation reaction; the porous structure of the carbon nitride composite photocatalyst increases the surface active sites of the photocatalyst, the ultrathin nanosheet-shaped structure is beneficial to promoting electron transfer, so that electrons can react with persulfate adsorbed by the porous structure on the surface more easily, the photocatalytic reaction activity is stronger, and further the carbon nitride composite photocatalyst can effectively activate persulfate to remove the atrazine in pesticide wastewater; meanwhile, the carbon nitride composite photocatalyst also has a high specific surface area, and can provide abundant reaction sites for activating persulfate. Therefore, the carbon nitride composite photocatalyst has a larger photoresponse range, higher photocatalytic capacity, high photocatalytic activity and photocatalysisGood chemical stability and good reusability.
According to the invention, in order to further improve the catalytic performance and stability of the carbon nitride composite photocatalyst, the weight ratio of the nitrogen-rich carbon nitride to the common carbon nitride is preferably 1 to 20, more preferably 1 to 5.
The second aspect of the invention provides a preparation method of a carbon nitride composite photocatalyst, which comprises the following steps:
s1, grinding and mixing common carbon nitride and 3-amino-1, 2, 4-triazole to obtain mixed powder;
s2, calcining I is carried out on the mixed powder obtained in the step S1, so as to obtain a carbon nitride composite photocatalyst consisting of common carbon nitride and nitrogen-rich carbon nitride, wherein a homojunction is formed between the common carbon nitride and the nitrogen-rich carbon nitride, and the carbon nitride composite photocatalyst is in a porous lamellar structure;
wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
According to the preparation method of the carbon nitride composite photocatalyst, common carbon nitride and nitrogen-rich carbon nitride are combined together by a method of matching grinding mixing and thermal polycondensation, so that the common carbon nitride and the nitrogen-rich carbon nitride are tightly combined to form a homojunction structure, and the carbon nitride composite photocatalyst is in a porous lamellar structure, so that the photocatalyst is good in stability and high in repeatability.
According to the invention, in order to further improve the catalytic performance and stability of the carbon nitride composite photocatalyst, the weight ratio of the nitrogen-rich carbon nitride to the common carbon nitride is preferably 1.
According to the invention, in order to further improve the catalytic performance and stability of the carbon nitride composite photocatalyst, the weight ratio of the 3-amino-1, 2, 4-triazole to the common carbon nitride is preferably 1. The yield of the product obtained by calcining the 3-amino-1, 2, 4-triazole is 60-70%, and is about 66% under the condition that the temperature is increased from room temperature to 550 ℃ for 4 hours at the temperature rising rate of 2 ℃/min, so that the weight ratio of the nitrogen-enriched carbon nitride to the common carbon nitride in the carbon nitride composite photocatalyst obtained after grinding, mixing and calcining the 3-amino-1, 2, 4-triazole and the common carbon nitride is controlled within a preferred range.
According to the invention, said ordinary carbon nitride is preferably obtained by calcining II urea. The inventor finds that in the preferred embodiment, ammonia gas released by calcining urea in the air is used as a gas template, so that a plurality of holes with different sizes exist in the prepared photocatalyst thin sheet, conditions are provided for forming abundant porous homojunctions for the photocatalyst, the catalytic activity of the photocatalyst is further improved, and the degradation efficiency of atrazine can be improved when the photocatalyst is applied to pesticide wastewater treatment.
According to the invention, preferably, the conditions of the calcination II comprise: the speed of calcination temperature rise is 1-3 ℃/min, specifically 1 ℃/min, 2 ℃/min, 3 ℃/min, or any value between the two values; 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 between the above two values; the time is 3-5h, specifically 3h, 3.5h, 4h, 4.5h, 5h, or any value between the two values.
According to the invention, in the step S1, grinding and mixing refers to that common carbon nitride and 3-amino-1, 2, 4-triazole are fully mixed and refined by grinding, so that the efficiency of calcining I in the step S2 is improved, and the structure formation of the carbon nitride composite photocatalyst is facilitated.
According to the present invention, in order to improve the preparation efficiency of the carbon nitride composite photocatalyst, preferably, in step S2, the conditions of calcination I include: the calcining heating rate is 1-3 ℃/min, and can be 1 ℃/min, 2 ℃/min, 3 ℃/min, or any value between the two values; 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 between the above two values; the time is 3-5h, specifically 3h, 3.5h, 4h, 4.5h, 5h, or any value between the two values.
Based on the carbon nitride composite photocatalyst and the preparation method thereof, the third aspect of the invention provides the carbon nitride composite photocatalyst and the application of the carbon nitride composite photocatalyst prepared by the preparation method in pesticide wastewater treatment. The carbon nitride composite photocatalyst provided by the invention can efficiently activate persulfate, has higher catalytic activity and catalytic stability and better reusability for persulfate advanced oxidation technology, and can be widely used for photocatalytic degradation of pesticide pollutants in wastewater.
According to the invention, preferably, the pesticide in the pesticide wastewater is atrazine, and the carbon nitride composite photocatalyst has the advantages of high efficiency of removing atrazine in the wastewater, simple method and low treatment cost.
The fourth aspect of the present invention provides a method for treating pesticide wastewater, comprising the steps of:
(1) Under the condition of keeping out of the sun, mixing and adsorbing the carbon nitride composite photocatalyst or the carbon nitride composite photocatalyst prepared by the preparation method with the pesticide wastewater to obtain a mixed solution;
(2) And (2) under the condition of visible light, mixing the mixed liquor obtained in the step (1) with persulfate, and carrying out photocatalytic reaction.
According to the method for treating pesticide wastewater, the carbon nitride composite photocatalyst is adopted to treat pesticide wastewater, and the advantages of stable photocatalytic performance, good reusability and the like of the carbon nitride composite photocatalyst are utilized, so that pollutants in the pesticide wastewater are effectively degraded, and the method has high practical value and good application prospect.
According to the present invention, preferably, the pesticide in the pesticide waste water is atrazine.
According to the present invention, the initial concentration of the pesticide in the pesticide wastewater may be any concentration, and preferably, the initial concentration of the pesticide in the pesticide wastewater is 2 to 10mg/L, and the concentration of the pesticide in the pesticide wastewater may be adjusted by dilution with water.
According to the invention, the dosages of the pesticide, the carbon nitride composite photocatalyst and the persulfate in the pesticide wastewater are not particularly limited, and the carbon nitride composite photocatalyst is applied to improve the efficiency of degrading and removing the pesticide by the persulfate. Preferably, the weight ratio of the pesticide in the pesticide wastewater, the carbon nitride composite photocatalyst and the persulfate is 1:20-80:4-20, more preferably 1:35-45:6-12.
According to the invention, in order to further improve the efficiency of treating the pesticide wastewater, in step (1), the adsorption time is preferably 15-25min, specifically 15min, 17min, 19min, 21min, 23min, 25min, or any value between the two values.
According to the present invention, in order to further improve the efficiency of treating the pesticide wastewater, preferably, in step (2), the wavelength λ of the visible light is >420nm, and 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 pH is 3-9, specifically 3, 4, 5, 6, 7, 8, 9, or any value between the two values; the rotation speed is 500-700rpm, specifically 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, or any value between the two values; the time is 1-2h, specifically 1h, 1.5h, 2h, or any value between the two values.
According to the present invention, there is no particular limitation on the species of the persulfate, and preferably, the persulfate is at least one selected from the group consisting of oxone, sodium persulfate, potassium persulfate and sodium persulfate. The above substances are commercially available, and for example, oxone is a complex oxone produced by Michelin corporation and produced by 2KHSO 5 ·KHSO 4 ·K 2 SO 4 The composition, wherein the content of the potassium hydrogen persulfate is 42-46 wt%.
According to a particularly preferred embodiment of the present invention, the method for treating pesticide wastewater comprises the steps of:
(1) Heating urea at the speed of 1-3 ℃/min to 500-600 ℃, calcining for 3-5h to obtain common carbon nitride C 3 N 4 Grinding and mixing 3-amino-1, 2, 4-triazole and common carbon nitride in a weight ratio of 1.6-14 to obtain mixed powder;
(2) Will be described in detail(1) Heating the obtained mixed powder to 500-600 ℃ at the speed of 1-3 ℃/min, and calcining for 3-5h to obtain the nitrogen-rich carbon nitride C 3 N 5 And ordinary carbon nitride C 3 N 4 1-20, wherein the common carbon nitride C is carbon nitride composite photocatalyst and comprises the following components in a weight ratio of 1 3 N 4 With said nitrogen-rich carbon nitride C 3 N 5 Homogeneous junctions are formed between the two, and the carbon nitride composite photocatalyst is of a porous lamellar structure;
(3) Under the condition of keeping out of the sun, mixing the carbon nitride composite photocatalyst obtained in the step (2) with the pesticide wastewater, and then adsorbing for 15-25min to obtain a mixed solution, wherein the weight ratio of the pesticide in the pesticide wastewater to the carbon nitride composite photocatalyst is 1:20-80 parts of;
(4) Mixing the mixed solution obtained in the step (3) with persulfate under the condition of visible light with the wavelength lambda of more than 420nm, and carrying out photocatalytic reaction for 1-2h under the conditions of the temperature of 5-40 ℃, the pH value of 3-9 and the rotating speed of 500-700rpm, wherein the weight ratio of pesticide to persulfate in the pesticide wastewater is 1:4-20.
The present invention will be described in detail below by way of examples.
In the following examples, the atrazine concentration was analyzed and measured by a high performance liquid chromatograph; if not specifically stated, the raw materials and instruments used are conventional commercial products, wherein the composite potassium hydrogen persulfate is purchased from Shanghai Michellin Biochemical technology Co., ltd (the content of the potassium hydrogen persulfate is 42-46 wt%), the urea is purchased from Shanghai Michellin Biochemical technology Co., ltd, the 3-amino-1, 2, 4-triazole is purchased from Shanghai Michellin Biochemical technology Co., ltd, the pesticide wastewater adopts a self-prepared atrazine solution as simulated pesticide wastewater, and the atrazine is purchased from Shanghai Michellin Biochemical technology Co., ltd; the light source system was a PLS-SXE 300C xenon lamp, available from Beijing Pofely technologies, inc.
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
S1, weighing 10g of urea, placing the urea in a boat-shaped ceramic crucible, wrapping the urea with tinfoil, and adding 2 g of the ureaCalcining at the temperature rising rate of room temperature to 550 ℃ for 4h, and naturally cooling to obtain the common carbon nitride C 3 N 4 ;
S2, weighing 200mg of common carbon nitride C in the step S1 3 N 4 Grinding and mixing with 30mg of 3-amino-1, 2, 4-triazole, placing the obtained mixed powder in a boat-shaped ceramic crucible, wrapping with tinfoil, calcining at 2 deg.C/min from room temperature to 550 deg.C for 4h, naturally cooling, and adding common carbon nitride C 3 N 4 With said nitrogen-rich carbon nitride C 3 N 5 Homojunction is formed between the two to obtain the carbon nitride composite photocatalyst (AT-CN) with a porous lamellar structure; wherein the 3-amino-1, 2, 4-triazole is calcined to obtain nitrogen-rich carbon nitride C 3 N 5 The yield of (A) was about 66%, as calculated from the weight of the product before and after the reaction, ordinary carbon nitride C in AT-CN 3 N 4 And nitrogen-rich carbon nitride C 3 N 5 The weight ratio of (A) to (B) is 10.
Example 2
S1, weighing 10g of urea, placing the urea in a boat-shaped ceramic crucible, wrapping the urea with tinfoil, heating the urea from room temperature to 550 ℃ at the heating rate of 2 ℃/min, calcining the urea for 4 hours, and naturally cooling the urea to obtain common carbon nitride C 3 N 4 ;
S2, weighing 200mg of common carbon nitride C in the step S1 3 N 4 Grinding and mixing with 60mg of 3-amino-1, 2, 4-triazole, placing the obtained mixed powder in a boat-shaped ceramic crucible, wrapping with tinfoil, calcining at 2 deg.C/min from room temperature to 550 deg.C for 4h, naturally cooling, and adding common carbon nitride C 3 N 4 With said nitrogen-rich carbon nitride C 3 N 5 Homojunction is formed between the two to obtain the carbon nitride composite photocatalyst (AT-CN) with a porous lamellar structure; wherein the 3-amino-1, 2, 4-triazole is calcined to obtain nitrogen-enriched carbon nitride C 3 N 5 The yield of (A) was about 66%, as calculated from the weights before and after the reaction, ordinary carbon nitride C in AT-CN 3 N 4 And nitrogen-rich carbon nitride C 3 N 5 The weight ratio of (A) to (B) is 5.
Example 3
S1, weighing 10g of urea and placing the urea in a boatWrapping with tinfoil in a ceramic crucible, calcining at 2 deg.C/min from room temperature to 550 deg.C for 4 hr, and naturally cooling to obtain common carbon nitride C 3 N 4 ;
S2, weighing 200mg of common carbon nitride C in the step S1 3 N 4 Grinding and mixing with 20mg of 3-amino-1, 2, 4-triazole, placing the obtained mixed powder in a boat-shaped ceramic crucible, wrapping with tinfoil, calcining at room temperature to 550 deg.C at a heating rate of 2 deg.C/min for 4h, naturally cooling, and adding common carbon nitride C 3 N 4 With said nitrogen-rich carbon nitride C 3 N 5 Homojunction is formed between the two to obtain the carbon nitride composite photocatalyst (AT-CN) with a porous lamellar structure; wherein the 3-amino-1, 2, 4-triazole is calcined to obtain nitrogen-rich carbon nitride C 3 N 5 The yield of (A) was about 66%, as calculated from the weights before and after the reaction, ordinary carbon nitride C in AT-CN 3 N 4 And nitrogen-rich carbon nitride C 3 N 5 The weight ratio of (A) to (B) is 15:1.
example 4
S1, weighing 10g of urea, placing the urea in a boat-shaped ceramic crucible, wrapping the urea with tinfoil, heating the urea from room temperature to 550 ℃ at the heating rate of 2 ℃/min, calcining the urea for 4 hours, and naturally cooling the urea to obtain common carbon nitride C 3 N 4 ;
S2, weighing 200mg of common carbon nitride C in the step S1 3 N 4 Grinding and mixing with 15mg of 3-amino-1, 2, 4-triazole, placing the obtained mixed powder in a boat-shaped ceramic crucible, wrapping with tinfoil, calcining at 2 deg.C/min from room temperature to 550 deg.C for 4h, naturally cooling, and adding common carbon nitride C 3 N 4 With said nitrogen-rich carbon nitride C 3 N 5 Homojunction is formed between the two to obtain the carbon nitride composite photocatalyst (AT-CN) with a porous lamellar structure; wherein the 3-amino-1, 2, 4-triazole is calcined to obtain nitrogen-rich carbon nitride C 3 N 5 The yield of (A) was about 66%, as calculated from the weight of the product before and after the reaction, ordinary carbon nitride C in AT-CN 3 N 4 And nitrogen-rich carbon nitride C 3 N 5 In a weight ratio of 20:1.
comparative example 1
Weighing 10g of urea, placing the urea in a boat-shaped ceramic crucible, wrapping the urea by tinfoil, heating the urea from room temperature to 550 ℃ at the heating rate of 2 ℃/min, calcining the urea for 4 hours, and naturally cooling to obtain the common carbon nitride C 3 N 4 。
Comparative example 2
3g of 3-amino-1, 2, 4-triazole is weighed and placed in a boat-shaped ceramic crucible, wrapped by tinfoil, heated from room temperature to 550 ℃ at the heating rate of 2 ℃/min and calcined for 4h, and after natural cooling, nitrogen-enriched carbon nitride C is obtained 3 N 5 。
Test example 1
The carbon nitride composite photocatalyst (AT-CN) obtained in example 1 and the ordinary carbon nitride C obtained in comparative example 1 were mixed 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 The results of Transmission Electron Microscopy (TEM) analysis are shown in FIG. 1, wherein (a) is C 3 N 4 And (b) is C 3 N 5 And (c) is a local high-resolution transmission electron microscope image of AT-CN. As can be seen from FIG. 1, ordinary carbon nitride (C) 3 N 4 ) And nitrogen-rich carbon nitride (C) 3 N 5 ) All have typical laminated structures, and the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 is in a porous flake shape, which indicates that common carbon nitride (C) is adopted 3 N 4 ) With nitrogen-rich carbon nitride (C) 3 N 5 ) After the porous homojunction is formed, the shape of the material is changed, and the successful preparation of the carbon nitride homojunction composite photocatalyst is also shown.
The carbon nitride composite photocatalyst (AT-CN) obtained in example 1 and the ordinary carbon nitride C obtained in comparative example 1 were mixed 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 The results of XRD analysis are shown in FIG. 2. As can be seen from FIG. 2, ordinary carbon nitride (C) 3 N 4 ) And nitrogen-rich carbon nitride (C) 3 N 5 ) All show typical diffraction peaks of carbon nitride, while the composite material AT-CN obtained in example 1 shows diffraction peaks similar to those of graphite-phase carbon nitride nanosheets, which indicates that the overall structure of carbon nitride is not changed after homojunction is formed, and the method has very important significance for maintaining excellent photocatalytic performance of the composite materialThe significance of (1).
The carbon nitride composite photocatalyst (AT-CN) obtained in example 1 and the ordinary carbon nitride C obtained in comparative example 1 were mixed 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 Ultraviolet-visible spectrum diffuse reflectance analysis (UV-VIS) was performed, respectively, and the results are shown in fig. 3. As can be seen from FIG. 3, ordinary carbon nitride (C) 3 N 4 ) Nitrogen-rich carbon nitride (C) 3 N 5 ) And carbon nitride homojunctions (AT-CN) all exhibit efficient absorption of visible light. Wherein, C 3 N 5 Since the powder is orange, result in C 3 N 5 Exhibiting absorption of visible light and even a small portion of near infrared light. The carbon nitride composite photocatalyst (AT-CN) obtained in example 1 was found to have good ultraviolet-visible absorption capacity, and the absorption capacity in the visible light region was higher than that of ordinary carbon nitride (C) 3 N 4 ) The result shows that the carbon nitride homojunction composite photocatalyst is successfully prepared.
Test example 2
(1) The carbon nitride composite photocatalyst (AT-CN) obtained in example 1 and the ordinary carbon nitride C obtained in comparative example 1 were added under the protection from light 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 Respectively weighing 20mg and 50mL of atrazine wastewater with the initial concentration of 10mg/L, mixing, and adsorbing for 20min to obtain a mixed solution;
(2) Using a 300W xenon lamp as a light source, in the visible light region (lambda)>420 nm), mixing the mixed solution obtained in the step (1) with 10mg of composite potassium hydrogen persulfate, and carrying out photocatalytic reaction for 60min under the conditions of the temperature of 25 ℃, the natural pH value and the rotating speed of 600rpm to finish the treatment of atrazine in the wastewater; respectively sampling when the photocatalytic reaction time t is 0min, 10min, 20min, 40min and 60min, filtering by using a filter membrane of 0.22 mu m, and detecting the concentration C of atrazine in the sample solution; according to the formula (concentration ratio = C/C) 0 X 100% where C 0 As the initial concentration of atrazine), the residual amount of atrazine in the reaction solution was calculated, representing the degrading effect on atrazine, and the results obtained are shown in fig. 4 according to the formula (D = (C) 0 -C)/C 0 X 100% where C 0 As the initial concentration of atrazine), the atrazine removal rate D was calculated.
As can be seen from FIG. 4, the visible light region (λ)>420 nm) the AT-CN obtained in example 1 showed better than that of ordinary carbon nitride C 3 N 4 And nitrogen-rich carbon nitride C 3 N 5 The photocatalytic activity of the persulfate for degrading atrazine is improved. The removal rate D of atrazine in wastewater by AT-CN obtained in example 1 after 60min of illumination is 90%, and C 3 N 4 And C 3 N 5 The removal rate D of the atrazine in the wastewater is 53 percent and 23 percent respectively.
Test example 3
(1) Under the condition of keeping out of the sun, mixing 20mg of the carbon nitride composite photocatalyst obtained in example 1 with 50mL of atrazine wastewater with the initial concentration of 10mg/L, and adsorbing for 20min to obtain a mixed solution;
(2) Adopting a 300W xenon lamp as a light source, mixing the mixed solution obtained in the step (1) with 10mg of composite potassium hydrogen persulfate in a visible light region (lambda >420 nm), and carrying out photocatalytic reaction for 60min under the conditions of a temperature of 25 ℃, a natural pH value and a rotation speed of 600rpm to obtain a reaction solution;
(3) Centrifuging the reaction solution obtained in the step (2), collecting the carbon nitride composite photocatalyst, washing with a large amount of deionized water and absolute ethyl alcohol, and then placing in a 60 ℃ drying oven for drying for 12 hours to obtain a regenerated carbon nitride composite photocatalyst;
(4) Repeating the steps (1) to (3) for five times, taking a reaction solution sample obtained each time, filtering the reaction solution sample by using a filter membrane of 0.22 mu m, and detecting the atrazine concentration C in the sample solution; according to the formula (D = (C) 0 -C)/C 0 X 100% where C 0 Is the initial concentration of atrazine), the atrazine removal rate D is calculated, and the effect of the carbon nitride composite photocatalyst on the cyclic degradation of atrazine is obtained, and the result is shown in fig. 5.
As can be seen from fig. 5, after 5 times of recycling, the removal rate of atrazine by the carbon nitride composite photocatalyst obtained in example 1 is still as high as 82% within 1 hour, which indicates that the carbon nitride composite photocatalyst provided by the present invention has good stability and reusability.
Test example 4
The carbon nitride composite photocatalyst (AT-CN) obtained in examples 1 to 4 and the ordinary carbon nitride C obtained in comparative example 1 were each tested by the method of test example 2 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 The effect on the atrazine-removing effect in the simulated pesticide wastewater is shown in fig. 6.
FIG. 6 shows different nitrogen-enriched carbon nitrides (C) 3 N 5 ) With ordinary carbon nitride (C) 3 N 4 ) Carbon nitride composite photocatalyst in mass ratio, ordinary carbon nitride C obtained in comparative example 1 3 N 4 Nitrogen-enriched carbonitride C obtained in comparative example 2 3 N 5 Histogram of atrazine removal. As can be seen from fig. 6, the carbon nitride composite photocatalyst obtained in example 1 exhibited very good photocatalytic performance, and was capable of effectively removing atrazine from wastewater, wherein when C is 3 N 5 And C 3 N 4 The mass ratio of (1): 5. 1, 15, 1 3 N 4 And C 3 N 5 The removal rate D of atrazine was 53% and 23%, respectively. Obviously, when C is 3 N 5 And C 3 N 4 When the mass ratio of (1) to (10) is in a range from 1 to 10, the carbon nitride homojunction composite photocatalyst obtains the best catalytic effect, which shows that the carbon nitride homojunction composite photocatalyst has the best photocatalytic performance.
Test example 5
(1) Under the condition of keeping out of the sun, mixing 20mg of the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 with 50mL of atrazine wastewater with initial concentrations of 1,2, 5 and 10mg/L respectively, and adsorbing for 20min to obtain a mixed solution;
(2) Using a 300W xenon lamp as a light source, in the visible light region (lambda)>420 nm), mixing the mixed solution obtained in the step (1) with 10mg of potassium hydrogen persulfate complex, carrying out photocatalytic reaction for 60min at the temperature of 25 ℃, the natural pH value and the rotation speed of 600rpm, finishing the treatment of the atrazine in the wastewater to obtain reaction solutions, respectively taking reaction solution samples, and using the reaction solution samplesThe atrazine concentration C in the sample solution was measured after filtration through a 0.22 μm filter according to the formula (concentration ratio = C/C) 0 X 100% where C 0 The initial concentration of atrazine), the residual amount of atrazine in the reaction solution was calculated, and the effect of degrading atrazine was expressed, and the results are shown in fig. 7.
Fig. 7 is a graph showing the atrazine degradation of the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 under different atrazine concentrations. As can be seen from fig. 7, the AT-CN obtained in example 1 has a high degradation effect on the pesticide atrazine within the studied atrazine concentration range; particularly, in the atrazine solution with low concentration, AT-CN can completely degrade the atrazine solution, and the application prospect of the homogemc photocatalyst in removing the pesticide atrazine in pesticide wastewater is shown again.
Test example 6
(1) Under the condition of keeping out of the sun, mixing 20mg of the carbon nitride composite photocatalyst (AT-CN) obtained in the example 1 with 50mL of atrazine wastewater with the initial concentration of 10mg/L, and adsorbing for 20min to obtain a mixed solution;
(2) Using a 300W xenon lamp as a light source, in the visible light region (lambda)>420 nm), mixing the mixed solution obtained in the step (1) with 10mg of potassium hydrogen persulfate complex, carrying out photocatalytic reaction for 60min under the conditions that the temperature is 25 ℃, the pH is 3, 5, 7 and 9 respectively and the rotating speed is 600rpm, finishing the treatment of atrazine in wastewater to obtain reaction solutions, taking reaction solution samples respectively, filtering the reaction solution samples by using a filter membrane of 0.22 mu m, detecting the concentration C of atrazine in the sample solutions, and detecting the concentration C of atrazine in the sample solutions according to a formula (concentration ratio = C/C) 0 X 100% where C 0 The initial concentration of atrazine), the residual amount of atrazine in the reaction solution was calculated, and the effect of degrading atrazine was expressed, and the results are shown in fig. 8.
FIG. 8 is a graph showing the degradation of atrazine by the carbon nitride composite photocatalyst (AT-CN) obtained in example 1 under different pH conditions. As can be seen from fig. 8, the AT-CN obtained in example 1 has a high degradation effect on the atrazine pesticide within the studied pH range, and the applicable pH range is wide; particularly, for atrazine in an acidic water body, the degradation effect of the AT-CN obtained in example 1 is obviously improved, and for example, when the pH value is 3, the degradation effect of the homogemc photocatalyst on the pesticide atrazine is 97%.
The embodiment and the test example show that the carbon nitride composite photocatalyst provided by the invention can effectively degrade atrazine in wastewater and realize effective removal of pesticides in the wastewater, and the homojunction between common carbon nitride and nitrogen-rich carbon nitride is constructed in the carbon nitride composite photocatalyst, so that the photoproduction electron-hole separation efficiency can be greatly improved, and the degrading capability of atrazine is improved.
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 common carbon nitride and nitrogen-rich carbon nitride, and is in a porous lamellar structure, and homojunctions are formed between the common carbon nitride and the nitrogen-rich carbon nitride, wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
2. The carbon nitride composite photocatalyst according to claim 1, wherein the weight ratio of the nitrogen-rich carbon nitride to the common carbon nitride is 1.
3. A preparation method of a carbon nitride composite photocatalyst is characterized by comprising the following steps:
s1, grinding and mixing common carbon nitride and 3-amino-1, 2, 4-triazole to obtain mixed powder;
s2, calcining the mixed powder obtained in the step S1 to obtain a carbon nitride composite photocatalyst consisting of common carbon nitride and nitrogen-rich carbon nitride, wherein a homojunction is formed between the common carbon nitride and the nitrogen-rich carbon nitride, and the carbon nitride composite photocatalyst is in a porous sheet-like structure;
wherein the common carbon nitride is C 3 N 4 The nitrogen-rich carbon nitride is C 3 N 5 。
4. The method of claim 3, wherein the weight ratio of the nitrogen-rich carbon nitride to the common carbon nitride is 1;
preferably, the weight ratio of the 3-amino-1, 2, 4-triazole to the common carbon nitride is 1.
5. The method according to claim 3 or 4, wherein the ordinary carbon nitride is obtained by subjecting urea to calcination II;
preferably, the conditions of calcining II include: the calcining heating rate is 1-3 ℃/min, the temperature is 500-600 ℃, and the time is 3-5h.
6. The method according to claim 3 or 4, wherein in step S2, the conditions for calcining I comprise: the calcining heating rate is 1-3 ℃/min, the temperature is 500-600 ℃, and the time is 3-5h.
7. The use of the carbon nitride composite photocatalyst as defined in claim 1 or 2, or the carbon nitride composite photocatalyst prepared by the preparation method as defined in any one of claims 3 to 6, for treating pesticide wastewater;
preferably, the pesticide in the pesticide wastewater is atrazine.
8. A method of treating pesticidal wastewater comprising the steps of:
(1) Mixing and adsorbing the carbon nitride composite photocatalyst of claim 1 or 2 or the carbon nitride composite photocatalyst prepared by the preparation method of any one of claims 3 to 6 with the pesticide wastewater under a dark condition to obtain a mixed solution;
(2) And (2) under the condition of visible light, mixing the mixed solution obtained in the step (1) with persulfate, and carrying out photocatalytic reaction.
9. The method as claimed in claim 8, wherein the pesticide in the pesticide waste water is atrazine;
preferably, the initial concentration of the pesticide in the pesticide wastewater is 2-10mg/L;
the weight ratio of the pesticide in the pesticide wastewater, the carbon nitride composite photocatalyst and the persulfate is 1:20-80:4-20, more preferably 1:35-45:6-12.
10. The method according to claim 8 or 9, wherein in step (1), the adsorption time is 15-25min;
in the step (2), the wavelength lambda of the visible light is more than 420nm, and the conditions of the photocatalytic reaction comprise: the temperature is 5-40 ℃, the pH is 3-9, the rotating speed is 500-700rpm, and the time is 1-2h;
the persulfate is at least one selected from potassium hydrogen persulfate, sodium hydrogen persulfate, potassium persulfate and sodium persulfate.
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