CN114904547B - Mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst - Google Patents
Mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst Download PDFInfo
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 84
- 239000002131 composite material Substances 0.000 title claims abstract description 69
- 238000002360 preparation method Methods 0.000 title claims abstract description 37
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten trioxide Chemical compound O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 claims abstract description 104
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- CMPGARWFYBADJI-UHFFFAOYSA-L tungstic acid Chemical compound O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 claims description 17
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- 229960005404 sulfamethoxazole Drugs 0.000 description 1
- JLKIGFTWXXRPMT-UHFFFAOYSA-N sulphamethoxazole Chemical compound O1C(C)=CC(NS(=O)(=O)C=2C=CC(N)=CC=2)=N1 JLKIGFTWXXRPMT-UHFFFAOYSA-N 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
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- 231100000419 toxicity Toxicity 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
-
- B01J35/39—
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
-
- 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
- C02F2101/40—Organic compounds containing sulfur
-
- 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
- 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 discloses a mixed crystal phase WO 3 @g‑C 3 N 5 The preparation method of the composite photocatalyst comprises the following steps: step A: preparation of tungsten trioxide WO 3 The method comprises the steps of carrying out a first treatment on the surface of the And (B) step (B): preparation g-C 3 N 5 The method comprises the steps of carrying out a first treatment on the surface of the Step C: tungsten trioxide WO 3 And g-C 3 N 5 Dispersing into absolute ethyl alcohol to obtain mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle to make hydrothermal reaction, after the reaction is finished, washing solid product A obtained by reaction, drying so as to obtain mixed crystal phase WO 3 @g‑C 3 N 5 A composite photocatalyst. The mixed crystal phase WO prepared by the invention 3 @g‑C 3 N 5 The composite photocatalyst has better catalytic stability and higher catalytic utilization rate, and the highest degradation rate of rhodamine B can reach 97 percent, namely tungsten trioxide WO respectively 3 And g-C 3 N 5 9.8 times and 2.5 times of (a).
Description
Technical Field
The invention relates to the technical field of composite photocatalysts. In particular mixed crystal phase WO 3 @g-C 3 N 5 A preparation method of a composite photocatalyst.
Background
With the rapid development of modern industry, the amount and kind of pollutants discharged into the environment are also increasing, especially water pollution. And in severe cases, the water ecological system can be completely destroyed, so that the water body loses function. Water is a source of life, all life on earth cannot leave water, but available fresh water resources are only groundwater and inland surface water, so water pollution is becoming more interesting and important. Wherein the water pollutants are classified according to the properties of the substances and mainly comprise organic pollutants and inorganic pollutants. The most typical inorganic pollutants are heavy metal ions discharged into water, and heavy metal poisoning can be caused to endanger life once the heavy metal ions are seriously absorbed by animals or human bodies. Organic pollutants commonly comprise halogenated olefins, dyes, medicines, antibiotics, pesticides and the like, most of the organic pollutants are substances which are difficult to degrade naturally and remain in water all the time, and the harmful substances can be transmitted through a food chain, so that the natural world and the human health are greatly damaged, and the organic pollutants are irreversible. It is important to find a method for innocuous treatment of sewage.
The current sewage treatment method mainly comprises the following steps: (1) The physical method is to remove dye in water by using an adsorbent, a filter screen film, an extraction method and the like, but the method only removes organic matters in the water by phase transfer and does not convert the organic matters into matters which have no pollution to the environment; (2) Biological methods, namely, decomposing the wastewater into small-molecular carbon dioxide and water by utilizing microorganisms or degrading the wastewater by utilizing a microorganism co-metabolism method, wherein the concentration of the industrial wastewater which is generally discharged into the water is relatively large and is not a single pollutant, so that the toxicity to the microorganisms is large and the degradation effect cannot be achieved in some cases; (3) The chemical precipitation method utilizes metal ions and organic matters in wastewater to form metal organic complexes to generate precipitation, thereby achieving the effect of sewage treatment, but the sensitivity is generally lower and the precipitated metal organic complexes need further treatment. (4) This approach has now been accepted by many people, using environmentally friendly solar photocatalytic systems for degradation. Therefore, the material for catalyzing and degrading the environmental pollutants is economically and effectively sought, is green and safe, solves the problem that the current refractory organic matters pollute the water body, and is a hot spot subject for the current intensive attention and research of students at home and abroad.
The metal oxide semiconductor material has the characteristics of no toxicity, no harm, proper forbidden bandwidth, high photocatalytic activity and the like, and has good application prospect in the photocatalytic degradation neighborhood, wherein WO 3 As a wide bandgap n-type semiconductor material, has high surface area, good chemical stability and biocompatibility. In recent years, with the research workers on WO 3 Deep research on photocatalytic performance of materialsThe number of published articles increases significantly, which suggests WO 3 As a photocatalyst, the photocatalyst has great research value. However, the catalytic effect of the metal oxide photocatalyst alone is not ideal, and agglomeration easily occurs in the synthesis process, so that the specific surface area and the photocatalytic performance of the material are reduced. To improve WO 3 There are many methods for applying to WO 3 Such as noble metal doping, semiconductor material compounding, metal ion doping, etc., but these modification methods are generally costly, complex to operate, and for WO 3 The improvement effect of the photocatalytic activity of (c) is not ideal.
Nonmetallic g-C with graphite-like structure 3 N 4 The material is a star material in the fields of energy and environmental application because of good chemical stability, stable chemical structure, low preparation cost, high corrosion resistance and unique electronic energy band structure. But g-C 3 N 4 The availability of visible light is insufficient, so that the low-band-gap nitrogen-rich graphite carbonitride g-C 3 N 5 Great research attention is being paid to the field of photocatalysis. By means of g-C 3 N 5 Morphology adjustability of (2) can be used for preparing g-C with different structural morphologies through different synthesis means 3 N 5 The combination of the characteristics of different morphologies can accelerate electron transfer and widen the optical response (band gap value is 1.70 eV) of a visible light region, thereby improving the photocatalysis performance of the material. Synthesis of g-C by Wei et al using 3-amino-1, 2, 4-triazole 3 N 5 Successful preparation of Er 3+ /Tb 3+ @BiOBr-g-C 3 N 5 The photocatalysis experiment result shows that the material has good degradation effect on sulfamethoxazole, and the removal rate can reach 94.2 percent after the visible light is irradiated for 60 minutes. But now how to utilize low band gap nitrogen rich graphite carbonitride g-C 3 N 5 For WO 3 The composite photocatalyst with good catalytic effect can be obtained by modification, which has not been reported yet.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalystTo solve the current WO 3 The catalytic effect after modification is not ideal enough, and the catalytic stability is poor.
In order to solve the technical problems, the invention provides the following technical scheme:
mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the following steps:
step A: preparation of tungsten trioxide in Mixed Crystal phase WO 3 ；
And (B) step (B): preparation of g-C 3 N 5 ；
Step C: tungsten trioxide in mixed crystal phase WO 3 And g-C 3 N 5 Dispersing into absolute ethyl alcohol to obtain mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle for hydrothermal reaction, after the reaction is finished, the solid product A obtained by the reaction is washed and dried to obtain the mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst.
The above mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst, in step C, mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 The mass ratio of (2) is 1:0.25 to 4.
The above mixed crystal phase WO 3 @g-C 3 N 5 In the step C, the mixed dispersion liquid A is mixed with tungsten trioxide WO in a crystalline phase 3 The content of (2) is 0.01-0.05 g/mL; the use of absolute ethanol as solvent can increase the pressure in the reactor during the hydrothermal reaction to allow for the mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Better compounding of the two materials to form a mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst.
The above mixed crystal phase WO 3 @g-C 3 N 5 A preparation method of a composite photocatalyst, in step C, the hydrothermal reaction conditions are: the reaction temperature is 100-200 ℃ and the reaction time is 6-16 h; the hydrothermal reaction temperature is higher than 200 ℃ or lower than 150 ℃ and lower than 6 hours or higher than 16 hours, so that the prepared mixed crystal phase WO is reduced 3 @g-C 3 N 5 Photocatalytic activity of the composite photocatalyst.
The above mixed crystal phase WO 3 @g-C 3 N 5 In the step C, tungsten trioxide WO with mixed crystal phase is prepared 3 And g-C 3 N 5 When dispersing into absolute ethyl alcohol, stirring for 50-70 min by adopting a magnetic stirring mode, and mixing the tungsten trioxide WO in a crystalline phase 3 And g-C 3 N 5 The more uniform the dispersion in absolute ethanol, the more favorable the hydrothermal reaction is for compounding to form a homogeneous composite photocatalyst, if the uniformity of the dispersion is not good, the tungsten trioxide WO in mixed crystal phase can be caused 3 And g-C 3 N 5 The hydrothermal reaction is not completely compounded, so that the catalytic activity of the prepared composite photocatalyst is reduced to a certain extent; when the two materials are stirred for 50-70 min by adopting a magnetic stirring mode, the two materials are sufficiently dispersed to be fully contacted in absolute ethyl alcohol, and if the stirring time is too short, the two materials are insufficiently contacted, so that the composite effect is affected; after the reaction is finished, washing the solid product A obtained by the reaction for 3 times by using absolute ethyl alcohol, impurities on the surface of the product can be cleaned, and the subsequent drying is accelerated after the product is washed by absolute ethyl alcohol; then drying for 10-12 h at 75-85 ℃; drying at a temperature of 75-85 ℃ close to the boiling point of ethanol can accelerate volatilization of ethanol, and if the temperature is too low, the drying time can be influenced, so that the activation of the composite photocatalyst material is influenced.
The above mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst, in step A, mixed crystal phase tungsten trioxide WO 3 The preparation method of (2) comprises the following steps:
step A-1: placing tungstic acid and sodium sulfate in distilled water, and stirring and uniformly mixing to obtain a mixed dispersion liquid B;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle for hydrothermal reaction, and obtaining a solid product B after the reaction is finished;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately, drying the washed solid product B, and grinding after drying to obtainMixed crystal phase tungsten trioxide WO 3 . The mixed crystal phase tungsten trioxide WO is prepared by adopting the preparation method 3 With mixed crystal phase, whereas commercially available tungsten trioxide is usually in a single crystal phase, and cannot be used for preparing mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst.
The above mixed crystal phase WO 3 @g-C 3 N 5 In the step A-1, the mass ratio of the tungstic acid to the sodium sulfate is 1:1.5-2.5, the sodium sulfate can play a role of a morphology guiding agent, and the crystal phase of the generated tungsten trioxide is regulated by regulating the ratio of the tungstic acid to the sodium sulfate; if the mass ratio of tungstic acid to sodium sulfate exceeds this range, the formation of a crystal phase during the synthesis of the material is affected, thereby affecting the finally produced mixed crystal phase WO 3 @g-C 3 N 5 Catalytic performance of the composite photocatalyst; in the mixed dispersion liquid B, the content of the tungstic acid is 0.05-0.08 g/mL, which is beneficial to WO 3 Is formed in the mixed crystal phase;
in the step A-2, the hydrothermal reaction conditions are as follows: the reaction temperature is 150-200 ℃, the reaction time is 10-15 h; too high or too low a hydrothermal reaction temperature, too long or too short a hydrothermal reaction time can affect WO 3 Thereby affecting the photocatalytic activity of the prepared composite photocatalyst.
In the step A-3, the drying temperature of the solid product B is 75-85 ℃ and the drying time is 7.5-8.5 h; too low a drying temperature or too short a drying time can cause the moisture to be not volatilized completely, affect the activation of the material, and too high a drying temperature or too long a drying time can affect WO 3 A crystalline phase composition of (a); mixed crystal phase tungsten trioxide WO 3 The particle size of the mixed crystal phase tungsten trioxide WO is 90-110 mu m 3 Can better match g-C 3 N 5 Compounding to form mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst.
Mixing the above crystalline phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst, in step B, g-C 3 N 5 The preparation method of (2) comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, stirring and dissolving to obtain mixed dispersion liquid C;
step B-2: heating the mixed dispersion liquid C while magnetically stirring to completely evaporate water in the mixed dispersion liquid C, grinding the residual solid after evaporating the water to dryness to obtain a solid product C; the purpose of dissolving 3-amino-1, 2, 4-triazole and then evaporating water at a specific temperature is to recrystallize 3-amino-1, 2, 4-triazole, and the internal structure of the crystalline 3-amino-1, 2, 4-triazole may be changed to a certain extent after crystallization, so that the g-C obtained by calcination 3 N 5 Can better be mixed with the mixed crystal phase WO 3 Compounding to generate a compound photocatalyst with better photocatalytic activity;
step B-3: placing the solid product C into a tube furnace for high-temperature calcination; obtaining yellow solid powder after the calcination is finished, namely g-C 3 N 5 . The g-C prepared by the preparation method 3 N 5 Can be combined with a mixed crystal phase WO 3 Compounding to form a mixed crystal phase WO 3 @g-C 3 N 5 Composite photocatalyst and g-C prepared by adopting the preparation method 3 N 5 And mixed crystal phase WO 3 In the compounding process, WO 3 The monoclinic phase of the mixed crystal phase is easier to change into the hexagonal phase, thereby preparing the mixed crystal phase WO with better catalytic activity and catalytic stability 3 @g-C 3 N 5 A composite photocatalyst.
The above mixed crystal phase WO 3 @g-C 3 N 5 In the step B-1, the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 2-8wt%; if the mass fraction of 3-amino-1, 2, 4-triazole is too high, the rate of evaporative crystallization is affected, whereas if the mass fraction of 3-amino-1, 2, 4-triazole is too low, the amount after crystallization is too small, and the yield is affected;
in step B-2, the heating temperature of the mixed dispersion liquid C is 75-85 ℃, and if the heating temperature is too high or too low, the crystallization effect is affected, thereby affecting the preparation of g-C 3 N 5 Is unfavorable for preparing the composite photocatalyst with better catalytic performance, and the particle size of the solid product C is80-120 mu m; the particle size of the solid product C is controlled within the range, so that all components of the solid product C can be heated uniformly in the calcination process, if insufficient grinding is caused, the particle size of the material is uneven, and the material is heated unevenly in the calcination process, so that the prepared g-C is caused 3 N 5 Catalyst performance becomes poor;
in the step B-3, during high-temperature calcination, firstly, the temperature is raised to 480-560 ℃ at a heating rate of 4-6 ℃/min, and then the temperature is kept for 2.5-3.5 h; during calcination, the internal structure of the material is influenced by the too high or too low temperature rising speed, the structure is imperfect if the temperature rising speed is too high, and the g-C is caused if the temperature rising speed is too low 3 N 5 Internal structure stacking, which is unfavorable for obtaining g-C with ideal structure 3 N 5 The method comprises the steps of carrying out a first treatment on the surface of the In the test, it was found that if the calcination temperature was less than 480℃or greater than 560℃the g-C produced 3 N 5 And mixed crystal phase WO 3 Composite obtained mixed crystal phase WO 3 @g-C 3 N 5 The catalytic performance of the composite photocatalyst is relatively poor.
The above mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst, in step C, mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 The mass ratio of (2) is 1:2; in the mixed dispersion liquid A, tungsten trioxide WO with mixed crystal phase 3 Is 0.033g/mL; the hydrothermal reaction conditions are as follows: the reaction temperature is 180 ℃ and the reaction time is 12 hours; tungsten trioxide in mixed crystal phase WO 3 And g-C 3 N 5 When the water-soluble polymer is dispersed into absolute ethyl alcohol, stirring for 60min by adopting a magnetic stirring mode; washing the solid product A obtained by the reaction with absolute ethyl alcohol for 3 times after the reaction is finished; drying at 80deg.C for 10 hr;
in step A, tungsten trioxide in mixed crystal phase WO 3 The preparation method of (2) comprises the following steps:
step A-1: placing tungstic acid and sodium sulfate in distilled water, and stirring and uniformly mixing to obtain a mixed dispersion liquid B; the mass ratio of the tungstic acid to the sodium sulfate is 1:2, and the content of the tungstic acid in the mixed dispersion liquid B is 0.067g/mL;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle for hydrothermal reaction, and obtaining a solid product B after the reaction is finished; the hydrothermal reaction conditions are as follows: the reaction temperature is 180 ℃ and the reaction time is 12 hours;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 The method comprises the steps of carrying out a first treatment on the surface of the The drying temperature of the solid product B is 80 ℃ and the drying time is 8 hours; mixed crystal phase tungsten trioxide WO 3 The grain diameter of the particles is 90-110 mu m;
in step B, g-C 3 N 5 The preparation method of (2) comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, stirring and dissolving to obtain mixed dispersion liquid C; the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion C is 5wt%;
step B-2: heating the mixed dispersion liquid C while magnetically stirring to completely evaporate water in the mixed dispersion liquid C, and grinding the residual solid after evaporating the water to obtain a solid product C; the heating temperature of the mixed dispersion liquid C is 80 ℃, and the particle size of the solid product C is 80-120 mu m;
step B-3: placing the solid product C into a tube furnace for high-temperature calcination; obtaining yellow solid powder after the calcination is finished, namely g-C 3 N 5 The method comprises the steps of carrying out a first treatment on the surface of the During high-temperature calcination, the temperature is raised to 540 ℃ at a heating rate of 5 ℃/min, and then the temperature is kept at 540 ℃ for 3 hours.
The technical scheme of the invention has the following beneficial technical effects:
1. the invention mixes the tungsten trioxide WO with the crystal phase 3 And g-C 3 N 5 The mixed crystal phase WO is prepared by hydrothermal reaction 3 @g-C 3 N 5 Composite photocatalyst and mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Compared with the mixed crystal phase composite photocatalyst, the mixed crystal phase composite photocatalyst has better catalytic activity when catalyzing rhodamine B: under the condition that a 500W xenon lamp is used as an irradiation light source, the highest degradation rate of rhodamine B in 120min can reach 97 percent, and the degradation rate is respectively mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 9.8 times and 2.5 times of (a).
2. The mixed crystal phase WO prepared by the invention 3 @g-C 3 N 5 (1:2) when the composite photocatalyst is used for repeatedly degrading rhodamine B, the more the repeated use times are, the better the photocatalysis effect on the rhodamine B is; and after rhodamine B is repeatedly degraded for six times, the rhodamine B has good degradation effect on tetracycline and methylene blue: WO after six times of repeated degradation of rhodamine B 3 @g-C 3 N 5 (1:2) the degradation rate of the composite photocatalyst to tetracycline can reach 73% in 120min, and the degradation rate to methylene blue can reach 90%; thus the invention prepares WO 3 @g-C 3 N 5 The (1:2) composite photocatalyst has better catalytic stability and higher catalytic utilization rate.
3. The invention respectively adjusts and controls the tungsten trioxide WO in the mixed crystal phase 3 And g-C 3 N 5 The preparation method of (2) prepares tungsten trioxide WO with mixed crystal phase 3 Mixed crystal phase tungsten trioxide WO 3 And g-C prepared by the method 3 N 5 When the hydrothermal reaction is carried out, the mixed crystal phase WO with better catalytic activity and catalytic stability can be obtained by compounding 3 @g-C 3 N 5 A composite photocatalyst; in the hydrothermal reaction process, tungsten trioxide WO 3 And g-C 3 N 5 The mass ratio of the two, the hydrothermal reaction temperature, the reaction time, the drying temperature and the like are controlled in a specific range, so that the tungsten trioxide WO 3 At the same time as g-C 3 N 5 The monoclinic phase in the mixed crystal phase is converted to the hexagonal crystal phase during compounding, so that the prepared WO 3 @g-C 3 N 5 The composite photocatalyst has higher light catalytic activity and photocatalytic stability; the WO 3 @g-C 3 N 5 In the process of catalyzing rhodamine B degradation, the mixed crystal phase WO is formed along with the increase of the catalysis times of the composite photocatalyst 3 @g-C 3 N 5 The monoclinic phase in the composite photocatalyst is converted to the hexagonal phase, so that the hexagonal phase increases with the increase of the photocatalytic frequency, and the catalytic activity of the composite photocatalyst increases with the increase of the catalytic frequency.
Drawings
FIG. 1 is an XRD spectrum of a different photocatalyst in an embodiment of the invention;
FIG. 2a photocatalyst WO in an embodiment of the invention 3 Scanning electron microscope images of (2);
FIG. 2b photocatalyst g-C in an embodiment of the invention 3 N 5 Scanning electron microscope images of (2);
FIG. 2c photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 A scanning electron microscope image of (1:2);
FIG. 3a photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 EDX spectrogram (tungsten W element) of (1:2);
FIG. 3b photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 EDX spectrogram (oxygen O element) of (1:2);
FIG. 3c photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 EDX spectrogram of (1:2) (element C carbon);
FIG. 3d photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 EDX spectrum (nitrogen N element) of (1:2).
FIG. 4 shows a UV-vis DRS spectrum of different photocatalysts in an embodiment of the present invention;
FIG. 5 is a graph of degradation of rhodamine B by various photocatalysts in an embodiment of the present invention;
FIG. 6a photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 (1:2) a stable test result graph;
FIG. 6b photocatalyst WO in an embodiment of the invention 3 @g-C 3 N 5 (1:2) a catalytic degradation mechanism test result graph;
FIG. 6c photocatalyst WO after six times of repeated degradation of rhodamine B (RhB) in the embodiment of the present invention 3 @g-C 3 N 5 (1:2) a graph of catalytic degradation test results for Tetracycline (TC) and Methylene Blue (MB);
FIG. 6d WO in the embodiment of the invention 3 @g-C 3 N 5 (1:2) degradation of rhodamine B six times repeatedly before use (Fresh)The XRD patterns were compared later (cycle 6 th).
Detailed Description
1. Experimental part
1.1 pure tungsten trioxide WO 3 Is prepared from
Weighing 2g of tungstic acid and 4g of sodium sulfate, placing the tungstic acid and the sodium sulfate in a beaker filled with 30mL of distilled water, and stirring to uniformly disperse the tungstic acid and the sodium sulfate to obtain a mixed dispersion liquid B; transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction for 12 hours at the temperature of 180 ℃, after the reaction is finished, alternately washing a solid product B obtained by the reaction with distilled water and absolute ethyl alcohol for a plurality of times, drying for 8 hours at the temperature of 80 ℃, and grinding after drying to ensure that the particle size of the solid product B reaches 90-110 mu m to obtain tungsten trioxide WO 3 And (3) powder.
1.2 pure g-C 3 N 5 Is prepared from
Adding 1.5g of 3-amino-1, 2, 4-triazole into 30mL of deionized water, stirring to fully dissolve the mixture, and obtaining a mixed dispersion liquid C; magnetically stirring the mixed dispersion liquid C at 80 ℃, evaporating the water to dryness, and grinding the mixture until the particle size of the powder is 80-120 mu m to obtain a solid product C; putting the solid product C into a tube furnace, heating to 540 ℃ at a heating rate of 5 ℃/min, and then preserving heat for 3 hours at a constant temperature of 540 ℃ to obtain yellow g-C 3 N 5 And (5) naturally cooling the powder for later use.
1.3 Mixed Crystal phase WO 3 @g-C 3 N 5 Preparation of composite photocatalyst
1g of tungsten trioxide WO is weighed separately 3 And 2g of pure g-C 3 N 5 Placing in a beaker filled with 30mL of absolute ethyl alcohol, magnetically stirring for 1h to obtain a mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle, performing hydrothermal reaction at 180 ℃ for 12h, washing the obtained solid product A with the absolute ethyl alcohol for 3 times, and drying at 80 ℃ for 10h to obtain a mixed crystal phase WO 3 @g-C 3 N 5 Composite photocatalyst, expressed as WO 3 :g-C 3 N 5 (1:2). By the same method, by changing g-C 3 N 5 The added mass of (2) is 0.25 g, 0.5g, 1g, 3g and 4g, and the mixed crystal phase WO is prepared respectively 3 @g-C 3 N 5 Composite photocatalyst: WO (WO) 3 :g-C 3 N 5 (1:0.25)、WO 3 :g-C 3 N 5 (1:0.5)、WO 3 :g-C 3 N 5 (1:1)、WO 3 :g-C 3 N 5 (1:3)、 WO 3 :g-C 3 N 5 (1:4)。
1.4 photo-catalytic Performance test
Rhodamine B (RhB) was selected as a simulated contaminant in this example, for g-C 3 N 5 、WO 3 、 WO 3 @g-C 3 N 5 The degradation performance of three photocatalysts was tested: 20mg of the photocatalyst was added to 40mL of rhodamine B having a concentration of 10mg/mL, respectively, and stirred in the dark for 30 minutes, respectively, to ensure that the rhodamine B reached an absorption-desorption equilibrium on the photocatalyst surface, to obtain a sample solution. Taking samples (5 mL) from the sample solution every 15min by taking a 500W xenon lamp as a light source (a 420nm optical filter); the sampled samples were centrifuged to remove the catalyst added to the samples, the supernatants were collected, and the absorbance of the supernatants was measured at the maximum absorption wavelength of rhodamine B (λmax=554 nm) using an ultraviolet-visible spectrophotometer, respectively.
3. Results and analysis
3.1 XRD analysis
In order to determine the crystal structure of the prepared photocatalyst, XRD characterization was performed on the prepared photocatalyst, and the test results are shown in FIG. 1, and as can be seen from the analysis of the graph, pure g-C 3 N 5 There was a spike at 2θ=12.8°, indicating the synthesized g-C 3 N 5 The internal structure is ordered, the front appears at 2θ=27.4°, the corresponding crystal face is 002, indicating g-C 3 N 5 A very good crystal structure is formed and stacked between layers in the form of conjugated chains in the CN skeleton. From WO 3 The XRD diffraction peaks of (a) can be seen as characteristic diffraction peaks occurring at 2θ=22.9 (002), 23.49 (020), 24.15 (200), which is attributed to WO of monoclinic phase 3 Is in accordance with the standard card JCPDS-83-0950; diffraction peaks appearing at 2θ=13.74 (100), 27.83 (101), 28.82 (200), 31.92 (111), 33.64 (201), 36.33 (210) are attributed to WO of hexagonal phase 3 According with the standard card JCPDS-33-1387, the tungsten trioxide WO prepared by the implementation is illustrated 3 The single-inclined crystal phase and the six-directional crystal phase are provided at the same time, and the single-inclined crystal phase and the six-directional crystal phase are a mixed crystal phase WO 3 . At the same time, the XRD diffraction peak analysis of the composite catalyst can obtain that: with g-C 3 N 5 Increase of doping amount, m-WO 3 The intensities of the three diffraction peaks 22.9, 23.49, 24.15 present a tendency to increase before decrease. At the same time due to g-C 3 N 5 Is doped with h-WO 3 The characteristic diffraction peak at 27.83 was progressively higher in intensity and the diffraction peak was also broadened to some extent, indicating g-C 3 N 5 And WO 3 After compounding, it affects WO 3 The crystal structure ratio of the two is as follows g-C 3 N 5 Increase in doping amount WO 3 The crystals of (2) are mainly oriented towards the hexagonal phase (h-WO 3 ) Growth. For g-C 3 N 5 The diffraction peak of 002 crystal face may be due to h-WO 3 The diffraction peak positions of the 101 crystal face are similar, so after the two materials are compounded, g-C 3 N 5 The diffraction peak of 002 crystal face is shifted and h-WO 3 The diffraction peaks of the 101 crystal plane overlap, further explaining WO 3 With g-C 3 N 5 Well coupled together.
2.2 SEM analysis
To determine the surface morphology of the prepared catalyst, the prepared catalyst tungsten trioxide WO 3 、 g-C 3 N 5 And WO 3 @g-C 3 N 5 (1: 2) SEM analysis was performed, and the analysis results are shown in FIGS. 2a to 2 c. As can be seen from FIG. 2a, tungsten trioxide WO prepared by the above method 3 Is in a rod-shaped structure, and simultaneously, agglomeration occurs in the hydrothermal process, so that the catalyst has a larger size. As can be seen from FIG. 2b, g-C was prepared 3 N 5 Exhibiting a sheet-like stacked porous structure. It can be seen from FIG. 2c that when WO 3 With g-C 3 N 5 The morphology is changed into particles from a rod-shaped structure after the composition, the morphology is changed, and meanwhile, the g-C 3 N 5 The gaps between the layers of the catalyst become larger, and the composite catalyst presents a certain gap structure, which is beneficial to the reduction in the photocatalytic degradation experimentThe adsorption of the solution is released, so that the photocatalytic activity of the material is improved.
Based on the above results, WO is aimed at confirming the kind of elements and the distribution of elements existing in the composite catalyst 3 @g-C 3 N 5 (1: 2) energy dispersive X-ray (EDX) imaging was performed, verifying the presence of element W, O, C, N (fig. 3a to 3 d). At the same time as available from EDX profiling, in this region WO 3 In g-C 3 N 5 And is moderately highly dispersed.
2.3 UV-vis DRS spectrogram analysis
FIG. 4 is a graph showing the ultraviolet-visible diffuse reflectance spectrum of the prepared photocatalyst, and it can be seen from an analysis of FIG. 4 that the light absorption value of the prepared composite catalyst in the visible light region is smaller than that of pure g-C 3 N 5 More than pure WO 3 . This is probably due to WO 3 With g-C 3 N 5 The recombination then affects the optical bandgap of the semiconductor, thus exhibiting a red shift in the ultraviolet-visible spectrum; second, probably because of g-C 3 N 5 Higher nitrogen content in the structure, enhanced charge transfer capability and thus improved photocatalytic activity, which suggests WO 3 @g-C 3 N 5 The sunlight can be fully utilized in the visible light range. Meanwhile, according to DRS test result analysis of the composite catalyst after six times of repeated use, the light absorption value of the composite material after repeated use is increased, which shows that the photocatalytic degradation effect of the composite photocatalyst after repeated use is improved, and the result is consistent with the subsequent experimental result.
2.4 photocatalytic Performance test
In order to detect the optical activity of the prepared photocatalyst, in this example, rhodamine B is mainly used as a simulated pollutant, a 500W xenon lamp is used as an irradiation light source, and the performance of the photocatalyst is tested, and the experimental result is shown in FIG. 5. As can be seen from FIG. 5, when WO is used 3 With g-C 3 N 5 After compounding, the mixture was compared with pure WO 3 And pure g-C 3 N 5 Has good photocatalytic effect when WO 3 With g-C 3 N 5 When the mass ratio of the rhodamine B to the aqueous solution is 1:2, the removal rate of the rhodamine B can reach 97 percent (within 120 min), and the rhodamine B is pure WO respectively 3 And pure g-C 3 N 5 9.8 times and 2.5 times of (a).
2.5 stability test
Stability is one of the important markers for measuring the performance of the photocatalyst, so this example shows that the photocatalyst WO 3 @g-C 3 N 5 The stability of (1:2) was tested, and the experimental results are shown in FIG. 6a, and it can be seen from the experimental results that the photocatalytic effect of rhodamine B tends to be better as the number of times of use of the material increases, and the degradation performance of the composite photocatalyst is basically stable after 5 times are reached, which can greatly improve the catalyst WO 3 @g-C 3 N 5 (1:2).
In order to determine the degradation mechanism of the photo-composite catalyst, in this embodiment, disodium ethylenediamine tetraacetate (EDTA-2 Na) is taken as a hole inhibitor, tert-butyl alcohol (TBA) is taken as a hydroxyl inhibitor, p-Benzoquinone (BQ) is taken as a super-oxygen free radical inhibitor, and the photo-composite catalyst is tested for the photo-catalytic mechanism, and the experimental result is shown in FIG. 6b, and it can be seen from the graph that in the degradation process h + 、·OH、O 2 All play a role, but the main role is OH.
In order to further test the performance of the composite photocatalyst after six times of degradation of rhodamine B (RhB), the composite photocatalyst after six times is used for detecting the photocatalytic degradation performance of Tetracycline (TC) and Methylene Blue (MB), and experimental results are shown in figure 6c, and according to graph analysis, the composite photocatalyst still has a certain degradation effect on tetracycline and methylene blue after six times of degradation, the removal rate of the tetracycline can reach 73% within 120min, and the removal rate of the methylene blue can reach 90%. This shows that the stability of the composite photocatalyst prepared in this embodiment is very good, and the utilization rate of the composite photocatalyst can be greatly improved.
FIG. 6d shows the composite photocatalyst after six times of repeated use and before no use (WO 3 @g-C 3 N 5 As is clear from the analysis of the XRD spectrum of (1:2)), the composition of the crystal structure in the photo-composite catalyst changes after six times of repeated use, and peaks corresponding to the original hexagonal crystal phases 100 and 101 crystal faces are obtainedThe intensity is increased, the peak width is narrowed, and the peak corresponding to the 111 crystal face disappears, which shows that the crystal is converted from monoclinic phase to hexagonal phase in the use process of the composite photocatalyst, and the WO of hexagonal phase is further shown by combining the stability test result 3 The photocatalytic performance is better.
Claims (5)
1. Mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized by comprising the following steps:
step A: preparation of tungsten trioxide in Mixed Crystal phase WO 3 ；
Mixed crystal phase tungsten trioxide WO 3 The preparation method of (2) comprises the following steps:
step A-1: placing tungstic acid and sodium sulfate in distilled water, and stirring and uniformly mixing to obtain a mixed dispersion liquid B; the mass ratio of the tungstic acid to the sodium sulfate is 1:1.5-2.5; in the mixed dispersion liquid B, the content of the tungstic acid is 0.05-0.08 g/mL;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle for hydrothermal reaction, and obtaining a solid product B after the reaction is finished; the hydrothermal reaction conditions are as follows: the reaction temperature is 150-200 ℃ and the reaction time is 10-15 h;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 The method comprises the steps of carrying out a first treatment on the surface of the The drying temperature of the solid product B is 75-85 ℃ and the drying time is 7.5-8.5 h; mixed crystal phase tungsten trioxide WO 3 The grain diameter of the particles is 90-110 mu m;
and (B) step (B): preparation of g-C 3 N 5 ；
g-C 3 N 5 The preparation method of (2) comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, stirring and dissolving to obtain mixed dispersion liquid C; the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 2 to 8 weight percent;
step B-2: heating the mixed dispersion liquid C while magnetically stirring to completely evaporate water in the mixed dispersion liquid C, and grinding the residual solid after evaporating the water to obtain a solid product C; the heating temperature of the mixed dispersion liquid C is 75-85 ℃, and the particle size of the solid product C is 80-120 mu m;
step B-3: placing the solid product C into a tube furnace for high-temperature calcination; obtaining yellow solid powder after the calcination is finished, namely g-C 3 N 5 The method comprises the steps of carrying out a first treatment on the surface of the During high-temperature calcination, firstly, the temperature is raised to 480-560 ℃ at a heating rate of 4-6 ℃/min, and then the temperature is kept for 2.5-3.5 h;
step C: tungsten trioxide in mixed crystal phase WO 3 And g-C 3 N 5 Dispersing into absolute ethyl alcohol to obtain mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle to make hydrothermal reaction, after the reaction is finished, washing solid product A obtained by reaction, drying so as to obtain mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst; tungsten trioxide in mixed crystal phase WO 3 And g-C 3 N 5 When the water-soluble polymer is dispersed into absolute ethyl alcohol, stirring for 50-70 min by adopting a magnetic stirring mode; washing the solid product A obtained by the reaction with absolute ethyl alcohol for 3 times after the reaction is finished; and then drying for 10-12 h at 75-85 ℃.
2. The mixed crystal phase WO according to claim 1 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase is mixed 3 And g-C 3 N 5 The mass ratio of (2) is 1:0.25 to 4.
3. The mixed crystal phase WO according to claim 2 3 @g-C 3 N 5 A process for producing a composite photocatalyst, characterized by comprising the step C of mixing tungsten trioxide WO in a mixed crystal phase in a mixed dispersion liquid A 3 The content of (C) is 0.01-0.05 g/mL.
4. The mixed crystal phase WO according to claim 3 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, the hydrothermal reaction conditions are as follows: the reaction temperature is 100-2The reaction time is 6-16 h at 00 ℃.
5. A mixed crystal phase WO according to any one of claims 1 to 4 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase is mixed 3 And g-C 3 N 5 The mass ratio of (2) is 1:2; in the mixed dispersion liquid A, tungsten trioxide WO with mixed crystal phase 3 Is 0.033g/mL; the hydrothermal reaction conditions are as follows: the reaction temperature is 180 ℃ and the reaction time is 12 hours; tungsten trioxide in mixed crystal phase WO 3 And g-C 3 N 5 When the water-soluble polymer is dispersed into absolute ethyl alcohol, stirring for 60min by adopting a magnetic stirring mode; washing the solid product A obtained by the reaction with absolute ethyl alcohol for 3 times after the reaction is finished; drying at 80deg.C for 10 hr;
in step A, tungsten trioxide in mixed crystal phase WO 3 The preparation method of (2) comprises the following steps:
step A-1: placing tungstic acid and sodium sulfate in distilled water, and stirring and uniformly mixing to obtain a mixed dispersion liquid B; the mass ratio of the tungstic acid to the sodium sulfate is 1:2, and the content of the tungstic acid in the mixed dispersion liquid B is 0.067g/mL;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle for hydrothermal reaction, and obtaining a solid product B after the reaction is finished; the hydrothermal reaction conditions are as follows: the reaction temperature is 180 ℃ and the reaction time is 12 hours;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 The method comprises the steps of carrying out a first treatment on the surface of the The drying temperature of the solid product B is 80 ℃ and the drying time is 8 hours; mixed crystal phase tungsten trioxide WO 3 The grain diameter of the particles is 90-110 mu m;
in step B, g-C 3 N 5 The preparation method of (2) comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, stirring and dissolving to obtain mixed dispersion liquid C; the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion C is 5wt%;
step B-2: heating the mixed dispersion liquid C while magnetically stirring to completely evaporate water in the mixed dispersion liquid C, and grinding the residual solid after evaporating the water to obtain a solid product C; the heating temperature of the mixed dispersion liquid C is 80 ℃, and the particle size of the solid product C is 80-120 mu m;
step B-3: placing the solid product C into a tube furnace for high-temperature calcination; obtaining yellow solid powder after the calcination is finished, namely g-C 3 N 5 The method comprises the steps of carrying out a first treatment on the surface of the During high-temperature calcination, the temperature is raised to 540 ℃ at a heating rate of 5 ℃/min, and then the temperature is kept at 540 ℃ for 3 hours.
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| CN104772158A (en) * | 2015-03-23 | 2015-07-15 | 上海应用技术学院 | Preparation method of WO3/C3N4 mixed photocatalyst |
| CN110339853A (en) * | 2019-07-22 | 2019-10-18 | 成都理工大学 | C3N5Material and its preparation method and application |
| CN112221531A (en) * | 2020-11-13 | 2021-01-15 | 长沙学院 | Heterogeneous core-shell g-C3N5@MnO2Composite and preparation method thereof |
| CN112495420A (en) * | 2020-12-09 | 2021-03-16 | 北华大学 | Preparation method of nitrogen-rich graphite phase carbon nitride/silver metavanadate composite photocatalyst |
| CN113751048A (en) * | 2021-10-15 | 2021-12-07 | 阜阳师范大学 | Molybdenum trioxide in-situ intercalation carbon nitride composite catalyst and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104772158A (en) * | 2015-03-23 | 2015-07-15 | 上海应用技术学院 | Preparation method of WO3/C3N4 mixed photocatalyst |
| CN110339853A (en) * | 2019-07-22 | 2019-10-18 | 成都理工大学 | C3N5Material and its preparation method and application |
| CN112221531A (en) * | 2020-11-13 | 2021-01-15 | 长沙学院 | Heterogeneous core-shell g-C3N5@MnO2Composite and preparation method thereof |
| CN112495420A (en) * | 2020-12-09 | 2021-03-16 | 北华大学 | Preparation method of nitrogen-rich graphite phase carbon nitride/silver metavanadate composite photocatalyst |
| CN113751048A (en) * | 2021-10-15 | 2021-12-07 | 阜阳师范大学 | Molybdenum trioxide in-situ intercalation carbon nitride composite catalyst and preparation method thereof |
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