CN117299172B - Carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst and preparation method and application thereof - Google Patents
Carbon nitride/molybdenum disulfide heterojunction piezoelectric 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 101
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 title claims abstract description 86
- 229910052982 molybdenum disulfide Inorganic materials 0.000 title claims abstract description 86
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 13
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims abstract description 84
- 239000000243 solution Substances 0.000 claims abstract description 35
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000003054 catalyst Substances 0.000 claims abstract description 19
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 10
- 235000015393 sodium molybdate Nutrition 0.000 claims abstract description 10
- 239000011684 sodium molybdate Substances 0.000 claims abstract description 10
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- 239000011259 mixed solution Substances 0.000 claims abstract description 9
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- 238000009210 therapy by ultrasound Methods 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000002525 ultrasonication Methods 0.000 claims description 2
- 229910052724 xenon Inorganic materials 0.000 claims description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical group [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 2
- 230000001699 photocatalysis Effects 0.000 abstract description 34
- 238000007146 photocatalysis Methods 0.000 abstract description 25
- 238000002474 experimental method Methods 0.000 description 17
- 230000000694 effects Effects 0.000 description 13
- 238000000926 separation method Methods 0.000 description 9
- 239000000843 powder Substances 0.000 description 8
- 239000003344 environmental pollutant Substances 0.000 description 7
- 231100000719 pollutant Toxicity 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
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- 239000000463 material Substances 0.000 description 3
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- 238000002604 ultrasonography Methods 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
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- 230000007613 environmental effect Effects 0.000 description 2
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- 229910000510 noble metal Inorganic materials 0.000 description 1
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- 229920006395 saturated elastomer Polymers 0.000 description 1
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- RWVGQQGBQSJDQV-UHFFFAOYSA-M sodium;3-[[4-[(e)-[4-(4-ethoxyanilino)phenyl]-[4-[ethyl-[(3-sulfonatophenyl)methyl]azaniumylidene]-2-methylcyclohexa-2,5-dien-1-ylidene]methyl]-n-ethyl-3-methylanilino]methyl]benzenesulfonate Chemical compound [Na+].C1=CC(OCC)=CC=C1NC1=CC=C(C(=C2C(=CC(C=C2)=[N+](CC)CC=2C=C(C=CC=2)S([O-])(=O)=O)C)C=2C(=CC(=CC=2)N(CC)CC=2C=C(C=CC=2)S([O-])(=O)=O)C)C=C1 RWVGQQGBQSJDQV-UHFFFAOYSA-M 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
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Classifications
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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
-
- 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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- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
-
- 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
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
-
- 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
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Abstract
The invention discloses a carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst and a preparation method and application thereof, wherein sodium molybdate, thiourea and carbon nitride with certain proportion are dissolved in water to form a mixed solution, the pH value of the solution is regulated to be 0.1-2.0, after uniform stirring, the solution reacts for 20-30 hours at 180-220 ℃, and after cooling, washing and drying, the carbon nitride/molybdenum disulfide heterojunction catalyst is obtained; the efficiency of hexavalent chromium removal in the water body can be greatly improved under the condition of piezoelectric photocatalysis by utilizing the carbon nitride/molybdenum disulfide heterojunction. In addition, the catalyst provided by the invention can be recycled after reaction and is easy to recycle, and pollution to the water environment is avoided.
Description
Technical Field
The invention relates to the field of environmental pollution treatment, in particular to a carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst and a preparation method and application thereof.
Background
The photocatalysis technology is an environment-friendly and efficient technology, has a worldwide prospect in the aspects of environmental treatment and energy communication, and is greatly interesting to researchers. The photocatalyst with ideal performance is the key to popularization and application of the photocatalysis technology. However, the traditional single-component photocatalyst has low sunlight utilization rate, high recombination rate of photoelectron and hole pairs and low photocatalytic activity, and greatly limits the practical application of the photocatalytic technology. Although current modification methods such as doping, dye sensitization, noble metal deposition, heterostructure construction, etc. can promote separation of photocarriers, most photocarriers are easy to recombine before photocatalytic reaction, which greatly limits improvement of photocatalytic performance. Therefore, how to promote the separation of photoelectrons from holes while suppressing the secondary recombination of photoelectrons with holes is a core problem of concern in the environmental contaminant removal process. In the modification method, the heterojunction structure is used as a technology which is most widely researched, has stable performance and outstanding practical application prospect in the aspect of improving the photocatalytic performance, and thus, great interest of researchers is aroused. However, structural defects at the heterojunction interface tend to induce the formation of luminescent charge carrier recombination centers, reducing charge carrier separation efficiency to some extent. It is worth noting that the built-in electric field formed by polarization of the piezoelectric/ferroelectric material is used as an internal driving force for separating upper photoelectrons from holes, so that the separation efficiency of carriers can be improved, and the photocatalytic activity can be improved. In addition, under the electrostatic shielding effect, the built-in electric field is very easy to withdraw, so that free carriers are saturated, and the separation efficiency of polarization on carriers is reduced. Thus, the constant enhancement of the built-in electric field formed by the heterojunction consisting of the piezoelectric photocatalyst will greatly promote the separation of the photogenerated carriers under the drive of mechanical forces.
Molybdenum disulfide is a common piezoelectric catalytic material, and by applying mechanical stress (such as ultrasound, stirring, wind power, water flow, friction, extrusion and the like) to the material, the interior of the molybdenum disulfide is polarized, and electrons and holes are generated.
Disclosure of Invention
In order to overcome the defects and shortcomings of the existing photocatalysis technology, the invention aims to provide a carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst, and a preparation method and application thereof.
Aiming at the piezoelectric property of molybdenum disulfide, the invention utilizes common photocatalyst carbon nitride to modify molybdenum disulfide to obtain a carbon nitride/molybdenum disulfide heterojunction. Under the ultrasonic condition, photo-generated electrons and holes generated by illumination are effectively separated to directly or indirectly reduce and remove high-toxicity hexavalent chromium, so that the removal efficiency of hexavalent chromium is improved.
The technical scheme of the invention is as follows:
A preparation method of a carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst comprises the following steps:
Dissolving sodium molybdate, thiourea and carbon nitride in water to form a mixed solution, regulating the pH value of the solution to 0.1-2.0, uniformly stirring, reacting for 20-30 h at 180-220 ℃, cooling, washing and drying to obtain a carbon nitride/molybdenum disulfide heterojunction catalyst; the mass ratio of the sodium molybdate, the thiourea and the carbon nitride is (3-15): 40-80): 0.5-3.
Preferably, the ratio of the amounts of sodium molybdate, thiourea and carbon nitride is 10+ -5:50+ -10:1; the concentration of the sodium molybdate in the solution is 0.01 to 0.03mol/L.
Preferably, the pH value of the solution is 0.5-1.0; the stirring time is 60+/-30 minutes; the reaction temperature is 200+/-10 ℃; the reaction time is 24+/-2 hours; the drying temperature is 60+/-20 ℃; the drying time is 12+/-6 hours.
Preferably, the preparation method of the nitrogen carbide comprises the following steps: dissolving urea in water, regulating pH to 4-5, drying at 60+ -20 deg.C for 12+ -6 hr, heating to 530-570 deg.C, maintaining for 2-3 hr, and cooling to obtain carbon nitride.
Preferably, the concentration of the urea in water is 0.5-1 g/mL; the heating rate of the heating process is 5-15 ℃/min.
The carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst prepared by the method.
The application of the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst in hexavalent chromium removal is provided.
Preferably, the application comprises the steps of:
1) Adding a carbon nitride/molybdenum disulfide heterojunction catalyst into hexavalent chromium-containing water to be treated, and stirring; the concentration of the carbon nitride/molybdenum disulfide heterojunction catalyst in water is 0.3-1.5 g/L;
2) Carrying out ultrasonic and illumination treatment on the water to be treated obtained in the step 1); the power of the ultrasonic treatment is 50-150W; the intensity of the light treatment is 100-300 mW/cm 2.
Preferably, the concentration of the carbon nitride/molybdenum disulfide heterojunction catalyst in water is 0.5-1.0 g/L; the power of the ultrasonic treatment is 90-120W; the intensity of the light treatment is 175-225 mW/cm 2.
Preferably, the ultrasonic treatment uses an ultrasonic cleaner; the light source for the illumination treatment is a xenon lamp or a solar lamp.
The principle of the invention is that aiming at the excellent piezoelectric electro-optic catalytic performance of carbon nitride/molybdenum disulfide, a built-in electric field formed by piezoelectric polarization can lead photo-generated carriers to directionally move, promote the separation of photo-generated electron hole pairs to reduce hexavalent chromium, and achieve the purpose of removing high-toxicity hexavalent chromium.
Compared with the prior art, the invention has the following advantages and beneficial effects:
The carbon nitride/molybdenum disulfide catalyst prepared by the invention has obvious piezoelectric photocatalytic performance, good stability and excellent catalytic performance, can greatly improve the separation efficiency of photo-generated electron hole pairs, and can greatly improve the efficiency of hexavalent chromium wastewater removal in water under the condition of piezoelectric photocatalysis. In addition, the catalyst provided by the invention can be recycled after reaction and is easy to recycle, and pollution to the water environment is avoided.
Drawings
FIG. 1 is a TEM pattern and XRD pattern of carbon nitride/molybdenum disulfide prepared in example 1 of the present invention.
FIG. 2A is a graph showing the removal of hexavalent chromium by exposure to visible light for a carbon nitride/molybdenum disulfide heterojunction in the presence of a different ratio of carbon nitride in example 2 of the present invention; fig. 2B is a graph showing the removal performance of hexavalent chromium by ultrasonic vibration of a carbon nitride/molybdenum disulfide heterojunction in the presence of carbon nitride in different proportions in example 2 of the present invention.
FIG. 3 is a graph showing the effect of piezoelectric photocatalysis on removal of hexavalent chromium by carbon nitride/molybdenum disulfide heterojunctions of different concentrations in example 3 of the present invention.
FIG. 4 is a graph showing the effect of piezoelectro-optic catalytic removal of hexavalent chromium for different samples in example 4 of the present invention.
Fig. 5 is a graph showing the effect of the piezo-electric photocatalytic removal of hexavalent chromium by carbon nitride/molybdenum disulfide heterojunction at different ultrasonic powers in example 5 of the present invention.
FIG. 6 is a graph showing the effect of the piezoelectric photocatalysis of the heterojunction of carbon nitride/molybdenum disulfide on removing hexavalent chromium in example 6 of the present invention under different illumination intensities.
FIG. 7 is a graph showing the effect of piezoelectro-optic catalytic removal of hexavalent chromium in real wastewater by carbon nitride/molybdenum disulfide in example 7 of the present invention.
FIG. 8 is a graph showing the periodic performance of the piezoelectric photocatalytic removal of hexavalent chromium using carbon nitride/molybdenum disulfide in example 8 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
The reagents used in the examples are commercially available as usual unless otherwise specified.
Example 1
The example provides a preparation method of a carbon nitride/molybdenum disulfide heterojunction catalyst, which comprises the following specific steps:
1) First, using reference (DOI: 10.1016/j.apcatb.2016.10.012) is prepared from urea as raw material, and comprises the following steps: 10g of urea was dissolved in 15mL of deionized water, then the pH was adjusted to 4-5 with hydrochloric acid, then the urea solution was dried at 60℃for 12 hours, then the sample was transferred to a covered crucible, finally the crucible was heated to 550℃in a muffle furnace at a heating rate of 10℃per minute and kept at this temperature for 2 hours, and after cooling, a carbon nitride (C 3N4) sample was obtained.
2) 0.242G of sodium molybdate dihydrate, 0.381g of thiourea and 0.009g of carbon nitride were weighed out separately in 80mL of deionized water, then the pH of the solution was adjusted to 0.5 with 1M hydrochloric acid solution, and after stirring for 60 minutes, the solution was transferred to a reaction vessel and reacted at 200℃for 24 hours. And then cooling the reaction kettle to room temperature, washing the reactant with water and ethanol for three times respectively, and drying at 60 ℃ for 12 hours to finally obtain the product carbon nitride/molybdenum disulfide heterojunction.
The TEM and XRD patterns of the carbon nitride/molybdenum disulfide heterojunction catalyst prepared in the embodiment of the invention are shown in figure 1. The method described in the examples was demonstrated to successfully produce a carbon nitride/molybdenum disulfide heterojunction.
Example 2
This embodiment differs from embodiment 1 in that: under the condition that the adding amount of sodium molybdate and thiourea is not changed, carbon nitride/molybdenum disulfide heterojunctions accounting for 5%, 10%, 20% and 30% of molybdenum atomic substances are prepared by changing the adding amount of carbon nitride to be 0.0045, 0.009, 0.018 and 0.027g respectively, hexavalent chromium is selected as the representative of pollutants, and an experiment of removing hexavalent chromium by piezoelectric photocatalysis of the carbon nitride/molybdenum disulfide heterojunctions is performed.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. 20mg of carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the hexavalent chromium solution is stirred to reach equilibrium. The mixed solution was placed in an ultrasonic cleaner, and the reaction was started by ultrasonic. Wherein the heterojunction concentration of carbon nitride/molybdenum disulfide is 0.5g/L.
The performance of the carbon nitride/molybdenum disulfide heterojunction in the presence of different proportions of carbon nitride in the example of the invention in removing hexavalent chromium under irradiation of visible light and ultrasonic vibration is shown in fig. 2. For carbon nitride/molybdenum disulfide heterojunctions with 100% and 0% carbon nitride, the removal rates of hexavalent chromium after 20 minutes of photocatalytic and piezocatalytic reactions were 32.2% and 41.3% and 9.27% and 44.3%, respectively. After the carbon nitride is compounded with the molybdenum disulfide, the removal efficiency of the photocatalysis and the piezocatalysis hexavalent chromium shows the phenomenon of increasing and then decreasing along with the gradual increase of the compounding content of the carbon nitride, and the removal efficiency of the photocatalysis and the piezocatalysis hexavalent chromium reaches the maximum when the content of the carbon nitride accounting for 10 percent of the molybdenum atomic substance. This result demonstrates that the ratio of the amounts of the substances of sodium molybdate, thiourea and carbon nitride is preferred for preparing the carbon nitride/molybdenum disulfide heterojunction in the present invention: 10:50:1.
Example 3
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and experiments for removing hexavalent chromium through piezoelectric photocatalysis of the carbon nitride/molybdenum disulfide heterojunction with different concentrations are performed.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. And respectively weighing 4 mg, 10 mg, 20 mg and 40mg of carbon nitride/molybdenum disulfide heterojunction powder, adding the carbon nitride/molybdenum disulfide heterojunction powder into the hexavalent chromium solution, and stirring to balance the adsorption of the hexavalent chromium solution. The mixed solution was placed in an ultrasonic cleaner, and the reaction was started by ultrasonic.
The effect diagram of removing hexavalent chromium by piezophotocatalysis of the heterojunction of the carbon nitride/molybdenum disulfide with different concentrations in the embodiment of the invention is shown in fig. 3, and the graph shows that the removal efficiency of hexavalent chromium is continuously improved along with the continuous increase of the heterojunction concentration of the carbon nitride/molybdenum disulfide, when the heterojunction concentration reaches 0.5g/L, the removal efficiency of hexavalent chromium is 99.8%, and when the heterojunction concentration reaches 1g/L, the removal efficiency of hexavalent chromium is 100%. This result demonstrates that the preferred concentration of hexavalent chromium removed by the carbon nitride/molybdenum disulfide heterojunction in the context of the present invention is 0.5g/L, due to economic considerations in practical applications.
Example 4
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and experiments for removing hexavalent chromium through piezoelectric photocatalysis of the carbon nitride/molybdenum disulfide heterojunction are performed at different times.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. 20mg of carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the hexavalent chromium solution is stirred to reach equilibrium. The mixed solution was placed in an ultrasonic cleaner, and the reaction was started by ultrasonic. Wherein the concentration of the carbon nitride/molybdenum disulfide heterojunction is 0.5g/L.
The effect of the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis for removing hexavalent chromium in the embodiment of the invention is shown in fig. 4, and it can be seen from the graph that the carbon nitride/molybdenum disulfide heterojunction hardly adsorbs hexavalent chromium, and the adsorption rate is less than 5% in 30 minutes. Ultrasound, light and piezo photocatalysis alone, no hexavalent chromium was reduced within 20 minutes. The carbon nitride and the molybdenum disulfide are independently piezoelectric, 37.5% and 62.7% of hexavalent chromium can be removed within 20 minutes respectively, and compared with the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis shows excellent effect on the reduction and removal of hexavalent chromium, and the removal rate within 20 minutes reaches 99.8%. The result shows that the carbon nitride/molybdenum disulfide heterojunction has excellent carrier separation efficiency, and can remarkably improve the reduction removal efficiency of hexavalent chromium.
Example 5
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and experiments for removing hexavalent chromium through piezoelectric photocatalysis of the carbon nitride/molybdenum disulfide heterojunction under different ultrasonic powers are performed.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. 20mg of carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the hexavalent chromium solution is stirred to reach equilibrium. The mixed solution was placed in an ultrasonic cleaner, and the power of the ultrasonic cleaner was adjusted to 25, 50, 75 and 100W, respectively, to start the reaction. Wherein the concentration of the carbon nitride/molybdenum disulfide heterojunction is 0.5g/L.
The effect of removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis under different ultrasonic powers in the embodiment of the invention is shown in fig. 5, the performance of removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis is continuously improved along with the continuous increase of the ultrasonic power, and the removal efficiency of hexavalent chromium is close to 100 percent when the ultrasonic power is increased to 100W, so that the power of an ultrasonic cleaner for removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction in the invention is verified to be 100W.
Example 6
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and experiments for removing hexavalent chromium through piezoelectric photocatalysis of the carbon nitride/molybdenum disulfide heterojunction under different illumination intensities are performed.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. 20mg of carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the hexavalent chromium solution is stirred to reach equilibrium. The mixed solution was placed in an ultrasonic cleaner, and the light intensities were adjusted to 50, 100, 150 and 200mW/cm 2, respectively, to start the reaction. Wherein the concentration of the carbon nitride/molybdenum disulfide heterojunction is 0.5g/L.
The effect of removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis in the embodiment of the invention is shown in fig. 6, the performance of removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis is continuously improved along with the continuous increase of the illumination intensity, and the removal efficiency of hexavalent chromium is close to 100% when the illumination intensity is increased to 200mW/cm 2, so that the preferred illumination intensity of removing hexavalent chromium by the carbon nitride/molybdenum disulfide heterojunction in the embodiment of the invention is verified to be 200mW/cm 2.
Example 7
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and the carbon nitride/molybdenum disulfide heterojunction is used for performing an experiment of removing hexavalent chromium in a real water body through piezoelectric photocatalysis.
The experimental procedure was as follows:
40mL of 50mg/L hexavalent chromium solution was prepared in 5 beakers with rainwater, soil digestion solution and deionized water, respectively. 5 parts of 20mg carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the mixture is stirred to balance the adsorption of hexavalent chromium, and the reaction is started. Wherein the heterojunction concentration of carbon nitride/molybdenum disulfide is 0.5g/L.
FIG. 7 is a graph showing the effect of the carbon nitride/molybdenum disulfide heterojunction in the piezoelectric electro-optic catalytic removal of hexavalent chromium in real wastewater in an embodiment of the present invention. Experiments show that hexavalent chromium in soil, rainwater and deionized water can be effectively removed within 20 minutes. The example shows that the carbon nitride/molybdenum disulfide heterojunction can efficiently remove hexavalent chromium through piezoelectric photocatalysis in different water environments, and a feasible scheme is provided for treating hexavalent chromium pollution industrially.
Example 8
In the embodiment, the carbon nitride/molybdenum disulfide heterojunction prepared in the embodiment 1 is adopted, hexavalent chromium is selected as a representative of pollutants, and an experiment of recycling the catalyst is performed.
The experimental procedure was as follows:
40mL of a 50mg/L hexavalent chromium solution was prepared in a beaker. 20mg of carbon nitride/molybdenum disulfide heterojunction powder is weighed and added into hexavalent chromium solution, and the hexavalent chromium solution is stirred to reach equilibrium. The mixed solution was placed in an ultrasonic cleaner and treated with 100W ultrasound and 200mW/cm 2 of light for 20min. After the reaction is finished, the residual solution is centrifuged for 15min in a high-speed centrifuge at the rotating speed of 12000r, the catalyst is recovered, the catalyst is added into a 40mL beaker of hexavalent chromium solution with the concentration of 50mg/L, and the step experiment of removing hexavalent chromium is repeated for six times.
FIG. 8 is a graph showing the effect of the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis on the recycling of the catalyst in hexavalent chromium removal in an embodiment of the present invention. Experiments show that after six cycles of use, the removal efficiency of hexavalent chromium in 20 minutes is reduced from 99.8% to 94.9%, and the performance is reduced by about 5%. The example illustrates that the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalysis for removing hexavalent chromium has recycling property and property stability in practical application.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (8)
1. The application of the carbon nitride/molybdenum disulfide heterojunction piezoelectric photocatalyst in removing hexavalent chromium in water is characterized in that the preparation method of the catalyst comprises the following steps:
Dissolving sodium molybdate, thiourea and carbon nitride in water to form a mixed solution, regulating the pH value of the solution to 0.1-2.0, uniformly stirring, reacting for 20-30 h at 180-220 ℃, cooling, washing and drying to obtain a carbon nitride/molybdenum disulfide heterojunction catalyst; the ratio of the amounts of sodium molybdate, thiourea and carbon nitride is 10+/-5:50+/-10:1.
2. The use according to claim 1, characterized in that the concentration of sodium molybdate in solution is between 0.01 and 0.03mol/L.
3. The use according to claim 2, wherein the pH of the solution is between 0.5 and 1.0; the stirring time is 60+/-30 minutes; the reaction temperature is 200+/-10 ℃; the reaction time is 24+/-2 hours; the drying temperature is 60+/-20 ℃; the drying time is 12+/-6 hours.
4. Use according to claim 1 or 2 or 3, characterized in that the preparation method of the nitrogen carbide is: dissolving urea in water, regulating pH to 4-5, drying at 60+ -20 deg.C for 12+ -6 hr, heating to 530-570 deg.C, maintaining for 2-3 hr, and cooling to obtain carbon nitride.
5. The use according to claim 4, characterized in that the concentration of urea in water is between 0.5 and 1g/mL; the heating rate of the heating process is 5-15 ℃/min.
6. The use according to claim 5, characterized by the steps of:
1) Adding a carbon nitride/molybdenum disulfide heterojunction catalyst into hexavalent chromium-containing water to be treated, and stirring; the concentration of the carbon nitride/molybdenum disulfide heterojunction catalyst in water is 0.3-1.5 g/L;
2) Carrying out ultrasonic and illumination treatment on the water to be treated obtained in the step 1); the power of the ultrasonic treatment is 50-150W; the intensity of the light treatment is 100-300 mW/cm 2.
7. The use according to claim 6, wherein the concentration of the carbon nitride/molybdenum disulfide heterojunction catalyst in water is 0.5-1.0 g/L; the power of the ultrasonic treatment is 90-120W; the intensity of the light treatment is 175-225 mW/cm 2.
8. The use according to claim 7, wherein the ultrasonic treatment uses an ultrasonic cleaner; the light source for the illumination treatment is a xenon lamp or a solar lamp.
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