CN112156804B - MQDs/NCDs/TiO2Composite material, composite catalytic system and method for improving degradation efficiency of organic pollutants - Google Patents
MQDs/NCDs/TiO2Composite material, composite catalytic system and method for improving degradation efficiency of organic pollutants Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 70
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 41
- 230000015556 catabolic process Effects 0.000 title claims abstract description 34
- 238000006731 degradation reaction Methods 0.000 title claims abstract description 34
- 239000002957 persistent organic pollutant Substances 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 16
- 239000000463 material Substances 0.000 title description 22
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 97
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims abstract description 40
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims abstract description 38
- 239000002135 nanosheet Substances 0.000 claims abstract description 22
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical class S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 claims abstract description 11
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 9
- 230000002195 synergetic effect Effects 0.000 claims abstract description 9
- 238000011068 loading method Methods 0.000 claims description 17
- PYWVYCXTNDRMGF-UHFFFAOYSA-N rhodamine B Chemical compound [Cl-].C=12C=CC(=[N+](CC)CC)C=C2OC2=CC(N(CC)CC)=CC=C2C=1C1=CC=CC=C1C(O)=O PYWVYCXTNDRMGF-UHFFFAOYSA-N 0.000 claims description 17
- 229940043267 rhodamine b Drugs 0.000 claims description 17
- 238000003756 stirring Methods 0.000 claims description 11
- 238000013032 photocatalytic reaction Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 3
- 229960000907 methylthioninium chloride Drugs 0.000 claims description 2
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 claims 1
- 230000001699 photocatalysis Effects 0.000 description 19
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 12
- 238000001035 drying Methods 0.000 description 12
- 239000002096 quantum dot Substances 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 239000008367 deionised water Substances 0.000 description 10
- 229910021641 deionized water Inorganic materials 0.000 description 10
- 238000003786 synthesis reaction Methods 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 238000013033 photocatalytic degradation reaction Methods 0.000 description 8
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- 239000000356 contaminant Substances 0.000 description 6
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 description 5
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 4
- 239000004202 carbamide Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
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- 239000004065 semiconductor Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- APQHKWPGGHMYKJ-UHFFFAOYSA-N Tributyltin oxide Chemical compound CCCC[Sn](CCCC)(CCCC)O[Sn](CCCC)(CCCC)CCCC APQHKWPGGHMYKJ-UHFFFAOYSA-N 0.000 description 2
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
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- 239000002064 nanoplatelet Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
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- 238000001228 spectrum Methods 0.000 description 2
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- 238000002411 thermogravimetry Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910001868 water Inorganic materials 0.000 description 2
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
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- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
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- 239000002440 industrial waste Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- CXKWCBBOMKCUKX-UHFFFAOYSA-M methylene blue Chemical compound [Cl-].C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 CXKWCBBOMKCUKX-UHFFFAOYSA-M 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 231100000956 nontoxicity Toxicity 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- FHHJDRFHHWUPDG-UHFFFAOYSA-L peroxysulfate(2-) Chemical compound [O-]OS([O-])(=O)=O FHHJDRFHHWUPDG-UHFFFAOYSA-L 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
- 238000002211 ultraviolet spectrum Methods 0.000 description 1
- 238000001429 visible spectrum Methods 0.000 description 1
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- 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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- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
-
- 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
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/04—Sulfides
- B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
- B01J27/051—Molybdenum
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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
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/053—Sulfates
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- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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- B82Y40/00—Manufacture or treatment of nanostructures
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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Abstract
The invention discloses MQDs/NCDs/TiO2Composite material, said MQDs/NCDs/TiO2The composite material is made of TiO2Nanosheets supported on the TiO2The nano-sheet is composed of nitrogen-doped carbon quantum dots and molybdenum disulfide quantum dots. The invention also discloses a method for preparing the MQDs/NCDs/TiO by using the MQDs/NCDs/TiO2A composite catalytic system consisting of the composite material and persulfate and a method for improving the degradation efficiency of organic pollutants. MQDs/NCDs/TiO of the present invention2Composite material, solves the problem of TiO2The composite material and persulfate form a composite catalytic system which can generate a synergistic catalytic effect, and further promote the degradation of organic pollutants.
Description
Technical Field
The invention relates to the technical field of photocatalysts, in particular to MQDs/NCDs/TiO2Composite materials made of MQDs/NCDs/TiO2Composite materials with persulfuric acidA composite catalytic system formed by salt and a method for improving the degradation efficiency of organic pollutants.
Background
With the accelerated development of economy and industrialization, the pollution of industrial waste pollutants to water environment is increasingly serious, and the health of human beings and the normal life of aquatic organisms are influenced. Advanced oxidation technology is an effective method for treating organic pollutants, based on sulfate radical (SO)4 ·-) The advanced oxidation technology is a very potential technology developed in recent years, and mainly generates sulfate radicals by activating persulfate or peroxymonosulfate so as to oxidize and degrade pollutants. The application of the photocatalysis activated persulfate for pollutant degradation has the advantages of good stability, wide application range, strong oxidation capacity, mild reaction conditions and the like, and attracts the continuous attention of scientific researchers. However, the single semiconductor photocatalytic material has two critical defects of low solar energy utilization rate and low quantum efficiency, and the potential industrial application of the single semiconductor photocatalytic material is limited. Therefore, designing and developing a high-efficiency photocatalyst for activating persulfate becomes urgent in the field of scientific research.
Among the numerous semiconductor photocatalysts, TiO2The excellent physical and chemical properties make it attract extensive attention in the research field. TiO 22According to different atom arrangement modes, the crystal can be divided into three crystal forms: rutile, anatase and brookite. In which anatase form of TiO2The internal atoms are sparsely arranged, the dielectric constant is small, the electron mobility is relatively high, and the method has great application potential in the field of photoelectron. TiO 22The method has the advantages of stable chemical structure, no toxicity, no pollution, various synthetic methods, low cost and the like, and is widely researched in the field of photocatalysis in recent years. It also has drawbacks such as: the wide band gap (3.0-3.2eV) makes it responsive only to UV light; the photogenerated electron-hole pairs readily recombine.
Disclosure of Invention
The technical problem to be solved by the invention is to provide MQDs/NCDs/TiO with high-efficiency photocatalytic performance2A composite material.
In order to solve the technical problems, the invention provides the following technical scheme:
in a first aspect, the present invention provides MQDs/NCDs/TiO2Composite material, said MQDs/NCDs/TiO2The composite material is made of TiO2Nanosheets supported on the TiO2Nitrogen-doped carbon quantum dots (NCDs) and molybdenum disulfide quantum dots (MQDs) on the nanosheets.
Due to TiO2Due to the wide band gap (3.0-3.2eV), the photocatalyst can only respond to ultraviolet light but not visible light, and the photogenerated electron-hole pairs are easy to recombine, so that the photocatalytic efficiency is influenced. Referring to fig. 4, to solve this problem, the inventors have focused on TiO2NCDs and MQDs are respectively deposited on the nano-chips for modification, and the NCDs have the capacity of light conversion, so that long-wavelength visible light can be converted into excitable TiO2So that visible light can be made TiO2Nanosheet response, hence TiO2Can be excited by visible light to generate electron-hole pairs. And a large number of active sites exist on MQDs, and the active sites can be used as reaction centers and can promote the photocatalytic reaction. Referring to FIG. 6, MQDs/NCDs/TiO of the present invention2The composite material can absorb visible light and has continuous light absorption in the range of 400nm-800nm, thereby overcoming TiO2A defect that responds only to ultraviolet light.
In addition, the selective TiO of the present invention2NCDs and MQDs, and also considering the principle of energy band matching, MQDs and TiO2Between them, there will be formed I-type heterojunctions, NCDs and TiO2A Z-type heterojunction is formed therebetween (see fig. 4). TiO 22A part of electrons on the conduction band are transferred to the conduction band of MQDs, and a part of electrons on the conduction band are transferred to the valence band of NCDs to be recombined with holes. TiO 22Holes in the valence band are transferred to the valence band of the MQDs. Therefore, the separation and transfer of electron holes can be effectively promoted, and the photocatalysis effect can be improved.
Further, the MQDs/NCDs/TiO2In the composite material, the loading amounts of the nitrogen-doped carbon quantum dots and the molybdenum disulfide quantum dots are preferably 1wt% -2 wt%; more preferably 1.5 wt%. If the load is less than 1wt%The catalytic effect is poor; if the loading is more than 2wt%, the quantum dots can be mutually aggregated to cover part of active sites, so that the improvement of the photocatalytic performance is not facilitated; meanwhile, the quantum dot loading is too high, which is not beneficial to light absorption and can also influence the photocatalytic performance.
In the present invention, TiO is used2The nanoplatelets, NCDs and MQDs can be prepared by methods well known in the art. For example, TiO2The nano-sheet can be prepared by the following method: a certain volume of TBOT and HF are added into a high-pressure hydrothermal reaction kettle containing a polytetrafluoroethylene lining, and the high-pressure hydrothermal reaction kettle is heated for 12 to 25 hours at the temperature of 150 ℃ and 220 ℃. Cooling to room temperature, washing with deionized water and anhydrous ethanol for several times, and drying at 60 deg.C for 12 hr to obtain TiO2Nanosheets.
NCDs can be loaded on TiO by the following method2On the nano-chip: 0.5g of TiO2Dispersing the nano-sheets in 50ml of deionized water, adding a certain amount of citric acid and urea into the solution, carrying out ultrasonic treatment and stirring for 0.5-1h, transferring the solution to a high-pressure hydrothermal reaction kettle containing a polytetrafluoroethylene lining, and heating the solution at the temperature of 160-240 ℃ for 3-6 h. Cooling to room temperature, washing with deionized water for several times, and drying at 60 deg.C for 12 hr to obtain nitrogen-doped carbon dots (NCDs) loaded on TiO2NCDs/TiO nanosheets2A material.
MQDs can be loaded on TiO by the following method2On the nano-chip: mixing a certain volume concentration of molybdenum disulfide quantum dot solution and 0.2g of NCDs/TiO2Mixing, ultrasonic treating for a certain time, adding acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/NCDs/TiO2A composite material.
In a second aspect, the invention also provides a composite catalytic system for catalyzing and degrading organic pollutants, and the composite catalytic system consists of the MQDs/NCDs/TiO2The composite material is composed of persulfate. Wherein the persulfate may be a persulfate well known in the art, including but not limited to sodium persulfate, potassium persulfate, ammonium persulfate.
The composite catalytic system of the invention can efficiently catalyze the degradation of organic pollutants, and the principle is as follows: due to NCDsPotential of conduction band lower than O2The free electrons in the conduction band of which can reduce O2Production of O2 -，·O2 -Can be further converted into OH, and the position of the conduction band of MQDs is higher than O2So that O cannot be reduced2. The valence band potential of MQDs is lower than H2Oxidation potential of O, holes in its valence band, not oxidizing H2O produces OH, which is not conducive to degradation if electrons and holes are not consumed in time and recombine. Persulfate is introduced into a catalytic system, and electrons on conduction bands of NCDs and MQDs can activate persulfate to generate SO4 ·-And SO4 ·-Can be further converted into OH, and more free radicals participate in the degradation of pollutants. Meanwhile, persulfate consumes free electrons, and inhibits the recombination of electron holes to a great extent, so that more holes on the MQDs valence band participate in the degradation of pollutants. The synergistic effect of the photocatalyst and the activated persulfate can thus achieve a high efficiency of degradation of the contaminant (see figure 5).
Furthermore, in the composite catalytic system, MQDs/NCDs/TiO2The mass ratio of the composite material to the persulfate is preferably 1 (0.25-1), and the ratio can achieve better catalytic effect. More preferably, the MQDs/NCDs/TiO2The mass ratio of the composite material to the persulfate is 2: 1.
In a third aspect, the present invention also provides a method for improving the degradation efficiency of organic pollutants, comprising the following steps:
(1) MQDs/NCDs/TiO in the composite catalytic system2Adding the composite material into an organic pollutant solution to be treated, and uniformly stirring in the dark;
(2) adding persulfate with the formula amount into the organic pollutant solution, and carrying out photocatalytic reaction under visible light, wherein the photocatalytic reaction is carried out on MQDs/NCDs/TiO2The composite material and the activated persulfate realize the efficient degradation of the organic pollutants under the synergistic action.
Further, in step (1), the organic contaminants may be common organic contaminants including, but not limited to, rhodamine B, methylene blue.
Further, in the step (2), the molar concentration of the persulfate in the organic pollutant solution is 1-4 mM.
Compared with the prior art, the invention has the beneficial effects that:
1. MQDs/NCDs/TiO of the present invention2The composite material solves the problem of TiO through the synergistic effect of the excellent light conversion capability of NCDs, a large number of active sites existing in MQDs and a formed heterojunction2The defect of low utilization rate of visible light, and the high-efficiency separation and transfer efficiency of photo-generated electrons and holes are realized. And the MQDs/NCDs/TiO2The composite material can generate a synergistic catalytic effect with persulfate, and the degradation of organic pollutants is promoted.
2. The light degradation result shows that the MQDs/NCDs/TiO of the invention2The removal rate of the compound photocatalyst for activating the persulfate to the rhodamine B within 80min can reach 100%, and the compound photocatalyst shows excellent photocatalytic performance.
Drawings
FIG. 1 shows MQDs/NCDs/TiO2SEM images of the composite;
FIG. 2 shows MQDs/NCDs/TiO2TEM images of the composite;
FIG. 3 is MQDs/NCDs/TiO2HRTEM images of the composite;
FIG. 4 shows MQDs/NCDs/TiO2A schematic diagram of a heterojunction formed by the composite material;
FIG. 5 shows MQDs/NCDs/TiO2A schematic diagram of the synergistic effect of the composite material and persulfate;
FIG. 6 is a graph of the diffuse reflectance of different materials in the UV and visible spectrum;
FIG. 7 is a thermogravimetric analysis of the catalytic materials prepared in examples 1-4;
FIG. 8 is a graph comparing the degradation of rhodamine B by different catalysts in the presence or absence of persulfate;
FIG. 9 shows MQDs/NCDs/TiO at different ratios2And (4) comparing the degradation of the persulfate to rhodamine B.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The experimental methods used in the following examples are conventional methods unless otherwise specified, and materials, reagents and the like used therein are commercially available without otherwise specified.
2 2 2 2Synthesis of TiO nano-sheet, NCDs/TiO, MQDs/TiO and MQDs/NCDs/TiO
Example 1: synthesis of TiO2Nano-sheet
35ml of TBOT and 2ml of HF were added to a polytetrafluoroethylene-lined autoclave and heated at 200 ℃ for 18 hours. Cooling to room temperature, washing with deionized water and anhydrous ethanol for several times, and drying at 60 deg.C for 12 hr to obtain TiO2Nanosheets.
Example 2: synthesis of NCDs/TiO2
0.5g of TiO2Dispersing the nano-sheets in 50ml of deionized water, adding 1g of citric acid and 0.3g of urea into the solution, carrying out ultrasonic treatment and stirring for 1h, transferring the solution into a high-pressure hydrothermal reaction kettle containing a polytetrafluoroethylene lining, and heating the solution at 160 ℃ for 5 hours. Cooling to room temperature, washing with deionized water for several times, and drying at 60 deg.C for 12 hr to obtain nitrogen-doped carbon dots (NCDs) loaded on TiO2NCDs/TiO nanosheets2A material.
Example 3: synthesis of NCDs/TiO2
0.5g of TiO2The nanoplatelets are dispersed in 50ml of deionized water and 1.2g ofCitric acid and 0.5g urea were added to the solution, sonicated and stirred for 1 hour, transferred to a high pressure hydrothermal autoclave containing a polytetrafluoroethylene liner, and heated at 170 ℃ for 4 hours. Cooling to room temperature, washing with deionized water for several times, and drying at 60 deg.C for 12 hr to obtain nitrogen-doped carbon dots (NCDs) loaded on TiO2NCDs/TiO nanosheets2A material.
Example 4: synthesis of NCDs/TiO2
0.5g of TiO2Dispersing the nano-sheets in 50ml of deionized water, adding 1.4g of citric acid and 0.5g of urea into the solution, carrying out ultrasonic treatment and stirring for 1h, transferring the solution into a high-pressure hydrothermal reaction kettle containing a polytetrafluoroethylene lining, and heating the solution at 190 ℃ for 6 hours. Cooling to room temperature, washing with deionized water for several times, and drying at 60 deg.C for 12 hr to obtain nitrogen-doped carbon dots (NCDs) loaded on TiO2NCDs/TiO nanosheets2A material.
Example 5: synthesis of MQDs/TiO2
8ml of molybdenum disulfide quantum dot solution with the concentration of 0.3g/L and 0.2g of TiO are added2Mixing, performing ultrasonic treatment for a certain time, adding 10ml acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/TiO2A composite material.
Example 6: synthesis of MQDs/NCDs/TiO2
6ml of molybdenum disulfide quantum dot solution with the concentration of 0.4g/L and 0.2g of NCDs/TiO synthesized in example 32Mixing, performing ultrasonic treatment for a certain time, adding 10ml acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/NCDs/TiO2Composite materials (MQDs loading ≈ 1.2 wt%).
Example 7: synthesis of MQDs/NCDs/TiO2
4ml of molybdenum disulfide quantum dot solution with the concentration of 0.5g/L and 0.2g of NCDs/TiO synthesized in example 32Mixing, performing ultrasonic treatment for a certain time, adding 10ml acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/NCDs/TiO2Composite materials (MQDs loading ≈ 1.0 wt%).
Example 8: synthesis of MQDs/NCDs/TiO2
8ml of molybdenum disulfide quantum dot solution with the concentration of 0.4g/L and 0.2g of NCDs/TiO synthesized in example 32Mixing, performing ultrasonic treatment for a certain time, adding 10ml acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/NCDs/TiO2Composite materials (MQDs loading ≈ 1.6 wt%).
Example 9: synthesis of MQDs/NCDs/TiO2
10ml of molybdenum disulfide quantum dot solution with 0.3g/L and 0.2g of NCDs/TiO synthesized in example 32Mixing, performing ultrasonic treatment for a certain time, adding 10ml acetone, magnetically stirring until the solvent is naturally evaporated, and drying to obtain MQDs/NCDs/TiO2Composite materials (MQDs loading ≈ 1.5 wt%).
FIG. 2 shows the MQDs/NCDs/TiO2TEM spectrum of the composite material, from which the lamellar TiO can be observed2Shows that TiO is successfully synthesized2Nanosheets. FIG. 3 shows MQDs/NCDs/TiO2HRTEM spectrum of the composite material, from which TiO can be observed in FIG. 32The quantum dots dispersed randomly on the nano-chip prove that the quantum dots are successfully loaded on TiO2And (4) nano-chips.
Performance testing
Effect of NCDs loading on photocatalytic Performance
FIG. 7 is a thermogravimetric analysis of the catalytic materials synthesized in examples 1-4. As can be seen from the figure, the NCDs/TiO synthesized in examples 2-42In the catalytic material, the loading amounts of NCDs were 1wt%, 1.5 wt%, and 2wt%, respectively.
The catalytic materials synthesized in examples 1 to 4 were added to 100mL of rhodamine B solution with a concentration of 10mg/L, respectively, stirred in the dark for 30min, then a photocatalytic degradation experiment was performed under visible light, the photocatalytic degradation time lasted 80min, the obtained sample liquid was measured with an ultraviolet-visible spectrophotometer to calculate the degradation effect, and the obtained results are shown in table 1 below.
Table 1 removal of organic contaminants by catalytic materials synthesized in examples 1-4
NCDs loading vs. NCDs/TiO2The photocatalytic degradation effect of the composite catalytic material has great influence, and the photocatalytic efficiency is influenced when the load is too small or too large. As is clear from the results in Table 1, when the loading of NCDs is in the range of 1wt% to 2wt%, the removal of organic contaminants is increased and then decreased, and the optimum loading is 1.5 wt%.
Effect of MQDs loading on photocatalytic Performance
The catalytic materials synthesized in examples 6 to 9 were added to 100mL of rhodamine B solution with a concentration of 10mg/L, respectively, stirred in the dark for 30min, then a photocatalytic degradation experiment was performed under visible light, the photocatalytic degradation time lasted 80min, the obtained sample liquid was measured with an ultraviolet-visible spectrophotometer to calculate the degradation effect, and the obtained results are shown in table 2 below.
Table 2 removal of organic contaminants by catalytic materials synthesized in examples 6-9
As is clear from the results in Table 2, it is found that MQDs/NCDs/TiO are treated with2The photocatalytic efficiency of the composite catalytic material is influenced by the small and large loading of MQDs. Wherein, when the loading of MQDs is 1.5 wt%, the maximum removal rate of organic pollutants can be achieved. The reason is that: when the amount is too small, TiO2The active sites on the nanosheets are few, thus affecting the photocatalytic efficiency; when the load capacity is too large, the quantum dots can be mutually aggregated to cover part of active sites, so that the improvement of the photocatalytic performance is not facilitated; meanwhile, the quantum dot loading is too high, which is not beneficial to light absorption and can also influence the photocatalytic performance.
3.MQDs/NCDs/TiO2Photocatalytic performance of composite catalytic system with persulfate
The catalytic materials synthesized in the embodiments 1, 3, 5 and 8 are respectively added into 100mL of 10mg/L rhodamine B solution, the mixture is stirred for 30min in the dark, then 2mM persulfate is added into the solution, a photocatalytic degradation experiment is carried out under visible light, the photodegradation time lasts for 80min, and the obtained sample liquid is measured by an ultraviolet visible spectrophotometer to calculate the degradation effect.
The results of the above tests are shown in fig. 8. As can be seen from FIG. 8, in the absence of persulfate, it was associated with TiO2Nanosheets, NCDs/TiO2、MQDs/TiO2In contrast, MQDs/NCDs/TiO2The composite material shows stronger catalytic degradation performance, after the composite material is degraded by light for 80min, the removal rate of rhodamine B reaches 96%, and the removal rate of other materials to rhodamine B is not enough than 75%. After persulfate is added, MQDs/NCDs/TiO2The removal rate of the composite material to rhodamine B after 20min of photodegradation exceeds 80%, and the removal rate of the composite material to rhodamine B after 60min of photodegradation is close to 100%, which is far better than that of other materials. This indicates that the MQDs/NCDs/TiO of the present invention2The composite material has excellent photocatalytic degradation performance, and can generate a synergistic effect with persulfate, so that rhodamine B is catalyzed to be rapidly degraded, and the catalytic degradation efficiency is greatly improved.
4.MQDs/NCDs/TiO2Effect of the proportion of persulfate on photocatalytic Properties
4 parts of 0.1g of MQDs/NCDs/TiO synthesized in example 82The composite materials are respectively added into 100mL of 10mg/L rhodamine B solution, stirred in the dark for 30min, then 0.025g, 0.033g, 0.05g and 0.1g of persulfate are respectively added into the rhodamine B solution, a photocatalytic degradation experiment is carried out under visible light, the photodegradation time lasts for 60min, and the obtained sample liquid is measured by an ultraviolet-visible spectrophotometer to calculate the degradation effect.
The results of the above tests are shown in fig. 9. As can be seen from the figure, the addition of persulfate can accelerate the speed of MQDs/NCDs/TiO2The catalytic degradation efficiency of the composite material on rhodamine B is improved. When MQDs/NCDs/TiO2When the ratio of the composite material to the persulfate is 2:1, the catalytic degradation efficiency on rhodamine B is highest, and the catalytic degradation efficiency reaches 100% in 60 min.
In conclusion, the MQDs/NCDs/TiO of the present invention2Composite material, solves the problem of TiO2Low visible light utilizationHigh-efficiency photocatalysis efficiency is realized; and a composite catalytic system formed by the catalyst and persulfate can generate a synergistic catalytic effect, so that the degradation of organic pollutants is further promoted. The MQDs/NCDs/TiO2The composite material has wide application prospect in the aspect of catalytic degradation of organic pollutants.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (6)
1. MQDs/NCDs/TiO2The composite material is characterized in that the MQDs/NCDs/TiO2The composite material is made of TiO2Nanosheets supported on the TiO2The nano-sheet is composed of nitrogen-doped carbon quantum dots and molybdenum disulfide quantum dots, and the MQDs/NCDs/TiO2In the composite material, the loading amounts of the nitrogen-doped carbon quantum dots and the molybdenum disulfide quantum dots are 1wt% -2 wt%.
2. A composite catalytic system for catalytic degradation of organic pollutants, characterized by the MQDs/NCDs/TiO as claimed in claim 12The composite material consists of a composite material and persulfate, wherein in the composite catalytic system, MQDs/NCDs/TiO2The mass ratio of the composite material to the persulfate is 1 (0.25-1).
3. The composite catalytic system for catalytic degradation of organic pollutants as claimed in claim 2, wherein, in the composite catalytic system, MQDs/NCDs/TiO2The mass ratio of the composite material to the persulfate is 2: 1.
4. A method for improving the degradation efficiency of organic pollutants, which is characterized by comprising the following steps:
(1) MQDs/NCDs/TiO in the composite catalytic system of claim 2 or 32Composite materialAdding the mixture into an organic pollutant solution to be treated, and stirring the mixture evenly in the dark;
(2) adding persulfate with the formula amount into the organic pollutant solution, and carrying out photocatalytic reaction under visible light, wherein the photocatalytic reaction is carried out on MQDs/NCDs/TiO2The composite material and the activated persulfate realize the efficient degradation of the organic pollutants under the synergistic action.
5. The method for improving degradation efficiency of organic pollutants according to claim 4, wherein in the step (1), the organic pollutants are rhodamine B or methylene blue.
6. The method for improving the degradation efficiency of organic pollutants according to claim 4, wherein the molar concentration of the persulfate in the organic pollutant solution in the step (2) is 1-4 mM.
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