CN115193439B - Three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 Preparation method and application of photocatalyst - Google Patents
Three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 Preparation method and application of photocatalyst Download PDFInfo
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- CN115193439B CN115193439B CN202210420370.5A CN202210420370A CN115193439B CN 115193439 B CN115193439 B CN 115193439B CN 202210420370 A CN202210420370 A CN 202210420370A CN 115193439 B CN115193439 B CN 115193439B
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims description 12
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 44
- 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 claims abstract description 25
- 229960000907 methylthioninium chloride Drugs 0.000 claims abstract description 25
- 239000004005 microsphere Substances 0.000 claims abstract description 23
- 239000004793 Polystyrene Substances 0.000 claims abstract description 20
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000011259 mixed solution Substances 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 15
- 150000003839 salts Chemical class 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 13
- 239000006185 dispersion Substances 0.000 claims abstract description 11
- 239000002243 precursor Substances 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000007788 liquid Substances 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract description 6
- 239000008139 complexing agent Substances 0.000 claims abstract description 5
- 238000001035 drying Methods 0.000 claims abstract description 5
- 238000001704 evaporation Methods 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 5
- 150000000703 Cerium Chemical class 0.000 claims abstract description 3
- 150000002603 lanthanum Chemical class 0.000 claims abstract description 3
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 24
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid group Chemical group C(CC(O)(C(=O)O)CC(=O)O)(=O)O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 21
- 229920002223 polystyrene Polymers 0.000 claims description 14
- 239000002351 wastewater Substances 0.000 claims description 12
- 230000003197 catalytic effect Effects 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 8
- -1 lanthanum ions Chemical class 0.000 claims description 7
- 238000001179 sorption measurement Methods 0.000 claims description 6
- 229910052684 Cerium Inorganic materials 0.000 claims description 5
- 229910052746 lanthanum Inorganic materials 0.000 claims description 5
- 230000015556 catabolic process Effects 0.000 claims description 4
- 238000006731 degradation reaction Methods 0.000 claims description 4
- 238000006555 catalytic reaction Methods 0.000 claims description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 3
- 229910021645 metal ion Inorganic materials 0.000 claims description 3
- 230000000593 degrading effect Effects 0.000 claims description 2
- 235000019441 ethanol Nutrition 0.000 claims description 2
- 230000000630 rising effect Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 11
- 238000003980 solgel method Methods 0.000 abstract description 5
- 229920003229 poly(methyl methacrylate) Polymers 0.000 abstract description 3
- 239000004926 polymethyl methacrylate Substances 0.000 abstract description 3
- 150000002739 metals Chemical class 0.000 abstract description 2
- 238000013033 photocatalytic degradation reaction Methods 0.000 abstract description 2
- 229920005553 polystyrene-acrylate Polymers 0.000 abstract description 2
- 239000003054 catalyst Substances 0.000 description 37
- 229910017771 LaFeO Inorganic materials 0.000 description 24
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 9
- 238000005516 engineering process Methods 0.000 description 7
- 230000031700 light absorption Effects 0.000 description 7
- 239000011148 porous material Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000001699 photocatalysis Effects 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 238000004220 aggregation Methods 0.000 description 3
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- 239000000987 azo dye Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 description 3
- SZQUEWJRBJDHSM-UHFFFAOYSA-N iron(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O SZQUEWJRBJDHSM-UHFFFAOYSA-N 0.000 description 3
- GJKFIJKSBFYMQK-UHFFFAOYSA-N lanthanum(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GJKFIJKSBFYMQK-UHFFFAOYSA-N 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 229910017135 Fe—O Inorganic materials 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
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- 125000003118 aryl group Chemical group 0.000 description 1
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- 239000003795 chemical substances by application Substances 0.000 description 1
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- 238000004042 decolorization Methods 0.000 description 1
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- 238000004043 dyeing Methods 0.000 description 1
- 238000007210 heterogeneous catalysis Methods 0.000 description 1
- 239000002815 homogeneous catalyst Substances 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- MCPLVIGCWWTHFH-UHFFFAOYSA-L methyl blue Chemical compound [Na+].[Na+].C1=CC(S(=O)(=O)[O-])=CC=C1NC1=CC=C(C(=C2C=CC(C=C2)=[NH+]C=2C=CC(=CC=2)S([O-])(=O)=O)C=2C=CC(NC=3C=CC(=CC=3)S([O-])(=O)=O)=CC=2)C=C1 MCPLVIGCWWTHFH-UHFFFAOYSA-L 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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- 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
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/009—Compounds containing, besides iron, two or more other elements, with the exception of oxygen or hydrogen
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/722—Oxidation by peroxides
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
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- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
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Abstract
The invention relates to a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A method of preparing a photocatalyst comprising: s1, dispersing polystyrene and/or polymethyl methacrylate microspheres in anhydrous lower alcohol to obtain a dispersion liquid; dissolving soluble lanthanum salt, cerium salt, ferric salt and complexing agent in water to obtain a metal salt mixed solution; s2, mixing the dispersion liquid with the metal salt mixed solution, carrying out ultrasonic treatment, evaporating at the temperature of less than or equal to 90 ℃ until a gel substance is obtained, and drying to obtain the three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A precursor; s3, 3DOMLa 0.4 Ce 0.6 FeO 3 Roasting the precursor in air atmosphere at multiple steps to obtain three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A photocatalyst. According to the invention, polystyrene (PS) microspheres are used as templates, and then a sol-gel method is used for doping active metals of specific types and specific proportions to prepare the three-dimensional ordered macroporous structural material, so that the activity of photocatalytic degradation of methylene blue and the removal rate of COD and TOC can be remarkably improved, and the utilization rate of hydrogen peroxide is improved.
Description
Technical Field
The invention relates to the technical field of photocatalysts, in particular to a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A preparation method and application of a photocatalyst.
Background
The printing and dyeing wastewater has the characteristics of large discharge amount, high content of refractory organic matters, strong alkalinity and the like, so that the treatment difficulty is extremely high. Methylene blue is an azo dye, and the aromatic structure of the azo dye is not easily damaged, so that the azo dye is difficult to degrade by the traditional methods such as biochemical method, chemical oxidation and the like. Advanced oxidation technology is carried out by external energy (light energy, electric energy, etc.) and substances (O) 3 、H 2 O 2 Etc.) through a series of physicochemical processes, generating hydroxyl radicals (.oh). As the oxidation potential of OH is as high as 2.8V, most of organic matters in the wastewater can be oxidized, so that the advanced oxidation technology has wide application prospect. Photo Fenton technology and photocatalytic technology are commonly used advanced oxidation technologies. The two technologies can produce extremely strong oxidizing free radicals by absorbing light radiation to realize the efficient degradation of pollutants, and have the advantages of mild reaction conditions, wide application range, high treatment efficiency, thorough damage to pollutants and the like. The traditional homogeneous photocatalyst has higher catalytic activity, but has the problems of narrow pH range, difficult recovery, large iron mud production and the like, so the heterogeneous photocatalyst becomes a research hot spot. Commonly used photocatalysts such as TiO 2 Requires ultraviolet light to excite, while ultraviolet light only occupies natural lightAbout 5%, which limits its efficient operation in sunlight.
Perovskite type oxides are a class of oxides having a structure similar to natural perovskite (CaTiO 3 ) Composite oxide with same cubic crystal structure and its chemical general formula is ABO 3 The A and B positions can be replaced by ions of the same or different valence, with A 1-x A′ x B 1-y B′ y O 3+δ And (3) representing. The perovskite oxide has wide application prospect in the heterogeneous catalysis field due to the stable crystal structure, high catalytic activity and great flexibility of lattice adaptation cation substitution. However, in the prior art, perovskite catalysts prepared by a traditional sol-gel method and a coprecipitation method exist in nano-scale particles, so that the particle aggregation degree is high, the specific surface area is small, the exposure of active sites is not facilitated, and the application of the perovskite catalysts in the field of catalysis is further limited.
Disclosure of Invention
First, the technical problem to be solved
In view of the defects and shortcomings of the prior art, the invention provides a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 The preparation method and the application of the photocatalyst solve the problems of narrow pH application range, high particle aggregation degree, small specific surface area, less exposure of active sites, high iron mud yield and unfavorable recovery and separation of the traditional homogeneous catalyst.
(II) technical scheme
In order to achieve the above purpose, the main technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A method of preparing a photocatalyst, comprising:
s1, dispersing polystyrene and/or polymethyl methacrylate microspheres in anhydrous lower alcohol to obtain a dispersion liquid; dissolving soluble lanthanum salt, cerium salt, ferric salt and complexing agent in water to obtain a metal salt mixed solution;
s2, mixing the dispersion liquid with the metal salt mixed solution, carrying out ultrasonic treatment, evaporating at the temperature of less than or equal to 90 ℃ until a gel-like substance is obtained, and drying to obtain the three-dimensional ordered macroporousLa 0.4 Ce 0.6 FeO 3 A precursor;
s3, 3DOMLa 0.4 Ce 0.6 FeO 3 Roasting the precursor in air atmosphere at multiple steps to obtain three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A photocatalyst.
According to the preferred embodiment of the invention, in S1, polystyrene microspheres are placed in absolute ethyl alcohol and stirred for at least 30min to obtain a dispersion; the mass ratio of the polystyrene microsphere to the absolute ethyl alcohol is 2:6-10, preferably 2:8. In addition, the polystyrene microsphere can be replaced by polymethyl methacrylate microsphere or the two microspheres can be mixed for use. Both microspheres can be thoroughly removed by roasting, and have specific gravity very similar to that of water, and can be suspended in a system under the condition of stirring or ultrasound, so that the three-dimensional ordered macroporous structure is distributed in the whole catalyst material.
According to a preferred embodiment of the present invention, in S1, the molar ratio of lanthanum, cerium and iron ions in the metal salt mixed solution is 0.4:0.59-0.61:0.99-1.02; preferably 0.4:0.6:1.
according to a preferred embodiment of the present invention, in S1, in the metal salt mixed solution, the complexing agent is citric acid, and a total molar ratio of citric acid to metal ions is 1:1.
According to the preferred embodiment of the invention, in S1, the molar concentration of lanthanum ions in the metal salt mixed solution is 0.029-0.0306mol/L, and the concentration of cerium ions is 0.0445-0.045mol/L, and 0.074-0.075mol/L.
According to a preferred embodiment of the invention, in S2, the gel-like material is dried at 80-100deg.C for 6-12h.
According to the preferred embodiment of the invention, in S3, the temperature rising speed of the multi-stage temperature roasting is 70-80 ℃/h; and the roasting is divided into three stages: the first stage: heating to 180-250 ℃ in an air atmosphere (preferably 200 ℃) and roasting for 1.5-2.5 hours, wherein in the second stage: heating to 350-450 deg.c (preferably 300 deg.c) and roasting for 1.5-2.5 hr, and roasting at 750-850 deg.c (preferably 800 deg.c) and 2.5-3.5 hr. In the multi-stage temperature roasting process, PS is burnt out and removed, three-dimensional macropores are left, meanwhile, after high-temperature roasting, solid solution is formed between metal elements, and Ce plays a better doping role, so that the photocatalytic activity is improved.
In a second aspect, the present invention provides a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A photocatalyst prepared by the preparation method of any one of the above examples.
In a third aspect, the invention also provides a three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 The application of the photocatalyst in heterogeneous photo Fenton catalytic degradation of methylene blue.
Preferably, the method comprises the steps of:
step 1: three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 The photocatalyst is added into the wastewater containing methylene blue to carry out dark adsorption, and the adding amount is as follows>0.4g/L；
Step 2: turning on a light source, adding hydrogen peroxide, adjusting pH to be 2-10, wherein the wavelength of the light source is 400-460 nm, and the adding amount of the hydrogen peroxide is 0.1-0.5mL/L.
Preferably, the three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 The addition amount of the photocatalyst is 0.5g/L; the light source wavelength was 420nm.
Preferably, the reaction time in step 2 is not less than 60min.
Wherein the concentration of the methylene blue is 50-100mg/L, and the COD is 50-200mg/L.
(III) beneficial effects
(1) According to the invention, the Polystyrene (PS) microspheres are used as templates to prepare the three-dimensional ordered macroporous structural material, the specific structure of the three-dimensional ordered macroporous structural material can obviously improve the specific surface area of the catalyst, more active sites are exposed, the number of active sites on the surface of the catalyst is greatly increased, and the catalytic activity of the photocatalyst is effectively improved. Compared with the traditional perovskite catalyst, the three-dimensional ordered macroporous structure has rich pore channels and larger specific surface area, and the pore channels have the characteristics of large pore diameter, uniform distribution and ordered arrangement. The abundant pore canal structure can increase the specific surface area of the catalyst, is beneficial to the contact of reactants and active sites, and further improves the activity of the catalyst.
(2) According to the invention, on the basis of taking Polystyrene (PS) microspheres as templates, a sol-gel method is used in combination to dope active metals of specific types and specific proportions, so that the catalytic effect is greatly improved. The doped Ce increases the light absorption capacity, and can remarkably improve the catalytic methylene blue removal rate, COD removal rate and TOC removal rate.
(3) The preparation method is simple, has better industrial application prospect, can greatly improve the catalytic performance through multi-stage calcination treatment, and is a reliable photocatalyst preparation process in the field of water treatment.
Drawings
FIG. 1 shows the product of example 1 and 3DOMLa of example 2 0.4 Ce 0.6 FeO 3 Fourier transform infrared spectrogram of photocatalyst.
FIG. 2 shows the product of example 1 and 3DOMLa of example 2 0.4 Ce 0.6 FeO 3 X-ray diffraction pattern of the photocatalyst.
Fig. 3 is an SEM image of PS microspheres.
FIG. 4 shows a block La prepared in example 1 0.4 Ce 0.6 FeO 3 SEM images of (a).
FIGS. 5 and 6 show 3DOMLa of three-dimensional ordered macroporous structures at different multiples 0.4 Ce 0.6 FeO 3 SEM images of (a).
FIG. 7 shows the observation of LaFeO by X-ray photoelectron spectroscopy 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 Pattern one of the surface active component element valence states.
FIG. 8 shows the observation of LaFeO by X-ray photoelectron spectroscopy 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 Surface active component elementAnd a second diagram of valence state.
FIG. 9 is a graph of LaFeO observed using UV-visible diffuse reflection technique 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 Absorbance spectrum of the catalyst.
FIG. 10 is a graph of La at various initial pH values 0.4 Ce 0.6 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.2 Ce 0.8 FeO 3 、LaFeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 And ferrous sulfate heptahydrate is used for decoloring methylene blue and comparing the removal rates of COD and TOC; (a) is the effect of initial pH on the decolorization ratio, (b) is the effect of initial pH on COD, and (c) is the effect of initial pH on TOC (total organic carbon).
FIG. 11 shows La at various hydrogen peroxide addition levels 0.4 Ce 0.6 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.2 Ce 0.8 FeO 3 、LaFeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 And ferrous sulfate heptahydrate is used for decoloring methylene blue and comparing the removal rates of COD and TOC; (a) is the influence of the addition amount of hydrogen peroxide on the decoloring rate, (b) is the influence of the addition amount of hydrogen peroxide on COD, and (c) is the influence of the addition amount of hydrogen peroxide TOC (total organic carbon).
Detailed Description
The invention will be better explained by the following detailed description of the embodiments with reference to the drawings.
Example 1
LaFeO was prepared by the following steps 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 。
(1) Dissolving lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, 1.0000g ferric nitrate nonahydrate and 1.0403g citric acid in 100ml deionized water, and placing the solution on a magnetic stirrer for stirring for 30min to obtain a mixed solution;
(2) Evaporating the mixed solution to gel at 80 ℃, and drying the gel at 80-100 ℃ for 6-12h to obtain a precursor;
(3) And (3) placing the precursor in a tubular heating furnace, and roasting for 2h at a constant speed for 3h to 200 ℃ and for 2h at a constant speed for 3h to 400 ℃ and for 2h and for 3h to 750 ℃ in an air atmosphere to obtain the target product.
Sequentially controlling the molar quantity of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate and ferric nitrate nonahydrate in the step (1) to ensure that the molar ratio of lanthanum, cerium and iron elements in the mixed solution is 1:0:1, 0.8:0.2:1, 0.6:0.4:1, 0.4:0.6:1 and 0.2:0.8:1, wherein the citric acid dosage is the total molar quantity of metal ions, and finally obtaining the product LaFeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 。
The photocatalytic activity of each of the above products as a photocatalyst for degrading methylene blue in wastewater was tested by the following method:
the photocatalyst LaFeO prepared above is treated under the condition of pH=3 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 Adding the catalyst into the wastewater containing methylene blue, performing dark adsorption for 30min, turning on a light source, simultaneously adding hydrogen peroxide with the catalyst dosage of 0.5g/L, the light source wavelength of 420nm, the hydrogen peroxide adding amount of 0.5mL/L, and the reaction time of 60min. In the wastewater, the concentration of methylene blue is 50mg/L, and the COD is 200mg/L.
The experimental results are shown in table 1.
TABLE 1
| Catalyst | Methylene blue removal/% | COD removal rate/% |
| LaFeO 3 | 62.33 | 45.66 |
| La 0.8 Ce 0.2 FeO 3 | 75.42 | 54.89 |
| La 0.6 Ce 0.4 FeO 3 | 80.26 | 61.24 |
| La 0.4 Ce 0.6 FeO 3 | 95.89 | 85.46 |
| La 0.2 Ce 0.8 FeO 3 | 85.46 | 78.55 |
As is clear from Table 1, the reaction conditions are different from LaFeO 3 (Ce-undoped) photocatalyst, la 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 And La (La) 0.2 Ce 0.8 FeO 3 The catalyst has higher methylene blue removal rate and COD removal rate, which shows that doping Ce can obviously improve LaFeO 3 Is a catalyst activity of (a). La (La) 0.4 Ce 0.6 FeO 3 The highest methylene blue degradation efficiency is achieved in the test range, so that the optimal doping ratio is selected as La: ce=0.4: 0.6. thus in the following experiments La of three-dimensional ordered macroporous structure was prepared 0.4 Ce 0.6 FeO 3 。
Example 2
La of three-dimensional ordered macroporous Structure was prepared in this example 0.4 Ce 0.6 FeO 3 The preparation method of the photocatalyst comprises the following steps:
(1) 2.0g of Polystyrene (PS) microspheres were placed in 10mL of absolute ethanol and stirred on a magnetic stirrer for 60min to obtain a dispersion.
(2) 1.2862g of lanthanum nitrate hexahydrate, 1.9346g of cerium nitrate hexahydrate, 3.0000g of ferric nitrate nonahydrate and 3.1206g of citric acid were weighed and dissolved in 100ml of deionized water, and placed on a magnetic stirrer to stir for 30 minutes, thereby obtaining a metal mixed solution.
(3) Mixing the dispersion with the metal mixed solution, ultrasonic treating, mixing, evaporating at 80deg.C to gel, and drying gel at 80-100deg.C for 6-12 hr to obtain 3DOM (three-dimensional ordered macroporous structure) La 0.4 Ce 0.6 FeO 3 A precursor.
(4) The precursor is placed in a tubular heating furnace, and is heated to 200 ℃ at a constant speed for 3 hours under the air atmosphere, roasting for 2h, uniformly heating to 400 ℃ for 3h, roasting for 2h, uniformly heating to 750 ℃ for 3h, and roasting for 3h to obtain the 3DOMLa 0.4 Ce 0.6 FeO 3 A photocatalyst.
3DOMLa was tested as follows 0.4 Ce 0.6 FeO 3 Photocatalytic activity of photocatalyst to degrade methylene blue in wastewater:
3DOMLa photocatalyst under the condition of pH=3 0.4 Ce 0.6 FeO 3 Adding the catalyst into wastewater containing methylene blue, performing dark adsorption for 30min, turning on a light source, simultaneously adding hydrogen peroxide with the catalyst dosage of 0.5g/L, the light source wavelength of 420nm and the hydrogen peroxide adding amount of 0.5mL/L, and reactingThe time was 60min. In the wastewater, the concentration of methylene blue is 50mg/L, and the COD is 200mg/L. The experimental results are: methylene blue removal/% = 99%, COD removal/% = 92.55%.
La prepared in example 1 0.4 Ce 0.6 FeO 3 Compared with the three-dimensional ordered macroporous structure 3DOMLa prepared in the embodiment 0.4 Ce 0.6 FeO 3 The catalyst has remarkably higher methyl blue removal rate, COD removal rate and TOC (total organic carbon) removal rate, because the three-dimensional ordered macroporous structure has rich pore channels, the specific surface area of the catalyst is increased, and the catalytic activity of the catalyst is further improved. From this, it can be demonstrated that the 3DOMLa of the present invention 0.4 Ce 0.6 FeO 3 The photocatalyst has remarkable progress in photocatalytic degradation of organic matters in water.
Characterization of the product
(1) The product prepared in example 1 was combined with 3DOMLa prepared in example 2 0.4 Ce 0.6 FeO 3 The phase structure of each material is shown in figures 1-2, which are observed by adopting a Fourier transform infrared spectrum and an X-ray diffractometer.
In FIG. 1, the transmittance curves correspond to LaFeO from top to bottom 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.2 Ce 0.8 FeO 3 、La 0.4 Ce 0.6 FeO 3 、3DOMLa 0.4 Ce 0.6 FeO 3 。
In FIG. 2, the X-ray intensity curves correspond to 3DOMLa from top to bottom 0.4 Ce 0.6 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、LaFeO 3 。
As shown in FIG. 1, 3DOMLa 0.4 Ce 0.6 FeO 3 、La 1-x Ce x FeO 3 (x= 0.2,0.4,0.6,0.8) and LaFeO 3 Are all 540cm in spectral line -1 Asymmetric stretching vibration with Fe-O bond nearbyAbsorption peak representing typical FeO 6 The octahedral clusters prove that all the catalysts prepared by experiments show perovskite structures. As can be seen from FIG. 2, the XRD spectrum shows that doping Ce does not destroy the perovskite structure, la 0.4 Ce 0.6 FeO 3 The diffraction peak of (c) is stronger and sharper, indicating that the doped catalyst crystallinity is higher when x=0.6. 3DOMLa 0.4 Ce 0.6 FeO 3 The intensity and sharpness of the diffraction peaks were significantly higher, indicating 3DOMLa 0.4 Ce 0.6 FeO 3 Has a specific La 0.4 Ce 0.6 FeO 3 Higher crystallinity and crystal stability.
(2) PS microspheres were observed by scanning electron microscopy, la prepared in example 1 0.4 Ce 0.6 FeO 3 And 3DOMLa of three-dimensional ordered macroporous structure prepared in example 2 0.4 Ce 0.6 FeO 3 Is a surface morphology of (a). As shown in fig. 3-6. FIG. 3 shows PS microspheres with regular morphology and uniform diameter distribution around 2. Mu.m. FIG. 4 shows a block La prepared in example 1 0.4 Ce 0.6 FeO 3 5-6 are SEM images of three-dimensional ordered macroporous structures of 3DOMLa 0.4 Ce 0.6 FeO 3 SEM images of (a). As can be seen from fig. 4 to 6, the perovskite catalyst prepared by the conventional sol-gel method and coprecipitation method mostly exists as nano-sized particles, the aggregation degree of the particles is high, a block structure with smooth surface is formed, the specific surface area of the catalyst is limited by the structure (fig. 4), and 3DOMLa prepared by using PS microspheres as a template agent 0.4 Ce 0.6 FeO 3 The surface has a large number of holes (FIGS. 5-6), the pore diameter is about 2 μm, which is equivalent to the diameter of PS microsphere and La 0.4 Ce 0.6 FeO 3 Compared with the 3DOM structure, the specific surface area of the catalyst is obviously improved, the exposure of active sites is facilitated, and the activity of the catalyst is further improved. In the preparation process, the microsphere dispersion liquid and the mixed salt solution are subjected to ultrasonic dispersion, and the specific gravity of the PS microspheres is close to that of water, so that the PS microspheres can be suspended in a reaction system, and then evaporated to dryness, gelled and roasted in multiple stages to obtain the 3DOMLa 0.4 Ce 0.6 FeO 3 The pores on the surface are distributed very uniformly.
(3) By specific surface area and holesThe clearance degree analyzer observes 3DOMLa 0.4 Ce 0.6 FeO 3 And La (La) 0.4 Ce 0.6 FeO 3 Texture properties of (a) are shown in table 2 below:
TABLE 2
| Catalyst | Specific surface area/m 2 ·g -1 |
| 3DOMLa 0.4 Ce 0.6 FeO 3 | 70.89 |
| La 0.4 Ce 0.6 FeO 3 | 5.231 |
Calculated 3DOMLa 0.4 Ce 0.6 FeO 3 Is La 0.4 Ce 0.6 FeO 3 13.55 times of the specific surface area shows that the 3DOM structure remarkably increases the specific surface area of the catalyst.
(4) Observation of LaFeO by X-ray photoelectron spectrometer 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 The surface active component element valence states are shown in fig. 7-8.
As can be seen from FIG. 7, for Fe2p 3/2 Performing peak-splitting fitting on the track, and performing LaFeO 3 Fe is Fe 3+ In the form of a gel. La (La) 1-x Ce x FeO 3 In the presence of Fe 2+ It is shown that doping Ce promotes Fe in the crystal lattice 3+ To Fe 2+ Conversion, and further improves catalytic efficiency. When x=0.6, fe 2+ The content is 100 percent, 3DOMLa 0.4 Ce 0.6 FeO 3 Wherein Fe is also Fe 2+ In the form of a gel.
As shown in FIG. 8, in 3DOMLa 0.4 Ce 0.6 FeO 3 And La (La) 1-x Ce x FeO 3 In Ce 3+ And Ce (Ce) 4+ Is coexistent and has a content of about 15% and 85%. A great deal of literature indicates Fe 2+ Catalytic activity in photo Fenton is higher than that of Fe 3+ Doping Ce significantly increases the activity of the perovskite catalyst.
(5) Observing LaFeO by ultraviolet visible diffuse reflection technology 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.2 Ce 0.8 FeO 3 And 3DOMLa 0.4 Ce 0.6 FeO 3 Light absorption properties of the catalyst. As shown in FIG. 9, the curves correspond to 3DOMLa from top to bottom 0.4 Ce 0.6 FeO 3 、La 0.4 Ce 0.6 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.2 Ce 0.8 FeO 3 、LaFeO 3 。
As shown in FIG. 9, laFeO prepared by sol-gel method 3 Has obvious absorption band in the wavelength range of 200-800nm, la 1-x Ce x FeO 3 The catalyst has a specific LaFeO in the visible light region 3 Higher light absorption intensity, showing that doping Ce improves LaFeO 3 The light absorbing capacity of the catalyst. When x=0.6, la 0.4 Ce 0.6 FeO 3 The light absorption intensity is strong, which indicates that the light absorption capacity is good. 3DOMLa 0.4 Ce 0.6 FeO 3 Has a specific La 0.4 Ce 0.6 FeO 3 The higher light absorption capacity shows that the 3DOM structure is beneficial to the increase of the specific surface area of the catalyst, the light transmittance is enhanced, the light absorption capacity is improved, and the photocatalytic activity is further improved.
Comparative example 1
Taking 0.6561g of commercial ferrous sulfate heptahydrate as a catalyst, adding the ferrous sulfate heptahydrate into wastewater containing methylene blue under a certain pH value range, performing dark adsorption for 30min, turning on a light source, simultaneously adding hydrogen peroxide with the pH of 2-0, wherein the dosage of the catalyst is 0.5g/L, the wavelength of the light source is 420nm, the adding amount of the hydrogen peroxide is 0.5mL/L, the reaction time is 60min, and detecting the concentration of Fe in the water by adopting ICP-MS after the reaction. Meanwhile, la prepared in example 1 was also tested 0.4 Ce 0.6 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.2 Ce 0.8 FeO 3 、LaFeO 3 And 3DOMLa prepared in example 2 0.4 Ce 0.6 FeO 3 Parallel comparison experiments were performed. The experimental results are shown in table 3 and fig. 10.
TABLE 3 Table 3
| Initial pH | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Fe/mg·L -1 | 0.45 | 0.32 | 0.25 | 0.20 | 0.19 | 0.06 | 0.02 | 0.00 | 0.00 |
FIG. 10 (a) shows the effect of initial pH on the decoloring ratio, (b) shows the effect of initial pH on COD, and (c) shows the effect of initial pH on TOC (total organic carbon).
As is clear from Table 3, the iron ion content was 0.50mg/L lower than that of ferrous sulfate heptahydrate (132 mg/L in terms of iron). As can be seen from FIG. 10, compared with LaFeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.2 Ce 0.8 FeO 3 And ferrous sulfate heptahydrate (bottom curve of each figure), 3DOMLa prepared by the present invention 0.4 Ce 0.6 FeO 3 The highest methylene blue removal rate, COD removal rate and TOC removal rate (corresponding to the uppermost curve of each graph) were all obtained in the pH range of 2 to 10, indicating that La with 3DOM morphology 0.4 Ce 0.6 FeO 3 Has wider pH application range (pH=2-10) and less iron sludge generation.
Comparative example 2
Taking 0.6561g of commercial ferrous sulfate heptahydrate as a catalyst, adding the catalyst and the ferrous sulfate heptahydrate into wastewater containing methylene blue at the pH value of 3, carrying out dark adsorption for 30min, turning on a light source, simultaneously adding hydrogen peroxide, wherein the adding amount of the catalyst is 0.5g/L, the wavelength of the light source is 420nm, the adding amount of the hydrogen peroxide is 0.1-0.5mL/L, and the reaction time is 60min. Meanwhile, the experiment is also performed as in example 1La of the preparation 0.4 Ce 0.6 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.2 Ce 0.8 FeO 3 、LaFeO 3 And 3DOMLa prepared in example 2 0.4 Ce 0.6 FeO 3 Parallel comparison experiments were performed. The experimental results are shown in FIG. 11.
Fig. 11 (a) shows the influence of the amount of hydrogen peroxide added on the decoloring rate, (b) shows the influence of the amount of hydrogen peroxide added on COD, and (c) shows the influence of the amount of hydrogen peroxide added TOC (total organic carbon).
As can be seen from FIG. 11, compared with LaFeO 3 、La 0.8 Ce 0.2 FeO 3 、La 0.6 Ce 0.4 FeO 3 、La 0.2 Ce 0.8 FeO 3 And ferrous sulfate heptahydrate (second curve from top), 3DOMLa 0.4 Ce 0.6 FeO 3 (corresponding to the uppermost curve of each graph) the removal rate of methylene blue, COD and TOC in the hydrogen peroxide range of 0.1-0.5mL/L are all highest, showing that the 3DOMLa prepared by the invention 0.4 Ce 0.6 FeO 3 Has higher hydrogen peroxide utilization rate.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (8)
1. Three-dimensional ordered macroporous La for heterogeneous photo Fenton catalysis 0.4 Ce 0.6 FeO 3 A method for preparing a photocatalyst, comprising:
s1, dispersing polystyrene microspheres in anhydrous lower alcohol to obtain a dispersion liquid; dissolving soluble lanthanum salt, cerium salt, ferric salt and complexing agent in water to obtain a metal salt mixed solution; in the metal salt mixed solution, the molar concentration of lanthanum ions is 0.029-0.0306mol/L, and the concentration of cerium ions is 0.0445-0.045mol/L, and 0.074-0.075 mol/L; in the metal salt mixed solution, the mole ratio of lanthanum, cerium and iron ions is 0.4:0.59-0.61:0.99-1.02;
s2, mixing the dispersion liquid with the metal salt mixed solution, carrying out ultrasonic treatment, evaporating at the temperature of less than or equal to 90 ℃ until a gel substance is obtained, and drying to obtain the three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A precursor;
s3, 3DOMLa 0.4 Ce 0.6 FeO 3 Roasting the precursor in air atmosphere at multiple steps to obtain three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 A photocatalyst;
the temperature rising speed of the multi-stage temperature roasting is 70-80 ℃/h; and the roasting is divided into three stages: the first stage: heating to 180-250 ℃ in an air atmosphere, roasting for 1.5-2.5h, and in the second stage: heating to 350-450 deg.c and roasting for 1.5-2.5 hr, and in the third stage, roasting at 750-850 deg.c for 2.5-3.5 hr.
2. The preparation method according to claim 1, wherein in S1, polystyrene microspheres are placed in absolute ethanol and stirred for at least 30min to obtain a dispersion; the mass ratio of the polystyrene microsphere to the absolute ethyl alcohol is 2:6-10.
3. The preparation method according to claim 1, wherein in S1, the complexing agent is citric acid, and the total molar ratio of citric acid to metal ions is 1:1.
4. The method according to claim 1, wherein the gel-like material is dried at 80 to 100℃for 6 to 12 hours in S2.
5. Three-dimensional ordered macroporous La for heterogeneous photo Fenton catalysis 0.4 Ce 0.6 FeO 3 A photocatalyst, characterized by the followingThe process according to any one of claims 1 to 4.
6. A three-dimensional ordered macroporous La as defined in claim 5 0.4 Ce 0.6 FeO 3 The application of the photocatalyst in heterogeneous photo Fenton catalytic degradation of methylene blue.
7. The use according to claim 6, wherein the step of degrading methylene blue comprises: step 1: three-dimensional ordered macroporous La 0.4 Ce 0.6 FeO 3 The photocatalyst is added into the wastewater containing methylene blue to carry out dark adsorption, and the adding amount is as follows>0.4 g/L；
Step 2: turning on a light source, adding hydrogen peroxide, adjusting pH to be 2-10, wherein the wavelength of the light source is 400-460 nm, and the adding amount of the hydrogen peroxide is 0.1-0.5mL/L.
8. The use according to claim 7, characterized in that the three-dimensionally ordered macropores La 0.4 Ce 0.6 FeO 3 The addition amount of the photocatalyst is 0.5g/L; the light source wavelength was 420nm.
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| CN101992089A (en) * | 2010-10-29 | 2011-03-30 | 中国石油大学(北京) | Three-dimensional ordered porous-mesoporous iron-based perovskite oxide catalyst and preparation method thereof |
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