CN117160437A - Defective calcium hydroxystannate photocatalyst and preparation method and application thereof - Google Patents
Defective calcium hydroxystannate photocatalyst and preparation method and application thereof Download PDFInfo
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- 239000011575 calcium Substances 0.000 title claims abstract description 45
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 229910052791 calcium Inorganic materials 0.000 title claims abstract description 35
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 30
- 230000002950 deficient Effects 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims abstract description 108
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims abstract description 38
- 230000007547 defect Effects 0.000 claims abstract description 35
- 239000002253 acid Substances 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 19
- 229910006404 SnO 2 Inorganic materials 0.000 claims abstract description 17
- 230000001699 photocatalysis Effects 0.000 claims abstract description 17
- 238000012986 modification Methods 0.000 claims abstract description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 30
- 229910004767 CaSn Inorganic materials 0.000 claims description 29
- 238000006731 degradation reaction Methods 0.000 claims description 21
- 230000015556 catabolic process Effects 0.000 claims description 20
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 16
- 150000003839 salts Chemical class 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 239000000843 powder Substances 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 8
- 239000002244 precipitate Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 4
- 229910002651 NO3 Inorganic materials 0.000 claims description 4
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 3
- 230000001376 precipitating effect Effects 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 2
- 229910017604 nitric acid Inorganic materials 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 14
- 238000000926 separation method Methods 0.000 abstract description 8
- 230000003197 catalytic effect Effects 0.000 abstract description 7
- 239000011148 porous material Substances 0.000 abstract description 7
- 238000005530 etching Methods 0.000 abstract description 6
- 239000000969 carrier Substances 0.000 abstract description 4
- 238000000975 co-precipitation Methods 0.000 abstract description 2
- 230000032683 aging Effects 0.000 abstract 1
- 150000001669 calcium Chemical class 0.000 abstract 1
- 230000002779 inactivation Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 43
- 230000000052 comparative effect Effects 0.000 description 23
- 238000001179 sorption measurement Methods 0.000 description 11
- 239000003054 catalyst Substances 0.000 description 9
- 230000004048 modification Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- -1 hydroxyl radicals Chemical class 0.000 description 5
- 239000000543 intermediate Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 150000003254 radicals Chemical class 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 230000002195 synergetic effect Effects 0.000 description 4
- 229910010413 TiO 2 Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 230000002708 enhancing effect Effects 0.000 description 3
- TUJKJAMUKRIRHC-UHFFFAOYSA-N hydroxyl Chemical compound [OH] TUJKJAMUKRIRHC-UHFFFAOYSA-N 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 2
- 238000004435 EPR spectroscopy Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 230000009849 deactivation Effects 0.000 description 2
- 238000001362 electron spin resonance spectrum Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 230000036541 health Effects 0.000 description 2
- 150000004677 hydrates Chemical class 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 229940071182 stannate Drugs 0.000 description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000000809 air pollutant Substances 0.000 description 1
- 231100001243 air pollutant Toxicity 0.000 description 1
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- 230000033558 biomineral tissue development Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 231100000315 carcinogenic Toxicity 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000012824 chemical production Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000003933 environmental pollution control Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 230000001089 mineralizing effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 238000013033 photocatalytic degradation reaction Methods 0.000 description 1
- 238000013032 photocatalytic reaction Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
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- 238000001308 synthesis method Methods 0.000 description 1
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- 239000012855 volatile organic compound Substances 0.000 description 1
Classifications
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- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The application relates to the field of photocatalytic materials, and discloses a defective calcium hydroxystannate photocatalyst, and a preparation method and application thereof. The defective calcium hydroxystannate photocatalyst of the application uses hydroxyl defects and SnO 2 Co-modification. The application firstly prepares calcium hydroxystannate by coprecipitation method, then constructs hydroxyl defects by acid etching method, and synchronously generates SnO 2 . The hydroxyl group defect and SnO of the application 2 The co-modified calcium hydroxystannate photocatalyst has high separation efficiency of photo-generated carriers, large specific surface area and pore volume and good catalytic activity for toluene removalThe photocatalyst has long aging time, high stability, difficult inactivation and wide application prospect.
Description
Technical Field
The application relates to the technical field of photocatalytic materials, in particular to a defective calcium hydroxystannate photocatalyst, and a preparation method and application thereof.
Background
Currently, air pollutants pose a serious threat to humans and the environment, and have attracted a great deal of attention. Toluene (C) 7 H 8 ) Is one of important raw materials and common solvents in the chemical production process, and is one of important components of organic gaseous pollutants. The emission of toluene not only seriously damages the environmental safety, causes environmental problems such as photochemical smog, but also is determined by world health organization WHO to be a cancerogenic substance, thereby seriously threatening the health of human bodies. Therefore, there is an urgent need for an efficient, stable and economical low-consumption toluene degradation technology. Semiconductor photocatalytic oxidation technology is considered one of the most promising toluene removal technologies because it can thoroughly mineralize toluene to CO under mild conditions using clean and sustainable solar energy as an energy input 2 And H 2 O, etc.
Titanium dioxide (TiO) 2 ) The method has the advantages of high deactivation speed in the process of photocatalytic degradation of volatile organic compounds, low conversion efficiency, and particularly in the degradation process of aromatic hydrocarbons. This is mainly due to the fact that the benzene ring in toluene has a highly stable large pi-bond structure, and the stable structure needs a strong oxidizing power to be broken, while TiO 2 The problem of insufficient charge separation/transfer kinetics in the photocatalyst, unbalanced free radical generation, which results in lack of sufficient deep oxidation capability, and reduced commercial value. On the other hand, insufficient oxidation capacity produces incompletely oxidized intermediates, which cannot be desorbed effectively, accumulate and occupy the catalyst surface active sites, resulting in TiO 2 Deactivation reduces stability and makes it less catalytic durable.
Calcium hydroxystannate (CaSn (OH) 6 ) The material is considered to promote the generation of hydroxyl radicals with strong oxidizing ability due to the abundant hydroxyl radicals on the surface and proper band gap, and is a possible substitute for TiO 2 Is a novel photocatalytic toluene degradation material. However, caSn (OH) 6 The commercial application of photocatalytic materials still has many challenges to be solved, such as low charge separation efficiency, weak adsorption capacity due to the bulk structure and inert surface, and lack of active sites. To solve such problems, caSn (OH) is mainly prepared by doping, morphology regulation, noble metal deposition and other methods 6 And (5) performing performance optimization. But these are for CaSn (OH) 6 The modification strategy of (2) is often complicated in steps and high in costAnd is not suitable for large-scale industrial production.
Disclosure of Invention
Aiming at the defects existing in the prior art, the application aims to provide a defective calcium hydroxystannate photocatalyst and a preparation method and application thereof, so as to solve the problems of low separation efficiency, weak adsorption capacity, lack of active surface, complicated preparation process steps with optimized performance, high cost and adverse industrialized production of calcium hydroxystannate carriers prepared in the prior art.
In order to solve the technical problems, the application adopts the following technical scheme:
the preparation method of the defective calcium hydroxystannate photocatalyst specifically comprises the following steps:
step 1: preparing an aqueous NaOH solution as a solution A; in the solution A, the concentration of NaOH is 0.2-0.4 mol/L;
step 2: adding Sn salt into the solution A, and uniformly stirring; in the solution A, the concentration of Sn salt is 0.03-0.06 mol/L;
step 3: preparing Ca saline solution as solution B; slowly adding the solution B into the solution A obtained in the step 2, and stirring at a constant speed in the adding process, and reacting for 3-5 h; then, standing and precipitating for 10-14 h to obtain white precipitate, and washing, centrifuging and drying the white precipitate to obtain CaSn (OH) 6 Powder; wherein, in the solution B, the concentration of Ca salt is 0.03-0.06 mol/L;
step 4: caSn (OH) obtained in step 3 6 Adding the powder into acid liquor, stirring for 60-120 min, and washing, centrifuging and drying to obtain the calcium hydroxystannate; wherein CaSn (OH) 6 The molar ratio of the acid solution to the water is 1 (0.5-3).
Preferably, the preparation is CaSn (OH) 6 The raw materials of (1) comprise Ca salt raw materials, sn salt raw materials and acid liquor.
Preferably, the Ca salt includes one or more of hydrochloride, nitrate, sulfate, acetate or their hydrates.
Preferably, the Sn salt includes one or more of hydrochloride, nitrate, sulfate, acetate, or hydrates thereof.
Preferably, the acid solution comprises one or more of hydrochloric acid, nitric acid, sulfuric acid and acetic acid.
Preferably, the defective calcium hydroxystannate has hydroxyl defects and SnO 2 Co-modification.
The application also provides application of the defective calcium hydroxystannate, and the defective calcium hydroxystannate prepared by the preparation method is used for a photocatalyst.
Preferably, the defective calcium hydroxystannate is used to catalyze toluene degradation under ultraviolet light.
Compared with the prior art, the application has the following beneficial effects:
1. the preparation method is improved, so that the prepared calcium hydroxystannate has a huge specific surface area, under the synergistic effect of hydroxyl defects and tin dioxide, the adsorption of the catalyst on toluene and water is enhanced, the carrier separation and the generation of hydroxyl free radicals are accelerated, the surface active sites are enriched, the photocatalytic performance of volatile organic pollutants such as toluene and the like is excellent, the toluene degradation and mineralization rate almost reaches 100%, and the preparation method has wide application prospect in the field of environmental pollution control.
2. The preparation method disclosed by the application is simple to operate, mild in reaction condition, capable of completing preparation of the defective calcium hydroxystannate at normal temperature and normal pressure, high in yield and low in cost, and the obtained defective calcium hydroxystannate has higher catalytic efficiency and has an industrial application prospect.
Drawings
Fig. 1 is an X-ray diffraction (XRD) pattern of example 2 and comparative example 1. Examples 1 to 4 are abbreviated as CSOH-0.05, CSOH-0.1, CSOH-0.15 and CSOH-0.2, comparative example 1 is abbreviated as CSOH, and comparative example 2 is abbreviated as HY (hereinafter).
Fig. 2 is a Scanning Electron Microscope (SEM) image of the samples obtained in example 2 and comparative example 1.
FIG. 3 is a graph showing the (a) specific surface area and (b) pore volume distribution of the samples obtained in example 2 and comparative example 1.
FIG. 4 is an electron paramagnetic resonance spectrum (EPR) of the samples obtained in examples 1 to 4 and comparative example 1.
FIG. 5 is an Electron Spin Resonance (ESR) diagram of hydroxyl radicals of the sample obtained in example 2.
Fig. 6 (a) is a graph of photocatalytic toluene degradation activity of the samples obtained in examples 1 to 4 and comparative examples 1 to 2 and (b) is a graph of photocatalytic toluene degradation cycle test activity of the sample obtained in example 2.
Detailed Description
In order to enable those skilled in the art to better understand the technical solution of the present application, the present application will be further described with reference to specific examples, but the embodiments of the present application are not limited thereto.
Numerical ranges in this disclosure are understood to also specifically disclose each intermediate value between the upper and lower limits of the ranges. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
1. Preparation method of defective calcium hydroxystannate photocatalyst
Step 1: preparing an aqueous NaOH solution as a solution A; in the solution A, the concentration of NaOH is 0.2-0.4 mol/L;
step 2: adding Sn salt into the solution A, and uniformly stirring; in the solution A, the concentration of Sn salt is 0.03-0.06 mol/L;
step 3: preparing Ca saline solution as solution B; slowly adding the solution B into the solution A obtained in the step 2, and stirring at a constant speed in the adding process, and reacting for 3-5 h; then, standing and precipitating for 10-14 h to obtain white precipitate, and washing, centrifuging and drying the white precipitate to obtain CaSn (OH) 6 Powder; wherein, in the solution B, the concentration of Ca salt is 0.03-0.06 mol/L,
step 4: caSn (OH) obtained in step 3 6 Adding the powder into acid liquor, stirring for 60-120 min, and washing, centrifuging and drying to obtain the defective calcium hydroxystannate; wherein CaSn (OH) 6 The molar ratio of the acid solution to the water is 1 (0).5～3)。
In the prior art, tiO 2 Is the most commonly used photocatalytic toluene degradation material, but is rapidly deactivated in the process of degrading aromatic hydrocarbon such as toluene and has low conversion efficiency. This is mainly due to the small number of hydroxyl radicals and the weak oxidizing power, which results in accumulation of intermediate products and occupation of active sites on the catalyst surface, reducing the catalytic stability. The present application contemplates CaSn (OH) with a suitable band gap and enriched surface hydroxyl groups 6 Materials prepared by forming surface hydroxyl defects and SnO 2 Accelerating the generation of hydroxyl free radicals, enhancing the oxidation capability and completely mineralizing toluene into CO 2 And H 2 O has excellent catalytic performance and high stability. The photocatalytic material has rich sources and low price; the preparation is carried out at normal temperature and normal pressure, the synthesis method is simple, convenient and quick, clean and low in carbon consumption, and has the potential of large-scale generation and application.
In some embodiments, the defective calcium hydroxystannate is obtained using an acid etch; wherein CaSn (OH) 6 The molar ratio of the acid solution to the water is 1 (0.5-3). CaSn (OH) 6 The molar ratio of the catalyst to the acid solution is controlled within the range of 1 (0.5-3), which is mainly due to H in the acid solution + And CaSn (OH) 6 Surface hydroxyl groups react to generate hydroxyl defects; on the other hand, hydroxy stannate (Sn (OH) 6 ) 2- Collapse to Sn 4+ Formation of SnO 2 ，Ca 2+ Is removed with the solution to form hydroxyl defects and SnO 2 Co-modified CaSn (OH) 6 A material. However, too high an acid concentration can cause the material to collapse as a whole, with the final product being SnO only 2 Too low a concentration of acid solution only increases the concentration of surface hydroxyl defects and does not form SnO 2 CaSn (OH) 6 The molar ratio of the acid solution to the acid solution needs to be controlled within the range. In addition, the huge specific surface area and pores formed by acid etching enhance the adsorption capacity of the catalyst, and the adsorption capacity of the catalyst is matched with hydroxyl defects and SnO 2 The modification improves the toluene degradation activity and stability of the photocatalyst, almost completely degrades toluene pollutants, and has catalytic performance obviously superior to that of CaSn (OH) which is not subjected to acid etching 6 CaSn (OH) prepared by hydrothermal method 6 And (3) a sample.CaSn (OH) 6 The molar ratio to acid may be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.3, 1:2.0, 1:2.6, 1:3.0, etc., as well as all ranges and subranges therebetween. It is to be understood that any of the above ranges may be combined with any of the other ranges in embodiments.
In some embodiments, the defective calcium hydroxystannate has hydroxyl defects and SnO 2 Co-modification. The hydroxyl defects come mainly from two aspects, firstly the CaSn (OH) 6 And the co-precipitation method is adopted for synthesis, the crystallization is incomplete, department hydroxyl defects can be formed, and then the concentration of the surface hydroxyl defects is further increased by acid etching. SnO (SnO) 2 From H in the acid etching process + Reaction with hydroxy stannate. The hydroxyl defects enable CaSn (OH) 6 The intermediate energy level is generated in the forbidden band to promote the absorption of ultraviolet light, while SnO 2 The synergistic effect of the hydroxyl defect and the hydroxyl defect enhances the separation of carriers; at the same time, snO 2 Co-modification with hydroxyl defects alters its inert surface, increases active sites, promotes H 2 Adsorption activation of O, generation of hydroxyl radical, hydroxyl defect and SnO 2 The synergistic effect of the catalyst greatly improves the photocatalytic toluene degradation activity.
2. Examples and comparative examples
Example 1
Step 1: pouring 0.06mol of NaOH and 250ml of deionized water into a 250ml beaker, and placing the beaker into a water bath kettle to be stirred to form a solution A;
step 2: weigh 0.01mol of SnCl 4 Adding the powder into the solution A;
step 3: weigh 0.01mol CaCl 2 The solution B was dissolved in 20ml of deionized water, and was added dropwise to the solution A to form a mixed solution. The whole preparation process was stirred at constant speed and maintained for 4 hours. Finally, standing the mixed solution for precipitation for 12 hours to obtain white precipitate, respectively centrifuging for 3 times by using deionized water and absolute ethyl alcohol for further purification, and placing the mixture in an oven for drying treatment at 60 ℃ to obtain CaSn (OH) 6 And (3) powder.
Step 4: 0.4g of CaSn (OH) was weighed separately 6 Sample, add to 20mlPlacing in 0.05mol/L hydrochloric acid solution, stirring on a stirrer for 90min, washing with deionized water and absolute ethanol, centrifuging for 3 times, and drying at 60deg.C to obtain SnO containing hydroxyl defects 2 Co-modified CaSn (OH) 6 A photocatalyst.
The defective calcium hydroxystannate prepared by the preparation method is used for photocatalytic toluene degradation under ultraviolet irradiation, and the specific process is as follows: the toluene degradation performance was tested in a homemade continuous flow (1.0L/min) reactor covered by quartz glass plates. In this study, toluene (1000 ppm in N) was obtained from a compressed gas cylinder in the reactor at a concentration of 100mL/min 2 In) was diluted to 50ppm with 0.5L/min of wet air and 0.4L/min of dry air. 0.4g of the sample was uniformly dispersed on four glass plates (0.1 g/piece) with ethanol, dried and placed in a reactor. The light source above the reactor was from a mercury lamp (300 w,365 nm). When the adsorption-desorption equilibrium was reached, the mercury lamp was turned on to trigger the photocatalytic reaction, the toluene concentration was continuously detected with a photoacoustic spectro-gas analyzer (gaserane, duke Technology co.ltd.) for 1h, and finally the lamp was turned off. By the following calculation formula, η (%) = (1-C/C) 0 ) Toluene degradation was calculated at x 100%, where C 0 For the initial toluene concentration, C is the instantaneous concentration of toluene.
Example 2
The modification is made on the basis of example 1, which differs therefrom in that: in the solution A, the concentration of NaOH is 0.24mol/L, and SnCl 4 The concentration of (C) is 0.04mol/L, caCl 2 The concentration of (C) is 0.04mol/L; in the step 3, the reaction time is 3 hours, and the standing precipitation is 10 hours; in the step 4, the concentration of the hydrochloric acid solution is 0.1mol/L.
Example 3
The modification is made on the basis of example 1, which differs therefrom in that: in the solution A, the concentration of NaOH is 0.30mol/L, and SnCl 4 The concentration of (C) is 0.05mol/L, caCl 2 The concentration of (2) is 0.05mol/L; in the step 3, the reaction time is 5 hours, and the standing precipitation is 14 hours; in the step 4, the concentration of the hydrochloric acid solution is 0.15mol/L.
Example 4
The improvement was made on the basis of example 1,the difference is that: in the solution A, the concentration of NaOH is 0.36mol/L, and SnCl 4 The concentration of (C) is 0.06mol/L, caCl 2 The concentration of (C) is 0.06mol/L; in the step 3, the reaction time is 5 hours, and the standing precipitation is 14 hours; in the step 4, the concentration of the hydrochloric acid solution is 0.2mol/L.
Comparative example 1
The modification is made on the basis of example 1, which differs therefrom in that: step 4 is not performed.
Comparative example 2
The modification is made on the basis of example 1, which differs therefrom in that: the reaction in the step 3 is carried out under the hydrothermal condition, the reaction temperature is 130 ℃, and the reaction time is 5 hours; and step 4 is not performed.
3. Application of calcium hydroxystannate
By characterizing the defective calcium hydroxystannate photocatalyst prepared in the examples of the present application, it is known that it has the following characteristics:
(1) XRD analysis was performed on the photocatalysts obtained in example 2 and comparative example 1 (as shown in FIG. 1), and SnO could be detected simultaneously in the sample obtained in example 2 2 And CaSn (OH) 6 And comparative example 1 can detect only CaSn (OH) 6 Illustrating that SnO can be successfully modified on the surface of a sample according to the preparation method in example 2 2 While comparative example 1 cannot produce SnO 2 。
(2) SEM analysis (as shown in fig. 2) was performed on the photocatalysts prepared in example 2 and comparative example 1, and the sample prepared in example 2 had smaller particle size, coarser surface and gaps compared with comparative example 1, indicating that the surface morphology of the sample could be changed according to the preparation method in example 2, possibly enhancing the adsorption of contaminants by the sample. .
(3) The specific surface area and pore volume of the photocatalysts prepared in example 2 and comparative example 1 were analyzed (as shown in fig. 3), and the specific surface area and pore volume of example 2 were 12 times and 11 times, respectively, that of comparative example 1, confirming that the specific surface area and pore volume of the sample can be greatly increased according to the preparation method in example 2, thereby enhancing the adsorption capacity.
(4) For example 1EPR analysis (as shown in fig. 4) was performed on both the photocatalyst prepared in comparative example 1 and on the prepared samples, there was a distinct peak at g=2.03, due to typical hydroxyl defects formed by incomplete crystallization upon precipitation of the samples; in addition, the peak intensity of the examples is significantly stronger than that of comparative example 1, indicating that the acid etching method increases the number of hydroxyl defects on the surface of the sample, and that the concentration of hydroxyl defects increases with increasing acid concentration. However, the concentration of the hydroxyl defects is not too high, and if the concentration of the hydroxyl defects is too high, the overall structure of the material collapses, and the morphology structure required by the application cannot be formed. Therefore, in combination with the XRD analysis result, the hydroxyl defects and SnO can be successfully produced according to the production method in the examples 2 Co-modified CaSn (OH) 6 A material.
(5) ESR analysis (as shown in FIG. 5) was performed on the photocatalyst obtained in example 2, under ultraviolet irradiation, due to hydroxyl defects and SnO 2 CaSn (OH) 6 A large number of hydroxyl radicals (·oh) are generated at the surface of the material. Hydroxyl radical is the main active species for photocatalytic toluene degradation, has extremely strong oxidizing capacity and can thoroughly mineralize toluene into CO 2 And H 2 O。
(6) The photocatalysts obtained in examples 1 to 4 and comparative examples 1 to 2 were subjected to a toluene degradation activity test under ultraviolet light irradiation (as shown in fig. 6). The photocatalytic toluene degradation rates of the photocatalysts prepared in the examples 1 to 4 reach more than 95% within 60min, wherein the toluene degradation rate of the sample prepared in the example 2 almost reaches 100%, and the photocatalytic activity is not obviously reduced after 4 times of cyclic test, thus proving the high catalytic activity and stability. This is mainly due to the large specific surface area and pore volume of the sample in the examples, which enhances the adsorption of toluene and water vapor; second, surface hydroxyl defects enable CaSn (OH) 6 The intermediate energy level is generated in the forbidden band to promote the absorption of ultraviolet light, while SnO 2 The synergistic effect of the hydroxyl defect and the hydroxyl defect enhances the separation of carriers; at the same time, snO 2 Co-modification with hydroxyl defects alters its inert surface, increases active sites, promotes H 2 Adsorption activation of O and generation of hydroxyl radical, thereby greatly extractingThe photocatalytic toluene degradation activity is high. However, the photocatalyst prepared in comparative example 1 has a toluene degradation rate of only 53.4%, which is far lower than that of the examples, mainly because of its low concentration of hydroxyl defects and no SnO 2 Modification, small specific surface area, weak adsorption and activation capacity, incomplete carrier separation, small active free radical generation amount and low activity. In addition, comparative example 2 prepared CaSn (OH) by hydrothermal method 6 The material has no hydroxyl defect on the surface and no SnO 2 The catalyst of comparative example 2 was very unstable, and deactivated in a short period of time, and deactivated continuously during the subsequent catalysis, although the catalyst had a relatively remarkable degradation effect in the first 15 minutes.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the technical solution, and those skilled in the art should understand that modifications and equivalents may be made to the technical solution of the present application without departing from the spirit and scope of the present application, and all such modifications and equivalents are included in the scope of the claims.
Claims (7)
1. The preparation method of the defective calcium hydroxystannate photocatalyst is characterized by comprising the following steps of:
step 1: preparing an aqueous NaOH solution as a solution A; in the solution A, the concentration of NaOH is 0.2-0.4 mol/L;
step 2: adding Sn salt into the solution A, and uniformly stirring; in the solution A, the concentration of Sn salt is 0.03-0.06 mol/L;
step 3: preparing Ca saline solution as solution B; slowly adding the solution B into the solution A obtained in the step 2, and stirring at a constant speed in the adding process, and reacting for 3-5 h; then, standing and precipitating for 10-14 h to obtain white precipitate, and washing, centrifuging and drying the white precipitate to obtain CaSn (OH) 6 Powder; wherein, in the solution B, the concentration of Ca salt is 0.03-0.06 mol/L;
step 4: caSn (OH) obtained in step 3 6 Adding the powder into acid liquor, stirringStirring for 60-120 min, washing, centrifuging and drying to obtain the calcium hydroxystannate; wherein CaSn (OH) 6 The molar ratio of the acid solution to the water is 1 (0.5-3).
2. The method for preparing a defective calcium hydroxystannate photocatalyst according to claim 1, wherein the Ca salt comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof.
3. The method for preparing a defective calcium hydroxystannate photocatalyst according to claim 1, wherein the Sn salt comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof.
4. The method for preparing a defective calcium hydroxystannate photocatalyst according to claim 1, wherein the acid solution comprises one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid.
5. The method for preparing a defective calcium hydroxystannate photocatalyst according to any one of claims 1 to 4, wherein the defective calcium hydroxystannate has a hydroxyl group defect and SnO 2 Co-modification.
6. Use of defective calcium hydroxystannate, prepared by the method of any of claims 1 to 5, as a photocatalyst.
7. The use of a defective calcium hydroxystannate photocatalyst according to claim 6, wherein the calcium hydroxystannate is used to photocatalytic toluene degradation under ultraviolet light.
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