CN101632940A - Polyoxometallate organic-inorganic composite film with visible light photo-catalytic activity and preparation method and application thereof - Google Patents

Abstract

The invention relates to a polyoxometallate organic-inorganic composite film with visible light photo-catalytic activity and a preparation method and application thereof. The composite film consists of heteropoly acid anion PW12O40<3-> or SiW12O40<4-> and thionine, and is prepared by a layer-by-layer self-assembly method. The film has good photo-catalytic degradation property to methyl orange coloring matter molecules under the illumination of sunlight, and has potential application prospect in the aspects of environmental protection and energy conservation.

Description

Has polyoxometallate organic and inorganic composite membrane of visible light photocatalysis active and its production and use

Technical field

The present invention relates to a kind of photochemical catalyst, relate in particular to a kind of polyoxometallate laminated film catalyst that in visible-range, has high catalytic activity by polyoxometallate-thionine laminated film.

Background technology

21 century, the environmental problem problem that becomes international is developed fewly to resources and energy consumption, and eco-environmental impact is little, and is renewable recycling or directly have and repair and the new material of environment purification function, become the important channel of solution human survival crisis.In China, dyestuff contaminant is one of primary pollution source of water, the photocatalytic degradation technology that grows up the eighties, and the purification of, the priority pollutant that be difficult to transform low to concentration in the water body provides a good solution route.Yet in 20 years of researches, a large amount of notices concentrates on the photocatalytic degradation with the UV-irradiation organic pollution, especially concentrates on the research of optically catalytic TiO 2 in the past.The restriction of wavelength but titanium dioxide is stimulated can only utilize the ultraviolet light of less than 5% in the sunshine, and, use ultraviolet light to have some limitations, big as power consumption, cost an arm and a leg etc.; And wavelength to be the visible light 43% of 400～750nm can't utilize, therefore, research and develop novel catalysis material, utilize the pollutant in the sunshine degraded environment, to environmental protection with energy-conservationly all will be extremely important.

Polyoxometallate (Polyoxometalates, POMs) generally has catalytic action because of light sensitivity in the ultraviolet light zone, the photocatalysis chemical research of polyoxometallate starts from phase early 1980s, studies show that, POMs can the efficient oxidation decomposing organic pollutant, but because of having the little (1-10m of specific area ²/ g), isopolarity solvent soluble in water and be difficult to reclaim, and can only absorb the shortcoming of ultraviolet light, limited its extensive use.But, POMs is made film can effectively solve this problem soluble in water.From the purpose of practical application, the application of polyoxometallate film in photocatalysis do not need can reuse better through special separation.With POMs as inorganic anion, and some organic matter that can absorb visible light as cation, make it can absorb visible light, can effectively solve POMs can only be in this problem of photocatalysis in ultraviolet light zone.At present, static self-assembly method layer by layer is a kind of simple method of constructing the organic and inorganic composite membrane, such as not needing special equipment, and it is environmentally friendly, this method is based on electrostatic attraction, the multilayer self-assembled film that alternately is immersed in the material of nominal price and negative valency and obtains because it simple and adaptability widely, has obtained people's extensive concern.

We utilize static assembling in vain layer by layer, and as inorganic anion, the dye molecule thionine is prepared into polyoxometallate-thionine organic and inorganic composite membrane as organic cation, utilizes this film under sunshine illumination, carries out the degraded of organic dyestuff POMs.This film carries out the organic dyestuff degraded as catalysis material and yet there are no report, especially utilizes thionine sensitization heteropoly acid, utilizes sunshine to carry out the degraded of organic dyestuff.Methyl orange is a kind of compound of difficult degraded, azo and quinoid structure under acid and alkali condition are the agent structures of dye composition, therefore, can be used as and have one of certain representational dyestuff, the present invention is the model dyestuff of methyl orange as photocatalytic degradation.

Summary of the invention

The present invention has prepared a kind of photochemical catalyst by polyoxometallate-thionine laminated film, even hybrid inorganic-organic materials that also can the high efficiency photocatalysis degradating organic dye in visible-range.

The polyoxometallate laminated film catalyst with visible light photocatalysis active of the present invention's preparation is by heteropolyacid anions PW ₁₂O ₄₀ ^3-(or SiW ₁₂O ₄₀ ^4-) and the laminated film constructed of thionine.

Organic dye sensitized dose of the present invention's employing is thionine (Thionine is abbreviated as TH), and its structural formula is as follows:

The present invention adopts layer by layer, and self-assembling method prepares polyoxometallate-thionine laminated film catalyst.

The polyoxometallate catalyst of the present invention preparation is used for degradating organic dye, and methyl orange or have the organic dyestuff of identical chromophore with methyl orange especially can be used for degrading.

The organic, inorganic composite film with visible light photocatalysis active of the present invention's preparation is synthetic first.This material is by electrostatic interaction two kinds of zwitterions to be combined, it has not only kept polyoxometallate photocatalytic activity efficiently, and, help improving the photocatalysis efficiency of POMs in the visible region because the existence of thionine can effectively absorb visible light.The organic, inorganic composite film with visible light photocatalysis active of the present invention's preparation has very high degradation to organic dyestuff such as methyl oranges.

The specific embodiment

Embodiment 1:(PW ₁₂O ₄₀/ TH) ₁₀The laminated film preparation

At first, quartz plate or simple glass or silicon chip are cleaned: substrate is placed 98%H ₂SO ₄With 30%H ₂O ₂In 80 ℃ of following impregnation process 40min, take out the back and clean in the mixed liquor of (7: 3 v/v) with distilled water; Immerse H again ₂O: H ₂O ₂: NH ₃=5: in 80 ℃ of following impregnation process 20min, take out the back and clean with distilled water in the mixed liquor of 1: 1 (v/v/v), nitrogen dries up, and promptly obtains the stand-by substrate of film forming.

Again substrate is carried out the PEI cationization: will immerse in the polymine PEI solution of 10mg/mL through the substrate of aforementioned processing program and place 20min, and take out the back and clean with distilled water, nitrogen dries up.

And then, alternately immerse the PW of 5mM substrate through the PEI cationization ₁₂O ₄₀In solution and the 0.5mM TH solution, place 20min respectively, each immerses and cleans with distilled water after step is taken out, and nitrogen dries up; The above step of repetitive cycling can make required (PW ₁₂O ₄₀/ TH) ₁₀Multilayer organic and inorganic film.

The uv-vis spectra of film is characterized in the ultraviolet-visual spectrometer of the Lambda-35 type of U.S. PerkinElmer company production.Uv-vis spectra shows the film (PW of preparation ₁₂O ₄₀/ TH) ₁₀In the increase linear of the absorbance at wavelength 570nm place, illustrate that the film of preparation has the good homogeneous growth property along with the increase of the number of plies.Absorb at visible light 570nm, show that dye molecule TH can carry out sensibilization to polyoxometallate, make film can carry out photocatalysis in the visible region.

Embodiment 2: the sunlight photocatalysis active testing of film

The photocatalysis experiment: the model organic dye molecule is selected methyl orange (MO) for use, and molecular formula is as follows:

Get 5ml MO (10mg/L) and put in the quartz test tube, put into the quartz glass plate ((PW of big or small 25mm * 12mm * 1mm) again ₁₂O ₄₀/ TH) ₁₀Self-assembled film is placed on and carries out the solar illuminating experiment under the sunshine, and intensity of solar radiation is 4.2J/cm ². divide, mean temperature is 20 ℃.

Photocatalytic activity is estimated: film sample is put in the methyl orange solution of 10mg/L of 5ml, under sunshine, shine certain hour, take out film, methyl orange solution records the absorbance value ε of reactant liquor in the maximum absorption wave strong point with the variation of ultraviolet-visible spectrophotometer mensuration dyestuff absorption spectrum in the illumination process ₁Carry out blank and control experiment simultaneously, blank assay only adds the dye solution of the same concentration of equal volume and does not add film sample, the time that illumination under the same conditions is identical, records the absorbance value ε of reactant liquor in the maximum absorption wave strong point ₂Control experiment is the dye solution that adds the same concentration of equal volume, and adds film sample, under the lucifuge condition, surveys its absorbance value ε in the maximum absorption wave strong point ₃Thereby, calculate the variation of dye solution respective concentration.

Sample to the calculating formula of methyl orange photocatalytic degradation rate is:

$D=\{\frac{{\mathrm{\&epsiv;}}_0-{\mathrm{\&epsiv;}}_1}{{\mathrm{\&epsiv;}}_0}-\frac{{\mathrm{\&epsiv;}}_0-{\mathrm{\&epsiv;}}_2}{{\mathrm{\&epsiv;}}_0}-\frac{{\mathrm{\&epsiv;}}_0-{\mathrm{\&epsiv;}}_3}{{\mathrm{\&epsiv;}}_0}\}\&times;100\%$

In the formula: ε ₀Be the absorbance value of stock staining solution in the maximum absorption wave strong point, methyl orange is 463nm.

Methyl orange is carried out sunshine illumination or is added film sample under the lucifuge condition not adding film sample, and its solution absorbency does not all change, so the calculating formula of its degradation rate is: D=(ε ₀-ε ₁)/ε ₀* 100%

Add film (PW at methyl orange solution ₁₂O ₄₀/ TH) ₁₀, 2 hours degradation rate of illumination can reach 85.78% under sunshine, and degradation rate increases along with the increase of light application time is linear; After 2.5 hours, degradation rate reaches 92.62% in illumination.

The photocatalytic activity evaluation of this thin-film material shows: the TH in the film can the sensitization polyoxometallate, make its in the UV absorption regional expansion to the visible region, can carry out good degraded to methyl orange model dyestuff under sunshine illumination, the present invention contains in processing and has a wide range of applications aspect the organic dyestuff waste water.

Claims (4)

1. have the organic and inorganic film of the polyoxometallate of visible light photocatalysis active, it is characterized in that: this film is by heteropolyacid anions PW ₁₂O ₄₀ ^3-Or SiW ₁₂O ₄₀ ^4-Form with thionine.

2. the preparation method of the organic and inorganic film of the described polyoxometallate of claim 1 is characterized in that: adopt self-assembling method preparation layer by layer.

3. the purposes of the organic and inorganic film of the described polyoxometallate of claim 1, it is characterized in that: this film is used for degradating organic dye.

4. the purposes of the organic and inorganic film of polyoxometallate as claimed in claim 3, it is characterized in that: described organic dyestuff is the methyl orange dye molecule, or has the organic dyestuff of identical chromophore with the methyl orange dye molecule.