阅读说明：本技术 一种锰掺杂软铋矿光催化剂及其制备方法和在同步降解六价铬和有机污染物中的应用 (Manganese-doped sillenite photocatalyst, preparation method thereof and application thereof in synchronous degradation of hexavalent chromium and organic pollutants ) 是由 湛菁 王焕伟 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种锰掺杂软铋矿光催化剂及其制备方法和在同步降解六价铬和有机污染物中的应用,其制备方法包括：将含Bi原料加入到盐酸中在室温下混匀得到透明澄清溶液,随后加入含Mn原料后搅拌并加入过量的碱液,继续搅拌得到悬浊液,最后将悬浊液置于油浴中加热搅拌,在110-130℃下反应5-7h后收集沉淀,即得。本发明通过优化浓盐酸和碱液的加入量,合理控制水热反应温度和时间,在确保得到纯相Bi-(12)MnO-(20)基础上促进其向二维平面扩展生长,制得片状结构的Bi-(12)MnO-(20)；其在光照下可产生具有强还原性的电子与强氧化性的空穴,能同步降解六价铬和有机污染物,可提高光催化消减效率,适合产业应用。(The invention discloses a manganese-doped sillenite photocatalyst, a preparation method thereof and application thereof in synchronously degrading hexavalent chromium and organic pollutants, wherein the preparation method comprises the following steps: adding a Bi-containing raw material into hydrochloric acid, uniformly mixing at room temperature to obtain a transparent clear solution, then adding a Mn-containing raw material, stirring, adding excessive alkali liquor, continuously stirring to obtain a suspension, finally placing the suspension in an oil bath, heating and stirring at 110-130 DEG CAnd (5) reacting for 5-7h, and collecting the precipitate to obtain the product. The invention reasonably controls the hydrothermal reaction temperature and time by optimizing the addition of concentrated hydrochloric acid and alkali liquor, thereby ensuring that pure-phase Bi is obtained 12 MnO 20 Promoting the Bi to expand and grow to a two-dimensional plane on the basis to prepare Bi with a sheet structure 12 MnO 20 (ii) a The composite material can generate electrons with strong reducibility and holes with strong oxidizability under illumination, can synchronously degrade hexavalent chromium and organic pollutants, can improve the photocatalytic reduction efficiency, and is suitable for industrial application.)

1. A preparation method of a manganese-doped sillenite photocatalyst is characterized in that,

the method comprises the following steps: adding a Bi-containing raw material into hydrochloric acid, uniformly mixing at room temperature to obtain a transparent clear solution, then adding a Mn-containing raw material, stirring, adding excessive alkali liquor, continuously stirring to obtain a suspension, finally placing the suspension in an oil bath, heating and stirring, reacting at the temperature of 110 ℃ and 130 ℃ for 5-7h, and collecting precipitate to obtain the catalyst.

2. The method for preparing the manganese-doped sillenite photocatalyst according to claim 1, characterized in that,

corresponds to 1molBi³⁺The addition amount of the hydrochloric acid is 3-5L, and the pH value of the transparent clear solution is controlled to be less than or equal to 2; preferably, the hydrochloric acid is concentrated hydrochloric acid with the mass fraction of 36-38%;

and/or, controlling the addition amount of the alkali liquor to be 15-30% in excess after the precipitate does not appear in the suspension, and controlling the pH value of the suspension to be more than or equal to 10; preferably, the alkali liquor is 0.8-1.3mol/L NaOH solution.

3. The method for preparing the manganese-doped sillenite photocatalyst according to claim 1, characterized in that,

the mixing time of the Bi-containing raw material in hydrochloric acid is 30-45 min;

and/or the stirring time after the Mn-containing raw material is added is 28-35 min;

and/or the temperature of the oil bath is 115-125 ℃, and the reaction time is 5.5-6.5 h.

4. The method for preparing a manganese-doped sillenite photocatalyst according to any one of claims 1 to 3,

the raw material containing Bi is one or more of bismuth trioxide, bismuth nitrate, bismuth acetate and bismuth chloride;

and/or the Mn-containing raw material is one or more of manganese nitrate, manganese acetate and manganese chloride;

and/or the Bi-containing raw material and the Mn-containing raw material are used in an amount such that the molar weight ratio of Bi to Mn is controlled to be 12: 1.

5. The method for preparing the manganese-doped sillenite photocatalyst according to any one of claims 1 to 4,

also comprises washing the collected precipitate with deionized water, drying at 100 deg.C for 10-15 hr, cooling, and grinding.

6. Bi produced by the production method according to any one of claims 1 to 5₁₂MnO₂₀A photocatalyst.

7. The Bi according to claim 6₁₂MnO₂₀A photocatalyst characterized in that it comprises, in a solid state,

the Bi₁₂MnO₂₀The thickness, specific surface area and flake size of the photocatalyst are respectively 8-10nm and 3-5m²G and 1-3 μm²。

8. The method of any one of claims 1 to 5 or the Bi of any one of claims 6 to 7₁₂MnO₂₀The application of the photocatalyst in synchronously degrading hexavalent chromium and organic pollutants is characterized in that,

comprises the steps of mixing the Bi₁₂MnO₂₀The photocatalyst is added into sewage containing hexavalent chromium and organic pollutants simultaneously, and is degraded through a light reaction.

9. The use according to claim 8,

the Bi₁₂MnO₂₀The addition amount of the photocatalyst is 2 g/L;

and/or the concentration ratio of the hexavalent chromium to the organic pollutants in the sewage is 1: 1-3;

and/or the pH value of the sewage is less than or equal to 3.

10. Use according to claim 8 or 9,

the light source power of the illumination is respectively 300-600W;

and/or the time for reaction degradation is 2.5-5 h;

and/or the organic pollutant is one or more of methyl orange, tetracycline, malachite green, rhodamine B, Congo red and acid red.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and particularly relates to Bi₁₂MnO₂₀A photocatalyst, a preparation method thereof and application thereof in synchronously degrading hexavalent chromium and organic pollutants.

Background

In recent years, water pollution, especially pollution caused by sewage containing hexavalent chromium heavy metals and refractory organic matters, is a key point and a difficult point of sewage treatment due to great toxicity, high concentration and difficult natural degradation, which causes great harm to the environment and human beings; however, in the wastewater discharged actually, heavy metals often coexist with organic pollutants to form composite wastewater, which greatly increases the difficulty of effective treatment of the wastewater.

Photocatalysis is a novel green sewage treatment technology, can reduce toxic and harmful pollutants into substances with weak toxicity or even no toxicity, has strong environmental protection advantages, and has wide application and excellent effect in treating a plurality of toxic and harmful pollutants.

The core of the photocatalysis technology lies in the photocatalysis material with high visible light response and low photon-generated carrier recombination rate, and the catalysis efficiency is improved.

The semiconductor bismuth-based catalytic material is a novel visible light response photocatalyst, and the manganese doping can effectively reduce the recombination rate of photo-generated electron-hole pairs, however, the manganese-doped soft bismuth ore material Bi has not been found to be related to the manganese-doped soft bismuth ore material₁₂MnO₂₀The research reports on the simultaneous degradation of hexavalent chromium and organic pollutants.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a manganese-doped sillenite photocatalyst, a preparation method thereof and application thereof in synchronously degrading hexavalent chromium and organic pollutants.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of a manganese-doped sillenite photocatalyst comprises the following steps:

adding a Bi-containing raw material into hydrochloric acid, uniformly mixing at room temperature to obtain a transparent clear solution, then adding a Mn-containing raw material, stirring, adding excessive alkali liquor, continuously stirring to obtain a suspension, finally placing the suspension in an oil bath, heating and stirring, reacting at the temperature of 110 ℃ and 130 ℃ for 5-7h, and collecting precipitate to obtain the catalyst.

In the above scheme, corresponding to 1mol of Bi³⁺The addition amount of the hydrochloric acid is 3-5L, and the pH value of the transparent clear solution is controlled to be less than or equal to 2.

Preferably, in the above technical solution, the hydrochloric acid is concentrated hydrochloric acid with a mass fraction of 36-38%.

In the technical scheme, the addition amount of the alkali liquor is controlled to be 15-30% in excess after no precipitation appears in the suspension, and the pH value of the suspension is controlled to be more than or equal to 10.

Preferably, in the technical scheme, the alkali liquor is 0.8-1.3mol/L NaOH solution.

In the technical scheme, the mixing time of the Bi-containing raw material in the hydrochloric acid is 30-45 min.

In the technical scheme, the stirring time after the Mn-containing raw material is added is 28-35 min.

In the technical scheme, the temperature of the oil bath is 115-125 ℃, and the reaction time is 5.5-6.5 h.

Further, in the above technical scheme, the Bi-containing raw material is one or more of bismuth trioxide, bismuth nitrate, bismuth acetate and bismuth chloride.

Further, in the above technical solution, the Mn-containing raw material is one or more of manganese nitrate, manganese acetate, and manganese chloride.

Further, in the above technical solution, the Bi-containing raw material and the Mn-containing raw material are used in an amount such that the molar ratio of Bi to Mn is controlled to be 12: 1.

Still further, in the above technical solution, the preparation method of the manganese-doped bismuthate photocatalyst further includes:

washing the collected precipitate with deionized water, drying at 100 deg.C for 10-15 hr, cooling, and grinding.

The invention also provides Bi prepared by the preparation method₁₂MnO₂₀A photocatalyst.

Specifically, in the above technical solution, the Bi₁₂MnO₂₀The thickness, specific surface area and flake size of the photocatalyst are respectively 8-10nm and 3-5m²G and 1-3 μm²。。

The invention also provides the preparation method or the Bi₁₂MnO₂₀The application of the photocatalyst in synchronously degrading hexavalent chromium and organic pollutants comprises the following steps,

the Bi is added₁₂MnO₂₀The photocatalyst is added into sewage containing hexavalent chromium and organic pollutants simultaneously, and is degraded through a light reaction.

In the above technical solution, the Bi₁₂MnO₂₀The amount of the photocatalyst added was 2 g/L.

In the technical scheme, the concentration ratio of the hexavalent chromium to the organic pollutants in the sewage is 1: 1-3.

In the technical scheme, the pH of the sewage is less than or equal to 3.

In the above technical solution, the light source frequency and power of the illumination are 300-.

In the technical scheme, the time for reaction degradation is 2.5-5 h.

Specifically, in the above technical solution, the organic pollutant is one or more of methyl orange, tetracycline, malachite green, rhodamine B, congo red and acid red.

Compared with the prior art, the invention has the following advantages:

(1) the manganese-doped sillenite Bi provided by the invention₁₂MnO₂₀The preparation method of the photocatalyst comprises the steps of firstly dissolving the Bi-containing raw material in concentrated hydrochloric acid to avoid impurity precipitation caused by hydrolysis, and simultaneously controlling Bi in a transparent clear solution³⁺The concentration of 0.2-0.33mol/L prevents subsequent particle agglomeration, then Mn-containing raw materials are added in proportion, stirred and added with excessive alkali liquor, so that the bismuth-manganese coprecipitation is beneficial to subsequent hydrothermal coupling, and reasonable hydrothermal temperature and time are controlled to ensure that pure-phase Bi can be obtained₁₂MnO₂₀Promote it to two-dimensionPlanar extension growth is carried out, the sheet shape with larger effective light radiation absorption area is obtained, high-temperature calcination is not needed in the preparation method, a coupling agent is not needed, and the synthesis condition is easy to control;

(2) the manganese-doped sillenite Bi prepared by the invention₁₂MnO₂₀The photocatalyst is added into the sewage containing hexavalent chromium and organic pollutants simultaneously, electrons with strong reducibility and holes with strong oxidizability are generated under illumination, the hexavalent chromium can be reduced simultaneously, the organic pollutants can be degraded by oxidation, the photoproduction holes and the electrons are consumed while the pollutants are removed, the self-recombination rate of the hexavalent chromium and the organic pollutants can be reduced, and the photocatalytic reduction efficiency can be improved without further adding a hole or electron consumption agent;

(3) the Mn-doped bismuth sillenite structure Bi provided by the invention₁₂MnO₂₀The material has wide band gap, can realize full-spectrum response, has high sunlight utilization efficiency, and has unique sheet structure to ensure that the Bi has high efficiency₁₂MnO₂₀The material has a high effective light radiation absorption area, the generation rate of photon-generated carriers is high, reactants are not easy to accumulate on active sites, and the oxidation-reduction reaction can be timely carried out, so that the material has good photocatalytic activity and high chemical stability, and is suitable for industrial application.

Drawings

FIG. 1 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀X-ray diffraction pattern of the photocatalyst;

FIG. 2 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀Scanning electron micrographs of the photocatalyst;

FIG. 3 shows Bi obtained by the present invention₁₂MnO₂₀The specific surface area and adsorption/desorption curve of the photocatalyst (wherein: a is Bi prepared in example 1)₁₂MnO₂₀Results of the photocatalyst, b is Bi obtained in comparative example 1_i2MnO₂₀Results of the photocatalyst);

FIG. 4 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀The photocatalyst synchronously degrades the efficiency curve of simulated sewage containing hexavalent chromium and methyl orange;

FIG. 5 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀The photocatalyst synchronously degrades a circulation stability curve of simulated sewage containing hexavalent chromium and methyl orange;

FIG. 6 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀The photocatalyst synchronously degrades an efficiency curve of hexavalent chromium and tetracycline-containing simulated sewage;

FIG. 7 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀The photocatalyst synchronously degrades a circulation stability curve of the simulated sewage containing hexavalent chromium and tetracycline by photocatalysis;

FIG. 8 shows Bi obtained in example 1 of the present invention₁₂MnO₂₀And (3) carrying out photocatalytic degradation on the simulated sewage efficiency curves respectively containing hexavalent chromium, tetracycline and methyl orange by using the photocatalyst.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the examples, the means used are conventional in the art unless otherwise specified.

The terms "comprises," "comprising," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The experimental raw materials used in the examples of the present invention and the comparative examples are all commercially available products.

Example 1

The embodiment of the invention provides a manganese-doped sillenite Bi₁₂MnO₂₀The preparation method of the photocatalyst specifically comprises the following steps:

(1) dissolving 6mmol of bismuth trioxide in 40ml of 38% hydrochloric acid, controlling the pH value to be 1.8 +/-0.2, and continuously stirring at room temperature for 40min to obtain a transparent clear solution;

(2) adding 1mmol of manganese chloride tetrahydrate into the transparent clear solution, adding 20ml of sodium hydroxide solution with the concentration of 1mol/L under the condition of room temperature while stirring, and continuously stirring for 30 minutes to obtain a suspension with the pH value of 11.5;

(3) transferring the suspension into a flask with a condensation reflux device, heating and stirring for 6 hours in an oil bath at 120 ℃, then filtering, and washing for 3 times with deionized water to obtain a precipitate;

(4) and (3) drying the precipitate in an oven at 100 ℃ for 12h, cooling, and grinding into fine powder in an agate mortar.

Example 2

The embodiment of the invention provides a manganese-doped sillenite Bi₁₂MnO₂₀The preparation method of the photocatalyst specifically comprises the following steps:

(1) dissolving 6mmol of bismuth chloride in 25m of hydrochloric acid with the mass fraction of 1 being 38%, controlling the pH value to be 1.8 +/-0.2, and continuously stirring for 45min at room temperature to obtain a transparent clear solution;

(2) adding 0.5mmol of manganese chloride tetrahydrate into the transparent clear solution, adding 10.0ml of 1mol/L sodium hydroxide solution under stirring at room temperature, and continuously stirring for 30 minutes to obtain a suspension with the pH of 10.8;

(3) transferring the suspension into a flask attached with a condensation reflux device, heating and stirring for 5.5h in an oil bath at 125 ℃, then filtering and washing for 3 times with deionized water to obtain a precipitate;

(4) and (3) drying the precipitate in an oven at 100 ℃ for 12h, cooling, and grinding into fine powder in an agate mortar.

Comparative example 1

The invention provides a manganese-doped sillenite Bi₁₂MnO₂₀PhotocatalysisThe preparation method of the preparation specifically comprises the following steps:

(1) dissolving 6mmol of bismuth trioxide in 40ml of 38% hydrochloric acid, controlling the pH value to be 1.8 +/-0.2, and continuously stirring at room temperature for 40min to obtain a transparent clear solution;

(2) adding 1mmol of manganese chloride tetrahydrate into the transparent clear solution, adding 9ml of sodium hydroxide solution with the concentration of 1mol/L under the condition of room temperature while stirring, and continuously stirring for 30 minutes to obtain a suspension with the pH value of 8.5;

(3) transferring the suspension into a flask with a condensation reflux device, heating and stirring for 6 hours in an oil bath at 140 ℃, then filtering and washing for 3 times with deionized water to obtain a precipitate;

(4) and (3) drying the precipitate in an oven at 100 ℃ for 12h, cooling, and grinding into fine powder in an agate mortar.

FIGS. 1 and 2 are views showing Bi prepared in example 1 of the present invention₁₂MnO₂₀X-ray diffraction pattern and SEM photograph of the photocatalyst.

As can be seen from FIG. 1, Bi obtained in example 1 of the present invention₁₂MnO₂₀The characteristic peak position of the X-ray diffraction result of the photocatalyst completely accords with that of a standard card JCPDS 00-045-₁₂MnO₂₀High purity and no obvious impurity phase; as can be seen from FIG. 2, Bi obtained in example 1 of the present invention₁₂MnO₂₀The photocatalyst is in the shape of a sheet, the thickness of the photocatalyst is about 10nm, and the areas of the photocatalyst are about 2 mu m²No obvious agglomeration and stacking phenomenon, and large specific surface area.

FIGS. 3(a) and 3(b) are Bi prepared in example 1 of the present invention and comparative example 1 of the present invention, respectively₁₂MnO₂₀The specific surface area and the adsorption and desorption curve of the photocatalyst; as can be seen from FIG. 3, Bi obtained in example 1 of the present invention and comparative example 1 of the present invention₁₂MnO₂₀The nitrogen adsorption and desorption curves of the photocatalyst are all 1V type curves and have H3 type hysteresis loops, but the specific surface area of the sample prepared in the comparative example 1 is 3.621m²Is much larger than the specific surface area 0 of the sample prepared in comparative example 1.694m²The/g indicates that the prepared Bi can be obtained by controlling the pH value of the suspension to be more than or equal to 10 and the oil bath temperature to be 115-125 DEG C₁₂MnO₂₀The photocatalyst has larger specific surface area, thereby obtaining more catalytic reaction active sites.

Bi provided for further illustration of the embodiments of the present invention₁₂MnO₂₀The method for synchronously degrading sewage containing hexavalent chromium and organic pollutants by using a photocatalyst is described by taking a plurality of examples and combining the examples with the attached drawings.

Application example 1

Preparing simulated sewage containing hexavalent chromium (10mg/L) and organic pollutants (10mg/L) by using methyl orange (organic dye) and potassium dichromate which is dried in an oven at 60 ℃ for 4 hours; and regulating the pH value of the simulated sewage to 2 by using high-grade pure sulfuric acid.

2ml of the simulated sewage is taken, and the initial absorbance and the concentration of the hexavalent chromium under the wavelength of 540nm are calibrated by a dibenzoyl dihydrazide spectrophotometry; 2ml of the simulated sewage is taken, and the initial absorbance and the concentration of the methyl orange at the wavelength of 463nm are directly calibrated by an ultraviolet-visible spectrophotometry.

100mL of the simulated wastewater was taken and added with Bi prepared in example 1₁₂MnO₂₀0.2g of photocatalyst, continuously stirring for 30 minutes in the absence of light, then respectively taking 2m1 of simulated sewage, and measuring the absorbance and corresponding concentration of hexavalent chromium and methyl orange again according to the same method.

Starting a xenon lamp, continuously stirring for 60 minutes under the condition of simulated sunlight, respectively taking 2ml of simulated sewage, measuring the absorbance and the corresponding concentration of hexavalent chromium and methyl orange, taking 5 times, and taking 5 hours in total.

FIG. 4 shows Bi as above₁₂MnO₂₀The efficiency curve of the photocatalyst for synchronously degrading simulated sewage containing hexavalent chromium and methyl orange under photocatalysis can be seen from the figure, and the Bi₁₂MnO₂₀The photocatalyst has good water pollution treatment capacity, and after 5 hours of photocatalytic reaction, the reduction rate of hexavalent chromium is 95.6 percent, and the degradation rate of methyl orange is 92.6 percent.

Subsequently, the used Bi is recovered₁₂MnO₂₀Photocatalyst, using anhydrous BWashing with alcohol and deionized water for 5 times, and drying in 60 deg.C oven for 12 hr; the above degradation process was repeated 3 times, and the prepared Bi was tested₁₂MnO₂₀The reusability and stability of the photocatalyst.

FIG. 5 shows Bi as above₁₂MnO₂₀The circulation stability curve of simulated sewage containing hexavalent chromium and methyl orange under the photocatalytic synchronous degradation of photocatalyst can be seen from the figure, and the prepared Bi₁₂MnO₂₀After the photocatalyst is circulated for 4 times, the reduction rate of hexavalent chromium is only reduced by 8.1 percent, and the degradation rate of methyl orange is only reduced by 7.4 percent, which shows that the prepared Bi₁₂MnO₂₀The photocatalyst has good reusability and stability.

Application example 2

Preparing simulated sewage containing hexavalent chromium (10mg/L) and organic pollutant tetracycline (10mg/L) simultaneously by using tetracycline (organic spectrum bacteriostatic agent) and potassium dichromate which is dried in an oven at 60 ℃ for 4 hours; and regulating the pH value of the simulated sewage to 2 by using high-grade pure sulfuric acid.

2ml of the simulated sewage is taken, and the initial absorbance and the concentration of the hexavalent chromium under the wavelength of 540nm are calibrated by a dibenzoyl dihydrazide spectrophotometry; 2ml of the simulated sewage is taken, and the initial absorbance and the concentration of the tetracycline at the wavelength of 355nm are calibrated directly by an ultraviolet-visible spectrophotometry.

100mL of the simulated wastewater was taken and added with Bi prepared in example 1₁₂MnO₂₀0.2g of photocatalyst, continuously stirring for 30 minutes in the absence of light, then respectively taking 2m1 of simulated sewage, and measuring the absorbance and corresponding concentration of hexavalent chromium and tetracycline again according to the same method.

Starting a xenon lamp, continuously stirring for 60 minutes under the condition of simulated sunlight, respectively taking 2ml of simulated sewage, measuring the absorbance and the corresponding concentration of the hexavalent chromium and the tetracycline, taking 5 times, and taking 5 hours in total.

FIG. 6 shows Bi as above₁₂MnO₂₀The efficiency curve of the photocatalyst for synchronously degrading hexavalent chromium and tetracycline-containing simulated sewage through photocatalysis can be seen from the figure, and the Bi₁₂MnO₂₀The photocatalyst has good water pollution treatment capacity, and can be used for treating water pollutionAfter the catalytic reaction is carried out for 5 hours, the reduction rate of hexavalent chromium is 92.3 percent, and the degradation rate of methyl orange is 90.6 percent.

Subsequently, the used Bi is recovered₁₂MnO₂₀The photocatalyst is washed by absolute ethyl alcohol and deionized water for 5 times respectively, and is dried in an oven at 60 ℃ for 12 hours; the above degradation process was repeated 3 times, and the prepared Bi was tested₁₂MnO₂₀The reusability and stability of the photocatalyst.

FIG. 7 shows Bi as above₁₂MnO₂₀The circulation stability curve of the simulated sewage containing hexavalent chromium and tetracycline is synchronously degraded by the photocatalysis, and the prepared Bi can be seen from the figure₁₂Mn0₂₀After the photocatalyst is circulated for 4 times, the reduction rate of hexavalent chromium is only reduced by 9.5 percent, and the degradation rate of methyl orange is only reduced by 7.2 percent, which shows that the prepared Bi₁₂MnO₂₀The photocatalyst has good reusability and stability.

Application example 3

Methyl orange (organic dye), tetracycline (organic spectrum bacteriostatic agent) and potassium dichromate after being dried in an oven at 60 ℃ for 4 hours are respectively prepared into simulated sewage containing methyl orange (10mg/L), simulated sewage containing tetracycline (10mg/L) and simulated sewage containing hexavalent chromium (10mg/L), and the pH of the simulated sewage is adjusted to 2 by using high-grade pure sulfuric acid.

Similarly, 2ml of the simulated sewage is taken, the initial absorbance and the concentration of methyl orange at the wavelength of 463nm in the simulated sewage containing methyl orange (10mg/L) are calibrated by an ultraviolet-visible spectrophotometry method, the initial absorbance and the concentration of tetracycline at the wavelength of 355nm in the simulated sewage containing tetracycline (10mg/L) are calibrated by an ultraviolet-visible spectrophotometry method, and the initial absorbance and the concentration of hexavalent chromium at the wavelength of 540nm in the simulated sewage containing hexavalent chromium (10mg/L) are calibrated by a dibenzoyl dihydrazide spectrophotometry method.

100mL of each simulated wastewater was taken and added with Bi prepared in example 1₁₂MnO₂₀0.2g of photocatalyst, continuously stirring for 30 minutes in the absence of light, respectively taking 2ml of simulated sewage, and measuring the absorbance and the corresponding contents of methyl orange, tetracycline and hexavalent chromium again by the same methodThe concentration of chromium.

Similarly, the xenon lamp is turned on, 2ml of the simulated sewage is respectively taken after continuously stirring for 60 minutes under the simulated sun illumination condition, the absorbance and the corresponding concentration of the contained methyl orange, tetracycline and hexavalent chromium are measured, and the total time is taken for 5 hours for 6 times.

FIG. 8 shows Bi as above₁₂MnO₂₀The efficiency curve of the photocatalyst for photocatalytic degradation of methyl orange, tetracycline and hexavalent chromium.

As can be seen from FIG. 8, Bi prepared by example 1₁₂MnO₂₀After the photocatalyst is subjected to photocatalytic reaction for 5 hours, the degradation rate of methyl orange is 65.34%, the degradation rate of tetracycline is 79.54%, and the reduction rate of hexavalent chromium is 47.9%.

Application example 4

Preparing simulated sewage containing hexavalent chromium (10mg/L) and organic pollutant methyl orange (10mg/L) by using methyl orange (organic dye) and potassium dichromate which is dried in an oven at 60 ℃ for 4 hours; and regulating the pH value of the simulated sewage to 2 by using high-grade pure sulfuric acid.

2ml of the simulated sewage is taken, and the initial absorbance and the concentration of the hexavalent chromium under the wavelength of 540nm are calibrated by a dibenzoyl dihydrazide spectrophotometry; taking the simulated sewage 2m1, and calibrating the initial absorbance and concentration of methyl orange directly by an ultraviolet-visible spectrophotometry.

100mL of the simulated sewage is taken and added with Bi prepared in the comparative example 1₁₂MnO₂₀0.2g of photocatalyst, continuously stirring for 30 minutes in the absence of light, then respectively taking 2m1 of simulated sewage, and measuring the absorbance and corresponding concentration of hexavalent chromium and methyl orange again according to the same method.

Starting a xenon lamp, continuously stirring for 60 minutes under the condition of simulated sunlight, respectively taking 2m1 of simulated sewage, measuring the absorbance and the corresponding concentration of hexavalent chromium and methyl orange, taking 5 times, and taking 5 hours in total.

The following Table 1 shows the above Bi₁₂MnO₂₀The efficiency of the photocatalyst for synchronously degrading simulated sewage containing hexavalent chromium and methyl orange through photocatalysis.

Table 1 test results of efficiency of photocatalytic synchronous degradation of simulated sewage containing hexavalent chromium and methyl orange

Subsequently, the used Bi is recovered₁₂MnO₂₀The photocatalyst is washed by absolute ethyl alcohol and deionized water for 5 times respectively, and is placed in a drying oven at 60 ℃ for drying for 12 hours; the above degradation process was repeated 3 times, and the prepared Bi was tested₁₂MnO₂₀The reusability and stability of the photocatalyst.

The following Table 2 shows the above Bi₁₂MnO₂₀And (3) carrying out photocatalytic synchronous degradation on the circulation stability test result of simulated sewage containing hexavalent chromium and methyl orange by using the photocatalyst.

Table 2 circulation stability test results of photocatalytic synchronous degradation of simulated sewage containing hexavalent chromium and methyl orange

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention.

It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.