CN102513091A - Preparation method for graphene self-assembled nanometer bismuth vanadate photocatalyst - Google Patents

Abstract

The invention relates to a preparation method of graphene self-assembled nano bismuth vanadate photocatalyst, comprising: (1) adding bismuth salt and stabilizer to phosphate buffer solution, stirring to form a suspension; uniformly mixing metavanadate dissolved in phosphate buffer, then added to the suspension, stirred evenly to form a transparent solution; (2) adjust the pH range of the above transparent solution to 4.5-9.0, and then add the Graphene with a bismuth salt mass ratio of 5-20:1 is stirred and mixed, refluxed for 6-24 hours, centrifuged, filtered and washed to obtain a product, and finally the obtained product is roasted, cooled and ground to obtain the product. The invention has the advantages of low cost, simple and easy preparation method, and low requirements on equipment; the prepared graphene powder bismuth vanadate self-assembles uniformly, can efficiently degrade persistent toxic and harmful substances under ultraviolet light and visible light conditions, and can be recycled and reused It is simple and has broad application prospects.

Description

A kind of preparation method of graphene self-assembly nano bismuth vanadate photocatalyst

technical field

The invention belongs to the field of preparation of nano bismuth vanadate photocatalyst, in particular to a preparation method of graphene self-assembled nano bismuth vanadate photocatalyst.

Background technique

In recent years, photocatalytic technology represented by titanium dioxide (TiO ₂ ) has been widely used in the field of environmental pollution control, especially in microbial degradation wastewater treatment and air purification. However, due to its wide band gap, it can only It has photocatalytic effect only under ultraviolet light irradiation, which limits the further expansion of its application field. In order to improve _the utilization efficiency of TiO ₂ to sunlight, many experts and scholars at home and abroad have carried out a lot of research work on TiO ₂ photocatalysts responding to visible light. Hybrid modification, etc., aiming to expand its spectral response range and improve its visible light catalytic activity. Nevertheless, the modified _TiO2 photocatalysts still have problems such as unsatisfactory visible light catalytic activity and poor photodegradation ability at the current stage, which lead to their poor practicability.

Recent studies have found that bismuth vanadate (BiVO ₄ ), a compound oxide with a monoclinic scheelite structure, has photocatalytic activity under visible light irradiation, and can decompose water molecules to produce oxygen and degrade organic pollutants. potential photocatalyst. However, the adsorption performance of BiVO ₄ is poor, and the generated photogenerated carriers are difficult to migrate and easy to recombine, which affects its visible light activity. At present, there are few research reports on the compound modification and doping of BiVO ₄ , and there are not many reports on its self-assembly in porous materials with good adsorption properties, such as activated carbon. Therefore, how to enhance its performance in the visible light range The absorption of , and the improvement of its visible light catalytic activity are the main research focus of the current research and development of BiVO ₄ high-efficiency photocatalysts.

The conventional methods of sewage treatment mainly include: physical separation method, biodegradation method, chemical decomposition method, etc., but these methods have certain limitations. Therefore, researchers have begun to work on the development of high efficiency, low energy consumption, wide application range and deep oxidation Capable water purification technology. In recent years, many scholars have used TiO ₂ for photocatalytic degradation of organic pollutants in water bodies. Although some effects have been achieved, the treatment effect is often not ideal due to the limitation of its photoresponse range. In contrast, BiVO ₄ has good photocatalytic activity in the visible region and is a potential ideal photocatalyst.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method of graphene self-assembled nano bismuth vanadate photocatalyst. The self-assembly is uniform, it can efficiently degrade persistent toxic and harmful substances under the conditions of ultraviolet light and visible light, and it is easy to recycle and reuse, which is very suitable for advanced treatment of wastewater.

A kind of preparation method of graphene self-assembled nano-bismuth vanadate photocatalyst of the present invention comprises:

(1) Add bismuth salt and stabilizer to phosphate buffer, stir for 15-60 minutes to form a suspension; dissolve metavanadate evenly in phosphate buffer, and then add it to the suspension , stir evenly to form a transparent solution, wherein the molar ratio of bismuth salt and metavanadate is 1:1, the amount concentration of bismuth salt and metavanadate is 0.01～0.15mol/L, the content of stabilizer The dosage concentration is 0.01～0.05mol/L;

(2) Use an alkaline solution to adjust the pH range of the transparent solution to 4.5-9.0, then add graphene with a mass ratio of 5-20:1 to the bismuth salt at 20-100°C, stir and mix, and reflux for 6-24h , After centrifugation, filtration, and washing, a yellow product can be obtained. Finally, the obtained yellow product is roasted at 180-400°C for 2-4 hours, cooled and ground, and obtained.

The bismuth salt described in step (1) is bismuth nitrate, bismuth subcarbonate, bismuth chloride or bismuth acetate.

The stabilizer described in the step (1) is disodium edetate, tetrasodium edetate, sodium gluconate or butane tetracarboxylic acid.

The metavanadate described in step (1) is sodium metavanadate, potassium metavanadate or ammonium metavanadate.

The phosphate buffer solution described in the step (1) is composed of 0.025-0.05 mol/L sodium dihydrogen phosphate and 0.05-0.1 mol/L disodium hydrogen phosphate.

The alkaline solution described in the step (2) is an aqueous solution of sodium hydroxide or potassium hydroxide with a concentration of 0.5mol/L˜1.5mol/L.

The invention utilizes graphene's unique layer chain structure characteristics, large specific surface area, strong adsorption capacity, chemical inertness and other characteristics, combined with the visible light catalytic activity of BiVO ₄ , successfully self-assembles nano-BiVO ₄ onto graphene, and prepares a Visible light photocatalytic materials with high catalytic activity suspended in water, and applied to the advanced treatment of wastewater, can achieve efficient removal of organic pollutants in water, especially for persistent micro-pollutants that are difficult to effectively remove by conventional treatment, and without Secondary pollution is an environmentally friendly process technology.

In my country, graphene resource reserves are large, but due to the late discovery, its development and utilization level is low, and the foundation of the national non-metallic mineral processing industry is relatively weak, so that the application of this economically significant mineral deposit is limited to General fillers, therefore, the self-assembled visible light photocatalytic material prepared by the present invention also has the advantage of low cost, and has very broad practical application prospects.

Beneficial effect

(1) The present invention has low cost, simple and easy preparation method, low requirement on equipment, and good operability;

(2) The graphene powder bismuth vanadate prepared by the present invention has uniform self-assembly, can efficiently degrade persistent toxic and harmful substances under the conditions of ultraviolet light and visible light, and is easy to recycle and reuse, and is very suitable for advanced treatment of wastewater, and has broad application potential. Application prospect;

(3) Graphene itself is a conductive compound with good performance, which can reduce the coincidence of photogenerated holes and electrons, significantly improve the photocatalytic activity of _BiVO4 , and remove heavy metal ions and other beneficial effects.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

(1) Add bismuth nitrate and disodium edetate into the phosphate buffer, and stir magnetically for 15 minutes to form a suspension; dissolve sodium metavanadate evenly in the phosphate buffer, and then add it dropwise to the In the above-mentioned suspension, the magnetic stirring is uniform to form a transparent solution; wherein the amount concentration of bismuth nitrate, sodium metavanate and disodium edetate is 0.01mol/L, and the phosphate buffer is composed of 0.025mol /L sodium dihydrogen phosphate and 0.05mol/L sodium hydrogen phosphate;

(2) Adopt the sodium hydroxide aqueous solution that concentration is 0.5mol/L to adjust the pH value of above-mentioned transparent solution to be 4.5, then add a certain proportion of graphene at 60 ℃, wherein the mass ratio of bismuth salt and graphene is 1: 5 , continuous magnetic stirring and mixing, reflux for 6h, centrifugation, filtration, and washing, the yellow product can be obtained, and finally the obtained product is roasted at 180°C for 2h, and after cooling and grinding, the graphene photocatalyst assembled with nano-bismuth vanadate is obtained Powder.

Example 2

(1) Add bismuth chloride and sodium gluconate to the phosphate buffer, stir magnetically for 35 minutes to form a suspension; dissolve ammonium metavanadate evenly in the phosphate buffer, and then add it dropwise to the above suspension In the liquid, the magnetic stirring is uniform to form a transparent solution; wherein the molar concentration of bismuth chloride substance is 0.06mol/L, the molar concentration of sodium gluconate substance is 0.03mol/L, and the molar concentration of ammonium metavanitate substance is 0.06mol/L L, phosphate buffer is composed of 0.03mol/L sodium dihydrogen phosphate and 0.08mol/L sodium hydrogen phosphate;

(2) The pH value of the above-mentioned transparent solution is adjusted to be 7 by an aqueous potassium hydroxide solution with a concentration of 1mol/L, and then a certain proportion of graphene is added at 80° C., wherein the mass ratio of bismuth salt and graphene is 1: 12, Continuous magnetic stirring and mixing, reflux for 15 hours, centrifugation, filtration, and washing, the yellow product can be obtained, and finally the obtained product is roasted at 300°C for 3 hours, and after cooling and grinding, the graphene photocatalyst powder assembled with nano-bismuth vanadate is obtained body.

Example 3

(1) Add bismuth acetate and butane tetracarboxylic acid into the phosphate buffer, stir magnetically for 60 minutes to form a suspension; dissolve potassium metavanadate evenly in the phosphate buffer, and then add it dropwise to the above suspension In the turbid liquid, the magnetic stirring is uniform to form a transparent solution; wherein the molar concentration of bismuth acetate is 0.15mol/L, butane tetracarboxylic acid is 0.05mol/L, and potassium metavanate is 0.05mol/L. 0.15mol/L, the phosphate buffer is composed of 0.05mol/L sodium dihydrogen phosphate and 0.1mol/L sodium hydrogen phosphate;

(2) Adopting a concentration of 1.5mol/L sodium hydroxide aqueous solution to adjust the pH value of the above-mentioned transparent solution to 9, and then adding a certain proportion of graphene at 100 ° C, wherein the mass ratio of bismuth salt to graphene is 1: 20 , continuous magnetic stirring and mixing, reflux for 24h, centrifugation, filtration, and washing, the yellow product can be obtained, and finally the obtained product is roasted at 400°C for 4h, and after cooling and grinding, the graphene photocatalyst assembled with nano-bismuth vanadate is obtained Powder.

Wastewater treatment experiment: take the printing and dyeing wastewater finally discharged from a printing and dyeing factory as the treatment object, after pretreatment by microfiltration membrane filtration, add the same amount of photocatalysts prepared in Examples 1 to 3, and continuously Under irradiation for 6 hours, the decolorization rate and COD _Cr removal rate of printing and dyeing wastewater are shown in the following table:

Decolorization rate COD _Cr removal rate Example 1 99.2% 89.6% Example 2 98.3% 93.8% Example 3 99.4% 95.6%

Claims (6)

1. a preparation method of graphene self-assembled nano bismuth vanadate photocatalyst, comprising: (1) Add bismuth salt and stabilizer to phosphate buffer, stir for 15-60 minutes to form a suspension; dissolve metavanadate evenly in phosphate buffer, and then add it to the suspension , stir evenly to form a transparent solution, wherein the molar ratio of bismuth salt and metavanadate is 1:1, the amount concentration of bismuth salt and metavanadate is 0.01～0.15mol/L, the content of stabilizer The dosage concentration is 0.01～0.05mol/L; (2) Use an alkaline solution to adjust the pH range of the transparent solution to 4.5-9.0, then add graphene with a mass ratio of 5-20:1 to the bismuth salt at 20-100°C, stir and mix, and reflux for 6-24h , after centrifugation, filtration, and washing, the product is obtained, and finally the obtained product is roasted at 180-400°C for 2-4 hours, cooled and ground to obtain the product. 2. the preparation method of a kind of graphene self-assembly nano bismuth vanadate photocatalyst according to claim 1 is characterized in that: the bismuth salt described in step (1) is bismuth nitrate, bismuth subcarbonate, chloride Bismuth or bismuth acetate. 3. the preparation method of a kind of graphene self-assembly nano-bismuth vanadate photocatalyst according to claim 1 is characterized in that: the stabilizing agent described in step (1) is disodium edetate, ethylene diamine tetraacetate Tetrasodium amine tetraacetate, sodium gluconate, or butane tetracarboxylic acid. 4. the preparation method of a kind of graphene self-assembly nano-bismuth vanadate photocatalyst according to claim 1 is characterized in that: the metavanadate described in step (1) is sodium metavanadate, metavanadate Potassium or ammonium metavanadate. 5. the preparation method of a kind of graphene self-assembled nano-bismuth vanadate photocatalyst according to claim 1, is characterized in that: the phosphate buffer solution described in step (1) is that the amount concentration of substance is 0.025 ~0.05mol/L sodium dihydrogen phosphate and 0.05~0.1mol/L disodium hydrogen phosphate. 6. The preparation method of a kind of graphene self-assembly nano bismuth vanadate photocatalyst according to claim 1, is characterized in that: the alkaline solution described in step (2) is concentration 0.5mol/L～1.5mol/L L of sodium hydroxide or potassium hydroxide aqueous solution.