CN103112898B - Method for preparing flowerlike bismuth tungstate by hydrothermal process - Google Patents

Abstract

The invention discloses a method for preparing flowerlike bismuth tungstate by a hydrothermal process, which comprises the following steps: evenly mixing bismuth nitrate, sodium tungstate and potassium sulfate used as raw materials in a mol ratio of 2:1:(20-60), regulating the PH value of the solution, transferring into a reaction kettle to react, carrying out centrifugal separation on the product, washing, and drying to obtain the bismuth tungstate. The bismuth tungstate prepared by the simple hydrothermal reaction is in a micro flower shape, and has the advantages of uniform appearance and favorable dispersity. By utilizing the high-concentration salt environment, the substance has higher dispersity; and meanwhile, the formed bismuth tungstate has the advantages of novel appearance, pure phase, simple synthesis method and the like, and has favorable degradation effect on tetracycline.

Description

Method for preparing flower rod-shaped bismuth tungstate by hydrothermal method

technical field

The invention belongs to the technical field of nanomaterial synthesis, and in particular relates to a method for preparing flower rod-shaped bismuth tungstate by a hydrothermal method.

Background technique

Bismuth tungstate (Bi ₂ WO ₆ ) is a bismuth layered perovskite family Bi ₂ A _n-1 B _n O _3n+3 (A=Ca, Sr, Ba, Pb, Bi, Na, K, B=Ti, The simplest oxide among Nb, Ta, Mo, W, Fe) has a forbidden band width of 2.75 eV, and its energy band structure is a conduction band composed of W _5d orbitals and a valence composed of Bi _6s and O _2p orbital hybrids. band composition. Because of its absorption in the visible light region, Bi ₂ WO ₆ is a potential visible light-responsive semiconductor photocatalytic material.

The catalytic performance of photocatalytic materials has a great relationship with the particle size, crystal form, and specific surface area of the substance. Therefore, synthesizing a photocatalytic material with a relatively large specific surface area is a relatively effective method to improve its photocatalytic performance. At present, Bi ₂ WO ₆ nanomaterials with various shapes have been successfully synthesized, including nest shape, microsphere shape, octahedron shape, red blood cell shape, flower shape, nanocage shape, disc shape and so on.

The traditional methods for synthesizing the morphology of Bi ₂ WO ₆ materials are mainly through hydrothermal method and solid phase method. The agglomeration of the substances produced by the hydrothermal method is relatively serious, and the dispersion is poor, which will reduce the specific surface area of the substances; while the substances produced by the solid-state method are often formed under high temperature conditions, which requires more energy. Therefore, it is necessary to develop facile methods to synthesize materials with better dispersion and lower energy requirements.

Bismuth tungstate is also a kind of antibiotic that has better degradation effect under visible light. In recent years, antibiotics have been detected in many regions of the world, and there are more and more types of antibiotics. The ecological risk of antibiotics has aroused widespread concern. Tetracycline is a typical antibiotic drug, which is widely used in agricultural production and livestock feeding. The use of a large number of tetracyclines leads to the accumulation of tetracycline pollutants in water and soil, because antibiotics are stable and durable, and because of their antibacterial effect. Therefore, the problem of removing tetracyclines in the environment needs to be solved urgently.

Contents of the invention

The purpose of the present invention is to provide a method that utilizes bismuth nitrate (Bi(NO ₃ ) ₃ ), sodium tungstate (Na ₂ WO ₄ ) and potassium sulfate (K ₂ SO ₄ ) raw materials and has a simple preparation process without adding surfactants, Novel and uniform flower rod-like bismuth tungstate (Bi ₂ WO ₆ ) method.

In order to achieve the above object, the technical solution adopted in the present invention is:

A method for preparing flower rod-shaped bismuth tungstate by hydrothermal method, the method is carried out according to the following steps:

Step 1, dissolving Bi(NO ₃ ) ₃ in deionized water, and forming a milky white solution after ultrasonic treatment;

Step 2: Add Na ₂ WO ₄ to the milky white solution in Step 1, so that the ratio of Bi(NO ₃ ) ₃ to Na ₂ WO ₄ is 2:1, and stir thoroughly;

Step 3, using NaOH solution and dilute H ₂ SO ₄ to adjust the pH value of the solution obtained in Step 2, so that the pH value of the solution is between 1 and 3;

Step 4: Add K ₂ SO ₄ so that the ratio of K ₂ SO ₄ and Na ₂ WO ₄ is (20-60): 1, mix evenly and transfer to the reaction kettle, at 180-200°C Reaction, kept at a constant temperature for 24 hours, then naturally cooled to obtain a hydrothermal product;

In step five, the hydrothermal product obtained in step four is centrifuged to obtain a precipitate, and then the precipitate is washed three times with distilled water and analytically pure absolute ethanol, and the washed product is vacuum-dried at 60°C to obtain Bi ₂ WO ₆ .

The application of the bismuth tungstate prepared in the above steps for the preparation of a catalyst for photodegradation of tetracycline.

In order to test the photocatalytic activity of the bismuth tungstate prepared by the method of the present invention, a photocatalytic degradation test was carried out on it. Under the condition of visible light irradiation, add 100mL of tetracycline simulated wastewater with a mass concentration of 20mg/L into the reactor of the DW-01 photochemical reaction apparatus, then add 0.1g of bismuth tungstate prepared by the present invention, magnetically stir and turn on the aeration The device is fed with air to keep the bismuth tungstate in a suspended or floating state. During the illumination process, samples are taken at intervals of 10 minutes for analysis. After centrifugation, the supernatant is taken to measure the absorbance at the spectrophotometer λ _max =357nm, and the formula is: DR=[(A ₀ -A _i )/A ₀ ]×100% to calculate the degradation rate, where A ₀ is the absorbance of the tetracycline solution when the adsorption equilibrium is reached, A _i is the absorbance of the tetracycline solution measured by regular sampling, and is evaluated by the degradation degree of tetracycline within 60 minutes Photocatalytic activity of bismuth tungstate.

Beneficial effects of the present invention:

The invention adopts simple hydrothermal reaction to prepare the bismuth tungstate, which has a uniform appearance and a micron flower rod shape with good dispersibility. The material uses a high-concentration salt environment to make the substance have better dispersibility. At the same time, the bismuth tungstate formed has the advantages of novel shape and pure substance, and has a good degradation effect on the residual antibiotic tetracycline in the environment. The process of the invention is simple and reproducible, and the raw materials used are inorganic compounds, which are cheap and easy to obtain, and the cost is low. Since the process does not require high-temperature calcination treatment, the self-assembly of bismuth tungstate sheets can be realized at an appropriate temperature. Therefore, the energy consumption and reaction cost are reduced, and the novel morphology has stronger significance for the theoretical research of bismuth tungstate.

Description of drawings

Fig. 1 is the X-ray diffraction spectrum of bismuth tungstate, among the figure: curve a, b, c represent the X-ray diffraction spectrum of the bismuth tungstate prepared by embodiment 1,3,4 respectively;

Fig. 2 is the scanning electron micrograph of the bismuth tungstate prepared in embodiment 1;

Fig. 3 is the scanning electron micrograph of the bismuth tungstate prepared in embodiment 2;

Fig. 4 is the scanning electron micrograph of the bismuth tungstate prepared by embodiment 3;

Fig. 5 is the scanning electron micrograph of the bismuth tungstate prepared by embodiment 4;

Fig. 6 is the detailed scanning figure of the flower rod shape bismuth tungstate prepared in embodiment 1;

Figure 7 is a tenfold enlarged view of Figure 6;

FIG. 8 is a graph showing the variation of photodegradation of tetracycline catalyzed by the flower-rod-shaped bismuth tungstate prepared in Example 1. FIG.

Detailed ways

The present invention will be described in detail below in conjunction with the examples, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following examples.

Example 1:

Step 1, dissolving 1 mmol of Bi(NO ₃ ) ₃ in 20 ml of deionized water, and forming a milky white solution after ultrasonic treatment;

Step 2: Dissolve 0.5 mmol of Na ₂ WO ₄ in 20 ml of deionized water, mix the solution uniformly after ultrasonic treatment, then gradually add the uniformly mixed solution to the milky white solution in step 1, and stir thoroughly;

Step 3, using NaOH solution with a concentration of 1mol/L and dilute H ₂ SO ₄ to adjust the pH value of the solution obtained in Step 2, so that the pH of the solution is 1;

Step 4: Add 0.010mol of K ₂ SO ₄ to the reaction solution in Step 3, dissolve and disperse evenly; transfer the reaction system to a 50mL polytetrafluoroethylene-lined reactor, and keep it at a constant temperature for 24 hours at 180°C , and then naturally cooled to room temperature to obtain a hydrothermal product;

Step 5: Centrifuge the hydrothermal product obtained in Step 4, wash with absolute ethanol and deionized water three times respectively; dry the washed product in a vacuum drying oven at 60°C for 3 hours to obtain pure white Bi ₂ WO ₆ powder.

As shown in Figure 2 and Figure 6, the Bi ₂ WO ₆ prepared by the method in this example is in the shape of a flower rod, and the length of the flower rod-shaped bismuth tungstate material is 5-15 μm; Figure 7 is ten times that of the bismuth tungstate in Figure 6 Enlarged view, as shown in the figure, rod-shaped bismuth tungstate is composed of nano-sheet-shaped bismuth tungstate with a length of 200-300nm.

In order to check the photocatalytic activity of the bismuth tungstate prepared by _the method of the present invention, 0.1 g of _Bi2W06 prepared by the method of this example was carried out in a DW-01 photochemical reaction apparatus for photocatalytic degradation of tetracycline. The degradation of tetracycline within 60min To evaluate the photocatalytic activity of bismuth tungstate.

experiment method:

Under the condition of visible light irradiation, add 100mL of tetracycline simulated wastewater with a mass concentration of 20mg/L into the reactor of the DW-01 photochemical reactor, then add 0.1g of bismuth tungstate prepared by the method of the present invention, magnetically stir and turn on the aeration The device is fed with air to keep the bismuth tungstate in a suspended or floating state. During the illumination process, samples are taken at intervals of 10 minutes for analysis. After centrifugation, the supernatant is taken to measure the absorbance at the spectrophotometer λ _max =357nm, and the formula is: DR=[(A ₀ -A _i )/A ₀ ]×100% to calculate the degradation rate, where A ₀ is the absorbance of tetracycline solution when adsorption equilibrium is reached, and A _i is the absorbance of tetracycline solution measured by regular sampling.

The degradation rate of tetracycline antibiotics by the bismuth tungstate prepared in this example reached 75% within 60 minutes through the above tests. The micron flower rod-shaped photocatalyst has strong photocatalytic activity, as shown in FIG. 8 .

Example 2:

The preparation method in the present embodiment is the same as that in Example 1, the difference is only that the conditions in the preparation process are different, the pH=3 of the solution is adjusted in the step 3 of the present embodiment, and 0.030mol potassium sulfate is taken in the step 4 and the reaction temperature is 200 °C, and the rest of the conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 68% within 60 minutes.

Example 3:

The preparation method in this example is the same as that in Example 1, the only difference being that the conditions in the preparation process are different. In step 4, 0.030 mol of potassium sulfate is taken and the reaction temperature is 200° C., and the rest of the conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 70% within 60 minutes.

Example 4:

The preparation method in this example is the same as that in Example 1, the only difference is that the conditions in the preparation process are different. In step 3 of this example, the pH of the solution is adjusted to 3, and the other conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 69% within 60 minutes.

Example 5:

The preparation method in this example is the same as that in Example 1, the only difference being that the conditions in the preparation process are different, the reaction temperature in Step 4 of this example is 200° C., and the other conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 63% within 60 minutes.

Embodiment 6:

The preparation method in this embodiment is the same as that in Example 1, the only difference being that the conditions in the preparation process are different, the pH=3 of the solution is adjusted in the step 3 of the present embodiment, 0.030mol potassium sulfate is taken in the step 4, and all the other conditions are unchanged .

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of the photocatalyst for tetracycline antibiotics reaches 65% within 60 minutes.

Embodiment 7:

The preparation method in this embodiment is the same as that in Example 1, the only difference being that the conditions in the preparation process are different, 0.015mol potassium sulfate is taken in step 4 of the present embodiment, and all the other conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 73% within 60 minutes.

Embodiment 8:

The preparation method in this embodiment is the same as that in Example 1, the only difference being that the conditions in the preparation process are different. In step 4 of this embodiment, 0.020 mol of potassium sulfate is used, and all the other conditions remain unchanged.

Take 0.1 g of Bi ₂ WO ₆ prepared in this example to conduct a photocatalytic degradation test of tetracycline in a photochemical reactor, and it is measured that the degradation rate of tetracycline antibiotics by the photocatalyst reaches 72% within 60 minutes.

It can be seen from the above examples and the corresponding photocatalytic degradation test of tetracycline that the bismuth tungstate prepared in Example 1 has the strongest photocatalytic activity.

As shown in Figure 1, a, b, and c in the figure represent the X-ray diffraction patterns (XRD) of the bismuth tungstate prepared in Examples 1, 3, and 4, respectively. From the figure, it can be seen that the positions and relative positions of each diffraction peak The intensity is consistent with the JCPDS (Joint Committee on Powder Diffraction Standards) card (39-0256), indicating that the product is orthorhombic Bi ₂ WO ₆ , and there are no other diffraction peaks in the XRD pattern, indicating that the method of the present invention prepares Bi _{2 WO 6} The phase of WO ₆ is pure.

Shown in Fig. 2 to Fig. 6 is the scanning electron micrograph (SEM) of the bismuth tungstate prepared by embodiment 1, 2, 3, 4, as can be seen from the figure the shape of the micron flower rod-shaped bismuth tungstate prepared by embodiment 1 The appearance is the most uniform.

Claims (2)

1. a method for preparing flower rod-shaped bismuth tungstate by hydrothermal method, is characterized in that, the method is carried out according to the following steps: Step 1, dissolving Bi(NO ₃ ) ₃ in deionized water, and forming a milky white solution after ultrasonic treatment; Step 2: Add Na ₂ WO ₄ to the milky white solution in Step 1, so that the ratio of Bi(NO ₃ ) ₃ to Na ₂ WO ₄ is 2:1, and stir thoroughly; Step 3, using NaOH solution and dilute H ₂ SO ₄ to adjust the pH value of the solution obtained in Step 2, so that the pH value of the solution is 1-3; Step 4: Add K ₂ SO ₄ to the solution obtained in Step 3, so that the ratio of K ₂ SO ₄ and Na ₂ WO ₄ is (20-60): 1, and after uniform mixing, transfer the reaction system to the reaction In the kettle, react at 180-200 °C, keep the temperature for 24 hours, and then cool naturally to obtain the hydrothermal product; Step five, centrifuging the hydrothermal product obtained in step four to obtain a precipitate, then washing the precipitate three times with distilled water and analytical pure absolute ethanol, and drying the washed product in vacuum at 60°C to obtain Bi ₂ WO ₆ . 2. hydrothermal method as claimed in claim 1 prepares the method for flower rod shape bismuth tungstate, it is characterized in that, Step 1, dissolving 1 mmol of Bi(NO ₃ ) ₃ in 20 mL of deionized water, and forming a milky white solution after ultrasonic treatment; Step 2, add 0.5 mmol of Na ₂ WO ₄ to the milky white solution in Step 1, and stir thoroughly; Step 3, using NaOH solution and dilute H ₂ SO ₄ to adjust the pH of the solution obtained in Step 2, so that the pH value of the solution is 1; Step 4: Add 0.010 mol of K ₂ SO ₄ to the solution obtained in Step 3, mix evenly, transfer the reaction system to a reactor, react at 180°C, keep the temperature for 24 hours, and then cool naturally to obtain a hydrothermal product ; Step five, centrifuging the hydrothermal product obtained in step four to obtain a precipitate, then washing the precipitate three times with distilled water and analytical pure absolute ethanol, and drying the washed product in vacuum at 60°C to obtain Bi ₂ WO ₆ .