Pompon-shaped nano tungstic acid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of tungsten metallurgy, and particularly relates to pompon-shaped nano tungstic acid and a preparation method and application thereof.The preparation method comprises the steps that S1, hydrochloric acid is added into a container, continuous stirring is conducted in the adding process, and the temperature in the container is made to be stable; s2, dropwise adding 2-5mL of an ammonium tungstate solution B into the container, continuously stirring in the adding process, and enabling the temperature in the container to be stable; s3, 0.6-1.0 L of an ammonium tungstate solution A is added into the container, continuous stirring is conducted in the adding process, and the temperature in the container is made to be stable; the amount of hydrochloric acid added in the step S1 is 1.5-2.0 times of the theoretical amount of hydrochloric acid required for preparing tungstic acid according to the concentration of tungstate radicals in the ammonium tungstate solution A; s4, repeating the steps S1 and S3; and S5, filtering the prepared tungstic acid, washing with hydrochloric acid, and drying to obtain the pompon-like nano tungstic acid. The prepared tungstic acid is good in grain uniformity, pompon-shaped and porous, and the specific surface area is larger than or equal to 80 m < 2 > / g.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten metallurgy, and particularly relates to a flocculent nano tungsten acid, a preparation method thereof and an application thereof. Background Art

[0002] Nano tungsten acid (H 2 WO 4 ) as a nano-scale inorganic material, due to its high specific surface area, excellent optoelectronic properties, catalytic activity, as well as chemical and thermal stability, shows broad application potential in multiple fields. In the field of catalysis, it is used for photocatalytic degradation of pollutants and water splitting for hydrogen production; in energy storage, as an electrode material for supercapacitors and lithium / sodium batteries, it can improve efficiency; its sensitive gas sensing ability and antibacterial properties also make it highly concerned in the fields of sensors, environmental protection and biomedicine.

[0003] However, the large-scale preparation of nano tungsten acid still faces many challenges: traditional methods such as hydrothermal method and sol-gel method can control the morphology and purity, but they have high costs, complex processes, poor particle uniformity and serious agglomeration; although the chemical precipitation method is simple and cheap, it is difficult to avoid impurity residues. In addition, the environmental toxicity, long-term stability of nano materials and the problem of uniformity control in large-scale production still need further research. With the technological progress and update iteration in the application fields of nano materials in recent years, the performance requirements for nano materials are getting higher and higher, so it is crucial to develop nano tungsten acid with high purity, high specific surface area and good uniformity. Summary of the Invention

[0004] To solve the problems existing in the prior art, the main object of the present invention is to propose a flocculent nano tungsten acid, a preparation method thereof and an application thereof.

[0005] According to one aspect of the present invention, the present invention provides the following technical solutions: A preparation method of a flocculent nano tungsten acid, comprising the following steps: S1. Add hydrochloric acid to a container, and continuously stir during the addition process to keep the temperature in the container stable; S2. Drop 2-5 mL of ammonium tungstate solution B into the container, and continuously stir during the addition process to keep the temperature in the container stable; S3. Add 0.6-1.0 L of ammonium tungstate solution A to the container, and continuously stir during the addition process to keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 1.5-2.0 times the theoretical amount of hydrochloric acid required for preparing tungstic acid according to the tungstate ion concentration in ammonium tungstate solution A; S4. Repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid and then dry it to obtain flocculent nano tungsten acid.

[0006] According to another aspect of the present invention, the present invention provides the following technical solutions: A kind of fluffy spherical nano-tungstic acid is prepared by using the above-mentioned preparation method of fluffy spherical nano-tungstic acid. The grains of the fluffy spherical nano-tungstic acid have good uniformity and are in the shape of fluffy spheres, with porous characteristics, and the specific surface area ≥ 80m 2 / g.

[0007] According to another aspect of the present invention, the present invention provides the following technical solutions: The application of the fluffy spherical nano-tungstic acid in photocatalytic degradation of organic pollutants.

[0008] The beneficial effects of the present invention are as follows: The present invention provides a kind of fluffy spherical nano-tungstic acid, its preparation method and application. By means of pre-preparing seeds and adding materials in segments, nano-tungstic acid with high specific surface area and good uniformity is prepared. Alternately adding hydrochloric acid and ammonium tungstate solution A can keep the concentration of hydrochloric acid in the reaction system within a relatively stable range all the time, can control the reaction rate and the concentration of solutes in the solution, and make the particle size of the formed tungstic acid more uniform. The prepared tungstic acid grains have good uniformity and are in the shape of fluffy spheres, with porous characteristics, and the specific surface area ≥ 80m 2 / g. Description of the drawings

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0010] Figure 1 It is the electron microscope image of the fluffy spherical nano-tungstic acid prepared in Example 1 of the present invention; Figure 2 It is the electron microscope image of the fluffy spherical nano-tungstic acid prepared in Example 2 of the present invention; Figure 3 It is the electron microscope image of the fluffy spherical nano-tungstic acid prepared in Example 3 of the present invention; Figure 4 It is the electron microscope image of the tungstic acid prepared in Comparative Example 1 of the present invention; Figure 5 It is the electron microscope image of the tungstic acid prepared in Comparative Example 2 of the present invention; Figure 6 It is the electron microscope image of the tungstic acid prepared in Comparative Example 3 of the present invention; Figure 7 It is the electron microscope image of the tungstic acid prepared in Comparative Example 4 of the present invention.

[0011] The realization, functional features, and advantages of the present invention will be further described in conjunction with embodiments and with reference to the accompanying drawings. Detailed Embodiments

[0012] The technical solutions in the embodiments will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention.

[0013] The present invention provides a method for preparing and applying a flocculent nano-tungstic acid. By using the method of pre-preparing seeds and adding materials in segments at a certain temperature, nano-tungstic acid with a high specific surface area and uniform particles can be prepared, which can solve the problems of generally low specific surface area, poor particle uniformity, and serious agglomeration of nano-tungstic acid at present. Alternately adding hydrochloric acid and ammonium tungstate solution A can keep the concentration of hydrochloric acid in the reaction system within a relatively stable range all the time, control the reaction rate and the concentration of solutes in the solution, and make the particle size of the formed tungstic acid more uniform. If hydrochloric acid is not added alternately in batches, the concentration of hydrochloric acid will become lower and lower, resulting in tungstic acid with greatly different sizes and morphologies.

[0014] According to one aspect of the present invention, the present invention provides the following technical solutions: A method for preparing a flocculent nano-tungstic acid, comprising the following steps: S1. Add hydrochloric acid to a container, continuously stir during the adding process and keep the temperature in the container stable; S2. Drop 2 - 5 mL of ammonium tungstate solution B into the container, continuously stir during the adding process and keep the temperature in the container stable; S3. Add 0.6 - 1.0 L of ammonium tungstate solution A to the container, continuously stir during the adding process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 1.5 - 2.0 times the theoretical amount of hydrochloric acid required for preparing tungstic acid according to the concentration of tungstate in ammonium tungstate solution A; S4. Repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain the flocculent nano-tungstic acid.

[0015] Preferably, in the steps S1 - S3, the temperature in the container is 80 - 110 °C, and the stirring speed is 100 - 400 r / min. If the temperature is too high, it will lead to high energy consumption, large hydrochloric acid volatilization, large acid loss, and low specific surface area of the prepared tungstic acid; if the temperature is too low, the nucleation rate is slow, the deposition and growth effect is obvious, the tungstic acid is seriously agglomerated, and the uniformity is poor. Specifically, the temperature in the container can be any one of, for example, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C or the range between any two of them. If the stirring speed is too low, the tungstic acid is prone to deposit and grow, and the specific surface area is low; if the stirring speed is too high, the tungstic acid is easily broken, with poor crystal form and uniformity. Specifically, the stirring speed can be any one of, for example, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min or the range between any two of them.

[0016] Preferably, in the step S1, the concentration of hydrochloric acid is 16 - 22 wt%; there is no special requirement for the addition speed of hydrochloric acid, and it can be added as soon as possible; for example, each time hydrochloric acid is added, it can be added within 5 - 10 s. If the hydrochloric acid concentration is too high, the volatilization amount is large at high temperature, resulting in large acid loss, and local over - acidity and large nucleation amount, with serious agglomeration and hardening, which is not conducive to the preparation of uniform tungstic acid; if the hydrochloric acid concentration is too low, the total volume of the solution is large, reducing the reaction efficiency, increasing equipment energy consumption, and high production and preparation costs. Specifically, the concentration of hydrochloric acid can be any one of, for example, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt% or the range between any two of them.

[0017] Preferably, in the step S2, based on WO 3 calculation, the concentration of ammonium tungstate solution B is 220 - 250 g / L; in the step S3, based on WO 3 calculation, the concentration of ammonium tungstate solution A is 220 - 250 g / L. Specifically, the concentration of ammonium tungstate solution B and the concentration of ammonium tungstate solution A can be the same or different. The concentration of ammonium tungstate solution A can be any one of, for example, 220 g / L, 225 g / L, 230 g / L, 235 g / L, 240 g / L, 245 g / L, 250 g / L or the range between any two of them; the concentration of ammonium tungstate solution B can be any one of, for example, 220 g / L, 225 g / L, 230 g / L, 235 g / L, 240 g / L, 245 g / L, 250 g / L or the range between any two of them.

[0018] Preferably, in step S2, after dropping 2-5 mL of ammonium tungstate solution B into the container, stir for 8-12 min, and then proceed to step S3; the dropping rate of ammonium tungstate solution B is 20-30 mL / min. The function of dropping 2-5 mL of ammonium tungstate solution B in this step is to first form a small amount of tungstic acid as the seed crystal for the subsequent growth of tungstic acid crystals. The dropping amount of ammonium tungstate solution B enables the amount of seed crystals to be controlled within a certain range. Too much or too little will lose the meaning of adding seed crystals, resulting in the inability to stably obtain fluffy spherical nano-tungstic acid. Specifically, the dropping amount of ammonium tungstate solution B can be any one of 2 mL, 3 mL, 4 mL, 5 mL or the range between any two of them. At the same time, controlling the dropping rate of ammonium tungstate solution B at 20-30 mL / min and stirring for 8-12 min after dropping ammonium tungstate solution B is beneficial to the uniform formation of seed crystals. Specifically, the dropping rate of ammonium tungstate solution B can be, for example, any one of 20 mL / min, 21 mL / min, 22 mL / min, 23 mL / min, 24 mL / min, 25 mL / min, 26 mL / min, 27 mL / min, 28 mL / min, 29 mL / min, 30 mL / min or the range between any two of them; the stirring time after dropping ammonium tungstate solution B can be any one of 8 min, 9 min, 10 min, 11 min, 12 min or the range between any two of them.

[0019] Preferably, in step S3, the adding rate of ammonium tungstate solution A is 40-80 mL / min; after the addition of ammonium tungstate solution A is completed, stir for 10-30 min and then proceed to step S4. If the adding rate of ammonium tungstate solution A is too fast, there will be more nucleation of tungstic acid and it is easy to agglomerate and cake; if the adding rate of ammonium tungstate solution A is too slow, it is easy to deposit and grow, and the particle size of tungstic acid is coarse. Specifically, the adding rate of ammonium tungstate solution A can be, for example, any one of 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min, 60 mL / min, 65 mL / min, 70 mL / min, 75 mL / min, 80 mL / min or the range between any two of them; the stirring time after the addition of ammonium tungstate solution A is completed can be, for example, any one of 10 min, 15 min, 20 min, 25 min, 30 min or the range between any two of them. The volume of ammonium tungstate solution A can be, for example, any one of 0.6 L, 0.65 L, 0.7 L, 0.75 L, 0.8 L, 0.85 L, 0.9 L, 0.95 L, 1.0 L or the range between any two of them. The dosage of hydrochloric acid can be any one of 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times the theoretical amount of dilute hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in ammonium tungstate solution A or the range between any two of them.

[0020] Preferably, in step S4, after repeating 4 to 8 times, step S5 is carried out. Specifically, the number of repetitions can be 4, 5, 6, 7, or 8.

[0021] Preferably, in step S5, the concentration of hydrochloric acid is 3 wt%, and it is washed 2 to 4 times, and the drying temperature is 100 to 120 °C. Adopting a relatively high drying temperature is beneficial to the volatilization of the residual hydrochloric acid in tungstic acid at this drying temperature, but if the temperature is too high, the water evaporates too quickly and it is not easy to obtain loose tungstic acid. Specifically, the drying temperature can be, for example, any one of 100 °C, 105 °C, 110 °C, 115 °C, 120 °C or the range between any two of them.

[0022] According to another aspect of the present invention, the present invention provides the following technical solution: A kind of fluffy nano tungstic acid is prepared by using the above-mentioned preparation method of fluffy nano tungstic acid. The fluffy nano tungstic acid has good grain uniformity and is in a fluffy shape, has porous characteristics, and the specific surface area ≥ 80 m 2 / g. Specifically, the specific surface area of the fluffy nano tungstic acid can be, for example, any one of 80 m 2 / g, 85 m 2 / g, 90 m 2 / g, 95 m 2 / g, 100 m 2 / g or the range between any two of them.

[0023] According to another aspect of the present invention, the present invention provides the following technical solution: The application of the fluffy nano tungstic acid in photocatalytic degradation of organic pollutants.

[0024] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1 A preparation method of fluffy nano tungstic acid includes the following steps: S1. Add hydrochloric acid to the container, and continuously stir during the addition process and keep the temperature in the container stable; S2. Drop 2 mL of ammonium tungstate solution B into the container, and continuously stir during the addition process and keep the temperature in the container stable; S3. Add 0.6 L of ammonium tungstate solution A to the container, and continuously stir during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 1.5 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in ammonium tungstate solution A; S4. Repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain fluffy nano tungstic acid.

[0026] In the steps S1 - S3, the temperature in the container is 80°C and the stirring speed is 400 r / min; in the step S1, the concentration of hydrochloric acid is 16 wt%; in the step S2, based on WO 3 calculation, the concentration of ammonium tungstate solution B is 250 g / L; in the step S3, based on WO 3 calculation, the concentration of ammonium tungstate solution A is 250 g / L; in the step S2, after dropping 2 mL of ammonium tungstate solution B into the container, stir for 10 min and then proceed to step S3; the dropping speed of ammonium tungstate solution B is 20 mL / min; in the step S3, the adding speed of ammonium tungstate solution A is 40 mL / min; after the addition of ammonium tungstate solution A is completed, stir for 10 min and then proceed to step S4; in the step S4, repeat 8 times and then proceed to step S5. In the step S5, the concentration of hydrochloric acid is 3 wt%, wash 3 times, and the drying temperature is 110°C.

[0027] The wool ball - shaped nano - tungsten acid obtained in this example is as Figure 1 shown, and its specific surface area is 95 m 2 / g.

[0028] Example 2 A preparation method of wool ball - shaped nano - tungsten acid, comprising the following steps: S1. Add hydrochloric acid into the container, stir continuously during the addition process and keep the temperature in the container stable; S2. Drop 5 mL of ammonium tungstate solution B into the container, stir continuously during the addition process and keep the temperature in the container stable; S3. Add 1.0 L of ammonium tungstate solution A into the container, stir continuously during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 2.0 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the concentration of tungstate in ammonium tungstate solution A; S4. Repeat steps S1 and S3; S5. Filter the obtained tungstic acid, wash it with hydrochloric acid and then dry it to obtain wool ball - shaped nano - tungsten acid.

[0029] In the steps S1 - S3, the temperature in the container is 110°C and the stirring speed is 100 r / min; in the step S1, the concentration of hydrochloric acid is 22 wt%; in the step S2, based on WO 3 calculation, the concentration of ammonium tungstate solution B is 220 g / L; in the step S3, based on WO 3It is calculated that the concentration of ammonium tungstate solution A is 220 g / L; in the step S2, after dropping 5 mL of ammonium tungstate solution B into the container and stirring for 10 min, step S3 is carried out; the dropping rate of ammonium tungstate solution B is 30 mL / min; in the step S3, the adding rate of ammonium tungstate solution A is 80 mL / min; after the addition of ammonium tungstate solution A is completed, stir for 30 min and then carry out step S4; in the step S4, repeat 4 times and then carry out step S5. In the step S5, the concentration of hydrochloric acid is 3 wt%, wash 3 times, and the drying temperature is 100 °C.

[0030] The present embodiment obtains flocculent nano tungsten acid as Figure 2 shown, and its specific surface area is 82.1 m 2 / g.

[0031] Example 3 A preparation method of flocculent nano tungsten acid includes the following steps: S1. Add hydrochloric acid to the container, continuously stir during the addition process and keep the temperature in the container stable; S2. Drop 4 mL of ammonium tungstate solution B into the container, continuously stir during the addition process and keep the temperature in the container stable; S3. Add 0.8 L of ammonium tungstate solution A to the container, continuously stir during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 1.8 times the theoretical amount of hydrochloric acid required to prepare tungstic acid according to the tungstate ion concentration in ammonium tungstate solution A; S4. Repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid and then dry it to obtain flocculent nano tungsten acid.

[0032] In the steps S1-S3, the temperature in the container is 95 °C and the stirring speed is 300 r / min; in the step S1, the concentration of hydrochloric acid is 19 wt%; in the step S2, calculated by WO 3 the concentration of ammonium tungstate solution B is 230 g / L; in the step S3, calculated by WO 3 the concentration of ammonium tungstate solution A is 230 g / L; in the step S2, after dropping 4 mL of ammonium tungstate solution B into the container and stirring for 10 min, step S3 is carried out; the dropping rate of ammonium tungstate solution B is 25 mL / min; in the step S3, the adding rate of ammonium tungstate solution A is 60 mL / min; after the addition of ammonium tungstate solution A is completed, stir for 20 min and then carry out step S4; in the step S4, repeat 6 times and then carry out step S5. In the step S5, the concentration of hydrochloric acid is 3 wt%, wash 3 times, and the drying temperature is 120 °C.

[0033] The present embodiment obtains flocculent nano tungsten acid as Figure 3 shown, and its specific surface area is 89.4 m2 / g.

[0034] Comparative Example 1 The difference from Example 3 is that hydrochloric acid and ammonium tungstate solution A were not added in a segmented and alternating manner: that is, all hydrochloric acid was added first, and then ammonium tungstate solution B was dropped in and then all ammonium tungstate solution A was added.

[0035] The tungstic acid obtained in this comparative example was as Figure 4 shown, which was flaky, and the specific surface area was 40 m 2 / g.

[0036] Comparative Example 2 The difference from Example 3 was that step S2 was not carried out.

[0037] The tungstic acid obtained in this comparative example was as Figure 5 shown, which was in irregular flaky shape, and the specific surface area was 64.7 m 2 / g.

[0038] Comparative Example 3 The difference from Example 3 was that the temperature inside the container was at room temperature.

[0039] The tungstic acid obtained in this comparative example was as Figure 6 shown, which was in irregular flaky shape, with poor uniformity, and the specific surface area was 25.73 m 2 / g.

[0040] Comparative Example 4 The difference from Example 3 was that a sodium tungstate solution with the same concentration in terms of WO 3 was used to replace ammonium tungstate solution A.

[0041] The tungstic acid obtained in this comparative example was as Figure 7 shown, which was in regular flaky shape, and the specific surface area was 34.24 m 2 / g.

[0042] The tungstic acids prepared in Example 3 and Comparative Example 4 were used to degrade a methylene blue solution with a concentration of 10 -5 mol / L, and the results were as follows: After using the fluffy spherical nano-tungstic acid prepared in Example 3 to degrade the methylene blue solution and irradiating it under a 500 W xenon lamp for 120 min, the degradation rate was 95.5%.

[0043] However, after using the conventional flaky tungstic acid prepared in Comparative Example 4 to degrade the methylene blue solution and irradiating it under a 500 W xenon lamp for 120 min, the degradation rate was only 51.6%.

[0044] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields shall be included within the patent protection scope of the present invention.

Claims

1. A method for preparing fluff-shaped nano-tungstic acid, characterized in that: The steps include: S1. Add hydrochloric acid to the container, stirring continuously during the addition process and keeping the temperature in the container stable; S2. Add 2-5 mL of ammonium tungstate solution B to the container, stirring continuously and keeping the temperature in the container stable during the addition process; S3, add 0.6~1.0L of ammonium tungstate solution A to the container, keep stirring during the addition process and keep the temperature in the container stable; the amount of hydrochloric acid added in step S1 is 1.5~2.0 times the theoretical amount of hydrochloric acid required for preparing tungstic acid according to the tungstate concentration in the ammonium tungstate solution A; S4, repeat steps S1 and S3; S5. Filter the prepared tungstic acid, wash it with hydrochloric acid, and then dry it to obtain fluff-shaped nano tungstic acid.

2. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In the steps S1-S3, the temperature in the container is 80-110° C., and the stirring speed is 100-400 r / min.

3. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In step S1, the concentration of hydrochloric acid is 16-22 wt %.

4. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In the step S2, the concentration of the ammonium tungstate solution B is 220-250 g / L in terms of WO3; in the step S3, the concentration of the ammonium tungstate solution A is 220-250 g / L in terms of WO3.

5. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In the step S2, 2-5 mL of ammonium tungstate solution B is dripped into the container and stirred for 8-12 min, and then step S3 is performed; the dripping speed of ammonium tungstate solution B is 20-30 mL / min.

6. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In the step S3, the rate of adding the ammonium tungstate solution A is 40-80 mL / min; after the addition of the ammonium tungstate solution A is completed, the solution is stirred for 10-30 min before proceeding to step S4.

7. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In the step S4, step S5 is performed after repeating 4 to 8 times.

8. The method for preparing the flocculent nano-tungstic acid according to claim 1, characterized in that: In step S5, the concentration of hydrochloric acid is 3 wt %, washing is performed 2 to 4 times, and the drying temperature is 100 to 120° C.

9. A flocculent nano-tungstic acid, characterized in that: The velvet-shaped nano-tungstic acid is prepared by the preparation method of any one of claims 1 to 8, wherein the velvet-shaped nano-tungstic acid has good uniformity and is velvet-shaped, has porous characteristics, and has a specific surface area of ​​≥80m 2 / g.

10. Use of the flocculent nano-tungstic acid according to claim 9 in photocatalytic degradation of organic pollutants.

Images