Functional nano tungsten oxide as well as preparation method and application thereof

Abstract

The invention provides functional nano tungsten oxide and a preparation method and application thereof, and belongs to the field of tungsten-based nanometers.The preparation method of the functional nano tungsten oxide comprises the following steps that S1, a tungsten source is taken and dissolved in water to prepare a tungsten source solution, the pH of the tungsten source solution is regulated to 3.5-5.0, ethylene glycol is added into the tungsten source solution, and the mixture is mixed to be uniform to obtain a mixed solution; s2, carrying out hydrothermal reaction on the mixed solution at 120-150 DEG C, cooling to room temperature after the reaction is finished, and carrying out centrifugal separation, washing and drying to obtain a tungstic acid precursor; and S3, calcining the tungstic acid precursor, preserving heat at 250-350 DEG C for 1-2 hours, heating to 500-700 DEG C, preserving heat for 2-4 hours, cooling, grinding and sieving to obtain the functional nano tungsten oxide. The functional nano tungsten oxide prepared by the method is narrow in particle size distribution and good in dispersity, and shows excellent performance in the field of photocatalysis.

Description

Technical Field

[0001] This invention relates to the field of tungsten-based nanomaterials technology, specifically to a functional nano-tungsten oxide, its preparation method, and its applications. Background Technology

[0002] Due to its unique semiconductor properties and surface effects, nano-tungsten oxide exhibits great application potential in functional fields such as photocatalytic degradation of pollutants, smart window electrochromism, and gas sensors. Crystal size, morphology, and crystal phase purity directly determine its optical band gap, charge migration path, and surface active site density. Therefore, the controllable synthesis of nano-tungsten oxide with uniform size, good dispersion, and a single crystal phase is key to improving its application performance.

[0003] At present, the hydrothermal method for preparing nano-tungsten oxide is widely used due to its advantages such as mild reaction conditions and controllable product morphology. However, the traditional hydrothermal process has the following problems: (1) the tungsten source is not completely dissolved, which easily forms agglomerated blocky precipitates, resulting in a wide particle size distribution of the final product; (2) the lack of precise control of the weak acid environment makes the polymerization morphology of tungstate ions unstable, affecting the uniformity of tungsten oxide crystal form; (3) the dispersant is not properly selected and is easily decomposed and ineffective under high temperature and high pressure, which cannot effectively inhibit particle agglomeration.

[0004] Therefore, there is an urgent need to develop a new hydrothermal process to achieve controllable preparation of nano-tungsten oxide particles with uniform particle size, single crystal phase, and good dispersibility. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a functional nano-tungsten oxide, its preparation method and application, aiming to solve the technical problems of wide particle size distribution, impure crystal phase and poor dispersibility of nano-tungsten oxide prepared by traditional hydrothermal method.

[0006] In a first aspect, the present invention provides a method for preparing functional nano-tungsten oxide, comprising the following steps: S1. Dissolve tungsten source in water to obtain tungsten source solution, adjust the pH of tungsten source solution to 3.5~5.0, add ethylene glycol to tungsten source solution and mix well to obtain mixed solution; S2. The mixed solution is subjected to a hydrothermal reaction at 120~150℃. After the reaction is completed, it is cooled to room temperature, and then centrifuged, washed, and dried to obtain the tungstic acid precursor. S3, tungstate precursor is calcined at 250~350℃ for 1~2h, then heated to 500~700℃ for 2~4h, cooled, ground and sieved to obtain functional nano tungsten oxide.

[0007] Preferably, the tungsten source includes sodium tungstate or ammonium tungstate.

[0008] Preferably, the concentration of the tungsten source solution is 0.1~0.5 mol / L.

[0009] Preferably, adjusting the pH of the tungsten source solution to 3.5~5.0 specifically involves adding ammonium chloride to the tungsten source solution, wherein the molar ratio of ammonium chloride to tungsten source is (1~3):1.

[0010] Preferably, the volume ratio of ethylene glycol to water is 1:(5~10).

[0011] Preferably, the hydrothermal reaction of the mixed solution at 120~150℃ specifically involves: transferring the mixed solution into a polytetrafluoroethylene hydrothermal reactor with a filling degree of 70%~80%, placing the hydrothermal reactor in an oven, and reacting at 120~150℃ for 4~12 hours.

[0012] Preferably, in step S2, the washing process specifically involves washing with deionized water and anhydrous ethanol alternately 3 to 5 times.

[0013] Preferably, in step S2, the drying temperature is 60~80℃ and the drying time is 2~4h.

[0014] Secondly, the present invention provides a functional nano-tungsten oxide, which is prepared by the method for preparing functional nano-tungsten oxide described in the first aspect.

[0015] Thirdly, this invention provides an application of functional nano-tungsten oxide in the photocatalytic degradation of wastewater.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a functional nano-tungsten oxide, its preparation method, and its applications. A stable weakly acidic environment (pH 3.5-5.0) is created using ammonium chloride, allowing tungstate ions to polymerize at a controllable rate, forming uniform nano-sized tungstate precipitates. During the hydrothermal process, ethylene glycol coordinates with the tungstate surface through hydroxyl groups, effectively inhibiting particle agglomeration. Furthermore, the segmented calcination process avoids the crystal form mixing problem caused by traditional one-step calcination. The 500-700℃ holding stage allows for precise control of the tungsten oxide crystal form, improving crystal purity.

[0017] The preparation method of this invention is simple and easy to implement, with mild reaction conditions, making it easy to achieve large-scale production. The functional nano-tungsten oxide prepared by this method has the characteristics of narrow particle size distribution, single crystal phase, and good dispersibility, exhibiting excellent application performance in the field of photocatalysis. Attached Figure Description

[0018] Figure 1 This is a SEM image of the functional nano-tungsten oxide prepared in Example 1 of the present invention. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0020] To address the technical problems of wide particle size distribution, mixed crystal phases, and poor dispersibility of nano-tungsten oxide prepared by traditional hydrothermal methods, this invention provides a functional nano-tungsten oxide, its preparation method, and its application. In this invention, by controlling the morphology of tungstic acid precipitation and the crystal transformation process, nano-tungsten oxide materials with excellent photocatalytic performance are obtained.

[0021] In a first aspect, embodiments of the present invention provide a method for preparing functional nano-tungsten oxide, comprising the following steps: S1. Dissolve tungsten source in water to obtain tungsten source solution, adjust the pH of tungsten source solution to 3.5~5.0, add ethylene glycol to tungsten source solution and mix well to obtain mixed solution; S2. The mixed solution is subjected to a hydrothermal reaction at 120~150℃. After the reaction is completed, it is cooled to room temperature, and then centrifuged, washed, and dried to obtain the tungstic acid precursor. S3, tungstate precursor is calcined at 250~350℃ for 1~2h, then heated to 500~700℃ for 2~4h, cooled, ground and sieved to obtain functional nano tungsten oxide.

[0022] In the technical solution of this invention embodiment, in step S1, selecting an appropriate tungsten source and adjusting the pH of the solution to a weakly acidic range can effectively prevent excessive polymerization of tungstate ions; the hydroxyl groups of ethylene glycol coordinate with the surface of tungstic acid to form a soluble complex, which completely dissolves the tungsten source and disperses it uniformly, effectively inhibiting particle agglomeration from the source; in step S2, the control of hydrothermal reaction conditions ensures the uniform generation of the precursor, while the subsequent centrifugation and washing processes remove impurities that affect the purity of the product; the segmented calcination process in step S3 is the key to crystal form control. The low-temperature calcination stage helps to remove the water of crystallization and residual organic matter in the precursor material, and the large number of micropores / mesopores generated by the decomposition of the complex can prevent particle sintering, while the high-temperature calcination stage promotes the decomposition of tungstic acid and its conversion into tungsten oxide, so that the tungsten oxide material has higher crystal form purity and better performance.

[0023] Furthermore, in some embodiments, the tungsten source includes sodium tungstate or ammonium tungstate.

[0024] Furthermore, in some embodiments, the concentration of the tungsten source solution is 0.1~0.5 mol / L.

[0025] In the technical solution of this invention, if the concentration of tungstate ions in the reaction system is too low, it is not conducive to the formation of uniform precipitation; while if the concentration is too high, it is easy to cause local supersaturation, leading to an aggravation of particle agglomeration. Therefore, controlling the concentration of the tungsten source solution within the range of 0.1~0.5 mol / L can ensure a sufficient supply of tungstate ions in the reaction system, and effectively avoid particle agglomeration caused by excessive concentration, thereby obtaining nano-tungsten oxide materials with uniform particle size and good dispersibility.

[0026] Furthermore, in some embodiments, adjusting the pH of the tungsten source solution to 3.5~5.0 specifically involves adding ammonium chloride to the tungsten source solution, wherein the molar ratio of ammonium chloride to tungsten source is (1~3):1.

[0027] In the technical solution of this invention embodiment, ammonium chloride is used as a pH adjuster, which can slowly release hydrogen ions in aqueous solution, thereby constructing a stable weakly acidic environment. Compared with strong acids, the weakly acidic environment provided by ammonium chloride can more gently promote the polymerization process of tungstate ions, avoiding rapid precipitation and uncontrollable morphological changes caused by excessive acidity. At the same time, the ammonia gas produced by the decomposition of ammonium chloride is easily volatilized and will not introduce additional impurities into the product, which helps to improve the purity of the final product.

[0028] Furthermore, in some embodiments, the volume ratio of ethylene glycol to water is 1:(5~10).

[0029] In the technical solution of this invention embodiment, during the preparation of the mixed solution, the amount of ethylene glycol added needs to be precisely controlled according to the concentration and volume of the tungsten source solution to ensure that it is fully coordinated with tungstate ions to form a uniform and stable complex system.

[0030] Furthermore, in some embodiments, the hydrothermal reaction of the mixed solution at 120~150°C specifically involves: transferring the mixed solution into a polytetrafluoroethylene hydrothermal reactor with a filling degree of 70%~80%, placing the hydrothermal reactor in an oven, and reacting at 120~150°C for 4~12 hours.

[0031] Furthermore, in some embodiments, in step S2, the washing specifically involves washing with deionized water and anhydrous ethanol alternately 3 to 5 times.

[0032] In the technical solution of this invention embodiment, the purpose of alternating washing with deionized water and anhydrous ethanol is to remove residual chloride ions and unreacted organic matter.

[0033] Furthermore, in some embodiments, in step S2, the drying temperature is 60~80°C and the drying time is 2~4 hours.

[0034] Secondly, embodiments of the present invention provide a functional nano-tungsten oxide, which is prepared by the preparation method of the functional nano-tungsten oxide described in the first aspect.

[0035] Thirdly, embodiments of the present invention provide an application of functional nano-tungsten oxide in photocatalytic degradation of wastewater.

[0036] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0037] Example 1 A method for preparing functional nano-tungsten oxide, the specific steps of which are as follows: (1) Weigh 0.3 mol ammonium tungstate (123.45 g) and dissolve it in 1 L of deionized water. Add 0.6 mol ammonium chloride (32.10 g) and stir to dissolve. The pH value is 3.8. Add 100 mL of ethylene glycol (dispersant) and stir for 45 min to form a uniform mixture. (2) The mixture was transferred to a polytetrafluoroethylene hydrothermal reactor with a filling degree of 80%; the hydrothermal reactor was placed in an oven and reacted at 150°C under high temperature and high pressure for 8 hours; after the reaction was completed, it was naturally cooled to room temperature, centrifuged to obtain a white tungstic acid precipitate, washed three times with deionized water and anhydrous ethanol to remove residual chloride ions and unreacted organic matter, and dried under vacuum at 80°C for 2 hours to obtain the tungstic acid precursor; (3) The tungstic acid precursor was subjected to high-temperature calcination to transform its crystal form. The first stage was held at 300℃ for 2 hours, and the second stage was held at 600℃ for 2 hours. After cooling, it was ground and sieved to obtain functional nano tungsten oxide.

[0038] Figure 1 The image shows a SEM image of the functional nano-tungsten oxide obtained in this embodiment. The average particle size is 50-200 nm, and the particles are well dispersed.

[0039] Example 2 A method for preparing functional nano-tungsten oxide, the specific steps of which are as follows: (1) Weigh 0.3 mol ammonium tungstate (123.45 g) and dissolve it in 1 L of deionized water. Add 0.9 mol ammonium chloride (48.20 g) and stir to dissolve. The pH value is 3.6. Add 80 mL of ethylene glycol (dispersant) and stir for 60 min to form a uniform mixture. (2) The mixture was transferred to a polytetrafluoroethylene hydrothermal reactor with a filling degree of 80%; the hydrothermal reactor was placed in an oven and reacted at 130°C under high temperature and high pressure for 8 hours; after the reaction was completed, it was naturally cooled to room temperature, centrifuged to obtain a white tungstic acid precipitate, washed three times with deionized water and anhydrous ethanol to remove residual chloride ions and unreacted organic matter, and dried under vacuum at 80°C for 2 hours to obtain the tungstic acid precursor; (3) The tungstic acid precursor was subjected to high-temperature calcination to transform its crystal form. The first stage was held at 300℃ for 2 hours, and the second stage was held at 600℃ for 2 hours. After cooling, it was ground and sieved to obtain functional nano tungsten oxide.

[0040] Example 3 A method for preparing functional nano-tungsten oxide, the specific steps of which are as follows: (1) Weigh 0.3 mol ammonium tungstate (123.45 g) and dissolve it in 1 L of deionized water. Add 0.4 mol ammonium chloride (21.4 g) and stir to dissolve. The pH value is 4.1. Add 100 mL of ethylene glycol (dispersant) and stir for 45 min to form a uniform mixture. (2) The mixture was transferred to a polytetrafluoroethylene hydrothermal reactor with a filling degree of 80%; the hydrothermal reactor was placed in an oven and reacted at 150°C under high temperature and high pressure for 8 hours; after the reaction was completed, it was naturally cooled to room temperature, centrifuged to obtain a white tungstic acid precipitate, washed three times with deionized water and anhydrous ethanol to remove residual chloride ions and unreacted organic matter, and dried under vacuum at 80°C for 2 hours to obtain the tungstic acid precursor; (3) The tungstic acid precursor was subjected to high-temperature calcination to transform its crystal form. The first stage was held at 300℃ for 2 hours, and the second stage was held at 600℃ for 4 hours. After cooling, it was ground and sieved to obtain functional nano tungsten oxide.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1), 0.3 mol ammonium tungstate (123.45 g) was weighed and dissolved in 1 L of deionized water, and 1.8 mol ammonium chloride (96.40 g) was added and stirred to dissolve, with a pH value of 2.5; the remaining steps are the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (1), ethylene glycol is replaced with sodium dodecylbenzenesulfonate; the remaining steps are the same as in Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that step (3) is a one-step calcination: the tungstic acid precursor is subjected to high-temperature calcination to transform its crystal form, kept at 600°C for 4 hours, and then ground and sieved after cooling.

[0044] Comparative Example 4 The difference between this comparative example and Example 1 is that step (3) is: the tungstic acid precursor is subjected to high-temperature calcination for crystal transformation. The first stage is held at 300°C for 2 hours, and the second stage is held at 800°C for 4 hours. After cooling, it is ground and sieved.

[0045] Test Example 1 The physical properties of the nano-tungsten oxide prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0046] Table 1

[0047] Table 1 shows that the nano-tungsten oxide materials prepared in Examples 1-3 of this invention all have a purity greater than 99%, a particle size distribution range of 50-200 nm, and good particle dispersibility. In contrast, Comparative Example 1 suffered from rapid precipitation of tungstate ions due to excessively low pH, resulting in uncontrollable morphology and a wide particle size distribution and poor dispersibility in the final product. In Comparative Example 2, after ethylene glycol was replaced with sodium dodecylbenzenesulfonate (SDBS), SDBS easily decomposed and failed under hydrothermal high temperature, failing to effectively inhibit particle agglomeration. Furthermore, SDBS contains sulfur, generating SO2 after calcination but leaving residual SO4 in some areas. 2- It forms WOSO4 impurity phase with WO3; Comparative Example 3 uses a one-step calcination process, but the problem of mixed crystal forms cannot be effectively solved, and the purity decreases; Comparative Example 4 has an excessively high temperature in the high-temperature stage, which aggravates the particle sintering phenomenon.

[0048] Test Example 2 Photocatalytic degradation performance test of nano-tungsten oxide: The nano-tungsten oxide powders prepared in Examples 1-3 were uniformly sprinkled into wastewater (the wastewater was prepared with Rhodamine B to simulate wastewater). The mixture was magnetically stirred for 60 minutes in the dark. A simulated solar xenon lamp was turned on, and samples were taken at 0 min, 10 min, 20 min, 30 min, and 60 min of illumination. After filtration through a 0.22 μm filter membrane, the absorbance at 554 nm was measured using a UV-Vis spectrophotometer. The degradation rate and rate constant were calculated. The test results are shown in Table 2.

[0049] Table 2

[0050] The data in Table 2 show that the nano-tungsten oxide materials prepared in Examples 1-3 of this invention exhibit excellent photocatalytic degradation performance.

[0051] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing functional nano tungsten oxide, characterized in that, The method comprises the following steps: S1, a tungsten source is dissolved in water to obtain a tungsten source solution, the pH of the tungsten source solution is adjusted to 3.5-5.0, ethylene glycol is added into the tungsten source solution and mixed to obtain a mixed solution; S2, the mixed solution is subjected to hydrothermal reaction at 120-150℃, and after the reaction is completed, the solution is cooled to room temperature, centrifuged, washed and dried to obtain a tungsten acid precursor; S3, the tungsten acid precursor is calcined, heated to 500-700℃ for 2-4h after being heated at 250-350℃ for 1-2h, cooled, ground and sieved to obtain the functional nano tungsten oxide.

2. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The tungsten source comprises sodium tungstate or ammonium tungstate.

3. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The concentration of the tungsten source solution is 0.1-0.5mol / L.

4. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The pH of the tungsten source solution is adjusted to 3.5-5.0 by adding ammonium chloride into the tungsten source solution, and the molar ratio of the ammonium chloride to the tungsten source is (1-3):

1.

5. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The volume ratio of the ethylene glycol to water is 1:(5-10).

6. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The hydrothermal reaction of the mixed solution at 120-150℃ is specifically as follows: the mixed solution is transferred into a polytetrafluoroethylene hydrothermal kettle, the filling degree is 70%-80%, the hydrothermal kettle is placed in an oven, and the hydrothermal reaction is carried out at 120-150℃ for 4-12h.

7. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, The washing is specifically as follows: the solution is washed with deionized water and anhydrous ethanol alternately for 3-5 times.

8. The method for preparing functional nano-tungsten oxide according to claim 1, characterized in that, In step S2, the drying temperature is 60-80℃, and the drying time is 2-4h.

9. A functional nano tungsten oxide, characterized in that, The functional nano tungsten oxide is prepared by the method of any one of claims 1-8.

10. The functional nano tungsten oxide of claim 9 is applied to photocatalytic degradation of wastewater.

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