Bi2WO6-based photocatalytic material containing W-O double defects as well as preparation method and application of Bi2WO6-based photocatalytic material
By introducing WO double defects into Bi2WO6-based photocatalysts, their photocatalytic performance was improved, solving the problems of low visible light utilization and strong pH dependence of Bi2WO6 in the degradation of antibiotics. This enabled efficient degradation of ofloxacin and reduced preparation costs.
Patent Information
- Application Number
- CN202511173041.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-21
- Publication Date
- 2025-11-28
AI Technical Summary
Existing Bi2WO6 photocatalysts have limited visible light utilization, strong pH dependence, and are difficult to recover when degrading antibiotics, which limits their catalytic performance and practicality.
Bi2WO6-based photocatalytic materials containing WO double defects were prepared by hydrothermal method and alkaline etching method, and tungsten defects and oxygen defects were introduced to improve their photocatalytic performance.
The photocatalytic performance of Bi2WO6-based photocatalysts has been improved, especially in the degradation of ofloxacin, where it exhibits excellent results. Furthermore, the material has good reusability and degradation efficiency, and is low in cost.
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Figure CN121016731A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of environmental chemical photocatalysis, and particularly relates to a Bi2WO6-based photocatalytic material containing W-O double defects and a preparation method and application thereof. BACKGROUND
[0002] With the development of industrialization, environmental problems are becoming increasingly serious. Among various pollutants, the use of a large amount of antibiotics makes the concentration of antibiotics remaining in the environment higher and higher, and the antibiotics are stable in molecular structure, high in content and difficult to be degraded. Among them, ofloxacin is widely detected in the environment due to its difficulty in biodegradation and extensive use. Among all the treatment technologies, photocatalysis technology occupies a place in environmental purification technology due to its advantages of green, environmental friendly, broad-spectrum applicability and the like.
[0003] In the practical application of photocatalysis technology, Bi-based photocatalysts have a relatively wide absorption range for visible light, and their stability can also prevent secondary pollution during the treatment process. At present, a large number of photocatalytic materials are available for selection, among which bismuth tungstate (Bi2WO6) with a special layered structure and energy band structure has become the first choice of many scholars. Pure-phase Bi2WO6 has the advantage of high separation rate of photo-generated electrons and holes compared with other pure-phase photocatalytic materials. However, bismuth tungstate has defects such as limited visible light utilization rate, strong pH dependence and difficulty in recovery when degrading antibiotics. Therefore, how to modify Bi2WO6 to optimize its catalytic performance and practicability has become a problem to be solved. SUMMARY
[0004] In view of the problems in the prior art, the application provides a Bi2WO6-based photocatalytic material containing W-O double defects and a preparation method and application thereof. The Bi2WO6-based photocatalytic material containing anion defects (tungsten defects) and cation defects (oxygen defects) is prepared to be applied to the treatment of antibiotic wastewater, so as to effectively enhance the photocatalytic performance and solve the problem of limited application of semiconductor photocatalysts in degrading pollutants.
[0005] In order to achieve the above-mentioned purpose, the application provides a Bi2WO6-based photocatalytic material containing W-O double defects.
[0006] The application further provides a preparation method of the Bi2WO6-based photocatalytic material containing W-O double defects, comprising the following steps:
[0007] Step 1, preparing Bi2WO6 containing oxygen defects by a hydrothermal method;
[0008] Step 2, the oxygen defect-containing Bi2WO6 and NaOH are put into a beaker to carry out an alkali etching reaction, after the reaction is completed, the oxygen defect-containing Bi2WO6 is washed and dried to obtain the W-O double defect-containing Bi2WO6-based photocatalytic material.
[0009] Preferably, step 1 is specifically as follows: the bismuth nitrate pentahydrate is dispersed in ethylene glycol, after being stirred to be transparent by magnetic stirring, the sodium tungstate dihydrate is added, and the stirring is continued to be uniform to obtain a solution B; the solution B is transferred to a polytetrafluoroethylene liner to carry out a hydrothermal reaction, after the reaction is completed, the solution B is naturally cooled and washed, and is dried to obtain the oxygen defect-containing Bi2WO6.
[0010] Further preferably, in step 1, the bismuth nitrate pentahydrate is 1.5-2.5 mmol, the ethylene glycol is 30-50 ml, the sodium tungstate dihydrate is 0.5-1.5 mmol, the hydrothermal reaction time is 3-18 h, and the hydrothermal temperature is 180 DEG C.
[0011] Further preferably, in step 2, the oxygen defect-containing Bi2WO6 is 0.2-0.4 g, the NaOH is 35-55 ml, and the pH value of the NaOH is 10-14.
[0012] Further preferably, in step 1, the hydrothermal time is 12 h, and in step 2, the alkali etching reaction time is 30 min.
[0013] The application further provides an application of the W-O double defect-containing Bi2WO6-based photocatalytic material in degrading ofloxacin.
[0014] Preferably, the application comprises the following steps:
[0015] The W-O double defect-containing Bi2WO6-based photocatalytic material is added into the ofloxacin solution, and is dark adsorbed for 10-40 min, and then, under visible light irradiation, the magnetic stirring is continued to carry out the reaction, wherein, the visible light irradiation time is 90-120 min.
[0016] Further preferably, the addition amount of the W-O double defect-containing Bi2WO6-based photocatalytic material is 0.4 g / L, and the pH value of the ofloxacin solution is 5-9.
[0017] Further preferably, the visible light irradiation adopts a 400 W xenon lamp irradiation, and the photocatalytic reaction process is carried out at normal temperature and pressure.
[0018] The Bi2WO6-based photocatalytic material containing W-O double defects provided by the application is prepared by a hydrothermal method and an alkali etching method, the prepared photocatalytic material is a Bi2WO6-based photocatalytic material (BWvOv) containing anion defects (tungsten defects) and cation defects (oxygen defects) at the same time, and can be used for treating antibiotic sewage. The morphology structure of the BWvOv photocatalytic material does not change obviously before and after modification, proving that the BWvOv is modified on the basis of Bi2WO6 containing oxygen vacancies, and the morphology structure of the BWvOv is regular and good, and does not collapse due to the introduction of tungsten defects. However, the surface morphology of the BWvOv is looser than that of the material without tungsten defects, which shows that the introduction of tungsten defects and oxygen defects increases the active sites of the reaction, promotes the adsorption performance and also improves the photocatalytic performance of the material. At the same time, the tungsten defects and the oxygen defects produce a synergistic effect, and exhibit excellent degradation performance of ofloxacin under visible light. After drying, the material can still exhibit good redox performance under visible light irradiation, and has excellent reusability. The BWvOv photocatalytic material uses low-cost bismuth nitrate pentahydrate, greatly reduces the preparation cost of the material, and the modified photocatalytic material exhibits good degradation efficiency. The raw materials used in the application are common and easy to obtain, the process operation is simple, and industrial production is easy to realize. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The scanning electron microscope image and the mapping scanning image of the BWO photocatalytic material prepared in Example 2.
[0020] Figure 2 The scanning electron microscope image and the mapping scanning image of the BWvOv prepared in Example 2.
[0021] Figure 3 The photocatalytic degradation performance graph of the BWO photocatalytic material prepared in Examples 2, 4, 5 and 6 under simulated visible light.
[0022] Figure 4 The photocatalytic performance graph of the BWvOv photocatalytic material prepared in Examples 2, 7, 8 and 9 under different alkali etching times.
[0023] Figure 5 The TEM image and the HRTEM image of the BWO prepared in Example 2 and the TEM image and the HRTEM image of the BWvOv prepared in Example 2.
[0024] Figure 6 The XRD spectrum and the FITR spectrum of the BWvOv prepared in Example 2.
[0025] Figure 7XPS survey spectra, Bi 4f spectra, O 1s spectra and W 4f spectra of BWvOv and BWO prepared in Example 2.
[0026] Figure 8 Line graph of degradation efficiency of ofloxacin by different dosages of catalysts in Examples 10-13.
[0027] Figure 9 Column chart of influence of degradation efficiency of ofloxacin by setting different adsorption time in Examples 14-18.
[0028] Figure 10 Line graph of influence of degradation rate of ofloxacin by BWvOv at different pH in Examples 19-23.
[0029] Figure 11 Result graph of Examples 24-26, (a) is the structure of active species capture experiment under simulated visible light, (b) is the result of cycle experiment of BWvOv, (c-d) are the results of ESR electron spin resonance test of BWvOv. DETAILED DESCRIPTION
[0030] The steps of the present application will be further described in detail below in combination with the drawings and specific examples.
[0031] In one aspect, the present application discloses a Bi2WO6-based photocatalytic material containing W-O double defects, wherein the Bi2WO6-based photocatalytic material containing W-O double defects is rich in W and O defects.
[0032] The present application also provides a preparation method of the above-mentioned Bi2WO6-based photocatalytic material containing W-O double defects, comprising the following steps:
[0033] Step 1, preparing Bi2WO6(BWO) containing oxygen defects by a hydrothermal method;
[0034] Specifically, bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) is dispersed in ethylene glycol, and after being stirred by a magnetic force to be transparent (solution A), sodium tungstate dihydrate (Na2WO4·2H2O) is added, and the stirring is continued to be uniform to obtain solution B; the solution B is transferred to a polytetrafluoroethylene liner for hydrothermal reaction, after the reaction is completed, the natural cooling and washing are performed, and after drying, Bi2WO6 containing oxygen defects is obtained.
[0035] Preferably, the bismuth nitrate pentahydrate is 1.5-2.5 mmol, the ethylene glycol is 30-50 ml, the sodium tungstate dihydrate is 0.5-1.5 mmol, the hydrothermal reaction time is 3-18 h, and the hydrothermal temperature is 180℃.
[0036] Further preferably, the hydrothermal time is 12 h.
[0037] Step 2, the oxygen-defect-containing Bi2WO6 (BWO) and NaOH are put into a beaker to carry out an alkali etching reaction, after the reaction is completed, the oxygen-defect-containing Bi2WO6-based photocatalytic material (denoted as BWvOv, wherein, Wv represents a tungsten vacancy, and Ov represents an oxygen vacancy) containing W-O double defects is obtained after washing and drying;
[0038] Preferably, the oxygen-defect-containing Bi2WO6 is 0.2-0.4 g, the NaOH is 35-55 mL, and the pH value of the NaOH is 10-14.
[0039] Further preferably, the time of the alkali etching reaction is 30 min.
[0040] Through the above method, the Bi2WO6-based photocatalytic material containing W-O double defects can be prepared, wherein the morphology structure of the prepared Bi2WO6-based photocatalytic material containing W-O double defects has no obvious change compared with that without introducing a W defect.
[0041] The application further provides an application of the Bi2WO6-based photocatalytic material containing W-O double defects in degrading ofloxacin.
[0042] The specific application steps are as follows:
[0043] The Bi2WO6-based photocatalytic material containing W-O double defects is added into the ofloxacin solution, and dark adsorption is carried out for 10-40 min, and then the reaction is carried out under visible light irradiation and magnetic stirring, wherein the visible light irradiation time is 90-120 min.
[0044] Preferably, the adding amount of the Bi2WO6-based photocatalytic material containing W-O double defects is 0.4 g / L, and the pH value of the ofloxacin solution is 5-9.
[0045] Further preferably, the visible light irradiation adopts 400W xenon lamp irradiation, and the photocatalytic reaction process is carried out at normal temperature and pressure.
[0046] Example 1
[0047] The Bi2WO6-based photocatalytic material containing W-O double defects is prepared, and the steps are as follows:
[0048] Step 1, take 1.5 mmol of Bi(NO3)3·5H2O into a beaker, add 30 ml of ethylene glycol into the beaker, stir by magnetic force to a transparent solution (solution A), then add 0.5 mmol of Na2WO4·2H2O into solution A, continue to stir for 0.5 h to obtain a uniform solution (solution B), move solution B into a polytetrafluoroethylene liner for hydrothermal reaction, set the temperature to 180℃, and the time to 3 h, after the reaction, naturally cool, then wash with pure water and anhydrous ethanol each for 3 times, and then dry in a drying box at 50℃ for 5 h to obtain Bi2WO6 containing oxygen defects (denoted as: BWO).
[0049] Step 2, take 0.2 g of BWO into a beaker, add 35 ml of NaOH (pH = 12) into the beaker for 15 min of alkali etching reaction, after the reaction, wash with pure water and anhydrous ethanol each for 3 times, and then dry in a drying box at 50℃ for 4 h to obtain Bi2WO6-based photocatalytic material containing W-O double defects (denoted as: BWvOv).
[0050] Example 2
[0051] Bi2WO6-based photocatalytic material containing W-O double defects is prepared, the steps are as follows:
[0052] Step 1, take 2 mmol of Bi(NO3)3·5H2O into a beaker, add 40 ml of ethylene glycol into the beaker, stir by magnetic force to a transparent solution (solution A), then add 1 mmol of Na2WO4·2H2O into solution A, continue to stir for 1 h to obtain a uniform solution (solution B), move solution B into a polytetrafluoroethylene liner for hydrothermal reaction, set the temperature to 180℃, and the time to 12 h, after the reaction, naturally cool, then wash with pure water and anhydrous ethanol each for 3 times, and then dry in a drying box at 60℃ for 6 h to obtain Bi2WO6 containing oxygen defects (BWO).
[0053] Step 2, take 0.3 g of BWO into a beaker, add 45 ml of NaOH (pH = 12) into the beaker for 30 min of alkali etching reaction, after the reaction, wash with pure water and anhydrous ethanol each for 3 times, and then dry in a drying box at 60℃ for 6 h to obtain Bi2WO6-based photocatalytic material containing W-O double defects (BWvOv).
[0054] Example 3
[0055] Bi2WO6-based photocatalytic material containing W-O double defects is prepared, the steps are as follows:
[0056] Step 1, take 2.5 mmol of Bi(NO3)3·5H2O into a beaker, add 50 ml of ethylene glycol into the beaker, stir by magnetic force to a transparent solution (solution A), then add 1.5 mmol of Na2WO4·2H2O into solution A, continue to stir for 1.5 h to obtain a uniform solution (solution B), move solution B into a polytetrafluoroethylene liner for hydrothermal reaction, set the temperature to 180℃, and the time to 18 h, after the reaction, naturally cool, then wash with pure water and anhydrous ethanol each 3 times, and then dry in a drying oven at 70℃ for 8 h, to obtain Bi2WO6(BWO) containing oxygen defects.
[0057] Step 2, take 0.4 g of BWO into a beaker, add 55 ml of NaOH (pH = 12) into the beaker for 60 min of alkali etching reaction, after the reaction, wash with pure water and anhydrous ethanol each 3 times, and then dry in a drying oven at 70℃ for 8 h, to obtain Bi2WO6-based photocatalytic material (BWvOv) containing W-O double defects.
[0058] wherein, Figure 1 The scanning electron microscope image and mapping scanning image of the BWO photocatalytic material prepared in Example 2 are shown. From Figure 1 it can be seen that the morphology of BWO is good, and the element distribution is uniform and good, and the elements Bi, O and W are represented by green, cyan and purple respectively.
[0059] Figure 2 The scanning electron microscope image and mapping scanning image of the BWvOv prepared in Example 2 are shown. By comparison with Figure 1 , it is observed that the morphology structure of the two photocatalysts has no obvious change, proving that BWvOv is modified on the basis of BWO; and the morphology structure of BWvOv is good, and there is no structure collapse due to the introduction of defects, and Figure 1 b-c and Figure 2 b-c are compared, there will be a more obvious difference, and the surface morphology of BWvOv is more loose. It is shown that the introduction of tungsten defects and oxygen defects increases the chemical reaction active site, promotes the adsorption performance and thus improves the photocatalytic performance. Figure 1 and Figure 2 The EDS spectra of and can see that the element distribution of the two samples is uniform and good, and it is worth noting that the tungsten content and oxygen content of the modified BWvOv sample are relatively low.
[0060] The photocatalytic materials prepared in Examples 1-3 all have good photocatalytic degradation performance, but the degradation effect of Example 2 is slightly higher than that of Examples 1 and 3. In accordance with the principle of selecting photocatalytic materials with higher degradation effect, and the morphology characteristics and element distribution of Example 2 are uniform and good. The degradation effect of Example 2 is slightly higher than that of Examples 1 and 3, which may be because the surface morphology of the samples obtained in Examples 1 and 3 is not as loose as that of Example 2, resulting in a slightly lower degradation efficiency than Example 2.
[0061] From the above conclusion, the material prepared in Example 2 is more suitable as a research object for photocatalytic application.
[0062] Examples 4-6
[0063] The difference from Example 2 is that the hydrothermal time in step 1 is 3h, 6h, and 18h, respectively.
[0064] Comparative Example 1
[0065] The BWO sample prepared in Example 2 was weighed and placed in a 10mg / L ofloxacin solution, and after 30min dark adsorption experiment, a 400W xenon lamp was turned on for photodegradation experiment. The BWO adsorption efficiency was 23.9%, and the degradation efficiency of ofloxacin was 85.17%.
[0066] Comparative Example 2
[0067] The BWO sample prepared in Example 4 was weighed and placed in a 10mg / L ofloxacin solution, and after 30min dark adsorption experiment, a 400W xenon lamp was turned on for photodegradation experiment. The BWO adsorption efficiency was 29.95%, and the degradation efficiency of ofloxacin was 80.33%.
[0068] Comparative Example 3
[0069] The BWO sample prepared in Example 5 was weighed and placed in a 10mg / L ofloxacin solution, and after 30min dark adsorption experiment, a 400W xenon lamp was turned on for photodegradation experiment. The BWO adsorption efficiency was 22.68%, and the degradation efficiency of ofloxacin was 80.58%.
[0070] Comparative Example 4
[0071] The BWO sample prepared in Example 6 was weighed and placed in a 10mg / L ofloxacin solution, and after 30min dark adsorption experiment, a 400W xenon lamp was turned on for photodegradation experiment. The BWO adsorption efficiency was 26.62%, and the degradation efficiency of ofloxacin was 78.8%.
[0072] Figure 3The photocatalytic degradation performance of BWO prepared by different hydrothermal time in Example 2, 4-6 under simulated visible light is shown. It can be found from the observation results that the four samples show a high-low-high trend. In-depth analysis shows that the adsorption effect of the sample at 3h is the best, which may be due to the effect of material morphology rather than oxygen vacancies. It is caused by shorter hydrothermal time, poor crystallinity and loose sample itself; and with the extension of hydrothermal time, the crystallization effect of the sample is better and better, and the introduction of oxygen vacancies is gradually increased. It is found that the introduction of oxygen vacancies can promote the adsorption of the sample to a certain extent. However, too many oxygen vacancies cannot make the degradation effect better and better, and the transition adsorption will block the oxygen defects of the sample, thereby affecting the photocatalytic degradation performance. This shows that the sample with hydrothermal time of 12h is the most suitable for modification.
[0073] Examples 7-9
[0074] The difference from Example 2 is that the alkali etching time in step 2 is 15min, 45min and 60min respectively.
[0075] Comparative Examples 5-8
[0076] The BWvOv samples prepared in Example 2, Example 7, Example 8 and Example 9 were weighed respectively and placed in an oxyfluorfen solution of 10mg / L. After 30min dark adsorption experiment, a 400W xenon lamp was turned on for light degradation experiment.
[0077] In Example 2, the BWvOv adsorption efficiency is 31.97%, and the degradation efficiency of oxyfluorfen is 94.55%.
[0078] In Example 7, the BWvOv adsorption efficiency is 30.5%, and the degradation efficiency of oxyfluorfen is 93.24%.
[0079] In Example 8, the BWvOv adsorption efficiency is 28.92%, and the degradation efficiency of oxyfluorfen is 92.77%.
[0080] In Example 9, the BWvOv adsorption efficiency is 28.42%, and the degradation efficiency of oxyfluorfen is 89.08%.
[0081] Figure 4The photocatalytic degradation performance of BWvOv prepared in different alkali etching time in example 2, 7-9 under simulated visible light is shown. The adsorption performance and photocatalytic degradation performance of the sample can reach the best at 30 min, and the change of photocatalytic degradation performance and adsorption performance is consistent. It is worth noting that the reason for this is that the introduction of tungsten defects changes the chemical properties of the BWO surface, providing more adsorption active sites, thereby promoting the synergistic effect of adsorption and photocatalysis. By comparing the data before and after the alkali modification, it can be clearly observed that the introduction of tungsten defects can significantly improve the photocatalytic degradation effect of the prepared sample. In summary, the selection of alkali etching time for 30 min is the most appropriate.
[0082] Next, the BWvOv photocatalytic material prepared in example 2 is characterized and analyzed:
[0083] Figure 5 a and Figure 5 c are TEM images and HRTEM images of BWO prepared in example 2, respectively; Figure 5 b and 5d are TEM images and HRTEM images of BWvOv prepared in example 2. From Figure 5 It can be observed that BWvOv and BWO have similar macroscopic structures, and the introduction of tungsten defects makes the crystal structure become thinner; HRTEM can observe the same lattice fringes (d=0.315nm) corresponding to the (131) crystal plane of Bi2WO6, which further proves that BWvOv can see the same lattice fringes as BWO, proving that the sample does not introduce other substances, and BWvOv does not change the macroscopic structure of BWO, and increases the photocatalytic degradation performance of the material on the basis of retaining the original catalyst properties.
[0084] Figure 6 The XRD spectrum and FITR spectrum of BWvOv prepared in example 2 are shown.
[0085] Figure 6It can be seen that pure phase BWO contains nine obvious diffraction peaks, respectively corresponding to (131), (200), (202), (331), (262), (400), (193), (402), (462), which is consistent with the standard card (JCPDS No. 39-0256) of Bi2WO6orthorhombic phase, indicating that Bi2WO6with high purity and no other phase is successfully prepared, and the clear peak shape indicates that Bi2WO6has excellent crystallinity. In BWvOv, the diffraction peaks corresponding to Bi2WO6can be clearly observed. The diffraction peaks at 2θ = 28.3°, 32.9°, 47.1°, 55.8°, 58.5°, 68.8°, 76.0°, 78.3° and 87.5° correspond to the above Bi2WO6crystal faces. Compared with pure phase BWO, the diffraction peak position and number of BWvOv do not change, only the diffraction peak intensity is slightly lower than that of pure phase BWO. It shows that BWvOv also has high crystallinity and stability; at the same time, it proves that the tungsten defect is successfully introduced and does not cause the collapse of the Bi2WO6crystal structure, which is verified by the TEM image.
[0086] Figure 6 It can be seen that the absorption peaks at 559 cm -1 and 728 cm -1 correspond to the stretching vibration of Bi-O and W-O bonds in BWO and BWvOv, respectively; the absorption peak at 1632 cm -1 is attributed to the bending vibration of O-H group in water molecules adsorbed on the surface of the photocatalyst, and BWvOv has a wider range of stretching vibration than BWO at this position, indicating that the introduction of tungsten defects and oxygen defects provides more adsorption sites for active species; the absorption peaks at about 3435 cm -1 represent the stretching vibration of hydroxyl H-O-H adsorbed on the surface of the catalyst. In summary, the FTIR spectrum of the modified catalyst still shows good chemical bond stretching vibration phenomenon, proving that its chemical structure remains in good condition, the tungsten defect and oxygen defect are introduced in a proper amount, and the crystal structure collapse does not occur, which is verified by the XRD spectrum.
[0087] Figure 7 The XPS general spectrum, Bi 4f spectrum, O 1s spectrum and W 4f spectrum of BWvOv and BWO prepared in Example 2 are shown.
[0088] Figure 7 It can be observed that both catalysts have obvious peaks of Bi, W and O elements and no foreign matter pollution, proving that the synthesis purity of the catalyst is very high; at the same time, it can be observed that the peak shape of BWvOv is almost completely consistent with that of pure phase BWO, only the peak intensity is slightly reduced, indicating that BWvOv is modified on the basis of pure phase BWO and the sample is successfully prepared, which is consistent with the previous characterization results. Figure 7b Containing Bi 4f two characteristic peaks corresponding to the Bi in BWO 3+ , Figure 7 c Containing W 4f two characteristic peaks corresponding to the W in BWO 6+ ; Figure 7 d The characteristic peaks of O1s correspond to lattice oxygen, oxygen vacancies or oxygen elements chemisorbed on the surface of the material, respectively. Figure 7 d, the W4f of BWvOv 5 / 2 and the binding energy peak of W 4f 7 / 2 The two binding energy peaks are found to move in the direction of low binding energy, which is attributed to the introduction of tungsten defects, which increases the electron density around the tungsten vacancies. This result also proves the successful introduction of tungsten vacancies. Figure 7 b Bi 4f two characteristic peaks shift to the direction of higher binding energy, which is due to the generation of tungsten vacancies, which exposes more Bi elements, and Bi elements correspond to Bi in BWO 3+ Therefore, the Bi 4f characteristic peak moves to the direction of higher binding energy. Figure 7 c Bi-O and W-O are representatives of lattice oxygen in the catalyst. By comparing the observations, it can be found that the peak intensity of W-O bond is weakened, which proves that the content of W-O bond is reduced, and tungsten defects are generated; the breaking of W-O bond leads to the exposure of more Bi-O bond, and the oxygen atoms in Bi-O bond distribute dense charge cloud, so Bi-O bond shifts to the direction of low binding energy; because BWvOv contains more oxygen vacancies than pure BWO, oxygen vacancies are electron traps themselves with positive charge, so the characteristic peak at 533.4eV is positively shifted by 0.1eV from 533.3eV.
[0089] In summary, the photocatalytic material BWvOv prepared in Example 2 has better degradation performance.
[0090] Example 10
[0091] The BWvOv photocatalytic material prepared in Example 2 was used to degrade ofloxacin, and the method was as follows:
[0092] 0.2g / L of BWvOv photocatalytic material prepared in Example 2 was added to 160mL of ofloxacin mixed solution, the concentration of ofloxacin in the solution was 10mg / L, and the solution was stirred in the dark. After 30min of dark reaction, the ofloxacin on the surface of the photocatalytic material reached adsorption-desorption equilibrium, then under the irradiation of 400W xenon lamp, the degradation was carried out every 10min, and the concentration of ofloxacin was determined. After 90min of light irradiation, the degradation efficiency of BWvOv photocatalytic material on ofloxacin could reach 78.50%.
[0093] Example 11
[0094] The difference between Example 10 is that the BWvOv photocatalytic material dosage is 0.3 g / L.
[0095] The BWvOv photocatalytic degradation of pefloxacin degradation efficiency can reach 94.55%.
[0096] Example 12
[0097] The difference between Example 10 is that the BWvOv photocatalytic material dosage is 0.4 g / L.
[0098] The BWvOv photocatalytic degradation of pefloxacin degradation efficiency can reach 95.96%.
[0099] Example 13
[0100] The difference between Example 10 is that the BWvOv photocatalytic material dosage is 0.5 g / L.
[0101] The BWvOv photocatalytic degradation of pefloxacin degradation efficiency can reach 96.65%.
[0102] As Figure 8 shown in the results of Examples 10-13, the W-O double defect containing photocatalyst BWvOv prepared in Example 2 has good degradation performance for pefloxacin. The degradation performance is proportional to the dosage, and when the dosage increases from 0.2 g / L to 0.5 g / L, the degradation performance of the material for pefloxacin is significantly improved, and after 90 min of light irradiation, the degradation performance can reach about 96%. However, due to economic consumption and practicality, and 0.4 g / L has reached a degradation rate of more than 95%, therefore, the photocatalytic material dosage of 0.4 g / L is selected.
[0103] Example 14
[0104] The BWvOv photocatalytic material prepared in Example 2 is used to degrade pefloxacin, and the method is as follows:
[0105] 0.4 g / L of the BWvOv photocatalytic material prepared in Example 2 is added to 160 mL of a pefloxacin mixed solution, the concentration of pefloxacin in the solution is 10 mg / L, the adsorption time is set to 0 min, then direct degradation is carried out under visible light irradiation of a 400 W xenon lamp, the pefloxacin concentration is measured every 10 min, when the total experimental time is 90 min, the BWvOv photocatalytic degradation of pefloxacin prepared in Example 2 can reach 92.73% degradation efficiency, and when the total experimental time is 120 min, the BWvOv photocatalytic degradation of pefloxacin prepared in Example 2 can reach 95.03% degradation efficiency.
[0106] Example 15
[0107] The difference from Example 14 is that the adsorption time is set to 10 min.
[0108] When the total experimental duration is 90 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 94%; when the total experimental duration is 120 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 95.96%.
[0109] Example 16
[0110] The difference from Example 14 is that the adsorption time is set to 20 min.
[0111] When the total experimental duration is 90 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 92.55%; when the total experimental duration is 120 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 95.29%.
[0112] Example 17
[0113] The difference from Example 14 is that the adsorption time is set to 30 min.
[0114] When the total experimental duration is 90 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 91.96%; when the total experimental duration is 120 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 95.33%.
[0115] Example 18
[0116] The difference from Example 14 is that the adsorption time is set to 40 min.
[0117] When the total experimental duration is 90 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 88.09%; when the total experimental duration is 120 min, the degradation efficiency of BWvOv photocatalytic degradation of ofloxacin prepared by 0.4 g / L of Example 2 can reach 94.9%.
[0118] As Figure 9As shown in Examples 14-18, the results indicate that when the total experimental time is 90 min, the final photocatalytic degradation efficiency reaches 92.73%, 94%, 92.55%, 91.96%, and 88.09%, respectively, and the efficiency is above 88% after 90 min of illumination. Further analysis reveals that adsorption time affects the photocatalytic degradation reaction rate. A suitable adsorption time allows the reaction to reach the ideal degradation effect earlier; however, excessively long adsorption times reduce the degradation rate. This may be because excessively long adsorption times cause pollutants to occupy the activation sites of active free radicals, thus affecting the reaction activation rate, or because the pollutants bind more tightly to the catalyst, making them less prone to degradation. Based on the above experimental phenomena, the optimal adsorption time for the BWvOv photocatalytic material is 10 min.
[0119] Example 19
[0120] The BWvOv photocatalytic material prepared in Example 2 was used to degrade ofloxacin, and the method is as follows:
[0121] 0.4 g / L of the BWvOv photocatalytic material prepared in Example 2 was added to 160 mL of an ofloxacin mixed solution with a concentration of 10 mg / L of ofloxacin. The pH of the ofloxacin solution was adjusted to 3 using HCl / NaOH, and the adsorption time was set to 10 min to allow ofloxacin to reach adsorption-desorption equilibrium on the surface of the photocatalytic material. Then, degradation was carried out under visible light irradiation from a 400 W xenon lamp. The ofloxacin concentration was measured every 10 min. After 120 min of irradiation, the degradation efficiency of ofloxacin by the 0.4 g / L BWvOv photocatalytic degradation reached 68.08%.
[0122] Example 20
[0123] The difference from Example 19 is that the ofloxacin solution was adjusted to pH 5 using HCl / NaOH.
[0124] BWvOv photocatalytic degradation of ofloxacin can reach an efficiency of 93.73%.
[0125] Example 21
[0126] The difference from Example 19 is that the ofloxacin solution was adjusted to pH 7 using HCl / NaOH.
[0127] BWvOv photocatalytic degradation of ofloxacin can reach an efficiency of 93.30%.
[0128] Example 22
[0129] The difference from Example 19 is that the ofloxacin solution was adjusted to pH 9 using HCl / NaOH.
[0130] The efficiency of photocatalytic degradation of ofloxacin by BWvOv can reach 91.36%.
[0131] Example 23
[0132] The difference from Example 19 is that the ofloxacin solution is adjusted to pH = 11 by using HCl / NaOH.
[0133] The efficiency of photocatalytic degradation of ofloxacin by BWvOv can reach 70.43%.
[0134] As Figure 10 shown in Table 2, the results of Examples 19-23 show that when the pH value of the ofloxacin solution is in the middle range, the degradation performance of BWvOv photocatalyst containing W-O double defects prepared in Example 2 on ofloxacin is higher, but when the pH value is in the extremely acidic or extremely alkaline condition, the degradation rate is reduced, but overall it is still in a good range.
[0135] Example 24
[0136] The BWvOv photocatalytic material prepared in Example 2 was subjected to free radical capture experiment, and the method was as follows:
[0137] 50 mM isopropyl alcohol (IPA), ascorbic acid (AsA) and disodium ethylenediaminetetraacetate (EDTA-2Na) were used as capture agents to remove hydroxyl radicals (OH), superoxide radicals (O2 · ) and photo-generated holes (h · ). - +
[0138] As Figure 11 shown in Table 3, the results show that, compared with the blank group, the addition of isopropyl alcohol has no significant effect on the photocatalytic degradation of ofloxacin by BWvOv, and the removal rate of ofloxacin still maintains a high value; while for the addition of ascorbic acid and disodium ethylenediaminetetraacetate, the removal rate of ofloxacin is obviously affected. It is concluded that in this experiment, superoxide radicals are the main active radicals, followed by photo-generated holes, and finally hydroxyl radicals.
[0139] Example 25
[0140] The BWvOv photocatalytic material prepared in Example 2 was subjected to free radical capture experiment, and the method was as follows:
[0141] ESR test was performed.
[0142] As Figure 11 As shown in c-d, the results show that when the light is turned on for 5 min and 10 min, very obvious superoxide radical signals appear, proving the existence of superoxide radicals in the experiment; when testing hydroxyl radicals, a seven-peak signal appears, which proves the existence of active radicals in the degradation process, but it cannot be determined whether it is a hydroxyl radical. Further analysis shows that superoxide radicals and holes play a decisive role in the degradation process, and the superoxide radical signal is very obvious, and there is no condition to generate singlet oxygen, therefore, it is believed that the above uncertain active radicals are hydroxyl radicals.
[0143] Example 26
[0144] The integrity method for evaluating the photocatalytic performance of the BWvOv photocatalytic material prepared in Example 2 is as follows:
[0145] The cycle experiment test is performed.
[0146] As shown in Figure 11 b, the results show that the cycle experiment has a total of three cycle periods, and after the end of the third period, the removal rate of BWvOv to ofloxacin is about 84.73%, it can be seen that BWvOv has strong stability in the process of degrading ofloxacin, and has practical application potential.
[0147] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these changes and modifications should be considered as the protection scope of the present application.
Claims
1. A Bi 2 WO 6 -based photocatalytic material containing W-O double defects, characterized in that, The W-O double-defect-containing Bi2WO6-based photocatalytic material is rich in W and O defects.
2. A method for preparing the Bi2WO6-based photocatalytic material containing W-O double defects according to claim 1, characterized in that, The preparation method comprises the following steps: Step 1, preparing the oxygen-defect-containing Bi2WO6 by a hydrothermal method; Step 2, placing the oxygen-defect-containing Bi2WO6 and NaOH in a beaker to perform an alkali etching reaction, and after the reaction is completed, the W-O double-defect-containing Bi2WO6-based photocatalytic material is obtained after washing and drying.
3. The preparation method of the W-O double-defect-containing Bi2WO6-based photocatalytic material according to claim 2, characterized in that: In step 1, the bismuth nitrate pentahydrate is dispersed in ethylene glycol, and after being stirred to be transparent by a magnetic stirrer, the sodium tungstate dihydrate is added, and the stirring is continued until the solution B is obtained; the solution B is transferred into a polytetrafluoroethylene liner to perform a hydrothermal reaction, and after the reaction is completed, the oxygen-defect-containing Bi2WO6 is obtained after natural cooling and washing and drying.
4. The preparation method of the W-O double-defect-containing Bi2WO6-based photocatalytic material according to claim 3, characterized in that: In step 1, the bismuth nitrate pentahydrate is 1.5-2.5 mmol, the ethylene glycol is 30-50 ml, the sodium tungstate dihydrate is 0.5-1.5 mmol, the hydrothermal reaction time is 3-18 h, and the hydrothermal temperature is 180 DEG C.
5. The method for preparing the Bi2WO6-based photocatalytic material containing WO double defects according to claim 4, characterized in that: In step 2, the oxygen-defect-containing Bi2WO6 is 0.2-0.4 g, the NaOH is 35-55 mL, and the pH value of the NaOH is 10-14.
6. The method of claim 5, wherein the method comprises: In step 1, the hydrothermal time is 12 h, and in step 2, the alkali etching reaction time is 30 min.
7. The application of the W-O double-defect-containing Bi2WO6-based photocatalytic material prepared by the preparation method of the W-O double-defect-containing Bi2WO6-based photocatalytic material in claim 2 to 6 in degrading ofloxacin.
8. Use according to claim 7, characterized in that, The preparation method comprises the following steps: The W-O double-defect-containing Bi2WO6-based photocatalytic material is added into a ofloxacin solution, and dark adsorption is performed for 10-40 min, and then the reaction is continued under visible light irradiation and magnetic stirring, wherein the visible light irradiation time is 90-120 min.
9. Use according to claim 7, characterized in that, The dosage of the W-O double-defect-containing Bi2WO6-based photocatalytic material is 0.4 g / L, and the pH value of the ofloxacin solution is 5-9.
10. Use according to claim 7, characterized in that, The visible light irradiation adopts a 400 W xenon lamp, and the photocatalytic reaction process is performed at normal temperature and pressure.