Application of carbon-nitrogen co-doped oxygen vacancy-enriched TiO2 photocatalyst in removal of bisphenol A in water

Abstract

The invention discloses application of a carbon and nitrogen co-doped oxygen vacancy-enriched TiO2 photocatalyst in removal of bisphenol A in water, and relates to the technical field of photocatalytic treatment of organic wastewater. The method comprises the following steps: adding a synthesized carbon-nitrogen co-doped oxygen vacancy-enriched TiO2 photocatalyst into bisphenol A-containing water, stirring for a period of time to achieve adsorption-desorption balance, turning on a 300W xenon lamp provided with a 420nm cut-off filter for illumination, and continuously stirring to remove bisphenol A in water; and after the removal is finished, the recycling of the carbon-nitrogen co-doped oxygen vacancy-enriched TiO2 photocatalyst in the system is realized through centrifugation, washing and drying. The prepared carbon and nitrogen co-doped oxygen vacancy-enriched TiO2 photocatalyst is used for removing bisphenol A in water, and the method has the advantages that the removal efficiency is high, materials are convenient to recycle and recycle, and the removal effect is slightly influenced by factors such as pH values, various inorganic anions and different water samples.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic treatment of organic wastewater, and in particular to application of a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in removing bisphenol A from water. Background Art

[0002] With the acceleration of industrialization and urbanization, environmental pollution is becoming increasingly serious. The endocrine disruptor bisphenol A (BPA) has drawn considerable attention. Widely used in plastics, BPA release into the environment poses a potential hazard to human health. Therefore, the development of efficient and environmentally friendly BPA degradation technologies is urgent. Photocatalysis, as a green and environmentally friendly technology, demonstrates significant potential for degrading organic pollutants.

[0003] Titanium dioxide (TiO2) is one of the most commonly used photocatalysts due to its non-toxicity, low cost, and excellent stability. However, the photocatalytic activity of TiO2 is limited by its wide band gap, which only absorbs ultraviolet light, restricting its practical application. Metal-organic frameworks (MOFs) have shown great potential in the field of photocatalysis due to their advantages such as high specific surface area, tunable pore size, and abundant active sites. MIL-125(Ti) is a Ti-based MOF material with a strong framework.

[0004] Studies have shown that doping TiO2 with nitrogen is the most effective strategy to improve the visible light activity of photocatalysts, because the mixing of N 2p and O 2p states in VB helps to narrow the band gap. In addition, the co-doping of C and N elements can introduce oxygen vacancies (Vo) in the TiO2 lattice, which will significantly improve the electron transfer efficiency and inhibit the recombination of photogenerated carriers. Oxygen vacancies can broaden the photoresponse range of TiO2 by improving the band structure and improving the photocatalytic performance of TiO2. Previous studies on the construction of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalysts were relatively dangerous and complicated. The present invention converts the MIL-125 (Ti) precursor into a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst by calcining in a vacuum tube furnace, which is safer and simpler. The use of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalysts to degrade bisphenol A is expected to develop an efficient and environmentally friendly bisphenol A degradation technology. Summary of the Invention

[0005] In view of the above problems, the present invention provides a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst for the removal of bisphenol A from water. The synthesized MIL-125 (Ti) precursor is placed in a vacuum tube furnace and calcined to obtain a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst, which is designated as C / N-TiO2-Vo-450. The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is added to water containing bisphenol A and stirred for a period of time to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm cutoff filter is then turned on for illumination, and stirring is continued to achieve the removal of bisphenol A from the water. After removal, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the system is recovered and reused by centrifugation, washing, and drying. The present invention uses the prepared carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst to remove bisphenol A from water, with the advantages of high removal efficiency, easy material recovery and recycling, and minimal impact of factors such as pH value, various inorganic anions, and different water samples on the removal effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is used to remove bisphenol A from water. The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst C / N-TiO2 is obtained by calcining a MIL-125(Ti) precursor prepared by reacting a titanate solution with an organic linker solution. The removal method is to add the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst to water containing bisphenol A, stir for a period of time to achieve adsorption-desorption equilibrium, then turn on a xenon lamp for illumination, and continue stirring to achieve the removal of bisphenol A from the water.

[0008] As a preferred technical solution of the present invention, the dosage of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the system is preferably 0.3-0.4 g / L. The xenon lamp has a power of 300 W and is equipped with a 420 nm cutoff filter as the light source for the photocatalytic reaction. The concentration of bisphenol A in the system is preferably 5-20 mg / L. After removal, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the system is recovered and reused through centrifugation, washing, and drying.

[0009] As a preferred technical solution of the present invention: the preparation method of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst C / N-TiO2 is:

[0010] First, in step 1, the organic linker solution is obtained by dissolving 3 g of terephthalic acid in 54 mL of N,N-dimethylformamide, and the titanate solution is obtained by slowly dripping 1.56 mL of tetrabutyl titanate into 6 mL of methanol.

[0011] Next, the mixed solution is transferred to an oil bath for heating reaction, wherein the oil bath temperature is preferably 110-140° C., more preferably 130° C. The reaction time is preferably 23-25 h, more preferably 24 h.

[0012] After the reaction is completed, the mixture is cooled to room temperature, and the mixed solution is centrifuged, washed, and dried to obtain a MIL-125(Ti) precursor. The washing conditions are: one wash with N,N-dimethylformamide and three washes with methanol. The drying conditions are: drying in an 80°C drying oven for 5 hours.

[0013] Next, the MIL-125(Ti) precursor is calcined in a vacuum tube furnace to obtain a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst. The calcination conditions are preferably 400-500°C for 1-3 hours, more preferably 450°C for 2 hours.

[0014] Experiments have confirmed that the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst prepared in the present invention, when used in conjunction with a xenon lamp, achieves efficient removal of bisphenol A in water. Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The method of converting MIL-125(Ti) into carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst by calcining in a vacuum tube furnace is safer and simpler.

[0016] 2. Carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst has high removal efficiency of bisphenol A in water.

[0017] 3. The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is easy to recycle and reuse.

[0018] 4. Applied to the removal of bisphenol A in water, its removal effect is less affected by factors such as pH value, various inorganic anions and different water samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a schematic diagram of the process of preparing the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst and applying it to remove bisphenol A in water.

[0020] Figure 2 These are the phase characterization results of the synthesized carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst.

[0021] Figure 3 This is a scanning electron microscope image of the synthesized carbon and nitrogen co-doped oxygen vacancy-rich TiO2 photocatalyst.

[0022] Figure 4 Transmission electron micrograph of the synthesized carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst.

[0023] Figure 5 X-ray photoelectron spectroscopy of the synthesized carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst.

[0024] Figure 6 This is the electron paramagnetic resonance spectrum of the synthesized carbon and nitrogen co-doped oxygen vacancy-rich TiO2 photocatalyst.

[0025] Figure 7 The removal rate of bisphenol A in water when carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is added; wherein, the reaction system is 30mL, the concentration of bisphenol A is 10mg / L, the addition amount of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10mg, and the xenon lamp power is 300W (with 420nm cutoff filter).

[0026] Figure 8 The recycled carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is used to remove bisphenol A from water; the reaction system is 30mL, the concentration of bisphenol A is 10mg / L, the dosage of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10mg, and the xenon lamp power is 300W (with a 420nm cutoff filter).

[0027] Figure 9 is the removal rate of bisphenol A in water in the presence of humic acid or different anions; wherein, the reaction system is 30 mL, the concentration of bisphenol A is 10 mg / L, the concentration of anions is 1 mmol / L, the dosage of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10 mg, and the xenon lamp power is 300 W (with a 420 nm cutoff filter).

[0028] Figure 10 The removal rate of bisphenol A in water at different initial pH values of the solution; wherein, the reaction system is 30mL, the concentration of bisphenol A is 10mg / L, the dosage of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10mg, and the xenon lamp power is 300W (with a 420nm cutoff filter).

[0029] Figure 11 The removal rate of bisphenol A in water in the presence of different pollutants is shown in the following table. The reaction volume is 30 mL, the pollutant concentration is 10 mg / L, the dosage of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10 mg, and the xenon lamp power is 300 W (with a 420 nm cutoff filter). The different pollutants include tetracycline (TC), norfloxacin (NFX), rhodamine B (MB), phenol (PH), and sulfamethoxazole (SMX).

[0030] Figure 12The removal rate of bisphenol A in different water samples is shown in Figure 1. The reaction volume is 30 mL, the bisphenol A concentration is 10 mg / L, the dosage of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is 10 mg, and the xenon lamp power is 300 W (with a 420 nm cutoff filter). The different water samples include tap water, Chaohu Lake water, and Feicui Lake water. DETAILED DESCRIPTION

[0031] The application of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst of the present invention in removing bisphenol A from water is further described in detail below with reference to the examples and drawings.

[0032] See also Figure 1 As shown, the present invention first prepares a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst, and uses it to remove bisphenol A in wastewater, that is, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is added to water containing bisphenol A, stirred for a period of time to reach adsorption-desorption equilibrium, and then turned on a xenon lamp for illumination, and continued stirring to achieve the removal of bisphenol A in the water.

[0033] Example 1

[0034] Preparation of Carbon and Nitrogen Co-doped TiO2 Photocatalyst with Oxygen Vacancy

[0035] To a clean 250 mL round-bottom flask, add 3 g of terephthalic acid and 54 mL of N,N-dimethylformamide and sonicate to dissolve. In another clean 50 mL beaker, slowly add 1.56 mL of tetrabutyl titanate dropwise to 6 mL of methanol while stirring vigorously. Quickly pour the entire solution from the beaker into the round-bottom flask. The round-bottom flask is then placed in a 130°C water bath and stirred at 550 rpm for 24 hours. After heating in the oil bath and cooling to room temperature, the mixed solution is centrifuged at 8000 rpm for 3 minutes, and the supernatant is discarded. The solid is then washed once with 25 mL of N,N-dimethylformamide and three times with 25 mL of methanol. After each wash, the solid is ultrasonically dispersed and centrifuged again at 8000 rpm for 3 minutes, with the supernatant discarded. Finally, the centrifuged product is dried in an 80°C oven for 5 hours to obtain the MIL-125(Ti) precursor.

[0036] The obtained MIL-125(Ti) precursor was placed in a porcelain boat, put into a tube furnace, and heated to 450°C at a rate of 5°C / min under vacuum conditions. The temperature was maintained for 2 hours, and then naturally cooled to obtain a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst, which was recorded as C / N-TiO2-Vo-450.

[0037] Figure 2The phase characterization results of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst synthesized by the method described in this example; Figure 3 This is a scanning electron micrograph of a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst synthesized by the method described in this example. The image shows a pancake-like structure of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst prepared by the present invention. Figure 4 This is a transmission electron micrograph of a carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst synthesized by the method described in this example; Figure 5 This is the X-ray photoelectron spectrum of the synthesized carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst. The figure shows the presence of carbon and nitrogen elements in the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst prepared by the present invention. Figure 6 The electron paramagnetic resonance spectrum of the synthesized carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is shown in FIG. As can be seen from the figure, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst prepared by the present invention is rich in oxygen vacancies.

[0038] Example 2

[0039] Application of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the removal of bisphenol A from water

[0040] The carbon-nitrogen co-doped oxygen vacancy-rich TiO2 photocatalyst (10 mg) obtained in Example 1 was added to a 30 mL reaction system containing a 10 mg / L bisphenol A solution and ultrasonically dispersed. The mixture was stirred at 550 rpm for 60 min to achieve adsorption-desorption equilibrium. A xenon lamp was turned on for photocatalysis, with a power of 300 W (with a 420 nm cutoff filter). The stirring speed was maintained at 550 rpm. The results are shown in Table 1. Figure 7 . Figure 7 The figure shows the removal efficiency of bisphenol A in water using carbon-nitrogen co-doped, oxygen-vacancy-rich TiO2 photocatalysts calcined at different temperatures according to the scheme described in this example. As can be seen, under illumination alone and without a catalyst, bisphenol A does not degrade. However, under illumination and the presence of a catalyst, the MIL-125(Ti) precursor fails to degrade bisphenol A, while the carbon-nitrogen co-doped, oxygen-vacancy-rich TiO2 photocatalyst exhibits excellent bisphenol A degradation performance.

[0041] Example 3

[0042] Regeneration of Carbon-Nitride Co-doped TiO2 Photocatalyst with Oxygen Vacancy

[0043] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst from Example 2 was centrifuged at 8000 rpm for 5 minutes, and the supernatant was discarded. The product was then washed three times with 25 mL of ultrapure water and three times with 15 mL of ethanol. During each wash, the solid was ultrasonically dispersed and centrifuged again at 8000 rpm for 3 minutes, with the supernatant discarded. Finally, the centrifuged product was dried in a 60°C drying oven for 6 hours to obtain the regenerated carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst.

[0044] Example 4

[0045] Application of regenerated carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the removal of bisphenol A from water

[0046] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst can be used and regenerated in accordance with the schemes described in Examples 2 and 3, thereby achieving the purpose of recycling. After being used and regenerated once, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst can be reused in accordance with the schemes described in Examples 2 and 3, and the removal rate of bisphenol A can reach 100% within 70 minutes. Figure 8 . Figure 8 The carbon-nitrogen co-doped, oxygen-vacancy-rich TiO2 photocatalyst was used to remove bisphenol A from water. After being used and regenerated four times, the carbon-nitrogen co-doped, oxygen-vacancy-rich TiO2 photocatalyst was reused according to the protocols described in Examples 2 and 3. The removal rate of bisphenol A within 70 minutes was still 90%.

[0047] Example 5

[0048] Application of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the removal of bisphenol A from water under humic acid or different anion conditions

[0049] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst (10 mg) obtained in Example 1 was added to a 30 mL reaction system containing a 10 mg / L bisphenol A solution, 1 mmol / L humic acid or a common inorganic anion (the corresponding cation is sodium ion), and ultrasonically dispersed. Stir at 550 rpm for 60 min to reach adsorption-desorption equilibrium. Turn on the xenon lamp for photocatalysis, the xenon lamp power is 300 W (with a 420 nm cutoff filter). The stirring speed is maintained at 550 rpm. The results are shown in FIG. Figure 9 . Figure 9 According to the scheme described in this embodiment, in addition to adding HPO4 2- and CO3 2- After addition, the removal rate of bisphenol A decreased slightly within 70 min; under the influence of humic acid and other anions, 100% removal of bisphenol A could be achieved within 70 min.

[0050] Example 6

[0051] Application of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the removal of bisphenol A from water under different pH conditions

[0052] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst (10 mg) obtained in Example 1 was added to a 30 mL reaction system containing a 10 mg / L bisphenol A solution, adjusted to different pH values (4 to 12), and ultrasonically dispersed. Stirred at 550 rpm for 60 min to achieve adsorption-desorption equilibrium. A xenon lamp was turned on for photocatalysis, with a power of 300 W (420 nm cutoff filter). The stirring speed was maintained at 550 rpm. The results are shown in FIG. Figure 10 . Figure 10 According to the scheme described in this embodiment, except for the conditions of pH = 10 and pH = 12, the removal rate of bisphenol A within 70 minutes decreased slightly; under other pH conditions, 100% removal of bisphenol A was achieved within 70 minutes.

[0053] Example 7

[0054] Application of carbon and nitrogen co-doped oxygen vacancy-rich TiO2 photocatalyst in removing different pollutants in water

[0055] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst (10 mg) obtained in Example 1 was added to a 30 mL reaction system containing 10 mg / L of different pollutants and ultrasonically dispersed. The mixture was stirred at 550 rpm for 60 min to reach adsorption-desorption equilibrium. A xenon lamp was turned on for photocatalysis, with a power of 300 W (with a 420 nm cutoff filter). The stirring speed was maintained at 550 rpm. The results are shown in FIG. Figure 11 . Figure 11 According to the scheme described in this embodiment, except for the slightly poor degradation effects on phenol (PH) and sulfamethoxazole (SMX), nearly 100% removal of other pollutants can be achieved within 70 minutes.

[0056] Example 8

[0057] Application of carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the removal of bisphenol A in water under different water samples

[0058] The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst (10 mg) obtained in Example 1 was added to 30 mL of a reaction system containing 10 mg / L bisphenol A in different water samples and ultrasonically dispersed. The mixture was stirred at 550 rpm for 60 min to achieve adsorption-desorption equilibrium. A xenon lamp was turned on for photocatalysis, with a power of 300 W (with a 420 nm cutoff filter). The stirring speed was maintained at 550 rpm. The results are shown in Table 1. Figure 12 . Figure 12According to the scheme described in this embodiment, considering that the actual water sample composition is relatively complex, the removal rate of bisphenol A decreases slightly within 70 minutes.

[0059] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst for the removal of bisphenol A from water, wherein the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst C / N-TiO2 is prepared by reacting a titanate solution with an organic linker solution to prepare a MIL-125 (Ti) precursor, which is then calcined; characterized in that: The carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst is added to water containing bisphenol A, stirred for a period of time to reach adsorption-desorption equilibrium, and then the xenon lamp is turned on for illumination and continued stirring to achieve the removal of bisphenol A in the water.

2. The use according to claim 1, characterized in that The dosage of the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the system is 0.3-0.4 g / L.

3. The use according to claim 1, characterized in that The xenon lamp has a power of 300W and is equipped with a 420nm cut-off filter as the light source for the photocatalytic reaction.

4. The use according to claim 1, wherein The concentration of bisphenol A in the system is 5 to 20 mg / L.

5. The use according to claim 1, characterized in that After the removal is completed, the carbon-nitrogen co-doped oxygen-vacancy-rich TiO2 photocatalyst in the system is recovered and reused through centrifugation, washing and drying.

Images