Ga2O3-Bi4O7 / CTF composite material and application of Ga2O3-Bi4O7 / CTF composite material in removal of fully / polyhalogenated mixed pollutants

Abstract

The invention belongs to the technical field of water treatment, and discloses a Ga2O3-Bi4O7 / CTF composite material and an application of the Ga2O3-Bi4O7 / CTF composite material in removal of all / polyhalogenated mixed pollutants, and the Ga2O3-Bi4O7 / CTF composite material is constructed based on the structural advantages and good adsorption and photocatalysis characteristics of a fluorine-doped covalent triazine porous material (CTF) and a Ga2O3-Bi4O7 heterojunction. The adsorption characteristic of the fluorine-doped CTF is fully utilized, so that the contact area between the full / polyhalogenated mixed pollutants and the catalyst is increased; meanwhile, a Ga2O3-Bi4O7 photocatalyst is combined, so that mixed pollutants adsorbed on the surface of the material can be effectively removed, adsorption sites are released, the regeneration capacity of the catalyst is improved, and efficient adsorption-photocatalysis synergistic removal of all / polyhalogenated mixed pollutants in wastewater is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a Ga2O3-Bi4O7 / CTF composite material and its application in efficiently removing per- / polyhalogenated mixed pollutants in wastewater. Background Art

[0002] Per- / polyhalogenated mixed pollutants include perfluorinated compounds, polychlorophenols, polybrominated diphenyl ethers, etc. Perfluorooctanoic acid (PFOA) and 2,4,6-trichlorophenol (2,4,6-TCP) are typical representatives among them, and both belong to environmental persistent organic pollutants, having bioaccumulation properties, which greatly threaten the ecological environment and human health. At present, the most commonly used wastewater treatment method for per- / polyhalogenated mixed pollutants is adsorption, which is simple to operate, has low energy consumption, and does not produce intermediates. However, adsorption is only a process of transferring pollutants from one medium to another, and cannot mineralize them. Moreover, the adsorption process is prone to saturation, has a slow regeneration rate, and the desorbed pollutants are not ideal. While the semiconductor photocatalytic technology has a good effect on removing persistent organic pollutants and can convert refractory organic compounds into harmless small molecules. However, due to the fact that the active free radicals of photocatalysis are easily quenched in water, the catalytic reaction only occurs in a very small area on the catalyst surface and is easily limited by pollutant mass transfer.

[0003] Due to the complex composition and difficulty in degradation of per- / polyhalogenated mixed pollutants, a single treatment method is not sufficient to remove them efficiently. Therefore, the adsorption-photocatalysis synergistic technology has become a very promising water treatment solution, because adsorption can concentrate pollutants around the catalytic sites, improving the photocatalytic effect of the material, while photocatalytic degradation is beneficial to the regeneration of adsorption sites, thus promoting adsorption. Moreover, combining an adsorbent with excellent adsorption performance and a photocatalyst with excellent catalytic performance can further exert the advantages of the composite material. All in all, the adsorption-photocatalysis synergistic technology not only has a high removal efficiency, but also has low energy consumption and is environmentally friendly, and is expected to achieve the efficient removal of per- / polyhalogenated mixed pollutants in wastewater.

[0004] Chinese Patent Application No. CN111514859A discloses a composite adsorbent for efficiently removing mixed pollutants in wastewater and its preparation method. The invention prepares nano-sheet-like zinc oxide microspheres, and then uses them as sacrificial templates to prepare metal-organic framework Zn-MOF-74, thereby obtaining a composite adsorbent ZnO@Zn-MOF-74 of nano-zinc oxide and metal-organic framework for adsorbing antibiotics and heavy metal ions in wastewater. However, this invention cannot degrade and mineralize pollutants. Moreover, the regeneration process of this adsorbent is complex, and the organic regeneration solvent is toxic and volatile, which has the hazard of causing secondary pollution.

[0005] Chinese Patent Application No. CN115178299A discloses a preparation method of a nano-composite photocatalytic material capable of treating mixed wastewater containing chromium ions and tetracycline. In this invention, Bi(NO3)3·5H2O and KBr are used as starting materials, and in the presence of MIL-125(Ti), the MIL-125(Ti) / BiOBr nano-composite material is synthesized and used to treat the mixed wastewater containing chromium ions and tetracycline. However, this invention lacks the test on the recyclability of the material, and there may be problems such as metal leaching leading to a decrease in the catalyst activity.

[0006] Chinese Patent Application No. CN114751582A discloses a treatment method for electroplating mixed wastewater. In this invention, sodium hypochlorite is added to oxidize pollutants such as sodium cyanide and organic amines containing hydroxyl groups; ferrous chloride solution is added to reduce hexavalent chromium in the wastewater to trivalent chromium and form chromium hydroxide precipitate; activated carbon is used to adsorb the precipitate and heavy metal capturer. However, this invention has complex processes and disadvantages such as a long treatment cycle and high energy consumption. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, based on the adsorption-photocatalysis synergistic technology, the present invention aims to provide a Ga2O3-Bi4O7 / CTF composite material and its application in the efficient removal of per- and polyhalogenated mixed pollutants in wastewater.

[0008] The technical solution provided by the present invention is as follows:

[0009] A Ga2O3-Bi4O7 / CTF composite material and its preparation method, including the following steps:

[0010] (1) Disperse Ga2O3 powder in ethanol, and obtain a Ga2O3 suspension after ultrasonic treatment;

[0011] (2) Disperse a certain mass of Bi2O4 into the Ga2O3 suspension, after ultrasonic treatment, stir the obtained mixed solution under water bath conditions until the ethanol evaporates completely;

[0012] (3) Sinter the powder obtained in step (2) at high temperature to obtain Ga2O3-Bi4O7;

[0013] (4) Grind Ga2O3-Bi4O7 and fluorine-doped CTF after dropping them into an appropriate amount of ethanol;

[0014] (5) Dry the mixture obtained in step (4) to obtain Ga2O3-Bi4O7 / CTF.

[0015] Preferably, in step (2), by mass ratio, Bi2O4:(Bi2O4 + Ga2O3)=1:8 - 15, and the water bath temperature is 50 - 80 °C.

[0016] Preferably, in step (3), the high-temperature sintering temperature is 200 - 250 °C, and the high-temperature sintering time is 3 - 5 h.

[0017] Preferably, in step (4), tetrafluoroterephthalonitrile and ZnCl2 are thoroughly mixed by grinding. After vacuum calcination, the obtained product is washed and dried to obtain fluorine-doped CTF, wherein the molar ratio of tetrafluoroterephthalonitrile to ZnCl2 is 1:6; the vacuum calcination temperature is 400 - 500 °C, and the vacuum calcination time is 35 - 45 h.

[0018] Preferably, in step (4), 5 - 10 drops of ethanol are added dropwise to every 100 mg of the powder.

[0019] Preferably, in step (4), by mass ratio, fluorine-doped CTF : (fluorine-doped CTF + Ga2O3 - Bi4O7) = 1:10 - 20.

[0020] The present invention also provides the use of the above Ga2O3 - Bi4O7 / CTF composite material in the synergistic adsorption - photocatalytic removal of per- and polyhalogenated mixed pollutants in wastewater, and the specific steps are as follows: The simulated wastewater containing PFOA and 2,4,6-trichlorophenol is placed in a quartz tube with a cooling jacket, the Ga2O3 - Bi4O7 / CTF composite material is added, and then the mixed system is placed in a photocatalytic reaction device, and the adsorption reaction is carried out under dark stirring. After reaching the adsorption - desorption equilibrium, the ultraviolet light source is turned on for the photocatalytic reaction.

[0021] Preferably, 0.2 - 0.5 g / L of Ga2O3 - Bi4O7 / CTF is added to every 50 mL of the simulated wastewater for the synergistic adsorption - photocatalytic reaction, wherein the concentrations of PFOA and 2,4,6-TCP in the simulated wastewater are both 10 - 40 mg / L.

[0022] Preferably, the adsorption reaction is carried out under dark stirring, the stirring rate is 200 - 400 rpm, and the stirring time is 0.5 - 1 h.

[0023] Preferably, the ultraviolet light source is turned on for the photocatalytic reaction, the intensity of the ultraviolet light source is 6 - 30 W, and the ultraviolet light wavelength is 254 nm.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0025] 1. The preparation method of the Ga2O3-Bi4O7 / CTF composite material prepared by the present invention is simple and the production cost is relatively low. The good electrical conductivity of fluorinated CTF further promotes the separation of photo-generated electrons and holes in Ga2O3-Bi4O7, thereby generating more active species to participate in the degradation process of per- and poly-fluoroalkyl substances (PFAS) mixed pollutants, thus showing excellent removal effects. Using UV as the light source, the removal rates of 15.00 mg / L PFOA and 14.22 mg / L 2,4,6-TCP in the mixed pollutants reach 93.0% and 100% respectively within 90 min.

[0026] 2. The reaction conditions for removing per- and poly-fluoroalkyl substances (PFAS) mixed pollutants by the method of the present invention are mild, the operation is simple, easy, rapid and effective. By adjusting the dosage of the composite material and the reaction duration, the performance and efficiency of the catalyst for removing per- and poly-fluoroalkyl substances (PFAS) mixed pollutants can be controlled. At the same time, the composite material after the treatment by this method is easy to recycle, and the adsorption-photocatalysis synergistic effect can effectively avoid the secondary pollution problem that may be induced after the single adsorption treatment method reaches the adsorption saturation of pollutants, thus avoiding harm to the environment. Brief Description of the Drawings

[0027] Figure 1 It is the preparation process diagram of Ga2O3-Bi4O7 / CTF of the present invention;

[0028] Figure 2 It is the scanning electron microscope images of (a) CTF, (b) Ga2O3-Bi4O7 and (c) Ga2O3-Bi4O7 / CTF of the present invention;

[0029] Figure 3 It is the UV-Vis diffuse reflectance spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF of the present invention;

[0030] Figure 4 It is the transient photocurrent response spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF of the present invention;

[0031] Figure 5 It is the electrochemical impedance spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF of the present invention;

[0032] Figure 6 It is the effect diagrams of (a) PFOA and (b) 2,4,6-TCP for the synergistic removal of per- and poly-fluoroalkyl substances (PFAS) mixed pollutants by UV photolysis, Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF adsorption-photocatalysis;

[0033] Figure 7 It is the cyclic performance diagram of Ga2O3-Bi4O7 / CTF of the present invention under adsorption-photocatalysis conditions. Detailed implementation mode

[0034] To further understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0035] Combined with Figure 1 , a preparation method of a Ga2O3-Bi4O7 / CTF composite material according to the present invention includes the following steps:

[0036] (1) Preparation of Ga2O3-Bi4O7: Add NaBiO3·2H2O to an appropriate amount of deionized water, stir well, transfer it to a stainless-steel autoclave with a polytetrafluoroethylene inner liner, and carry out a hydrothermal reaction. After the reaction is completed, wash and dry the obtained product to obtain Bi2O4. Disperse commercial Ga2O3 in an appropriate amount of ethanol, after ultrasonic treatment, disperse a certain mass of Bi2O4 into the Ga2O3 suspension. After ultrasonic treatment, heat and stir the mixed solution in a water bath. After the ethanol is evaporated to dryness, sinter the obtained solid powder at high temperature to obtain a Ga2O3-Bi4O7 photocatalyst.

[0037] (2) Preparation of Ga2O3-Bi4O7 / CTF: Mix tetrafluoroterephthalonitrile and ZnCl2 thoroughly by grinding, after vacuum calcination, wash and dry the obtained product to obtain fluorine-doped CTF. Add the prepared Ga2O3-Bi4O7 and fluorine-doped CTF to a mortar at a certain ratio, drop an appropriate amount of ethanol, and grind thoroughly. Dry the obtained mixture to obtain a Ga2O3-Bi4O7 / CTF composite material.

[0038] (3) Use the Ga2O3-Bi4O7 / CTF composite material to adsorb-photocatalytically synergistically remove per- and polyhalogenated mixed pollutants in wastewater: Place the PFOA and 2,4,6-TCP mixed solution in a quartz tube with a cooling jacket, add a certain amount of Ga2O3-Bi4O7 / CTF prepared in step (2), and then place the mixed system in a photocatalytic reaction device, stir in the dark for the adsorption reaction, and after reaching the adsorption-desorption equilibrium, turn on the ultraviolet light source for the photocatalytic reaction.

[0039] Example 1

[0040] 0.56 g of NaBiO3·2H2O was added to 60 mL of deionized water. After sufficient stirring, it was transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner and heated to 180 °C in an oven for 4 h. After the reaction, it was naturally cooled to room temperature. The obtained product was washed and dried to obtain Bi2O4 powder. 0.20 g of commercial Ga2O3 powder was dispersed in 60 mL of ethanol. After ultrasonic treatment, a Ga2O3 suspension was obtained. Then, 22.22 mg of Bi2O4 was dispersed into the Ga2O3 suspension. After ultrasonic treatment, the mixed solution was stirred in a 60 °C water bath. After the ethanol evaporated completely, the obtained solid powder was put into a crucible. Finally, the crucible was placed in a muffle furnace and maintained at 250 °C for 3 h for high-temperature sintering to obtain Ga2O3-Bi4O7.

[0041] 1.00 g of tetrafluoro-p-benzenedicarbonitrile and 6.82 g of ZnCl2 were thoroughly mixed by grinding, and the mixture was transferred to a quartz ampoule. After evacuation, it was sealed and calcined in a muffle furnace at 400 °C for 40 h, and then cooled to room temperature. The calcined product was stirred and washed with 1 mol / L hydrochloric acid for 48 h, then washed with deionized water until the solution was neutral, and dried at 60 °C to obtain fluorine-doped CTF. 0.20 g of the prepared Ga2O3-Bi4O7 and 11.11 mg of fluorine-doped CTF were simultaneously added to a mortar, and an appropriate amount of ethanol was dropped and ground thoroughly. The obtained mixture was dried to obtain Ga2O3-Bi4O7 / CTF.

[0042] Figure 2 Scanning electron microscope images of CTF, Ga2O3-Bi4O7, and Ga2O3-Bi4O7 / CTF prepared in Example 1 of the present invention Figure 2 The fluorine-doped CTF in (a) shows a stacked layered structure with a rough surface and grooves, resulting in its large specific surface area, which can adsorb pollutants well. Figure 2 The Ga2O3-Bi4O7 heterojunction is shown in (b). From Figure 2 It can be observed from (c) that Ga2O3-Bi4O7 adheres to the surrounding of the fluorine-doped CTF.

[0043] Figure 3 Ultraviolet-visible diffuse reflectance spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF prepared in Example 1 of the present invention. A red shift can be observed from the optical absorption edge of Ga2O3-Bi4O7 / CTF in the figure. The introduction of fluorine-doped CTF broadens the optical absorption range of the composite material compared with Ga2O3-Bi4O7.

[0044] Figure 4Transient photocurrent response spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF prepared in Example 1 of the present invention. After being compounded with fluorinated CTF, the transient photocurrent response value of Ga2O3-Bi4O7 / CTF is higher than that of Ga2O3-Bi4O7, indicating that the carriers of the composite catalyst exhibit better separation efficiency.

[0045] Figure 5 Electrochemical impedance spectra of Ga2O3-Bi4O7 and Ga2O3-Bi4O7 / CTF prepared in Example 1 of the present invention. Compared with Ga2O3-Bi4O7, the arc radius of the electrochemical impedance spectrum of Ga2O3-Bi4O7 / CTF is smaller, indicating that fluorinated CTF has good electron conduction ability, can improve the interfacial charge transfer performance of the composite material, and thus improve its photocatalytic performance.

[0046] Application Example 1

[0047] Experimental group: Prepare a simulated wastewater of 15.00 mg / L PFOA and 14.22 mg / L 2,4,6-TCP (molar concentration ratio of 1:2) with deionized water, take 50 ml and add it to a quartz tube with a cooling jacket. Then add 20 mg of the Ga2O3-Bi4O7 / CTF composite material prepared in Example 1, add a magnetic stir bar, and place the mixed system in a photocatalytic reaction device. Turn on the condensation circulating water, first stir magnetically at 300 rpm in the dark for the adsorption reaction. After stirring for 0.5 h to reach the adsorption-desorption equilibrium, turn on the ultraviolet light source with an output power of 30 W and a wavelength of 254 nm for the photocatalytic reaction, and continue to stir magnetically at 300 rmp. Sample regularly, each time draw 1 ml of the reaction solution, filter it through a filter membrane and enter the sample vial. Finally, use high performance liquid chromatography to measure the concentrations of PFOA and 2,4,6-TCP in the solution.

[0048] Control Group 1: Take the Ga2O3-Bi4O7 prepared in Example 1 as the catalyst to conduct an adsorption-photocatalytic synergistic removal experiment on the mixed pollutants of PFOA and 2,4,6-TCP. The experimental process is the same as that of the above experimental group.

[0049] Control Group 2: Without adding a catalyst, directly photocatalyze the mixed pollutants of FOA and 2,4,6-TCP with UV. The experimental process is the same as that of the above experimental group.

[0050] The removal effect of this application example is as Figure 6As shown. It can be seen that under UV conditions, without a catalyst, PFOA hardly degrades within 90 min, while there is a certain degree of photocatalytic degradation for 2,4,6-TCP. The photocatalytic degradation efficiencies of Ga2O3-Bi4O7 for PFOA and 2,4,6-TCP are 74.9% and 86.1% respectively. Ga2O3-Bi4O7 / CTF can play the synergistic effect of adsorption-photocatalysis, and the removal rates of PFOA and 2,4,6-TCP in the mixed pollutants within 90 min are 93.0% and 100% respectively, effectively improving the overall removal effect of the mixed pollutants.

[0051] Application Example 2

[0052] Experimental group: The composite materials after the end of the experimental group in Application Example 1 were collected, subjected to suction filtration, washing, and drying, and then used for the next round of experiments. The experimental process of each round was the same as that of the experimental group in Application Example 1 to evaluate the stability of the Ga2O3-Bi4O7 / CTF composite material.

[0053] The experimental removal effect of this application example is as Figure 7 shown. As Figure 7 shown, after being used four times continuously, the overall removal rate of the composite material for the mixed pollutants of PFOA and 2,4,6-TCP can still remain above 80%. This indicates that the Ga2O3-Bi4O7 / CTF composite material has good stability and reusability, and proves that the adsorption-photocatalysis synergistic technology is a method that can efficiently remove per- or polyhalogenated mixed pollutants in wastewater.

Claims

1. A preparation method of Ga2O3-Bi4O7 / CTF composite material, characterized in that, It includes the following steps: (1) Disperse Ga2O3 powder in ethanol, and obtain a Ga2O3 suspension after ultrasonic treatment; (2) Disperse a certain mass of Bi2O4 into the Ga2O3 suspension, after ultrasonic treatment, stir the obtained mixed solution under water bath conditions until the ethanol is evaporated to dryness; (3) Sinter the powder obtained in step (2) at high temperature to obtain Ga2O3-Bi4O7; (4) Grind Ga2O3-Bi4O7 and fluorinated CTF after dropping appropriate ethanol into them; (5) Dry the mixture obtained in step (4) to obtain Ga2O3-Bi4O7 / CTF.

2. The method according to claim 1, characterized in that, In step (2), by mass ratio, Bi2O4:(Bi2O4 + Ga2O3)=1:8-15, and the water bath temperature is 50-80°C.

3. The method according to claim 1, characterized in that, In step (3), the high-temperature sintering temperature is 200-250°C, and the high-temperature sintering time is 3-5 h.

4. The method according to claim 1, wherein In step (4), tetrafluoroterephthalonitrile and ZnCl2 are fully mixed by grinding, after vacuum calcination, the obtained product is washed and dried to obtain fluorinated CTF, wherein the molar ratio of tetrafluoroterephthalonitrile to ZnCl2 is 1:6; the vacuum calcination temperature is 400-500°C, and the vacuum calcination time is 35-45 h.

5. The method according to claim 1, characterized in that In step (4), by mass ratio, fluorinated CTF:(fluorinated CTF + Ga2O3-Bi4O7)=1:10-20.

6. The Ga2O3-Bi4O7 / CTF composite material prepared by the method according to any one of claims 1-5.

7. The use of the Ga2O3-Bi4O7 / CTF composite material prepared by the method according to any one of claims 1-5 in the synergistic adsorption-photocatalysis for removing per- and polyhalogenated mixed pollutants in wastewater.

8. The use according to claim 7, wherein, The specific steps are as follows: Place the simulated wastewater containing PFOA and 2,4,6-trichlorophenol in a quartz tube with a cooling jacket, add the Ga2O3-Bi4O7 / CTF composite material, and then place the mixed system in a photocatalytic reaction device, stir in the dark for the adsorption reaction, after reaching the adsorption-desorption equilibrium, turn on the ultraviolet light source for the photocatalytic reaction.

9. The use according to claim 8, characterized in that, Add 0.2-0.5 g / L of Ga2O3-Bi4O7 / CTF to every 50 mL of simulated wastewater for the synergistic adsorption-photocatalysis reaction, wherein the concentrations of PFOA and 2,4,6-TCP in the simulated wastewater are both 10-40 mg / L.

10. The use according to claim 8, characterized in that, Stir in the dark for the adsorption reaction, the stirring rate is 200-400 rpm, and the stirring time is 0.5-1 h; turn on the ultraviolet light source for the photocatalytic reaction, and the intensity of the ultraviolet light source is 6-30 W, and the ultraviolet light wavelength is 254 nm.

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