Preparation of crystal face co-exposed flaky Bi0 / Bi4NbO8Cl wave-absorbing material and application of wave-absorbing material in removal of perfluorooctanoic acid in water

Abstract

The invention belongs to the field of preparation of wave-absorbing materials, and relates to a high-activity 0D / 2D crystal face co-exposed Bi0 / Bi4NbO8Cl microwave (MW) absorbing material as well as a preparation method and application thereof. The crystal face co-exposed flaky Bi0 / Bi4NbO8Cl wave-absorbing material is a 0D / 2D Bi0 / Bi4NbO8Cl Schottky junction wave-absorbing material with high-activity crystal faces {001} and {110} which are co-exposed. According to the invention, Bi4NbO8Cl is modified through a crystal face engineering technology, and a 2D sheet structure with exposed {001} and {110} high-activity crystal faces is generated. And carrying out hydrothermal treatment to enable 0D semimetal Bi0 to grow on the surface in situ, so as to obtain the 2D flaky Bi0 / Bi4NbO8Cl binary composite MW absorbing material with high-activity {001} and {110} crystal faces co-exposed. Under MW driving, the material shows ultrahigh catalytic degradation activity on PFOA, and has potential application prospects in the aspect of purification of environmental water bodies polluted by PFAS.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of microwave absorbing materials, and particularly relates to a Bi 0 / Bi 4 NbO 8 Cl microwave absorbing material, a preparation method thereof, and an application thereof in the efficient defluorination and degradation of perfluorooctanoic acid (PFOA). Background Art

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been widely adopted in commercial and industrial fields due to their excellent physicochemical properties. However, more and more evidence shows that PFAS pose a serious threat to the environment and human health. Studies have confirmed their carcinogenicity, immunotoxicity, and endocrine disrupting effects. In the PFAS family, perfluorooctanoic acid (PFOA, chemical formula C 7 F 15 COOH) is frequently detected in human blood due to its wide application. Due to the presence of abundant C-F bonds with extremely high dissociation energy (exceeding 500 kJ mol -1 ), PFOA is extremely difficult to be biodegraded under conventional water treatment technologies, and its half-life in water is about 50 years. Given the widespread distribution, persistence, and potential health risks of PFOA, people have been actively seeking technologies for effectively degrading PFOA in recent decades.

[0003] Microwave (MW)-induced catalytic technology provides a practical solution for improving treatment efficiency, reducing energy consumption, and shortening the reaction cycle with its fast and uniform heating characteristics and the ability to eliminate temperature gradients. This technology highly conforms to the goals of energy conservation and efficient water treatment. Compared with traditional wastewater treatment methods, microwave-induced catalytic technology effectively avoids challenges such as sludge bulking, residual sludge treatment, and secondary pollution. However, designing an efficient microwave (MW) catalyst is the core of improving the efficiency of MW-induced catalytic technology. Bi 4 NbO 8 Cl, due to its high structural symmetry, unique layered structure, and alternately arranged [Bi 2 O 2 2+ layers and Cl - layers, is conducive to the separation of carriers and the migration of substances between layers, and exhibits excellent intercalation, adsorption, and microwave absorption properties. Bi 4 NbO 8 ​Different crystal planes of Cl exhibit anisotropy, making it possible to optimize its charge separation and aggregation performance by adjusting the degree of crystal plane exposure. To further improve the carrier separation efficiency and extend the carrier lifetime of the material, constructing a Schottky junction is an effective method. In this study, a 0D / 2D Bi with co-exposed high-activity crystal planes {001} and {110} was successfully synthesized through the molten salt method and the solvothermal method. 0 / Bi 4 NbO 8 Cl microwave-absorbing material with Schottky junction shows excellent catalytic activity in the process of microwave-assisted catalytic degradation of PFOA. Summary of the Invention

[0004] To achieve the above object, the technical solution of the present invention is as follows: A sheet-like Bi 0 / Bi 4 NbO 8 Cl microwave-absorbing material with co-exposed crystal planes is a 0D / 2D Bi 0 / Bi 4 NbO 8 Cl microwave-absorbing material with Schottky junction.

[0005] The preparation method of the above-mentioned sheet-like Bi 0 / Bi 4 NbO 8 Cl microwave-absorbing material with co-exposed crystal planes includes the following steps:

[0006] 1) Preparation of the precursor BiOCl: Dissolve Bi(NO 3 ) 3 ·5H 2 O in ethylene glycol to obtain solution A, dissolve KCl in ethylene glycol to form solution B. Under vigorous stirring, slowly drop solution B into solution A, mix and stir, transfer to an autoclave for hydrothermal reaction, wash and dry to obtain the precursor BiOCl;

[0007] 2) Preparation of 2D sheet-like Bi 4 NbO 8 Cl: Grind and mix BiOCl, Bi 2 O 3 , Nb 2 O 5 and a certain amount of LiCl and KCl, transfer to an alumina crucible, calcine in a muffle furnace, repeatedly rinse the obtained powder with deionized water to remove residual LiCl and KCl, dry overnight, change the amount of LiCl and KCl used to make Bi 4 NbO 8 Cl / (Bi 4 NbO 8(Cl + LiCl + KCl) = 1% - 6%, obtaining Bi with different exposed crystal planes 4 NbO 8 Cl absorbing material;

[0008] 3) 0D / 2D Bi 0 / Bi 4 NbO 8 Preparation of Cl composite absorbing material: Take Bi(NO 3 ) 3 ·5H 2 O and dissolve it in ethylene glycol, then add 2D flaky Bi 4 NbO 8 Cl. After ultrasonic dispersion and homogenization, transfer it to a reaction kettle for reaction. After washing and drying the precipitate, the composite absorbing material is obtained.

[0009] In the preparation method of the above-mentioned flaky Bi0 / Bi4NbO8Cl absorbing material with co-exposed crystal planes, in step 1), the hydrothermal reaction is carried out at 160 °C for 10 h.

[0010] In the preparation method of the above-mentioned flaky Bi 0 / Bi 4 NbO 8 Cl absorbing material, in step 2), the calcination is carried out at 750 °C for 6 hours.

[0011] In the preparation method of the above-mentioned flaky Bi 0 / Bi 4 NbO 8 Cl absorbing material, in step 2), the reaction is carried out at 160 °C for 10 h.

[0012] In the preparation method of the above-mentioned flaky Bi 0 / Bi 4 NbO 8 Cl absorbing material, in step 2), when Bi 4 NbO 8 Cl / (Bi 4 NbO 8 Cl + LiCl + KCl) = 1%, the {001} crystal plane is mainly exposed. When Bi 4 NbO 8 Cl / (Bi 4 NbO 8 Cl + LiCl + KCl) = 6%, the {110} crystal plane is mainly exposed. Other ratios are co-exposure of the {001} crystal plane and the {110} crystal plane.

[0013] In the above-mentioned preparation method of the flaky Bi 0 / Bi4 NbO 8 Application of Cl microwave absorbing material in synergistic microwave removal of perfluorooctanoic acid in water.

[0014] For the above application, the method is as follows: Add Bi 0 / Bi 4 NbO 8 Cl microwave absorbing material and catalytically degrade PFOA under microwave conditions.

[0015] Beneficial effects of the present invention: The present invention modifies Bi 4 NbO 8 Cl through crystal plane engineering technology to generate a 2D sheet structure with exposed {001} and {110} highly active crystal planes. Hydrothermal treatment in situ grows 0D semimetal Bi 0 on its surface, obtaining a 2D sheet-like Bi 0 / Bi 4 NbO 8 Cl binary composite MW absorbing material with co-exposed {001} and {110} crystal planes. Bi 0 / Bi 4 NbO 8 Cl with co-exposed {001} and {110} crystal planes can perform dual-path defluorination degradation on PFOA due to the simultaneous presence of oxidation crystal planes and reduction crystal planes, realizing the efficient mineralization of PFOA. Description of the drawings

[0016] Figure 1 are the XRD patterns of BNOC-1, BNOC-2, BNOC-5, BNOC-6 and 25% B / BNOC-5.

[0017] Figure 2 In (a) is the SEM image of BNOC-5, and in (b) is the SEM image of 25% B / BNOC-5. Detailed implementation manners

[0018] Example 1 Preparation of Bi 0 / Bi 4 NbO 8 Cl microwave absorbing material

[0019] Preparation of precursor BiOCl: Dissolve 3.3950 g of Bi(NO 3 ) 3 ·5H 2 O in 30 mL of ethylene glycol to obtain solution A, and dissolve 0.5218 g of KCl in 30 mL of ethylene glycol to form solution B. Under vigorous stirring, slowly drop solution B into solution A, mix and stir for 30 min, transfer to an autoclave and react at 160 °C for 10 h. After washing and drying, the precursor BiOCl is obtained.

[0020] 2D flaky Bi 4 NbO 8 Preparation of Cl: Grind and mix 0.2604 g of BiOCl, 0.6989 g of Bi 2 O 3 , 0.1329 g of Nb 2 O 5 with a certain amount of LiCl and KCl, transfer to an alumina crucible, and calcine in a muffle furnace at 750 °C for 6 hours. Wash the obtained powder repeatedly with deionized water to remove residual LiCl and KCl, and dry it overnight in an oven at 80 °C. Change the amounts of LiCl and KCl to make Bi 4 NbO 8 Cl / (Bi 4 NbO 8 Cl + LiCl + KCl) = 1%, 2%, 5%, 6%, and obtain Bi 4 NbO 8 Cl microwave absorption materials with different exposed crystal planes, denoted as BNOC-1, BNOC-2, BNOC-5, and BNOC-6. Among them, the mass of LiCl corresponding to BNOC-1 is 2.1196 g, and the mass of KCl is 3.7276 g; the mass of LiCl corresponding to BNOC-2 is 1.0600 g, and the mass of KCl is 1.8640 g; the mass of LiCl corresponding to BNOC-5 is 0.4239 g, and the mass of KCl is 0.7455 g; the mass of LiCl corresponding to BNOC-6 is 0.3606 g, and the mass of KCl is 0.6210 g

[0021] 0D / 2D Bi 0 / Bi 4 NbO 8 Cl composite microwave absorption material preparation: Weigh 0.0625 g, 0.0993 g, 0.1407 g, 0.1875 g, and 0.2411 g of Bi(NO 3 ) 3 ·5H 2 O and dissolve it in 40 mL of ethylene glycol. Then add 0.2424 g of the prepared BNOC-5, ultrasonically disperse it evenly, and transfer it to a 100 mL reaction kettle. Keep it at 160 °C for 10 h. After washing and drying the precipitate, obtain the composite microwave absorption material, denoted as 10% B / BNOC-5, 15% B / BNOC-5, 20% B / BNOC-5, 25% B / BNOC-5, and 30% B / BNOC-5.

[0022] Figure 1 is the XRD pattern of the sample. It can be seen that several different Bi 4 NbO 8Cl has similar diffraction peak positions. The diffraction peaks at 2θ = 12.30°, 22.87°, 23.70°, 29.58°, 31.08°, 31.68°, and 32.58° are respectively attributed to the (004), (110), (112), (116), (0010), (117), and (020) crystal planes of Bi 4 NbO 8 Cl (JCPDS No. 84 - 0843), but there are significant differences in the relative intensities of the {001} and {110} peaks. The co - exposure degrees of the {001} and {110} crystal planes of several Bi 4 NbO 8 Cl are different. BNOC - 1 exposes more {001} crystal planes, BNOC - 6 exposes more {110} crystal planes, and BNOC - 5 exposes both {001} and {110} crystal planes simultaneously. In the 25%B / BNOC - 5 composite material, new diffraction peaks appear at 2θ = 27.16°, 37.94°, and 39.61°, corresponding to the (012), (104), and (110) crystal planes of metallic Bi 0 (JCPDS No. 44 - 1246), proving the successful loading of Bi 0 .

[0023] Figure 2 Figure Figure 2 a shows the SEM image of BNOC - 5, and it can be observed that BNOC - 5 is a 2D sheet - like structure with a size of about 3 - 4 μm Figure 2 Figure 0 b is the SEM image of 25%B / BNOC - 5, and it can be seen that Bi

[0024] Example 2 Bi 0 / Bi 4 NbO 8 Cl microwave - absorbing material for catalytic degradation of PFOA

[0025] The catalytic experiment was carried out in a special microwave instrument in the laboratory, whose temperature, power, and reaction time are controllable and equipped with a condensation reflux device. Measure 50 mL of 10 mg·L -1 PFOA standard solution and place it in a 250 mL three - necked flask. Add 15 mg of 25%B / BNOC - 5 composite microwave - absorbing material, set the power to 700 W, and sample and test the content change every 1 minute

[0026] 1. MW - driven catalytic degradation of PFOA by different materials

[0027] As shown in Table 1, the degradation effect of MW radiation alone on PFOA is almost negligible, and the removal rate of 25% B / BNOC-5 for PFOA adsorption alone within 5 min is only 21.6%. Under the drive of MW, the degradation efficiency of BNOC-5 monomer for PFOA within 5 min is 24.2%, which is significantly higher than that of BNOC-1, BNOC-2, and BNOC-6. The MW synergistic degradation efficiency of 25% B / BNOC-5 composite material for PFOA can reach 97.7%, demonstrating extremely high MW-induced catalytic activity.

[0028] Table 1 Comparison of the removal effects of different methods on PFOA within 5 min

[0029]

[0030] 2. Influence of the dosage of B / BNOC-5 on the degradation efficiency of PFOA

[0031] In the experiment, the following parameters were controlled unchanged: the concentration of PFOA was 10 mg L -1 , and the MW power was 700 W. 25% B / BNOC-5 with masses of 5 mg, 10 mg, 15 mg, and 20 mg were added to 50 mL of solution respectively. As the dosage of the catalyst increased, the degradation efficiency also increased. When the dosage of the catalyst was 15 mg, the degradation rate could reach 97.7%. Further increasing the dosage did not result in a significant improvement in the catalytic efficiency.

[0032] Table 2 Influence of the dosage of the catalyst on the degradation effect of PFOA

[0033]

[0034] 3. Influence of the reaction time on the degradation efficiency of PFOA

[0035] As shown in Table 3, the concentration of PFOA was 10 mg L -1 , the MW power was 700 W, and 15 mg of 25% B / BNOC-5 was added to 50 mL of solution. As the MW time was extended, the degradation efficiency also increased. When irradiated by MW for 5 min, the degradation rate could reach 97.7%. Further extending the reaction time did not result in a significant improvement in the catalytic efficiency.

[0036] Table 3 Influence of the MW radiation time on the degradation effect of PFOA

[0037]

[0038] 4. Influence of the Bi 0 loading amount in the wave-absorbing material on the degradation efficiency of PFOA

[0039] As shown in Table 4, in order to investigate Bi 0Effect of loading amount on catalytic efficiency: 50 mL 10 mg L -1 PFOA solution was placed in a 250 mL three-necked round-bottom flask, and then Bi 0 15 mg of catalytic materials with mass percentages of 10%, 15%, 20%, 25% and 30% were added to the round-bottom flask, and MW radiation (700 W) was turned on.

[0040] Under MW radiation, the catalytic degradation effect of B / BNOC-5 on PFOA increases with the increase of Bi 0 The increase of load showed a trend of first increasing and then decreasing. 0 The catalyst with a loading of 25% had the best degradation efficiency for PFOA within 5 minutes.

[0041] Table 4 Different Bi 0 Effect of loading amount on PFOA degradation efficiency

[0042]

[0043] 5. Effect of different solution pH values ​​on PFOA degradation

[0044] As shown in Table 5, in order to explore the effect of solution pH on the catalytic degradation performance of PFOA, the solution pH was adjusted to 2, 4.3, 7 and 10, and the catalytic reaction was carried out. The results showed that as the pH decreased from 10 to 4.3, the degradation efficiency of PFOA by 25% B / BNOC-5 increased, and the catalytic activity was optimal at pH 4.3. Further reducing the pH to 2 reduced the catalytic activity.

[0045] Table 5 Effect of different pH on PFOA degradation efficiency

[0046]

Claims

1. A crystal plane co-exposed sheet Bi 0 / Bi4NbO8Cl absorbing material, characterized in that: It is a 0D / 2D Bi with highly active crystal planes {001} and {110} co-exposed 0 / Bi4NbO8Cl Schottky junction absorbing material.

2. The crystal plane co-exposed sheet Bi according to claim 1 0 / Bi4NbO8Cl absorbing material preparation method, characterized in that, The steps include: 1) Preparation of BiOCl precursor: Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain solution A, KCl was dissolved in ethylene glycol to form solution B, solution B was slowly added dropwise to solution A under vigorous stirring, mixed and stirred, transferred to an autoclave for hydrothermal reaction, washed and dried to obtain the precursor BiOCl; 2) Preparation of 2D flake Bi4NbO8Cl: BiOCl, Bi2O3, Nb2O5 and a certain amount of LiCl and KCl were ground and mixed, transferred to an alumina crucible, and calcined in a muffle furnace. The obtained powder was repeatedly rinsed with deionized water to remove residual LiCl and KCl, dried overnight, and the amount of LiCl and KCl was changed to make Bi4NbO8Cl / (Bi4NbO8Cl+LiCl+KCl)=1%-6%, thereby obtaining Bi4NbO8Cl absorbing materials with different crystal planes exposed; 3) 0D / 2D Bi 0 Preparation of / Bi4NbO8Cl composite absorbing material: Take Bi(NO3)3·5H2O and dissolve it in ethylene glycol, then add 2D flake Bi4NbO8Cl, and transfer it to a reactor for reaction after ultrasonic dispersion. The precipitate is washed and dried to obtain a composite absorbing material.

3. A crystal plane co-exposed sheet Bi according to claim 2 0 / Bi4NbO8Cl absorbing material preparation method, characterized in that, In step 1), the hydrothermal reaction is carried out at 160° C. for 10 hours.

4. The crystal plane co-exposed sheet Bi according to claim 2 0 / Bi4NbO8Cl absorbing material preparation method, characterized in that, In step 2), the calcination is carried out at 750° C. for 6 hours.

5. The crystal plane co-exposed sheet Bi according to claim 2 0 / Bi4NbO8Cl absorbing material preparation method, characterized in that, In step 2), the reaction is maintained at 160° C. for 10 h.

6. The crystal plane co-exposed sheet Bi according to claim 2 0 / Bi4NbO8Cl absorbing material preparation method, characterized in that, In step 2), when Bi4NbO8Cl / (Bi4NbO8Cl+LiCl+KCl)=1%, the {001} crystal plane is mainly exposed, and when Bi4NbO8Cl / (Bi4NbO8Cl+LiCl+KCl)=6%, the {110} crystal plane is mainly exposed, and the other proportions are that the {001} crystal plane and the {110} crystal plane are co-exposed.

7. The crystal plane co-exposed sheet Bi according to claim 1 0 Application of / Bi4NbO8Cl absorbing material in synergistic microwave removal of perfluorooctanoic acid in water.

8. The use according to claim 8, characterized in that: The method is as follows: add Bi to the PFOA solution 0 / Bi4NbO8Cl absorbing material, catalytic degradation of PFOA under microwave conditions.

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