A method for preparing and applying the hydrotalcite material NiFe LDH / Br-Cu2O

Abstract

This invention provides a method for preparing the hydrotalcite material NiFe LDH / Br-Cu2O. The method includes adding Ni(NO3)2·6H2O and Fe(NO3)3·9H2O to water, then adding urea to the solution and stirring in a polytetrafluoroethylene-lined autoclave. The reaction is carried out at 100–120°C for 7–10 h to prepare the NiFe LDH catalyst. CuSO4·5H2O is added to water at 50–60°C, followed by the addition of NiFe LDH and NaOH, and the mixture is stirred under a water bath at 50–60°C. A glucose solution is then added to the solution, followed by the addition of NH4Br, and the mixture is stirred under a water bath at 50–60°C for 2–4 h to obtain the reddish-black solid NiFe LDH / Br-Cu2O. The NiFe LDH / Br-Cu2O prepared by this method exhibits mild reaction conditions and high degradation efficiency as a photocatalytic material for degrading the pollutant catechol in water, achieving a degradation rate of nearly 90% within 90 minutes, demonstrating significant effectiveness.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic degradation, and in particular to a method for preparing and applying the hydrotalcite material NiFe LDH / Br-Cu2O. Background Technology

[0002] Environmental protection of wastewater containing highly toxic and poorly biodegradable organic substances, particularly ionizable aromatic phenols, naphtha, and naphthylamine, generated during industrial and agricultural production processes, is one of the greatest challenges facing the scientific community. It is necessary to remove these ecotoxic hazards from wastewater before it is discharged into the environment to maintain government wastewater environmental regulations, as it can lead to serious health problems such as respiratory, gastrointestinal, and cardiovascular effects. Catechol exists in nature in various derivative forms and is an important fine chemical raw material, widely used in pesticides, pharmaceuticals, fragrances, dyes, photosensitive materials, and rubber industries. Catechol is also used as a rubber hardener, electroplating additive, skin antiseptic and antibacterial agent, hair dye, photographic developer, color antioxidant, fur dyeing developer, and paint anti-peeling agent. Although catechol has a wide range of applications in production, it is also a highly toxic organic compound that is difficult to degrade and seriously pollutes the environment.

[0003] Due to the high stability of organic pollutants, they are difficult to degrade using conventional methods at room temperature without light irradiation. Light energy, as a clean and renewable energy source, has been widely applied in various fields over time. The emergence of photocatalysis research has further promoted the application of light energy. Currently, the main research directions in photocatalysis include photocatalytic hydrogen production, photocatalytic CO2 reduction, photocatalytic wastewater treatment, and air purification. Among these, the degradation of pollutants using photocatalytic reactions has attracted widespread attention due to its energy efficiency, low energy input, and mild conditions. Photocatalysis is a type of advanced oxidation process. Currently, researchers mainly use the construction of heterojunctions to improve the redox capacity of photocatalysts. According to the photophysics of catalysts, the smaller the band gap, the higher the light utilization efficiency. Doping non-metallic elements (chlorine, bromine, nitrogen) with lower electronegativity than oxygen into metal semiconductors to replace oxygen in the crystal lattice allows these lower electronegative elements to participate in the formation of the semiconductor valence band, thereby effectively improving the bandgap position of the catalyst and reducing the band gap.

[0004] Based on this, the present invention prepares cuprous oxide doped with non-metallic bromine, which then forms a heterojunction with nickel-iron hydrotalcite to form NiFe LDH / Br-Cu2O to degrade catechol. Summary of the Invention

[0005] The present invention aims to provide a method for preparing and applying the hydrotalcite material NiFe LDH / Br-Cu2O.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing the hydrotalcite material NiFe LDH / Br-Cu2O, characterized by comprising the following steps:

[0008] Step (1): Preparation of NiFe LDH

[0009] Ni(NO3)2·6H2O and Fe(NO3)3·9H2O were added to water and stirred for 30–50 min. Then, urea was added to the above solution and stirred for 30–50 min to dissolve. The dissolved solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 100–120 °C for 7–10 h. After cooling to room temperature, the product was collected by centrifugation, washed three times with ethanol and distilled water respectively, and finally dried under vacuum at 50–60 °C to obtain NiFe LDH.

[0010] Step (2): Preparation of NiFe LDH / Br-Cu2O

[0011] CuSO4·5H2O was added to water at 50–60°C, NiFe LDH and NaOH were added, and the mixture was stirred for 20–40 min under water bath heating at 50–60°C. Then, glucose solution was added to the above solution, followed by NH4Br. The mixture was stirred for 2–4 h under water bath heating at 50–60°C. After cooling to room temperature, the product was collected by centrifugation and finally dried under vacuum at 50–60°C to obtain a reddish-black solid NiFe LDH / Br-Cu2O.

[0012] Furthermore, in step (1), the molar ratio of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and urea is 2:1:4.5~5.

[0013] Furthermore, in step (2), the mass ratio of NiFe LDH:CuSO4·5H2O is 0.25 to 0.75:1, and the molar ratio of NaOH to CuSO4·5H2O in step (2) is 4:1.

[0014] Furthermore, in step (2), the concentration of the glucose solution is 0.3 mol / L, and the molar ratio of glucose to CuSO4·5H2O is 1:1.

[0015] Furthermore, in step (2), the molar ratio of CuSO4·5H2O and NH4Br is 1:1.2 to 1.4.

[0016] This invention provides a hydrotalcite material NiFe LDH / Br-Cu2O prepared by the aforementioned method.

[0017] This invention also provides the application of the aforementioned hydrotalcite material NiFe LDH / Br-Cu2O in the photocatalytic degradation of catechol. The method involves placing 10–100 mg of NiFe LDH / Br-Cu2O in an aqueous solution of catechol, placing the reaction solution in a double-layered reaction tube, introducing high-purity N2, and stirring for 30–60 min for dark treatment to remove dissolved O2 from the water, while simultaneously achieving adsorption-desorption equilibrium between the catalyst and N2. N2 is continuously introduced, and the mixture is irradiated under a xenon lamp for 0.5–2 h, with continuous stirring to degrade the catechol. The initial mass concentration of the catechol is 10–100 mg / L.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] First, the NiFe LDH / Br-Cu2O provided by this invention has a relatively small band gap and grain size. Under suitable light, it can generate electron-hole pairs with catalytic activity. When pollutants (catechol) are adsorbed on the surface of hydrotalcite, they will capture electron-hole pairs, causing the pollutants to degrade, thereby achieving the purpose of purifying wastewater.

[0020] Secondly, the NiFe LDH / Br-Cu2O provided by this invention, as a photocatalytic material, exhibits mild reaction conditions and high degradation efficiency, with a degradation rate of nearly 90% in 90 minutes, demonstrating significant effectiveness. Attached Figure Description

[0021] Figure 1 The XRD diffraction patterns are of NiFe LDH, NiFe LDH / Br-Cu2O in Example 1 and Br-Cu2O in Comparative Example 2.

[0022] Figure 2 The images show the SEM images of NiFe LDH in Example 1 (a), Br-Cu2O in Comparative Example 2 (b), and NiFe LDH / Br-Cu2O in Example 1 (cd).

[0023] Figure 3 This is the standard curve for catechol.

[0024] Figure 4 The graphs show the degradation rates of catechol in Examples 1, 1, 2, and 3, as well as the blank control.

[0025] Figure 5 This is the EDX elemental mapping diagram of NiFe LDH / Br-Cu2O in Example 1. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention. Specific techniques or conditions not specified in the embodiments are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified can be obtained commercially through conventional products.

[0027] Example 1

[0028] Step (1): Preparation of NiFe LDH

[0029] 3 mmol Ni(NO3)2·6H2O and 1.5 mmol Fe(NO3)3·9H2O were added to 50 mL of water and stirred for 30 min. Then, 14.85 mmol urea was added to the above solution and stirred for 30 min to dissolve. The dissolved solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 100 °C for 10 h. After cooling to room temperature, the product was collected by centrifugation, washed three times with ethanol and three times with distilled water, and finally dried under vacuum at 60 °C to obtain NiFe LDH. The sample was characterized by XRD diffraction and scanning electron microscopy. The results are as follows: Figure 1 , 2 As shown.

[0030] Step (2): Preparation of NiFe LDH / Br-Cu2O

[0031] 5 mmol CuSO4·5H2O was added to 100 mL of water at 50 °C. Then, 200 mg NiFe LDH and 20 mmol NaOH were added and stirred in a 50 °C water bath for 20 min. Next, 10 mL of 0.3 mol / L glucose solution was added to the above solution, followed by 0.375 g NH4Br. The mixture was stirred in a 50 °C water bath for 2 h, cooled to room temperature, and the product was collected by centrifugation. Finally, the product was vacuum dried at 60 °C to obtain a reddish-black solid NiFe LDH / Br-Cu2O. To confirm the successful synthesis, the sample was characterized by XRD diffraction, scanning electron microscopy, and EDX elemental mapping. The results are as follows: Figure 1 , 2 As shown in Figure 5.

[0032] Comparative Example 1

[0033] The NiFe LDH prepared in step (1) of Example 1 was used directly.

[0034] Comparative Example 2

[0035] Add 5 mmol CuSO4·5H2O to 100 mL of water at 50 °C, then add 20 mmol NaOH and mix and stir in a 50 °C water bath for 20 min. Next, add 10 mL of 0.3 mol / L glucose solution to the above solution, followed by 0.375 g NH4Br. Continue stirring in a 50 °C water bath for 2 h, cool to room temperature, collect the product by centrifugation, and finally vacuum dry at 60 °C to obtain Br-Cu2O. Characterize the sample by XRD diffraction and scanning electron microscopy. The results are as follows: Figure 1 , 2 As shown.

[0036] Comparative Example 3

[0037] Add 5 mmol CuSO4·5H2O to 100 mL of water at 50 °C, add 20 mmol NaOH, and mix and stir in a water bath at 50 °C for 20 min. Then add 10 mL of 0.3 mol / L glucose solution to the above solution and continue stirring in a water bath at 50 °C for 2 h. Cool to room temperature, centrifuge to collect the product, and finally vacuum dry at 60 °C to obtain Cu2O.

[0038] Preparation of standard curve

[0039] Based on an initial catechol solution with a concentration of 100 mg / L, solutions with concentrations of 10.00 mg / L, 20.00 mg / L, 30.00 mg / L, 40.00 mg / L, and 50.00 mg / L were prepared. Deionized water was used as a blank reference. The absorbance of each solution was measured at 275 nm using a Shimadzu 2550 UV-Vis spectrophotometer. A linear fitting was performed to obtain a standard curve of absorbance A versus concentration C for the catechol solution. (See figure...) Figure 3 As shown.

[0040] Photocatalytic degradation performance test of catechol

[0041] A 300W xenon lamp (with a filter to remove ultraviolet light and retain visible light within 400nm < λ < 800nm) was used to simulate the degradation of catechol under sunlight as a model reaction. The light source was 20cm away from the reaction solution. The absorbance of the catechol solution at 275nm was measured using a UV-Vis spectrophotometer to determine its relative concentration, thereby evaluating the photocatalytic performance of the material.

[0042] Under conditions of 20℃ and pH=7, 20 mg of the NiFe LDH / Br-Cu2O catalyst from Example 1 was added to a double-layered quartz reaction tube containing 100 mL of a 15 mg / L catechol solution. High-purity N2 was introduced and the mixture was stirred for 30 min in the dark to remove dissolved O2 from the water and simultaneously reach adsorption-desorption equilibrium between the catalyst and N2. N2 was continuously introduced, and then a xenon lamp was turned on to conduct a photocatalytic degradation experiment of catechol under continuous illumination and magnetic stirring. After the reaction started, samples were taken every 15 min, filtered through a 0.22 μm organic filter membrane, and the absorbance of the filtrate at 275 nm was measured using a UV-Vis spectrophotometer. Based on the standard curve, the relative mass concentration C (mg / L) of catechol was calculated. The degradation rate (η%) of catechol was calculated based on C / C0, where C0 (mg / L) is the initial mass concentration of catechol. The degradation rate curve is shown below. Figure 4 As shown.

[0043] η=C / C0(1)

[0044] In Example 1, the NiFe LDH / Br-Cu2O was successively replaced with no catalyst (blank control), NiFe LDH in Comparative Example 1, Br-Cu2O in Comparative Example 2, and Cu2O in Comparative Example 3. The degradation rate curves were obtained as follows: Figure 5 As shown.

[0045] As shown in the figure, catechol is relatively stable under xenon lamp irradiation, with little change in concentration. NiFe LDH adsorbed nearly 20% of catechol in the first 30 minutes, but showed weak degradation ability in the subsequent 1.5 hours of photoreaction, with a degradation efficiency of only 20.21%. Cu2O and Br-Cu2O had weak adsorption capacity, but their degradation capacity was higher than that of NiFe LDH, degrading 34.02% and 55.92% respectively after 1.5 hours of photoreaction. The composite catalyst NiFeLDH / Br-Cu2O also had weak adsorption capacity, but showed particularly high degradation efficiency, with a degradation rate of nearly 90% in 90 minutes.

[0046] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a hydrotalcite material NiFeLDH / Br-Cu2O in the photocatalytic degradation of catechol, wherein the hydrotalcite material NiFeLDH / Br-Cu2O is obtained by the following preparation method: Step (1): Preparation of NiFe LDH Ni(NO3)2·6H2O and Fe(NO3)3·9H2O were added to water and stirred for 30-50 min. Then, urea was added to the above solution and stirred for 30-50 min to dissolve. The dissolved solution was transferred to a high-pressure reactor with a polytetrafluoroethylene liner and reacted at 100-120℃ for 7-10 h. After cooling to room temperature, the product was collected by centrifugation, washed three times with ethanol and distilled water respectively, and finally dried under vacuum at 50-60℃ to obtain NiFe LDH. Step (2): Preparation of NiFe LDH / Br-Cu2O CuSO4·5H2O was added to water at 50-60℃, NiFe LDH and NaOH were added, and the mixture was stirred for 20-40 min under water bath heating at 50-60℃. Then, glucose solution was added to the above solution, followed by NH4Br. The mixture was stirred for 2-4 h under water bath heating at 50-60℃. After cooling to room temperature, the product was collected by centrifugation. Finally, the product was dried under vacuum at 50-60℃ to obtain a reddish-black solid NiFe LDH / Br-Cu2O.

2. The application according to claim 1, characterized in that, In step (1), the molar ratio of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and urea is 2:1:4.5~5.

3. The application according to claim 1, characterized in that, In step (2), the mass ratio of NiFe LDH:CuSO4·5H2O is 0.25~0.75:1, and the molar ratio of NaOH to CuSO4·5H2O in step (2) is 4:

1.

4. The application according to claim 1, characterized in that, In step (2), the concentration of the glucose solution is 0.3 mol / L, and the molar ratio of glucose to CuSO4·5H2O is 1:

1.

5. The application according to claim 1, characterized in that, In step (2), the molar ratio of CuSO4·5H2O and NH4Br is 1:1.2~1.

4.

6. The application according to claim 5, characterized in that, The application includes the following steps: 10-100 mg of NiFe LDH / Br-Cu2O was placed in an aqueous solution of catechol. The reaction solution was placed in a double-layered reaction tube, and high-purity N2 was introduced and stirred for 30-60 min for dark treatment to remove dissolved O2 in the water and achieve adsorption-desorption equilibrium between the catalyst and N2. N2 was continuously introduced and the mixture was irradiated under a xenon lamp for 0.5-2 h with continuous stirring to degrade the catechol. The initial mass concentration of the catechol was 10-100 mg / L.

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