Preparation method of composite photocatalyst for efficiently treating high-concentration dye wastewater

Abstract

The application aims to provide a preparation method of a composite photocatalyst for efficiently treating high-concentration dye wastewater, and belongs to the technical field of photocatalysts. The application prepares a TiO2 photocatalyst modified by 2-amino terephthalic acid through an in-situ acid etching strategy of sacrificing metal organic frameworks (MOF), and then prepares a YCQDs / NH2BDC loaded with carbon quantum dots through solvent deposition 10 -TiO2 composite photocatalyst. NH2BDC 10 The TiO2 photocatalyst has excellent visible light response and enhanced adsorption capacity. YCQDs / NH2BDC 10 The TiO2 composite photocatalyst has obviously improved photo-generated carrier separation efficiency and widened light absorption range (up to near-infrared light). Based on the above reasons, the 5CQDs / NH2BDC10-TiO2 composite photocatalyst has ideal adsorption and photocatalytic degradation efficiency on a high-concentration RhB solution.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, specifically relating to a method for preparing a composite photocatalyst for the efficient treatment of high-concentration dye wastewater. Background Technology

[0002] With the rapid development of the textile industry in many countries, large quantities of high-concentration dye wastewater are widely discharged into soil and water bodies, causing serious dye pollution. Most dye molecules contain aromatic rings, which are highly toxic to organisms and have mutagenic effects on humans and aquatic life. Furthermore, the color of dyes affects light transmission in water, delaying photosynthesis in aquatic organisms and impacting their growth, thus disrupting the aquatic ecosystem. Therefore, there is an urgent need to develop a feasible technology for treating high-concentration dye wastewater.

[0003] Currently, various feasible methods, including adsorption, biological treatment, electrochemistry, and photocatalysis, have been used to treat dye wastewater. However, the limitations of adsorption technology—its inability to convert pollutants into harmless compounds, the tendency for secondary pollution from toxic byproducts in biological treatment, and the high energy consumption of electrochemical technology—limit their application in treating high-concentration dye wastewater. Photocatalysis, with its advantages of converting pollutants into harmless compounds, no secondary pollution, and low energy consumption, has become an ideal method for removing dye pollutants. TiO2 is considered one of the most promising photocatalysts due to its excellent photocatalytic activity, good chemical stability, low cost, and non-toxicity. Unfortunately, TiO2 still has some drawbacks that limit its practical application in the efficient treatment of high-concentration dye wastewater. First, its poor adsorption performance prevents it from rapidly adsorbing dye molecules in wastewater to improve light transmittance, and low light transmittance severely affects its photocatalytic activity in treating high-concentration dye wastewater. Second, TiO2 has a narrow light absorption range, responding only to ultraviolet light, resulting in low efficiency in utilizing solar energy. Finally, TiO2's weak photogenerated carrier separation capability leads to a rapid decrease in the number of effective carriers during degradation, which greatly limits its photocatalytic activity.

[0004] Metal-organic frameworks (MOFs), composed of metal ions and organic ligands, are a new class of materials with high specific surface areas and ease of functionalization. In recent years, the application of MOFs as precursors in the derivatization of modified metal oxide photocatalysts has gradually attracted researchers' attention. Among MOFs, MIL-125(Ti) has been widely used for the derivatization of modified TiO2. However, in most reports, the 2-aminoterephthalic acid (NH2-BDC) organic ligand is only considered as a precursor for the preparation of non-metallic element-modified TiO2. For example, He et al. used NH2-BDC organic ligand as a carbon source to prepare C-modified TiO2 via high-temperature pyrolysis, which improved its adsorption performance to some extent, but did not significantly improve the light absorption range. Ismail et al. used the NH2-BDC organic ligand of NH2-MIL-125(Ti) as a precursor for both carbon and nitrogen sources to prepare C / N-TiO2 via high-temperature pyrolysis, effectively enhancing photogenerated electron-hole separation, but without significantly broadening the light absorption range. However, it has been reported that the NH2-BDC organic ligand can effectively broaden the light absorption range of TiO2. Furthermore, Fan et al. used NH2-MIL-125(Ti) to adsorb MB, and the results showed that the interaction provided by the benzene ring and amino functional groups in the NH2-BDC organic ligand significantly enhanced the adsorption of dye molecules. Therefore, we propose to synthesize TiO2 through NH2-MIL-125(Ti) derivatization while retaining the NH2-BDC organic ligand. This is expected to improve the shortcomings of TiO2 and promote its effective treatment of high-concentration dye wastewater.

[0005] Furthermore, carbon quantum dots (CQDs), with their excellent electron transport and upconversion fluorescence properties, have been widely used to enhance photogenerated electron-hole separation and light absorption in photocatalysts. For example, Xia et al. prepared a CQDs / Bi₂WO₆ composite photocatalyst, which exhibited significantly higher photocatalytic activity than pure Bi₂WO₆ in the photocatalytic degradation of organic pollutants. This was attributed to the enhancement of photogenerated electron-hole separation by CQDs in the composite photocatalyst. Lin et al. prepared a MIL-53(Fe) / CQDs composite photocatalyst using CQDs as a co-catalyst. The results showed that CQDs could induce photogenerated electrons and holes to separate from the internal structure of MOFs, which greatly improved their photocatalytic degradation activity for Cr(VI). Wang et al. prepared a CQDs / NH₂-MMIL-125(Ti) composite photocatalyst. The results showed that CQDs not only inhibited photogenerated electron-hole recombination in NH₂-MIL-125 (titanium) but also greatly broadened the light absorption range and improved its light utilization efficiency. Furthermore, CQDs possess advantages such as low cost, good chemical stability, and simple preparation methods. Therefore, CQDs are ideal materials for further enhancing the activity of photocatalysts. Summary of the Invention

[0006] To address the above problems, the present invention aims to provide a method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater.

[0007] This invention prepares a 2-aminoterephthalic acid modified TiO2 photocatalyst (NH2BDC) by sacrificing a metal-organic framework (MOF) through in-situ acid etching. X -TiO2), and then YCQDs / NH2BDC loaded with carbon quantum dots were prepared by solvent deposition. 10 -TiO2 composite photocatalyst. Characterization results confirm that NH2BDC 10 -TiO2 photocatalysts exhibit excellent visible light response and enhanced adsorption capacity. Furthermore, the successful loading of CQDs on its surface effectively enhances the photogenerated electron-hole separation capability, while further improving the light absorption intensity and photoresponse range of the composite photocatalyst. 5CQDs / NH2BDC 10 The TiO2 composite photocatalyst exhibited good removal efficiency when treating high-concentration RhB solutions. This work provides new insights into the design of TiO2-based composite photocatalysts for the practical treatment of high-concentration dye wastewater.

[0008] The present invention adopts the following technical solution:

[0009] A method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater includes the following steps:

[0010] The first step was to synthesize NH2-MIL-125(Ti) via a solvothermal method.

[0011] DMF and MeOH were mixed in a beaker, and then 2-aminoterephthalic acid was added to the mixed solution and sonicated until a clear solution was formed. Then, tetrabutyl titanate was added to the clear solution and sonicated for 30 min. The solution was then transferred to an 80 mL stainless steel autoclave lined with polytetrafluoroethylene and reacted at 150 °C for 48 h. The collected sample was washed several times with DMF and methanol and then dried overnight in an oven at 60 °C. The obtained NH2-MIL-125(Ti) was named NM(Ti).

[0012] The second step is to obtain NH2BDC through an acid etching strategy. X -TiO2

[0013] An acetic acid solution with a concentration of X mol / L was prepared in a beaker. NM(Ti) was then added to the acetic acid solution, followed by ultrasonic treatment for 1 h. The mixture was then placed in a reactor lined with polytetrafluoroethylene (PTFE) and reacted at 90 °C for 12 h. Finally, the target material was obtained by centrifugation, washing, and drying, and was named NH2BDC.X -TiO2, where X represents the concentration of acetic acid, which are 5, 10, 15, and 20, respectively;

[0014] The third step involves preparing CQDs using an alkali-assisted ultrasonic method.

[0015] Glucose was uniformly dissolved in deionized water, then NaOH solution was added and stirred to achieve complete mixing. The colorless solution was then sonicated at room temperature for 120 min to obtain a yellow-brown solution. Finally, the CQDs stock solution was further purified using a dialysis bag.

[0016] The fourth step involves preparing YCQDs / NH2BDC using a solvent deposition method. 10 -TiO2 composite photocatalyst

[0017] Choosing an acetic acid concentration of 10 mol / L, NH2BDC 10 TiO2 and Y mLCQDs solution were uniformly dispersed in deionized water and immersed in a cryogenic bath at 90℃ for 3 h. Finally, the sample was collected and named YCQDs / NH2BDC. 10 -TiO2, where Y is the mass percentage of CQDs.

[0018] Furthermore, the ratio of DMF, MeOH, 2-aminoterephthalic acid, and tetrabutyl titanate in the first step is 27 mL: 3 mL: 1.36 g: 0.51 mL.

[0019] Furthermore, the amount of NM(Ti) added in the second step is 200 mg.

[0020] Furthermore, in the third step, the concentration of NaOH is 1 mol / L, and the ratio of glucose, deionized water, and NaOH is 9 g: 50 mL: 50 mL.

[0021] Furthermore, in step four, the concentration of the CQDs solution is 16.03 g / L, and the volumes Y mL are 0.16, 0.31, 0.47, and 0.62 mL, respectively, corresponding to a photocatalyst of 2.5 CQDs / NH2BDC. 10 -TiO2、5CQDs / NH2BDC 10 -TiO2, 7.5CQDs / NH2BDC 10 -TTiO2 and 10CQDs / NH2BDC 10 -TiO2;NH2BDC 10 - The amounts of TiO2 and deionized water added were 100 mg and 30 mL, respectively.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention is the first to prepare an organic ligand (NH2-BDC) modified TiO2 photocatalyst by an in-situ acid etching strategy using NH2-MIL-125 (Ti), which gives it excellent visible light response and enhanced adsorption capacity.

[0024] 2. Through NH2BDC 10 -TiO2 surface loading of CQDs yields 5CQDs / NH2BDC 10 -TiO2 composite photocatalysts, with surface-supported CQDs, effectively enhance the separation of photogenerated electrons and holes, and further expand the light absorption range of the composite photocatalyst to the near-infrared region, thus meeting the requirements for efficient photocatalytic removal of high-concentration RhB solutions. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the sample prepared according to this invention.

[0026] Figure 2 The image shown is the FT-IR spectrum of the sample prepared according to the present invention.

[0027] Figure 3 The images are SEM and TEM images of the sample prepared in this invention, where a and b represent NM(Ti) and NH2BDC, respectively. 10- SEM image of TiO2; c and d are 5CQDs / NH2BDC. 10 TEM image of TiO2;

[0028] Figure 4 The image shows the photoelectrochemical spectrum of the sample prepared in this invention, where a is the UV-vis DRS spectrum; b is the PL spectrum; c is the electrochemical impedance spectroscopy; and d is the transient photocurrent spectrum.

[0029] Figure 5 For NH2BDC X -TiO2, NM(Ti), P25+NH2BDC and P25 exhibit photocatalytic activity in the degradation of RhB under visible light.

[0030] Figure 6 YCQDs / NH2BDC with different CQDs loads 10 - Determination of the photocatalytic activity of TiO2 in the degradation of RhB under visible light and various parameters. Detailed Implementation

[0031] A method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater includes the following steps:

[0032] 1. Preparation of NH2-MIL-125(Ti)

[0033] NH2-MIL-125(Ti) was synthesized via a solvothermal method. Specifically, 27 mL of DMF and 3 mL of MeOH were mixed in a beaker, and then 1.36 g of 2-aminoterephthalic acid was added to the mixture and sonicated until a clear solution was formed. Then, 0.51 mL of tetrabutyl titanate was added to the clear solution and sonicated for 30 min. The mixture was then transferred to an 80 mL PTFE-lined stainless steel autoclave and reacted at 150 °C for 48 h. The collected sample was washed several times with DMF and methanol and then dried overnight in an oven at 60 °C. The obtained NH2-MIL-125(Ti) was named NM(Ti).

[0034] 2. NH2BDC X Preparation of TiO2

[0035] NH2BDC was obtained based on the following acid etching strategy. X -TiO2 photocatalyst. Specifically, an acetic acid solution with a concentration of X mol / L (X=5, 10, 15, and 20) was prepared in a beaker. Then, 200 mg of NM(Ti) was added to the acetic acid solution and sonicated for 1 h. After sonication, the mixture was placed in a reactor lined with polytetrafluoroethylene and reacted at 90 °C for 12 h. Finally, the target material was obtained by centrifugation, washing, and drying, and was named NH2BDC. X -TiO2, where X represents the concentration of acetic acid. The prepared composite photocatalysts are NH2BDC5-TiO2 and NH2BDC5-TiO2, respectively. 10 -TiO2, NH2BDC 15 -TiO2 and NH2BDC 20- TiO2.

[0036] 3. Preparation of CQDs

[0037] Carbon quantum dots (CQDs) were prepared using an alkali-assisted sonication method. Specifically, 9.0 g of glucose was uniformly dissolved in 50 mL of deionized water, followed by the addition of 50 mL of 1 mol / L NaOH solution and stirring to achieve complete mixing. The colorless solution was then sonicated at room temperature for 120 min to obtain a yellow-brown solution. Finally, the CQD stock solution was further purified using a dialysis bag (MWCO 3000).

[0038] 4. YCQDs / NH2BDC 10 Preparation of TiO2

[0039] YCQDs / NH2BDC were prepared by solvent deposition. 10 -TiO2 composite photocatalyst. Specifically, 100 mg NH2BDC10 TiO2 and Y mL (Y = 0.16, 0.31, 0.47, and 0.62) CQDs solution (16.03 g / L) were uniformly dispersed in 30 mL of deionized water and immersed in a cryogenic bath at 90 °C for 3 h. The samples were then collected and named YCQDs / NH2BDC10-TiO2, where Y is the mass percentage of CQDs. The prepared photocatalysts were 2.5 CQDs / NH2BDC10-TiO2. 10 -TiO2、5CQDs / NH2BDC 10 -TiO2, 7.5CQDs / NH2BDC 10 -TTiO2 and 10CQDs / NH2BDC 10 -TiO2.

[0040] Result characterization

[0041] XRD results confirm that NH2BDC has been successfully prepared. X -TiO2 and YCQDs / NH2BDC 10 -TiO2. Comparing the characteristic diffraction peaks of NM(Ti) and P25, it was found that in NH2BDC... X In the XRD patterns of the TiO2 series, as the acetic acid concentration gradually increases, the intensity of the characteristic diffraction peaks attributed to NM(Ti) gradually decreases until they disappear, while the characteristic diffraction peaks associated with anatase TiO2 gradually appear and their intensity gradually increases. This indicates that as the acetic acid concentration gradually increases, the crystal structure of NM(Ti) is destroyed during the etching process, and this process is accompanied by the formation of anatase TiO2. For YCQDs / NH2BDC... 10 The XRD patterns of the TiO2 series retain the relationship with NH2BDC. 10 -TiO2 exhibits the same broad diffraction peaks as anatase TiO2. The difference lies in the YCQDs / NH2BDC... 10 -TiO2 shows a diffraction peak near 2θ=27° corresponding to the (002) crystal plane in CQDs, indicating the successful loading of CQDs.

[0042] FT-IR results further confirm YCQDs / NH2BDC 10 - Retention of NH2BDC and successful loading of CQDs in TiO2 composite photocatalysts. Comparison of characteristic absorption peaks of NM(Ti) and P25 shows the retention of NH2BDC in NH2BDC. X In the FT-IR spectra of TiO2 series, 400-800 cm⁻¹ -1 It exhibits broad peaks consistent with TiO2 within the range of 1380-1690 cm⁻¹. -1The absorption peaks within the range are consistent with those of NH2BDC in NM(Ti), indicating that after acid etching, not only TiO2 is formed in NM(Ti), but NH2BDC is also retained. For YCQDs / NH2BDC... 10 The FT-IR spectra of the TiO2 series not only show characteristic absorption peaks associated with TiO2 and NH2BDC, but also at 1085 cm⁻¹. -1 and 2959 cm -1 The characteristic absorption peak of CQDs is shown at the position, and the peak intensity increases with the increase of CQD loading, which again shows that CQDs were successfully loaded on the surface of NH2BDC10-TiO2 photocatalyst by solvent deposition.

[0043] SEM and TEM results show that after etching, the originally regularly shaped and large-sized NM(Ti) particles were transformed into irregularly shaped TiO2 particle aggregates with a particle size of about 100 nm. TEM results confirm that CQDs were uniformly dispersed and deposited on NH2BDC. 10 -TiO2 surface, simultaneously from 5CQDs / NH2BDC 10 Two distinct lattice fringes can be clearly observed in the high-resolution TEM of TiO2, corresponding to the (101) crystal plane of anatase TiO2 and the (002) crystal plane of CQDs, respectively, further confirming the presence of CQDs in NH2BDC. 10 -TiO2 surface successfully loaded.

[0044] UV-vis DRS spectroscopy results show that, compared with NM(Ti) and TiO2, NH2BDC modification significantly broadens the light absorption range of TiO2, with a red shift at the light absorption edge reaching 550 nm. Furthermore, for 5CQDs / NH2BDC... 10 Loading with TiO2 and CQDs further improves the light absorption range, even approaching the near-infrared region. PL spectroscopy, electrochemical impedance spectroscopy, and transient photocurrent plots demonstrate that loading with CQDs effectively improves the absorption range of NH2BDC. 10 - The ability of photogenerated electrons and holes to separate and migrate in TiO2 photocatalysts.

[0045] Photocatalytic degradation results showed that when the acetic acid concentration was 10 mol / L, i.e., NH2BDC 10 TiO2 showed the best removal effect on high concentrations of RhB solution, therefore subsequent research focused on NH2BDC. 10 The process is based on TiO2. Under the combined action of NH2BDC and CQDs, 5CQDs / NH2BDC 10-TiO2 composite photocatalysts exhibited the best removal efficiency for high-concentration RhB solutions, with adsorption and photocatalytic degradation efficiencies of 24.8% and 86.3%, respectively. Furthermore, 5CQDs / NH2BDC 10 The optimal conditions for TiO2 photocatalytic removal of high concentrations of RhB are: RhB solution concentration (80 mg / L), composite photocatalyst dosage (20 mg), and initial pH of the reaction solution (pH = 7).

Claims

1. A method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater, characterized in that: Includes the following steps: The first step was to synthesize NH2-MIL-125(Ti) via a solvothermal method. DMF and MeOH were mixed in a beaker, and then 2-aminoterephthalic acid was added to the mixed solution and sonicated until a clear solution was formed. Then, tetrabutyl titanate was added to the clear solution and sonicated for 30 min. The solution was then transferred to an 80 mL stainless steel autoclave lined with polytetrafluoroethylene and reacted at 150 °C for 48 h. The collected sample was washed several times with DMF and methanol and then dried overnight in an oven at 60 °C. The obtained NH2-MIL-125(Ti) was named NM(Ti). The ratio of DMF, MeOH, 2-aminoterephthalic acid, and tetrabutyl titanate is 27 mL: 3 mL: 1.36 g: 0.51 mL; The second step is to obtain NH2BDC through an acid etching strategy. X -TiO2 An acetic acid solution with a concentration of X mol / L was prepared in a beaker. NM(Ti) was then added to the acetic acid solution, followed by ultrasonic treatment for 1 h. The mixture was then placed in a reactor lined with polytetrafluoroethylene (PTFE) and reacted at 90 °C for 12 h. Finally, the target material was obtained by centrifugation, washing, and drying, and was named NH2BDC. X -TiO2, where X represents the concentration of acetic acid, with a value of 10; The third step involves preparing CQDs using an alkali-assisted ultrasonic method. Glucose was uniformly dissolved in deionized water, then NaOH solution was added and stirred to achieve complete mixing. The colorless solution was then sonicated at room temperature for 120 min to obtain a yellow-brown solution. Finally, the CQDs stock solution was further purified using a dialysis bag. The fourth step involves preparing YCQDs / NH2BDC using a solvent deposition method. 10 -TiO2 composite photocatalyst Choosing an acetic acid concentration of 10 mol / L, NH2BDC 10 TiO2 and Y mLCQDs solution were uniformly dispersed in deionized water and immersed in a cryogenic bath at 90℃ for 3 hours. Finally, the sample was collected and named YCQDs / NH2BDC. 10 -TiO2, where Y is the mass percentage of CQDs.

2. The method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater according to claim 1, characterized in that: The amount of NM(Ti) added in the second step is 200 mg.

3. The method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater according to claim 1, characterized in that: The concentration of NaOH in the third step is 1 mol / L, and the ratio of glucose, deionized water and NaOH is 9 g: 50 mL: 50 mL.

4. The method for preparing a composite photocatalyst for efficiently treating high-concentration dye wastewater according to claim 1, characterized in that: In step four, the concentration of the CQDs solution was 16.03 g / L, and the volumes Y mL were 0.16, 0.31, 0.47, and 0.62 mL, respectively, corresponding to a photocatalyst of 2.5 CQDs / NH2BDC. 10 -TiO2、5CQDs / NH2BDC 10 -TiO2, 7.5CQDs / NH2BDC 10 -TTiO2 and 10CQDs / NH2BDC 10 -TiO2;NH2BDC 10 - The amounts of TiO2 and deionized water added were 100 mg and 30 mL, respectively.

Images