A doped uiO-66(zr) metal-organic framework material, and methods of making and using the same

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a doped UiO-66(Zr) metal organic framework material and a preparation method and application thereof. The application changes the energy band structure by doping iron ions on the basis of the UiO-66(Zr) metal organic framework material, increases the carrier density, reduces the electron hole recombination rate, and thus improves the photocatalytic performance. The doped UiO-66(Zr) metal organic framework material is prepared by using a zirconium source, an iron source and terephthalic acid in a polar solvent through a one-step solvothermal method. The doped UiO-66(Zr) metal organic framework material has excellent anti-interference performance and cycle performance, can be applied to photocatalytic removal of heavy metals such as uranyl ions, lead ions and copper ions, and organic pollutants such as antibiotics and pesticides in wastewater, and has a very high removal rate and effect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a doped UiO-66(Zr) metal-organic framework material, its preparation method, and its application. Background Technology

[0002] Currently, nuclear energy remains one of the cleanest energy sources due to its high efficiency, low carbon emissions, and continuous power supply, and is widely used in power generation in some countries. However, the rapid development of the nuclear industry inevitably has adverse effects on the environment and human safety. Uranium, as the primary fuel for nuclear energy, generates highly toxic and radioactive uranium-containing wastewater during uranium mining and nuclear power plant operation. The toxicity of uranium-containing wastewater mainly depends on the content of hexavalent uranium (U(VI)), in which U(VI) is primarily expressed as uranyl ions (UO2). 2+ It exists in wastewater in the form of ).

[0003] Commonly used methods for treating uranium-containing wastewater include chemical precipitation, adsorption, biological methods, chemical reduction, ion exchange, and photocatalysis. Among these, photocatalysis has promising applications in the treatment of uranium-containing wastewater and the degradation of organic pollutants due to its advantages such as environmental sustainability, high efficiency, selectivity, wide applicability, and no secondary pollution.

[0004] In recent years, the emerging photocatalyst UiO-66, a three-dimensional metal-organic framework material assembled with Zr as the metal center and terephthalic acid as the organic ligand, has shown promising application potential in environmental remediation, including photocatalytic uranium removal, heavy metal removal, and degradation of organic pollutants. However, similar to common semiconductors, pure-phase UiO-66 exhibits generally low light absorption and a high recombination rate of photogenerated electron-hole pairs, which severely limits its photocatalytic activity. Summary of the Invention

[0005] The purpose of this invention is to provide a doped UiO-66(Zr) metal-organic framework material, its preparation method and application. The doped UiO-66(Zr) metal-organic framework material provided by this invention has excellent anti-interference performance and cycling performance, and has good photocatalytic activity.

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

[0007] The present invention provides a doped UiO-66(Zr) metal-organic framework material, comprising a UiO-66(Zr) matrix and iron ions doped in the UiO-66(Zr) matrix.

[0008] Preferably, the molar ratio of zirconium to iron ions in the UiO-66(Zr) matrix is ​​10 to 25:1.

[0009] Preferably, the pore size of the doped UiO-66(Zr) metal-organic framework material is 3.23–5.75 nm; the pore volume of the doped UiO-66(Zr) metal-organic framework material is 0.41–1.03 cm³. 3 / g.

[0010] This invention also provides a method for preparing the doped UiO-66(Zr) metal-organic framework material described in the above technical solution, comprising the following steps:

[0011] A precursor solution is obtained by mixing a zirconium source, an iron source, terephthalic acid, and a polar organic solvent.

[0012] The precursor solution was subjected to a solvothermal reaction to obtain the doped UiO-66(Zr) metal-organic framework material.

[0013] Preferably, the zirconium source includes one or more of ZrCl4, Zr(NO3)4, and Zr(SO4)2·4H2O; the iron source includes FeCl3·6H2O, FeCl4·6H2O, etc. x Fe(NO3) x Or Fe(NO3) x ·9H2O, X = 2 or 3.

[0014] Preferably, in the precursor solution, the concentration of the zirconium source is 0.0416–0.0625 mol / L, the concentration of the iron source is 0.0208–0.0416 mol / L, and the concentration of terephthalic acid is 0.0827–0.0835 mol / L.

[0015] Preferably, the polar organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0016] Preferably, the temperature of the solvothermal reaction is 100–200°C and the time is 10–24 h.

[0017] Preferably, after the solvothermal reaction, the product of the solvothermal reaction is further subjected to washing, centrifugation and drying in sequence;

[0018] The washing process includes washing with water and anhydrous ethanol, respectively, and the number of washing cycles is 2 to 5.

[0019] The centrifugation speed is 6000-10000 rpm, and the time is 5-30 min;

[0020] The drying temperature is 50–70°C, and the time is 15–24 hours.

[0021] This invention also provides the application of the doped UiO-66(Zr) metal-organic framework material described in the above technical solution or the doped UiO-66(Zr) metal-organic framework material prepared by the preparation method described in the above technical solution as a photocatalyst in the treatment of uranium-containing wastewater or the degradation of organic pollutants.

[0022] This invention provides a doped UiO-66(Zr) metal-organic framework material, comprising a UiO-66(Zr) matrix and iron ions doped into the UiO-66(Zr) matrix. The UiO-66(Zr-Fe) metal-organic framework material provided by this invention is in the form of spherical nanoparticles. Due to iron ion doping, the material's pore volume increases, providing more active sites and thus improving photocatalytic activity. The doped UiO-66(Zr) metal-organic framework material provided by this invention exhibits good thermal stability, remaining structurally stable below 402℃. The photocurrent density and charge transfer performance of the doped UiO-66(Zr) metal-organic framework material provided by this invention are significantly enhanced compared to UiO-66. The photoluminescence peak intensity of the UiO-66(Zr) metal-organic framework material provided by this invention is the lowest, and the average fluorescence lifetime of UiO-66(Zr-Fe-2) (0.974 ns) is longer than that of UiO-66 (0.844 ns). This indicates that iron ion doping of UiO-66 can effectively improve electron-hole separation efficiency and prolong electron lifetime, thereby promoting the formation of UO2. 2+ The photocatalytic reduction of Zr-Fe-2 is shown in this invention. The doped UiO-66(Zr) metal-organic framework material exhibits superior dark adsorption and photocatalytic efficiencies compared to UiO-66, particularly the UiO-66(Zr-Fe-2) with a zirconium to iron molar ratio of 2:1 in the reaction solution, which has a reaction rate constant of 0.022 min⁻¹ under illumination. -1 It is 11 times that of UiO-66. The UO2 content of the doped UiO-66 (Zr) metal-organic framework material provided by this invention under illumination conditions... 2+ The removal rate and removal amount are higher than under dark conditions. (Regarding UO2) 2+ At initial concentrations of 5 and 10 mg / L, UiO-66(Zr-Fe) under light irradiation produces UO2 2+ The removal rates were 99.09% and 90.28%, respectively, which were 3.01 times and 3.22 times that under darkness. Furthermore, in UO2... 2+ At an initial concentration of 100 mg / L, UiO-66(Zr-Fe-2) under light irradiation produces UO2 2+ The removal rate reached 141.33 mg / g, which is 5.45 times that in the dark environment.

[0023] The present invention also provides a method for preparing the doped UiO-66(Zr) metal-organic framework material described in the above technical solution, comprising the following steps: mixing a zirconium source, an iron source, terephthalic acid and a polar organic solvent to obtain a precursor solution; subjecting the precursor solution to a solvothermal reaction to obtain the doped UiO-66(Zr) metal-organic framework material.

[0024] This invention also provides the application of the doped UiO-66(Zr) metal-organic framework material described in the above-described technical solutions, or the doped UiO-66(Zr) metal-organic framework material prepared by the preparation method described in the above-described technical solutions, as a photocatalyst in the treatment of uranium-containing wastewater and the degradation of organic pollutants. The doped UiO-66(Zr) metal-organic framework material provided by this invention exhibits excellent chemical stability, anti-interference performance, and cycling performance, and has broad application prospects in uranium-containing wastewater treatment, seawater uranium extraction, and the removal of heavy metals and organic pollutants from water. Attached Figure Description

[0025] Figure 1 The image is a SEM image at high magnification of UiO-66(a);

[0026] Figure 2 This is a high-magnification SEM image of UiO-66(Zr-Fe-2) prepared in Example 2;

[0027] Figure 3 N2 adsorption-desorption isotherms (a) and pore size distribution (b) of the doped UiO-66 (Zr) metal-organic framework materials prepared in Examples 1-3;

[0028] Figure 4 Thermogravimetric curve of UiO-66(Zr-Fe-2) prepared in Example 2;

[0029] Figure 5 Transient photocurrent response diagrams of UiO-66 and UiO-66(Zr-Fe-2) prepared in Example 2;

[0030] Figure 6 Electrochemical impedance spectroscopy for UiO-66 and UiO-66(Zr-Fe-2) prepared in Example 2;

[0031] Figure 7 Photoluminescence spectra (a) and time-resolved photoluminescence spectra (b) of UiO-66 and UiO-66 (Zr-Fe-2) prepared in Example 2;

[0032] Figure 8UO2 content of UiO-66 and the doped UiO-66(Zr) metal-organic framework materials prepared in Examples 1-3 under light and dark conditions 2+ Remove performance graph;

[0033] Figure 9 Photocatalytic kinetics of UiO-66 and the UiO-66(Zr) metal-organic framework materials prepared in Examples 1-3 under light irradiation;

[0034] Figure 10 The UiO-66(Zr-Fe-2) prepared in Example 2 exhibits different UO2 efficiencies under both light and dark conditions. 2+ Removal rate graph (a) and removal amount graph (b) based on initial concentration;

[0035] Figure 11 The effect of UiO-66(Zr-Fe-2) prepared in Example 2 on UO2 at different pH values 2+ Photocatalytic removal effect diagram;

[0036] Figure 12 The UiO-66(Zr-Fe-2) prepared in Example 2 was used to treat UO2 under different interfering ions. 2+ Photocatalytic removal effect diagram;

[0037] Figure 13 The image shows the photocatalytic cycle performance of UiO-66(Zr-Fe-2) prepared in Example 2.

[0038] Figure 14 The graph shows the photocatalytic uranium removal performance of UiO-66(Zr-Fe-2) prepared in Example 2 in simulated seawater.

[0039] Figure 15 The image shows the photocatalytic performance of UiO-66 (Zr-Fe-2) prepared in Example 2 in wastewater containing heavy metal ions.

[0040] Figure 16 The image shows the DMPO-·OH(a) electron paramagnetic resonance spectrum of UiO-66(Zr-Fe-2) prepared in Example 2. - ·O 2- (b) Electron paramagnetic resonance spectrum, TEMPO - h + (c) Electron paramagnetic resonance spectrum;

[0041] Figure 17 The image shows the photocatalytic performance of UiO-66 (Zr-Fe-2) prepared in Example 2 in wastewater containing organic pollutants. Detailed Implementation

[0042] The present invention provides a doped UiO-66(Zr) metal-organic framework material, comprising a UiO-66(Zr) matrix and iron ions doped in the UiO-66(Zr) matrix.

[0043] In this invention, the molar ratio of zirconium to iron ions in the UiO-66(Zr) matrix is ​​preferably 10 to 25:1.

[0044] In this invention, the pore size of the doped UiO-66(Zr) metal-organic framework material is preferably 3.23–5.75 nm; the pore volume of the doped UiO-66(Zr) metal-organic framework material is preferably 0.41–1.03 cm³. 3 / g.

[0045] This invention also provides a method for preparing the doped UiO-66(Zr) metal-organic framework material described in the above technical solution, comprising the following steps:

[0046] A precursor solution is obtained by mixing a zirconium source, an iron source, terephthalic acid, and a polar organic solvent.

[0047] The precursor solution was subjected to a solvothermal reaction to obtain the doped UiO-66(Zr) metal-organic framework material.

[0048] In this invention, unless otherwise specified, all raw materials are commercially available products well known to those skilled in the art.

[0049] This invention mixes a zirconium source, an iron source, terephthalic acid, and a polar organic solvent to obtain a precursor solution.

[0050] In this invention, the zirconium source preferably includes one or more of ZrCl4, Zr(NO3)4, and Zr(SO4)2·4H2O; more preferably, it is ZrCl4; the iron source preferably includes FeCl3·6H2O, FeCl x Fe(NO3) x Or Fe(NO3) x ·9H2O, X = 2 or 3; further preferably FeCl3·6H2O.

[0051] In this invention, the polar organic solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide; more preferably N,N-dimethylformamide.

[0052] In this invention, the mixing preferably includes mixing a zirconium source, an iron source, and a portion of a polar organic solvent to obtain a first solution; mixing terephthalic acid and the remaining polar organic solvent to obtain a second solution; and mixing the first solution and the second solution to obtain the precursor solution.

[0053] In this invention, the concentration of the zirconium source in the precursor solution is preferably 0.0416–0.0625 mol / L, more preferably 0.0555 mol / L; the concentration of the iron source is preferably 0.0208–0.0416 mol / L, more preferably 0.0278 mol / L; and the concentration of the terephthalic acid is preferably 0.0827–0.0835 mol / L, more preferably 0.0833 mol / L.

[0054] After obtaining the precursor solution, the present invention performs a solvothermal reaction on the precursor solution to obtain the doped UiO-66(Zr) metal-organic framework material.

[0055] In this invention, the temperature of the solvothermal reaction is preferably 100-200°C, more preferably 120°C; the time of the solvothermal reaction is preferably 10-24 hours, more preferably 24 hours.

[0056] In this invention, the solvothermal reaction is preferably carried out in a reaction vessel; the volume of the reaction solution in the solvothermal reaction is preferably 60-80% of the volume of the reaction vessel, and more preferably 72%.

[0057] After the solvothermal reaction, the present invention preferably further includes naturally cooling the solvothermal reaction system to room temperature and then separating it to obtain the solvothermal reaction product; the separation method is preferably centrifugal separation.

[0058] After obtaining the solvothermal reaction product, the present invention preferably further includes washing, centrifuging and drying the solvothermal reaction product sequentially; the washing preferably includes washing with water and anhydrous ethanol respectively, and the number of washings is preferably 2 to 5 times; the centrifugation speed is preferably 6000 to 10000 rpm, more preferably 8000 rpm; the centrifugation time is preferably 5 to 30 min, more preferably 10 min; the drying temperature is preferably 50 to 70°C, more preferably 60°C; the drying time is preferably 15 to 24 h, more preferably 24 h.

[0059] This invention also provides the application of the doped UiO-66(Zr) metal-organic framework material described in the above technical solution or the doped UiO-66(Zr) metal-organic framework material prepared by the preparation method described in the above technical solution as a photocatalyst in the treatment of uranium-containing wastewater or the degradation of organic pollutants.

[0060] In this invention, the application of the UiO-66(Zr) metal-organic framework material as a photocatalyst in the treatment of uranium-containing wastewater preferably includes the photocatalytic removal of UO2 from the wastewater. 2+Photocatalytic extraction of uranium from seawater or photocatalytic removal of heavy metal ions from wastewater.

[0061] In this invention, the photocatalytic removal of UO2 from wastewater 2+ For this application, the preferred photocatalytic conditions are: the dosage of UiO-66(Zr) metal-organic framework material is 0.1–1 g / L, and UO2… 2+ The solution concentration is 5–100 mg / L, the temperature is 25℃, and the pH is 5–10.

[0062] In this invention, the preferred photocatalytic conditions for uranium extraction from seawater are: an addition amount of 0.5 g / L of UiO-66(Zr) metal-organic framework material, and UO2... 2+ The solution concentration was 5 mg / L, and the temperature was 25℃.

[0063] In this invention, the photocatalytic removal of heavy metal ions from wastewater is preferably performed under the following conditions: the dosage of UiO-66(Zr) metal-organic framework material is 0.5 g / L, the concentration of heavy metal ion solution is 1 mmol / L, and the temperature is 25°C.

[0064] In this invention, the application of the doped UiO-66(Zr) metal-organic framework material as a photocatalyst in the degradation of organic pollutants is preferably carried out under the following conditions: the dosage of the doped UiO-66(Zr) metal-organic framework material is 0.5 g / L, the organic pollutants preferably include one or more of tetracycline hydrochloride, ciprofloxacin, chlortetracycline, oxytetracycline, quinoline and atrazine, the concentration is 10 mg / L, and the temperature is 25°C.

[0065] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a doped UiO-66(Zr) metal-organic framework material, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] (1) Mix 4.5 mmol of ZrCl4 and 1.5 mmol of FeCl3·6H2O with 36 mL of DMF and stir until fully dissolved;

[0068] (2) Mix 6 mmol of terephthalic acid with 36 mL of DMF and stir until fully dissolved;

[0069] (3) Mix the solutions obtained in steps (1) and (2), control the concentration of ZrCl4 to be 0.0625 mol / L, the concentration of FeCl3·6H2O to be 0.0208 mol / L, and the concentration of terephthalic acid to be 0.0833 mol / L, stir evenly, and obtain a precursor solution with a molar ratio of zirconium source to iron source of 3:1.

[0070] (4) Place the precursor solution obtained in step (3) into a 10 mL reactor, so that the volume of the precursor solution accounts for 72% of the volume of the reactor. After reacting at a constant temperature of 120°C for 15 hours, naturally cool to room temperature and separate the solvothermal product.

[0071] (5) Wash the solvothermal product obtained in step (4) three times with water and anhydrous ethanol respectively, and centrifuge at 8000 rpm for 10 min to obtain a solid.

[0072] (6) The solvothermal product solid obtained in step (5) is vacuum dried at 60°C for 24 hours to obtain the doped UiO-66(Zr) metal-organic framework material, denoted as UiO-66(Zr-Fe-1).

[0073] Example 2

[0074] (1) Mix 4 mmol of ZrCl4 and 2 mmol of FeCl3·6H2O with 36 mL of DMF and stir until fully dissolved;

[0075] (2) Mix 6 mmol of terephthalic acid with 36 mL of DMF and stir until fully dissolved;

[0076] (3) Mix the solutions obtained in steps (1) and (2), control the concentration of ZrCl4 to be 0.0555 mol / L, the concentration of FeCl3·6H2O to be 0.0278 mol / L, and the concentration of terephthalic acid to be 0.0833 mol / L, stir evenly, and obtain a precursor solution with a molar ratio of zirconium source to iron source of 2:1.

[0077] (4) Place the precursor solution obtained in step (3) into a 100mL reactor, so that the volume of the precursor solution accounts for 72% of the volume of the reactor. After reacting at a constant temperature of 120℃ for 15 hours, naturally cool to room temperature and separate the solvothermal product.

[0078] (5) Wash the solvothermal product obtained in step (4) three times with water and anhydrous ethanol respectively, and centrifuge at 8000 rpm for 10 min to obtain the solvothermal product solid.

[0079] (6) The solvothermal product solid obtained in step (5) is dried at 60°C for 24 hours to obtain the doped UiO-66(Zr) metal-organic framework material, which is denoted as UiO-66(Zr-Fe-2).

[0080] Example 3

[0081] (1) Mix 3 mmol of ZrCl4 and 3 mmol of FeCl3·6H2O with 36 mL of DMF and stir until fully dissolved;

[0082] (2) Mix 6 mmol of terephthalic acid with 36 mL of DMF and stir until fully dissolved;

[0083] (3) Mix the solutions obtained in steps (1) and (2), control the concentration of ZrCl4 to be 0.0416 mol / L, the concentration of FeCl3·6H2O to be 0.0416 mol / L, and the concentration of terephthalic acid to be 0.0833 mol / L, stir evenly, and obtain a precursor solution with a molar ratio of zirconium source and iron source of 1:1.

[0084] (4) Place the precursor solution obtained in step (3) into a 100mL reactor, so that the volume of the precursor solution accounts for 72% of the volume of the reactor. After reacting at a constant temperature of 120℃ for 15 hours, naturally cool to room temperature and separate the solvothermal product.

[0085] (5) Wash the solvothermal product obtained in step (4) three times with water and anhydrous ethanol respectively, and centrifuge at 8000 rpm for 10 min to obtain the solvothermal product solid.

[0086] (6) The solvothermal product solid obtained in step (5) is vacuum dried at 60°C for 24 hours to obtain the doped UiO-66(Zr) metal-organic framework material, denoted as UiO-66(Zr-Fe-3).

[0087] Performance testing

[0088] The UiO-66(Zr) and the doped UiO-66(Zr) metal-organic framework materials prepared in the examples were observed using scanning electron microscopy. The results showed that:

[0089] Figure 1 The image is a SEM image of UiO-66(Zr) at high magnification. Figure 2 This is a high-magnification SEM image of UiO-66(Zr-Fe-2) obtained in Example 2.

[0090] Depend on Figure 1 and Figure 2It is evident that both UiO-66(Zr) and UiO-66(Zr-Fe-2) exhibit irregular spherical particle shapes. Furthermore, due to iron ion doping, the diameter of the UiO-66(Zr-Fe-2) nanospheres decreases. This change shortens the electron transport path within the nanospheres, thereby improving the electron-hole separation efficiency and enhancing the material's dispersion properties. This contributes to uniform distribution within the reaction medium, ultimately improving the efficiency of photocatalysis.

[0091] Figure 3 (a) shows the N2 adsorption-desorption isotherms of UiO-66(Zr) and the doped UiO-66(Zr) metal-organic framework materials prepared in Examples 1-3; Figure 3 (b) is a pore size distribution diagram of UiO-66(Zr) and the doped UiO-66(Zr-Fe-1) organic framework material, doped UiO-66(Zr-Fe-2) organic framework material and doped UiO-66(Zr-Fe-3) organic framework material prepared in Examples 1 to 3, respectively.

[0092] Depend on Figure 3 It can be seen that all samples exhibit type IV adsorption-desorption isotherms accompanied by type H3 hysteresis loops, mainly due to capillary condensation, indicating the presence of mesoporous structures in the materials. This is consistent with... Figure 3 The results are consistent with those in (b). A distinct step appears at low pressure (P / P0 < 0.1), indicating the presence of a microporous structure within the material. Due to the rational design of Fe insertion, the pore volume and pore size of UiO-66(Zr) are significantly increased, helping to reduce mass transfer resistance and allowing the removed material to diffuse more easily from the solution into the internal channels of the nanospheres, thus accelerating the reaction rate. Specifically, when the molar ratio of Zr to Fe is 2:1, the specific surface area of ​​the doped UiO-66(Zr-Fe-2) metal-organic framework material reaches 713.79 m². 2 / g, and pore size (5.75nm) and pore volume (1.03cm³) 3 The value of / g) reaches its maximum, as shown in Table 1. This makes the doped UiO-66(Zr-Fe-2) metal-organic framework material potentially possess the best photocatalytic performance.

[0093] Table 1. Specific surface area, pore volume, and pore size of UiO-66, UiO-66(Zr-Fe-1), UiO-66(Zr-Fe-2), and UiO-66(Zr-Fe-3).

[0094]

[0095] Figure 4 The thermogravimetric curve of UiO-66(Zr-Fe-2) prepared in Example 2 is shown.

[0096] Depend on Figure 4 It can be seen that UiO-66(Zr-Fe-2) only loses 11.80% of its weight within the temperature range of 30–402℃, indicating that the crystal structure of UiO-66(Zr-Fe-2) is not destroyed at temperatures below 402℃. When the temperature rises to 439℃, UiO-66(Zr-Fe-2) loses 45.92% of its weight due to framework structure destruction and collapse. When the temperature is above 439℃, the weight remains stable at 42.28% of the original weight, which should be due to the oxides of zirconium and iron. These results demonstrate that Fe ion-doped UiO-66(Zr-Fe-2) exhibits excellent thermal stability as a photocatalytic material.

[0097] Figure 5 Transient photocurrent response diagrams for UiO-66(Zr) and UiO-66(Zr-Fe-2) prepared in Example 2. Figure 5 It can be seen that the photocurrent density of UiO-66(Zr-Fe-2) is significantly enhanced compared with that of pure phase UiO-66(Zr), indicating that UiO-66(Zr-Fe-2) can generate more photoinduced electrons for photocatalytic reaction during the photocatalytic reaction.

[0098] Figure 6 Electrochemical impedance spectroscopy (EIS) plots for UiO-66(Zr) and UiO-66(Zr-Fe-2) prepared in Example 2 are shown. Generally, a smaller arc radius indicates a lower interfacial resistance, suggesting good interfacial charge migration properties. Figure 6 It can be seen that the doped UiO-66 (Zr-Fe-2) with the smallest arc radius has the best charge migration performance.

[0099] Figure 7 Photoluminescence spectra (a) and time-resolved photoluminescence spectra (b) of UiO-66(Zr) and UiO-66(Zr-Fe-2) prepared in Example 2.

[0100] Depend on Figure 7 As shown in (a), UiO-66(Zr) exhibits a significant emission peak at 377 nm, while the fluorescence of UiO-66(Zr-Fe-2) is partially quenched, and the photoluminescence peak intensity is the lowest, indicating that UiO-66(Zr-Fe-2) has a better inhibitory effect on charge recombination. Figure 7 As shown in (b), compared with UiO-66(Zr)(0.844ns), UiO-66(Zr-Fe-2)(0.974ns) obviously has a longer average fluorescence lifetime, indicating that Fe ion doping can reduce photoinduced electron deactivation and thus improve photocatalytic activity.

[0101] Application Example 1

[0102] This application example demonstrates the use of doped UiO-66 (Zr-Fe) metal-organic framework materials for the photocatalytic removal of uranyl ions from wastewater.

[0103] The uranyl ion removal performance of UiO-66(Zr) and the doped UiO-66(Zr) metal-organic framework materials prepared in Examples 1-3 was compared and analyzed under dark and light conditions. The method was as follows:

[0104] 25 mg of UiO-66(Zr) and the doped UiO-66(Zr) metal-organic framework materials prepared in Examples 1-3 were weighed and added to a beaker containing 50 mL of 5 mL of ethanol and a 5 mg / L uranyl ion aqueous solution. The pH was then adjusted to 5 with negligible amounts of NaOH and HNO3 solution. A 300 W xenon lamp with an AM 1.5G filter was used to simulate sunlight, which was then vertically irradiated onto the reaction vessel. After a certain time, 1 mL of the supernatant was taken, filtered through a 0.22 μm injection filter, and the UO2 content was measured. 2+ The concentration was adjusted, and the reaction was continued for 180 minutes. Before irradiation, the solution was bubbled with argon gas for 30 minutes to remove oxygen and achieve an anaerobic state. The argon atmosphere was maintained until uranium extraction was completed.

[0105] A similar adsorption experiment was conducted under dark conditions as a control.

[0106] Figure 8 The UO2 content of UiO-66(Zr) and the doped UiO-66(Zr) metal-organic framework materials obtained in Examples 1-3 under light and dark environments. 2+ Remove performance graphs.

[0107] Depend on Figure 8 It can be seen that, under both light and dark conditions, the uranium removal performance of iron-doped UiO-66(Zr) organic framework materials is improved compared to UiO-66(Zr), with UiO-66(Zr-Fe-2) exhibiting the strongest uranium removal performance. Furthermore, compared to dark environments, light exposure is more effective in enhancing the uranium removal performance of UiO-66(Zr) and UiO-66(Zr-Fe-1~3) metal-organic framework materials.

[0108] To further evaluate the reaction kinetics, the photoreaction rate constant (k) of the sample was calculated, and the photocatalytic reaction rate was fitted using a quasi-first-order reaction kinetic equation. Figure 9 Photocatalytic kinetics of the doped UiO-66 (Zr-Fe-1) organic framework material, doped UiO-66 (Zr-Fe-2) organic framework material, and doped UiO-66 (Zr-Fe-3) organic framework material prepared in Examples 1-3, respectively, under light irradiation.

[0109] Depend on Figure 9 It can be seen that the photocatalytic reactions of all UiO-66(Zr) metal-organic framework materials conform to the pseudo-first-order reaction kinetic model ln(C0 / C) t )=kt(t is the reaction time, k is the reaction rate constant, C0 is the initial uranium concentration, C t The reaction exhibits a good linear relationship (where the uranium concentration during the reaction is 0.022 min). Furthermore, UiO-66(Zr-Fe-2) shows the largest reaction rate constant, at 0.022 min. -1 It is 11 times more efficient than UiO-66(Zr), exhibiting the best photocatalytic efficiency. This is likely due to UiO-66(Zr-Fe-2) having a larger specific surface area, the highest charge separation efficiency, and the best charge migration performance.

[0110] Application Example 2

[0111] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for the photocatalytic removal of uranyl ions from wastewater.

[0112] Different UO2 2+ Effect of initial concentration on the photocatalytic performance of doped UiO-66 (Zr-Fe-2) metal-organic framework materials:

[0113] The method is the same as in Application Example 1 above, except that only 25 mg of UiO-66 (Zr-Fe-2) is weighed out and distributed at different initial UO2. 2+ The reaction was continued in a solution of a certain concentration for 300 minutes.

[0114] Specifically, initial UO2 2+ The concentrations are 5, 10, 20, 50, and 100 mg / L.

[0115] Figure 10 To evaluate the effects of UiO-66(Zr-Fe-2) on different UO2 under both light and dark conditions. 2+ Removal rate (a) and removal amount (b) of initial concentration.

[0116] Depend on Figure 10 As shown in (a), compared with the adsorption under dark conditions, the UO2 of UiO-66(Zr-Fe-2) under light conditions... 2+ The removal rate and removal amount were significantly improved. (Regarding UO2) 2+ At initial concentrations of 5 and 10 mg / L, UO2 under illumination 2+ The removal rates were 99.09% and 90.28%, respectively, which are 3.01 times and 3.22 times that under darkness.

[0117] Depend on Figure 10From (b), we can see that in UO2 2+ At an initial concentration of 100 mg / L, UiO-66(Zr-Fe-2) under light irradiation produces UO2 2+ The removal rate reached 141.33 mg / g, which is 5.45 times that under dark conditions. These results indicate that UiO-66(Zr-Fe-2) exhibits superior UO2 removal under light irradiation. 2+ The removal effect.

[0118] Application Example 3

[0119] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for the photocatalytic removal of uranyl ions from wastewater.

[0120] Effects of different pH values ​​on the photocatalytic performance of UiO-66(Zr-Fe-2):

[0121] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is omitted, and only 25 mg of UiO-66 (Zr-Fe-2) is weighed into UO2 at different pH values. 2+ Light irradiation experiments were conducted in the solution.

[0122] Specifically, the different pH values ​​were 4.92, 5.92, 6.86, 8.05, 9.03, and 10.07.

[0123] Figure 11 To illustrate the effect of UiO-66(Zr-Fe-2) obtained in Example 2 on UO2 at different pH values 2+ The photocatalytic removal effect.

[0124] Depend on Figure 11 It can be seen that UiO-66(Zr-Fe-2) has a very high UO2 content in the pH range of 4.92 to 10.07. 2+ Removal rate (>92.00%). This may be due to the increase in pH and the resulting H+. + Concentration decreases, photogenerated electron content increases and UO2 increases 2+ The combined effects of self-hydrolysis and precipitation under high pH conditions result in UiO-66 (Zr-Fe-2) exhibiting good chemical stability and effectively removing UO2 over a wide pH range. 2+ .

[0125] Application Example 4

[0126] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for the photocatalytic removal of uranyl ions from wastewater.

[0127] Effects of different interfering ions on the photocatalytic performance of UiO-66(Zr-Fe-2):

[0128] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is omitted, and only 25 mg of UiO-66 (Zr-Fe-2) is weighed into UO2 containing different interfering ions. 2+ The solution was subjected to light irradiation for 360 minutes.

[0129] Specifically, the different interfering ions are Na + Ca 2+ Zn 2+ Mg 2+ Co 2+ Ni 2+ ,Cl - CO3 2- SO4 2- ,Br - HCO3 - HPO4 2- The concentrations were all 1 mmol / L.

[0130] Figure 12 The effect of UiO-66(Zr-Fe-2) obtained in Example 2 on UO2 under different interfering ions 2+ The photocatalytic removal effect.

[0131] Depend on Figure 12 It can be seen that in the interfering ion solution, UiO-66(Zr-Fe-2) has an effect on UO2. 2+ The removal rates were all above 90%. Experimental results show that UiO-66(Zr-Fe-2) still exhibits excellent anti-interference ability in 1 mmol / L interfering ion solution.

[0132] Application Example 5

[0133] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for the photocatalytic removal of uranyl ions from wastewater.

[0134] Photocatalytic cycling performance of UiO-66(Zr-Fe-2):

[0135] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is removed. Instead, 25 mg of UiO-66 (Zr-Fe-2) is weighed out and subjected to light irradiation for 300 min. Then, it is desorbed with Na2CO3 solution, dried under vacuum, and then recycled for the next cycle.

[0136] Specifically, the concentration of the Na2CO3 eluent solution was 0.5 mol / L, and the desorption time was 12 hours.

[0137] Specifically, the desorbed sample was washed three times each with deionized water and ethanol, and then dried in a vacuum oven at 60°C for 12 hours.

[0138] Figure 13 The photocatalytic cycling performance of UiO-66(Zr-Fe-2) prepared in Example 2 is shown.

[0139] Depend on Figure 13 It can be seen that UiO-66(Zr-Fe-2) can undergo five photocatalytic-desorption cycles, and the fifth cycle of UO2... 2+ The removal rate remained above 90%, indicating that UiO-66(Zr-Fe-2) has excellent photocatalytic cycling performance.

[0140] Application Example 6

[0141] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for photocatalytic uranium extraction from seawater.

[0142] Photocatalytic performance of UiO-66(Zr-Fe-2) in simulated seawater:

[0143] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is removed, and only 25 mg of UiO-66 (Zr-Fe-2) is weighed and subjected to a light irradiation experiment in simulated seawater for 180 min.

[0144] Specifically, the simulated seawater volume is 50 mL, and the UO2 content is... 2+ The concentration is 5 mg / L.

[0145] Figure 14 The photocatalytic uranium removal performance of UiO-66(Zr-Fe-2) prepared in Example 2 in simulated seawater.

[0146] Depend on Figure 14 It can be seen that within 180 minutes, the UO2 of UiO-66(Zr-Fe-2) 2+ With a removal rate of 99.9% and a uranium removal amount of 9.95 mg / g, UiO-66 (Zr-Fe-2) has broad application prospects in the field of seawater uranium extraction.

[0147] Application Example 7

[0148] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for photocatalytic removal of heavy metal ions from wastewater.

[0149] Photocatalytic performance of UiO-66(Zr-Fe-2) in wastewater containing heavy metal ions:

[0150] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is removed, and only 25 mg of doped UiO-66 (Zr-Fe-2) metal-organic framework material is weighed and subjected to a light irradiation experiment for 360 min in wastewater containing heavy metal ions.

[0151] Specifically, the concentration of heavy metal ions was 1 mmol / L.

[0152] Figure 15 The photocatalytic performance of UiO-66(Zr-Fe-2) prepared in Example 2 in wastewater containing heavy metal ions is shown.

[0153] Depend on Figure 15 It can be seen that UiO-66(Zr-Fe-2) has good removal performance for heavy metal lead ions and copper ions within 360 min.

[0154] Application Example 8

[0155] This application example demonstrates the use of iron-doped UiO-66(Zr) metal-organic framework materials for photocatalytic removal of organic pollutants from wastewater.

[0156] Photocatalytic performance of UiO-66 (Zr-Fe-2) in wastewater containing organic pollutants:

[0157] The method is the same as in Application Example 1 above, except that the adsorption experiment under dark conditions is removed, and only 25 mg of UiO-66 (Zr-Fe-2) is weighed into 50 mL of wastewater containing organic pollutants without the addition of ethanol and subjected to a light irradiation experiment for 360 min.

[0158] Specifically, the organic pollutants include: tetracycline hydrochloride, ciprofloxacin, chlortetracycline, oxytetracycline, quinoline, and atrazine, all at a concentration of 10 mg / L.

[0159] Figure 16 DMPO of UiO-66(Zr-Fe-2) prepared in Example 2 - ·OH(a) electron paramagnetic resonance spectrum, DMPO - ·O 2- (b) Electron paramagnetic resonance spectrum, TEMPO - ·h + (c) Electron paramagnetic resonance (EPR) spectra. In photocatalytic systems, free radicals can degrade organic pollutants into CO2, H2O, and other harmless substances through processes such as addition, substitution, and electron transfer. Therefore, EPR spectra can be used to study the generation of free radicals during photocatalysis. Figure 16 (a) and Figure 16As shown in (b), no obvious free radical signal was detected under dark conditions, while obvious characteristic signal peaks were generated under illumination, belonging to hydroxyl radicals (·OH) and superoxide radicals (·O), respectively. 2- The results showed that UiO-66(Zr-Fe-2) did indeed generate free radicals ·OH and ·O. 2- Furthermore, more free radicals are generated with prolonged light exposure. Additionally, holes (h) are produced under light. + The EPR signal of the trap TEMPO gradually weakens, such as Figure 16 (c) demonstrates that the photocatalyst UiO-66 (Zr-Fe-2) can generate more holes to oxidize and decompose organic pollutants as the illumination time increases.

[0160] Figure 17 The photocatalytic performance of UiO-66 (Zr-Fe-2) prepared in Example 2 in wastewater containing organic pollutants.

[0161] Depend on Figure 17 It can be seen that UiO-66(Zr-Fe-2) achieved a removal rate of approximately 90% for organic pollutants within 360 minutes. Therefore, UiO-66(Zr-Fe-2) has broad application prospects in the removal of organic pollutants.

[0162] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Application of doped UiO-66(Zr) metal-organic framework material as a photocatalyst in the treatment of uranium-containing wastewater; the doped UiO-66(Zr) metal-organic framework material includes a UiO-66(Zr) matrix and iron ions doped in the UiO-66(Zr) matrix; The preparation method of the doped UiO-66(Zr) metal-organic framework material adopts the following steps: A precursor solution is obtained by mixing a zirconium source, an iron source, terephthalic acid, and a polar organic solvent. The precursor solution was subjected to a solvothermal reaction. The solvothermal reaction system was naturally cooled to room temperature and then separated to obtain the solvothermal reaction product. The solvothermal reaction product was washed, centrifuged and dried in sequence to obtain the doped UiO-66(Zr) metal-organic framework material. The molar ratio of zirconium source to iron source in the precursor solution is 2:1; The temperature of the solvothermal reaction is 100–200°C, and the time is 10–24 h. The pore size of the doped UiO-66(Zr) metal-organic framework material is 3.23–5.75 nm; the pore volume of the doped UiO-66(Zr) metal-organic framework material is 0.41–1.03 cm³. 3 / g.

2. The application according to claim 1, characterized in that, The zirconium source includes one or more of ZrCl4, Zr(NO3)4, and Zr(SO4)2·4H2O; the iron source includes FeCl3·6H2O, FeCl4, etc. x Fe(NO3) x Or Fe(NO3) x ·9H2O, X = 2 or 3.

3. The application according to claim 1, characterized in that, In the precursor solution, the concentration of zirconium source is 0.0416–0.0625 mol / L, the concentration of iron source is 0.0208–0.0416 mol / L, and the concentration of terephthalic acid is 0.0827–0.0835 mol / L.

4. The application according to claim 1, characterized in that, The polar organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

5. The application according to claim 1, characterized in that, The washing process includes washing with water and anhydrous ethanol, respectively, and the number of washing cycles is 2 to 5. The centrifugation speed is 6000-10000 rpm, and the time is 5-30 min; The drying temperature is 50–70°C, and the time is 15–24 hours.

Images