A self-supported catalyst with zinc foam as substrate and ZIF-L supported by zinc foam, its preparation method and its application

Abstract

This invention discloses a zinc foam catalyst, its preparation method, and its application, belonging to the technical field of metal-organic framework supported materials. The purpose of this invention is to address the shortcomings of current methods for treating sulfamethoxazole pollution in water bodies, such as high cost, low degradation efficiency, and difficulties in separation and recovery. This invention first uses a room-temperature impregnation method to immerse zinc foam in a ZIF-L solution to obtain the catalyst. The catalyst prepared by this invention has abundant functional groups on its surface; it possesses a unique self-supporting integrated structure, facilitating separation and recovery; the catalyst surface is cross-linked, increasing the specific surface area and improving catalytic efficiency. It exhibits excellent activation of persulfate, possesses certain resistance to ion interference and environmental adaptability, and maintains high cycling stability after 10 cycles.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework technology. Background Technology

[0002] With rapid societal development, the widespread use of antibiotics has generated substantial amounts of antibiotic wastewater. Antibiotics pose significant risks to the environment and human health, and also possess a degree of biotoxicity. Sulfamethoxazole is a common pollutant in antibiotic wastewater, which traditional wastewater treatment technologies struggle to address due to their poor biodegradability. In recent years, advanced oxidation technologies based on persulfate (PMS) (SR-AOPs) have emerged. These technologies offer strong oxidation capabilities, a wide pH adaptability range, and relatively mild reaction conditions. The catalyst activation of PMS essentially generates sulfate free radicals (SO42-). ·- ), hydroxyl radicals (·OH), superoxide radicals (O2) ·- ) and singlet oxygen ( 1 The efficient degradation of pollutants by using O2 has become a research hotspot for many researchers.

[0003] In recent years, cobalt-based metal-organic frameworks (MOFs) have attracted much attention due to their unique porous structure and excellent catalytic performance, especially zeolite imidazole frameworks (ZIFs), which possess abundant functional groups on their surface, along with rich Co species and good chemical stability. However, traditional powder catalysts suffer from problems such as easy agglomeration, small specific surface area, and difficulty in separation and recovery. By loading powder catalysts into porous metal foams, mass transfer efficiency can be significantly improved, and more active sites can be exposed. Summary of the Invention

[0004] To address the shortcomings of current methods for treating sulfamethoxazole (SMX) pollution in water bodies, such as high cost and low degradation efficiency, this invention aims to provide a ZIF-L self-supporting catalyst supported on zinc foam substrate.

[0005] This invention is achieved through the following technical solution:

[0006] The present invention discloses a self-supporting catalyst with zinc foam as a substrate and ZIF-L supported on it. The substrate is zinc foam and ZIF-L is supported on its surface. ZIF-L exhibits a smooth nanosheet structure on the surface of zinc foam, and the nanosheets are stacked on the surface of zinc foam in a cross-linked form. The thickness of the nanosheets is 1 μm and the length is 4-5 μm.

[0007] The present invention discloses a method for preparing a self-supporting catalyst with zinc foam as a substrate and ZIF-L supported thereon, which specifically includes the following steps:

[0008] 1) Prepare 2-methylimidazole solutions with concentrations of 0.63–0.65 mol / L and cobalt nitrate solutions with concentrations of 0.07–0.09 mol / L, respectively;

[0009] 2) The zinc foam was ultrasonically treated in water and ethanol for 10 min each; the porosity of the zinc foam was 95% to 98%, and the pore size was 110 PPI;

[0010] 3) Quickly add an equal volume of cobalt nitrate solution to 2-methylimidazole solution, and immerse the foamed zinc treated in step 2) in the mixture of the two solutions at room temperature for 1-2 hours;

[0011] 4) After removing the zinc foam, wash it with deionized water and dry it at 60°C to obtain a self-supporting catalyst with zinc foam as the substrate and ZIF-L supported on it.

[0012] Preferably, the concentration of the cobalt nitrate solution in step 1) is 0.08 mol / L and the concentration of the 2-methylimidazole solution is 0.64 mol / L.

[0013] Preferably, the soaking time in step 3) is 1.5 hours.

[0014] In this invention, zinc foam is used as a substrate to support a self-supporting catalyst of ZIF-L for the degradation of sulfamethoxazole in water. Specifically, the catalyst and persulfate (PMS) are added to water containing sulfamethoxazole. The PMS concentration in the water is 0.4 mM, which activates the PMS and catalyzes the degradation of sulfamethoxazole.

[0015] Preferably, the catalytic degradation temperature is 15°C.

[0016] The beneficial effects of this invention are:

[0017] Compared to traditional powder catalysts, the catalyst prepared in this invention has a simple and feasible preparation process and low cost. Using porous zinc foam as a substrate facilitates material separation and recovery; moreover, this invention exhibits a nanosheet-like cross-linked stacked state with uniform distribution. This structure increases the catalyst's specific surface area, which is beneficial for contact between pollutants and the catalyst. This catalyst has extremely high applicability and is suitable for large-scale treatment of pollutants in wastewater.

[0018] Tests have shown that this catalyst has a very good activation effect on PMS, has a certain degree of resistance to ion interference, can adapt to more complex environments, and also has high recyclability and cycle stability. Attached Figure Description

[0019] Figure 1 XRD patterns of ZIF-L / ZF;

[0020] Figure 2(a), (b), (c), and (d) are SEM images of ZIF-L / ZF at different magnifications, respectively; (e) is the mapping image of ZIF-L / ZF.

[0021] Figure 3 FT-IR spectra of ZIF-L / ZF;

[0022] Figure 4 XPS of ZIF-L / ZF: Total spectrum (a) Total spectrum, (b) C 1s, (c) N 1s, (d) O 1s, (e) Co 2p, (f) Zn 2p spectrum;

[0023] Figure 5 Catalytic degradation curves (a) and first-order kinetic curves (b) of SMX by ZIF-L and ZIF-L / ZF;

[0024] Figure 6 Effects of PMS dosage, pH and temperature on catalytic activity;

[0025] Figure 7 Anti-ion interference experiment: (a) Cl - (b)HCO3 - (c)HPO4 2- (d) Effect of HA on SMX removal Figure 8 Active species capture experiments of SMX catalytic degradation by ZIF-L / ZF activated PMS;

[0026] Figure 9 Fukui function calculation;

[0027] Figure 10 SMX degradation pathways;

[0028] Figure 11 Toxicity analysis of intermediate products;

[0029] Figure 12 Cyclic experiments of SMX degradation catalyzed by ZIF-L / ZF activated PMS;

[0030] Figure 13 XPS images of SMX before and after ZIF-L / ZF activated PMS catalytic degradation;

[0031] Figure 14 XRD and FT-IR images of SMX catalytic degradation by ZIF-L / ZF activated PMS before and after degradation.

[0032] Figure 15 SEM images of SMX catalytic degradation before and after ZIF-L / ZF activated PMS. Detailed Implementation

[0033] The technical solution of the present invention will be further explained and illustrated below with specific examples.

[0034] Example 1

[0035] 1) Weigh 1.3g (16mmol) of 2-methylimidazole and 0.582g (2mmol) of Co(NO3)2·6H2O and dissolve them in 25mL of deionized water respectively. Stir the two solutions separately for 30min.

[0036] 2) The zinc foam was ultrasonically treated in water and ethanol for 10 min each; the porosity of the zinc foam was 95% to 98%, and the pore size was 110 PPI;

[0037] 3) Quickly add an equal volume of cobalt nitrate solution to 2-methylimidazole solution, and immerse the zinc foam (2cm×2cm) treated in step 2) in the mixture of the two solutions for 1.5h at room temperature;

[0038] 4) After removing the zinc foam, wash it with deionized water and dry it overnight at 60°C to obtain a self-supporting catalyst (ZIF-L / ZF) with zinc foam as the substrate supporting ZIF-L.

[0039] Effect verification:

[0040] like Figure 1 As shown, due to the strong diffraction peaks of zinc foam (ZF) and the low loading of ZIF-L, the ZIF-L diffraction peaks are not obvious. Most diffraction peaks correspond to Zn (JCPDS 04-0831). In the magnified local image, small diffraction peaks belonging to ZIF-L can be seen in the ZIF-L / ZF combination. Among them, the characteristic peaks at 10.4°, 10.9°, 12.7°, 13.6°, 14.8°, 15.2°, 16.8°, 17.0°, 18.0°, and 29.0° are in good agreement with the simulation results. Furthermore, the target sample was compared with a sample loaded with Co... 2+ The ZF diffraction peaks were compared with those of Co (JCPDS15-0806), and the diffraction peaks were consistent with those of Co (JCPDS15-0806). These results demonstrate that a well-structured self-supporting material was synthesized.

[0041] like Figure 2 ZIF-L / ZF exhibits a smooth nanosheet structure. ZIF-L nanosheets are stacked on the ZF surface in a cross-linked form, with a length of about 4-5 μm and a thickness of about 1 μm. This structure can increase the specific surface area of ​​the catalyst, which is beneficial to the contact between pollutants and the catalyst.

[0042] like Figure 3The image shows the Fourier Transform Infrared (FT-IR) spectrum of ZIF-L / ZF. The FT-IR spectra of ZIF-L powder and ZIF-L powder scraped from ZIF-L / ZF are compared. Specifically, the 700-1400 cm⁻¹... -1 This peak belongs to the characteristic peak of imidazole ring stretching vibration, located at 1100 cm⁻¹. -1 The nearby absorption peak is caused by the stretching vibration of CO, at 1384 cm⁻¹. -1 The peak at 1585 cm⁻¹ is the bending vibration peak of C=O. -1 The absorption peaks in the vicinity are generated by the stretching vibrations of C=N, and are located in the 3000-3600 cm⁻¹ range. -1 The broad peaks within the range are due to the stretching vibration of OH. All these results indicate that ZIF-L / ZF contains abundant functional groups, which is beneficial for dispersion in water and improves degradation efficiency.

[0043] like Figure 4 The elemental composition and valence states of ZIF-L / ZF were determined by XPS. The XPS total spectrum showed the presence of C, N, O, Co, and Zn. In the high-resolution C1s spectrum, the characteristic peaks at 284.81 eV and 285.99 eV correspond to sp... 2 C and CO bonds, some reports suggest sp 2 Hybridized carbon is a carbon bridge that accelerates electron transfer processes. At N1s, it can be divided into two components, with binding energies at 398.86 and 400.58 eV corresponding to CN and Co-N, respectively. Furthermore, to compare the effects of the Co species, a high-resolution spectrum of Co 2p was studied. Co 2p comprises six components, and the two peaks at 781.46 and 796.37 eV are attributed to Co. 3+ 2p 3 / 2 and 2p 1 / 2 The peaks at 786.27 and 798.2 eV are attributed to Co. 2+ 2p 3 / 2 and 2p 1 / 2 The satellite peaks are located at 789.27 and 802.73 eV. The Co content on the catalyst surface was further calculated by measuring the area covered by the fitted curve. 2+ / Co 3+ Atomic ratio, Co content of catalyst 2+ / Co 3+ The atomic ratio is 33%. Studies have shown that Co... 2+ It is the activation of PMS to generate SO4 ·- The true catalytic active center, which means Co 2+ Higher content helps to improve catalyst activity.

[0044] Example 2

[0045] To verify the effectiveness of ZIF-L / ZF in activating PMS, its degradation performance against sulfamethoxazole (SMX) was investigated. The degradation experiment was conducted in a 50 mL beaker. A 2 cm × 2 cm ZIF-L / ZF sample obtained in Example 1 was placed in a container filled with 10 mg / L of SMX. -1 Add 9.2 mg PMS to a 50 mL solution, take 1 mL of the reaction solution at regular intervals, filter the obtained sample through a 0.22 μm filter membrane, and immediately quench with 1 mL of saturated sodium thiosulfate solution. Determine the content of SMX by high performance liquid chromatography (HPLC).

[0046] like Figure 5 As shown, the ability of the catalyst to activate PMS was investigated. When ZIF-L / ZF and PMS were added simultaneously, 97.0% of SMX was degraded within 10 min, and the degradation was complete within 30 min. These results indicate that the prepared ZIF-L / ZF has a strong activating effect on PMS.

[0047] like Figure 6 As shown, factors that may affect the degradation rate were investigated. Regarding catalyst and PMS dosage, the reaction rate did not change significantly when the dosage increased to a certain level. As for external factors, the reaction rate was fastest when the solution pH was neutral; increasing temperature accelerated the reaction process.

[0048] like Figure 7 As shown, since carbonates, chloride ions, phosphates, and humic acids are commonly present in water bodies, their effects on SMX degradation were investigated. The results indicate that the catalyst exhibits a certain degree of resistance to ion interference.

[0049] like Figure 8 As shown in the free radical capture experiment, the degradation of SMX by ZIF-L / ZF activated PMS was inhibited by quenchers methanol (ME), tert-butanol (TBA), ascorbic acid (AA), and furfuryl alcohol (FFA) compared with the system without quenchers.

[0050] like Figure 9 As shown, reactive active sites are predicted based on the Fukui function, and the reactive degradation pathway is predicted.

[0051] like Figure 10 As shown, LC-MS experiments were performed, and the degradation pathway was summarized by Fukui function. It mainly consists of: amino oxidation; attack of the bond between sulfur and nitrogen by reactive oxygen species; oxidation of the methyl group on the isoxazole ring to a carboxyl group; oxidation of the isoxazole ring; and chemical bonds undergoing a series of breakages to finally form small molecule compounds.

[0052] like Figure 11As shown, the developmental toxicity, bioaccumulation factors, and mutagenicity of SMX and its intermediates were evaluated using the toxicity assessment software (TEST). Most intermediates were found to be non-toxic or at low toxicity levels.

[0053] like Figure 12 As shown, after 10 consecutive cycles of SMX degradation experiments, ZIF-L / ZF did not significantly reduce the degradation rate of SMX, indicating that ZIF-L / ZF has high recyclability.

[0054] like Figure 13 The XPS spectra of ZIF-L / ZF before and after SMX degradation show that the surface elemental valence composition of ZIF-L / ZF did not change significantly after the degradation reaction, further demonstrating that the ZIF-L / ZF catalyst has good cycle stability.

[0055] like Figure 14 The XRD and FT-IR spectra of ZIF-L / ZF before and after SMX degradation are shown. The phase structure of ZIF-L / ZF changes little, and the crystallinity decreases slightly. In the FT-IR after the reaction, some of the vibrational characteristic peaks attributed to 2-methylimidazole disappear, indicating that some ligands are detached during the degradation process.

[0056] like Figure 15 As shown, the morphology of ZIF-L / ZF remains intact after the reaction, demonstrating its good structural stability and reusability.

[0057] The above embodiments are merely preferred embodiments of the present invention and do not represent the full scope of the present invention. The specific scope of implementation shall be determined by the scope described in the invention content.

Claims

1. A self-supporting catalyst with zinc foam as a substrate and ZIF-L supported on it, characterized in that, The catalyst is based on zinc foam with ZIF-L loaded on its surface. The ZIF-L exhibits a smooth nanosheet structure on the zinc foam surface, and the nanosheets are stacked on the zinc foam surface in a cross-linked manner. The nanosheets are 1 μm thick and 4-5 μm long. The specific steps of its preparation method are as follows: 1) Prepare 2-methylimidazole solutions with concentrations of 0.63~0.65 mol / L and cobalt nitrate solutions with concentrations of 0.07~0.09 mol / L respectively; 2) The zinc foam was ultrasonically treated in water and ethanol for 10 min each; the porosity of the zinc foam was 95%~98% and the pore size was 110 PPI; 3) Quickly add an equal volume of cobalt nitrate solution to 2-methylimidazole solution, and immerse the foamed zinc treated in step 2) in the mixture of the two solutions at room temperature for 1-2 hours; 4) After removing the zinc foam, wash it with deionized water and dry it at 60°C to obtain a self-supporting catalyst with zinc foam as the substrate and ZIF-L supported on it.

2. The self-supporting catalyst of zinc foam as a substrate supported on ZIF-L according to claim 1, characterized in that, The soaking time in step 3) is 1.5 h.

3. The self-supporting catalyst of zinc foam as a substrate supported on ZIF-L according to claim 1, characterized in that, The concentration of the cobalt nitrate solution in step 1) is 0.08 mol / L, and the concentration of the 2-methylimidazole solution is 0.64 mol / L.

4. The zinc foam as described in claim 1, as a substrate-supported ZIF-L self-supporting catalyst, is used for the degradation of sulfamethoxazole in water.

5. The use of zinc foam as a substrate-supported self-supporting catalyst for ZIF-L according to claim 4, characterized in that, Adding the self-supporting catalyst ZIF-L supported on zinc foam as a substrate and persulfate to water containing sulfamethoxazole, with a persulfate concentration of 0.4 mM in the water, activates the persulfate and catalyzes the degradation of sulfamethoxazole.

6. The use of zinc foam as a substrate-supported self-supporting catalyst for ZIF-L according to claim 5, characterized in that, The catalytic degradation temperature is 15 ℃.

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