Hydrothermal method for preparing high-crystallization MIL-100 (Fe) catalyst for wastewater treatment
The highly crystalline MIL-100(Fe) catalyst was prepared by hydrothermal method. By utilizing the oxidation process of ferrous ions under acidic conditions, the problem of using HF and DMF was solved, and efficient and safe catalyst preparation and wastewater treatment were achieved.
Patent Information
- Application Number
- CN202510815492.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-11-04
AI Technical Summary
The use of HF and DMF in existing MIL-100(Fe) preparation methods affects the purity and crystallinity of the catalyst, and poses difficulties in environmental treatment and equipment corrosion risks. The versatility and safety of the synthesis process are also insufficient.
A hydrothermal method was adopted to replace the etching and mineralization effect of HF with the slow oxidation of nitric acid. Ferrous ions were gradually oxidized to ferric ions under acidic conditions to promote their binding with ligands, thus preparing a highly crystalline MIL-100(Fe) catalyst and avoiding the use of toxic and harmful solvents.
The preparation of highly crystalline MIL-100(Fe) catalyst was achieved, which improved safety and ease of operation, and demonstrated excellent photocatalytic-ozone oxidation activity in wastewater treatment, providing a highly efficient solution for removing actual discharged pharmaceutical pollutants.
Smart Images
Figure FT_1 
Figure FT_2 
Figure FT_3
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of photocatalytic-ozone oxidation degradation of emerging organic pollutants, and particularly relates to a preparation technology of a high-crystalline MIL-100(Fe) catalyst for wastewater treatment prepared by a hydrothermal method. BACKGROUND
[0002] Medicines are increasingly regarded as emerging pollutants, which pose a significant threat to human health and aquatic ecosystems. For example, non-steroidal anti-inflammatory drugs (NSAIDs) are widely used as fever and pain relievers, and have been shown to cause harmful histopathological changes in various tissues, including the gastrointestinal tract, liver and kidney. Therefore, how to efficiently treat emerging organic pollutants in water has become an urgent problem for researchers. Among many water treatment technologies, photocatalytic-ozone oxidation has become a research hotspot due to its simple reaction device, wide treatment object, high treatment efficiency, green environmental protection and no secondary pollution. The core of photocatalytic-ozone oxidation is to develop a high-efficiency and stable dual-functional catalyst. Iron-based metal-organic framework materials (Fe-MOFs) have low cost, non-toxicity, periodic pore structure, rich Lewis acid sites and adjustable light absorption characteristics. High-crystalline MIL-100(Fe) exhibits excellent photocatalytic-ozone oxidation activity and can achieve efficient degradation of pollutants.
[0003] Current MIL-100(Fe) preparation methods generally rely on Fe(III) precursors (e.g., FeCl3 or Fe(NO3)3) with hydrofluoric acid (HF) as the mineralizer and water / N,N-dimethylformamide (DMF) as the solvent. For example, Du et al. used iron powder and H3BTC as raw materials, added HNO3, HF and solvent (H2O / DMF mixed system), and obtained MIL-100(Fe) by solvothermal reaction, cooling, washing and drying. However, goethite and other iron oxides were easily generated, and impurities affected the crystallization of the catalyst (Du M, Xu G, Zhang J, et al. Journal of Solid State Chemistry 312 (2022) 123248). Li et al. dissolved FeCl3·6H2O and H3BTC in DMF, and obtained MIL-100(Fe) powder by solvothermal reaction, cooling, washing and drying (Li M, Ma Y, Jiang J, et al. Environmental Research 212 (2022) 113399). Yuan et al. proposed a HF-free room temperature synthesis method, but introduced benzoquinone (BQ) as an oxidant to generate hydroperoxyl (HOO·) radicals to accelerate crystallization and use DMF as a solvent (Yuan B, Wang X, Zhou X, et al. Chemical Engineering Journal 355 (2019) 679-686). The dependence on additives in this route may affect the universality of the synthesis process, and the cost and residual problems of the additives need to be considered additionally. The large use of HF, DMF and BQ in the above examples is toxic and harmful, and the waste liquid treatment is difficult, which increases the process risk and environmental protection treatment cost of the equipment corrosion, and the intermediate phase of Fe compounds generated by the side reaction affects the purity and crystallinity of MIL-100(Fe). SUMMARY
[0004] The purpose of the present application is to provide a hydrothermal method for preparing high-crystallinity MIL-100(Fe) catalyst. By replacing the etching mineralization of HF with the slow oxidation of nitric acid and using ferrous sulfate as the metal source, MIL-100(Fe) is prepared, avoiding the excessive use of dangerous HF and DMF and other organic solvents. Our method uniquely utilizes the controllable oxidation process of ferrous ions to trivalent iron ions under acidic conditions, which is beneficial to the preliminary combination and coordination of trivalent iron and ligands, and promotes the crystallization and growth of MIL-100(Fe) in the subsequent hydrothermal process.
[0005] The purpose of the present application is achieved by the following technical solutions:
[0006] 1. A technology for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment by a hydrothermal method, characterized in that the highly crystalline MIL-100(Fe) catalyst is prepared by a hydrothermal method, in which ferrous sulfate heptahydrate (FeSO4·7H2O) and trimesic acid (H3BTC) are dissolved in ultrapure water to obtain a mixed solution, concentrated nitric acid (HNO3) is added dropwise to the solution and stirred, the green solution is converted into an orange suspension, the suspension is poured into a polytetrafluoroethylene-lined autoclave, and a solid-liquid mixture is obtained by hydrothermal treatment at high temperature. The obtained solid-liquid mixture is sequentially soaked in water and ethanol, heated in a water bath, then centrifuged, washed with water / ethanol alternately, and finally the sample is vacuum dried to obtain the catalyst.
[0007] Further, in the above process, ferrous sulfate heptahydrate (FeSO4·7H2O) and trimesic acid (H3BTC) are added to ultrapure water, the ultrapure water is 30-60 mL, the mass of ferrous sulfate heptahydrate is 2-3 g, and the mass of trimesic acid is 1-2 g, and the volume of concentrated HNO3 is 180-190 μL.
[0008] Further, the above suspension is poured into a 50 mL / 100 mL polytetrafluoroethylene-lined autoclave and placed in an oven for hydrothermal reaction.
[0009] Further, the temperature of the oven is set to 150-180℃, and the placement time is set to 24 h.
[0010] Preferably, the obtained solid-liquid mixture is sequentially soaked in water and ethanol and heated in a water bath for 1-4 h.
[0011] Further, the centrifugation is performed, and the washing is performed with water / ethanol alternately for 2-6 times, and the centrifuge speed is set to 8000-10000 r / min.
[0012] Further, the precipitate after washing should be dried in a vacuum drying oven at 40-60℃ overnight to obtain the highly crystalline MIL-100(Fe).
[0013] The highly crystalline MIL-100(Fe) catalyst for wastewater treatment is prepared by a hydrothermal method, which utilizes the fact that ferrous ions will gradually oxidize to trivalent iron ions under acidic conditions, and promotes the crystallization and growth of MIL-100(Fe) in the hydrothermal process through the slow coordination of trivalent iron and ligands. The method does not use hydrogen fluoride (HF), solving the problem of toxicity and harm of HF. The synthesized MIL-100(Fe) has high crystallinity and exhibits excellent activity in photocatalytic-ozone oxidation treatment of wastewater.
[0014] Most specifically, a technical preparation method for preparing a high-crystallinity MIL-100(Fe) catalyst for wastewater treatment based on a hydrothermal method, characterized in that the following steps are performed:
[0015] First, 40 mL of ultrapure water was taken in a beaker, 2.21 g of FeSO4·7H2O and 1.12 g of H3BTC were dissolved in the ultrapure water to obtain a light green precursor solution. 185 μL of concentrated HNO3 was added dropwise to the solution, and then stirring was continued at room temperature for 3 h. During the stirring process, the green solution turned into an orange suspension, indicating that the divalent iron ions were gradually oxidized to trivalent iron ions, and a slow coordination reaction occurred between the generated trivalent iron ions and the H3BTC ligand. The suspension was poured into a 50 mL polytetrafluoroethylene-lined autoclave, and hydrothermal treatment was performed at 150℃ for 24 h. The obtained solid-liquid mixture was sequentially immersed in water and ethanol and treated in a water bath for 3 h. After centrifugal separation of the mixture after water bath treatment, it was washed with water / ethanol alternately for 6 times, and vacuum dried at 50℃ to obtain a high-crystallinity MIL-100(Fe).
[0016] The present application has the following technical effects:
[0017] The high-crystallinity MIL-100(Fe) catalyst preparation method developed by the method of the present application uses slow oxidation of nitric acid instead of etching mineralization of HF, and uses ferrous sulfate as a metal source to prepare MIL-100(Fe), avoiding the excessive use of dangerous HF and DMF and other organic solvents, greatly improving the safety, environmental friendliness and operation simplicity of the experimental process. Our method uniquely utilizes the controllable oxidation process in which ferrous ions are gradually oxidized to trivalent iron ions under acidic conditions, which is conducive to the preliminary combination and coordination of trivalent iron and ligands, and promotes the crystallization and growth of MIL-100(Fe) in the subsequent hydrothermal process. Based on the high-crystallinity MIL-100(Fe), it is used for photocatalysis-ozone combined technology to degrade and treat pharmaceutical wastewater, providing an expandable and energy-saving solution for efficient removal of actual discharged pharmaceutical pollutants. BRIEF DESCRIPTION OF DRAWINGS
[0018] Figure 1 : XRD pattern of the high-crystallinity MIL-100(Fe) sample prepared by the present application.
[0019] Figure 2 : SEM and TEM images of the high-crystallinity MIL-100(Fe) prepared by the present application.
[0020] (a) is an SEM image, and (b) is a TEM image.
[0021] Figure 3The catalyst is used for treating the changes of colority, turbidity and chemical oxygen demand (COD) of wastewater in the process of wastewater treatment by combination of photocatalysis and ozone oxidation.
[0022] (a) is a wastewater colority and turbidity change diagram, (b) is a wastewater chemical oxygen demand (COD) change.
[0023] Figure 4 The recyclability and recoverability of the prepared high-crystalline MIL-100 (Fe) in treating wastewater by the combination of photocatalysis and ozone are explored.
[0024] (a) is a repetitive degradation experiment, (b) is an XRD diagram of the catalyst after 5 cycles.
Claims
1. A technology for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment based on a hydrothermal method, characterized in that: The highly crystalline MIL-100(Fe) catalyst was prepared by a hydrothermal method, in which ferrous sulfate heptahydrate (FeSO4•7H2O) and trimesic acid (H3BTC) were dissolved in ultrapure water to obtain a mixed solution. Concentrated nitric acid (HNO3) was added dropwise to the solution with stirring, and the green solution transformed into an orange suspension. The suspension was poured into a polytetrafluoroethylene-lined autoclave and subjected to hydrothermal treatment at high temperature. The resulting solid-liquid mixture was then sequentially immersed in water and ethanol for water bath heating, followed by centrifugation, washing with alternating water / ethanol, and finally vacuum drying to obtain the catalyst.
2. The highly crystalline MIL-100(Fe) catalyst for wastewater treatment prepared by hydrothermal method as described in claim 1, characterized in that: The above mixed solution is mixed with ferrous sulfate heptahydrate and trimellitic acid. The amount of ultrapure water is 30-60 mL, the mass of ferrous sulfate heptahydrate is 2-3 g, and the mass of trimellitic acid is 1-2 g.
3. The hydrothermal method for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment as described in claim 1 or 2, characterized in that, to improve the crystallinity of the catalyst, the following features are provided: During the dropwise addition of 180-190 µL of concentrated HNO3 to the above mixed solution, stirring should be performed for 2-5 h.
4. The hydrothermal preparation of a highly crystalline MIL-100(Fe) catalyst for wastewater treatment according to any one of claims 1-3, characterized in that: Pour the suspension into a 50 mL / 100 mL polytetrafluoroethylene-lined autoclave, place it in an oven, set the temperature to 150-180 ℃, and set the incubation time to 24 h.
5. A hydrothermal method for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment as described in claim 4, characterized in that: The resulting solid-liquid mixture was separated by centrifugation, with the centrifuge speed set to 8000-10000 r / min.
6. A hydrothermal method for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment as described in claim 5, characterized in that: The resulting solid-liquid mixture was sequentially immersed in water and ethanol and heated in a water bath for 1-4 hours, followed by centrifugation and washing with water / ethanol alternately 2-6 times.
7. A hydrothermal method for preparing a highly crystalline MIL-100(Fe) catalyst for wastewater treatment as described in claim 5 or 6, characterized in that: The washed precipitate should be dried overnight in a vacuum drying oven at 40-60°C to obtain highly crystalline MIL-100(Fe).