A dual-catalytic composite filler, a preparation method thereof and application thereof in constructed wetlands

Abstract

The application discloses a double-catalytic type composite filler, which has a core-shell structure, wherein the core is a manganese iron ore, and the shell is (Fe / Mn)-MOF. Compared with the prior art, the double-catalytic type composite filler combines the inorganic catalytic ability of the manganese iron ore with the organic catalytic ability of the MOF metal organic framework, and forms a high-efficiency double-catalytic system. The double-catalytic type composite filler can not only serve as an ideal adhesion carrier for microorganisms, but also can enhance the degradation of pollutants by the microorganisms, so that the pollutant purification ability of a wetland system is greatly improved, and the problem of low pollutant removal efficiency caused by the lack of electron acceptors in a traditional artificial wetland is successfully overcome.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a dual-catalytic composite packing material for constructed wetlands. Background Technology

[0002] Constructed wetland technology, with its advantages of economy and ease of management, has shown great application potential in the field of wastewater treatment. As a green and sustainable wastewater treatment solution, constructed wetland technology provides a practical alternative for environmental protection and sustainable resource utilization, and has been widely applied and researched. However, traditional constructed wetland technology still faces many challenges, such as the relatively low oxygen transfer efficiency in constructed wetlands, leading to a long-term hypoxic state within the system and a severe shortage of electron acceptors, thus limiting pollutant removal. Therefore, targeted optimization and innovation of constructed wetland technology to improve its treatment efficiency and stability are key to promoting the widespread application of this technology.

[0003] Manganese iron ore, a natural mineral rich in manganese and iron, possesses excellent catalytic properties and can naturally release Fe and Mn ions under acidic conditions. These iron and manganese ions can act as electron transport mediators, interconverting between different oxidation states and participating in redox reactions, promoting electron transfer processes and thus enhancing catalytic activity. This characteristic makes manganese iron ore a promising candidate for wastewater treatment.

[0004] Metal-organic frameworks (MOFs), as novel materials, possess highly ordered porous structures, large porosity, and specific surface area, providing numerous reaction sites. Simultaneously, their abundant chemical functional groups effectively promote processes such as adsorption, catalysis, and ion exchange, and can accommodate a large number of molecules or ions. Furthermore, MOF materials exhibit high stability under various chemical environments, especially acidic conditions, allowing them to maintain good functionality in diverse settings. By selecting different metal centers and organic ligands, MOFs can be designed into materials with specific functions and structures, and their synthesis can be optimized using green chemistry methods, aligning with the needs of sustainable development. Summary of the Invention

[0005] To overcome the problem of low pollutant removal efficiency caused by insufficient electron acceptors in traditional constructed wetlands, this invention provides a dual-catalytic composite packing material combining manganese iron ore and MOF.

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

[0007] A dual-catalytic composite packing material has a core-shell structure, wherein the core is manganese iron ore and the shell is (Fe / Mn)-MOF.

[0008] Preferably, the manganese iron ore has a manganese content of 25% to 45% and an iron content of 30% to 75%.

[0009] Preferably, the organic ligand of the (Fe / Mn)-MOF is 2-aminoterephthalic acid.

[0010] The preparation method of the above-mentioned dual-catalytic composite filler includes: thoroughly mixing manganese iron ore, acidifying agent and organic ligand in an organic solvent, and then heating to react to obtain the dual-catalytic composite filler.

[0011] Preferably, the acidifying agent is sulfuric acid.

[0012] Preferably, the mass ratio of the manganese iron ore, acidifying agent and organic ligand is 1:0.5~0.8:1~2.

[0013] Preferably, the organic solvent is N,N-dimethylformamide.

[0014] Preferably, the reaction is carried out at a temperature of 180°C for 48 hours.

[0015] Preferably, the particle size of the manganese iron ore is 5-10 mm.

[0016] The application of the above-mentioned dual-catalytic composite filler in the preparation of constructed wetlands.

[0017] An artificial wetland comprises, from top to bottom, an aquatic plant layer, a biological ceramsite layer, a volcanic rock filler layer, a coarse sand layer, a gravel layer, and a washed sand layer, wherein the volcanic rock filler layer contains a dual-catalytic composite filler as described above.

[0018] Preferably, the volume percentage of the dual-catalytic composite packing material in the volcanic rock packing layer is 5%.

[0019] Preferably, the particle size of the bio-ceramic granules is 15-25 mm, the particle size of the volcanic rock is 5-10 mm, the particle size of the coarse sand is 3-8 mm, the particle size of the gravel is 10-20 mm, and the particle size of the washed sand is 1-2 mm.

[0020] Preferably, the thickness ratio of the bio-ceramic granule layer, the volcanic rock filler layer, the coarse sand layer, the gravel layer, and the washed sand layer is 2:8:2:2:1.

[0021] This invention presents a dual-catalytic composite packing material that combines the inorganic catalytic ability of manganese iron ore with the organic catalytic ability of MOF (metal-organic framework) to form a highly efficient dual-catalytic system. It serves as an ideal attachment carrier for microorganisms and enhances their degradation of pollutants, thereby significantly improving the pollutant purification capacity of wetland systems and successfully overcoming the problem of low pollutant removal efficiency in traditional constructed wetlands due to insufficient electron acceptors. The high-valence iron-manganese ions in this composite packing material act as electron acceptors for ammonia nitrogen, improving ammonia nitrogen removal efficiency. Simultaneously, the low-valence iron-manganese ions generated during the reaction process act as electron donors for nitrate nitrogen, promoting nitrate nitrogen removal in the system. Furthermore, the excellent characteristics of the packing material enable it to release iron-manganese ions more stably and continuously in constructed wetland systems, thus fully utilizing the inorganic catalytic effect of the packing material. At the same time, this composite packing material combines the excellent adsorption and complexation properties of manganese iron ore and the MOF metal framework, effectively achieving multiple functions such as phosphorus and heavy metal removal and resource utilization. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a dual-catalytic composite packing material, in which A-manganese iron ore and B-(Fe / Mn)-MOF.

[0023] Figure 2 This is a schematic diagram of the (Fe / Mn)-MOF formation process.

[0024] Figure 3 This is a schematic diagram of the BESs-constructed wetland treatment system, where 1-washed sand layer, 2-gravel layer, 3-coarse sand layer, 4-volcanic rock filler layer, 5-water distribution pipe, 6-biological ceramsite layer, 7-electrode, 8-central water collection pipe, 9-aquatic plant layer, and 10-water collection pipe.

[0025] Figure 4 The removal efficiency of ammonia nitrogen and COD before and after adding dual-catalytic composite filler, manganese iron ore, and (Fe / Mn)-MOF was studied. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0027] Example 1

[0028] like Figure 1-2 As shown, this invention uses manganese iron ore as the attachment carrier of MOF, and at the same time utilizes the iron and manganese ions released by manganese iron ore under acidic conditions as the metal central ions of MOF, successfully combining manganese iron ore with MOF metal-organic framework to form a dual-catalytic composite filler with manganese iron ore core and (Fe / Mn)-MOF shell.

[0029] The specific preparation process of the dual-catalytic composite packing is as follows:

[0030] (1) Weigh 15g of manganese iron ore particles (Hunan Daji Manganese Industry Co., Ltd., manganese content is 27wt%, iron content is 32wt%), then wash them repeatedly with water 3 times, and grind them to a particle size of 5-10 mm after they are naturally dried.

[0031] (2) Measure 21.3 mL of N,N-dimethylformamide solvent into a beaker using a graduated cylinder. Then, slowly add the manganese iron ore particles ground in step (1) into the beaker containing N,N-dimethylformamide solvent under vigorous stirring. Next, under vigorous stirring, slowly add 28.69 mL of 30% dilute sulfuric acid solution and 20 g of 2-aminoterephthalic acid into the beaker in sequence to ensure that the manganese iron ore particles, dilute sulfuric acid solution, and 2-aminoterephthalic acid are fully contacted in the N,N-dimethylformamide solvent.

[0032] (3) Pour the mixture obtained in step (2) into a stainless steel high-pressure reactor, and place the reactor on a magnetic stirrer with a rotation speed of 400 r / min and continue stirring for 45 min;

[0033] (4) After stirring in step (3), the stainless steel high-pressure reactor is sealed and placed in an oven with the temperature set at 180°C for 48 hours. After that, it is taken out and allowed to cool naturally to room temperature.

[0034] (5) The reaction product obtained in step (4) is centrifuged at a rotation speed of 5000 r / min for 10 min, then washed with anhydrous ethanol and centrifuged again. This process is repeated 2-3 times. The centrifuged sample is then dried in a vacuum drying oven at 80℃ for 8 h to obtain the dual-catalytic composite filler (Fe / Mn)-MOF-manganese iron ore.

[0035] Preparation of (Fe / Mn)-MOF as a comparison sample:

[0036] (1) Measure 21.3 mL of N,N-dimethylformamide solvent into a beaker using a graduated cylinder, and then add 8.2 g FeCl2 and 9.4 g MnCl2 while stirring vigorously;

[0037] (2) Add 20 g of 2-aminoterephthalic acid slowly to the beaker while stirring vigorously;

[0038] (3) Then, slowly add 28.69 mL of a 30% dilute sulfuric acid solution while stirring vigorously;

[0039] (4) Pour the mixture obtained in step (3) into a stainless steel high-pressure reactor and place the reactor on a magnetic stirrer with a rotation speed of 400 r / min and continue stirring for 45 min;

[0040] (5) After stirring in step (4), the stainless steel high-pressure reactor is sealed and placed in an oven with a temperature of 180°C for 48 hours. After that, it is taken out and allowed to cool naturally to room temperature.

[0041] (6) The reaction product obtained in step (5) is centrifuged at a rotation speed of 5000 r / min for 10 min, then washed with anhydrous ethanol and centrifuged again. This process is repeated 2-3 times. The centrifuged sample is then dried in a vacuum drying oven at 80℃ for 8 h to obtain (Fe / Mn)-MOF.

[0042] according to Figure 3 The BESs-constructed wetland treatment system was constructed as follows: First, water distribution pipes, water collection pipes, central water collection pipes, and electrodes were installed. Then, the following materials were added sequentially: 1-2 mm washed sand (100 mm thick), 10-20 mm gravel (200 mm thick), 3-8 mm coarse sand (200 mm thick), 5-10 mm volcanic rock (800 mm thick, mixed with 5% dual-catalytic composite filler by volume), and 15-25 mm bio-ceramic particles (200 mm thick). Finally, aquatic plants were planted. Control groups: (1) No dual-catalytic composite filler was added (blank group), (2) The dual-catalytic composite filler was completely replaced with manganese iron ore, and (3) The dual-catalytic composite filler was completely replaced with (Fe / Mn)-MOF.

[0043] The system hydraulic retention time was 10 days, and the applied voltage to the system electrodes was 2V. Sampling was performed every three days at both the inlet and outlet of the system, using sterile bottles to avoid sample contamination. The concentrations of ammonia nitrogen and COD in the influent and effluent were measured according to the standard methods specified in the "Wastewater Testing Methods". Specific experimental results are shown in Table 1 and... Figure 4 .

[0044] Table 1. Comparison of pollutant removal effects before and after adding dual-catalytic composite filler, manganese iron ore, and (Fe / Mn)-MOF.

[0045]

[0046] The results of the comparative experiments above show that, compared with manganese iron ore and (Fe / Mn)-MOF, the (Fe / Mn)-MOF-manganese iron ore dual-catalytic composite filler with core-shell structure of the present invention can significantly improve the removal efficiency of ammonia nitrogen and COD in constructed wetlands.

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-catalytic composite packing material, characterized in that: The composite filler has a core-shell structure, wherein the core is manganese iron ore and the shell is Fe / Mn-MOF; The organic ligand of the Fe / Mn-MOF is 2-aminoterephthalic acid.

2. The dual-catalytic composite packing according to claim 1, characterized in that: The manganese iron ore has a manganese content of 25% to 45% and an iron content of 30% to 75%.

3. The method for preparing the dual-catalytic composite packing according to any one of claims 1-2, characterized in that, The preparation method includes: thoroughly mixing manganese iron ore, acidifying agent and organic ligand in an organic solvent, and then heating to react to obtain the dual-catalytic composite filler.

4. The preparation method according to claim 3, characterized in that: The acidifying agent is sulfuric acid.

5. The preparation method according to claim 3, characterized in that: The organic solvent is N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that: The reaction was carried out at a temperature of 180°C for 48 hours.

7. The preparation method according to claim 3, characterized in that: The particle size of the manganese iron ore is 5~10 mm.

8. The application of the dual-catalytic composite filler according to any one of claims 1-2 in the preparation of constructed wetlands.

9. An artificial wetland, characterized in that: The constructed wetland comprises, from top to bottom, an aquatic plant layer, a biological ceramsite layer, a volcanic rock filler layer, a coarse sand layer, a gravel layer, and a washed sand layer, wherein the volcanic rock filler layer contains a dual-catalytic composite filler as described in any one of claims 1-2.

10. The constructed wetland according to claim 9, characterized in that: The volume percentage of the dual-catalytic composite packing material in the volcanic rock packing layer is 5%.

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