Dual-catalysis type composite filler, preparation method thereof and application of dual-catalysis type composite filler in constructed wetland

Abstract

The invention discloses a dual-catalysis type composite filler, the composite filler has a core-shell structure, the core is ferromanganese ore, and the shell is (Fe / Mn)-MOF. Compared with the prior art, the dual-catalysis type composite filler has the advantages that the inorganic catalysis capability of the ferromanganese ore is combined with the organic catalysis capability of the MOF metal organic framework, so that an efficient dual-catalysis system is formed. The prepared artificial wetland can be used as an ideal attachment carrier of microorganisms, and can enhance the degradation effect of the microorganisms on pollutants, so that the pollutant purification capacity of a wetland system is greatly improved, and the problem of low pollutant removal efficiency caused by insufficient electron acceptors of a traditional artificial wetland is successfully solved.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment, and in particular relates to a dual-catalytic composite filler for artificial wetlands. Background Art

[0002] With its advantages of economy and easy management, artificial wetland technology has shown great application potential in the field of sewage treatment. As a green and sustainable sewage treatment solution, artificial wetland technology provides a practical alternative for environmental protection and sustainable resource utilization, and has been widely used and studied. However, traditional artificial wetland technology still faces many challenges. For example, the oxygen transfer efficiency in artificial wetlands is relatively low, resulting in a long-term hypoxia state inside the system, causing a serious shortage of electron acceptors, thereby limiting the removal of pollutants. Therefore, targeted optimization and innovation of artificial wetland technology to improve its treatment efficiency and stability have become the key to promoting the widespread application of this technology.

[0003] As a natural mineral, ferromanganese is rich in manganese and iron elements, has excellent catalytic properties, and can naturally release Fe and Mn ions under acidic conditions. These iron and manganese ions can act as electron migration media, convert between different oxidation states, participate in redox reactions, promote the electron transfer process in the reaction, and thus enhance catalytic activity. This characteristic makes ferromanganese have great application potential in the field of sewage treatment.

[0004] As a new type of material, MOF (Metal organic Framework) has a highly ordered porous structure, large porosity and specific surface area, and can provide a large number of reaction sites for reactions. At the same time, its rich chemical functional groups can effectively promote processes such as adsorption, catalysis and ion exchange, and can accommodate a large number of molecules or ions. In addition, MOF materials show high stability in different chemical environments, especially under acidic conditions, which enables them to maintain good functionality in a variety of environments. By selecting different metal centers and organic ligands, MOF can be designed into materials with specific functions and structures, and the synthesis process of MOF can be optimized through green chemical methods, which meets the needs of sustainable development. Summary of the invention

[0005] In order to overcome the problem of low pollutant removal efficiency in traditional artificial wetlands due to insufficient electron acceptors, the present invention provides a dual-catalytic composite filler combining manganese iron ore and MOF.

[0006] To achieve the above object, the present invention adopts the following technical solution: A dual-catalytic composite filler has a core-shell structure, wherein the core is manganese iron ore and the shell is (Fe / Mn)-MOF.

[0007] Preferably, the manganese content of the ferromanganese ore is 25% to 45%, and the iron content is 30% to 75%.

[0008] Preferably, the organic ligand of the (Fe / Mn)-MOF is 2-aminoterephthalic acid.

[0009] The preparation method of the dual-catalytic composite filler comprises: fully mixing manganese iron ore, an acidulant and an organic ligand in an organic solvent, and heating the mixture to react to obtain the dual-catalytic composite filler.

[0010] Preferably, the acidifying agent is sulfuric acid.

[0011] Preferably, the mass ratio of the manganese ore, the acidifier and the organic ligand is 1:0.5~0.8:1~2.

[0012] Preferably, the organic solvent is N,N-dimethylformamide.

[0013] Preferably, the reaction temperature is 180° C. and the reaction time is 48 h.

[0014] Preferably, the particle size of the manganese iron ore is 5 to 10 mm.

[0015] The application of the above dual catalytic composite filler in the preparation of artificial wetlands.

[0016] 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 is added with the above-mentioned dual-catalytic composite filler.

[0017] Preferably, the volume proportion of the dual-catalytic composite filler in the volcanic rock filler layer is 5%.

[0018] Preferably, the particle size of the bioceramsite 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.

[0019] Preferably, the thickness ratio of the bioceramsite layer, the volcanic rock filler layer, the coarse sand layer, the gravel layer and the washed sand layer is 2:8:2:2:1.

[0020] The dual-catalytic composite filler of the present invention forms an efficient dual-catalytic system by combining the inorganic catalytic ability of ferromanganese with the organic catalytic ability of the MOF metal organic framework. It can be used as an ideal attachment carrier for microorganisms and can enhance the degradation of pollutants by microorganisms, thereby greatly improving the pollutant purification ability of the wetland system, and successfully overcoming the problem of low pollutant removal efficiency due to insufficient electron acceptors in traditional artificial wetlands. The high-valent iron-manganese ions in the composite filler can be used as electron acceptors for ammonia nitrogen to improve the removal efficiency of ammonia nitrogen. At the same time, the low-valent iron-manganese ions generated during the reaction can be used as electron donors for nitrate nitrogen to promote the removal of nitrate nitrogen in the system. In addition, the excellent characteristics of the filler enable it to release iron-manganese ions more stably and continuously in the artificial wetland system, thereby giving full play to the inorganic catalytic effect of the filler; at the same time, the composite filler combines the excellent adsorption and complexing properties of ferromanganese and the MOF metal skeleton, and can effectively achieve multiple functions such as the removal of phosphorus and heavy metals and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of dual-catalytic composite filler, where A is manganese iron ore and B is (Fe / Mn)-MOF.

[0022] Figure 2 Schematic diagram of the (Fe / Mn)-MOF formation process.

[0023] Figure 3 This is a schematic diagram of the structure 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.

[0024] Figure 4 The removal effect of ammonia nitrogen and COD before and after adding dual-catalytic composite filler, manganese iron ore, and (Fe / Mn)-MOF. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0026] Example 1 like Figure 1-2 As shown, the present invention uses ferromanganese as the attachment carrier of MOF, and uses the iron and manganese ions released by ferromanganese under acidic conditions as the metal center ions of MOF, successfully combining ferromanganese with the MOF metal organic framework to form a dual-catalytic composite filler with ferromanganese as the core and (Fe / Mn)-MOF as the shell.

[0027] The specific preparation process of the dual-catalytic composite filler is as follows: (1) Weigh 15 g of manganese iron ore particles (Hunan Daji Manganese Industry Co., Ltd., manganese content 27wt%, iron content 32wt%), then wash it repeatedly with clean water for 3 times, wait for it to dry naturally and grind it to a particle size of 5-10 mm; (2) Use a measuring cylinder to measure 21.3 mL of N,N-dimethylformamide solvent and pour it into a beaker. Then slowly add the ground ferromanganese ore particles in step (1) into the beaker containing N,N-dimethylformamide solvent under vigorous stirring. Then, slowly add 28.69 mL of 30% dilute sulfuric acid solution and 20 g of 2-aminoterephthalic acid into the beaker in sequence under vigorous stirring to ensure that the ferromanganese ore particles, dilute sulfuric acid solution, and 2-aminoterephthalic acid are fully in contact with each other in the N,N-dimethylformamide solvent. (3) Pour the mixed solution obtained in step (2) into a stainless steel high-pressure reactor, and place the reactor on a magnetic stirrer at a speed of 400 r / min and continue stirring for 45 min; (4) After the stirring in step (3) is completed, the stainless steel autoclave is sealed and placed in an oven set at 180° C. for 48 hours, and then taken out to allow the stainless steel autoclave to cool naturally to room temperature; (5) The reaction product obtained in step (4) is centrifuged in a centrifuge at a rotation rate of 5000 r / min for 10 minutes, taken out, washed with anhydrous ethanol and centrifuged again, and the operation is repeated 2-3 times. The centrifuged sample is then dried in a vacuum drying oven at 80°C for 8 hours to obtain a dual catalytic composite filler (Fe / Mn)-MOF-manganese iron ore.

[0028] Preparation of comparative sample (Fe / Mn)-MOF: (1) Use a measuring cylinder to measure 21.3 mL of N,N-dimethylformamide solvent and pour it into a beaker. Then add 8.2 g FeCl2 and 9.4 g MnCl2 under vigorous stirring. (2) Slowly add 20 g of 2-aminoterephthalic acid into the beaker while stirring vigorously; (3) Then, 28.69 mL of 30% dilute sulfuric acid solution was slowly added under vigorous stirring; (4) Pour the mixed solution obtained in step (3) into a stainless steel high-pressure reactor, and place the reactor on a magnetic stirrer at a speed of 400 r / min and continue stirring for 45 min; (5) After the stirring in step (4) is completed, the stainless steel autoclave is sealed and placed in an oven set at 180° C. for 48 hours, and then taken out to allow the stainless steel autoclave to cool naturally to room temperature; (6) The reaction product obtained in step (5) was centrifuged in a centrifuge at a rotation rate of 5000 r / min for 10 min, taken out, washed with anhydrous ethanol and centrifuged again, and the operation was repeated 2-3 times. The centrifuged sample was then dried in a vacuum drying oven at 80°C for 8 h to obtain (Fe / Mn)-MOF.

[0029] according to Figure 3 The BESs-constructed wetland treatment system was constructed as shown in the figure: first, water distribution pipes, water collection pipes, central water collection pipes and electrodes were set up, and then washed sand with a particle size of 1-2 mm (thickness of 100 mm), gravel with a particle size of 10-20 mm (thickness of 200 mm), coarse sand with a particle size of 3-8 mm (thickness of 200 mm), volcanic rock with a particle size of 5-10 mm (thickness of 800 mm, mixed with a volume ratio of 5% of dual catalytic composite filler), biological ceramsite with a particle size of 15-25 mm (thickness of 200 mm), and finally aquatic plants were planted. Comparative groups: (1) no dual catalytic composite filler was added (blank group), (2) all dual catalytic composite fillers were replaced by manganese iron ore, and (3) all dual catalytic composite fillers were replaced by (Fe / Mn)-MOF.

[0030] The hydraulic retention time of the system is 10 days, and the external voltage for powering the system electrodes is 2V. The system is sampled every three days, and sampling points are set at the water inlet and outlet of the system. Sterile bottles are used for sampling to avoid sample contamination. The concentrations of ammonia nitrogen and COD in the system inlet and outlet water are tested according to the standard method specified in the "Wastewater Testing Method". The specific experimental results are shown in Table 1 and Figure 4 .

[0031] Table 1 Comparison of pollutant removal effects before and after adding dual catalytic composite fillers, manganese iron ore, and (Fe / Mn)-MOF

[0032] It can be seen from the above comparative experimental results that compared with ferromanganese and (Fe / Mn)-MOF, the (Fe / Mn)-MOF-ferromanganese dual-catalytic composite filler with a core-shell structure of the present invention can more significantly improve the removal effect of artificial wetlands on ammonia nitrogen and COD.

[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual-catalytic composite filler, 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.

2. The dual-catalytic composite filler according to claim 1, characterized in that: The manganese content of the ferromanganese ore is 25% to 45%, and the iron content is 30% to 75%.

3. The dual-catalytic composite filler according to claim 1, characterized in that: The organic ligand of the (Fe / Mn)-MOF is 2-aminoterephthalic acid.

4. The method for preparing the dual-catalytic composite filler according to any one of claims 1 to 3, characterized in that: The preparation method comprises: fully mixing manganese iron ore, an acidifier and an organic ligand in an organic solvent, and heating the mixture for reaction to obtain the dual-catalytic composite filler.

5. The preparation method according to claim 4, characterized in that: The acidulant is sulfuric acid.

6. The preparation method according to claim 4, characterized in that: The organic solvent is N,N-dimethylformamide.

7. The preparation method according to claim 4, characterized in that: The reaction temperature is 180°C and the reaction time is 48 hours.

8. The preparation method according to claim 4, characterized in that: The particle size of the manganese iron ore is 5-10 mm.

9. Use of the dual-catalytic composite filler according to any one of claims 1 to 3 in the preparation of artificial wetlands.

10. An artificial wetland, characterized in that: The 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 is added with a dual-catalytic composite filler as described in any one of claims 1 to 3, preferably, the volume proportion of the dual-catalytic composite filler in the volcanic rock filler layer is 5%.

Images