Open type in-situ deodorization system and method for MOF-DBD synergistic active species release and application of open type in-situ deodorization system and method

Abstract

The invention provides an open type in-situ deodorization system and method for MOF-DBD synergistic active species release and application, and the system comprises a DBD active species generation unit which is used for in-situ release of oxygen free radicals, hydroxyl free radicals, ozone and active nitrogen oxides in an open air environment and preliminary oxidation of ammonia gas, hydrogen sulfide and volatile organic compounds; and the MOF light-oxygen catalysis unit is arranged at the downstream or adjacent area of the DBD active species generation unit in an open manner and is used for carrying out catalytic decomposition on byproducts generated by the DBD active species generation unit under the action of light and further converting the byproducts into harmless or high-reactivity oxide species. The device can efficiently degrade ammonia gas, hydrogen sulfide and volatile organic compounds generated in livestock and poultry breeding and other scenes, has the advantages of high removal efficiency, low energy consumption, long material service life and stable operation, and is suitable for tail end deodorization and industrial waste gas treatment of farms.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically relating to an open in-situ deodorization system, method, and application of MOF-DBD synergistic release of active species. Background Technology

[0002] Odorous gases (mainly composed of NH3, H2S and VOCs) produced during the anaerobic degradation of undigested nutrients in livestock and poultry manure during the production process of livestock and poultry farms are an important source of environmental pollution, which has a significant impact on the health and production of livestock and poultry and restricts the sustainable development of the livestock and poultry farming industry.

[0003] Traditional livestock odor control technologies, such as biofilters, activated carbon adsorption, and catalytic oxidation, all have limitations in practical applications. Specifically: biofilters utilize the metabolic activity of microorganisms to convert pollutants in waste gas into harmless carbon dioxide, water, and microbial cell matter. This method offers advantages such as simple equipment, low operating costs, and no secondary pollution. However, it has specific requirements regarding the temperature, humidity, and concentration of the waste gas, and the growth and metabolism of microorganisms are easily affected by environmental factors. Activated carbon has a large specific surface area and abundant microporous structure, making adsorption a good treatment method for low-concentration, high-volume waste gas. However, once activated carbon reaches saturation, it needs to be regenerated or replaced. The regeneration process is complex, and replacing activated carbon is costly. Furthermore, improper handling can cause secondary pollution if the activated carbon has adsorbed pollutants. Catalytic oxidation, under the action of a catalyst, causes pollutants in waste gas to undergo an oxidation reaction at a lower temperature, converting them into harmless carbon dioxide and water. It offers advantages such as high treatment efficiency, low energy consumption, and no secondary pollution. However, catalysts are expensive and easily deactivated by impurities in the waste gas, requiring strict pretreatment of the waste gas. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide an open in-situ deodorization system, method, and application for the synergistic release of active species by MOF-DBD (metal-organic framework-dielectric barrier discharge), so as to achieve continuous, safe, and efficient in-situ purification of open air environments, especially within the air volume of livestock and poultry houses.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides an open in-situ deodorization system for synergistic release of MOF-DBD active species, comprising:

[0007] The DBD active species generation unit is used to release oxygen free radicals, hydroxyl free radicals, ozone and active nitrogen oxides in situ in an open air environment, and to perform preliminary oxidation of ammonia, hydrogen sulfide and volatile organic compounds.

[0008] The MOF photocatalytic unit is disposed in an open manner in the downstream or adjacent region of the DBD active species generating unit, and is used to catalytically decompose the by-products generated by the DBD active species generating unit under light irradiation, and further convert them into harmless or highly reactive oxide species.

[0009] Preferably, the DBD active species generating unit and the MOF photocatalytic oxidation unit maintain an open diffusion coupling distance of 2 to 20 cm.

[0010] Preferably, the operating conditions of the DBD active species generating unit include: discharge voltage 1~35 kV; frequency 1~50 kHz; power 1~1000 W; discharge gap 0.5~20 mm; ambient humidity 10~95%; and air, oxygen-enriched air, or oxygen as the discharge medium.

[0011] Preferably, the MOF photocatalytic oxidation unit satisfies at least one of the following characteristics:

[0012] a) It has a semiconductor band structure and can generate photogenerated electrons and photogenerated holes under natural light or ultraviolet / visible light irradiation generated by discharge;

[0013] b) Under light, it can remove ozone, NO2, and NO3. - Its derivative byproducts are transformed into hydroxyl radicals, superoxide radicals, or singlet oxygen.

[0014] c) The pore structure contains polar or charged functional groups, which are used to enrich NH3, H2S or active oxide species generated by discharge;

[0015] d) It has reversibly variable valence metal active sites to promote the photocatalytic decomposition of ozone and reactive nitrogen oxides.

[0016] Preferably, in the MOF photocatalytic oxidation unit, the metal-organic framework material is fixed on a honeycomb ceramic, metal foam, glass fiber, or porous oxide support in the form of particles, thin films, coatings, supporting layers, or three-dimensional porous structures, so that the formed structure has a diameter of ≥300 μm. 2 / m 3 The apparent specific surface area and air pressure drop ≤30 Pa / m.

[0017] More preferably, the central metal of the metal-organic framework material is selected from a single metal or a combination of multiple metals such as Fe, Cu, Co, Zr, Ti, Ce, Mn, and Ni; the organic ligand is selected from ligands containing carboxylic acid structures, nitrogen-containing heterocyclic structures, or conjugated electron systems.

[0018] This invention also provides an open-system in-situ deodorization method for the synergistic release of active species by MOF-DBD, implemented through the aforementioned system. This method includes: continuously operating a DBD active species generating unit and a MOF photocatalytic oxidation unit in an open air environment, causing oxygen free radicals, hydroxyl free radicals, ozone, and active nitrogen oxides released by the DBD active species generating unit to come into contact with ammonia, hydrogen sulfide, and volatile organic compounds in the air for oxidation. The MOF photocatalytic oxidation unit then decomposes the discharge byproducts, converting them into harmless or highly reactive oxide species, ultimately generating N2, CO2, and water.

[0019] This invention also provides the application of an open-system in-situ deodorization system with MOF-DBD synergistic release of active species in deodorization of open air environments.

[0020] Preferably, the open air environment includes an open livestock and poultry breeding environment as well as manure ditches, manure scraping channels, fermentation workshops, composting areas, sludge areas, or temporary garbage storage areas.

[0021] The core concept of this invention is to construct a continuous reaction channel within an open aquaculture space, encompassing "discharge-active species generation – natural diffusion – MOF photo-oxidation catalysis." During system operation, no sealed reactor or fan is required. Short-lived reactive oxygen / nitrogen species generated by the DBD active species generation unit diffuse naturally in the air, crossing the pre-defined 2-20 cm spatial gap between themselves and the MOF photo-oxidation catalysis unit to enter its pore region. The MOF photo-oxidation catalysis unit enriches these species using its polar groups, reversible variable-valence metal sites, and hierarchical porous structure, thereby enhancing the local concentration of short-lived species, extending their effective lifespan, and promoting the deep oxidation of NH3, H2S, and VOCs within the pores. Simultaneously, the MOF photo-oxidation catalysis unit also reacts with ozone and NO. x The photocatalytic degradation capability further constructs an open "closed-loop removal of byproducts" pathway, avoiding the secondary pollution problems common in DBD systems. Through the above synergistic approach, a unified process of odor oxidation and byproduct mineralization is achieved, significantly reducing ozone residues in the aquaculture environment and improving biosafety.

[0022] Compared with existing technologies, the system of this invention, through a synergistic strategy of "open-loop action mode + photocatalytic elimination of by-products + MOF pore enrichment effect," has the following advantages over traditional DBD or photocatalytic technologies: it can achieve air volume purification without the need for a closed reactor or fan conveying, making it more suitable for large livestock and poultry housing spaces; it can effectively treat DBD by-products, significantly reduce ozone residues, and improve biosafety; the selective pores and variable valence centers of MOF provide enhanced odor adsorption and deep oxidation capabilities, enabling efficient mineralization of NH3, H2S, and VOCs; the system is easy to install, low in cost, and stable in operation, and can be applied for long-term in-situ deodorization in open livestock and poultry farming environments. It is suitable not only for open livestock and poultry farming environments such as pig, laying hen, broiler, beef cattle, and ruminant housing, but also for odor control in manure ditches, manure scraping channels, fermentation workshops, composting areas, sludge areas, or garbage storage areas. Attached Figure Description

[0023] Figure 1 SEM image of MIL-100(Fe) prepared in Example 1 of this invention.

[0024] Figure 2 FTIR spectrum of MIL-100(Fe) prepared in Example 1 of this invention.

[0025] Figure 3 XRD pattern of MIL-100(Fe) prepared in Example 1 of this invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. The following specific embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0027] The implementation of this invention mainly involves the following aspects:

[0028] I. Preparation of Photo-oxidizing MOF Catalysts. Metal precursors and ligands with photoresponsiveness and reversible variable valence metal centers were selected, and materials with adsorption capacity, photogenerated carrier formation capacity, and ozone / NO3 oxidation properties were prepared using hydrothermal and solvothermal methods. x The MOF material's catalytic decomposition capabilities make it a photo-oxidation catalytic material specifically designed for odor control systems in livestock and poultry houses.

[0029] Preferably, in the preparation of the photo-oxidation MOF catalytic material, the molar ratio of the central metal precursor to the organic ligand is controlled at 1:1 to 1:6, the concentrations of the metal ion and ligand solutions are maintained in the ranges of 0.01 to 1.0 mol / L and 0.01 to 0.8 mol / L, respectively, the solid-liquid ratio is maintained at 1:20 to 1:500 (g / mL), the pH of the system is adjusted to 1.0 to 8.0, and the reaction is carried out at 120 to 180 °C for 12 to 24 h in the presence of crystal regulators, pore inducing agents or valence state regulating agents (0.01 to 10 wt%) using hydrothermal, solvothermal, microwave-assisted or redox-enhanced methods, to obtain a MOF photo-oxidation catalytic material with a large specific surface area, hierarchical pore structure and photoresponse capability.

[0030] II. MOF Molding and Support Structure Construction. The MOF material prepared in step one is fixed onto honeycomb ceramics, metal foam, or other ventilated supports in the form of particles, thin films, coatings, or three-dimensional porous structures, so that it remains stable in a high-humidity, high-ammonia-corrosion open airflow environment and forms an air-permeable gas-solid mass transfer interface.

[0031] Preferably, the prepared metal-organic framework material is formed by particle pressing, thin film deposition, coating, three-dimensional porous structure construction, or in-situ growth, and fixed on a support such as honeycomb ceramics, metal foam, porous oxides, or glass fiber, so that the formed structure has a diameter of ≥300 μm. 2 / m 3 The apparent specific surface area and air pressure drop of ≤30 Pa / m ensure that short-lived active species can stably contact the MOF channels and achieve continuous catalytic reactions in an open air environment.

[0032] III. Construction of DBD Active Speciation Unit. A unit capable of continuously generating ROS (·OH, ·O2) in an open-air environment was constructed. - (NO2, NO3) and RNS (NO2, NO3) - The plasma excitation unit of the plasma can achieve initial cracking and oxidation of odor molecules in the air by in-situ release.

[0033] Preferably, the discharge operating conditions of the dielectric barrier discharge unit are: discharge voltage 1~35 kV, frequency 1~50 kHz, power 1~1000 W, discharge gap 0.5~20 mm, and relative humidity of the air during operation controlled at 10~95%. The discharge medium can be air, oxygen-enriched air or oxygen to ensure the continuous and stable generation of oxygen free radicals, hydroxyl free radicals, ozone and active nitrogen oxides in an open environment, and to achieve good spatial diffusion effect.

[0034] IV. Coordinated Installation Layout and Formation of Active Species Coupling Channels. The MOF photo-oxidation catalytic unit and the DBD active species generation unit are arranged in an open space at a diffusion distance of 2~20 cm, allowing short-lived active species to enter the MOF structure during natural diffusion, realizing a continuous coupling reaction of DBD primary oxidation and MOF deep photo-oxidation, avoiding the use of any closed reaction chambers or pipeline transport structures.

[0035] Preferably, in the collaborative installation layout, the metal-organic frame molding structure is arranged on the top, side walls, manure volatilization zone, or main airflow path area of ​​the livestock and poultry house, maintaining an open diffusion coupling distance of 2~20 cm with the dielectric barrier discharge unit, so that the active oxide species generated by DBD enter the MOF channels in the natural diffusion path, thereby achieving a continuous coupling reaction of primary discharge oxidation and photo-oxidation deep mineralization without relying on any closed reaction chamber or mechanical transport.

[0036] V. Open-type in-situ synergistic deodorization operation. The DBD active species generation unit and MOF photocatalytic oxidation unit operate simultaneously in the livestock and poultry house environment, so that odor and DBD by-products undergo primary oxidation, deep mineralization by photooxidation and decomposition of by-products in the air space in sequence, and finally generate harmless substances (N2, CO2 and H2O), significantly reducing the concentration of NH3, H2S and VOCs, and ensuring that ozone and nitrogen oxide residues are controllable and safe.

[0037] Preferably, during the open-site synergistic deodorization operation, odor pollutants come into contact with the discharge-photo-oxidation synergistic structure through natural diffusion or low-speed airflow. This allows ammonia, hydrogen sulfide, and volatile organic compounds to undergo primary bond breaking during discharge, deep oxidation by MOF photo-oxidation, and ultimately mineralization into nitrogen, carbon dioxide, and water. Simultaneously, MOF can catalytically degrade ozone and reactive nitrogen oxides released by DBD, ensuring that the system can operate for a long time in an open aquaculture environment without causing secondary pollution or ozone exceeding the standard.

[0038] Example 1

[0039] 202 g of Fe(NO3)3·9H2O and 69.4 g of 1,3,5-benzenetricarboxylic acid (H3BTC) were weighed and dissolved in 500 mL of deionized water. The mixture was magnetically stirred at 25 °C for 1 h. The solution was then transferred to a sealed pressure-resistant reactor and reacted at 160 °C for 12 h. After cooling, the mixture was filtered and repeatedly washed with deionized water to obtain the primary product MIL-100(Fe). The obtained solid was added to 400 mL of deionized water and heated at 80 °C for 3 h, followed by filtration and drying. The solid was then soaked in 400 mL of anhydrous ethanol at 65 °C for 3 h, followed by washing and drying. Finally, the solid was added to 400 mL of 38 mM NH4F solution and treated at 70 °C for 3 h, followed by washing and drying to obtain the final product MIL-100(Fe).

[0040] SEM image of MIL-100(Fe) is shown below Figure 1 As shown, the characterization results indicate that the synthesized MIL-100(Fe) exhibits a regular nanopolyhedral morphology, composed of uniform nanoparticles with a particle size of approximately 150–200 nm. The particle surfaces are smooth, the crystal shapes are clear, and there are obvious packing pores between the particles, forming a locally cross-linked interconnected pore network, which reflects the structural characteristics of a typical porous MOF. The clear polyhedral boundaries in the magnified local images further indicate that the material has high crystallinity and good structural stability.

[0041] FTIR results as follows Figure 2 As shown, the FTIR spectrum at 1620 cm⁻¹ -1 A C=O stretching vibration peak appears at 1380 cm⁻¹. -1 A symmetrical stretching vibration peak appears at 760–600 cm⁻¹, and continues to occur between 760 and 600 cm⁻¹. -1 The region exhibits characteristic Fe–O absorption, and the characteristic peak of carboxylic acid shows a red shift and weakening, confirming the interaction between BTC ligands and Fe. 3+ A stable Fe–O–C coordination structure is formed between them.

[0042] XRD results are as follows Figure 3 As shown, the XRD pattern shows obvious characteristic diffraction peaks at 2θ = 11.020°, 18.620°, 20.120° and 26.7°, indicating that the sample successfully constructed a well-crystallized Fe–BTC three-dimensional coordination framework.

[0043] Comprehensive analysis shows that the material has a regular polyhedral morphology, high crystallinity, and abundant pore structure, which lays the structural foundation for its excellent adsorption and catalytic performance and subsequent construction of regenerative air purification filter materials.

[0044] Example 2

[0045] 3.00 g of FeCl3·6H2O was weighed and dissolved in a mixed solvent of 40 mL DMF and 10 mL deionized water, and stirred at 25 °C for 20 min. Then, 1.98 g of NH2-BDC was added, and stirring was continued for another 40 min to obtain a homogeneous precursor solution. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted solvothermically at 150 °C for 18 h. After cooling, the solid was collected by centrifugation and washed three times each with 30 mL DMF and 30 mL anhydrous ethanol. The solid was then soaked in ethanol at 60 °C for 6 h to remove residual solvent, and finally dried under vacuum at 80 °C for 12 h to obtain MIL-53-NH2(Fe) powder, which can be used as a metal-organic framework catalytic material with visible light response in the system of this invention.

[0046] Application Example 1

[0047] The MIL-100(Fe) solid catalyst material prepared in Example 1 was packed onto the surface of a honeycomb ceramic carrier (400 cpsi, wall thickness approximately 0.17 mm) to form a catalytic packing unit that allows air circulation. This unit was then installed in the downstream region of a dielectric barrier discharge device, ensuring continuous contact with the active oxide species generated during discharge. The dielectric barrier discharge device was powered by AC 380 V (±10%) input, with an average power of 2–5 kW. It consisted of a pulse power supply (10 kg, 250×200×360 mm) and a pulse transformer (32 kg, 340×340×350 mm). It could operate stably at -10–50 °C, relative humidity <93% (non-condensing), and atmospheric pressure 86–106 kPa, and was suitable for storage environments of -25–55 °C. The assembled MOF-DBD synergistic open in-situ deodorization system is fixed in the odor-emitting area of ​​the livestock and poultry breeding house. Naturally diffused ammonia, hydrogen sulfide, and volatile organic compounds sequentially pass through the dielectric barrier discharge zone and the catalytic zone. During system operation, the discharge power supply is connected, and the dielectric barrier discharge device is adjusted to a stable discharge state. The discharge voltage is set to 12 kV, the discharge frequency to 10 kHz, the operating power to approximately 50 W, and the discharge gap to 2 mm. The relative humidity inside the breeding house is approximately 60%, and natural ventilation or low-volume air supply is maintained. This allows the active oxides generated during discharge to enter the MIL-100(Fe) catalytic structure during airflow diffusion, completing a synergistic reaction.

[0048] The results showed that the MOF-DBD synergistic system operating in an open aquaculture environment had a significant removal effect on multiple odor pollutants. Before the system was put into operation, the average concentrations of NH3, H2S, and VOCs in the ambient air were approximately 6.0 mg·m³. -3 0.09 mg·m -3 and 2.8 mg·m -3 After treatment with the MOF-DBD system, the NH3 concentration was reduced to approximately 1.1 mg·m³. -3 (Reduced by 81%), H2S concentration decreased to approximately 0.012 mg·m³. -3 (Reduced by 87%), VOCs concentration decreased to approximately 0.5 mg·m³. -3 (Reduced by 82%). During 72 hours of continuous operation in an open environment, the removal efficiency of each pollutant remained stable, and no significant performance degradation was observed.

[0049] Application Example 2

[0050] The MIL-53-NH2(Fe) powder obtained in Example 2 was mixed with 8 wt% polytetrafluoroethylene aqueous emulsion to form a slurry. The mass ratio of MIL-53-NH2(Fe) powder to polytetrafluoroethylene emulsion was approximately 5:3. This slurry was uniformly coated onto the surface of a honeycomb ceramic carrier and dried at 80 °C for 2 h before use. The coated catalyst carrier was fixedly installed in the gas diffusion area at the outlet of the dielectric barrier discharge electrode, maintaining a spatial coupling distance of 3 cm from the center of the discharge plate, so that the active oxide species generated by the discharge could directly diffuse to the catalyst surface. During operation, the dielectric barrier discharge power supply was turned on, and the discharge voltage was set to 11 kV, the discharge frequency to 10 kHz, the system operating power to 45 W, the discharge gap was maintained at 2 mm, and natural ventilation was maintained. The synergistic system was suspended 1.6 m above the manure ditch of the livestock and poultry house, so that ammonia, hydrogen sulfide, and volatile organic compounds would pass through the discharge area and the MIL-53-NH2(Fe) catalyst area in sequence during the diffusion process, completing the open in-situ deodorization operation. The results showed that the average concentration of NH3 decreased by 82.5%, the average concentration of H2S decreased by 89%, the average concentration of VOCs decreased by 79%, and the residual concentration of O3 decreased by 80%.

[0051] Obviously, the above embodiments of the present invention are merely examples to illustrate the present invention more clearly, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An open-system in-situ deodorization system for synergistic release of active species via MOF-DBD, comprising: The DBD active species generation unit is used to release oxygen free radicals, hydroxyl free radicals, ozone and active nitrogen oxides in situ in an open air environment, and to perform preliminary oxidation of ammonia, hydrogen sulfide and volatile organic compounds. The MOF photocatalytic unit is disposed in an open manner in the downstream or adjacent region of the DBD active species generating unit, and is used to catalytically decompose the by-products generated by the DBD active species generating unit under light irradiation, and further convert them into harmless or highly reactive oxide species.

2. The system according to claim 1, characterized in that, The DBD active species generating unit and the MOF photocatalytic oxidation unit maintain an open diffusion coupling distance of 2~20 cm.

3. The system according to claim 1, characterized in that, The operating conditions of the DBD active species generation unit include: discharge voltage 1~35 kV; frequency 1~50 kHz; power 1~1000 W; discharge gap 0.5~20 mm; ambient humidity 10~95%; and the use of air, oxygen-enriched air, or oxygen as the discharge medium.

4. The system according to claim 1, characterized in that, The MOF photocatalytic oxidation unit satisfies at least one of the following characteristics: a) It has a semiconductor band structure and can generate photogenerated electrons and photogenerated holes under natural light or ultraviolet / visible light irradiation generated by discharge; b) Under light, it can remove ozone, NO2, and NO3. - Its derivative byproducts are transformed into hydroxyl radicals, superoxide radicals, or singlet oxygen. c) The pore structure contains polar or charged functional groups, which are used to enrich NH3, H2S or active oxide species generated by discharge; d) It has reversibly variable valence metal active sites to promote the photocatalytic decomposition of ozone and reactive nitrogen oxides.

5. The system according to claim 1, characterized in that, In the MOF photocatalytic oxidation unit, the metal-organic framework material is fixed on a honeycomb ceramic, metal foam, glass fiber, or porous oxide support in the form of particles, thin films, coatings, supporting layers, or three-dimensional porous structures, so that the formed structure has a diameter of ≥300 μm. 2 / m 3 The apparent specific surface area and air pressure drop ≤30 Pa / m.

6. The system according to claim 5, characterized in that, The central metal of the metal-organic framework material is selected from single metals or combinations of multiple metals such as Fe, Cu, Co, Zr, Ti, Ce, Mn, and Ni; the organic ligands are selected from ligands containing carboxylic acid structures, nitrogen-containing heterocyclic structures, or ligands with conjugated electron systems.

7. An open-system in-situ deodorization method for synergistic release of active species by MOF-DBD, implemented by the system described in any one of claims 1 to 6, comprising: The DBD active species generation unit and MOF photocatalytic oxidation unit operate continuously in an open air environment. The oxygen free radicals, hydroxyl free radicals, ozone and active nitrogen oxides released by the discharge of the DBD active species generation unit come into contact with ammonia, hydrogen sulfide and volatile organic compounds in the air and undergo oxidation. The discharge byproducts are decomposed by the MOF photocatalytic oxidation unit and transformed into harmless or highly reactive oxide species, ultimately generating N2, CO2 and water.

8. The application of the system according to any one of claims 1 to 6 in deodorization of open air environments.

9. The application according to claim 8, characterized in that, The open air environment includes open livestock and poultry farming environments as well as manure ditches, manure scraping channels, fermentation workshops, composting areas, sludge areas, or temporary garbage storage areas.

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