A denitrification catalyst applied to aquaculture water body and a preparation method thereof

Abstract

This invention belongs to the field of catalyst technology, specifically providing a denitrification catalyst for aquaculture water and its preparation method. The denitrification catalyst comprises a modified functional carrier and a supported active component. The active component, by mass percentage, comprises: Pd 1-1.5% and Cu 0.5-1%. The denitrification catalyst of this invention exhibits excellent application efficiency in aquaculture water purification, with highly efficient and stable catalytic action, and can effectively cope with high load shocks.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a denitrification catalyst for use in aquaculture water and its preparation method. Background Technology

[0002] Aquaculture, a crucial pillar of the global food supply chain, has seen its intensive and large-scale development meet the ever-increasing demand for protein and create enormous economic value. However, this has also triggered a series of severe ecological and environmental challenges, with eutrophication being particularly prominent. Aquaculture systems, especially high-density recirculating aquaculture systems or pond aquaculture, constitute highly intensive artificial ecosystems. Large quantities of formulated feed are not fully absorbed and utilized by farmed organisms; a significant portion enters the water as uneaten feed, feces, and excrement from fish gills and body mucus. These organic wastes, rich in protein, nitrogen, and phosphorus, undergo complex biochemical decomposition by microorganisms, first converting into highly toxic ammonia nitrogen, which is then converted into nitrite by nitrifying bacteria. Even at low concentrations, ammonia nitrogen and nitrite can have strong physiological toxicity to aquatic organisms such as fish, shrimp, and shellfish. Ammonia nitrogen can damage the gill tissue structure and function of aquatic organisms, interfere with their osmotic pressure regulation and respiration, and damage the nervous system; nitrite can quickly enter the bloodstream, oxidize hemoglobin into methemoglobin that cannot carry oxygen, leading to tissue hypoxia and causing "halothemia". The continuous accumulation of ammonia nitrogen and nitrite, once the concentration exceeds the critical threshold, can easily trigger large-scale acute poisoning and death events. This not only directly threatens the success or failure of a single aquaculture cycle but also constitutes a core bottleneck for the sustainable development of the industry as a whole. Traditional methods that rely on large-scale water exchange to dilute pollutants are not only extremely wasteful of water resources but also transfer pollution to the external environment, making them unsustainable. Developing efficient, stable, and environmentally friendly water denitrification and purification technologies to achieve the harmless transformation and removal of nitrogen pollutants within aquaculture systems has become a key technical challenge that urgently needs to be addressed to promote the transformation and upgrading of aquaculture towards a green, circular, and low-carbon model.

[0003] Currently, the main methods for treating nitrogen compounds in wastewater include physicochemical methods, biological denitrification methods, and catalytic reduction methods. Physicochemical methods mainly include processes such as ion exchange, reverse osmosis, electrodialysis, and distillation. Their commonality lies in separating nitrates from water and concentrating them in a specific medium or concentrate through physical or chemical means, without achieving complete degradation of the pollutants. These methods are not only costly to operate, but also essentially only transfer or concentrate nitrates, failing to fundamentally solve the pollution problem. Biological denitrification technology mainly relies on the biochemical action of microorganisms, typically including two stages: nitrification and denitrification. Nitrification converts ammonium nitrogen into nitrates under aerobic conditions, while denitrification, in anoxic or anaerobic environments, involves denitrifying bacteria using nitrate ions as electron acceptors to gradually reduce them to nitrogen gas, which is then released into the atmosphere, thus achieving complete nitrogen removal. Chemical catalytic reduction denitrification uses substances such as hydrogen and formic acid as reducing agents, and under the action of a suitable catalyst, directly reduces nitrates in water to nitrogen gas. This method boasts a rapid reaction rate and catalytic activity approximately 30 times higher than biological denitrification, demonstrating a significant efficiency advantage. The core of this process lies in developing high-performance catalysts that simultaneously possess high catalytic activity and high selectivity to ensure efficient and targeted nitrogen production and minimize the accumulation of harmful intermediate byproducts.

[0004] Chinese invention patent CN102458652B discloses a bimetallic Pd-Cu nanocatalyst supported on activated carbon cloth. The nanocatalyst comprises approximately 1% by weight Pd and approximately 0.35-0.45% by weight Cu, and has a molecular weight of approximately 8-10 μm. 2 / m 2 The surface Cu / Pd metal ratio is high; this nanocatalyst can remove nitrates and / or nitrites from wastewater with high selectivity for nitrogen. However, the nanocatalyst has low dispersion, resulting in poor activity, with a maximum of only 77.6%, and the activated carbon cloth loading makes it difficult to ensure the binding stability of the active component with the support, which is not conducive to application. Summary of the Invention To address the existing technical problems, the present invention aims to provide a denitrification catalyst for aquaculture water and its preparation method. The denitrification catalyst of the present invention exhibits excellent application efficiency in aquaculture water purification, with highly efficient and stable catalytic action, and can effectively cope with high load shocks.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a denitrification catalyst for use in aquaculture water bodies. The denitrification catalyst is prepared by comprising a modified functional carrier and a supported active component. The active component has the following content in the denitrification catalyst by mass percentage: Pd 1-1.5%, Cu 0.5-1%. A second aspect of this invention provides a method for preparing a denitrification catalyst for use in aquaculture water, comprising the following steps: S1: Styrene, 1,2-divinylbenzene, 4-vinylpyridine, initiator and porogen are mixed to obtain a first mixture; S2: Mix gelatin and water, heat to 52-55℃ and stir until the mixture is homogeneous to obtain the second mixture; S3: Mix the first mixture from step S1 and the second mixture from step S2, heat to 70-75℃ with stirring, react for 3-6 hours, continue heating to 85-90℃, react for 6-7 hours with stirring, filter, wash and purify to obtain the modified functional carrier. S4: The modified functional carrier from step S3 is immersed in the active liquid, the pH is adjusted to 5-7, and the mixture is shaken at 25-30℃ for 12-24 hours. After filtration and washing, the catalyst precursor is obtained. S5: Dry the catalyst precursor from step S4, treat it at 200-300℃ for 2-4 hours under an inert atmosphere, and then cool it to obtain the denitrification catalyst.

[0006] In some embodiments of the present invention, in step S1, the mass ratio of styrene, 1,2-divinylbenzene, and 4-vinylpyridine is 1:(0.18-0.3):(0.06-0.15).

[0007] Preferably, in step S1, the initiator is benzoyl peroxide, and the amount added is 0.5-2% of the total mass of styrene, 1,2-divinylbenzene, and 4-vinylpyridine.

[0008] In some embodiments of the present invention, in step S1, the pore-forming agent is one or more of toluene, n-heptane, and liquid paraffin, and the amount added is 1-1.5 times the total mass of styrene, 1,2-divinylbenzene, and 4-vinylpyridine.

[0009] In some embodiments of the present invention, in step S3, the dispersant is gelatin, and the mass ratio of the gelatin to styrene is (2-3):1.

[0010] Preferably, in step S3, the purification is performed by reflux extraction with ethanol in a Soxhlet extractor for 24-48 hours, followed by drying.

[0011] In some embodiments of the present invention, in step S4, the active liquid is an aqueous solution of metal Pd salt and metal Cu salt in ethanol.

[0012] Preferably, in step S4, the preparation steps of the active solution are as follows: add metal Pd salt and metal Cu salt to an aqueous ethanol solution to obtain the active solution.

[0013] In some embodiments of the present invention, in step S4, the metal Pd salt is PdCl2, and its concentration in the active liquid is 2-3 wt%.

[0014] In some embodiments of the present invention, in step S4, the metal Cu salt is Cu(NO3)2, and the concentration in the active liquid is 3-5 wt%.

[0015] Preferably, in step S4, the concentration of the ethanol aqueous solution is 20-30 wt%.

[0016] In some embodiments of the present invention, in step S4, the ratio of the modified functional carrier to the active liquid is 1g:0.8-1.1mL.

[0017] In some embodiments of the present invention, in step S5, the catalyst precursor of step S4 is freeze-dried, treated at 200-300°C for 2-4 hours at 2-5°C / min under an inert atmosphere, and then cooled to room temperature to obtain the denitrification catalyst.

[0018] Existing denitrification catalysts often employ low loading or complex processes to achieve high dispersion, but these result in weak binding forces and easy loss. Conversely, high loading is frequently used to improve binding forces, but this leads to the problem of active component agglomeration and deactivation. Therefore, this invention selects a resin support for modification, introducing strong coordination sites that firmly bind with the active components. Under the preparation method of this invention, each anchor site becomes an independently distributed entity, thereby limiting the growth and migration of the active components and achieving a balance between binding stability and catalytic activity.

[0019] Meanwhile, the applicant also discovered that the high uniformity of the macroporous structure and the interconnected channels of the resin carrier not only provide channels for high-flow-rate mass transfer, but also make it easier for suspended solids and organic colloids in the water to pass through, and less likely to clog inside, thus maintaining the application effect and stability of the denitrification catalyst. On the other hand, the presence of pyridine groups on the resin carrier may also play a certain role in inhibiting bacteria, thereby reducing the adhesion of microorganisms in the water to the catalyst surface, which is beneficial for coping with complex water bodies and high load impacts.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The denitrification catalyst of the present invention has excellent application efficiency in the purification of aquaculture water, and its catalytic effect is highly efficient and stable, and it can effectively cope with high load shocks.

[0021] 2. This invention further modifies the carrier resin of the denitrification catalyst, increasing the dispersibility of the active components while ensuring their binding force on the carrier resin, thereby exerting a highly efficient and stable denitrification catalytic effect. It has excellent application efficiency in in-situ purification systems for aquaculture water and can effectively cope with high load shocks. Detailed Implementation

[0022] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the invention, but rather as a more detailed description of certain aspects, features, and embodiments of the invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in the invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0024] To facilitate implementation of this invention by those skilled in the art, the sources of some raw materials in the specific embodiments are described below: Gelatin was purchased from Henan Mingang Food Ingredients Co., Ltd.; liquid paraffin was purchased from Shaanxi Panlong Yihai Pharmaceutical Co., Ltd. Other raw materials, unless otherwise specified, can be purchased from the market.

[0025] Unless otherwise specified, the post-processing steps such as "freeze-drying", "filtration", and "washing" mentioned in the following specific embodiments are routine operations for those skilled in the art, and can be selected according to actual operation.

[0026] Preparation Example 1 The preparation steps of the active solution are as follows: PdCl2 and Cu(NO3)2 are added to a 25wt% ethanol aqueous solution to obtain the active solution; The concentration of PdCl2 in the active solution is 2.5 wt%, and the concentration of Cu(NO3)2 in the active solution is 4 wt%.

[0027] Preparation Example 2 The preparation steps of the active liquid in this preparation example are the same as those in Preparation Example 1, except that the concentration of PdCl2 in the active liquid is 3.5 wt%.

[0028] Preparation Example 3 The preparation steps of the active liquid in this preparation example are the same as those in Preparation Example 1, except that the concentration of Cu(NO3)2 in the active liquid is 5.5 wt%.

[0029] Example 1 A denitrification catalyst for use in aquaculture water bodies comprises a modified functional carrier and supported active components, wherein the active components are Pd and Cu.

[0030] The method for preparing the denitrification catalyst for aquaculture water in this embodiment includes the following steps: S1: Mix 50g styrene, 10g 1,2-divinylbenzene, 6g 4-vinylpyridine, 1g benzoyl peroxide and 82.5g liquid paraffin to obtain the first mixture; S2: Mix gelatin with three times its volume of water, heat to 54°C and stir until the mixture is homogeneous to obtain the second mixture; S3: Mix all of the first mixture from step S1 with the second mixture from step S2 containing 125g of gelatin, heat to 72°C with stirring, react for 5 hours, continue heating to 88°C, react for 6.5 hours with stirring, filter, wash alternately with deionized water and ethanol, reflux extract with ethanol in a Soxhlet extractor for 36 hours, and then dry to obtain the modified functional carrier. S4: The modified functional carrier from step S3 was immersed in the active liquid at a ratio of 1g:1mL, the pH was adjusted to 5.5, and the mixture was shaken at 28℃ for 20h. After filtration and washing with deionized water, the catalyst precursor was obtained. S5: The catalyst precursor from step S4 is freeze-dried, treated at 250°C for 3 hours at 4°C / min under a nitrogen atmosphere, and then cooled to 25°C to obtain the denitrification catalyst.

[0031] The active liquid used in step S4 was obtained from preparation example 1.

[0032] According to the test, the content of each active component in the denitrification catalyst prepared in this embodiment, by mass percentage, is: Pd 1.2%, Cu 0.8%.

[0033] Example 2 A denitrification catalyst for use in aquaculture water bodies comprises a modified functional carrier and supported active components, wherein the active components are Pd and Cu.

[0034] The method for preparing the denitrification catalyst for aquaculture water in this embodiment includes the following steps: S1: Mix 50g styrene, 9g 1,2-divinylbenzene, 3g 4-vinylpyridine, 0.9g benzoyl peroxide and 74.4g liquid paraffin to obtain the first mixture; S2: Mix gelatin with three times its volume of water, heat to 54°C and stir until the mixture is homogeneous to obtain the second mixture; S3: Mix all of the first mixture from step S1 with the second mixture from step S2 containing 125g of gelatin, heat to 72°C with stirring, react for 5 hours, continue heating to 88°C, react for 6.5 hours with stirring, filter, wash alternately with deionized water and ethanol, reflux extract with ethanol in a Soxhlet extractor for 36 hours, and then dry to obtain the modified functional carrier. S4: The modified functional carrier from step S3 was immersed in the active liquid at a ratio of 1g:0.8mL, the pH was adjusted to 5.5, and the mixture was shaken at 28℃ for 20h. After filtration and washing with deionized water, the catalyst precursor was obtained. S5: The catalyst precursor from step S4 is freeze-dried, treated at 250°C for 3 hours at 4°C / min under a nitrogen atmosphere, and then cooled to 25°C to obtain the denitrification catalyst.

[0035] The active liquid used in step S4 was obtained from preparation example 1.

[0036] According to the test, the content of each active component in the denitrification catalyst prepared in this embodiment, by mass percentage, is: Pd 1%, Cu 0.5%.

[0037] Example 3 A denitrification catalyst for use in aquaculture water bodies comprises a modified functional carrier and supported active components, wherein the active components are Pd and Cu.

[0038] The method for preparing the denitrification catalyst for aquaculture water in this embodiment includes the following steps: S1: Mix 50g styrene, 15g 1,2-divinylbenzene, 7.5g 4-vinylpyridine, 1.1g benzoyl peroxide and 87g liquid paraffin to obtain the first mixture; S2: Mix gelatin with three times its volume of water, heat to 54°C and stir until the mixture is homogeneous to obtain the second mixture; S3: Mix all of the first mixture from step S1 with the second mixture from step S2 containing 125g of gelatin, heat to 72°C with stirring, react for 5 hours, continue heating to 88°C, react for 6.5 hours with stirring, filter, wash alternately with deionized water and ethanol, reflux extract with ethanol in a Soxhlet extractor for 36 hours, and then dry to obtain the modified functional carrier. S4: The modified functional carrier from step S3 was immersed in the active liquid at a ratio of 1g:1.1mL, the pH was adjusted to 5.5, and the mixture was shaken at 28℃ for 20h. After filtration and washing with deionized water, the catalyst precursor was obtained. S5: The catalyst precursor from step S4 is freeze-dried, treated at 250°C for 3 hours at 4°C / min under a nitrogen atmosphere, and then cooled to 25°C to obtain the denitrification catalyst.

[0039] The active liquid used in step S4 was obtained from preparation example 1.

[0040] According to the test, the content of each active component in the denitrification catalyst prepared in this embodiment, by mass percentage, is: Pd 1.5%, Cu 1%.

[0041] Example 4 A denitrification catalyst for aquaculture water and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the active liquid used in step S4 of this example is obtained from preparation example 2.

[0042] Example 5 A denitrification catalyst for aquaculture water and its preparation method are described. The specific implementation method is the same as that in Example 1, except that the active liquid used in step S4 of this example is obtained from preparation example 3.

[0043] Example 6 A denitrification catalyst for aquaculture water and its preparation method are described. The specific implementation method is the same as that in Example 1, except that the ratio of modified functional carrier to active liquid in step S4 of this example is 1g:1.2mL.

[0044] Example 7 A denitrification catalyst for aquaculture water and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the amount of 4-vinylpyridine added in step S1 of this example is 9g.

[0045] Comparative Example 1 A denitrification catalyst for aquaculture water and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the modified functional carrier is replaced in an equal amount with commercially available macroporous polystyrene resin (model AB-8 resin).

[0046] Performance testing: The denitrification catalysts prepared in Examples 1-7 and Comparative Example 1 were applied to simulated aquaculture wastewater with a nitrate nitrogen concentration of 100 mg / L and a pH of 7.2. The main operating conditions were: H2 flow rate of 50 mL / min, pH adjusted to 6.0, reactor volume of 100 mL, denitrification catalyst dosage of 0.15 g, and reaction time of 60 min. The nitrate nitrogen removal rate, the nitrate nitrogen removal rate after five repetitions, and nitrogen selectivity were calculated.

[0047] Table 1 As shown in Table 1, the denitrification catalysts prepared in Examples 1-3 exhibit efficient and stable catalytic activity.

[0048] Compared to Example 1, Examples 4 and 5 changed the loading amounts of Pd and Cu, respectively. The former may have inhibited the reducing ability of Cu, leading to ammonia nitrogen accumulation, significantly reduced nitrogen selectivity, and decreased stability; while the latter may have partially covered or isolated the active sites of Pd, resulting in a decrease in catalytic denitrification efficiency. Compared to Example 1, Example 6 changed the impregnation ratio of the modified functional support and the active liquid, affecting the performance of the denitrification catalyst to varying degrees. In particular, the loose external particles were easily lost during operation, leading to a significant decrease in stability. Compared to Example 1, Example 7 changed the amount of 4-vinylpyridine added during the preparation of the denitrification catalyst. Although this improved the removal rate, it negatively impacted nitrogen selectivity and caused a slight decrease in stability. Comparative Example 1, compared to Example 1, replaced the modified functional support of the present invention with an equal amount of commercially available macroporous polystyrene resin. This may have resulted in a lack of directional anchoring points, poor metal dispersion, and easy loss, leading to insufficient activity and stability of the denitrification catalyst and a decrease in catalytic denitrification efficiency.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application in any way. Although the present application discloses the preferred embodiment as described above, it is not intended to limit the present application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A denitrification catalyst for use in aquaculture water, characterized in that, The denitrification catalyst is prepared by comprising a modified functional support and a supported active component, wherein the active component comprises, by mass percentage, Pd 1-1.5% and Cu 0.5-1%.

2. A method for preparing the denitrification catalyst as described in claim 1 for use in aquaculture water, characterized in that, Includes the following steps: S1: Styrene, 1,2-divinylbenzene, 4-vinylpyridine, initiator and porogen are mixed to obtain a first mixture; S2: Mix the dispersant and water, heat to 52-55℃ and stir until the mixture is homogeneous to obtain the second mixture; S3: Mix the first mixture from step S1 and the second mixture from step S2, heat to 70-75℃ with stirring, react for 3-6 hours, continue heating to 85-90℃, react for 6-7 hours with stirring, filter, wash and purify to obtain the modified functional carrier. S4: The modified functional carrier from step S3 is immersed in the active liquid, the pH is adjusted to 5-7, and the mixture is shaken at 25-30℃ for 12-24 hours. After filtration and washing, the catalyst precursor is obtained. S5: Dry the catalyst precursor from step S4, treat it at 200-300℃ for 2-4 hours under an inert atmosphere, and then cool it to obtain the denitrification catalyst.

3. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 2, characterized in that, In step S1, the mass ratio of styrene, 1,2-divinylbenzene, and 4-vinylpyridine is 1:(0.18-0.3):(0.06-0.15).

4. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 2, characterized in that, In step S1, the pore-forming agent is one or more of toluene, n-heptane, and liquid paraffin, and the amount added is 1-1.5 times the total mass of styrene, 1,2-divinylbenzene, and 4-vinylpyridine.

5. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 2, characterized in that, In step S3, the dispersant is gelatin, and the mass ratio of gelatin to styrene is (2-3):

1.

6. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 2, characterized in that, In step S4, the active solution is an aqueous solution of metal Pd salt and metal Cu salt in ethanol.

7. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 6, characterized in that, In step S4, the metal Pd salt is PdCl2, and its concentration in the active solution is 2-3 wt%.

8. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 6, characterized in that, In step S4, the metal Cu salt is Cu(NO3)2, and its concentration in the active solution is 3-5 wt%.

9. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 6, characterized in that, In step S4, the ratio of the modified functional carrier to the active liquid is 1g:0.8-1.1mL.

10. The method for preparing a denitrification catalyst for aquaculture water bodies according to claim 2, characterized in that, In step S5, the catalyst precursor from step S4 is freeze-dried, treated at 200-300℃ for 2-4 hours under an inert atmosphere at a rate of 2-5℃ / min, and then cooled to room temperature to obtain the denitrification catalyst.

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