NFMat-Al2O3 ozone catalytic material and method for deeply treating aquaculture wastewater by using NFMat-Al2O3 ozone catalytic material

Abstract

According to the method, aluminum oxide serves as a carrier, iron and manganese oxides serve as active components, ammonium nitrate serves as a modification auxiliary agent, the NFMat-Al2O3 ozone catalytic material is obtained through a dipping-calcining method, the NFMat-Al2O3 ozone catalytic material is used for deep treatment of carbon and phosphorus residues in breeding wastewater, the removal rates of COD and TP are up to 86.15% and 95.98% respectively, the treated breeding wastewater reaches the livestock and poultry breeding emission standard, and the method is suitable for industrial production. Meanwhile, the phosphate adsorbed and recovered by the NFM-coated gamma-Al2O3 ozone catalyst can also be used for producing a phosphate fertilizer, so that the dependence on natural phosphorite mining is reduced, and the related environmental influence is reduced. And the income generated by phosphorus recovery can further counteract the wastewater treatment cost. Generally speaking, the invention provides a sustainable and cost-effective solution, which not only conforms to the environmental protection goal, but also conforms to the resource utilization goal.

Description

Technical Field

[0001] The present invention relates to an NFM@Al 2 O 3 ozone catalytic material and a method for the advanced treatment of aquaculture wastewater, belonging to the technical field of sewage treatment. Background Art

[0002] In the past decade, the significant expansion of large-scale pig farms in China has led to the annual generation of approximately 160 million tons of pig farm wastewater. Approximately 90% of the pig farm wastewater is treated by anaerobic digestion, accompanied by the generation of a large amount of biogas slurry while obtaining energy. However, the limited land resources in the southern region restrict the effective utilization of the nutrient-rich biogas slurry, usually exceeding the agricultural absorption capacity of the region and breaking the ecological balance between the planting and breeding industries. Traditional biogas slurry treatment methods mainly rely on biological and physicochemical methods. Among them, the biological method can achieve a removal rate of more than 85% of chemical oxygen demand (COD) and total phosphorus (TP) in pig farm wastewater, but incomplete biodegradation still leaves a large amount of complex organic substances in the secondary biochemical effluent of pig farms, resulting in the COD and TP concentrations often unable to stably meet the discharge standards of ≤400 mg / L and ≤8.0 mg / L. The Second National Pollution Source Census Bulletin shows that livestock and poultry breeding wastewater contains 6.0483 million tons of COD and 0.0804 million tons of TP, accounting for 60.45% and 67.17% of the total COD and TP emissions of water pollutants, respectively. Therefore, it is crucial to develop a cost-effective method that can efficiently remove carbon and phosphorus residues, especially for pig farms that need to comply with China's strict wastewater discharge standards.

[0003] Phosphorus in water is divided into inorganic phosphorus (IP) and organic phosphorus (OP). IP mainly exists in the form of phosphates, including orthophosphate (PO 4 3- ), hydrogen phosphate (HPO 4 2- ), and dihydrogen phosphate (H 2 PO 4 - ), while OP consists of various organic compounds. Under specific conditions, these forms can be converted into each other. Phosphorus removal methods mainly include biological, chemical, and physical methods, such as adsorption, chemical precipitation, aerobic granular sludge, and ion exchange, all of which show effective removal effects. Among them, the adsorption method is particularly favored due to its simple operation and flexible design. Zou et al. ( J. Zou, H. Zhang, K. Zheng, J. Li, Pilot-scale phosphorus recovery from biogas slurry to produce battery-grade FePO 4 : Chemical enhanced primary treatment coupled adsorption process, Separation and Purification Technology 348 (2024) 127677 ) reported that at a pH value of 8.0, chemically enhanced pretreatment with Fe-NH 2-Combined with PAN adsorption, it can continuously achieve a phosphorus removal efficiency of over 80%. The phosphorus removal mechanism involves Fe 3+ and PO 4 3- forming a complex. Li et al. ( M. Li, S. Fu, Y. Han, J. Zheng, C. Wang, X. Xu, L. Zhu, Synergistic removal of carbon and phosphorus by modified carbon-based magnetic materials, Chemical Engineering Journal 491 (2024) 151244 ) synthesized acid-modified and magnetic-doped biochar (A / M-BC) and used it to remove COD and TP in the pipe network water of urban sewage treatment plants, achieving removal efficiencies of 64.4% and 93.7% respectively. The research shows that although phosphate ions can form discrete compounds with metal ions such as iron (Fe), aluminum (Al), and calcium (Ca), the mainly removed phosphorus species is adsorbed PO 4 3- . In most wastewaters, PO 4 3- is usually considered the main phosphorus species, while in pig farm wastewater, OP is the main form. In addition, the OP in the secondary biochemical effluent of pig farms shows complex composition and high COD concentration and is difficult to degrade. Therefore, the above treatment methods are difficult to efficiently remove COD and TP simultaneously.

[0004] The catalytic ozonation process enhances the oxidation of refractory organic pollutants by using solid catalysts, has significant advantages, and will not have an adverse impact on water quality. This method can generate high concentrations of reactive oxygen species (ROS), including hydroxyl radicals (·OH), superoxide radicals (·O 2 - ) and singlet oxygen ( 1 O 2 ), and these ROS can effectively degrade organic pollutants into water, carbon dioxide, and inorganic salts. The IP transformed from OP can be removed by adsorption, precipitation, and / or forming a complex with the catalyst. The prior art uses calcium oxide as a catalyst and precipitant to treat organic phosphorus compounds in wastewater by catalytic ozonation. The research shows that calcium oxide can effectively remove COD and TP. However, the excess Ca 2+ in the solution needs to introduce carbon dioxide for removal, which poses a risk of secondary pollution. Therefore, choosing a suitable catalyst is crucial for optimizing the efficiency and sustainability of the catalytic ozonation system. Summary of the Invention The purpose of the present invention is to provide a method for advanced treatment of breeding wastewater to solve the above problems existing in the prior art.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows: A preparation method of an NFM@Al 2 O 3 ozone catalytic material, which includes the following steps: Pre-treat Al 2 O 3 to increase the surface roughness; Dissolve ferric nitrate and manganese nitrate in an ammonium nitrate solution to obtain a precursor solution; Place the pre-treated Al 2 O 3 in the precursor solution and impregnate for at least 12 h, then take it out, dry at 100 - 110 °C, and then calcine at 400 - 600 °C for at least 4 h to obtain the NFM@Al 2 O 3 ozone catalytic material.

[0007] As a preferred embodiment, the pre-treatment method of the Al 2 O 3 is as follows: Completely immerse Al 2 O 3 in a citric acid solution for at least 1 h, and then dry to constant weight at 70 - 90 °C.

[0008] As a preferred embodiment, the crystal form of the alumina is γ-type.

[0009] As a preferred embodiment, the molar ratio of ferric nitrate to manganese nitrate is (1 - 4):(4 - 1).

[0010] As a preferred embodiment, the molar ratio of ferric nitrate to manganese nitrate is 3:1.

[0011] As a preferred embodiment, the heating rate of the calcination is 5 - 15 °C / min.

[0012] An NFM@Al 2 O 3 ozone catalytic material obtained by the aforementioned preparation method.

[0013] An NFM@Al 2 O 3 ozone catalytic material as described above for use in the advanced treatment of aquaculture wastewater.

[0014] An advanced treatment method for aquaculture wastewater, comprising the following steps: S1. Wet the aforementioned NFM@Al 2 O 3 ozone catalytic material with deionized water for 12 h, then drain it and fill it into an ozone reactor; S2. Pass the secondary biochemical effluent of aquaculture wastewater into the ozone reactor, then start an ozone generator to pass in O 3 , and take a sample for detection after the reaction.

[0015] As an optimal solution, the pH value of the secondary biochemical effluent is 8-9, and the filling rate of the NFM@Al 2 O 3 ozone catalytic material in the ozone reactor is 20 v / v%, the ozone concentration is 100 mg / L, and the reflux ratio is 100:1.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Ingeniously using iron element, which is environmentally friendly, rich in the earth's reserves, and has strong complexing ability for phosphate radicals, and manganese element, which has strong catalytic activity for ozone, as active components. The co-loading of iron and manganese elements significantly reduces the risk of active component loss. It can not only efficiently remove carbon and phosphorus residues in the secondary biochemical effluent of pig farms, protect the ecological environment, and promote the sustainable and healthy development of the livestock and poultry breeding industry, but also avoid secondary pollution to the environment caused by metal leaching.

[0017] 2. Using ammonium nitrate and Fe(NO 3 ) 3 and Mn(NO 3 ) 2 for co-impregnation promotes the generation of oxygen vacancies (Ov) and surface hydroxyl groups. As a modification auxiliary agent, ammonium nitrate enters the surface and internal pores of the γ-Al 2 O 3 carrier together with the iron and manganese active components during the impregnation process. Then, during the calcination process, ammonium nitrate decomposes at high temperature and releases a large amount of heat. Due to the "popcorn effect", the particles formed by the iron and manganese active components are smaller and more dispersed, increasing the concentration of Ov. At the same time, the iron and manganese active components located at Ov dissociate the adsorbed water to generate hydrogen protons and hydroxide ions. The hydroxide ions combine with NFM@γ-Al 2 O 3 to form NFM@γ-Al 2 O 3 -OH, promoting the generation of surface hydroxyl groups. The surface hydroxyl groups located at the Fe active sites combine with phosphate radicals through ligand exchange to form iron phosphate complexes. The synergistic effect of Ov and surface hydroxyl groups promotes the efficient removal of carbon and phosphorus residues in the secondary biochemical wastewater of pig farms.

[0018] 3. The phosphate recovered by complexation of NFM@γ-Al 2 O 3 can be used for the production of phosphate fertilizers, reducing the dependence on the exploitation of natural phosphate rocks and mitigating the related environmental impacts. The income generated from phosphorus recovery can further offset the wastewater treatment cost. At the same time, the service life of NFM@γ-Al 2 O 3 is up to 5 years, with significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings: Figure 1 It is a schematic diagram of a deep treatment process device for breeding wastewater; Figure 2 It is the NFM@γ-Al prepared in Examples 1-7 2 O 3 Comparison of the removal rates of COD and TP after treating the secondary biochemical effluent from a pig farm with an ozone catalytic material (effect of the iron / manganese molar ratio on the removal rates of COD and TP); Figure 3 It is a comparison of the COD removal effects after treating the secondary biochemical effluent from a pig farm in Comparative Examples 1-5; Figure 4 It is a comparison of the TP removal effects after treating the secondary biochemical effluent from a pig farm in Comparative Examples 1-5; Figure 5 It is the growth inhibition rate of Escherichia coli by carbon and phosphorus residues and their degradation products; Figure 6 It is the NFM@γ-Al prepared in Example 1 2 O 3 Sustainability of the catalyst; Figure 7 It is the NFM@γ-Al prepared in Example 1 2 O 3 Leaching amounts of Fe and Mn in it. Detailed implementation manners

[0020] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0021] Example 1 This example relates to a preparation method of an NFM@γ-Al 2 O 3 ozone catalytic material, which specifically includes the following steps: Pre-treat γ-Al 2 O 3 Specifically, completely immerse γ-Al 2 O 3 in a 0.5 mol / L citric acid solution for 1 hour, then wash it to neutral, and dry it at 80°C to constant weight. This can promote surface etching, increase surface roughness, and increase the Ov concentration; Put 1 kg of pre-treated γ-Al 2 O3 In a precursor solution composed of 2.5 L of 0.003 mol / L Fe(NO 3 ) 3 , 0.001 mol / L Mn(NO 3 ) 2 and 0.04 mol / L ammonium nitrate, after impregnation for 12 hours, take out, dry at 105 °C for 2 hours, then heat to 500 °C at a rate of 10 °C / min, calcine for 4 h, and finally after cooling, washing, separating and drying, obtain the NFM@γ-Al 2 O 3 ozone catalytic material.

[0022] Example 2 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 1:1.

[0023] Example 3 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 1:2.

[0024] Example 4 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 2:1.

[0025] Example 5 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 1:3.

[0026] Example 6 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 1:4.

[0027] Example 7 The difference between this example and Example 1 is only that the molar ratio of iron ions to manganese ions is 4:1.

[0028] Comparative Example 1 The difference between this comparative example and Example 1 is only that ammonium nitrate was not added during the preparation process, and the product is denoted as FM@γ-Al 2 O 3 .

[0029] Comparative Example 2 The difference between this comparative example and Example 1 is only that manganese nitrate was not added during the preparation process, and the product is denoted as NF@γ-Al 2 O 3 .

[0030] Comparative Example 3 The difference between this comparative example and Example 1 is only that iron nitrate was not added during the preparation process, and the product is denoted as NM@γ-Al 2O 3 。

[0031] Comparative Example 4 The difference between this comparative example and Example 1 is only that α-Al 2 O 3 is used to replace γ-Al 2 O 3 , and the product is denoted as NFM@α-Al 2 O 3 。

[0032] Comparative Example 5 The difference between this comparative example and Example 1 is only that β-Al 2 O 3 is used to replace γ-Al 2 O 3 , and the product is denoted as NFM@β-Al 2 O 3 。

[0033] The structure of the advanced treatment process device for aquaculture wastewater adopted in the present invention is as Figure 1 shown: The oxygen tank 1 and the ozone generator 2 are connected to the bottom of the ozone reactor 5 through pipelines. A flow meter 3 and an ozone concentration analyzer 4 are provided between the ozone generator 2 and the ozone reactor 5. An aeration head 6 and an ozone catalyst 8 (i.e., the NFM@γ-Al 2 O 3 ozone catalytic material prepared in Example 1) are arranged in the ozone reactor 5. The ozone destructor 11 and the KI absorption liquid 12 are connected to the top of the ozone reaction column 5. The secondary biochemical effluent of aquaculture wastewater is introduced into the ozone reactor 5 from the inlet 9 through a peristaltic pump, and then the peristaltic pump is changed to a circulation pump 7. The treated aquaculture wastewater is discharged from the outlet 10 to the storage tank 13.

[0034] The advanced treatment method for aquaculture wastewater is as follows: Step a: Add NFM@γ-Al 2 O 3 ozone catalytic material (adopting the "wet sample addition" method, soaked in deionized water for 12 h and then drained before use) into the ozone reactor (made of plexiglass), and the filling rate is 20 v / v%; Step b: Introduce the secondary biochemical effluent of aquaculture wastewater (pH value is 8.17) into the ozone reactor from the inlet through a peristaltic pump, and then start the ozone generator to introduce O 3 , keep the concentration of O 3 at 100 mg / L, the reflux ratio is 100:1, and samples are taken for detection after reacting for a certain time (react for 60 min, and samples are taken for detection every 10 min).

[0035] Step c: Conduct repeated performance evaluation under the optimal process conditions.

[0036] Table 1 O 3 / NFM@γ-Al 2 O 3 Water quality indicators in the secondary biochemical effluent of pig farms before and after treatment

[0037] From Figure 2 、 3 and 4, it can be seen that the performance of γ-Al 2 O 3 used as a catalyst support is superior to that of β-Al 2 O 3 and α-Al 2 O 3 , and the introduction of ammonium nitrate improves the removal rates of COD and TP. This is because the high-temperature decomposition of ammonium nitrate releases a large amount of heat, and due to the "popcorn effect", smaller iron and manganese active component particles are dispersed on the surface and pores of the catalyst, increasing the Ov concentration, thereby improving the catalytic activity and efficiency. When the molar ratio of Fe(NO 3 ) 3 ·9H 2 O to Mn(NO 3 ) 2 ·4H 2 O is 3:1, the removal rates of COD and TP are the highest, reaching 86.15% and 95.98% respectively. After catalytic ozonation treatment with NFM@γ-Al 2 O 3 , the COD and TP concentrations of the aquaculture wastewater are reduced to below 109.81 mg / L and 7.49 mg / L respectively (as shown in Table 1), and other key water quality indicators, including BOD 5 , TOC, NH 3 -N and Escherichia coli, all meet the discharge standards for livestock and poultry breeding sewage (GB 18596-2001). Among them, BOD 5 increases significantly, and the BOD 5 / COD ratio increases by an average of 136.5 times. According to the Escherichia coli growth test, the inhibition rate first rises and then drops sharply, and the toxicity of the secondary biochemical effluent of the aquaculture wastewater is almost negligible at the end of the reaction (as Figure 5 shown), indicating the effectiveness of the O 3 / NFM@γ-Al 2 O 3 process in the advanced treatment of the secondary biochemical effluent of aquaculture wastewater and its potential to meet strict discharge standards. The NFM@γ-Al 2 O 3 catalyst still shows excellent performance after twenty cycles, and the removal efficiencies of COD and TP exceed 76.26% and 87.35% respectively (asFigure 6 as shown). In addition, the leaching amounts of Fe and Mn are only 0.15 and 0.11 μg / L. Although the leaching amounts of Fe and Mn are the highest during the fifth cycle (as Figure 7 shown), their levels are still far lower than the allowable limits of the drinking water quality standards stipulated by the World Health Organization (Fe: 0.3 mg / L, Mn: 0.1 mg / L). In summary, the synergistic effect of Mn and Fe effectively prevents the leaching of Mn- and Fe-oxides during the catalytic ozonation process. The NFM@γ-Al 2 O 3 catalyst prepared by the present invention causes extremely little secondary pollution, highlighting its applicability in practical applications.

[0038] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A method for preparing NFM@Al2O3 ozone catalytic material, characterized in that: The steps include: Al2O3 is pre-treated to increase the surface roughness; dissolving iron nitrate and manganese nitrate in an ammonium nitrate solution to obtain a precursor solution; The pretreated Al2O3 is immersed in the precursor solution for at least 12 hours, taken out, dried at 100-110°C, and then calcined at 400-600°C for at least 4 hours to obtain the NFM@Al2O3 ozone catalytic material.

2. The method for preparing the NFM@Al2O3 ozone catalytic material according to claim 1, characterized in that: The pretreatment method of Al2O3 is: After Al2O3 was completely immersed in the citric acid solution for at least 1 h, it was dried at 70-90 °C to constant weight.

3. The method for preparing the NFM@Al2O3 ozone catalytic material according to claim 1 or 2, characterized in that: The crystal form of the aluminum oxide is γ-type.

4. The method for preparing the NFM@Al2O3 ozone catalytic material according to claim 1, characterized in that: The molar ratio of the iron nitrate to the manganese nitrate is (1-4): (4-1).

5. The method for preparing the NFM@Al2O3 ozone catalytic material according to claim 4, characterized in that: The molar ratio of the iron nitrate to the manganese nitrate is 3:

1.

6. The method for preparing the NFM@Al2O3 ozone catalytic material according to claim 1, characterized in that: The heating rate of the calcination is 5-15°C / min.

7. A NFM@Al2O3 ozone catalytic material obtained by the preparation method according to claim 1.

8. Use of the NFM@Al2O3 ozone catalytic material as claimed in claim 6 in deep treatment of aquaculture wastewater.

9. A method for deep treatment of aquaculture wastewater, characterized in that: The steps include: S1. Soak the NFM@Al2O3 ozone catalytic material according to claim 6 with deionized water for 12 hours, drain it, and fill it into an ozone reactor; S2. Pass the secondary biochemical effluent of aquaculture wastewater into the ozone reactor, then start the ozone generator and pass O3, and take samples for testing after the reaction.

10. The method for deep treatment of aquaculture wastewater according to claim 9, characterized in that: The pH value of the secondary biochemical effluent is 8-9, the filling rate of the NFM@Al2O3 ozone catalytic material in the ozone reactor is 20v / v%, the ozone concentration is controlled to be 100 mg / L, and the reflux ratio is 100:1.

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