Biological filter material with nitration system as well as preparation method and application of biological filter material

Abstract

The invention provides a biological filter material with a nitrification system and a preparation method and application thereof.The biological filter material comprises a hollow resin shell, the hollow resin shell is filled with one or more modified polyurethane foam blocks, and nitrifying bacteria are adsorbed on the surfaces of the modified polyurethane foam blocks; the material of the modified polyurethane foam block is carboxyl betaine methacrylate / polyethylene glycol modified polyurethane. The hydrophilicity and surface energy of the modified polyurethane carrier are improved, 'migration 'of nitrifying bacteria from water to the surface of the material is accelerated, and the initial adhesion time is greatly shortened. And films can be hung inside and outside the carrier, and are not limited to the surface, and the film hanging density and speed are simultaneously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of biological filter materials, and in particular to a biological filter material with a self-contained nitrification system, a preparation method thereof, and applications thereof. Background Art

[0002] In the aquarium ecosystem, the stable operation of the nitrification system is the core link to maintain healthy water quality. Nitrifying bacteria convert toxic ammonia (NH3) into nitrite (NO2 - ), and further converted into low-toxic nitrate (NO3 - ). Traditional aquarium filtration systems usually rely on biological filter media as the attachment carrier of nitrifying bacteria, and its performance directly affects nitrification efficiency and system stability.

[0003] The mainstream biological filter materials currently on the market include hard filter materials such as ceramic rings, glass cups, bacterial rings, and nanospheres. These biological filter materials lack inherent nitrification capabilities and rely primarily on microbial adsorption, resulting in long cycles, difficult attachment, and poor nitrification. Therefore, a biological filter material with excellent adhesion, short biofilm formation time, and strong nitrification capacity is urgently needed. Summary of the Invention

[0004] In view of this, the present invention proposes a biological filter material with a built-in nitrification system, a preparation method and an application thereof, which has the advantages of good adhesion effect, fast biofilm formation and strong nitrification ability.

[0005] The technical solution of the present invention is achieved as follows: In the first aspect, the present invention provides a biological filter material with a built-in nitrification system, wherein the biological filter material comprises a hollow resin shell, the interior of which is filled with one or more modified polyurethane foam blocks, nitrifying bacteria are adsorbed on the surface of the modified polyurethane foam blocks, and the material of the modified polyurethane foam blocks is carboxybetaine methacrylate / polyethylene glycol modified polyurethane.

[0006] On the basis of the above technical solution, preferably, the preparation method of the modified polyurethane comprises the following steps: S1, mixing polyether polyol, diethylene glycol, carboxybetaine methacrylate and polyethylene glycol, and then adding silicone foam stabilizer, water and triethylamine in sequence and stirring evenly to form a mixed solution A; S2, adding toluene diisocyanate to the mixed solution A, stirring evenly and then pouring into a foaming box for foaming. After the foam is foamed, the foam is taken out, aged and then cut to obtain a modified polyurethane foam.

[0007] Carboxybetaine methacrylate (CBMA) is a zwitterionic monomer, which has both positive (quaternary ammonium group) and negative (carboxyl group) groups. It can form a super-hydrophilic hydration layer on the surface of polyurethane, which can form ion-dipole and hydrogen bond with a large number of water molecules, greatly reducing the water contact angle. In addition, the zwitterionic structure of CBMA also helps to attract the negatively charged extracellular surface of microorganisms, making it easy to undergo preliminary adsorption and reducing the non-specific adsorption of other organic matter, protein and other garbage impurities (anti-pollution).

[0008] Polyethylene glycol (PEG) molecular backbone is rich in ether oxygen (–O–), which can easily form hydrogen bonds with water, greatly improving the surface and internal hydrophilicity of the material. PEG chain has good flexibility and can be uniformly distributed in the polyurethane network, further enhancing the hydrophilicity. The chain structure of PEG reduces the adsorption potential barrier of the surface, increases the surface lubricity and flexibility, and makes the probability of microorganisms "staying" on the surface rise. In addition, PEG can also endow the foam with higher deformation resistance and toughness, and improve the long-term underwater service life.

[0009] CBMA enhances selective hydrophilicity and anti-bacteria, and PEG provides structural wetting and space—both of which create an optimal microenvironment for nitrobacteria colonization. The hydrophilicity and surface energy of the modified polyurethane carrier are improved, which accelerates the "migration" of nitrobacteria from water to the surface of the material, greatly shortening the initial attachment time. Moreover, the carrier can be colonized inside and outside, not limited to the surface, and the colonization density and rate are improved at the same time. The anti-pollution effect of CBMA can reduce the occupation of carrier surface space by heterotrophic bacteria and adhesive organic matter, reserve space for nitrobacteria, improve the "purity" of early biofilm colonization, and improve the overall biofilm quality.

[0010] On the basis of the above technical scheme, preferably, the mass ratio of the polyether polyol, diethylene glycol, carboxybetaine methacrylate, polyethylene glycol, silicone foam stabilizer, water, triethylamine, and toluene diisocyanate is 100:5-15:8-12:5-8:1-2:2-5:0.1-0.5:55-65.

[0011] On the basis of the above technical scheme, preferably, the preparation method of the modified polyurethane further comprises the following steps: S3. Dissolve polyvinyl alcohol in deionized water, add boric acid after stirring to form a complex, and filter out particles with a 200-mesh filter screen; S4. Soak the modified polyurethane prepared in step S2 in the complex for 1-2 hours, take out the modified polyurethane after the end, drain, and dry in ventilation.

[0012] PVA itself is extremely hydrophilic, after deposition, the foam surface and cavity are covered with a layer of hydrophilic polymer film. After drying, the film can absorb water faster than the original hydrophilic foam, and can completely eliminate the possible hydrophobic "dead angle", further improving the hydrophilicity of the carrier.

[0013] After drying, the borate ester bond of polyvinyl alcohol (PVA)-boric acid complex forms a cross-linked network that can protect the internal foam structure, increase the mechanical strength of the coating, and reduce physical wear caused by water flow, extrusion or mechanical friction during long-term use. Cross-linked PVA coating also has certain anti-protein adsorption ability, reducing the blockage of foam pores by organic impurities, thereby prolonging the overall life of the filter material.

[0014] On the basis of the above technical scheme, preferably, the polyvinyl alcohol has a polymerization degree of 1000-2000 and an alcoholysis degree of 60%-99%, and is purchased from Guangzhou Suixin Chemical Co., Ltd.

[0015] On the basis of the above technical scheme, preferably, the mass ratio of polyvinyl alcohol, water and boric acid is 5:95:0.5-1.

[0016] On the basis of the above technical scheme, preferably, the European nitrosomonas is Nitrosomonas europaea SZG-AOB-003, deposited on December 29, 2023 at the China Center for Type Culture Collection (China. Wuhan. Wuhan University), with the preservation number CCTCC NO: M20232717, and the Vibrio nitroreducens is Nitrobacter winogradskyi SZG-NOB-002, deposited on June 12, 2023 at the China Center for Type Culture Collection (China. Wuhan. Wuhan University), with the preservation number CCTCC NO: M2023989.

[0017] In a second aspect, the application provides an application of a biological filter material with a nitrification system in water treatment. The modified polyurethane and nitrifying bacteria agent are put into the device, the culture medium is added, and the aeration device is turned on to make the biological filter material in a fluidized state, which is convenient for nitrifying bacteria to form a biofilm. After the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the biological filter material can be placed in an aquarium system for water treatment.

[0018] On the basis of the above technical scheme, preferably, the filling volume of the modified polyurethane is 25%-35% of the volume of the device, the dosage of the bacteria agent is 0.5%-1.5% of the volume of the culture medium, and the concentration of dissolved oxygen is 3-5 mg / L.

[0019] On the basis of the above technical solutions, preferably, the components of the culture medium include: NaNO2 0.1-1.2 g / L, KH2PO4 0.01-0.1 g / L, NaCl 0.1-1 g / L, NaHCO3 0.1-1 g / L, riboflavin 0.8-1.2 g / L, biotin 0.1-0.2 g / L, glycine 0.1-0.3 g / L, and the balance is water.

[0020] In a third aspect, the application provides a use of a biological filter material with a nitrification system in water treatment.

[0021] The biological filter material with a nitrification system and the use thereof have the following beneficial effects relative to the prior art: (1) The hydrophilicity and surface energy of the modified polyurethane carrier are improved, which accelerates the migration of nitrifying bacteria from water to the surface of the material, greatly shortens the initial adhesion time, and allows the carrier to be covered with a biofilm on the inside and outside, not limited to the surface, and the biofilm density and rate are improved. The CBMA anti-pollution effect can reduce the occupation of the carrier surface space by heterotrophic bacteria and adhesive organic matter, reserve space for nitrifying bacteria, improve the early biofilm formation effect, and improve the overall biofilm quality. PEG can also impart higher deformation resistance and toughness to the foam, improving the service life of long-term underwater use.

[0022] (2) The PVA-boric acid complex coating can further optimize the superhydrophilic, anti-pollution, and microbial adhesion performance of the foam surface based on the acrylate / polyethylene glycol modified polyurethane foam.

[0023] (3) The biological filter material of the application has a load of up to 0.24 g N / d and a maximum load of up to 0.77 g N / d, and can be applied to high-salinity seawater fish tanks with a maximum salinity tolerance of 30000 mg / L and a minimum temperature tolerance of 10℃, and is suitable for aquarium cold-water fish tank systems. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 is a physical diagram of the biological filter material of the application; Figure 2 is the biofilm amount of the biological filter material at different biofilm formation times; Figure 3 is the biofilm thickness of the biological filter material at different biofilm formation times; Figure 4 is an ammonia nitrogen change trend graph under different salt concentrations; Figure 5 Figure is a trend chart of nitrite under different salt concentrations; Figure 6 Figure is a trend chart of ammonia nitrogen under different temperatures; Figure 7 Figure is a trend chart of nitrite under different temperatures. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] The hollow resin shell used in the present application is purchased from Guangzhou Senbao Trading Company, with a diameter of 4 cm.

[0028] Example 1 The biofilter material with a nitrification system in this embodiment is a hollow resin shell, which is filled with modified polyurethane foam blocks, and the surface of the modified polyurethane foam blocks is adsorbed with nitrifying bacteria: European nitrosomonas (CCTCC NO: M20232717) and Vickers nitrobacter (CCTCC NO: M2023989). The modified polyurethane is carboxybetaine methacrylate / polyethylene glycol modified polyurethane.

[0029] The preparation method of the modified polyurethane includes the following steps: S1, under room temperature, 200 g of polyether polyol, 25 g of diethylene glycol, 22 g of carboxybetaine methacrylate and 15 g of polyethylene glycol are mixed uniformly, then 3.5 g of silicone foam stabilizer, 8.8 g of water and 0.8 g of triethylamine catalyst are added in sequence, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 125 g of toluene diisocyanate is added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into a foaming box for foaming, after the foaming is finished, the foam body is taken out, and after room temperature curing for 48 h, the foam body is cut into a modified polyurethane foam block with a side length of 2 cm.

[0030] The preparation method of the biological filter material of the present embodiment is as follows: a modified polyurethane foam block is filled into a spherical resin shell with a diameter of 4 cm to obtain a filter material, then the filter material and a nitrifying bacteria agent are put into a 10 L model device, the filter material fills 30% of the volume of the device, the agent is added in an amount of 1% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10 L of culture medium is added, the aeration device is turned on, the dissolved oxygen is controlled to be 4 mg / L, the biological filter material is in a fluidized state, which is convenient for the nitrifying bacteria to form a biofilm; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the modified polyurethane can be placed in an aquarium system for water treatment.

[0031] The culture medium components are as follows: NaNO2 0.8 g / L, KH2PO4 0.06 g / L, NaCl 0.5 g / L, NaHCO3 0.5 g / L, riboflavin 0.9 g / L, biotin 0.15 g / L, glycine 0.2 g / L, and the balance is water.

[0032] Example 2 The difference between Example 2 and Example 1 is that the modified polyurethane further carries a polyvinyl alcohol borate complex. The specific preparation method is as follows: S3, 100 g of polyvinyl alcohol is dissolved in 1900 g of deionized water, 17.5 g of boric acid is added and stirred to form a complex, and the complex is filtered through a 200 mesh filter screen to remove particles; S4, the modified polyurethane prepared in step S2 of Example 1 is immersed in the complex for 1.5 h, then the modified polyurethane is taken out, drained, and dried in a ventilated environment.

[0033] The preparation method of the biological filter material is the same as that of Example 1.

[0034] Example 3 The biological filter material with a nitrification system of the present embodiment comprises a hollow resin shell, which is filled with modified polyurethane, and the surface of the modified polyurethane adsorbs nitrifying bacteria: European nitrosomonas (CCTCC NO: M20232717) and Vickers nitrobacter (CCTCC NO: M2023989). The modified polyurethane is carboxybetaine methacrylate / polyethylene glycol modified polyurethane.

[0035] The preparation method of the modified polyurethane comprises the following steps: S1, at room temperature, 200 g of polyether polyol, 10 g of diethylene glycol, 16 g of carboxybetaine methacrylate and 10 g of polyethylene glycol are uniformly mixed, then 2 g of silicone foam stabilizer, 4 g of water and 0.2 g of triethylamine catalyst are sequentially added, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 110 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into the foaming box and left to foam, after the end, the foam body was taken out, and after curing for 48 h at room temperature, the modified polyurethane foam was cut into cubes with a side length of 2 cm.

[0036] S3, 100 g of polyvinyl alcohol was dissolved in 1900 g of deionized water, after adding 10 g of boric acid, the complex was formed by stirring and reacting, and the particles were removed by filtering with a 200 mesh filter screen; S4, the modified polyurethane prepared in step S2 was immersed in the complex for 1 h, after the end, the modified polyurethane was taken out, drained, and dried in a ventilated place.

[0037] The preparation method of the biological filter material of the present embodiment is as follows: a piece of modified polyurethane foam is filled into a spherical resin shell with a diameter of 4 cm to obtain a filter material, then the filter material and a nitrifying bacteria agent are put into a 10 L model device, the filter material fills 25% of the volume of the device, the agent is added in an amount of 0.5% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10 L of culture medium is added, the aeration device is started, and the dissolved oxygen is controlled at 3 mg / L to make the biological filter material in a fluidized state, which is convenient for nitrifying bacteria to form a biofilm; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the modified polyurethane can be placed in an aquarium system for water treatment.

[0038] The composition of the culture medium is as follows: NaNO2 0.1 g / L, KH2PO4 0.01 g / L, NaCl 0.1 g / L, NaHCO3 0.1 g / L, riboflavin 0.8 g / L, biotin 0.1 g / L, glycine 0.1 g / L, and the rest is water.

[0039] Example 4 The biological filter material with a nitrification system of the present embodiment comprises a hollow resin shell, which is filled with modified polyurethane, and the surface of the modified polyurethane is adsorbed with nitrifying bacteria: European nitrosomonas (CCTCC NO: M20232717) and Vickers nitrobacter (CCTCC NO: M2023989); the modified polyurethane is carboxyl betaine methacrylate / polyethylene glycol modified polyurethane.

[0040] The preparation method of the modified polyurethane comprises the following steps: S1, under room temperature conditions, 200 g of polyether polyol, 15 g of diethylene glycol, 18 g of carboxyl betaine methacrylate, and 12 g of polyethylene glycol were mixed uniformly, then 2.5 g of silicone foam stabilizer, 5.5 g of water, and 0.4 g of triethylamine catalyst were added in sequence, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 115 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into the foaming box and left to foam, after the end, the foam body was taken out, and after curing for 48 h at room temperature, it was cut into a 2 cm side length cube modified polyurethane foam.

[0041] S3, 100 g of polyvinyl alcohol was dissolved in 1900 g of deionized water, after adding 12.5 g of boric acid, the complex was formed by stirring and reacting, and the particles were removed by filtering with a 200 mesh filter screen; S4, the modified polyurethane prepared in step S2 was immersed in the complex for 1.5 h, after the end, the modified polyurethane was taken out, drained, and dried in a ventilated place.

[0042] The preparation method of the biological filter material of the present embodiment is as follows: a piece of modified polyurethane foam is filled into a spherical resin shell with a diameter of 4 cm to obtain a filter material, then the filter material and a nitrifying bacteria agent are put into a 10 L model device, the filter material fills 28% of the volume of the device, the agent is added in an amount of 0.8% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10 L of culture medium is added, the aeration device is started, and the dissolved oxygen is controlled at 3-5 mg / L, so that the biological filter material is in a fluidized state, facilitating the nitrifying bacteria to form a biofilm; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the modified polyurethane can be placed in an aquarium system for water treatment.

[0043] The composition of the culture medium is as follows: NaNO2 0.4 g / L, KH2PO4 0.03 g / L, NaCl 0.4 g / L, NaHCO3 0.3 g / L, riboflavin 0.9 g / L, biotin 0.13 g / L, glycine 0.15 g / L, and the balance is water.

[0044] Example 5 The biological filter material with a nitrification system of the present embodiment comprises a hollow resin shell, which is filled with modified polyurethane, and the surface of the modified polyurethane is adsorbed with nitrifying bacteria: European nitrosomonas (CCTCC NO: M20232717) and Vickers nitrobacter (CCTCC NO: M2023989); the modified polyurethane is carboxyl betaine methacrylate / polyethylene glycol modified polyurethane.

[0045] The preparation method of the modified polyurethane comprises the following steps: S1, under room temperature conditions, 200 g of polyether polyol, 30 g of diethylene glycol, 24 g of carboxyl betaine methacrylate, and 16 g of polyethylene glycol are mixed uniformly, then 4 g of silicone foam stabilizer, 4-10 g of water, and 1 g of triethylamine catalyst are added in sequence, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 130 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into the foaming box and left to foam, after the end, the foam body was taken out, and after curing for 48 h at room temperature, the modified polyurethane foam was cut into cubes with a side length of 2 cm.

[0046] S3, 100 g of polyvinyl alcohol was dissolved in 1900 g of deionized water, after adding 20 g of boric acid, the mixture was stirred to form a complex, and then filtered with a 200 mesh filter screen to remove particles; S4, the modified polyurethane prepared in step S2 was immersed in the complex for 2 h, after the end, the modified polyurethane was taken out, drained, and dried in a ventilated place.

[0047] The preparation method of the biological filter material of the present embodiment is as follows: a piece of modified polyurethane foam is filled into a spherical resin shell with a diameter of 4 cm to obtain a filter material, then the filter material and a nitrifying bacteria agent are put into a 10 L model device, the filter material fills 35% of the volume of the device, and the bacteria agent is added in an amount of 1.5% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10 L of culture medium is added, the aeration device is started, and the dissolved oxygen is controlled at 3-5 mg / L, so that the biological filter material is in a fluidized state, facilitating the nitrifying bacteria to form a biofilm; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the modified polyurethane can be placed in an aquarium system for water treatment.

[0048] The composition of the culture medium is as follows: NaNO2 1.2 g / L, KH2PO4 0.1 g / L, NaCl 1 g / L, NaHCO3 1 g / L, riboflavin 1.2 g / L, biotin 0.2 g / L, glycine 0.3 g / L, and the balance is water.

[0049] Example 6 The biological filter material with a nitrification system of the present embodiment comprises a hollow resin shell, which is filled with modified polyurethane, and the surface of the modified polyurethane is adsorbed with nitrifying bacteria: European nitrosomonas (CCTCC NO: M20232717) and Vickers nitrobacter (CCTCC NO: M2023989), and the modified polyurethane is carboxy betaine methacrylate / polyethylene glycol modified polyurethane.

[0050] The preparation method of the modified polyurethane comprises the following steps: S1, under room temperature, 200 g of polyether polyol, 20 g of diethylene glycol, 20 g of carboxy betaine methacrylate, and 14 g of polyethylene glycol were mixed uniformly, then 3 g of silicone foam stabilizer, 7 g of water, and 0.6 g of triethylamine catalyst were added in sequence, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 120 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into a foaming box and left to foam, after the end, the foam body was taken out, and after curing at room temperature for 48 h, the modified polyurethane foam with a side length of 2 cm was cut into a cube.

[0051] S3, 100 g of polyvinyl alcohol was dissolved in 1900 g of deionized water, after adding 15 g of boric acid, the mixture was stirred to form a complex, and then filtered with a 200 mesh filter screen to remove particles; S4, the modified polyurethane prepared in step S2 was immersed in the complex for 2 h, after the end, the modified polyurethane was taken out, drained, and dried in a ventilated place.

[0052] The preparation method of the biological filter material of the present embodiment is as follows: a piece of modified polyurethane foam is filled into a spherical resin shell with a diameter of 4 cm to obtain a filter material, then the filter material and a nitrifying bacteria agent are put into a 10 L model device, the filter material fills 32% of the volume of the device, and the bacteria agent is added in an amount of 1.2% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10 L of culture medium is added, the aeration device is started, and the dissolved oxygen is controlled at 3-5 mg / L, so that the biological filter material is in a fluidized state, facilitating the nitrifying bacteria to form a biofilm; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, the modified polyurethane is placed in an aquarium system for water treatment.

[0053] The composition of the culture medium is as follows: NaNO2 1 g / L, KH2PO4 0.08 g / L, NaCl 0.9 g / L, NaHCO3 0.5 g / L, riboflavin 1.1 g / L, biotin 0.17 g / L, glycine 0.25 g / L, and the balance is water.

[0054] Comparative Example 1 Comparative Example 1 uses a conventional polyurethane, and the preparation method is as follows: S1, at room temperature, 200 g of polyether polyol and 25 g of diethylene glycol were mixed uniformly, then 3.5 g of silicone foam stabilizer, 8.8 g of water, and 0.8 g of triethylamine catalyst were added in sequence, stirred at 500 rpm for 1 min to form a mixed solution A; S2, 125 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into a foaming box and left to foam, after the end, the foam body was taken out, and after curing at room temperature for 48 h, the modified polyurethane foam with a side length of 2 cm was cut into a cube.

[0055] The preparation method of the biological filter material is the same as that of Example 1.

[0056] Comparative Example 2 Comparative Example 2 uses a carboxybetaine methacrylate modified polyurethane, and the preparation method is as follows: S1, under room temperature, 200 g of polyether polyol, 25 g of diethylene glycol and 22 g of carboxybetaine methacrylate were mixed uniformly, then 3.5 g of silicone foam stabilizer, 8.8 g of water and 0.8 g of triethylamine catalyst were added in sequence, stirred at 500 rpm for 1 min, to form a mixed solution A; S2, 125 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into a foaming box to stand for foaming, after the end, the foam body was taken out, cut into a 2 cm side length cube modified polyurethane foam after room temperature curing for 48 h.

[0057] The preparation method of the biological filter material was the same as that of Example 1.

[0058] Comparative Example 3 Comparative Example 3 was compared with Example 1, the modified polyurethane was polyethylene glycol modified polyurethane, and the preparation method was as follows: S1, under room temperature, 200 g of polyether polyol, 25 g of diethylene glycol and 22 g of carboxybetaine methacrylate were mixed uniformly, then 3.5 g of silicone foam stabilizer, 8.8 g of water and 0.8 g of triethylamine catalyst were added in sequence, stirred at 500 rpm for 1 min, to form a mixed solution A; S2, 125 g of toluene diisocyanate was added into the mixed solution A, stirred at 800 rpm for 2 min, then poured into a foaming box to stand for foaming, after the end, the foam body was taken out, cut into a 2 cm side length cube modified polyurethane foam after room temperature curing for 48 h.

[0059] The preparation method of the biological filter material of the present example was the same as that of Example 1.

[0060] Comparative Example 4 The filter material of Comparative Example 4 was a conventional ceramic ring filter material, which was purchased from Taobao Guangdong Not Guangdong Aquarium Products Store.

[0061] Experiment 1 Hydrophilicity and biofilm Biofilm detection method: KOMA bright blue method was used to measure protease to characterize the amount of biofilm, laser confocal was used to characterize the thickness of biofilm, biofilm time was used to characterize the biofilm efficiency, and the weight multiple of 10 filter materials after soaking in water for 1 h was used to characterize the hydrophilicity. The results are shown in Table 1.

[0062] Table 1 Hydrophilicity and biofilm amount after 96 h of biofilm of the biological filter material

[0063] As shown in Table 1, compared with Comparative Examples 1-3, the hydrophilicity of the polyurethane of Example 1 is significantly improved after being modified by carboxybetaine methacrylate + polyethylene glycol, the surface water absorption is high, and the total amount and thickness of the biofilm are better than those of Comparative Example 1 (ordinary polyurethane), indicating that the synergistic modification of polyurethane by carboxybetaine methacrylate + polyethylene glycol promotes rapid biofilm formation and accelerates the start-up time. On the basis of Example 1, Example 2 further loads a layer of polyvinyl alcohol-boric acid complex coating, and the hydrophilicity and biofilm amount are better than those of Example 1, indicating that the PVA-boric acid complex greatly optimizes the biofilm environment, and the coating brings about micro-nano structure lubrication and extreme hydrophilic effect on the surface, so that the microorganisms can attach and grow more fully, indicating that the synergistic effect of the composite hydrophilic structure + surface coating is excellent.

[0064] Comparative Example 1 (conventional polyurethane PU) has no any hydrophilic modification or active group, and has low hydrophilicity, so it is difficult for microorganisms to initially attach, and the biofilm formation speed and amount are low. Comparative Example 2 is modified only by carboxybetaine (without PEG), which is slightly better than ordinary PU, indicating that CBMA has a promoting effect on hydrophilicity and biofilm formation, but is not as good as CBMA + PEG synergy, and still has a large gap with Examples 1 and 2. Comparative Example 3 is modified only by polyethylene glycol (without CBMA), and the effect is similar to that of Comparative Example 2, which is slightly better than ordinary PU, but the hydrophilicity and biofilm promoting effect are not as good as CBMA or composite modification. Comparative Example 4 has no hydrophilic organic functional group and is mostly inert and microporous surface, has the worst hydrophilicity, the lowest biofilm amount and thickness, and is difficult to form biofilm rapidly, which is a typical performance of the short board of traditional inorganic carriers.

[0065] The biofilm amount and biofilm thickness of the biofilter at different biofilm formation times are shown in Table 1. Figure 2 and 3 The law is the same as Table 1.

[0066] Experiment Two: Water treatment effect of filter material in high-salt and low-temperature environment 1. Seawater salinity experiment The filter materials of Example 2 (Case 1), Comparative Example 1 (Case 3) and Comparative Example 4 (Case 2) were selected for biofilm formation, and the 14d biofilm filter materials were taken for fish tank live fish nitrification experiments. The initial concentration of ammonia nitrogen in the fish tank was controlled at 2mg / L, and the initial concentration of nitrite was controlled at 0.5mg / L. Three filter materials were added to each fish tank, and the fish tank was fed in small amounts every 3 days. The salinity of the fish tank was 0ppt, 5ppt, 15ppt and 30ppt (1ppt is 1g salt / 1L water), the change value of ammonia nitrogen and nitrite concentration was calculated at 0-7h, and the change curve was drawn, and the results are shown in Figures 4-5 .

[0067] Under high salt environment, the protection ability of filter material to nitrifying bacteria determines the level of filter material effect: modified polyurethane has multiple hydrophilic, chelation and weak charge effects, which can keep the bacteria membrane moist, ion slow release, and reduce the adverse effects of osmotic pressure on bacteria. Ordinary polyurethane and ceramic ring cannot provide enough survival barrier for microorganisms, and the state of microorganisms deteriorates and the reaction rate decreases under high salt.

[0068] Therefore, the removal effect of the filter material of Example 2 on ammonia nitrogen and nitrite is the best, and the salt tolerance is outstanding; the salt tolerance of the ordinary polyurethane filter material of Comparative Example 1 is moderate, and the removal efficiency is obviously limited as the salinity increases; the hydrophilicity and biocompatibility of the ceramic ring filter material of Comparative Example 4 are weak, and it is poor in adapting to high salt environment, and the degradation ability of ammonia nitrogen and nitrite is also low (see Figures 4-5 ).

[0069] 2. Low temperature test The filter materials of Example 2 (Case 1), Comparative Example 1 (Case 3) and Comparative Example 4 (Case 2) were selected for biofilm formation, and the 14d biofilm formation filter materials were taken for fish tank live fish nitrification experiment. The initial concentration of ammonia nitrogen in the fish tank was controlled at 2mg / L, and the initial concentration of nitrite was controlled at 0.5mg / L. Three filter materials were added to each fish tank, and the fish tank was fed in small amounts every 3 days. The temperature was set at 10℃ and 15℃, the change value of ammonia nitrogen and nitrite concentration was calculated in 0-7h, and the change curve was drawn, and the results are shown in Figures 6-7 .

[0070] The optimum temperature of nitrifying bacteria is 20-30℃, and 10-15℃ is close to its tolerance limit, the physiological metabolism speed slows down, and the growth and substrate conversion ability decreases.

[0071] Example 2 uses carboxybetaine methacrylate / polyethylene glycol modified polyurethane, and adds surface PVA-boric acid complex modification, compared with ordinary PU and ceramic ring: it has higher hydrophilicity and moisture retention capacity, which can ensure that the bacteria membrane will not be inactivated due to environmental dehydration or surface icing at low temperature; excellent pore and interface microenvironment helps to maintain cell viability and active enzyme system stability, and buffers the inhibition effect brought by low temperature. Ordinary PU and ceramic ring materials themselves have poor hydrophilicity, which can easily lead to deterioration of bacterial metabolic environment, bacterial biofilm shedding or slow recovery at low temperature, resulting in significant limitation of reaction kinetics.

[0072] Therefore, under low temperature environment, the filter material of Example 2 performs best, which is significantly better than ordinary PU (Comparative Example 1) and ceramic ring filter material (Comparative Example 4), and has excellent low temperature adaptability to nitrification reaction. The higher the temperature, the better the nitrification removal efficiency of all filter materials, but the structure and surface hydrophilicity / function of the material itself are the core to determine the level of low temperature performance. The nitrification activity of ceramic ring is significantly inhibited at low temperature, and ordinary PU has certain ability but is not as good as the strong modified material (see Figures 6-7 ).

[0073] Experiment three Filter material load The modified polyurethane and nitrifying bacteria agent are put into a 10L model device, the modified polyurethane fills 25% of the volume of the device, the bacteria agent is added in an amount of 0.5% of the volume of the culture medium (the volume ratio of the two bacteria is 1:1), 10L of the culture medium is added, the aeration device is turned on, the dissolved oxygen is controlled at 3mg / L, the biological filter material is in a fluidized state, which facilitates the nitrifying bacteria to form a biofilm; nitrite is added to make the concentration of nitrite in the device 100mg / L, when the concentration of nitrite decreases to 20mg / L, nitrite is added again to control the concentration at 100mg / L, when the concentration of nitrate in the device reaches 1500mg / L, in order to avoid the occurrence of nitrate inhibition, half of the culture medium in the device is replaced (culture medium without NaNO2), the pH of the water sample is tested every day to keep the overall pH between 7.5-8, and according to the pH value, a proper amount of solid sodium bicarbonate and 25% volume concentration of dilute sulfuric acid are added. When the nitrite decreases rapidly, the corresponding culture medium concentration is increased according to the nitrite concentration of 100-150-200-300mg / L.

[0074] The water samples in the devices of the examples 1, 2 and the comparative example 1 are taken respectively, the nitrite and nitrate indicators in the devices are detected every 24h, the filter material load is calculated at 14d, 21d and 30d respectively, and the results are shown in Table 2.

[0075] Table 2 Filter material load

[0076] As shown in Table 2, whether it is the average slope K, the average load of each filter material or the highest load of each filter material, the examples 1 and 2 are always much higher than the comparative example 1, and as the culture period is prolonged (14d→21d→30d), the difference is further increased, which shows that the modified filter material releases the nitrification activity "faster" as the biofilm formation time is prolonged.

[0077] On the basis of the double hydrophilic modification, the PVA-boric acid complex coating of example 2 further brings: higher limit hydrophilicity, "water wet layer" is beneficial to the biofilm formation and activity maintenance of bacteria. Whether it is the average or maximum filter material load in the medium or long term, example 2 is better than example 1, and the difference accumulates and amplifies day by day, which reflects the significant advantages of the composite surface engineering.

[0078] The comparative example 1 (conventional PU) has low microbial adhesion rate and slow start of the biofilm in the early stage due to the lack of hydrophilic and functional modification; the material internal and surface hydrophobicity cannot provide effective interface for the transfer and reaction of bacteria, substrate and oxygen, resulting in low unit filter material load; the growth and repair speed of the biofilm is slow, and the material itself lacks favorable regulation of the microecological environment.

[0079] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A biological filter material with a built-in nitrification system, characterized by: The biological filter material comprises a hollow resin shell filled with one or more modified polyurethane foam blocks. Nitrifying bacteria are adsorbed on the surface of the modified polyurethane foam blocks. The material of the modified polyurethane foam blocks is carboxybetaine methacrylate / polyethylene glycol modified polyurethane.

2. The biological filter material with a self-contained nitrification system according to claim 1, characterized in that: The preparation method of the modified polyurethane comprises the following steps: S1, mixing polyether polyol, diethylene glycol, carboxybetaine methacrylate and polyethylene glycol, and then adding silicone foam stabilizer, water and triethylamine in sequence and stirring evenly to form a mixed solution A; S2, adding toluene diisocyanate to the mixed solution A, stirring evenly and then pouring into a foaming box for foaming. After the foam is foamed, the foam is taken out, aged and then cut to obtain a modified polyurethane foam.

3. The biological filter material with a self-contained nitrification system according to claim 2, characterized in that: The mass ratio of the polyether polyol, diethylene glycol, carboxybetaine methacrylate, polyethylene glycol, silicone foam stabilizer, water, triethylamine and toluene diisocyanate is 100:5-15:8-12:5-8:1-2:2-5:0.1-0.5:55-65.

4. The biological filter material with a self-contained nitrification system according to claim 2, characterized in that: The preparation method of the modified polyurethane further comprises the following steps: S3, dissolving polyvinyl alcohol in deionized water, adding boric acid and stirring to react to form a complex, and filtering with a 200-mesh filter to remove particles; S4, immersing the modified polyurethane prepared in step S2 in the complex for 1-2 hours, taking out the modified polyurethane after immersion, draining it, and drying it under ventilation.

5. The biological filter material with a self-contained nitrification system according to claim 4, characterized in that: The polyvinyl alcohol has a polymerization degree of 1000-2000 and an alcoholysis degree of 60%-99%.

6. The biological filter material with a self-contained nitrification system according to claim 4, characterized in that: The mass ratio of the polyvinyl alcohol, water and boric acid is 5:95:0.5-1.

7. The biological filter material with a self-contained nitrification system according to claim 4, characterized in that: The European Nitrosomonas Nitrosomonas europaea SZG-AOB-003, the deposit number is CCTCC NO: M20232717, Nitrobacter wilkeri is Nitrobacter winogradskyi SZG-NOB-002, the accession number is CCTCC NO: M2023989.

8. The method for preparing a biological filter material with a self-contained nitrification system according to any one of claims 1 to 7, characterized in that: Put the modified polyurethane and nitrifying bacteria agent into the device, add the culture medium, turn on the aeration device, and make the biological filter material fluidized to facilitate the formation of nitrifying bacteria; after the nitrifying bacteria form a biofilm on the surface of the modified polyurethane, it can be placed in the aquarium system for water treatment.

9. The preparation method according to claim 8, wherein: The modified polyurethane filling volume is 25%-35% of the device volume, the bacterial agent dosage is 0.5%-1.5% of the culture medium volume, and the dissolved oxygen concentration is 3-5 mg / L; the components of the culture medium include: NaNO2 0.1-1.2 g / L, KH2PO4 0.01-0.1 g / L, NaCl 0.1-1 g / L, NaHCO3 0.1-1 g / L, riboflavin 0.8-1.2 g / L, biotin 0.1-0.2 g / L, glycine 0.1-0.3 g / L, and the balance is water.

10. Use of the biological filter material with a self-contained nitrification system according to any one of claims 1 to 7 in water treatment.

Images