Sulfur-iron autotrophic denitrification polyurethane reticular foam filler, and preparation method and application thereof

Abstract

The present application relates to sewage treatment technical field, specifically to a kind of sulfur-iron autotrophic denitrification polyurethane reticular foam fillings and its preparation method and application.The fillings include the following weight parts of raw materials:polyol 100 parts, hydrophobic auxiliary agent 1.0 parts, silicone oil 0.5 parts-2 parts, composite catalyst 0.1 parts-0.4 parts, modified iron powder 8 parts-20 parts, modified sulfur powder 10 parts-25 parts, activated carbon black 3 parts-8 parts, moisture 2-4 parts, isocyanate 40 parts-55 parts.The fillings inside are uniformly loaded with modified sulfur powder, modified reduced iron powder and conductive carbon black;Conductive carbon black and sulfur powder, iron powder jointly constitute electron conduction medium network, accelerate electron from electron donor to microorganism and nitrate transmission.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a sulfur-iron self-trophic denitrifying polyurethane mesh foam packing, its preparation method, and its application. Background Technology

[0002] Nitrate is a major pollutant in water bodies, widely originating from excessive application of nitrogen fertilizers in agriculture, livestock and poultry wastewater, and industrial solid waste leakage. Biological denitrification is an important pathway for nitrate removal. Traditional heterotrophic denitrification technology relies on organic carbon sources to drive biological metabolic processes, requiring the addition of external organic carbon sources to maintain the ratio of chemical oxygen demand (COD) to nitrogen (COD / N) in the influent wastewater to achieve the denitrification process. The large addition of organic carbon not only increases treatment costs but also increases sludge production and greenhouse gas emissions. Autotrophic denitrification, due to its advantages such as not requiring external organic carbon sources, low sludge production, and economical operating costs, has become a current research hotspot.

[0003] Sulfur autotrophic denitrification with elemental sulfur (S) 0 Using nitrate as the electron donor and nitrate as the electron acceptor, nitrate nitrogen is reduced to generate nitrogen gas. This process uses readily available and inexpensive raw materials, but it has two inherent drawbacks: (1) the reaction produces acid, leading to a decrease in the system's pH and inhibiting microbial activity; (2) the transfer of electrons from sulfur powder to nitrate relies on the microbial enzyme system, making electron transfer efficiency the rate-limiting step. Iron autotrophic denitrification uses zero-valent iron (Fe2+) as the electron donor and nitrate as the electron acceptor. 0 ) or Fe 2+ As an electron donor, the reaction rate is fast, and Fe 0 H can be consumed + It has pH buffering capacity, but when used alone, the iron powder is consumed quickly and is easily passivated.

[0004] Chinese patent CN112624329A discloses a deep denitrification packing material and treatment method for wastewater based on sulfur autotrophic denitrification. The technical solution involves heating polyols and isocyanate compounds, adding sulfur powder and zeolite powder, foaming, demolding, and cutting to obtain a sulfur-loaded mesh polyurethane packing material. This technical solution uses only sulfur powder as a single electron donor, which cannot solve the pH decrease problem caused by sulfur autotrophic denitrification and acid production.

[0005] Chinese patent CN201810404533.4 discloses a composite biological packing material for promoting rapid start-up and stable operation of anammox, its preparation method, and its application. The technical solution is as follows: The packing material comprises polyurethane foam, activated carbon, and iron powder linked by a crosslinking agent (polyvinyl alcohol, glucomannan, and calcium chloride); it is prepared by directly adding activated carbon, iron powder, and the crosslinking agent during the foaming process of the polyurethane foam; the particle size of the iron powder is 0.1~0.25 mm; this packing material is applied in a UASB reactor to promote rapid start-up and stable operation of anammox. This technical solution serves the anaerobic ammonia oxidation process, with its core objective being to "promote the rapid start-up and stabilization of Anammox bacteria," rather than sulfur autotrophic denitrification. Anaerobic ammonia oxidation and sulfur autotrophic denitrification are two completely different nitrogen removal processes, involving entirely different microbial communities (Anammox bacteria vs. sulfur-oxidizing denitrifying bacteria) and metabolic pathways. Iron powder and activated carbon are connected to the surface of polyurethane foam through a crosslinking agent, which functions as a biological carrier to enhance the adhesion of Anammox bacteria. Relying on crosslinking agents (polyvinyl alcohol, glucomannan, calcium chloride) to connect activated carbon and iron powder to the foam surface increases the complexity and cost of preparation, and the crosslinking agent may affect the open-cell structure of the foam.

[0006] In existing sulfur autotrophic denitrification technologies, alkalinity-slowing materials such as limestone and siderite are typically added to maintain pH stability. For example, Chinese patent (CN114524511B) achieves alkalinity slow release by setting a porous spherical shell on the outside of the packing material and embedding limestone and siderite particles inside. However, this method increases the complexity of the packing structure, and the alkalinity release rate is difficult to precisely match the acid production rate.

[0007] In the one-step foaming process, iron powder (density 7.86 g / cm³) 3 ) and polyurethane matrix (density approximately 0.1 g / cm³) 3 There is a density difference of about 80 times. Although existing technologies use crosslinking agents to improve powder bonding, crosslinking agents alone cannot completely solve the problem of gravity settling during the foaming process, resulting in uneven distribution of active components on the upper and lower end faces of the filler. Summary of the Invention

[0008] In view of the above-mentioned technical problems, this invention proposes a sulfur-iron autotrophic denitrification polyurethane mesh foam filler, its preparation method, and its application. The filler is uniformly loaded with modified sulfur powder, modified reduced iron powder, and conductive carbon black; the conductive carbon black, sulfur powder, and iron powder together form an electron conduction medium network, accelerating the transfer of electrons from the electron donor (S0). 0 / Fe 0 (Transfer of nitrates to microorganisms)

[0009] A sulfur-iron self-trophic denitrifying polyurethane mesh foam filler comprises the following raw materials in parts by weight: 100 parts polyol, 1.0 part hydrophobic additive, 0.5-2 parts silicone oil, 0.1-0.4 parts composite catalyst, 8-20 parts modified iron powder, 10-25 parts modified sulfur powder, 3-8 parts activated carbon black, 2-4 parts water, and 40-55 parts isocyanate.

[0010] Furthermore, the polyol is a polyether polyol and / or a polyester polyol.

[0011] Preferably, the polyether polyol is one or more combinations of difunctional and trifunctional polyether polyols such as 3050, 2020, and 330N.

[0012] Preferably, the polyester polyol is one or more of the following: PE-2010, PE2020, etc., used in elastomers.

[0013] Furthermore, the hydrophobic additive is hydrophobic silicone oil L-618.

[0014] Furthermore, the silicone oil is an open-cell silicone oil, either L-580 or B8002.

[0015] Furthermore, the composite catalyst is a combination of ammonia-based and tin-based catalysts; wherein the ammonia-based catalyst is 0.10-0.15 parts of A-33 (foaming), and the tin-based catalyst is 0.18-0.25 parts of T-9 (stannous octoate, gel).

[0016] Further, the modified iron powder is prepared as follows: 15 parts of anhydrous ethanol and 2.5-3 parts of KH550 are stirred evenly and sprayed into 100 parts of reduced iron powder that has been dried and dehydrated in advance. While spraying, the mixture is stirred at 500 rpm for 20 minutes, left to stand at room temperature for 30 minutes, and then dried at 60°C for 4 hours to obtain modified iron powder.

[0017] Preferably, the particle size of the reduced iron powder is 80-120 mesh.

[0018] Furthermore, the modified sulfur powder is prepared by mixing 100 parts of sulfur powder and 4-6 parts of polyol, stirring at 100 rpm for 30 minutes at room temperature until uniformly coated.

[0019] Preferably, the polyols include polyether polyols and / or polyester polyols.

[0020] Preferably, the sulfur powder is 200-320 mesh ultrafine sublimed sulfur powder.

[0021] Furthermore, the activated carbon black is conductive carbon black or spray-dried carbon black with a particle size of 300 mesh or larger; the carbon black is dried at 105°C for 2 hours, cooled, and sealed for later use.

[0022] Furthermore, the isocyanate is TDI, MDI, or PAPI, with an index of 1.01-1.02.

[0023] A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler includes the following steps: Step 1: Add polyol, hydrophobic additive, silicone oil, modified iron powder, modified sulfur powder and activated carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add water and composite catalyst to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add isocyanate to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 30mm-50mm to obtain sulfur-iron self-trophic denitrified polyurethane mesh foam filler.

[0024] The above-mentioned sulfur-iron self-trophic denitrifying polyurethane mesh foam packing can be used in wastewater treatment. The packing is filled in an upflow fixed bed reactor or filter bed to remove nitrates and / or phosphates from water.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0026] 1. Improved electron transfer efficiency: This invention clarifies that the activated carbon black is conductive carbon black or spray-dried carbon black, which is embedded in the polyurethane skeleton as an electronic conduction medium to form a "sulfur-carbon-iron" electronic conduction medium network.

[0027] Activated carbon black forms a continuous conductive path within the filler, providing three electron transport pathways: Path A (direct contact): S 0 / Fe 0 →Attached bacteria→NO3 - (Traditional approach); Path B (conductive mediator): S 0 / Fe 0 →Carbon black conductive network→Distant bacteria→NO3 - (New feature in this invention); Pathway C (electrochemical reduction): Carbon black, as an electronic conductor, expands the electron donor (S) 0 / Fe 0 ) and electron acceptor (NO3) - An effective reaction interface between (a new feature of this invention); This reduces the electron transfer distance from the micrometer level to the nanometer level; reduces reliance on direct contact between sulfur powder and microorganisms, and expands the reaction interface; and increases the denitrification rate.

[0028] 2. pH self-stabilization: By optimizing the mass ratio of sulfur powder to iron powder (sulfur:iron = 1:0.45-1.2), the autotrophic acid production of sulfur accelerates the corrosion and release of Fe from zero-valent iron. 2+ Fe 2+ It is further utilized by iron-autotrophic denitrifying bacteria, so that the acid production rate of sulfur autotrophic denitrification and the acid consumption rate of iron autotrophic denitrification reach a dynamic balance.

[0029] Sulfur autotrophy (acid production): S 0 +1.2NO3 - +0.6CO2+0.6H2O→0.6C5H7O2N+0.6N2+SO4 2- +1.2H + ; Iron autotrophy (acid consumption): Fe 0 +2H + →Fe 2+ +H2↑.

[0030] The effluent pH is kept stable in the range of 6.8-7.5 without the need for additional alkaline materials such as limestone or siderite. Compared with existing solutions that require the addition of alkaline slow-release materials, this invention achieves internal self-buffering and does not require complex external structural design.

[0031] 3. Uniform distribution of active components: While existing technologies incorporate iron powder and activated carbon during the foaming process, they rely on crosslinking agents for bonding, failing to address the issue of gravity settling during foaming. In the one-step foaming method of this invention, high-density iron powder (7.86 g / cm³) is used. 3 It settles rapidly in low-viscosity polyurethane systems (initial viscosity <500 cP). Through a combination of "coupling agent modification + feeding sequence control + carbon black thickening", uniform loading without crosslinking agents is achieved.

[0032] 4. Sustained release and long-lasting effect: The sulfur powder is pre-coated with polyether / polyester polyol (sulfur powder: polyol = 100: 4-6), forming a hydrophobic oil film on the surface. This suppresses the melting and leakage of sulfur powder during the exothermic foaming stage (temperatures can reach 80℃-100℃); it enables the slow release of sulfur ions in water, avoiding "sulfur shock"; and it extends the service life of the filler.

[0033] 5. Also has phosphorus removal function: The active material of this invention combines sulfur autotrophic denitrification and iron autotrophic denitrification. On the one hand, zero-valent iron can act as a direct electron donor in iron autotrophic denitrification to remove nitrates, thereby improving the denitrification effect. On the other hand, the acid produced during sulfur autotrophic denitrification can enhance iron dissolution, which not only alleviates the surface passivation problem during iron autotrophic denitrification and enhances nitrate removal, but also releases Fe. 2+ It can also react with PO4 in water. 3- It forms an insoluble precipitate, which promotes the removal of phosphorus.

[0034] Reticulated polyurethane foam has high hydrolysis resistance. Its internal network structure gives it a large specific surface area, good water permeability, and low resistance, making it easy for bacteria to attach and grow. It is very suitable as a carrier for autotrophic denitrification packing. Attached Figure Description

[0035] Figure 1 The image shows the actual sulfur-iron self-trophic denitrifying polyurethane mesh foam filler prepared in Example 1.

[0036] Figure 2 The image shows the actual sulfur-iron self-trophic denitrifying polyurethane mesh foam filler prepared in Example 2.

[0037] Figure 3 It is a traditional particle-mixed filler. Detailed Implementation

[0038] The embodiments of the technical solution of this application are described in detail below. These embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore merely examples and should not be used to limit the scope of protection of this application.

[0039] A sulfur-iron self-trophic denitrifying polyurethane mesh foam filler comprises the following raw materials in parts by weight: 100 parts polyol, 1.0 part hydrophobic additive, 0.5-2 parts silicone oil, 0.1-0.4 parts composite catalyst, 8-20 parts modified iron powder, 10-25 parts modified sulfur powder, 3-8 parts activated carbon black, 2-4 parts water, and 40-55 parts isocyanate.

[0040] In one possible embodiment, the polyol is a polyether polyol and / or a polyester polyol.

[0041] Preferably, the polyether polyol is one or more combinations of difunctional and trifunctional polyether polyols such as 3050, 2020, and 330N.

[0042] Preferably, the polyester polyol is one or more of the following: PE-2010, PE2020, etc., used in elastomers.

[0043] In one possible embodiment, the hydrophobic additive is hydrophobic silicone oil L-618; the silicone oil is open-cell silicone oil L-580 or B8002.

[0044] In one possible embodiment, the composite catalyst is a combination of ammonia-based and tin-based catalysts; wherein the ammonia-based catalyst is 0.10-0.15 parts of A-33 (foaming), and the tin-based catalyst is 0.18-0.25 parts of T-9 (stannous octoate, gel).

[0045] In one possible embodiment, the modified iron powder is prepared by: mixing 15 parts of anhydrous ethanol and 2.5-3 parts of KH550 evenly, spraying the mixture into 100 parts of 80-120 mesh reduced iron powder that has been dried and dehydrated in advance, stirring at 500 rpm for 20 minutes while spraying, letting it sit at room temperature for 30 minutes, and then drying the ethanol at 60°C for 4 hours to obtain the modified iron powder.

[0046] In one possible embodiment, the modified sulfur powder is prepared by mixing 100 parts of sulfur powder and 4-6 parts of polyol, and stirring at 100 rpm for 30 minutes at room temperature until uniformly coated.

[0047] Preferably, the polyols include polyether polyols and / or polyester polyols; the polyols in the modified sulfur powder are not included in the proportion of the main polyol in the formulation.

[0048] Preferably, the sulfur powder is 200-320 mesh ultrafine sublimed sulfur powder.

[0049] In one possible embodiment, the activated carbon black is conductive carbon black or spray-dried carbon black with a particle size of 300 mesh or larger; wherein the carbon black is dried at 105°C for 2 hours, cooled, and sealed for later use.

[0050] In one possible embodiment, the isocyanate is TDI, MDI, or PAPI with an index of 1.01-1.02.

[0051] A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler includes the following steps: Step 1: Add polyol, hydrophobic additive, silicone oil, modified iron powder, modified sulfur powder and activated carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add water and composite catalyst to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add isocyanate to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 30mm-50mm to obtain sulfur-iron self-trophic denitrified polyurethane mesh foam filler.

[0052] Example 1.

[0053] Preparation of modified iron powder: 15 parts anhydrous ethanol and 3 parts KH550 are mixed evenly and sprayed into 100 parts of 80-120 mesh reduced iron powder that has been dried and dehydrated in advance. While spraying, the mixture is stirred at 500 rpm for 20 minutes, left to stand at room temperature for 30 minutes, and then dried at 60℃ for 4 hours to obtain modified iron powder.

[0054] Preparation of modified sulfur powder: 100 parts of 200-320 mesh ultrafine sublimed sulfur powder and 6 parts of polyether polyol 330N were mixed and stirred at 100 rpm for 30 minutes at room temperature to coat evenly.

[0055] A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler includes the following steps: Step 1: Add 100g of polyether polyol 330N (Mn=3000), 1g of hydrophobic silicone oil L-618, 1.4g of open-cell silicone oil L-580, 10.8g of modified iron powder, 22.2g of modified sulfur powder, and 4.3g of conductive carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add 3.3g of deionized water and composite catalyst (A33 tertiary amine catalyst: 0.15g, T9 organotin catalyst: 0.25g) to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add 50.35g of isocyanate MDI (index: 1.01) to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 30mm to obtain sulfur-iron self-trophic denitrified polyurethane mesh foam filler.

[0056] like Figure 1 As shown, the foam filler has a standard continuous network structure with uniform foam ribs, no dead closed cells, and a soft, network-like texture. It has good toughness, low water resistance, and stable slow release of sulfur source, making it suitable for long-term continuous operation.

[0057] Example 2.

[0058] Preparation of modified iron powder: 15 parts anhydrous ethanol and 3 parts KH550 are mixed evenly and sprayed into 100 parts of 80-120 mesh reduced iron powder that has been dried and dehydrated in advance. While spraying, the mixture is stirred at 500 rpm for 20 minutes, left to stand at room temperature for 30 minutes, and then dried at 60℃ for 4 hours to obtain modified iron powder.

[0059] Preparation of modified sulfur powder: 100 parts of 200-320 mesh ultrafine sublimed sulfur powder and 6 parts of adipic acid polyester polyol were mixed and stirred at 100 rpm for 30 minutes at room temperature to coat evenly.

[0060] A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler includes the following steps: Step 1: Add 100g of adipic acid polyester polyol (Mn=2000), 1g of hydrophobic silicone oil L-618, 1.2g of open-cell silicone oil L-580, 9.9g of modified iron powder, 21.3g of modified sulfur powder, and 4.1g of conductive carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add 3.0g of deionized water and composite catalyst (A33 tertiary amine catalyst: 0.15g, T9 organotin catalyst: 0.25g) to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add 46.75g of isocyanate MDI (index: 1.02) to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 50mm to obtain sulfur-iron self-trophic denitrification polyurethane mesh foam filler.

[0061] like Figure 2 As shown, the foam filler is a high-hardness network foam with high cross-linking density, high pressure resistance, wear resistance, and water erosion resistance; the network pores are intact, and the active components are not easy to fall off, making it suitable for high-pressure, long-term static filter beds.

[0062] Example 3.

[0063] Preparation of modified iron powder: 15 parts anhydrous ethanol and 3 parts KH550 are mixed evenly and sprayed into 100 parts of 80-120 mesh reduced iron powder that has been dried and dehydrated in advance. While spraying, the mixture is stirred at 500 rpm for 20 minutes, left to stand at room temperature for 30 minutes, and then dried at 60℃ for 4 hours to obtain modified iron powder.

[0064] Preparation of modified sulfur powder: 100 parts of 200-320 mesh ultrafine sublimed sulfur powder and 6 parts of polyol (70% polyether polyol 330N and 30% adipic acid polyester polyol) are mixed and stirred at 100 rpm for 30 minutes at room temperature to coat evenly.

[0065] A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler includes the following steps: Step 1: Add 70g of polyether polyol 330N, 30g of adipic acid polyester polyol (Mn=2000), 1g of hydrophobic silicone oil L-618, 1.3g of open-cell silicone oil L-580, 10.2g of modified iron powder, 21.6g of modified sulfur powder, and 4.2g of conductive carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add 3.1g of deionized water and composite catalyst (A33 tertiary amine catalyst: 0.15g, T9 organotin catalyst: 0.25g) to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add 48.57g of isocyanate MDI (index: 1.02) to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 40mm to obtain sulfur-iron self-trophic denitrified polyurethane mesh foam filler.

[0066] This foam filler is a standard mesh semi-rigid foam with a balance of rigidity and flexibility, and excellent resilience; it has open pores, moderate water flow resistance, and excellent mechanical strength and hydrolysis resistance.

[0067] Comparative Example 1 (no carbon black control).

[0068] Except for the absence of conductive carbon black, the rest is the same as in Example 1.

[0069] Comparative Example 2 (Ordinary activated carbon control).

[0070] Replace the conductive carbon black with an equal amount of ordinary activated carbon (300 mesh), and the rest is the same as in Example 1.

[0071] Comparative Example 3 (Optimization of Sulfur-Free Iron Ratio).

[0072] The sulfur:iron ratio was adjusted to 1:0.3, and the rest was the same as in Example 1.

[0073] Comparative Example 4 used sulfur (2-5mm) + limestone (3-5mm) as fillers in a ratio of 7:3.

[0074] Comparative Example 5 uses sulfur (2-5mm) + iron powder (2-5mm) + limestone (3-5mm) as filler in a ratio of 7:1:2, which is a traditional granular mixed filler.

[0075] Nitrogen removal experiment: The foam packing material prepared in the examples and comparative examples was added to an upflow fixed bed reactor (reactor diameter 110 mm), and anaerobic digestion sludge / anoxic tank sludge from a municipal wastewater treatment plant was added for inoculation. After inoculation, simulated wastewater containing nitrate was introduced into the fixed bed reactor, wherein the concentration of nitrate in the simulated wastewater was 50 mg / L. After running for 48 hours, the concentration of nitrate in the water was tested. Table 1. Performance test results of the foam fillers prepared in the examples and comparative examples.

[0076] In Examples 1, 2, and 3, the packing material achieved a flow rate of 4 L / h while maintaining stable nitrate concentration and pH value. In Comparative Examples 4 and 5, due to the use of large-diameter particle packing material, the specific surface area is small and the mass transfer resistance is large. The flow rate can only reach 2 L / h while maintaining stable nitrate concentration and pH value, which is far lower than the mesh foam packing material of the present invention (4 L / h).

[0077] Comparative Example 1, due to the absence of conductive carbon black, cannot generate an electrochemical effect, thus reducing treatment efficiency; it can only reduce the flow rate to meet the effluent requirements.

[0078] Comparative Example 2, due to the addition of activated carbon, cannot effectively generate an electrochemical effect, thus reducing treatment efficiency; it can only reduce the flow rate to meet the effluent requirements.

[0079] In Comparative Example 3, the pH value of the effluent was too low due to the reduction in the amount of active iron powder added, so additional alkali had to be added to neutralize the pH value, which also affected the phosphorus removal effect.

Claims

1. A sulfur-iron self-trophic denitrifying polyurethane mesh foam filler, characterized in that, The raw materials include the following parts by weight: 100 parts polyol, 1.0 part hydrophobic additive, 0.5-2 parts silicone oil, 0.1-0.4 parts composite catalyst, 8-20 parts modified iron powder, 10-25 parts modified sulfur powder, 3-8 parts activated carbon black, 2-4 parts water, and 40-55 parts isocyanate.

2. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The polyol is a polyether polyol and / or a polyester polyol.

3. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The hydrophobic additive is hydrophobic silicone oil L-618; the silicone oil is open-cell silicone oil L-580 or B8002.

4. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The composite catalyst is a combination of ammonia-based and tin-based catalysts; wherein the ammonia-based catalyst is 0.10-0.15 parts of A-33 and the tin-based catalyst is 0.18-0.25 parts of T-9.

5. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The modified iron powder is prepared as follows: 15 parts of anhydrous ethanol and 2.5-3 parts of KH550 are stirred evenly and sprayed into 100 parts of reduced iron powder that has been dried and dehydrated in advance. While spraying, the mixture is stirred at 500 rpm for 20 minutes, left to stand at room temperature for 30 minutes, and then dried at 60℃ for 4 hours to obtain modified iron powder.

6. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The modified sulfur powder is prepared by mixing 100 parts of sulfur powder and 4-6 parts of polyol, stirring at 100 rpm for 30 minutes at room temperature until evenly coated.

7. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The activated carbon black is conductive carbon black or spray-dried carbon black with a particle size of 300 mesh or larger; the carbon black is dried at 105°C for 2 hours, cooled, and sealed for later use.

8. The sulfur-iron self-trophic denitrifying polyurethane mesh foam filler according to claim 1, characterized in that, The isocyanate is TDI, MDI or PAPI, with an index of 1.01-1.

02.

9. A method for preparing a sulfur-iron self-trophic denitrifying polyurethane mesh foam filler, characterized in that, Includes the following steps: Step 1: Add polyol, hydrophobic additive, silicone oil, modified iron powder, modified sulfur powder and activated carbon black in sequence, stir at 100 rpm for 10 minutes to obtain mixture 1; Step 2: Add water and composite catalyst to mixture 1, stir at 1000 rpm for 10-15 seconds to obtain mixture 2; Step 3: Add isocyanate to mixture 2 and stir at 1000 rpm for 7-10 seconds. After stirring, quickly pour the stirred material into a square mold, let it rise and open up, and then cure at room temperature for 72 hours. Cut it into squares with a side length of 30mm-50mm to obtain sulfur-iron self-trophic denitrified polyurethane mesh foam filler.

10. The application of the sulfur-iron self-trophic denitrifying polyurethane mesh foam packing according to any one of claims 1-8 in wastewater treatment, characterized in that, The packing material is filled in an upflow fixed-bed reactor or filter bed to remove nitrates and / or phosphates from water.

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