Carbon fiber modified biological carriers, their preparation methods and applications

Abstract

This invention belongs to the fields of environmental functional materials and wastewater treatment, specifically relating to a carbon fiber-modified autotrophic denitrification and phosphorus removal active biological carrier and its preparation method, as well as its application in advanced wastewater treatment. The biological carrier is configured as a blocky sphere with sulfur as its matrix, with granular buffer material and columnar carbon fiber material distributed on its surface and interior. The buffer material has an island-like structure on its surface, accounting for 10-80% of the total surface area of ​​the biological carrier; the carbon fiber material is uniformly dispersed in the sulfur on the surface, protruding in a spiky manner, accounting for 0.01-25% of the total biological carrier. This biological carrier effectively solves the problems of limited electron transfer efficiency and limited microbial utilization efficiency at the solid-water interface in packed bed or fixed bed filters, achieving efficient and simultaneous advanced denitrification and phosphorus removal.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and wastewater treatment technology, specifically relating to a carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier and its preparation method, as well as the application of the carrier in advanced wastewater treatment. Background Technology

[0002] In recent years, eutrophication of water bodies persists due to the continuous discharge of nitrogenous pollutants. Even after secondary treatment, wastewater still contains a certain concentration of nitrogenous pollutants. Further treatment of the secondary effluent can reduce pollutant discharge, enabling water reuse for industrial purposes, thereby improving water resource utilization and alleviating water shortage pressures. Wastewater denitrification has gradually shifted from targeting ammonia nitrogen (NH4+)... + The focus has shifted from controlling nitrogen (N-N) to controlling total nitrogen (TN). In some cities, such as Beijing, Zhejiang, and Kunming, the TN concentration in effluent discharged into surface water bodies after treatment at municipal wastewater treatment plants is stricter than the Class A discharge standard. Therefore, upgrading and improving traditional advanced treatment processes is an inevitable trend.

[0003] In existing technologies, sulfur is often combined with buffer materials (such as siderite) to form biological carriers. For example, CN201811113486.4 discloses a denitrification and phosphorus removal active biological carrier formed by physical melting of sulfur and siderite. The biological carrier has sulfur as its base and a large number of siderite particles embedded on its surface and inside, which can achieve deep denitrification and phosphorus removal. However, this biological carrier has problems such as small specific surface area, limited electron transfer efficiency, low microbial utilization efficiency, asynchronous consumption of sulfur and iron elements during operation, low proportion of iron autotrophic denitrification, and iron accumulation clogging the filter. CN201910326682.8 obtains a siderite-modified sulfur lightweight material by melting and foaming siderite and sulfur, and cooling it into shape. Although this patent document increases the specific surface area, due to its porous nature, the overall hardness of the material decreases. In fluidized bed and fixed bed reactors, long-term hydraulic scouring can easily cause physical wear of the material, reduce its lifespan, and lead to an increase in suspended solids in the effluent, thus causing secondary pollution. CN201910123257.9 describes a slow-release electron donor prepared by filling microporous hollow spheres with siderite and sulfur particles. However, this slow-release electron donor cannot directly contact the electron acceptor, resulting in low denitrification efficiency (only 85% removal rate for 20 mg / L nitrate at a 12-hour hydraulic retention time). Furthermore, the small-diameter particles are prone to caking under prolonged hydraulic scouring, causing blockage of the microporous carrier and reducing denitrification efficiency. In addition, CN202311442274.1 uses a binder to achieve multi-component composite composition, posing a potential risk of secondary pollution.

[0004] Carbon fiber, as a carbon material, possesses properties such as easy dispersion and enhanced electrical conductivity. Existing research has shown that carbon fiber materials can be applied in the field of wastewater treatment and are excellent biofilm carriers. However, the application of carbon fiber in wastewater treatment, especially in the preparation of biocarriers with high efficiency in nitrogen and phosphorus removal, good mechanical stability, and long lifespan, has not yet been reported. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a carbon fiber-modified autotrophic nitrogen and phosphorus removal biocarrier, its preparation method, and its applications. By introducing carbon fibers, this carrier effectively improves the electron transfer efficiency and mechanical properties of the biocarrier. Furthermore, using this biocarrier, long-term simultaneous nitrogen and phosphorus removal can be achieved in the field of wastewater treatment.

[0006] To achieve the above objectives, the first aspect of the present invention provides a carbon fiber modified biological carrier, wherein the biological carrier is configured as a blocky sphere with sulfur as the matrix, and granular buffer material and columnar carbon fiber material are distributed on its surface and inside. The buffer material has an island-like structure on the surface, and the island-like structure accounts for 10-80% of the total surface area of ​​the biological carrier, preferably 30-70%. The carbon fiber material is uniformly dispersed in sulfur on the surface and protrudes in a spiky manner. The spiky structure accounts for 0.01-25% of the total biological carrier, preferably 0.1%-10%, and more preferably 0.1%-1%.

[0007] The maximum directional dimension of the biological carrier is 1-10 mm, preferably 2-5 mm.

[0008] The buffer material is selected from one or more of siderite, iron ore and limestone, and its particle size is 0.2-5 mm, preferably 0.5-1 mm.

[0009] Preferably, the buffer material is siderite.

[0010] The carbon fiber material is carbon fiber powder, which has a columnar or elongated microstructure and a density of 1.5-2.0 g / cm³. 3 Preferably, it is 1.7-1.8 g / cm³. 3 The tensile strength is ≥4500 GPa, preferably ≥4900 GPa, the monofilament diameter is 2-12 μm, preferably 6-8 μm, the aspect ratio is 2:1-12:1, preferably 6:1-9:1, and the fineness is 20-80 mesh, preferably 40-60 mesh.

[0011] The sulfur is sublimed sulfur or other known sulfur, with a Mohs hardness of 1-6, preferably 2-5; and a gloss level of 1-4 cd / m². 2 2-3 cd / m 2 .

[0012] The mass ratio of sulfur to carbon fiber material in the biological carrier is 10:1-10000:1, preferably 100:1-1000:1.

[0013] The mass ratio of sulfur to buffer material in the biological carrier is 1:5-5:1, preferably 4:5-5:4.

[0014] A second aspect of this invention provides a method for preparing a carbon fiber-modified autotrophic denitrification and phosphorus removal active biological carrier, comprising the following steps: (1) Sulfur is melted at 119-175℃ to obtain liquid sulfur; (2) Maintain the temperature in (1), add the carbon fiber material to the liquid sulfur, and stir and mix at 200-800 rpm for 20-200 seconds to obtain the first mixture; (3) Maintain the temperature in (2), add the buffer material to the first mixture, and stir at 200-800 rpm for 20-200 seconds to obtain the second mixture; (4) The second mixture is passed through a mixture distributor at a mixture outflow rate of 2-5 ml / hole per minute into water at 25-75°C and cooled and solidified for 0.5-10 minutes; (5) Filter out the formed solid material through a 1-10 mesh sieve to obtain the biological carrier.

[0015] Preferably, the sulfur melting temperature in step (1) is 125-160℃, and more preferably 140-150℃.

[0016] Preferably, the stirring speed in step (2) is 400-600 rpm and the time is 40-80 seconds.

[0017] Preferably, the stirring speed in step (3) is 400-600 rpm and the time is 40-80 seconds.

[0018] Preferably, in step (4), the cooling water temperature is 45-65°C and the time is 2-5 minutes.

[0019] Preferably, the sieve in step (5) is 3 to 5 mesh.

[0020] A third aspect of the present invention provides a method for treating wastewater using the above-mentioned biological carrier, wherein the biological carrier is used to remove nitrogen and phosphorus from the wastewater.

[0021] Furthermore, the biological carrier is loaded into a column-type fixed-bed filter reactor to play a role, and the porosity of the biological carrier is 50%-55%, and the Mohs hardness is 5-5.5.

[0022] The carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier is the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier as described above, or it is the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier prepared by the preparation method described above, and is used as a filler or filter material in a packed bed or fixed bed filter.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier, which can be used as a filler or filter material for packed bed, deep bed and fixed bed filter in the field of water treatment, and can achieve long-term simultaneous removal of nitrogen and phosphorus.

[0024] (2) The carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier prepared by the present invention has the characteristics of high hardness, wear resistance and stability, and effectively reduces the suspended solids in the effluent.

[0025] (3) The present invention can effectively solve the problems of limited electron transfer efficiency and limited microbial utilization efficiency at the solid-water interface in packed bed or fixed bed filter tanks, and achieve efficient and simultaneous deep nitrogen and phosphorus removal. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of Example 1, a preferred embodiment of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier prepared according to the present invention. Figure 2 This is a physical image of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier obtained in Example 1 of this invention. Figure 3 SEM image of the surface of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier obtained in Example 1 of this invention. Figure 4 The diagram shows the nitrate removal effect of Example 1, prepared as a packing material or filter media, during the operation of a fixed-bed filter. Detailed Implementation

[0028] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0029] This invention provides a carbon fiber-modified autotrophic denitrification and phosphorus removal bioactive carrier. Carbon fiber, as a carbon material, possesses properties of easy dispersion and enhanced conductivity. Existing research indicates that carbon fiber materials can be applied in wastewater treatment and are excellent biofilm carriers. Optimizing the structure of a sulfur-coupled siderite bioactive carrier using carbon fiber molding expands the electron transfer pathway between the packing surface and the liquid phase, enhancing solid-liquid mass transfer efficiency, demonstrating feasibility.

[0030] The biological carrier is configured as a blocky sphere with sulfur as the matrix, and its surface and interior are distributed with granular buffer material and columnar carbon fiber material. The buffer material has an island-like structure on the surface, which accounts for 10-80% of the total surface area of ​​the biological carrier, preferably 30-70%; the carbon fiber material is uniformly dispersed in the sulfur on the surface, and protrudes in a spiky manner, which accounts for 0.01-25% of the total surface area of ​​the biological carrier, preferably 0.1%-10%, and more preferably 0.1%-1%.

[0031] The maximum directional dimension of the biological carrier is 1-10 mm, preferably 2-5 mm.

[0032] The buffer material is selected from one or more of siderite, iron ore and limestone, and its particle size is 0.2-5 mm, preferably 0.5-1 mm.

[0033] Preferably, the buffer material is siderite, and the siderite can be any known type of siderite. This invention does not limit the origin or specific composition of the siderite.

[0034] The carbon fiber material is carbon fiber powder, which has a columnar or elongated microstructure and a density of 1.5-2.0 g / cm³. 3 Preferably, it is 1.7-1.8 g / cm³. 3 The carbon fiber powder has a tensile strength ≥4500 GPa, preferably ≥4900 GPa, a single filament diameter of 2-12 μm, preferably 6-8 μm, an aspect ratio of 2:1-12:1, preferably 6:1-9:1, and a fineness of 20-80 mesh, preferably 40-60 mesh. The carbon fiber powder can be produced by any manufacturer; this invention does not modify the specific composition of the carbon fiber, nor does it limit the manufacturer.

[0035] The sulfur is sublimed sulfur or other known sulfur, with a Mohs hardness of 1-6, preferably 2-5; and a gloss level of 1-4 cd / m². 2 2-3 cd / m 2 .

[0036] The mass ratio of sulfur to carbon fiber material in the biological carrier is 10:1-10000:1, preferably 100:1-1000:1.

[0037] The mass ratio of sulfur to buffer material in the biological carrier is 1:5-5:1, preferably 4:5-5:4.

[0038] The principle behind this configuration is that carbon fiber materials possess excellent electrical conductivity and, as demonstrated in existing research, serve as excellent biofilm carriers. The establishment of island-like and spiky protrusion structures helps increase the specific surface area of ​​the packing material, while simultaneously adding efficient electron transfer channels during the reaction. Laboratory studies have shown that constructing such surface structures facilitates the colonization of denitrification-related functional microorganisms during wastewater denitrification, significantly increasing the relative abundance of denitrifying bacteria in the microbial community. This is because electrons generated at the sulfur interface are more easily transferred to the liquid phase and utilized by microorganisms. Furthermore, due to potential differences, the sulfur interface has a lower potential due to the presence of reduced substances, while the liquid phase contains oxidizing substances, primarily nitrates, resulting in a higher potential. Electrons can spontaneously transfer from the solid-phase surface to the liquid phase through transfer channels, replacing some of the electroactive bacterial functions and promoting an increase in denitrifying functional microorganisms in the system, thus facilitating the denitrification process. Meanwhile, by selecting carbon fiber materials with a high aspect ratio, the surface structure of the above-mentioned biological carrier can be constructed. In addition, the excellent properties of carbon fiber can significantly increase the hardness and wear resistance of the biological carrier after addition, making the biological carrier more stable during long-term water scouring.

[0039] A second aspect of this invention provides a method for preparing a carbon fiber-modified autotrophic denitrification and phosphorus removal active biological carrier, comprising the following steps: (1) Sulfur is melted at 119-175℃ to obtain liquid sulfur; (2) Maintain the temperature in (1), add the carbon fiber material to the liquid sulfur, and stir and mix at 200-800 rpm for 20-200 seconds to obtain the first mixture; (3) Maintain the temperature in (2), add the buffer material to the first mixture, and stir at 200-800 rpm for 20-200 seconds to obtain the second mixture; (4) The second mixture is passed through a mixture distributor at a mixture outflow rate of 2-5 ml / hole per minute into water at 25-75°C and cooled and solidified for 0.5-10 minutes; (5) Filter out the formed solid material through a 1-10 mesh sieve to obtain the biological carrier.

[0040] Preferably, the sulfur melting temperature in step (1) is 125-160℃, and more preferably 140-150℃.

[0041] Preferably, the stirring speed in step (2) is 400-600 rpm and the time is 40-80 seconds.

[0042] Preferably, the stirring speed in step (3) is 400-600 rpm and the time is 40-80 seconds.

[0043] Preferably, in step (4), the cooling water temperature is 45-65°C and the time is 2-5 minutes.

[0044] Preferably, the sieve in step (5) is 3 to 5 mesh.

[0045] The third aspect of this invention provides an application of carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier in the field of water treatment.

[0046] The carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier is the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier as described above, or it is the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier prepared by the preparation method described above. It is used as a filler or filter material in a packed bed or fixed bed filter to achieve simultaneous denitrification and phosphorus removal functions.

[0047] The following description is based on specific embodiments: Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available, and techniques not described in detail were performed according to standard methods well known to those skilled in the art.

[0048] Example 1 The specific preparation method of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier in this embodiment is as follows: (1) Select sublimed sulfur with a Mohs hardness of 3 and a brightness of 3 cd / m², and melt it into liquid at 150°C to obtain liquid sulfur; (2) Maintaining the temperature at 150°C, add the carbon fiber powder to the liquid sulfur and stir at 500 rpm for 60 seconds to obtain the first mixture; the density of the carbon fiber powder is 1.75 g / cm³. 3 The tensile strength of the carbon fiber powder is ≥4900 GPa, the diameter of the single filament of the carbon fiber powder is 6-8 μm, the aspect ratio of the carbon fiber powder is 6:1-9:1, and the fineness of the carbon fiber powder is 50 mesh. (3) Maintain 150°C, add siderite particles to the first mixture, stir and mix at 500 rpm for 60 seconds to obtain the second mixture; the siderite particles are from Luoyang, Henan, and have a size of 0.5-1 mm. (4) The second mixture is passed through a mixture distributor and cooled and solidified in 45°C water at a mixture outflow rate of 5 ml / min for 5 minutes. (5) Filter out the formed solid material through a 3-5 mesh sieve to obtain the biological carrier.

[0049] In this embodiment, the mass ratio of sulfur to carbon fiber is 1000:2; the mass ratio of sulfur to siderite is 1:1.

[0050] A carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier prepared by the above method is shown below. Figure 2 SEM images of the prepared carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier are shown below. Figure 3 .

[0051] Example 2 The specific preparation method of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier in this embodiment is as follows: (1) Select sublimed sulfur with a Mohs hardness of 5 and a brightness of 2 cd / m², and melt it into liquid at 175°C to obtain liquid sulfur; (2) Maintaining the temperature at 175°C, add the carbon fiber powder to the liquid sulfur and stir at 200 rpm for 200 seconds to obtain the first mixture; the density of the carbon fiber powder is 2.0 g / cm³. 3 The carbon fiber powder has a tensile strength ≥4500 GPa, a single filament diameter of 6-8 μm, an aspect ratio of 6:1-9:1, and a fineness of 60 mesh. (3) Maintain 175°C, add siderite particles to the first mixture, stir and mix at 200 rpm for 200 seconds to obtain the second mixture; the siderite particles are from Luoyang, Henan, and have a size of 0.5-1 mm. (4) The second mixture is passed through a mixture distributor and cooled and solidified in 75°C water at a mixture outflow rate of 2 ml / min for 10 minutes. (5) Filter out the formed solid material through a 3-5 mesh sieve to obtain the biological carrier.

[0052] In this embodiment, the mass ratio of sulfur to carbon fiber is 1000:1; the mass ratio of sulfur to siderite is 4:5.

[0053] Comparative Example 1 Referring to the parameters of Example 1, a carrier containing only sulfur and siderite was prepared without adding carbon fiber powder.

[0054] Example 3 The carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier from Example 1 was loaded into a column-type fixed-bed filter reactor. The carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier had a porosity of 50% and a Mohs hardness of 5. Activated sludge from the anaerobic zone of a wastewater treatment plant was injected into the reactor and operated under sequencing batch reactor (SBR) conditions using an acclimation culture medium. The hydraulic retention time (HRT) was 4 days, and the reactor underwent internal circulation during the SBR phase at a flow rate of 15 ml / min. Subsequently, the hydraulic retention time of the fixed-bed filter reactor was set to 6 h, 4 h, 2 h, and 1 h, respectively, and simulated wastewater was continuously and stably pumped into the reactor. The nitrate nitrogen concentration in the simulated wastewater was 30 ± 2 mg / L, and the total dissolved phosphorus concentration was 10 ± 1 mg / L. The nitrate, nitrite, and phosphate levels in the reactor effluent were measured daily, and the total nitrogen removal load of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier column reactor was calculated. The reactor operation results are shown in [the table below]. Figure 4 .

[0055] As shown in the figure, under continuous flow conditions, the maximum nitrate removal load of the carbon fiber modified autotrophic denitrification and phosphorus removal active biocarrier reactor can reach 0.7 kg N / m³. 3 •d, phosphate removal capacity is 0.5-1.5 mg P / L, pH can be maintained at 7±0.2, and effluent SS < 10 mg / L.

[0056] As can be seen from the above, the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier of the present invention has stable denitrification and phosphorus removal efficiency. Under the modification conditions of carbon fiber, the Mohs hardness of the carbon fiber modified autotrophic denitrification and phosphorus removal active biological carrier described in Example 1 is significantly improved, the SS in the effluent is well controlled, and the application prospects are broad.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A carbon fiber modified biological carrier, characterized in that, The biological carrier is configured as a blocky sphere with sulfur as the matrix, and granular buffer material and columnar carbon fiber material are distributed on its surface and inside. The buffer material has an island-like structure on the surface, and the island-like structure accounts for 10-80% of the total surface area of ​​the biological carrier. The carbon fiber material is uniformly dispersed in sulfur on the surface and has a spiky protrusion structure. The mass of the carbon fiber material accounts for 0.01-25% of the total mass of the biological carrier.

2. The biological carrier according to claim 1, characterized in that, The maximum directional dimension of the biological carrier is 1-10 mm.

3. The biological carrier according to claim 1, characterized in that, The cushioning material is selected from one or more of siderite, iron ore and limestone, and its particle size is 0.2-5 mm.

4. The biological carrier according to claim 1, characterized in that, The carbon fiber material is carbon fiber powder, which has a columnar or elongated microstructure and a density of 1.5-2.0 g / cm³. 3 Tensile strength ≥4500 GPa, single filament diameter 2-12 μm, aspect ratio 2:1-12:1, fineness 20-80 mesh.

5. The biological carrier according to claim 1, characterized in that, The sulfur is sublimed sulfur or other known sulfur, with a Mohs hardness of 1-6 and a brightness of 1-4 cd / m². 2 .

6. The biological carrier according to claim 1, characterized in that, The mass ratio of sulfur to carbon fiber material in the biological carrier is 10:1-10000:1, and the mass ratio of sulfur to buffer material is 1:5-5:

1.

7. The method for preparing a biological carrier according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Sulfur is melted at 119–175°C to obtain liquid sulfur; S2: Maintain the temperature in step S1, add the carbon fiber material to the liquid sulfur, and stir and mix at 200-800 rpm for 20-200 seconds to obtain the first mixture; S3: Maintain the temperature in step S2, add the buffer material to the first mixture, and stir at 200-800 rpm for 20-200 seconds to obtain the second mixture; S4: The second mixture is passed through a mixture distributor at a flow rate of 2-5 ml / min into water at 25-75°C and cooled and solidified for 0.5-10 minutes. S5: Filter out the formed solid material using a 1-10 mesh sieve to obtain the biological carrier.

8. The preparation method according to claim 7, characterized in that, The cushioning material is selected from one or more of siderite, iron ore and limestone, and its particle size is 0.2-5 mm.

9. A method for treating wastewater using a biological carrier according to any one of claims 1-6, characterized in that, The biological carrier is used to remove nitrogen and phosphorus from the wastewater.

10. The method according to claim 9, characterized in that, The biological carrier is loaded into a column-type fixed-bed filter reactor to perform its function, and the porosity of the biological carrier is 50%-55%, and the Mohs hardness is 5-5.5.

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