Sulfur-based denitrification filler and preparation method thereof

Abstract

The present application relates to the technical field of sewage treatment, and specifically discloses a sulfur-based denitrification filler and a preparation method thereof. The method comprises the following steps: (1) mixing sulfur, calcium carbonate, and activated carbon, then adding a thickener and ethyl cellulose and uniformly mixing to obtain a solid mixture; (2) mixing the solid mixture with a low-carbon alcohol and continuously stirring until the ethyl cellulose is completely dissolved to obtain a gray paste; (3) granulating the paste to obtain initial particles; (4) heat-treating the initial particles to obtain a filler; the heat treatment comprises the following steps: heat treatment at 70-90°C for 2-4 hours and heat treatment at 115-145°C for 1-2 hours. The sulfur-based denitrification filler of the present application has the advantages of high strength and excellent toughness.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and more specifically, to a sulfur-based denitrification filler and a preparation method thereof. Background Art

[0002] Traditional denitrification uses an organic carbon source to denitrify nitrate nitrogen in water to produce nitrogen gas under the action of heterotrophic microorganisms, but this reaction requires the consumption of a certain carbon source. Sulfur autotrophic denitrification uses elemental sulfur to denitrify nitrate nitrogen in water to produce nitrogen gas under the action of autotrophic denitrifying bacteria. This reaction does not require the addition of an organic carbon source, but does require the supplementation of alkalinity and inorganic carbon sources. Both denitrification processes have their own advantages and disadvantages, but studies have found that synergizing the two denitrification methods can significantly increase the denitrification rate. In particular, heterotrophic denitrification produces alkalinity, while sulfur autotrophic denitrification consumes alkalinity. Combining the two can reduce alkalinity replenishment and keep the water pH within the optimal range for denitrifying bacteria.

[0003] However, the only fillers currently available on the market are sulfur autotrophic denitrifying fillers. However, this type of filler still has the disadvantages of low strength, low toughness, small specific surface area, and a narrow range of use (only applicable to fixed bed filters). In addition, additional alkalinity and inorganic carbon are required during use to provide a growth environment and growth materials for sulfur autotrophic denitrifying bacteria. Summary of the Invention

[0004] In order to improve the strength and toughness of sulfur-based autotrophic denitrification filler, the present application provides a sulfur-based denitrification filler and a preparation method thereof.

[0005] In a first aspect, the present application provides a method for preparing a sulfur-based denitrification filler, which adopts the following technical solution:

[0006] A method for preparing a sulfur-based denitrification filler comprises the following steps:

[0007] (1) sulfur, calcium carbonate and activated carbon are mixed, and then a thickener and ethyl cellulose are added and uniformly mixed to obtain a solid mixture;

[0008] (2) mixing the solid mixture and the low-carbon alcohol, and continuously stirring until the ethyl cellulose is completely dissolved to obtain a paste;

[0009] (3) granulating the paste to obtain primary particles;

[0010] (4) heat-treating the initial particles to obtain;

[0011] The heat treatment comprises the following steps: heat treatment at a temperature that allows the low-carbon alcohol to volatilize for 2-4 hours, and heat treatment at 120-135° C. for 1-2.5 hours.

[0012] By adopting the above technical solution, sulfur autotrophic denitrification is a zero-order reaction. Under the action of microorganisms, the reaction rate is positively correlated only with the specific surface area of ​​the sulfur-based denitrification filler. The larger the specific surface area of ​​the filler, the higher the rate of sulfur autotrophic denitrification and denitrification. When making the filler, the present application uses low-carbon alcohol to dissolve sulfur. Sulfur is a non-polar molecule and low-carbon alcohol is a polar molecule. Therefore, sulfur is difficult to dissolve in low-carbon alcohol. Due to the volatile nature of low-carbon alcohol, the content of low-carbon alcohol will gradually decrease during the high-temperature drying process, and sulfur also tends to be enriched on the surface of the sulfur-based denitrification filler under the action of the surface tension of low-carbon alcohol. Ethyl cellulose is a water-insoluble non-ionic cellulose ethyl ether that is insoluble in water but soluble in low-carbon alcohol. It has good film-forming properties and mechanical strength. Ethyl cellulose is completely or almost completely dissolved in low-carbon alcohol, and ethyl cellulose is cross-linked through intermolecular hydrogen bonds. After heat treatment, the space originally occupied by low-carbon alcohol in the ethyl cellulose forms a skeleton structure with pores of various sizes due to the volatilization of low-carbon alcohol. As the lower alcohol evaporates, most of the sulfur powder accumulates on the surface of the sulfur-based denitrification filler. Ethyl cellulose, leveraging its excellent film-forming properties, gradually encapsulates the sulfur powder within the pores of the ethyl cellulose, creating a microencapsulated structure. This enriches the surface of the sulfur-based denitrification filler, forming a porous, porous structure within the filler. Microorganisms can attach to both the inner and outer surfaces of the filler. When activated carbon powder is added, the ethyl cellulose also encapsulates the activated carbon without affecting its active pore properties. Furthermore, the activated carbon's three-dimensional structure further increases the specific surface area of ​​the sulfur-based denitrification filler, providing more attachment sites for microorganisms and ultimately improving water treatment capacity. Furthermore, the activated carbon exhibits a significant adsorption capacity, further absorbing pollutants from the water. Therefore, the synergistic effects of activated carbon, ethyl cellulose, ethanol, and sublimated sulfur significantly enhance the water treatment capacity of the prepared sulfur-based denitrification filler.

[0013] In addition, since the sulfur-based denitrification filler has an internal porous structure, compared with the commercially available sintered sulfur autotrophic filler, when the filler diameter is 5 mm, under the same volume, the mass of the sulfur-based denitrification filler of the present application is only 40% of that of the commercially available sintered sulfur autotrophic filler.

[0014] Ethyl cellulose has excellent film-forming properties, forming numerous closed pores on the surface of the sulfur-based denitrification packing. The ratio of closed pores to open pores in the overall sulfur-based denitrification packing determines its buoyancy in water. Sulfur-based denitrification packing with a diameter of 3-5mm has greater buoyancy and can be used in fluidized bed processes. Sulfur-based denitrification packing with a diameter of 5-10mm has less buoyancy and can be used in fixed bed processes.

[0015] In addition, in the above scheme, "the temperature at which the low-carbon alcohol volatilizes" is a temperature within the range of ±5°C from the boiling point of the low-carbon alcohol. The heat treatment in step (4) has the following effects: 1. After the heat treatment, the low-carbon alcohol as a solvent is volatilized as completely as possible, and the pores occupied by the low-carbon alcohol in the ethyl cellulose are opened, and channels for the entry and exit of substances are formed in the ethyl cellulose, thereby avoiding affecting the adsorption performance and increase in specific surface area of ​​the sulfur-based denitrification filler. 2. Ethyl cellulose has good thermoplasticity and can undergo flow deformation during heat treatment, thereby improving the uniformity and integrity of the sulfur-based denitrification filler molding and improving the strength and toughness of the sulfur-based denitrification filler. In this scheme, the choice of heat treatment temperature is crucial. The glass transition temperature (Tg) of ethyl cellulose is approximately 130°C. Temperatures near this point cause polymer creep, resulting in certain structural changes in the ethyl cellulose. The melting point of ethyl cellulose is 175°C; temperatures exceeding this point can cause membrane rupture and substantially degrade the mechanical properties of the sulfur-based denitrification filler. The boiling point of lower alcohols is between 60 and 85°C; temperatures below this point prevent the alcohols from evaporating. Therefore, in this scheme, a temperature that allows the alcohols to volatilize is used for slow evaporation and thermoplastic transformation of the ethyl cellulose. Subsequently, the heat treatment temperature is increased to 120-135°C. This high temperature accelerates the evaporation of the lower alcohols, opening up the internal pores of the ethyl cellulose, while also causing the ethyl cellulose to undergo glass transition creep, enhancing its mechanical properties. It is important to note that the heat treatment begins at a low temperature and then at a high temperature, but the recommended temperature for the high temperature treatment is between 120 and 135°C. This is because the high temperature treatment should not exceed 135°C, as this can cause the filler particles to break or develop noticeable cracks.

[0016] After the vitrification structure creep of ethyl cellulose, the sulfur-based denitrification filler is transformed from a brittle material to a tough material, and the toughness of the filler is greatly increased. After the addition of activated carbon as an aggregate, the hardness of the filler is increased, and the addition of thickener further enhances the hardness. Therefore, compared with commercially available fillers, the sulfur-based denitrification filler of the present application has higher hardness and greatly improved toughness; when the sulfur-based denitrification filler is impacted, the commercially available sintered sulfur autotrophic filler shows glass-like shattering, while the sulfur-based denitrification filler of the present application is only partially concave, and the filler remains intact and has a certain impact resistance.

[0017] Regarding wastewater treatment using this sulfur-based denitrifying filler, the main components are sulfur, calcium carbonate, and a thickener. Sulfur provides an electron donor for autotrophic denitrification, reducing nitrate nitrogen in the water to nitrogen gas and generating hydrogen ions. Calcium carbonate neutralizes the generated hydrogen ions, stabilizing the pH of the system. It also provides inorganic carbon sources such as carbonate and carbon dioxide for sulfur autotrophic denitrification. Heterotrophic denitrification, while reducing nitrate nitrogen to nitrogen gas, also produces a certain amount of hydroxide ions, which neutralize the hydrogen ions generated during sulfur autotrophic denitrification. Furthermore, calcium carbonate is consumed, generating calcium ions that react with inorganic phosphorus in the water to form an unstable precipitated calcium hydrogen phosphate. This precipitate then converts to calcium phosphate precipitate as the calcium ion concentration increases; or, under alkaline conditions, the calcium ions directly form calcium phosphate precipitate. Therefore, this sulfur-based denitrifying filler has excellent wastewater treatment capabilities.

[0018] In summary, the sulfur-based denitrification filler prepared by this method has a higher specific surface area, adjustable filler buoyancy, good strength and toughness, and excellent denitrification and phosphorus removal effects.

[0019] Optionally, the low-carbon alcohol is selected from any one or both of methanol and ethanol.

[0020] Optionally, when the low-carbon alcohol is methanol, the heat treatment includes the following steps: heat treatment at 60-70°C for 2-4 hours, and heat treatment at 120-135°C for 1-2.5 hours; when the low-carbon alcohol is ethanol, the heat treatment includes the following steps: heat treatment at 73-83°C for 2-4 hours, and heat treatment at 120-135°C for 1-2.5 hours.

[0021] Optionally, the sulfur is sublimed sulfur or sulfur powder; further optionally, the sulfur is sublimed sulfur.

[0022] In this embodiment, sublimed sulfur has a higher purity, and therefore sublimed sulfur is preferred.

[0023] Optionally, the particle size D of the solid mixture is 0<D<150 mesh.

[0024] Optionally, in step (1), the weight ratio of the sulfur to the calcium carbonate is (1-4):1, the weight ratio of the sulfur to the thickener is (1-4):1; the weight ratio of the sulfur to the activated carbon is (3-6):1, and the mass ratio of the sulfur to the ethyl cellulose is (0.8-2):1.

[0025] By adopting the above technical solution, the sulfur-based denitrification filler is prepared with an appropriate raw material ratio to obtain a sulfur-based denitrification filler with excellent performance.

[0026] Optionally, in step (1), the weight ratio of the sulfur to the calcium carbonate is 3:1, and the weight ratio of the sulfur to the thickener is 3:1; the weight ratio of the sulfur to the activated carbon is 4:1, and the mass ratio of the sulfur to the ethyl cellulose is 1:1.

[0027] Optionally, the thickener is selected from any one or more of dextrin, glutinous rice paste and starch. Further optionally, the thickener is dextrin.

[0028] Through the above technical solution, dextrin, a starch derivative obtained through low-grade hydrolysis, exhibits high viscosity, strong thickening properties, and high strength after solidification. While providing a binding effect and enhancing the strength of the sulfur-based denitrification filler, dextrin can also serve as an organic carbon source for heterotrophic denitrification after further hydrolysis in wastewater, demonstrating excellent synergistic effects when used in conjunction with other components.

[0029] Optionally, in step (2), when the solid mixture and the low-carbon alcohol are mixed, the amount of the low-carbon alcohol added is 200-400% of the weight of the solid mixture.

[0030] By adopting the above technical solution, the excess low-carbon alcohol completely dissolves the ethyl cellulose and makes the formed paste have a lower solid content.

[0031] Optionally, in step (3), the granulation diameter is 3-5 mm or 5-10 mm.

[0032] By adopting the above technical solution, different filler particle sizes are set according to the water treatment process. When treating water in a fluidized bed process, the diameter of the sulfur-based denitrification filler is set within the range of 3-5 mm, as this has a higher buoyancy and is suitable for fluidized bed processes. When treating water in a fixed bed process, the diameter of the sulfur-based denitrification filler is set within the range of 5-10 mm, as this has a lower buoyancy and is suitable for fixed bed processes. The relationship between the particle size of the sulfur-based denitrification filler and the magnitude of the buoyancy is as follows: ethyl cellulose forms a film on the surface of the sulfur-based denitrification filler, forming closed pores. The larger the sphere (i.e., the larger the diameter), the greater the specific surface area, the more closed pores are formed, and the air is trapped within the closed pores. This reduces the density of the sulfur-based denitrification filler and facilitates buoyancy. Ethyl cellulose exists in a filamentous form within the sulfur-based denitrification filler, cross-linking with the activated carbon and preventing film formation, thus ensuring the existence of through pores within the sulfur-based denitrification filler.

[0033] Optionally, in step (2), the stirring speed of the continuous stirring is 1000-1400 r / min.

[0034] Optionally, in step (4), the heat treatment is selected to be drying.

[0035] In a second aspect, the present application provides a sulfur-based denitrification filler, which adopts the following technical solution:

[0036] A sulfur-based denitrification filler is prepared by the above-mentioned preparation method.

[0037] In summary, this application has the following beneficial effects:

[0038] 1. The sulfur-based denitrification filler of this application is prepared by dissolving and dispersing sulfur and ethyl cellulose in a low-carbon alcohol solvent. This solution utilizes the insolubility of sulfur in low-carbon alcohols and the film-forming properties of ethyl cellulose to distribute the sulfur on the surface of the sulfur-based denitrification filler and encapsulate it within the ethyl cellulose. Furthermore, the sulfur-based denitrification filler is prepared through a two-step heating process, utilizing the volatility of low-carbon alcohols to form a porous structure within the ethyl cellulose, thereby improving the water treatment performance of the filler.

[0039] 2. The sulfur-based denitrification filler of the present application forms pores in ethyl cellulose through the volatilization of low-carbon alcohols, and because of the film-forming properties of ethyl cellulose and the distribution of sulfur on the surface of the sulfur-based denitrification filler, closed pores are formed on the surface of the sulfur-based denitrification filler. The density of the sulfur-based denitrification filler is adjusted by adjusting the particle size of the sulfur-based denitrification filler, and its buoyancy in sewage is changed to obtain a sulfur-based denitrification filler that can be used in a fluidized bed or a fixed bed. Specifically, when the diameter of the sulfur-based denitrification filler is within the range of 3-5 mm, the buoyancy is greater and it can be used for fluidized bed sewage treatment; when the diameter of the sulfur-based denitrification filler is within the range of 5-10 mm, the buoyancy is smaller and it can be used for fixed bed sewage treatment.

[0040] 3. The present application prepares a sulfur-based denitrification filler by setting up a two-step heating process, namely: heat treatment at a temperature that allows the volatilization of low-carbon alcohols for 2-4 hours, and further heat treatment at 120-135°C for 1-2.5 hours. In the first stage of the process, the heat treatment is performed at a lower temperature (the temperature that allows the volatilization of low-carbon alcohols) to control the volatilization rate of low-carbon alcohols, thereby controlling the pores of appropriate size and quantity; in the second stage of the process, the heat treatment is performed at a higher temperature (120-135°C, the temperature of ethyl cellulose glass transition creep) to accelerate the overflow of low-carbon alcohols and cause the ethyl cellulose to creep, thereby obtaining a sulfur-based denitrification filler with strong impact toughness and high hardness.

[0041] 4. In the preparation raw materials of this application, activated carbon and ethyl cellulose work together to ensure the hardness of the sulfur-based denitrification filler. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the action process of the sulfur-based denitrification filler in the denitrification process of the present application;

[0043] Figure 2This is an example diagram of the sulfur-based denitrification filler of Example 2;

[0044] Figure 3 This is an electron micrograph of a section of the sulfur-based denitrification filler particles of Example 2;

[0045] Figure 4 Graph showing the changes in total nitrogen content and total nitrogen removal rate when sewage is treated with the sulfur-based denitrification filler of Example 2. DETAILED DESCRIPTION

[0046] The present application is further described in detail below with reference to the accompanying drawings and examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0047] Example

[0048] The main components of the sulfur-based denitrification filler of this application are sulfur, calcium carbonate and thickener. Its working principle is as follows Figure 1 As shown, the sulfur-based denitrifying filler contains microbial attachment sites both on its exterior surface and within its internal pores. When placed in wastewater, the microorganisms begin to remove nitrogen through denitrification. Sulfur provides an electron donor for autotrophic denitrification, reducing nitrate nitrogen in the water to nitrogen gas and generating hydrogen ions. Heterotrophic denitrification, while reducing nitrate nitrogen to nitrogen gas, also produces a certain amount of hydroxide ions, which neutralize the hydrogen ions produced by the sulfur autotrophic denitrification process.

[0049] Example 1

[0050] A method for preparing a sulfur-based denitrification filler comprises the following steps:

[0051] (1) Prepare the raw materials: 60 g of sulfur powder, 60 g of calcium carbonate powder, 60 g of starch, 20 g of activated carbon (pass through a 150-mesh sieve and take the sieve contents), and 75 g of ethyl cellulose.

[0052] The above amounts of sublimed sulfur and calcium carbonate are mixed and ground to a particle size that can pass a 150-mesh sieve, and then mixed with the above amount of activated carbon. Subsequently, the above amounts of dextrin and ethyl cellulose are added and uniformly mixed to obtain a solid mixture.

[0053] (2) Add 550 g of anhydrous methanol to the solid mixture and continue stirring at a speed of 1000 r / min until the ethyl cellulose is completely dissolved. Continue stirring to obtain a gray paste.

[0054] (3) Pour the paste into a granulation mold with a granulation diameter of 4 mm to obtain initial particles.

[0055] (4) The initial particles are heat-treated by drying at 65°C for 4 hours and at 120°C for 2.5 hours to obtain a sulfur-based denitrification filler.

[0056] Example 2

[0057] A method for preparing a sulfur-based denitrification filler comprises the following steps:

[0058] (1) Prepare the raw materials: 60 g of sublimed sulfur powder, 20 g of calcium carbonate powder, 20 g of dextrin, 15 g of activated carbon (pass through a 150-mesh sieve and take the sieve contents), and 60 g of ethyl cellulose.

[0059] The above amounts of sublimed sulfur and calcium carbonate are mixed and ground to a particle size that can pass a 150-mesh sieve, and then mixed with the above amount of activated carbon. Subsequently, the above amounts of dextrin and ethyl cellulose are added and uniformly mixed to obtain a solid mixture.

[0060] (2) Add 525 g of anhydrous ethanol to the solid mixture and continue stirring at a speed of 1200 r / min until the ethyl cellulose is completely dissolved. Continue stirring to obtain a gray paste.

[0061] (3) Pour the paste into a granulation mold with a granulation diameter of 8 mm to obtain initial particles.

[0062] (4) The initial particles are heat-treated by drying at 80°C for 3 hours and at 130°C for 2 hours to obtain a sulfur-based denitrification filler.

[0063] The example of the sulfur-based denitrification filler obtained in this embodiment is shown in FIG. Figure 2 As shown, the sulfur-based denitrification filler has a porous structure both on the surface and inside, and the filler is spherical with good sphericity.

[0064] Example 3

[0065] A method for preparing a sulfur-based denitrification filler comprises the following steps:

[0066] (1) Prepare the raw materials: 60 g of sublimed sulfur powder, 15 g of calcium carbonate powder, 15 g of dextrin, 10 g of activated carbon (pass through a 150-mesh sieve and take the sieve contents), and 30 g of ethyl cellulose.

[0067] The above amounts of sublimed sulfur and calcium carbonate are mixed and ground to a particle size that can pass a 150-mesh sieve, and then mixed with the above amount of activated carbon. Subsequently, the above amounts of dextrin and ethyl cellulose are added and uniformly mixed to obtain a solid mixture.

[0068] (2) Add 520 g of anhydrous ethanol to the solid mixture and continue stirring at a speed of 1400 r / min until the ethyl cellulose is completely dissolved. Continue stirring to obtain a gray paste.

[0069] (3) Pour the paste into a granulation mold with a granulation diameter of 8 mm to obtain initial particles.

[0070] (4) The initial particles are heat-treated by drying at 83°C for 2 hours and at 135°C for 1 hour to obtain a sulfur-based denitrification filler.

[0071] Examples 4-7

[0072] A method for preparing a sulfur-based denitrification filler, which differs from Example 2 in that the mass ratio of sublimated sulfur to ethyl cellulose is different.

[0073] Specifically, in Example 4, the mass ratio of the two is 0.5: 1. More specifically, the raw materials are prepared: 60g of sublimed sulfur powder, 20g of calcium carbonate powder, 20g of dextrin, 15g of activated carbon (passed through a 150-mesh sieve, and the sieve underfill is taken), and 120g of ethyl cellulose.

[0074] Specifically, in Example 5, the mass ratio of the two is 0.8: 1. More specifically, the raw materials are prepared: 60g sublimed sulfur powder, 20g calcium carbonate powder, 20g dextrin, 15g activated carbon (passed through a 150-mesh sieve, and the sieve underfill is taken), and 75g ethyl cellulose.

[0075] Specifically, in Example 6, the mass ratio of the two is 2: 1. More specifically, the raw materials are prepared: 60g of sublimed sulfur powder, 20g of calcium carbonate powder, 20g of dextrin, 15g of activated carbon (passed through a 150-mesh sieve, and the sieve underfill is taken), and 30g of ethyl cellulose.

[0076] Specifically, in Example 7, the mass ratio of the two is 3: 1. More specifically, the raw materials are prepared: 60g of sublimed sulfur powder, 20g of calcium carbonate powder, 20g of dextrin, 15g of activated carbon (passed through a 150-mesh sieve, and the sieve underfill is taken), and 20g of ethyl cellulose.

[0077] Examples 8-11

[0078] A method for preparing a sulfur-based denitrification filler is different from that of Example 2 in that the process parameters of the heat treatment in step (4) are different.

[0079] The details are as follows:

[0080] In Example 8, the initial particles were heat-treated by drying at 73° C. for 3 h and then at 130° C. for 2 h to obtain a sulfur-based denitrification filler.

[0081] In Example 9, the initial particles were heat-treated by drying at 83° C. for 3 h and then at 130° C. for 2 h to obtain a sulfur-based denitrification filler.

[0082] In Example 10, the initial particles were heat-treated by drying at 80° C. for 3 h and then at 120° C. for 2 h to obtain a sulfur-based denitrification filler.

[0083] In Example 11, the initial particles were heat-treated by drying at 80° C. for 3 h and then at 135° C. for 2 h to obtain a sulfur-based denitrification filler.

[0084] Comparative Example

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 2 is that the heat treatment step in step (4) is different, specifically: the initial particles are dried at 135° C. for 5 hours to obtain the sulfur-based denitrification filler.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 2 is that the raw materials for preparing the sulfur-based denitrification filler do not contain activated carbon; specifically, the raw materials are: 60g of sublimated sulfur powder, 20g of calcium carbonate powder, 20g of dextrin, and 60g of ethyl cellulose.

[0089] Comparative Examples 3-4

[0090] A method for preparing a sulfur-based denitrification filler is different from that of Example 2 in that the process parameters of the heat treatment in step (4) are different.

[0091] The details are as follows:

[0092] In Comparative Example 3, the initial particles were heat-treated by drying at 90° C. for 3 h and then at 130° C. for 2 h to obtain a sulfur-based denitrification filler.

[0093] In Comparative Example 4, the initial particles were heat-treated by drying at 80° C. for 3 h and then at 140° C. for 2 h to obtain a sulfur-based denitrification filler.

[0094] Comparative Example 5

[0095] A method for preparing a sulfur-based denitrification filler is different from that of Example 2 in that the heat treatment in step (4) is different. Specifically, the initial particles are allowed to stand at room temperature for 24 hours to obtain the sulfur-based denitrification filler.

[0096] Comparative Example 6

[0097] This comparative example provides a commercially available sulfur-based denitrification filler purchased from Jiangxi Huihua Technology Co., Ltd. The product particle size is 3-5 mm, and its main components are sulfur and clay.

[0098] Performance testing

[0099] 1. Electron microscopy experiment

[0100] The sulphur-based denitrification filler particles obtained in Example 2 were subjected to a section electron microscopy experiment using a Thermo Fisher FEI-Q45 electron scanning microscope. The results are shown in FIG. Figure 3 shown. Figure 3 This indicates that the filler contains a large number of pores with a pore diameter of 1-100 μm.

[0101] 2. Monitoring of sewage treatment effects.

[0102] The sulfur-based denitrification filler prepared in Example 2 was placed in a 2L biofilter, with the sulfur-based denitrification filler occupying 1.5L of the filter volume. The effluent from the three sedimentation tanks of a leather factory in Fujian was used as the experimental wastewater, and the hydraulic retention time (HRT) was set to 3h; the total nitrogen averaged 36mg / L, the dissolved oxygen was controlled below 0.5mg / L, and no additional alkalinity was added. Anaerobic sludge from a municipal sewage treatment plant in Shaanxi was used for acclimatization, and the reactor was started with sodium thiosulfate solution. After the start-up was completed, the addition of sodium thiosulfate was stopped, and a continuous water inlet experiment was subsequently carried out. Water samples were taken every day to detect total nitrogen. The results are as follows: Figure 4 As shown, the final total nitrogen in the effluent was stabilized at 10 mg / L, and the removal rate after stabilization was 72%.

[0103] In addition, referring to the above method, the water treatment effects of the sulfur-based denitrifying fillers of Examples 4-7 and Comparative Example 5 were monitored, with an HRT of 3 hours and no additional alkalinity added. The total nitrogen content of the final effluent was calculated, and the average total nitrogen removal rate was calculated. The results are shown in Table 1.

[0104] Table 1 Water treatment effects of different sulfur-based denitrification fillers

[0105]

[0106] As can be seen from the data in Table 1, the sulfur-based denitrification filler of the present application has relatively excellent water treatment capabilities. However, based on the denitrification effect, it is recommended that the mass ratio of sublimated sulfur to ethyl cellulose be within the range of (0.8-2):1 when preparing the sulfur-based denitrification filler.

[0107] 3. Mechanical properties test of sulfur-based denitrification filler

[0108] The impact toughness of the sulfur-based denitrification filler was tested according to the method for determining the impact toughness of inorganic glass and glass crystal materials in GOST 11067-1985. The hardness of the sulfur-based denitrification filler was tested according to the method in GB / T 3398.2-2008, using the R scale. The above mechanical property tests were performed on the sulfur-based denitrification fillers of Examples 1-11 and Comparative Examples 1-6. The specific results are shown in Table 2.

[0109] Table 2 Impact toughness, hardness and fracture strength of different sulfur-based denitrification fillers

[0110]

[0111]

[0112] As can be seen from the data in Table 2, the sulfur-based denitrification filler prepared in the present application has excellent impact toughness and Rockwell hardness compared to the commercially available filler in Comparative Example 6. Examples 2 and Examples 4-7 investigated the effect of the mass ratio of sublimated sulfur to ethyl cellulose on the performance of the sulfur-based denitrification filler when preparing the sulfur-based denitrification filler. The results showed that when preparing the sulfur-based denitrification filler, a mass ratio of sublimated sulfur to ethyl cellulose within the range of (0.8-2):1 can ensure that the resulting sulfur-based denitrification filler has good impact toughness and Rockwell hardness.

[0113] Example 2, Example 8-11 and Degree Ratio 3-4 explored the influence of the condition parameters of the two-step heat treatment process on the performance of the sulfur-based denitrification filler when preparing the sulfur-based denitrification filler. The results showed that when preparing the sulfur-based denitrification filler, the recommended process parameters are: heat treatment at a temperature around the boiling point of ethanol (78±5°C) for 2-4h, and heat treatment at 120-135°C for 1-2.5h. If the treatment temperature in the first stage is too high, the ethanol evaporates too quickly, which affects the flow deformation of the ethyl cellulose, resulting in poor uniformity and integrity during the molding of the sulfur-based denitrification filler, affecting the preparation process of the sulfur-based denitrification filler, and further having a negative impact on the impact toughness and Rockwell hardness of the sulfur-based denitrification filler; if the treatment temperature in the first stage is too low, the ethanol cannot evaporate in time, and the excessive presence of ethanol affects the creep plasticization process of the ethyl cellulose, resulting in reduced impact toughness and Rockwell hardness of the sulfur-based denitrification filler. The temperature and time control in the second stage are also very important. Specifically, if the temperature is too high, the sulfur-based denitrification filler will easily break, which will damage the integrity of the sulfur-based denitrification filler and reduce its strength. If the temperature is too low, the glass transition creep temperature of ethyl cellulose cannot be reached, which will still lead to a significant decrease in the impact toughness and Rockwell hardness of the sulfur-based denitrification filler.

[0114] In addition, further combining the data results of Comparative Examples 1 and 5, it was found that when preparing sulfur-based denitrification fillers, direct high-temperature heat treatment or room-temperature reaction instead of a two-step heat treatment method could not obtain sulfur-based denitrification fillers with excellent performance.

[0115] In addition, the results of Comparative Example 2 show that the addition of activated carbon is one of the necessary raw materials to ensure the impact toughness and Rockwell hardness of the sulfur-based denitrification filler.

[0116] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a sulfur-based denitrification filler, characterized in that: The following steps are involved: (1) Sulfur, calcium carbonate and activated carbon are mixed, and then a thickener and ethyl cellulose are added and uniformly mixed to obtain a solid mixture; (2) mixing the solid mixture and the low-carbon alcohol, and continuously stirring until the ethyl cellulose is completely dissolved to obtain a paste; (3) granulating the paste to obtain primary particles; (4) heat-treating the initial particles to obtain; The heat treatment comprises the following steps: heat treatment at a temperature that allows the volatilization of low-carbon alcohol for 2-4 hours, and heat treatment at 120-135° C. for 1-2.5 hours; the low-carbon alcohol is selected from any one or both of methanol and ethanol; In the step (1), the weight ratio of the sulfur to the calcium carbonate is 3:1, the weight ratio of the sulfur to the thickener is 3:1; the weight ratio of the sulfur to the activated carbon is 4:1, and the mass ratio of the sulfur to the ethyl cellulose is 1:1; The thickener is selected from any one or more of dextrin, glutinous rice paste and starch; In step (2), when the solid mixture and the low-carbon alcohol are mixed, the amount of the low-carbon alcohol added is 200-400% of the weight of the solid mixture; In step (3), the granulation diameter is 3-5 mm or 5-10 mm.

2. The method for preparing a sulfur-based denitrification filler according to claim 1, wherein: In step (2), the stirring speed for continuous stirring is 1000-1400 r / min.

3. The method for preparing a sulfur-based denitrification filler according to claim 1, wherein: In step (4), the heat treatment is selected as drying.

4. A sulfur-based denitrification filler, characterized in that: The sulfur-based denitrification filler is prepared by the preparation method of the sulfur-based denitrification filler according to any one of claims 1 to 3.

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