Sulfur autotrophic denitrification filler and preparation method thereof

Abstract

The invention relates to the technical field of sewage treatment, in particular to a sulfur autotrophic denitrification filler and a preparation method thereof. The sulfur autotrophic denitrification filler comprises the following components in parts by weight: 60 parts of sulfur powder, 4-8 parts of pyrite powder, 3-5 parts of a pH buffer agent, 2-5 parts of starch, 10-15 parts of an adhesive and 0.05-0.08 part of triethanolamine, the adhesive is epoxy resin and glycerol. Epoxy resin and glycerol are catalyzed by triethanolamine to form a stable three-dimensional network structure, so that the water flow impact resistance of the filler is improved, and the service life of the filler is prolonged; meanwhile, the starch is used as a soft spacer to prevent excessive densification of the epoxy resin, so that the three-dimensional network structure has more mesopores, the attachment of denitrifying bacteria is promoted, and the contact of wastewater, a sulfur source and microorganisms is facilitated, thereby improving the denitrification performance of the filler.

Description

Technical Field

[0001] This application relates to the technical field of sewage treatment, and specifically relates to a sulfur autotrophic denitrification filler and a preparation method thereof. Background Art

[0002] Sulfur autotrophic denitrification is a biological process that uses elemental sulfur or sulfur-containing compounds as electron donors to reduce nitrates or nitrites in sewage to nitrogen gas. Because it does not require an external organic carbon source, has low operating costs, and is environmentally friendly, it has attracted much attention in the field of sewage denitrification. Through this technology, nitrogen pollutants in sewage can be effectively removed, which is of great significance for preventing water eutrophication and protecting the ecological environment.

[0003] Currently, common sulfur autotrophic denitrification fillers mainly include sulfur particles and pyrite particles, etc. Sulfur particles can provide an electron donor for denitrification, but they have poor mechanical strength and are easily broken under the impact of water flow. Pyrite particles have better stability, but have a small specific surface area and a low microbial attachment amount.

[0004] With the development of modern industry and the increasing attention of people to environmental governance, the demand for efficient and stable denitrification in actual sewage treatment projects is gradually increasing, and there is an urgent need to develop a sulfur autotrophic denitrification filler with better performance. Summary of the Invention

[0005] In order to improve the problems of poor mechanical strength of sulfur particles and low microbial attachment amount of pyrite particles, this application provides a sulfur autotrophic denitrification filler and a preparation method thereof.

[0006] In the first aspect, this application provides a sulfur autotrophic denitrification filler, adopting the following technical solution: A sulfur autotrophic denitrification filler, comprising the following components in parts by weight: 60 parts of sulfur powder, 4 - 8 parts of pyrite powder, 3 - 5 parts of pH buffer, 2 - 5 parts of starch, 10 - 15 parts of binder, and 0.05 - 0.08 parts of triethanolamine; the binder is epoxy resin and glycerol.

[0007] By adopting the above technical solution, epoxy resin and glycerol can form a stable and strong three-dimensional network structure under the catalytic action of triethanolamine, endowing the filler with excellent mechanical properties, enabling it to withstand greater pressure and water flow impact; at the same time, the ether bonds and ester bonds in the cross-linked polymer formed by epoxy resin and glycerol can resist acid-base corrosion, adapt to the acidic environment that may be generated during the sulfur autotrophic denitrification process, and improve the long-term use performance of the filler in a complex chemical environment.

[0008] The hydroxyl groups of starch can form hydrogen bond interactions with the epoxy groups in epoxy resin and act as a "soft spacer" during the cross-linking process to prevent the over-densification of epoxy resin, so that more mesopores are retained in the finally formed three-dimensional network structure. This porous structure provides a large number of attachment sites for denitrifying bacteria, promotes the contact between wastewater, sulfur source and microorganisms, shortens the diffusion path of the substrate, increases the diffusion coefficient of the substrate, and enables the reaction to proceed more efficiently. At the same time, starch itself has a certain adhesive effect after gelatinization, which can further improve the mechanical properties of the filler.

[0009] During the sulfur autotrophic denitrification process, acidic substances will be produced by microbial metabolism, resulting in a decrease in the pH of the system. The acidic catalyst will further reduce the environmental pH, which may inhibit the activity of denitrifying bacteria. Although the strong base catalyst can temporarily increase the pH, excessive alkali will cause the pH of the system to fluctuate too much, which is also not conducive to the growth of microorganisms. Triethanolamine itself has a certain pH buffering ability and can cooperate with the pH buffer in the filler to stabilize the pH of the system within an appropriate range, provide a milder living environment for denitrifying bacteria, and enhance their metabolic activity and attachment ability.

[0010] In this application, triethanolamine is used to catalyze the formation of a stable three-dimensional network structure of epoxy resin and glycerol, improving the water flow impact resistance of the filler and extending the service life of the filler. At the same time, starch is used as a "soft spacer" to prevent the over-densification of epoxy resin, ensuring that the three-dimensional network structure has more mesopores, promoting the attachment of denitrifying bacteria, and facilitating the contact between wastewater, sulfur source and microorganisms, thereby improving the denitrification and nitrogen removal performance of the filler.

[0011] Preferably, the mass ratio of the epoxy resin to glycerol is 5:(4 - 5).

[0012] By adopting the above technical solution, when the content of glycerol is too low, the epoxy resin cannot be fully cured, the cross-linking network density decreases, resulting in an increase in the brittleness of the filler and a weakening of the water flow impact resistance. When the content of glycerol is too high, the excessive glycerol will dilute the epoxy resin, resulting in too low cross-linking density and a decrease in the structural strength of the filler. Therefore, after a large amount of research and experimental verification by the applicant, it is finally determined that the mass ratio of the epoxy resin to glycerol in this application is preferably as above.

[0013] Preferably, the mass ratio of the epoxy resin to starch is 5:(2 - 3).

[0014] By adopting the above technical solution, when the starch content is too low, it is difficult for starch to fully play the role of "soft spacer", and the epoxy resin is prone to excessive densification, resulting in a reduction in the number of mesopores in the formed three-dimensional network structure; when the starch content is too high, excessive starch will affect the cross-linking reaction between epoxy resin and glycerol, resulting in poor mechanical properties of the filler and shortening the service life of the filler; therefore, after a large amount of research and experimental verification, the applicant finally determined that the mass ratio of epoxy resin to starch in this application is preferably the above.

[0015] Preferably, the sulfur autotrophic denitrification filler further comprises a filler aid, and the filler aid comprises at least one of tin dioxide and titanium dioxide.

[0016] By adopting the above technical solution, tin dioxide and titanium dioxide, as semiconductor materials, can act as electron shuttles to accelerate the electron transfer between the sulfur source and nitrate / nitrite. By reducing the electron transfer resistance, it promotes the transfer of electrons generated by the oxidation of sulfur by microorganisms to nitrate reductase, thereby enhancing the reaction rate; at the same time, the surface defect sites of tin dioxide and titanium dioxide can serve as cofactor binding sites for enzymes (such as nitrate reductase and nitrite reductase), enhancing the enzyme activity and accelerating the reduction process of nitrogen oxides, improving the denitrification efficiency; at the same time, tin dioxide and titanium dioxide are dispersed in the three-dimensional network structure formed by epoxy resin and glycerol, which can play a role of "skeleton strengthening", thereby further improving the stability of the sulfur autotrophic denitrification filler in water flow.

[0017] Preferably, the filler aid is tin dioxide.

[0018] By adopting the above technical solution, sulfur autotrophic denitrification will release acidic substances, resulting in a decrease in the system pH. The chemical stability of tin dioxide in an acidic environment is better than that of titanium dioxide, and it can maintain structural integrity for a long time; at the same time, the band gap of tin dioxide is narrower, which can more effectively promote the transfer of electrons from the electron donor generated in the microbial metabolism process to its surface and then to electron acceptors such as nitrate, enhancing the electron transfer efficiency of the entire reaction system and improving the denitrification effect. Therefore, tin dioxide is preferred.

[0019] Preferably, the weight part of the tin dioxide is 1-2 parts.

[0020] By adopting the above technical solution, when the content of tin dioxide is low, there are insufficient channels and sites for electron transfer, and it is difficult to effectively accelerate the electron transfer between sulfur oxidation and nitrate reduction, resulting in a small improvement in the denitrification reaction rate; when the content of tin dioxide is high, the high content of tin dioxide may lead to too high local substance concentration, which has an inhibitory effect on denitrifying bacteria, and instead causes the denitrification reaction to be inhibited; therefore, after a large amount of research and experimental verification, the applicant finally determined that the weight part of tin dioxide in this application is preferably the above.

[0021] Preferably, the filler additive is a mixture of tin dioxide and titanium dioxide.

[0022] By adopting the above technical solution, when tin dioxide and titanium dioxide are used in combination, tin dioxide has high stability in an acidic environment and can offset the influence of acidic substances generated by sulfur autotrophic denitrification on the system; while titanium dioxide has a surface charge that is more conducive to microbial attachment under weakly alkaline conditions, and the combination of tin dioxide and titanium dioxide enables the filler to maintain stable performance within a wide pH range.

[0023] At the same time, tin dioxide, as an efficient electron mediator, accelerates the oxidation reaction of the sulfur source and quickly transfers electrons to nitrate reductase, while the surface active sites of titanium dioxide can further promote the nitrate reduction reaction, forming a "double electron transfer channel" and further improving the denitrification efficiency of the filler.

[0024] Preferably, the mass ratio of tin dioxide to titanium dioxide is 5:(1 - 2).

[0025] By adopting the above technical solution, when the content of titanium dioxide is too low, it is difficult to achieve the synergistic effect between titanium dioxide and tin dioxide, and the improvement effect on the performance of the sulfur autotrophic denitrification filler is not obvious; when the content of titanium dioxide is too high, the content of tin dioxide is relatively too small, and the improvement effect of titanium dioxide itself on the denitrification effect of the filler is not as good as that of tin dioxide, but instead leads to a decrease in the denitrification effect of the filler; therefore, after a large amount of research and experimental verification by the applicant, it is finally determined that the mass ratio of tin dioxide to titanium dioxide in this application is preferably as above.

[0026] In a second aspect, the present application provides a method for preparing a sulfur autotrophic denitrification filler, adopting the following technical solution: A method for preparing a sulfur autotrophic denitrification filler, used to prepare the above sulfur autotrophic denitrification filler, includes the following steps: S1. Thoroughly mix the formula amounts of sulfur powder, pyrite powder, pH buffer, starch and other additives to obtain mixed particles; S2. Uniformly mix the formula amounts of epoxy resin and glycerin, add the mixed particles, stir evenly, and then slowly add triethanolamine and stir thoroughly to form a sulfur autotrophic denitrification wet material; S3. Granulate the sulfur autotrophic denitrification wet material to obtain the sulfur autotrophic denitrification filler.

[0027] By adopting the above technical solution, by first fully mixing sulfur powder, pyrite powder and other additives such as starch, the starch and other particles in the formula are preliminarily bonded. Then, the mixed particles are added into the mixed solution of epoxy resin and glycerol. The hydrogen bond between the hydroxyl group of starch and the epoxy group of epoxy resin can promote the uniform dispersion of the mixed particles in the system, thereby optimizing the performance of the sulfur autotrophic denitrification filler prepared.

[0028] Preferably, the particle size of the sulfur autotrophic denitrification filler is 3-5 mm.

[0029] By adopting the above technical solution, when the particle size of the sulfur autotrophic denitrification filler is too small, the porosity between the fillers will also become smaller, resulting in an increase in the resistance when water flows through, and the diffusion path of the substrate will also be hindered, thereby affecting the full contact between the wastewater and the sulfur source and microorganisms, and reducing the denitrification efficiency of the reaction system; when the particle size of the sulfur autotrophic denitrification filler is too large, the specific surface area of the filler will be significantly reduced, resulting in a reduction in the contact area between the wastewater and the sulfur source and microorganisms, and the diffusion path of the substrate becomes longer, which will also reduce the denitrification efficiency of the reaction system; Therefore, after a large amount of research and experimental verification by the applicant, it is finally determined that the particle size of the sulfur autotrophic denitrification filler of the present application is preferably the above.

[0030] In summary, the present application has the following beneficial effects: 1. In the present application, a stable three-dimensional network structure is formed by epoxy resin and glycerol, which improves the service life of the filler; at the same time, starch is used as a "soft spacer" to prevent the over-densification of epoxy resin, and promote the attachment of denitrifying bacteria, thereby improving the denitrification performance of the filler; 2. In the present application, tin dioxide and titanium dioxide are used as electron shuttles to accelerate the electron transfer between the sulfur source and nitrate / nitrite, and improve the reaction rate by reducing the electron transfer resistance; at the same time, the surface defect sites can serve as cofactor binding sites for enzymes (such as nitrate reductase, nitrite reductase), improving the enzyme activity, thereby improving the denitrification efficiency. Brief Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the test for detecting the water flow impact resistance performance in the embodiment of the present application.

[0032] Description of the reference numerals: 1. Sulfur autotrophic denitrification filler; 2. Plexiglass container; 21. Water inlet; 22. Water outlet. Detailed Embodiments

[0033] The raw materials in the present application include the following parts: Sulfur powder: A commercially available product with a CAS number of 63705-05-5 is used; Pyrite powder: A commercially available product with a CAS number of 1309-36-0 is used; pH buffer: Sodium carbonate, sodium bicarbonate, etc. are all acceptable. In this application, a commercially available product of sodium carbonate with CAS No. 497-19-8 is used; Starch: A commercially available product with CAS No. 9005-25-8 is used; Epoxy resin: A commercially available product with CAS No. 38891-59-7 is used; Glycerol: A commercially available product with CAS No. 56-81-5 is used; Triethanolamine: A commercially available product with CAS No. 102-71-6 is used; Tin dioxide: A commercially available product with CAS No. 18282-10-5 is used; Titanium dioxide: A commercially available product with CAS No. 1317-80-2 is used; p-Toluenesulfonic acid: A commercially available product with CAS No. 104-15-4 is used; Sodium hydroxide: A commercially available product with CAS No. 1310-73-2 is used; The present application will be further described in detail below in conjunction with examples and comparative examples.

[0034] Example 1 A preparation method of a sulfur autotrophic denitrification filler for preparing the above-mentioned sulfur autotrophic denitrification filler, comprising the following steps: S1. Add 6000 g of sulfur powder, 600 g of pyrite powder, 400 g of pH buffer and 350 g of starch to a mixer for blending, and mix at 1000 rpm for 10 min to obtain mixed particles; S2. Add 700 g of epoxy resin and 600 g of glycerol to a stirrer, stir at 1200 rpm for 10 min to obtain a uniformly mixed solution; then add the mixed particles to the uniformly mixed solution, stir for 10 min, and slowly add 7 g of triethanolamine, and continue to stir for 15 min to form sulfur autotrophic denitrification wet material; S3. Add the sulfur autotrophic denitrification wet material to a mold with an inner diameter of 5 mm (3-5 mm is acceptable) for granulation, then keep it warm at 60 °C for 2 h, and after demolding, let it stand for 3 days to obtain the sulfur autotrophic denitrification filler.

[0035] Examples 2-3 Based on the preparation method of Example 1, the content of each component in the formula is adjusted in Examples 2-3, and the specific adjustments are shown in Table 1.

[0036] Comparative Examples 1-4 Based on the preparation method of Example 1, the content of each component in the formula is adjusted in Comparative Examples 1-4, and the specific adjustments are shown in Table 1.

[0037] Table 1 Raw material table and performance test table of sulfur autotrophic denitrification fillers in Examples 1-3 and Comparative Examples 1-4

[0038] Performance detection test (1)Water flow impact resistance Refer to Figure 1 to weigh the original mass of the sulfur autotrophic denitrification filler 1, then fill the sulfur autotrophic denitrification filler 1 into the plexiglass container 2. The water flow enters from the water inlet 21 at the bottom of the plexiglass container 2 and flows out from the water outlet 22 at the top of the plexiglass container 2. Control the water flow velocity at 5 m / s. After 12 h, take out the sulfur autotrophic denitrification filler 1, dry it and weigh it, and calculate the weight loss rate: Weight loss rate = (original mass - mass after water flow impact) / original mass × 100%.

[0039] Note: The lower the weight loss rate, the better the water flow impact resistance of the sulfur autotrophic denitrification filler.

[0040] (2)Denitrification effect Add the sulfur autotrophic denitrification filler to the fixed-bed reactor, add the Thiobacillus denitrificans bacterial solution for inoculation. After the inoculation is completed, introduce the simulated wastewater containing nitrate into the fixed-bed reactor. The concentration of nitrate in the simulated wastewater is 50 mg / L. After running for 48 h, measure the concentration of nitrate in the effluent water.

[0041] Note: The lower the concentration of nitrate in the effluent water, the better the denitrification effect of the sulfur autotrophic denitrification filler.

[0042] Perform the above performance detections on the sulfur autotrophic denitrification fillers in Examples 1-3 and Comparative Examples 1-4. The detection results are shown in Table 1.

[0043] Referring to Table 1 and comparing Examples 1-3 and Comparative Examples 1-4, it can be seen that the nitrate concentration in the effluent of Comparative Example 1 is higher than that in Examples 1-3. This is because starch was not added in the comparative example to prevent the epoxy resin from becoming overly dense, resulting in fewer mesoporous structures in the three-dimensional network structure formed by the epoxy resin and glycerol. It is difficult for Thiobacillus denitrificans to attach, which is not conducive to the full contact between the simulated wastewater and the sulfur source and microorganisms, resulting in the denitrification effect of Comparative Example 1 being not as good as that of Examples 1-3.

[0044] The weight loss rate and the nitrate concentration in the effluent of Comparative Examples 2-4 are both inferior to those of Examples 1-3, indicating that the resistance to water flow impact and the denitrification effect of the sulfur autotrophic denitrification filler in Comparative Examples 2-4 are both inferior to those of Examples 1-3. This is because epoxy resin is missing in Comparative Example 2, glycerol is missing in Comparative Example 3, and triethanolamine is missing in Comparative Example 4. The lack of raw materials in Comparative Examples 2-4 results in the inability of the sulfur autotrophic denitrification filler to form a stable and firm three-dimensional network structure, thus leading to the water flow impact resistance of the filler. Under the water flow impact, the core components such as sulfur powder and pyrite powder in the filler are lost, resulting in a significant decrease in the denitrification effect of Comparative Examples 2-4.

[0045] Comparing with Examples 1-3, the sulfur autotrophic denitrification filler in Example 1 has better resistance to water flow impact and denitrification effect. Therefore, Example 1 is preferred.

[0046] Comparative Examples 5-6 On the basis of the preparation method of Example 1, in Comparative Example 5, 7 g of triethanolamine was replaced with 7 g of p-toluenesulfonic acid, and the other conditions remained unchanged.

[0047] On the basis of the preparation method of Example 1, in Comparative Example 6, 7 g of triethanolamine was replaced with 7 g of sodium hydroxide, and the other conditions remained unchanged.

[0048] The sulfur autotrophic denitrification fillers of Comparative Examples 5-6 were subjected to the above performance tests, and the test results are shown in Table 2.

[0049] Table 2 Performance test table of Example 1 and Comparative Examples 5-6

[0050] Referring to Table 2, comparing Example 1 with Comparative Examples 5-6, it can be seen that the nitrate concentration in the effluent of Example 1 is lower than that of Comparative Examples 5-6. This is because in Comparative Example 5, an acidic catalyst (p-toluenesulfonic acid) was added to catalyze the cross-linking reaction of epoxy resin and glycerol. The sulfur autotrophic denitrification process itself will cause the pH of the system to decrease, and the addition of the acidic catalyst further reduces the environmental pH, inhibiting the growth of microorganisms; while in Comparative Example 6, a strong alkaline catalyst (sodium hydroxide) was added to catalyze the cross-linking reaction of epoxy resin and glycerol, and the strong alkaline environment is also not conducive to the growth of microorganisms.

[0051] Examples 4-7 On the basis of the preparation of Example 1, in Examples 4-7, the total mass of epoxy resin and glycerol was kept at 1300 g, and the mass ratio of epoxy resin to glycerol was adjusted, as specifically shown in Table 3.

[0052] The sulfur autotrophic denitrification fillers of Examples 4-7 were subjected to the above performance tests, and the test results are shown in Table 3.

[0053] Table 3 Mass ratio of epoxy resin and glycerol in Example 1 and Examples 4 - 7 and performance test table

[0054] Referring to Table 3, by comparing Example 1 with Examples 4 - 7, it can be seen that too low or too high content of glycerol will lead to an increase in the weight loss rate of the autotrophic denitrification filler and the nitrate concentration in the effluent. This is because when the content of glycerol is too low, the epoxy resin cannot be fully cured, the cross - linked network density decreases, and the ability of the filler to resist water flow impact weakens; when the content of glycerol is too high, the excessive glycerol dilutes the epoxy resin, which also results in too low cross - linked density, thus leading to a weakening of the filler's ability to resist water flow impact. The decline in the water flow impact resistance of the filler means that the effective components in the filler will be lost under the action of water flow, resulting in a decline in the denitrification effect of the filler.

[0055] Examples 8 - 11 Based on the preparation method of Example 1, while keeping the total mass of epoxy resin and starch at 1050 g, the mass ratio of epoxy resin and starch was adjusted in Examples 8 - 11. The specific adjustments are shown in Table 4.

[0056] The sulfur autotrophic denitrification fillers of Examples 8 - 11 were subjected to the above - mentioned performance tests, and the test results are shown in Table 4.

[0057] Table 4 Mass ratio of epoxy resin and starch in Example 1 and Examples 8 - 11 and performance test table

[0058] Referring to Table 4, by comparing Example 1 with Examples 8 - 11, it can be seen that too low content of starch will lead to an increase in the nitrate concentration in the effluent of the autotrophic denitrification filler, and too high content of starch will lead to an increase in both the weight loss rate and the nitrate concentration in the effluent of the autotrophic denitrification filler. This is because when the content of starch is too low, it is difficult for starch to fully play the role of the "soft spacer", and the number of mesopores in the three - dimensional network structure formed by the reaction of epoxy resin and glycerol decreases, which is not conducive to microbial attachment; when the content of starch is too high, starch will interfere with the cross - linking reaction of epoxy resin and glycerol, resulting in poor mechanical properties of the filler, thus leading to a decline in the water flow resistance and denitrification effect of the filler.

[0059] Examples 12 - 13 Based on the preparation method of Example 1, in step S1 of Example 12, 300 g of tin dioxide, sulfur powder, pyrite powder, pH buffer, and starch were added to the mixer for co - blending, and the other conditions remained unchanged.

[0060] Based on the preparation method of Example 12, in Example 13, 300 g of tin dioxide was replaced with 300 g of titanium dioxide, and the other conditions remained unchanged.

[0061] Perform the above performance tests on the sulfur autotrophic denitrification fillers of Examples 12 - 13, and the test results are shown in Table 5.

[0062] Table 5 Performance Test Table of Example 1 and Examples 12 - 13

[0063] Referring to Table 5, by comparing Example 1 with Examples 12 - 13, it can be seen that the nitrate concentration in the effluent of Example 1 is higher than that of Examples 12 - 13, indicating that adding tin dioxide or titanium dioxide can improve the denitrification effect of the sulfur autotrophic denitrification filler. This is because both tin dioxide and titanium dioxide can act as electron shuttles, accelerating the electron transfer between the sulfur source and nitrate / nitrite, promoting the transfer of electrons generated by the oxidation of sulfur by microorganisms to nitrate reductase, and enhancing the reaction rate. At the same time, tin dioxide and titanium dioxide are dispersed in the three-dimensional network structure formed by epoxy resin and glycerol, playing a role of "skeleton strengthening" and further improving the water flow impact resistance of the filler.

[0064] By comparing Examples 12 - 13, it can be seen that the nitrate concentration in the effluent of Example 12 is lower, indicating that adding tin dioxide has a better denitrification effect on the sulfur autotrophic denitrification filler than adding titanium dioxide. This is because sulfur autotrophic denitrification will cause the pH of the system to decrease, and the chemical stability of tin dioxide in an acidic environment is better than that of titanium dioxide, which can maintain the structural integrity for a long time. At the same time, the band gap of tin dioxide is narrower, which can more effectively promote electron transfer and enhance the electron transfer efficiency of the entire reaction system. Therefore, Example 12 is preferred.

[0065] Examples 14 - 17 Based on the preparation method of Example 12, Examples 14 - 17 adjust the addition amount of tin dioxide in the formula, and the specific adjustment is shown in Table 6.

[0066] Perform the above performance tests on the sulfur autotrophic denitrification fillers of Examples 14 - 17, and the test results are shown in Table 6.

[0067] Table 6 Addition Amount and Performance Test Table of Tin Dioxide in Example 12 and Examples 14 - 17

[0068] Referring to Table 6, by comparing Example 12 with Examples 14 - 17, it can be seen that too little or too much tin dioxide will cause the nitrate concentration in the effluent to increase. This is because when the content of tin dioxide is too low, the formed channels and sites for electron transfer are insufficient, making it difficult to effectively accelerate the electron transfer between sulfur oxidation and nitrate reduction. When the content of tin dioxide is too high, it may lead to too high a local concentration, inhibiting the denitrifying bacteria, resulting in a decline in the denitrification effect of the filler.

[0069] Examples 18 - 22 Based on the preparation method of Example 12, in Example 18, 300 g of tin dioxide was replaced with a mixture of 300 g of tin dioxide and titanium dioxide, and the mass ratio of tin dioxide to titanium dioxide in the mixture was 5:1.5, with other conditions remaining unchanged.

[0070] Based on the preparation method of Example 18, in Examples 19 - 22, the mass ratio of tin dioxide to titanium dioxide in the mixture was adjusted, and the specific adjustments are shown in Table 7.

[0071] The sulfur autotrophic denitrification fillers of Examples 18 - 22 were subjected to the above performance tests, and the test results are shown in Table 7.

[0072] Table 7 Mass ratio of tin dioxide and titanium dioxide and performance test table of Examples 12 and Examples 18 - 22

[0073] Referring to Table 7, by comparing Example 12 with Examples 18 - 22, it can be seen that the nitrate concentration in the effluent of Examples 18 - 22 is lower than that of Example 12, indicating that mixing tin dioxide and titanium dioxide can further improve the denitrification effect of the filler. This is because when tin dioxide and titanium dioxide are used in combination, tin dioxide, as an efficient electron mediator, accelerates the oxidation reaction of the sulfur source and rapidly transfers electrons to nitrate reductase, while the surface active sites of titanium dioxide further promote the nitrate reduction reaction, forming a "double electron transfer channel" and further improving the denitrification efficiency of the filler.

[0074] By comparing Examples 18 - 22, it can be seen that too low or too high content of titanium dioxide will lead to an increase in the nitrate concentration in the effluent of the filler. This is because when the content of titanium dioxide is too low, the synergistic effect between titanium dioxide and tin dioxide is difficult to achieve, and the improvement effect on the performance of the sulfur autotrophic denitrification filler is not obvious; when the content of titanium dioxide is too high, the content of tin dioxide is relatively too small, and the improvement effect of titanium dioxide itself on the denitrification effect of the filler is not as good as that of tin dioxide, which will instead lead to a decrease in the denitrification effect of the sulfur autotrophic denitrification filler.

[0075] Example 23 Based on the preparation method of Example 1, in Example 23, step S1 was skipped, and 6000 g of sulfur powder, 600 g of pyrite powder, 400 g of pH buffer, and 350 g of starch were directly added to the homogeneous mixture in step S2, with other conditions remaining unchanged.

[0076] The sulfur autotrophic denitrification filler of Example 23 was subjected to the above performance tests, and the test results are shown in Table 8.

[0077] Table 8 Performance test table of Example 1 and Example 23

[0078] Referring to Table 8, by comparing Example 1 and Example 23, it can be seen that the weight loss rate and the nitrate concentration in the effluent of Example 1 are both lower than those of Example 23. This is because in step S1 of Example 1, sulfur powder, pyrite powder and starch are fully mixed first, so that the starch and other particles in the formula achieve preliminary adhesion. Then, the hydrogen bond between the hydroxyl group of starch and the epoxy group of epoxy resin promotes the uniform dispersion of each component in the cross-linked structure formed by epoxy resin and glycerol, making the structure of the sulfur autotrophic denitrification filler prepared in Example 1 more stable, and thus improving the denitrification effect of Example 1.

[0079] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions according to needs, 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 sulfur autotrophic denitrification filler, characterized in that, The invention comprises the following components in parts by weight: 60 parts of sulfur powder, 4-8 parts of pyrite powder, 3-5 parts of pH buffer, 2-5 parts of starch, 10-15 parts of adhesive and 0.05-0.08 parts of triethanolamine; the adhesive is epoxy resin and glycerol.

2. The sulfur autotrophic denitrification filler according to claim 1, characterized in that: The mass ratio of the epoxy resin to glycerol is 5:(4-5).

3. The sulfur autotrophic denitrification filler according to claim 1, wherein: The mass ratio of the epoxy resin to the starch is 5:(2-3).

4. The sulfur autotrophic denitrification filler according to claim 1, wherein: Also included is a filler auxiliary, which includes at least one of tin dioxide and titanium dioxide.

5. The sulfur autotrophic denitrification filler according to claim 4, wherein: The filler auxiliary agent is tin dioxide.

6. The sulfur autotrophic denitrification filler according to claim 5, wherein: The weight portion of the tin dioxide is 1-2 parts.

7. The sulfur autotrophic denitrification filler according to claim 4, wherein: The filler auxiliary agent is a mixture of tin dioxide and titanium dioxide.

8. The sulfur autotrophic denitrification filler according to claim 7, characterized in that: The mass ratio of tin dioxide to titanium dioxide is 5:(1-2).

9. The preparation method of the sulfur autotrophic denitrification filler according to any one of claims 1-8, characterized in that, The following steps are involved: S1. The formula amount of sulfur powder, pyrite powder and starch are fully mixed to obtain mixed particles; S2. The epoxy resin and glycerol are uniformly mixed and added to the mixed particles, and triethanolamine is slowly added after stirring, and stirred thoroughly to form a sulfur autotrophic denitrification wet material; S3. Granulating the sulfur autotrophic denitrification wet material to obtain the sulfur autotrophic denitrification filler.

10. The preparation method of the sulfur autotrophic denitrification filler according to claim 9, characterized in that: The particle size of the sulfur autotrophic denitrification filler is 3-5 mm.

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