Sulfur autotrophic denitrification filler and preparation method thereof

Abstract

The present application relates to the technical field of sewage treatment, and specifically to a sulfur autotrophic denitrification filler and a preparation method thereof. A 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 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. The present application uses triethanolamine to catalyze epoxy resin and glycerol to form a stable three-dimensional network structure, thereby improving the filler's resistance to water flow impact and increasing the filler's service life; at the same time, starch is used as a "soft spacer" to prevent the epoxy resin from over-densifying, ensuring that the three-dimensional network structure has more mesopores, promoting the attachment of denitrifying bacteria, and facilitating the contact between wastewater and sulfur sources and microorganisms, thereby improving the denitrification and denitrification performance of the filler.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular 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 wastewater to nitrogen gas. Because it requires no external organic carbon source, offers low operating costs, and is environmentally friendly, it has attracted significant attention in the field of wastewater denitrification. This technology effectively removes nitrogen pollutants from wastewater, significantly contributing to the prevention and control of water eutrophication and the protection of the ecological environment.

[0003] At present, common sulfur autotrophic denitrification fillers mainly include sulfur granules and pyrite granules. Although sulfur granules can provide electron donors for denitrification, they have poor mechanical strength and are easily broken by water impact. Pyrite granules have good stability, but small specific surface area and low microbial attachment.

[0004] With the development of modern industry and people's increasing attention to environmental governance, the demand for efficient and stable denitrification in actual sewage treatment projects has gradually increased, 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 of pyrite particles, the present application provides a sulfur autotrophic denitrification filler and a preparation method thereof.

[0006] In the first aspect, the present application provides a sulfur autotrophic denitrification filler, which adopts the following technical solution:

[0007] A 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 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.

[0008] 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, giving the filler 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 and alkali corrosion, adapt to the acidic environment that may be generated during sulfur autotrophic denitrification, and improve the long-term performance of the filler in complex chemical environments.

[0009] The hydroxyl groups of starch can form hydrogen bonds with the epoxy groups in the epoxy resin, acting as a "soft spacer" during the cross-linking process to prevent the epoxy resin from over-densifying, so that more mesopores are retained in the final three-dimensional network structure. This porous structure provides a large number of attachment points for denitrifying bacteria, promotes the contact between wastewater and sulfur sources 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, the starch itself has a certain adhesive effect after gelatinization, which can further promote the improvement of the mechanical properties of the filler.

[0010] During the sulfur autotrophic denitrification process, microbial metabolism produces acidic substances, causing the system pH to drop. Acidic catalysts will further lower the environmental pH, which may inhibit the activity of denitrifying bacteria. Although strong alkaline catalysts can temporarily increase the pH, excessive alkali will cause the system pH to fluctuate too much, which is also not conducive to microbial growth. Triethanolamine itself has a certain pH buffering capacity and can work synergistically with the pH buffer in the filler to stabilize the system pH within an appropriate range, providing a milder living environment for denitrifying bacteria and enhancing their metabolic activity and adhesion ability.

[0011] This application uses triethanolamine to catalyze epoxy resin and glycerol to form a stable three-dimensional network structure, thereby improving the filler's resistance to water flow impact and increasing the filler's service life; at the same time, starch is used as a "soft spacer" to prevent the epoxy resin from becoming excessively densified, ensuring that the three-dimensional network structure has more mesopores, promoting the attachment of denitrifying bacteria, and facilitating the contact between wastewater, sulfur sources, and microorganisms, thereby improving the denitrification and denitrification performance of the filler.

[0012] Preferably, the mass ratio of the epoxy resin to glycerol is 5:(4-5).

[0013] By adopting the above technical solution, when the glycerol content is too low, the epoxy resin cannot be fully cured, the cross-linking network density is reduced, and the filler brittleness increases and the ability to resist water impact is weakened; when the glycerol content is too much, the excess glycerol will dilute the epoxy resin, resulting in too low a cross-linking density and a decrease in the filler structure strength; for this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of the epoxy resin and glycerol in this application is preferably as mentioned above.

[0014] Preferably, the mass ratio of the epoxy resin to the starch is 5:(2-3).

[0015] By adopting the above technical solution, when the starch content is too low, it is difficult for the starch to fully play the role of a "soft spacer", and the epoxy resin is prone to over-densification, resulting in a reduction in the number of mesopores in the formed three-dimensional network structure; when the starch content is too high, the excessive starch will affect the cross-linking reaction of the epoxy resin and glycerol, the mechanical properties of the filler will deteriorate, and the service life of the filler will be shortened; for this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of the epoxy resin and starch in this application should be as above.

[0016] Preferably, the sulfur autotrophic denitrification filler further includes a filler auxiliary agent, and the filler auxiliary agent includes at least one of tin dioxide and titanium dioxide.

[0017] 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, and by reducing the electron transfer resistance, promote microorganisms to transfer the electrons generated by sulfur oxidation to nitrate reductase, thereby increasing 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), thereby increasing the activity of the enzyme, accelerating the reduction process of nitrogen oxides, and 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 reinforcement", thereby further improving the stability of the sulfur autotrophic denitrification filler in the water flow.

[0018] Preferably, the filler auxiliary agent is tin dioxide.

[0019] By adopting the above technical solution, sulfur autotrophic denitrification will release acidic substances, causing the pH of the system to decrease. Tin dioxide has better chemical stability in acidic environments than titanium dioxide and can maintain its structural integrity for a long time. At the same time, tin dioxide has a narrower band gap and can more effectively promote the transfer of electrons from electron donors generated during microbial metabolism to its surface, and then transfer them to electron acceptors such as nitrate, thereby enhancing the electron transfer efficiency of the entire reaction system and improving the denitrification effect. Therefore, tin dioxide is preferred.

[0020] Preferably, the weight portion of the tin dioxide is 1-2 parts.

[0021] By adopting the above technical solution, when the tin dioxide content is low, the channels and sites for electron transfer are insufficient, making it difficult to effectively accelerate the electron transfer between sulfur oxidation and nitrate reduction, and the effect of improving the denitrification reaction rate is small; when the tin dioxide content is high, the tin dioxide content may cause the local concentration of substances to be too high, which will inhibit denitrifying bacteria and lead to the inhibition of the denitrification reaction. For this reason, the applicant finally determined after extensive research and experimental verification that the weight of tin dioxide in this application is preferably the above.

[0022] Preferably, the filler auxiliary agent is a mixture of tin dioxide and titanium dioxide.

[0023] By adopting the above technical solution, when tin dioxide and titanium dioxide are mixed, tin dioxide has high stability in an acidic environment and can offset the impact of acidic substances produced by sulfur autotrophic denitrification on the system; while the surface charge of titanium dioxide under weakly alkaline conditions is more conducive to microbial attachment. The mixture of tin dioxide and titanium dioxide can enable the filler to maintain stable performance in a wider pH range.

[0024] 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.

[0025] Preferably, the mass ratio of tin dioxide to titanium dioxide is 5:(1-2).

[0026] By adopting the above technical solution, when the titanium dioxide content is too low, the synergistic effect between titanium dioxide and tin dioxide is difficult to achieve, and the performance improvement effect on the sulfur autotrophic denitrification filler is not obvious; when the titanium dioxide content is too high, the tin dioxide content is relatively too small, and the effect of titanium dioxide itself on improving the denitrification effect of the filler is not as good as that of tin dioxide, which instead leads to a decrease in the denitrification effect of the filler; for this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of tin dioxide and titanium dioxide in this application is preferably the above.

[0027] In a second aspect, the present application provides a method for preparing a sulfur autotrophic denitrification filler, which adopts the following technical solution:

[0028] A method for preparing a sulfur autotrophic denitrification filler, for preparing the above-mentioned sulfur autotrophic denitrification filler, comprises the following steps:

[0029] S1. The formulated amount of sulfur powder, pyrite powder, pH buffer and starch and other additives are fully mixed to obtain mixed granules;

[0030] S2. The amount of epoxy resin and glycerol was uniformly mixed and added to the mixed particles, and triethanolamine was slowly added after stirring, and stirred thoroughly to form a sulfur autotrophic denitrification wet material;

[0031] S3. Granulating the sulfur autotrophic denitrification wet material to obtain the sulfur autotrophic denitrification filler.

[0032] By adopting the above technical solution, sulfur powder, pyrite powder and other additives such as starch are first fully mixed to achieve preliminary bonding between the starch and other particles in the formula, and then the mixed particles are added to a mixture of epoxy resin and glycerol. The hydrogen bonding between the hydroxyl groups of the starch and the epoxy groups of the epoxy resin can promote the uniform dispersion of the mixed particles in the system, thereby optimizing the performance of the prepared sulfur autotrophic denitrification filler.

[0033] Preferably, the particle size of the sulfur autotrophic denitrification filler is 3-5 mm.

[0034] 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 increased resistance to water flow and obstructed diffusion path of the substrate, thereby affecting the sufficient contact between the wastewater, the sulfur source and the 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, the sulfur source and the microorganisms, and a longer diffusion path of the substrate, which will also reduce the denitrification efficiency of the reaction system; for this reason, the applicant finally determined after extensive research and experimental verification that the particle size of the sulfur autotrophic denitrification filler of this application is preferably the above.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. This application forms a stable three-dimensional network structure by epoxy resin and glycerol, thereby increasing the service life of the filler. At the same time, starch is used as a "soft spacer" to prevent the epoxy resin from becoming overly dense, promoting the attachment of denitrifying bacteria and thus improving the denitrification and denitrification performance of the filler.

[0037] 2. This application uses tin dioxide and titanium dioxide as electron shuttles to accelerate the electron transfer between the sulfur source and nitrate / nitrite, thereby increasing the reaction rate by reducing the electron transfer resistance; at the same time, its surface defect sites can serve as cofactor binding sites for enzymes (such as nitrate reductase and nitrite reductase), thereby increasing the activity of the enzyme and thus improving the denitrification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the water flow impact resistance test in the embodiment of the present application.

[0039] Explanation of the accompanying symbols: 1. Sulfur autotrophic denitrification filler; 2. Organic glass container; 21. Water inlet; 22. Water outlet. DETAILED DESCRIPTION

[0040] The raw materials in this application include the following parts:

[0041] Sulfur powder: a commercial product with CAS number 63705-05-5 was used;

[0042] Pyrite powder: a commercially available product with CAS number 1309-36-0;

[0043] pH buffer: sodium carbonate, sodium bicarbonate, etc. can be used. This application uses a commercially available product of sodium carbonate with CAS number 497-19-8;

[0044] Starch: a commercial product with CAS number 9005-25-8 was used;

[0045] Epoxy resin: a commercial product with CAS number 38891-59-7 was used;

[0046] Glycerol: a commercial product with CAS number 56-81-5 was used;

[0047] Triethanolamine: a commercially available product with CAS number 102-71-6;

[0048] Tin dioxide: a commercially available product with CAS number 18282-10-5;

[0049] Titanium dioxide: a commercially available product with CAS number 1317-80-2 was used;

[0050] p-Toluenesulfonic acid: a commercially available product with CAS number 104-15-4 was used;

[0051] Sodium hydroxide: a commercially available product with CAS number 1310-73-2 was used;

[0052] The present application is further described in detail below with reference to the following examples and comparative examples.

[0053] Example 1

[0054] A method for preparing a sulfur autotrophic denitrification filler, for preparing the above-mentioned sulfur autotrophic denitrification filler, comprises the following steps:

[0055] S1. 6000g of sulfur powder, 600g of pyrite powder, 400g of pH buffer and 350g of starch were added to a mixer and blended at 1000rpm for 10min to obtain mixed particles;

[0056] S2 700g of epoxy resin and 600g of glycerol were added to a blender and stirred at 1200rpm for 10min to obtain a uniform mixture; the mixed particles were then added to the uniform mixture, stirred for 10min, and then 7g of triethanolamine was slowly added, and stirring was continued for 15min to form a sulfur autotrophic denitrification wet material;

[0057] S3. Add the sulfur autotrophic denitrification wet material into a mold with an inner diameter of 5 mm (3-5 mm is acceptable) for granulation, then keep it at 60°C for 2 hours, demold it, and let it stand for 3 days to obtain the sulfur autotrophic denitrification filler.

[0058] Example 2-3

[0059] In Example 2-3, based on the preparation method of Example 1, the content of each component in the formula was adjusted. The specific adjustments are shown in Table 1.

[0060] Comparative Examples 1-4

[0061] Comparative Examples 1-4 are based on the preparation method of Example 1, and the content of each component in the formula is adjusted. The specific adjustments are shown in Table 1.

[0062] Table 1 Raw materials and performance test table of sulfur autotrophic denitrification fillers of Examples 1-3 and Comparative Examples 1-4

[0063]

[0064] Performance testing

[0065] (1) Water impact resistance

[0066] Reference Figure 1 , weigh the original mass of the sulfur autotrophic denitrification filler 1, then fill the sulfur autotrophic denitrification filler 1 into the organic glass container 2, and let water flow in from the water inlet 21 at the bottom of the organic glass container 2 and out from the water outlet 22 at the top of the organic glass container 2. The flow rate of the water is controlled to be 5m / s. After 12 hours, take out the sulfur autotrophic denitrification filler 1, dry and weigh it, and calculate the weight loss rate:

[0067] Weight loss rate = (original mass - mass after water impact) / original mass × 100%.

[0068] Note: The lower the weight loss rate, the better the sulfur autotrophic denitrification filler's resistance to water flow impact.

[0069] (2) Denitrification effect

[0070] Sulfur autotrophic denitrification filler was added to the fixed-bed reactor, and denitrifying Thiobacillus bacterial solution was added for inoculation. After the inoculation was completed, simulated wastewater containing nitrate was introduced into the fixed-bed reactor, wherein the nitrate concentration in the simulated wastewater was 50 mg / L. After running for 48 hours, the nitrate concentration in the effluent was tested.

[0071] Note: The lower the nitrate concentration in the effluent, the better the denitrification effect of the sulfur autotrophic denitrification filler.

[0072] The sulfur autotrophic denitrification fillers of Examples 1-3 and Comparative Examples 1-4 were subjected to the above performance tests, and the test results are shown in Table 1.

[0073] Referring to Table 1, a comparison of Examples 1-3 and Comparative Examples 1-4 shows that the effluent nitrate concentration in Comparative Example 1 is higher than in Examples 1-3. This is because starch was not added in the Comparative Example to prevent excessive densification of the epoxy resin, resulting in fewer mesoporous structures in the three-dimensional network structure formed by the epoxy resin and glycerol, making it difficult for denitrifying Thiobacillus to attach. This is not conducive to sufficient contact between the simulated wastewater, the sulfur source, and the microorganisms, resulting in the inferior denitrification effect of Comparative Example 1 to that of Examples 1-3.

[0074] The weight loss rate and effluent nitrate concentration of Comparative Examples 2-4 were both inferior to those of Examples 1-3, indicating that the sulfur-autotrophic denitrification filler in Comparative Examples 2-4 was inferior to Examples 1-3 in both water shock resistance and denitrification effectiveness. This is due to the lack of epoxy resin in Comparative Example 2, glycerin in Comparative Example 3, and triethanolamine in Comparative Example 4. These raw material deficiencies prevented the sulfur-autotrophic denitrification filler from forming a stable and robust three-dimensional network structure, thus impairing its water shock resistance. Under water shock, core components such as sulfur powder and pyrite powder within the filler were lost, significantly reducing the denitrification effectiveness of Comparative Examples 2-4.

[0075] Compared with Examples 1-3, the sulfur autotrophic denitrification filler of Example 1 has better water flow impact resistance and single nitrate removal effect, so Example 1 is preferred.

[0076] Comparative Examples 5-6

[0077] Comparative Example 5 Based on the preparation method of Example 1, 7 g of triethanolamine was replaced with 7 g of p-toluenesulfonic acid, and the other conditions remained unchanged.

[0078] Comparative Example 6 Based on the preparation method of Example 1, 7 g of triethanolamine was replaced with 7 g of sodium hydroxide, and the other conditions remained unchanged.

[0079] 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.

[0080] Table 2 Performance test table of Example 1 and Comparative Examples 5-6

[0081]

[0082] Referring to Table 2, by comparing Example 1 with 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) is added to catalyze the cross-linking reaction between the epoxy resin and glycerol. The sulfur autotrophic denitrification process itself causes the pH of the system to decrease. The addition of the acidic catalyst further lowers the environmental pH and inhibits the growth of microorganisms. In Comparative Example 6, a strong alkaline catalyst (sodium hydroxide) is added to catalyze the cross-linking reaction between the epoxy resin and glycerol. The strong alkaline environment is also not conducive to the growth of microorganisms.

[0083] Examples 4-7

[0084] Examples 4-7 are prepared according to Example 1, but the total mass of the epoxy resin and glycerin is maintained at 1300 g, and the mass ratio of the epoxy resin to glycerin is adjusted. The specific adjustments are shown in Table 3.

[0085] 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.

[0086] Table 3 Mass ratio of epoxy resin and glycerin and performance test table of Example 1 and Examples 4-7

[0087]

[0088] Referring to Table 3, it can be seen from the comparison between Example 1 and Examples 4-7 that a glycerol content that is too low or too high will lead to an increase in the weight loss rate of the autotrophic denitrification filler and the nitrate concentration of the effluent. This is because when the glycerol content is too low, the epoxy resin cannot be fully cured, the cross-linking network density is reduced, and the filler's resistance to water flow impact is weakened; when the glycerol content is too high, the excess glycerol dilutes the epoxy resin, which also leads to too low a cross-linking density, thereby weakening the filler's resistance to water flow impact; the decrease in the filler's resistance to water flow impact means that the effective ingredients in the filler will be lost under the action of water flow, thereby reducing the denitrification effect of the filler.

[0089] Examples 8-11

[0090] Examples 8-11 are based on the preparation method of Example 1, except that the total mass of the epoxy resin and starch is maintained at 1050 g, and the mass ratio of the epoxy resin to starch is adjusted. The specific adjustments are shown in Table 4.

[0091] The sulfur autotrophic denitrification fillers of Examples 8-11 were subjected to the above performance tests, and the test results are shown in Table 4.

[0092] Table 4 Mass ratio of epoxy resin and starch and performance test table of Example 1 and Examples 8-11

[0093]

[0094] Referring to Table 4, by comparing Example 1 with Examples 8-11, it can be seen that when the starch content is too low, the nitrate concentration in the effluent of the autotrophic denitrification filler will increase, and when the starch content is too high, the weight loss rate and the effluent nitrate concentration of the autotrophic denitrification filler will both increase. This is because when the starch content is too low, the starch is difficult to fully play the role of a "soft spacer", and the number of mesopores in the three-dimensional network structure formed by the reaction of epoxy resin and glycerol is reduced, which is not conducive to the attachment of microorganisms; when the starch content is too high, the starch will interfere with the cross-linking reaction of epoxy resin and glycerol, causing the mechanical properties of the filler to deteriorate, thereby resulting in a decrease in the water flow impact resistance and denitrification effect of the filler.

[0095] Examples 12-13

[0096] Example 12 Based on the preparation method of Example 1, in step S1, 300 g of tin dioxide, sulfur powder, pyrite powder, pH buffer, and starch are added to a mixer for blending, and other conditions remain unchanged.

[0097] Example 13 Based on the preparation method of Example 12, 300g of tin dioxide is replaced by 300g of titanium dioxide, and the other conditions remain unchanged.

[0098] The sulfur autotrophic denitrification fillers of Examples 12-13 were subjected to the above performance tests, and the test results are shown in Table 5.

[0099] Table 5 Performance test table of Example 1 and Examples 12-13

[0100]

[0101] Referring to Table 5, by comparing Example 1 and Examples 12-13, it can be seen that the effluent nitrate concentration of Example 1 is higher than that of Examples 12-13, indicating that the addition of 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 to accelerate the electron transfer between the sulfur source and nitrate / nitrite, promote microorganisms to transfer the electrons generated by sulfur oxidation to nitrate reductase, and increase 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 reinforcement", further improving the filler's resistance to water flow impact.

[0102] Comparing Examples 12-13, it can be seen that the nitrate concentration of the effluent of Example 12 is lower, indicating that the denitrification effect of adding tin dioxide on the sulfur autotrophic denitrification filler is better than that of adding titanium dioxide. This is because sulfur autotrophic denitrification will cause the pH of the system to decrease, and tin dioxide has better chemical stability in an acidic environment than titanium dioxide, and can maintain structural integrity for a long time; at the same time, tin dioxide has a narrower band gap, which can more effectively promote electron transfer and enhance the electron transfer efficiency of the entire reaction system; therefore, Example 12 is preferred.

[0103] Examples 14-17

[0104] In Examples 14-17, based on the preparation method of Example 12, the amount of tin dioxide added in the formula was adjusted. The specific adjustments are shown in Table 6.

[0105] The sulfur autotrophic denitrification fillers of Examples 14-17 were subjected to the above performance tests, and the test results are shown in Table 6.

[0106] Table 6 Addition amount and performance test table of tin dioxide in Example 12 and Examples 14-17

[0107]

[0108] Referring to Table 6, by comparing Example 12 with Examples 14-17, it can be seen that when the tin dioxide content is too little or too high, the nitrate concentration in the effluent will increase. This is because when the tin dioxide content is too low, the 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 tin dioxide content is too high, it may lead to excessively high local concentrations, which inhibits denitrifying bacteria, thereby reducing the denitrification effect of the filler.

[0109] Examples 18-22

[0110] Example 18 Based on the preparation method of Example 12, 300g of tin dioxide is replaced by 300g of a mixture of tin dioxide and titanium dioxide, the mass ratio of tin dioxide to titanium dioxide in the mixture is 5:1.5, and the other conditions remain unchanged.

[0111] In Examples 19-22, based on the preparation method of Example 18, the mass ratio of tin dioxide to titanium dioxide in the mixture was adjusted. The specific adjustments are shown in Table 7.

[0112] 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.

[0113] Table 7 Mass ratio of tin dioxide to titanium dioxide and performance test table of Example 12 and Examples 18-22

[0114]

[0115] Referring to Table 7, by comparing Example 12 with Examples 18-22, it can be seen that the effluent nitrate concentrations of Examples 18-22 are all lower than that of Example 12, indicating that the mixed addition of tin dioxide and titanium dioxide can further improve the denitrification effect of the filler. This is because when tin dioxide and titanium dioxide are mixed, tin dioxide acts as an efficient electron mediator to accelerate the oxidation reaction of the sulfur source and quickly transfer electrons to nitrate reductase, while the surface active sites of titanium dioxide further promote the nitrate reduction reaction, forming a "double electron transfer channel", which further improves the denitrification efficiency of the filler.

[0116] By comparing Examples 18-22, it can be seen that when the titanium dioxide content is too low or too high, the nitrate concentration of the effluent of the filler will increase. This is because when the titanium dioxide content is too low, the synergistic effect between titanium dioxide and tin dioxide is difficult to achieve, and the performance improvement effect on the sulfur autotrophic denitrification filler is not obvious; when the titanium dioxide content is too high, the tin dioxide content is relatively too low, and the effect of titanium dioxide itself on improving the denitrification effect of the filler is not as good as that of tin dioxide, which will lead to a decrease in the denitrification effect of the sulfur autotrophic denitrification filler.

[0117] Example 23

[0118] Example 23 Based on the preparation method of Example 1, step S1 is skipped and 6000 g of sulfur powder, 600 g of pyrite powder, 400 g of pH buffer and 350 g of starch are directly added to the uniform mixture in step S2, while the other conditions remain unchanged.

[0119] The sulfur autotrophic denitrification filler of Example 23 was subjected to the above performance test, and the test results are shown in Table 8.

[0120] Table 8 Performance test table of Example 1 and Example 23

[0121]

[0122] Referring to Table 8, by comparing Example 1 and Example 23, it can be seen that the weight loss rate and the effluent nitrate concentration of Example 1 are lower than those of Example 23. This is because in step S1 of Example 1, the sulfur powder, pyrite powder and starch are first fully mixed, so that the starch and other particles in the formula are initially bonded. Then, the hydrogen bonding between the hydroxyl groups of the starch and the epoxy groups of the epoxy resin promotes the uniform dispersion of the various components in the cross-linked structure formed by the epoxy resin and glycerol, making the structure of the sulfur autotrophic denitrification filler prepared in Example 1 more stable, thereby improving the denitrification effect of Example 1.

[0123] 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 sulfur autotrophic denitrification filler, characterized in that: The method comprises the following raw materials 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 glycerin; The mass ratio of the epoxy resin to glycerol is 5:(4-5); The mass ratio of the epoxy resin to the starch is 5:(2-3); Also included is a filler auxiliary, which is a mixture of tin dioxide and titanium dioxide; The mass ratio of tin dioxide to titanium dioxide is 5:(1-2); The method for preparing the sulfur autotrophic denitrification filler comprises the following steps: S1. The formulated amount of sulfur powder, pyrite powder, pH buffer, starch, tin dioxide and titanium dioxide are thoroughly mixed to obtain mixed particles; S2. The amount of epoxy resin and glycerol was uniformly mixed and added to the mixed particles, and triethanolamine was 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.

2. The sulfur autotrophic denitrification filler according to claim 1, characterized in that: The particle size of the sulfur autotrophic denitrification filler is 3-5 mm.

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