A sulfur-rich polymer denitrification biological filler, a preparation method and application thereof

Abstract

The application discloses a kind of sulfur-rich polymer denitrification biological fillers and its preparation method and application, belong to water treatment technical field, the method is under anoxic environment, sulfur is heated and fused, when solution changes from yellow to orange, add vinyl acetate, crosslinking agent and catalyst, carry out reverse vulcanization by heating stirring, and the crude product is prepared under vacuum or nitrogen condition;Crude product is reprocessed to obtain heterotrophic and autotrophic coupled denitrification biological filler.The method utilizes the ring-opening and chain-forming tendency of sulfur at high temperature through reverse vulcanization, and combines the sulfur radicals formed when the ionized organic molecules and the S8 ring of sulfur are opened together.The denitrification biological filler prepared by the application can realize sulfur autotrophic and heterotrophic coupled denitrification denitrification effect, enhance denitrification capacity, and solve the problems of long biofilm formation time, unsatisfactory denitrification efficiency and secondary pollution of effluent in existing autotrophic and heterotrophic denitrification treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and particularly relates to a sulfur-rich polymer denitrification biological filler as well as a preparation method and application thereof. BACKGROUND

[0002] Currently, denitrification technologies mainly include heterotrophic denitrification and autotrophic denitrification. The heterotrophic denitrification mainly uses external organic carbon sources (methanol, ethanol, acetic acid, etc.) as substrates to treat wastewater with low C / N, has large treatment capacity per unit volume of reactor, but has high cost and causes secondary pollution. The autotrophic denitrification uses inorganic carbon as a carbon source and inorganic substances (H2S, HS-, S2O3-, Fe, Fe2+, etc.) as electron donors to complete the metabolism of microorganisms, and finally reduces nitrate to nitrogen. However, the autotrophic denitrification has the disadvantages of low treatment rate and accumulation of sulfates, which restricts the practical application of this technology. 2- - 2- 2+

[0003] For example, patent CN202110783537.X provides a denitrification biological filler and a preparation method and application thereof. Beta-cyclodextrin with a certain space network structure is used as the main body. The hydroxyl functional groups on the periphery of the filler are first activated by soaking in a sodium hydroxide ethanol solution, so as to be easily replaced by halogen atoms. Sodium hydrosulfide ethanol solution can further replace the halogen element with a mercapto functional group, and load the sulfur element in the filler. Then, dehydration condensation can further convert the mercapto functional group into a more stable disulfide bond with a modified space network structure. After hot melting and granulation, the denitrification biological filler is obtained. The denitrification biological filler prepared by the invention can enhance the effect of sulfur autotrophic and heterotrophic coupled denitrification, but the preparation cost is high, the operation process is complex, and the slow-release performance is difficult to control, which restricts the development of denitrification treatment of this technology. Patent CN202111552471.X provides a biological composite filler and a preparation method and application thereof. The biological composite filler can not only serve as a microbial carrier, but also facilitate the adhesion and metabolic activity of microorganisms. The slow-release carbon source material provides a slow-release carbon source for heterotrophic denitrifying bacteria, and sulfur provides a sulfur source for sulfur autotrophic denitrifying bacteria. The coupling of heterotrophic denitrification and sulfur autotrophic denitrification realizes deep denitrification of nitrogen-containing wastewater. Moreover, the ferric oxide powder in the biological composite filler not only promotes the enrichment of microorganisms, but also endows the biological composite filler with weak magnetism, which is beneficial to the aggregation of the biological composite filler and prevents it from being washed away. However, the price of polyhydroxyalkanoate is high, and the initial COD release concentration of the filler is too high in practical application, which easily causes COD shock of effluent, and the practical application is not ideal. SUMMARY

[0004] ​​​​The application provides a sulfur-rich polymer denitrification biological filler, a preparation method and application thereof, and adopts a countercurrent polymerization reaction, so that the prepared denitrification biological filler can greatly improve the biological availability of sulfur, maintain the stable structure of sulfur chain-organic matter, has good slow-release performance, and realizes efficient denitrification of low-carbon wastewater by using a sulfur autotrophic and heterotrophic coupling system.

[0005] In order to achieve the above object, the application adopts the following technical solutions:

[0006] A preparation method of a sulfur-rich polymer denitrification biological filler, comprising the following steps:

[0007] Ethyl vinyl acetate and a crosslinking agent are heated and mixed to obtain a mixed solution;

[0008] In an anoxic environment, sulfur is heated and melted, the catalyst and the mixed solution are added when the solution changes from yellow to orange, and the preliminary product is obtained by heating and stirring for inverse vulcanization;

[0009] The preliminary product is dried and cooled in a vacuum or nitrogen environment to obtain a crude product;

[0010] The crude product and a binder are mixed and hot-melt granulated to obtain the sulfur-rich polymer denitrification biological filler.

[0011] In the above steps, the mass ratio of the ethyl vinyl acetate and the crosslinking agent is (30-50):(5-20), the crosslinking agent is one or more of acrylic acid and dicyclopentadiene, the heating and mixing mode is stirring, the temperature is 50-70 DEG C, and the time is 10-15 min;

[0012] The heating and melting temperature of the sulfur is 160-200 DEG C, preferably 180 DEG C, the mass ratio of the sulfur and the mixed solution is (15-40):(15-40), preferably 25:25, the catalyst is zinc diethyl dithiocarbamate, the amount of the zinc diethyl dithiocarbamate is 1-5% of the total mass of the sulfur and the mixed solution, preferably 1%, the inverse vulcanization temperature is 160-200 DEG C, preferably 170 DEG C, and the stirring time is 2-5 h, preferably 3 h;

[0013] The drying temperature is 100-120 DEG C, preferably 110 DEG C, and the time is 8-14 h, preferably 12 h;

[0014] The hot-melt granulation temperature is 180-260 DEG C, preferably 240 DEG C, the stirring speed is 120-300 rpm, and the vacuum feeding is performed by using one of an electric vacuum feeding machine and a pneumatic vacuum feeding machine;

[0015] The particle size of the sulfur-rich polymer denitrification biological filler is 5-20 mm.

[0016] Beneficial effects: The present application provides a sulfur-rich polymer denitrification biological filler and its preparation method and application, compared with the prior art, the present application has the following advantages:

[0017] Sulfur is easy to aggregate and float on the surface of water or condense into blocks and deposit at the bottom of the reactor due to its strong hydrophobicity, thereby seriously affecting the contact between sulfur and sulfur autotrophic denitrifying bacteria and reducing the denitrification rate; the sulfur-rich polymer biological filler prepared by the reverse sulfurization reaction in the present application can enrich, capture and fix polysulfides through chemical bonds (carbon-sulfur bonds), thereby reducing the difficulty of sulfur bioavailability, and the sulfur in the sulfur-rich polymer exists in the form of a sulfur chain and generates carbon-sulfur bonds; sulfur autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria can simultaneously utilize sulfur source and carbon source in an anoxic or anaerobic environment, thereby achieving the goal of slow release of carbon source; the advantage is that no additional carbon source is needed, the upper limit of treatment is high, and the advantage of heterotrophic denitrification is that the degradation speed is fast and the treatment capacity is large; the present application couples sulfur autotrophic denitrification with heterotrophic denitrification, which can well utilize the characteristics of each bacterial group and achieve complementary advantages, thereby achieving the purpose of deep denitrification; in addition, in the reaction process, sulfur autotrophic denitrification is an acid-producing process, while heterotrophic denitrification is an alkali-producing process, and the coupling of the two is conducive to ensuring the relative stability of the pH value of the system and reducing the concentration of sulfate in the effluent and the treatment cost; the crosslinking agent is added to protect the double bond in vinyl acetate from being destroyed and promote the reverse sulfurization reaction; the zinc diethyl dithiocarbamate catalyst can better promote the completion of the reverse sulfurization reaction; the denitrification and denitrification biological filler prepared in the present application can achieve efficient denitrification, and microorganisms can simultaneously utilize sulfur source and carbon source, thereby strengthening the cooperation between heterotrophic denitrifying bacteria and sulfur autotrophic denitrifying bacteria, combining the advantages of both to enhance the denitrification capacity; at the same time, the biological availability of sulfur and the slow release performance of carbon source are improved, the denitrification capacity is enhanced, and the problems of long biofilm formation time, unsatisfactory denitrification efficiency and secondary pollution of effluent in existing autotrophic and heterotrophic denitrification treatment are solved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the reverse sulfurization reaction mechanism diagram of the present application;

[0019] Figure 2 is the total nitrogen removal rate effect diagram of the reactor in example 1-4 of the present application. DETAILED DESCRIPTION

[0020] The present application will be described in detail below in combination with the drawings and specific examples:

[0021] As Figure 1As shown, sulfur is difficult to be utilized by microorganisms due to its stable S8 ring structure, and when S8 is heated above 159℃, the S-S bond begins to break, forming a liquid chain radical •S8• and causing a reversible reaction of S8 ring-opening polymerization, thereby obtaining chain radical (•n•) polysulfides with various n values (n>1). The reverse vulcanization reaction enables elemental sulfur to become a stable chain polymer. At 159-444℃, sulfur radicals are prone to react with the reaction structure or polymerizable groups of organic molecules. Through reverse vulcanization, the ionized organic molecules are combined with the sulfur radicals formed when the S8 ring of sulfur is opened. Example 1

[0022] A preparation method of a sulfur-rich polymer denitrification biological filler, comprising the following steps:

[0023] Vinyl acetate and acrylic acid are mixed in a mass ratio of 50:15, heated and stirred at 50℃ for 15 min to obtain a mixed solution. 30 parts of sulfur is heated and melted at 180℃ in an anoxic environment. When the solution changes from yellow to orange, 1% zinc diethyl dithiocarbamate and 20 parts of the mixed solution are added, and the reverse vulcanization reaction is carried out at 180℃ for 5 h to obtain a preliminary product. The preliminary product is dried at 120℃ for 14 h, and then cooled under vacuum or nitrogen to obtain a crude product. The crude product and a binder are mixed, and then fed by a vacuum feeding machine. The hot melt granulation is carried out at 180℃ and a rotation speed of 150 rpm by using a granulator. Through granulation, the biological composite filler has larger mechanical strength, smaller particle size, and larger specific surface area. A denitrification biological filler is obtained. Example 2

[0024] A preparation method of a sulfur-rich polymer denitrification biological filler, comprising the following steps:

[0025] Vinyl acetate and dicyclopentadiene are mixed in a mass ratio of 50:15, heated and stirred at 50℃ for 15 min to obtain a mixed solution. 30 parts of sulfur is heated and melted at 180℃ in an anoxic environment. When the solution changes from yellow to orange, 2% zinc diethyl dithiocarbamate and 20 parts of the mixed solution are added, and the reverse vulcanization reaction is carried out at 160℃ for 3 h to obtain a preliminary product. The preliminary product is dried at 120℃ for 9 h, and then cooled under vacuum or nitrogen to obtain a crude product. The crude product and a binder are mixed, and then fed by a vacuum feeding machine. The hot melt granulation is carried out at 200℃ and a rotation speed of 200 rpm by using a granulator. A denitrification biological filler is obtained. Example 3

[0026] A preparation method of a sulfur-rich polymer denitrification biological filler, comprising the following steps:

[0027] Vinyl acetate and polystyrene are mixed in a mass ratio of 50:15, heated and stirred at 70 DEG C for 10 min to obtain a mixed solution; 25 parts of sulfur are heated and melted at 160 DEG C in an oxygen-deficient environment, and when the solution changes from yellow to orange, 1% zinc diethyl dithiocarbamate and 30 parts of the mixed solution are added, and the inverse vulcanization reaction is carried out at 160 DEG C for 3 h to obtain a preliminary product; the preliminary product is dried at 120 DEG C for 12 h, and then cooled in a vacuum or nitrogen environment to obtain a crude product; the crude product and a binder are mixed, and the vacuum feeding machine is used for feeding, and the hot melt granulation is carried out at 260 DEG C and a rotating speed of 300 rpm to obtain the denitrification biological filler. Example 4

[0028] A preparation method of a sulfur-rich polymer denitrification biological filler, comprising the following steps:

[0029] Vinyl acetate and dicyclopentadiene are mixed in a mass ratio of 40:10, heated and stirred at 60 DEG C for 10 min to obtain a mixed solution; 25 parts of sulfur are heated and melted at 180 DEG C in an oxygen-deficient environment, and when the solution changes from yellow to orange, 1% zinc diethyl dithiocarbamate and 25 parts of the mixed solution are added, and the inverse vulcanization reaction is carried out at 170 DEG C for 3 h to obtain a preliminary product; the preliminary product is dried at 110 DEG C for 12 h, and then cooled in a vacuum or nitrogen environment to obtain a crude product; the crude product and a binder are mixed, and the vacuum feeding machine is used for feeding, and the hot melt granulation is carried out at 240 DEG C and a rotating speed of 200 rpm to obtain the denitrification biological filler.

[0030] The application provides application of the biological composite filler prepared in the above method in sewage treatment.

[0031] The biological composite filler is filled into a reactor, then sulfur autotrophic denitrifying bacteria liquid and heterotrophic denitrifying bacteria liquid are added into the reactor to carry out biofilm formation; after the biofilm formation is completed, nitrogen-containing wastewater is introduced into the reactor, different microbial bands are formed at different positions of the reactor, and the nitrogen elements in the nitrogen-containing wastewater are removed through the metabolic action of the microorganisms.

[0032] The above reactor is preferably a fixed bed biological column reactor, inoculated with liquid of enriched culture of nitrate-dependent sulfur autotrophic denitrifying bacteria and liquid of heterotrophic denitrifying bacteria, and is used for biofilm formation; after biofilm formation, a simulated nitrogen-containing wastewater is introduced into the reactor by using a peristaltic pump, the simulated nitrogen-containing wastewater is prepared by sodium nitrate and tap water, and the concentration of nitrate nitrogen and the hydraulic retention time in the simulated nitrogen-containing wastewater are each; the reactor is divided into a first phase (0-20d): 60mg / L, 8h; a second phase (20-35d): 40mg / L, 4h; and a third phase (35-50d): 40mg / L, 3h. Among them, the reactor corresponding to the biological composite filler particles prepared in Example 1 is recorded as reactor E1, the reactor corresponding to the biological composite filler particles prepared in Example 2 is recorded as reactor E2, the reactor corresponding to the biological composite filler particles prepared in Example 3 is recorded as reactor E3, and the reactor corresponding to the biological composite filler particles prepared in Example 4 is recorded as reactor E4, and the results are respectively as shown in Figure 2

[0033] As can be seen from Figure 2 , the effluent effect of the reactor E3 is relatively excellent in the early stage, but the overall effect of E4 is better, and the total nitrogen removal rate is 90% in the third phase, while the removal rates of the reactors E1 and E2 are basically about 83%. From the treatment effects of the reactors E1, E2 and E3, it can be seen that dicyclopentadiene is the most optimal crosslinking agent. At the same time, the treatment effect of the filler with less ethylene acetate content is slightly lower, which is caused by the low concentration of the released carbon source in the treatment; the treatment effects of the reactors E3 and E4 are similar in the early stage, and the removal rate of E3 decreases in the later stage, which is caused by the high concentration of the slow-release carbon source and the low content of S in the early stage, which affects the slow-release effect and is not conducive to long-term denitrification operation, and the long-term stable treatment capacity of the reactor E4 proves that the biological filler provided by the present application can achieve excellent denitrification effect in the treatment of wastewater, and has good application value and effect.

[0034] The above is only a preferred embodiment of the present application, which will help those skilled in the art to further understand the present application, but does not limit the present application in any form. It should be pointed out that for those skilled in the art, some modifications and improvements made without departing from the concept of the present application all belong to the protection of the present application.​

Claims

1. A process for the preparation of a sulphur-rich polymeric denitrifying biofiller, characterized in that, The method comprises the following steps: heating and mixing vinyl acetate and a crosslinking agent to obtain a mixed solution; under anoxic environment, heating and melting sulfur, adding a catalyst and the mixed solution when the solution changes from yellow to orange, and heating and stirring to perform inverse vulcanization to obtain a preliminary product; after drying the preliminary product, cooling the preliminary product under vacuum or nitrogen environment to obtain a crude product; mixing the crude product and a binder, and performing hot melt granulation to obtain a sulfur-rich polymer denitrification biological filler.

2. The process for preparing sulfur-rich polymeric denitrification biofiller according to claim 1, characterized in that, The mass ratio of the vinyl acetate to the crosslinking agent is (30-50):(5-20); the heating and mixing mode is stirring, the temperature is 50-70 DEG C, and the time is 10-15 min.

3. The process for the preparation of a sulphur-rich polymeric denitrification biofiller according to claim 1 or 2, characterized in that, The crosslinking agent is one or more of acrylic acid and dicyclopentadiene.

4. The process for preparing sulfur-rich polymeric denitrification biofiller according to claim 1, characterized in that, The heating and melting temperature of the sulfur is 160-200 DEG C, the inverse vulcanization temperature is 160-200 DEG C, and the stirring time is 2-5 h.

5. The process for preparing the sulfur-rich polymeric denitrification biofiller according to claim 1 or 4, characterized in that, The mass ratio of the sulfur to the mixed solution is (15-40):(15-40), and the mass fraction of the catalyst is 1-5%.

6. The process for preparing sulfur-rich polymeric denitrification biofiller according to claim 5, characterized in that, The catalyst is zinc diethyl dithiocarbamate.

7. The process for preparing sulfur-rich polymeric denitrification biofiller according to claim 1, characterized in that, The drying temperature is 100-120 DEG C, and the time is 8-14 h.

8. The process for preparing sulfur-rich polymeric denitrification biofiller according to claim 1, characterized in that, The hot melt granulation temperature is 180-260 DEG C, and the stirring speed is 120-300 rpm.

9. The denitrifying biological fillers enriched with sulphur prepared by the method according to any of claims 1-8, characterized in that, In the sulfur-rich polymer, sulfur exists in the form of a sulfur chain, and there is a carbon-sulfur bond; the particle size of the filler is 5-20 mm.

10. Use of the sulphur-rich polymer denitrification biological packing according to claim 9, characterised by the fact that it is used in the denitrification of waste water. The biological filler is applied to sewage treatment, and microorganisms utilize sulfur source and carbon source simultaneously, and utilize heterotrophic denitrification and sulfur autotrophic denitrification to cooperatively perform denitrification and denitrogenation.

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