A thiol-containing chelate denitrification biological filler, a preparation method and application thereof

Abstract

The application discloses a kind of thiol chelate denitrification biological fillers and its preparation method and application, belong to sewage treatment field, the application will hexamethylene diamine with sulfur at high temperature reaction, form polysulfide long chain structure, the thiol generated is chelated with ferrous ion, nickel ion and cobalt ion, obtain the polymer loaded with metal ion;The product is granulated, and the final denitrification biological filler is obtained.The advantage of the denitrification biological filler prepared by the application is that it can provide the nutrients necessary for microbial growth, which is also a key component of hemoglobin and anaerobic ammonia oxidation protease, promotes the growth and reproduction of anaerobic ammonia oxidation bacteria, and provides sulfur source for sulfur autotrophic denitrifying bacteria, realizes sulfur autotrophic denitrification and anaerobic ammonia oxidation coupling denitrification, has excellent mechanical strength, stability and high-efficiency denitrification capacity, and is very suitable for long-term application in sulfur autotrophic denitrification and anaerobic ammonia oxidation coupling process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a thiol-containing chelate denitrification biological filler as well as a preparation method and application thereof. BACKGROUND

[0002] Nitrogen pollution has become one of the main problems of global water pollution. With the acceleration of industrialization and urbanization, a large amount of nitrogen-containing wastewater is directly discharged without effective treatment, leading to environmental problems such as water eutrophication and ecological imbalance. Nitrogen mainly exists in the form of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in wastewater, which poses a threat to the water ecosystem and human health. Therefore, it is of great environmental protection significance to develop efficient biological denitrification technology for wastewater.

[0003] Biological denitrification is an effective technology for removing nitrogen in wastewater through microbial metabolic processes. Its main advantages include high treatment efficiency, simple operation and relatively low cost. Biological denitrification can effectively remove ammonia nitrogen, nitrite nitrogen and nitrate nitrogen, reducing the consumption of chemical drugs and energy required in traditional chemical treatment methods. This technology also has low sludge production and good environmental adaptability, and can be stably operated under different wastewater concentrations and flow conditions. In addition, biological denitrification can achieve high nitrogen removal efficiency by controlling and optimizing the growth and metabolism of microorganisms, and has good economy and sustainability.

[0004] Anaerobic ammonium oxidation (ANAMMOX) process is a process that converts ammonia nitrogen and nitrite nitrogen into nitrogen gas under anaerobic conditions. The main advantage of this process is that it can effectively remove ammonia nitrogen while reducing energy consumption and operational complexity in the nitrification-denitrification process. ANAMMOX process not only reduces operating costs, but also reduces oxygen demand, making it more environmentally friendly and economical compared to traditional ammonia nitrogen removal methods. Sulfur autotrophic denitrification process uses sulfide as an electron donor to reduce nitrate nitrogen to nitrogen gas; the main advantage of this process is its high utilization rate of sulfide and its ability to remove nitrogen in anoxic environment. Sulfur autotrophic denitrification not only reduces nitrate nitrogen emissions, but also effectively reduces the external carbon source required in traditional denitrification processes, thereby reducing operating costs. Coupling ANAMMOX process and sulfur autotrophic denitrification process can take advantage of each other and improve nitrogen removal efficiency. ANAMMOX process is responsible for the removal of ammonia nitrogen and nitrite nitrogen, while sulfur autotrophic denitrification process handles nitrate nitrogen, which can further reduce nitrogen emissions and optimize resource use. The main advantage of the coupled process is that it can utilize the characteristics of both processes to reduce overall energy consumption and cost in the nitrogen removal process.

[0005] However, this coupling process also faces some challenges. First, anaerobic ammonia oxidation bacteria and sulfur autotrophic denitrifying bacteria are prone to competition when treating nitrite nitrogen, leading to instability of the system. Second, when the concentration of nitrate nitrogen in the system is too high, it is difficult to ensure the balance between anaerobic ammonia oxidation bacteria and sulfur autotrophic denitrifying bacteria, affecting the overall treatment effect. Solving these problems requires precise control of reaction conditions, optimization of the synergistic effect of bacterial flora, and ensuring that the two bacterial flora can coexist well in the system, so as to achieve efficient nitrogen removal.

[0006] To solve these difficulties, patent CN116715355A provides an iron oxide-based composite filler and its preparation method and application. By loading carbon materials in the iron oxide-based composite filler, the iron oxide inside the filler and the carbon materials form countless iron-carbon microcells, which release Fe 2+ reducing NO 3- -N to NH 4+ -N, providing an electron donor for anaerobic ammonia oxidation bacteria, but the prepared filler has difficulty in controlling the release rate of ferrous ions, and has limited effect in treating high ammonia-nitrogen wastewater. In actual operation, iron-carbon microcells are prone to decomposition, and the effective period is short. For example, patent CN116199335A provides a denitrification biological filler and its preparation method. By reacting sulfur with vinyl acetate, a polymer filler rich in sulfur is prepared, achieving sulfur autotrophic and heterotrophic coupled denitrification, and enhancing the denitrification effect. However, this filler has deficiencies in stability, is prone to decomposition, and the release rate of active substances is unstable, affecting the sustained denitrification capacity of the filler. SUMMARY

[0007] The present application provides a kind of containing thiol chelate denitrification biological filler and its preparation method and application, utilize the characteristics that thiol can form stable chelate with metal ions, sulfur is heated to melt, and it is reacted with the organic matter with amine group and generates the chain polymer with thiol, again with ferrous ion, nickel ion and cobalt ion forms chelate, provides stable ferrous ion and nickel, cobalt ion supply for anaerobic ammonia oxidation and sulfur autotrophic denitrification, can effectively solve the problem in current coupling process.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0009] A thiol chelate denitrification biological filler, the denitrification biological filler is a chain polymer with thiol and a chelate formed by ferrous ions, nickel ions and cobalt ions; the particle size of the filler is 2-4 mm.

[0010] The preparation method of the above-mentioned sulfur-containing thiol chelate denitrification biological filler comprises the following steps:

[0011] Step1: Heat hexamethylenediamine (HMDA) to melt, add sulfur to the molten HMDA, continue to heat and continuously stir until completely dissolved;

[0012] Step2: Add catalyst triethylamine (TEA), continue to heat the mixed solution to maintain constant temperature, and continue to stir;

[0013] Step3: Add ferrous chloride, nickel chloride and cobalt chloride to the above mixed solution, keep heating and continuously stirring;

[0014] Step4: After the reaction is completed, stop heating and let the solution cool to room temperature, and the preliminary product is precipitated, the reaction product is dissolved in anhydrous ethanol, the unreacted sulfur is filtered off, and the filtered solution is subjected to reduced pressure evaporation to precipitate the reaction product from the solvent, and then filtered, washed and dried in a vacuum oven;

[0015] Step5: Mix the dried reaction product with an appropriate amount of binder polyvinyl alcohol uniformly, and heat melt granulation in a granulator to obtain a uniform granular final product.

[0016] In the above steps, the raw materials are as follows: sulfur 80-100 parts, hexamethylenediamine (HMDA) 100-120 parts, ferrous chloride 40-60 parts, nickel chloride 20-40 parts, cobalt chloride 20-40 parts, triethylamine (TEA) 3-5 parts, and polyvinyl alcohol 5-10 parts;

[0017] The heating temperature in Step1 is kept at 160-180℃, the stirring speed is 60-80rpm, and the stirring time is 10-30 minutes;

[0018] The heating temperature in Step2 is kept at 180-200℃, the stirring speed is 120-160rpm, and the stirring time is 4-6 hours;

[0019] The heating temperature in Step3 is kept at 80-90℃, the stirring speed is 100-120rpm, and the stirring time is 2-4 hours;

[0020] The drying temperature in Step4 is 80-90℃, and the time is 8-12h;

[0021] The temperature for heat melt granulation in Step5 is 120-140℃, and the stirring speed is 120-300rpm.

[0022] Beneficial effects: The present application provides a thiol-containing chelate denitrification biological filler and its preparation method and application, which has the following advantages compared with the prior art:

[0023] 1. The amine group of hexamethylene diamine reacts with the active sulfur atoms generated by the ring opening of sulfur at high temperature to form carbon-sulfur bonds and mercapto groups; the mercapto groups then undergo coordination reaction with metal ions to generate Fe-S, Ni-S, and Co-S chelate structures;

[0024] 2. The long-chain polysulfide structure provides a stable biofilm carrier: The long-chain polysulfide structure of the present invention not only provides a sulfur source, but also increases the surface activity of the material, promotes the attachment and growth of anaerobic ammonia oxidation bacteria, and provides a stable biofilm carrier for the anaerobic ammonia oxidation process, making the denitrification effect in the coupling process more stable and sustainable;

[0025] 3. Carbon-sulfur bond generates persistent sulfur source, promotes sulfur autotrophic denitrification: The carbon-sulfur bond structure generated by hexamethylene diamine and polysulfide chain at high temperature can slowly release sulfur elements in water treatment for a long time, providing a continuous and stable sulfur source for sulfur autotrophic denitrifying bacteria, thereby ensuring the denitrification efficiency of sulfur autotrophic denitrification, especially in the case of limited sulfur resources, which is more effective;

[0026] 4. Mercapto chelates metal ions, provides trace elements: The mercapto groups generated during preparation combine with metal ions (such as Fe²⁺, Ni²⁺, Co²⁺) to form stable chelate structures, thereby providing key trace elements required for the coupling process for microorganisms. These elements are important components for promoting the normal metabolism and activity of anaerobic ammonia oxidation bacteria and sulfur autotrophic denitrifying bacteria;

[0027] 5. Slow-release metal ions improve the efficiency of the coupling process: Metal ions are chelated on the mercapto chain, and under acidic conditions generated by water environment or microbial metabolism, the chelated metal ions will gradually dissociate. In the polymer network structure, metal ions may be chelated with multiple mercapto groups, and only the outermost metal ions can dissociate preferentially, while the inner layer metal ions are released layer by layer, thereby achieving slow release and providing long-term nutritional support for denitrifying microorganisms, avoiding the decline of the coupling denitrification process efficiency due to the rapid consumption of trace elements, while reducing the need for additional metal salt addition, improving the economic efficiency of the process;

[0028] 6. Mechanical strength suitable for long-term operation of the coupling process: The long-chain polysulfide and metal chelate structure of the present invention endows the material with high mechanical strength, making it exhibit excellent resistance to flushing and durability in the fluidized bed or fixed bed system of the sulfur autotrophic denitrification and anaerobic ammonia oxidation coupling process, ensuring long-term stable operation of the process and reducing the frequency of material replacement;

[0029] 7. The material stability reduces secondary pollution in the coupling process: the polysulfide and metal chelate structure of the filler has high chemical stability, and is not easy to degrade or release excess sulfur and metal ions in the water treatment process, thereby reducing the risk of secondary pollution to the environment and ensuring the environmental protection and sustainability of the coupled denitrification process. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The denitrification effect diagram of the R1 reactor in the embodiment of the present application;

[0031] Figure 2 The denitrification effect diagram of the R2 reactor in the embodiment of the present application;

[0032] Figure 3 The denitrification effect diagram of the R3 reactor in the embodiment of the present application;

[0033] Figure 4 The reaction mechanism diagram of the preparation method of the denitrification biological filler in the embodiment of the present application. DETAILED DESCRIPTION

[0034] The present application will be described in detail below in conjunction with the drawings and specific embodiments:

[0035] The raw materials used below are: sulfur, hexamethylene diamine (HMDA), ferrous chloride, nickel chloride, cobalt chloride, triethylamine (TEA), and polyvinyl alcohol; the parts of each component are parts by weight. Example 1

[0036] A preparation method of a thiol chelate-containing denitrification biological filler, comprising the following steps:

[0037] Take HMDA and sulfur with a mass ratio of 110:90, add sulfur to molten HMDA, heat and stir at 170℃ until completely dissolved, add 4 parts of TEA to the mixed solution in mass fraction, and keep heating and stirring at 190℃ for 5 hours. Add 50 parts of ferrous chloride, 30 parts of nickel chloride, and 30 parts of cobalt chloride to the mixed solution, adjust the heating temperature to 85℃, and continue stirring for 3 hours, then cool to room temperature. The preliminary product is precipitated using anhydrous ethanol; the crude product is obtained after drying the preliminary product in a vacuum oven at 85℃ for 10h; the crude product and polyvinyl alcohol powder are mixed, and hot melt granulation is carried out in a granulator at 130℃ and a rotation speed of 120rpm to obtain a sulfur-containing thiol chelate denitrification biological filler with stable chelate structure. Example 2

[0038] A preparation method of a thiol chelate-containing denitrification biological filler, comprising the following steps:

[0039] Take the mass ratio of 120:100 of HMDA and sulfur, sulfur is added to the molten HMDA, heated to completely dissolved under stirring at 180℃. 5 parts of TEA is added to the mixed solution in mass fraction, keep heating and stirring at 200℃ for 6 hours. 40 parts of ferrous chloride, 20 parts of nickel chloride, 20 parts of cobalt chloride are added to the mixed solution, adjust the heating temperature to 80℃, continue to stir for 2 hours and then cool to room temperature. The preliminary product is precipitated by using anhydrous ethanol. The crude product is obtained after drying the preliminary product in a vacuum oven at 90℃ for 12 hours. The crude product is mixed with polyvinyl alcohol powder, and hot melt granulation is carried out in a granulator at 140℃ and a rotating speed of 250 rpm to obtain a sulfur-containing mercapto chelate denitrification biological filler with stable chelate structure. Example 3

[0040] A preparation method of a mercapto chelate denitrification biological filler, comprising the following steps:

[0041] Take the mass ratio of 120:80 of HMDA and sulfur, sulfur is added to the molten HMDA, heated to completely dissolved under stirring at 200℃. 3 parts of TEA is added to the mixed solution in mass fraction, keep heating and stirring at 180℃ for 4 hours. 60 parts of ferrous chloride, 40 parts of nickel chloride, 40 parts of cobalt chloride are added to the mixed solution, adjust the heating temperature to 90℃, continue to stir for 4 hours and then cool to room temperature. The preliminary product is precipitated by using anhydrous ethanol. The crude product is obtained after drying the preliminary product in a vacuum oven at 80℃ for 8 hours. The crude product is mixed with polyvinyl alcohol powder, and hot melt granulation is carried out in a granulator at 120℃ and a rotating speed of 200 rpm to obtain a sulfur-containing mercapto chelate denitrification biological filler with stable chelate structure.

[0042] The above prepared denitrification biological filler is applied in sewage treatment.

[0043] The fillers prepared in examples 1, 2 and 3 are respectively filled in a 5L UASB reactor in the laboratory, and the filler filling rate is 60%. The sludge is inoculated with anaerobic ammonia oxidation and sulfur autotrophic denitrification sludge which is domesticated for 160d in a sewage treatment plant. The sludge is used for hanging film by inoculating once every five days. After three cycles, the water quality index, i.e. the culture medium utilization, is monitored every day. When the water quality index is stable and the culture medium utilization is good for three consecutive cycles, it is considered that the film hanging is successful. The three reactors are respectively recorded as R1, R2 and R3. Under the same conditions, a continuous flow experiment is carried out to verify the denitrification effect. The influent of the reactor is laboratory simulated wastewater prepared by laboratory tap water. Only potassium nitrate (KNO3) is added as the only nitrogen source in each reactor. The concentration of NO3 - -N is about 120mg / L. The initial pH of each reactor is about 7. The temperature is controlled by a constant temperature water bath pot, and the temperature is about 35℃. During the reaction process, the internal NO3 - -N and NO2 --N, NH 4+ The sum of N is regarded as the content of total nitrogen TN in the reactor. The total nitrogen removal effect of R1, R2, R3 and the reactor is respectively shown in the following table. Figure 1 , Figure 2 , Figure 3 .

[0044] It can be seen from Figure 1 that the reaction effect of R1 reactor is general in the first 20 days. With the accumulation of ammonia nitrogen and nitrite, the removal rate rapidly rises, and the total nitrogen removal rate reaches 70% at 50 days. With the reaction, the removal rate continuously rises, and the effluent nitrogen concentration rapidly drops, reaching 90% at 80 days, and can be maintained above 98% when the reaction is carried out to 120 days.

[0045] It can be seen from Figure 2 that the R2 reactor starts relatively fast, and the TN removal rate reaches above 70% at 40 days. However, due to the low content of nutrients such as ferrous ions required by anaerobic ammonia oxidation bacteria, the removal of nitrite and ammonia nitrogen is affected, and in turn the nitrate denitrification reaction is affected, resulting in that the total nitrogen removal rate does not reach 80% until 80 days. The removal rate reaches above 87% at 120 days.

[0046] It can be seen from Figure 3 that the total nitrogen removal rate of R3 reactor reaches 70% at 45 days. Due to the low content of sulfur in the filler, the growth rate of sulfur autotrophic denitrifying bacteria is slow in the early stage, and the nitrate removal rate is low. Therefore, the reactor starts relatively slowly, which cannot meet the demand of fast start in actual production.

[0047] The reactor R1 has excellent and stable nitrogen removal performance. By scientifically adjusting the composition and proportion of the filler, the system can maintain low effluent nitrogen concentration and improve the total nitrogen removal efficiency in long-term operation. At the same time, even under the impact of high concentration of nitrate, R1 still shows excellent treatment effect, which gives it significant economic value and engineering application potential. The process plays a positive role in promoting the combination and development of sulfur autotrophic denitrification and anaerobic ammonia oxidation technology.

[0048] The above are only preferred embodiments of the present application, which will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, some modifications and improvements made are within the protection of the present application.

Claims

1. A process for the preparation of a denitrifying biological packing containing a sulphur-containing thiol chelate, characterized in that, The method comprises the following steps: Step 1: heating hexamethylene diamine to melt, adding sulfur into the molten hexamethylene diamine, continuously heating and stirring until completely dissolved; Step 2: adding a catalyst, continuously heating and keeping constant temperature, continuously stirring; Step 3: adding ferrous chloride, nickel chloride and cobalt chloride into the above mixed solution, keeping heating and continuously stirring; Step 4: after the reaction is completed, stopping heating, allowing the solution to cool to room temperature, precipitating the preliminary product, filtering the unreacted sulfur from the reaction product, evaporating the filtered solution under reduced pressure to precipitate the reaction product from the solvent, filtering, washing and drying; Step 5: mixing the dried reaction product with an appropriate amount of binder, uniformly hot-melt granulating in a granulator to obtain the uniform granular final product.

2. The process for preparing a sulfur-containing mercapto-chelate denitrifying biological packing material according to claim 1, characterized in that, The raw materials are as follows by weight fraction: sulfur 80-100 parts, hexamethylene diamine 100-120 parts, ferrous chloride 40-60 parts, nickel chloride 20-40 parts, cobalt chloride 20-40 parts, catalyst 3-5 parts, and binder 5-10 parts.

3. The process for the preparation of a denitrifying biological packing of sulphur-containing mercapto chelates according to claim 1 or 2, characterized in that, The heating temperature in Step 1 is kept at 160-180℃, the stirring speed is 60-80rpm, and the stirring time is 10-30 minutes.

4. The process for the preparation of a denitrifying biological packing of sulphur-containing mercapto chelates according to claim 1 or 2, characterized in that, The heating temperature in Step 2 is kept at 180-200℃, the stirring speed is 120-160rpm, and the stirring time is 4-6 hours.

5. The process for the preparation of a denitrifying biological packing of sulphur-containing mercapto chelates according to claim 1 or 2, characterized in that, The heating temperature in Step 3 is kept at 80-90℃, the stirring speed is 100-120rpm, and the stirring time is 2-4 hours.

6. The process for the preparation of a denitrifying biological packing of sulphur-containing mercapto chelates according to claim 1 or 2, characterized by the fact that, The drying temperature in Step 4 is 80-90℃, and the time is 8-12h.

7. The process for the preparation of a denitrifying biological packing of sulphur-containing mercapto chelates according to claim 1 or 2, characterized by the fact that, The catalyst is triethylamine.

8. The process for preparing a sulfur-containing mercapto chelate denitrification biological filler according to claim 1, characterized by, The prepared filler has a particle size of 2-4mm.

9. A denitrifying biological packing comprising a sulfur-containing thiol chelate, characterized in that, The denitrification biological filler is prepared by the method of any one of claims 1-8, and is a chelate formed by a chain polymer with a sulfhydryl group and metal ions.

10. The sulfur-containing sulfhydryl chelate denitrification biological filler of claim 9 is applied to nitrogen-containing wastewater treatment.

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