Denitrification biological filler containing sulfydryl chelate as well as preparation method and application of denitrification biological filler

Abstract

The invention discloses a sulfydryl-containing chelate denitrification biological filler and a preparation method and application thereof, and belongs to the field of sewage treatment.The preparation method comprises the steps that hexamethylenediamine and sulfur react at a high temperature to form a polysulfide long-chain structure, and generated sulfydryl is chelated with ferrous ions, nickel ions and cobalt ions to obtain a high-molecular polymer loaded with metal ions; and granulating the product to obtain the final denitrification biological filler. The prepared nitrogen removal biological filler has the advantages that nutrient substances necessary for growth of microorganisms can be provided, the nitrogen removal biological filler is also a key component of heme and anaerobic ammonia oxidation protease, growth and reproduction of anaerobic ammonia oxidation bacteria are promoted, a sulfur source is provided for sulfur autotrophic denitrification bacteria, nitrogen removal through coupling of sulfur autotrophic denitrification and anaerobic ammonia oxidation is achieved, and the nitrogen removal efficiency is improved. The catalyst has excellent mechanical strength, stability and efficient denitrification capability, and is very suitable for long-term application in a sulfur autotrophic denitrification and anaerobic ammonia oxidation coupling process.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a denitrification biological filler containing a thiol chelate, and a preparation method and application thereof. Background Art

[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 eutrophication of water bodies and ecological imbalance. Nitrogen mainly exists in wastewater in the form of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen, posing a threat to aquatic ecosystems and human health. Therefore, the development of efficient wastewater biological denitrification technology is of great significance for environmental protection.

[0003] Biological denitrification is an effective technology for removing nitrogen from 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 chemicals and energy consumption required in traditional chemical treatment methods. This technology also has low sludge production and good environmental adaptability, and can operate stably under different wastewater concentrations and flow conditions. In addition, biological denitrification can also achieve a higher nitrogen removal efficiency by controlling and optimizing the growth and metabolic processes of microorganisms, and has good economy and sustainability.

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

[0005] However, this coupling process also faces some challenges. First, anaerobic ammonium oxidizing bacteria and sulfur autotrophic denitrifying bacteria are prone to competition when treating nitrite-nitrogen, resulting in system instability. Second, when the nitrate-nitrogen concentration in the system is too high, it is difficult to ensure the balance between anaerobic ammonium oxidizing bacteria and sulfur autotrophic denitrifying bacteria, affecting the overall treatment effect. Solving these problems requires precise control of reaction conditions, optimizing the synergistic effect of the bacterial community, and ensuring that the two bacterial communities can coexist well in the system, thereby achieving efficient nitrogen removal.

[0006] In order to solve these difficulties, patent CN116715355A provides an iron oxide-based composite filler and its preparation method and application. By loading carbon material in the iron oxide-based composite filler, the iron oxide and carbon material inside the filler form countless iron-carbon micro batteries. 2+ Restore NO 3- —N is NH 4+ -N, provides electron donors for anaerobic ammonia-oxidizing bacteria, but the filler prepared by this method is difficult to control the release rate of ferrous ions, and has limited effect when treating high-ammonia nitrogen wastewater. In actual operation, the iron-carbon microbattery is easy to decompose and has a short validity period. For example, patent CN116199335A provides a denitrification biological filler and a preparation method thereof, by reacting sulfur with vinyl acetate to obtain a sulfur-rich polymer filler, realizing sulfur autotrophic and heterotrophic coupling of denitrification and denitrification, and enhancing the denitrification effect. However, this filler is insufficient in stability, is easy to decompose, and the release rate of the active substance is unstable, which affects the continuous denitrification ability of the filler. Summary of the invention

[0007] The present invention provides a thiol-containing chelate denitrification biological filler and a preparation method and application thereof. The property that thiol can form a stable chelate with metal ions is utilized, sulfur is heated to be molten, and reacted with organic matter with amine groups to generate a chain polymer with thiol groups, and then a chelate is formed with ferrous ions, nickel ions and cobalt ions, so as to provide a stable supply of ferrous ions, nickel and cobalt ions for anaerobic ammonia oxidation and sulfur autotrophic denitrification, and can effectively solve the problems in the current coupling process.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions: A thiol-containing chelate denitrification biological filler, which is a chelate formed by a chain polymer with thiol and ferrous ions, nickel ions and cobalt ions; the filler particle size is 2-4mm.

[0009] The method for preparing the above-mentioned sulfur-containing mercapto chelate denitrification biological filler comprises the following steps: Step 1: Heat hexamethylenediamine (HMDA) until it is melted, add sulfur into the melted HMDA, continue heating and stirring until it is completely dissolved; Step 2: Add the catalyst triethylamine (TEA), continue to heat the mixed solution to maintain a constant temperature, and continue stirring; Step 3: Add ferrous chloride, nickel chloride and cobalt chloride to the above mixed solution, keep heating and stirring; Step 4: After the reaction is completed, stop heating, let the solution cool to room temperature, precipitate the preliminary product, dissolve the reaction product in anhydrous ethanol, filter out the unreacted sulfur, evaporate the filtered solution under reduced pressure to precipitate the reaction product from the solvent, filter, wash, and dry in a vacuum oven; Step 5: Evenly mix the dried reaction product with an appropriate amount of binder polyvinyl alcohol, and perform hot-melt granulation in a granulator to obtain a uniform granular final product.

[0010] In the above steps, the raw materials are as follows by weight: 80-100 parts of sulfur, 100-120 parts of hexamethylenediamine (HMDA), 40-60 parts of ferrous chloride, 20-40 parts of nickel chloride, 20-40 parts of cobalt chloride, 3-5 parts of triethylamine (TEA), and 5-10 parts of polyvinyl alcohol; In step 1, the heating temperature is maintained at 160-180°C, the stirring speed is 60-80 rpm, and the stirring time is 10-30 minutes; In step 2, the heating temperature is maintained at 180-200°C, the stirring speed is 120-160 rpm, and the stirring time is 4-6 hours; In step 3, the heating temperature is maintained at 80-90°C, the stirring speed is 100-120 rpm, and the stirring time is 2-4 hours; The drying temperature in Step 4 is 80~90℃ and the time is 8~12h; The temperature of hot melt granulation in Step 5 is 120-140°C, and the stirring speed is 120-300rpm.

[0011] Beneficial effects: The present invention provides a denitrification biofiller containing a thiol chelate and a preparation method and application thereof, which has the following advantages over the prior art: 1. The present invention utilizes the amine group of hexamethylenediamine to react with the active sulfur atom generated by sulfur ring opening under high temperature conditions to form a carbon-sulfur bond and a thiol group; the thiol group then undergoes a coordination reaction with the metal ion to generate a chelate structure of Fe-S, Ni-S and Co-S; 2. The long-chain structure of polysulfide provides a stable biofilm carrier: The long-chain structure of polysulfide of the present invention can not only provide a sulfur source, but also increase the surface activity of the material, promote the attachment and growth of anaerobic ammonium-oxidizing bacteria, provide a stable biofilm carrier for the anaerobic ammonium-oxidation process, and make the denitrification effect in the coupling process more stable and sustainable; 3. Carbon-sulfur bonds generate a lasting sulfur source to promote sulfur autotrophic denitrification: The carbon-sulfur bond structure generated by hexamethylenediamine and polysulfide chains at high temperatures 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 when sulfur resources are limited; 4. Sulfhydryl chelates metal ions to provide trace elements: The sulfhydryl groups generated during the preparation process combine with metal ions (such as Fe²⁺, Ni²⁺, Co²⁺) to form a stable chelate structure, thereby providing microorganisms with key trace elements required for the coupling process. These elements are important components for promoting the normal metabolism and activity of anaerobic ammonia oxidizing bacteria and sulfur autotrophic denitrifying bacteria; 5. Slow release of metal ions improves coupling process efficiency: Metal ions are chelated on thiol chains. Under acidic conditions of water environment or microbial metabolism, chelated metal ions will gradually dissociate. In the polymer network structure, metal ions may be chelated with multiple thiols. Only the outermost metal ions can be preferentially dissociated, while the inner metal ions are released layer by layer, thus achieving slow release, thereby providing long-term nutritional support for denitrification microorganisms, avoiding the decrease in coupling denitrification process efficiency due to excessive consumption of trace elements, and reducing the need for additional metal salt addition, thereby improving the economic efficiency of the process; 6. Mechanical strength is suitable for long-term operation of the coupling process: The long polysulfide chain and metal chelate structure of the present invention give the material high mechanical strength, so that it exhibits excellent anti-scouring ability and durability in the fluidized bed or fixed bed system of the sulfur autotrophic denitrification and anaerobic ammonia oxidation coupling process, ensuring the long-term stable operation of the process and reducing the frequency of material replacement; 7. Material stability reduces secondary pollution in the coupling process: The polysulfide and metal chelate structures of the filler of the present invention have high chemical stability and are not easily degraded or release excessive sulfur and metal ions during 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 THE DRAWINGS

[0012] Figure 1 This is a diagram showing the denitrification effect of the R1 reactor in an embodiment of the present invention; Figure 2 This is a diagram showing the denitrification effect of the R2 reactor in an embodiment of the present invention; Figure 3 This is a diagram showing the denitrification effect of the R3 reactor in an embodiment of the present invention; Figure 4 This is a reaction mechanism diagram of the method for preparing the denitrification biological filler described in an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: The following raw materials are used: sulfur, hexamethylenediamine (HMDA), ferrous chloride, nickel chloride, cobalt chloride, triethylamine (TEA), and polyvinyl alcohol; the parts of each component are parts by weight. Example 1

[0014] A method for preparing a thiol chelate-containing denitrification biological filler comprises the following steps: Take HMDA and sulfur in a mass ratio of 110:90, add sulfur to molten HMDA, heat and stir at 170°C until completely dissolved, add 4 parts of TEA by mass fraction to the mixed solution, and keep heating and stirring at 190°C 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°C, continue stirring and reacting for 3 hours, then cool to room temperature, and use anhydrous ethanol to precipitate the preliminary product; the preliminary product is dried at 85°C in a vacuum oven for 10 hours to obtain a crude product; the crude product is mixed with polyvinyl alcohol powder, and hot-melt granulated in a granulator at 130°C and a speed of 120rpm to obtain a sulfur-containing thiol chelate denitrification biofiller with a stable chelate structure. Example 2

[0015] A method for preparing a thiol chelate-containing denitrification biological filler comprises the following steps: Take HMDA and sulfur in a mass ratio of 120:100, add sulfur to molten HMDA, and heat and stir at 180°C until completely dissolved. Add 5 parts of TEA by mass fraction to the mixed solution, and keep heating and stirring at 200°C for 6 hours. Add 40 parts of ferrous chloride, 20 parts of nickel chloride, and 20 parts of cobalt chloride to the mixed solution, adjust the heating temperature to 80°C, continue stirring and reacting for 2 hours, then cool to room temperature, and use anhydrous ethanol to precipitate the preliminary product; the preliminary product is dried at 90°C in a vacuum oven for 12 hours to obtain a crude product; the crude product is mixed with polyvinyl alcohol powder, and hot-melt granulated at 140°C and 250rpm in a granulator to obtain a sulfur-containing thiol chelate denitrification biofiller with a stable chelate structure. Example 3

[0016] A method for preparing a thiol chelate-containing denitrification biological filler comprises the following steps: Take HMDA and sulfur in a mass ratio of 120:80, add sulfur to molten HMDA, and heat and stir at 200°C until completely dissolved. Add 3 parts of TEA to the mixed solution by mass fraction, and keep heating and stirring at 180°C for 4 hours. Add 60 parts of ferrous chloride, 40 parts of nickel chloride, and 40 parts of cobalt chloride to the mixed solution, adjust the heating temperature to 90°C, continue stirring and reacting for 4 hours, then cool to room temperature, and use anhydrous ethanol to precipitate the preliminary product; the preliminary product is dried at 80°C in a vacuum oven for 8h to obtain a crude product; the crude product is mixed with polyvinyl alcohol powder, and hot-melt granulated at 120°C and 200rpm in a granulator to obtain a sulfur-containing thiol chelate denitrification biofiller with a stable chelate structure.

[0017] The denitrification biological filler prepared above is used in sewage treatment.

[0018] The fillers prepared in Examples 1, 2, and 3 were respectively filled in a 5L UASB reactor in the laboratory, with a filler filling rate of 60%. The sludge was inoculated with anaerobic ammonia oxidation and sulfur autotrophic denitrification sludge from a sewage treatment plant that had been domesticated for 160 days. The biofilm formation sludge was inoculated once every five days. After three cycles, the water quality indicators, i.e., the utilization of the culture medium, were monitored every day. When the water quality indicators were stable and the utilization of the culture medium was good for three consecutive cycles, the biofilm formation was considered successful. The three reactors were respectively denoted as R1, R2, and R3. Under the same other conditions, a continuous flow experiment was carried out to verify the denitrification effect. The reactor inlet water used laboratory simulated wastewater and was prepared with laboratory tap water. Only potassium nitrate (KNO3) was added to each reactor as the only nitrogen source. NO3 - -N concentration is about 120mg / L. The initial pH of each reactor is about 7, and the temperature is controlled by a constant temperature water bath at about 35℃. During the reaction, the internal NO3 - -N, NO2 - -N, NH 4+ The sum of -N was taken as the total nitrogen TN content in the reactor. The reactor was operated for a total of 120 days. The denitrification effects of R1, R2, R3 and Figure 1 , Figure 2 , Figure 3 .

[0019] from Figure 1 It can be seen that the reaction effect of the R1 reactor was average in the first 20 days. With the accumulation of ammonia nitrogen and nitrite, the removal rate increased rapidly, and the total nitrogen removal rate reached 70% on day 50. As the reaction progressed, the removal rate continued to rise, and the nitrogen concentration of the effluent decreased rapidly, reaching 90% on day 80, and could be maintained above 98% when the reaction was carried out for 120 days.

[0020] from Figure 2It can be seen that the R2 reactor started up quickly and reached a TN removal rate of more than 70% in 40 days. However, due to the low content of nutrients such as ferrous ions required by anaerobic ammonium oxidizing bacteria, the removal of nitrite and ammonia nitrogen was affected, which in turn affected the nitrate denitrification reaction, resulting in the total nitrogen removal rate not reaching 80% until 80 days. The removal rate reached more than 87% at 120 days.

[0021] from Figure 3 It can be seen that the total nitrogen removal rate of the R3 reactor reached 70% at 45 days. Due to the low sulfur content in the filler, the growth rate of sulfur autotrophic denitrifying bacteria was slow in the early stage and the nitrate removal rate was low. Therefore, the startup of this reactor was relatively slow and could not meet the demand for rapid startup in actual production.

[0022] Reactor R1 has excellent and stable nitrogen removal performance. By scientifically adjusting the composition ratio of the filler, the system can maintain low nitrogen effluent concentration and improve the total nitrogen removal efficiency in long-term operation. At the same time, even under the impact of high-concentration nitrates, R1 still shows excellent treatment effects, which gives it significant economic value and engineering application potential. This process has played a positive role in promoting the combination and development of sulfur autotrophic denitrification and anaerobic ammonia oxidation technology.

[0023] The above are only preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements made are all protected by the present invention.

Claims

1. A denitrification biofiller containing a thiol chelate, characterized in that: The denitrification biological filler is a chelate formed by a chain polymer with a thiol group and a metal ion.

2. A method for preparing a denitrification biological filler containing a thiol chelate, characterized in that: The following steps are involved: Step 1: Heat hexamethylenediamine until it is melted, add sulfur into the melted hexamethylenediamine, continue heating and stirring until it is completely dissolved; Step 2: Add the catalyst, continue to heat the mixed solution to maintain a constant temperature, and continue stirring; Step 3: Add ferrous chloride, nickel chloride and cobalt chloride to the above mixed solution, keep heating and stirring; Step 4: After the reaction is completed, stop heating, let the solution cool to room temperature, precipitate the preliminary product, filter the reaction product to remove unreacted sulfur, evaporate the filtered solution under reduced pressure to precipitate the reaction product from the solvent, filter, wash and dry; Step 5: Evenly mix the dried reaction product with an appropriate amount of binder, and perform hot-melt granulation in a granulator to obtain a uniform granular final product.

3. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2, characterized in that: The raw materials are as follows by weight: 80-100 parts of sulfur, 100-120 parts of hexamethylenediamine, 40-60 parts of ferrous chloride, 20-40 parts of nickel chloride, 20-40 parts of cobalt chloride, 3-5 parts of catalyst and 5-10 parts of binder.

4. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2 or 3, characterized in that: In Step 1, the heating temperature is maintained at 160-180°C, the stirring speed is 60-80 rpm, and the stirring time is 10-30 minutes.

5. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2 or 3, characterized in that: In Step 2, the heating temperature is maintained at 180-200°C, the stirring speed is 120-160 rpm, and the stirring time is 4-6 hours.

6. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2 or 3, characterized in that: In Step 3, the heating temperature is maintained at 80-90°C, the stirring speed is 100-120 rpm, and the stirring time is 2-4 hours.

7. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2 or 3, characterized in that: The drying temperature in Step 4 is 80~90°C and the time is 8~12h.

8. The method for preparing the thiol-chelate-containing denitrification biological filler according to claim 2 or 3, characterized in that: The catalyst is triethylamine.

9. The method for preparing the denitrification biological filler containing thiol chelate according to claim 2, characterized in that: The prepared filler has a particle size of 2-4 mm.

10. The thiol-chelate-containing denitrification biological filler according to claim 1 is used in the treatment of nitrogen-containing wastewater.

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