Amorphous iron-manganese oxygen cluster, preparation method thereof and application of the amorphous iron-manganese oxygen cluster in strengthening function of methanogen

Abstract

This invention provides an amorphous iron-manganese oxide cluster, its preparation method, and its application in enhancing methanogenesis through functional enzymes. It belongs to the interdisciplinary technical fields of environmental functional materials, waste biological treatment, and resource utilization. The invention first mixes manganese salt and hydrochloric acid solution to obtain a hydrochloric acid solution of manganese salt; dissolves iron salt in water to obtain an iron salt solution; mixes the hydrochloric acid solution of manganese salt and the iron salt solution, heats the mixture, and then adds isopropanolamine solution to react, obtaining amorphous iron-manganese oxide clusters. The dispersion of the above amorphous iron-manganese oxide clusters is added to mixed bacterial granular sludge for sequential activation and anaerobic digestion. This can serve as an enhancer and protectant for anaerobic microbial functional enzymes, eliminating the influence of intermediate acids on the methanogenesis process through chelation or adsorption. It can also increase the adenine triphosphate yield of methanogenic archaea, accelerate archaea growth, and balance the growth differences between archaea and acidogenic bacteria.

Description

Technical Field

[0001] This invention relates to the interdisciplinary fields of environmental functional materials, biological treatment and resource utilization of waste, and particularly to an amorphous iron-manganese-oxygen cluster, its preparation method, and its application in enhancing the methanogenesis of functional enzymes. Background Technology

[0002] Anaerobic biological treatment technology is a process in which facultative anaerobic and anaerobic microbial communities convert organic matter into methane and carbon dioxide under anaerobic conditions; it is also known as anaerobic digestion. With the development of anaerobic biological technology for wastewater treatment, the removal of organic matter from wastewater can basically meet the requirements for effluent quality. As the main component of anaerobic biological treatment—anaerobic sludge—its highly efficient bio-methanogenic performance not only ensures the efficient operation of anaerobic biological treatment processes but may also provide a new pathway for future energy development. However, current anaerobic biological treatment technology faces the following bottlenecks in waste treatment and resource utilization:

[0003] (1) Substrate-induced inhibition: Various inhibitory substances and intermediate products are rate-limiting factors. During anaerobic digestion, substrate-induced inhibition can affect anaerobic stability. For example, high concentrations of free ammonia, volatile fatty acids (VFAs), and sulfides / sulfates can inhibit microbial activity, leading to instability or even collapse of the anaerobic digestion system.

[0004] (2) Poor process stability: Acidogens (belonging to bacteria) and methanogens (belonging to archaea) differ physiologically, and their growth rates and sensitivities to anaerobic digestion process operating conditions also differ. Changes in environmental factors (including temperature, pH, H2 partial pressure, and organic loading rate) can affect the population balance and functional coordination of both, leading to imbalance and decreased efficiency in the anaerobic digestion process;

[0005] (3) Electron Transfer Restriction: Mediated interspecies electron transfer (MIET) is an important mechanism in traditional anaerobic digestion. MIET is the process of transferring electrons from one microorganism to another using H2 or formate (HCOOH) as electron carriers. H2 and HCOOH are usually transferred via diffusion in anaerobic environments. However, diffusion-based MIET is slow, and compounds are prone to escape during mass transfer, easily resulting in electron loss. In addition, MIET is also susceptible to interference from environmental factors, such as substrate-induced inhibition leading to MIET interruption. On the other hand, direct interspecies electron transfer (DIET) pathways can be formed by utilizing the conductive cilia and membrane-bound electron transport proteins of microorganisms, but these also suffer from problems such as electron transfer interruption and low substrate utilization efficiency.

[0006] Search results indicate that electron transfer pathways enhanced by conductive materials are a potential solution to the aforementioned technical bottlenecks. Therefore, based on the structure and characteristics of functional enzymes in anaerobic methanogens, this invention proposes a method for the targeted design of an amorphous iron-manganese-oxygen cluster and its preparation, using an enzyme-mimicking process. This method is then applied to enhance the anaerobic methanogenesis process in microorganisms, overcoming the limitations of electron transfer in anaerobic methanogenesis. Summary of the Invention

[0007] The purpose of this invention is to provide an amorphous iron-manganese-oxygen cluster and its preparation method, as well as its application in enhancing the methanogenesis of functional enzymes, in order to solve the problems of substrate-induced inhibition, poor process stability, and limited electron transfer in existing anaerobic biological treatment methanation technology.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] This invention provides a method for preparing amorphous iron-manganese-oxygen clusters, comprising the following steps:

[0010] (1) Mix manganese salt and hydrochloric acid solution to obtain manganese salt hydrochloric acid solution;

[0011] (2) Dissolve the iron salt in water to obtain an iron salt solution;

[0012] (3) Mix the hydrochloric acid solution of manganese salt and the iron salt solution and heat them. Then add isopropanolamine solution to react and obtain amorphous iron-manganese-oxygen cluster.

[0013] Preferably, in step (1), the molar volume ratio of manganese salt to hydrochloric acid solution is 5-15 mmol: 2-10 mL, wherein the concentration of hydrochloric acid solution is 1-4 mol / L.

[0014] Preferably, in step (2), the molar volume ratio of iron salt to water is 15-25 mmol: 20-60 mL.

[0015] Preferably, the molar volume ratio of the iron salt to the isopropanolamine solution is 15–25 mmol: 150–250 mL; and the concentration of the isopropanolamine solution is 2–4 mol / L.

[0016] Preferably, in step (3), the reaction temperature is 80-120°C and the reaction time is 1-3 hours.

[0017] This invention provides an amorphous iron-manganese-oxygen cluster prepared by the above-described method.

[0018] This invention provides an application of the above-mentioned amorphous iron-manganese-oxygen cluster enhanced functional enzyme methanogenesis, comprising the following steps: adding the amorphous iron-manganese-oxygen cluster dispersion into mixed bacterial granular sludge for sequential activation treatment and anaerobic digestion;

[0019] The mixed microbial granular sludge contains Actinomycetota and Euryarchaeota.

[0020] Preferably, the volume ratio of the amorphous iron-manganese-oxygen cluster dispersion to the mixed bacterial granular sludge is 5-10:20-40; and the concentration of the amorphous iron-manganese-oxygen cluster dispersion is 0.4-0.5 g / L.

[0021] Preferably, the activation treatment first adjusts the pH value to 7.3-7.5, and then performs the activation treatment at a temperature of 30-40°C until the pH value fluctuation of the system is less than 0.1 or the pH value of the system is lower than 3.5, at which point the activation treatment ends.

[0022] Preferably, the pH value is adjusted to 7.0-7.2 before anaerobic digestion is started.

[0023] The beneficial effects of this invention are:

[0024] (1) In this invention, an amorphous iron-manganese oxygen cluster (FMOc) was synthesized and added to the anaerobic reaction system of the target bacterial group. It can be absorbed into the cell through the microbial "diet" process, which stimulates the activity of iron-sulfur protein oxidoreductase (FTR). The interaction between FTR and FMOc enhances the anaerobic methanogenesis process and simultaneously increases the methane production and the methane / carbon dioxide ratio. The absorbed amorphous iron-manganese oxygen cluster can achieve efficient utilization of carbon sources in the anaerobic system and produce methane in a long-lasting and sustained manner.

[0025] (2) Amorphous iron-manganese-oxygen clusters have electron transfer and storage functions, and can build direct electron transfer pathways between bacteria and archaea, replacing the traditional indirect electron transfer mediated by H2 and HCOOH. They can be used as buffers in anaerobic digestion and can eliminate the influence of intermediate acid on the methanogenesis process through chelation or adsorption.

[0026] (3) By utilizing the amorphous iron-manganese oxygen cluster to mimic the function of cytochrome, the production of adenine nucleoside triphosphate (ATP) in archaea is increased, the growth of archaea is accelerated, and the growth difference between archaea and acidogenic bacteria is balanced. This shows that the amorphous iron-manganese oxygen cluster of the present invention can efficiently activate the methanogenic efficiency of functional enzyme genes in anaerobic systems, and solve the technical problems of low carbon source utilization and system instability caused by severe acidification in conventional anaerobic systems.

[0027] (4) The preparation method of amorphous iron-manganese-oxygen clusters provided by the present invention is simple, environmentally friendly and has broad application prospects. Attached Figure Description

[0028] Figure 1 The images show the physicochemical characterization of the amorphous iron-manganese-oxygen clusters prepared in Example 1, where A is a high-resolution transmission electron microscope image, and B and C are elemental analysis diagrams.

[0029] Figure 2 The graphs show the changes in COD concentration and cumulative methane production over anaerobic digestion time during the anaerobic digestion process in Example 1. In the graphs, A represents the change in COD concentration over anaerobic digestion time, and B represents the change in cumulative methane production over anaerobic digestion time.

[0030] Figure 3 The images show electron micrographs and elemental analysis diagrams of the mixed microbial granular sludge after anaerobic digestion in Application Example 1 and Comparative Example 1. In Comparative Example 1, A is an electron micrograph of the mixed microbial granular sludge after anaerobic digestion; B is an elemental analysis diagram of the mixed microbial granular sludge after anaerobic digestion; C is an electron micrograph of the mixed microbial granular sludge after anaerobic digestion; and D is an elemental analysis diagram of the mixed microbial granular sludge after anaerobic digestion.

[0031] Figure 4 The figures show the differences in microbial community composition and expression of key functional genes in the mixed granular sludge after anaerobic digestion in Application Example 1 and Application Comparative Example 1. Figure A shows the differences in microbial community composition in the mixed granular sludge after anaerobic digestion in Application Example 1 and Application Comparative Example 1, and Figure B shows the differences in expression of functional genes related to methanogenesis and carbon fixation pathways in the mixed granular sludge after anaerobic digestion in Application Example 1 and Application Comparative Example 1. Detailed Implementation

[0032] This invention provides a method for preparing amorphous iron-manganese-oxygen clusters, comprising the following steps:

[0033] (1) Mix manganese salt and hydrochloric acid solution to obtain manganese salt hydrochloric acid solution;

[0034] (2) Dissolve the iron salt in water to obtain an iron salt solution;

[0035] (3) Mix the hydrochloric acid solution of manganese salt and the iron salt solution and heat them. Then add isopropanolamine solution to react and obtain amorphous iron-manganese-oxygen cluster.

[0036] In this invention, in step (1), the molar volume ratio of manganese salt to hydrochloric acid solution is 5-15 mmol: 2-10 mL, preferably 8-12 mmol: 3-8 mL, and more preferably 10 mmol: 5-6 mL, wherein the concentration of hydrochloric acid solution is 1-4 mol / L, preferably 2-3 mol / L, and more preferably 2.4-2.6 mol / L.

[0037] The present invention does not have any special restrictions on the type of manganese salt, as long as it is a manganese salt that can be dissolved in hydrochloric acid solution. In the embodiments of the present invention, manganese chloride is preferred.

[0038] In this invention, in step (2), the molar volume ratio of iron salt to water is 15-25 mmol: 20-60 mL, preferably 18-22 mmol: 30-50 mL, and more preferably 20 mmol: 40 mL.

[0039] The present invention does not have any special restrictions on the type of iron salt, as long as it is an iron salt that can be dissolved in water. In the embodiments of the present invention, ferric chloride is preferred.

[0040] In this invention, it is preferable to heat the hydrochloric acid solution of manganese salt and the iron salt solution to 50°C and then mix them. The resulting mixed solution is then heated to 100°C, and then isopropanolamine solution is quickly added.

[0041] In this invention, the molar volume ratio of the iron salt to the isopropanolamine solution is 15-25 mmol:150-250 mL, preferably 18-22 mmol:180-220 mL, and more preferably 20 mmol:200 mL; the concentration of the isopropanolamine solution is 2-4 mol / L, preferably 2.5-3.5 mol / L, and more preferably 3 mol / L.

[0042] In this invention, in step (3), the reaction temperature is 80-120°C, preferably 90-110°C, more preferably 100°C, and the reaction time is 1-3 hours, preferably 1.5-2.5 hours, more preferably 2 hours.

[0043] In this invention, the products of the reaction are preferably subjected to sequential cooling, centrifugation, washing, and drying to obtain amorphous iron-manganese-oxygen clusters.

[0044] In this invention, the amorphous iron-manganese-oxygen cluster is preferably dispersed in an aqueous solution of tetramethylammonium hydroxide and stored for later use.

[0045] The present invention selects tetramethylammonium hydroxide aqueous solution as dispersant, which has the following advantages: (1) high efficiency, tetramethylammonium hydroxide has good solubility in water, which can effectively reduce the surface tension of liquid and thus improve the dispersion effect; (2) wide applicability, tetramethylammonium hydroxide aqueous solution is suitable for a variety of types of particles and liquids; (3) environmental friendliness, compared with some organic solvents, tetramethylammonium hydroxide has less impact on the environment and higher safety; (4) good stability; (5) provides an alkaline environment, which is conducive to the formation and stable preservation of amorphous iron-manganese-oxygen clusters.

[0046] This invention provides an amorphous iron-manganese-oxygen cluster prepared by the above-described method.

[0047] This invention provides an application of the above-mentioned amorphous iron-manganese-oxygen cluster enhanced functional enzyme methanogenesis, comprising the following steps: adding the amorphous iron-manganese-oxygen cluster dispersion into mixed bacterial granular sludge for sequential activation treatment and anaerobic digestion;

[0048] The mixed microbial granular sludge contains Actinomycetota and Euryarchaeota.

[0049] In this invention, the volume ratio of the amorphous iron-manganese-oxygen cluster dispersion to the mixed bacterial granular sludge is 5-10:20-40; the concentration of the amorphous iron-manganese-oxygen cluster dispersion is 0.4-0.5 g / L.

[0050] In this invention, the activation treatment first adjusts the pH value to 7.3-7.5, and then performs the activation treatment at a temperature of 30-40°C until the pH value fluctuation of the system is less than 0.1 or the pH value of the system is lower than 3.5, at which point the activation treatment ends.

[0051] In this invention, the pH value is adjusted to 7.0-7.2 before anaerobic digestion is started.

[0052] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] The mixed microbial granular sludge used in this embodiment of the invention comes from the expanded granular sludge bed reactor of Guangxi Yipu Environmental Engineering Co., Ltd., wherein the abundance of Actinomycetota is 37.90% and the abundance of Euryarchaeota is 13.66%, and the COD removal load of the mixed microbial granular sludge is preferably set to 5.45 kg COD / L·d; the concentration of suspended solids (SS) in the mixed microbial granular sludge is 44.8 g SS / L, and the concentration of volatile suspended solids (VSS) is 36.89 g VSS / L.

[0054] Example 1

[0055] 10 mmol of MnCl₂·4H₂O was dissolved in 5 mL of hydrochloric acid solution (concentration 2.4 mol / L) to obtain a hydrochloric acid solution of manganese chloride; 20 mmol of FeCl₃·6H₂O was dissolved in 40 mL of deionized water to obtain a ferric chloride solution. The two solutions were then heated to 50 °C, mixed, and rapidly stirred mechanically. Heating continued until the temperature of the mixed solution reached 100 °C, at which point 200 mL of isopropanolamine solution (concentration 3 mol / L) was rapidly added, and the reaction was continued at 100 °C for 2 h with stirring. After the reaction was complete, the reaction mixture was cooled to room temperature, and the brown precipitate was separated using a high-speed centrifuge. The brown precipitate was washed with anhydrous ethanol and finally dried in a vacuum dryer at 60 °C for 48 h to obtain amorphous iron-manganese oxide clusters. The obtained amorphous iron-manganese oxide clusters were dispersed in a 0.1 mol / L tetramethylammonium hydroxide aqueous solution and stored for later use.

[0056] Example 2

[0057] 15 mmol of MnCl₂·4H₂O was dissolved in 10 mL of hydrochloric acid solution (4 mol / L) to obtain a hydrochloric acid solution of manganese chloride; 25 mmol of FeCl₃·6H₂O was dissolved in 60 mL of deionized water to obtain a ferric chloride solution. The two solutions were then heated to 50 °C, mixed, and rapidly stirred mechanically. Heating continued until the temperature of the mixed solution reached 100 °C, at which point 250 mL of isopropanolamine solution (4 mol / L) was rapidly added, and the reaction was continued at 80 °C for 1 h with stirring. After the reaction was complete, the reaction mixture was cooled to room temperature, and the brown precipitate was separated using a high-speed centrifuge. The brown precipitate was washed with anhydrous ethanol and finally dried in a vacuum dryer at 60 °C for 48 h to obtain amorphous iron-manganese oxide clusters. The obtained amorphous iron-manganese oxide clusters were dispersed in a 0.1 mol / L tetramethylammonium hydroxide aqueous solution and stored for later use.

[0058] Example 3

[0059] 5 mmol of MnCl₂·4H₂O was dissolved in 3 mL of hydrochloric acid solution (1 mol / L) to obtain a hydrochloric acid solution of manganese chloride; 15 mmol of FeCl₃·6H₂O was dissolved in 20 mL of deionized water to obtain a ferric chloride solution. The two solutions were then heated to 50 °C, mixed, and rapidly stirred mechanically. Heating continued until the temperature of the mixed solution reached 100 °C, at which point 150 mL of isopropanolamine solution (2 mol / L) was rapidly added, and the reaction was continued at 120 °C with stirring for 3 h. After the reaction was complete, the reaction mixture was cooled to room temperature, and the brown precipitate was separated using a high-speed centrifuge. The brown precipitate was washed with anhydrous ethanol and finally dried in a vacuum dryer at 60 °C for 48 h to obtain amorphous iron-manganese oxide clusters. The obtained amorphous iron-manganese oxide clusters were dispersed in a 0.1 mol / L tetramethylammonium hydroxide aqueous solution and stored for later use.

[0060] Figure 1 The above is a physicochemical characterization diagram of the amorphous iron-manganese-oxygen clusters prepared in Example 1. Figure 1 It can be seen that Mn and Fe exist in amorphous form, and Fe forms FeMn oxygen clusters by bonding with Mn through oxygen bridging bonds.

[0061] Application Example 1

[0062] Mixed-culture granular sludge was selected as the target sludge, with an abundance of 37.9% for Actinomycetota and 13.66% for Euryarchaeota. The COD removal load of the mixed-culture granular sludge was set at 5.45 kg COD / L·d, the suspended solids (SS) concentration was 44.8 g SS / L, and the volatile suspended solids (VSS) concentration was 36.89 g VSS / L. The mixed-culture granular sludge was placed in a 120 mL anaerobic bottle, with an inoculum size of 30 mL.

[0063] The amorphous iron-manganese oxide cluster (the amorphous iron-manganese oxide cluster prepared in Example 1 above) dispersed in tetramethylammonium hydroxide aqueous solution was centrifuged, washed three times with anhydrous ethanol, and then placed in a vacuum dryer and dried at 60°C for 48 hours. After drying, 0.45 g of amorphous iron-manganese oxide cluster was weighed and added to 100 mL of deionized water, and ultrasonically dispersed for 30 min. Then, 8 mL of the dispersion was added to the anaerobic bottle mentioned above to form an anaerobic digestion system.

[0064] The pH of the anaerobic digestion system was adjusted to 7.3–7.5 using a 1 mol / L sodium hydroxide solution. The COD in the wastewater was 5000 mg / L, and the C / N / P ratio was 200 / 5 / 1. The system was then purged with nitrogen for 5 minutes, sealed with a rubber stopper, and connected to a 500 mL gas bag via a connecting device. The system was placed in a constant temperature environment at 35°C. Water and gas samples were taken every 2 hours, maintaining a sealed state during sampling. The activation process ended when the pH of the system stabilized (fluctuation less than 0.1 within 2 hours) or the pH of the system fell below 3.5. The pH of the system was then adjusted to approximately 7.0–7.2 using a 1 mol / L sodium hydroxide solution, and anaerobic digestion was initiated. Water and gas samples were then taken every 24 hours, maintaining a sealed state throughout the sampling process. The anaerobic digestion process ended when the COD concentration in the water sample stabilized, and sludge samples were collected.

[0065] Application Comparative Example 1

[0066] The difference from Application Example 1 is that no dispersion of amorphous iron-manganese-oxygen clusters was added to the anaerobic digestion system.

[0067] Figure 2 This graph shows the changes in COD concentration and cumulative methane yield during anaerobic digestion over time. In the graph, C represents Comparative Application Example 1, and M represents Application Example 1. Figure 2 It can be seen that when amorphous iron-manganese oxide clusters were added to the anaerobic digestion system, the cumulative methane production in the system was lower than that in the anaerobic digestion system without amorphous iron-manganese oxide clusters after 24 hours of anaerobic digestion (Comparative Application Example 1). After 48 hours, the cumulative methane production was slightly higher than that in the anaerobic digestion system without amorphous iron-manganese oxide clusters (Comparative Application Example 1). After 72 hours of anaerobic digestion, the cumulative methane production was much higher than that in the anaerobic digestion system without amorphous iron-manganese oxide clusters (Comparative Application Example 1). This indicates that the amorphous iron-manganese oxide clusters prepared in this invention can increase the ATP production of archaea and accelerate the growth of archaea.

[0068] After anaerobic digestion, sludge samples from Application Example 1 and Comparative Example 1 were collected. Genomic DNA extracted from the granular sludge was detected by 1% agarose gel electrophoresis, followed by fragmentation using a Covaris M220. A PE library was then constructed, specifically through the following steps: ligation of Y-shaped adapters; removal of adapter self-ligated fragments using magnetic beads; enrichment of the library template using PCR amplification; and denaturation with sodium hydroxide to generate single-stranded DNA fragments. Finally, Illumina sequencing was used to obtain the sequence of the template DNA fragments. The original sequences underwent optimization processes including splitting, quality shearing, and decontamination. The optimized sequences were then used for assembly and gene prediction, and the resulting genes were annotated and classified according to species and function. Simultaneously, the sludge samples were lyophilized, sectioned, and then analyzed by electron microscopy.

[0069] Figure 3 Electron microscopy and elemental analysis images of cross-sections of mixed microbial granular sludge after anaerobic digestion in Application Example 1 and Comparative Example 1 are provided. Figure 3 As can be seen from Figures A and B, the Fe and Mn elements of the target bacterial species are evenly distributed inside and around the cells. Figure 3 As can be seen from Figures C and D, the amorphous iron-manganese-oxygen clusters have entered the target bacteria, and the iron-manganese-oxygen clusters are distributed inside the cells and in the cell membrane.

[0070] from Figure 4 It can be seen that amorphous iron-manganese-oxygen clusters enhanced the methanogenic archaea in mixed bacterial granular sludge, resulting in a rapid increase in their abundance. Furthermore, after normalization, the functional gene tables of various methanogenic pathways in the archaea were represented by Log2TPM. The intervention of amorphous iron-manganese-oxygen clusters significantly improved the expression of methanogenic-related functional genes and their carbon fixation capacity. Figure 4 In this context, C represents Comparative Application Example 1, and M represents Application Example 1.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing amorphous iron-manganese-oxygen clusters, characterized in that, Includes the following steps: (1) Mix manganese salt and hydrochloric acid solution to obtain manganese salt hydrochloric acid solution; (2) Dissolve the iron salt in water to obtain an iron salt solution; (3) Mix the hydrochloric acid solution of manganese salt and the iron salt solution and heat them. Then add isopropanolamine solution to react and obtain amorphous iron-manganese-oxygen cluster.

2. The method for preparing amorphous iron-manganese-oxygen clusters according to claim 1, characterized in that, In step (1), the ratio of the amount of manganese salt to the volume of hydrochloric acid solution is 5-15 mmol: 2-10 mL, wherein the concentration of hydrochloric acid solution is 1-4 mol / L.

3. The method for preparing amorphous iron-manganese-oxygen clusters according to claim 1 or 2, characterized in that, In step (2), the ratio of the amount of iron salt to the volume of water is 15-25 mmol: 20-60 mL.

4. The method for preparing amorphous iron-manganese-oxygen clusters according to claim 3, characterized in that, The molar ratio of the iron salt to the volume of the isopropanolamine solution is 15–25 mmol: 150–250 mL; the concentration of the isopropanolamine solution is 2–4 mol / L.

5. The method for preparing amorphous iron-manganese-oxygen clusters according to claim 1, 2, or 4, characterized in that, In step (3), the reaction temperature is 80-120℃ and the reaction time is 1-3h.

6. The amorphous iron-manganese oxide cluster prepared by the method of any one of claims 1 to 5.

7. The application of the amorphous iron-manganese-oxygen cluster-enhanced functional enzyme for methanogenesis as described in claim 6, characterized in that, The process includes the following steps: adding the amorphous iron-manganese-oxygen cluster dispersion into the mixed bacterial granular sludge for sequential activation and anaerobic digestion; The mixed microbial granular sludge contains Actinomycetota and Euryarchaeota.

8. The application of the amorphous iron-manganese-oxygen cluster-enhanced functional enzyme for methanogenesis according to claim 7, characterized in that, The volume ratio of the amorphous iron-manganese-oxygen cluster dispersion to the mixed bacterial granular sludge is 5-10:20-40; the concentration of the amorphous iron-manganese-oxygen cluster dispersion is 0.4-0.5 g / L.

9. The application of the amorphous iron-manganese-oxygen cluster-enhanced functional enzyme for methanogenesis according to claim 7 or 8, characterized in that, The activation process begins by adjusting the pH value to 7.3–7.5, followed by activation at 30–40°C until the pH fluctuation of the system is less than 0.1 or the pH value of the system is lower than 3.5, at which point the activation process ends.

10. The application of the amorphous iron-manganese-oxygen cluster-enhanced functional enzyme for methanogenesis according to claim 9, characterized in that, Before anaerobic digestion, the pH value is adjusted to 7.0-7.2 and then anaerobic digestion is started.

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