Oxygen deficiency type double-metal hydroxide accelerant for biogas fermentation, preparation method thereof and fermentation method

Abstract

The invention discloses an oxygen-deficient double-metal hydroxide accelerant for biogas fermentation and a preparation method thereof and a fermentation method, the expression of the oxygen-deficient double-metal hydroxide accelerant for biogas fermentation is Vo-NiFe-LDH, Vo represents oxygen vacancy defect, LDH represents layered double-metal hydroxide, Vo represents oxygen vacancy defect, LDH represents layered double-metal hydroxide, Vo represents oxygen vacancy defect, and Vo represents oxygen vacancy defect. According to the accelerant and the method, the anaerobic digestion process can be optimized, the microbial metabolism efficiency is improved, and the stability of a system is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomass energy and waste resource utilization, and relates to an oxygen-deficient double-metal hydroxide accelerator for biogas fermentation, a preparation method thereof and a fermentation method. BACKGROUND

[0002] The large-scale livestock industry in China provides an important basis for the application of anaerobic digestion technology. According to statistics, the annual output of livestock and poultry manure exceeds 3 billion tons. If not properly treated, it can easily cause water eutrophication, soil pollution and greenhouse gas emissions. At the same time, the high load of organic matter in urban sewage and industrial organic wastewater also poses a huge pressure on the environment.

[0003] In addition to organic waste in the agricultural and industrial fields, the problem of kitchen waste brought about by rapid urbanization is also increasingly prominent. The annual output of kitchen waste in China has exceeded 120 million tons, and fruit and vegetable processing waste has also increased year by year. If such organic waste is directly landfilled or incinerated, not only resources will be wasted, but also pollutants such as leachate and dioxin will be produced. The Ministry of Housing and Urban-Rural Development emphasizes the promotion of anaerobic digestion technology for organic waste to reduce environmental pollution and recover biological energy. However, the rich lignocellulose and other refractory components in fruit and vegetable processing waste, as well as the characteristics of seasonal output fluctuations, pose special challenges to the stable operation of anaerobic digestion systems.

[0004] Although anaerobic digestion has significant advantages in organic waste treatment, it still faces many problems in practical application: (1) Low gas production, affected by factors such as substrate composition and C / N ratio, biogas production is unstable; (2) Low methane content, some systems have methane content less than 40% due to acidification or insufficient microbial activity; (3) Low degradation efficiency, lignocellulose and other refractory organic matter decompose slowly; (4) Unstable system operation, easily affected by temperature, pH, ammonia inhibition and toxic substances. Therefore, optimizing anaerobic digestion process, improving microbial metabolic efficiency and enhancing system stability have become the focus of current research. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provides an oxygen-deficient double-metal hydroxide accelerator for biogas fermentation, a preparation method thereof and a fermentation method. The accelerator and method can optimize the anaerobic digestion process, improve the microbial metabolic efficiency and enhance the stability of the system.

[0006] To achieve the above-mentioned purpose, the present application discloses an oxygen-deficient double-metal hydroxide accelerator for biogas fermentation, and the expression of the oxygen-deficient double-metal hydroxide accelerator for biogas fermentation is Vo-NiFe-LDH, wherein Vo represents oxygen vacancy defects, and LDH represents layered double-metal hydroxide.

[0007] The application discloses a preparation method of an oxygen-defect type bimetallic hydroxide accelerator for biogas fermentation.

[0008] 1) Dissolve nickel nitrate hexahydrate, iron sulfate heptahydrate and urea in deionized water to obtain a mixed solution A, and sequentially perform hydrothermal reaction, centrifugation, washing and drying treatment on the mixed solution A to obtain NiFe-LDH.

[0009] 2) Dissolve sodium borohydride in deionized water to obtain a mixed solution B, place the NiFe-LDH in the mixed solution B, and then sequentially perform reaction, suction filtration and drying to obtain the oxygen-defect type bimetallic hydroxide accelerator Vo-NiFe-LDH for biogas fermentation.

[0010] The preparation method of the oxygen-defect type bimetallic hydroxide accelerator for biogas fermentation has further improvement.

[0011] Further, the mass fractions of the nickel nitrate hexahydrate, the iron sulfate heptahydrate, the urea and the sodium borohydride are 30-70 parts, 10-30 parts, 100-280 parts and 10-20 parts respectively.

[0012] Further, the mass ratio of the nickel nitrate hexahydrate, the iron sulfate heptahydrate and the urea is 3:1:12.

[0013] Further, in the step 1), the temperature of the hydrothermal reaction is 120-180 DEG C, the time is 12-24 hours, and the washing is performed by alternately washing 2-3 times with anhydrous ethanol and deionized water.

[0014] Further, in the step 2), the concentration of the sodium borohydride in the mixed solution B is 1M, the reaction time is 30-40 minutes, the drying temperature is 60-90 DEG C, and the drying time is 12-18 hours.

[0015] The application discloses a fermentation method of an oxygen-defect type bimetallic hydroxide accelerator for biogas fermentation.

[0016] The fermentation substrate, the inoculant and the oxygen-defect type bimetallic hydroxide accelerator for biogas fermentation according to claim 1 are mixed, and then fully stirred and placed in a microbial electrolysis cell for fermentation, wherein the fermentation temperature is 30-40 DEG C.

[0017] The fermentation method of the oxygen-defect type bimetallic hydroxide accelerator for biogas fermentation has further improvement.

[0018] Further, the fermentation substrate is a mixture of livestock and poultry manure and agricultural and forestry waste or kitchen waste.

[0019] Furthermore, the mass fractions of livestock and poultry manure, agricultural and forestry waste or kitchen waste, anaerobic sludge and oxygen-deficient bimetallic hydroxide promoters for biogas fermentation are 30-60 parts, 280-560 parts, 90-180 parts and 10-35 parts, respectively.

[0020] Furthermore, the inoculum is anaerobic sludge from an urban wastewater treatment plant.

[0021] The present invention has the following beneficial effects:

[0022] The oxygen-deficient bimetallic hydroxide promoter for biogas fermentation described in this invention, along with its preparation and fermentation methods, utilizes the catalytic properties of nickel-iron trace elements and the unique layered structure of the layered bimetallic hydroxide to promote the enrichment and reproduction of dominant fermentation microorganisms by regulating the oxygen vacancy defect structure in the material. In an anaerobic fermentation coupled with a microbial electrolysis cell system, the introduction of oxygen vacancy defects significantly enhances the electron transfer capacity of the material and optimizes the interaction between microorganisms and the electrode interface. Simultaneously, the synergistic effect of the nickel-iron bimetallic hydroxide activates key enzyme activity, promoting metabolic efficiency at each stage of anaerobic digestion, including hydrolysis, acidification, and methanogenesis. Furthermore, the high specific surface area and adjustable gaps of the layered structure provide abundant active sites for microbial attachment, further enhancing the system's substrate conversion capacity and stability. Ultimately, this achieves a simultaneous increase in biogas production and energy recovery efficiency, solving the technical problems of low electron transfer efficiency and insufficient methane yield in traditional anaerobic digestion (AD) systems. Attached Figure Description

[0023] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 a is a scanning electron microscope image of NiFe-LDH;

[0025] Figure 1 b is a magnified view of the morphology of NiFe-LDH;

[0026] Figure 1 c is the energy dispersive X-ray spectrum of NiFe-LDH;

[0027] Figure 1 d is the energy dispersive X-ray spectrum of element O in NiFe-LDH;

[0028] Figure 1 e is the energy dispersive X-ray spectrum of element Ni in NiFe-LDH;

[0029] Figure 1f is the energy dispersive X-ray spectrum of element Fe in NiFe-LDH;

[0030] Figure 2 a shows the XRD patterns of nickel-iron layered bimetallic hydroxide (NiFe-LDH) and oxygen-vacancy nickel-iron layered bimetallic hydroxide (Vo-NiFe-LDH);

[0031] Figure 2 b is the EPR diagram of Vo-NiFe-LDH;

[0032] Figure 2 c shows the XPS images of NiFe-LDH and Vo-NiFe-LDH;

[0033] Figure 2 d is the energy dispersive X-ray spectrum of element O in Vo-NiFe-LDH;

[0034] Figure 2 e is the energy dispersive X-ray spectrum of element Ni in Vo-NiFe-LDH;

[0035] Figure 2 f is the energy dispersive X-ray spectrum of element Fe in Vo-NiFe-LDH;

[0036] Figure 3 A comparison chart of the cumulative gas production of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0037] Figure 4 The pH comparison chart shows the system stability of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, Example 4, and Example 5. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0040] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0042] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0043] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0046] The formula for the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation described in this invention is Vo-NiFe-LDH, where Vo represents oxygen vacancy defect and LDH represents layered bimetallic hydroxide, that is, nickel-iron layered bimetallic hydroxide with oxygen vacancy defect.

[0047] The oxygen-deficient bimetallic hydroxide promoter for biogas fermentation is prepared using nickel nitrate hexahydrate, ferric sulfate heptahydrate, urea, and sodium borohydride, wherein the mass fractions of nickel nitrate hexahydrate, ferric sulfate heptahydrate, urea, and sodium borohydride are 30-70 parts, 10-30 parts, 100-280 parts, and 10-20 parts, respectively.

[0048] The morphology of the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation is a flower-like structure composed of clusters of sheet-like nanosheets with a diameter of 300 nm.

[0049] The preparation method of the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation according to the present invention includes the following steps:

[0050] 1) Dissolve nickel nitrate hexahydrate, ferric sulfate heptahydrate and urea in deionized water to obtain mixed solution A. Perform hydrothermal reaction, centrifugation, washing and drying on mixed solution A in sequence to obtain NiFe-LDH.

[0051] 2) Dissolve sodium borohydride in deionized water to obtain mixed solution B. Place NiFe-LDH in mixed solution B, and then proceed with reaction, filtration and drying to obtain Vo-NiFe-LDH, an oxygen-deficient bimetallic hydroxide promoter for biogas fermentation.

[0052] In step 1), the mass ratio of nickel nitrate hexahydrate, ferric sulfate heptahydrate, and urea is 3:1:12. The hydrothermal reaction temperature is 120℃-180℃, and the time is 12-24 hours. During washing, the product is washed 2-3 times alternately with anhydrous ethanol and deionized water.

[0053] In step 2), the concentration of sodium borohydride in mixed solution B is 1M, the reaction time is 30-40 minutes, the drying temperature is 60℃-90℃, and the drying time is 12-18 hours.

[0054] The method for biogas fermentation using an oxygen-deficient bimetallic hydroxide promoter according to the present invention includes the following steps:

[0055] The fermentation substrate, inoculum, and oxygen-deficient bimetallic hydroxide promoter for biogas fermentation are mixed, stirred thoroughly, and then placed in a microbial electrolysis tank for fermentation at a temperature of 30℃-40℃.

[0056] The fermentation substrate is a mixture of livestock and poultry manure and agricultural and forestry waste or kitchen waste;

[0057] The inoculum is anaerobic sludge;

[0058] The mass fractions of livestock and poultry manure, agricultural and forestry waste or kitchen waste, anaerobic sludge and oxygen-deficient bimetallic hydroxide promoter for biogas fermentation are 30-60 parts, 280-560 parts, 90-180 parts and 10-35 parts, respectively.

[0059] The livestock and poultry manure is cow manure, pig manure, or chicken manure.

[0060] The inoculum is anaerobic sludge from an urban wastewater treatment plant.

[0061] The cathode / anode materials of the microbial electrolysis cell are carbon rods with a diameter of 10 mm.

[0062] Example 1

[0063] 1) Prepare nickel-iron layered bimetallic powder with oxygen-rich vacancy defects.

[0064] 30 parts nickel nitrate hexahydrate, 10 parts ferric sulfate heptahydrate, 120 parts urea, and 10 parts sodium borohydride.

[0065] 2) The anaerobic fermentation coupled microbial electrolysis cell system was started using a vacancy-rich bimetallic additive.

[0066] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 90 parts by weight of anaerobic sludge was used as the inoculum, and 10 parts by weight of vacancy-rich nickel-iron bimetallic hydroxide promoter were added. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 402.2 mL / g VS, the methane production was 245.3 mL / g VS, and the methane content was 61%.

[0067] Example 2

[0068] 1) Prepare nickel-iron layered bimetallic powder with oxygen-rich vacancy defects.

[0069] 40 parts nickel nitrate hexahydrate, 13 parts ferric sulfate heptahydrate, 156 parts urea, and 15 parts sodium borohydride.

[0070] 2) The anaerobic fermentation coupled microbial electrolysis cell system was started using a vacancy-rich bimetallic additive.

[0071] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 90 parts by weight of anaerobic sludge was used as the inoculum, and 25 parts by weight of vacancy-rich nickel-iron bimetallic hydroxide promoter were added. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 413.2 mL / g VS, the methane production was 264.4 mL / g VS, and the methane content was 64%.

[0072] Example 3

[0073] 1) Prepare nickel-iron layered bimetallic powder with oxygen-rich vacancy defects.

[0074] 50 parts nickel nitrate hexahydrate, 17 parts ferric sulfate heptahydrate, 204 parts urea, and 20 parts sodium borohydride.

[0075] 2) The anaerobic fermentation coupled microbial electrolysis cell system was started using a vacancy-rich bimetallic additive.

[0076] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 90 parts by weight of anaerobic sludge was used as the inoculum, and 30 parts by weight of vacancy-rich nickel-iron bimetallic hydroxide promoter were added. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 449.0 mL / g VS, the methane production was 300.8 mL / g VS, and the methane content was 67%.

[0077] Example 4

[0078] 1) Prepare nickel-iron layered bimetallic powder with oxygen-rich vacancy defects.

[0079] 60 parts nickel nitrate hexahydrate, 20 parts ferric sulfate heptahydrate, 240 parts urea, and 20 parts sodium borohydride.

[0080] 2) The anaerobic fermentation coupled microbial electrolysis cell system was started using a vacancy-rich bimetallic additive.

[0081] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 90 parts by weight of anaerobic sludge was used as the inoculum, and 35 parts by weight of vacancy-rich nickel-iron bimetallic hydroxide promoter were added. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 425.8 mL / g VS, the methane production was 259.7 mL / g VS, and the methane content was 61%.

[0082] Example 5

[0083] 1) Prepare nickel-iron layered bimetallic powder with oxygen-rich vacancy defects.

[0084] 70 parts nickel nitrate hexahydrate, 23 parts ferric sulfate heptahydrate, 280 parts urea, and 20 parts sodium borohydride.

[0085] 2) The anaerobic fermentation coupled microbial electrolysis cell system was started using a vacancy-rich bimetallic additive.

[0086] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 90 parts by weight of anaerobic sludge was used as the inoculum, and 35 parts by weight of vacancy-rich nickel-iron bimetallic hydroxide promoter were added. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 36℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 423.6 mL / g VS, the methane production was 249.9 mL / g VS, and the methane content was 59%.

[0087] Comparative Example 1

[0088] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate, and 90 parts by weight of anaerobic sludge was used as the inoculum. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The cumulative biogas production was 341.1 mL / g VS, the methane production was 143.3 mL / g VS, and the methane content was 42%.

[0089] Comparative Example 2

[0090] A mixture of 30 parts by weight of livestock and poultry manure and 280 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate, and 90 parts by weight of anaerobic sludge was used as the inoculum. The fermentation slurry was thoroughly stirred, and the anaerobic fermentation temperature was controlled at 37℃. The digester was connected to a 0.6V DC power supply for fermentation. The cumulative biogas production was 364.4 mL / g VS, the methane production was 200.4 mL / g VS, and the methane content was 55%.

[0091] The comparison of the test results of the examples and the comparative examples is shown in Table 1.

[0092] Table 1

[0093]

[0094] Based on the data in Table 1, this invention uses Vo-NiFe-LDH as a promoter, which demonstrates a significant performance improvement effect in an anaerobic fermentation coupled with a microbial electrolysis cell system. The following is a detailed analysis and explanation of its advantages:

[0095] 1. Significantly increases biogas and methane production

[0096] Cumulative gas production: After adding Vo-NiFe-LDH, the cumulative gas production of the system reached 449.0 mL / gVS (Example 3), which is 31.6% higher than Comparative Example 1 (341.1 mL / gVS) and significantly higher than other examples and comparative examples, indicating that it can effectively promote the decomposition of organic matter and gas conversion.

[0097] Methane production and content: The methane production reached 300.8 mL / g VS (Example 3), and the methane content increased to 67%, which is much higher than that of Comparative Example 1 (42%), demonstrating that Vo-NiFe-LDH can directionally optimize the activity of methanogenic bacteria and enhance methane selectivity.

[0098] 2. Highly efficient degradation of organic matter and removal of COD

[0099] COD removal rate: The COD removal rate of Example 3 was 59.98%, which was 56.2% higher than that of Comparative Example 1 (38.41%). This indicates that Vo-NiFe-LDH can accelerate the decomposition of macromolecular organic matter and enhance electron transfer efficiency, thereby improving the overall degradation capacity of the system.

[0100] To comprehensively evaluate the operational efficiency of anaerobic fermentation systems, pH monitoring is a key indicator. pH not only directly affects the metabolic activity and community structure of microorganisms but is also closely related to the acidification risk and long-term stability of the system. Therefore, by analyzing the dynamic changes of pH in different embodiments, its regulatory role in the fermentation environment can be revealed. The following section provides a detailed analysis of pH data to explore its performance and mechanism in maintaining system stability. Table 2 shows the pH changes over time in the fermentation systems of the present invention embodiments and comparative examples.

[0101] Table 2

[0102] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Day 1 7.05 6.80 7.63 7.31 6.91 7.05 6.80 Day 5 5.51 5.50 5.42 5.37 5.42 5.51 5.50 Day 10 6.15 6.04 6.46 6.59 6.75 6.15 6.04 Day 15 6.43 6.73 7.02 6.86 6.87 6.43 6.73 Day 20 6.75 7.27 7.18 7.47 7.60 6.75 7.27 Day 25 7.26 7.74 7.74 7.65 7.79 7.26 7.74 Day 30 7.80 7.76 7.88 7.78 7.86 7.80 7.76 Day 35 7.89 8.03 7.92 7.88 7.91 7.89 8.03

[0103] The results showed that the pH values ​​of all experimental groups exhibited a typical trend of first decreasing and then increasing. pH monitoring of the anaerobic fermentation system in Example 3 showed that the initial pH value was 6.91 (day 1), which then decreased to 5.42 (day 5) after acidification, but began to steadily recover from day 10, eventually reaching 7.91 (day 35). This process indicates that Example 3 can quickly recover to the pH range suitable for methanogen growth after a short period of acidification. Particularly noteworthy is that during the critical recovery period of days 15-25, the pH value rapidly increased from 6.87 to 7.79, demonstrating a significantly higher recovery efficiency than other examples. Compared with other implementation cases during the same period, Example 3 demonstrated outstanding performance in system stability and recovery speed, effectively mitigating the impact of acidification on the system and maintaining the high metabolic activity of the methanogen community in the later stages, ensuring the long-term stable operation of the anaerobic fermentation system.

[0104] The present invention has the following specific features:

[0105] The construction of oxygen vacancy defects significantly improves the electron exchange capacity of nickel-iron layered bimetallic hydroxides, promotes the enrichment and metabolism of electrochemically active microorganisms, and thus enhances the electron transfer efficiency of the anaerobic fermentation coupled microbial electrolysis cell system.

[0106] By fully utilizing the petal-like structure of nickel-iron layered bimetallic hydroxide, its high specific surface area and abundant active sites provide an ideal attachment interface for microorganisms. At the same time, the synergistic effect of nickel-iron trace elements optimizes the nutrient supply for microorganisms, further enhancing the biocatalytic performance of the system.

[0107] The material exhibits excellent stability and catalytic activity in the system, which not only significantly improves the biogas production rate and methane content, but also enhances the system's resistance to load shocks, making the anaerobic fermentation process more efficient and controllable.

[0108] This invention provides an efficient and low-cost promoter solution for anaerobic fermentation coupled with microbial electrolysis cell technology. The process is simple and easy to scale up, opening up a new technical path for the efficient conversion and resource utilization of biomass energy.

[0109] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0110] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0111] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An oxygen-deficient bimetallic hydroxide promoter for biogas fermentation, characterized in that, The formula for the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation is Vo-NiFe-LDH, where Vo represents oxygen vacancy defect and LDH represents layered bimetallic hydroxide.

2. A method for preparing the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation as described in claim 1, characterized in that, Includes the following steps: 1) Dissolve nickel nitrate hexahydrate, ferric sulfate heptahydrate and urea in deionized water to obtain mixed solution A. Perform hydrothermal reaction, centrifugation, washing and drying on mixed solution A in sequence to obtain NiFe-LDH; 2) Dissolve sodium borohydride in deionized water to obtain mixed solution B. Place NiFe-LDH in mixed solution B, and then proceed with reaction, filtration and drying to obtain Vo-NiFe-LDH, an oxygen-deficient bimetallic hydroxide promoter for biogas fermentation.

3. The preparation method of the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation according to claim 2, characterized in that, The mass fractions of nickel nitrate hexahydrate, ferric sulfate heptahydrate, urea, and sodium borohydride are 30-70 parts, 10-30 parts, 100-280 parts, and 10-20 parts, respectively.

4. The preparation method of the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation according to claim 2, characterized in that, The mass ratio of nickel nitrate hexahydrate, ferric sulfate heptahydrate, and urea is 3:1:

12.

5. The method for preparing the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation according to claim 2, characterized in that, In step 1), the hydrothermal reaction temperature is 120℃-180℃ and the time is 12-24 hours. During washing, the water is washed 2-3 times alternately with anhydrous ethanol and deionized water.

6. The method for preparing the oxygen-deficient bimetallic hydroxide promoter for biogas fermentation according to claim 2, characterized in that, In step 2), the concentration of sodium borohydride in mixed solution B is 1M, the reaction time is 30-40 minutes, the drying temperature is 60℃-90℃, and the drying time is 12-18 hours.

7. A method for biogas fermentation using an oxygen-deficient bimetallic hydroxide promoter, characterized in that, Includes the following steps: The fermentation substrate, inoculum, and oxygen-deficient bimetallic hydroxide promoter for biogas fermentation as described in claim 1 are mixed, stirred thoroughly, and then placed in a microbial electrolysis tank for fermentation, wherein the fermentation temperature is 30℃-40℃.

8. The method for fermentation using the oxygen-deficient bimetallic hydroxide promoter according to claim 7, characterized in that, The fermentation substrate is a mixture of livestock and poultry manure and agricultural and forestry waste or kitchen waste.

9. The method for fermentation using the oxygen-deficient bimetallic hydroxide promoter according to claim 7, characterized in that, The mass fractions of livestock and poultry manure, agricultural and forestry waste or kitchen waste, anaerobic sludge and oxygen-deficient bimetallic hydroxide promoters for biogas fermentation are 30-60 parts, 280-560 parts, 90-180 parts and 10-35 parts, respectively.

10. The method for fermentation using the oxygen-deficient bimetallic hydroxide promoter according to claim 7, characterized in that, The inoculum is anaerobic sludge from an urban wastewater treatment plant.

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