Preparation of polyaniline magnetic biochar based on biogas residue and application thereof in promoting enrichment of anaerobic co-digestion synergistic functional bacteria and methanogenic archaea in an anaerobic co-digestion system

Abstract

The present application belongs to the technical field of kitchen waste resource, and particularly relates to a kind of polyaniline magnetic biochar prepared based on biogas residue and its application in promoting anaerobic co-digestion system anaerobic co-digestion synergistic function bacteria and methanogenic archaea enrichment. The present application optimizes the microbial community structure of the dry anaerobic digestion system of kitchen waste by adding an appropriate amount of phosphate activated magnetic Enteromorpha hydrothermal carbon to enhance microbial activity, enrich functional microorganisms such as Clostridium and Methanocella, effectively promote the dry anaerobic digestion process of kitchen waste, and increase the amount of biogas production. It has great significance for realizing kitchen waste reduction, harmless and resource.

Description

Technical Field

[0001] This invention belongs to the field of anaerobic digestion technology, specifically relating to a polyaniline magnetic biochar prepared from biogas residue and its application in promoting the enrichment of anaerobic co-digestion synergistic bacteria and methanogenic archaea in anaerobic co-digestion systems. Background Technology

[0002] Anaerobic co-digestion of food waste and sewage sludge (KWAS-CoAD) is an important pathway for the resource utilization of organic solid waste, but it generally suffers from bottlenecks such as low substrate mass transfer efficiency and unstable methanogenesis. In anaerobic co-digestion systems, the presence and activity of specific microbial populations are crucial to the success of the entire fermentation process. Anaerobic co-digestion is a complex, multi-step biochemical process, including hydrolysis, acidification, acetogenesis, and methanogenesis, each stage relying on the participation of specific microorganisms. Among these, anaerobic co-digestion synergistic microorganisms (KWAS-CoAD) play a vital role. Massilibacterium Methanogenic archaea play an important role in the decomposition of organic matter and electron transfer. Methanosarcina Microorganisms are key microorganisms in the methanogenesis stage, and their abundance and activity directly affect the methane production and system stability.

[0003] Current research has revealed that the intermediate electron transfer mechanism mediated by conductive materials provides a new approach to enhancing anaerobic digestion. However, traditional biochar materials suffer from insufficient surface active sites and limited electron transfer efficiency, making it difficult to effectively promote the enrichment and functionalization of target microorganisms. Therefore, developing a biochar capable of efficiently enriching anaerobic co-digestion synergistic bacteria and methanogenic archaea is of great significance for improving the efficiency of anaerobic co-digestion of food waste and sewage sludge. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a polyaniline magnetic biochar prepared from biogas residue and its application in promoting the enrichment of anaerobic co-digestion synergistic bacteria and methanogenic archaea in anaerobic co-digestion systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a polyaniline magnetic biochar prepared from biogas residue, the preparation of which includes the following steps:

[0007] S1. Modify biochar with ferrate solution to obtain magnetic biochar MDPC;

[0008] S2. Measure the magnetic biochar, add aniline solution and hydrochloric acid solution and stir;

[0009] S3. Add ammonium persulfate and hydrochloric acid to the solution obtained in step S2, disperse by ultrasonication, stir in an ice bath, and wash and dry the solid product to obtain the polyaniline magnetic biochar.

[0010] The biochar is obtained by gradient pyrolysis of biogas residue.

[0011] In some embodiments of the present invention, step S1 specifically includes: obtaining biochar by gradient pyrolysis of sludge under a protective atmosphere, and modifying the biochar in a ferrate solution to obtain magnetic biochar MDPC.

[0012] In some embodiments of the present invention, step S1 specifically includes: under a protective atmosphere, gradient pyrolysis of biogas residue; after pyrolysis, washing, drying, and sieving through a 140-150 mesh sieve to obtain biochar; and modifying the biochar in a ferrate solution to obtain magnetic biochar MDPC.

[0013] In some embodiments of the present invention, after mixing biochar with ferrate solution, 10 mol / L NaOH is added dropwise to adjust the pH to 9-11, and the mixture is stirred continuously for 1 h and then boiled for 1 h to obtain magnetic biochar MDPC.

[0014] In this invention, the pH value after mixing biochar and ferrate solution can be 9, 10 or 11, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0015] In some embodiments of the present invention, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0016] In some embodiments of the present invention, the gradient pyrolysis is performed at a temperature of 550~600 ℃ for 2~3 h, with a heating rate of 3~5 ℃ / min.

[0017] In this invention, the gradient pyrolysis temperature can be 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, etc., the gradient pyrolysis time can be 2h, 2.5h or 3h, etc., and the heating rate can be 3℃ / min, 4℃ / min or 5℃ / min, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0018] In some embodiments of the present invention, after pyrolysis, the biochar is washed, dried, and sieved to collect particles smaller than 150 mesh before undergoing subsequent modification reactions.

[0019] In some embodiments of the present invention, the washing is performed using ethanol and water.

[0020] In some embodiments of the present invention, the drying temperature is 100~105 ℃ and the drying time is 10~12 h.

[0021] In this invention, the drying temperature can be 100℃, 101℃, 102℃, 103℃, 104℃, or 105℃, etc., and the drying time can be 10h, 11h, or 12h, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0022] In some embodiments of the present invention, the drying is vacuum drying.

[0023] In some embodiments of the present invention, the ferrate solution is a mixed solution of FeCl3·6H2O and FeSO4·7H2O.

[0024] In some embodiments of the present invention, the FeCl3·6H2O and FeSO4·7H2O mixed solution contains Fe 3+ and Fe 2+ The molar ratio is 1.85:1.

[0025] In some embodiments of the present invention, in step S2, the mass-to-volume ratio of magnetic biochar, aniline solution and hydrochloric acid solution is (1~10):(5~10):(90~110), g:mL:mL.

[0026] In some embodiments of the present invention, the mass-to-volume ratio of magnetic biochar, aniline solution and hydrochloric acid solution is 5:8:100, g:mL:mL.

[0027] In some embodiments of the present invention, step S3 specifically includes: adding ammonium persulfate and hydrochloric acid to the solution obtained in step S2, dispersing by ultrasonication, stirring in an ice bath, washing the solid product with deionized water and methanol until the washing liquid is neutral, and drying to obtain the polyaniline magnetic biochar.

[0028] In some embodiments of the present invention, step S3 specifically includes: adding ammonium persulfate and hydrochloric acid to the solution obtained in step S2, ultrasonically dispersing the mixture, stirring it in an ice bath at 780-800 r / min for 3-4 h at 2-6°C, washing the solid product with deionized water and methanol until the washing liquid is neutral, drying it at 60-80°C for 20-25 h, grinding it after drying and passing it through a 150-mesh sieve to obtain the polyaniline magnetic biochar.

[0029] The ice bath temperature can be 2℃, 3℃, 4℃, 5℃, or 6℃, etc.; the stirring speed can be 780 r / min, 782 r / min, 784 r / min, 786 r / min, 788 r / min, 790 r / min, 792 r / min, 794 r / min, 796 r / min, 798 r / min, or 800 r / min, etc.; the stirring time can be 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h, or 4 h, etc.; the drying temperature can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 78℃, 79℃, or 80℃, etc.; and the drying time can be 20... h, 21 h, 22 h, 23 h, 24 h or 25 h, etc., but not limited to the values ​​listed above. Other unlisted values ​​within the above range also apply.

[0030] A second aspect of the present invention provides a method for promoting the enrichment of anaerobic co-digestion synergistic bacteria and methanogenic archaea in an anaerobic co-digestion system for kitchen waste and waste sludge, comprising adding the above-mentioned polyaniline magnetic biochar to the anaerobic co-digestion system, wherein the concentration of the polyaniline magnetic biochar in the anaerobic co-digestion system, calculated as TS, is 25-50 mg / g.

[0031] In some embodiments of the present invention, the volume ratio of food waste to inoculated sludge (TS) is 2 to 4:1.

[0032] In some embodiments of the present invention, the solids content in the anaerobic digestion system is 3% to 5%.

[0033] In some embodiments of the present invention, the pH of the digestible substrate in the anaerobic digestion system is 6.0 to 8.0.

[0034] In some embodiments of the present invention, the reaction temperature in the anaerobic digestion system is 25°C to 35°C.

[0035] In some embodiments of the present invention, the reaction cycle within the anaerobic digestion system is 30 days.

[0036] The dosage concentration of polyaniline magnetic biochar can be 25 mg / g, 26 mg / g, 27 mg / g, 28 mg / g, 29 mg / g, 30 mg / g, 31 mg / g, 32 mg / g, 33 mg / g, 34 mg / g, 35 mg / g, 36 mg / g, 37 mg / g, 38 mg / g, 39 mg / g, 40 mg / g, 41 mg / g, 42 mg / g, 43 mg / g, 44 mg / g, 45 mg / g, 46 mg / g, 47 mg / g, 48 mg / g, etc. The volume ratio of food waste to inoculated sludge (TS) can be 2:1, 3:1, or 4:1, etc. The solids content in the anaerobic digestion system can be 3%, 4%, or 5%, etc. The pH in the anaerobic digestion system can be 6, 7, or 8, etc. The reaction temperature in the anaerobic digestion system can be 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, or 35℃, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0037] A third aspect of the present invention provides the application of the above-described polyaniline magnetic biochar or the above-described method in the production of methane.

[0038] In some embodiments of the present invention, the application is to add 25 mg / g to 50 mg / g (as TS) of polyaniline magnetic biochar to an anaerobic co-digestion system.

[0039] The beneficial effects of this invention are as follows:

[0040] This invention effectively promotes synergistic effects of anaerobic co-digestion by adding specific polyaniline / ferric oxide bifunctional modified biochar (PANI@MDPC) from biogas residue into an anaerobic co-digestion system. Massilibacterium ) and methanogenic archaea ( MethanosarcinaThe biochar prepared from biogas residue resources in this invention has a high specific surface area, porous structure, and good electrical conductivity. The introduction of polyaniline significantly improves the conductivity of the biochar and introduces abundant amino / imine functional groups. This invention uses FeCl3·6H2O + FeSO4·7H2O modification to generate a ferromagnetic material mainly composed of Fe3O4, with a saturation magnetization of 30-50 emu / g. It can be rapidly separated under an external magnetic field. Fe3O4 nanoparticles are loaded onto the surface of the biochar through electrostatic adsorption or chemical bonding, forming a rough porous structure. The loading of iron(III) oxide nanoparticles enhances the magnetic response characteristics of the material. These characteristics enable the modified biochar to provide a suitable growth environment for target microorganisms, promote interspecies electron transfer, improve the metabolic activity and synergistic effect of microorganisms, thereby optimizing the anaerobic co-digestion process and increasing methane production. The polyaniline magnetic biochar provided by this invention can significantly improve the methane production performance of anaerobic co-digestion systems, which is of great significance for realizing the efficient energy conversion of organic solid waste. Attached Figure Description

[0041] Figure 1 The images shown are SEM and XPS images of the polyaniline / ferric oxide bifunctional modified biochar (PANI@MDPC) prepared in the embodiments of the present invention, wherein (a) is the SEM image of the unmodified biochar, (b) is the SEM image of PANI@MDPC, (c) is the XPS image of the unmodified biochar, and (d) is the XPS image of PANI@MDPC.

[0042] Figure 2 The images show the FTIR spectra of unmodified biochar (DPC), magnetic biochar (MDPC), and polyaniline magnetic biochar (PANI@MDPC) prepared in the embodiments of the present invention.

[0043] Figure 3 This is a graph showing the methane production curves for different treatment groups in this embodiment of the invention.

[0044] Figure 4 This is a diagram showing the microbial biodiversity index of different treatment groups in this embodiment of the invention;

[0045] Figure 5 This is a diagram showing the microbial richness of different treatment groups at the phylum level in this embodiment of the invention;

[0046] Figure 6 This is a diagram showing the microbial richness of different treatment groups at the bacterial genus level in the embodiments of the present invention;

[0047] Figure 7 This is a diagram showing the microbial richness of different treatment groups at the Archaea level in the embodiments of the present invention. Detailed Implementation

[0048] To further illustrate the present invention, the preparation and application effects of PANI@MDPC are described in detail, enabling those skilled in the art to more clearly understand the technical solution of the present invention. The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0049] Example 1

[0050] The preparation processes of unmodified biochar (DPC), magnetic biochar (MDPC), and polyaniline magnetic biochar (PANI@MDPC) are described below. 200 g of biogas residue from the anaerobic digestion project of kitchen waste at Qingdao Shifang Bioenergy Co., Ltd. was placed in a 105 ℃ hot air drying oven for 24 h to dehydrate to constant weight (moisture content <5%). After manual sorting to remove inert impurities such as gravel, the residue was ground into powder using a planetary ball mill, passed through a 150-mesh sieve (sieve aperture size 0.106 mm), and sealed and protected from light in a desiccator for later use.

[0051] Preparation of DPC by gradient pyrolysis: 20 g of pretreated biogas residue was loaded into a quartz tube and placed in a temperature-controlled tube furnace. High-purity nitrogen was introduced at a flow rate of 0.1 L / min for 20 min to purge the air. Then, the temperature was increased to 600℃ at a rate of 5℃ / min and maintained at this temperature for 2 h. Nitrogen was continuously introduced throughout the process to create an anaerobic environment. After the tube furnace cooled naturally to room temperature, the pyrolysis product was removed and washed alternately with ethanol and deionized water 5–10 times. After filtration, the product was dried in a 105℃ drying oven for 12 h and ground through a 150-mesh sieve to obtain DPC.

[0052] Preparation of MDPC by coprecipitation: 5 g of DPC was accurately weighed using an electronic analytical balance and dissolved in 200 mL of deionized water. The solution was stirred with a magnetic stirrer at 800 r / min for 5 min until uniformly dispersed. Separately, 20.0 g of FeCl3•6H2O and 11.1 g of FeSO4•7H2O were weighed and dissolved in 600 mL of deionized water. The two solutions were mixed and stirred continuously at 800 r / min for 20 min. 10 mol / L NaOH solution was added dropwise to adjust the pH to 10. The mixture was stirred with a magnetic stirrer for 1 h, then heated to 100 ℃ and boiled for 1 h. The mixture was then allowed to cool naturally to room temperature. The residue was filtered using a Buchner funnel. The residue was washed alternately with deionized water and ethanol 5–10 times, dried in a drying oven at 70 ℃ for 24 h, and then ground through a 150-mesh sieve to obtain MDPC.

[0053] In-situ polymerization preparation of PANI@MDPC: 8 mL of aniline (purity ≥99.5%) and 2 g of MDPC were dissolved in 100 mL of 1 mol / L HCl solution and magnetically stirred for 5 min until uniformly dispersed. Separately, 2.5 g of ammonium persulfate (APS) was dissolved in 100 mL of 1 mol / L HCl solution and slowly added dropwise to the above mixed solution (dropping rate <3 drops / second). The mixture was ultrasonically dispersed for 1 h. The ultrasonically dispersed solution was continuously reacted in a magnetically stirred water bath at 5℃ and 800 r / min for 4 h to achieve in-situ polymerization. After complete reaction, the dark green solid product was washed alternately with deionized water and methanol 5–10 times, dried in a vacuum oven at 70℃ for 24 h, ground, and passed through a 150-mesh sieve to obtain the carbon material PANI@MDPC of this embodiment.

[0054] Figure 1 and Figure 2 These are SEM, XPS, and FTIR plots of DPC, MDPC, and PANI@MDPC, obtained through... Figure 1 (c) (d) and Figure 2 It can be known that Fe 2+ / Fe 3+ The successful loading of PANI onto biochar demonstrates the success of the modification. As shown in Table 1, the PANI@MDPC material prepared in this example has a specific surface area of ​​30.341 m². 2 / g, micropore volume 2.596 m³ 2 / g, total pore volume 0.168 cm³ 3 / g, average pore size 24.014 nm.

[0055]

[0056] Example 2

[0057] The reactor setup consists of five 500 mL borosilicate glass reactors (400 mL working volume), equipped with PTFE-sealed gas sampling valves and 1.0 L aluminum-plastic gas bags, connected to a constant-temperature shaking incubator. Reactor operating parameters can include: dosage (25 mg / g~50 mg / g), temperature (25~35℃), pH (6.0-8.0), solids content (3%~5%), and total sludge volume (TS = 2~4:1).

[0058] After adding biochar to each reactor group, an anaerobic environment (ORP < -300 mV) was created by purging the headspace with high-purity nitrogen at 0.5 L / min for 60 s. The reactors were then sealed with butyl rubber stoppers and incubated on a constant-temperature shaker (150 r / min) for 30 days. The CH4 / CO2 / H2 gas composition was monitored daily using gas chromatography (Agilent 7890B). Every 48 h, 5 mL of the mixture was collected, centrifuged (8000×g, 10 min), and parameters such as VFAs and SCOD were analyzed. When the cumulative methane production showed no significant increase, 50 mL of digested samples were collected from each reactor on day 30, frozen, and sent to Shanghai Meiji Biopharmaceutical Technology Co., Ltd. Metagenomic sequencing was performed using the Illumina NovaSeq platform to analyze the microbial community structure and functional gene expression.

[0059] Example 3

[0060] The reactor was set with the following parameters: dosage 50 mg / g PANI@MDPC, TS = 2:1, initial pH = 8.0, and temperature 35°C; solids content was set at 3%, 4%, and 5%. The reactor was operated as described in Example 2.

[0061] When the solids content is 3%, the cumulative methane yield is 95.3 mL / g TS. Massilibacterium The abundance was 22.6%. Methanosarcina Abundance was 55.2%; solids content was 4%; cumulative methane yield was 108.7 mL / g TS. Massilibacterium The abundance was 24.9%. Methanosarcina Abundance was 57.5%; solids content was 5%; cumulative methane yield was 102.6 mL / g TS. Massilibacterium The abundance was 21.1%. Methanosarcina The abundance was 52.7%. The optimal solids content was determined to be 4%.

[0062] Example 4

[0063] The reactor was set with the following parameters: dosage 50 mg / g PANI@MDPC, solids content 4%, TS = 2:1, and temperature 35°C; initial pH settings were 6.0, 7.0, and 8.0. The reactor was operated as described in Example 2.

[0064] At pH=6.0, the cumulative methane yield was 98.9 mL / g TS. Massilibacterium The abundance was 20.8%. Methanosarcina Abundance was 53.3%; pH=7.0; cumulative methane production was 112.5 mL / g TS. Massilibacterium The abundance was 26.3%. Methanosarcina Abundance was 59.8%; pH=8.0; cumulative methane production was 100.7 mL / g TS. MassilibacteriumThe abundance was 23.7%. Methanosarcina The abundance was 54.9%. The optimal pH was determined to be 7.0.

[0065] Example 5

[0066] The reactor was set with the following parameters: dosage 50 mg / g PANI@MDPC, solids content 4%, initial pH 7.0, and TS 2:1; temperatures were set at 25°C, 30°C, and 35°C. The reactor was operated as described in Example 2.

[0067] At a temperature of 25℃, the cumulative methane production was 92.4 mL / g TS. Massilibacterium The abundance was 19.5%. Methanosarcina Abundance was 51.1%; temperature 30℃: cumulative methane production was 118.4 mL / g TS. Massilibacterium The abundance was 28.1%. Methanosarcina The abundance was 61.3%; at a temperature of 35℃, the cumulative methane yield was 105.6 mL / g TS. Massilibacterium The abundance was 25.5%. Methanosarcina The abundance was 56.8%. The optimal temperature was determined to be 30℃.

[0068] Example 6

[0069] The reactor was set with the following parameters: dosage 50 mg / g PANI@MDPC, solids content 4%, initial pH 7.0, and temperature 30°C; the TS ratio was set to 2:1, 3:1, and 4:1. The reactor was operated as described in Example 2.

[0070] When TS = 2:1, the cumulative methane yield is 112.56 mL / g TS. Massilibacterium The abundance was 25.2%. ​ The abundance was 58.1%; TS = 3:1, and the cumulative methane yield was 120.2 mL / g TS. ​ The abundance was 28.4%. ​ The abundance was 59.2%; TS = 4:1, and the cumulative methane yield was 123.56 mL / g TS. ​ The abundance was 30.8%. ​ The abundance was 64.0%. The optimal TS ratio was determined to be 4:1.

[0071] Example 7

[0072] Based on Examples 3-6, optimal parameters (4% solids content, pH=7.0, temperature 30℃, TS=4:1) were optimized, and five treatment groups were set up: (a) control group (CK, no biochar added), (b) 25 mg / g MDPC group, (c) 25 mg / g PANI@MDPC group, (d) 37.5 mg / g PANI@MDPC group, and (e) 50 mg / g PANI@MDPC group. The reactor was operated as described in Example 2.

[0073] The methane production curves of each reactor obtained in this embodiment are as follows: ​ As shown in Table 2.

[0074]

[0075] As shown in Table 2, the 25 mg / g PANI@MDPC group increased the methanogenesis to 150.63 mg / L TS, a 15.9% increase compared to the control group, thus enhancing the system's methanogenesis capacity.

[0076] Microbial community analysis of the reactor

[0077] ​ The alpha diversity of each bacterial group was shown. ​ and ​ These figures reflect the abundance of microorganisms at the phylum and genus levels, respectively. ​ It describes the changes in the species composition of the archaea community.

[0078] From the perspective of Alpha diversity (e.g.) ​ As shown in the figure, the Chao index of the control group and the 25 mg / g PANI@MDPC group were 3605 and 3703, respectively; the Simpson index was 0.100584 and 0.147211, respectively; and the Shannon index was 3.945855 and 3.878272, respectively. These results indicate that although the addition of PANI@MDPC has a certain impact on the overall microbial diversity, it increases the relative abundance of the target functional bacteria. This may be because the unique structure of PANI@MDPC is that of an anaerobic co-digesting synergistic functional bacterium (…). ​ ) and methanogenic archaea ( ​ This provides a suitable microenvironment for growth, promoting their enrichment while inhibiting the growth of some irrelevant microorganisms.

[0079] Depend on ​ (Changes at the phylum level) indicate that Bacillus phylum ( ​ Bacteroidetes ( ​ ), Actinobacteria ( ​ ) and Proteobacteria ( ​Bacillus was the dominant phylum in each group. However, PANI@MDPC significantly altered the relative abundance of microorganisms at the phylum level. The relative abundance of Bacillus increased by 11.95% and the relative abundance of Proteobacteria increased by 114.5% in the PANI@MDPC group. This indicates that the addition of PANI@MDPC further enhanced the status of dominant phyla related to anaerobic digestion, which can be attributed to its high specific surface area and good electron transport properties, thus benefiting the metabolic activities of related bacterial communities.

[0080] At the bacterial level, changes in microbial community structure significantly reflected the promoting effect of PANI@MDPC on the proliferation of specific microorganisms (e.g., ​ As shown). In the 25 mg / g PANI@MDPC group, *Masilebacterium* spp. ( ​ The relative abundance of PANI@MDPC reached 34.22%, significantly higher than the 27.48% of the control group. This is because PANI@MDPC possesses a unique conductive network that promotes interspecies electron transfer, enabling *Streptococcus masiliformes* (*Streptococcus* spp.) to achieve a higher abundance of electrons. ​ PANI@MDPC can participate more efficiently in the hydrolysis of carbohydrates or proteins, generating short-chain fatty acids (SCFAs), alcohols, or hydrogen, providing substrates for subsequent hydrogen-producing, acetic-producing, and methanogenic bacteria, thereby improving the overall performance of the system. Therefore, the addition of PANI@MDPC further enhances its dominant bacterial genera.

[0081] Archaea play a crucial role in anaerobic co-digestion and methanogenesis. ​ This study demonstrates the effect of PANI@MDPC on the relative abundance of Archaea. Compared to the control group, *Methanocytoplasma* spp. ( ​ The number of cases was significantly increased in groups that added PANI@MDPC. Specifically, *Methanococcus* spp. ​ The relative abundance of *Bacillus methanogenus* in the control group was 60.59%, while in the 25 mg / g PANI@MDPC group, the relative abundance increased to 66.14%, becoming the dominant bacterium. In addition, *Bacillus methanogenus* spp. (… ​ ), Methanotherium ( ​ ), Methanoplasma ( ​ The percentages in the control group were 2.52%, 0.48%, and 0.78%, respectively, while in the 25 mg / g PANI@MDPC group, these percentages increased to 7.01%, 0.79%, and 0.82%, respectively. Previous studies have shown that *Methanococcus* spp. (…) ​ Methanobacteria spp. are a diverse group of multi-nutritional methanogens that can produce methane not only by utilizing H2 / CO2, but also by cleaving acetic acid to produce methane using methyl compounds such as methanol and methylamine as substrates, and play a crucial role in electron transfer. ​ ) and Methanoplasma (​ They belong to the same hydrogenotrophic methanogens, producing methanogens via H2 / CO2; *Methanphyta* genus ( ​ These are acetic acid-nutritional methanogens that produce methane via acetic acid lysis. The significant increase in the relative abundance of these archaea in the PANI@MDPC group indicates that PANI@MDPC can effectively enhance archaea diversity and selectively enrich *Methanocytoplasma* genus. ​ Functional microorganisms such as PANI@MDPC and 25 mg / g PANI@MDPC increased the methanogenesis to 150.63 mg / L TS, which was 15.9% higher than the control group, thus enhancing the system's methanogenesis capacity.

[0082] In summary, the microbial community structure analysis clearly demonstrates that PANI@MDPC selectively enriches *Bacillus masiliforme* (…). ​ ), Methanocytocium spp. ( ​ The presence of anaerobic co-digesting synergistic bacteria and methanogenic archaea, primarily composed of anaerobic co-digesting synergistic bacteria, enhanced the function of key bacterial groups, accelerated material transformation and electron transfer during anaerobic co-digestion, and thus significantly improved the system's methanogenic performance. This discovery has important theoretical and practical significance for achieving efficient anaerobic co-digestion of food waste and sewage sludge.

[0083] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above, they are not intended to limit the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A polyaniline magnetic biochar prepared from biogas residue, characterized in that, The preparation of the polyaniline magnetic biochar includes the following steps: S1. Modify biochar with ferrate solution to obtain magnetic biochar MDPC; Step S1 specifically includes: under a protective atmosphere, gradient pyrolysis of biogas residue; after pyrolysis, washing, drying, and sieving to obtain biochar; modifying the biochar in ferrate solution to obtain magnetic biochar MDPC; in step S1, the ferrate solution is a mixed solution of FeCl3·6H2O and FeSO4·7H2O; the FeCl3·6H2O and FeSO4·7H2O mixed solution contains Fe 3+ and Fe 2+ The molar ratio is 1.85:1; S2. Measure the magnetic biochar, add aniline solution and hydrochloric acid solution and stir; in step S2, the mass-volume ratio of magnetic biochar, aniline solution and hydrochloric acid solution is 5:8:100, g:mL:mL; S3. Add ammonium persulfate and hydrochloric acid to the solution obtained in step S2, disperse ultrasonically, stir in an ice bath, and wash and dry the solid product to obtain the polyaniline magnetic biochar; Step S3 specifically includes: adding ammonium persulfate and hydrochloric acid to the solution obtained in step S2, dispersing ultrasonically, stirring at 780-800 r / min for 3-4 h in an ice bath at 2-6℃, washing the solid product with deionized water and methanol until the washing liquid is neutral, drying at 60-80℃ for 20-25 h, grinding after drying and passing through a 150-mesh sieve to obtain the polyaniline magnetic biochar; The polyaniline magnetic biochar is used to enrich anaerobic co-digestion synergistic bacteria and methanogenic archaea in an anaerobic co-digestion system of kitchen waste and residual sludge.

2. A method for promoting the enrichment of anaerobic co-digestion synergistic bacteria and methanogenic archaea in an anaerobic co-digestion system of kitchen waste and sewage sludge, characterized in that, The polyaniline magnetic biochar of claim 1 is added to the anaerobic co-digestion system, wherein the concentration of the polyaniline magnetic biochar in the anaerobic co-digestion system is 25-50 mg / g, calculated as TS.

3. The application of the polyaniline magnetic biochar of claim 1 or the method of claim 2 in the production of methane.

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