Fluorine-doped carbon quantum dot accelerant of anaerobic fermentation coupled light field, preparation and application

Abstract

The invention discloses an anaerobic fermentation coupled light field fluorine-doped carbon quantum dot accelerant and preparation and application thereof.Aloe peel serves as a raw material for preparing carbon quantum dots, fluoride serves as a fluorine source, a solvothermal synthesis method is adopted for heating reaction, a mixed solution is subjected to ultracentrifugation, centrifugate is taken and subjected to suction filtration through a microporous membrane, and obtained liquid is dialyzed and freeze-dried to obtain the fluorine-doped carbon quantum dot accelerant. The fluorine-doped carbon quantum dot F-CQDs solid powder is obtained. When the accelerant is applied to an anaerobic fermentation coupling light field system with livestock and poultry manure, a fermentation substrate and an inoculum, the accumulated biogas yield of the system can be remarkably increased, conversion of carbon dioxide to methane is effectively promoted, the biogas yield, the methane conversion rate and the substrate degradation efficiency of anaerobic fermentation are remarkably increased, and the method is suitable for industrial production. And efficient resource utilization of the biomass waste is achieved.

Description

Technical Field

[0001] This invention relates to the field of anaerobic fermentation technology, and in particular to a fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with an optical field, its preparation method, and its application. Background Technology

[0002] Currently, facing climate change, developing clean and renewable energy sources and reducing dependence on traditional energy sources have become urgent technological challenges. As a major agricultural country, China generates a massive amount of biomass waste annually. It is estimated that my country's total annual biomass waste production conservatively exceeds 3.5 billion tons, specifically including approximately 960 million tons of agricultural waste, 1.9 billion tons of livestock and poultry manure, and about 40 million tons of sewage sludge. This waste not only impacts the environment but also poses health risks. Therefore, how to rationally and efficiently treat this waste to reduce its environmental harm and transform it into usable energy is a crucial research topic.

[0003] Anaerobic digestion (AD) technology has garnered significant attention due to its ability to effectively utilize organic waste and generate renewable energy for everyday human use. Firstly, AD can convert organic waste (such as agricultural residues, food waste, and sludge) into biogas (primarily methane), reducing greenhouse gas emissions from landfill and incineration, thereby mitigating climate change. Secondly, biogas, as a renewable energy source, can replace fossil fuels, reducing carbon emissions and promoting energy structure transformation. Furthermore, the byproducts of AD—organic fertilizer—can replace chemical fertilizers, reducing soil and water pollution and promoting sustainable agriculture. Through resource recycling and pollution reduction, AD technology offers an effective solution for mitigating environmental pollution and promoting a green economy.

[0004] Anaerobic fermentation technology has attracted much attention due to its ability to effectively treat waste and convert it into a new energy source for human use. However, anaerobic fermentation systems still have some shortcomings, such as low gas production efficiency, low system stability, long fermentation cycle, and high post-treatment costs. Therefore, optimizing anaerobic digestion processes, improving microbial metabolic efficiency, and enhancing system stability have become the focus of current research. Summary of the Invention

[0005] To address the aforementioned shortcomings in existing technologies, this invention provides a fluorine-doped carbon quantum dot promoter for anaerobic fermentation with light field coupling, its preparation method, and its application. This aims to solve technical problems in traditional anaerobic fermentation systems, such as low biogas production, low electron transfer efficiency, and long fermentation cycles. By optimizing the electron transfer pathway, this promoter significantly increases the cumulative biogas production of the system, promotes the efficient conversion of carbon dioxide to methane, and improves methane yield. This invention also improves the operational stability of the anaerobic fermentation system, enhances the degradation efficiency of organic substrates, and achieves efficient resource utilization of biomass waste.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides a method for preparing a fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field, comprising the following steps:

[0008] After drying, grinding, and sieving, aloe vera peel is obtained as aloe vera peel powder.

[0009] Fluoride and aloe vera peel powder were dissolved in 30-40 parts of organic solvent at a mass ratio of (20-30):(35-45), mixed and stirred, and heated to obtain a mixed solution.

[0010] The mixed solution was ultracentrifuged, the centrifuged liquid was filtered through a microporous membrane, the resulting liquid was dialyzed, and then freeze-dried to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder.

[0011] As a preferred method, aloe vera peel is dried and ground at 50℃~60℃, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0012] Preferably, the fluoride is sodium fluoride, potassium fluoride, or ammonium fluoride.

[0013] Preferably, the organic solvent is ethylene glycol, propylene glycol, or ethylenediamine.

[0014] Preferably, the mixture is stirred for 2-3 hours, heated to a reaction temperature of 190-210℃, and the reaction time is 6-8 hours.

[0015] Preferably, the mixed solution is ultracentrifuged at 2500-3500 rpm for 5-7 min; filtered through a 0.22 μm microporous membrane; the filtrate is dialyzed for 2-5 days and then freeze-dried for 24-48 hours.

[0016] In another aspect, the present invention provides a fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field prepared by the method described above.

[0017] In another aspect, the present invention provides a method for anaerobic fermentation using a fluorine-doped carbon quantum dot promoter coupled with an anaerobic fermentation optical field, comprising the following steps:

[0018] Mix 30-50 parts by weight of livestock and poultry manure, 280-300 parts by weight of fermentation substrate and 90-110 parts by weight of inoculum to make fermentation slurry. Adjust the fermentation pH value and add 10-22 parts by weight of fluorine-doped carbon quantum dot promoter. Stir the fermentation slurry thoroughly and ferment it under mesophilic anaerobic conditions under light field intensity.

[0019] Preferably, the fermentation substrate is agricultural or forestry waste or kitchen waste.

[0020] The livestock and poultry manure is one of cow manure, pig manure, or chicken manure.

[0021] The inoculum is anaerobic sludge from an urban wastewater treatment plant.

[0022] The light field is illuminated by fluorescent lamps, with the light intensity adjusted to 5000-7000 Lux; the mesophilic anaerobic fermentation temperature is 35-38℃; and the fermentation pH is controlled to 5.5-7.5 by adjusting the fermentation substrate or adding buffers.

[0023] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0024] 1. This invention uses fluorine-doped carbon quantum dots as the main functional material. Compared with ordinary carbon quantum dot additives, the innovation of this invention lies in the significant advantages of fluorine-doped carbon quantum dots: fluorine doping optimizes the physicochemical properties of carbon quantum dots, resulting in stronger electron transfer efficiency and better promotion of interspecies electron transfer in microorganisms; it also exhibits superior surface activity and substrate affinity, improving substrate hydrolysis and acidification efficiency; it demonstrates higher chemical stability and environmental tolerance, maintaining activity over a long period in complex fermentation environments; it provides more specific promotion to methanogens, enhancing the activity of key enzymes and the expression of functional genes; and in coupled light field systems, it offers a wider light absorption range, higher photogenerated carrier separation efficiency, and a more significant photo-microbial metabolic synergistic effect, thereby more efficiently improving biogas production, methane conversion rate, and system stability.

[0025] The features of this invention are:

[0026] 1. Fluorine doping significantly improves the electron exchange capacity of carbon quantum dots, promotes the enrichment and metabolism of electrochemically active microorganisms, and thus enhances the electron transfer efficiency of the anaerobic fermentation coupled light field system.

[0027] 2. Fluorine doping introduces more fluorine-containing functional groups, making the surface polarity and charge distribution of carbon quantum dots more suitable for substrates (such as cellulose and protein in livestock and poultry manure, lipids in kitchen waste, etc.) and microbial extracellular polymers in anaerobic fermentation environments, thereby enhancing the adsorption and activation capacity of substrates and promoting the hydrolysis and acidification efficiency of substrates.

[0028] 3. Fluorine doping can broaden the light absorption range of carbon quantum dots (especially in the ultraviolet to visible light region) and improve the separation efficiency of photogenerated carriers (electron-hole pairs), reducing the recombination probability. These photogenerated electrons can directly participate in the electron transport chain of microorganisms or promote the reduction of carbon dioxide to methane through photocatalysis.

[0029] 4. This invention provides an efficient and low-cost accelerator solution for anaerobic fermentation technology. The process is simple and easy to scale up, opening up new technical avenues for the resource utilization of biomass waste. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 Transmission electron microscopy (TEM) images of F-CQDs;

[0032] Figure 2 FTIR spectra of carbon quantum dots (CQDs) and fluorine-doped carbon quantum dots (F-CQDs);

[0033] Figure 3 (a) XPS total spectra of CQDs and F-CQDs. Figure 3 (b)-(d) are the fine XPS spectra of F-CQDs. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0035] This invention provides a method for preparing a fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field, comprising the following steps:

[0036] Step 1: The aloe vera peel is dried and ground at 50℃~60℃, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0037] Step 2: Dissolve sodium fluoride, potassium fluoride or ammonium fluoride and aloe vera peel powder in (30-40) parts of organic solvent (ethylene glycol, propylene glycol or ethylenediamine) at a mass ratio of (20-30):(35-45), mix and stir for 2-3 hours, and heat at 190-210℃ for 6-8 hours to obtain a mixed solution.

[0038] Step 3: The mixed solution is ultracentrifuged at 2500-3500 rpm for 5-7 min; the centrifuged material is filtered through a 0.22 μm microporous membrane, the filtrate is dialyzed for 2-5 days, and then freeze-dried for 24-48 hours to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder.

[0039] Its morphology presents as well-dispersed dark spots, which are nearly spherical in shape and range in size from 1 to 10 nanometers. Figure 1 As shown, the FTIR spectra of carbon quantum dots (CQDs) and fluorine-doped carbon quantum dots (F-CQDs) are shown below. Figure 2 As shown.

[0040] from Figure 3 (a) XPS total spectra of CQDs and F-CQDs, and Figure 3 The fine XPS spectra of (b)-(d)F-CQDs show that fluorine has been successfully incorporated into the CQDs.

[0041] An example of anaerobic fermentation using fluorine-doped carbon quantum dots as a promoter is as follows:

[0042] Mix 30-50 parts by weight of livestock and poultry manure, 280-300 parts by weight of fermentation substrate, and 90-110 parts by weight of inoculum to form fermentation slurry. Control the fermentation pH value to 5.5-7.5 by adjusting the fermentation substrate or adding a buffer. Then add 10-22 parts by weight of fluorine-doped carbon quantum dot promoter, stir the fermentation slurry thoroughly, control the anaerobic fermentation temperature at 35-38℃, and adjust the light field intensity to 5000-7000 Lux to carry out anaerobic fermentation.

[0043] The fermentation substrate is agricultural and forestry waste or kitchen waste; the livestock and poultry manure is one of cow manure, pig manure or chicken manure; the inoculum is anaerobic sludge from an urban sewage treatment plant; and the light field is fluorescent lamps.

[0044] Introducing fluorine-doped carbon quantum dots (F-CQDs) as a promoter in anaerobic fermentation systems can improve anaerobic fermentation efficiency, but its performance is still limited by the catalyst activity. Quantum dot materials are a class of nanomaterials with unique optical and electronic properties; fluorine-doped carbon quantum dots exhibit superior catalytic activity and conductivity in anaerobic fermentation systems under illumination. The introduction of a light field can significantly improve the electronic structure of the material in the anaerobic fermentation system and enhance its redox activity. This invention prepares fluorine-doped carbon quantum dots via a hydrothermal method, significantly improving their electron exchange capacity (EEC), and applies them to an anaerobic fermentation system coupled with a light field, significantly improving gas production performance.

[0045] Following the steps described above, the preparation of the promoter of the present invention and the different raw material components in the anaerobic fermentation coupled light field are further illustrated below through examples and comparative examples.

[0046] Example 1

[0047] (1) Preparation of fluorine-doped carbon quantum dot promoters:

[0048] Aloe vera peel is dried at 50℃, ground, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0049] Sodium fluoride and aloe vera peel powder were dissolved in 35 parts of ethylene glycol at a mass ratio of 25:40. The mixture was stirred for 2 hours and then heated at 200℃ for 8 hours to obtain a mixed solution.

[0050] The mixed solution was ultracentrifuged at 3000 rpm for 6 min; the centrifuged material was filtered through a 0.22 μm microporous membrane, the filtrate was dialyzed for 3 days, and then freeze-dried for 36 hours to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder. Its morphology exhibits well-dispersed dark spots, which are nearly spherical in shape and range in size from 1 to 10 nanometers.

[0051] (2) Anaerobic fermentation was initiated by using a fluorine-doped carbon quantum dot promoter to start an anaerobic fermentation coupled with a light field system.

[0052] A mixture of 30 parts by weight of livestock and poultry manure and 290 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 95 parts by weight of anaerobic sludge was used as the inoculum, and 15 parts by weight of fluorine-doped carbon quantum dot promoter were added. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 36℃, and the light intensity was adjusted to 6000 Lux. The cumulative biogas production was 486.7 mL / g VS, the methane production was 319.1 mL / g VS, and the methane content was 65%.

[0053] Example 2

[0054] (1) Preparation of fluorine-doped carbon quantum dot promoters:

[0055] Aloe vera peel is dried at 60℃, ground, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0056] Potassium fluoride and aloe vera peel powder were dissolved in 40 parts of propylene glycol at a mass ratio of 20:40. The mixture was stirred for 3 hours and then heated at 210℃ for 6 hours to obtain a mixed solution.

[0057] The mixed solution was ultracentrifuged at 2500 rpm for 7 min; the centrifuged material was filtered through a 0.22 μm microporous membrane, the filtrate was dialyzed for 4 days, and then freeze-dried for 30 hours to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder. Its morphology exhibits well-dispersed dark spots, which are nearly spherical in shape and range in size from 1 to 10 nanometers.

[0058] (2) Anaerobic fermentation was initiated by using a fluorine-doped carbon quantum dot promoter to start an anaerobic fermentation coupled with a light field system.

[0059] A mixture of 40 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. 100 parts by weight of anaerobic sludge was used as the inoculum, and 14 parts by weight of fluorine-doped carbon quantum dot promoter were added. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 38℃, and the light intensity was adjusted to 5000 Lux. The cumulative biogas production was 503.3 mL / g VS, the methane production was 335.4 mL / g VS, and the methane content was 66%.

[0060] Example 3

[0061] (1) Preparation of fluorine-doped carbon quantum dot promoters:

[0062] The aloe vera peel is dried at 55℃, ground, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0063] Ammonium fluoride and aloe vera peel powder were dissolved in 35 parts of ethylenediamine organic solvent at a mass ratio of 30:35. The mixture was stirred for 2 hours and then heated at 190℃ for 8 hours to obtain a mixed solution.

[0064] The mixed solution was ultracentrifuged at 3500 rpm for 5 min; the centrifuged material was filtered through a 0.22 μm microporous membrane, the filtrate was dialyzed for 2 days, and then freeze-dried for 48 hours to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder. Its morphology exhibits well-dispersed dark spots, which are nearly spherical in shape and range in size from 1 to 10 nanometers.

[0065] (2) Use fluorine-doped carbon quantum dot additives to start an anaerobic fermentation coupled light field system.

[0066] A mixture of 45 parts by weight of livestock and poultry manure and 300 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 fluorine-doped carbon quantum dot promoter were added. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 37℃, and the light intensity was adjusted to 6000 Lux. The cumulative biogas production was 530.6 mL / g VS, the methane production was 370.3 mL / g VS, and the methane content was 69%.

[0067] Example 4

[0068] (1) Preparation of fluorine-doped carbon quantum dot promoters:

[0069] Aloe vera peel is dried at 60℃, ground, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

[0070] Sodium fluoride and aloe vera peel powder were dissolved in 30 parts of ethylene glycol at a mass ratio of 25:45. The mixture was stirred for 2.5 hours and then heated at 200°C for 7 hours to obtain a mixed solution.

[0071] The mixed solution was ultracentrifuged at 2800 rpm for 7 min; the centrifuged material was filtered through a 0.22 μm microporous membrane, the filtrate was dialyzed for 5 days, and then freeze-dried for 24 hours to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder. Its morphology exhibits well-dispersed dark spots, which are nearly spherical in shape and range in size from 1 to 10 nanometers.

[0072] (2) Use fluorine-doped carbon quantum dot additives to start an anaerobic fermentation coupled light field system.

[0073] A mixture of 50 parts by weight of livestock and poultry manure and 285 parts by weight of agricultural and forestry waste or kitchen waste was used as the fermentation substrate. 110 parts by weight of anaerobic sludge was used as the inoculum, and 22 parts by weight of fluorine-doped carbon quantum dot promoter were added. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 35℃, and the light intensity was adjusted to 7000 Lux. The cumulative biogas production was 518.6 mL / g VS, the methane production was 356.8 mL / g VS, and the methane content was 68%.

[0074] The following comparative examples are given in comparison with the embodiments of the present invention to further illustrate the effects of the present invention.

[0075] Comparative Example 1

[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, with 90 parts by weight of anaerobic sludge as the inoculum. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 36℃, and the light intensity was adjusted to 6000 Lux. The cumulative biogas production was 359.1 mL / g VS, the methane production was 163.8 mL / g VS, and the methane content was 45%.

[0077] Comparative Example 2

[0078] 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 carbon quantum dot promoter were added. The fermentation slurry was thoroughly stirred, the anaerobic fermentation temperature was controlled at 36℃, and the light intensity was adjusted to 6000 Lux. The cumulative biogas production was 487.1 mL / g VS, the methane production was 276.7 mL / g VS, and the methane content was 56%.

[0079] Table 1 shows a comparison of the test results between the examples and the comparative examples.

[0080] Table 1. Performance comparison of the embodiments of the present invention and comparative examples.

[0081]

[0082] Based on the data in Table 1, this invention, using F-CQDs as a promoter, exhibits superior performance enhancement in an anaerobic fermentation coupled light field system. The following is a detailed analysis and explanation of its advantages:

[0083] 1. Significantly increases biogas and methane production

[0084] Cumulative gas production: After adding F-CQDs, the cumulative gas production of the system reached 530.6 mL / g VS (Example 3), which is 47.7% higher than Comparative Example 1 (359.1 mL / g VS) and significantly higher than other examples and comparative examples, indicating that it can effectively promote the degradation and gas conversion of fermentation substrates.

[0085] Methane production and content: The methane production reached 370.3 mL / g VS (Example 3), and the methane content increased to 69%, which is much higher than that of Comparative Example 1 (45%), proving that F-CQDs can selectively enrich dominant methanogenic bacteria and enhance methane production.

[0086] 2. Highly efficient degradation of organic matter and COD removal

[0087] The addition of F-CQDs promoters (Examples 1-4) can efficiently degrade organic matter, significantly improving the total solids degradation rate, volatile solids degradation rate, and COD removal rate; and effectively reducing the pyrolysis loss of fermentation residue. After adding pure carbon quantum dots to a conventional anaerobic fermentation system, the total solids degradation rate, volatile solids degradation rate, and COD removal rate of Comparative Example 2 were increased by 23%-75% compared to Comparative Example 1. In Examples 1-4, the total solids degradation rate, volatile solids degradation rate, and COD removal rate of Example 3 reached 60%, 64%, and 65.08%, respectively. This indicates that the addition of 18 parts of fluorine-doped carbon quantum dots has the best promoting effect on substrate degradation in the anaerobic digestion coupled light field system.

[0088] To comprehensively evaluate the operational efficiency of an anaerobic fermentation system, pH monitoring is a key indicator. The core function of pH measurement is to monitor the acid-base state of the system's microenvironment in real time, thereby determining the metabolic balance between acid-producing and methanogenic bacteria. By tracking pH changes, it's possible to promptly detect excessive accumulation of volatile fatty acids (VFAs) or excessively high ammonia nitrogen concentrations, providing early warnings of system acidification risks or bacterial activity inhibition. This provides a basis for adjusting fermentation conditions (such as adding buffers or adjusting substrate ratios), ensuring that methanogenic bacteria remain active within the optimal pH range, maintaining efficient substrate degradation and stable methane production, and guaranteeing the stable operation and metabolic efficiency of the entire fermentation system. The following section provides a detailed analysis of pH data to explore its performance and mechanisms in maintaining system stability.

[0089] Table 2. pH changes over time in the fermentation systems of the embodiments and comparative examples of the present invention.

[0090] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Day 1 7.33 7.37 7.40 7.41 7.39 7.37 Day 5 5.52 5.55 5.60 5.63 5.55 5.61 Day 10 6.16 6.35 6.76 6.89 6.97 6.38 Day 15 6.91 7.14 7.31 7.33 7.33 7.35 Day 20 7.22 7.30 7.39 7.36 7.41 7.38 Day 25 7.29 7.36 7.44 7.39 7.43 7.40 Day 30 7.39 7.43 7.49 7.41 7.46 7.47 Day 35 7.40 7.49 7.51 7.46 7.53 7.50

[0091] 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 7.49 (day 1), which then decreased to 5.55 (day 5) after acidification, but began to steadily increase from day 10, eventually recovering to 7.53 (day 35). This change 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 10-25, the pH value rapidly increased from 6.97 to 7.53, 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.

[0092] The F-CQDs of this invention, as a promoter in an anaerobic fermentation coupled light field system, have stronger electron transfer efficiency, which can better promote interspecies electron transfer among microorganisms; they have better surface activity and substrate affinity, which can improve substrate hydrolysis and acidification efficiency and shorten the fermentation cycle; at the same time, they have a wider light absorption range, higher photogenerated carrier separation efficiency, and more significant photo-microbial metabolic synergistic effect, thereby more efficiently improving biogas production, methane conversion rate and system stability.

[0093] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for preparing a fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field, characterized in that, Includes the following steps: After drying, grinding, and sieving, aloe vera peel is obtained as aloe vera peel powder. Fluoride and aloe vera peel powder were dissolved in 30-40 parts of organic solvent at a mass ratio of (20-30):(35-45), mixed and stirred, and heated to obtain a mixed solution. The mixed solution was ultracentrifuged, the centrifuged liquid was filtered through a microporous membrane, the resulting liquid was dialyzed, and then freeze-dried to obtain fluorine-doped carbon quantum dot (F-CQD) solid powder.

2. The method for preparing the fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field according to claim 1, characterized in that, Aloe vera peel is dried at 50℃~60℃, ground, and then sieved through a 50-mesh sieve to obtain aloe vera peel powder.

3. The method for preparing the fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field according to claim 1, characterized in that, The fluoride is sodium fluoride, potassium fluoride or ammonium fluoride.

4. The method for preparing the fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field according to claim 1, characterized in that, The organic solvent is ethylene glycol, propylene glycol, or ethylenediamine.

5. The method for preparing the fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field according to claim 1, characterized in that, Mix and stir for 2-3 hours, and heat the reaction at 190-210℃ for 6-8 hours.

6. The method for preparing the fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field according to claim 1, characterized in that, The mixed solution was ultracentrifuged at 2500-3500 rpm for 5-7 min; filtered through a 0.22 μm microporous membrane; the filtrate was dialyzed for 2-5 days and then freeze-dried for 24-48 hours.

7. A fluorine-doped carbon quantum dot promoter for anaerobic fermentation coupled with a light field, prepared by the method according to any one of claims 1-6.

8. A method for anaerobic fermentation using the fluorine-doped carbon quantum dot promoter with an anaerobic fermentation coupled light field as described in claim 7, characterized in that, Includes the following steps: Mix 30-50 parts by weight of livestock and poultry manure, 280-300 parts by weight of fermentation substrate and 90-110 parts by weight of inoculum to make fermentation slurry. Adjust the fermentation pH value and add 10-22 parts by weight of fluorine-doped carbon quantum dot promoter. Stir the fermentation slurry thoroughly and ferment it under mesophilic anaerobic conditions under light field intensity.

9. The method for anaerobic fermentation using fluorine-doped carbon quantum dot promoters coupled with an anaerobic fermentation light field according to claim 8, characterized in that, The fermentation substrate is agricultural and forestry waste or kitchen waste; The livestock and poultry manure is one of cow manure, pig manure, or chicken manure; The inoculum is anaerobic sludge from an urban wastewater treatment plant.

10. The method for anaerobic fermentation using fluorine-doped carbon quantum dot promoters coupled with an anaerobic fermentation light field according to claim 8, characterized in that, The light field is illuminated by fluorescent lamps, with the light intensity adjusted to 5000-7000 Lux; the mesophilic anaerobic fermentation temperature is 35-38℃; and the fermentation pH is controlled to 5.5-7.5 by adjusting the fermentation substrate or adding buffers.

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