Method for mitigating acidification of an anaerobic reactor based on a binary electroactive material

Abstract

This invention relates to a method for alleviating acidification in anaerobic reactors based on binary electroactive materials. The invention utilizes the capacitance of binary electroactive materials to increase their ability to receive and release electrons, thereby attracting hydrogen ions and electrons accumulated in the acidified reactor and alleviating acidification. The conductivity of the binary electroactive materials can enrich iron-reducing bacteria, couple and enhance the degradation of organic matter, and increase the electron exchange rate between acid-producing bacteria and methanogenic archaea, accelerating the conversion of small molecule acids to methane and further clearing the accumulation of small molecule acids. This method can replace the traditional method of adding alkaline reagents and has broad application prospects in alleviating acidification in anaerobic reactors and maintaining stable reactor operation.

Description

Technical Field

[0001] This invention relates to a method for alleviating acidification in anaerobic reactors based on binary electroactive materials, as well as a method for preparing binary electroactive particles and binary electroactive fiber membranes. Background Technology

[0002] Large quantities of organic pollutants, such as crop straw, livestock and poultry manure, and kitchen waste, are a major cause of water pollution in my country. Anaerobic digestion, which rapidly decomposes organic matter into small-molecule organic acids by acid-producing bacteria, and then converts them into methane by methanogens for energy recovery, is one of the most effective methods for treating such pollutants and realizing their energy conversion, offering significant economic and environmental benefits. However, in traditional anaerobic digestion processes, the slow electron transfer efficiency between acid-producing bacteria and methanogens, coupled with the significantly lower physiological metabolic rate of methanogens compared to acid-producing bacteria, makes existing anaerobic digestion processes prone to problems such as the accumulation of small-molecule organic acids and reactor acidification when treating high-concentration organic wastewater. The consequences of anaerobic reactor acidification include the accumulation of large amounts of small-molecule acids and hydrogen ions within the reactor, leading to a sharp drop in pH and affecting microbial activity.

[0003] Currently, the following methods are commonly used to address reactor acidification: (1) Adding alkaline reagents such as calcium hydroxide, sodium hydroxide, and sodium bicarbonate to the system to adjust the pH to neutral using chemical methods. The disadvantage is that it is costly and requires repeated additions over a long period. At the same time, the large-scale introduction of potassium, sodium, and other salt ions can also cause microbial poisoning and inhibit microbial activity; (2) Reducing the concentration of organic matter in the feed, adding clean water to dilute the concentration of organic acids, or adding additional sludge to introduce the sludge, thereby reducing the overall treatment load per unit of microorganism. The disadvantage is that it does not fundamentally solve the reactor acidification problem, and once the organic load returns to the normal concentration, the acidification problem will continue to occur.

[0004] Therefore, the above methods only alleviate reactor acidification by temporarily altering the microbial living environment, and do not fundamentally solve the imbalance of metabolic rates and the slow interspecies electron transfer rate between acid-producing bacteria and methanogenic archaea. Summary of the Invention

[0005] The problem the invention aims to solve

[0006] In view of the above situation, there is a need for a method that is easy to operate, reduces the amount of chemical reagents used, fundamentally changes the electron transfer rate between acid-producing bacteria and methanogenic archaea and alleviates the imbalance between their metabolic rates, can accelerate the conversion of small molecule acids to methane, and avoids re-acidification of the reactor.

[0007] Solution for solving the problem

[0008] To overcome the shortcomings of the prior art, the present invention aims to provide a method for alleviating acidification in anaerobic reactors and promoting methanogenesis based on binary electroactive materials. This method enhances the electron transfer rate between acid-producing bacteria and methanogenic archaea through the conductivity of the binary electroactive materials. Furthermore, the capacitive properties of the binary electroactive materials buffer excess electrons and hydrogen ions generated from the decomposition of organic matter, which are then gradually released to the methanogenic bacteria. This regulates the imbalance in metabolic rates between the acid-producing bacteria and methanogenic archaea, effectively accelerating the methane conversion of small-molecule acids, alleviating acid inhibition in the anaerobic reactor, and maintaining stable reactor operation. Additionally, the present invention also provides a method for preparing the binary electroactive materials.

[0009] [1] Specifically, the present invention provides a method for alleviating acidification of an anaerobic reactor based on a binary electroactive material, the method comprising:

[0010] Anaerobic inoculation of anaerobic sludge into an anaerobic reactor is used to obtain inoculated sludge.

[0011] Add the organic wastewater to be treated to the anaerobic reactor; and

[0012] A binary electroactive material is added to the anaerobic reactor to alleviate its acidification.

[0013] The binary electroactive material is a composite electroactive material formed by a carbon material with oxygen-containing functional groups as a substrate, a conductive compound serving as an electron linker coating the surface of the carbon material, and Fe3O4 loaded on the surface of the conductive compound.

[0014] [2] According to the method described in [1] above, the oxygen-containing functional group is a quinone group; and / or, the carbon material is one or more of biochar particles, carbon fiber membranes, and carbon nanotubes; and / or, the conductive compound used as an electronic linker is selected from one or two of polydopamine and polyaniline.

[0015] [3] According to the method described in [1] or [2] above, the amount of the binary electroactive material added is 2-10 g / L relative to the amount of organic wastewater to be treated in the anaerobic reactor, and the amount of the inoculated sludge is 50-100 g / L.

[0016] [4] The method according to any one of [1]-[3] above, wherein when the pH value in the anaerobic reactor is below 6.5, a binary electroactive material is added to the anaerobic reactor; when the binary electroactive material is added, the temperature of the anaerobic reactor is 30-40°C; and / or,

[0017] The organic wastewater to be treated is fed in an intermittent or semi-continuous manner; the feeding of the organic wastewater to be treated is not stopped when the binary electroactive material is added to the anaerobic reactor.

[0018] [5] A method for preparing binary electroactive particles, characterized in that it includes the following steps:

[0019] Step S1: Place the carbon material in an aqueous solution of the monomer of the conductive compound used as an electronic linker and mix and stir for 10-15 hours. Then, perform filtration to retain the solid and dry the retained solid to obtain a capacitive carbon material with the conductive compound used as an electronic linker coated on the surface of the carbon material.

[0020] Step S2: Mix the capacitive carbon material obtained in step S1 with an ethanol solution of an organic iron source and stir for 1 to 3 hours, then perform filtration to retain the solid.

[0021] Step S3: The truncated solid from step S2 is calcined at 450-550°C in an inert atmosphere to obtain a carbon material with oxygen-containing functional groups as a substrate, the surface of which is coated with a conductive compound serving as an electron linker, and binary electroactive particles of conductive Fe3O4 on which the conductive compound is located.

[0022] [6] According to the preparation method described in [5] above, the carbon material is biochar particles; and / or, the monomer is selected from one or two of dopamine hydrochloride and aniline; and / or, the conductive compound used as an electron linker is selected from one or two of polydopamine and polyaniline; and / or, the organic iron source is selected from any one of ferric acetylacetone, ferrocene, ferric citrate, and ferric glycine; and / or, the oxygen-containing functional group is a quinone group.

[0023] [7] According to the preparation method described in [5] or [6] above, the mass ratio of the carbon material to the monomer of the conductive compound used as an electron linker is 1:1-1:3; and the concentration of the organic iron source is 20-30 mmol / L.

[0024] [8] A method for preparing a binary electroactive fiber membrane, characterized in that it includes the following steps:

[0025] Step S1: Dissolve the carbon source material, the monomer of the conductive compound used as the electron linker, and the organic iron source in an organic solvent to obtain a spinning solution, and perform electrospinning to obtain a fiber membrane.

[0026] Step S2: Place the fiber membrane obtained in step S1 in an oven at 250℃-300℃ for 1-2 hours to pre-oxidize it to increase oxygen-containing functional groups, thereby obtaining an oxidized fiber membrane.

[0027] Step S3: Carbonize the oxidized fiber membrane at 450-550℃ to obtain a binary electroactive fiber membrane with an oxygen-containing functional group as a substrate and containing a conductive compound used as an electron linker on the carbonized fiber membrane and Fe3O4 on the conductive compound.

[0028] [9] According to the preparation method described in [8] above, the carbon source material is selected from one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, and polystyrene; and / or, the monomer is selected from one or two of dopamine hydrochloride and aniline; and / or, the conductive compound used as an electron linker is selected from one or two of polydopamine and polyaniline; and / or, the organic iron source is selected from any one of ferric acetylacetone, ferrocene, ferric citrate, and ferric glycine; and / or, the oxygen-containing functional group is a quinone group.

[0029]

[10] According to the preparation method described in [8] or [9] above, in the spinning solution, the mass fraction of the carbon source material is 5%-20%, the mass fraction of the conductive compound is 5-8%, and the mass fraction of the organic iron source is 2-4%.

[0030] The effects of the invention

[0031] The technical solution of the present invention can have the following beneficial effects:

[0032] (1) Compared with adding alkaline reagents to the system, it reduces the input of chemical reagents and does not introduce a large amount of potassium, sodium and other salt ions that may have a toxic effect on microorganisms, thus making it more environmentally friendly.

[0033] (2) Compared with reducing the concentration of organic matter in the influent, adding clean water to dilute the concentration of organic acids, or adding additional sludge, the operation of this invention is simpler and can fundamentally change the electron transfer rate between acid-producing bacteria and methanogenic archaea and alleviate the imbalance between their metabolic rates.

[0034] (3) This invention differs from existing methods of adding biochar to acidified reactors by adding binary electroactive materials. The capacitance of these materials increases their electron-receiving capacity, thereby attracting hydrogen ions and electrons accumulated in the acidified reactor and alleviating acidification. Secondly, the conductivity of the materials enriches iron-reducing bacteria, increasing their abundance by 12%-24%, thus enhancing organic matter degradation and improving the electron exchange process between acid-producing bacteria and methanogenic archaea. This accelerates the conversion of small-molecule acids to methane, increasing methane production by 20-40% and further eliminating the accumulation of small-molecule acids.

[0035] (4) This invention can quickly alleviate the reactor acidification problem caused by excessively high organic matter concentration, and fundamentally solve the conversion rate of small molecule acids to methane, maintaining reactor stability and providing good economic and environmental benefits. The method of this invention can replace traditional methods and has broad application prospects in alleviating anaerobic reactor acidification and maintaining stable reactor operation. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process for preparing binary electroactive material particles in Example 1.

[0037] Figure 2 This is the Fourier Transmission Infrared (FTIR) spectrum of an electroactive material.

[0038] Figure 3 This is the XRD pattern of an electroactive material.

[0039] Figure 4 This is the cyclic voltammetry (CV) curve of the electroactive material.

[0040] Figure 5 This is a graph showing the electron receiving / releasing capabilities of the electroactive materials prepared in Example 1 and Comparative Examples 1 and 2.

[0041] Figure 6 This is a comparison chart of the conductivity of the electroactive materials prepared in Example 1 and Comparative Examples 1 and 2.

[0042] Figure 7 This is a schematic diagram of the process for preparing the binary electroactive fiber membrane in Example 2.

[0043] Figure 8 These are morphological images of the fiber membranes taken using a scanning electron microscope (SEM), where (a) is a morphological image of the binary electroactive fiber membrane prepared in Example 2; and (b) is a morphological image of the ordinary fiber membrane prepared in Comparative Example 3.

[0044] Figure 9 These are cyclic voltammetry diagrams of the electroactive fiber membranes prepared in Example 2 and Comparative Example 3.

[0045] Figure 10 This is a conductivity diagram of the electroactive fiber membranes prepared in Example 2 and Comparative Example 3.

[0046] Figure 11 The graphs show the effects of Example 3 and Comparative Examples 4, 5, and 6 on mitigating the pH of the reactor.

[0047] Figure 12 These are effect diagrams of methane generation in Example 3 and Comparative Examples 4, 5, and 6.

[0048] Figure 13These are microbial abundance diagrams in the reactors of Example 3 and Comparative Examples 4, 5, and 6. Detailed Implementation

[0049] To better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0050] Unless otherwise stated, all units used in this invention are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include unavoidable systematic errors in industrial production.

[0051] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0052] Unless otherwise required in this application, throughout the specification and the claims, the word "comprising" shall be interpreted in an open-ended, inclusive sense, meaning "including but not limited to".

[0053] Unless otherwise stated, in this instruction manual, "more" in "multiple", "multi-variety", "multiple", etc., means a value of 2 or more.

[0054] In this specification, the use of "may" or "can" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0055] Unless otherwise specified, "%" in this instruction manual refers to the percentage content by mass.

[0056] <First Aspect>

[0057] The first aspect of the present invention provides a method for mitigating acidification in anaerobic reactors based on binary electroactive materials.

[0058] When organic acids accumulate in large quantities in an anaerobic reactor due to excessively high or fluctuating organic matter concentration, it is necessary to add the binary electroactive material of this invention into the anaerobic reactor. The quinone functional groups on the surface of the binary electroactive material accept excess electrons and hydrogen ions in the reactor, and allow microorganisms to attach to the surface of the binary electroactive material, thereby establishing an electronic connection between acid-producing bacteria and methanogenic archaea and increasing the rate of small molecule acid to methane conversion.

[0059] The method for mitigating acidification in anaerobic reactors based on binary electroactive materials of the present invention includes the following steps:

[0060] Anaerobic inoculation of anaerobic sludge into an anaerobic reactor is used to obtain inoculated sludge.

[0061] Add the organic wastewater to be treated to the anaerobic reactor; and

[0062] A binary electroactive material is added to the anaerobic reactor to alleviate its acidification.

[0063] Furthermore, when the pH value in the anaerobic reactor is below 6.5, a binary electroactive material is added to the anaerobic reactor. Moreover, the feeding of the organic wastewater to be treated is not stopped while the binary electroactive material is added to the anaerobic reactor.

[0064] Furthermore, the anaerobic reactor in this invention is a mesophilic fermentation system with a temperature of 30-40°C.

[0065] Furthermore, the feeding method for the organic wastewater to be treated should be intermittent or semi-continuous, meaning that the reactor undergoes independent stages of water inlet, reaction, and drainage.

[0066] Furthermore, relative to the amount of organic wastewater to be treated in the anaerobic reactor, the dosage of the binary electroactive material can be 2-10 g / L, for example, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc. Relative to the amount of organic wastewater to be treated in the anaerobic reactor, the dosage of inoculated sludge can be 50-100 g / L, for example, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, etc.

[0067] The binary electroactive material of the present invention is a composite electroactive material formed by a carbon material having oxygen-containing functional groups as a substrate, a conductive compound serving as an electron linker coating the surface of the carbon material, and Fe3O4 loaded on the surface of the conductive compound.

[0068] In the binary electroactive material of the present invention, the oxygen-containing functional group in the carbon material with oxygen-containing functional group serving as the substrate is a quinone group, and the carbon material is one or more of biochar particles, carbon fiber membranes, and carbon nanotubes.

[0069] In the binary electroactive material of the present invention, the conductive compound used as the electron linker is selected from one or both of polydopamine and polyaniline.

[0070] In this invention, by adding a binary electroactive material with capacitance and conductivity to an acidified anaerobic reactor, the material's capacitance is used to accept hydrogen ions and electrons accumulated by the reactor's acidification, quickly restoring the pH to neutral and restoring microbial activity. On the other hand, the material's conductivity is used to construct a direct interspecies electron transfer process between acid-producing bacteria and methanogens, accelerating the interspecies electron transfer rate between them, accelerating the conversion of small molecule acids to methane, and preventing the reactor from acidifying again. This "dual-drive" approach solves the problem of anaerobic reactor acidification.

[0071] <Second aspect>

[0072] A second aspect of the present invention provides a method for preparing binary electroactive particles.

[0073] The binary electroactive particles are prepared by using calcined biochar as a capacitive substrate, coating the surface of the biochar with a layer of polydopamine as an electron linker, and then loading a layer of iron acetylacetone on the surface of the polydopamine. Through pyrolysis, the iron acetylacetone is converted into magnetite particles and used as a conductive medium, thus obtaining binary electroactive particles that have both capacitive and conductive properties.

[0074] The preparation method of the binary electroactive particles of the present invention includes the following steps:

[0075] Step S1: Place the carbon material in an aqueous solution of the monomer of the conductive compound used as an electronic linker and mix and stir for 10-15 hours. Then, perform filtration to retain the solid and dry the retained solid to obtain a capacitive carbon material with the conductive compound used as an electronic linker coated on the surface of the carbon material.

[0076] Step S2: Mix the capacitive carbon material obtained in step S1 with an ethanol solution of an organic iron source and stir for 1 to 3 hours, then perform filtration to retain the solid.

[0077] Step S3: The truncated solid from step S2 is calcined at 450-550°C in an inert atmosphere to obtain a carbon material with oxygen-containing functional groups as a substrate, wherein the surface of the carbon material is coated with a conductive compound serving as an electron linker, and wherein binary electroactive particles of Fe3O4 are present on the conductive compound.

[0078] The following provides a detailed explanation of each step.

[0079] Step S1

[0080] In step S1, the carbon material is placed in an aqueous solution of the monomer of the conductive compound used as an electronic linker and mixed and stirred. Then, the solid is retained by filtration and dried to obtain a capacitive carbon material with the conductive compound used as an electronic linker coated on the surface of the carbon material.

[0081] The carbon material in step S1 is biochar pellets. Biochar pellets can be obtained by processing various types of wood such as poplar and pine, as well as crop straw such as corn and wheat, into fragments, and then burning, drying, grinding, and sieving them.

[0082] For example, the process of preparing biochar can be as follows: After cleaning and drying the scraps, place them in a tube furnace, introduce nitrogen into the tube furnace to maintain an oxygen-free environment, then raise the temperature to the firing temperature at 2-4℃ / min and maintain it at the firing temperature for 1-2 hours, and then dry them; when the tube furnace naturally returns to room temperature, take out the fired biochar, grind it into powder using a grinder and sieve it to obtain a biochar sample.

[0083] The purpose of the firing process is to preliminarily carbonize the biochar fragments to form biochar with oxygen-containing functional groups. The firing temperature can be 400-550℃. This temperature is chosen because excessively high temperatures (>600℃) will damage the oxygen-containing functional groups on the surface of the biochar particles. The drying temperature range can be 90-105℃, preferably 100-105℃; the drying time can be 12-20 hours, preferably 16-20 hours. The size of the sieved biochar particles is 40-100 mesh, preferably 60-80 mesh.

[0084] In step S1 above, the monomer of the conductive compound used as the electron linker can be selected from one or both of dopamine hydrochloride and aniline. When the monomer includes dopamine hydrochloride, since dopamine hydrochloride is acidic, the pH of the monomer solution needs to be adjusted to 8-9, so that dopamine hydrochloride will polymerize on the surface of the biochar particles to form a polymer used as the electron linker, namely polydopamine. When the monomer is aniline, there is no need to adjust the pH, and the aniline attached to the surface of the biochar particles will polymerize to form polyaniline. Therefore, the conductive compound used as the electron linker in this invention is selected from one or both of polydopamine and polyaniline.

[0085] In the aqueous solution of the monomer, the concentration of the monomer can be 2-10 g / L, preferably 5-10 g / L, for example, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc. In some preferred embodiments, the pH of the monomer aqueous solution is adjusted to 8-9 using a buffer solution, such as 10 mM Tris-HCl.

[0086] In this invention, the mass ratio of carbon material to monomer of conductive compound used as electron linker is 1:1 to 1:3, for example, 1:1, 1:2, 1:3, etc.

[0087] In step S1, the time for mixing and stirring the carbon material with the aqueous solution of the monomer can be 10-15 hours, preferably 10-12 hours.

[0088] After mixing and stirring the carbon material with the monomer aqueous solution, and performing filtration to retain the suspended solids, the retained solids can be washed with ultrapure water 2-4 times. Then, the retained solids are placed in a drying oven to dry, thereby obtaining the capacitive carbon material. The drying temperature can be 50-100℃, preferably 50-80℃; the drying time can be 12-24h, preferably 20-24h.

[0089] Step S2

[0090] In step S2, the capacitive carbon material obtained in step S1 is mixed with an ethanol solution of an organic iron source and stirred for 1 to 3 hours, and then filtered to retain the solid.

[0091] In this invention, the organic iron source can be selected from any one of ferric acetylacetone, ferrocene, ferric citrate, and ferric glycine. The solvent used for the organic iron solution is a 75% (w / w) ethanol solution. In this invention, the concentration of the organic iron source is 20–30 mmol / L.

[0092] After mixing and stirring the capacitive carbon material obtained in step S1 with the organic iron source solution, and performing retention filtration to retain the solid, the retained solid can be rinsed with ultrapure water 2-4 times.

[0093] Step S3

[0094] In step S3, the truncated solid obtained in step S2 is calcined at a calcination temperature in an inert atmosphere to obtain a carbon material with oxygen-containing functional groups as a substrate, wherein the surface of the carbon material is coated with a conductive compound serving as an electron linker, and wherein binary electroactive particles of Fe3O4 are present on the conductive compound. In this invention, the oxygen-containing functional group is a quinone group.

[0095] In this step, the truncated solid obtained in step S2 is placed in a tube furnace, and nitrogen gas is introduced into the tube furnace to maintain an oxygen-free environment. The temperature is then increased to the firing temperature at a rate of 2-4°C / min and maintained for a certain period. The firing temperature can be 450-550°C, for example, 450°C, 460°C, 480°C, 500°C, 520°C, 550°C, etc.; the holding time can be 1-5 hours, preferably 2-4 hours.

[0096] Through the above-mentioned firing process, not only is the organic iron source transformed into Fe3O4, but the oxygen-containing functional groups on the surface of the carbon material are further increased, thereby further improving the performance of the binary electroactive particles of the present invention.

[0097] <Third aspect>

[0098] A third aspect of the present invention provides a method for preparing a binary electroactive fiber membrane.

[0099] The preparation of binary electroactive fiber membranes begins with a carbon source monomer as a precursor. A conductive compound and an organoferric reagent are added to the precursor to form an electrospinning solution. Polymer fiber membranes are then prepared via electrospinning. Following this, the membranes undergo pre-oxidation in an oven at a controlled temperature to impart oxygen-containing functional groups. The fiber membranes are then carbonized, converting the organoferric reagent into Fe3O4, which simultaneously increases the conductivity of the fiber membrane. The final result is a binary electroactive fiber membrane possessing both capacitive and conductive properties.

[0100] Specifically, the preparation method of the binary electroactive fiber membrane of the present invention includes the following steps:

[0101] Step S1: Dissolve the carbon source material, the monomer of the conductive compound used as the electron linker, and the organic iron source in an organic solvent to obtain a spinning solution, and perform electrospinning to obtain a fiber membrane.

[0102] Step S2: Place the fiber membrane obtained in step S1 in an oven at 250℃-300℃ for 1-2 hours to pre-oxidize it to increase oxygen-containing functional groups, thereby obtaining an oxidized fiber membrane.

[0103] Step S3: Carbonize the oxidized fiber membrane at 450-550℃ to obtain a binary electroactive fiber membrane with an oxygen-containing functional group as a substrate and containing a conductive compound used as an electron linker on the carbonized fiber membrane and Fe3O4 on the conductive compound.

[0104] It should be noted that the monomers of the conductive compounds used as electron linkers and the types of organic iron sources in this aspect are the same as those in the above-mentioned <Second Aspect>, and will not be repeated here. The following is a detailed description of each step.

[0105] Step S1

[0106] In step S1, a spinning solution is obtained by dissolving a carbon source material, a monomer of a conductive compound used as an electronic linker, and an organic iron source in an organic solvent.

[0107] In this invention, the carbon source material can be selected from one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, and polystyrene. In the spinning solution, the mass fraction of the carbon source material is 5-20%, preferably 5-15%, more preferably 8-12%, the mass fraction of the monomer of the conductive compound is 5-8%, more preferably 6-8%, and the mass fraction of the organic iron source is 2-4%, more preferably 3-4%.

[0108] In this invention, there is no particular limitation on the examples of organic solvents used to prepare the spinning solution, as long as they can dissolve the aforementioned materials. Examples may include N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc.

[0109] After preparing the spinning solution, the solution is spun using an electrospinning apparatus to obtain micron-sized fiber membranes. The spinning conditions are not particularly limited and can be conventional conditions used in the field. For example, the voltage during the spinning process can be 15-25 kV, the inner diameter of the spinning nozzle can be 0.4-0.8 mm, the spinning flow rate can be 0.05-0.09 mm / min, and the distance between the spinning nozzle and the metal receiving plate can be 15-20 cm.

[0110] Similar to the second aspect above, when the monomer includes dopamine hydrochloride, the pH of the spinning solution needs to be adjusted to 8-9 so that dopamine hydrochloride will polymerize on the fiber membrane surface to form a polymer that serves as an electron linker, namely polydopamine. When the monomer is aniline, pH adjustment is not required, and the aniline adhering to the fiber membrane surface will polymerize to form polyaniline.

[0111] Step S2

[0112] In step S2, the fiber membrane obtained in step S1 is placed in an oven for pre-oxidation to increase oxygen-containing functional groups, thereby obtaining an oxidized fiber membrane. The oxygen-containing functional group is a quinone group.

[0113] In this invention, the pre-oxidation temperature can be 250℃-300℃, preferably 260℃-280℃. The pre-oxidation time can be 1h-2h, preferably 1.5-2h.

[0114] Step S3

[0115] In step S3, the oxidized fiber membrane is placed in a muffle furnace and carbonized under conditions of nitrogen gas to maintain an oxygen-free environment, heating to the carbonization temperature at 2-4℃ / min and holding for a certain time, thereby carbonizing the fiber membrane and obtaining a binary electroactive fiber membrane with oxygen-containing functional groups as a substrate, and containing conductive compounds used as electron connecting bands on the carbonized fiber membrane and Fe3O4 on the conductive compounds.

[0116] In this invention, the carbonization temperature can be 500-550℃, preferably 520-550℃, and the holding time can be 2-3h.

[0117] Example

[0118] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0119] Example 1

[0120] Figure 1 The diagram illustrates the process of preparing binary electroactive material particles in this embodiment. Details are as follows.

[0121] 10g of poplar wood chips were washed and placed in a crucible, which was then placed in an oven and dried at 105℃ for 20 hours. The crucible was then placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 200 mL / min to maintain an oxygen-free environment. The temperature inside the furnace was then increased to 500℃ at a rate of 4℃ / min and maintained at 500℃ for 2 hours. After the furnace had naturally cooled to room temperature, the calcined biochar was removed, ground into powder using a grinder, and passed through an 80-mesh sieve to obtain the biochar sample, labeled as Biochar.

[0122] 5 g of biochar sample was placed in a 5 g / L dopamine hydrochloride solution, and the pH of the solution was adjusted to 8.5 with 10 mM Tris-HCl. The mixture was then stirred for 12 hours. The biochar and dopamine hydrochloride mixture was placed in a vacuum filtration device to trap the suspended solids, and then washed three times with ultrapure water. The trapped suspended solids were transferred to a crucible and then placed in a drying oven to dry at 50 °C for 24 hours to obtain capacitive biochar.

[0123] Capacitive biochar was placed in a 20 mmol / L ferric acetylacetone solution and mechanically stirred for 2 h; the solvent for the ferric acetylacetone solution was a 75% (w / w) ethanol solution. The mixture of capacitive biochar and ferric acetylacetone was placed in a vacuum filtration apparatus to trap suspended solids, and then washed three times with ultrapure water. The trapped solids were placed in a crucible and then placed in a tube furnace. Nitrogen gas was introduced into the tube furnace to maintain an oxygen-free environment at a flow rate of 200 mL / min. The temperature was then increased to 500 °C at a rate of 4 °C / min and maintained at 500 °C for 2 h to obtain a binary electroactive material with both capacitive and conductive properties. This material was labeled Fe3O4@Biochar.

[0124] Comparative Example 1

[0125] Compared to Example 1, biochar samples were prepared solely through pyrolysis without any subsequent processing and were labeled as Biochar.

[0126] Comparative Example 2

[0127] Comparative Example 2 is commercially available Fe3O4 powder.

[0128] Test conditions for electroactive materials

[0129] The Fourier transform infrared (FTIR) spectroscopy testing conditions for electroactive materials are as follows:

[0130] 50 mg of dried potassium bromide powder and 0.5 mg of sample powder were ground into a fine powder and mixed thoroughly in an agate mortar. An appropriate amount of the ground powder was pressed into a thin sheet under a pressure of 25 MPa and then tested. The infrared scanning range was 4000 to 400 cm⁻¹. -1 .

[0131] The X-ray powder diffraction (XRD) patterns of electroactive materials were tested under the following conditions:

[0132] The XRD scanning range is 5-80°, the scanning rate is 8° / min, the voltage is 45kV, and the current is 200mA.

[0133] The test conditions for the cyclic voltammetry curves of electroactive materials are as follows:

[0134] 10 mg of sample powder was added to 1 mL of a solution containing water and ethanol in a volume ratio of 4:1, and 40 μL of naphthol solution was added. 40 μL of the above mixed suspension was dropped onto a platinum electrode, and the electrode coated with the biochar suspension or mixed solution was dried at room temperature for 24 h.

[0135] Cyclic voltammetry was performed in a three-electrode system. The platinum electrode was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum electrode as the counter electrode. The minimum scan voltage was -0.4V, the maximum scan voltage was 0.8V, the scan rate was 0.05V / s, and a total of 4 scans were performed. The experimental data was taken from the 4th cycle, the sample interval was 0.001V, and the scan sensitivity was 10. -6 A.

[0136] The test conditions for the electron-receiving / releasing ability of electroactive materials are as follows:

[0137] The electron-receiving / releasing capabilities of electroactive materials were determined using dielectric electrochemical reduction and dielectric electrochemical reduction. The tests were conducted using a three-electrode system and an electrochemical workstation with chronoamperometry. The working electrode in the reaction cell was a glassy carbon electrode, the counter electrode was a platinum sheet electrode, and the reference electrode was a saturated Ag / AgCl electrode. Before testing, 24 mL of phosphate buffer solution was added to the reaction cell, and the potentials for electron-receiving and releasing capabilities were -0.49 V and +0.61 V, respectively. For electron-receiving capability testing, 520 μL of 10 mM diquat (DQ) was added to the reaction cell; for electron-releasing capability testing, 520 μL of 10 mM 2,2'-diazonium bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) was added. Subsequently, the powdered sample was added to the reaction cell. The EAC and EDC of the sample were the peak areas of the reduction and oxidation response current peaks, respectively, and the integral of the peak areas was calculated using the following formula:

[0138]

[0139]

[0140]

[0141] Where q(mol e) - ) is the number of electrons transferred, and F is the Faraday constant (96485 C / mol e). - I(C / sec) is the current, and t(sec) is the time. EAC and EDC are the number of electrons oxidized and reduced per gram of sludge-based biochar (μmol e). - / gbiochar).

[0142] The test conditions for the conductivity of electroactive materials are as follows:

[0143] The sample was ground into powder using an agate mortar. Then, the biochar powder sample was placed on a tablet press and pressed at 25 MPa for 20 minutes to produce a sheet. The resistivity of the biochar sheet was then measured using a four-probe resistivity meter, the thickness of the sheet was measured using vernier calipers, and the resistivity was calculated using formula (1):

[0144]

[0145] In the expression: ρ is the sample resistivity. The correction factor is 0.9788, where W is the thickness of the biochar sheet. denoted as , where is the sample resistance value and S is the probe spacing.

[0146] The conductivity of the sample is calculated based on the resistivity according to formula (2):

[0147]

[0148] Characterization and performance analysis

[0149] FTIR spectra ( Figure 2 This reveals the functional group information of the binary electroactive material Fe3O4@Biochar prepared in Example 1 and the Biochar prepared in Comparative Example 1. Among them, 960 cm⁻¹ -1 1056cm -1 These correspond to CO bonds on aliphatic and carbon skeletons, respectively; 1393cm -1 This corresponds to the CH bond; 1581cm -1 The corresponding position is the C=O bond of the quinone group; 3400cm -1 The corresponding functional groups are OH bonds; all of these functional groups are derived from the pyrolyzed biochar and are present in both samples, indicating that the prepared Fe3O4@Biochar is rich in quinone groups. The difference is that the Fe3O4@Biochar sample shows a higher concentration of quinone groups at 580 cm⁻¹. -1 The presence of a specific peak corresponds to an Fe-O bond, indicating the presence of iron oxides on the surface of biochar.

[0150] XRD chart ( Figure 3 The results showed that standalone biochar did not exhibit a distinct crystal structure. However, the Fe3O4@Biochar spectrum showed obvious Fe3O4 characteristic peaks, indicating that Fe3O4 crystals had been successfully grown on the biochar surface through complexation, pyrolysis, and other steps.

[0151] Cyclic voltammetry curve ( Figure 4 The reversible charge-discharge currents in the figure reflect the electron acceptance and contribution capabilities of the redox functional groups in each material, and the area under the curve represents the capacitance of the material. As can be seen from the figure, Biochar has the highest specific capacitance (4.70 F / g), followed by Fe3O4@Biochar (3.42 F / g), while Fe3O4 has the lowest specific capacitance (2.54 F / g). This indicates that the prepared Fe3O4@Biochar has charge-discharge capabilities close to those of Biochar, and higher than those of Fe3O4 in Comparative Example 2.

[0152] Figure 5 This is a graph showing the electron receiving / releasing capabilities of the electroactive materials prepared in Example 1 and Comparative Examples 1 and 2. Figure 5 It can be seen that the prepared binary electroactive material Fe3O4@Biochar has 251.08 and 7.22 μmol e - With its electron-accepting and electron-contributing capabilities, it can reversibly accept and release excess electrons and hydrogen ions in the anaerobic reactor.

[0153] Figure 6 This is a comparison of the conductivity of the electroactive materials prepared in Example 1 and Comparative Examples 1 and 2. Figure 6 It can be seen that the conductivity of the prepared binary electroactive material Fe3O4@Biochar is 10.2 μS / cm, while the conductivity of biochar prepared under the same conditions is only 0.01 μS / cm. This demonstrates that the binary electroactive material Fe3O4@Biochar possesses excellent conductivity and can facilitate electron exchange between acid-producing bacteria and methanogenic archaea.

[0154] Example 2

[0155] Figure 7 The diagram illustrates the process of preparing binary electroactive material particles in this embodiment. Details are as follows.

[0156] 2g of polyacrylonitrile, 1.6g of aniline and 0.8g of ferric acetylacetone were dissolved in 20mL of N,N-dimethylformamide solution to obtain a spinning solution. The electrospinning solution was spun using an electrospinning device to obtain nanoscale fiber membranes. The positive voltage of the spinning process was 15kV, the negative voltage was -5kV, the inner diameter of the spinning nozzle was 0.5mm, the spinning flow rate was 0.087mm / min, and the distance between the spinning nozzle and the metal receiving plate was 18cm.

[0157] The spun fiber membrane was placed in an oven at 280°C for 2 hours to undergo pre-oxidation and increase its oxygen-containing functional groups, thus obtaining an oxidized fiber membrane.

[0158] After the oxidized fiber membrane was naturally dried, it was placed in a muffle furnace for carbonization. Nitrogen gas was introduced into the tube furnace to maintain an oxygen-free environment. The temperature was then increased to 550°C at a rate of 4°C / min and maintained at 550°C for 2 hours to obtain the carbonized fiber membrane. After natural drying, the final binary active fiber membrane (PAN-Fe) with electrical conductivity and electroactivity was obtained.

[0159] Comparative Example 3

[0160] Compared with Example 2, Comparative Example 3 only added 2g of polyacrylonitrile to the spinning solution, while other treatment methods were the same, to obtain a common fiber membrane (PAN).

[0161] Depend on Figure 8 It can be seen that the diameter of the binary electroactive fiber membrane PAN-Fe prepared in Example 2 is approximately 200 nm, and it is wavy. Figure 8 (a)). The diameter of the ordinary fiber membrane PAN prepared in Comparative Example 3 was also 200 nm, and it was linear. Figure 8 (b)).

[0162] Depend on Figure 9It can be seen that the specific capacitance of the binary electroactive fiber membrane PAN-Fe prepared in Example 2 is 82.2 F / g, which is significantly higher than that of the ordinary fiber membrane PAN prepared in Comparative Example 3. The specific capacitance of Comparative Example 3 is only 3.5 F / g.

[0163] Figure 10 The results show that the conductivity of the binary electroactive fiber membrane in Example 2 is 5.0 mS / cm, which is significantly higher than that of the commercially available Fe3O4 in Comparative Example 2.

[0164] Example 3

[0165] An anaerobic serum bottle with an effective volume of 100 mL was used as the reactor. 8 g of anaerobic sludge was inoculated, with a volatile solids content of 35 g / L. 80 mL of organic wastewater to be treated was added. The wastewater had a COD concentration of 3.6 g / L, a pH of 7.6, and its main components were 16 g / L bovine serum albumin and 8 g / L dextran. Every two days, 40 mL of the treated wastewater was collected for water quality analysis, and 40 mL of fresh organic wastewater was added to the reactor. The temperature of the anaerobic reactor was controlled at 37℃. Simultaneously, 2 g / L of the binary electroactive material Fe3O4@Biochar prepared in Example 1 was added to the reactor.

[0166] Comparative Example 4

[0167] Compared to Example 3, Comparative Example 4 did not add any materials after the reactor was acidified and was marked as a blank reactor.

[0168] Comparative Example 5

[0169] Compared with Example 3, Comparative Example 5 added 2 g / L of Fe3O4 after the reactor was acidified, and the other conditions were the same as those in Example 3. It was labeled as Fe3O4 reactor.

[0170] Comparative Example 6

[0171] Compared with Example 3, Comparative Example 5 added 2 g / L of Biochar after the reactor was acidified, and the other conditions were the same as those in Example 3. It was labeled as a Biochar reactor.

[0172] Figure 11 The diagram shows the effect of each material in mitigating the pH of the reactor. From... Figure 11As can be seen, within one influent cycle, when organic wastewater enters the reactor, the pH of the blank reactor rapidly decreases from 7.7 to 6.0, recovering to 7.5 after 48 hours, but still not reaching the initial level. However, the pH in the reactor with the addition of the binary electroactive material Fe3O4@Biochar only decreases to 6.7 and then stops decreasing, recovering to the initial level within 36 hours and rising to 8.0 within 48 hours. This indicates that the binary electroactive material Fe3O4@Biochar can effectively alleviate reactor acidification and maintain stable reactor operation. Furthermore, its buffering effect on pH acidification is superior to that of Comparative Examples 5 and 6.

[0173] Depend on Figure 12 It can be seen that after long-term operation, the methane production in the blank reactor decreased continuously after 42 days due to acidification, with a daily methane production of approximately 120 ml. In contrast, the reactor with the addition of the binary electroactive material Fe3O4@Biochar showed a continuous increase in methane production, which stabilized after 42 days at approximately 240 ml per day, significantly higher than the blank reactor in Comparative Example 4. In comparison, the daily methane production in Comparative Example 5 was 209 ml, and in Comparative Example 6 it was 182 ml.

[0174] Figure 13 The results showed that *Gracilibacter* was the dominant bacterium in the control reactor of Comparative Example 4 at the genus level, with an abundance of 10.66%. *Gracilibacter* can degrade carbohydrates to produce acetic acid, lactic acid, and ethanol, but it cannot reduce metal oxides, indicating that it lacks extracellular electron transport capabilities. In the Fe3O4, Biochar, and Fe3O4@Biochar reactors, *Youngiibacter* and *Anaerolinea* were the dominant bacteria. *Youngiibacter* exhibited type IV *pili* that could establish direct electron transport with methanogens through conductive materials, indicating that it is a typical extracellular respiratory bacterium. *Anaerolinea* possessed the ability to transport electrons to the electrodes and reduce metal oxides. Along with Bacillus, Clostridium sensu stricto, Clostridium XlVb, and Bacteroides, which also possess extracellular electron transfer capabilities, the total abundance of these microorganisms in the four reactors of Comparative Example 4, Comparative Example 5, Comparative Example 6, and Example 3 was 12.55%, 20.31%, 18.19%, and 24.28%, respectively. This indicates that electroactive materials can enrich electroactive microorganisms and accelerate the decomposition of organic matter, with the binary electroactive material in Example 3 showing the best effect.

[0175] Industrial availability

[0176] The method for mitigating anaerobic reactor acidification based on binary electroactive materials of the present invention can quickly alleviate the reactor acidification problem caused by excessive organic matter concentration, and fundamentally solve the conversion rate of small molecule acids to methane, maintain reactor stability, and has good economic and environmental benefits.

Claims

1. A method for mitigating acidification in an anaerobic reactor based on binary electroactive materials, characterized in that, The method includes: Anaerobic inoculation of anaerobic sludge into an anaerobic reactor is used to obtain inoculated sludge. Add the organic wastewater to be treated to the anaerobic reactor; and A binary electroactive material is added to the anaerobic reactor to alleviate its acidification. The binary electroactive material is a composite electroactive material formed by a carbon material with oxygen-containing functional groups as a substrate, a conductive compound serving as an electron linker coating the surface of the carbon material, and Fe3O4 loaded on the surface of the conductive compound. The conductive compound used as the electronic linker is polydopamine.

2. The method according to claim 1, wherein the oxygen-containing functional group is a quinone group; and / or, the carbon material is one or more of biochar particles, carbon fiber membranes, and carbon nanotubes.

3. The method according to claim 1 or 2, wherein the dosage of the binary electroactive material is 2-10 g / L relative to the amount of organic wastewater to be treated in the anaerobic reactor, and the dosage of the inoculated sludge is 50-100 g / L.

4. The method according to claim 1 or 2, wherein a binary electroactive material is added to the anaerobic reactor when the pH value in the anaerobic reactor is below 6.5; and the temperature of the anaerobic reactor is 30-40°C when the binary electroactive material is added; and / or, The organic wastewater to be treated is fed in an intermittent or semi-continuous manner; the feeding of the organic wastewater to be treated is not stopped when the binary electroactive material is added to the anaerobic reactor.

5. A method for preparing binary electroactive particles, characterized in that, It includes the following steps: Step S1: Place the carbon material in an aqueous solution of the monomer of the conductive compound used as an electronic linker and mix and stir for 10-15 hours. Then perform filtration to retain the solid and dry the retained solid to obtain a capacitive carbon material with the conductive compound used as an electronic linker coated on the surface of the carbon material. Step S2: Mix the capacitive carbon material obtained in step S1 with an ethanol solution of an organic iron source and stir for 1 to 3 hours, then perform filtration to retain the solid. Step S3: The truncated solid from step S2 is calcined at 450-550°C in an inert atmosphere to obtain a carbon material with oxygen-containing functional groups as a substrate, the surface of which is coated with a conductive compound serving as an electron linker, and binary electroactive particles of conductive Fe3O4 on which the conductive compound is located.

6. The preparation method according to claim 5, wherein the carbon material is biochar particles; and / or, the monomer is selected from one or two of dopamine hydrochloride and aniline; and / or, the conductive compound used as the electron linker is selected from one or two of polydopamine and polyaniline; and / or, the organic iron source is selected from any one of ferric acetylacetone, ferrocene, ferric citrate, and ferric glycine; and / or, the oxygen-containing functional group is a quinone group.

7. The preparation method according to claim 5 or 6, wherein the mass ratio of the carbon material to the monomer of the conductive compound used as the electron linker is 1:1 to 1:3; and the concentration of the organic iron source is 20-30 mmol / L.

8. A method for preparing a binary electroactive fiber membrane, characterized in that, It includes the following steps: Step S1: Dissolve the carbon source material, the monomer of the conductive compound used as the electron linker, and the organic iron source in an organic solvent to obtain a spinning solution, and perform electrospinning to obtain a fiber membrane. Step S2: Place the fiber membrane obtained in step S1 in an oven at 250℃-300℃ for 1-2 hours to pre-oxidize it to increase oxygen-containing functional groups, thereby obtaining an oxidized fiber membrane. Step S3: Carbonize the oxidized fiber membrane at 450-550℃ to obtain a binary electroactive fiber membrane with an oxygen-containing functional group as a substrate and containing a conductive compound used as an electron linker on the carbonized fiber membrane and Fe3O4 on the conductive compound.

9. The preparation method according to claim 8, wherein the carbon source material is selected from one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, and polystyrene; and / or, the monomer is selected from one or two of dopamine hydrochloride and aniline; and / or, the conductive compound used as an electron linker is selected from one or two of polydopamine and polyaniline; and / or, the organic iron source is selected from any one of ferric acetylacetone, ferrocene, ferric citrate, and ferric glycine; and / or, the oxygen-containing functional group is a quinone group.

10. The preparation method according to claim 8 or 9, wherein in the spinning solution, the mass fraction of the carbon source material is 5%-20%, the mass fraction of the conductive compound is 5-8%, and the mass fraction of the organic iron source is 2-4%.

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