Process for promoting sludge hydrolysis and synthesis of medium-chain fatty acids by using ferrocene

Abstract

The present invention relates to the field of sludge treatment technology, and in particular to a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising: S10, adding ferrocene to the sludge and adjusting the pH to 3.0-5.0; S20, adding hydrogen peroxide to carry out a Fenton-like reaction, wherein the ferrocene undergoes a solid-liquid phase transition during the reaction; S30, adding ethanol, anaerobic seed sludge, and culture medium to carry out anaerobic fermentation and carbon chain extension; ferrocene generates hydroxyl radicals in the Fenton-like reaction to destroy sludge flocs and cell wall membranes; the converted liquid ferrocene cation acts as an electron mediator in step S30 to improve electron transfer efficiency; the liquid ferrocene cation simultaneously inhibits ethanol oxidation and methanogenesis. The present invention combines the Fenton-like reaction with a biological anaerobic process to construct a sludge hydrolysis, fermentation, and carbon chain extension process based on ferrocene regulation, thereby simultaneously promoting sludge hydrolysis, enhancing medium-chain fatty acid synthesis, and inhibiting substrate competition reactions, thereby expanding the high-value recovery rate of sludge resources.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge treatment, and in particular to a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis by utilizing ferrocene. Background Art

[0002] The resource utilization of municipal wastewater sludge has become an inevitable trend. Anaerobic fermentation of sludge produces short-chain fatty acids (C2-C5), which in turn produce medium-chain fatty acids (C6-C8) through microbial metabolic carbon chain extension with ethanol, showing great potential for application. However, the construction of an anaerobic fermentation-carbon chain extension process chain faces the following challenges: First, the low biodegradability of sludge makes hydrolysis the rate-limiting step in the resource utilization process; second, traditional processes suffer from insufficient electron flux or low electron transfer efficiency, which hinders the interaction of carbon chain extension functional strains and thus limits the production of medium-chain fatty acids; third, the existence of ethanol over-oxidation and methanogenesis, which compete for the consumption of ethanol and organic acids in the carbon chain extension process, respectively.

[0003] Related technologies address only the first or second deficiency. For the first, existing technologies primarily focus on physical, chemical, biological, and combined pretreatment methods. Physical methods, such as ultrasound and mechanical shearing, can disrupt sludge structure and accelerate organic matter release; chemical methods enhance hydrolysis efficiency through alkalinity adjustment or oxidants; biological methods utilize exogenous hydrolytic enzymes or highly efficient bacterial communities to enhance degradation capacity; and combined approaches combine physical, chemical, or chemical-biological techniques to synergistically enhance hydrolysis. These technologies and patents offer diverse solutions to address sludge hydrolysis bottlenecks, promoting efficient sludge resource utilization and industrial development. Regarding the second deficiency, technological advances in enhancing the electron transfer function of anaerobic biological systems primarily focus on optimizing electron mediators, adding conductive materials, and enhancing microbial enhancement. Electron transfer efficiency is enhanced by adding electron mediators such as ferroferric oxide and potassium polyferrocyanide; conductive nanomaterials, such as carbon nanotubes, graphene, or conductive polymers, improve the system's electronic conductivity; and microbial communities with efficient electron transfer capabilities, such as electroactive bacteria, are selected and domesticated to enhance overall system performance. Regarding the third drawback, existing processes only address methane synthesis through the addition of expensive sodium 2-bromoethylsulfonate, but currently lack a method for synergistically inhibiting ethanol overoxidation and methanogenesis. Consequently, no process can simultaneously enhance sludge hydrolysis, inhibit the primary competing process, and selectively promote medium-chain fatty acid synthesis. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene. The process adopts a Fenton-like reaction process combined with a biological anaerobic process, utilizes inexpensive ferrocene, and constructs a sludge fermentation-carbon chain extension process based on ferrocene regulation. The process does not require the addition of sodium 2-bromoethylsulfonate to inhibit methane synthesis, and can simultaneously achieve the promotion of sludge hydrolysis, the enhancement of medium-chain fatty acid synthesis, and the inhibition of substrate competition reactions, thereby expanding the high-value recovery rate of sludge resources.

[0005] The purpose of the present invention is achieved by adopting the following technical solutions:

[0006] The first aspect of the present invention provides a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising the following steps:

[0007] S10, adding ferrocene to the sludge and adjusting the pH to 3.0-5.0;

[0008] S20, adding hydrogen peroxide to carry out a Fenton-like reaction, wherein the ferrocene undergoes a solid-liquid phase transition to form a ferrocene cation during the reaction;

[0009] S30, adding ethanol, anaerobic seed mud and culture medium to perform anaerobic fermentation and carbon chain extension;

[0010] The ferrocene in step S10 generates hydroxyl radicals in the Fenton-like reaction in step S20, which destroy the sludge flocs and cell wall membranes;

[0011] The liquid ferrocenium cation converted in step S20 is used as an electron mediator in step S30 to improve the electron transfer efficiency;

[0012] The liquid ferrocenium cation inhibits both ethanol oxidation and methanogenesis processes.

[0013] In the first aspect of the present invention, as an optional embodiment, in step S10, the amount of ferrocene added is 2-5 g / L.

[0014] In the first aspect of the present invention, as an optional embodiment, in step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5-2):1.

[0015] In the first aspect of the present invention, as an optional embodiment, in step S20, the pH of the system spontaneously rises to 4.5-5.5 after the reaction, which is the suitable pH condition range for the carbon chain extension process.

[0016] In the first aspect of the present invention, as an optional embodiment, in step S30, the amount of ethanol added is 90-150 mM.

[0017] In the first aspect of the present invention, as an optional embodiment, in step S30, the anaerobic seed sludge is an activated sludge that has been acclimated, and the acclimation treatment steps are: taking sludge from a sewage treatment plant, heating it at 100-110°C for 25-35 minutes to kill methanogens, and then placing it in an anaerobic environment with a sludge retention time of 25-35 days; the inoculation amount of the anaerobic seed sludge is 5-15% of the system volume.

[0018] In the first aspect of the present invention, as an optional embodiment, in step S30, the reaction time is 12-20 days.

[0019] In the first aspect of the present invention, as an optional embodiment, the process is continuously implemented in a single reactor. First, municipal excess sludge is collected into the reactor. After completing steps S10 and S20 in sequence, the reactor is sealed to form an anaerobic fermentation reactor, which is placed in a constant temperature shaking incubator at 35±2°C to complete step S30.

[0020] In the first aspect of the present invention, as an optional embodiment, the oscillation frequency of the constant temperature oscillating shaker is controlled to be set to 120-180 rpm.

[0021] In the first aspect of the present invention, as an optional embodiment, after the reaction of step S30 is completed, the method further includes S40: centrifuging the supernatant to collect the fermentation broth containing medium-chain fatty acids, which is a high-value resource recovery product.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The process of the present invention achieves enhanced sludge hydrolysis and directional regulation of medium-chain fatty acid synthesis by regulating the morphological transformation of ferrocene. Specifically, by adding ferrocene and hydrogen peroxide to form a Fenton-like reaction, hydroxyl radicals are generated to attack sludge flocs and cell wall membranes, thereby improving the biodegradability of sludge. During the Fenton reaction, solid ferrocene is converted into liquid ferrocenium cations. The coexistence of ferrocene and its cations in the system as electron mediators can improve the system's electron transfer efficiency and increase bacterial interactions. Finally, liquid ferrocenium cations have the effect of inhibiting ethanol oxidation and methane production, and can optimize the utilization of substrates ethanol and short-chain fatty acids during carbon chain extension, thereby improving the reaction efficiency of ethanol and short-chain fatty acids in sludge fermentation, and directionally strengthening medium-chain fatty acid synthesis.

[0024] The process of the present invention is a process based on the anaerobic metabolism of microorganisms as the main reaction body. The main body of the equipment can be constructed using an anaerobic fermentation tank and a stirring device, and has the significant advantages of simple operation, low energy consumption and controllable costs. This process does not require complex equipment configuration. By optimizing the stirring and reaction conditions, the high efficiency of material transfer and metabolic processes can be achieved. At the same time, it has strong adaptability and can process a variety of organic wastes to achieve resource utilization. In addition, the closed operation of the reaction system effectively reduces the generation of odor and secondary pollution; combined with the automated control of feeding and discharging, the operational stability and operating efficiency can be further improved, providing good scalability for large-scale applications. The overall process is both economical and environmentally friendly, and has broad application prospects in the fields of energy recovery and pollution control.

[0025] The process of the present invention utilizes ferrocene to stimulate a Fenton-like reaction to produce highly active free radicals, which significantly enhances sludge hydrolysis and is highly efficient and environmentally friendly. From the perspective of the Fenton reaction, ferrocene can be recycled as a catalyst. The traditional Fenton reaction is limited to pH (the traditional method has a pH value of 3-4). Free radicals are efficiently produced within a loose elastic pH range (pH of 3-5), which helps to reduce acid consumption. From the perspective of sludge hydrolysis, the strong oxidizing property of free radicals can destroy the sludge structure, release more soluble organic matter, and break through the bottleneck of hydrolysis rate. Through this stage, the available substrate in the sludge supernatant increases by 3.77 times (in terms of COD), significantly improving the decomposition efficiency of difficult-to-degrade organic matter. The overall process is simple to operate, highly adaptable, and synergistic with biological processes, providing an innovative solution for sludge resource utilization.

[0026] The process of this invention offers multiple advantages for carbon chain extension by flexibly adjusting the morphological transformation of ferrocene, particularly the use of liquid ferrocene. Liquid ferrocene can regulate the utilization of ethanol in the reaction, effectively reducing its consumption in the side reaction of ethanol overoxidation, with an inhibition rate of up to 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the process of the present invention;

[0028] Figure 2 This is a graph showing changes in the synthesis of medium-chain fatty acids in Comparative Example 1 of the present invention;

[0029] Figure 3 This is a graph showing changes in the synthesis of medium-chain fatty acids in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] Further description will be made to the present application in combination with the drawings and specific embodiments, and it should be noted that the embodiments described below or the technical features between the embodiments can be combined to form new embodiments without conflict. Except for the special description, the materials and equipment used in the embodiments can be purchased from the market.

[0031] Please refer to Figure 1 The first aspect of the present application provides a process for promoting sludge hydrolysis and synthesis of medium-chain fatty acids by using ferrocene, comprising the following steps:

[0032] S10, adding ferrocene to the sludge and adjusting the pH to 3.0-5.0;

[0033] S20, adding hydrogen peroxide for Fenton-like reaction; wherein the ferrocene undergoes solid-liquid form transformation to form ferrocene cation during the reaction;

[0034] S30, adding ethanol, anaerobic seed sludge and culture medium for anaerobic fermentation and carbon chain extension;

[0035] The ferrocene in step S10 generates hydroxyl radicals to destroy sludge flocs and cell wall membranes in the Fenton-like reaction in step S20;

[0036] The liquid ferrocene cation converted in step S20 acts as an electron mediator to improve the efficiency of electron transfer in step S30;

[0037] The liquid ferrocene cation simultaneously inhibits ethanol oxidation and methanogenesis.

[0038] On the basis of the above scheme, the present application realizes the enhancement of sludge hydrolysis and the directional regulation of medium-chain fatty acid synthesis by regulating the form transformation of ferrocene. Specifically, by adding ferrocene and hydrogen peroxide to form a Fenton-like reaction, hydroxyl radicals (see formula 1) attack sludge flocs and cell wall membranes to improve sludge biodegradability. After the reaction, solid ferrocene is converted into liquid ferrocene cation, and the coexisting ferrocene and its cation in the system act as an electron mediator to improve the efficiency of electron transfer in the system and increase the interaction between bacterial populations. Finally, the liquid ferrocene cation has the effect of inhibiting ethanol oxidation and methanogenesis, and can optimize the utilization of substrate ethanol and short-chain fatty acids during carbon chain extension (see formula 2), thereby improving the reaction efficiency of ethanol and short-chain fatty acids from sludge fermentation and directional strengthening of medium-chain fatty acid synthesis.

[0039] Formula 1: Fc (ferrocene) + H2O2→ Fc + (ferrocene cation) + OH - +·OH (hydroxyl radical).

[0040] Formula 2: 5C n H2n-1 O2 - +6CH3CH2OH→5C n+2 H 2n+3 O2 - +CH3COO - +4H2O+H + +2H2.

[0041] As a preferred embodiment, in step S10, the amount of ferrocene added is 2-5 g / L. When the amount is higher than 5 g / L, the production of medium-chain fatty acids is saturated and the bioactivity of the ferrocene cation after conversion has an inhibitory effect.

[0042] As a preferred embodiment, in step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5-2):1.

[0043] As a preferred embodiment, in step S20, the pH of the system after the reaction spontaneously rises to 4.5-5.5, which is the suitable pH range for the carbon chain extension process.

[0044] As a preferred embodiment, in step S30, the amount of ethanol added is 90-150 mM.

[0045] In the first aspect of the present application, as an optional embodiment, in step S30, the anaerobic seed sludge is an activated sludge that has been subjected to a domestication process, wherein the domestication process comprises the following steps: taking sludge from a sewage treatment plant, heating at 100-110°C for 25-35 min to kill methanogens, and then placing in an anaerobic environment, with a sludge retention time of 25-35 d; the inoculation amount of the anaerobic seed sludge is 5-15% of the volume of the system.

[0046] In the first aspect of the present application, as an optional embodiment, in step S30, the domestication process comprises the following steps: taking sludge from a sewage treatment plant, heating at 105°C for 30 min, and then maintaining in an anaerobic environment, with a sludge retention time of 30 d.

[0047] In the first aspect of the present invention, as an optional embodiment, the culture medium comprises the following substances: 5.04g / L NaHCO3, 3.6g / L NH4H2PO4, 0.33g / L MgCl2·6H2O, 0.2g / L CaCl2·2H2O, 0.2g / LMgSO4·7H2O, 0.15g / L KCl, 0.5mg / L MnCl2·4H2O, 0.05mg / L H3BO3, 0.05mg / LZnCl2, 0.03mg / L CuCl2, 0.01mg / L Na2MoO4·2H2O, 1mg / L CoCl2·6H2O, 0.1mg / L NiCl2·6H2O, 0.05mg / L Na2SeO3, 0.106mg / L biotin, 0.005mg / L folic acid, 0.0025mg / L pyridoxal hydrochloride, 0.266mg / L vitamin B1, 0.0125mg / L vitamin B2, 0.413mg / L Ca-D-pantothenic acid, 0.0125mg / L vitamin B12, 0.0125mg / L p-aminobenzoic acid, 0.0125mg / L niacin, 0.015mg / L lipoic acid.

[0048] As a preferred embodiment, in step S30, the reaction time is 12-20 days.

[0049] As a preferred embodiment, the process is continuously implemented in a single reactor. First, municipal excess sludge is collected into the reactor. After completing steps S10 and S20 in sequence, the reactor is sealed to form an anaerobic fermentation reactor, which is placed in a constant temperature shaking incubator at 35±2°C to complete step S30.

[0050] As a preferred embodiment, the oscillation frequency of the constant temperature oscillating shaker is controlled to be set to 120-180 rpm.

[0051] As a preferred embodiment, after the reaction in step S30 is completed, the process further includes S40: centrifuging the supernatant to collect the fermentation liquid containing medium-chain fatty acids, which is a high-value resource recovery product.

[0052] The following are some embodiments listed in this application, and the application is further illustrated by the following embodiments.

[0053] Example 1:

[0054] Reactor configuration: anaerobic fermentation tank, equipped with pH probe and automatic dosing system.

[0055] A process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene comprises the following steps:

[0056] S10, municipal sludge (containing solid rate TS = 5%) is taken to an anaerobic fermentation tank, 5 g / L of ferrocene is added to the sludge and the pH is adjusted to 4.0;

[0057] S20, hydrogen peroxide is added to carry out a Fenton-like reaction, the molar ratio of the hydrogen peroxide to the iron in the ferrocene is 1.5:1; the Fenton-like reaction is completed within 10 minutes, and the pH of the system spontaneously rises to 5 after the reaction;

[0058] S30, the reactor is sealed to form an anaerobic fermentation reactor, placed in a constant temperature shaking incubator at 35°C, and ethanol, anaerobic seed sludge and culture medium are added for anaerobic fermentation and carbon chain extension, and the fermentation time is 15 days;

[0059] Among them, the ethanol addition amount is 120 mM; the shaking frequency of the constant temperature shaking incubator is set to 150 rpm.

[0060] Among them, the anaerobic seed sludge is a kind of activated sludge after domestication treatment, the steps of the domestication treatment are: taking sludge from a sewage treatment plant, heating at 105°C for 30 min, and then keeping in an anaerobic environment, the sludge retention time is 30d; the inoculation amount of the anaerobic seed sludge is 10% of the system volume.

[0061] The culture medium comprises the following substances: 5.04 g / L NaHCO3, 3.6 g / L NH4H2PO4, 0.33 g / L MgCl2·6H2O, 0.2 g / L CaCl2·2H2O, 0.2 g / L MgSO4·7H2O, 0.15 g / L KCl, 0.5 mg / L MnCl2·4H2O, 0.05 mg / L H3BO3, 0.05 mg / L ZnCl2, 0.03 mg / L CuCl2, 0.01 mg / L Na2MoO4·2H2O, 1 mg / L CoCl2·6H2O, 0.1 mg / L NiCl2·6H2O, 0.05 mg / L Na2SeO3, 0.106 mg / L biotin, 0.005 mg / L folic acid, 0.0025 mg / L pyridoxal hydrochloride, 0.266 mg / L vitamin B1, 0.0125 mg / L vitamin B2, 0.413 mg / L Ca-D-pantothenic acid, 0.0125 mg / L vitamin B12, 0.0125 mg / L p-aminobenzoic acid, 0.0125 mg / L nicotinic acid, 0.015 mg / L lipoic acid.

[0062] S40, centrifugal separation of supernatant, collection of fermentation broth containing medium-chain fatty acids, i.e. high-value resource recovery products.

[0063] The related data in the process of the above embodiment 1 are detected, as follows:

[0064] Bioactivity inhibition rate (%): 0;

[0065] Sludge COD release amount (gCOD / L): 3.27;

[0066] Medium-chain fatty acid production (gCOD / L): 5.72;

[0067] Medium-chain fatty acid recovery rate in fermentation liquor (%): 42.75.

[0068] On the basis of the above-mentioned embodiment 1, the influence of different ferrocene concentrations on the medium-chain fatty acid production, the medium-chain fatty acid recovery rate in fermentation liquor, and the bioactivity inhibition rate was further explored. In the process, different ferrocene concentrations were set, but other conditions remained consistent with embodiment 1. The specific data are as follows in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] As can be seen from Table 1, when the ferrocene dosage is 2-5 g / L, higher medium-chain fatty acid production and recovery rate are obtained, which is because the use of ferrocene to stimulate the Fenton-like reaction promotes sludge hydrolysis and serves as an electron mediator to direct the synthesis of medium-chain fatty acids. When the dosage is lower than 2 g / L, the free radical excitation effect is weak, which is difficult to promote sludge hydrolysis, resulting in less medium-chain fatty acid synthesis substrate; when it is higher than 5 g / L, a large amount of soluble ferrocene cations are produced by the ferrocene-based Fenton reaction, and the sludge microbial activity is inhibited in the ferrocene cation environment, reducing the energy metabolism rate, which leads to the synthesis of medium-chain fatty acids being blocked.

[0073] On the basis of the above-mentioned embodiment 1, the influence of different ferrocene concentrations on the medium-chain fatty acid production, the medium-chain fatty acid recovery rate in fermentation liquor, and the bioactivity inhibition rate was further explored. In the process, different ferrocene concentrations were set, but other conditions remained consistent with embodiment 1. The specific data are as follows in Table 1.

[0074] Table 2

[0075]

[0076]

[0077] As can be seen in Table 2 above, when the pH range is 3-5, higher sludge COD release, medium-chain fatty acid production, and recovery rates are achieved. This is due to the advanced oxidation effect within this range, which promotes sludge lysis and hydrolysis by stimulating free radicals. Traditional Fenton processes generally have significant effects within the pH range of 3-4, while the pH range of ferrocenyl Fenton reactions is milder and more flexible, which can reduce the acid cost of the process. When the pH is greater than 5, the advanced oxidation effect does not occur, only the oxidation effect of hydrogen peroxide occurs, and the ferrocene morphology does not change, making it difficult to exert the role of directional regulation of medium-chain fatty acid synthesis, resulting in a lower product recovery rate.

[0078] Based on Example 1, the effects of different molar ratios of hydrogen peroxide to iron in ferrocene on sludge COD release, medium-chain fatty acid production, and medium-chain fatty acid recovery in the fermentation broth were further investigated. Different pH values ​​were set during the process, but other conditions remained consistent with those in Example 1. Specific data are shown in Table 3.

[0079] Table 3

[0080]

[0081] As shown in Table 3 above, when the molar ratio of hydrogen peroxide to ferrocene iron is between 1-2:1, an advanced oxidation reaction occurs, promoting COD release in sludge. When the molar ratio of hydrogen peroxide to ferrocene iron is between 1.5-2:1, COD release and medium-chain fatty acid production are even more significant, with a medium-chain fatty acid recovery rate exceeding 40%. When the ratio is below 1.5:1, hydrogen peroxide is insufficient to stimulate the Fenton-like reaction of the ferrocene group, thus hindering medium-chain fatty acid synthesis.

[0082] Example 2:

[0083] Example 2 provides a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene. The difference between Example 2 and Example 1 is that the solid content TS of the municipal sludge is 3%, and other conditions remain the same as those of Example 1.

[0084] Comparative Example 1:

[0085] On the basis of the above-mentioned Example 2, Comparative Example 1 further explored the case where no ferrocene was added, that is, step S10 and S10: sludge hydrolysis and medium-chain fatty acid synthesis process-related operations based on ferrocene regulation were not adopted; step S30: anaerobic fermentation and addition of ethanol for carbon chain extension were directly performed, and other conditions remained the same as in Example 2.

[0086] By the end of the reaction, the COD of the fermentation liquid of Comparative Example 1 increased by 0.91 gCOD / L, and that of Example 2 increased by 3.43 gCOD / L, which was 3.77 times that of Comparative Example 1, indicating that ferrocene stimulated the Fenton-like reaction to promote the release of COD from sludge.

[0087] Reference Figures 2-3 In Comparative Example 1, as the reaction proceeds to the 10th day, acetic acid gradually accumulates to 1.80gCOD / L. This is the result of excessive oxidation of ethanol into acetic acid, which results in a large amount of ethanol being unable to be directed for the synthesis of medium-chain fatty acids. The reaction then reaches a steady state, with a medium-chain fatty acid output of 2.35gCOD / L and a recovery rate of 17.72%. Hexanoic acid is the main medium-chain fatty acid, with an output of 1.11gCOD / L, accounting for 47.05% of medium-chain fatty acids. In Example 2, the accumulation of acetic acid was not significantly observed in the first 10 days of the reaction, and the ethanol excessive oxidation inhibition rate was 50%. The medium-chain fatty acid output was 4.47gCOD / L, 1.90 times that of Comparative Example 1, and the recovery rate was 28.48%. Hexanoic acid is the main medium-chain fatty acid, with an output of 4.13gCOD / L, 3.72 times that of Comparative Example 1, accounting for 92.55% of medium-chain fatty acids.

[0088] In summary, the sludge hydrolysis and medium-chain fatty acid synthesis process based on ferrocene regulation promoted the release of sludge COD and the efficient and directional synthesis of medium-chain fatty acids (especially hexanoic acid).

[0089] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by those skilled in the art on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising the following steps: S10, adding ferrocene to the sludge and adjusting the pH to 3.0-5.0; S20, adding hydrogen peroxide to perform a Fenton-like reaction to promote sludge hydrolysis; wherein the ferrocene undergoes a solid-liquid phase transition to form a ferrocene cation during the reaction; S30, adding ethanol, anaerobic seed mud and culture medium to perform anaerobic fermentation and carbon chain extension; The ferrocene in step S10 generates hydroxyl radicals in the Fenton-like reaction in step S20, which destroy the sludge flocs and cell wall membranes; The liquid ferrocenium cation converted in step S20 is used as an electron mediator in step S30 to improve the electron transfer efficiency; The liquid ferrocenium cation inhibits both ethanol oxidation and methanogenesis processes.

2. The process according to claim 1, wherein The added amount of ferrocene is 2-5 g / L.

3. The process according to claim 1, wherein In step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5-2):

1.

4. The process according to claim 1, wherein In step S20, after the reaction, the pH of the system spontaneously rises to 4.5-5.5, which is the pH range suitable for carbon chain extension.

5. The process according to claim 1, wherein In step S30, the amount of ethanol added is 90-150 mM.

6. The process according to claim 1, wherein In step S30, the anaerobic seed sludge is an activated sludge that has been acclimated. The acclimation treatment steps are as follows: taking sludge from a sewage treatment plant, heating it at 100-110°C for 25-35 minutes to kill methanogens, and then placing it in an anaerobic environment with a sludge retention time of 25-35 days; the inoculation amount of the anaerobic seed sludge is 5-15% of the system volume.

7. The process according to claim 1, wherein In step S30, the reaction time is 12-20 days.

8. The process according to claim 1, wherein The process is continuously implemented in a single reactor. First, municipal excess sludge is collected into the reactor. After completing steps S10 and S20 in sequence, the reactor is sealed to form an anaerobic fermentation reactor, which is placed in a constant temperature shaking incubator at 35±2°C to complete step S30. The shaking frequency of the constant temperature shaking incubator is controlled to be set to 120-180 rpm.

9. The process according to claim 1, wherein After the reaction in step S30 is completed, the process further includes S40: centrifuging the supernatant to collect the fermentation liquid containing medium-chain fatty acids, which is a high-value resource recovery product.

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