Sludge energy utilization and efficient degradation method of persistent organic pollutants
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGBO UNIV
- Filing Date
- 2026-04-24
- Publication Date
- 2026-06-16
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solid waste treatment and resource utilization technology, specifically to methods for the energy utilization of sludge and the efficient degradation of persistent organic pollutants. Background Technology
[0002] The large amount of sludge generated during wastewater treatment contains abundant organic matter, pathogens, and persistent organic pollutants, and its treatment and disposal has long been a technical challenge in the field of environmental protection.
[0003] Among existing sludge treatment technologies, biological treatment technologies, such as anaerobic digestion, have long treatment cycles, limited volume reduction effects, and are difficult to effectively degrade structurally stable persistent organic pollutants. While thermochemical technologies such as incineration and pyrolysis can achieve rapid sludge reduction, their prerequisite is that the sludge must undergo energy-intensive deep dewatering and thermal drying, resulting in huge energy inputs and poor economic efficiency. Furthermore, incineration or pyrolysis processes do not completely destroy persistent organic pollutants, and there is a possibility of generating other toxic and harmful byproducts.
[0004] Hydrothermal liquefaction technology can directly treat wet sludge with high water content without pre-drying, utilizing the unique properties of water in subcritical or supercritical states to promote the decomposition of organic matter in the sludge. However, traditional hydrothermal liquefaction processes still have shortcomings in the conversion efficiency of organic matter into high-value products such as biomass oil, and the degradation of structurally stable persistent organic pollutants in sludge is incomplete, leading to their redistribution in the final product and limiting the application of this technology. Therefore, developing a technology that can achieve efficient energy conversion of organic matter in wet sludge and complete degradation of persistent organic pollutants in one step under mild conditions is of great significance. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for the energy utilization of sludge and the efficient degradation of persistent organic pollutants, solving the problems of low resource recovery rate, high energy consumption, and ineffective removal of persistent organic pollutants in existing sludge treatment technologies.
[0006] To achieve the above objectives, the present invention provides a method for the energy utilization of sludge and the efficient degradation of persistent organic pollutants. This method introduces specific additives during the hydrothermal liquefaction process to simultaneously realize the energy conversion of wet sludge and the degradation of persistent organic pollutants therein.
[0007] The technical solution provided by this invention is as follows: A method for the energy utilization of sludge and the efficient degradation of persistent organic pollutants includes the following steps: S1. Wet sludge containing persistent organic pollutants is mixed with a eutectic solvent to obtain a reaction mixture. The wet sludge has a solids content of 0.5-30 wt%, and the eutectic solvent consists of hydrogen bond acceptors and hydrogen bond donors. The amount of the eutectic solvent added is 0.1-20 wt% of the total volume of the wet sludge. S2. Place the reaction mixture obtained in step S1 into a reaction vessel and carry out a hydrothermal liquefaction reaction at a reaction temperature of 150-370℃ and autogenous pressure for a reaction time of more than 5 minutes. S3. After the reaction is complete, the products are separated to obtain biomass oil, aqueous phase, solid phase and gaseous phase products.
[0008] In the technical solution provided by this invention, water serves as both the reaction medium and reactant in a subcritical or near-critical state. Under hydrothermal conditions, macromolecular organic matter in the sludge first undergoes hydrolysis, decomposing into smaller monomeric substances such as amino acids and monosaccharides. Subsequently, these monomeric substances undergo a series of reactions, including deamination, decarboxylation, and pyrolysis, transforming into active intermediates. Finally, these active intermediate fragments undergo condensation and recombination reactions to form a hydrophobic biomass oil composed of compounds such as alkanes and esters.
[0009] During this hydrothermal liquefaction process, reactive substances such as singlet oxygen, hydrated electrons, and hydroxyl radicals are generated within the system. These reactive substances can attack the chemical bonds in persistent organic pollutant molecules, causing their structure to break and thus achieving degradation.
[0010] The eutectic solvent added in this invention plays the following roles in this process: First, the eutectic solvent interacts with extracellular polymers and persistent organic pollutants in the sludge, which helps in the dissolution, transformation, and redistribution of persistent organic pollutants in the sludge; Second, the eutectic solvent can provide active protons to catalyze the generation of active substances in the hydrothermal process, thereby affecting the transformation of organic matter and the degradation of persistent organic pollutants; Third, the eutectic solvent changes the occurrence state of persistent organic pollutants bound to macromolecular organic matter by affecting the hydrothermal transformation behavior of macromolecular organic matter in the sludge, which helps in their degradation.
[0011] In some specific embodiments, the wet sludge is municipal sludge or industrial organic sludge.
[0012] In some specific embodiments, the solids content of the wet sludge is 3-20 wt%, specifically 3 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%.
[0013] In some specific embodiments, the reaction temperature is 250-350℃, specifically 250℃, 280℃, 310℃, or 350℃.
[0014] In some specific implementations, the reaction time is 60 minutes or more.
[0015] In some specific embodiments, the amount of the eutectic solvent added is 0.1-20% of the total volume of the wet sludge, preferably 3-7% of the total volume of the wet sludge.
[0016] In some specific embodiments, the hydrogen bond acceptor is selected from one or more of choline chloride, choline bromide, betaine, and tributylphosphine oxide; the hydrogen bond donor is selected from one or more of zinc chloride, urea, ethylene glycol, lactic acid, malic acid, oxalic acid, glutaric acid, and 2-methylpiperazine.
[0017] In a preferred embodiment, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is selected from lactic acid, malic acid, oxalic acid, and glutaric acid.
[0018] In a more specific embodiment, the eutectic solvent is a combination of choline chloride and oxalic acid.
[0019] In some embodiments, the eutectic solvent is prepared by the following steps: mixing the hydrogen bond acceptor and the hydrogen bond donor in a preset molar ratio, stirring and heating at 60-100°C for 1-4 hours until a homogeneous and clear liquid is formed.
[0020] This invention provides a method for the energy utilization of sludge and the efficient degradation of persistent organic pollutants. It has the following beneficial effects: 1. In the reaction step, this invention completes the degradation of persistent organic pollutants in sludge and the energy conversion of sludge organic matter into biomass oil. By introducing a low eutectic solvent during the hydrothermal liquefaction process, it not only promotes the generation of active substances in the system to break the chemical bonds of pollutants, but also directly acts on the conversion pathway of sludge organic matter, thereby integrating the two target processes of pollutant removal and energy recovery into one.
[0021] 2. The eutectic solvent added in this invention can effectively deconstruct the complex structure of macromolecular organic matter in sludge. This deconstruction reduces the degree of polymerization of organic matter, making it easier for it to undergo hydrolysis and subsequent conversion reactions under hydrothermal conditions. This improves the conversion efficiency of solid organic matter to liquid biomass oil and enhances the energy recovery value of sludge.
[0022] 3. This invention directly uses wet sludge with a solid content as low as 0.5% as the raw material for treatment, without the need for energy-intensive pre-drying treatment. Unlike methods such as pyrolysis and gasification that require the use of dried materials, this method transforms the large amount of water present in the sludge into a reaction medium and solvent, thus eliminating the need for a separate drying unit and the corresponding energy consumption, significantly simplifying the process and reducing the system operating cost. Attached Figure Description
[0023] Figure 1 The degradation rate (C) of perfluorobutane sulfonic acid (PFBS) in pure water after hydrothermal liquefaction with different eutectic solvents (DES) and its single-component degradation rate (C) PFBS =0.176ppm, DES dosage =5%, reaction temperature =340℃, reaction time =60min);
[0024] Figure 2 The degradation rate (C) of PFBS in pure water after hydrothermal liquefaction with the addition of choline chloride and oxalic acid (ChCl + OA) at different time points was measured. PFBS =0.176ppm, ChCl+OA dosage =5%, reaction temperature =340℃, reaction time =30, 60, 90, 210, 360min). Figure 3 The defluorination rate (C) of PFBS in pure water after adding different DES and hydrothermal liquefaction of its single components was measured. PFBS =1.76ppm, DES dosage =5%, reaction temperature =340℃, reaction time =60min). Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] Example: Example 1 This embodiment provides a method for hydrothermal liquefaction of sludge using a eutectic solvent, the specific steps of which are as follows: S1. Take municipal wet sludge with an initial solids content of 8.5%, without adjusting the solids content. Weigh 500g of this wet sludge sample. Separately, weigh 2.125g of a pre-prepared eutectic solvent of choline chloride-oxalic acid (ChCl+OA, molar ratio 1:1), which is equivalent to 5% (w / w) of the dry weight of the sludge. Add the eutectic solvent to the wet sludge and mechanically stir at room temperature for 20 minutes to obtain a homogeneous reaction mixture. S2. Transfer the reaction mixture obtained in step S1 to a 1L high-pressure reactor. After sealing, purge and replace the reactor three times with nitrogen to remove all internal air. Start the temperature program and heat the reactor to 340°C. Once the set temperature is reached, start timing and maintain the temperature for 60 minutes. The pressure during the reaction is the system's autogenous pressure. S3. After the reaction is complete, the reactor is forcibly cooled to room temperature using cooling water. After opening the reactor, the product inside is vacuum filtered to separate the solid phase and the liquid phase. The liquid phase is extracted with dichloromethane, and the organic phase is subjected to rotary evaporation to remove the solvent, yielding the oil phase product.
[0027] Example 2 This embodiment provides a method for hydrothermal liquefaction of sludge using a eutectic solvent, the specific steps of which are as follows: S1. Weigh 500g of municipal wet sludge with an initial solids content of 8.5%. Separately weigh 0.425g of a pre-prepared eutectic solvent of choline chloride and oxalic acid (ChCl+OA, molar ratio 1:1), which is equivalent to 1% (w / w) of the dry weight of the sludge. Add the eutectic solvent to the wet sludge and mechanically stir at room temperature for 20 minutes to obtain a homogeneous reaction mixture.
[0028] S2. Transfer the reaction mixture obtained in step S1 to a 1L high-pressure reactor. After sealing, purge and replace the reactor three times with nitrogen. Start the temperature program to heat the reactor to 260°C. Once the set temperature is reached, start timing and maintain the temperature for 30 minutes. The pressure during the reaction is the system's autogenous pressure.
[0029] S3. After the reaction is complete, the reactor is forcibly cooled to room temperature using cooling water. The subsequent product separation steps are the same as step S3 described in Example 1.
[0030] Example 3 This embodiment provides a method for hydrothermal liquefaction of sludge using different types of eutectic solvents, the specific steps of which are as follows: S1. Weigh 500g of municipal wet sludge with an initial solids content of 8.5%. Separately weigh 4.25g of a pre-prepared eutectic solvent of choline chloride and lactic acid (ChCl+LA, molar ratio 1:1), which is equivalent to 10% (w / w) of the dry weight of the sludge. Add the eutectic solvent to the wet sludge and mechanically stir at room temperature for 20 minutes to obtain a homogeneous reaction mixture.
[0031] S2. Transfer the reaction mixture obtained in step S1 to a 1L high-pressure reactor. After sealing, purge and replace the reactor three times with nitrogen. Start the temperature program to heat the reactor to 340°C. Once the set temperature is reached, start timing and maintain the temperature for 120 minutes. The pressure during the reaction is the system's autogenous pressure.
[0032] S3. After the reaction is complete, the reactor is forcibly cooled to room temperature using cooling water. The subsequent product separation steps are the same as step S3 described in Example 1.
[0033] Comparative example: Comparative Example 1 Compared with Example 1, the difference is that no eutectic solvent is added in step S1, while the other steps and parameters are the same.
[0034] Comparative Example 2 Compared with Example 1, the difference is that the hydrothermal liquefaction reaction temperature in step S2 is 130°C, while the other steps and parameters are the same.
[0035] Comparative Example 3 Compared with Example 1, the difference is that in step S1, instead of adding a choline chloride-oxalic acid eutectic solvent, an equal mass of solid choline chloride is added. The remaining steps and parameters are the same.
[0036] Comparative Example 4 Compared with Example 1, the difference is that in step S1, instead of adding the choline chloride-oxalic acid eutectic solvent, an oxalic acid solid of equal mass to the eutectic solvent is added. The remaining steps and parameters are the same. Test example: Test Example 1: Determination of Biomass Oil Yield Experimental steps After the hydrothermal liquefaction reaction in Examples 1-3 and Comparative Examples 1-4 was completed, all product mixtures were taken out of the reactor and separated into solid and liquid phases by vacuum filtration to obtain solid products and liquid phases.
[0037] Transfer the liquid phase to a separatory funnel, add 100 mL of dichloromethane as the extraction solvent, shake for 5 minutes, and allow to stand for separation. Collect the lower organic phase, and repeat this extraction operation twice for the upper aqueous phase, adding 100 mL of dichloromethane each time. Combine all collected organic phases (i.e., the dichloromethane phase).
[0038] The combined organic phases were transferred to a rotary evaporator and subjected to vacuum distillation at a water bath temperature of 40°C and a vacuum degree of -0.08 MPa until no more dichloromethane was distilled off. The remaining viscous oil phase was the biomass oil.
[0039] The obtained biomass oil was weighed using an electronic balance with an accuracy of 0.1 mg, and its mass was recorded. Based on the initial dry basis mass of the added sludge, the biomass oil yield was calculated using the following formula: Biomass oil yield (%) = (Mass of biomass oil obtained / Initial sludge dry basis mass) × 100% Experimental data Table 1: Biomass oil yield test results of each embodiment and comparative example Results Explanation The data in Table 1 show that the biomass oil yields of Examples 1 and 3 are both higher than those of Comparative Example 1. The only difference between Comparative Example 1 and Example 1 is the absence of a eutectic solvent, indicating that the introduction of a eutectic solvent composed of hydrogen bond acceptors and hydrogen bond donors into the hydrothermal liquefaction reaction system is a factor affecting the final biomass oil yield.
[0040] Comparing the results of Example 1 with Comparative Examples 3 and 4, the biomass oil yield was lower when either choline chloride or oxalic acid was added alone compared to the eutectic solvent system composed of both. This phenomenon indicates that the eutectic system formed by hydrogen bond acceptors and hydrogen bond donors, rather than a single component, plays a role in the liquefaction and conversion process of sludge organic matter. This system facilitates the deconstruction and dissolution of large organic molecules such as cellulose and proteins in the sludge, reducing their degree of polymerization under hydrothermal conditions, thereby providing more small molecule precursors for subsequent dehydration, decarboxylation, and cyclization reactions to generate biomass oil.
[0041] The results of Examples 1, 2, and 3 show that the method can produce biomass oil within a temperature range of 260-340℃. Data from Comparative Example 2, however, shows that no biomass oil is produced at reaction temperatures below 150℃, even with the addition of a eutectic solvent. This indicates that a sufficient reaction temperature is necessary for the hydrolysis and pyrolysis of sludge organic matter, ultimately converting it into biomass oil, and the eutectic solvent plays a role in the conversion process within this temperature range. Furthermore, sludge systems generally require temperatures above 240℃ to produce oil; the addition of a eutectic solvent lowers the lower limit of the oil-producing temperature to approximately 180-200℃.
[0042] Test Example 2: Determination of the Degradation Rate of Persistent Organic Pollutants Experimental steps After step S3 in Examples 1-3 and Comparative Examples 1-4, PFBS was purified or extracted from the aqueous, oil, and solid phase products.
[0043] ① Aqueous phase product: PFBS isotope internal standard and a certain volume of methanol were added to the aqueous phase product, and purification was performed using an ENVI-Carb non-porous graphitized carbon column with a 0.22 μL filter. The sample was filtered using a polyethersulfone syringe filter to obtain the test sample. ② Oil phase product: PFBS isotope internal standard was added to the oil phase product, followed by equal volumes of dichloromethane and alkaline methanol (a 1:1 volume ratio of 0.5% ammonia solution and methanol), followed by shaking and centrifugation. The supernatant was diluted and passed through an ENVI-Carb column using a 0.22... The sample was filtered using a polyethersulfone needle filter to obtain the test sample. ③ Solid product: PFBS isotope internal standard was added to the solid product and shaken for 24 h. Then, a methanol solution containing 1% ammonia was added, followed by sonication and centrifugation, and the supernatant was collected. After three repeated extractions, the extracts were combined and evaporated to dryness under nitrogen. After reconstitution, the solution was passed through an ENVI-Carb column and subjected to 0.22... The sample to be tested was obtained by filtering with a polyethersulfone needle filter.
[0044] The final concentration of PFBS in the sample was quantitatively analyzed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS). Chromatographic conditions were: C18 column (2.1 mm × 100 mm, 1.7 μm). Mobile phase A was 5 mmol / L ammonium acetate aqueous solution, and mobile phase B was methanol; a gradient elution program was used; the column temperature was 40℃; and the injection volume was 5 μL / L. The mass spectrometry conditions were as follows: negative ion mode using an electrospray ionization source, with multiple reaction monitoring (MRM).
[0045] The concentration of PFBS in the sample was calculated by comparing it with a standard curve prepared using PFBS standards. Based on the concentrations before and after the reaction, the degradation rate of PFBS was calculated using the following formula: PFBS degradation rate (%) = (1 - PFBS content in the three-phase products / initial PFBS content in the sludge) × 100%.
[0046] Experimental data Table 2: PFBS degradation rate test results of each example and comparative example Results Explanation The data in Table 2 show that the PFBS degradation rate of Example 1 was significantly higher than that of Comparative Example 1. The only difference between Comparative Example 1 and Example 1 was that no components were added to the reaction system. This result indicates that, under hydrothermal conditions at 340°C, the introduction of a choline chloride-oxalic acid eutectic solvent is a key factor affecting the PFBS degradation efficiency. The eutectic solvent can provide protons and promote the formation of active substances in a hydrothermal environment. These active substances can attack the stable carbon-fluorine bonds in the PFBS molecule, thereby causing its structural destruction.
[0047] Comparing the results of Example 1 with Comparative Examples 3 and 4, the degradation rate of PFBS was significantly higher in the eutectic solvent system than in systems containing only choline chloride or only oxalic acid. This phenomenon indicates that the eutectic system formed by hydrogen bond acceptors and hydrogen bond donors through hydrogen bonding, rather than its single component, provides a more efficient reaction environment for PFBS degradation. The hydrogen bond donor provides the key acidic sites and protons, and proton catalysis is one of the main mechanisms promoting the breaking of chemical bonds in PFBS.
[0048] A comparison of the data from Examples 1 and 2 with Comparative Example 2 shows that reaction temperature is a necessary condition for PFBS degradation. Under the low-temperature conditions (130°C) of Comparative Example 2, even with the presence of a eutectic solvent, the degradation rate of PFBS remained extremely low. This indicates that the degradation reaction of PFBS requires reaching a certain energy input threshold. The role of the eutectic solvent is to influence the pathway and efficiency of the degradation reaction under the condition of reaching this temperature threshold. Furthermore, a comparison of the results from Examples 1 and 3 shows that different types of eutectic solvents and their dosages also affect the final degradation rate of PFBS.
[0049] Reference Appendix Figure 1 Test column 3: Experimental steps: The initial concentration of PFBS in pure water was 0.176 ppm. Under conditions of 5% DES addition and single-component treatment, the degradation rate of PFBS in pure water after hydrothermal liquefaction at 340℃ for 60 min was as follows: The control group without any additives showed the lowest PFBS degradation rate, only 4.39%, indicating that the degradation effect of PFBS under hydrothermal liquefaction conditions was poor without any solvent. After adding choline chloride (ChCl), the PFBS degradation rate significantly increased to 61.96%, suggesting that ChCl, as a hydrogen bond acceptor of DES, may interact with functional groups or chemical bonds in PFBS, leading to incomplete degradation. The PFBS degradation rate was significantly improved after adding different amounts of DES.
[0050] The degradation rate of PFBS was similar to that of the control group (4.31%) after adding only lactic acid (LA) via hydrothermal treatment. However, the degradation rate of PFBS significantly increased to 76.88% after adding ChCl and LA via hydrothermal treatment. This indicates that the combined effect of LA and ChCl or the synergistic effect of hydrogen bonds between them promotes the hydrolysis of PFBS. The degradation rate of PFBS was slightly higher than that of LA (12.27%) after adding only malic acid (MA) via hydrothermal treatment. Compared with the control group, the degradation rate of PFBS was improved to a certain extent, indicating that malic acid alone has a certain promoting effect on the hydrothermal degradation of PFBS. However, the degradation rate of PFBS reached 74.23% after adding ChCl and MA via hydrothermal treatment. The degradation effect was significantly better than that of MA alone. This also indicates that the combined effect of MA and ChCl or the synergistic effect of hydrogen bonds between them promotes the degradation of PFBS.
[0051] The degradation rate reached 24.71% after adding only oxalic acid OA, which is the best among all single-component organic acids. This may be because the strong acid environment of OA itself promotes the degradation of PFBS. After adding ChCl+OA hydrothermally, the degradation rate of PFBS was the highest, at 78.36%. Studies have shown that DES with high α and dicarboxylic acid DES have better H proton generation ability, and proton-catalyzed bond cleavage is one of the main mechanisms of DES action.
[0052] Therefore, the dicarboxylic acid type ChCl+OA, with its stronger proton-donating ability, may thermally decompose to generate a large number of H radicals, and its low pH can provide a strongly acidic environment for PFBS degradation, thus promoting PFBS degradation. After adding the single component glutaric acid (GA), the PFBS degradation rate was only 15.43%, and after hydrothermal treatment with ChCl+GA, the degradation rate was only 60.34%. Studies show that increasing the carbon chain length hinders the ability of DES to contribute H protons in the solute solvent. Therefore, it is possible that due to the excessively long carbon chain length and low α value of glutaric acid, its ability to generate hydrogen protons is poor, and its large molecular structure and steric hindrance limit its contact with PFBS, resulting in the lowest degradation efficiency among the four types of DES.
[0053] In summary, ChCl+OA exhibits the strongest proton-donating capacity and acidity, providing an acidic hydrothermal environment and abundant H+ ions for PFBS. Proton catalysis promotes the breaking of chemical bonds in PFBS and may lead to redox reactions. Furthermore, given the good degradation effect of choline chloride (ChCl) alone on PFBS, it is reasonable to speculate that ChCl may interact with functional groups or chemical bonds in PFBS, resulting in incomplete degradation. Further investigation of the PFBS degradation mechanism and reaction pathway is needed. Subsequent experiments used ChCl+OA, which showed the best degradation effect, to determine its degradation efficiency on PFBS at different time points.
[0054] Furthermore, comparing the data in Table 2, the presence of sludge substrate can improve the degradation efficiency of PFBS to some extent. This is because natural acidic components such as humic acid in the sludge may synergistically lower the reaction pH with DES, creating a more efficient catalytic environment; and organic matter or metal components in the sludge may form a composite catalytic system with DES, enhancing the catalytic reaction efficiency; simultaneously, the destructive effect of DES on sludge EPS may improve the mass transfer efficiency of PFBS between different phases, thus potentially further strengthening the DES mechanism in the sludge system and improving the degradation efficiency of PFBS in the sludge substrate.
[0055] In addition, see appendix Figure 2 The degradation rate (C) of PFBS in pure water after hydrothermal liquefaction with the addition of ChCl and OA at different time points. PFBS=0.176ppm, ChCl+OA dosage=5%, reaction temperature=340 ℃, reaction time=30, 60, 90, 210, 360min). The data in the figure show that in the control group, the degradation rate of PFBS showed a slow increasing trend with increasing time. At 30 min, the degradation rate was only 1.85%. After extending the time to 90 min, the degradation rate was still low at only 7.80%. When the time was extended to 210 min, the degradation rate further increased to 17.77%. When the time was extended to 360 min, the degradation rate reached its maximum of 38.34%. After adding ChCl+OA, the degradation rate of PFBS basically showed a trend of rapid increase followed by slow increase. Specifically, at 30 min, the degradation rate was 9.95%, while at 60 min, the degradation rate significantly increased, reaching 78.36%. However, when the time was extended to 90 min, the degradation rate slightly decreased to 76.88%, which may be because the reactant concentration decreased as the reaction proceeded, thus slowing down the reaction rate. Furthermore, the accumulation of reaction intermediates may also have inhibited the degradation rate. With a further increase in time to 210 min, the degradation rate slowly increased to 82.8%, reaching its maximum of 85.45% at 360 min. This indicates that ChCl+OA played a significant catalytic role in the degradation of PFBS. Studies have shown that the degradation of PFAS is generally significantly affected by the catalyst and reaction conditions. ChCl+OA may have promoted the degradation of PFBS by providing active sites or altering the reaction pathway. In addition, the unique solvent properties of DES may have helped to increase the solubility of reactants and the reaction rate, thereby accelerating the degradation process.
[0056] In summary, ChCl+OA exhibits significant catalytic effects in PFBS degradation, and its mechanism of action may be related to providing active sites, altering the reaction pathway, and increasing the solubility of reactants. Future research could further optimize reaction conditions, explore the application potential of DES in the degradation of other PFAS, and further investigate the degradation mechanism and pathway.
[0057] In addition, Figure 3The effects of different DES on PFBS defluorination were further investigated. In the control group without DES, the defluorination rate of PFBS was 3.15%. After adding ChCl, the defluorination rate was 3.51%, which was not significantly different from the control group. After adding four different DES, except for ChCl+OA which showed a better defluorination rate, the defluorination rates of the other groups were basically not significantly different from the control group. When adding single-component LA, the defluorination rate reached 4.09%. After adding ChCl+LA, the defluorination rate of PFBS was only 3.57%. Therefore, regardless of whether ChCl+LA or LA was added, the defluorination rate was not significantly different from the control group. When adding single-component MA, the defluorination rate was only 1.29%. After adding ChCl+MA, the defluorination rate reached 2.93%, which was not significantly different from the control group. After adding single-component OA, the defluorination rate of PFBS was only 3.05%. However, after adding ChCl+OA, the defluorination rate of PFBS reached 6.71%, which was significantly different from the control group and consistent with the degradation effect. Furthermore, there was a significant difference between OA and ChCl+OA, indicating a synergistic effect between OA and ChCl on the defluorination rate of PFBS. This may be related to the strong acidity and polarity of ChCl+OA. After adding single-component GA, the defluorination rate of PFBS was -0.12%. After adding ChCl+GA, the defluorination rate of PFBS was only 2.89%, with no significant difference from the control group. However, there was a significant difference between the GA and ChCl+GA groups, indicating a synergistic effect between GA and ChCl on the defluorination rate of PFBS. Among the four DES, ChCl+OA showed the highest defluorination efficiency for PFBS.
[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for the energy utilization of sludge and the efficient degradation of persistent organic pollutants, characterized in that, Includes the following steps: S1. Wet sludge containing persistent organic pollutants is mixed with a eutectic solvent to obtain a reaction mixture, wherein the eutectic solvent is composed of hydrogen bond acceptors and hydrogen bond donors; S2. Place the reaction mixture obtained in step S1 into a reaction vessel and carry out a hydrothermal liquefaction reaction at a reaction temperature of 150-370℃ and autogenous pressure for a reaction time of more than 5 minutes. S3. After the reaction is complete, the products are separated to obtain biomass oil, aqueous phase, solid phase and gaseous phase products.
2. The method for sludge energy utilization and efficient degradation of persistent organic pollutants according to claim 1, characterized in that, The wet sludge is municipal sludge or industrial organic sludge.
3. The method for sludge energy utilization and efficient degradation of persistent organic pollutants according to claim 1, characterized in that, The solids content of the wet sludge is 0.5-30 wt%, preferably 3-20 wt%.
4. The method for efficient degradation of persistent organic pollutants through sludge energy utilization according to any one of claims 1-3, characterized in that, The reaction temperature is 250-350℃.
5. The method for efficient degradation of persistent organic pollutants through sludge energy utilization according to any one of claims 1-3, characterized in that, The reaction time is 60 minutes or more.
6. The method for efficient degradation of sludge for energy utilization and persistent organic pollutants according to any one of claims 1-3, characterized in that, The amount of the eutectic solvent added is 0.1-20% of the total volume of the wet sludge, preferably 3-7% of the total volume of the wet sludge.
7. The method for efficient degradation of persistent organic pollutants through sludge energy utilization according to any one of claims 1-3, characterized in that, The hydrogen bond acceptor is selected from one or more of choline chloride, choline bromide, betaine, and tributylphosphine oxide; the hydrogen bond donor is selected from one or more of zinc chloride, urea, ethylene glycol, lactic acid, malic acid, oxalic acid, glutaric acid, and 2-methylpiperazine.
8. The method for efficient degradation of persistent organic pollutants through sludge energy utilization according to claim 7, characterized in that, The hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is selected from one of lactic acid, malic acid, oxalic acid, and glutaric acid.
9. The method for sludge energy utilization and efficient degradation of persistent organic pollutants according to claim 8, characterized in that, The eutectic solvent is a combination of choline chloride and oxalic acid.
10. The method for efficient degradation of sludge for energy utilization and persistent organic pollutants according to any one of claims 1-3, characterized in that, The eutectic solvent is prepared by the following steps: the hydrogen bond acceptor and the hydrogen bond donor are mixed in a preset molar ratio and stirred and heated at 60-100°C for 1-4 hours until a homogeneous and clear liquid is formed.