A method of biobased amino acid surfactant enhanced low temperature plasma degradation of short chain perfluorinated compounds

Abstract

The application discloses a method for degrading short-chain perfluorinated compounds by using bio-based amino acid surfactant enhanced low-temperature plasma. In view of the problem that the degradation efficiency is limited due to weak interfacial activity and difficult enrichment of short-chain perfluorinated compounds (PFAS), a surfactant composed of a bio-based hydrophobic alkyl chain and an amino acid cationic head group is designed and constructed, which has interfacial tendency and specific electrostatic pairing ability to short-chain PFAS. After being added to water, the agent can spontaneously form an interfacial response type self-assembled layer, capture short-chain PFAS from the bulk phase and migrate to the gas-liquid interface through electrostatic interaction, so as to realize accurate enrichment of pollutants in the plasma reaction zone. The method significantly improves the effective contact probability of short-chain PFAS and hydrated electrons, breaks through the interfacial mass transfer limitation in the low-temperature plasma treatment process, and greatly enhances the degradation and defluorination efficiency of short-chain PFAS without introducing secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of polluted water remediation technology, specifically a method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by bio-based amino acid surfactants. Background Technology

[0002] With the rapid development of fluorinated and fine chemicals, perfluorinated compounds (PFAS) are widely used in waterproof and oil-repellent coatings, fire-fighting foams, and electronics manufacturing. Their highly fluorinated carbon skeletons endow them with extremely strong chemical and thermal stability, making them difficult to remove from the environment by natural processes. They tend to accumulate in water bodies, plants, animals, and the human body over long periods, exhibiting adverse effects such as endocrine disruption, immunotoxicity, and reproductive and developmental toxicity. Therefore, they have been listed as key controlled new pollutants and typical persistent organic pollutants, becoming a significant environmental risk factor threatening ecosystem security and human health.

[0003] With the gradual restriction or banning of long-chain PFAS, short-chain PFAS has been widely promoted as an alternative and has gradually become the mainstream form in current fluorinated products. However, studies have shown that short-chain PFAS also have significant environmental persistence and biotoxicity, and accumulate in water bodies and organisms. Moreover, the degradation of long-chain PFAS in existing remediation processes often further generates more stable short-chain PFAS, causing short-chain components to continuously accumulate in environmental media and treatment units, making them more difficult to remove.

[0004] Currently, among the technologies for treating PFAS, low-temperature plasma is considered an important means of achieving PFAS defluorination and mineralization because it can generate a large number of hydrated electrons and reactive oxygen / nitrogen species in situ at ambient temperature and pressure. Studies have confirmed its effective decomposition of some long-chain PFAS. However, for short-chain PFAS, existing plasma systems still have significant shortcomings. The perfluoroalkyl backbone of short-chain PFAS has strong electron-withdrawing ability and large steric hindrance, making it difficult to effectively activate the CF bond through electrophilic oxidation. Its degradation mainly relies on reducing species such as hydrated electrons generated by plasma. Simultaneously, short-chain PFAS exhibits strong hydrophilicity and weak interfacial activity, making it difficult to accumulate at the gas-liquid interface, while hydrated electrons are mainly concentrated in the thin-layer region near the gas-liquid interface. The electrons that dominate the defluorination reaction cannot fully contact short-chain PFAS, resulting in significantly limited mass transfer and reaction efficiency. To alleviate this spatial mismatch, existing technologies often employ methods such as external electric field driving, electrophoresis, or microbubble aeration to promote the migration of PFAS to the gas-liquid interface. However, these devices are complex in structure, consume high energy, and struggle to achieve precise and controllable adjustment of the interfacial distribution of short-chain PFAS. Therefore, actively enhancing the enrichment of short-chain PFAS at the gas-liquid interface and improving their mass transfer and spatiotemporal coupling with plasma hydrated electrons, thereby significantly improving their deep defluorination and mineralization effects, has become a core technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for low-temperature plasma degradation of short-chain PFAS by bio-based amino acid surfactants with high reaction efficiency and good degradation effect. By constructing an interface-responsive self-assembly system, the enrichment degree of short-chain PFAS at the gas-liquid interface is significantly improved, thereby enhancing the mass transfer and reaction efficiency between PFAS and hydrated electrons, and thus overcoming the technical problem of poor degradation effect of low-temperature plasma on short-chain PFAS.

[0006] Technical Solution: The present invention provides a method for low-temperature plasma degradation of short-chain PFAS enhanced by a bio-based amino acid surfactant. The bio-based amino acid surfactant is an N-acyl amino acid surfactant obtained by condensation of fatty acids and amino acids, possessing a long-chain hydrophobic tail chain, a guanidinium-type cationic head group, and a carboxyl-containing amino acid skeleton. The bio-based amino acid surfactant is added to the polluted water to be treated, and then the mixed water is subjected to discharge treatment by low-temperature plasma. After the treatment, remediated water with a significantly reduced concentration of short-chain PFAS is obtained.

[0007] The above technical solution addresses the challenges of short-chain PFAS accumulation at the gas-liquid interface and limited mass transfer with hydrated electrons by designing and preparing a bio-based amino acid surfactant composed of bio-based hydrophobic alkyl chains and amino acid cationic head groups. This surfactant forms electrostatic pairings with short-chain PFAS through the amino acid cationic head groups and spontaneously constructs an interface-responsive self-assembled layer based on the interfacial orientation of the hydrophobic alkyl chains. This transports and enriches the short-chain PFAS, originally dispersed in bulk water, at the gas-liquid interface. Under low-temperature plasma discharge conditions, the interface-enriched PFAS fully contact the hydrated electrons generated in the interfacial region, thereby achieving efficient and green remediation of water bodies contaminated with short-chain PFAS.

[0008] Preferably, the low-temperature plasma device adopts a dielectric barrier discharge structure. Its reactor body is a quartz disc-shaped reactor with a diameter of approximately 100 mm, equipped with a pulse power supply, high-voltage electrodes, and a grounding electrode to provide plasma discharge conditions. Inlet and outlet ports are located on both sides of the reactor, and the flow rate of the incoming gas is adjusted by a gas flow meter. During the discharge process, an oscilloscope is used to monitor and record parameters such as real-time voltage, current, and discharge waveform to achieve visualized control and operational optimization of the discharge state.

[0009] Furthermore, the working gas of the low-temperature plasma reactor is air, argon, or nitrogen, with a gas flow rate of 20-100 mL / min.

[0010] Furthermore, the processing conditions of the low-temperature plasma reactor are: input voltage of 50-100 V, frequency of 150-200 Hz, duty cycle of 40%-60%, and processing time of 60-120 min.

[0011] Furthermore, the raw materials for preparing bio-based amino acid surfactants include long-chain fatty acids, amino acids, nucleophilic auxiliaries, and carbodiimide condensing agents. Among them, the long-chain fatty acids are lauric acid, myristic acid, and palmitic acid; the amino acid is arginine; the nucleophilic auxiliaries are N-hydroxysuccinimide or N-hydroxybenzotriazole; and the carbodiimide condensing agent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride or N,N′-dicyclohexylcarbodiimide.

[0012] Preferably, the preparation method of the bio-based amino acid surfactant includes, in sequence, the steps of long-chain fatty acid activation, amino acid solution preparation, condensation reaction, and post-treatment purification. Specifically, the preparation method of the bio-based amino acid surfactant is as follows: long-chain fatty acids are activated to generate ester intermediates, the ester intermediates are mixed with an amino acid solution adjusted by pH and subjected to a condensation reaction, and the bio-based amino acid surfactant is obtained after acidification, desalting, and crystallization.

[0013] Preferably, the activation step of the long-chain fatty acid is to dissolve the fatty acid in an organic solvent, then add a nucleophilic auxiliary agent and a condensing agent in sequence, and stir for 15-30 min to obtain an active fatty acid ester intermediate.

[0014] Preferably, during the activation process of long-chain fatty acids, the molar ratio of long-chain fatty acids: condensing agent: nucleophilic auxiliaries: amino acids is 1:1.1~1.5:1.1~1.5:1.0~1.5, and the organic solvent is methanol or ethanol.

[0015] Furthermore, the amino acid solution is prepared by dissolving the amino acid in a mixed solvent of water and ethanol in a volume ratio of 1:1 and stirring for 15-30 min.

[0016] Furthermore, the condensation reaction involves slowly adding the activated fatty acid ester solution dropwise to the amino acid solution, maintaining the pH of the system at 8-9 using sodium hydroxide aqueous solution, and stirring thoroughly.

[0017] Furthermore, the post-processing purification step involves adjusting the pH of the reaction solution to 5-6 with dilute hydrochloric acid, removing ethanol under reduced pressure and concentrating the system, then adding a small amount of ethanol to dissolve the product and cooling to crystallize. The crystals are then collected by filtration and dried under vacuum to obtain the bio-based amino acid surfactant.

[0018] Preferably, the temperature for removing ethanol under reduced pressure is 40–60 °C, the cooling crystallization is carried out at 0–5 °C for 2–6 h, and the vacuum drying temperature is 40–60 °C.

[0019] Furthermore, the concentration of short-chain PFAS is 0.1-50 mg / L, and the amount of surfactant added is 1-500 mg / L.

[0020] In a specific scheme, a method for enhancing the low-temperature plasma degradation of short-chain PFAS with bio-based amino acid surfactants includes the following steps:

[0021] S1. Preparation of bio-based amino acid surfactant: The bio-based amino acid surfactant is prepared by condensing activated long-chain fatty acids with amino acids and then purifying them.

[0022] S2. Preparation before degradation: After thoroughly mixing the bio-based amino acid surfactant with the short-chain PFAS-contaminated water, the mixture is placed in a low-temperature plasma disk reactor, and the gas flow rate is regulated by a gas flow meter to provide a stable reaction atmosphere.

[0023] S3. Water treatment: The input voltage, duty cycle and pulse frequency are set and controlled by a pulse generator and voltage regulator to turn on the high-voltage pulse power supply and discharge the polluted water.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention introduces a bio-based amino acid surfactant into water polluted by short-chain PFAS. The surfactant can form stable ion pairs with short-chain PFAS and construct self-assembled aggregates through multi-point hydrogen bonding. This promotes the directional enrichment and migration of short-chain PFAS to the gas-liquid interface reaction zone of low-temperature plasma discharge under no external field conditions, effectively shortening the mass transfer distance between electrons and pollutants, and significantly improving the degradation rate and defluorination efficiency of short-chain PFAS.

[0025] The bio-based amino acid surfactant provided by this invention possesses both a long-chain alkyl hydrophobic tail chain and a guanidine-type cationic head group, enabling it to spontaneously form a stable molecular self-assembly structure and interfacial enrichment layer in aqueous phase. It exhibits excellent resistance to coexisting inorganic ions and pH fluctuations in water. Furthermore, this surfactant is prepared by the condensation of long-chain fatty acids and natural guanidine-containing amino acids. Its molecular backbone contains degradable groups such as amide bonds and carboxyl groups, exhibiting low toxicity and biodegradability. It can also be further transformed under plasma irradiation, avoiding the risk of secondary pollution and enhancing the greenness and engineering applicability of the technology. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the bio-based amino acid surfactant in this invention.

[0027] Figure 2 This is the NMR spectrum of the bio-based amino acid surfactant in this invention, where a is... 1H NMR spectrum, b is 13 C NMR spectrum.

[0028] Figure 3 This is a schematic diagram of the dielectric barrier discharge low-temperature plasma device in this invention; in the figure: 1-high pressure gas cylinder, 2-gas flow meter, 3-disc-type dielectric barrier discharge low-temperature plasma reactor, 4-voltage regulator, 5-pulse generator, 6-high voltage pulse power supply, 7-oscilloscope.

[0029] Figure 4 This is a physical image of the dielectric barrier discharge low-temperature plasma device in this invention.

[0030] Figure 5 This is a schematic diagram of the overall method for enhancing the low-temperature plasma degradation of short-chain PFAS using bio-based amino acid surfactants in this invention.

[0031] Figure 6 This is a scanning electron microscope image of the self-assembled structure formed by the bio-based amino acid surfactant and short-chain PFAS in this invention.

[0032] Figure 7 This is a comparative graph showing the effects of bio-based amino acid surfactants and their synthetic raw materials on the performance of low-temperature plasma degradation of short-chain PFAS in this invention, where a is the degradation rate and b is the defluorination rate.

[0033] Figure 8 This is a comparative graph showing the effect of carbon chain length on the performance of bio-based amino acid surfactants in enhancing the low-temperature plasma degradation of short-chain PFAS, where a represents the degradation rate and b represents the defluorination rate.

[0034] Figure 9 This is a comparative graph showing the effect of amino acid type on the performance of bio-based amino acid surfactants in enhancing the low-temperature plasma degradation of short-chain PFAS, where a represents the degradation rate and b represents the defluorination rate.

[0035] Figure 10 This is a comparative graph showing the effect of the bio-based amino acid surfactant of the present invention on the performance of low-temperature plasma degradation of short-chain PFAS under different dosage conditions, where a is the degradation rate and b is the defluorination rate.

[0036] Figure 11 This is a comparative graph showing the effect of the bio-based amino acid surfactant of the present invention on the performance of low-temperature plasma degradation of short-chain PFAS under different gas conditions, where a represents the effect of gas atmosphere and b represents the effect of gas flow rate.

[0037] Figure 12This is a comparative graph showing the effect of the bio-based amino acid surfactant of the present invention on the performance of low-temperature plasma degradation of short-chain PFAS under different discharge conditions, where a represents the effect of input voltage, b represents the effect of duty cycle, c represents the effect of pulse frequency, and d represents the effect of discharge time.

[0038] Figure 13 This is a comparative graph showing the effect of the bio-based amino acid surfactant of the present invention on the performance of low-temperature plasma degradation of short-chain PFAS with different initial concentrations, where a is the degradation rate and b is the defluorination rate.

[0039] Figure 14 This invention describes the enhancing effect of the bio-based amino acid surfactant on the low-temperature plasma degradation of different short-chain PFAS, where a is the degradation rate and b is the defluorination rate.

[0040] Figure 15 This is a comparison graph of the bio-based amino acid surfactant of the present invention and other commercial surfactants in enhancing the performance of low-temperature plasma degradation of short-chain PFAS, where a is the degradation rate and b is the defluorination rate. Detailed Implementation

[0041] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0042] This invention provides a method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by bio-based amino acid surfactants. The specific method is as follows:

[0043] S1. Preparation of Bio-based Amino Acid Surfactant: The bio-based amino acid surfactant is prepared by condensing activated long-chain fatty acids with an amino acid solution, and the reaction product is purified. Specifically, the preparation method of the bio-based amino acid surfactant is as follows: the molar ratio of fatty acid: condensing agent: nucleophilic auxiliary agent: amino acid is 1:1.1~1.5:1.1~1.5:1.0~1.5. The fatty acid is dissolved in an organic solvent, and then the nucleophilic auxiliary agent and condensing agent are added sequentially. After the reaction, an active fatty acid ester intermediate is obtained. The amino acid is dissolved in a mixed solvent of water and ethanol and stirred to obtain an amino acid solution. The activated fatty acid ester solution is slowly added dropwise to the amino acid solution, and the pH of the system is adjusted and maintained at 8-9. The reaction is carried out under stirring to obtain a reaction solution. The pH of the reaction solution is adjusted to 5-6 with dilute hydrochloric acid, the ethanol is evaporated under reduced pressure, and the system is concentrated. Then, a small amount of ethanol is added to dissolve the product, and the product is cooled and crystallized. The crystals are collected by filtration and dried under vacuum to obtain the bio-based amino acid surfactant.

[0044] S2. Preparation before degradation: The bio-based amino acid surfactant is thoroughly mixed with the short-chain PFAS-contaminated water and placed in a low-temperature plasma disc reactor. The gas flow rate is controlled by a gas flow meter to provide a stable reaction atmosphere. The concentration of short-chain PFAS is 0.1-50 mg / L, and the amount of surfactant added is 1-500 mg / L.

[0045] S3. Water Treatment: The input voltage, duty cycle, and pulse frequency are set and controlled via a pulse generator and voltage regulator. The high-voltage pulse power supply is then activated to discharge polluted water. The working gas is air, argon, or nitrogen, with a gas flow rate of 20-100 mL / min. The processing conditions for the low-temperature plasma reactor are: input voltage 50-100V, frequency 150-200 Hz, duty cycle 40%-60%, and processing time 60-120 min.

[0046] Example 1

[0047] This embodiment provides a bio-based amino acid surfactant and its preparation method, the preparation method comprising the following steps:

[0048] Weigh out the raw materials according to the molar ratio of lauric acid: N,N′-dicyclohexylcarbodiimide (DCC): N-hydroxysuccinimide (NHS): arginine of 1:1.1:1.1:1.2. Dissolve lauric acid in ethanol, then add DCC and NHS sequentially, stirring to fully activate them. Subsequently, add an arginine solution with a solvent volume ratio of water / ethanol = 1:1 dropwise to the system, and react for 6 h under stirring, maintaining the pH of the system at approximately 8 by adding sodium hydroxide solution dropwise. After the reaction is complete, adjust the pH of the system to 5 with dilute hydrochloric acid, then evaporate the ethanol under reduced pressure at 50 °C and concentrate the system. Add a small amount of ethanol to the concentrate to dissolve the product, then cool and crystallize at 4 °C for 4 h. Filter and collect the obtained crystals, then dry under vacuum at 40 °C to obtain the bio-based amino acid surfactant.

[0049] The structure of the prepared bio-based amino acid surfactant is as follows: Figure 1 As shown. Combined with Figure 2The NMR spectrum shown confirms that its molecular framework mainly consists of three parts: First, the guanidinium-type cationic head group introduced by the arginine side chain has a high pKa and remains essentially protonated under environmental conditions, forming a high-charge-density, stable positively charged center. This head group can generate strong electrostatic attraction with ionized short-chain PFAS anions and enhances the complexation and binding stability through multi-point hydrogen bonds, thus providing a structural basis for the selective capture and directional migration of short-chain PFAS. Second, the hydrophobic alkyl tail chain derived from long-chain fatty acids endows the molecule with clear amphiphilicity, making it easy to self-assemble in the aqueous phase and form an interfacial enrichment layer, which is beneficial for enriching the weakly interfacially active short-chain PFAS in the gas-liquid interface discharge reaction region. Finally, the amide bond (-CO-NH-) between the tail chain and the amino acid backbone achieves a stable connection between fatty acids and arginine, ensuring the chemical stability of the molecular structure and introducing degradable fragments such as amide / carboxyl groups, reducing the risk of secondary pollution from surfactant residues.

[0050] According to the preparation method of Example 1, the molar ratio of lauric acid:DCC:NHS:arginine was changed to 1:1.1:1.1:1. Sodium hydroxide solution was added dropwise to the active ester solution after fatty acid activation to maintain the pH of the system at 9. After the reaction was completed, the pH of the system was adjusted to 6 with dilute hydrochloric acid. Other conditions were the same as in Example 1, and finally a bio-based amino acid surfactant with the same structure as in Example 1 was prepared.

[0051] According to the preparation method of Example 1, the molar ratio of lauric acid:DCC:NHS:arginine was changed to 1:1.5:1.5:1.5, and other conditions were the same as in Example 1. Finally, a bio-based amino acid surfactant with the same structure as in Example 1 was prepared.

[0052] The low-temperature plasma reaction device selected in the embodiments of the present invention is as follows: Figure 3 As shown, a high-pressure gas cylinder 1 continuously supplies gas to the system to form a discharge atmosphere, and a gas flow meter 2 is used to precisely control the gas flow rate. The reactor is a disc-type dielectric barrier discharge low-temperature plasma reactor 3 with a diameter of approximately 100 mm. The high-voltage energy required for discharge is output by a high-voltage pulse power supply 6, and the input voltage, power, and pulse parameters are regulated by a voltage regulator 4 and a pulse generator 5. The real-time operating conditions of the device, such as voltage, current, and discharge waveform, are monitored online by an oscilloscope 7. A physical diagram of the low-temperature plasma reactor is shown below. Figure 4 As shown.

[0053] like Figure 5As shown, after the power is turned on, a strong electric field is formed between the high-voltage electrode and the ground electrode of the low-temperature plasma. Water molecules are ionized and solvated under the action of high-energy electrons, generating key active species such as hydrated electrons in the gas-liquid interface region. Short-chain PFAS are highly hydrophilic and difficult to accumulate in the interface region, resulting in a low probability of effective contact with hydrated electrons, thus limiting the degradation efficiency of the low-temperature plasma system alone. The bio-based amino acid surfactant introduced in this invention can form electrostatic pairing with negatively charged short-chain PFAS through positively charged cationic head groups, and at the same time, relying on the spontaneous attraction of hydrophobic alkyl chains to the interface, an interface-responsive self-assembled layer is constructed at the gas-liquid interface. Figure 6 As shown in the diagram, PFAS, originally dispersed in the bulk phase, are directionally captured and enriched in the interfacial reaction region with the highest hydrated electron yield. Under the regulation of this interfacial structure, the mass transfer resistance between PFAS and hydrated electrons is significantly reduced, which is beneficial for the reduction and breaking of C–F bonds and the further mineralization of subsequent intermediates. In addition, the interfacial self-assembled layer can instantaneously fix and position PFAS molecules, prolonging their residence time in the interfacial region and increasing their probability of interaction with hydrated electrons and free radical reactive species, thus forming a significant "interfacial reaction enrichment effect". Ultimately, this coupling system significantly improves the utilization efficiency of hydrated electrons and plasma energy efficiency without the need for external chemical oxidants or the introduction of secondary pollution, achieving efficient degradation and deep defluorination of short-chain PFAS.

[0054] Example 2

[0055] This embodiment provides a method for enhancing the degradation of short-chain PFAS by low-temperature plasma with bio-based amino acid surfactants. First, bio-based amino acid surfactants are prepared, and perfluorobutyric acid (PFBA) polluted water is used as a model system. Treatment groups are set up with no additives, only long-chain fatty acids, only amino acids, both long-chain fatty acids and amino acids (uncondensed), and the bio-based amino acid surfactants. The differences in the degradation and defluorination effects of low-temperature plasma on PFBA with different additives are compared and investigated.

[0056] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. The raw materials were accurately weighed according to the molar ratio of lauric acid:DCC:NHS:arginine 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system. The reaction was carried out under stirring for 6 h, and the pH of the system was maintained at approximately 8 by adding sodium hydroxide solution dropwise. After the reaction was completed, the pH of the system was adjusted to 5 with dilute hydrochloric acid. Ethanol was then evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. Subsequently, 10 mg (100 mg / L) of lauric acid, arginine, a mixture of the two, and the prepared surfactant were weighed and added to the PFBA-contaminated water body. After thorough mixing, the mixture was placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a gas flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are as follows: Figure 7 As shown.

[0057] After 60 minutes of discharge treatment, the low-temperature plasma device showed some remediation ability for PFBA-contaminated water. However, due to the weak interfacial activity of short-chain PFAS, pollutants were difficult to continuously accumulate in the interfacial discharge region, resulting in a low overall reaction rate. The degradation rate after 60 minutes was only 30.2%, and the defluorination rate was 7.9%, with the growth trend gradually slowing down over time. When only long-chain fatty acids were added, the hydrophobic tail chains could alter the solution microenvironment to some extent, slightly enhancing interfacial enrichment and increasing the degradation rate to 38.0%, but the overall promoting effect was limited. When only arginine was added, due to its lack of hydrophobic structure and interfacial enrichment ability, it had almost no significant effect on degradation, with a degradation rate of only 29.3%. After directly physically mixing long-chain fatty acids and amino acids (without condensation), due to the absence of effective ion pairs and self-assembled structures in the system, only a limited synergistic effect was produced, with a degradation rate of 38.8%. In contrast, the bio-based amino acid surfactant prepared in this invention, through its hydrophobic tail chain and guanidinium-type cationic head group, can rapidly pair with PFBA and orderly self-assemble into a structure, enriching the originally hydrophilic PFBA in the plasma-active region of the gas-liquid interface. After 60 minutes of treatment, the degradation rate reached as high as 90.8%, and the defluorination rate exceeded 70%, demonstrating excellent coupling repair effect.

[0058] Example 3

[0059] This embodiment provides a method for comparing the enhancement of short-chain PFAS degradation by bio-based amino acid surfactants with different carbon chain lengths in low-temperature plasma. During the preparation process, fatty acids with different carbon chain lengths are selected as precursors to synthesize corresponding bio-based amino acid surfactants. The obtained surfactants are then added to PFBA-contaminated water and mixed thoroughly. Subsequently, each treatment system is placed in a low-temperature plasma reactor. Under the condition that other discharge conditions remain consistent, the degradation efficiency and defluorination effect of the coupled system on PFBA are systematically evaluated.

[0060] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. Octanoic acid (C8), capric acid (C10), lauric acid (C12), myristic acid (C14), and palmitic acid (C16) were selected as fatty acid precursors, weighed according to a fatty acid:DCC:NHS:arginine molar ratio of 1:1.1:1.1:1.2. The fatty acids were dissolved in ethanol, and DCC and NHS were added sequentially, stirred to ensure complete activation. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system, and the reaction was carried out under stirring for 6 h, maintaining the pH of the system at approximately 8 by adding sodium hydroxide solution. After the reaction was complete, the pH of the system was adjusted to 5 with dilute hydrochloric acid, and then the ethanol was evaporated under reduced pressure at 50 °C and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The product was filtered and dried under vacuum at 40 °C to obtain bio-based amino acid surfactants with different carbon chain lengths. A blank control group (without surfactant) was then set up. 10 mg (100 mg / L) of surfactant was weighed and added to the PFBA-contaminated water, mixed thoroughly, and then placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 8 As shown.

[0061] As the carbon chain length of fatty acids increases, the hydrophobicity of the prepared bio-based amino acid surfactants gradually increases, and the ordered self-assembled structure formed at the gas-liquid interface becomes more compact, thereby significantly improving the migration and enrichment capacity of PFBA at the interface and increasing its contact probability with active species. The C12-C16 group exhibits the most significant enhancement effect; however, when the carbon chain length exceeds 12 carbons, the interface tends to saturate, and the enhancement magnitude remains basically consistent, indicating that interfacial mass transfer is no longer the rate-limiting step in PFBA degradation at this stage. Therefore, the bio-based amino acid surfactants prepared in this invention, due to their suitable carbon chain length, can effectively promote the enrichment of short-chain PFAS at the interface and significantly improve the repair efficiency of low-temperature plasma.

[0062] Example 4

[0063] This embodiment provides a method for comparing the enhanced degradation performance of short-chain PFAS by different amino acid-derived bio-based amino acid surfactants in low-temperature plasma. During the preparation process, different amino acids were selected as precursors to synthesize corresponding bio-based amino acid surfactants, which were then added to PFBA-contaminated water and mixed thoroughly. Subsequently, each treatment system was placed in a low-temperature plasma reactor, and under the same discharge conditions, the degradation efficiency and defluorination effect of different surfactant-coupled systems on PFBA were systematically evaluated.

[0064] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. Arginine, histidine, and lysine were selected as amino acid precursors, and each raw material was weighed according to the molar ratio of lauric acid:DCC:NHS:amino acid = 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an amino acid solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system, and the reaction was carried out under stirring for 6 h, maintaining the pH of the system at approximately 8 by adding sodium hydroxide solution dropwise. After the reaction was completed, the pH of the system was adjusted to 5 with dilute hydrochloric acid, and then the ethanol was evaporated under reduced pressure at 50 °C and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The solution was filtered and dried under vacuum at 40 °C to obtain bio-based amino acid surfactants derived from different amino acids. A blank control group was then set up, and 10 mg (100 mg / L) of surfactant was weighed and added to the PFBA-contaminated water. After thorough mixing, the mixture was placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 9 As shown.

[0065] With the addition of bio-based surfactants derived from different amino acids, PFBA exhibits enhanced enrichment at the gas-liquid interface due to its hydrophobic alkyl chain, resulting in varying degrees of improvement in both degradation and defluorination rates. Among the three types of surfactants, arginine derivatives performed best. Their side chains contain high pKa guanidinium cations, which are almost completely positively charged under normal conditions and provide multiple hydrogen bonding sites. These cations can form more stable interfacial complexes with short-chain PFAS through electrostatic attraction and multi-site hydrogen bonding, exhibiting the highest degradation and defluorination efficiencies. In contrast, lysine only forms a primary ammonium salt structure, with limited charge delocalization ability and fewer available hydrogen bonding sites; while histidine has a lower pKa side chain, only partially carrying a positive charge under neutral conditions, resulting in weaker electrostatic interactions with PFAS. Neither histidine nor histidine can form stable interfacial complexes, therefore their improvements in degradation and defluorination efficiency are significantly lower than those of arginine derivatives. Therefore, this invention can significantly optimize the interfacial coordination ability of surfactant side chains by regulating their chemical structure, increasing their positive charge density, hydrogen bond donor quantity, and charge delocalization stability, thereby effectively improving the degradation and defluorination efficiency of short-chain PFAS in low-temperature plasma systems.

[0066] Example 5

[0067] This embodiment provides a method for enhancing the degradation of short-chain PFAS by low-temperature plasma using a bio-based amino acid surfactant at different dosages. First, the bio-based amino acid surfactant is prepared, and different dosages of the surfactant are added to PFBA-contaminated water and mixed thoroughly. Then, each treatment system is placed in a low-temperature plasma reactor, and under the condition that other discharge conditions remain consistent, the effect of the coupled system on the degradation and defluorination remediation of PFBA is investigated.

[0068] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. The raw materials were weighed according to the molar ratio of lauric acid:DCC:NHS:arginine 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system. The reaction was carried out under stirring for 6 h, and the pH of the system was maintained at approximately 8 by adding sodium hydroxide solution dropwise. After the reaction was completed, the pH of the system was adjusted to 5 with dilute hydrochloric acid. Ethanol was then evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. A blank control group (without surfactant) was then set up. 0.5 mg (5 mg / L), 1 mg (10 mg / L), 5 mg (50 mg / L), 10 mg (100 mg / L), and 50 mg (500 mg / L) of surfactant were weighed and added to the PFBA-contaminated water. After thorough mixing, the mixture was placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 10 As shown.

[0069] With increasing dosage of the bio-based amino acid surfactant, the enrichment of PFBA at the gas-liquid interface significantly increased, thereby enhancing its effective contact and reaction probability with active electrons at the interface, resulting in a simultaneous increase in degradation rate and defluorination efficiency. The 100 mg / L group showed the most significant enhancement, with a defluorination rate up to 9 times higher than the control group. However, when the dosage was further increased to 500 mg / L, its degradation and defluorination performance were essentially equivalent to the 100 mg / L group, indicating that interfacial mass transfer no longer constituted the rate-limiting step of the reaction at this stage. Therefore, the bio-based amino acid surfactant prepared in this invention can achieve efficient interfacial enrichment of short-chain PFAS at appropriate dosages, significantly improving the remediation efficiency of low-temperature plasma for short-chain PFAS-contaminated water by enhancing the interfacial reaction process.

[0070] Example 6

[0071] This embodiment provides a method for degrading short-chain PFAS using bio-based amino acid surfactant-enhanced low-temperature plasma under different gas atmospheres and gas flow rates. First, the bio-based amino acid surfactant is prepared, added to PFBA-contaminated water, and mixed thoroughly. Then, the treatment system is placed in a low-temperature plasma reactor, and the discharge atmosphere type and gas flow rate are adjusted to evaluate the degradation and defluorination effects of the coupled system on short-chain PFAS under different gas atmospheres and gas flow rates.

[0072] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. The raw materials were weighed according to the molar ratio of lauric acid:DCC:NHS:arginine of 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system, and the reaction was carried out under stirring for 6 h, maintaining the pH of the system at approximately 8 by adding sodium hydroxide solution. After the reaction was complete, the pH of the system was adjusted to 5 with dilute hydrochloric acid, and then the ethanol was evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. 0.01 g (100 mg / L) of the surfactant was weighed and added to the PFBA-contaminated water, mixed thoroughly, and then placed in a low-temperature plasma disc reactor (DBD). The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz. Experiments were conducted by varying the discharge gas atmosphere and gas flow rate. The discharge atmosphere consisted of air, argon, nitrogen, and air, with gas flow rates set to 0, 20, 30, 40, 50, 80, and 100 mL / min. Discharge was initiated to generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 11 As shown.

[0073] Experiments show that the bio-based amino acid surfactant coupled with low-temperature plasma system of this invention can effectively degrade and rapidly defluorinate PFBA under different discharge gas atmospheres and gas flow rates, indicating that the coupled system has good adaptability and operational stability to gas conditions. Compared with air, argon, and nitrogen systems, the degradation and defluorination efficiency under oxygen conditions is slightly reduced. This is mainly attributed to the strong oxidizing species generated during oxygen discharge, which to some extent quenches the interfacial electrons, thereby weakening the effectiveness of electron participation in the interfacial reaction. With the increase of gas flow rate, the degradation and defluorination efficiency of PFBA shows a trend of first increasing and then stabilizing, and slightly decreasing at higher flow rates. This indicates that a moderate gas flow rate helps maintain a stable discharge state in the reactor and improves the effective utilization rate of active species; while too low a gas flow rate limits the generation of active species, and too high a flow rate may shorten the gas-liquid interface residence time and dilute the local energy density, thereby weakening the interfacial reaction efficiency. It is worth noting that the removal rate of PFBA remained at a high level under all investigated conditions, further demonstrating that the interfacial enrichment enhancement mechanism constructed by this coupled system can effectively play a role in different discharge environments.

[0074] Example 7

[0075] This embodiment provides a method for degrading short-chain PFAS using bio-based amino acid surfactant-enhanced low-temperature plasma under different discharge conditions. First, the bio-based amino acid surfactant is prepared, added to PFBA-contaminated water, and mixed thoroughly. Then, the treatment system is placed in a low-temperature plasma reactor, and the input voltage, duty cycle, pulse frequency, and discharge time are adjusted to evaluate the degradation and defluorination effects of the coupled system on short-chain PFAS under different discharge conditions.

[0076] Specifically, 100 mL of PFBA-contaminated water at a concentration of 10 mg / L was prepared in the laboratory. The raw materials were weighed according to the molar ratio of lauric acid:DCC:NHS:arginine of 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system, and the reaction was carried out under stirring for 6 h, maintaining the pH of the system at approximately 8 by adding sodium hydroxide solution. After the reaction was complete, the pH of the system was adjusted to 5 with dilute hydrochloric acid, and then the ethanol was evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. 0.01 g (100 mg / L) of the surfactant was weighed and added to the PFBA-contaminated water, mixed thoroughly, and then placed in a low-temperature plasma disc reactor (DBD). Using air as the working gas and a gas flow rate set at 30 mL / min, the discharge parameters were varied to conduct experiments. Specifically, the input voltage of the high-voltage pulse power supply was adjusted to 25 V, 37.5 V, 50 V, 62.5 V, 75 V, and 100 V; the duty cycle was adjusted to 30%, 40%, 50%, 60%, and 70%; the pulse frequency was adjusted to 100 Hz, 125 Hz, 150 Hz, 175 Hz, and 200 Hz; and the discharge time was adjusted to 40 min, 60 min, 80 min, 100 min, and 120 min. The discharge was initiated to generate active species. Water samples were collected through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 12 As shown.

[0077] Experiments show that, within the preferred input voltage, duty cycle, pulse frequency, and discharge time range described above, the bio-based amino acid surfactant coupled with low-temperature plasma system of this invention can achieve efficient degradation and stable defluorination of PFBA, demonstrating good operational stability and parameter adaptability. With increasing input voltage and duty cycle, the plasma discharge intensity and energy injection level gradually increase. Under lower input conditions, insufficient electric field strength within the discharge gap makes stable breakdown difficult, thus limiting the generation of active species. As the plasma discharge intensity significantly increases, the generation rate of active species accelerates, thereby significantly promoting PFBA removal. However, when the input energy is further increased, the increase in PFBA removal rate gradually slows down. While excessively high energy input can shorten the reaction time, it also leads to some energy loss as heat, thus reducing the overall energy utilization efficiency of the system. With increasing pulse frequency, the PFBA removal rate only shows a slow upward trend, indicating that under similar input power conditions, frequency mainly has a secondary impact on the reaction process by regulating the micro-discharge distribution and the active species renewal rate. In contrast, extending the discharge time can continuously improve the degree of PFBA removal, but the increase gradually slows down in the later stages of the reaction, reflecting that the system is gradually limited by the reaction kinetics. In summary, the optimized discharge parameters can ensure high PFBA removal efficiency while also taking into account energy utilization efficiency, further demonstrating the potential advantages of this coupling system in practical applications.

[0078] Example 8

[0079] This embodiment provides a method for enhancing the degradation of short-chain PFAS with different initial concentrations using a bio-based amino acid surfactant via low-temperature plasma. First, the bio-based amino acid surfactant is prepared and added at a fixed dosage to PFBA-contaminated water bodies with different initial concentrations, and then mixed thoroughly. Subsequently, each treatment system is placed in a low-temperature plasma reactor, and under the condition that other discharge conditions remain consistent, the degradation efficiency and adaptability of the coupled system under different PFAS pollution loads are systematically evaluated.

[0080] Specifically, 100 mL of PFBA-contaminated water at concentrations of 0.1, 0.5, 1.5, 10, 20, and 50 mg / L were prepared in the laboratory. Each raw material was accurately weighed according to a molar ratio of lauric acid:DCC:NHS:arginine of 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system. The reaction was carried out under stirring for 6 h, and the pH was maintained at approximately 8 by adding sodium hydroxide solution. After the reaction was complete, the pH was adjusted to 5 with dilute hydrochloric acid. Ethanol was then evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. 0.01 g (100 mg / L) of the surfactant was weighed and added to PFBA-contaminated water bodies with different initial concentrations. After thorough mixing, the mixture was placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 13 As shown.

[0081] Experiments show that the bio-based amino acid surfactant coupled with low-temperature plasma system of this invention exhibits a significant enhancement effect on PFBA-contaminated water bodies with different initial concentrations. Both the degradation rate and defluorination rate of DBD alone decrease significantly with increasing pollutant concentration, reflecting that under high pollution loads, the effective contact between electrons and PFBA is limited, and the reaction is constrained by interfacial mass transfer. In contrast, the DBD + bio-based amino acid surfactant system shows a significantly improved treatment capacity across the entire concentration range. At lower initial concentrations (0.1-1 mg / L), the surfactant rapidly constructs a stable interfacial self-assembled layer, significantly enhancing the enrichment of PFBA at the gas-liquid interface, achieving a degradation rate approaching 100% and a defluorination rate exceeding 80%, demonstrating extremely high electron utilization efficiency. As the initial PFBA concentration increases to 5-50 mg / L, although DBD alone shows a significant decrease, the degradation rate remains at a high level of 82-92% and the defluorination rate remains in the 60-75% range after adding the surfactant, showing a stable and continuous enhancement effect, indicating that this coupled system can maintain good interfacial reaction efficiency even under high pollution loads.

[0082] Example 9

[0083] This embodiment provides a method for enhancing the degradation of different short-chain PFAS by low-temperature plasma using a bio-based amino acid surfactant. First, the bio-based amino acid surfactant is prepared and then added to water bodies contaminated with typical short-chain PFAS, such as perfluorobutyric acid (PFBA), perfluorovalerate (PFPeA), perfluorohexanoic acid (PFHxA), perfluorobutanesulfonic acid (PFBS), and perfluorohexanesulfonic acid (PFHxS), and mixed thoroughly. Subsequently, each treatment system is placed in a low-temperature plasma reactor. Under conditions where other discharge conditions remain consistent, the remediation effect of the bio-based amino acid surfactant coupled with the low-temperature plasma system on water bodies contaminated with different short-chain PFAS is systematically evaluated.

[0084] Specifically, 100 mL of each of PFBA, PFPeA, PFHxA, PFBS, and PFHxS at a concentration of 10 mg / L were prepared in the laboratory. Each raw material was accurately weighed according to a molar ratio of lauric acid:DCC:NHS:arginine of 1:1.1:1.1:1.2. Lauric acid was dissolved in ethanol, and DCC and NHS were added sequentially, stirring to fully activate the solution. Then, an arginine solution with a solvent volume ratio of water / ethanol = 1:1 was added dropwise to the system. The reaction was carried out under stirring for 6 h, and the pH was maintained at approximately 8 by adding sodium hydroxide solution. After the reaction was complete, the pH was adjusted to 5 with dilute hydrochloric acid. Ethanol was then evaporated under reduced pressure at 50 °C, and the system was concentrated. A small amount of ethanol was added to the concentrate to dissolve the product, and the solution was cooled and crystallized at 4 °C for 4 h. The resulting crystals were collected by filtration and dried under vacuum at 40 °C to obtain the bio-based amino acid surfactant. 0.01 g of the surfactant was weighed and added to different PFAS-contaminated water bodies, mixed thoroughly, and then placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, duty cycle to 50%, and pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFAS concentration was measured. The results are shown below. Figure 14 As shown.

[0085] As the carbon chain length of short-chain PFAS increases, their hydrophobic enrichment capacity at the gas-liquid interface gradually enhances, resulting in a degradation efficiency in the DBD system that increases with chain length. This further confirms the crucial role of interfacial mass transfer and interfacial reaction in the treatment process. The introduction of bio-based amino acid surfactants significantly restructured the interfacial activity of various PFAS, with PFBA showing the greatest enhancement due to its relatively weak interfacial activity. PFHxS, with its higher interfacial activity, also exhibited a significant performance improvement. This demonstrates that the surfactant can not only effectively compensate for the limited mass transfer of low-interfacial-activity species but also continuously promote the reaction process in short-chain PFAS systems where interfacial advantages are already prominent, showcasing good structural universality and application potential.

[0086] Comparative Example

[0087] This comparative example provides a method for comparing the enhancement of short-chain PFAS remediation performance of bio-based amino acid surfactants and different types of commercial surfactants in a low-temperature plasma system. First, the bio-based amino acid surfactant was prepared (using the same method as in Example 1), and commercially available typical surfactants were selected, including the cationic surfactant hexadecyltrimethylammonium bromide (CTAB), the anionic surfactant sodium dodecyl sulfonate (SDS), the nonionic surfactant octylphenoxypolyethoxylate (Triton X-100), and the amphoteric surfactant cocamidopropyl betaine (CAPB). Each surfactant was added to PFBA-contaminated water prepared from deionized water or actual water and mixed thoroughly. Subsequently, each treatment system was placed in a low-temperature plasma reactor, and under the condition that other discharge conditions remained consistent, the enhancing effect of different surfactants on the low-temperature plasma degradation of short-chain PFAS was systematically evaluated.

[0088] 0.01 g of the above-mentioned surfactants, along with the cationic surfactant CTAB, the anionic surfactant SDS, the nonionic surfactant Triton X-100, and the amphoteric surfactant CAPB, were weighed and added to the PFBA-contaminated water. After thorough mixing, the mixture was placed in a low-temperature plasma disc reactor (DBD). Air was used as the working gas, with a gas flow rate set to 30 mL / min. The high-voltage pulse power supply input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz to initiate discharge and generate active species. The total discharge time was 60 min. Water samples were collected every 10 min through the sampling port, and the residual PFBA concentration was measured. The results are shown below. Figure 15 As shown.

[0089] The bio-based amino acid surfactant of this invention achieves the highest degradation and defluorination rates in low-temperature plasma systems. Its advantages stem from the high positive charge density and multiple hydrogen bonding sites on its side chains, enabling stable adsorption and enrichment of short-chain PFAS at the gas-liquid interface, significantly increasing the interfacial reaction probability between PFBA and active species. Furthermore, the charge delocalization of the guanidinium group effectively weakens the competitive interference of various inorganic ions on electrostatic pairing in actual water bodies, thus maintaining its excellent enhancement ability. In contrast, CTAB, SDS, Triton X-100, and CAPB, due to their singular charge properties, weak charge delocalization, or lack of hydrogen bonding interactions, struggle to form stable PFAS complexes at the interface, resulting in limited enhancement capabilities. Simultaneously, their fragile interfacial coordination ability is significantly inhibited in actual water bodies, further reducing degradation and defluorination effects.

[0090] In summary, the bio-based amino acid surfactant-enhanced low-temperature plasma system of the present invention can not only effectively enrich and promote the interfacial reaction of short-chain PFAS, but also has excellent resistance to the complex interference of water bodies, showing outstanding potential for practical application.

Claims

1. A method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by bio-based amino acid surfactants, characterized in that, The water containing short-chain perfluorinated compounds is placed in a low-temperature plasma reactor. A bio-based amino acid surfactant is added to the water and mixed evenly to obtain a mixture. The surfactant is an N-acyl amino acid surfactant obtained by condensation of fatty acids and arginine, which has a long-chain hydrophobic tail chain, a guanidinium-type cationic head group, and a carboxyl-containing amino acid skeleton. The mixture is then subjected to low-temperature plasma discharge treatment to degrade the short-chain perfluorinated compounds, resulting in treated water. The fatty acid is lauric acid, myristic acid, or palmitic acid.

2. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 1, characterized in that, The concentration of short-chain perfluorinated compounds is 0.1-50 mg / L, and the amount of surfactant added is 1-500 mg / L.

3. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 1, characterized in that, The working gas of the low-temperature plasma reactor is air, argon, or nitrogen.

4. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 1, characterized in that, The gas flow rate is 20-100 mL / min.

5. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 1, characterized in that, The processing conditions of the low-temperature plasma reactor are: input voltage of 50-100 V, frequency of 150-200 Hz, duty cycle of 40%-60%, and processing time of 60-120 min.

6. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 1, characterized in that, The raw materials for preparing bio-based amino acid surfactants include long-chain fatty acids, arginine, nucleophilic auxiliaries, and carbodiimide condensing agents. The nucleophilic auxiliaries are N-hydroxysuccinimide or N-hydroxybenzotriazole, and the carbodiimide condensing agents are 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride or N,N′-dicyclohexylcarbodiimide.

7. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 6, characterized in that, The preparation method of bio-based amino acid surfactant is as follows: long-chain fatty acids are activated to generate ester intermediates, the ester intermediates are mixed with an amino acid solution adjusted by pH and subjected to a condensation reaction, and the bio-based amino acid surfactant is obtained by acidification, desalting and crystallization.

8. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 7, characterized in that, The activation process of long-chain fatty acids involves dissolving the fatty acid in an organic solvent, then adding a nucleophilic auxiliary agent and a condensing agent in sequence, and stirring to obtain an ester intermediate.

9. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 7, characterized in that, The molar ratio of long-chain fatty acids, condensing agents, nucleophilic auxiliaries, and amino acids is 1:1.1~1.5:1.1~1.5:1.0~1.

5.

10. The method for low-temperature plasma degradation of short-chain perfluorinated compounds enhanced by a bio-based amino acid surfactant according to claim 7, characterized in that, The condensation reaction involves adding the ester intermediate dropwise into the amino acid solution and adjusting and maintaining the pH of the system at 8-9.

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