Method for degrading perfluorooctanoic acid and substitute thereof by electrochemically activating sulfate radicals

Abstract

The invention relates to the technical field of organic pollutant wastewater treatment, and discloses a method for degrading perfluorooctanoic acid and a substitute thereof by electrochemically activating sulfate radicals, in an electrochemical reaction device, a Pt / CeO2 (at) Ti4O7 electrode is used as an anode, a 304 stainless steel sheet is used as a cathode, and a reaction solution in the electrochemical reaction device comprises a to-be-degraded substance, an electrolyte and deionized water; under the action of an external direct-current electric field, the to-be-degraded object is subjected to electrochemical degradation; the to-be-degraded product is perfluorooctanoic acid and / or hexafluoropropylene oxide dimer acid. The Pt / CeO2 (at) Ti4O7 electrode can effectively degrade perfluorooctanoic acid and hexafluoropropylene oxide dimer acid in water under the action of an external electric field, and development of an effective treatment method for the environment polluted by perfluorinated substances is promoted.

Description

Technical Field

[0001] This invention relates to the field of organic pollutant wastewater treatment technology, and in particular to a method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes. Background Technology

[0002] Perfluorooctanoic acid (PFOA), as a persistent pollutant, has a unique helical conformation and strong carbon-fluorine bonds (531.5 kJ / mol). -1 This substance is widely used in industrial and everyday applications, such as in non-stick cookware coatings, fire extinguishing foams, and waterproof fabrics. The extensive use of PFOA has led to the continuous accumulation of its residues in the environment, and it has been widely detected in surface water, sediments, and soil. More seriously, this compound, frequently detected in human blood, can cause developmental toxicity and multi-system adverse effects through mechanisms of action involving the nervous, endocrine, immune, and reproductive systems. In 2024, the U.S. Environmental Protection Agency (EPA) issued its first legally binding national drinking water standard, setting the limit for this substance in drinking water at 4 ng / L. -1 Therefore, more and more countries and regions around the world are phasing out the use of PFOA.

[0003] Hexafluoropropylene oxide dimer (GenX) has been used in the production of fluoropolymers as a substitute for PFOA. However, studies have found that GenX's persistence in the environment is comparable to that of its predecessor, PFOA. The U.S. Environmental Protection Agency has set a limit of 10 ng / L for GenX in drinking water. -1 The maximum limits for pollutants. Against this backdrop, effectively removing perfluorinated or polyfluoroalkyl substances (PFASs) has become a crucial issue in environmental governance. Electrochemical oxidation technology, due to its advantages such as low energy consumption, modular processing, and the elimination of the need for additional chemical reagents, is now widely recognized as the most promising treatment method.

[0004] Studies have shown that hydroxyl radicals ( • OH radicals cannot directly oxidize PFOA, but they can participate in subsequent defluorination processes. Sulfate radicals (SO4) •- (2.5~3.1 V vs SHE) • OH (1.8–2.7 V vs SHE) has a higher oxidation potential and can effectively degrade PFOA. Meanwhile, SO42- •- Compare • OH has a longer lifespan (SO4) •- =30~40μs, • OH < 1 μs, resulting in a wider working pH range. It has been reported that sulfate ions (SO4) 2- As a common inorganic anion in wastewater, it has a high concentration (mg / L) in municipal and industrial wastewater.-1 ~ g L -1 It can not only act as an electrolyte, but also as SO42-. •- An important precursor.

[0005] Boron-nitrogen co-doped diamond electrodes can electrochemically activate SO4. 2- Generate SO4 •- It promotes the degradation of perfluorinated compounds. However, the high cost of the electrode severely hinders its widespread application. In contrast, Ti4O7 electrodes are inexpensive (approximately US$0.36 per square meter) and can activate SO4 to some extent. 2- It promotes the degradation of PFOA. However, its activation efficiency is usually limited by low interfacial charge transfer efficiency and high energy consumption.

[0006] Therefore, there is an urgent need for a method to electrochemically activate sulfate ions to degrade perfluorooctanoic acid and its substitutes to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to solve the problem of SO4 activation by existing electrodes. 2- To address the problems of high cost and low mass transfer rate, a novel electrode was constructed using a co-loading method with Pt and CeO2 support oxide to improve the electron transfer rate and effectively activate SO4. 2- To promote the degradation of recalcitrant organic pollutants such as PFOA and GenX, and to achieve efficient removal of recalcitrant organic pollutants from wastewater.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0009] A method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes includes the following steps: In the electrochemical reaction device, a Pt / CeO2@Ti4O7 electrode is used as the anode and a 304 stainless steel sheet is used as the cathode. The reaction solution in the electrochemical reaction device contains the product to be degraded, electrolyte, and deionized water. Under the action of an applied DC electric field, the product to be degraded is electrochemically degraded. The substances to be degraded are PFOA and / or GenX.

[0010] Under the influence of an applied DC electric field, the Pt / CeO2@Ti4O7 anode can effectively activate SO42-. 2- SO4 is produced •- It promotes the degradation of PFOA and / or GenX.

[0011] Preferably, the Pt / CeO2@Ti4O7 electrode is prepared as follows: Ti4O7 and NaCl were mixed in a mass ratio of 3:1 and pressed into shape. The mixture was then kept at 1200 °C for 2 h to obtain a preform. The preform was boiled in ultrapure water to remove residual NaCl and then dried to obtain the Ti4O7 electrode. The Ti4O7 electrode was immersed in Ce(NO3)3·6H2O solution and then dried. The dried sample was calcined at 300 °C for 2 h to obtain the CeO2-Ti4O7 electrode. The mass of Ce element in the Ce(NO3)3·6H2O solution was 1% of the mass of Ti4O7 in the Ti4O7 electrode. The CeO2-Ti4O7 electrode was immersed in H2PtCl6 solution and then dried. The dried sample was kept at 500 ℃ for 2 h to obtain the Pt / CeO2@Ti4O7 electrode. The mass of Pt element in H2PtCl6 solution was 1% of the mass of Ti4O7 in CeO2-Ti4O7 electrode.

[0012] Preferably, the concentration of the substance to be degraded in the reaction solution is 2 μM.

[0013] Preferably, the concentration of the electrolyte in the reaction solution is 50-79.4 mM.

[0014] Preferably, the electrolyte is Na2SO4 or NaNO3.

[0015] Preferably, when the electrolyte is Na2SO4, the concentration of Na2SO4 in the reaction solution is 50 mM; when the electrolyte is NaNO3, the concentration of NaNO3 in the reaction solution is 79.4 mM.

[0016] Preferably, the current density of the applied DC electric field is 15-20 mA cm⁻¹. -2 .

[0017] Preferably, the degradation time is not less than 150 min.

[0018] In the above units, "mM" refers to "mmol / L". -1 "μM" refers to "μmol L". -1 ".

[0019] Beneficial effects: (1) The present invention uses Pt / CeO2@Ti4O7 electrodes under the action of an external electric field to achieve effective degradation of PFOA and / or GenX in water, which helps to promote the development of effective treatment methods for environmental pollution caused by perfluorinated substances; (2) Compared with Ti4O7 electrode, Pt / CeO2@Ti4O7 electrode increases SO4 content. 2- The activation efficiency of its activation of SO4 2-It has a stronger ability to remove recalcitrant organic matter; (3) The present invention uses a Pt / CeO2@Ti4O7 electrode to generate strong oxidizing SO4 under the action of an external electric field. •- No additional oxidant is required, which reduces costs compared to traditional methods, and the system operates under stable conditions. Attached Figure Description

[0020] Figure 1 Examples 1, 2, 3, and 4 illustrate the degradation effect of Pt / CeO2@Ti4O7 electrodes on PFOA in Na2SO4 or NaNO3 systems at different current densities. Figure 2 The degradation effects of Pt / CeO2@Ti4O7 electrode and Ti4O7 electrode on PFOA in Na2SO4 or NaNO3 systems are shown in Examples 2, 4, Comparative Example 1, and Comparative Example 2. Figure 3 Examples 5, 6, Comparative Example 3, and Comparative Example 4 illustrate the degradation effects of Pt / CeO2@Ti4O7 and Ti4O7 electrodes on GenX in Na2SO4 or NaNO3 systems. Figure 4 Linear sweep voltammetry (LSV) curves of Pt / CeO2@Ti4O7 electrode when Na2SO4 or NaNO3 is used as electrolyte; Figure 5 Cyclic voltammetry (CV) curves of Ti4O7 electrode and Pt / CeO2@Ti4O7 electrode in Na2SO4 or NaNO3 system; Figure 6 Electron spin resonance (EPR) diagram of Pt / CeO2@Ti4O7 electrode when Na2SO4 or NaNO3 is used as electrolyte. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0022] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0023] There are no particular restrictions on the purity of any of the raw materials used in this invention; however, it is preferred to use materials with conventional purity levels used in the field.

[0024] All processes in this invention are referred to by abbreviations that are common abbreviations in the field. Each abbreviation is clear and specific in its relevant application area, and those skilled in the art can understand the conventional process steps based on the abbreviation.

[0025] The Pt / CeO2@Ti4O7 electrode preparation method is as follows in the following embodiments: First, 4.5 g of Ti4O7 powder and 1.5 g of NaCl were mixed evenly and compressed into a tablet using a powder tablet press to obtain a preform with a diameter of 30 mm. The preform was then sintered in a vacuum sintering furnace, with the vacuum level maintained at 10 during the sintering process. -2 Pa below; sintering procedure as follows: at 10 ℃ min -1 The heating rate was increased from room temperature to 1000 °C, and then increased at a rate of 5 °C / min. -1 The heating rate was increased to 1200 °C, and then held at 1200 °C for 2 h. The sintered preform was boiled in ultrapure water for 2 h to remove residual NaCl, and then sonicated and dried to obtain the Ti4O7 electrode. The obtained Ti4O7 electrode was immersed in Ce(NO3)3·6H2O solution (the mass of Ce element in Ce(NO3)3·6H2O solution was 1% of the mass of Ti4O7 in the Ti4O7 electrode) under vacuum for 30 min, and then evaporated at 70 °C for 24 h to remove the liquid; the dried sample was placed in a box furnace and evaporated at 5 °C for 5 min. -1 The temperature was increased to 300 °C at a certain rate. Then, it was calcined at 300 °C for 2 h to obtain a CeO2-Ti4O7 electrode; The CeO2-Ti4O7 electrode was immersed in an H2PtCl6 solution (the mass of Pt in the H2PtCl6 solution was 1% of the mass of Ti4O7 in the CeO2-Ti4O7 electrode) under vacuum for 30 min to ensure that the solution penetrated into the electrode. The solution was then dried at 70 °C. Finally, the electrode was sintered in a vacuum furnace at a vacuum level below 10 °C. -2 Heating to 500℃ under Pa conditions and holding for 2 h yields a Pt / CeO2@Ti4O7 electrode.

[0026] To prevent PFOA and GenX from adsorbing onto the glass during the reaction, the electrochemical reaction device in the following examples is made of acrylic sheet.

[0027] The conductivity of both a 50 mM Na₂SO₄ aqueous solution and a 79.4 mM NaNO₃ aqueous solution is 8.4 mS / cm. -1 In the following examples, the substances to be degraded in the reaction solution have a slight effect on the conductivity of the reaction solution, but this effect is negligible due to the low concentration of the substances.

[0028] Example 1: A method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes includes the following steps: 12.5 mL of Na₂SO₄ solution, 100 μL of PFOA solution, and 37.4 mL of deionized water were added to an electrochemical reaction apparatus, resulting in a final reaction solution with a total volume of 50 mL. The PFOA concentration in the reaction solution was 2 μM, and the Na₂SO₄ concentration was 50 mM. A Pt / CeO₂@Ti₄O₇ electrode was used as the anode, and a 304 stainless steel sheet was used as the cathode. The reaction was continuously stirred to degrade the PFOA in the PFOA solution. The total degradation time was 150 min, and the applied DC current density was 15 mA cm⁻¹. -2 .

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that the current density is 20 mA cm⁻¹. -2 .

[0030] Example 3: The difference between this embodiment and Example 1 is that 12.5 mL of Na2SO4 solution was replaced with 12.5 mL of NaNO3 solution; the final reaction solution has a total volume of 50 mL; in the reaction solution, the concentration of PFOA is 2 μM and the concentration of NaNO3 is 79.4 mM; other conditions remain unchanged.

[0031] Example 4 The difference between this embodiment and Embodiment 3 is that the current density is 20 mA cm⁻¹. -2 .

[0032] like Figure 1 The figure shows the degradation effect of Pt / CeO2@Ti4O7 electrode on PFOA in Na2SO4 or NaNO3 systems at different current densities for Examples 1, 2, 3, and 4; samples were taken every 30 min during the degradation process. The figure shows "Na2SO4 15 mA cm⁻¹". -2 "This corresponds to Example 1, "Na2SO4 20 mA cm" -2 "This corresponds to Example 2, "NaNO3 15 mAcm" -2 "This corresponds to Example 3, "NaNO3 20 mA cm" -2 "This corresponds to Example 4."

[0033] Figure 1Comparative analysis revealed that the degradation efficiency of the Pt / CeO2@Ti4O7 electrode gradually increased with increasing current density, and the removal efficiency of PFOA in the Na2SO4 system was significantly higher than that in the NaNO3 system. At 20 mA cm⁻¹ -2 Below, the degradation rate constant of PFOA in the Na2SO4 system ( = 8.33×10 -3 min -1 ) is the degradation rate constant in the NaNO3 system. = 1.76×10 -3 min -1 The concentration of NaNO3 electrolyte is 4.7 times that of NaNO3 electrolyte. Because NaNO3 electrolyte is an inert electrolyte, besides direct electron transfer reactions, only a small amount of active substances are produced in its system. • OH, while SO4 in the Na2SO4 system 2- It can be activated and converted into SO4 •- Therefore, it can be inferred that new active substances were generated in the Na2SO4 system, which enhanced the degradation ability of the Pt / CeO2@Ti4O7 electrode for PFOA.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that a Ti4O7 electrode is used as the anode, and the current density is 20 mAcm⁻². -2 .

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that a Ti4O7 electrode is used as the anode, and the current density is 20 mAcm⁻². -2 Replace 12.5 mL of Na2SO4 solution with 12.5 mL of NaNO3 solution, so that the concentration of NaNO3 in the reaction solution is 79.4 mM, while keeping other conditions unchanged.

[0036] like Figure 2 The figures show the degradation effects of Pt / CeO2@Ti4O7 and Ti4O7 electrodes on PFOA in Na2SO4 or NaNO3 systems for Examples 2, 4, Comparative Example 1, and 2. In the figures, "Pt / CeO2@Ti4O7Na2SO4" represents Example 2, "Pt / CeO2@Ti4O7NaNO3" represents Example 4, "Ti4O7Na2SO4" represents Comparative Example 1, and "Ti4O7NaNO3" represents Comparative Example 2.

[0037] At 20 mA cm -2In the Na2SO4 system, compared with the Ti4O7 electrode, the Pt / CeO2@Ti4O7 electrode significantly improved the degradation efficiency of PFOA.

[0038] Example 5: The difference between this embodiment and Example 1 is that 100 μL of PFOA solution was replaced with 100 μL of GenX solution, the concentration of GenX in the reaction solution was 2 μM, and the current density was 20 mA cm⁻¹. -2 All other conditions remain unchanged.

[0039] Example 6: The difference between this embodiment and Example 5 is that 12.5 mL of Na₂SO₄ solution is replaced with 12.5 mL of NaNO₃ solution, the NaNO₃ concentration in the reaction solution is 79.4 mM, and the current density is 20 mA cm⁻¹. -2 Other conditions remain unchanged.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that a Ti4O7 electrode is used as the anode, and the current density is 20 mAcm⁻². -2 Replace 100 μL of PFOA solution with 100 μL of GenX solution, and the concentration of GenX in the reaction solution is 2 μM.

[0041] Comparative Example 4 The difference between this comparative example and Example 1 is that a Ti4O7 electrode is used as the anode, and the current density is 20 mAcm⁻². -2 Replace 100 μL of PFOA solution with 100 μL of GenX solution, and the concentration of GenX in the reaction solution is 2 μM. Replace 12.5 mL of Na2SO4 solution with 12.5 mL of NaNO3 solution, and the concentration of NaNO3 in the reaction solution is 79.4 mM. Keep other conditions unchanged.

[0042] like Figure 3 The figures show the degradation effects of Pt / CeO2@Ti4O7 and Ti4O7 electrodes on GenX in Na2SO4 or NaNO3 systems for Examples 5, 6, Comparative Examples 3, and 4. In the figures, "Pt / CeO2@Ti4O7Na2SO4" represents Example 5, "Pt / CeO2@Ti4O7NaNO3" represents Example 6, "Ti4O7Na2SO4" represents Comparative Example 3, and "Ti4O7NaNO3" represents Comparative Example 4.

[0043] from Figure 3It can be seen that, compared with the Ti4O7 electrode, the Pt / CeO2@Ti4O7 electrode significantly improves the removal efficiency of GenX. The Pt / CeO2@Ti4O7 electrode shows a more significant removal effect on PFOA compared to GenX.

[0044] To further analyze the degradation mechanism of PFOA and GenX, linear sweep spectroscopy and CV were used to perform linear scans on the Pt / CeO2@Ti4O7 electrode and the Ti4O7 electrode. The specific reaction conditions are as follows: Reaction conditions: ① A Pt / CeO2@Ti4O7 electrode was used as the working electrode, a Pt electrode as the auxiliary electrode, and an Ag / AgCl electrode as the reference electrode. The volume of the reaction solution was 50 mL, and the electrolyte in the reaction solution was Na2SO4 with a concentration of 50 mM. Reaction conditions ②: A Pt / CeO2@Ti4O7 electrode was used as the working electrode, a Pt electrode as the auxiliary electrode, and an Ag / AgCl electrode as the reference electrode. The volume of the reaction solution was 50 mL, and the electrolyte in the reaction solution was NaNO3 with a concentration of 79.4 mM. Reaction conditions ③: Ti4O7 electrode is used as working electrode, Pt electrode as auxiliary electrode, Ag / AgCl electrode as reference electrode, the volume of reaction solution is 50 mL, the electrolyte in the reaction solution is Na2SO4, and the concentration of the electrolyte is 50 mM. Reaction conditions ④: Ti4O7 electrode was used as the working electrode, Pt electrode as the auxiliary electrode, Ag / AgCl electrode as the reference electrode, the volume of the reaction solution was 50 mL, the electrolyte in the reaction solution was NaNO3, and the concentration of the electrolyte was 79.4 mM.

[0045] Figure 4 The figures show the LSV curves of the Pt / CeO2@Ti4O7 electrode when Na2SO4 or NaNO3 is used as the electrolyte. The curve for "Pt / CeO2@Ti4O7Na2SO4" represents reaction condition ①, and the curve for "Pt / CeO2@Ti4O7NaNO3" represents reaction condition ②. The LSV curves of the Pt / CeO2@Ti4O7 electrode show that when the potential is greater than 1.5 V, the current density in Na2SO4 is greater than the current density in NaNO3, indicating that electron transfer occurs in the Na2SO4 solution.

[0046] Figure 5These are the CV curves of Ti4O7 and Pt / CeO2@Ti4O7 electrodes in the Na2SO4 or NaNO3 system. The curve for "Pt / CeO2@Ti4O7Na2SO4" represents reaction condition ①; the curve for "Pt / CeO2@Ti4O7NaNO3" represents reaction condition ②; the curve for "Ti4O7Na2SO4" represents reaction condition ③; and the curve for "Ti4O7NaNO3" represents reaction condition ④. The scan rate is 50 mV / s. -1 .

[0047] Compared to Ti4O7 electrodes, the Pt / CeO2@Ti4O7 electrode exhibits nearly 1.4 times higher electroactivated surface area. Furthermore, the Pt / CeO2@Ti4O7 electrode has a larger electroactivated surface area in Na2SO4 than in the NaNO3 system, which facilitates its electroactivated SO4. 2- Degrades PFOA and GenX.

[0048] To further verify SO4 •- The formation of free radicals was achieved by adding DMPO (50 mM concentration) to the reaction solutions under reaction conditions ⑤ and ⑥, and detecting it using EPR technology.

[0049] Reaction conditions ⑤: A Pt / CeO2@Ti4O7 electrode was used as the anode, a 304 stainless steel sheet as the cathode, the volume of the reaction solution was 50 mL, the electrolyte in the reaction solution was Na2SO4 with a concentration of 50 mM, and the current density was 20 mA cm⁻¹. -2 .

[0050] Reaction conditions ⑥: A Pt / CeO2@Ti4O7 electrode was used as the anode, a 304 stainless steel sheet as the cathode, the volume of the reaction solution was 50 mL, the electrolyte in the reaction solution was NaNO3 with a concentration of 79.4 mM, and the current density was 20 mA cm⁻¹. -2 .

[0051] Figure 6 This is the EPR spectrum of the Pt / CeO2@Ti4O7 electrode when Na2SO4 or NaNO3 is used as the electrolyte; from Figure 6 It can be seen that the signal is more pronounced in the Na2SO4 system. Due to the superposition effect of multiple nuclear spin couplings, the EPR spectrum shows more splitting peaks, indicating that the Pt / CeO2@Ti4O7 electrode can effectively activate SO4 in the Na2SO4 system. 2- SO4 is produced •- .

[0052] The embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The technical solutions of the present invention are not limited to the specific embodiments described above; all technical modifications made according to the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes, characterized in that, Includes the following steps: In the electrochemical reaction device, a Pt / CeO2@Ti4O7 electrode is used as the anode and a 304 stainless steel sheet is used as the cathode. The reaction solution in the electrochemical reaction device contains the product to be degraded, electrolyte, and deionized water. Under the action of an applied DC electric field, the product to be degraded is electrochemically degraded. The substances to be degraded are perfluorooctanoic acid and / or hexafluoropropylene oxide dimer.

2. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The Pt / CeO2@Ti4O7 electrode is prepared as follows: Ti4O7 and NaCl were mixed in a mass ratio of 3:1 and pressed into shape. The mixture was then kept at 1200 °C for 2 h to obtain a preform. The preform was boiled in ultrapure water to remove residual NaCl and then dried to obtain the Ti4O7 electrode. The Ti4O7 electrode was immersed in Ce(NO3)3·6H2O solution and then dried. The dried sample was calcined at 300 °C for 2 h to obtain the CeO2-Ti4O7 electrode. The mass of Ce element in the Ce(NO3)3·6H2O solution was 1% of the mass of Ti4O7 in the Ti4O7 electrode. The CeO2-Ti4O7 electrode was immersed in H2PtCl6 solution and then dried. The dried sample was kept at 500 ℃ for 2 h to obtain the Pt / CeO2@Ti4O7 electrode. The mass of Pt element in H2PtCl6 solution was 1% of the mass of Ti4O7 in CeO2-Ti4O7 electrode.

3. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The concentration of the substance to be degraded in the reaction solution is 2 μM.

4. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The concentration of the electrolyte in the reaction solution is 50-79.4 mM.

5. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The electrolyte is Na2SO4 or NaNO3.

6. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 5, characterized in that: When the electrolyte is Na2SO4, the concentration of Na2SO4 in the reaction solution is 50 mM; when the electrolyte is NaNO3, the concentration of NaNO3 in the reaction solution is 79.4 mM.

7. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The current density of the applied DC electric field is 15-20 mA cm⁻¹. -2 .

8. The method for electrochemically activating sulfate to degrade perfluorooctanoic acid and its substitutes according to claim 1, characterized in that: The degradation time should be no less than 150 min.

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