Method for electrochemical capture and conversion coupling to promote the purification of perfluorinated compounds

Abstract

The application develops a three-dimensional graphene and redox polymer composite electrode material through polymer interface engineering, optimizes the material structure and electrochemical properties by regulating and controlling the heat preparation parameters, realizes efficient capture of typical perfluorinated compounds, further integrates a boron-doped diamond electrode, constructs an electrochemical capture and conversion system, and can effectively separate and degrade trace concentration of perfluorinated compounds in industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of perfluorinated compound degradation, specifically relating to a method for promoting the purification of perfluorinated compounds through electrochemical capture and conversion coupling. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are synthetically produced fluorine compounds with extremely strong carbon-fluorine bonds, excellent chemical and thermal stability, and are difficult to degrade naturally. They also exhibit both hydrophobic and hydrophilic properties, posing a significant challenge to the global water treatment field. Traditional adsorption technologies are mostly irreversible processes, typically requiring incineration after adsorption saturation or harsh conditions such as strong acids or alkalis for desorption, which not only increases operating costs and reagent consumption but also easily generates secondary pollution. Direct oxidation degradation technology, on the other hand, is inefficient and extremely energy-intensive at low concentrations. Developing a reversible, efficient adsorption separation platform that can be coupled with downstream degradation technologies is crucial for the sustainable treatment of PFAS.

[0003] Electrochemical capture and conversion (ECC) technology can selectively enrich trace amounts of PFAS from complex matrices and achieve their efficient degradation. The core of this technology lies in the design of the electrode materials. Carbon-based electrodes, with their large surface area, low porosity, good electrochemical stability, and high conductivity, are widely used in electroadsorption technologies. However, their surface functional groups are limited, resulting in a weak driving force for the electrostatic adsorption of anionic PFAS, leading to poor adsorption capacity and selectivity. Furthermore, they are susceptible to interference from coexisting ions in the water. In addition, during long-term cycling, carbon materials are prone to structural collapse and oxidative corrosion, exhibiting poor regeneration performance and cycling stability, making it difficult to meet the requirements for efficient PFAS removal and practical engineering applications.

[0004] In contrast, redox-active materials have significant advantages for ECC technology. They possess reversible redox active sites, which can significantly increase adsorption capacity through Faraday reactions. They also exhibit stronger ion selectivity, high structural and functional designability, good charge-discharge reversibility, and easy gentle desorption and regeneration. Furthermore, they have excellent flexibility and film-forming properties, making it easy to prepare electrodes suitable for different scenarios. However, these polymers also have significant drawbacks. Their conductivity is generally poor, and they usually need to be used in combination with carbon materials and conductive agents. Long-term charge-discharge can easily lead to structural stability problems such as swelling and dissolution. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention develops a three-dimensional graphene-redox polymer composite electrode material through polymer interface engineering. By adjusting the thermal preparation parameters to optimize the material structure and electrochemical properties, efficient capture of typical perfluorinated compounds is achieved. Furthermore, a boron-doped diamond electrode is integrated to construct an electrochemical capture and conversion system capable of effectively separating and degrading trace concentrations of perfluorinated compounds in industrial wastewater. The specific technical solution of this invention is as follows:

[0006] A method for promoting the purification of perfluorinated compounds through electrochemical capture and conversion coupling includes the following steps:

[0007] Step 1: Constructing the composite electrode. First, select carbon cloth of a certain size, clean and dry it, and arrange the obtained carbon in a mixed solution of graphene oxide and ethylenediamine. Perform a hydrothermal reaction at 90-180℃ for 6-12 h to prepare a three-dimensional graphene structure on the surface of the carbon cloth, thus obtaining the initial working electrode. Next, electrochemical deposition is used to deposit polyaniline on the initial working electrode. Using an Ag / AgCl electrode as the reference electrode, a graphite rod as the counter electrode, and the initial working electrode as the working electrode, the electrolyte solution is prepared by mixing aniline hydrochloride and sulfuric acid. Electrodeposition is performed using cyclic voltammetry within a specific voltage range, and finally, a redox polymer / three-dimensional graphene / carbon cloth composite electrode is prepared.

[0008] Step 2: Adsorption and enrichment of perfluorinated compounds. A three-electrode electrochemical system was used, with an Ag / AgCl electrode as the reference electrode, a graphite rod as the counter electrode, and the composite electrode prepared in Step 1 as the working electrode. The electrolyte solution was prepared by mixing perfluorooctanoic acid and sodium chloride. A constant positive voltage was applied to the composite electrode. During the adsorption and enrichment process, the electrolyte solution was stirred at a constant speed, and the concentration change of perfluorooctanoic acid in the solution was monitored in real time. When the concentration of perfluorooctanoic acid in the solution was lower than the preset threshold, the adsorption and enrichment was stopped.

[0009] Step 3: Transfer the saturated electrode from Step 2 to a container to construct a three-electrode working system. Apply a negative voltage to allow the perfluorinated compound to desorb from the electrode, thus obtaining a concentrated solution of the perfluorinated compound.

[0010] Step 4: Place the boron-doped diamond electrode in the perfluorinated compound concentrate obtained in Step 3 for electrochemical degradation treatment. Apply voltage to carry out degradation. The degradation conditions are: temperature controlled at 50℃, constant potential of +4.0 V applied, and treatment time of 60-200 min.

[0011] In step 1, the carbon cloth is cleaned with ethanol to remove surface impurities, then placed in deionized water for ultrasonic treatment for 10 min, and then dried at 100℃ for 2 h.

[0012] In step 1, the concentration of graphene oxide in the mixed solution of graphene oxide and ethylenediamine is 1-5 mg / mL, and the volume fraction of ethylenediamine is 0.5-1.5%.

[0013] In step 1, the electrochemical deposition method uses an electrolyte solution prepared by mixing 0.05-0.3 mol / L aniline hydrochloride and 0.2-1.0 mol / L sulfuric acid. The deposition voltage range is -0.2 V to 1.2 V, the scan rate is 5-50 mV / s, and the number of cycles is 10-50.

[0014] In step 2, the constant positive voltage is 0 V - +1.0 V, the adsorption and enrichment time is 30-180 min, and the stirring rate is 200-800 rpm.

[0015] The preset threshold in step 2 is 0.01-0.5 mM.

[0016] In step 3, the electrolyte is a sodium chloride or sodium sulfate solution with a concentration of 5-20 mM / L, the applied negative voltage is -1.0 V to 0 V, and the desorption time is 30-90 min.

[0017] In step 4, the electrochemical degradation treatment uses a boron-doped diamond electrode or a titanium-coated electrode as the anode and a stainless steel or titanium plate as the cathode. Stirring or ultrasonic assistance is maintained during the degradation process to improve mass transfer efficiency. The degradation treatment time in step 4 is 1-4 V at a temperature of 20-50 °C. O C, the time is 120 min.

[0018] This invention relates to a three-dimensional graphene-redox polymer composite electrode material. By optimizing the material structure and electrochemical properties through controlled thermal preparation parameters, it achieves efficient capture of typical perfluorinated compounds. Integrating a boron-doped diamond electrode, it constructs an electrochemical capture and conversion system to effectively separate and degrade trace concentrations of perfluorinated compounds in industrial wastewater. The principles of this invention are: first, utilizing the high specific surface area and interconnected network structure of three-dimensional graphene, high dispersion of redox polymers such as polyaniline can be achieved, effectively suppressing their self-agglomeration effect, increasing the effective surface area, improving the accessibility of redox reaction active sites, and solving the problem of electron transfer from the electrode to the surface and interface; second, enhancing the adsorption mechanism by using the amine functional groups in the redox polymer structure to generate electrostatic interactions with the anionic head groups such as carboxylates or sulfonates of PFAS molecules, and synergizing with the Faraday redox reaction, significantly improving the deep capture effect of PFAS; and third, by electrochemically controlling the redox state of the composite electrode material, efficient desorption of perfluorinated compounds is achieved, further integrating an electrochemical oxidation electrode to achieve efficient degradation of PFAS.

[0019] The beneficial technical effects of this invention are as follows: By utilizing the amine groups (PFAS binding sites) and redox activity (adsorption-desorption control switch) inherent in three-dimensional graphene / redox polymers, efficient electronic control of PFAS adsorption behavior can be achieved. At the same time, coupled with downstream electrochemical oxidation technology, a low-energy PFAS treatment solution of "concentration first, then degradation" is proposed. Attached Figure Description

[0020] Figure 1 This is an SEM image of the product obtained in step 1 of Embodiment 1 of the present invention. Detailed Implementation

[0021] Example 1

[0022] Electrochemical capture and conversion coupling can be used to promote the purification of perfluorinated compounds through the following steps:

[0023] Step 1: Constructing a composite electrode. First, select a carbon cloth of 1cm×1cm×0.2cm, clean it with ethanol to remove surface impurities, and then place it in deionized water for ultrasonic treatment for 10 min to further remove residual impurities and oil stains; then dry the carbon cloth at 100℃ for 2 h to obtain a clean and dry carbon cloth substrate. The obtained carbon was arranged in a mixed solution of graphene oxide and ethylenediamine. The mixed solution was an aqueous solution with a graphene oxide concentration of 1-5 mg / mL and an ethylenediamine volume fraction of 0.5-1.5%. The hydrothermal reaction was carried out at 90-180℃ for 6-12 h to prepare a three-dimensional graphene structure on the carbon cloth surface, which was then used as the initial working electrode. Next, polyaniline was deposited on the initial working electrode using electrochemical deposition. An Ag / AgCl electrode was used as the reference electrode, a graphite rod was used as the counter electrode, and the initial working electrode was used as the working electrode. The electrolyte solution was prepared by mixing aniline hydrochloride and sulfuric acid. Electrodeposition was performed using cyclic voltammetry within a specific voltage range. The electrochemical deposition process was as follows: the electrolyte solution was prepared by mixing 0.05-0.3 mol / L aniline hydrochloride and 0.2-1.0 mol / L sulfuric acid; the deposition voltage range was -0.2 V to 1.2 V; the scan rate was 5-50 mV / s; and the number of cycles was 10-50. Finally, a redox polymer / three-dimensional graphene / carbon cloth composite electrode was prepared, and the SEM image of the obtained product is shown below. Figure 1 As shown, by Figure 1 It is evident that the obtained product is a three-dimensional porous network structure;

[0024] Step 2: Adsorption and enrichment of perfluorinated compounds using a three-electrode electrochemical system. An Ag / AgCl electrode was used as the reference electrode, a graphite rod as the counter electrode, and the composite electrode prepared in Step 1 as the working electrode. The electrolyte solution was prepared by mixing perfluorooctanoic acid (PFOA) and sodium chloride. A constant positive voltage of 0 V to +1.0 V was applied to the composite electrode. The adsorption and enrichment time was 30-180 min. During the adsorption and enrichment process, the electrolyte solution was stirred at a constant speed of 200-800 rpm, and the concentration of PFOA in the solution was monitored in real time. When the concentration of PFOA in the solution fell below a preset threshold (0.01-0.5 mM), the adsorption and enrichment was stopped. The removal efficiency of PFOA reached up to 95.3%, and the adsorption capacity reached 650 mg / g.

[0025] Step 3: Transfer the saturated electrode from Step 2 to a container to construct a three-electrode working system. Support the electrolyte with a sodium chloride or sodium sulfate solution of 5-20 mM / L, apply a negative voltage of -1.0 V to 0 V, and desorption time of 30-90 min to allow the perfluorinated compound to desorb from the electrode and obtain a concentrated perfluorinated compound solution with a desorption rate of up to 90%.

[0026] Step 4: The boron-doped diamond electrode is placed in the concentrated perfluorinated compound solution obtained in Step 3 for electrochemical degradation. Degradation is carried out under the following conditions: temperature controlled at 50℃, constant potential of +3.0 V, and treatment time of 60-200 min. The electrochemical degradation treatment uses a boron-doped diamond electrode or a titanium-coated electrode as the anode and a stainless steel or titanium plate as the cathode. Stirring or ultrasonic assistance is maintained during the degradation process to improve mass transfer efficiency, achieving a degradation efficiency of over 85%.

[0027] Example 2

[0028] This embodiment is basically the same as Embodiment 1, except that the hydrothermal reaction temperature and the number of polyaniline deposition cycles in step 1 were adjusted to explore their effects on electrode performance.

[0029] 1. Electrode preparation: The hydrothermal reaction temperature was adjusted to 160℃ (reaction time 8 h), and the number of electrochemical deposition cycles was increased to 40 (other parameters remained unchanged). The higher hydrothermal temperature resulted in a denser three-dimensional graphene framework, but excessive polyaniline cycling led to slight surface agglomeration.

[0030] 2. Adsorption performance test: Under the same adsorption conditions (+0.8 V), the adsorption capacity of this electrode for PFOA was 600 mg / g, and the removal efficiency was 88.5%. This is slightly lower than that in Example 1, indicating that an excessively thick polymer layer may block some pores and reduce the accessibility of active sites.

[0031] 3. Desorption and Degradation: The desorption rate remained above 88%, and the final degradation rate (+3.5 V, 120 min) was 85.2%. The results show that the material structure and electrochemical performance can be optimized by adjusting the thermal preparation parameters (temperature, number of cycles), and the optimal parameter window can maximize the performance.

[0032] Example 3

[0033] This embodiment aims to verify the universality of the method for other types of perfluorinated compounds by replacing the target pollutant with perfluorooctanoic acid (PFOS).

[0034] 1. Electrode preparation: Same as in Example 1.

[0035] 2. Adsorption and enrichment: The PFOA in the electrolyte was replaced with 50 mg / L PFOS, and adsorption was performed under a voltage of +0.9 V for 150 min. The results showed that the removal efficiency of PFOS was 93.5%, and the adsorption capacity reached 640 mg / g.

[0036] 3. Desorption and Concentration: Desorption was performed at -0.8 V for 60 min, with a desorption rate of 89%. This demonstrates that the composite electrode also exhibits good electro-controlled adsorption-desorption performance for sulfonic acid head groups of PFAS.

[0037] 4. Electrochemical degradation: Using a BDD electrode, the concentrated solution was degraded at +4.0 V for 120 min, and the PFOS degradation rate was 86.1%. This indicates that the system is also suitable for the efficient treatment of PFOS.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for promoting the purification of perfluorinated compounds through electrochemical capture and conversion coupling, characterized in that, Includes the following steps: Step 1: Constructing the composite electrode. First, select carbon cloth of a certain size, clean and dry it, and arrange the obtained carbon in a mixed solution of graphene oxide and ethylenediamine. Perform a hydrothermal reaction at 90-180℃ for 6-12 h to prepare a three-dimensional graphene structure on the surface of the carbon cloth, thus obtaining the initial working electrode. Next, electrochemical deposition is used to deposit polyaniline on the initial working electrode. Using an Ag / AgCl electrode as the reference electrode, a graphite rod as the counter electrode, and the initial working electrode as the working electrode, the electrolyte solution is prepared by mixing aniline hydrochloride and sulfuric acid. Electrodeposition is performed using cyclic voltammetry within a specific voltage range, and finally, a redox polymer / three-dimensional graphene / carbon cloth composite electrode is prepared. Step 2: Adsorption and enrichment of perfluorinated compounds. A three-electrode electrochemical system was used, with an Ag / AgCl electrode as the reference electrode, a graphite rod as the counter electrode, and the composite electrode prepared in Step 1 as the working electrode. The electrolyte solution was prepared by mixing perfluorooctanoic acid and sodium chloride. A constant positive voltage was applied to the composite electrode. During the adsorption and enrichment process, the electrolyte solution was stirred at a constant speed, and the concentration change of perfluorooctanoic acid in the solution was monitored in real time. When the concentration of perfluorooctanoic acid in the solution was lower than the preset threshold, the adsorption and enrichment was stopped. Step 3: Transfer the saturated electrode from Step 2 to a container to construct a three-electrode working system. Apply a negative voltage to allow the perfluorinated compound to desorb from the electrode, obtaining a concentrated solution of the perfluorinated compound. Step 4: Place the boron-doped diamond electrode in the perfluorinated compound concentrate obtained in Step 3 for electrochemical degradation treatment. Apply voltage to carry out degradation. The degradation conditions are: temperature controlled at 50℃, constant potential of +4.0 V applied, and treatment time of 60-200 min.

2. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, In step 1, the carbon cloth is cleaned with ethanol to remove surface impurities, then placed in deionized water for ultrasonic treatment for 10 min, and then dried at 100℃ for 2 h.

3. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, In step 1, the concentration of graphene oxide in the mixed solution of graphene oxide and ethylenediamine is 1-5 mg / mL, and the volume fraction of ethylenediamine is 0.5-1.5%.

4. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, In step 1, the electrochemical deposition method uses an electrolyte solution prepared by mixing 0.05-0.3 mol / L aniline hydrochloride and 0.2-1.0 mol / L sulfuric acid. The deposition voltage range is -0.2 V to 1.2 V, the scan rate is 5-50 mV / s, and the number of cycles is 10-50.

5. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, In step 2, the constant positive voltage is 0 V - +1.0 V, the adsorption and enrichment time is 30-180 min, and the stirring rate is 200-800 rpm.

6. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, The preset threshold in step 2 is 0.01-0.5 mM.

7. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, Step 3 supports chloride solutions with an electrolyte concentration of 5-20 mM / L. Alternatively, a sodium sulfate solution can be used, with an applied negative voltage of -1.0 V to 0 V and a desorption time of 30-90 min.

8. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1, characterized in that, In step 4, the electrochemical degradation process uses boron-doped diamond electrodes or titanium-coated electrodes as anodes and stainless steel or titanium plates as cathodes. Stirring or ultrasonic assistance is maintained during the degradation process to improve mass transfer efficiency.

9. The method for promoting the purification of perfluorinated compounds by electrochemical capture and conversion coupling according to claim 1 or 8, characterized in that, In step 4, the degradation treatment time is 1-4 V, and the temperature is 20-50 °C. O C, the time is 120 min.

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