A method for degrading perfluorohexane sulfonic acid in wastewater based on ionizing radiation technology

Abstract

This invention provides a method for degrading perfluorohexanesulfonic acid (PFHA) in wastewater based on ionizing irradiation technology. The method includes: adding reagent A to wastewater containing PFHA, followed by ionizing irradiation treatment to reduce and defluorinate the PFHA in the wastewater. Hydrogen peroxide is then added to the defluorinated solution, followed by a second ionizing irradiation treatment to complete the deep decomposition and mineralization of PFHA in the wastewater. This invention has advantages such as simple process, mild conditions, high defluorination efficiency, good mineralization effect, and ease of scale-up. It can efficiently reduce, defluorinate, and mineralize PFHA in wastewater and is suitable for treating various wastewaters containing PFHA pollutants.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, and specifically to a method for degrading perfluorohexanesulfonic acid in wastewater based on ionization irradiation technology. Background Technology

[0002] Per- or polyfluoroalkyl substances (PFAS) are a class of man-made organofluorine compounds that are widely used in the manufacture of flame retardants due to their highly stable molecular structure. Because of their widespread use, PFAS have been frequently detected in the environment and pose a potential threat to the ecological environment and human health. Therefore, measures have been taken both domestically and internationally to restrict or ban the use of PFAS.

[0003] Perfluorohexanesulfonic acid (PFHxS) is often used as a substitute for PFAS due to its similar properties. It is widely used in fire-fighting water film-forming foam (AFFF), metal electroplating, textile and leather processing, interior decoration, polishing and cleaning agents, waterproof coating treatment, and electronics and semiconductor manufacturing.

[0004] Effective removal of PFHxS from water is a pressing issue in water treatment. Due to the high electronegativity of fluorine, breaking carbon-fluorine bonds requires significant energy. Furthermore, the smaller atomic radius of covalently bonded carbon atoms compared to fluorine atoms ensures the carbon-carbon bonds in PFHxS are well-protected, making them difficult to decompose and mineralize. Most current research focuses on the removal of PFAS from water, with limited research on PFHxS removal. For example, adsorption can remove some PFAS from water, but the adsorbed PFAS and adsorbent require further treatment (see Non-Patent Literature 1). Biological methods are commonly used for wastewater treatment, but their ability to remove PFAS is limited, and no strains capable of decomposing PFAS have been reported. Advanced oxidation processes (AOS) are commonly used for advanced wastewater treatment, relying on strong oxidizing groups such as hydroxyl radicals generated during the process to remove most recalcitrant organic pollutants from water; however, AOS is not ideal for removing PFAS from water. In contrast, advanced reduction processes have shown some ability to remove PFAS from water (see Non-Patent Literature 2). This study shows that hydrated electrons generated during ultraviolet irradiation can remove fluoride from PFAS, leading to PAFS decomposition. However, ultraviolet light has weak penetration in water, resulting in low hydrated electron yield. Long irradiation times (≥24h) are required to achieve satisfactory defluorination efficiency. Ionizing irradiation is a novel advanced oxidation technology. Compared with conventional advanced oxidation technologies, ionizing irradiation not only generates oxidizing reactive particles such as hydroxyl radicals but also reducing reactive species such as hydrated electrons. Compared with ultraviolet irradiation, ionizing irradiation has stronger penetration capabilities. Studies have shown that ionizing irradiation can degrade PFAS in water, but the required irradiation dose is high (hundreds of kGy), leading to high energy consumption (non-patent literature 3). How to reduce the required ionizing irradiation dose for treating PFAS in water and improve the treatment effect is currently the bottleneck limiting the application of ionizing irradiation technology to remove PFAS from actual wastewater. It is worth noting that the concentration of PFAS in water is usually low; how to selectively remove PFAS in water with the coexistence of other organic matter is also a problem that urgently needs to be solved.

[0005] Non-patent literature

[0006] Non-patent literature 1: Park, M., Wu, S., Lopez, IJ, Chang, JY, Karanfil, T. and Snyder, SA2020. Water Research 170, 115364.

[0007] Non-patent literature 2: Bentel, MJ, Liu, Z., Yu, Y., Gao, J., Men, Y. and Liu, J. 2020. Environmental Science & Technology Letters 7(5), 351-357.

[0008] Non-patent literature 3: Lassalle, J., Gao, R., Rodi, R., Kowald, C., Feng, M., Sharma, VK, Hoelen, T., Bireta, P., Houtz, EF, Staack, D. 2021. Radiation Physics and Chemistry 189, 109705. Summary of the Invention

[0009] To address the aforementioned problems, this invention aims to propose a method for degrading perfluorohexanesulfonic acid (PFHA) in wastewater based on ionizing radiation technology. This method solves the difficulty in treating PFHA in water bodies. Specifically, this invention proposes a method for degrading PFHA in wastewater based on ionizing radiation technology. This method constructs a system using hydrated electrons / SO2· - SO3 - Hydrated electrons / CO2· - Two systems are proposed that can effectively break the carbon-fluorine bonds in perfluorinated compounds, achieving efficient defluorination while lowering the energy barrier required to break other carbon-fluorine bonds. Subsequently, the defluorinated organic products are further processed through oxidation, mineralizing them into CO2 and H2O. This technology is simple to operate, has excellent processing results, and is easily scalable for practical engineering applications.

[0010] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0011] A method for degrading perfluorohexane sulfonic acid in wastewater based on ionizing radiation technology, characterized by the following steps:

[0012] (1) Add reagent A to the wastewater containing perfluorohexanesulfonic acid and then perform ionization irradiation treatment; (2) Add a certain amount of hydrogen peroxide to the solution obtained after the ionization irradiation treatment in step (1) and then perform a second ionization irradiation treatment, thereby completing the degradation treatment of perfluorohexanesulfonic acid in the water.

[0013] Further, reagent A in step (1) is sodium sulfite or sodium formate.

[0014] Further, the molar ratio of reagent A to perfluorohexanesulfonic acid in the wastewater in step (1) is 1 to 30.

[0015] Furthermore, the irradiation source for the ionization irradiation treatment in step (1) is an electron accelerator, 60 Co or 137 Any of the following in Cs.

[0016] Further, the irradiation dose of the irradiation treatment in step (1) is 1 kGy to 100 kGy. Preferably, the irradiation dose is between 5 kGy and 30 kGy.

[0017] Furthermore, the hydrogen peroxide used in step (2) has a mass fraction of approximately 20-40%. The amount of hydrogen peroxide added is 0.02‰-1‰, and the irradiation dose is between 1-50 kGy.

[0018] Furthermore, the preferred irradiation dose in step (2) is 5 to 20 kGy.

[0019] In addition, in step (2), the irradiation source for the second ionization irradiation treatment is also an electron accelerator. 60 Co or 137 Any of the following in Cs.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention provides a method for degrading perfluorohexanesulfonic acid in wastewater based on ionization irradiation technology. It fully utilizes the oxidizing and reducing active species generated during electron beam irradiation, first constructing a selective hydrated electron / SO2· - SO3 - Hydrated electrons / CO2· - A reduction system is used to effectively defluorinate PFHxS. The structural stability of defluorinated PFHxS decreases, and then an oxidation system based on hydroxyl radicals is constructed to mineralize the defluorinated organic matter, thereby achieving degradation. This method is simple to operate, has strong processing capacity and high efficiency, and can effectively remove PFHxS from actual water bodies, providing a solution for the effective removal of PFHxS from water. Detailed Implementation

[0022] The present invention will be described in detail below through specific embodiments. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] Example 1:

[0024] Wastewater containing 5 mg / L PFHxS was artificially prepared by adding 2 mM sodium sulfite to the wastewater. 60The wastewater was irradiated with a Co source at a rate of 10 kGy. Then, 1 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation of 5 kGy. The final defluorination rate of PFHxS was 82.4%, and the mineralization rate was 44.1%.

[0025] Example 2:

[0026] Wastewater containing 5 mg / L PFHxS was artificially prepared by adding 2 mM sodium formate to the wastewater. 60 The wastewater was irradiated with a Co source at a rate of 20 kGy. Then, 1 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation of 5 kGy. The final defluorination rate of PFHxS was 66.2%, and the mineralization rate was 24.1%.

[0027] Example 3:

[0028] Wastewater containing 5 mg / L PFHxS was artificially prepared by adding 2 mM sodium sulfite to the wastewater. 60 The wastewater was irradiated with a Co source at a rate of 30 kGy. Then, 2 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation at 10 kGy. The final defluorination rate of PFHxS was 85.3%, and the mineralization rate was 78.1%.

[0029] Example 4:

[0030] Wastewater containing 5 mg / L PFHxS was artificially prepared by adding 4 mM sodium sulfite. 60 The wastewater was irradiated with a Co source at a rate of 15 kGy. Then, 1 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation at 20 kGy. The final defluorination rate of PFHxS was 95.1%, and the mineralization rate was 82.1%.

[0031] Example 5:

[0032] A measured amount of PFHxS was added to the effluent from the secondary sedimentation tank of an actual wastewater treatment plant to achieve a concentration of 5 mg / L. Then, 2 mM sodium sulfite was added to the wastewater. 60 The wastewater was irradiated with a Co source at a rate of 10 kGy. Then, 4 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation at 20 kGy. The final defluorination rate of PFHxS was 77.1%, and the mineralization rate was 46.2%.

[0033] Example 6:

[0034] A measured amount of PFHxS was added to the effluent from the secondary sedimentation tank of an actual wastewater treatment plant to achieve a concentration of 5 mg / L. Then, 4 mM sodium formate was added to the wastewater. 60 The wastewater was irradiated with a Co source at a rate of 10 kGy. Then, 4 mM hydrogen peroxide was added to the treated wastewater, followed by a second irradiation at 20 kGy. The final defluorination rate of PFHxS was 68.2%, and the mineralization rate was 22.1%.

[0035] Measurement methods and instruments

[0036] Fluoride ion concentration in wastewater:

[0037] The concentration of fluoride ions (mg / L) in wastewater was determined using a fluoride ion selective electrode and ion chromatography.

[0038] Defluorination rate:

[0039] The calculation method is to divide the fluoride ion concentration in the wastewater by the total fluoride ion concentration in the PFAS structure to obtain the percentage.

[0040] The concentration of organic carbon (TOC) in wastewater:

[0041] The concentration of organic carbon in the wastewater was analyzed using a total organic carbon analyzer.

[0042] Mineralization rate:

[0043] The result is (1 - TOC concentration in solution after the reaction ends / TOC concentration in solution at the beginning of the reaction).

[0044] As can be seen from the results of the above embodiments, the method of degrading perfluorohexanesulfonic acid in wastewater based on ionizing radiation technology of the present invention utilizes the active species generated by the synergistic effect of ionizing radiation and sulfite / formate to complete the primary defluorination of perfluorohexanesulfonic acid, thereby reducing the carbon-fluorine bond energy in perfluorohexanesulfonic acid. Then, the deep decomposition and mineralization of perfluorohexanesulfonic acid are completed through the subsequent oxidation by hydroxyl radicals. As can be seen from the above embodiments, this method can effectively achieve the defluorination and mineralization of perfluorinated compounds. In particular, in Example 3, the defluorination rate of PFHxS was 85.3%, and the mineralization rate was 78.1%; in Example 4, the defluorination rate of PFHxS was 95.1%, and the mineralization rate was 82.1%. Such results are fully applicable to practical daily life and production. Furthermore, from the perspective of the treatment method, this method is simple to operate, has strong treatment capacity, and can effectively remove PFHxS from actual water bodies. It can efficiently reduce, defluorinate, and mineralize perfluorohexanesulfonic acid in wastewater, demonstrating its applicability to the treatment of various wastewater containing perfluorohexanesulfonic acid pollutants.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0046] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0047] The above provides a detailed description of a method for degrading perfluorohexanesulfonic acid in wastewater based on ionization irradiation technology. Specific examples have been used to illustrate the principle and implementation of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A method for degrading perfluorohexanesulfonic acid in wastewater based on ionizing radiation technology, characterized in that, The steps are as follows: (1) Add reagent A to the wastewater containing perfluorohexanesulfonic acid, and then subject it to ionization irradiation treatment; (2) Add a certain amount of hydrogen peroxide to the solution obtained after the ionizing radiation treatment in step (1), and then perform a second ionizing radiation treatment to complete the degradation treatment of perfluorohexanesulfonic acid in water; Reagent A is sodium sulfite or sodium formate. In step (1), the irradiation dose of the ionization irradiation treatment is 5 kGy to 30 kGy. In step (2), the irradiation dose of the second ionization irradiation treatment is 5~20 kGy.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of reagent A to perfluorohexanesulfonic acid in the wastewater is 1 to 30.

3. The method according to claim 1, characterized in that, In step (1), the irradiation source for the ionization irradiation treatment is an electron accelerator, 60 Co and 137 Any of the following in Cs.

4. The method according to claim 1, characterized in that, In step (2), the mass fraction of the hydrogen peroxide is 20-40%, and the amount of hydrogen peroxide added is 0.02‰-1‰.

5. The method according to claim 1, characterized in that, In step (2), the irradiation source for the second ionization irradiation treatment is an electron accelerator. 60 Co and 137 Any of the following in Cs.