EB degradation of perfluorooctanoic acid and perfluorooctane sulfonate in aqueous solution

EB degradation of perfluorooctanoic acid and perfluorooctane sulfonate in aqueous solution 1 first-author 2 corresp Corresponding author: mhwu@staff.shu.edu.cn (M. Wu), Corresponding author: mhwu@staff.shu.edu.cn (M. Wu), mhwu@staff.shu.edu.cn 1 1 1 1 1 1 1 corresp xugang@shu.edu.cn (G. Xu) xugang@shu.edu.cn (G. Xu) xugang@shu.edu.cn School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China Shanghai Applied Radiation Institute, Shanghai University, 99 Shangda Road, Shanghai 200444, China Shanghai Applied Radiation Institute, Shanghai University, 99 Shangda Road, Shanghai 200444, China Electron beam (EB) degradation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in aqueous solutions was studied. Their degradation followed the pseudo-first-order kinetics. The decomposition efficiencies were 95.7% for PFOA and 85.9% for PFOS, by EB irradiation in an anoxic alkaline solution (pH=13). In presence of different radical scavengers, this work indicated hydrated electron and hydrogen radical were important in the electron beam degradation of PFOA and PFOS, especially hydrated electron. The potential degradation pathways of PFOA and PFOS by electron beam irradiation through defluorination and the removal of CH 2  unit were proposed. Perfluorooctanoic acid (PFOA) Perfluorooctane sulfonate (PFOS) Electron beam irradiation Degradation Defluorination 1. Introduction 1 Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are among the perfluorinated compounds (PFCs) that received a great deal of concern in recent years. Because of their extraordinary stability, hydrophobicity, oleophobicity and excellent surfactant performance, many PFCs have been widely applied to industrial and domestic production for over sixty years. PFOA and PFOS have been found almost ubiquitously in various environmental media including waters [ 1 1 - 4 4 1-4 ] , air [ 5 5 - 7 7 5-7 ] , sediments [ 8 8 , 9 9 ] , wildlife [ 10 10 , 11 11 ] and human [ 12 12 , 13 13 ] . Moreover, toxic and bioaccumulative effects of contaminants also have been confirmed by extensive studies [ 14 14 - 17 17 14-17 ] . These indicate that the toxic pollutants can accumulate in human body, and may pose a risk to human health. As a result, PFOS was listed as a Persistent Organic Pollutant under the Stockholm Convention in 2009, calling for restricted production and use worldwide. Recently, the degradation of PFOA and PFOS has received increasing attention. Various techniques including adsorption [ 18 18 , 19 19 ] , photolytic methods [ 20 20 - 23 23 20-23 ] , photoelectrocatalysis [ 24 24 ] , ultrasonic irradiation [ 25 25 , 26 26 ] , thermolysis [ 27 27 ] , gamma-irradiation [ 28 28 ] etc . [ 29 29 - 33 33 29-33 ] were used to remove PFOA and PFOS. However, PFCs are chemically inert due to the unique properties of fluorine and relatively strong carbon−fluorine bond (C−F, 116 kcal/mol) making them resistant to conventional advanced oxidation processes. Therefore, new techniques are desirable to efficiently decompose PFOA and PFOS. Electron beam (EB) irradiation has been recognized as effective method to treat organic pollutants [ 34 34 - 38 38 34-38 ] . Water is degraded into hydroxyl radicals ( • OH), hydrogen radical (H • ), and hydrated electron ( e aq − ) with different G-values (μmol/J) under EB irradiation as Eq. (1). The radicals react with the pollutants and cause their degradation [ 39 39 ] . While hydroxyl radical can oxidize the organic compounds in aqueous solutions, hydrogen radical and hydrated electron have reductive ability to reduce the targeted organic compounds [ 40 40 , 41 41 ] . Hydrated electron is a strong reducing agent, reacting rapidly with halogenated organic compounds [ 41 41 - 44 44 41-44 ] . <math id="M1"><mrow><msub><mtext>H</mtext><mn>2</mn></msub><mtext>O</mtext><mo>→</mo><mrow><mo>(</mo><mrow><mn>0.28</mn></mrow><mo>)</mo></mrow><msubsup><mtext>e</mtext><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><mrow><mo>(</mo><mrow><mn>0.06</mn></mrow><mo>)</mo></mrow><mtext>H</mtext><mo>⋅</mo><mo>+</mo><mrow><mo>(</mo><mrow><mn>0.27</mn></mrow><mo>)</mo></mrow><mtext>OH</mtext><mo>⋅</mo><mo>+</mo><mrow><mo>(</mo><mrow><mn>0.27</mn></mrow><mo>)</mo></mrow><msup><mtext>H</mtext><mo>+</mo></msup><mo>+</mo><mrow><mo>(</mo><mrow><mn>0.05</mn></mrow><mo>)</mo></mrow><msub><mtext>H</mtext><mn>2</mn></msub><mo>+</mo><mrow><mo>(</mo><mrow><mn>0.07</mn></mrow><mo>)</mo></mrow><msub><mtext>H</mtext><mn>2</mn></msub><msub><mtext>O</mtext><mn>2</mn></msub><mo>.</mo></mrow></math> <math display="block" id="M2"><mrow/></math> In the present study, the degradation kinetics of EB-irradiated PFOA and PFOS were determined. The effects of initial concentrations and initial pH on the degradation of contaminants were discussed. The roles of oxidative or reductive species in PFOA and PFOS degradation were investigated by selectively adding specific promoters or inhibitors, such as O 2 , N 2 , and tert-butanol (t-BuOH). Possible mechanisms of the radiolysis degradation of PFOA and PFOS were proposed. Our findings may brinan efficient and environmentally friendly technique for PFCs degradation. 2. Materials and methods 1 2.1. Materials 2 Perfluorooctanoic acid (PFOA, C 8 F 15 HO 2 , 95.5%) and perfluorooctane Sulfonate (PFOS, C 8 F 17 SO 3 K, 98.0%) were supplied by Dr. Ehrenstorfer (Augsburg, Germany). Ammonium acetate (LC grade, 99%), fluoride standard (99.99%) and methanol (HPLC grade, 99.99%) were provided by Shanghai Anpel scientific instrument corporation. Sodium carbonate (Na 2 CO 3 ), Sodium bicarbonate (NaHCO 3 ), Hydrogen chloride (HCl), sodium hydroxide (NaOH) and tert-butanol (t-BuOH) were purchased from Sinopharm Chemical Reagent Co., Ltd. All aqueous solutions were prepared by a Millipore Milli-Q system (resistance [18.2 MΩ]). 2.2. The samples and their irradiation 2 Four initial concentrations of PFOA and PFOS solutions in 100 mL polypropylene vessels were stored at 4°C before use. Samples pouched in high-density polyethylene (HDPE) bags were irradiated to 100–500 kGy at ambient temperatures by 1.8 MeV electron beams of up to 10 mA. The samples were placed about 30 cm away under the beam-scan horn. 2.3. Analytical methods 2 Concentrations of PFOA, PFOS and their degradation products were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using an Agilent 1260 LC chromatograph coupled to an Agilent 6460 mass spectrometer with electron spray ionization (ESI) interface and a heated nebulizer. HPLC separation was carried out by ZORBAX SB-C18 reversed-phase column (4.6×50 mm, 5μm, Agilent) and EC-C18 (3.0×100 mm, 2.7 μm, Agilent) at 40°C using a gradient composition of solvent A (methanol) and solvent B (water containing 2 mmol/L of ammonium acetate). The injection volume was 5 μL. The gradient (%A) was as follows: 0−0.75 min, a linear increase from 5% to 60%; 0.75−5 min, increase to 92% A; 5−5.1 min, further increase to 100% A; 5.1−8.5 min, being held at 100% A; 8.5−9.0 min, the mobile phase returning to the initial conditions; and 9−10 min, being held at 5% A. The flow rate was 0.4 mL/min. Quantification was performed using multiple reaction monitoring (MRM) of the transitions m/z 499→80.1 (PFOS) and m/z 413→368.9 (PFOA). Mass spectrometry full scanning analysis (m/z 100−550) was used to identify the intermediate products of PFOS and PFOA after irradiation. The instrument conditions were as follows: capillary voltage, 4.0 kV; drying gas flow, 3 L/min; drying gas temperature, 350°C; and source gas flow, 10 L/min; nebulizer pressure, 38 psi and nozzle voltage of 1 kV. An ion-chromatograph system (Dionex ICS-1100, USA) was used to determine the concentration of F − . It consisted of an automatic sample injector (sample injection volume: 25μL), a degasser, a pump, a guard column (Dionex AG22, 4×50 mm, USA), a separation column (Dionex AS22, 4×250 mm, USA), a column oven (30°C), and a conductivity detector with a suppressor device. The mobile phase was composed of 4.5 mmol/L Na 2 CO 3 and 1.4 mmol/L NaHCO 3 , and the flow rate was set at 1.0 mL/min. The lowest detection limit of F − was 0.02 mg/L. 3. Results and Discussion 1 3.1. Kinetic studies of PFOA and PFOS under electron beam radiolysis 2 PFOA and PFOS aqueous solutions in initial concentrations of 10–40 mg/L were irradiated to 100–500 kGy. As shown in Fig.1(a) Fig.1(a) , the PFOA and PFOS contents decreased with increasing doses. At initial concentrations of 10, 20, 30 and 40 mg/L, the PFOA degradation rates at 500 kGy were 63.6%, 51.4%, 48.2% and 41.7%, respectively; and the PFOS degradation rates were 57.1%, 42.4%, 35.5% and 32.4%, respectively. The PFOA and PFOS concentration changing rate were plotted in natural logarithm versus the irradiation dose, and each of the data sets could be fitted linearly with R 2 > 0.90, suggesting that the EB degradation of PFOA and PFOS followed pseudo-first order kinetics at different initial concentrations. Also, as shown in Fig.1(b) Fig.1(b) , certain amounts of fluoride ions were detected at different doses, implying that the EB-degradation of PFOA and PFOS was mainly through the defluorination. 3.2. Effect of initial pH on PFOA and PFOS degradation 2 Initial pH is an important factor in the degradation processes, as hydroxyl radicals, hydrated electron and hydrogen radical may react with OH − and H + in aqueous solution. PFOA and PFOS aqueous solutions (20 mg/L) in initial pH 3–13 were irradiated to 100–500 kGy. The degradation ( Fig. 2a Fig. 2a ) and the fluoride release ( Fig. 2b Fig. 2b ) increased with the pH value. At pH13 and 500 kGy, the degradation rates of PFOA and PFOS at were 88.1% and 63.4%, respectively; and the concentration of fluoride ions increased rapidly to 239.5 μmol/L and 352.6 μmol/L with the corresponding defluorination percentage of 37.5% and 51.8%, respectively. Decomposition of PFOS is more difficult than that of PFOA, as oxidation of sulphonate to sulfate is more difficult. However, the generated fluoride ions concentrations of PFOS were slightly higher than those of PFOA. This can be attributed to hydrogen radical, which can be inverted into hydrated electron in alkaline condition, and the loss of hydrated electron in acidic condition, as shown in Eqs. (2) and (3). Thus, the solutions in alkaline conditions may be helpful to the degradation of PFOA and PFOS. <math display="block" id="M3"><mrow><mtext>H</mtext><mo>⋅</mo><mo>+</mo><msup><mrow><mtext>OH</mtext></mrow><mo>−</mo></msup><mo>→</mo><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><msub><mtext>H</mtext><mn>2</mn></msub><mtext>O</mtext><mo>,</mo></mrow></math> <math display="block" id="M4"><mrow><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><msup><mtext>H</mtext><mo>+</mo></msup><mo>→</mo><mtext>H</mtext><mo>⋅</mo></mrow></math> 3.3. Effect of radical scavengers on PFOA and PFOS degradation 2 In order to investigate which active species played the leading role in degradation of PFOA and PFOS, the aqueous solutions (20 mg/L) was saturated by N 2 , O 2 and 0.1 mol/L tert-butanol with N 2 . In N 2 -saturated solution, hydroxyl radicals, hydrated electron and hydrogen radical were all existed and should be considered in the reactions process. It is well known that the reducing radicals hydrated electron and hydrogen radical can react with O 2 through Eqs. (4) and (5), and turn into activated radicals O 2 − • and HO 2 • . Hydroxyl radicals were the main reactive species in O 2 saturated solution. However, both hydrated electron and hydrogen radical existed in N 2 -saturated solution containing 0.1 mol/L tert-butanol, because hydroxyl radicals was scavenged by tert-butanol, as shown in Eq. (6). <math display="block" id="M5"><mrow><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><msub><mtext>O</mtext><mn>2</mn></msub><mo>→</mo><msubsup><mtext>O</mtext><mn>2</mn><mo>−</mo></msubsup><mo>⋅</mo><mo>,</mo></mrow></math> <math display="block" id="M6"><mrow><mtext>H</mtext><mo>⋅</mo><mo>+</mo><msub><mtext>O</mtext><mn>2</mn></msub><mo>→</mo><msub><mrow><mtext>HO</mtext></mrow><mn>2</mn></msub><mo>⋅</mo></mrow></math> <math display="block" id="M7"><mrow><msub><mrow><mrow><mo>(</mo><mrow><msub><mrow><mtext>CH</mtext></mrow><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow><mn>3</mn></msub><mtext>COH</mtext><mo>+</mo><mtext>OH</mtext><mo>⋅</mo><mo>→</mo><msub><mtext>H</mtext><mn>2</mn></msub><mtext>O</mtext><mo>+</mo><mo>⋅</mo><msub><mrow><mtext>CH</mtext></mrow><mn>2</mn></msub><msub><mrow><mrow><mo>(</mo><mrow><msub><mrow><mtext>CH</mtext></mrow><mn>3</mn></msub></mrow><mo>)</mo></mrow></mrow><mn>2</mn></msub><mtext>COH</mtext><mtext>.</mtext></mrow></math> Fig. 3 Fig. 3 shows the degradation and fluoride release of PFOA and PFOS under the different conditions. At 500 kGy, the degradation rates were higher in N 2 -saturated solutions, being 81.6% for PFOA and 71.3% for PFOS, and in N 2 -saturated solution containing 0.1 mol/L tert-butanol, being 87.4% for PFOA and 76.9% for PFOS; while the degradation rates were low in O 2 -situated solutions, being just 11.0% for PFOA and 8.7% for PFOS. For PFOA, the higher concentrations of fluoride ions were observed in N 2 -situated solution (200.3 μmol/L) and N 2 -saturated solution containing 0.1mol/L tert-butanol (232.9 μmol/L) at 500 kGy, while it reached 27.5 μmol/L in O 2 -saturated solution. Similarly, the formation of fluoride ions of PFOS showed the same trends as that of PFOA. Lower degradation rates and fluoride ions concentrations of PFOA and PFOS were observed in O 2 -saturated solution indicated that hydroxyl radicals was not favorable for degrading PFOA and PFOS under electron beam irradiation. Consequently, higher degradation rates and concentrations of fluoride ions occurred in N 2 -saturated solution and N 2 -saturated solution containing 0.1 mol/L tert-butanol. Due to the strong reductive property and the relatively higher concentration of hydrated electron [ 41 41 - 43 43 41-43 ] , we considered that hydrated electron, and hydrogen radical especially, played key roles in electron beam degradation of PFOA and PFOS. Furthermore, the quantum yield of hydrated electron increases greatly in alkaline solutions as the transformation of hydrogen atoms into hydrated electrons, i.e. Eq. (2). As the results show, the PFOA and PFOS degradation rates and concentrations of fluoride ions are higher in alkaline condition. Thus, the effect of pH on PFOA and PFOS decomposition further implies that hydrated electrons play the key role in the decomposition of PFOA and PFOS. In order to investigate the optimal EB degradation condition of PFOA and PFOS, the aqueous solutions (20 mg/L) were saturated by N 2 and adjusted to pH 13. The results are shown in Fig. 3 Fig. 3 . At 500 kGy, the degradation rates of PFOA and PFOS in nitrogen atmosphere were 95.7% and 85.9%, and their fluoride ion concentrations increased rapidly to 324.6 and 416.9 μmol/L, respectively, indicating that PFOA and PFOS in an anoxic alkaline solution are efficiently decomposed by EB irradiation. 3.4. Mechanism of PFOA and PFOS degradation by irradiation 2 PFOA, PFOS and their degradation products in the aqueous solutions were identified using LC-MS/MS method. The results are shown in Fig. 4 Fig. 4 . C 7 F 14 HCOOH, C 6 F 12 HCOOH, C 5 F 10 HCOOH, C 4 F 9 COOH, C 3 F 7 COOH, C 2 F 5 COOH, C 7 F 14 HSO 3 − , C 6 F 12 HSO 3 − , C 5 F 11 SO 3 − , C 3 F 7 SO 3 − , C 2 F 5 SO 3 − and other intermediate products appeared after irradiation. 3.4.1. Mechanism of PFOA degradation by irradiation 3 Based on these results, a mechanism for PFOA degradation by EB irradiation is proposed in Fig. 5(a) Fig. 5(a) . Under nitrogen atmosphere, the hydrated electrons attack PFOA, induce the fluoride elimination and react with hydrogen radical to yield the C 6 F 13 CHFCOOH radical via Eqs. (7−9) [ 45 45 , 46 46 ] . The electrophilic radicals are attacked by hydrated electrons to cause an intramolecular defluorination and react further with hydrogen radical to yield C 6 F 13 CH 2 COOH, via Eqs. (10–12) [ 47 47 , 48 48 ] . The generated C 6 F 13 CH 2 COOH can transform to C 6 F 13 COOH, via Eqs. (13) and (14) [ 46 46 ] . Other short-chain perfluorocarboxylic acid such as PFHxA, PFPA and PFBA are formed successively by similar reaction. <math display="block" id="M8"><mrow><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msup><mrow><mtext>COO</mtext></mrow><mo>−</mo></msup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>COO</mtext><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>,</mo></mrow></math> <math display="block" id="M9"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>COO</mtext><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msup><mrow><mtext>FCOO</mtext></mrow><mo>−</mo></msup><mo>+</mo><msup><mtext>F</mtext><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M10"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msup><mrow><mtext>FCOO</mtext></mrow><mo>−</mo></msup><mo>+</mo><mtext>H</mtext><mo>⋅</mo><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><msup><mrow><mtext>CHFCOO</mtext></mrow><mo>−</mo></msup></mrow></math> <math display="block" id="M11"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><msup><mrow><mtext>CHFCOO</mtext></mrow><mo>−</mo></msup><mo>+</mo><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>CHFCOO</mtext><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>,</mo></mrow></math> <math display="block" id="M12"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>CHFCOO</mtext><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msup><mrow><mtext>HCOO</mtext></mrow><mo>−</mo></msup><mo>+</mo><msup><mtext>F</mtext><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M13"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msup><mrow><mtext>HCOO</mtext></mrow><mo>−</mo></msup><mo>+</mo><mtext>H</mtext><mo>⋅</mo><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><msub><mrow><mtext>CH</mtext></mrow><mn>2</mn></msub><msup><mrow><mtext>COO</mtext></mrow><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M14"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><msub><mrow><mtext>CH</mtext></mrow><mn>2</mn></msub><mtext>COOH</mtext><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mo>⋅</mo><mo>+</mo><mmultiscripts><mtext>C</mtext><mprescripts/><mo>⋅</mo><mo>⋅</mo></mmultiscripts><msub><mtext>H</mtext><mn>2</mn></msub><mo>+</mo><mtext>COOH</mtext><mo>⋅</mo><mo>,</mo></mrow></math> <math display="block" id="M15"><mrow><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mo>⋅</mo><mo>+</mo><mtext>COOH</mtext><mo>⋅</mo><mo>→</mo><msub><mtext>C</mtext><mn>6</mn></msub><msub><mtext>F</mtext><mrow><mn>13</mn></mrow></msub><mtext>COOH</mtext><mo>⋅</mo></mrow></math> 3.4.2. Mechanism of PFOS degradation by irradiation 3 On the basis of the intermediate products identified, the possible degradation pathway of PFOS is proposed in Fig. 5(b) Fig. 5(b) . The degradation pathway of PFOS is similar to that of PFOA. Reaction of PFOS with hydrated electron yields the radical anion C 8 F 17 SO 3 •2– via Eq. (15). The radical anion is decomposed by fluoride elimination and react further with hydrogen radical to yield C 7 F 15 CHFSO 3 − via Eqs. (16–19). The C 7 F 15 CHSO 3 •− may react with hydrogen radical to form C 7 F 15 CH 2 SO 3 − , via Eq. (20) [ 48 48 , 49 49 ] . The generated C 7 F 15 CH 2 SO 3 − transforms to C 7 F 15 SO 3 − via Eqs. (21) and (22) and finally complete degradation. <math display="block" id="M16"><mrow><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>+</mo><msub><mi>C</mi><mn>8</mn></msub><msub><mi>F</mi><mrow><mn>17</mn></mrow></msub><mi>S</mi><msub><mi>O</mi><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>→</mo><msub><mi>C</mi><mn>8</mn></msub><msub><mi>F</mi><mrow><mn>17</mn></mrow></msub><mi>S</mi><msub><mi>O</mi><mn>3</mn></msub><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>,</mo></mrow></math> <math display="block" id="M17"><mrow><msub><mtext>C</mtext><mn>8</mn></msub><msub><mtext>F</mtext><mrow><mn>17</mn></mrow></msub><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msub><mrow><mtext>FSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>+</mo><msup><mtext>F</mtext><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M18"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msub><mrow><mtext>FSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>+</mo><mtext>H</mtext><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CHFSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M19"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CHFSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>+</mo><msubsup><mi>e</mi><mrow><mtext>aq</mtext></mrow><mo>−</mo></msubsup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CHFSO</mtext></mrow><mn>3</mn></msub><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>,</mo></mrow></math> <math display="block" id="M20"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CHFSO</mtext></mrow><mn>3</mn></msub><msup><mo>⋅</mo><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msub><mrow><mtext>HSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>+</mo><msup><mtext>F</mtext><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M21"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mtext>C</mtext><mo>⋅</mo><msub><mrow><mtext>HSO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>+</mo><mtext>H</mtext><mo>⋅</mo><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CH</mtext></mrow><mn>2</mn></msub><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M22"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>CH</mtext></mrow><mn>2</mn></msub><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mo>⋅</mo><mo>+</mo><mmultiscripts><mtext>C</mtext><mprescripts/><mo>⋅</mo><mo>⋅</mo></mmultiscripts><msub><mtext>H</mtext><mn>2</mn></msub><mo>+</mo><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mo>⋅</mo><mo>−</mo></msup><mo>,</mo></mrow></math> <math display="block" id="M23"><mrow><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><mo>⋅</mo><mo>+</mo><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mo>⋅</mo><mo>−</mo></msup><mo>→</mo><msub><mtext>C</mtext><mn>7</mn></msub><msub><mtext>F</mtext><mrow><mn>15</mn></mrow></msub><msub><mrow><mtext>SO</mtext></mrow><mn>3</mn></msub><msup><mrow/><mo>−</mo></msup></mrow></math> The proposed degradation mechanisms of PFOA and PFOS were different from previous studies [ 23 23 , 28 28 , 30 30 , 50 50 ] . The present degradation mechanisms have two main differences from those in Ref. [ 50 50 ]. One is the main reactive species. While the hydroxyl radical took part in the mineralization process, hydrated electron and hydrogen radical played key roles in the EB degradation, especially hydrated electron. Another is the main reaction pathway. In electrolysis system, ·OH-initiated process was the main degradation pathway, and decarboxylation reaction occurred on anode first in electrolysis system. However, direct defluorination was the important pathway in electron beam degradation. 4. Conclusion 1 Electron beam radiolysis of PFOA and PFOS were performed. The degradation of PFOA and PFOS followed the pseudo-first-order kinetics. At 500 kGy, the degradation rates of PFOA and PFOS in N 2 atmosphere were 95.7% and 85.9% at pH13, and the fluoride ion concentration rapidly increased to 324.6 and 416.9 μmol/L with corresponding defluorination rates of 46.8% and 71.4%, respectively. The results showed that PFOA and PFOS could be efficiently decomposed by EB irradiation in an anoxic alkaline solution. The work with radical scavengers demonstrated hydrated electron, and hydrogen radical especially, played key roles in EB degradation of PFOA and PFOS. Based on effects of the radicals and detected intermediate products, the EB degradation pathways of PFOA and PFOS were proposed. Further work may include adding catalyst to improve the degradation efficiencies at low dose, and toxicity of PFCs by-products. References M. K. So , S. Taniyasu , N. Yamashita et al ., Perfluorinated compounds in coastal waters of Hong Kong, South China, and Korea . Environ. Sci. Technol . 38 ( 15 ), 4056 - 4063 ( 2004 ). doi: 10.1021/es049441z http://doi.org/10.1021/es049441z Perfluorinated compounds in coastal waters of Hong Kong, South China, and Korea Y. L. Mak , S. Taniyasu , L. W. Y. Yeung et al ., Perfluorinated compounds in tap water from China and several other countries . Environ. Sci. Technol . 43 ( 13 ), 4824 - 4829 ( 2009 ). doi: 10.1021/es900637a http://doi.org/10.1021/es900637a Perfluorinated compounds in tap water from China and several other countries L. Ahrens , S. Felizeter , R. Sturm et al ., Polyfluorinated compounds in waste water treatment plant effluents and surface waters along the River Elbe, Germany . Mar. Pollut Bull . 58 ( 9 ), 1326 - 1333 ( 2009 ). doi: 10.1016/j.marpolbul.2009.04.028 http://doi.org/10.1016/j.marpolbul.2009.04.028 Polyfluorinated compounds in waste water treatment plant effluents and surface waters along the River Elbe, Germany L. Ahrens , J. L. Barber , Z. Xie et al . Longitudinal and latitudinal distribution of perfluoroalkyl compounds in the surface water of the Atlantic Ocean . Environ. Sci. Technol . 43 ( 9 ), 3122 - 3127 ( 2009 ). doi: 10.1021/es803507p http://doi.org/10.1021/es803507p Longitudinal and latitudinal distribution of perfluoroalkyl compounds in the surface water of the Atlantic Ocean M. Shoeib , T. Harner , G. M. Webster , et al . Indoor sources of poly- and perfluorinated compounds (PFCS) in Vancouver, Canada: Implications for human exposure . Environ Sci Technol . 45 ( 19 ), 7999 - 8005 ( 2011 ). doi: 10.1021/es103562v http://doi.org/10.1021/es103562v Indoor sources of poly- and perfluorinated compounds (PFCS) in Vancouver, Canada: Implications for human exposure E. Goosey , S. Harrad . Perfluoroalkyl substances in UK indoor and outdoor air: Spatial and seasonal variation, and implications for human exposure . Environ Int . 45 , 86 - 90 ( 2012 ). doi: 10.1016/j.envint.2012.04.007 http://doi.org/10.1016/j.envint.2012.04.007 Perfluoroalkyl substances in UK indoor and outdoor air: Spatial and seasonal variation, and implications for human exposure B. Liu , H. Zhang , D. Yao , et al . Perfluorinated compounds (PFCs) in the atmosphere of Shenzhen, China: Spatial distribution, sources and health risk assessment . Chemosphere . 138 , 511 - 518 ( 2015 ). doi: 10.1016/j.chemosphere.2015.07.012 http://doi.org/10.1016/j.chemosphere.2015.07.012 Perfluorinated compounds (PFCs) in the atmosphere of Shenzhen, China: Spatial distribution, sources and health risk assessment C. P. Higgins , J. A. Field , C. S. Criddle , et al . Quantitative determination of perfluorochemicals in sediments and domestic sludge . Environ Sci Technol . 39 ( 11 ), 3946 - 3956 ( 2005 ). doi: 10.1021/es048245p http://doi.org/10.1021/es048245p Quantitative determination of perfluorochemicals in sediments and domestic sludge H. Nakata , K. Kannan , T. Nasu , et al . Perfluorinated contaminants in sediments and aquatic organisms collected from shallow water and tidal flat areas of the Ariake Sea, Japan: Environmental fate of perfluorooctane sulfonate in aquatic ecosystems . Environ Sci Technol . 40 ( 16 ), 4916 - 4921 ( 2006 ). doi: 10.1021/es0603195 http://doi.org/10.1021/es0603195 Perfluorinated contaminants in sediments and aquatic organisms collected from shallow water and tidal flat areas of the Ariake Sea, Japan: Environmental fate of perfluorooctane sulfonate in aquatic ecosystems C. G. Pan , J. L. Zhao , Y. S. Liu , et al . Bioaccumulation and risk assessment of per- and polyfluoroalkyl substances in wild freshwater fish from rivers in the Pearl River Delta region, South China . Ecotoxicol Environ Saf . 107 , 192 - 199 ( 2014 ). doi: 10.1016/j.ecoenv.2014.05.031 http://doi.org/10.1016/j.ecoenv.2014.05.031 Bioaccumulation and risk assessment of per- and polyfluoroalkyl substances in wild freshwater fish from rivers in the Pearl River Delta region, South China M. Houde , A. O. De Silva , D. C. G. Muir , et al . Monitoring of Perfluorinated Compounds in Aquatic Biota: An Updated Review PFCs in Aquatic Biota . Environ Sci Technol . 45 ( 19 ), 7962 - 7973 ( 2011 ). doi: 10.1021/es104326w http://doi.org/10.1021/es104326w Monitoring of Perfluorinated Compounds in Aquatic Biota: An Updated Review PFCs in Aquatic Biota A. Karrman , J. L. Domingo , X. Llebaria , et al . Biomonitoring perfluorinated compounds in Catalonia, Spain: concentrations and trends in human liver and milk samples . Environ Sci Pollut R . 17 ( 3 ), 750 - 758 ( 2010 ). doi: 10.1007/s11356-009-0178-5 http://doi.org/10.1007/s11356-009-0178-5 Biomonitoring perfluorinated compounds in Catalonia, Spain: concentrations and trends in human liver and milk samples L. W. Y. Yeung , M. K. So , G. B. Jiang , et al . Perfluorooctanesulfonate and related fluorochemicals in human blood samples from China . Environ Sci Technol . 40 ( 3 ), 715 - 720 ( 2006 ). doi: 10.1021/es052067y http://doi.org/10.1021/es052067y Perfluorooctanesulfonate and related fluorochemicals in human blood samples from China F. Suja , B. K. Pramanik , S. M. Zain . Contamination, bioaccumulation and toxic effects of perfluorinated chemicals (PFCs) in the water environment: a review paper . Water Sci Technol . 60 ( 6 ), 1533 - 1544 ( 2009 ). doi: 10.2166/wst.2009.504 http://doi.org/10.2166/wst.2009.504 Contamination, bioaccumulation and toxic effects of perfluorinated chemicals (PFCs) in the water environment: a review paper K. S. Guruge , L. W. Y. Yeung , N. Yamanaka , et al . Gene expression profiles in rat liver treated with perfluorooctanoic acid (PFOA) . Toxicol Sci . 89 ( 1 ), 93 - 107 ( 2006 ). doi: 10.1093/toxsci/kfj011 http://doi.org/10.1093/toxsci/kfj011 Gene expression profiles in rat liver treated with perfluorooctanoic acid (PFOA) N. Johansson , A. Fredriksson , P. Eriksson . Neonatal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) causes neurobehavioural defects in adult mice . Neurotoxicology . 29 ( 1 ), 160 - 169 ( 2008 ). doi: 10.1016/j.neuro.2007.10.008 http://doi.org/10.1016/j.neuro.2007.10.008 Neonatal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) causes neurobehavioural defects in adult mice J. Jeon , K. Kannan , H. K. Lim , et al . Bioaccumulation of Perfluorochemicals in Pacific Oyster under Different Salinity Gradients . Environ Sci Technol . 44 ( 7 ), 2695 - 2701 ( 2010 ). doi: 10.1021/es100151r http://doi.org/10.1021/es100151r Bioaccumulation of Perfluorochemicals in Pacific Oyster under Different Salinity Gradients E. S. Darling , M. Reinhard . Nanofiltration for trace organic contaminant removal: Structure, solution, and membrane fouling effects on the rejection of perfluorochemicals . Environ Sci Technol . 42 ( 14 ), 5292 - 5297 ( 2008 ). doi: 10.1021/es703207s http://doi.org/10.1021/es703207s Nanofiltration for trace organic contaminant removal: Structure, solution, and membrane fouling effects on the rejection of perfluorochemicals Q. Zhou , S. Deng , Q. Yu , et al . Sorption of perfluorooctane sulfonate on organo-montmorillonites . Chemosphere . 78 ( 6 ), 688 - 694 ( 2010 ). doi: 10.1016/j.chemosphere.2009.12.005 http://doi.org/10.1016/j.chemosphere.2009.12.005 Sorption of perfluorooctane sulfonate on organo-montmorillonites H. Hori , A. Yamamoto , E. Hayakawa , et al . Efficient decomposition of environmentally persistent perfluorocarboxylic acids by use of persulfate as a photochemical oxidant . Environ Sci Technol . 39 ( 7 ), 2383 - 2388 ( 2005 ). doi: 10.1021/es0484754 http://doi.org/10.1021/es0484754 Efficient decomposition of environmentally persistent perfluorocarboxylic acids by use of persulfate as a photochemical oxidant M. Sansotera , F. Persico , V. Rizzi , et al . The effect of oxygen in the photocatalytic oxidation pathways of perfluorooctanoic acid . J Fluorine Chem . 179 , 159 - 168 ( 2015 ). doi: 10.1016/j.jfluchem.2015.06.019 http://doi.org/10.1016/j.jfluchem.2015.06.019 The effect of oxygen in the photocatalytic oxidation pathways of perfluorooctanoic acid S. Gatto , M. Sansotera , F. Persico , et al . Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid . Catal Today . 241 , 8 - 14 ( 2015 ). doi: 10.1016/j.cattod.2014.04.031 http://doi.org/10.1016/j.cattod.2014.04.031 Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid J. Ling , P. Zhang , S. Tian , et al . Ferric ion mediated photodecomposition of aqueous perfluorooctane sulfonate (PFOS) under UV irradiation and its mechanism . J Hazard Mater . 271 ( 4 ), 9 - 15 ( 2014 ). doi: 10.1016/j.jhazmat.2014.01.061 http://doi.org/10.1016/j.jhazmat.2014.01.061 Ferric ion mediated photodecomposition of aqueous perfluorooctane sulfonate (PFOS) under UV irradiation and its mechanism Q. Zhuo , S. Deng , B. Yang , et al . Efficient Electrochemical Oxidation of Perfluorooctanoate Using a Ti/SnO2-Sb-Bi Anode . Environ Sci Technol . 45 ( 7 ), 2973 - 2979 ( 2011 ). doi: 10.1021/es1024542 http://doi.org/10.1021/es1024542 Efficient Electrochemical Oxidation of Perfluorooctanoate Using a Ti/SnO2-Sb-Bi Anode H. Moriwaki , Y. Takagi , M. Tanaka , et al . Sonochemical decomposition of perfluorooctane sulfonate and perfluorooctanoic acid . Environ Sci Technol . 39 ( 9 ), 3388 - 3392 ( 2005 ). doi: 10.1021/es040342v http://doi.org/10.1021/es040342v Sonochemical decomposition of perfluorooctane sulfonate and perfluorooctanoic acid J. Cheng , C. D. Vecitis , H. Park , et al . Sonochemical Degradation of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA) in Landfill Groundwater: Environmental Matrix Effects . Environ Sci Technol . 42 ( 21 ), 8057 - 8063 ( 2008 ). doi: 10.1021/es8013858 http://doi.org/10.1021/es8013858 Sonochemical Degradation of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA) in Landfill Groundwater: Environmental Matrix Effects H. Hori , Y. Nagaoka , M. Murayama , et al . Efficient decomposition of perfluorocarboxylic acids and alternative fluorochemical surfactants in hot water . Environ Sci Technol . 42 ( 19 ), 7438 - 7443 ( 2008 ). doi: 10.1021/es800832p http://doi.org/10.1021/es800832p Efficient decomposition of perfluorocarboxylic acids and alternative fluorochemical surfactants in hot water Z. Zhang , J. J. Chen , X. J. Lyu , et al . Complete mineralization of perfluorooctanoic acid (PFOA) by γ-irradiation in aqueous solution . Scientific Reports . 4 , 7418 - 7418 ( 2014 ). doi: 10.1038/srep07418 http://doi.org/10.1038/srep07418 Complete mineralization of perfluorooctanoic acid (PFOA) by γ-irradiation in aqueous solution O. S. Arvaniti , Y. Hwang , H. R. Andersen , et al . Reductive degradation of perfluorinated compounds in water using Mg-aminoclay coated nanoscale zero valent iron . Chem Eng J . 262 , 133 - 139 ( 2015 ). doi: 10.1016/j.cej.2014.09.079 http://doi.org/10.1016/j.cej.2014.09.079 Reductive degradation of perfluorinated compounds in water using Mg-aminoclay coated nanoscale zero valent iron S. W. Yang , J. H. Cheng , J. Sun , et al . Defluorination of Aqueous Perfluorooctanesulfonate by Activated Persulfate Oxidation . Plos One . 8 ( 10 ), e74877 ( 2013 ). doi: 10.1371/journal.pone.0074877 http://doi.org/10.1371/journal.pone.0074877 Defluorination of Aqueous Perfluorooctanesulfonate by Activated Persulfate Oxidation Y. C. Lee , S. L. Lo , P. T. Chiueh , et al . Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation . Water Res . 44 ( 3 ), 886 - 892 ( 2010 ). doi: 10.1016/j.watres.2009.09.055 http://doi.org/10.1016/j.watres.2009.09.055 Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation Y. C. Lee , S. L. Lo , P. T. Chiueh , et al . Efficient decomposition of perfluorocarboxylic acids in aqueous solution using microwave-induced persulfate . Water Res . 43 ( 11 ), 2811 - 2816 ( 2009 ). doi: 10.1016/j.watres.2009.03.052 http://doi.org/10.1016/j.watres.2009.03.052 Efficient decomposition of perfluorocarboxylic acids in aqueous solution using microwave-induced persulfate C. E. Schaefer , C. Andaya , A. Urtiaga , et al . Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming foams (AFFFs) . J Hazard Mater . 295 , 170 - 175 ( 2015 ). doi: 10.1016/j.jhazmat.2015.04.024 http://doi.org/10.1016/j.jhazmat.2015.04.024 Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming foams (AFFFs) G. Xu , J. Z. Yao , L. Tang , et al . Electron beam induced degradation of atrazine in aqueous solution . Chem Eng J . 275 , 374 - 380 ( 2015 ). doi: 10.1016/j.cej.2015.04.063 http://doi.org/10.1016/j.cej.2015.04.063 Electron beam induced degradation of atrazine in aqueous solution G. Xu , T. Bu , M. Wu , et al . Electron beam induced degradation of clopyralid in aqueous solutions . J Radioanal Nucl Chem . 288 ( 3 ), 759 - 764 ( 2011 ). doi: 10.1007/s10967-011-0986-1 http://doi.org/10.1007/s10967-011-0986-1 Electron beam induced degradation of clopyralid in aqueous solutions W. Park , M. H. Hwang , T. H. Kim , et al . Enhancement in characteristics of sewage sludge and anaerobic treatability by electron beam pre-treatment . Radiat Phys Chem . 78 ( 2 ), 124 - 129 ( 2009 ). doi: 10.1016/j.radphyschem.2008.09.010 http://doi.org/10.1016/j.radphyschem.2008.09.010 Enhancement in characteristics of sewage sludge and anaerobic treatability by electron beam pre-treatment J. Criquet , N. K. V. Leitner . Reaction pathway of the degradation of the p-hydroxybenzoic acid by sulfate radical generated by ionizing radiations . Radiat Phys Chem . 106 , 307 - 314 ( 2015 ). doi: 10.1016/j.radphyschem.2014.07.016 http://doi.org/10.1016/j.radphyschem.2014.07.016 Reaction pathway of the degradation of the p-hydroxybenzoic acid by sulfate radical generated by ionizing radiations C. Peng , Y. Ding , F. An , et al . Degradation of ochratoxin A in aqueous solutions by electron beam irradiation . J Radioanal Nucl Chem . 306 ( 1 ), 39 - 46 ( 2015 ). doi: 10.1007/s10967-015-4086-5 http://doi.org/10.1007/s10967-015-4086-5 Degradation of ochratoxin A in aqueous solutions by electron beam irradiation A. Kimura , M. Osawa , M. Taguchi . Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation . Radiat Phys Chem . 81 ( 9 ), 1508 - 1512 ( 2012 ). doi: 10.1016/j.radphyschem.2011.11.032 http://doi.org/10.1016/j.radphyschem.2011.11.032 Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation E. Illes , E. Takacs , A. Dombi , et al . Hydroxyl radical induced degradation of ibuprofen . Sci Total Environ . 447 , 286 - 292 ( 2013 ). doi: 10.1016/j.scitotenv.2013.01.007 http://doi.org/10.1016/j.scitotenv.2013.01.007 Hydroxyl radical induced degradation of ibuprofen G. V. Buxton , C. L. Greenstock , W. P. Helman , et al . Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O-) in Aqueous Solution . J Phys Chem Ref Data . 17 ( 2 ), 513 - 886 ( 1988 ). doi: 10.1063/1.555805 http://doi.org/10.1063/1.555805 Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O-) in Aqueous Solution O. Marsalek , F. Uhlig , J. Vandevondele , et al . Structure, dynamics, and reactivity of hydrated electrons by ab initio molecular dynamics . Acc Chem Res . 45 ( 1 ), 23 - 32 ( 2012 ). doi: 10.1021/ar200062m http://doi.org/10.1021/ar200062m Structure, dynamics, and reactivity of hydrated electrons by ab initio molecular dynamics M. H. Elkins , H. L. Williams , A. T. Shreve , et al . Relaxation mechanism of the hydrated electron . Science . 342 ( 6165 ), 1496 - 1499 ( 2013 ). doi: 10.1126/science.1246291 http://doi.org/10.1126/science.1246291 Relaxation mechanism of the hydrated electron D. C. Walker , in Radiation Chemistry , ed. by E.J. Hart ( American Chemical Society , Vancouver, Canada , 1968 ), pp. 49 - 64 Radiation Chemistry H. Park . Photolysis of aqueous perfluorooctanoate and perfluorooctane sulfonate . Rev Roum Chim . 55 ( 10 ), 611 - 619 ( 2010 ). Photolysis of aqueous perfluorooctanoate and perfluorooctane sulfonate S. Zhou , H. Tang , W. Nan , et al . Reductive defluorination of perfluorooctanoic acid by hydrated electrons in a sulfite-mediated UV photochemical system . J Hazard Mater . 262 ( 22 ), 332 - 338 ( 2013 ). doi: 10.1016/j.jhazmat.2013.08.059 http://doi.org/10.1016/j.jhazmat.2013.08.059 Reductive defluorination of perfluorooctanoic acid by hydrated electrons in a sulfite-mediated UV photochemical system C. Combellas , F. Kanoufi , A. Thiebault . Reduction of polyfluorinated compounds . J Phys Chem B . 107 ( 39 ), 10894 - 10905 ( 2003 ). doi: 10.1021/jp034846b http://doi.org/10.1021/jp034846b Reduction of polyfluorinated compounds H. Park , C. D. Vecitis , J. Cheng , et al . Reductive Defluorination of Aqueous Perfluorinated Alkyl Surfactants: Effects of Ionic Headgroup and Chain Length . J Phys Chem A . 113 ( 4 ), 690 - 696 ( 2009 ). doi: 10.1021/jp807116q http://doi.org/10.1021/jp807116q Reductive Defluorination of Aqueous Perfluorinated Alkyl Surfactants: Effects of Ionic Headgroup and Chain Length L. Jin , P. Zhang . Photochemical decomposition of perfluorooctane sulfonate (PFOS) in an anoxic alkaline solution by 185 nm vacuum ultraviolet . Chem Eng J . 280 , 241 - 247 ( 2015 ). doi: 10.1016/j.cej.2015.06.022 http://doi.org/10.1016/j.cej.2015.06.022 Photochemical decomposition of perfluorooctane sulfonate (PFOS) in an anoxic alkaline solution by 185 nm vacuum ultraviolet J. Niu , H. Lin , C. Gong , et al . Theoretical and experimental insights into the electrochemical mineralization mechanism of perfluorooctanoic acid . Environ Sci Technol . 47 ( 24 ), 14341 - 14349 ( 2013 ). doi: 10.1021/es402987t http://doi.org/10.1021/es402987t Theoretical and experimental insights into the electrochemical mineralization mechanism of perfluorooctanoic acid 10.1007/s41365-017-0278-8 **This work was supported by the National Natural Science Foundation of China (Nos. 41273126, 41273141, 41373098, 41430644, 41473090) and Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13078) 2016-08-26 2016-10-19 2016-10-25 2017-08-28 2017-09-01 2021-04-11 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2017 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-017-0278-8 http://dx.doi.org/10.1007/s41365-017-0278-8 . 2017 Nuclear Science and Techniques 09 28