Irradiation System Research Articles

Responses of hematopoietic cells after ionizing-irradiation in anemic adult medaka (Oryzias latipes)

Purpose Hematopoietic tissues of vertebrates are highly radiation sensitive and the effects of ionizing radiation on the hematopoiesis have been studied in mammals and teleosts for decades. In this study, radiation responses in the kidney, the main hematopoietic organ in teleosts, were investigated in Japanese medaka (Oryzias latipes), which has been a model animal and a large body of knowledge has been accumulated in radiation biology. Methods Kidney, the main hematopoietic tissue of adult medaka fish, was locally irradiated using proton and carbon ion beams irradiation system of Takasaki Ion Accelerator for Advanced Radiation Application (TIARA), QST, and the effects on peripheral blood cells and histology of the kidney were investigated. Results When only kidneys were locally irradiated with proton or carbon ion beam (15 Gy), the hematopoietic cells in the irradiated kidney and cell density in the peripheral blood decreased 7 days after the irradiation in the same manner as after the whole-body irradiation with γ-rays (15 Gy). These results demonstrate that direct irradiation of the hematopoietic cells in the kidney induced cell death and/or cell cycle arrest and stopped the supply of erythroid cells. Then, the cell density in the peripheral blood recovered to the control level within 4 days and 7 days after the γ-ray and proton beam irradiation (15 Gy), respectively, while the cell density in the peripheral blood did not recover after the carbon ion beam irradiation (15 Gy). The hematopoietic cells in the irradiated kidneys temporarily decreased and recovered to the control level within 21 days after the γ-ray or proton beam irradiation (15 Gy), while it did not recover after the carbon ion beam irradiation (15 Gy). In contrast, the recovery of the cell density in the peripheral blood delayed when anemic medaka were irradiated 1 day after the administration of phenylhydrazine. With and without γ-ray irradiation, a large number of hematopoietic cells was still proliferating in the kidney 7 days after the anemia induction. Conclusions The results obtained strongly suggest that the hematopoietic stem cells in medaka kidney prioritize to proliferate and increase peripheral blood cells to eliminate anemia, even when they are damaged by high-dose irradiation.

Enhancing carotenogenesis in terrestrial microalgae by UV-A light stress

Carotenoids are among the most widely distributed pigments in nature with broad application options in pharmacology, cosmetics and food industries. For commercial-scale production using microalgae, however, it is crucial to find the best performing strains regarding growth and yields of the products of interest. As terrestrial microalgae present the ability to quickly adapt to changing or unfavorable environmental conditions through cell-specific defense mechanisms, they constitute highly promising candidates. The present study thus aimed to investigate the potential of five terrestrial microalgal strains to increasingly produce the carotenoids β-carotene, canthaxanthin and astaxanthin when being exposed to UV-A stress. Light stress experiments were performed using a novel irradiation system based on UV-LED technology. Microalgal cultures were treated with UV-A radiation to stimulate carotenogenesis and the time-dependent effects were investigated by high-performance liquid chromatography analysis. The potential of the microalgae to enhance de novo biosynthesis of the targeted metabolites under the influence of UV-A light could be confirmed by significantly increased yields of canthaxanthin in four out of five strains and by a significantly enhanced β-carotene concentration in at least one strain during 72 h of investigation. Overall, the results provided evidence that UV-A light stress can be effective in rapidly inducing carotenogenesis in terrestrial microalgae and thus harbors vast potential for further exploitation regarding large-scale carotenoid production.

Wireless Control Industrial Robot Processing Irradiation System Based on Artificial Intelligence Technology

Radiation processing technology has been more and more widely used in light industry, chemical industry, food preservation, medical care, and other industries. Therefore, this paper designs a kind of wireless control system based on artificial intelligence technology γ radiation method, to strengthen the application of radiation processing equipment, and γ radiation monitoring can strengthen the radiation monitoring of its surrounding environment. The experimental results show that the C/Si atomic ratio of oxidized SiC fiber in air treated by this scheme is about 1.75, while the C/Si atomic ratio of SiC(Be) fiber treated by electron irradiation is close to 1 : 1.

Comparative thermal performance enhancement study of a reverse - irradiated and direct - irradiated direct absorption solar collector using silver nanofluid

ABSTRACT Plasmonic nanofluids have emerged as strong candidates for future working fluids in direct absorption solar collectors (DASC). However, in novel DASC systems, a significant temperature gradient exists over working fluid depth increasing emissive losses and hence, results in low thermal conversion efficiency. Considering these issues, a laboratory scale prototype of reverse-irradiated DASC system (RR–DASC) has been tested under controlled laboratory conditions and compared with a direct irradiated DASC system (DR–DASC) using silver nanofluids at three different mass concentrations i.e., 0.1 mg/L, 0.2 mg/L, and 0.4 mg/L. Ag nanoparticles were having monodisperse spherical shape with surface plasmon resonance (SPR) peak occurring around 395–400 nm. The experimental results showed that RR–DASC maintains uniform temperature over the fluid depth, while about 3–4°C temperature gradient was noticed in direct irradiated DASC system under similar operating conditions. A maximum photo-thermal conversion efficiency of about 80% was observed using 0.4 mg/L Ag nanofluids in RR–DASC system. The presented work can pave the ways for future development of highly efficient DASC systems for low to high temperature solar applications.

Sunlight Irradiated Pyrite-Fenton System for Advanced Oxidative Treatment of Textile Dyes Mixture

Sunlight Irradiated Pyrite-Fenton System for Advanced Oxidative Treatment of Textile Dyes Mixture

First Human Cell Experiments With FLASH Carbon Ions.

This study aimed to establish a setup for ultra-high-dose-rate (FLASH) carbon-ion irradiation, and to conduct the first human cell experiments using FLASH carbon ions. A system for FLASH carbon-ion irradiation (1-3 Gy at 13 or 50 keV/μm) was developed. The growth and senescence of HFL1 lung fibroblasts were assessed by crystal violet staining assays and senescence-associated β-galactosidase staining, respectively. Survival of HSGc-C5 cancer cells was assessed by clonogenic assays. The dose rates of carbon ions ranged from 96-195 Gy/s, meeting the definition of FLASH. With both 13 and 50 keV/μm beams, no FLASH sparing effect was observed on the growth suppression and senescence of HFL1 cells, nor on the survival of HSGc-C5 cells. We successfully conducted the first human cell experiments with FLASH carbon ions. No FLASH effect was observed under the conditions examined.

Heterogeneous irradiation system: enhanced degradation of methylene blue by electron beam irradiation combined with graphite carbon nitride/carbon nanodots

In the present work, the degradation of methylene blue (MB) was investigated by electron beam irradiation combined with graphite carbon nitride/carbon nanodots (EBI&g-C3N4/CDs). In comparison with EBI alone, the EBI&g-C3N4/CDs method showed a higher removal efficiency of high concentrations of MB (500 mg L-1) from aqueous solution. Investigation on the effect of the synthesized g-C3N4/CDs revealed that CDs and g-C3N4 were both contributing factors, while the latter could enhance the degradation of MB through surface reactions that occurred after adsorption. Experiments on the existence of hydrogen peroxide revealed the synergistic effect between g-C3N4/CDs and hydrogen peroxide. An excellent degradation effect was obtained at natural pH, and the total organic carbon was significantly reduced. Regeneration experiments revealed that the g-C3N4/CDs material has good stability and reusability. The studies in the presence of assorted radical scavengers suggested that ·OH played a vital role in the degradation process and a total of 17 intermediates were detected using liquid chromatograph-mass spectrometer (LC-MS) analysis. The possible degradation mechanisms of MB were proposed.

New beam delivery system design for industrial electron accelerator at Nuclear Science and Technology Research Institute, Iran

The output beams generated by industrial electron accelerators should be swept over the product. It is necessary to determine the exact scan length in order to ensure that an efficient dose reaches the product and to avoid the loss of the beam in contact with the sides of the product. Another challenge associated with scanning beams is the non-uniformity of the dose across the entire product during irradiation. In this study, the use of beam correction magnets is proposed for correcting products that receive a non-uniform dose. These magnets correct beams that are not swept in parallel. In addition, we simulated the dose received by the products in two non-uniform and uniform modes (modified by beam correction magnets) using the Monte Carlo method, and compared the results to assess the importance of using an appropriate irradiation system. Among the proposed magnets, a modified sector magnet is recommended for correcting the beam path and reducing the side effect. Using this magnet for a long horn does not require a cooling system, but using it for a short horn increases the need for a water-cooling system.

A comprehensive and efficient quality assurance program for an image-guided small animal irradiation system

In the field of preclinical radiotherapy, many new developments were driven by technical innovations. To make research of different groups comparable in that context and reliable, high quality has to be maintained. Therefore, standardized protocols and programs should be used. Here we present a guideline for a comprehensive and efficient quality assurance program for an image-guided small animal irradiation system, which is meant to test all the involved subsystems (imaging, treatment planning, and the irradiation system in terms of geometric accuracy and dosimetric aspects) as well as the complete procedure (end-to-end test) in a time efficient way. The suggestions are developed on a Small Animal Radiation Research Platform (SARRP) from Xstrahl (Xstrahl Ltd., Camberley, UK) and are presented together with proposed frequencies (from monthly to yearly) and experiences on the duration of each test. All output and energy related measurements showed stable results within small variation. Also, the motorized parts (couch, gantry) and other geometrical alignments were very stable. For the checks of the imaging system, the results are highly dependent on the chosen protocol and differ according to the settings. We received nevertheless stable and comparably good results for our mainly used protocol. All investigated aspects of treatment planning were exactly fulfilled and also the end-to-end test showed satisfying values. The mean overall time we needed for our checks to have a well monitored machine is less than two hours per month.

Validation of CD98hc as a Therapeutic Target for a Combination of Radiation and Immunotherapies in Head and Neck Squamous Cell Carcinoma.

Simple SummaryThe outcome of patients with locally advanced head and neck squamous cell carcinoma (HNSCC) has not changed for the past decade despite advances in treatment strategies. SLC3A2, which encodes CD98hc, was identified as a putative biomarker for HNSCC radioresistance. Chimeric antigen receptor (CAR) T cell therapy presents a promising immunotherapy approach for the treatment of different cancer types. Due to the limitations of this system, including a lack of self-control mechanisms, the adapter UniCAR system with a switchable mechanism was developed. This study demonstrated a synergistic effect of the combination of fractionated irradiation and immune targeting of CD98hc. The sequential combination of fractionated radiotherapy and UniCAR-based immunotherapy revealed itself to be a promising approach for the treatment of high-risk HNSCC patients.Most patients with head and neck squamous cell carcinomas (HNSCC) are diagnosed at a locally advanced stage and show heterogeneous treatment responses. Low SLC3A2 (solute carrier family 3 member 2) mRNA and protein (CD98hc) expression levels are associated with higher locoregional control in HNSCC patients treated with primary radiochemotherapy or postoperative radiochemotherapy, suggesting that CD98hc could be a target for HNSCC radiosensitization. One of the targeted strategies for tumor radiosensitization is precision immunotherapy, e.g., the use of chimeric antigen receptor (CAR) T cells. This study aimed to define the potential clinical value of new treatment approaches combining conventional radiotherapy with CD98hc-targeted immunotherapy. To address this question, we analyzed the antitumor activity of the combination of fractionated irradiation and switchable universal CAR (UniCAR) system against radioresistant HNSCC cells in 3D culture. CD98hc-redirected UniCAR T cells showed the ability to destroy radioresistant HNSCC spheroids. Also, the infiltration rate of the UniCAR T cells was enhanced in the presence of the CD98hc target module. Furthermore, sequential treatment with fractionated irradiation followed by CD98hc-redirected UniCAR T treatment showed a synergistic effect. Taken together, our obtained data underline the improved antitumor effect of the combination of radiotherapy with CD98hc-targeted immunotherapy. Such a combination presents an attractive approach for the treatment of high-risk HNSCC patients.

Catalyst-Free Periodate Activation by Solar Irradiation for Bacterial Disinfection: Performance and Mechanisms.

Periodate (PI)-based advanced oxidation process has recently attracted great attention in the water treatment processes. In this study, solar irradiation was used for PI activation to disinfect waterborne bacteria. The PI/solar irradiation system could inactivate Escherichia coli below the limit of detection (LOD, 10 CFU mL-1) with initial concentrations of 1 × 106, 1 × 107, and 1 × 108 CFU mL-1 within 20, 40, and 100 min, respectively. •O2- and •OH radicals contributed to the bacterial disinfection. These reactive radicals could attack and penetrate the cell membrane, thereby increasing the amount of intracellular reactive oxygen species and destroying the intracellular defense system. The damage of the cell membrane caused the leakage of intracellular K+ and DNA (that could be eventually degraded). Excellent bacterial disinfection performance in PI/solar irradiation systems was achieved in a wide range of solution pH (3-9), with coexisting humic acid (0.1-10 mg L-1) and broad solution ionic strengths (15-600 mM). The PI/solar irradiation system could also efficiently inactivate Gram-positive Bacillus subtilis. Moreover, PI activated by natural sunlight irradiation could inactivate 1 × 107 CFU mL-1 viable E. coli below the LOD in the river and sea waters with a working volume of 1 L in 40 and 50 min, respectively. Clearly, the PI/solar system could be potentially applied to disinfect bacteria in water.

A 265-Nanometer High-Power Deep-UV Light-Emitting Diode Rapidly Inactivates SARS-CoV-2 Aerosols.

ABSTRACTSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (COVID-19) is an acute respiratory infection transmitted by droplets, aerosols, and contact. Controlling the spread of COVID-19 and developing effective decontamination options are urgent issues for the international community. Here, we report the quantitative inactivation of SARS-CoV-2 in liquid and aerosolized samples by a state-of-the-art, high-power, AlGaN-based, single-chip compact deep-UV (DUV) light-emitting diode (LED) that produces a record continuous-wave output power of 500 mW at its peak emission wavelength of 265 nm. Using this DUV-LED, we observed a greater-than-5-log reduction in infectious SARS-CoV-2 in liquid samples within very short irradiation times (<0.4 s). When we quantified the efficacy of the 265-nm DUV-LED in inactivating SARS-CoV-2, we found that DUV-LED inactivation of aerosolized SARS-CoV-2 was approximately nine times greater than that of SARS-CoV-2 suspension. Our data demonstrate that this newly developed, compact, high-power 265-nm DUV-LED irradiation system with remarkably high inactivation efficiency for aerosolized SARS-CoV-2 could be an effective and practical tool for controlling SARS-CoV-2 spread.IMPORTANCE We developed a 265-nm high-power DUV-LED irradiation system and quantitatively demonstrated that the DUV-LED can inactivate SARS-CoV-2 in suspensions and aerosols within very short irradiation times. We also found that the inactivation effect was about nine times greater against aerosolized SARS-CoV-2 than against SARS-CoV-2 suspensions. The DUV-LED has several advantages over conventional LEDs and mercury lamps, including high power, compactness, and environmental friendliness; its rapid inactivation of aerosolized SARS-CoV-2 opens up new possibilities for the practical application of DUV-LEDs in high-efficiency air purification systems to control airborne transmission of SARS-CoV-2.

Single Cell Effects of Photobiomodulation on Mitochondrial Membrane Potential and Reactive Oxygen Species Production in Human Adipose Mesenchymal Stem Cells.

Photobiomodulation (PBM) has recently emerged in cellular therapy as a potent alternative in promoting cell proliferation, migration, and differentiation during tissue regeneration. Herein, a single-cell near-infrared (NIR) laser irradiation system (830 nm) and the image-based approaches were proposed for the investigation of the modulatory effects in mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS), and vesicle transport in single living human adipose mesenchymal stem cells (hADSCs). The irradiated-hADSCs were then stained with 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) and Rhodamine 123 (Rh123) to represent the ΔΨm and ROS production, respectively, with irradiation in the range of 2.5–10 (J/cm2), where time series of bright-field images were obtained to determine the vesicle transport phenomena. Present results showed that a fluence of 5 J/cm2 of PBM significantly enhanced the ΔΨm, ROS, and vesicle transport phenomena compared to the control group (0 J/cm2) after 30 min PBM treatment. These findings demonstrate the efficacy and use of PBM in regulating ΔΨm, ROS, and vesicle transport, which have potential in cell proliferation, migration, and differentiation in cell-based therapy.

Acceleration of amyloid fibril formation by multichannel sonochemical reactor

The formation of amyloid fibrils of various amyloidogenic proteins is dramatically enhanced by ultrasound irradiation. To apply this phenomenon to the study of protein aggregation science and diagnosis of neurodegenerative diseases, a multichannel ultrasound irradiation system with individually adjustable ultrasound irradiation conditions is necessary. Here, we develop a sonochemical reaction system, where an ultrasonic transducer is placed in each well of a 96-well microplate to perform ultrasonic irradiation of sample solutions under various conditions with high reproducibility, and applied it to study the amyloid fibril formation of amyloid β, α-synuclein, β2-microglobulin, and lysozyme. The results clearly show that our instrument is superior to the conventional shaking method in terms of the degree of acceleration and reproducibility of fibril formation reaction. The acceleration degree is controllable by controlling the driving voltage applied to each transducer. We have thus succeeded in developing a useful tool for the study of amyloid fibril formation in various proteins.

Evaluation of UV-C Radiation Efficiency in the Decontamination of Inanimate Surfaces and Personal Protective Equipment Contaminated with Phage ϕ6.

To help halt the global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), appropriate disinfection techniques are required. Over the last years, the interest in Ultraviolet-C (UV-C) radiation as a method to disinfect inanimate surfaces and personal protective equipment (PPE) has increased, mainly to efficiently disinfect and prevent SARS-CoV-2 from spreading and allow for the safe reuse of said equipment. The bacteriophage ϕ6 (or simply phage ϕ6) is an RNA virus with a phospholipid envelope and is commonly used in environmental studies as a surrogate for human RNA-enveloped viruses, including SARS-CoV-2. The present study investigated the use of two new UV irradiation systems ((2)2.4W and (8)5.5W)) constituted by conventional mercury UV-C lamps with a strong emission peak at ~254 nm to potentially inactivate phage ϕ6 on different surfaces (glass, plastic, stainless steel, and wood) and personal protective equipment, PPE, (surgical and filtering facepiece 2, FFP2, masks, a clear acetate visor, and disposable protective clothing). The results showed that both UV-C systems were effective in inactivating phage ϕ6, but the UV-C sterilizing chamber (8)5.5W had the best disinfection performance on the tested surfaces. The inactivation effectiveness is material-dependent on all surfaces, reaching the detection limit of the method at different times (between 60 and 240 s of irradiation). The glass surface needed less time to reduce the virus (30 s) when compared with plastic, stainless, and wood surfaces (60 s). The virus inactivation was more effective in the disposable surgical and FFP2 masks (60 and 120 s, respectively) than in the disposable vest and clear acetate visor (240 s). Overall, this study suggests that UV-C lamps with peak emission at ~254 nm could provide rapid, efficient, and sustainable sanitization procedures to different materials and surfaces. However, dosage and irradiation time are important parameters to be considered during their implementation as a tool in the fight against human coronaviruses, namely against SARS-CoV-2.

Effect of oxygen on the radiation of silicone rubber determined by gaseous chromatograph and DFT calculation

The radiation effects of silicone rubber under different atmospheres are of great significance to evaluate the aging behavior of materials, and to assess their practical application life. The radiation-induced cross-linking and degradation of polydimethylsiloxane rubber were confirmed firstly by 1H NMR and high-temperature GPC, respectively. By using the established gas collecting system and gaseous chromatography method, we systematically investigated the gaseous products of irradiated silicone rubber at different oxygen concentrations. With the increase of oxygen concentration, the yield of CH4 decreases sharply, while the yield of hydrogen changes slightly. It can be further demonstrated that the reduction of CH4 concentration in the irradiated silicone rubber system is mainly due to the inhibition of CH4 formation, instead of the CH4 degradation, indicating that oxygen directly influences the conversion process of methyl radicals. Similarly, by monitoring the oxygen consumption, it is proved that oxygen is directly involved in the degradation process of silicone rubber, and oxygen scavenged the methyl radicals, which supressed the conversion process of methyl radicals to CH4. Finally, the radiation-induced crosslinking and degradation mechanism of raw silicone rubber was deduced by combining the gaseous products analysis and DFT calculation. It is demonstrated that the release of CH4 can be used to assess the radiation effect of silicone rubber. This work provides a novel method to understand deeply the radiation-induced crosslinking and degradation mechanism of silicone rubber under different atmospheres.

Fabrication of poly(AA)-chitosan nanoparticles graft copolymer via microwave irradiation system for enhancing water solubility and antimicrobial properties

PurposeThis paper aims to study previously prepared and fully characterized chitosan nanoparticles (CNPs) as a starting substrate and microwave initiation technique for grafting acrylic acid (AA). This was done to see the influence of both CNPs with respect to well-dispersed nanosized particles, large surface areas, biodegradability, biocompatibility and reactivity and microwave initiation technique with respect to reduction in organic solvents, toxic chemical initiator and exposer time on exploiting the graft yield % and enhancing water solubility and antibacterial properties.Design/methodology/approachFor evaluating the best accurate standard metrological method for calculating the graft yield %, the grafting parameters were stated in terms of graft yield percent and measured gravimetrically (based on dry weight method) and titrimetrically (based on carboxyl content). Microwave power, AA and CNPs concentrations and reaction duration were shown to be the most important parameters influencing the grafting process.FindingsThe optimum reaction conditions were obtained when CNPs 1.5 g, AA 150 bows, microwave irradiation power 500 W and reaction duration 120 s were used. Various analytical methods were used to characterize CNPs and poly(AA)–CNPs graft copolymers. According to the findings, Fourier transform infrared spectroscopy examination determines the attachment of carboxyl groups to CNPs chains. The thermogravimetric analysis revealed that the copolymers were more thermally stable than CNPs counterparts. Furthermore, the resulting copolymers were shown to have greater water solubility biodegradability resistance and antibacterial properties than CNPs counterpart. Finally, a preliminary mechanism demonstrating all occasions that occur during the polymerization reaction has been proposed.Originality/valueThe advancement addressed here is undertaken using previously prepared and fully characterized CNPs as a green bio-nanocompatible polymer and microwave initiation technique as green and efficient tool with respect to reduction in organic solvents toxic chemical initiator and exposer time for grafting AA.

Real-time irradiation system using patterned light to actuate light-driven on-chip gel actuators

A light-driven gel actuator is a potential candidate for a single-cell manipulation tool because it allows cells to be manipulated while ensuring less damage. Moreover, a large number of actuators can be integrated into a microfluidic chip because no wiring is required. Previously, we proposed a method for cell manipulation using light-driven gel actuators. However, the system used in the previous work did not allow the targeted cells to be manipulated in real time because the system used in the previous work could only irradiate preprogrammed patterned light. Moreover, when a large number of gel actuators are integrated into a chip, the Gaussian distribution of the laser light source results in the response characteristics of the gel actuators varying with the location of the actuator. In this work, we constructed a system that homogenized the intensity of the patterned light used for irradiation, allowing multiple gel actuators to be driven in parallel in real time. The intensity-homogenized patterned light improved the variations in the response characteristics of the gel actuators, and as a result, we succeeded in actuating gel actuators with various light patterns in real time.

The magnetically recoverable C-ZnFe2O4 as a microwave absorption catalyst for the degradation of norfloxacin by persulfate: Mechanism, degradation pathway, toxicity, and stability

Norfloxacin (NOR), a widely used fluoroquinolone antibiotic, has been a focus of attention in recent years due to its adverse effect on human beings and aquatic ecosystems. Magnetic C-ZnFe2O4 (C-ZFO) composite was fabricated by a one-step hydrothermal method and characterized via SEM, TEM, XRD, XPS, VSM. Under given conditions:[NOR] = 5 mg/L, [persulfate (PS)] = 0.25 mM, [pH]0 = 6.7, [C-ZFO] = 1.5 g/L, MW = 400 W, T = 70 ℃, the degradation of NOR reached 86.2% in 40 min, and the highest TOC removal ratio reached 69.6%. The presence of active species (SO4·−,·O2−, HO·, h+) was monitored in C-ZFO activated persulfate under microwave irradiation system (MW-C-ZFO/PS) through radical scavenger study. Meanwhile, intermediate products of NOR and five possible degradation pathways were identified using HPLC-MS. Moreover, the toxicity of NOR intermediates was analyzed by the Vibrio fischeri to evaluate the health risk of the treated water. Overall, microwave irradiation is an efficient technology for degrading NOR in environmental remediation.

High energy radiation – Induced cooperative reductive/oxidative mechanism of perfluorooctanoate anion (PFOA) decomposition in aqueous solution

The mechanism of high-energy radiation induced degradation of perfluorooctanoate anion (PFOA, C7F15COO−) was investigated in aqueous solutions. Identification and quantification of transient species was performed by pulse radiolysis and of final products by gas and ion chromatography, electrochemical method using fluoride ion-selective electrode and ESI-MS after γ-radiolysis. Experimental data were further supported by kinetic simulations and quantum mechanical calculations. Radiation induced degradation of PFOA includes as a primary step one-electron reduction of PFOA by hydrated electrons (e−aq) resulting in formation of [C7F15COO−]●−. The rate constants of this reaction were found to be in the range 7.7 × 107−1.3 × 108 M−1s−1 for ionic strength of the solutions in the range 0.01–0.1 M and were independent of pH of the solutions. At pH > 11 [C7F15COO−]●− tends to defluorination whereas at lower pH undergoes protonation forming [C7F15COOH]•−. A sequence of consecutive reactions involving [C7F15COOH]•− leads to PFOA regeneration what explains a high radiation resistance of PFOA at moderately acidic solutions. A simultaneous presence of oxidizing transient species (●OH) in the irradiated system enhanced decomposition of (C7F14)·COO− as well as [C7F15COOH]•−. The key steps in this complex radical mechanism are the reactions of both these radical anions with ●OH leading to semi-stable products which further undergo consecutive thermal reactions. On the other hand, direct reactions of PFOA with ●OH and ●H were found to be relatively slow (7 × 103 and <4 × 107 M−1s−1, respectively) and do not play relevant role in PFOA degradation. Collected for the first time results, such as dependence of selected reaction rate constants and selected products radiation chemical yields on pH as well as finding of several semi-stable products, missing in previous studies, indicate incompleteness of published earlier reaction pathways of PFOA degradation. The presented overall mechanism explains experimental results and verifies previously suggested mechanisms found in the literature.