Radiation chemistry
Radiation chemistry is a subdivision of
Radiation interactions with matter
As ionizing radiation moves through matter its energy is deposited through interactions with the electrons of the absorber.[1] The result of an interaction between the radiation and the absorbing species is removal of an electron from an atom or molecular bond to form radicals and excited species. The radical species then proceed to react with each other or with other molecules in their vicinity. It is the reactions of the radical species that are responsible for the changes observed following irradiation of a chemical system.[2]
Charged radiation species (α and β particles) interact through Coulombic forces between the charges of the electrons in the absorbing medium and the charged radiation particle. These interactions occur continuously along the path of the incident particle until the kinetic energy of the particle is sufficiently depleted. Uncharged species (γ photons, x-rays) undergo a single event per photon, totally consuming the energy of the photon and leading to the ejection of an electron from a single atom.[3] Electrons with sufficient energy proceed to interact with the absorbing medium identically to β radiation.
An important factor that distinguishes different radiation types from one another is the linear energy transfer (
Areas containing a high concentration of reactive species following absorption of energy from radiation are referred to as spurs. In a medium irradiated with low LET radiation, the spurs are sparsely distributed across the track and are unable to interact. For high LET radiation, the spurs can overlap, allowing for inter-spur reactions, leading to different yields of products when compared to the same medium irradiated with the same energy of low LET radiation.[5]
Reduction of organics by solvated electrons
A recent area of work has been the destruction of toxic organic compounds by irradiation;
In addition to the work on the destruction of aryl chlorides, it has been shown that
In addition to the work on the reduction of organic compounds by irradiation, some work on the radiation induced oxidation of organic compounds has been reported. For instance, the use of radiogenic hydrogen peroxide (formed by irradiation) to remove sulfur from coal has been reported. In this study it was found that the addition of manganese dioxide to the coal increased the rate of sulfur removal.[14] The degradation of nitrobenzene under both reducing and oxidizing conditions in water has been reported.[15]
Reduction of metal compounds
In addition to the reduction of organic compounds by the solvated electrons it has been reported that upon irradiation a
It has been shown that the irradiation of aqueous solutions of lead compounds leads to the formation of elemental lead. When an inorganic solid such as bentonite and sodium formate are present then the lead is removed from the aqueous solution.[18]
Polymer modification
Another key area uses radiation chemistry to modify polymers. Using radiation, it is possible to convert monomers to polymers, to crosslink polymers, and to break polymer chains.[19][20] Both man-made and natural polymers (such as carbohydrates[21]) can be processed in this way.
Water chemistry
Both the harmful effects of radiation upon biological systems (induction of
It is important to note that the reactive species generated by the radiation can take part in following reactions; this is similar to the idea of the non-electrochemical reactions which follow the electrochemical event which is observed in cyclic voltammetry when a non-reversible event occurs. For example, the SF5 radical formed by the reaction of solvated electrons and SF6 undergo further reactions which lead to the formation of hydrogen fluoride and sulfuric acid.[22]
In water, the dimerization reaction of hydroxyl radicals can form hydrogen peroxide, while in saline systems the reaction of the hydroxyl radicals with chloride anions forms hypochlorite anions.
The action of radiation upon underground water is responsible for the formation of hydrogen which is converted by bacteria into methane.[23][24]
Equipment
Radiation chemistry applied in industrial processing equipment
To process materials, either a gamma source or an electron beam can be used. The international type IV (wet storage) irradiator is a common design, of which the JS6300 and JS6500 gamma sterilizers (made by 'Nordion International'[2], which used to trade as 'Atomic Energy of Canada Ltd') are typical examples.[25] In these irradiation plants, the source is stored in a deep well filled with water when not in use. When the source is required, it is moved by a steel wire to the irradiation room where the products which are to be treated are present; these objects are placed inside boxes which are moved through the room by an automatic mechanism. By moving the boxes from one point to another, the contents are given a uniform dose. After treatment, the product is moved by the automatic mechanism out of the room. The irradiation room has very thick concrete walls (about 3 m thick) to prevent gamma rays from escaping. The source consists of 60Co rods sealed within two layers of stainless steel. The rods are combined with inert dummy rods to form a rack with a total activity of about 12.6PBq (340kCi).
Research equipment
While it is possible to do some types of research using an irradiator much like that used for gamma sterilization, it is common in some areas of science to use a time resolved experiment where a material is subjected to a pulse of radiation (normally
In the latter experiment the sample is excited by a pulse of light to examine the decay of the excited states by spectroscopy;[27] sometimes the formation of new compounds can be investigated.[28] Flash photolysis experiments have led to a better understanding of the effects of halogen-containing compounds upon the ozone layer.[29]
Chemosensor
The SAW chemosensor[30] is nonionic and nonspecific. It directly measures the total mass of each chemical compound as it exits the gas chromatography column and condenses on the crystal surface, thus causing a change in the fundamental acoustic frequency of the crystal. Odor concentration is directly measured with this integrating type of detector. Column flux is obtained from a microprocessor that continuously calculates the derivative of the SAW frequency.
See also
References
- ISBN 0-471-61403-3
- ^ Turner, J.E. Atoms, Radiation, and Radiation Protection. United States: Pergamon Books Inc., Elmsford, NY, 1986. Print
- ^ Bigelow, R. A. Radiation Interactions in Matter.
- ^ Essentials of radiation, biology and protection, S. Forshier, Cengage Learning, Jul 22, 2008, p46
- , Publication Date: June 1994
- ^ Zhao C et al. (2007) Radiation Physics and Chemistry, 76:37-45
- ^ Ajit Singh and Walter Kremers, Radiation Physics and Chemistry, 2002, 65(4-5), 467-472
- ^ Bruce J. Mincher, Richard R. Brey, René G. Rodriguez, Scott Pristupa and Aaron Ruhter, Radiation Physics and Chemistry, 2002, 65(4-5), 461-465
- ^ A. G. Bedekar, Z. Czerwik and J. Kroh, "Pulse radiolysis of ethylene glycol and 1,3-propanediol glasses—II. Kinetics of trapped electron decay", 1990, 36, 739-742
- ^ Energy Citations Database (ECD) - - Document #10116942
- ^ Process for the solvent extraction for the radiolysis and dehalogenation of halogenated organic compounds in soils, sludges, sediments and slurries - US Patent 6132561 Archived 2007-03-11 at the Wayback Machine
- ^ V. Múka, *, R. Silber, M. Pospíil, V. Kliský and B. Bartoníek, Radiation Physics and Chemistry, 1999, 55(1), 93-97
- ^ Seiko Nakagawa and Toshinari Shimokawa, Radiation Physics and Chemistry, 2002, 63(2), 151-156
- ^ P. S. M. Tripathi, K. K. Mishra, R. R. P. Roy and D. N. Tewari, "γ-Radiolytic desulphurisation of some high-sulphur Indian coals catalytically accelerated by MnO2", Fuel Processing Technology, 2001, 70, 77-96
- ^ Shao-Hong Feng, Shu-Juan Zhang, Han-Qing Yu, and Qian-Rong Li, "Radiation-induced Degradation of Nitrobenzene in Aqueous Solutions", Chemistry Letters, 2003, 32(8), 718
- ^ T. Sekine, H. Narushima, T. Suzuki, T. Takayama, H. Kudo, M. Lin and Y. Katsumura, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004, 249(1-3), 105-109
- ^ Satoshi Seino, Takuya Kinoshita, Yohei Otome, Kenji Okitsu, Takashi Nakagawa, and Takao A. Yamamoto, "Magnetic Composite Nanoparticle of Au/γ-Fe2O3 Synthesized by Gamma-Ray Irradiation", Chemistry Letters, 2003, 32(8), 690
- ^ M. Pospίšil, V. Čuba, V. Múčka and B. Drtinová, "Radiation removal of lead from aqueous solutions- effects of various sorbants and nitrous oxide", Radiation Physics and Chemistry, 2006, 75, 403-407
- ^ Energy Citations Database (ECD) - - Document #7313004
- ^ IAEA report - Radiation Formation of Hydrogels for Biomedical Applications; the use of radiation technique - Mechanism of the radiation-induced crosslinking of polymers in aqueous solution Archived 2007-04-26 at the Wayback Machine
- ^ IAEA-TECDOC-1422
- ^ K.-D. Asmus and J.H. Fendler, "The reaction of sulfur hexafluoride with solvated electrons", The Journal of Physical Chemistry, 1968, 72, 4285-4289
- S2CID 4327881.
- hdl:1912/659. Archived from the original(PDF) on 2010-06-17.
- ^ Features of the design are discussed in the International Atomic Energy Agency report on a human error accident in such an irradiation plant [1]
- ^ "Pulse Radiolysis". dur.ac.uk. 2007-03-28. Archived from the original on 2007-03-28.
- ^ Hanley, Luke. "Flash Photolysis of Benzophenone" (PDF). Archived from the original (PDF) on 2011-07-20.
- ^ Porter, George (11 December 1967). "Flash photolysis and some of its applications (Nobel lecture)" (PDF). Archived from the original (PDF) on 2014-10-08. Retrieved 2022-08-09.
- ^ RE Huie; B Laszlo; MJ Kurylo; et al. (1995). Atmospheric Chemistry of Iodine Monoxide (PDF). Halon Options Technical Working Conference. Retrieved 2012-04-19.
- ^ Abnormal Chemosensory Jump 6 Is a Positive Transcriptional Regulator of the Cholinergic Gene Locus in Drosophila Olfactory Neurons - Lee and Salvaterra 22 (13): 5291 - Journal of Neuroscience