Radiation chemistry of the terephthalate dosimeter

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3575256· OSTI ID:5133836

Matthews, R W

Cobalt-60 ..gamma..-irradiated aqueous sodium terephthalate solutions have been studied; in aerated 4 x 10/sup -4/ M sodium hydroxide solutions, the main products are hydroxyterephthalate (HTA) (G = 0.99 +- 0.01), carbonate (G = 1.31 +- 0.08), and peroxides (G = 2.84 +- 0.04). The HTA and carbonate species are formed by hydroxyl radical attack and account for approximately 90% of hydroxyl radical reactions. The ortho-, meta-, and para-hydroxybenzoic acids, if formed at all, cannot have G values greater than 0.03, 0.10, and 0.27, respectively; their formation in concentrations corresponding to the maximum yields will not contribute significantly to the fluorescence attributed to the HTA. Oxygen must be present for efficient conversion of the terephthalate-OH radical adduct to HTA, and oxygenation increases G(HTA) above the aerated solution value; but no evidence was found for HTA and CO/sub 2/ formation from primary radiolytic species other than the hydroxyl radical. G(HTA) is unaffected by changes in terephthalate concentration between 1 x 10/sup -4/ and 1 x 10/sup -2/ M in sodium hydroxide solutions at pH 10, but it is affected in the solution pH is decreased. In phosphate-buffered solutions at pH 6.85, G(HTA) is 0.93 +- 0.01; a further decrease in solution pH yields lower values. The lowering of the G(HTA) value is attributed to recombination reactions between the terephthalate-OH radical products and reducing radical products. Support for the recombination postulate was obtained from measurement of a parallel decrease in the peroxide yield and the observation of a dose-rate efect on G(HTA). Competition kinetic studies with added solutes carbonate and bicarbonate gave the rate ratios k(OH + TA/sup 2 -/):k(OH + CO/sub 3//sup 2 -/):k(OH + HCO/sub 3//sup -/) = 1:0.106:0.0036.

• Research Organization: Australian Atomic Energy Commission, Sutherland
• OSTI ID: 5133836
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 83:1; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400700* -- Radiochemistry & Nuclear Chemistry
CARBOXYLIC ACIDS
CHEMICAL RADIATION DETECTORS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMISTRY
DICARBOXYLIC ACIDS
DOSEMETERS
DOSIMETRY
ELEMENTS
FLUORESCENCE
HYDROXYL RADICALS
IRRADIATION
KINETICS
LOW DOSE IRRADIATION
LUMINESCENCE
MEASURING INSTRUMENTS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN
PH VALUE
PHYSICAL PROPERTIES
RADIATION CHEMISTRY
RADIATION DETECTORS
RADIATION EFFECTS
RADICALS
REACTION KINETICS
RESPONSE MODIFYING FACTORS
TEREPHTHALIC ACID
THERMODYNAMIC PROPERTIES