Degradation of H-acid and its derivative in aqueous solution by ionising radiation.
The mechanism of high-energy radiation induced degradation of H-acid (4-amino-5-hydroxynaphthalene-2,7-disulphonic acid, (I)) and its derivative, 4-hydroxynaphthalene-2,7-disulphonic acid (II) (central parts of a large number of azo dyes), was investigated in aqueous solutions. These compounds can be efficiently destroyed by the (*)OH and hydrated electron intermediates produced during water radiolysis. As the first step of degradation mainly cyclohexadienyl-type radicals form, however, with I H-atom elimination from the NH(2) group is also observed yielding anilino-type radicals. Both the cyclohexadienyl and the anilino-type radicals decay on the millisecond timescale. In the (*)OH reactions as stable products hydroxylated molecules and quinone-type compounds form. These molecules by further decomposition of the ring structure transform to open chain molecules. In the case of hydrated electron, the primarily formed products have absorption spectra shifted to the low-wavelength region indicating the destruction of at least one of the aromatic rings.
Pálfi
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Institute of Isotopes, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 77, Hungary.
Takács
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Wojnárovits
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D004396:Coloring Agents / Q000737:chemistry / Q000528:radiation effects*; D005720:Gamma Rays; D017665:Hydroxyl Radical / Q000737:chemistry; D009282:Naphthalenesulfonates / Q000737:chemistry / Q000528:radiation effects*; D012996:Solutions; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects*; D018508:Water Purification / Q000379:methods
D004396:Coloring Agents; D009282:Naphthalenesulfonates; D012996:Solutions; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical