Gamma radiation induces degradation of phenolic acids
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resumo
The aim of this work was to study the degradation by gamma radiation of four phenolic acids
(gallic acid, protocatechuic acid, vanillic acid and syringic acid) that are recalcitrant pollutants
present in cork wastewaters [1]. The irradiations were carried out at room temperature using a
Co-60 experimental equipment, under different pH (natural, 3, 7 and 10) and atmospheres
(aerated, N2O and O2) for isolated and aqueous mixture phenolic acids’ solutions. The applied
absorbed doses were 5-20 kGy at a dose rate of 1.5 kGy/h. The degradation of phenolic acids
was analyzed by HPLC-DAD and the identification of radiolytic products was carried out by LCDAD-
ESI/MS. The obtained results indicated that the degradation of the compounds was higher
in isolated than in the mixture solutions suggesting a protective effect in the quaternary mixture
solution. The N2O saturation promoted the highest degradation rates in the mixture, at natural pH,
however in aerated conditions it was achieved degradation efficiencies >50% for a treatment dose
of 20 kGy. Concerning the identification of the radiolytic products two different compounds were
identified (trihydroxybenzoic acid, [M-H]- at m/z 169, and methyl gallate, [M-H]- at m/z 183) as
radiolytic products of the studied phenolic acids (Figure 1). The degradation mechanisms of the studied phenolic acids was proposed. The results highlighted
that ionizing radiation could be used as clean technology for pollutants degradation using doses
of 20 kGy.
