Ionizing radiation induced degradation of salicylic acid in aqueous solution

Abstract

The radiation-induced degradation of salicylic acid (SA–) in aqueous solutions (1.0 and 0.1 mmol dm−3) saturated with N2O or air or without oxygen were studied. Irradiation was carried out using a cobalt-60 source. With a 1 mmol dm−3 solution saturated with N2O a seemingly total degradation occurred at about 18 kGy, although small quantities of 2,3-dihydroxybenzoic acid, catechol and 2,5-dihydroxybenzoic acid were present at that dose at concentrations of 67, 22 and 6 μmol dm−3 respectively. Under air and when free oxygen, the three radiolytic products were present at 18.54 kGy while SA– was destroyed only to 90% and 62%, respectively. In the case of 0.1 mmol dm−3 SA– solutions, the acid was degraded at 3.5 kGy if the solution contained N2O, at 5.8 kGy in air and at 7 kGy without oxygen. The concentration of the radiolytic products increased with increasing dose and after a maximum they decreased. The oxidation was followed by measuring the chemical oxygen demand; the slopes were 0.48 and 0.11, 0.21 and 0.07, 0.15 and 0.03 mmol dm−3 kGy−1 for 1.0 and 0.10 mmol dm−3 solutions saturated with N2O or air or without oxygen, respectively.