The role of hydroxyl radicals for the decomposition of p-hydroxy phenylacetic acid in aqueous solutions

The chemical decomposition of p-hydroxyphenylacetic acid, a priority phenol ic pollutant present in wastewaters from some agro-industrial plants, is st udied by means of a single photochemical process produced by a polychromati c UV radiation and by hydroxyl radicals generated by the combination of UV radiation plus hydrogen peroxide and by the Fenton's reagent (hydrogen pero xide plus ferrous salts). Batch experiments were conducted to establish the degradation levels obtained and the quantum yields in the single photodeco mposition process. An improvement in the decomposition of the phenolic acid in the combined UV/H2O2 oxidation is observed, due to the generation of OH radicals, and the contribution of the radical reaction to the global proce ss is determined. In the Fenton's reagent oxidation, the effects of the ope rating variables (H2O2 and Fe2+ initial concentrations, pH, type of buffer used) are established and the rate constant for the reaction of p-hydroxyph enylacetic acid with OH radicals is evaluated from a kinetic model, its val ue being 7.02 x 10(8) M-1 s(-1) at 20 degreesC. (C) 2001 Elsevier Science L td. All rights reserved.