Determination of the rate constant of hydroperoxyl radical reaction with phenol

•Using formic acid and dissolved O2 almost all radicals are converted to HO2.•Using sodium formate and dissolved O2 almost all radicals are converted to O2−.•The kHO2+phenol was estimated to be (2.7±1.2)×103 L mol−1 s−1.•HO2 is suggested to contribute significantly to the degradation of phenol.

The rate constant of HO2 reaction with phenol (kHO2+phenol) was investigated. The primary radical set produced in water γ radiolysis (OH, eaq− and H) was transformed to HO2/O2− by using dissolved oxygen and formate anion (in the form of either formic acid or sodium formate). The concentration ratio of HO2/O2− was affected by the pH value of the solution: under acidic conditions (using HCOOH) almost all radicals were converted to HO2, while under alkaline conditions (using HCOONa) to O2−. The degradation rate of phenol was significantly higher using HCOOH. From the ratio of reaction rates under the two reaction conditions kHO2+phenol was estimated to be (2.7±1.2)×103 L mol−1 s−1.