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.