Carbonate-radical-anions, and not hydroxyl radicals, are the products of the Fenton reaction in neutral solutions containing bicarbonate

The Fenton reaction, Fe(H₂O)₆ ²⁺ + H₂O₂ → Oxidizing product, is of major importance in biology as the major cause of oxidative stress, and in advanced oxidation processes. It is commonly assumed that ·OH is the product of the Fenton reaction. The results presented herein point out that ·OH is indeed the oxidizing product in acidic solutions for [Fe(H₂O)₆ ²⁺] > [H₂O₂]; Fe^IV _aq is the active oxidizing product in neutral solutions; in slightly acidic solutions for [H₂O₂] > [Fe(H₂O)₆ ²⁺] a mixture of ·OH and Fe^IV _aq is formed. However CO₃·^- is the active oxidizing product in neutral solutions containing HCO₃ ^- even at low concentrations, i.e. under physiological conditions. The implications to our understanding of the origins of oxidative stress and of catalytic oxidations in advanced oxidation processes are discussed.