The pH enhancement (for pH > 5) decreases the E-Fenton efficiency, rapidly. This is due to the fact that H2O2 is unstable in the basic solution. H2O2 rapidly decomposes to oxygen and water (Eq. (10)). When pH decreases (for pH < 2), H2O2 changes to H3O2+ (H2O2 cannot be changed to OH• by Fe2+)