Stabilization of hydrogen peroxide using phthalic acids in the Fenton and Fenton-like oxidation.

The stabilization of hydrogen peroxide was evaluated in Fenton reaction with phthalic acid as a stabilizer. The stabilization effect was high at a low pH<pK(a1) and the effect was negligible at a high pH above pK(a2) in both Fenton and Fenton-like reactions. While the lifetime of hydrogen peroxide was prolonged by phthalic acid, the stabilization could not contribute on the increase of the reaction rate in the current Fenton and Fenton-like experimental systems because the systems were all well mixed systems. The interaction between dissolved iron and phthalic acid was spectroscopic monitored in variable pH over pK(a1) and pK(a2) of phthalic acid. Ferrous iron was well stabilized and the initial concentration was kept after mixing with phthalate while ferric iron was removed from the aqueous phase by the phthalic acid. It could be concluded that the stabilization by phthalic acid is due to inhibition of catalytic activity of dissolved iron and minimizes the self-decomposition of hydrogen peroxide. The stabilization is affected by ionization state of the organic acid.