Oxidative decomposition of atrazine by a Fenton-like reaction in a H2O2/ferrihydrite system

The oxidation of atrazine (ATZ) was studied in the presence of hydrogen peroxide (H2O2) and ferrihydrite at different concentrations and pHs. The rate of ATZ oxidation increased with H2O2 concentration and is independent of pH ranging from 4 to 8. However, at pH 3 an increase of ten times in the rate of ATZ oxidation was observed due to the mineral dissolution. The decomposition rate of H2O2 was three times higher at pH 8 than 3 and increased with increase of both H2O2 and ferrihydrite concentrations. The results indicate that ferrihydrite controls oxidation of ATZ by H2O2 in two different ways: (i) mineral dissolution at low pH allowing the Fenton reaction to proceed in solution and (ii) surface-mediated decomposition of H2O2 producing non-reactive oxygen species in particular at higher pH. Three degradation products (desethylatrazine, desisopropylatrazine, and 2-hydroxyatrazine) were identified and corroborate with a Fenton reaction taking place in solution.