Modeling the oxidation kinetics of Fenton's process on the degradation of humic acid

The degradation of humic acid (HA) was carried out in the presence of the Fenton reagent. The experiments demonstrated that HA was removed by oxidation and coagulation. Moreover, the oxidation occurred mainly at the first 60 min and predominated the HA removal efficiency. A new kinetic model was established according to the generally accepted mechanism of high active OH oxidation in order to well describe the Fenton oxidation reaction in HA aqueous solution. The model embraced two key operating factors affecting the HA degradation in Fenton process, including the dosages of hydrogen peroxide and ferrous ion. The experimental data were fitted by using the most commonly used first- and the second- order reaction models and the new model, respectively. The goodness of fittings demonstrated that the new model could better fit the experimental data than the other two models, which indicated that this analytical model could better describe the kinetics of Fenton reaction mathematically and chemically. Results indicated that the oxidation rate and removal efficiency were strongly dependent on initial pH, initial concentration of Fenton reagents, initial HA concentration and reaction temperature. The experiments demonstrated that hydrogen peroxide and ferrous ion would approach their saturated value with increasing dosage.