A new insight into Fenton and Fenton-like processes for water treatment

Abstract

In this study, two Fenton (Fe 2+/H 2O 2) and Fenton-like (Fe 3+/H 2O 2) reactions were compared to clarify their roles in phenol degradation under varying H 2O 2 concentrations, iron dosages and pHs, as well as in the presence of radical scavenger. The results of this study showed that a Fenton-like reaction must proceed concurrently with a classic Fenton reaction, and the concurrent Fenton reaction played a major role in the degradation of pollutants. For the Fenton-like reaction, some oxidation intermediates of phenolic compounds may promote the conversion of Fe(III) to Fe(II) in addition to the uni-molecular decomposition of the Fe(III)–hydroperoxy complexes. The results also showed that varying H 2O 2 concentrations exerted identical effects on the two reactions, and that phenol degradation in both reactions could be correlated to the decomposition of H 2O 2. At low levels of iron concentration, the Fenton reaction appeared to be more efficient than the Fenton-like reaction in terms of the phenol degradation and H 2O 2 decomposition. Additionally, the Fenton reaction had an effective pH range of 2.5–6.0, while the Fenton-like reaction was limited to a narrow pH range of 2.8–3.8. Although the Fenton-like reaction was much slower than that of the Fenton reaction, the overall extent of phenol degradation and H 2O 2 decomposition at the optimal conditions was equivalent.