A new insight into Fenton and Fenton-like processes for water treatment: Part II. Influence of organic compounds on Fe(III)/Fe(II) interconversion and the course of reactions.

The interconversion of Fe(III)/Fe(II) in Fenton (Fe(2+)/H2O2) and Fenton-like (Fe(3+)/H2O2) reactions has been studied to better understand their intrinsic mechanisms. The reactions were conducted at an initial pH of 3.0, with H2O2 in excess and iron in catalytic concentrations, and with nitrobenzene and atrazine as model organic compounds. The results of this study have shown that some intermediate species in the degradation of aromatic compounds can influence the interconversion of Fe(III)/Fe(II) in the Fenton and Fenton-like reactions, and hence influence the rate and course of the reactions. Thus, from the point of view of Fe(III)/Fe(II) interconversion, a Fenton-like reaction inevitably involves a classical Fenton reaction, and a Fenton reaction may also involve a Fenton-like reaction step. These two reactions may be somewhat interchangeable and proceed simultaneously. In the case of the degradation of aromatic compounds, the Fenton-like reactions display autocatalytic character, but no such effect is observed for non-aromatic compounds.