Characterization of hydrolyzed Fe(III) species produced in Fenton's reaction

In this paper, the applicability of the ferron assay for the characterization of hydrolyzed Fe(III) produced in the Fenton's reaction system was investigated, and then the hydrolysis process of Fe(III) under typical Fenton's reaction conditions was compared with that in a normal ferric sulphate solution system, by applying the ferron assay method and the modified hydrolyticity, B*, a parameter that takes into account all the possibilities of base generation and reduction. It was found that the residual Fe(II) and H2O2 under normal Fenton's reaction conditions had little influence on the Fe(III)-ferron colorimetric reaction. Experimental results showed that the hydrolysis process of Fe(III) in the Fenton system was quite different from that in the ferric salt solution system. Under the same hydrolyticity, the hydrolysis rate of Fe(III) in the Fenton system was faster and more complicated than that in the ferric sulphate system, and the Fe(III) species produced in the Fenton system had a larger polymerization degree. With the increase in H2O2/Fe, Fe(a) and Fe(b) (the monomers and small polymeric Fe(III) species) increased gradually while Fe(c) (the colloidal part) decreased, indicating that the increase in H2O2 had restrained the hydrolysis of Fe(III). This conclusion was also supported by the comparison of effective particulate diameters in the two systems. The fact that larger particles were produced with a shorter time in the Fenton system provided direct proof for the observation of the differences in the hydrolysis of Fe(III) in the two systems. The results of this study are useful for the possible utilization of the hydrolyzed Fe(III) produced in the Fenton's system for the removal of organic pollutants.