Bisulfite-induced drastic enhancement of bisphenol A degradation in Fe3+-H2O2 Fenton system

The present work aimed at using bisulfites (HSO3-) to enhance the oxidative degradation of bisphenol A (BPA) in a Fenton process based on the Fe3+-H2O2 reagents. It was confirmed that both the degradation and mineralization of BPA were drastically enhanced by the addition of HSO3-. Typically, the use of 0.1 mmol L-1 Fe3+, 0.3 mmol L-1 HSO3- and 10 mmol L-1 H2O2 achieved a complete degradation of BPA (0.05 mmol L-1) in only 2 min. The addition of HSO3- increased the BPA degradation rate constant from 0.045 min(-1) in the Fe3+-H2O2 system to 2.71 min(-1) in the Fe3+-HSO3--H2O2 system by 60 times. This drastic enhancement effect of HSO3 was attributed to its complexing and reducing abilities. The formation of FeSO3+ complex prevented the precipitation of Fe3+ and accelerated the cycling of Fe3+/Fe2+; the reducing ability of HSO3- further favored the transformation of Fe3+ to Fe2+. Several reactive species, including (OH)-O-center dot, SO3 center dot- and SO4 center dot- were responsible for the degradation of BPA, among which (OH)-O-center dot was the dominant one. The proposed Fe3+-HSO3--H2O2 system is suggested be able to act as the followed stage of a traditional Fe2+-H2O2 system in the engineering setting.