Experimental and theoretical study on Fe(VI) oxidative degradation of dichlorophen in water: Kinetics and reaction mechanisms.

Dichlorophenol (DCP), a commonly used fungicide and insecticide, is widely found in waters and wastewaters. Herein, the degradation of DCP by Ferrate (Fe(VI)) in different matrices was comprehensively investigated. In pure water, a complete removal of DCP was achieved in 300 s at [Fe(VI)]:[DCP] molar ratio of 2:1. The presence of HA (10 mg L-1) inhibited DCP degradation to a certain extent. A total of twenty degradation products were identified by HPLC/MS analysis. Based on these products, reaction pathways including the cleavage of C-C bridge bond, hydroxylation, and radical coupling were proposed. These reaction mechanisms were further rationalized by theoretical calculations. The analyses of Wiberg bond orders and transition state indicated that C7-C8 bond was the most vulnerable site for cleavage, and C12 site was the most likely site for hydroxyl addition. Mulliken atomic spin densities distribution suggested that self-coupling products was easily generated via C-O-C coupling ways. Finally, the feasibility of applying Fe(VI) to degrade DCP (20 mu M) in a municipal wastewater effluent and a lake water was evaluated and verified. The findings in this study are of relevance in designing Fe (VI)-based treatment strategy for chlorine-containing persistent pesticides.

Automated summary

This study comprehensively investigated the degradation of DCP by Fe (VI) in different matrices, identifying 20 degradation products and proposing reaction pathways. The most vulnerable cleavage site and the most likely hydroxylation site were revealed through theoretical calculations. The feasibility of using Fe (VI) to degrade DCP in municipal wastewater and lake water was evaluated and confirmed.