Degradation of the chlorophenols by ferrate

The ferrate oxidation of chlorophenols including 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP) in aqueous solution was investigated. It was found that the extent of chlorophenols degradation by potassium ferrate was highly pH dependent. The optimal pH for the three chlorophenols degradation was closely linked to their corresponding pK_a. When pH < pK_a, the reactions of ferrate and chlorophenols were mainly influenced by the extent of dissociation of chlorophenols; whereas, when pH > pK_a, the reactions were mainly controlled by the redox potential of ferrate. Our results also indicated that the reactivity of the undissociated species of chlorophenols with ferrate increased, and the reactivity of the dissociated species decreased instead, as chlorine substituent atoms in chlorophenol molecules increased.