Kinetics of the Oxidation of Phenols and Phenolic Endocrine Disruptors during Water Treatment with Ferrate (Fe(VI))

The ability of ferrate (Fe(VI)) to oxidize phenolic endocrine-disrupting chemicals (EDCs) and phenols during water treatment was examined by determining the apparent second-order rate constants (k_app) for the reaction of Fe(VI) with selected environmentally relevant phenolic EDCs (17α-ethinylestradiol, β-estradiol, and bisphenol A) and 10 substituted phenols at pH values ranging from 6 to 11. The three selected groups of EDCs showed appreciable reactivity with Fe(VI) (k_app at pH 7 ranged from 6.4 × 10² to 7.7 × 10² M^-1 s^-1). The k_app for the substituted phenols studied at pH 7 ranged from 6.6 to 3.6 × 10³ M^-1 s^-1, indicating that many other potential phenolic EDCs can be oxidized by Fe(VI) during water treatment. The Hammett-type correlations were determined for the reaction between HFeO₄^- and the undissociated (log(k) = 2.24−2.27σ⁺) and dissociated phenol (log(k) = 4.33−3.60σ⁺). A comparison of the Hammett correlation obtained for the reaction between HFeO₄^- and dissociated phenol with those obtained from other drinking water oxidants revealed that HFeO₄^- is a relatively mild oxidant of phenolic compounds. The effectiveness of Fe(VI) for the oxidative removal of phenolic EDCs was also confirmed in both natural water and wastewater.