Kinetics of the oxidation of phenols and phenolic endocrine disruptors during water treatment with ferrate (Fe(VI))
The ability of ferrate (Fe(Vl)) 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(17 alpha-ethinylestradiol, beta-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 x 10(2) to 7.7 x 10(2) M-1 s(-1)). The kapp for the substituted phenols studied at pH 7 ranged from 6.6 to 3.6 x 10(3) M-1 s(-1), indicating that many other potential phenolic ENS 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) = 2.24-2.27 sigma(+)) and dissociated phenol (log(k) = 4.33-3.60 sigma(+)). 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.