Kinetics and reaction pathways for the transformation of 4-tert-butylphenol by ferrate(VI).

4-tert-butylphenol (4-tBP) is a phenolic endocrine disrupting chemical that has attracted great attention due to its wide occurrence, environmental persistence, and possible toxic effects. In this study, we systematically investigated the transformation of 4-tBP in ferrate (VI) oxidation process. The second-order reaction rate constant (kapp) of Fe(VI) with 4-tBP decreases with solution pH, and the kapp value was determined as 295 M-1·s-1 at pH 8.0. The removal efficiency of 4-tBP was slightly decreased by Mg2+ and HCO3-, while accelerated at varying degrees by the presence of Cu2+ and humic acid. Product analysis revealed that 4-tBP was mainly transformed into hydroxylation products, benzene-ring cleavage products, dimers and higher polymerization products via oxygen atom transfer, ring-opening of the benzene ring and radical coupling reaction. Furthermore, initial reactions of 4-tBP were rationalized by theoretical analysis of atom partial charges, frontier electron densities, and spin densities. Nearly complete removal of 4-tBP (20 μM) was achieved after 5 min of reaction in both ultrapure water and natural waters, demonstrating the feasibility of this Fe(VI) oxidation method in treating phenols-contaminated waters.