Oxidation of benzophenone-3 during water treatment with ferrate(VI).

Benzophenone-3 (BP-3), a sunscreen agent widely used in many cosmetic products, has been found to have a wide presence in aquatic environments, which could affect the water quality and human health. We investigated oxidation of BP-3 by aqueous ferrate(VI) (Fe(VI)) to determine reaction kinetics, identify the reaction products, and evaluate the removal efficiency of BP-3 during water treatment with Fe(VI). The obtained apparent second-order rate constant (kapp) for Fe(VI) oxidation of BP-3was 81.8 M(-1) s(-1) at pH 8.0 and 24 ± 1 °C with the half-life (t1/2) of 167.8 s for BP-3 at an Fe(VI) concentration of 10 mg L(-1). The kapp of the reaction decreased with increasing pH values. Species-specific rate constants (k) for the reaction of HFeO4(-) with each of BP-3's acid-base species were used to model these pH-dependent variations of kapp. The value of k determined for neutral BP-3 was 3.4(±0.5) × 10(2) M(-1) s(-1), while that measured for dissociated BP-3 was 8.5(±0.7) × 10(3) M(-1) s(-1). The reaction between HFeO4(-) and the dissociated BP-3 controls the overall reaction. 4-Methoxybenzophenone and 4-methoxybenzoyl cation were formed during Fe(VI) degradation of BP-3. The removal efficiency of BP-3 by Fe(VI) treatment was dependent on coexisting constituents present in source water. Humic acids, Mn(2+) and NaCl significantly decreased the removal efficiency of BP-3, while Br(-) and Cu(2+) enhanced the removal. Besides, NH4(+), NO3(-), Fe(3+) and Fe(2+) had no effects on BP-3 removal within the tested concentrations. The results showed that Fe(VI) treatment technology appears to be a promising tool for the removal of hydroxylated benzophenone derivatives in water.