Electrochemical degradation of sunscreen agent benzophenone-3 and its metabolite by Ti/SnO2-Sb/Ce-PbO2 anode: Kinetics, mechanism, toxicity and energy consumption.

Electrochemical degradation of sunscreen agent benzophenone-3 (BP-3) and its metabolite 4-hydroxybenzophenone (4-OH-BP) was investigated by using a Ti/SnO2-Sb/Ce-PbO2 anode. Results showed that the degradation of BP-3 and 4-OH-BP followed pseudo-first-order kinetics, and the rate constants were 0.083 and 0.113 min-1 at a current density of 25 mA cm-2, respectively. The electrochemical degradation of BP-3 and 4-OH-BP was efficient over a wide range of pH values, and the degradation was obviously accelerated in the presence of Cl-. Degradation intermediates were identified during the electrochemical process, and the degradation pathways, mainly including hydroxylation, carbonyl group broken from aromatic ring, benzene ring opening and carboxylation, were proposed. Quantitative structure-activity relationship model indicated that the potential risks of BP-3 and 4-OH-BP to fish, daphnia and green algae were decreased with the increase of reaction time. The energy consumption for the degradation of 90% BP-3 and 4-OH-BP was 3.3-62.1 and 3.6-79.5 Wh L-1, respectively. The results illustrate that the electrochemical technique with Ti/SnO2-Sb/Ce-PbO2 anode is expected to be an effective way for removing BP-3 and its metabolite 4-OH-BP from wastewater.