Assessment of advanced oxidation processes for the degradation of three UV filters from swimming pool water

摘要

This work assesses different advanced oxidation processes (AOPs) for the elimination of 3 UV filters, ensulizole (PBSA), benzophenone-4 (BP-4) and benzophenone-3 (BP-3), in concentrations of few micrograms per liter, from synthetic and real swimming pool waters. AOPs experiments were performed in a lab-scale tubular photoreactor irradiated by UVA (lambda = 360 nm) or UVC (lambda = 254 nm) light. First, UVA heterogeneous photocatalysis using cellulose acetate monolithic structures coated with thin films of commercial Fe2O3 and TiO2 (P25, PC105, and PC500) nanoparticles were employed. The highest removal efficiencies values for PBSA (44%), BP-4 (90%) and BP-3 (91%) using synthetic swimming pool waters, after 30 min of irradiation, were achieved using TiO2-P25 (3 dips). The addition of H2O2 to the TiO2-P25/UVA and Fe2O3/UVA systems improved substantially the reaction rate, especially for the TiO2-P25/UVA system. The second approach consisted in the photochemical oxidation of the UV filters using a UVC/H2O2 system. The optimal H2O2 concentration obtained was 0.59 mM, resulting in removal efficiencies of 77%, 98% and 95% for PBSA, BP-4, and BP-3, respectively, after 6 min of irradiation, with photolysis half-lifes lower than 3 min. UVC (lambda = 254 nm) and UVA (lambda = 360 nm) photolysis showed lower degradation rates for the three target compounds when compared with the AOPs tested. Finally, heterogeneous TiO2-P25/UVA photocatalysis and photochemical UVC/H2O2 oxidation systems, under their optimal conditions, were applied to the treatment of real swimming pool waters containing simultaneously the three UV filters, reaching a complete degradation (LOD) for BP-4 and BP-3 and 50% for the recalcitrant PBSA in less than 6 min. Although several by-products, including chlorinated compounds, were identified during the oxidation process, its abundance was substantially decreased for extended period of reaction time. (C) 2017 Elsevier B.V. All rights reserved.