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

Abstract 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 (λ = 360 nm) or UVC (λ = 254 nm) light. First, UVA heterogeneous photocatalysis using cellulose acetate monolithic structures coated with thin films of commercial Fe 2 O 3 and TiO 2 (P25, PC105, and PC500) nanoparticles were employed. The highest removal efficiencies values for PBSA (44%), BP-4 (90%) and B P -3 (91%) using synthetic swimming pool waters, after 30 min of irradiation, were achieved using TiO 2 -P25 (3 dips). The addition of H 2 O 2 to the TiO 2 -P25/UVA and Fe 2 O 3 /UVA systems improved substantially the reaction rate, especially for the TiO 2 -P25/UVA system. The second approach consisted in the photochemical oxidation of the UV filters using a UVC/H 2 O 2 system. The optimal H 2 O 2 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 (λ = 254 nm) and UVA (λ = 360 nm) photolysis showed lower degradation rates for the three target compounds when compared with the AOPs tested. Finally, heterogeneous TiO 2 -P25/UVA photocatalysis and photochemical UVC/H 2 O 2 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 ( 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.