Intensification of UV-C treatment to remove emerging contaminants by UV-C/H2O2 and UV-C/S2O82−: Susceptibility to photolysis and investigation of acute toxicity

Abstract

In this study, the degradation of four emerging contaminants losartan potassium (LP), furosemide (FRSM), caffeine (CAF), and carbendazim (CBZ) under UV-C, UV-C/H2O2, and UV-C/S2O82− was investigated. A comparative evaluation of the efficiency of UV-C/H2O2 and UV-C/S2O82− in the degradation of these target CECs has not yet been reported. Moreover, target compounds were submitted to UV-C/AOPs individually in pure water and their simultaneous degradation was investigated in real surface water. Evolution of the acute toxicity of each compound during treatment was evaluated using Alivibrio fischeri. Quantum yields were determined for LP (0.011–0.016), FRSM (0.024–0.092), CAF (0.0007–0.0009), and CBZ (0.0016–0.0036) at different pH values. UV-C/H2O2 and UV-C/S2O82 achieved more than 98% removal of all compounds within 600 mJ cm−2, and pseudo-fist-order kinetic constants (k′app) for the degradation reactions were up to seven times higher in the presence of these oxidants when compared to k′app values obtained for UV-C photolysis. k′app measured for UV-C/H2O2 were higher than those calculated for UV-C/S2O82− except in the case of LP. Acute toxicity analysis suggested the formation of toxic intermediates during the UV-C photolysis of LP and FRSM, and the degradation of LP via UV-C/S2O82− also enhanced acute toxicity although electric energy efficiency per order identified UV-C/S2O82 as the most efficient process for the removal of this compound. Finally, different transformation products obtained during the degradation of caffeine under the different UV-C AOPs suggested that distinct degradation routes were involved in each treatment tested.