Application of vacuum-ultraviolet (VUV) to degrade β-blocker propranolol in aquatic environment: Efficiency, kinetics, pathways and acute toxicity

Good degradation of β -blocker propranolol (PrP) in the VUV/UV 254 system was achieved in both pure water and realistic water. Both hydroxyl radical (HO • ) and UV 254 photolysis have been evidenced to contribute to PrP degradation in the VUV/UV 254 system. A kinetic model by including both HO • and UV 254 photolysis was successfully applied to predict the observed rate constant ( k obs ) of PrP degradation in the VUV/UV 254 system under different conditions. Elevating initial PrP concentration would reduce the steady-state concentration of HO • , as a result to decreasing the k obs of PrP degradation. While elevating reaction temperature can significantly accelerate PrP degradation. The degradation of PrP in the VUV/UV 254 system was little affected by the variation of reaction pH. HCO 3 − /CO 3 2− , humic acid (HA) and Cl − significantly inhibit PrP degradation in the VUV/UV 254 system. The PrP degradation pathways initiated with hydroxylation and cleavage of side chain were proposed. Although some intermediate products containing higher acute toxicity than PrP were produced in the initial phase of PrP degradation, they could be further oxidized to low toxic products in the system. This study provides that VUV/UV 254 would be a good advanced oxidation process for the treatment of β -blockers in aquatic environment.