Degradation of organic pollutants by ultraviolet/ozone in high salinity condition: Non-radical pathway dominated by singlet oxygen

In this work, the combined ultraviolet ozone process (UV/O 3 ) was applied for organic contaminant (Reactive Blue K-GL, RB) degradation in high salinity . The degradation rates of RB in both O 3 and UV/O 3 systems were enhanced by NaCl (the k increased from 0.080 to 0.116 to 0.132 and 0.267 min −1 respectively), while mineralization rate varied at different salt conditions. In addition, UV irradiation promoted the degradation efficiency of RB with the presence of salt. Singlet oxygen ( 1 O 2 ) was the primary active species in the UV/O 3 system. The quenching experiments and signal intensity of 1 O 2 corresponded well to the mineralization of RB. Under conditions of high salinity and high pH, O 3 has high mass transfer coefficient (k La , 3.303 min −1 ) and self-decomposition (k d , 0.600 min −1 ), which further promoted the formation of 1 O 2 for mineralization of RB. Furthermore, UV/O 3 system was efficient in real textile wastewater treatment (COD Cr removal rate 91.7% and decolorization rate 98.7%).