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 (O-1(2)) was the primary active species in the UV/O-3 system. The quenching experiments and signal intensity of O-1(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 O-1(2) for mineralization of RB. Furthermore, UV/O-3 system was efficient in real textile wastewater treatment (CODCr removal rate 91.7% and decolorization rate 98.7%). (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The combined ultraviolet ozone process (UV/O-3) was found to be effective for organic contaminant degradation in high salinity, with singlet oxygen (O-1(2)) identified as the primary active species. Under high salt and pH conditions, O-3 exhibited high mass transfer coefficient (k(La)) and self-decomposition (k(d)), further promoting the formation of O-1(2) for the mineralization of contaminants like Reactive Blue K-GL (RB). Additionally, the UV/O-3 system showed high efficiency in real textile wastewater treatment, with significant CODCr removal and decolorization rates achieved.