Degradation of carbamazepine by the UVA-LED365/ClO2/NaClO process: Kinetics, mechanisms and DBPs yield.

• UVA 365 /ClO 2 /NaClO process showed excellent degradation efficiency of CBZ. • The UVA 365 /ClO 2 /NaClO process can effectively control the consumption of oxidants. • The main active species were HO • and Cl • at high ratios of ClO 2. • The UVA 365 /ClO 2 /NaClO process can reduce the formation of chlorate and chlorite. A mixed oxidant of chlorine dioxide (ClO 2) and NaClO was often used in water treatment. A novel UVA-LED (365 nm)-activated mixed ClO 2 /NaClO process was proposed for the degradation of micropollutants in this study. Carbamazepine (CBZ) was selected as the target pollutant. Compared with the UVA 365 /ClO 2 process, the UVA 365 /ClO 2 /NaClO process can improve the degradation of CBZ, with the rate constant increasing from 2.11×10−4 sec−1 to 2.74×10−4 sec−1. In addition, the consumption of oxidants in the UVA 365 /ClO 2 /NaClO process (73.67%) can also be lower than that of UVA 365 /NaClO (86.42%). When the NaClO ratio increased, both the degradation efficiency of CBZ and the consumption of oxidants can increase in the UVA 365 /ClO 2 /NaClO process. The solution pH can affect the contribution of NaClO in the total oxidant ratio. When the pH range of 6.0-8.0, the combination process can generate more active species to promote the degradation of CBZ. The change of active species with oxidant molar ratio was investigated in the UVA 365 /ClO 2 /NaClO process. When ClO 2 acted as the main oxidant, HO• and Cl• were the main active species, while when NaClO was the main oxidant, ClO• played a role in the system. Both chloride ion (Cl–), bicarbonate ion (HCO 3 –), and nitrate ion (NO 3 –) can promote the reaction system. As the concentration of NaClO in the reaction solution increased, the generation of chlorates will decrease. The UVA 365 /ClO 2 /NaClO process can effectively control the formation of volatile disinfection by-products (DBPs), and with the increase of ClO 2 dosage, the formation of DBPs can also decrease. [Display omitted] [ABSTRACT FROM AUTHOR]