Degradation of carbamazepine by the UVA-LED 365 /ClO 2 /NaClO process: Kinetics, mechanisms and DBPs yield.

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.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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