Insight into wavelength-dependent UVA-LED/chlorine process for micropollutant degradation: Performance, mechanism, and effects of water matrix.

[Display omitted] • ATL degradation was retarded with the increase in wavelengths and solution pH. • IBF and BZF were used to jointly detect the steady-state concentrations of ClO and Cl 2 −. • O 3 was the major contributor to ATL degradation in the pH range of 7.0–9.0. • The increase of pH decreased the contributions of OH and RCS, but enhanced the contribution of O 3. • Increase in pH and wavelength decreased the concentrations of DBPs. Ultraviolet A light-emitting diode (UVA-LED)-activated chlorine effectively degraded micropollutants at different irradiation wavelengths. Quenching experiments indicated that OH, reactive chlorine species (RCS), and O 3 were the main reactive species for degradation of atenolol (ATL). Bezafibrate and ibuprofen, were used for the first time to jointly quantify the concentrations of Cl 2 − and ClO. Notably, O 3 contributed most to the degradation of ATL (38.9%), following by OH (30.2%) and RCS (27.6%) at pH 7.0 by the UVA-LED/chlorine at 385 nm. ATL degradation increased with the decrease of wavelengths, due to the higher quantum yields of chlorine. The k obs of ATL was positively correlated to the quantum yield of chlorine at the UVA wavelength band. Higher light intensity could enhance the photolysis of chlorine, leading to enhanced ATL degradation. The protonated chlorine is more conducive to the degradation of ATL. Specifically, the contributions of OH, O 3 , and RCS to ATL degradation changed from 40.9%, 6.53%, and 41.0% at pH 4.0 to 11.6%, 59.9%, and 26.6% at pH 9.0, respectively. Cl− had no significant influence on ATL degradation, mainly due to the synergistic effect of different reactive species. HCO 3 − and HA inhibited ATL degradation owing to the quenching effect for reactive species and/or UV filtering effect. The primary transformation pathway of ATL included hydroxylation, chlorination, and bond-cleavage pathways based on the structures of the eight identified transformation products. Seven chlorinated disinfection by-products decreased as wavelengths and pH increased. The above results show that UVA-LED/chlorine might be an efficient process for water treatment. [ABSTRACT FROM AUTHOR]