%0 Journal Article
%T Chloride-mediated enhancement in Cu(II)-catalyzed Fenton-like reaction: The overlooked reactive chlorine species.
%A Xiao S
%A Liu T
%A Li N
%A Ding J
%A Chen J
%A Xu Y
%A Zhang L
%A Yang L
%A Zhou X
%A Ren N
%A Zhang Y
%J Environ Pollut
%V 360
%N 0
%D 2024 Jul 20
%M 39033841
%F 9.988
%R 10.1016/j.envpol.2024.124586
%X The practical application of Cu(II)-catalyzed Fenton-like reaction (Cu(II)/H2O2) exhibits a low efficiency in the degradation of refractory compounds of wastewater. The impact of chloride ions (Cl-) on Fenton-like reactions have been investigated, but the influence mechanism is still unclear. Herein, the presence of Cl- (5 mM) significantly accelerated the degradation of benzoic acid (BA) under neutral conditions. The degradation of BA follows pseudo-first-order kinetics, with a degradation rate 7.3 times higher than the Cu(II)/H2O2 system. Multiple evidences strongly demonstrated that this reaction enables the production of reactive chlorine species (RCS) rather than HO• and high-valent copper (Cu(III)). The kinetic model revealed that Cl- could shift reactive species from the key intermediate (Cu(III)-chloro complexes) to RCS. Dichlorine radicals (Cl2•-) was discovered to play a crucial role in BA degradation, which was largely overlooked in previous reports. Although the reaction rate of Cl2•- with BA (k = 2.0 × 106 M-1 s-1) is lower than that of other species, its concentration is 10 orders of magnitude higher than that of Cu(III) and HO•. Furthermore, the exceptional efficacy of the Cu(II)/H2O2 system in BA degradation was observed in saline aquatic environments. This work sheds light on the previously unrecognized role of the metal-chloro complexes in production the RCS and water purification.