Accelerated degradation of pharmaceuticals by ferrous ion/chlorine process: Roles of Fe(IV) and reactive chlorine species

In this study, we determined the mechanisms and kinetics of the degradations of ibuprofen (IBP) and sulfamethoxazole (SMX), and identified the active species contributions in ferrous ion (Fe(II))/free chlorine (FC) system. Reactive chlorine species (RCS) were the major contributor to the degradations of IBP (73.0%) and SMX (59.3%), respectively, at pH 3. Due to the low reaction rates between Fe(IV) and target pollutants (k(Fe(IV),IBP) = (1.5 +/- 0.03) x 10(3) M-1 s(-1) and kF(e(IV),SMX) = (4.8 +/- 0.2) x 10(3) M-1 s(-1)) and the low [Fe(IV)](ss) ((5.0 +/- 0.6) x 10(-8) M), Fe(IV) was not the main contributor and only contributed 0.17% and 0.86% to the degradation of IBP and SMX, respectively, at pH 3. The degradations of pharmaceuticals were facilitated by acidic conditions. Chloride (Cl-) accelerated the degradation of SMX and had a weak effect on the degradation of IBP. Natural organic matter limited the degradation of IBP and SMX. Overall, we demonstrated that multiple active oxidants (Fe (IV) and RCS) are produced by Fe(II)/FC and elucidated the mechanism of active oxidants degradation of pollutants. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study revealed that reactive chlorine species were the major contributors to the degradation of IBP and SMX in the Fe(II)/FC system. The production of active oxidants was influenced by acidic conditions and chloride ions. Multiple active oxidants, including Fe (IV) and RCS, were generated by Fe(II)/FC and played a role in the degradation of pollutants.