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

• Published in: The Science of the total environment 2021-09, Vol.787, p.147584-147584, Article 147584
• Main Authors: Mao, Yuanxiang, Liang, Jialiang, Ji, Fangying, Dong, Huiyu, Jiang, Lei, Shen, Qiushi, Zhang, Qian
• Format: Article
• Language: English
• Subjects: Advanced oxidation process; Fe(IV); Ferrous ion; Free chlorine
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.147584

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 (kFe(IV), IBP = (1.5 ± 0.03) × 103 M−1 s−1 and kFe(IV), SMX = (4.8 ± 0.2) × 103 M−1 s−1) and the low [Fe(IV)]ss ((5.0 ± 0.6) × 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. [Display omitted] •Degradations of IBP and SMX are accelerated by the Fe(II)/FC process.•The formation of Fe(IV) and Cl instead of HO in the Fe(II)/FC process•HO is a secondary free radical generated by the reaction of Cl and H2O.•RCS are the major contributor to the degradations of IBP and SMX.