Search

A novel "ferrate/percarbonate (Fe(VI)/SPC) co-oxidation process" was used to treat ciprofloxacin (CIP) and various micropollutants (MPs), which owned better performance than mixture of Fe(VI), Na 2 CO 3 and H 2 O 2. The mechanism investigation found that the low-concentration H 2 O 2 (1–2 µM) released by SPC can promote the high-valent iron intermediates (Fe(IV)/Fe(V)) of Fe(VI) to the MP oxidation, and Fe(VI) products can also activate SPC to produce hydroxyl radical (·OH). The interactive activation of Fe(VI) and SPC was realized, which retained the high selectivity of Fe(VI) to electron-rich pollutants, and also made up the oxidation of electron-deficient pollutants through •OH, improving the degradation effect of various MPs by 20–30%, and the rate constant was increased by 1 to 3 times. Moreover, non-purgeable organic carbon (NPOC) determination confirmed that •OH participation reduced the NPOC value of CIP from 5.43 mg/L to 4.37 mg/L. The transformation pathway of CIP showed that Fe(VI)/SPC resulted in more hydroxylation intermediates of CIP than Fe(VI) alone. Acute toxicity assays found that the photoinhibition rate of CIP treated with Fe(VI) alone was 14.5%, while the sample treated with Fe(VI)/SPC showed no significant photoinhibition effect, which proved that the new process had good detoxification properties for CIP. [Display omitted] • The interaction between SPC and Fe(VI) formed both·OH and Fe(IV)/Fe(V). • Low-concentration H 2 O 2 released by SPC improved the electron utilization of Fe(VI). • The·OH enables CIP to generate hydroxylation products possessing reduced toxicity. • SPC/Fe(VI) process is suitable for oxidation of electron rich and electron deficient pollutants. [ABSTRACT FROM AUTHOR]

Iron-based PAA activation process is a promising advanced oxidation process for water decontamination which depends on Fe(II) as the main reactive site for PAA activation, resulting in various reactive oxidative species (ROSs) generation. For practical application, the impact of water matrix chloride ion (Cl−) on ROSs production and contaminants removal should be carefully considered. In this study, it's found that the introduction of Cl− (0.1–10 mM) could significantly enhance the reaction rate of the rapid stage (k obs1) up to 2.15 times at the initial pH of 4.25 in the Fe(II)/PAA system. Further studies demonstrated that the improved removal capacity of NAP resulted from Cl− induced R-O• generation as indicated by the exposure dose of R-O• increasing from 7.74 × 10−11 M•s to 1.44 × 10−10 M•s, rather than chlorine-containing radicals' generation. DFT calculation results suggested that the formed Fe(II)-Cl− complexes could easily activate PAA to generate more ROSs for NAP removal. Moreover, Fe(II)/PAA treatment can alleviate the biological toxicity of pollutants via both the Escherichia coli test and toxicity assessment. The obtained new knowledge manifested that Cl− can boost ROSs generation and conversion in iron-based PAA systems, providing guidance for the efficient decontamination of chlorine-containing sewage with PAA-based AOPs. [Display omitted] • The presence of Cl− promotes NAP removal in the Fe(II)/PAA system at pH 3.0–9.0. • Cl− accelerates PAA depletion due to the formation of complex ([FeCl(H 2 O) 5 ]+ or [FeCl(OH)(H 2 O) 4 ]). • Cl− induced R-O• generation to become the dominant ROS in Fe(II)/PAA system. • Fe(II)/PAA/Cl− treatment can reduce the biological toxicity of wastewater. [ABSTRACT FROM AUTHOR]