Mechanistic insights into surface catalytic oxidation of fluoroquinolone antibiotics on sediment mackinawite

Unrecognized Role of Organic Acid in Natural Attenuation of Pollutants by Mackinawite (FeS): The Significance of Carbon-Center Free Radicals

“…Utilizing 2,3-bis­(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)­carbonyl]-2 H -tetrazolium hydroxide (XTT) as a probe molecule for the detection of O 2 •– in aqueous solution, the substantial formation of XTT formazan in the FeS/OA system was observed (Figure S16). This verifies the enhanced production of O 2 •– in the FeS/OA system . Additionally, the formation of H 2 O 2 was also observed by using TiOSO 4 /H 2 SO 4 as a chromogenic agent (Figure d).…”

“…This observation implies that the carbon-centered radicals trapped by DMPO might have the ability to generate secondary • OH radicals. As reported previously, carbon-centered radicals readily react with O 2 and induce the generation of O 2 •– , which might be the source of H 2 O 2 and • OH via the disproportionation and Fenton-like reactions, respectively. , In the present work, however, the DMPO-O 2 •– signal was absent in the EPR spectra, which can be attributed to its instability when exposed to an aqueous environment . Emerging evidence suggested that the generation of O 2 •– was accompanied by 1 O 2 formation through reactions such as O 2 •– + • OH → 1 O 2 + OH – and 2O 2 •– + 2H + → 1 O 2 + H 2 O 2 .…”

“…•− in the FeS/OA system. 20 Additionally, the formation of H 2 O 2 was also observed by using TiOSO 4 / H 2 SO 4 as a chromogenic agent (Figure 2d). For the FeS/OA system, the concentration of H 2 O 2 gradually increased to the maximum value of 0.29 mM in 3 h of reaction time and then slightly decreased to 0.26 mM in 4 h. In contrast, the H 2 O 2 concentration remained at a relatively low level in a pure FeS system.…”

“…18,19 During the abiotic oxidation of FeS by O 2 , reactive oxygen species (ROS), such as H 2 O 2 and • OH, emerge as crucial intermediates. 20,21 The transformation of environmental pollutants mediated by ROS represents a new natural attenuation pathway, potentially mitigating contamination impacts over extended periods ranging from months to years. 22 environmental factors may profoundly influence the oxidation activity of FeS-mediated reaction systems.…”

Degradation of Nitrobenzene by Mackinawite through a Sequential Two-Step Reduction and Oxidation Process

“…More recently, studies have identified the oxidative degradation of organic contaminants (e.g., phenol and trichloroethylene) 20 and the transformation of dissolved organic matter 21 sediment FeS could catalyze the degradation of fluoroquinolone antibiotics through the production of • OH. 22 While FeS has shown great potential in the removal of contaminants by either reduction or oxidation, there is apparently no study investigating the sequential two-step reduction and oxidation process for contaminant removal using FeS. In practice, many aromatic compounds (e.g., tetrabromobisphenol A and ArNO 2 ) are difficult to completely degrade through reduction or oxidation alone.…”