External oxidant-free remediation of antibiotics: Activation of oxygen molecules to generate hydroxyl radicals using Co-Fe3S4 nanoflowers

To overcome the obstacles of adding oxidants for the decontamination of antibiotics in natural aqueous envi-ronment, an external oxidant-free system was developed to in-situ generate reactive oxygen species (ROS) through the activation of dissolved oxygen molecules (O2). Guided by density functional theory (DFT) calcula-tion, cobalt-doped Fe3S4 (Co-Fe3S4) nanoflowers were designed and synthesized, which exhibited superior O2 adsorption and activation ability. Co-Fe3S4 triggered a long-lasting generation of center dot OH with a high yield of 16.63 mu M center dot OH, which was 3 times higher than that of Fe3S4. Furthermore, use of Co-Fe3S4 resulted in a 7.33-fold improvement in sulfamethoxazole's degradation rate and boosted the degradation efficiency from 43% to over 90% in the long-run experiments compared to Fe3S4. With 18O2 isotopic investigations, we quantitatively revealed that center dot OH was generated via O2 ' s one-step dissociative adsorption process and the directional electron transfer contributed by structural S(-II). Without the addition of external oxidants (e.g., H2O2, O3), we have reported an efficient one-step activation of O2 to generate ROS for effective degradation of antibiotics. Hence, we have provided a new strategy for the control of emerging organics in natural water systems, as well as shed light on the mechanisms of in-situ center dot OH generation.