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 environment, an external oxidant-free system was developed to in-situ generate reactive oxygen species (ROS) through the activation of dissolved oxygen molecules (O 2 ). Guided by density functional theory (DFT) calculation, cobalt-doped Fe 3 S 4 (Co-Fe 3 S 4 ) nanoflowers were designed and synthesized, which exhibited superior O 2 adsorption and activation ability. Co-Fe 3 S 4 triggered a long-lasting generation of •OH with a high yield of 16.63 μM •OH, which was 3 times higher than that of Fe 3 S 4 . Furthermore, use of Co-Fe 3 S 4 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 Fe 3 S 4 . With 18 O 2 isotopic investigations, we quantitatively revealed that •OH was generated via O 2 ′s one-step dissociative adsorption process and the directional electron transfer contributed by structural S(-II). Without the addition of external oxidants (e.g., H 2 O 2 , O 3 ), we have reported an efficient one-step activation of O 2 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 •OH generation.