Polypyrrole-encapsulated Fe3O4 nanoparticles with electron transfer channels for synergistic peroxymonosulfate activation and diclofenac sodium degradation

ABSTRACT In this work, an in-situ polymerization of pyrrole was performed to coat Fe3O4 nanoparticles with a polypyrrole (PPy) layer, yielding magnetically separable Fe3O4@PPy composites. The composite was employed to activate peroxymonosulfate (PMS), facilitating the rapid degradation of sodium diclofenac (DCFS). In this work, PPy encapsulates the metal oxides in a shell layer, effectively reducing the leaching of metal ions. Moreover, the PPy encapsulation promoted the formation of oxygen vacancies (Ovac). PPy and Ovac play a crucial role in promoting electron transfer, with Fe2+, PPy and Ovac being able to synergistically activate the PMS to yield abundant reactive oxygen species (ROS). These ROS contributed to the efficient degradation of DCFS. The degradation efficiency of DCFS (50 mg/L) reached 91.0% within just 2 minutes. Among the influential parameters, the initial pH value emerged as the most significant factor. The quenching experiments demonstrated that both the radical and non-radical pathways contributed synergistically to the DCFS degradation, with 1O2 being the dominant ROS. Finally, Fe3O4@PPy exhibited excellent stability and reusability, maintaining high catalytic performance over six consecutive cycles. This work provided a novel and efficient strategy for the removal of pollutants from wastewater, leveraging the synergistic effect of PPy-coated magnetic catalyst for pollutant removal.