One-step self-assembled ZIF-derived flower-like carbon enhances reactivity of zero-valent iron during persulfate activation

The sintering aggregation of carbon material (ZIF-N-C-600), as well as the tendency towards agglomeration and oxidation of zero-valent iron nanoparticles (Fe⁰) limit their applications in advanced oxidation processes. Hence, a flower-like Fe⁰@ZIF-N-C-600 was rationally constructed by facile one-step self-assembly to ameliorate peroxydisulfate (PDS) activation. The polyhedral ZIF-N-C-600 aggregates were exfoliated into thinner porous nanosheets and Fe⁰ nanoparticles were effectively dispersed and anchored onto ZIF-N-C-600. 96.7 % of metronidazole (MNZ) was eliminated by the Fe⁰@ZIF-N-C-600/PDS system, and the removal reaction rate constant k values were 2 and 2.55 times as high as Fe⁰@ZIF/PDS and Fe⁰/PDS, respectively. Fe⁰, defective sites, C=O and pyridinic N were identified as the active sites promoting PDS activation to produce ·OH, SO₄·^-, ·O₂^– and ¹O₂ for synergistic oxidative elimination of MNZ. The formation rate of ·OH was calculated to be 4.62 times higher than that of the SO₄·^- by multivariate nonlinear fitting, and the ·OH contributes up to 63.5 %. Fe⁰@ZIF-N-C-600/PDS system possesses excellent tolerance and selectivity to complicated water bodies, and the effective continuous degradation was achieved in a self-made catalytic reactor. Moreover, DFT calculations and LC-MS analysis were applied to deduce possible pathways for MNZ degradation. This work offers an effective strategy to regulate the morphology of sintered carbon materials and improve the application of metal nanoparticles in advanced oxidation processes.