In-situ reduction-passivation synthesis of magnetic octahedron accumulated by Fe@Fe3O4-C core@complex-shell for the activation of persulfate

The iron-based heterogeneous catalysts, especially the zero valent iron (ZVI) is an eco-friendly and cost-effective activator for persulfate (PS) excitation. However, the oxidation of surface ZVI reduces its service lifetime. Herein, a series of magnetic octahedrons accumulated by [email protected]3O4-C [email protected] were constructed by in-situ reduction-passivation of the MIL-101(Fe). The catalysts exhibited good activity, high stability and magnetic recyclability. The optimized [email protected]3O4-C-60 with largest proportion of active iron achieved a 100 % conversion of Rhodamine B (RhB) within 4 min and high mineralization efficiency of 667.34 % in 30 min. Moreover, [email protected]3O4-C-60 maintained its activity even after 3 times of cycling test and could be easily magnetic separation. The rate constant was 1.23 min−1 for [email protected]3O4-C-60+PS in first 3 min, which was 1.6, 5 and 323 times of Fe0+PS, FeSO4+PS and Fe3O4+PS. Fe0 and Fe2+ were identified as active sites for SO4•- generating, while the carbon shell was responsible for the high stability. The synergistic effect between Fe0 core and Fe3O4-C complex shell realized the sustained regeneration of active surface Fe2+ and inhibition leaching of Fe.