Fig. 1: Catalytic performance of iron oxyhalides in heterogenous Fenton systems and key factor in material deactivation.

a XRD patterns of iron oxyhalides. b SEM, SEM-EDS mapping, TEM, HAADF-TEM images, and inverse Fourier transformation of the selected region (6.25² nm²) in TEM for the FeOF. c Comparison of H₂O₂ activation efficiency for different catalysts from EPR ([catalyst] = 1 g L^–1, [H₂O₂] = 50 mM, [DMPO] = 200 mM, pH = 6.2 ± 0.1). d DMPO–OH signal generated by different catalysts ([catalyst] = 1 g L^–1, [H₂O₂] = 50 mM, [DMPO] = 200 mM, pH = 6.2 ± 0.1). e Removal efficiency for representative neonicotinoid ([catalyst] = 1 g L^–1, [H₂O₂] = 10 mM, [THI] = 10 μM, pH = 6.2 ± 0.1, reaction time = 60 min, standard deviations (n = 3) were presented). f F 1 s XPS spectra of FeOF before and after H₂O₂ activation. g H₂O₂ activation efficiency of spent FeOF after reacting with H₂O₂ for a certain period ([catalyst] = 1 g L^–1, [H₂O₂] = 10 mM, contact time = 1, 2, 3 or 4 h, [DMPO] = 200 mM, pH = 6.2 ± 0.1, reaction time = 1 min). h Element leaching over time in suspension systems ([catalyst] = 1 g L^–1, [H₂O₂] = 10 mM, pH = 6.2 ± 0.1).