Interface mechanism of catalytic ozonation in an α-Fe0.9Mn0.1OOH aqueous suspension for the removal of iohexol

[Display omitted] •1) α-Fe0.9Mn0.1OOH was synthesized by controlling Mn/Fe molar ratio of 0.1.•2)Mn can substitute Fe in α-FeOOH structure by isomorphous substitution.•3) OH played the key role in O3/ α-Fe0.9Mn0.1OOH catalytic system.•4)Oxygen vacancies on α-Fe0.9Mn0.1OOH serve as active sites for OH generation. A manganese-substituted goethite (α-FeOOH) catalyst was designed on the atomic scale by hydrothermal coprecipitation for use in the catalytic ozonation process. The results showed that manganese was successfully incorporated into the structure of α-FeOOH. Iohexol, a typical iodinated X-ray contrast media, was selected as the model compound. The removal and mineralization of iohexol in the catalytic ozonation system were significantly increased compared with those of the sole ozonation system. The rate constant of ozone decomposition in the catalytic ozonation system was 3.74 times that of the sole ozonation system. The results of the O1s XPS spectrum and the number of surface Lewis acid sites indicated that more oxygen vacancies were exposed on the surface of α-Fe0.9Mn0.1OOH than on the surface of α-FeOOH. The degradation mechanism of iohexol mainly includes H-abstraction, amide hydrolysis, oxidation of amines and OH substitution. According to the results of the in situ reaction of ozone with the surface of α-Fe0.9Mn0.1OOH in heavy water, the oxygen vacancies can serve as reaction sites for H2O and ozone, and catalyze ozone to generate hydroxyl radical on the interface.