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

摘要

A manganese-substituted goethite (alpha-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 alpha-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 alpha-Fe0.9Mn0.1OOH than on the surface of alpha-FeOOH. The degradation mechanism of iohexol mainly includes H-abstraction, amide hydrolysis, oxidation of amines and (OH)-O-center dot substitution. According to the results of the in situ reaction of ozone with the surface of alpha-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.