Catalytic ozonation of toxic pollutants over magnetic cobalt and manganese co-doped gamma -Fe sub(2)O sub(3)

Magnetic Co- and Co, Mn-doped gamma -Fe sub(2)O sub(3) (FC and FCM) were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in situ attenuated total reflection FTIR (ATR-FTIR) spectroscopy and cyclic voltammetry (CV) analyses. FCM was found to be highly effective for the mineralization of 2,4-dichlorophenoxyacetic acid and its derivatives 2,4-diclorophenol, 2,4,6-trichlorophenol in aqueous solution with ozone. The characterization studies showed that Co and Mn incorporated in gamma -Fe sub(2)O sub(3) existed as multivalence oxidation states, and there were more Lewis acid sites on the surface of FCM. The interaction of ozone with chemisorbed H sub(2)O and surface hydroxyl groups generated from dissociative adsorption of H sub(2)O on Lewis acid sites initiated the production of reactive oxygen species. Moreover, a redox process was observed in the catalytic decomposition of O sub(3) at the water-catalyst interface by CV analysis. The results indicated that the introduction of Mn not only increased the surface Lewis acid sites of FCM to cause more surface hydroxyl groups and chemisorbed water, but also enhanced the interfacial electron transfer, resulting in higher activity.