Characterization and reactivity of MnO(x) supported on mesoporous zirconia for herbicide 2,4-D mineralization with ozone.

Manganese oxide was supported on mesoporous zirconia (MnO(x)/ MZIW) by wet impregnation, drying, water washing, and calcinations with manganese acetate tetrahydrate as the metal precursor for the first time and was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectra (FTIR), temperature-programmed reduction (TPR), temperature-programmed oxygen desorption (O2-TPD), and UV-vis diffuse reflectance spectra (UV-vis DRS) measurements. The catalyst was found to be highly effective for the mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) aqueous solution with ozone. The characterization studies showed that nonstoichiometrically MnO(x) was highly dispersed on mesoporous zirconia by the strong interaction of the [Mn(H2O)6]2+ complex with surface hydroxyls of the support. Moreover, the multivalence oxidation states of MnO(x) enhanced the electron transfer, causing the higher catalytic reactivity. On the basis of all information obtained under different experimental conditions, MnO(x)/MZIW enhanced the mineralization of 2,4-D by the formation of *OH radicals resulting from the catalytic decomposition of ozone.