FACILE SYNTHESIS OF VARIOUS MANGANESE OXIDES NANO/MICRO-CRYSTALS BY A LIGNOSULFANATE-MEDIATED HYDROTHERMAL PROCESS: EFFECT OF THE REACTANT CONCENTRATION AND SOLUTION MEDIA

Abstract

Various manganese oxides nano/micro-crystals, including Mn 3 O 4 octahedrons, hierarchical flower-like K -δ- MnO 2 microspheres, multi-branch and strip-shaped γ- MnOOH , have been prepared by a lignosulfanate (LSN)-mediated hydrothermal process. The effect of LSN on the structure and morphology has been thoroughly investigated by X-ray powder diffraction and scanning electron microscopy (SEM). The results indicated that stepwise reduction and Ostwald's ripening occurred simultaneously in this hydrothermal process, and LSN could serve as both reducing agent and growth modifier. The appropriate reducing capacity and selective absorption ability of LSN played an important role for the formation of various manganese oxides nano/micro-crystals. The catalytic performance of the products for the oxidation of o-xylene has been also investigated. The result showed that the MnO 2 crystals prepared with LSN exhibited the highest catalytic activity.