Synthesis, characterization and photocatalytic activity study of synthetic zeolite supported- ZnO-Fe2O3-MnO2 nanocomposite for methylene blue degradation

Abstract

Trabajo presentado en el 30th Annual Congress of the Chemical Society of Ethiopia, celebrado en Mekelle (Etiopía) del 28 de febrero al 2 de marzo de 2014.ZnO-FeZ03-MnOZ nanocomposites were synthesized via one step impregnation of MnOz powder with an aqueous solution of Zn{lI) and Fe(lIl) nitrate salts. Zeolite supportedZnO-FezOrMnOz composite was prepared by solid state reaction. The morphology, structure and elemental analysis of as-synthesized nanocomposites were studied by using XRD, SEM/EDX, UV-visible and AAS spectrophotometry. Photocatalytic degradation activities of as-synthesized nanocomposites under visible light irradiation have been evaluated in the reduction of aqueous methylene blue (MB) dye solution and real sewage samples collected from Dire Dawa Textile Industry. Zeolite supported-ZnO-Fez03-MnOz photocatalyst exhibited effective degradation efficiency of methylene blue (MB) dye and real sewage sample to the extent of approximately 93% and 63%, respectively. The photocatalvtic efficiency of the naked ZnO-Fez03-MnOz nanocomposite was found to be 77% under visible light irradiation, significantly lower than the supported mixed oxide indicating that zeolite plays a role in the performance of the composite. When the visible light hit the VB of combined semiconductor, CB electrons can be ejected from the low band gap semiconductor (FeZ03) to the high band gap semiconductor (ZnO) and on the contrary, hole transfer can take place from the VB of high band gap semiconductors (ZnO) to the VB of small band gap semiconductor (FeZ03)' Additionally the presence of electron acceptor Mn(IV) could scavenge the excited electrons and altogether prevent the recombination of electron-hole pairs. While these constituents along with the zeolite framework, serve as an electron acceptor and delay the rate of photogene rated electron-hole pairs recombination as well as to increase the surface area that could give more active surface sites to absorb water molecules and to form active hydroxyl radical by trapping the photo-generated holes. Photocatalytic degradation of methylene blue dye (MB) follows pseudo first order kinetics for all as-synthesized nanocomposites.Peer Reviewe