Abstract
Tungstates of divalent transition metals ((MWO4)-W-II, M = Co-II, Ni-II, Cu-II, Zn-II) were synthesized by reaction of transition metal nitrates with sodium tungstate. The precipitates were then calcined at 500 degrees C. The materials were characterized by means of ICP-AES elemental analysis, UV-Visible spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and surface area analysis. The higher activity for the decolourization of Methylene Blue (MB) and Methyl Orange (MO) of ZnWO4 compared to that of the other investigated tungstates was correlated with its strong tendency of excitons self-trapping. (C) 2010 Elsevier B.V. All rights reserved.