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Tungstates of divalent transition metals (M^IIWO₄, 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°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.