Transition metal tungstates with general formula M2+WO4 (M2+ = Co, Cu, Mn and Ni) were synthesized by the co-precipitation method at 400 C. The prepared powders were characterized by X-ray powder diffraction (XRD), nitrogen adsorption-desorption isotherms and photoelectrochemical measurements. The quasi-Fermi potentials of electrons determined at pH 7 were -0.67, -0.54, -0.21 and -0.18 V (vs. NHE) for CoWO4, CuWO4, MnWO4 and NiWO4, respectively. Photodegradation of methanol and 4-chlorophenol was used to evaluate the photoactivity of the tungstate oxides under visible-light irradiation. The CuWO4 powders showed the best mineralization yields (about 12% for methanol after 25 h, and 23% for 4-chlorophenol after 6 h of irradiation). These results show the feasibility of organic photocatalytic mineralization using CuWO4. (c) 2012 Elsevier Ltd. All rights reserved.