Titanium dioxide doped with K+ up to 14.3 at.% was prepared by the sol-gel method and thermal treatment. The prepared samples were characterized and subjected to photodegradation of Everdirect Supra Blue BRL dyes (BRL). A mixture of various titanates, K4-4xTixO2, was recognized for the increase in photocaalytic activity. Doping K' decreases the crystal size of titanium dioxide, decreases the diminishing rate of surface area with calcination temperature, and increases the calcination temperature required to attain the optimum photocatalytic activity of the sample. TiO2 doped with 4.6% K+ and calcined at 973 K shows much higher photoactivity than the other samples when the doping level of K+ and calcination temperature are 0-14.3% and 673-1273 K, respectively. Photocatalytic degradation of BRL follows the Langmuir-Hinshelwood adsorption model, and the adsorption equilibrium constant and rate constant are 0.0072 min(-1) and 3.01 ppm/min, respectively. The reaction takes place much effectively at pH 7.2. (c) 2006 Elsevier B.V. All rights reserved.