Photocatalytic degradation of phenol in water was examined using Pr-doped TiO2 nanoparticles. These photocatalysts were synthesized by an acid-peptized sol-gel method from titanium tetra-isopropoxide with different concentrations of Pr(III) dopant and calcination temperatures. Several tools such as XRD, BET surface area, SEM, and EDX, were used to evaluate particle structure, size distribution, and composition. The optical absorption properties of the prepared particles were also measured. Photocatalytic activity of the particles was studied in a batch reactor containing phenol solution with 400 W UV irradiation. Parameters affecting photocatalytic process such as the catalyst crystallinity, light absorption efficiency, the dosage of catalyst, dopant and phenol concentrations were investigated. The Pr-doped TiO2 showed high activity for photocatalytic degradation of phenol. The presence of Pr ions in the TiO2 particles would cause a significant absorption shift towards the visible region. The degradation process was optimized using 1 g/L Pr-doped TiO2 with a Pr(III) concentration of 0.072 mol % after 2 h irradiation. It was shown that photodegradation followed a pseudo-first-order kinetics and the rate constant changed with phenol concentration. (C) 2007 Elsevier B.V. All rights reserved.