The behavior of Fe(III) aquacomplexes in TiO2 Suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the Surface of TiO2 retards the conversion of Fe(OH)2+ into oligomers and therefore increases the percentage of Fe(OH)2+ with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO2 system. The influence of iron addition on TiO2 was obtained when the regeneration of [Fe(OH)(2+) remained continuous with irradiation time. In an optimum TiO2 suspension (0.5 g/L with the addition of 0.1 mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO2 at a specified irradiation time. (C) 2008 Elsevier B.V. All rights reserved.