The photocatalytic degradation (PCD) of 4-nitroaniline was studied in the presence of TiO2 suspensions in a batch and continuous annular reactor. Artificial and solar radiation was employed as sources of UV radiation. The effect of catalyst loading, pH, presence of anions and initial concentration on the rate of photocatalytic degradation was investigated. p-Aminophenol, p-benzoquinone and hydroquinone were identified as the intermediates during the degradation process. A kinetic expression for PCD of 4-NA is provided. (c) 2005 Elsevier B.V. All rights reserved.