The photocatalytic and photochemical degradations (PCD) of aniline using concentrated solar radiation were studied. The photochemical reaction takes place on the surface of the catalyst material. Therefore, the adsorption behavior of aniline on the catalyst was also studied. The rates of aniline degradation in the case of the photocatalytic process were compared with the photochemical method. The effects of the presence of anions and cations, which are commonly present in industrial wastewaters, are reported. A plausible explanation for the anomalous behavior of HCO3- and CO32- is given. The effect of pH on the PC D of aniline was also studied. (C) 2003 Society of Chemical Industry.