The photocatalytic oxidation in TiO2 and IO3- has been found to be an effective process to degrade the aromatic organic pollutant, o-chloroaniline (o-CIA). The degradation of o-CIA is mainly attributed to the degrees OH attack. Several organic intermediates were identified and the existence of aromatic intermediates would not accumulate in the solution as their degradations were observed. A relatively high level of iodoaniline was solely owing to the use of IO3- which could experience further decay under UV/TiO2 condition. Further investigation on second IO3- dose has indicated a faster o-CIA degradation, but the degree of degradation depends on the time interval between each dose. It is observed that the disappearance of o-CIA and intermediates was the fastest when shorter interval of second IO3- dose (i.e., 5 min). Slower degradation at longer IO3- interval (i.e., 20 min) is possibly due to consumption of radicals from first dose and the inhibition of iodide, the eventual reduction product Of Io(3)(-) With the inclusion of the photo-products, the degradation pathway of o-CIA has been proposed accordingly. (c) 2007 Elsevier B.V. All rights reserved.