Photo-oxidation of o-chloroaniline in the presence of TiO2 and IO3−: A study of photo-intermediates and successive IO3− dose

The photocatalytic oxidation in TiO2 and IO3− has been found to be an effective process to degrade the aromatic organic pollutant, o-chloroaniline (o-ClA). The degradation of o-ClA is mainly attributed to the 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-ClA degradation, but the degree of degradation depends on the time interval between each dose. It is observed that the disappearance of o-ClA 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 IO3−. With the inclusion of the photo-products, the degradation pathway of o-ClA has been proposed accordingly.