Rosal et al. [82,83] studied the degradation of clofibric acid by
means of catalytic ozonation on titania. It was suggested that the
adsorption and subsequent reaction of organics on catalyst sites are
responsible for the enhancement of ozonation rate observed in catalytic
runs. The enhancement was however suggested not to result
from a greater production of surface hydroxyl radicals from ozone.
Both facts suggest that even if the catalytic surface plays a signifi-
cant role in the production of hydroxyl radicals, the interaction of
surface sites and organics is probably limited.
TiO2 deposited on activated carbon was also found to be effective
in the removal of methylene blue in the catalytic ozonation
process. Higher efficiency of TiO2/AC/O3 process was observed
when compared to AC/O3 and was hypothesised as being due to the
suspected acceleration of the formation of OH• radicals and adsorption
of methylene blue on AC [84]. Unfortunately, no adsorption
capacity of the catalyst was assessed and therefore the resulting
high efficiency of the process might be simply a sum of two separate
processes occurring: ozonation and adsorption.