PHOTOCATALYZED DEGRADATION OF PHENOL, 2,4-DICHLOROPHENOL, PHENOXYACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID OVER SUPPORTED TIO2 IN A FLOW SYSTEM

The photodegradation of phenol, 2,4-dichlorophenol, phenoxyacetic acid and 2,4-dichlorophenoxyacetic acid using TiO2 as photocatalyst is inv estigated. The photodegradations of these compounds have been conducte d in a continuous mode by means of a how system, in which TiO2 remains fixed onto glass pearls. The use of this system gives high yields of degradation for the chemicals tested, except for 2,4-dichlorophenol fo r which a slow dechlorination process is observed. The rate of photode gradation depends on the pH of the solution, the point of zero charge of TiO2 and the pK(a) of the chemicals being the key parameters. The m ain aromatic intermediates detected have been hydroquinone, paraquinon e and hydrohydroquinone during phenol degradation; phenol and hydroqui none during phenoxyacetic acid degradation; chlorohydroquinone and chl orophenol during 2,4-dichlorophenol degradation; and dichlorophenol du ring 2,4-dichlorophenoxyacetic acid degradation. Finally, some long te rm irradiations with phenol as model compound have been performed, sho wing high degrees of photodegradation. It has been observed that only a periodic evacuation of the effluent out of the reactor is needed to sustain high percentages of photodegradation.