Comparison between photocatalysis with TiO2 and ultrasound in the degradation of aqueous solutions of 1,2-dichlorobenzene

Chlorinated aromatic compounds form an important class of organic pollutants of industrial wastewater. Chlorobenzenes and other halo-aromatics, in fact, are widely employed as pesticides and raw materials for pesticide manufacture and have a variety of uses in chemical synthesis and other applications. Because of their acute toxicity, suspected endocrine, immunoand neuro-toxicity and bioaccumulation capability, they are of great health and environmental concern, for their potentiality to contaminate surface and groundwaters and also to be the origin of marine pollution, though typically present at sub-ppm concentration. Most of them, in fact, are highly hydrophobic and possess very low vapour pressure and aqueous solubility. 1,2-dichlorobenzene (1,2-DCB) degradation and mineralization in the aqueous phase was investigated either under direct photolysis or photocatalysis in the presence of commercial or home-made sol-gel synthesized TiO2, using both an internal and an external UV lamp emitting in the 253 nm and 340 - 400 nm wavelength range, respectively. The degradation was also performed under continuous and pulsed sonolysis at 20 kHz. In all cases, the degradation products were followed by HPLC and TOC.