Sonochemical degradation of chlorobenzene in the presence of additives.

The present work deals with establishing the pathway for the selection of additives for intensification of the sonolytic degradation of chlorobenzene. The degradation of chlorobenzene has been investigated in the presence of different additives such as CuO, TiO2, nano-TiO2 and NaCl. The reaction has been monitored in terms of the concentration of the parent pollutant as well as the extent of mineralization. The first-order kinetic rate constant for the removal of chlorobenzene has been evaluated for different loadings of additives. It has been observed that the extent of degradation and mineralization was maximum in the presence of nano-TiO2 and minimum in the presence of CuO. A three-step mechanism has been developed for the degradation of chlorobenzene based on the identification of intermediates. The removal of chloride from the benzene ring due to pyrolysis was the dominant mechanism with minimal contribution from the attack of hydroxyl radical present in the bulk of solution. The oxidation products also react subsequently with the hydroxyl radicals resulting in mineralization. The rate of mineralization has been quantified in terms of total organic carbon removal. The observed trends for the mineralization confirm that the extent of mineralization depends on the ease of generation of hydroxyl radicals.