Intensification of sonochemical degradation of chlorobenzene using additives

Abstract

This study evaluates the application of different additives viz. H₂O₂, Fe (II), Fe metal powder, sodium bicarbonate, and t-butanol, for intensifying the sonochemical degradation of chlorobenzene. It has been observed that the degradation of chlorobenzene is controlled by the pyrolysis mechanism, and dominant zone of degradation lies around the region of cavitating bubble. Hydroxyl radicals formed during cavitation were also useful for enhancing the mineralization of intermediates formed during degradation. It has been established that the use of Fe powder, sodium bicarbonate, and t-butanol, which leads to enhancement in the cavitational effects, gives better degradation of chlorobenzene among the different additives investigated in the study, and maximum degradation is observed in the presence of Fe powder. The presence of t-butanol, a conventional radical scavenger, leading to a marginal increase in the extent of degradation confirmed that degradation mechanism is dominated by the pyrolysis effect of cavitation. The higher Henry constant pollutant was easily degraded due to pyrolysis mechanism. A three-step degradation mechanism scheme has been established on the basis of the intermediate products formed in the process such as phenols, chlorophenols, and benzene. Rate of mineralization was also quantified in terms of total organic carbon removal, and it was established that the trends in mineralization are not necessarily the same as parent compound removal confirming that both radical and pyrolysis mechanism are important for overall mineralization.

Keywords:

• Chlorobenzene
• Additives
• Sonochemical degradation
• Process intensification
• Pyrolysis