Sonochemical degradation of CCl4 in alcohol-water system.

In this study, methanol (MeOH), ethanol (EtOH), 1-propanol (PrOH), and ethylene glycol (EG) were used as alcohol-CCl4 pretreatment solutions for the first time to investigate the effect of alcohol on the sonochemical degradation of CCl4. The results showed that this pretreatment method provided the homogeneous dissolution of CCl4 in aqueous solution in a short preparation time and the enhancement of the sonochemical degradation of CCl4. In addition, the rate of the degradation of CCl4 related to the hydrophobicity of the added alcohol. It was considered that high hydrophobic alcohol molecules accumulated at the interface region of cavitation bubbles contributed to the scavenging of •OH radicals produced by sonolysis of water and to the pyrolysis itself, resulting in the production of a large amount of •H radicals. The formation of •H radical and its secondary products, such as H2 could lead to the reductive degradation of CCl4. In previous studies, the addition of alcohol has been observed only as a negative effect on the sonochemical degradation of organic compounds such as the reduction of bubble temperature, and the quenching of the oxidative degradation by scavenging •OH radicals. However, our results indicated that the positive effects of alcohol on the sonochemical degradation of CCl4 were more significant than the negative effects.