Sonochemical degradation of CCl4 and its effects on the degradation of organic pollutants in water: A review.

•OH radicals formed from the sonolysis of water can be used for the degradation of various hazardous organic compounds. This water treatment technique is actively studied as an •OH-based advanced oxidation process. However, the sonochemical formation of •OH radicals requires a large amount of electrical energy so that this technique is facing the challenge of high costs. In this review, we focused on the sonlysis of CCl4, where the degradation rate of CCl4 is one to two orders of magnitude higher than that of water. Based on the comparison of the characteristics of CCl4 with related organic compounds, CCl4 was suggested to undergo the fastest sonochemical degradation among organic compounds. Weissler et al. proposed that •Cl radicals formed from the sonolysis of CCl4 in water act as effective oxidizing agents for I-. This reaction is known as the Weissler reaction and has been used to evaluate chemical effects of ultrasonic cavitation. In addition, •Cl radicals are effective in accelerating the degradation rate of various hazardous organic compounds such as dyes, aromatics, antibiotics, etc. in water. Since CCl4 can also undergo reductive degradation, the reduction of CCl4 is of interest for environmental remediation. To review the knowledge on the sonolysis of CCl4, a rapidly degradable organic compound, would be meaningful for the future development of a high efficient ultrasonic water treatment technique.