Effect of frequency on the sonolytic degradation of carbon tetrachloride

The sonolytic degradation of carbon tetrachloride (CCl₄) was examined under different frequency conditions (35, 72, 100 and 170 kHz) in the presence and absence of argon purging and radical scavenger. Also, the extent of mineralization during sonolysis of CCl₄ was measured using chloride production. At 170 kHz, the degradation CCl₄ and chloride production was only 25 and 20% within 60 min. However, the removal efficiency of CCl₄ increased more than 90% at the same time at lower frequencies (35, 72 and 100 kHz), and the production of chloride increased up to 67, 70 and 61% at 35, 72 and 100 kHz, respectively. The removal of CCl₄ at 170 kHz was enhanced by argon purging during sonication up to 87%, however, the degradation efficiency at lower frequencies decreased by argon purging. The addition of methanol, as a radical scavenger during sonolysis, also reduced the removal especially at higher frequency (170 kHz), indicating that the oxidation by OH radical is the main factor in the sonolysis for the removal of CCl₄ at higher frequency, and pyrolysis is the main effect factor for degradation of CCl₄ at lower frequency in the sonication. Finally, the mineralization extent during sonolysis was estimated using the mass balance of chloride production.