Carbon tetrachloride (CCl₄) is a type of volatile organic compound (VOC) that was once widely used as a refrigerant and cleaning agent, but is now strictly regulated due to its toxic properties. However, its environmental impact remains a concern and recent reports indicate that CCl₄ emissions have been detected in some countries. Therefore, the development of CCl₄ decomposition technology is critical, and holds promise for its application in decomposing and neutralizing various VOCs.
In search of a probable solution, Professor Kenji Okitsu and graduate student Aerfate Abulikemu from Osaka Metropolitan University's Graduate School of Sustainable System Sciences attempted ultrasonic decomposition and safe treatment of CCl4. Methanol, ethanol, 1-propanol, and ethylene glycol were used as solvents in pretreatment solutions and four CCl4 aqueous solutions consisting of argon-saturated water were irradiated.
It has been theorized that adding alcohol during ultrasonic decomposition slows the decomposition rate of the target harmful organic compounds. However, in this study, the researchers demonstrated that pre-dissolving CCl4 in alcohol when preparing aqueous samples containing CCl4 enhances the decomposition rate of CCl4. Further, it was found that high hydrophobic alcohols which are accumulated at the surface of ultrasonic bubbles affected the increase in CCl4 decomposition.
"The detailed decomposition mechanism of CCl4 remains unclear. In order to further enhance the decomposition rate, it is necessary to clarify the causal relationship between the decomposition rate and bubble characteristics," stated Professor Okitsu. "We believe that improving the decomposition rate of CCl4 will contribute to the development of practical ultrasonic water purification technology."
The study was published in Ultrasonics Sonochemistry.
