Carbon tetrachloride decomposition setup: A glass container with CCl₄ aqueous solution sits in an aquarium atop an ultrasonic transducer.
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.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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