Monitoring of Sonochemically Released Carbon Dioxide from a Methanol-Water System

Abstract

Ultrasonic waves (USW) are often applied in order to clean the surface of items such as glass ware and also to help dissolving chemicals in water or solvents. It is well known that USW produced in a fluid create a series of compression waves and partial vacuum bubbles are formed and collapse releasing extremely high energy. Here we report that a simple system consisting of only methanol (MeOH) and pure water sonochemically releases CO 2 under agitation by USW. Application of USW caused immediate and continuous release of CO 2 from a MeOH/water mixture. At 23 and 43 kHz, the optimal MeOH concentration for CO 2 production was 3 and 10% (v/v), respectively. Among 4 alcohols examined, MeOH was shown to be most suitable for production of CO 2 , suggesting that longer alkyl chains may significantly reduce participation in the reaction with water under USW. Since ascorbate and two different scavengers of hydroxy radicals (HO˙) lowered the rate of CO 2 production, sonochemical reactivity under USW can be largely attributed to the generation of HO˙. We believe that this phenomenon is noteworthy since MeOH is frequently employed as a solvent for extraction of various compounds from agricultural and biological materials and USW are also often applied for biochemical preparations without having the possibility of the solvents unexpectedly reacting under USW.