USE OF SONOCHEMISTRY IN MONITORING CHLORINATED HYDROCARBONS IN WATER

The U.S. Environmental Protection Agency (EPA) has been examining the potential of combining sonication with available measurement technologies for monitoring chlorinated hydrocarbons in water. The chloride ion (Cl-) concentration, conductivity, and pH were measured before and after sonication. Cl- could be detected in aqueous solutions of 3-80 ppm carbon tetrachloride (CCl4), chloroform (CHCl3), and trichloroethylene (TCE) after 1 min of sonication. The increases of Cl- were accompanied by increases in conductivity and decreases in pH. The conductivity changes were higher than expected based on measured Cl-. Ion chromatography of solutions before and after sonication showed that formate ion (HCOO-) was also formed. Other ions may have formed as well, but the concentrations were too low to allow their detection relative to HCOO- and Cl-. The results achieved serve as proof-of-principle and form a base of information which can be used to develop ultrasound monitoring methods for these compounds. Aromatic and polyaromatic chloro compounds represented by chlorobenzene (Ph-Cl) and polychlorobiphenyls (PCBs), respectively, did not release Cl- upon sonication as readily as did CCl4, CHCl3, and TCE. The PCB solutions gave no measurable changes in either Cl-, conductivity, or pH under the conditions of the experiments described.