APPLICATION OF ULTRASONIC IRRADIATION FOR THE DEGRADATION OF CHEMICALCONTAMINANTS IN WATER

The sonochemical degradation of a variety of chemical contaminants in aqueous solution has been investigated. Substrates such as chlorinated hydrocarbons, pesticides, phenols, explosives such as TNT, and esters are transformed into short-chain organic acids, CO2, and inorganic io ns as the final products. Time scales of treatment in simple batch rea ctors over the frequency range of 20 to 500 kHz are reported to range from minutes to hours for complete degradation. Ultrasonic irradiation appears to be an effective method for the rapid destruction of organi c contaminants in water because of localized high concentrations of ox idizing species such as hydroxyl radical and hydrogen peroxide in solu tion, high localized temperatures and pressures, and the formation of transient supercritical water. The degradation of chemical compounds b y acoustic cavitation is shown to involve three distinct pathways: 1) oxidation by hydroxyl radicals, 2) pyrolytic decomposition and 3) supe rcritical water oxidation. Detailed reaction mechanisms for the degrad ation of p-nitrophenol, carbon tetrachloride, parathion, p-nitrophenyl acetate and trinitrotoluene are presented.