Sonication of aqueous solutions of chlorobenzene

Sonication at two frequencies (20 and 900 kHz) was carried out on dilute (220 ppm) aqueous solutions of chlorobenzene. The formation of chloride ions was followed using ion chromatography. The solutions became more colored with time; the absorbance maximum was around 270 nm. Some of the compounds remaining in the solution could be identified; they were chlorinated phenols, chloronaphthalene, mono and dichlorobiphenyls, etc. At the same acoustic power, the rate of chloride formation with 20 kHz ultrasound was greater when a probe with a larger tip area was used, but significantly less than the rate with 900 kHz. The use of ultrasound for conversion of chlorine in organic compounds in water to chloride can thus be performed more efficiently using a higher frequency and with a lower intensity (power per area). There is, however, a possibility that the toxicity of the aqueous solution is increased by such treatment.