ULTRASONIC IRRADIATION OF PARA-NITROPHENOL IN AQUEOUS-SOLUTION

The kinetics and mechanism of the sonochemical reactions of p-nitrophenol have been investigated in oxygenated aqueous solutions. In the presence of ultrasound (20 kHz, 84 W) p-nitrophenol was degraded primarily by denitration to yield NO2-, NO3-, benzoquinone, hydroquinone, 4-nitrocatechol, formate, and oxalate. These reaction products and the kinetic observations are consistent with a model involving high-temperature reactions of p-nitrophenol in the interfacial region of cavitation bubbles. The main reaction pathway appears to be carbon-nitrogen bond cleavage. Reaction with hydroxyl radical provides a secondary reaction channel. The average effective temperature of the interfacial region surrounding the cavitation bubbles was estimated to be T congruent-to 800 K.