Polychlorinated biphenyls (PCBs) are pollutants of
environmental concern due to their widespread presence
and persistence. The sonolytic destruction of aqueous
polychlorinated biphenyls (PCBs) is reported in this article.
The kinetics and transformation pathways were investigated
at multiple frequencies and with various analytical
tools. The pseudo-first-order rate constants for 2-PCB (4.6
μM), 4-PCB (5.4 μM), and 2,4,5-PCB (7.6 × 10-2 μM)
were 2.1 × 10-3 ± 2.8 × 10 -5 s-1, 1.6 × 10-3 ± 3.4 ×
10-5 s-1, and 2.6 × 10-3 ± 9.4 × 10 -5 s-1, respectively, when
Ar-saturated solutions were sonicated at 20 kHz and an
acoustic intensity of 30.8 W cm-2. Chlorine recovery as
chloride ion was 77%, 79%, and 70% for 2-PCB, 4-PCB, and
2,4,5-PCB under the same conditions. Electron spin
resonance (ESR) experiments demonstrated that phenyl
radical was formed during sonolysis of 2-PCB and 4-PCB.
The formation of biphenyl, which was detected by mass
spectroscopy, also indicates PCB dechlorination during
sonication. Ethyl benzene, diethylbiphenyl, dibutylbiphenyl,
phenol, propylphenol, and di-tert-butyl phenol were also
detected by mass spectroscopy as products of PCB sonication.
The kinetics of 2-PCB composition as well as the role of
aqueous hydroxyl radical were examined at 20, 205, 358, 618,
and 1071 kHz. The ultrasonic frequency significantly
impacted the reaction rate and chloride recovery.
