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Published November 1995 | public
Journal Article

Sonochemical degradation of p-nitrophenol in a parallel-plate near-field acoustical processor


The sonochemical degradation of p-nitrophenol (p-NP) in a near-field acoustical processor (NAP) is investigated. The pseudo-first-order rate constant, k, for p N P degradation increases proportionally from 1.00 x to 7.94 x 10^(-4) s^(-l) with increasing power to volume ratio (i.e., power density) over the range of 0.98-7.27 W/cm^3. An increase in the power-to-area ratio (i.e., sound intensity) results in an increase in k up to a maximum value of 8.60 x 10^(-4) s^(-1) a sound intensity of 1.2 W/cm^2. A mathematical model for a continuous-flow loop reactor configuration is required in order to extract k from the experimentally observed rate constant, k_(obs), which is a function of the relative volumes of reactor and reservoir. The nature of the cavitating gas (Ar, O_2) is found to influence the overall degradation rate and the resulting product distribution. The rate constant for p-NP degradation in the presence of pure O_2, k_(O_2), = 5.19 x 10^(-14) s^(-1), is lower than in the presence of pure Ar, k_(Ar) = 7.94 x 10^(-4) s^(-1). A 4:l (v/v) Ar/O_2 mixture yields the highest degradation rate, k_(Ar/O_2) = 1.20 x 10^(-3) s^(-1). Results of these experiments demonstrate the potential application of large-scale, high-power ultrasound to the remediation of hazardous compounds present at low concentrations. The NAP is a parallel-plate reactor that allows for a lower sound intensity but a higher acoustical power per unit volume than conventional probe-type reactors.

Additional Information

© 1995 American Chemical Society. Received far review March 1, 1995. Revised manuscript received June 8, 1995. Accepted July 6, 1995. Publication Date: November 1995. The authors wish to thank Sayuri Desai for preliminary experiments and the power input measurements and Douglas A. Varela for his assistance with solving the partial differential equation. Financial support from the Advanced Research Projects Agency (ARPA Grant NAV SHFMN 0001492J1901), the Office of Naval Research (ONR), and the Electric Power Institute (EPRI Grant RP 8003-37) is gratefully acknowledged.

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