Oxidants emergence under dual-frequency sonication within single acoustic bubble: effects of frequency combinations

Document Type: Research Article

Authors

1 Second cycle department, Higher School of Industrial Technologies, Annaba

2 Department of Process Engineering, Faculty of Engineering, University of Annaba, P.O. Box 12, 23000 Annaba, Algeria

Abstract

The sonochemical activity of an oxygen bubble formed in an aqueous medium and oscillating under a dual-frequency excitation is studied in this paper. Several couples of frequencies are formed amongst 35, 140, 300 and 515 kHz, with a maximum acoustic amplitude of 1.5 atm. The molar yields of the emerging oxidants are analyzed in accordance with the combined frequencies and compared to the cases of mono-frequency excitations of similar maximum amplitude, i.e., 1.5 atm. Qualitatively, passing from a mono to a dual-frequency excitation demonstrated to be with no effect on the predominant species which remain 〖HO〗^•, 〖〖HO〗_2〗^•, O and O_3. However, the results exhibited a very selective quantitative evolution depending on the combined frequencies. Some couples proved to induce a negative effect and reduce the production at the single bubble level, particularly with basic frequencies of 140 and 300 kHz, while some others demonstrated a noticeable enhancement such as the couples (35, 140 kHz) and (515, 35 kHz), as compared to mono-frequency fields.

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