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Ultrason Sonochem. 2017 Jan;34:580-587. doi: 10.1016/j.ultsonch.2016.06.027. Epub 2016 Jun 23.

Persulfate-enhanced sonochemical degradation of naphthol blue black in water: Evidence of sulfate radical formation.

Author information

1
Laboratory of Environmental Engineering, Department of Process Engineering, Faculty of Engineering, Badji Mokhtar - Annaba University, P.O. Box 12, 23000 Annaba, Algeria.
2
Laboratory of Environmental Process Engineering, Department of Chemical Engineering, Faculty of Process Engineering, University of Constantine 3, 25000 Constantine, Algeria. Electronic address: s.merouani@yahoo.fr.
3
Laboratoire Rhéologie et Procédés, Université Joseph Fourier, 38041 Grenoble cedex 9, France.

Abstract

This work explores the effect of persulfate (PS) on the sonochemical degradation of organic pollutants taking naphthol blue black (NBB), an anionic diazo dye, as a substrate model. The sonolytic experiments were conducted in the absence and presence of PS under various experimental conditions including acoustic power (10-80W), frequency (20 and 585kHz) and saturating gas (argon, air and nitrogen). Experimental results showed that PS decomposition into sulfate radical (SO4-) takes place by sonolysis and increasing PS concentration up to 1g/L would result in an increase in the NBB degradation rate. It was found that the PS-enhanced effect was strongly operating parameters dependent. The positive effect of PS decreased with increasing power and the best enhancing effect was obtained for the lowest acoustic power. Correspondingly, the PS-enhanced effect was more remarkable at low frequency (20kHz) than that observed at high frequency ultrasound (585kHz). Nitrogen saturating gas gave the best enhanced effect of PS than argon and air atmospheres. Theoretical (computer simulation of bubble collapse) and experimental measurements of the yields of free radical generation under the different experimental conditions have been made for interpreting the obtained effects of PS on the sonochemical degradation of the dye pollutant. The experimental findings were attributed to the fact that radical-radical recombination reactions occur at faster rate than the radical-organic reaction when the concentration of free radicals is too high (at higher sonochemical conditions).

KEYWORDS:

()OH radical; Computer simulation; Naphthol blue black (NBB); Persulfate (PS); SO(4)(−) radical; Sonochemical degradation

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