Application of power ultrasound for azo dye degradation

Abstract

Power ultrasound of 850 kHz at 60, 90 and 120 W was used for the degradation of industrial azo dyes Acid Orange 5 and 52, Direct Blue 71, Reactive Black 5 and Reactive Orange 16 and 107. The results show that power ultrasound is able to mineralize azo dyes to non-toxic end products, which was confirmed by respiratory inhibition test of Pseudomonas putida. All investigated dyes have been decolorized and degraded within 3-15 h at 90 W and within 1-4 h at 120 W, respectively. Mass spectrometric investigations show, that hydroxyl radicals attack azo dyes by simultaneous azo bond scission, oxidation of nitrogen atoms and hydroxylation of aromatic ring structures. A volumetric scale-up showed a correlation between the energy input and the absolute amount of degraded dye. Up to an energy input of about 90 W no enzymatic deactivation of laccase was observed which might be helpful for a simultaneous action of sonochemical and enzymatic treatments.

Sono-oxidation of soils: degradation of naphthalene by sono-Fenton-like process

“…4 and 5) would be affected by the collapse temperature and pressure of the bubble and the bubble lifetime (Adewuyi 2005). Rehorek and coworkers also reported that the rate of OH• radical formation was only 14.9, 4, and 0.1 μM min -1 at 120, 90, and 60 W, respectively, of applied ultrasound irradiation under air atmosphere (Rehorek et al 2004), which was apparently too little for the efficient oxidation of target contaminants.…”

Ultrasonic degradation of Rhodamine B in aqueous solution: Influence of operational parameters

“…Sonochemical degradation methods are relatively new and involve exposing aqueous solutions containing the organic pollutant to ultrasound and the effect of different operational * Corresponding author. parameters on degradation could be found [12][13][14][15][16]. Sonochemical decomposition of organic compounds is resulted from the formation, growth and collapse of high-energy cavitation bubbles, which releasing large quantities of energy over a small location [17].…”

Degradation of AR 97 aqueous solution by combination of ultrasound and Fenton reagent

“…An explanation to this behavior is that as the initial concentration of AR 97 increases, higher concentrations of intermediates form. Assuming most of the reactions take place at the bubble-liquid interface, with increasing initial concentration of dye and correspondingly intermediates, the dye degradation has been limited by the available interfacial area [5,[12][13][14][15][16]. …”

“…Rehorek et al [5] reported the application of ultrasound for azo dye degradation. Some azo dyes in aqueous solution, such as Acid Orange 5, Acid Orange 52, Direct Blue 71, Reactive Black 5, Reactive Orange 16, and Reactive Orange 107, have been degraded to nontoxic end products under ultrasound.…”

“…However, under anaerobic conditions, azo dyes are cleaved by microorganisms to form potentially carcinogenic aromatic amines or reduced to more hazardous intermediates [10]. To the best of our knowledge, there is no report on the removal of AR 97 by the combination of Fenton reagent and ultrasound.…”