Sonolysis of surfactants in aqueous solutions: an accumulation of solute in the interfacial region of the cavitation bubbles

Abstract

The sonolysis of surfactants (such as sodium dodecylbenzenesulfonate (DBS), sodium dodecylsulfate (SDS), and polyethylene glycol monostearate), sodium 4-toluenesulfonate (STS), and 1-hexanol in aqueous solutions was investigated under an argon atmosphere with ultrasound of 200 kHz in order to compare the scavenging efficiency of the hydroxyl radical and the accumulation in the gas-liquid interfacial region of the cavitation bubbles. The degradation rate of the solute follows the order 1-hexanol > DBS and SDS > STS. The scavenging efficiency of the hydroxyl radical by non-volatile surfactants was much greater than that of the non-volatile and hydrophilic solute (e.g., STS). The surfactant was accumulated in a relatively high ratio in the interfacial region. The degradation of surfactants occurred by reaction with the hydroxyl radical and also by pyrolysis at high temperature. On the other hand, STS, due to its non-volatile and hydrophilic properties, was principally present in the bulk solution and the degradation by pyrolysis was not observed at the investigated concentration ranges.

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

“…When the bubble temperature is in the range of 4000 -6500 K, H 2 O 2 is the dominant product, whilst above ~6500K it is the O atom [101]. There are three reaction sites in sonochemical experiments; the gas phase region inside the bubble (pyrolysis reactions), the bubble surface (reactions occurring in pressure temperature gradients) and the bulk solution [100,[102][103][104]. Mason suggested a fourth site originating from a two site model that considers a liquid phase surrounding the hot bubble, that can either be a heated shell of liquid around the collapsing bubble or liquid droplets injected into the bubble by instabilities at the surface [100].…”

Sonochemical degradation of azo dyes in aqueous solution: a new heterogeneous kinetics model taking into account the local concentration of OH radicals and azo dyes

“…That is, there should be at least three of the following heterogeneities; (1) gas/liquid heterogeneity attributed to the cavitation bubbles formed in a liquid system, (2) heterogeneity attributed to the concentration of OH radicals, which locally exist at the interface region of the cavitation bubbles [15,16], and (3) heterogeneity attributed to the different concentration of organic solutes between the bulk solution and the interface region of the cavitation bubbles, which is affected by the degree of net accumulation (or adsorption) of the organic solutes toward the interface region of the cavitation bubbles [17,18].…”

Mineralisation of Surfactants Using Ultrasound and the Advanced Fenton Process

“…Several authors report surfactant remediation experiments using several oxidising agents (MendezDiaz et al 2009) and AOPs such as photocatalysis supported by TiO 2 (Hidaka et al 1995;Ohtaki et al 2000;Zhang et al 2003;Vohra and Tanaka 2003;Zhang et al 2004;Horvath et al 2005), ultrasound (US; Manousaki et al 2004;Yim et al 2002;Yang et al 2005) and Fenton or Fenton-like processes (Lin et al 1999;Bandala et al 2008;Amat et al 2004), and most of these achieve good remediation in short reaction times (a few hours instead of days as happens using conventional wastewater treatment with activated sludge). The classical Fenton oxidation process (Fenton 1894;Haber and Weiss 1934;Barb et al 1949Barb et al , 1951a utilises the reaction of aqueous iron (II) salt with hydrogen peroxide to generate hydroxyl radicals, which are then used to carry out chemical oxidation or to degrade recalcitrant organic pollutants in wastewater treatment Eq.…”