On the other hand, appropriate hydrophobic compounds, such as surfactant, and
potassium iodide may be used for probing the interfacial region. These compounds,
which are highly reactive toward
Á OH, have tendency to accumulate at the bubblesolution interface and create a strong completion if the bubble-solution interface is
the effective zone for degradation. Finally, more hydrophilic compounds such as
sucrose, glucose, and humic acids, i.e., of high reactivity with
Á OH, may be used for
appreciating the contribution of bulk solution in the degradation of dyes.
Table 5.3 regroups the results of some studies that have used radical probe
technique for the identification of the reaction zone and the degradation mechanism
of some dyes. Overall, this method indicated that the sonochemical degradation of
dyes mostly occurred at the bubble-solution interface via hydroxyl radical attack,
although some radical reactions may also take place in the solution bulk.
5.5.2 Data Fitting Using Mathematical Interfacial Models
Recent progresses in sonochemistry showed that the sonolytic degradation of nonvolatile compounds can be modeled by a heterogeneous kinetics models similar to
that of Langmuir–Hinshelwood in photocatalysis (Okitsu et al. 2005). The first
model, i.e., based on Eq. 5.3, assumes the adsorption–desorption equilibrium of
the pollutant molecules at the bubble-solution interface, i.e., this region is the
probable reaction zone for this model. Serpone et al. (1994) have proposed another
model, i.e., based on Eq. 5.4, governing the degradation rates in both the interfacial
region and the bulk of the solution:
r 0 ¼
kKC 0
1 þ KC 0
ð5:3Þ
r 0 ¼ K b þ
kKC 0
1 þ KC 0
ð5:4Þ
In these equations, r 0 is the initial degradation rate, K b is a constant representing the
rate of degradation in the bulk liquid, K is the equilibrium constant, k is the pseudorate constant, and C 0 is the initial pollutant concentration.
Equations (5.3) and (5.4) perfectly fitted the degradation kinetics of various dyes
under different experimental conditions, as can be consulted in refs. (Merouani et al.
2010c; Moumeni et al. 2012; Ferkous et al. 2015b; Taamallah et al. 2016; Boutamine
et al. 2017; Hamdaoui and Merouani 2017b; Merouani and Hamdaoui 2017). The
conclusion from all these studies was that the sonochemical degradation of dyes is
predominately an interfacial event occurring via reaction with
Á
OH radicals.
5 Sonochemical Treatment of Textile Wastewater
167
potassium iodide may be used for probing the interfacial region. These compounds,
which are highly reactive toward
Á OH, have tendency to accumulate at the bubblesolution interface and create a strong completion if the bubble-solution interface is
the effective zone for degradation. Finally, more hydrophilic compounds such as
sucrose, glucose, and humic acids, i.e., of high reactivity with
Á OH, may be used for
appreciating the contribution of bulk solution in the degradation of dyes.
Table 5.3 regroups the results of some studies that have used radical probe
technique for the identification of the reaction zone and the degradation mechanism
of some dyes. Overall, this method indicated that the sonochemical degradation of
dyes mostly occurred at the bubble-solution interface via hydroxyl radical attack,
although some radical reactions may also take place in the solution bulk.
5.5.2 Data Fitting Using Mathematical Interfacial Models
Recent progresses in sonochemistry showed that the sonolytic degradation of nonvolatile compounds can be modeled by a heterogeneous kinetics models similar to
that of Langmuir–Hinshelwood in photocatalysis (Okitsu et al. 2005). The first
model, i.e., based on Eq. 5.3, assumes the adsorption–desorption equilibrium of
the pollutant molecules at the bubble-solution interface, i.e., this region is the
probable reaction zone for this model. Serpone et al. (1994) have proposed another
model, i.e., based on Eq. 5.4, governing the degradation rates in both the interfacial
region and the bulk of the solution:
r 0 ¼
kKC 0
1 þ KC 0
ð5:3Þ
r 0 ¼ K b þ
kKC 0
1 þ KC 0
ð5:4Þ
In these equations, r 0 is the initial degradation rate, K b is a constant representing the
rate of degradation in the bulk liquid, K is the equilibrium constant, k is the pseudorate constant, and C 0 is the initial pollutant concentration.
Equations (5.3) and (5.4) perfectly fitted the degradation kinetics of various dyes
under different experimental conditions, as can be consulted in refs. (Merouani et al.
2010c; Moumeni et al. 2012; Ferkous et al. 2015b; Taamallah et al. 2016; Boutamine
et al. 2017; Hamdaoui and Merouani 2017b; Merouani and Hamdaoui 2017). The
conclusion from all these studies was that the sonochemical degradation of dyes is
predominately an interfacial event occurring via reaction with
Á
OH radicals.
5 Sonochemical Treatment of Textile Wastewater
167