1.9 Physical and Chemical Dosimetry Methods to Quantify …
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is monitored and plotted as a function of time over a short period (2–3 min) without
thermostatic control. The deduced slope T /t is then set into the next equation to
determine the calorimetric power of an incident ultrasonic wave:
Pcal(W ) m.Cp..T
t
(1.3)
where Cp is the isobaric thermal capacity.
In reason of the non-linear behaviour of acoustic waves and subsequent cavitation
bubbles at high amplitude, the bulk temperature might not be spatially homogeneous.
Different measurements location within the same reactor may thus present some
noticeable variations (Al-Juboori et al. 2014).
Another way to measure the acoustic pressure is the radiometric method which
is the measurement of the force exerted by a sound beam on any partially reflecting
surface (Lepoint and Lepoint-Mullié 1998). The spatial distribution of the ultrasonic
pressure intensity can be undertaken by mean of a hydrophone but their high sensitivity together with fragility are limiting parameters for non-linear high intensities
sound fields. The latest development in the physical characterization of the acoustic
cavitation has been recently enabled with the design of cavitometers. These latter
allow to study the cavitation noise spectra to analyse the dynamic process of cavitation by measuring acoustic pressures at particular frequencies but this equipment is
still on lab-stage development (Dezhkunov et al. 2013).
1.9.2 Chemical Methods
Previously described methods do macroscopically measure the acoustic pressure
through the effects produced in the propagation liquid, namely, heating and exerted
forces on a surface. However, they do not allow to determine the radical production consecutive of collapsing bubbles, that is, the chemical component of ultrasonic
effects (Lida et al. 2005). Several reactions bearing a radical pathway have been
designed to qualify/quantify the production of radicals, in particular in water with
the production of OH° by help of spectrophotometric reactions (Koda et al. 2003;
Kimura et al. 1996), para-chlorobenzoic acid degradation (Neppolian et al. 2004)
or fluorimetric methodologies (Hirano and Kobayashi 2016), terephthalate oxidation (Mason et al. 1994) and luminol sonochemiluminescence (Pétrier et al. 1994;
Hatanaka et al. 2000). Fricke and Weissler reactions being the most studied and used
chemical dosimetry methods, a quick insight is given here below:
• Fricke reaction: A Fe
2+ solution of FeSO 4 in the presence of H 2 SO 4 and NaCl
is submitted to ultrasound and the production of OH° can be estimated through
the oxidative conversion of Fe
2+ ions into Fe
3+ ions where the number of OH° is
approximatively equal to one-quarter the amount of produced Fe
3+ .
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is monitored and plotted as a function of time over a short period (2–3 min) without
thermostatic control. The deduced slope T /t is then set into the next equation to
determine the calorimetric power of an incident ultrasonic wave:
Pcal(W ) m.Cp..T
t
(1.3)
where Cp is the isobaric thermal capacity.
In reason of the non-linear behaviour of acoustic waves and subsequent cavitation
bubbles at high amplitude, the bulk temperature might not be spatially homogeneous.
Different measurements location within the same reactor may thus present some
noticeable variations (Al-Juboori et al. 2014).
Another way to measure the acoustic pressure is the radiometric method which
is the measurement of the force exerted by a sound beam on any partially reflecting
surface (Lepoint and Lepoint-Mullié 1998). The spatial distribution of the ultrasonic
pressure intensity can be undertaken by mean of a hydrophone but their high sensitivity together with fragility are limiting parameters for non-linear high intensities
sound fields. The latest development in the physical characterization of the acoustic
cavitation has been recently enabled with the design of cavitometers. These latter
allow to study the cavitation noise spectra to analyse the dynamic process of cavitation by measuring acoustic pressures at particular frequencies but this equipment is
still on lab-stage development (Dezhkunov et al. 2013).
1.9.2 Chemical Methods
Previously described methods do macroscopically measure the acoustic pressure
through the effects produced in the propagation liquid, namely, heating and exerted
forces on a surface. However, they do not allow to determine the radical production consecutive of collapsing bubbles, that is, the chemical component of ultrasonic
effects (Lida et al. 2005). Several reactions bearing a radical pathway have been
designed to qualify/quantify the production of radicals, in particular in water with
the production of OH° by help of spectrophotometric reactions (Koda et al. 2003;
Kimura et al. 1996), para-chlorobenzoic acid degradation (Neppolian et al. 2004)
or fluorimetric methodologies (Hirano and Kobayashi 2016), terephthalate oxidation (Mason et al. 1994) and luminol sonochemiluminescence (Pétrier et al. 1994;
Hatanaka et al. 2000). Fricke and Weissler reactions being the most studied and used
chemical dosimetry methods, a quick insight is given here below:
• Fricke reaction: A Fe
2+ solution of FeSO 4 in the presence of H 2 SO 4 and NaCl
is submitted to ultrasound and the production of OH° can be estimated through
the oxidative conversion of Fe
2+ ions into Fe
3+ ions where the number of OH° is
approximatively equal to one-quarter the amount of produced Fe
3+ .