Effect of Frequency on Ultrasonic

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Effect of Frequency on Ultrasonic Degradation of
Organic Pollutants
Myunghee Lima, Younggyu Sona, David Elenab,
Iordache Ioanb, Jeehyeong Khima a Civil,
Environmental Architectural Engineering, Korea
University, Korea bNational Research and
Development Institute for Cryogenics and Isotopic
Tech., Romania
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Introduction Ultrasound?
Ultrasound is applied to homogeneous or
heterogeneous aqueous phase
1. Irradiation of sound energy to aqueous phase
2. Formation of sound field
3. Induction of cavitation
Cavitation bubble
4. Chemical Physical effects of cavitation
? Transformation / Transfer phenomena
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Introduction Ultrasound?
Acoustic Cavitation collapse Hot spot theory
Pyrolytic center
Temp. 3000 5000 K Pressure 1000 atm
Bulk solution
Temp. 300 K
Interfacial region
Cavitation bubble
Temp. 300 2000 K
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Introduction Ultrasound?
Chemical effects Transformation (Degradation)
Volatiles Pyrolysis Non-volatiles Radical
oxidation
H2O O2 H H2O O H2O H O2 2HO 2HOO
? ? ? ? ? ? ?
H OH 2O HO H2 2OH HOO H2O2 H2O2 O2
Cavitation bubble
H2O / O2
5,000 K 1,000 atm
Pyrolysis Radical oxidation
Radical oxidation
Non-volatile pollutants
Volatile pollutants
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Introduction Ultrasound?
Physical effects Separation (Desorption /
mixing)
Microjets, Microstreaming
Microjets (Liquid jets) 100 m/s
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1. Introduction Effect of Frequency?
Motivation
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1. Introduction Effect of Frequency?
Motivation
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1. Introduction
Question?
Q 1. Optimum Frequency ? Q 2. Optimum Frequencies
vs. Organic Pollutants ?
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1. Introduction Frequency Effects
Backgrounds
Frequency
Temperature (Tmax) ? of Cavitation bubbles
? Mass transfer rate ?
OH
Volatile compounds
OH
Volatile compounds
OH
Volatile compounds
Temperature (Tmax) ? of Cavitation bubbles
? Mass transfer rate ?
OH
Volatile compounds
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2. Materials Methods
Schematic of batch reactor
Ultrasonic Generator
Reactor (240 mL)
((( ((( ((( (((
Cooling System
Transducer
Recirculation
Temp. 20 ?
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2. Materials Methods
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3. Results Discussion
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3. Results Discussion
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3. Results Discussion
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3. Results Discussion
H2O2 production
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3. Results Discussion
1,4-Dioxane degradation rate vs H2O2 production
rate

• 1,4-Dioxane degradation rate
• 358 kHz gt 205 kHz gt 618 kHz gt 1071 kHz
• H2O2 production rate
• 358 kHz gt 618 kHz gt 1071 kHz gt 205 kHz

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3. Results Discussion
TOC elimination for Phenol
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3. Results Discussion
TOC elimination
Bisphenol-A
Bisphenol-A
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4. Conclusion?
Optimal frequency ?
Pyrolysis vs. radical oxidation
Availability of radicals - Radical production -
Radical transfer - Hydroxyl radical vs. other
radicals - H2O2 vs. hydroxyl radical

• Mass transfer
• Mass transfer vs. surface area of bubbles
• - Bubble dynamics (size, number, temp.)
• - Hydrophobicity

Activation energy ?
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Thank you
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Frequency vs Tmax
(Kanthale et al., 2008)
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Resonant radious
(Hung and Hoffmann., 1999)
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1. Introduction
Motivation
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3. Results Discussion
CCl4 and Phenol
Q 1. Is the optimum frequency exist? Yes
Q 2. Is the optimum frequency different according
to materials? Yes
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3. Results Discussion
H2O2 production and TOC elimination
The maximum production rate of hydrogen peroxide
is observed at 110 kHz. Its not consistence
with TOC, phenol and 2-CP degradation.