• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.39-45
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• 2013

Many researchers have studied the effectiveness of ultrasound in chemical and environmental engineering fields including material synthesis, pollutant removal, cleaning, extraction, and disinfection. Acoustic cavitation induced by ultrasound irradiation in aqueous phase can cause various sonophysical and sonochemical reactions without any chemicals. However most of the previous studies focused only on the relationships between ultrasonic conditions and the results of sonochemical reactions in lab-scale sonoreactors. As a results of this, only a few studies have been devoted to design and optimization of industrial scale sonoreactors. In this study, the effect of the distance between two opposite transducer modules on sonochemical reactions was investigated in single and dual irradiation systems (334 kHz) for four distances including 50, 100, 150, and 200 mm using KI dosimetry. It was found that the dual irradiation systems provided higher performance in terms of the zeroth reaction coefficient and the cavitation yield compared to the single irradiation systems. The sonochemiluminescence (SCL) images for the visualization of the cavitation field showed that cavitation active zone was larger and sonochemical reaction intensity was much higher in the dual irradiation system than in the single irradiation system.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.80-85
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• 2016

Acoustic cavitation can induce various sonochemical effects including pyrolysis and radical reactions and sonophysical effects including microjets and shockwave. In environmental engineering field, ultrasound technology using sonochemical effects can be useful for the removal and mineralization of recalcitrant trace pollutants in aqueous phase as one of emerging advanced oxidation processes (AOPs). In this study, the effect of liquid height, the distance from the transducer to the water surface, on sonochemical oxidation reactions was investigated using KI dosimetry. As the liquid height/volume increased (40~400 mm), the cavitation yield steadily increased even though the power density drastically decreased. It was found that the enhancement at higher liquid height conditions was due to the formation of standing wave field, where cavitation events could stably occur and a large amount of oxidizing radicals such as OH radicals could be continuously provided.

• Journal of Korean Society on Water Environment
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• v.38 no.5
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• pp.211-219
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• 2022

In this study, the effect of liquid height/volume on sonochemical oxidation reactions was investigated in 300 kHz sonoreactors. The gas mixture of Ar/O₂ (50:50) was applied in two modes including saturation and sparging, and zero-order reaction (KI dosimetry) and first-order reaction (Bisphenol A (BPA) degradation) were used to quantitatively analyze sonochemical oxidation reactions. For the zero-order reaction, the highest sonochemical oxidation activity was obtained for the liquid height of 5𝛌, and the lowest height for both the gas saturation and sparging conditions. In addition, the sparging did not enhance the sonochemical oxidation activity for all height conditions except for 50𝛌, where very low activity was obtained. It was found that in sonochemiluminescence (SCL) images the sonochemical active zone was formed adjacent to the liquid surface for the gas sparging condition due to the formation of the standing wave field while the active zone was formed adjacent to the transducer at the bottom due to the blockage of ultrasound. For the first-order reaction, the highest activity was also obtained at 5𝛌 and the comparison based on the reactant mass was not appropriate because the concentration of the reactant (BPA) decreased significantly as the reaction time elapsed. Consequently, it was revealed that the determination of optimal liquid height (ultrasound irradiation distance) based on the wavelength of the applied ultrasound frequency was very important for the optimal design of sonoreactors in terms of reaction efficiency and reactor size.

• Journal of Soil and Groundwater Environment
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• v.22 no.5
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• pp.40-47
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• 2017

The effects of ultrasound in heterogeneous system were investigated in three kinds of ultrasonic systems including a bath-type system (System #1), a double-bath-type system (System #2), and a double-bath-type system partly filled with glass beads (System #3). The ultrasound energy and its attenuation were quantified using calorimetry and the sound pressure measurement method. The sonochemical effects mainly involved in radical oxidation reactions were quantified using KI dosimetry. It was found that ultrasound energy was significantly attenuated in System #2 and #3 due to the presence of solid materials such as a submerged stainless steel reactor and glass beads. However, in spite of low ultrasound energy status, sonochemical oxidation reactions occurred more violently due to the presence of glass beads in System #3. In addition, calorimetry was more adequate to estimate the total energy status of ultrasound in sonoreactors compared to the sound pressure measurement method.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.128-134
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• 2016

Acoustic emission spectra was analyzed to investigate the distribution of sound pressure in a 36 kHz sonoreactor. The sound pressure of fundamental frequency (f: 36 kHz), harmonics (2f: 72 kHz, 3f: 108 kHz, 4f: 144 kHz, 5f: 180 kHz, 6f: 216 kHz), and subharmonics (1.5f: 54 kHz, 2.5f: 90 kHz, 3.5f: 126 kHz, 4.5f: 162 kHz, 5.5f: 198 kHz, 6.5f; 234 kHz) was measured at every 5 cm from the ultrasonic transducer using a hydrophone and a spectrum analyzer. It was revealed that the input power of ultrasound, the application of mechanical mixing, and the concentration of SDS affected the sound pressure distributions of the fundamental frequency and total detected frequencies frequencies significantly. Moreover a linear relationship was found between the average total sound pressure and the degree of sonochemical oxidation while there was no significant linear relationship between the average sound pressure of fundamental frequency and the degree of sonochemical oxidation.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.17-28
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• 2007

Indium and gallium have emerged as useful metals in organic synthesis as a result of its intriguing chemical properties of reactivity, selectivity, and low toxicity. Although indium belongs to a main metal in group 13, its first ionization potential energy is very low and stable in H2O and O2. Therefore, indium-mediated organic reactions are of our current interest. On the basis of these properties of indium, many efficient indium-mediated organic reactions have been recently developed, such as the addition reactions of allylindium to carbonyl and iminium groups, the indium-mediated synthesis of 2-(2-hydroxyethyl)homoallenylsilanes, the indiummediated allylation of keto esters with allyl halides, sonochemical Reformatsky reaction using indium, the indium-mediated selective introduction of allenyl and propargyl groups at C-4 position of 2-azetidinones, the indium-mediated Michael addition and Hosomi-Sakurai reactions, the indium-mediated β-allylation, β- propargylation and β-allenylation onto α,β-unsaturated ketones, the highly efficient 1,4-addition of 1,3-diesters to conjugated enones by indium and TMSCl, and the intramolecular carboindation reactions. Also, we found gallium-mediated organic reactions such as addition reactions of propargylgallium to carbonyl group and regioselective allylgallation of terminal alkynes.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2331-2334
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• 2014

$Cu_2SnSe_3$ (CTSe) and $Cu_2ZnSnSe_4$ (CZTSe) nanoparticles were synthesized by sonochemical reactions under multibubble sonoluminescence (MBSL) conditions. First, $Cu_2SnSe_3$ nanoparticles were synthesized by the sonochemical method with an 85% yield, using CuCl, $SnCl_2$, and Se. Second, ZnSe was coated on the CTSe nanoparticles by the same method. Then, they were transformed into CZTSe nanoparticles of 5-7 nm diameters by heating them at $500^{\circ}C$ for 1 h. The ratios between Zn and Sn could be controlled from 1 to 3.75 by adjusting the relative concentrations of CTSe and ZnSe. With relatively lower Zn:Sn ratios (0.75-1.26), there are mostly CZTSe nanoparticles but they are believed to include very small amount of CTS and ZnSe particles. The prepared nanoparticles show different band gaps from 1.36 to 1.47 eV depending on the Zn/Sn ratios. In this sonochemical method without using any toxic or high temperature solvents, the specific stoichiometric element Zn/Sn ratios in CZTSe were controllable on demand and their experimental results were always reproducible in separate syntheses. The CZTSe nanoparticles were investigated by using X-ray diffractometer, a UV-Vis spectrophotometer, scanning electron microscope, Raman spectroscopy, and a high resolution-transmission electron microscope.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2207-2211
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• 2011

Colloidal cadmium telluride (CdTe) quantum dots (QDs) and their nanoparticles have been synthesized by one pot sonochemical reactions under multibubble sonoluminescence (MBSL) conditions, which are quite mild and facile compared to other typical high temperature solution-based methods. For a typical reaction, $CdCl_2$ and tellurium powder with hexadecylamine and trioctylphosphine/trioctylphosphineoxide (TOP/TOPO) as a dispersant were sonicated in toluene solvent at 20 KHz and a power of 220W for 5-40 min at 60 $^{\circ}C$. The sizes of CdTe particles, in a very wide size range from 2 nm-30 ${\mu}m$, were controllable by varying the sonicating and thermal heating conditions. The prepared CdTe QDs show different colors from pale yellow to dark brown and corresponding photoluminescence properties due mainly to the quantum confinement effect. The CdTe nanoparticles of about 20 nm in average were found to have band gap of 1.53 eV, which is the most optimally matched band gap to solar spectrum.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1998.10a
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• pp.1-1
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• 1998

Advanced (Chemical) oxidation processes (AOP) differ from most conventional ones in that hydroxyl radical(OH.) is considered to be the primary oxidant. Hydroxyl radicalcan react non-selectively with a great number of organic and inorganic chemicals. The typical rate constants of true hydroxyl radical reactions are in the range of between 109 to 1012 sec-1. Many processes are possible to generate hydroxyl radical. These include physical and chemical methods and their combinations. Physical means involves the use of high energy radiation such as gamma ray, electron beam, and acoustic wave. Under an applied high energy radiation, water molecules can be decomposed to yield hydroxyl radicals or aqueous electrons. Chemical means include the use of conventional oxidants such as hydrogen peroxide and ozone, two of the most efficient oxidants in the presence of promoter or catalyst. Hydrogen peroxide in the presence of a catalyst such as divalent iron ions can readily produce hydroxyl radicals. Ozone in the presence of specific chemical species such as OH- or hydrogen peroxide, can also generate hydroxyl radicals. Finally the combination of chemical and physical means can also yield hydroxyl radicals. Hydrogen peroxide in the presence of acoustic wave or ultra violet beam can generate hydroxyl radicals. The principles for hydroxyl radical generation will be discussed. Recent case studied of AOP for water treatment and other environmental of applications will be presented. These include the treatment of contaminated soils using electro-Fenton, lechate treatment with conventional Ponton, treatment of coal for sulfur removal using sonochemical and the treatment of groundwater with enhanced sonochemical processes.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.327-330
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• 2010

$LiCoO_2$, a cathode material for lithium rechargeable batteries, was prepared in a nanoscale through a simple sonochemistry. First, $Co_3O_4$ nanoparticles were prepared by reacting NaOH and $CoCl_2$ or $CoSO_4$ with a sonochemical method, operated at 20 kHz and 220 W for 20 min, very powerful multibubble sonoluminescence conditions for chemical reactions. Second, LiOH was coated onto the $Co_3O_4$ nanoparticles by the same method as above. Finally, $LiCoO_2$ nanoparticles of about 10~30 nm size in diameter were obtained by the thermal treatment of the resulting LiOH-coated $Co_3O_4$ nanoparticles at $500^{\circ}C$ for 3 hr. This synthetic process is relatively quite mild and simple compared to the known method for the synthesis of $LiCoO_2$ nanoparticles. The materials synthesized were characterized by infrared spectroscopy, X-ray diffraction, inductively coupled plasma spectrometer, and high resolution-transmission electron microscopy analyses.