• Title, Summary, Keyword: Sonochemical

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Effect of $H_2O_2$ and Metals on The Sonochemical Decomposition of Humic Substances in Wastewater Effluent

  • Jung, Oh-Jun
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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    • v.10 no.S_3
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    • pp.127-137
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    • 2001
  • The sonochemical Process has been applied as a treatment method and was investigated its effect on the decomposition of humic substances(HS). The reaction kinetics and mechanisms in the Process of sonochemical treatment for humic substances(HS) in wastewater have also been discussed. It was observed that the metal ions such as Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The mechanism of radical reaction is controlled by an oxidation process. The radicals are so reactive that most of them are consumed by HS radicals and hydroxyl radicals can be acted on organic solutes by hydroxyl addition, hydrogen abstraction, and electron transfer. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final steps of the reaction are the conversion of organic acids to carbon dioxide.

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EFFECTS OF H2O2, TURBIDITY AND METALS ON SONOCHEMICAL DECOMPOSITION OF HUMIC SUBSTANCES IN WASTEWATER EFFLUENT

  • Kim, Il-Kyu
    • Journal of Korean Society on Water Environment
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    • v.18 no.3
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    • pp.271-282
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    • 2002
  • The sonochemical process has been applied as a treatment method to investigate its effect on the decomposition of humic substances (HS). The reaction kinetics and mechanisms in the process of sonochemical treatment for humic substances in wastewater have also been discussed. It was observed that the metal ions such Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final step of the reaction is the conversion of organic acids to carbon dioxide.

The Effect of Liquid Height on Sonochemical Reactions in 74 kHz Sonoreactors (74 kHz 초음파 반응기에서 수위 변화에 따른 초음파 화학 반응의 변화)

  • Son, Younggyu
    • 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.

The Effect of Distance between Two Transducers on Sonochemical Reactions in Dual Irradiation Systems (이중 초음파 조사 시스템에서 진동부 사이의 거리가 초음파 화학 반응에 미치는 영향)

  • Kim, Eunkyung;Son, Younggyu
    • 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.

The Fabrication of Cobalt Nanopowder by Sonochemical Polyol Synthesis of Cobalt Hydroxide and Magnetic Separation Method (수산화코발트의 초음파 폴리올 합성과 자성 선별법을 이용한 코발트 나노 분말의 제조)

  • Byun, Jong Min;Choi, Myoung Hwan;Shim, Chang Min;Kim, Ji Young;Kim, Young Do
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.1
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    • pp.39-45
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    • 2015
  • In this study, cobalt nanopowder is fabricated by sonochemical polyol synthesis and magnetic separation method. First, sonochemical polyol synthesis is carried out at $220^{\circ}C$ for up to 120 minutes in diethylene glycol ($C_4H_{10}O_3$). As a result, when sonochemical polyol synthesis is performed for 50 minutes, most of the cobalt precursor ($Co(OH)_2$) is reduced to spherical cobalt nanopowder of approximately 100 nm. In particular, aggregation and growth of cobalt particles are effectively suppressed as compared to common polyol synthesis. Furthermore, in order to obtain finer cobalt nanopowder, magnetic separation method using magnetic property of cobalt is introduced at an early reduction stage of sonochemical polyol synthesis when cobalt and cobalt precursor coexist. Finally, spherical cobalt nanopowder having an average particle size of 22 nm is successfully separated.

Sonochemical Reformatsky Reaction Using Indium

  • Bang, Keuk-Chan;Lee, Koo-Yeon;Park, Yong-Kwang;Lee, Phil-Ho
    • Bulletin of the Korean Chemical Society
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    • v.23 no.9
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    • pp.1272-1287
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    • 2002
  • Sonochemical Reformatsky reaction of aldehydes or ketones with ethyl bromoacetate in the presence of indium afforded $\beta-hydroxyesters$ in good to excellent yields under mild conditions. 2- or 3-Hydroxybenzaldehyde that contains an acidic hydrogen r eacted with ethyl bromoacetate to provide the desired compounds with the same efficiency. In the case of ethyl 2-bromopropanoate and ethyl 2-bromo-2-methylpropanoate, the desired products were obtained in good yields. Reaction of aldehyde with indium reagent in the presence of ketone group proceeded chemoselectively.

Effect of Gas Sparging on Sonochemical Oxidation in a 300 kHz Sonoreactor (300 kHz 조건에서의 초음파화학적 산화반응에 대한 연속식 가스 주입 효과)

  • Seo, Jieun;Son, Younggyu
    • Journal of Korean Society on Water Environment
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    • v.34 no.6
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    • pp.642-649
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    • 2018
  • The effect of gas sparging on sonochemical oxidation was investigated in a 300 kHz sonoreactor under various liquid height/volume conditions ($5{\sim}30{\lambda}$, 3.4 ~ 9.0 L), determined by the wavelength of the applied frequency. The electrical input power was maintained constant for all cases . Sonochemical activity drastically decreased from $15{\lambda}$ and the liquid height of $10{\lambda}$ was suggested as the optimal height for 300 kHz without gas sparging. In our previous research, the sonochemical activity observed was five-times higher when air sparging was applied for 36 kHz. On the other hand, no enhancement was obtained at 10, 15, 25 and $30{\lambda}$ using air sparging (1, 3, and 6 L/min) for 300 kHz in this study $20{\lambda}$ and optimization of gas sparging was conducted at $20{\lambda}$ using various gases including air, Ar, $O_2$, $N_2$, and mixtures of Ar and $O_2$. It was found that gas sparging using pure Ar or pure $O_2$ resulted in lower sonochemical activity compared to that of air sparging due to the imbalance between the intensity of cavitation phenomena and the generation of oxidizing radical species. Consequently, the gas mixture of $Ar:O_2$ = 80 % : 20 % (DO saturation ${\approx}100%$) was suggested as an optimal gas sparging condition.

Synthesis of Monodisperse Magnetite Nanocrystallites Using Sonochemical Method (음향화학법을 이용한 균일한 나노 자성체의 합성)

  • Cho, Jun-Hee;Ko, Sang-Gil;Ahn, Yang-Kyu;Song, Ki-Chang;Choi, Eun-Jung
    • Journal of the Korean Magnetics Society
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    • v.16 no.3
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    • pp.163-167
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    • 2006
  • Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized magnetite particles using coprecipitation method, sonochemical method without surfactant, and sonochemical method with surfactant, in order to investigate the effect of ultrasonic irradiation and surfactant on the coprecipitates of metal ions. The size of the magnetite nanoparticles prepared by coprecipitation method, and sonochemical method without surfactant showed broad distributions. But we got uniform nanoparticles using a sonochemical method with oleic acid. The average size of the particles can be controlled by the ratio $R=[H_2O]/[surfactant]$. The size of the magnetite nanoparticles prepared by this method showed narrow distributions. We have characterized the nanoparticles using an X-ray diffraction (XRD), a superconducting quantum interference device (SQUID), and atomic force microscope (AFM). The size and distribution of the magnetite nanoparticles were measured by dynamic light scattering (DLS) method.