研究者詳細 - 安田　啓司

論文 - 安田　啓司

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Frequency and power dependence of ultrasonic degassing 査読有り Open Access

Asakura, Y; Yasuda, K

ULTRASONICS SONOCHEMISTRY 82 巻頁： 105890 - 1058908 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ultrasonics Sonochemistry

We investigated the time variation of ultrasonic degassing for air-saturated water and degassed water with a sample volume of 100 mL at frequencies of 22, 43, 129, 209, 305, 400, 514, 1018, and 1960 kHz and ultrasonic power of 15 W. Ultrasonic degassing was evaluated by dissolved oxygen concentration. Ultrasonic degassing was also investigated at a frequency of 1018 kHz and ultrasonic powers of 5, 10, 15, and 20 W. The dissolved oxygen concentration varied with the ultrasonic irradiation time and became constant after prolonged ultrasonic irradiation. The constant dissolved oxygen concentration value depended on the frequency and ultrasonic power but not the initial dissolved oxygen concentration. The degassing rate at 101.3 kPa was higher in the frequency range of 200 kHz to 1 MHz. The frequency dependence of the degassing rate was almost the same as that of the sonochemical efficiency obtained by the potassium iodide (KI) method. Ultrasonic degassing in the frequency range of 22–1960 kHz was also investigated under reduced pressure of 5 kPa. Degassing was accelerated when ultrasonic irradiation was applied under reduced pressure. However, under a reduced pressure of 5 kPa, the lower the frequencies, the higher is the degassing rate. The sonochemical reaction rate was examined by the KI method for varying dissolved air concentrations before ultrasonic irradiation. Cavitation did not occur when the initial dissolved oxygen concentration was less than 2 mg·L−1. Therefore, the lower limit of ultrasonic degassing under 101.3 kPa equals 2 mg·L−1 dissolved oxygen concentration. A model equation for the time variation of dissolved oxygen concentration due to ultrasonic irradiation was developed, and the degassing mechanism was discussed.

DOI： 10.1016/j.ultsonch.2021.105890

Frequency and power dependence of the sonochemical reaction 査読有り Open Access

Asakura, Y; Yasuda, K

ULTRASONICS SONOCHEMISTRY 81 巻頁： 105858 - 1058587 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ultrasonics Sonochemistry

The dependence of the sonochemical reaction on ultrasonic intensity was studied over a wide frequency range of 22–1960 kHz and sample volume range of 25–200 mL. The effect of a stainless steel reflector set on the water surface was also considered. Experiments were carried out by direct ultrasonic irradiation of a sample in a vessel. The potassium iodide (KI) method was used to evaluate the sonochemical reaction in terms of efficiency and reaction rate, and calorimetry was used to determine ultrasonic power. A quenching phenomenon, where the reaction rate decreased despite an increasing ultrasonic power, was observed at all frequencies and sample volumes, which indicated the existence of a maximum reaction rate. The maximum reaction rate increased with the frequency, except at 1960 kHz, and with the sample volume. The ultrasonic power at which quenching occurred increased with the frequency and sample volume. Sudden quenching occurred without the reflector, whereas gradual quenching occurred with the reflector. Based on the results, ultrasonic power density (i.e., ultrasonic power divided by the sample volume) can be used to estimate the ultrasonic power at which quenching occurs for various sample volumes.

DOI： 10.1016/j.ultsonch.2021.105858

超音波によるウルトラファインバブルの生成・消滅と高純度な金ナノ粒子の合成招待有り

安田啓司

化学工業 72 巻 ( 7 ) 頁： 441 - 446 2021年7月

超音波とウルトラファインバブルを活用した金ナノ粒子合成招待有り

安田啓司

化学工学 85 巻 ( 4 ) 頁： 232 - 235 2021年4月

Sonochemical green technology using active bubbles: Degradation of organic substances in water 招待有り査読有り Open Access

Yasuda, K

CURRENT OPINION IN GREEN AND SUSTAINABLE CHEMISTRY 27 巻頁： 100411 2021年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Current Opinion in Green and Sustainable Chemistry

This review introduces recent studies on the sonochemical degradation of organic substances in aqueous solutions. Since the main advantage of this method is absent in added chemicals, this is applicable to many kinds of solutes with safe operation. Sonochemical degradation of organic substances can be applied for not only water treatment but also food processing. In this review, organic substances are categorized as aromatic compounds, organic halogen compounds, polysaccharides, and microorganisms. Sonochemical degradation occurs in the three regions centered at cavitation bubbles. The optimum ultrasonic frequencies for the degradation are depended on the type of organic substances and are related to the chemical or physical effects of cavitation. The reaction kinetics and mechanism of sonochemical degradation are also discussed.

DOI： 10.1016/j.cogsc.2020.100411

Open Access

Web of Science

Scopus

ウルトラファインバブルの安定性招待有り

安田啓司

化学工学 54 巻 ( 12 ) 頁： 644 2020年12月

Effect of ultrafine bubbles on ethanol enrichment using ultrasonic atomization 査読有り

Yasuda, K; Nohara, Y; Asakura, Y

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( SK ) 頁： SKKD09 2020年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

To improve ethanol enrichment performance using ultrasonic atomization, ultrafine bubbles (UFB) were added to an ethanol aqueous solution. The ethanol concentration in the solution and the flow rate of carrier gas were changed, and the effect of UFB on the ethanol concentration in the collected mist was investigated. For all conditions, the ethanol concentration in the collected mist with UFB was higher than that without UFB. Especially, the enrichment effect by UFB was remarkable when the ethanol concentration in the solution and the flow rate of carrier gas were low.

DOI： 10.35848/1347-4065/ab83d9

Web of Science

Scopus

Size-controlled synthesis of gold nanoparticles by ultrafine bubbles and pulsed ultrasound 査読有り Open Access

Yasuda, K; Sato, T; Asakura, Y

CHEMICAL ENGINEERING SCIENCE 217 巻頁： 115527 2020年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Engineering Science

Size-controlled gold nanoparticles (AuNPs) were synthesized by ultrasonic irradiation of HAuCl<inf>4</inf> aqueous solutions with the aid of ultrafine bubbles (UFBs) in the absence of any capping and reducing agents. Upon addition of air-UFBs, the mean diameter of the spherical AuNPs decreased. This result was attributed to the sonochemical reduction of gold ions in aqueous solution being accelerated by the UFBs. Moreover, the AuNPs were stable in a solution containing UFBs because AuNPs electrostatically adsorbed onto UFBs, whose lifetime in water was very long. Compared with the mean diameter of AuNPs synthesized with argon-, nitrogen- and oxygen-UFBs, that of AuNPs synthesized with air-UFBs was smaller. Pulsed ultrasound delivered with the same time-averaged power as continuous-wave irradiation further decreased the mean diameter of the AuNPs. Size-controlled synthesis of AuNPs without the use of a capping or reducing agent was successful through optimization of the number air-UFBs and the pulsed ultrasound conditions.

DOI： 10.1016/j.ces.2020.115527

Open Access

Web of Science

Scopus

Responses to the comment on the paper "Generation and reduction of bulk nanobubbles by ultrasonic irradiation"

Yasuda, K; Matsushima, H; Asakura, Y

CHEMICAL ENGINEERING SCIENCE 207 巻頁： 1366 - 1367 2019年11月

超音波霧化濃縮における液滴中のアルコール濃度招待有り

安田啓司

超音波TECHNO 67 巻 ( 8 ) 頁： 350 - 353 2019年10月

超音波を利用した水中の汚染物質分解と有価物質分離招待有り Open Access

安田啓司

化学と教育 67 巻 ( 8 ) 頁： 350 - 353 2019年8月

Effect of Venturi Tube Shape on Reaction Performance by Hydrodynamic Cavitation

Yasuda, K; Ako, D

JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 52 巻 ( 3 ) 頁： 280 - 282 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人化学工学会

The effect of venturi tube shape on reaction rate by hydrodynamic cavitation was investigated. The apparatus mainly composed of the venturi tube, a liquid pump, a tank, a pipe arrangement, and a heat exchanger. The upstream and downstream pressures of the venturi tube were measured. The sample was an aqueous solution containing potassium iodine and chloroform. The generation rate of triiodide ion increased with increasing upstream pressure. This is because liquid velocity at the venturi tube is high and the amount of cavitation bubbles increases. When the throat diameter of the venturi tube was 2.5 mm, the generation rate of triiodide ion reached a maximum value. As the throat diameter of the venturi tube became smaller, the generation rate of triiodide ion per pass of venturi tube increased and the pass number of venturi tube decreased. Both low cavitation number and large pass number are important for high reaction performance.

DOI： 10.1252/jcej.18we183

Web of Science

Scopus

CiNii Research

Generation and reduction of bulk nanobubbles by ultrasonic irradiation 査読有り Open Access

Yasuda, K; Matsushima, H; Asakura, Y

CHEMICAL ENGINEERING SCIENCE 195 巻頁： 455 - 461 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Engineering Science

To develop a compact generator of bulk nanobubbles (ultrafine bubbles), ultrasound was irradiated to ultrapure water. Effects of ultrasonic power and frequency on nanobubble concentration and diameter were investigated. Nanobubbles with a diameter of 90–100 nm were generated. Number concentration of nanobubbles increased with time and approached asymptotically to an equilibrium value which was about 1.5 × 109 mL−1. Nanobubble concentration increased with increasing ultrasonic power and decreasing frequency. For comparison, ultrasound was also irradiated to high concentration nanobubble water prepared by pressurized dissolution method. Reduction of nanobubbles was measured and nanobubble concentration decreased to the equilibrium value. Nanobubble concentration decreased with increasing ultrasonic power and frequency. Generation and reduction of nanobubbles by ultrasound was modeled to analyze experimental data. The generation rate coefficient of nanobubbles increased with decreasing frequency because cavitation collapse became stronger. The reduction rate constant of nanobubbles at 488 kHz and 1 MHz in high concentration nanobubble water became much higher than those in ultrapure water due to aggregation and floatation of nanobubbles. The equilibrium number concentration increased with decreasing frequency. The results calculated by our model were in good agreement with the experimental data. The nanobubble generator using ultrasound is compact, simple in operation and produce nanobubbles in a short time. This method is contamination-free because the liquid pump is unnecessary.

DOI： 10.1016/j.ces.2018.09.044

Open Access

Web of Science

Scopus

ファインバブルによるオゾン反応の促進招待有り

安田啓司

エレクトロニクスコミュニケーション 34 巻頁： 9 - 12 2019年1月

資源利用・環境浄化のためのファインバブルの活用招待有り

安田啓司

ファインケミカル 47 巻 ( 10 ) 頁： 5-12 2018年10月

ファインバブルによる廃水処理性能の向上招待有り

安田啓司

ペトロテック 41 巻 ( 6 ) 頁： 432-436 2018年6月

Measurement of distribution of broadband noise and sound pressures in sonochemical reactor Open Access

Yasuda, K; Nguyen, TT; Asakura, Y

ULTRASONICS SONOCHEMISTRY 43 巻頁： 23 - 28 2018年5月

記述言語：英語出版者・発行元：Ultrasonics Sonochemistry

Cross-sectional area distribution of broadband noise in a sonochemical reactor was measured to estimate reaction fields. A needle-type hydrophone scanned the sonochemical reactor in horizontal and vertical directions at one-millimeter interval. To show an absolute value of broadband noise, average of broadband sound pressure was defined. The distribution of sound pressures at the fundamental and second harmonic frequencies were also measured. In the case of driving frequency at 130 kHz, sonochemical reaction fields were observed in several ellipse shapes. The reaction fields in upper part of the reactor was high because cavitation bubbles moved upper part due to radiation force. The sound pressure distribution at the fundamental frequency showed existence of standing wave and reaction fields were weak at pressure antinode because cavitation bubbles were repelled by primary Bjerknes force. The sound pressure distribution at the second harmonic frequency indicated that the pattern of bubbles distribution resembled to that of reaction fields closely. In the case at 43 kHz, distributions of reaction fields and sound pressures were complex due to coupled vibration. The reaction fields were relatively weak in areas which had very high sound pressures at the fundamental frequency.

DOI： 10.1016/j.ultsonch.2017.12.051

Production of β-carotene nanoemulsions with the emulsification-evaporation technique using supercritical CO2 and improvement of its efficiency by Z-isomerization pre-treatment 査読有り

M. Ono, M. Honda, Wahyudiono, K. Yasuda, H. Kanda and M. Goto

The Journal of Supercritical Fluids 138 巻頁： 124-131 2018年4月

Measurement of Distribution of Broadband Noise and Sound Pressures in Sonochemical Reactor 査読有り Open Access

K. Yasuda, T. T. Nguyen and Y. Asakura

Ultrasonics Sonochemistry 43 巻頁： 23-28 2017年12月

ハイブリッド型超音波反応器による有害物質の分解と除去招待有り

安田啓司

超音波TECHNO 29 巻 ( 6 ) 頁： 32-36 2017年12月

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