The ultrasonic power (ultrasonic energy per unit time) irradiated into a solution is determined either by a radiation force measuring method or by calorimetry. Ultrasonic power of a 1 MHz transducer was measured using radiation force balance measurement and showed frequency characteristics. Dependence on the ratio of the applied electric power to transducers and ultrasonic power on the liquid height was investigated using calorimetry. When the liquid height between the transducer and the water surface in a reactor is low, even in cases where a transducer is driven with a fixed electrical power to a water load, the actual ultrasonic power delivered to the solution in the reactor is reduced. The sound pressure distribution in the 129 kHz sonochemical reactor was measured using a hydrophone. Coupled vibration was observed in the sonochemical reactor. It can be observed that on changing the liquid height (in millimeters), the sonochemical efficiency measured using the KI method depends greatly on the liquid height. When the absolute value of the impedance of the transducer is at its maximum, the sonochemical efficiency shows a minimum. This result is important to the reproducibility of sonochemical experiments.

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In experiments of sonoluminescence (SL) at 1MHz, we found extraordinary light emission. The extraordinary light was observed only when we used transducer which was partly removed by cavitation erosion. To clarify the origin of the extraordinary light of SL, we have measured SL distribution and spectrum. With damaged transducer, SL intensity is much larger than that of normal SL. Also continuum components from SL increased and conformed to helium emission lines. We also measured AC voltage leaked from the damaged transducer surface and obtained A high value at near the part was removed.

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LiFePO_4 has attracted attention as promising cathode materials for lithium ion battery, because it consists of abundant elements. However, the battery capability of this material is limited by its low electronic conductivity. To overcome the low electronic conductivity, two major approaches has been taken. One is the miniaturization of the size of LiFePO_4 particles and the other is the deposition of a conductive carbon on the surface of LiFePO_4 particles (LiFePO_4/C). We have been studied about synthesis of cathode materials as fine particle using ultrasound irradiation. In this study, we focus on Au nanoparticles synthesized by ultrasound irradiation. We expect Au nanoparticles to improve electronic conductivity of LiFePO_4/C. We synthesized Au attached LiFePO_4/C by two conditions, (1) addition of LiFePO_4/C in the solution before ultrasound irradiation, (2) addition of LiFePO_4/C to the solution after Au nanoparticles generation. 0.1mM [AuCl_4]^- aqueous solution was irradiated by 200kHz-ultrasound for 20 minutes in Ar atmosphere. 2-propanol was added into the solution before ultrasound irradiation. 2-propanol worked as a reductant under ultrasound irradiation. As a result, the size of the Au nanoparticles on the surface of LiFePO_4/C was 10 nm (from TEM). The figure of Au nanoparticles was spherical shape. Especially, the sample of condition (1) showed a lot of Au nanoparticles existed in the carbon layer. Therefore, Au-LiFePO_4 composite cathode material was effectively synthesized by ultrasound reduction of Au(III) in LiFePO_4/C suspension.

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Nano/micro-structured conducting polymeric materials are of great importance for the significant range of applications such as sensors and energy storage. In this work, we wish to report an electropolymerization in the acoustically prepared foam to obtain polypyrrole (PPy) film with microporous structure on an electrode surface. In this process, ultrasonication was used to foam the electrolyte solution containing surfactant and the foamy electrolyte was employed as soft template for the polymer growth. SEM analysis revealed that the obtained PPy film possessed a porous structure composed of a number of micropores. In addition, it was also found that the porous PPy film exhibited a higher electrochemical response compared to that of the ordinary flat PPy film. This fact can be ascribed to the large surface area of the porous PPy film. Since no hard templates and cumbersome procedures are require for this synthetic method, it is advantageous in respect of environmental and economic sustainability.

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Sonochemiluminescence (SCL) from aqueous lucigenin (Luc^<2+>) solution is described in this study. It is found that strong SCL was observed from oxygen saturated alkaline solution containing small amount of Luc^<2+> when tripropylamine (TPA) was added as coreactant. A possible pathway for Luc^<2+> SCL reaction is discussed. In the ultrasonic field, TPA can adsorb onto the cavitation bubble/solution interface where TPA is oxidized by OH^. to form TPA^<.+> and subsequently produce a highly reducing TPA^. from the deprotonation reaction of the TPA^<.+>. TPA^. is suggested to initiate the reduction reactions of Luc^<2+> and O_2 and lead to the generation of Luc^<.+> and O_2^<.->, respectively. The radical-radical coupling reaction between Luc^<.+> and O_2^<.-> is expected to initiate the light emission.

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This study was carried out with the aim of investigating the cavitation threshold from 24 kHz to 5 MHz by measuring broad integrated voltage of white noise emitted from acoustic cavitation. Additionally, thresholds of chemical and mechanical effects were experimentally studied. Potassium iodide oxidation dosimetry was used to examine the threshold of chemical effect. The threshold of mechanical effect was quantified by observing the degradation of polyethylene oxide in aqueous solution of tert-butanol which was radical scavenger. All thresholds increased with increasing ultrasonic frequency. However, as compared with cavitation threshold, thresholds of chemical and mechanical effects were relatively higher at low frequency range (24 kHz to 500 kHz). This is because a certain amount of cavities is needed to produce these effects. The threshold of mechanical effect at very high frequencies (1 and 5 MHz) slightly changed perhaps due to the elevated acceleration in solution.

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Ultrasound (US) effect on aqueous poly(ionic liquid) (PIL) solution was investigated in viscosity and FT-IR spectroscopy, after the US having 23, 43 and 96 kHz frequencies at 50 W were exposed. The viscosity of the PIL aqueous solution decreased in the present of the US and then increased gradually as the US was stopped within about 10 min. In addition, the behavior of the aqueous PIL was followed by FT-IR spectroscopy. The FT-IR band of the OH stretching was enhanced in the intensity by the US exposure. The band intensity could also return to the original value after the US was stopped. These results were observed cyclically to respond to the US on/off. From the analysis of the FT-IR spectra, the US influenced breakage and reformation of the hydrogen bonds of PIL and water.

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Ultrasonic emulsification is known to be useful in preparation of nanoemulsions, because use of surfactant can be reduced. Moreover, nanoemulsions with droplet diameters of around 100 nm can be prepared by sequential ultrasonic irradiation from low to high frequency. In this study, oil-in-water systems of toluene-water emulsions were prepared by ultrasonic emulsification and mechanical emulsification. Ultrasound emulsification was found to be more suitable than mechanical emulsification with a homogenizer. In addition, a two-step emulsification method was applied to preparation of emulsion. Crude emulsion was prepared mechanically in the first stage, and this was irradiated with ultrasound in the second stage. The droplet size of the emulsion was found to be influenced by the relationship between droplet size of the crude emulsion and ultrasonic frequency in the second stage. Moreover, polymerization of styrene was carried out using two-step emulsification method. Particle size of polystyrene was almost same as the droplet size of emulsion. Therefore, a two-step emulsification method was useful for preparation of nano polymer particles.

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Poly (N-Isopropylacrylamide-co-2-hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)) was synthesized using ultrasonic irradiation in a mixed solvent of water and ethanol without chemical initiator. Effect of ultrasonic intensity on time courses of conversion ratio, copolymer composition, number average molecular weight, and polydispersity of synthesized polymers was investigated in order to clarify the reaction mechanism of radical copolymerization of temperature-responsive polymer with low molecular weight distribution (i.e., low polydispersity). The reaction kinetic model for ultrasonic synthesis process of P(NIPAM-co-HEMA) was constructed with considering the cross-propagation reaction and cross-termination reaction in the radical copolymerization of NIPAM and HEMA. The experimental results showed that PNIPAM fraction of the copolymer in the early stage was lower than initial NIPAM fraction. Those results suggested that HEMA terminated radical was more stable than NIPAM terminated radical so that consumption rate of NIPAM was slower than that of HEMA. The calculated results supported that the cross propagation reaction between HEMA terminated radical and NIPAM monomer was much slower than that between NIPAM terminated radical and HEMA monomer.

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Numerical simulations of acoustic cavitation noise have been performed under the experimental condition of Ashokkumar et al. [J. Am. Chem. Soc. 129, 2250 (2007)]. It is shown that the broadband noise is mainly originated in the temporal fluctuation in the number of bubbles. In other words, the broadband noise is originated in transient cavitation if transient cavitation is defined as the cavitation of bubbles with short lifetime due to fragmentation. The broadband noise is also resulted from non-periodic (chaotic) pulsation of bubbles. When the number density of bubbles is very large, the broadband noise is intensified by the bubble-bubble interaction. The bubble-bubble interaction is the influence of acoustic waves radiated from neighboring bubbles on the pulsation of a bubble.

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An ultrasonic atomization has been used for various things such as a humidifier and so on. An ultrasonic atomizer with a piezoelectric element generates the ultrasound. If you put the ultrasonic atomizer in liquid, the liquid surface uplift occurred along the water column by the vibrational energy, the atomization phenomenon is observed at the tip. In this study, we atomized aqueous surfactant solutions using the ultrasonic atomizer, measured the particle size of water atomized. As a result, the particle size of aqueous surfactant solutions was larger than that of distilled water. Further the particle size of aqueous surfactant solutions adding the salt was larger than that of aqueous surfactant solutions. From these result the particle size was found likely to rely on the coastal micelle concentration.

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We have successfully synthesized polymer (PMMA) nanoparticles which reflect precisely the size of monomer (MMA) droplets formed by the tandem acoustic emulsification. This new synthetic method involves sequential ultrasonic irradiation (20 kHz → 500 kHz → 1.6 MHz → 2.4 MHz) for acoustic emulsification of a water-insoluble MMA monomer in an aqueous medium, followed by emulsion photopolymerization in the obtained solution at an ambient temperature without using any surfactants. The present method is clearly a powerful tool for the synthesis of size-controlled polymer nanoparticles.

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Copper nanoparticles(CuNPs) are expected to be novel wiring materials because of low sintering temperature and low-priced ingredients. CuNPs are usable as a ink for wiring. This ink printed on a circuit board conducts electricity after proper heat treatment. However, CuNPs oxidize easily in the air. To prevent oxidation of CuNPs, additional costly process are needed such as atmosphere exchanging into an inert atmosphere. On the other hand, organic compounds have been used as protectors for CuNPs, but these non-metallic coverings often reduce conductivity of CuNPs. Hence, Cu-Ag nanocomposites(Cu-Ag NC) have been considered as an alternative method to prevent oxidation. In this study, Cu-Ag NC were easily synthesized under high concentration condition by using ultrasonic irradiation. Ultrasonic irradiation was easily process to combine metal nanoparticles with other materials. However, CuNPs and silver nanoparticles repel each other in a solvent because of positively charged particles. To change charge of CuNPs, oxidization of CuNPs is available. CuNPs were purposely oxidized, then synthesis of Cu-Ag NC became easily. Cu-Ag NC were reduced on a glass substlate, and electric resistivity of the sample were decreased from 2.267 Ωcm to 1.690 × 10^<-4> Ωcm.

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Perfluorochemicals (PFCs) is one of the fluorinated organic synthetic oil, and has been used as heat carrier and hydraulic oil for a vacuum pump used in the semiconductor clean room. This substance has extremely strong carbon-fluorine bonds in the internal structure, and these carbon-fluorine bonds give high resistance to heat and react with other chemicals. However, PFCs is harmful to a human body, and has high global warming potential. In this study, we investigated the effects of 200 kHz ultrasonication and short-wavelength UV irradiation on the degradation of hydrophobic PFCs (perfluorooctane: PFO) and its decomposition intermediate products. As an intermediate product of PFO, we chose perfluorooctanoic acid (PFOA) pentafluoropropionic acid (PFPrA). 93.7% of PFO was decomposed after 60 min by 200 kHz ultrasonic irradiation, and the concentration of PFO after 120 min was below the limit of quantitation. Defluorination of PFO after 120 min was improved 2.1% by the combination of UV_<254+185> irradiation. From these results, it was confirmed that 200 kHz ultrasonic irradiation was more effective for hydrophobic perfluorochemicals like PFO, and UV254+185 irradiation was more effective for hydrophilic perfluorochemicals which is considered one of the decomposition intermediates of PFO.

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This study reports effects of horn diameter and suspension concentration on specific surface area of hydroxyapatite (HAp) synthesized by ultrasound irradiation. HAp was synthesized by Ca(OH)_2-H_3PO_4-H_2O system with ultrasound. The frequency of ultrasound was 20 kHz. Amorphous calcium phosphate (ACP) was formed just after a reaction, and then ACP crystallized sequentially in HAp. In the case of horn diameter 16 mm, the optimum condition of initial temperature was 30 ℃, and the suspension concentration was 12.25 mass%. The optimum amplitude was 70 %. In the case of horn diameter 6 mm, the optimum condition of initial temperature was 30 ℃, and suspension concentration was 8.75 mass%. The optimum amplitude was 30 %. The specific surface area of sample rose over time because ACP crystallized to HAp. When HAp became single phase, the specific surface area showed maximum value. However, the specific surface area of HAp decreased when reaction time became longer. The reason was for the crystal growth of HAp. The maximum specific surface area of HAp with horn diameter 16 mm and 9 mm were 330, 298 m^2・g^<-1>, respectively. However, if horn diameter was thin, the sound at the time of the synthesis was not too loud.

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Advanced oxidation processes (AOPs) are very effective techniques for degradation and mineralization of organic pollutants. On the other hand, ultrasonic atomization is a very useful technique to produce ultrasonic mist which consists of submicron-scale droplets. Using these techniques, volatile organic compound (VOC) gas was decomposed on the mist surface by OH radicals generated by AOPs, and water-soluble decomposition intermediates were rapidly captured into the mist. As a result, the removal rate of toluene under UV/H_2O_2/mist condition was faster than that under UV/H_2O_2 condition. This result indicated that toluene gas could easily react with OH radicals on the mist surface, using ultrasonic atomization, because gas-liquid interfaces increased by the mist generation. Furthermore, we tried degradation experiments of toluene gas under conditions with ozone addition. Ozone also reacts with H_2O_2 to generate OH radicals (perozone reaction) on the mist surface, and toluene gas was effectively removed there by perozone reaction. Since this reaction is effective for various VOC gases, it could be a useful air purification technique. Finally, we evaluated the chemical reactivity of VOC gas with ultrasonic mist from the viewpoint of AOPs reactions.

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Sonolysis of 0.1MKI-NaHCO_3 solution was carried out under Ar by an ultrasonic extraction apparatus (Honda Electronics UMS, 200 kHz and maximum power 15 W). The rate of sono-oxidation was evaluated by potassium iodide (KI) dosimetry at 355 nm using UV-Vis spectrophotometer (JASCO V-650). We had more rate below 1.5 mM NaHCO_3-KI solution compared with the KI solution without NaHCO_3. Over 1.5 mM solution of NaHCO_3, on the contrary, the rate fell down. Thus, sono-oxidation rate of I^- depended on concentration of NaHCO_3. We also observed multi-bubble sonoluminescence (MBSL) of NaHCO_3 solution. The intensity of MBSL fell down with concentration of NaHCO_3. Namely, cavitation intensity decreases in the presence of NaHCO_3 because NaHCO_3 reacts to CO_2 during sonication and the temperature in bubbles fall down by CO_2. The rate of sono-oxidation, however, increased in the solution with a small amount of NaHCO_3. It has been known that CO_2 quenches ^.H radicals, which are produced from solvent (H_2O). Remaining ^.OH radicals oxidize I^-. Therefore, NaHCO_3 in an aqueous solution could play the role of rate control of sono-oxidation under ultrasonic irradiation.

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Solution plasma can synthesize many kinds of nano-sized metal powder, such as Au and Ag. But calcium compound of nano-sized powder synthesized by solution plasma has not been confirmed. In this study, we tried to synthesize the hydroxyapatite with solution plasma and compared with specific surface area of HAp synthesized by ultrasound irradiation. The specific surface area of HAp with ultrasound was maximum 330 m^2・g^<-1>. On the other hand, the specific surface area of HAp with solution plasma had lower 14 m^2・g^<-1> than that of HAp with ultrasound. We examined optimum conditions, such as initial temperature, suspension concentration and pulse width. The crystal shape of HAp with solution plasma was thin plate-like and the particle size was 70nm.

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Ultrasonic degradation of PEG in aqueous solutions was investigated to elucidate the degradation mechanism. Some studies have concluded that the degradation mechanism for polymers is scission by mechanical effects via ultrasonication, whereas others have reported a chemical mechanism via species such as OH radicals. In this work, the effects of four alcohols (ethanol, 2-propanol, n-butanol and tert-butanol) on the ultrasonic (400 kHz) degradation of PEG were investigated. Result, the addition of the alcohol to the solution suppressed the degradation of PEG6000 in the order ethanol < 2-propanol < n-butanol < tert-butanol. In addition, sonoluminescence spectra from Ar saturated water were measured in the range of 250-370 nm to observe the spectral peak from OH radical emission of 310 nm. The effect of the type of alcohol for both the suppression of PEG degradation and the quenching of sonoluminescence is consistent. These results indicate that ultrasonic degradation of PEG6000 at 400 kHz is via a chemical mechanism, particularly by OH radicals. The alcohols act as radical scavenger, and the strength of scavenging effect was in the order ethanol < 2-propanol < n-butanol < tert-butanol.

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Hollow nanocapsules of polymer materials are expected to be used as carriers for drug delivery systems in medical applications. In this work, we have developed a simple and novel method for the preparation of hollow nanocapsules covered with polypyrrole (PPy) using nanobubble soft templates formed by ultrasonic irradiation. The key features of the method are an effective nanobubble generation by ultrasonication and its application for the template synthesis of nano-sized hollow particles. 20 kHz ultrasonic irradiation (250 W cm^<-2>) was carried out in an aqueous solution of pyrrole. By this operation, a large number of nanobubbles could be obtained. Subsequently, FeCl_3 aqueous solution was added to the pyrrole solution to drive the oxidative polymerization of pyrrole, and finally PPy nanoparticles were synthesized (nanobubble template method). As a result, by using this method, much more amount of nanobubbles could be obtained compared to the conventional bubble generation methods. Furthermore, we have successfully synthesized of PPy hollow particles ranging from 300 to 700 nm by using the nanobubbles as templates. This method would contribute to environmental sustainability since it doesn't require template removing process such as evaporation, thermolysis, and dissolution.

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Graphene has outstanding characteristics for electroconductivity, thermal conductivity and mechanical strength. It is possible that nanocomposites synthesized by combining graphene with Pt nanoparticles have unique characteristics (e.g. improving of catalytic activity). In this study, we have synthesized nanocomposites composed of graphene (or graphene oxide) and Pt nanoparticles under ultrasonic and gamma-ray irradiation fields. It is considered that Pt ions and graphene oxide are reduced simultaneously by reductive radicals formed from water and organic additives under irradiation fields.

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Hard chromium plating has been used to improve hardness, resistance to corrosion, friction and heat in various fields. However, alternative technology of hard chromium plating is desired because of toxicity of raw materials. Thus, we developed a novel method to fabricate a hard film by using Cr nanoparticles. Although this method is easy and environmentally friendly, Cr nanoparticles are expensive at present because Cr nanoparticles are synthesized by vapor deposition. In this study, we tried to synthesize Cr nanoparticles in solvent by ultrasonic decomposition of Cr(CO)_6. Cr(CO)_6 was fully decomposed by ultrasonic irradiation in decanol at 50 ℃ for 30 min. The product had a low crystallinity and particles sizes were about 5 nm. In TG-DTA, products exhibited weight loss (33 %) around 1000 ℃ in Ar by decomposition of organics. In XRD, Cr and Cr_2O_3 were observed after heating at 1000 ℃ in Ar. It is considered that surfaces of Cr nanoparticles were formed oxide shells of Cr_2O_3 as passive layers. When the atmosphere was changed from Ar to air in 1000 ℃, products exhibited weight gain due to oxidation of Cr.

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Large amount of glycerol has been generated as a byproduct in the synthesis of biodiesel fuel and their effective utilization ways have been explored. Our previous studies have shown that addition of glycerol effectively enchanced photocatalytic hydrogen evolution. In this study, we investigated photocatalytic reforming of glycerol aqueous solution under sonication. In photocatalytic reforming of glycerol aqueous solution, hydrogen and carbon dioxide mainly evolved. On the other hand, in the presence of sonication, a large amount of carbon monoxide evolved but hydrogen and carbon dioxide decreased, which can be explained by contribution of sonochemically generated hydroxyl radicals.

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Recently, it has been reported that photocatalytic reaction drives using ultrasonic (US) irradiation even under dark condition. However, its mechanism does not become clear in detail. In this study, we evaluate the removal ratio of organic compounds in water phase based on photocatalytic activity with 50 kHz US irradiation under dark condition. In order to clarify the influences of TiO_2 crystal structure and the physical properties of target compounds, three crystal types of TiO_2 and two different aldehydes such benzaldehyde (C_6H_5CHO) and formaldehyde (HCHO) were used for degradation experiments. TiO_2 (P25) suspension with US irradiation under dark condition (US/P25) enhanced removal ratios of both aldehydes, from 8.2% (US only) to 17% (US/P25) in HCHO, and from 43% (US only) to 57% (US/P25) in C_6H_5CHO. On the other hand, the effect of crystal structure of TiO_2 was evaluated by comparing US/P25 with US/ST21. In the case of using TiO_2 including rutile type structure (P25), the removal ratio was slightly improved in C_6H_5CHO. Furthermore, US/ST21 was compared with US/ST01 from the viewpoint of the particle size. US/ST01 with smaller particle size enhanced removal ratio in C_6H_5CHO. In all experiments, no change of removal ratio was confirmed in HCHO indicating that TiO_2 crystal structure and the physical properties effect on removal ratio of hydrophobic compound. Thus, it was estimated that photocatalytic reaction by US/TiO_2 could be occurred in hydrophobic field near the cavitation bubble.

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The emission from the excitied state of OH radicals has been observed from water in single-bubble sonoluminescence (SBSL). We present the experimental results exploring the correlation of OH emission with bubble instability. This emission was observed at low acoustic pressures where the intensity of continuum emission is very small. We examined the dependence of the dissolved Ar pressure on the OH line spectra in SBSL. Using a high-speed shadowgraphy, we observed the bubble trajectory, indicating that the OH emission originates unstable bubble that repeats fragmentation and coalescence. It is suggested that the variation of OH spectra is caused by the lowering of bubble collapse temperature or the formation of ArOH exciplex.

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Hydroxyl (OH) radicals are produced by many methods such as ultrasound (US) irradiation and ultraviolet (UV) irradiation in the presence of photocatalyst. The OH radicals are reactive species and can oxidize hazardous organic substances into non-hazardous ones such as carbon dioxide and low molecular substances. In addition, ultrasonic irradiation of liquid causes atomization at the surface of the liquid bulk. In this work, we investigated the synergistic effect of US irradiation and UV irradiation on chemical oxidation rate using TiO_2 photocatalyst. The oxidation reaction of KI in aqueous solution was used to evaluate the effect. Results demonstrated that the rate constant of KI oxidation by simultaneous treatment of US/UV was higher than the sum of respective rate constants obtained by only US treatment and only UV treatment. Especially, when ultrasonic mists as well as solution bulk under ultrasonication were irradiated with UV, the oxidation reaction was significantly promoted. These results may suggest that efficient photocatalytic reactions are achieved via the production of ultrasonic mists not only containing photocatalyst particles but also having a higher specific surface area which are probably more favorable for effective irradiation with UV.

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Recently, scorodite has been studied as a promising storage material for arsenic. Scorodite is synthesized through a solution method using pentavalent arsenic [As(V)] and divalent iron [Fe(II)] in an acidic solution. The particle size of scorodite can vary but larger ones are preferred because the low surface-to-volume ratio makes it difficult to dissolve in an acidic solution. In the solution method, large scorodite particles (>10 μm) are synthesized at high temperature (>90℃) with a long reaction time (7 h). The high reaction temperature is an important factor in synthesizing scorodite with large particle sizes. In this study, we investigated the effect of reaction temperature (30℃) during ultrasound irradiation on the size and morphology of synthesized scorodite particles. When the scorodite is synthesized using stirrer with H_2O_2, ORP and yield showed higher values and it means that oxidation of Fe(II) was promoted in the reaction solution. However, we confirmed crystallization of scorodite when using ultrasound alone. The reason behind this may be due to the oxidation promotion by cavitation during ultrasound irradiation. We consider that oxidation promotion led to synthesize the scorodite with a short reaction time. To the best of our knowledge, this is the first report on the synthesis of scorodite at low temperature (30℃) using ultrasound irradiation.

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Arsenic in Acid mine drainage (AMD) is treated by coprecipitation method using a coexisting ion (Fe). Precipitate is generated at coprecipitation method by neutralization of the solution. The precipitate, sludge, containing arsenic is stored in the sludge storage dam. Therefore, decreasing the amount of sludge is a necessity. We consider that arsenic removal before the neutralization makes iron-based precipitate which can be used as an iron resource. Thus, we are investigating the adsorbent of arsenic which works in strong-acidic solution. Previous study on goethite showed effective performance at acidic region. The particle size of goethite is very fine. And it makes solid-liquid separation after adsorption of arsenic difficult. Recently, the porous iron oxide is promising because it has high adsorption capacity of arsenic and the particle size is larger than that of goethite. Porous iron oxide is synthesized from scorodite or iron phosphate using alkaline solution. The size and morphology of porous iron oxide maintains that of the origin materials after the treatment of alkaline solution. Thus in this study, synthesis of iron phosphate with large size is attempted using ultrasound effects. The synthesized iron phosphate had a diameter of about 1 μm and the morphology was spherical. Porous iron oxide was successfully synthesized from synthesized iron phosphate using alkali solution and the size and momhologv were maintained (about 1 μm and spherical).

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we investigated the effect of the concentration of calcium chloride on the morphology and size of calcite particles synthesized using ultrasound irradiation. Calcium carbonate was synthesized by addition of calcium chloride solution (0.01, 0.05, 0.10, 0.20 M) into CO_2-MEA solutions. To confirm the effect of ultrasound, we also investigated using stirrer at 1500 rpm for 5 min (without ultrasound). Crystal structure of calcium carbonate was identified using XRD and SEM. The particles synthesized under ultrasound irradiation were rhombohedral, and particle size was about 2-3 μm uniformly. This crystal structure was calcite. On the other hand, particles synthesized with stirring was spherical and the particle size was about 5μm. This crystal structure was identified as mainly vaterite by XRD analysis. The sample synthesized under ultrasound irradiation was calcite and that under stirring was a mixture of vaterite and calcite unrelated to the Ca/MEA ratio.

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Mg/Al-NO_3 Layered Double Hydroxide(LDH) has been studied as an arsenic adsorbent. However, the adsorption performance of As(III) is low. For As(V), the adsorption rate by Mg/Al-NO_3 LDH was the highest (77.4%) at pH 3 and the lowest (56.9%) at pH 8. On the other hand, in regards to As(III), the adsorption rate of arsenic was the lowest at pH3 and the highest (40.2%) at pH8. Hence, we know that regardless of the pH value, Mg/Al-NO_3 LDH has higher adsorption performance for As(V) compared to As(III). In this study, Mg/Al-NO_3 LDH and ultrasound oxidation were used to improve the adsorption performance of arsenic. In this experiment, by using ultrasound oxidation, within As(III) solution (76.2 ppm) was prepared and ultrasound was irradiated into the solution for 2 hour. 38.7 ppm of As(III) was oxidized to As(V). When using Mg/Al-NO_3 LDH under ultrasound oxidation for 76 ppm of As(III) solution, we found that after adsorption experiment of the solution, almost all of As(V) was adsorbed. Moreover, adsorbed amount (35.2 ppm) of arsenic from the solution using Mg/Al-NO_3 LDH under ultrasound irradiation is almost same amount of oxidized (38.7 ppm) from As(III) to As(V) by ultrasound oxidation (previous experiment). Therefore, we believe that adsorbed arsenic consists almost entirely of As(V). We concluded that Mg/Al-NO_3 LDH can work as an arsenic adsorbent at pH3 for As(V). Thus we planned to use the ultrasound not only oxidation of As(III) but also pH adjustment using HNO_3 and HNO_2 generated.

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The multibubble sonoluminescence (SL) from glycerin solutions saturated with krypton were measured at frequencies of 50.2 kHz, 81.3 kHz and 150.7 kHz and the power of 20W. We found that the SL intensity increased at the concentration of 80%. We observed characteristic behavior of bubble dynamics using high-speed photography in glycerin solutions. At higher concentrations, we observed large cloud bubbles emitting many tiny bubbles.

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Our previous study demonstrated growth enhancement of glycine particles in the crystallization under the irradiation of 1.6 MHz ultrasound. The result indicated that ultrasound enhanced mass-transfer around the solid particle in the suspension. To specify the effect of ultrasound contributing the enhancement, we took a simpler approach of observing dissolution of a sparingly soluble compound, benzoic acid, in water under the ultrasonic irradiation. Particles of benzoic acid having a limited size range were mixed into water under a mechanical stirring and sonication. At higher ultrasonic powers, rate coefficients for the dissolution strongly depend on ultrasonic power, which suggests that the ultrasound plays the major role in the enhancement. Even at this condition, the enhancement was lost by the use of degassed water as a solvent. This fact clearly shows that cavitation plays a significant role in the mass-transfer enhancement.

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Effective cascade extraction of sugar, vitamin E and vegetable oil has been studied by sonolysis of oil seeds. With low frequency ultrasound lower than 50 kHz, three components could be effectively extracted by water, methanol and hexane. Extracted components were degraded with higher than 100 kHz ultrasound. γ-tocotorienol which is the most important Vitamin E was extracted at high concentration of 0.51% of seed (w/w%) in Calophyllum inophyllum and 0.174% in Vernicia montana. Phitosterol, which is well known as the medicine to reduce the concentration of cholesterol in blood, could be effectively extracted with methanol or 80% ethanol aqueous solution. If we will be able to establish the system to produce BDF with γ-tocotorienol and phitosterol, which can be sold more than 100 times higher than oil, BDF price will be lower than petroleum light oil.

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Surface tension of any fluid is crucial for multiphase systems and is often manipulated during industrial processes by introducing surfactants. Normally, water used in an industry includes impurity such as salt. In this study, effect of NaCl concentrations on surface tension of aqueous solution, which is treated with bubbling process of CO_2 or N_2, was investigated under microwave irradiation. It has found that surface tension decreased quickly, while temperature increased during microwave. Once the radiation is turned off, the temperature returns rapidly as expected. However, surface tension recovery was much slower than temperature. Moreover, the reduction amounts obtained by non-thermal effect depend on salt concentrations and gas type. For example, effect of dissolved gas was obtained for CO_2 gas. Solubility of CO_2 is higher than that of N_2, and larger amount of CO_2 gas is released during microwave heating. The release prevents formation of nano-bubbles or cluster network of water molecules, which play important roles for surface tension reduction during microwave irradiation because the growth of larger bubbles captures smaller bubble. On the other hand, N_2 is not dissolved so much. Bubble formation of N_2 does not affect nano-bubble formation so much. Accordingly, similar non-thermal effect for surface tension reduction was obtained in case of N_2 gas.

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Anodic stripping voltammetry (ASV) with a hanging mercury-drop (or mercury film) electrode has been regarded as a versatile and sensitive analytical technique for monitoring environmental and clinical trace metals. However, the toxicity of mercury and the potential risks of it during disposal make it undesirable to use. Recently, mercury-free electrodes have been gained much attention. With solid electrodes, it is common to encounter the problems due to the lower preconcentration efficiency and the formation of intermetallic species at the electrode surface. Our previous studies have shown the advantages of using ultrasound in stripping analysis because acoustic streaming increases the mass transport of the system resulting in shorter deposition times, greater sensitivity and a corresponding lowered detection limit. The main purpose of this work is to further investigate the effects of ultrasound on ASV of trace Cu^<2+> at a gold electrode with a view to developing sono-ASV as an electroanalytical procedure.

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Aqueous aromatic diaminos (such as DAB and CPDA) (0.3 mM) were exposed ultrasound (US) with 141 kHz at 50 W out-put for generating triazole compound in US medium. After the US was exposed, fluorescence spectra of aromatic diaminos were measured to observe the generation of triazole compounds in US medium. The DAB and CPDA fluorescent band in the spectra was decrease at 340 nm and 355 nm and increased at 560 nm and 565 nm by the exposure, respectively. Also, it was observed that triazole band appeared at 560 nm and 565 nm after the US exposure. These results indicated that it enables to generate triazole compound by reacting of aromatic diaminos with NO_2^- formed in US medium.

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Naked gold nanoparticles synthesized through sonochemical reduction of gold chloride ions remained well dispersed in water even in the absence of any stabilizing agents such as alkylthiols and surfactants. In this work, we examine the mechanism on the colloidal stabilization of naked gold nanoparticles in water. We found that the naked gold nanoparticles dispersed in water were precipitated with the addition of sodium chloride into the naked gold nanoparticle dispersion. This suggests that the naked gold nanoparticles are dispersed in water by electrostatic repulsive interaction. Furthermore, we revealed that the naked gold nanoparticles dispersed in water were precipitated under dark condition. The zeta-potential of naked gold nanoparticles with -40 mV decreased with the elapsed time after the naked gold nanoparticle dispersion moved to dark condition from light condition. This indicates that the precipitation of naked gold nanoparticles under dark condition is caused by the decrease in the electrostatic repulsive interaction among naked gold nanoparticles. Namely, the colloidal stabilization of naked gold nanoparticles in water under light condition is most likely due to the increase in the surface change of naked gold nanoparticles induced by light.

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Recently we showed novel sonochemical preparation of carbon spheres (CSs) in solution at room temperature and atmospheric pressure. Furthermore, we could produce CSs from various substituted benzenes. FTIR spectra of CSs are mutually alike. Elementary analysis of CSs from styrene and toluene gave mutually similar results. Therefore, it is thought that reaction mechanism of CS formation is possibly similar. In order to clarify the mechanism of production of CS, we investigated products at the early stage of reactions from styrene and toluene by GC analysis. The results suggest that ultrasonic advanced oxidation of aromatic compounds starts the present CS formation and benzaldehyde is possibly a key material on CSs formation.

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The effects of inorganic salts (Na_2SO_4 or NaCl) on the rates of sonochemical degradation of phenolic compounds (4-chlorophenol, phenol, catechol and resorcinol) were investigated under argon. It was suggested that the rate of sonochemical degradation of phenolic compounds was affected by the following two points: the changes in argon solubility in the solution and the changes in pseudo hydrophobicity (diffusion behavior) of phenolic compounds. The decrease in argon solubility at higher salt concentration resulted in the low sonochemical efficiency: the yield of H_2O_2 formed decreased with increasing salt concentration. This effect should decrease the rate of degradation of phenolic compounds. In addition to this effect, it was suggested that phenolic compounds more easily accumulated at the interface region of the bubbles at higher salt concentration, resulting in the increment of the rates of sonochemical degradation. This effect should increase the rate of degradation of phenolic compounds. Taking into account these effects, the observed salt effects would consist of a positive and negative effect so that the salt effects were observed as an unclear effect.

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