Mechanism of ethanol separation from its aqueous solution through ultrasonic atomization is discussed from an aspect of evaporation. Difference between ethanol and water evaporation rate is examined without irradiating ultrasound. With changing the mixing strength in gas and liquid adjacent to the liquid surface, simple evaporation experiments are carried out for three contacting modes. The first is that both gas and liquid are disturbed, the second is disturbed gas and quiescent liquid, and the third is that both gas and liquid are quiet. The result suggests that selective ethanol evaporation occurs from well-stirred both gas and liquid. Such a liquid surface is seen at the liquid fountain jet formed above of the oscillator. Thus, ethanol evaporates selectively from the fountain jet. In addition, evaporation of water is slightly enhanced from stirred gas and quiescent liquid. The preferential evaporation contributes to form fine liquid droplets enriched with ethanol within the vapor phase.

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Sonochemical synthesis of various types of nanoparticles and nanostructured materials has received much attention in recent years. This is due to the unique reaction routes induced by acoustic cavitation in solution: the acoustic cavitation provides extreme conditions of transient high temperature and high pressure within the collapsing bubbles, shock wave generation and radical formation. The sonochemical reduction of Au(III) to produce Au nanoparticles was performed in the presence of a small amount of 1-propanol at different frequencies. Ultrasonic irradiation was carried out with two types of ultrasound irradiation systems: a horn type sonicator (20kHz) and a standing wave sonication system with a series of transducers operating at different ultrasound frequencies (213kHz, 358kHz, 647kHz, 1062kHz). An aqueous solution of HAuCl_4 (0.2mM, 70mL for 20kHz, 200mL for the others frequencies) was added to the reaction vessel and then purged with argon. As an accelerator for the reduction of Au(III) ions, 1-propanol was injected into the solution. The synthesized Au nanoparticles were analyzed by TEM. The rate of sonochemical reduction of Au(III) to produce Au nanoparticles in aqueous solutions containing 1-propanol has been found to be strongly dependent upon the ultrasound frequency. The size and distribution of the Au nanoparticles produced can also be correlated with the rate of Au(III) reduction, which in turn is influenced by the applied frequency. Our results suggest that the rate of Au(III) reduction as well as the size distribution of Au particles are governed by the chemical effects of cavitation and are not significantly affected by the physical effects accompanying ultrasound induced cavitation.

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The sonophotocatalytic degradation of endocrine disruptors was investigated. The synergy effect of sonophotocatalysis was studied. In order to examine the synergy effect of a combined method of photocatalysis and sonolysis, the degrasdation of endocrine disruptors was carried out. Degradation of 2,4-dichlorophenol, p-chlorophenol, bisphenol A and di-n-butyl phthalate were performed by three methods; sonolysis, photocatalysis and sonophotocatalysis. The degradation rate for 2,4-dichlorophenol, p-chlorophenol and bisphenol A by sonophotocatalysis was faster than that for sonolysis or photocatalysis. For endocrine disruptors, the degradation rate of substrate was addictive sum of photocatalysis and sonolysis. But, the mineralization rate of sonophotocatalysis was faster than the sumof sonolysis and phtocatalysis. Thus, synergy effect was achived.

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Various purification techniques are researched for water effluent treatment and environmental water clean-up. As one of those techniques, ultrasound (US) and the combined technique of ultraviolet irradiation (UV, main wavelength: 365 nm) with TiO_2 photocatalysis (UV/TiO_2) has been researched. It has been reported that the combined use of US with UV/TiO_2 (US/UV/TiO_2) synergistically improved the VOC degradation efficiency in water treatment. However, this synergistic effect has a large extent of unexplained features. Especially, reports about the influence of the characteristics of the organic matter are very few. Therefore, in order to clear this influence, degradation experiments using model substances with different characteristics such as benzaldehyde (C_6H_5CHO) and formaldehyde (HCHO), were carried out, considering about the behavior of decomposition products generated from the model substances. As a result, low degradation ratio was confirmed when using US for highly hydrophilic organic matter and low concentration organic matter, and also it was confirmed when using UV/TiO_2 for high concentration organic matter. However, because of the synergistic effect between ultrasound and the photocatalytic reactions, these disadvantages were improved and high concentration organic matter was completely decomposed.

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Introduction Sol-gel derived anatase phased TiO_2 powder was prepared by hydrolysis of titanium tetraisopropoxide (TTIP) developed under ultrasonic irradiation having different frequency. The ultrasound (US) influenced on the particles size of TiO_2 powder and the effect of US on the formation of fine particles was controlled by using reflection technique, in which the semi-cylindrical reflection plate was placed onto the vicinity of reaction vessel to make fine TiO_2 powder. We also examined photo-decomposition of rhodamine dye by the resultant TiO_2 under light irradiation. Experimental TiO_2 powder was synthesized by the hydrolysis of (0.125 mol) ITIP in the presence of 10% ethanol-water mixed solution under different frequency ultrasounds (28, 45, 100 kHz with 300 W/cm^2) for 1h at room temperature. The sol sample was aged to complete hydrolysis reaction for overnight. The precipitated TiO_2 particles were separated by centrifugation (3000 rpm) and dried at 100℃ for 8h. Dried sample was grinded and sintered at 300℃ for 1h. Characterization was accomplished by particle size distribution and Fourier transform infrared (FT-IR) spectroscope. The properties of US associated sol-gel derived TiO_2 powder was evaluated by photocatalytic decomposition activity to 10μM rhodamine dye. Results and discussion We found that the resultant sol-gel derived TiO_2 particles size was depended on the US intensity. The average TiO_2 particle size prepared in the absence of US was 52μm and 16, 28 and 50μm for TiO_2 particle prepared under 28, 45 and 100 kHz of US irradiation, respectively. For the preparation of TiO_2 particle under reflected US, the observed particle size was 11, 18 and 27μm as respective frequency 28, 45 and 100 kHz. It was examined that US frequency can controlled the particle size of resultant TiO_2 particle and US reflection technique is distinctly influenced at 100 kHz. Photocatalytic activity was determined by degradation of 10μM rhodamine percolate solution under UV irradiation. Changes of rohdamine percolate concentration were traced with decline of the absorption peak at 576 nm. The resultant absorbance data showed that the decomposition rate of the rhodamine dye was low with the sample prepared in the absence of US irradiation. It was known that the TiO_2 powder prepared under 28 kHz US had higher decomposition rate than those of 45 and 100 US. Further, it was presented that the reflection US technique was also affected to the decomposition of rhodamine percolate.

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The methanolysis of triolein was investigated as functions of an amount of (KOH) and molar ratio (triolein/methanol) by using ultrasonic irradiation to make methyl esters. From the results obtained, we have found the optimum condition to make methyl esters. In addition, the effect of sonication on the methanolysis of triolein was discussed in comparison to that of the sterring.

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Time-resolved measurement of single flash light from Single Bubble Sonoluminescence has been succeeded. In order to accomplish the measurement, we needed to satisfy the following schemes simultaneously. 1. high sensitive measurement 2. ultrafast time-resolved measurement 3. chromatic aberration free measurement 4. stable sonoluminescence under stable condition 5. well controlled experiment It was proved that the pulsewidth of SBSL was about 150 ps.

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Spectra of multibubble sonoluminescence (MBSL) were measured in ethanol solutions at the frequencies of 116 kHz and 1.0 MHz. Ethanol was added to argon-saturated water in the concentration range of 2mM-100mM. The MBSL spectra showed that the quenching of peaks attributed to OH radicals was more efficient than that of broadband spectrum. The concentration dependence of spectrum quenching indicated no frequency dependence. A new peak was observed at 385nm only at small ethanol concentrations and at the frequency of 1.0MHz. This peak was attributed to CH or CN molecule emission. In order to examine the scavenging effect of ethanol on OH radicals, KI oxidation dosimetry was performed. The results showed that the OH radicals still exist at 100mM where complete MBSL quenching occurs.

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The new semiconductor cleaning system by means of radicals generated by acoustic cavitation has been studied. In the high temperature and high pressure field generated by cavitation collapse, water is thermally decomposed to OH radical and H radical. In order to make radicals more effectively, it is very important to analyze in detail the relationship between the generation of radicals and the behavior of acoustic cavitation. In this study, we measure the amount of OH radicals generated by acoustic cavitation, and observe cavitation by using high-speed camera. First, the amount of OH radicals in the focused ultrasound field was measured with KI dosimetry. This time, the ultrasound was irradiated to Ar-saturated and He-saturated water. In both cases, the amount of radicals increased as the amplifier output increased. Comparing both cases, the amount of radicals in the case of Ar was larger than that in the case of He. Second, the acoustic cavitation was observed by high-speed camera. When ultrasound amplifier output increased from low level, cavitation occurred at the focal point of ultrasound firstly. As the output power became larger, the cavitation generated from the front of geometric focal point of the transducer. At much higher output, cavitation density became very high, and the density at the geometric focal point decreased. Comparing the cavitation behavior in Ar-saturated water to that in He-saturated water, the outline of cavitation distribution was almost same. But in the case of Ar, the cavitation density was larger. It is indicated that this result is related to solubility; the solubility of Ar is higher than that of He. This is one of the reasons that more amount of radicals is generated in Ar-saturated water than in He-saturated water.

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Recently, electroconductive polymer/carbon composites have been received much attention since they are promising materials for electrochemical capacitor with high capacitance. The capacitance of the composites depends greatly on their structures, and therefore the synthesis of composites having highly-regulated structure is important subject in this research field. Meanwhile, it is well known that ultrasound provides the extreme conditions, such as high temperature (over 5000 K), high pressure (over 2000 atm) and high-speed mass transfer, by the collapse of the cavities within a liquid. It can be expected that these extreme conditions introduce the novel synthesis of composites having highly-regulated structure. In this study, we prepared the polypyrrole (PPy)/vapor grown carbon fiber (VGCF) hybrid composites and investigated their structural and electrochemical properties. The nanocomposites were prepared by chemical deposition of PPy on VGCF with and without ultrasonication. As the result, the morphology of PPy film deposited on VGCF with ultrasonication was highly uniform. In addition, the electric capacity of the composite prepared with ultrasonication was higher than that without ultrasonication. Thus, the composites prepared with ultrasonication may be applied to high-performance electrochemical capacitor.

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Photocatalytic production of H_2 from aqueous solution of ethanol was studied using Pt/TiO_2 photocatalysts prepared by sonochemical reduction method. Aqueous solutions of chloroplatinic acid and polyethylenglycol monostearate were sonicated under argon atmosphere (200 kHz, 6 W/cm2) for 30min to form Pt colloidal dispersion. This dispersion was mixed with TiO_2 (better than 99.5%, P-25, Japan Aerosil Co. ) and followed by extended sonication. After filtration and drying(50℃, 12h), Pt nanoparticle supported TiO_2 was obtained. Beside sonochemical method, conventional impregnation method was also employed to prepare samples. Obtained samples were dispersed in an aqueous solution containing ethanol. The suspension was purged of air with argon flow and illuminated by amercury xenon lamp and generated H_2 was monitored. In the case of TiO_2 only, the generation of H_2 was hardly detected. When Pt nanoparticles were supported on the surface of TiO_2, the activities were enhanced probably due to the restrain effect of Pt for the recombination of holes and electrons. It was clear that the sonochemical catalysts showed higher activities than the conventional ones.

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We examined ultrasonic polymerization behavior of methyl 2-acetamidoacrylate (MAA) in the presence of various sodium salts. The rate of polymerization of MAA decreased in the presence of sodium halides. In particular, the polymerization of MAA was inhibited by sodium iodide. On the other hand, the rate of polymerization of MAA hardly changed by sodium sulfate. When adding sodium sulfate at a high concentration ([Na_2SO_4]=0.65M), the reaction solution became clouded after ultrasonic irradiation and the polymer adhered to the surface of solution and the side of the glass cell. The molecular weight (M_w) of PMAA decreased with sonication time in pure water due to polymer chain scission, while the decrease of M_w was not observed in the sodium sulfate solution. This result indicates that the chain scission did not occur because of the aggregation of PMAA produced.

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Various ketones were reacted with TiCl_4 and Zn under ultrasonication(using Sus-4005C, 50W, 40kHz) to give the corresponding coupling dimmers. Ketones were substituted with methoxy, hydroxy, acetoxy and bromine on the benzene ring. Using ultrasonication, the reaction time and yield of the reductive coupling reaction were changed for the better. Typical reaction was as follows. Substituted acetophenones(2.84 mmol) were dissolved in THF. The solution was added with TiCl_4 (4.60 mmol) and Zn (9.07 mmol) in THF at 0℃ and the reaction mixture was ultrasonicated under argon. The reaction mixture was added by sodium hydrogencarbonate solution and extracted with ethyl acetate. The ethyl acetate solution was concentrated in vacuo and the concentrated solution was chromatographed over silica gel, eluted with hexane-ethyl acetate, to give the corresponding dimer in good yield. [chemical formula] [table]

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Sonophotocatalysis of oxalic was performed using various kinds of photocatalysts such as TiO_2 coated glass beads and Pt loaded TiO_2 in an Ar atmosphere. The products of sonophotocatalysis were carbon dioxide, carbon monoxide, and hydrogen in the gas phase. The yield of carbon dioxide using glass beads was twice larger than the sum of yields of photocatalysis and sonolysis. Thus, synergistic effect was observed using not only powdered photocatalyst but also TiO_2 coated glass beads. The glass beads photocatalyst could be reused.

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Oscillations of gas bubble confined in a microspace, such as a microchannel of a few hundred micrometer width and depth, were observed with a video microscope and stroboscopic technique using a semiconductor laser operated in a pulsed mode. By virtue of the stroboscopic technique, we can observe the time resolved bubble oscillations in real time with a video monitor. However, the oscillation should be stable for the observation period, such as for a few seconds. A number of interesting oscillations of a gas bubble was observed when the bubble is tethered on a wall; a symmetrical breathing mode oscillation, a higher order spherical harmonic oscillation, a surface wave oscillation (Faraday wave), and a repetitive transient cavitation mode. Also, around the oscillating bubble, microstreaming of different modes and strength were observed depending on the size of bubble, input power and ultrasonic frequencies.

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Recent advances in the cavitation research urge us to take on a new picture of cavitation dynamics. Cavitation used to be regarded as a hot spot arising from adiabatic compression - a combined viewpoint of thermodynamics and hydrodynamics. However, sonoluminescence has revealed the existence of excited molecular species such as OH^* and C_2^*, suggesting that cavitation be understood with chemical processes taken into account. These species are commonly observed in flame and combustion, which can be modeled by a combined model of chemical dynamics and hydrodynamics. With the understanding that molecular aspects of cavitation are expected to become more and more important, chemical processes in the combustion are reviewed, and similarities and dissimilarities between cavitation and combustion are discussed. First, the well-known D-line emission of Na(^2P) from the injection of a NaCl solution into flame is discussed, since the same emission is also observed for the cavitation within saline water. The subtle nature of the third body, usually denoted by M, is pointed out. Tables of rate constants list those involving M, but they may be specific to the nature of combustion, and it may be misleading to adopt the values of such rate constants in the computer simulation of cavitation unless the environments are similar in the composition of chemical species. Finally, the dissociation of H_2O, one of the most fundamental elementary reactions within cavitation, is discussed on the basis of thermal and collisional excitations. In the former model, the dissociation is a result of thermal excitation of asymmetric stretching of H_2O. The latter dissociation model may have relevance to unimolecular reactions. It may also be characterized by an activated complex H_2O…M if M is a water molecule. To conclude, cavitation research will benefit from a close cooperation with conbustion science and quantum chemistry.

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In this study, pulsed ultrasound hydrodynamic modulation (PUHM) voltammetry was developed for determination of trace components in small sample volumes. With this method, the current components corresponding to ultrasonic pulse-on and pulse-off can be recorded separately, and the current difference between the two states was found to be proportional to the concentration of the electroactive species. Because the current difference is essentially free of high background interference arising from electrode surface processes, solvent decomposition and double-layer charging which are observed in normal voltammetric measurements, relatively lower detection limits were achieved. The analytical usefulness of this approach was exploited for determination of ferrocyanide ion in small sample volume as low as 200μl with the detection limit of sub-micromolar level. It also demonstrates the considerable promise of this technique for the detection of electroactive species in a region of the potential window normally obscured by solvent from the result of Ru(bpy)_3^<2+> determination.

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At the conventional production method of emulsion fuel, it was very difficult to mix water into oil minutely and homogeneously, which means that combustion of emulsion fuel was unstable and not able to use it as fuel for a diesel engine. It was mainly due to the lack of agitation ability for high quality emulsion fuel. Therefore, the production tests for the minute, homogeneous and water in oil type emulsion fuel were tried, by the method of using strong diffusion ability of ultrasonic cavitation. High shock wave area is created between the ultrasonic transducer horn and the reflector, both of which are immersed in the water. The test was executed by the method to agitate water and the fuel in this high shock wave area. The test equipment consists of ultrasonic transducer, mixing tank, metering pump and pipe structure. Then, fixed quantity of fuel and water were supplied to mixing tank. Gas oil and fuel oil were used as the test material oil and a small quantity of emulsifying agent was dissolved in the fuel, beforehand. Tap water was used as water material and mixed into oil with three kinds of volume ratio. The aimed quality was that emulsion fuel is water in oil type, submicron size homogeneous water, and its continuous stable period for five days. For the measurement of the water particle diameter, the light microscope, the electron microscope, and dynamic light scattering method were used. The deterioration of emulsified fuel was checked by observing the test liquid in the sample bottle at stable condition. The water particle diameter was measured with three kinds of different measurement method. And, it was confirmed that the diameter was approximately 0.2μm or less. The quality of emulsified fuel was maintained for five days or more, in all mixing test. As the result of our development, the technology to agitate water and oil minutely and homogeneously were developed and established, by the method of creating high shock wave between the ultrasonic transducer horn and reflector and adjusting the gap and liquid volume. It became possible to produce high quality emulsion fuel continuously, which can be used as fuel for diesel engine.

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Although rings of carbon nanotubes (CNTs) are predicted to have interesting magnetic properties, facile preparation or isolation methods of the rings with high purity are not yet reported. We describe here a convenient method for the isolation of ring- or coil-shaped single walled carbon nanotubes (SWCNTs) using ultrasonic atomization. A suspension of SWCNTs was bath-sonicated at 20℃ and the resulted mist above the surface was exposed to the flow of air (Figure 1). The black solid flowed down into the container (Teflon tube) was found to consist of ring- or coil-shaped SWCNTs exclusively by TEM analyses (Figures 2 and 3), while the ones from other parts of the glassware and residue included only little amount of the rings or coils. They have round or oval shape with 1.0-3.3μm in diameters, and some of them may be interlocked. The method presented here is very practical to isolate one specific shape of CNTs from the mixture by combined use of ultrasonic atomization and carrier gas. We believe that this finding accelerates the science and application of ring- or coil-shaped CNTs.

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Some factors that enhance or inhibit the bioeffects of ultrasound were investigated and possible mechanisms explored. The findings: (1) Low intensity, nonthermal ultrasound enhanced hyperthermia-induced apoptosis (2) A nonthermal hypotonia enhanced the ultrasound-induced cell killing due to increased susceptibility of the swollen cells and inhibited repair of damaged membranes. (3) Some agents, including known anticancer drugs and a temperature-dpendent free radical generator, enhanced the US-induced bioeffects. (increased uptake of the agent was likely involved). (4) Bioeffects can be enhanced by echo-contrast agents (ECAs) and can be inhibited by carbon dioxide, suggesting the role of cavitation in the bioeffects (Mechanical membrane damage is apparently a pivotal event in the bioeffects). and (5) The cell killing significantly declined at densities 10x10^6 cells/ml and above. At 2x10^6 cells/ml, incubation inhibited cell killing time dependently. However, at the inhibited conditions, cell killing was observed when cells were sonicated with ECAs. In summary, enhancing factors are potentially useful for therapeutic and biochemical applications of ultrasound, while inhibitory factors are also important in modulation the effects of ultrasound.

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We propose the use of nano-sized emulsion systems which change their phase from liquid to gas, generating microbubbles, upon exposure of ultrasound pulses for site-specific ultrasound contrast agent. They also have potentials to be used for sensitizers in ultrasonic therapies. In in vitro experiments, it was confirmed that our nano-sized emulsion system changes its phase by ultrasound exposure at relatively low acoustic intensity (less than 10W/cm2). Further, in vivo experiments using subcutaneously implanted murine tumor showed that the phase can be shifted by ultrasound exposure under the same conditions as above in vitro experiments. It was also found that focused ultrasound at an acoustic intensity of 40W/cm2 contiguously exposed after the phase shift is established in the tumor tissues induce therapeutic effects at the focus. Our results indicated the potential usefulness of the nano-sized emulsion system as a versatile agent for ultrasonic diagnosis and therapy. Part of this work was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology through a grant-in-aid for the creation of innovations through business-academic public sector cooperation.

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We propose the aging time as a new parameter to identify a starting solution and to control the nucleation in ceramic particles synthesis containing a non-aqueous solvent. That is, the aging treatment results in the increase of the incubation period (= delay of precipitation), the increase of particle size (= decrease of nucleation site), and the increase of monodispersity (= homogenization of nucleation). In our hypothesis, the structure of starting solutions (or the microscopic mixing state among the molecules of solutes and solvents) changes with an aging time of several days. This paper presents two examples where the aging effect of starting solutions on precipitation behavior was clearly shown in practice. One is an oxalate precipitation from ethanolic solution of oxalic acid, the other is the Stober synthesis of silica spheres. It has been found that soft sonication with a frequency of 40kHz and a power of 〜0.1mW absolutely enhances the aging process, compared to both quite aging and mechanical stirring. Cold spray ionization mass spectroscopy (CSI-MS), where soft ionization enables the measurement of weakly-bonded clusters, has been employed to shed light on the aging process of water-ethanol mixtures. It suggested that they contains some clusters which gradually decreases in size with aging.

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Methylene blue(MB) solutions were oxidized by ozone containing gas through two operation modes, "bubbles in liquid"(BL) and "droplets in gas"(DG). A bubble column producing bubbles of about 2mm in diameter was used forBL. As for DG, MB solution is ultrasonically atomized and is brought into contact with the gas containing ozone. The droplet diameter is less than 10μm. Under various conditions of ozone concentration or contacting time, changes of MB concentration were measured, and apparent rate constants of MB oxidation were determined. The rate constants for DG were approximately four orders magnitude bigger than those for BL. Required time to oxidize 99% of initial amount of MB was compared between BL and DG. The results suggest that the time for DG is 1s and that for BL is 3x10^4s. Ultrasonic atomization is advantageous for oxidizing organics with gas of low ozone concentration.

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When the high power ultrasound waves irradiates the liquid surface, a capillary fountain jet is formed and small liquid droplets are generated from it. This phenomenon is called as ultrasonic atomization. Recently, Sato et al. have reported that ethanol is concentrated from the aqueous solution by ultrasonic atomization [J. Chem. Phys. 114, 2382(2001)]. To investigate the properties of the ultrasonically irradiated liquids will help to find out the mechanism for the ultrasonic separation. In-situ x-ray diffraction measurements of the capillary fountain jet were carried out by using a special designed ultrasonic atomization system with x-ray windows. The x-ray diffraction patterns of pure water and ethanol show exactly the same patterns as those without ultrasonic irradiation. The diffraction pattern of the 20 mol% ethanol-water mixture also shows the same behavior. These results indicate that ethanol would be concentrated when the small liquid droplets are generated from the fountain jet.

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In this study, we suggest the VOCs removal process using ultrasonic atomization and photocatalysis. The removal process uses a special mist with TiO_2 photocatalyst (we named it Ultrasonic Mist with Photocatalyst: UMP), and in fact the presence of the photocatalyst in the mist was confirmed with a scanning electron microscope photo (SEM photo). UMP was dispersed in a reactor and that photocatalysis took place by UV light (main wavelength 365 nm or 254 nm (with 5% 185nm)). This process is able to remove a gaseous toluene. The toluene removal ratio increased at condition of UMP+UV and increasing photocatalyst amount in the water. Toluene removal ratio was higher using a 254nm (with 5% 185nm) UV lamp than using a 365nm UV lamp, because on the first generated O_3 and hydroxyl radical, have strong oxidation effect on VOCs.

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The ultrasonic atomization was combined with ozone irradiation to improve the decomposition performance of VOC. The sample was Trichloroethylene(TCE) aqueous solution. The kind and velocity of carrier gas were changed, and the TCE concentrations in gas and liquid phases were measured. From the change in TCE concentration in gas outlet, the decomposition conversion was estimated. By the application of ultrasonic atomization, the TCE concentration in the liquid decreased, which indicated that the evaporation of TCE from the liquid to the gas phase was promoted. With increasing velocity of carrier gas, the layer of atomized droplet became higher and the decomposition conversion of TCE became higher. From this, it was considered that the decomposition of TCE was promoted by the decomposition in the atomized droplets, where the TCE was concentrated.

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Effect of sonication on the photocatalytic mineralization of chlorobenzene was studied in TiO_2 suspended aqueous solutions. The yields of gaseous products, CO_2 and CO, were influenced by the simultaneous sonication. By the sonication in combination with photocatalysis, degradation efficiency of chlorobenzene was increased significantly, while the pre-sonication efficiency was not. The reaction process was examined by comparing the rate of product formation for the gaseous products and Cl^- with the decomposition rate of chlorobenzene. The results suggested the presence of many intermediate products that remained in aqueous solution. Decomposition of CB was performed in the solution containing with potassium ferrocyanide as a hydroxyl radical scavenger. The formation of gaseous products were remarkably reduced by the presence of radical scavenger both in the photocatalysis and in the sonolysis. These results indicate that hydroxyl radical has an important role in the sonochemical decomposition as well as in the photocatalysis.

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In order to examine the synergistic effects of combining sonolysis and photocatalysis, sonophotocatalysis of oxalic acid was performed using various kinds of TiO_2s such as anatase and rutile type. Synergistic effect was observed in all cases. The indexes of corroboration, however, were different. In this synergistic effect, hydrogen peroxide produced from solvent (H_2O) by sonolysis was thought to be played an important role. It is known that a photocatalytic reaction accelerates by addition of H_2O_2. Active oxygen species were produced in the process of decomposition of H_2O_2 by photocatalysis and they attacked to reactants. In the case of sonophotocatalysis, H_2O_2 also participated in the process of decomposition of oxalic acid. (Sonolysis of solvent) 2H_2O → H_2+H_2O_2 (Photocatalysis) 2H_2O_2 → 2H_2O+O_2 In order to confirm of role of H_2O_2, photocatalysis of H_2O_2 was performed. In the case of anatase type TiO_2, H_2O_2 was adsorbed on the surface of photocatalyst. In the case of rutile, on the other hand, O_2 was obtained stoichiometorically from H_2O_2.

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Effects of Fe powder on the photo-catalytic and sono-chemical reductions of carbon dioxide were examined. Methane was formed as a product in all of the reactions, photocatalysis, sono-chemical reactions in the solution with and without containing TiO_2, and both photo-catalytic and sono-chemical simultaneous reactions. Methane was not detected in the absence of Fe powder. The synergy effect of photo and ultrasonic simultaneous irradiation was not confirmed for the methane formation. Hydrogen was also found as a gaseous product. Cabon monoxide wasn't detected in all the reactions. Formation of Fe^<2+> and Fe^<3+> ions was confirmed in the solutions after the reactions. Sono-chemical methane formation was increased with the increase of added Fe powder up to 0.7g/100m1 in the solutions with containing TiO_2 powder.

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Generation of OH radicals by ultrasonic irradiation in the presence of TiO_2 was studied. OH radicals are oxidizing agents and effective for the degradation of hazardous organic compounds. However, the mechanisms of OH radicals formation have not been elucidated yet. In this work, the effects of cavitation induced by ultrasonic irradiation in water was considered and investigated. As the lifetime of OH radical is very short and can be hardly analyzed directly, then sodium salicylate was used as OH radicals trapping agent. The addition reaction of OH radicals and salicylate results in the formation of dihydroxy benzoic acid(DHBA). The generation of DHBA by ultrasonic irradiation in the presence of TiO_2 as an indicator of OH radicals was investigated in complete darkness. The effects of particles (TiO_2 and A1_2O_3) on the generation of DHBA were examined(Fig.2). While no generation of DHBA was detected in the solutions without particles, higher DHBA concentration was obtained in the presence of TiO_2 than that of Al_2O_3. This enhancement in the formation of OH radicals may be due to the pyrolysis of H_2O and the photocatalysis of TiO_2 with sonoluminessence. Sonoluminessence may be due to cavitation, and the exsitence of particles couse more cavitation whuch may increase sonoluminessence effect. [graph] Also, the effects of dissolved argon applied into the irradiating solutions were studied in the presence of TiO_2 and Al_2O_2 (Fig.5, 6). Higher amount of DHBA was obtained in the solutions in the presence of TiO_2. Thermal capacity of argon is higher than that of nitrogen and oxygen. Higher thermal capacity of dissolved argon causes higher local temperature during cavitation, and it results in the induced pyrolysis of H_2O and generation of OH radicals. Moreover, the effect of the photocatalysis of TiO_2 may be more intensified in the presence of dissolved argon. [graph] [graph] Consequently, the advantage of TiO_2 in the ultrasonic system for the formation of OH radicals was shown in this research.

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Phenolic solution was decomposed by ultrasonic irradiation. The best frequency was found to be 400kHz. To examine the influence of the ultrasonic power, experiments using 11.4, 29.0 and 41.5 W were carried out and the initial decomposition rate of the phenol solution was measured; keeping the frequency constant, higher decomposition rates were obtained increasing the ultrasonic power. The concentrations of hydrogen peroxide, nitric acid and organic acids such as formic acid, propionic acid and oxalic acid were measured during the phenol solution decomposition process. We found that, in case of phenol (0.5 mM), complete decomposition was obtained after 3 h of ultrasonic irradiation (400kHz, 41.5 W), and in case of bisphenol A (0.215 mM), complete decomposition was obtained after 2 h of ultrasonic irradiation (400kHz, 41.5 W). Total organic carbon (TOC) was also measured before and after 10 h of ultrasonic irradiation. Phenol solution (0.5 mM) presented a TOC reduction at the order of 30 % for the process using 400kHz and 41.0 W indicating that although complete decomposition was achieved, some organic carbon still remained in solution as organic acids.

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Sonolysis of cyclopentene in water performed under various kinds of dissolved gases.Ethylene, ethane, methane, carbon dioxide, carbon monoxide and hydrogen were detected as gaseous products. In general, sonolysis proceeds by pyrolysis or radical mechanism. The calculated results have indicated that the oxidant produced by a bubble is not only OH radical but also O atom. Although it has been establised that OH radical is the main oxidant, O atom has not been confirmed experimentally. The production of ethylene might be one of the evidence for producing active O atom.

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In the degradation of Bisphenol A (BPA) under various dissolved gases (argon, nitrogen, oxygen), generation of OH radicals by Fenton reagent (FeSO_4+H_2O_2) was examined in comparison with sonolysis. Dissolved oxygen had no effect on the degradation rate of BPA when OH radicals were major reactants. Of the three dissolved gases, the highest sonochemical degradation rate of BPA was obtained for oxygen. A characteristic decomposition intermediate was detected for gases containing oxygen. On the other hand, the degradation rate was not influenced by dissolved gases for Fenton reaction. All of the intermediates for Fenton reaction were found to be different from that for sonochemical degradation. Therefore, the intermediate for sonolysis was never formed by oxygen-gas-mediated OH radical reaction. We thus suspect that the intermediate was formed through the pathways not involving OH.

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In recentyears, it is reported that water has been polluted by various organic chemical materials such as phenol, chlorophenol and so on. The phenols and their derivatives have a strong toxicity to be used as a disinfectant and a sterilizer. In this research, the decomposition of phenol and p-chlorophenol with various concentration was investigated by using ultrasound. The products decomposed were analyzed by HPLC as a function of irradiation time to get the initial decomposition rates at the concentrations of phenol and p-chlorophenol. The results obtained were discussed in terms of the Langmuir-Hinshelwood mechanism.

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The effect of ultrasonic wave on degradation of an organic substance solution is investigated using the methylene blue as a modeling substance. The rate of decomposition of methylene blue is determined by measuring the change in light absorbance of the methylene blue solution. A great many cavitation hot spots can be evolved in the methylene blue solutions with various solvents. Experimental results indicate that the hydroxyl radical formed during the thermal decomposition of water molecule can decompose methylene blue due to its strong oxidizing action. The rate of decomposition is promoted in the case of the methylene blue solution with FeSO_4・7H_2O, in which Fe^<2+> ion acted as a catalyst. With respect to the effect of reactor conditions on the ultrasonic decomposition of organic substance, it was found that the differences of the materials and the shape have great influence on the decomposition rate of methylene blue. This is because resonance condition is changed, which in turn brings about the change of the temperature and the pressure achieved in the cavitation bubble and the incidence of acoustic cavitation. This fact suggests that the design of the resonance conditions in acoustic reactor is crucially important in the ultrasonic degradation of organic chemical substances.

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The formation of cavitation bubbles is the significant process for the sonochemical reactions. Pyrolysis in the cavitation bubbles and the radical-initiated reactions on the interfaces and in the bulk liquid are known to be the predominant decomposition pathways. Hydrophobic compounds, which are easily concentrated on the surface of the bubbles, are present in a higher concentration compared with in the bulk liquid. Such compounds are susceptible to the decomposition by the OH radical-initiated reaction on the interfaces between the cavitation bubbles and the bulk liquid, in addition to the pyrolytic reaction. In this work, STS and 3 kinds of aromatic surfactants were irradiated by 200kHz ultrasound for 60 minutes. Analysis of their concentrations and SO_4^<2-> concentrations was performed by HPLC and IC. Surface excess concentrations were also investigated.

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Introduction It has been reported that hydrophilic compounds were decomposed by OHgenerated from ultrasound cavitation or with catalyst as TiO_2 etc. Coal ash from a thermal power station is composed of inorganic oxides such as SiO_2, Al_2O_3, Fe_2O_3, TiO_2 etc. The ash is mainly used as cement or concrete materials, however not sufficiently used its advanced characteristic. We report the results of the study for catalysis of the coal ash on radical reaction for water treatment with ultrasound. Experimental Methods As shown in Fig.1, the experimental apparatus for the ultrasonic irradiation consisted of an ultrasonic generator, a barium titanate oscillator operation at 200 kHz, and a water bath for the maintenance of the constant temperature of 20℃. The glass vessel was fixed at a constant position (λ/2=3.8 mm from the oscillator) relative to the nodal plane of the sound wave. Phenol solution (100 mL) was prepared at 10 ppm (106 μM) in the vessel, and irradiated with ultrasound. Phenol was analyzed by JIS (Japanese Industrial Standards) 0102 28.1 (spectrophotometric analysis with 4-aminoantipyrine). Coal ash was a fly ash gotten from the thermal power station burns an Australian coal. Results and Discussion The initial degradation rate of phenol by sonication was 1.87 μM/min, and in the presence of coal ash (0.5 wt%) was 3.92 μM/min. In the case of only coal ash without sonication, phenol was not degraded (Fig.2). In the sonic treatment, the initial degradation rate of phenol increased with increasing the amount of coal ash (Fig.3). Iron was eluted from coal ash by sonication. It has been reported that organic compounds were decomposed by radical from the Fenton reaction in the presence of Fe^<2+> and H_2O_2. Degradation of phenol is assumed to be promoted by increase of radical which was formed in the presence of eluted Fe^<2+> and generated H_2O_2 by sonication.

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It is well known that bubbles produced by ultrasound in the frequency range from 20 kHz to a few MHz leads to various physical and chemical effects. However, there is little application of the ultrasound to the chemical process in an industrial scale. In order to design a large sonochemical reactor, it is important to investigate the sonochemical reactivity and the acoustic field in the reactor. The sealed type of a cylindrical reactor was made of acrylic pipe of a thickness of 5 mm and an inner diameter of 70 mm. The sonochemical efficiency for the cylindrical reactor was investigated with the upward, downward, and horizontal irradiation. A frequency of ultrasound was 490 kHz and a distance between a transducer and a reflector was 500 mm. The sonochemical reactivity was evaluated by KI dosimetry and the luminol image. The horizontal irradiation gave the concentration of I_3^- higher than upward irradiation by approximately 20%. The concentration of I_3^- for the downward irradiation was lower than that for upward irradiation by approximately 35%. In the cylindrical rector, the higher sonochemical reactivity was obtained near a reflector. This result was supported by the result of a luminol image.

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The spatial distribution of the acoustic amplitude in a sonochemical cell has been numerically calculated using a finite element method taking into account the effect of vibration of the walls. The calculated results have indicated that the vibration of the walls due to the sound propagation disturbs considerably the standing-wave field inside a sonochemical cell. The glass wall disturbs a standing-wave field more than the stainless steel wall does because it vibrates more. The mode of a standing-wave acoustic field in a cell depends on the thickness of the wall. The spatial intensity distribution of sonochemiluminescence of an aqueous luminol solution agrees qualitatively with the calculated spatial distribution of acoustic amplitude in a cell.

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In order to develop the ultrasonic reactor, the effects of the arrangement of ultrasonic transducers and the superposition of ultrasonic fields on the sonochemical reaction performance were experimentally investigated. Two PZT transducers at 176 kHz were used. The effects of installation position (bottom or side) of transducer and the distance between two transducers on the sonochemical reaction rate were small. By using the orthogonal superposition of ultrasonic fields, the synergy effect of sonochemical reaction rate was observed. At the part of orthogonal superposition of ultrasonic fields, the intensity of sonochemical luminescence becomes stronger. From these results, it is considered that the area where acoustic pressure is higher than cavitation threshold becomes larger by using the orthogonal superposition of ultrasonic fields.

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We studied dynamics of oil drop trapped in ultrasonic standing waves at 40 kHz. Stroboscopic visualization and laser light scattering techniques were used, which are similar to those used in SBSL measurements. Two types of oil drop were observed. One is containing air bubble inside the oil drop with the diameter of 0.3 mm. The air bubble rotates inside the oil drop, the speed of rotation depending on sound pressure. The oil leakage from the drop was observed when the rotation speed of air bubble was high. The second type is pure oil drop with the diameter of 0.5 mm. The drop surface seemed to be excited by some kind of waves.

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The hydration of OH radical is important in the sonochemical processes in aqueous systems. Information on intermolecular interaction between the radical and water is necessary for understanding sonochemical reaction processes. The infrared spectra of OH-H_2O and OH-(H_2O)_2 complexes isolated in solid Ne has been measured for the first time. The IR frequencies and intensities obtained experimentally of these species are compared with the calculation using a high-level quantum chemical calculations.

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Observation of malti-bubble sonoluminescence and analysis of sonochemical reaction products from water were performed under various kinds of dissolved gases. The intensities of sonoluminescence in several kinds of dissolved gases were shown in Table 1. The highest intensity was observed in an Ar atmosphere. H_2 and H_2O_2 were produced from water by sonolysis. As the index of chemical reactivity, H_2O_2 production rate was adapted. In order to improve the discussion, dependence of H_2O_2 yield on concentrations of O_2 in Ar matrix was also observed. In the case of 30%O_2-70%Ar, a higher yield of H_2O_2 was observed. On the other hand, the intensity of sonoluminescence decreased with increasing ratio of O_2. As the result, the chemical reactivity (the rate of H_2O_2 production) was not directly related to the sonoluminescence. More examination is required. [table]

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The pulsation of ultrasonic cavitation bubbles at various dissolved-air concentration in a sonochemical reaction field of standing-wave type is investigated experimentally by laser-light scattering. When a thin light sheet, finer than half the wavelength of sound, is introduced into the cavitation bubbles at an antinode of sound pressure, the scattered light intensity oscillates. The peak-to-peak light intensity is correlated with the number of bubbles that contribute to the sonochemical reaction. It is shown that as the dissolved air concentration becomes higher the weighted center of the spatial distribution of the peak-to-peak intensity tends to shift towards the liquid surface. At higher concentration of the dissolved air, a great deal of bubbles with size distribution generated due to coalescence between bubbles disturbs sound propagation to change the sound phase easily. A standing wave to trap tiny oscillating bubbles is established only at the side which is nearer to the liquid surface. Also at higher concentration, liquid flow induced by drag motion of bubbles by the action of radiation force becomes apparent and position-unstable region of bubble is enlarged from the side of sound source towards the liquid surface. Therefore, the position of oscillating bubbles active for sonochemical reaction is limited at the side which is nearer to the liquid surface at higher concentration of the dissolved air.

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It is important for sonochemical reactions to control the cavity that is generated in the liquid media under sonication. However, it is very difficult and there are still a lot of uncertainties due to a lot of parameters, which affects the efficiencies of sonochemical reactions. (e.g. frequency, physicochemical characteristics of solution and dissolved gas, etc.) Especially, it is thought that changing the temperature of the solution and the dissolved gas greatly influences the characteristic of the cavitation because it effects on specific characteristics such as the solubility, the thermal conductivity, the specific heat and the vapor pressure etc. In this study, the sonochemical reduction of Au(III) and decomposition of alcohols were carried out at various temperature of Ar-saturated solution(5, 10, 20 and 30℃). As a result, it was understood that sonochemical reactions strongly depend on the temperature of the solution. The sonochemical reactions were promoted as the decrease of the solution temperature. In addition, we used other rare gases. Our results suggest that sonochemical reactions depend on characteristics of dissolved gas rather than of solution

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A local concentration of the OH radicals in an interfacial region between the cavitation bubbles and the liquid is derived from the production rate of hydrogen peroxide and iodine in aqueous potassium iodide solutions. The products of hydrogen peroxide and iodine result from the competitive reactions of the OH+OHand the OH+I^-, respectively, because the total yield of the products is independent of solute concentration. At 650 kHz ultrasonic irradiation, 2×10^<-3> M was obtained for the concentration of the OH radicals in the interfacial region, which was 2 orders of magnitude higher than the concentration in the bulk liquid.

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