Long time single bubble sonoluminescence as long as thirty hours was achieved by suppression of amount of the dissolved oxygen. Under this condition, formation of nitric and nitrous acid from the single bubble was observed. The ratio of production of nitric to nitrous acid was 1:1 and the amount of the acids is 8×lO^<-7> mol・dm^<-3> under the sonication of thirty hours. The amount of formation both acids linearly increased with increasing in sonication time. Amount of formation for aqueous solution of methanol of 2.6×10^<-4> mol・dm^<-3> is about a half of those for water. The intensity of the sonoluminescence of the aqueous solution of methanol was a half of that of water. This fact implies that the amount of formation is affected by the temperature in the bubble. One of the possible reaction scheme for the formation of nitric and nitrous acid is written as follows, N_2 → 2N・ (1) NO+O・ → NQ (5) O_2 → 2O・ (2) NO+OH・→ HNQ (6) H_2O → H・+ OH・ (3) NO+OH・+O・ → HNO_3 (7) N・+O・→ NO (4) 2NO_2+H_2O → HNO_2+HNO_3 (8) If the reactions (5), (6) and (7) proceed with the same probability, the equal amount of nitric and nitrous acid is produced.

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When dissolved in water, a fluorescent solute absorbs the light of single-bubble sonoluminescence (SBSL), and emits light in longer wavelength region. This phenomenon is called single-bubble sonophotoluminescence (SBSPL). We measured SPSPL spectra for 1-pyrenebutyric acid (PBA), a kind of surfactant. Its molecules were expected to come closer to a bubble, absorbing the light of SL directly. However, for low concentrations of PBA, only insignificant changes were observed in the spectra in comparison with another fluorescent solute, fluorescein, which was not surface active. For high concentrations, a bubble became less stable, and SBSL did not occur for concentrations higher than 0.4mM, at which the surface activity began to play a significant role.

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Spectra of single-bubble sonoluminescence (SBSL) in aqueous luminol solutions were measured under acid and basic conditions in order to study the mechanism of sonochemiluminescence (SCL). A rectangular quartz glass cell of 56×56×70 mm^3 internal dimensions was used as the SBSL cell. The bottom of the cell was attached to a bolted Langevin-type transducer, which was driven by a function generator through an amplifier at 24.5 kHz. SBSL spectra were recorded by a spectroscope and ICCD system through a quartz optical fiber with 0.1 s exposures and 300 cycles accumulation. The results show that in the case of a stable bubble, which is normal SBSL case, the SBSL emission was absorbed by luminol in the excitation spectrum range, but no emission was observed in the fluorescence spectrum range. The absorbance depends on pH of the solutions. In the case of dancing bubbles in the solution which dissolved more than 1 % argon, where an unstable bubble grew and ejected daughter bubbles repeatedly, the fluorescence was observed at pH=11.2 but not at pH=2.5. These results are consistent with the pH dependence of multibubble SCL. It is found that the SCL occurs only at unstable collapse of bubbles. Therefore, the dynamic behavior of bubbles is important in sonochemistry related to reactions of radicals produced from cavitation collapse.

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If water is irradiated by strong ultrasound, radicals (OH・, H・etc.) are generated due to the collapse of the cavitation bubbles. These radicals can be used as initiators of radical polymerization using ultrasound. As the polymerization progresses, however, increase of the polymer concentration may affect the generation of the bubbles. In this study, aqueous solutions of polyethylene glycol (PEG) with various concentrations were sonicated and the MBSL was measured by a photo counter, and the radical generation was measured by ESR. If PEG of Mw=2×10^6was used, the initial generation rate of radicals decreases as the concentration of PEG increases. As the sonication time increased, radical generation rate and MBSL decreased and disappeared at about 1OOmin. GPC date of the sonicated sample showed that the molecular weight of PEG has decreased to about 104. If PEG of Mw=2×10^4 was used, MBSL and radical generation were not observed at all. These date suggest that PEG molecules of molecular weight of the order of 10^4 suppress the formation of cavitation bubbles.

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Ultrasonic medical treatments attract much attention in recent years, such as sonodynamic therapy using cavitation, ultrasound imaging with micro-bubble contrast agents and so on. These phenomena have closed relation to the motion of micro bubbles, so that it is essential to understand the dynamics in micro bubles. In sonodynamic therapy, it is important that the oscillation of micro bubbles generates the high pressure and high temperature. This phenomenon appears very strongly in the case of bubble cluster like cloud cavitation. As these dynamics of bubbles are strongly influenced by the thermal phenomena inside them, it is necessary to construct the model taking these phenomena into account to analyze the behavior of bubbles strictly. Thus the following effects are considered: the evaporation and condensation of liquid at the bubble wall, heat transfer through the bubble wall, and the compressibility of liquid. Then the spherical bubble cloud in pure water is numerically simulated. Initial cloud radius is equal to 0.5mm, bubble radius is 1.7μm, void fraction is 0.1%, ambient pressure is 101.3kPa, temperature is 293K and the amplitude of ultrasound is 50kPa. The resonant frequency of bubble cloud is about 180kHz in this case. It is about 1/10 of the case of a single bubble. When the frequency of ultrasound is sufficiently high, for example the resonant frequency of the single bubble, bubble cloud hardly oscillates. On the contrary, when the frequency of ultrasound is resonant frequency of bubble cloud, the high-pressure wave with the steep rising edge focuses on the center of bubble cloud and the pressure inside the bubble reaches about 5MPa. Meanwhile the pressure reaches no more than 0.6MPa in the case of a single bubble. Though this very high pressure relates the cavitation erosion, it is thought that it can be utilized for the field of sonochemistry, such as sonodynamic therapy.

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Radiative interaction between gas bubbles pulsating in an acoustic field is investigated theoretically and numerically. The recent theory for two interacting gas bubbles, due to Ida, predicts the existence of three eigenfrequencies per bubble, which make the phase difference between an external sound and a bubble's pulsation be π/2. Using this theory, we give an alternative interpretation of the reversal of sign of the secondary Bjerknes force, which may be more accurate than those given previously by Zabolotskaya, and Doinikov and Zavtrak. Furthermore, we carry out numerical experiments of two interaction bubbles in order to validate the theoretical results, by employing a modern simulation scheme in which the compressible Navier-Stokes equation with a surface-tension term is used as the governing equation. The numerical results reveal that the theoretical results are accurate and valid, at least in a qualitative sense.

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Computer simulations of bubble oscillations in water are performed for various noble gases taking into account the segregation of water vapor and noble gas inside a collapsing bubble, which was predicted by Storey and Szeri[J. Fluid Mech. 396(1999)203]. It is clarified that the number of water vapor molecules dissociated inside a collapsing bubble is larger for heavier noble gases because of the lower thermal conductivity and the segregation of vapor and noble gas. It is also clarified that the temperature inside a helium bubble at the collapse increases considerably by the mixture segregation because a lesser amount of vapor is trapped inside a collapsing bubble. It is also clarified that multibubble sonoluminescence from heavier noble gases is brighter because of the lower ionization potential which results in the higher electron density and stronger plasma emissions.

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Evaluation of the number of cavitation bubbles in an ultrasonic standing wave field is studied experimentally with light scattering through the measurements of the scattered light intensity from the bubbles with periodic variation synchronous to the period of sound at various contents of the dissolved oxygen (DO). It is shown that at moderate amplitude of sound pressure the averaged level of a waveform of scattered light from the bubbles at an antinode of sound pressure increases as a content of DO in a distilled water becomes larger, and then it decreases after the maximum appears. At higher amplitude of sound pressure, the maximum of the averaged level shifts towards the lower side of DO content. It is also shown that there is a cavitation threshold of DO content and at higher amplitude of sound pressure the threshold appears at lower DO content. The measured results correspond to the number of bubbles at the antinode, while the DO content does to the whole amount of cavitation bubbles in a vessel. The present method enables an evaluation of relative variation in the number of cavitation bubbles at antinode of sound pressure, which is important for accomplishment of high efficiency in sonochemical reaction.

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We have studied production of carbon materials by using sonochemical process. We reported production of arnorphous carbon [1,2], C_<60> [3] arid carbon nanotubes [4], For the production of carbon nanotube, it was found that solidification proceeded by mechanochemical effect induced by the collision of solid particles mixed in the solution. This is one of new effects for the sonochemical process. Here we examine the production of organic fine particles by sonomechanochemical process. We succeeded that the production of fine particles of Cu-phthalocyanine, perylene and C_<60> by applying strong ultrasound to organic powder dispersed in liquid. For Cu-phthaiocyanine, size of the fine particles was smaller than 1 μm and crystal structure seems to be modified by the treatment. For perylene and C_<60>, particle size distribution is very broad (0.1-1 μm). We are trying to improve the size distribution by optimizing reaction conditions.

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It has been well-known that ultrasonic irradiation of air-saturated aqueous solution results in the decrease of pH which attributed to the formation of nitrite and nitrate. In the present study, effects of ultrasonic intensity on the rate of formation of nitrite and nitrate were investigated in detail. The rate of formation of nitrite and nitrate increased with increasing ultrasonic intensity up to 0.70W・cm^<-2>. However, it decreased at the higher intensity. On the other hand, the ratio of nitrate to nitrite increased monotonously as the intensity increased. This phenomenon is suggested to be strongly influenced by the nature of cavitation bubbles with high temperature and high pressure. Thus, the formation mechanism of nitrite and nitrate is proposed on the basis of the thermodynamics and kinetics taking into account the Zeldovich mechanism and aqueous sonochemistry.

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Sonochemistry of pure water was studied under irradiation with 200kHz ultrasound. It is found that the formation rate of nitrite and nitrate ions is a function of irradiation time and gas (oxygen/nitrogen) component. The NO_3^- species will rise distinctly after irradiated 8 minutes by ultrasound. A higher formation rate is also found if the optimal oxygen/nitrogen ratio was offered. The absolute rate of formation of NO_x^- NO_2^- and NO_3^- ions are 7.2 × 10^<-9>mol・min^<-l>・W^<-1>,4.6×1O^<-9>mol・min^<-1>・W^<-1> and 8.6×10^<-9>mol・min^<-1>・W^<-1> respectively in this study. The formation mechanism of HNO_2 and HNO_3 was suggested in the end.

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Hydrogen peroxide is useful material for industry. It ia known that this material is produced by sonolysis. In this presentation, the possibility of sonolysis for industrial use is discussed. Sonolysis of water was carried out in various conditions. Hydrogen peroxide was obtained together with hydrogen under argon atmosphere. The production rate of H_2O_2 was 46 μmol / h(1.6mg / h). The effects of temperature, atmospheric gas and etc. were examined. No temperature effect was observed up to 25℃. In the high temperature region(>35℃), however, H_2O_2 production rate was decreased with increasing temperature. In air-saturated sample, H_2O_2 could not be detected in these experimental conditions. In order to obtain H_2O_2 from seawater by sonolysis, effects of presence of NaCl in the solution on production rates of products were examined. The amounts of products depended on the concentration of NaCl in the solution. The gradient for H_2O_2 was larger than that for H_2. The yields of H_2O_2, however, changed gradually at low concentration like seawater. Thus, the decomposion of seawater to H_2O_2 is expected to be accomplished using sonochemical reaction. The author also discussed about H_2O_2 decomposition by photocatalytic reaction. Photocatalytic reaction of H_2O_2 aqueous solution was performed using TiO_2 photocatlayst and 500-W Xenon lamp. Hydrogen peroxide in the solution was reduced obviously and off cource oxygen was produced stoichiometrically. Thus, it is confirmed that photocatalytic reaction is suitable for decomposition of H_2O_2.

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Recently it has been reported that ethanol is concentrated from ethanol aqueous solution by using ultrasonic atomization. Compared with distillation, the concentration by ultrasonic atomization is not accompanied with phase change. However, the study on ultrasonic atomization concentration from a standpoint of reactor engineering is rarely performed. An atomization vessel was cylindrical and transparent. The sample to be concentrated was ethanol aqueous solution. Air was used as a carrier gas. The initial concentration of alcohol, the solution temperature, the velocity and the location of inlet and outlet of carrier gas were changed, and the alcohol concentration in atomized liquid and atomization rate were measured. As atomization temperature become lower, the alcohol concentration in atomized liquid becomes higher and the atomization rate becomes lower. This is because the vaporization rate from liquid surface becomes lower. With decreasing velocity of the carrier gas, alcohol concentration in atomized liquid increases and the atomization rate decreases. This is because at the low gas velocity, relatively large liquid droplets, which consist of solution with low concentration of alcohol, are difficult to be carried to the exterior of vessel. In order to prevent from emission of large liquid droplets, the demister was attached atomization vessel. At fixed atomization rate, the alcohol concentration in atomized liquid for the atomization vessel with demister is higher than to that for the atomization vessel without demister.

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Various compounds with hydroxy group substituted with alkyl and methoxy groups were reacted with lipase, Pseudomonas naeruginosa under ultrasonicirradiation(Sus-4005C, 50W, 40kHz) for 12〜24h to give the corresponding monoacetylated compounds in good yields(ca.60-80%). When no irradiation of ultrasound was done in this reaction, low yield was found in lipase-catalysed acetylation. The effect of irradiation of ultrasound accelerated the acetylation of hydoxyl group of phenoloic or alcoholic compounds.[chemical formula]

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In 1991 we reported that the irradiation of ultrasound switched the course of the reaction of lead tetraacetate (LTA) with styrene in acetic acid from ionic one to radical. We have studied the detailed mechanism of the sonochemical excitation of the reaction. First, we thought that ultrasound accelerates the decomposition of LTA to produce methyl radical at the interface of the bubble. However, we found that the decomposition of LTA itself was not accelerated by ultrasound in the absence of styrene. Then, we observed a good linear free energy relationship (LFER) between the radical reactivity of 4-substituted styrenes with LTA and the vapor pressure of the styrenes, which indicates that the real activated species in the cavitation process must be volatile styrenes. We then observed a similar LFER for simple sonochemical excitation of substituted styrenes by quenching the radical species with pyrocatechol. However, there are still some ambiguities. First, direct activation of styrenes by sonication is unlikely to produce the radical cation species, but to yield benzene and acetylene by analogy with pyrolysis or shock wave decomposition. Second, the solvent acetic acid is much more abundant and volatile than styrenes under the experimental conditions used. The bubble atmosphere is mainly constituted by acetic acid. Thus, we studied the sonolysis of acetic acid itself. Sonolysis of acetic acid, pure or with added KOAc in the presence and absence of 1% water, was carried out with a thermostated glass reactor at 200 kHz at 25 ℃. Gaseous products evolved were followed by GC. Constant decomposition and evolution of gases were observed. Total volume of gases after 30 h sonication was about 2-3 mL from 30 mL of acetic acid,B Relative amounts of gases produced are in the following order: CO >> CH_4 > CO_2>H_2>>C_2H_6=C_2H_4. Although the detailed mechanism of the production of these gaseous products in sonolysis of acetic acid is still in speculation, it is evident that an oxidative species such as acetoxyl radical produced in this process must oxidize styrene to its radical cation in the gas phase of the bubble. The more important conclusion of this study is that most sonochemical reactions in organic solvents may originate in the sonolysis of solvent molecules as similarly as in aqueous sonochemistry.

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Hydrolysis of ZrOCl_2 aqueous solution was subjected to high intensity ultrasound. It should be noted that this slow reaction promptly proceeded at 60℃ in the presence of ultrasound, while usually in the absence of ultrasound it takes tens of hours at 100℃. ZrOCl_2+(n+1)H_2O→ZrO_2・nH_2O+2HCl Direct sonication using an ultrasonic homogenizer appeared inappropriate due to considerable erosion of Ti horn in the acidic condition. Employed was a standing-wave sonicator with a thermostat. Comparing two frequencies of 28 and 45 kHz, the latter was found to be effective in the enhancement of the hydrolysis. Products after centrifuged and dried were amorphous zirconia. Argon substitution of the starting solution increased the formation of zirconia.

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Acoustic-gravity coupled fields have been investigated for particle characterization and separation. When a plane standing ultrasound wave is generated in a cell containing water as a medium, particles move to the node of the wave along the ultrasound force gradient. When the particles undergo a sedimentation force in addition to the ultrasound force, they aggregate at the equilibrium position, where these two forces are balanced. The equilibrium position, which is determined by the density and compressibility of a medium and particles, provides the physical properties of the particles. The local ultrasound energy, which is necessary to quantitatively discuss particle behaviors, is evaluated using a standard particle, the physical parameters of which are unambiguously determined; aluminum particles are used in the present study. The local ultrasound energy makes possible the determination of the compressibility of unknown materials. In this study, we have measured equilibrium positions of alumina, silica grass, polystyrene and poly(acrylonitrile-co-vinyl chloride-co-methyl methacrylate)(PAVCMM) particles, and determined their density and compressibility. These nonporous particles of inorganic and polymeric materials follow a derived model, suggesting that the local ultrasound energy and a derived model be valid. Separation of porous particles based on the porosity is also possible. The equilibrium positions of porous particles in the standing ultrasound wave field are determined by the porosity of the particles as well as by the density and compressibility of silica glass. The porosity of some silica gel particles has been determined as 22, 34, 55 and 63% by the present method, which agrees with that determined by a water-penetration method (22.7, 38.9, 69.6 and 72.5%). The proposed external field can be used for separation of particles having different acoustic natures.

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The preparation of Pd clusters on Y-zeolite was investigated by the sonochemical reduction of Pd(NH_3)_4^<2+> complexes in an aqueous solution system. The measurements by UV-vis and XPS spectra showed that Pd(NH_3)_4^<2+> was found to be reduced by reducing species formed from 2-propanol sonolysis to yield zero-valent Pd. It was confirmed that the binding energy of the Pd 3d core level on the Y-zeolite was shifted to a higher value in comparison with that of Pd bulk metal. The formation of Pd metal, however, could not be observed by HRTEM and EXAFS measurements, implying the formation of ultrafine Pd clusters. On the other hand, the results of the XPS analyses for several standard Pd clusters of ca. lnm prepared by the conventional thermal treatment indicated that the peak values of the Pd core level increased with decreasing particle size: The maximum difference in binding energy between these samples was 0.6veV at the Pd 3d_<5/2> core level. This phenomenon was suggested to be attributed to a quantum size effect corresponding to the splitting of the band structure. In comparison with the standard samples, the size of sonochemically formed Pd clusters was roughly estimated to be less than 1nm.

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The corrosion of iron has been protected with passive films (Fe_2O_3 and Fe_3O_4) in the various solutions. In this work, the formation of (Fe_3O_4) film in H_2SO_4 solution and its corrosion resistance were studied using the electrochemical technique. The anodic I-V curves were measured from -0.6 to 5V vs. Ag/AgCl. An iron rod (99.99%, 5mmφ) was used as working electrode. The counter electrode was Pt wire, the reference electrode was Ag/AgCl. Sample solution used 0.5〜2.0 mol/dm^3 H_2SO_4 solutions. The sonication was prepared with using ultrasonic cleaner (28, 45 and 100 kHz, 100W). The first passivation potential (Flade potential ) and second passivation potential were observed in the stationary state and sonication. The current did not flow over the second passivation potential. The current flowed at the first passivation potential because Fe_2O_3 film was destroyed by the sonication. The current did not flow over the second passivation potential. An iron was dissolved as current flowed (Fe^<2+>→Fe_2O_3). The Fe_2O_3 film was enough covered on the surface at the Flade potential, the formation of Fe_2O_3 film increased with increasing of potential. (Fe^<2+>+O_2→Fe_2O_3) . However, the current flowed again, and Fe_3O_4 film was formed (Fe2C>3 + O2 - Fe3O4). The passive film was destroyed with liquid flow and sonication. The passive film which was formed at second passivation potential was firm film comparing with that at the first passivation potential. The passivation film at the second passivation potential had good corrosion resistance.

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Organofluorine compounds are highly useful in various fields such as material science, medicinal chemistry, and theoretical chemistry. As a novel synthetic method of organofluoro compounds, we have established electrochemical partial fluorination, which can be carried out without any hazardous reagents under mild conditions. However, these electrochemical fluorinations are not always easy due to the low nucleophilicity of fluoride ions and anode passivation. On the other hand, ultrasonic effects on electrochemical processes have received much interest, since the product yield and selectivity in the processes are greatly affected by promotion of mass transport caused by a cavitational micro-jet stream. Moreover, the micro-jet stream can also clean the electrode surface. From the above viewpoint, effects of ultrasound on the anodic fluorination of ethyl α-phenylthio acetate in an organic solvent were examined in this work. The yield and selectivity for the α-monofluorinated product was greatly increased by ultrasonication. This ultrasonic effect could be rationalized in term of mass-transport promotion of the substrate by the sonication. In addition, it was also demonstrated that the ultrasonication greatly increased the yield and selectivity in anodic fluorination of 3-methyl-2-phenyl-4-thiazolidinone in Et_3N-3HF ionic liquid, as shown in Table 1. Tablel Anodic fluorination of 3-methyl-2-phenyl-4-thiazolidinone in Et_3N-3HF ionic liquid[figure]

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In recent years, ultrasonic effects on electrochemical processes have received much interest, since the processes are typical heterogeneous reactions in solid (electrode)-liquid (electrolytic solution) interfaces and should be greatly affected by mass transport of the substrate and intermediate species across the interface. In this work, the ultrasonic effect on the anodic cyanation of N-methylpyrrole was examined. The current efficiency for the anodic cyanation was greatly increased by ultrasonic irradiation. In addition, the product selectivity for the monocyanated product (1) formed by two-electrons oxidation along with dicyanated product (2) formed by four-electrons oxidation, was significantly increased under ultrasonic irradiation. This ultrasonic effect could be rationalized in terms of mass-transport promotion of N-methylpyrrole molecules to the anode surface from the bulk of the electrolytic solution by ultrasonic irradiation. Thus, the ultrasonic effect can be purposively applied to control the efficiency and selectivity in the anodic cyanation. Moreover, It was found that the current efficiency and product selectivity under ultrasonic irradiation was relatively high even if the NaCN concentration was decreased. This is desirable from an environmental viewpoint.

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Sonochemical effects in liquids and solutions irradiated by sound wave with high intensity are influenced by many factors: the ultrasound frequency and intensity, the shape of the reaction cell, the sample volume, the experimental temperature, etc. Therefore, it is difficult to compare the reported results carried out by the different laboratories. Calorimetry or chemical dosimetry is sometimes used to measure the ultrasonic power or intensity in a reaction vessel. However, standardization of ultrasonic power for sonochemistry is desired. Last year, Japan Society of Sonochemistry has organized a working group for standardization of ultrasonic power for sonochemistry. In four laboratories, the following methods were examined in the frequency range from 20kHz to 1.2MHz with different apparatus: 1) Calorimetry, 2) Measurement of absorbance of Fe^<3+> produced in Fricke solution, 3) Measurement of absorbance of I_3^- generated in 0.1M KI solution, 4) Measurement of decomposition ratio of porphyrin in solution. There is good correlation between absorbance of Fe^<3+> and that of I_3^- reported by different laboratories. We recommend the method (3) for standardization of ultrasonic power for sonochemistry. We will also discuss the frequency dependence of the sonochemical effect on basis of the results obtained from four methods.

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Ultrasonic degradation of many polymers in solutions has been well investigated by many worker. As cellulose does not dissolvein water and dissolve in a few solvents, little study on ultrasonic degradation of cellulose in solutions has been repoeted. Ultrasonic degradation of cellulose is expected to give oligomers, which are valuable reagents in the biological field. In this work, we examined the effect of ultrasonic irradiation on cellulose solutions. Cellulose (Avicel-PH101) was dissolved in 8wt% lithium Chloride (LiCl)/dimethylacetamide(DMAc) solvent and 8wt% LiCl/N-methyl-2-pyrrolidone (NMP). The concentration of cellulose was 0.1 wt%. Ultrasonic homogenizer (BLANSON SONIFIRE 450D) was used. The ultrasonic frequency was 20kHz and sonication was carried at 25℃. The viscosity of cellulose solution after sonication was measured by ubbelohde capillary viscometer. Specific viscosity of cellulose solution decreased with sonicatiori time. The decrease of viscosity indicates that cellulose is degradated by sonication.

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The continuous flow ultrasonic reactor with the maximum volume of 3.9l was designed and constructed and oxidation in aqueous solution of 0.1M KI using the continuous flow ultrasonic reactor was investigated at the frequency of 132.2kHz. It is found out that there is the limiting value of yield of I_3^- on the outlet of the reactor after longer sonication time. In this study, we estimated the rate constant of I_3^- in KI solution for the continuous flow ultrasonic reactor on the basis of the traditional modeling equation of the continuous flow reactor. The rate constant of I_3^- in the continuous flow ultrasonic reactor is larger than that in the batch one at a constant electric power. This means that sonochemical effect is enhanced for the continuous flow ultrasonic reactor. One reason is that the number of acoustic bubbles in solution may increase when the flow rate increases.

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Effects of the sonication before UV irradiation on the rate of photocatalytic mineralization of some chlorinated organic comopounds in oxygen saturated aqueous solutions were examined using the pre-treated titanium dioxide (P25) of which suspensions were sonicated for 1 hour before use. The enhancement effect on the photocatalytic mineralization by the pre-sonolysis was not observed for the most of the chlorinated organic compounds examined here such as dichloroethane, chloroacetic acids, chloromethanes, trichloroethylene and tetrachloroethylene except trichloroacetic acid and tetrachloromethane. These results indicate that the sonolysis before the photo-irradiation does not always promoto the further oxidation to mineralization by the following photocatalysis. For trichloroacetic acid and tetrachloromethane, however, the pre-sonolysis enhanced the photocatalytic mineralization significantly. Both compounds are known to be resistive to the photocatalytic degradation, because they have no hydrogen atom to be abstracted by the OH radicals generated on the TiO_2 particles by the photo-irradiation since that reaction is generally considered to be the initiation step of the photocatalytical degradation of organic compounds. The. pre-sonolysis effect for these compounds would be caused by the formation of some products sonochemically at first, perhaps a partly dechlorinated compounds. Once these products are formed, they are oxidized rapidly further to carbon dioxide and chloride ion by the following photocatalytic reactions.

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Acoustic cavitation is a typical non-thermal phenomenon induced in liquids and biotissues exposed to ultrasound. Its effects may be useful for therapeutic purposes if properly controlled. Techniques for promotion and suppression of acoustic cavitation will provide such controlling methods. We have been pursuing acoustical and chemical approaches. As chemicals for reducing cavitation threshold, we found that certain photosensitizers, such as rose bengal, in xanthene family are effective both in water and murine liver. They also act as sensitizers of cavitational effects. One of our research targets is applying these chemicals to cancer treatment. However, such xanthenes have poor affinities with tumor tissues. As an approach to obtain xanthenes with improved affinities with tumor tissues, we synthesized amphiphilic rose bengal derivatives. We previously reported that a derivative with incorporated alkyl groups as the lipophilic group and carboxilic group as the hydrophilic group showed significantly increased affinities with subcutaneously-implanted murine tumor tissues while maintaining its ability to reduce cavitation threshold in water. We this time investigated the anti-tumor effect on subcutaneously-implanted murine tumor induced by ultrasound exposure (0.5 MHz and 1.0 MHz, 15 W/cm^2 each) with and without the new derivative. Significant synergistic effects of ultrasound and the derivative were observed. To ensure the effects are sonochemical ones, we measured the temperature rise in tumor tissues during the ultrasound exposure. We also measured the sub-harmonic emissions from tumor tissues. Results suggested that the synergistic effects are due to sonochemical mechanism rather than thermal one.

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In order to develop the ultrasonic reactor, the effect of mass transfer on the decomposition performance by ultrasonic irradiation is experimentally examined. The rectangular reactor (400 × 150 × 400(height)mm) was used and the sample to be decomposed was tetraphenylporhyrine tetrasulfonic acid. A stirrer was set in the reactor, and the location and rotation speed were changed. After a period of ultrasonic irradiation, the decomposition conversion was estimated. As a measure of liquid mixing behavior, the liquid mixing time in reactor was measured. As the rotation speed of stirrer becomes higher, the decomposition conversion increases in the case of stirrer located near the ultrasonic oscillator, but it decreases in the case of stirrer located far from the oscillator. The liquid mixing time decreases with increasing rotation speed of stirrer, independently of stirrer location. Based on the visualization of flow pattern in reactor and the results calculated by CFD, the reactor is modeled to consist of three parts. By using this model the data are analyzed, and the effect of stirrer location on the volumetric mass transfer coefficient is clarified.

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We have studied the effective decomposition of tetrachloroethylene (perchloroethylene; PCE) in aqueous solution by irradiation of ultrasonic-wave and ultraviolet-ray. In this study, the reactor is stainless cylinder (φ 110 x 412mm) with a ultrasonic oscillator (446 kHz, 100W, PZT) and four ultraviolet lamps (λ=260nm, 12.5W), and the temperature of aqueous solution in the reactor is maintained at 25℃ by cooling water surrounding the reactor. By irradiation of ultrasonic-wave and ultraviolet-ray to aqueous solution (3Liter) containing PCE of high concentration (about 150mg/L), PCE decomposed to O.1mg/L (sewerage discharge level) in about 60 minute. But in the both case of irradiation of only ultrasonic-wave and irradiation of only ultraviolet-ray, PCE did not decompose to 0.1mg/L by 180 minute. The mechanism of effective decomposition by irradiation of ultrasonic-wave and ultraviolet-ray was considered below. (1)OH radical generation at cavitation bubble interface by irradiation of ultrasonic-wave to water (2)Hydogen peroxide generation at liquid phase by recombination of OH radicals (3)OH radical generation at liquid phase by irradiation of ultraviolet-ray to hydrogen peroxide (4)Effective decomposition by OH radical at liquid phase We performed confirmatory experiment to inspect the above hypotheses and confirmed indirectly the mechanism.

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Recently, Cryptosporidium parvum, which causes a waterbome disease, has been detected in drinking water. Their destruction is the serious problem in drinking water processes for public health. Cryptosporidium parvum has high resistance to germicides because it has very hard oocyst. Therefore its inactivation by the chlorination using chlorine and chloamine is not effective. The possibility of application of the ultrasound as a physicochemical method for disinfection is expected, due to short-time high temperatures, high pressures and reactive free radicals induced by ultrasonic irradiation in water. We investigate the inactivation by ultrasonic irradiation using yeast cell (Saccharomyces cerevisiae) having a similar structure with Cryptosporidium Parvum as test species. The ultrasonic irradiation for the inactivation of yeast cell is carried out horn type of equipment (27.5kHz). After ultrasonic irradiation, the viability was observed by colony count. Yeast cell had almost completely inactivated with 3 min of ultrasonic irradiation with 4μ m(p-p) of amplitude. In this study, we describe the effect of cell concentration and amplitude of vibration face of yeast cell during ultrasonic irradiation.

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The sonochemistry for the degradation of alkylphenols, such as butylphenol, pentylphenol, octylphenol, and nonylphenol, in water was investigated at a sound frequency of 200 kHz with an acoustic intensity of 6 W cm^<-2> under argon, oxygen, and air atmospheres. The maximum pseudo first-order rate constant (0.1699 ± 0.0050 min^<-1>) was observed during the sonication of butylphenol under argon. The sonolytic degradation rate of the alkylphenols under the conditions of the present study depended upon their alkyl chain length. In the presence of Fe(II) and Fe(III), the degradation rate and mineralization of nonylphenol during sonication were faster with oxygen than with argon or air. The maximum pseudo first-order rate constants for the nonlyphenol degradation were observed at 50 μM Fe(II) (0.1393 ± 0.0083 min^<-1>) and 100 μM Fe(III) (0.1031 ± 0.0010 min^<-1>) under oxygen. The total organic carbon concentration decreased by about 60% and 70% for Fe(II) and Fe(III) during the sonication under oxygen, respectively. The enhancement of the sonochemical effects by the addition of Fe(II) and Fe(IH) during the sonication under the proper atmosphere results in a remarkable enhancement of degradation and mineralization.

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The influence of ultrasound (200 kHz) on the decomposition of chlorobenzene in the presence and absence of iron and palladium sulfates was investigated. The intermediates of the sonolysis were identified, leading to a deeper insight into the degradation mechanism. It was established that chlorobenzene, a volatile compound, believed to be mainly degraded by pyrolysis inside cavitation bubbles, is also decomposed in the bulk solution by HO radical attack. The bulk reaction definitely occurs by two mechanisms that include a ring attack leading to chlorophenols and ipso attack leading to the phenoxy radical, responsible for all the identified phenolic components. This study sheds some light on the reaction sites during the sonication of organic substances.

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