EFFECT OF ULTRASONIC WAVE ON THE ELECTROPOLYMERIZATION OF PYRROLE

Electropolymerization of pyrrole under ultrasonic field at 20kHz was performed ina series of aqueous and propylene carbonate (PC) solutions. The ultrasonic wave withmoderate intensity at the power of 44W, which is the power threshold of the ultrasonicgenerator used in this work to produce cavitation effect, enhance the conductivity andtensile strength of the polypyrrole films as prepared. However, too high intensity of theultrasonic wave is harmful to the polymerization.     

Possible evidence for production of an artificial radionuclide in cavitated water

We report the results of an experiment of cavitation, carried out by means of a sonotrode working at a frequency of 20 kHz and a power of 100 W. The analysis of water was carried out through an ICP mass spectrometer continuously during the cavitation process, in the mass regions from 90 to 150 amu and from 200 to 255 amu, that include also the rare earth elements. We found a significant peak corresponding to a nuclide with atomic mass (137.93±0.01) amu and a half-life 12±1 seconds, identified with ¹³⁸Eu. This result, together with those of two previous experiments (which evidenced changes in concentration of stable elements and production of transuranic elements induced by cavitation), seems to support sononuclear reactions (in particular sononuclear fusion).We propose some possible classical mechanisms for the explanation of these findings.     

Influence of ultrasonic field on microcystins produced by bloom-forming algae

Under the background of algae removal and growth inhibition by ultrasonic irradiation, the effects of ultrasonic irradiation on removal of Microcystis, the concentration variation of microcystins (MC) produced by Microcystis in Microcystis suspension, and sonochemical degradation of microcystins in water, were studied in the paper. The results showed that ultrasonic irradiation could efficiently inhibit the growth of Microcystis, and ultrasonic irradiation shorter than 5 min would not introduce the increase of microcystins dissolved in Microcystis suspension simultaneity. Also, microcystins dissolved in Microcystis suspension would not increase as ultrasonic power increasing. Further research showed that microcystins were effectively degraded in ultrasonic fields. After 20 min ultrasonic irradiation at 150 kHz and 30 W, the removal rate of microcystins reached 70%.     

Frequency effects on the surface coverage of nitrophenyl films ultrasonically grafted onto indium tin oxide

The covalent attachment of various organic molecules on conductive supports including indium tin oxide (ITO) using diazonium chemistry has been known for many years. A commonly used method to achieve this is the electrochemical reduction of diazonium compounds leading to radicals, followed by binding of the radicals to the support. In the present report, an alternative method using ultrasound at different frequencies (20, 582, 863, and 1142 kHz) to induce the surface grafting of nitrobenzene diazonium onto an ITO surface is described. It is shown that the grafting on ITO is more efficient in the lower ultrasonic frequency range that is ascribed to changes in the balance between the physical and chemical effects of cavitation with frequency. Both the physical and chemical effects of cavitation play important roles at all frequencies, but at high ultrasound frequencies, the physical effects are relatively small. At 20 kHz, the physical component, including mass transport, is larger than at higher frequencies, and mechanisms based on these observations have been proposed. Ultrasonic grafting has an advantage over electrografting in that it may provide more control over surface coverage, thus it is suggested that the ultrasonic method is used where the surface concentration of the organic layer must be controlled.     

Nonequilibrium vibrational excitation of OH radicals generated during multibubble cavitation in water

The sonoluminescence (SL) spectra of OH(A(2)Σ(+)) excited state produced during the sonolysis of water sparged with argon were measured and analyzed at various ultrasonic frequencies (20, 204, 362, 609, and 1057 kHz) in order to determine the intrabubble conditions created by multibubble cavitation. The relative populations of the OH(A(2)Σ(+)) v' = 1-4 vibrational states as well as the vibronic temperatures (T(v), T(e)) have been calculated after deconvolution of the SL spectra. The results of this study provide evidence for nonequilibrium plasma formation during sonolysis of water in the presence of argon. At low ultrasonic frequency (20 kHz), a weakly excited plasma with Brau vibrational distribution is formed (T(e) ~ 0.7 eV and T(v) ~ 5000 K). By contrast, at high-frequency ultrasound, the plasma inside the collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. The T(e) and T(v) values increase with ultrasonic frequency, reaching T(e) ~ 1 eV and T(v) ~ 9800 K at 1057 kHz.     

超声波破碎-高效液相色谱法定量检测核酸

采用超声波破碎结合高效液相色谱技术,建立了定量检测质粒DNA的方法,测量结果可以溯源至核苷酸标准物质.采用超声波破碎(功率300 W,频率24 kHz)技术将质粒DNA破碎成200～500 bp的小片段DNA,再用蛇毒磷酸二酯酶将其水解为4种核苷酸(dCMP:3.2 min;dTMP:4.7 min; dGMP:5.3...     

Effect of dual frequency on sonochemical reaction rates

An ultrasonic reactor that combined a standing-wave-type transducer and a horn-type emitter was constructed and the ultrasonic frequency of the standing-wave-type transducer was varied and the sonochemical reaction rates were estimated. The synergy effect was observed below 100 kHz. In order to consider the mechanism of effect of synergy, the acoustic noise, the sonochemical luminescence and the bubble behavior in the reactor were investigated. The frequency spectrum of acoustic noise indicated that the synergy effect came from the increase of number of cavitation bubbles.     

A new approach to nucleation of cavitation bubbles at chemically modified surfaces

Cavitation at the solid surface normally begins with nucleation, in which defects or assembled molecules located at a liquid-solid interface act as nucleation centers and are actively involved in the evolution of cavitation bubbles. Here, we propose a simple approach to evaluate the behavior of cavitation bubbles formed under high intensity ultrasound (20 kHz, 51.3 W cm(-2)) at solid surfaces, based on sonication of patterned substrates with a small roughness (less than 3 nm) and controllable surface energy. A mixture of octadecylphosphonic acid (ODTA) and octadecanethiol (ODT) was stamped on the Si wafer coated with different thicknesses of an aluminium layer (20-500 nm). We investigated the growth mechanism of cavitation bubble nuclei and the evolution of individual pits (defects) formed under sonication on the modified surface. A new activation behavior as a function of Al thickness, sonication time, ultrasonic power and temperature is reported. In this process cooperativity is introduced, as initially formed pits further reduce the energy to form bubbles. Furthermore, cavitation on the patterns is a controllable process, where up to 40-50 min of sonication time only the hydrophobic areas are active nucleation sites. This study provides a convincing proof of our theoretical approach on nucleation.     

Fibrils separated from polyacrylonitrile fiber by ultrasonic etching in dimethylsulphoxide solution

A novel method for the separation of polyacrylonitrile (PAN) fibrils from fibers by ultrasonic etching in a 90 wt % aqueous dimethylsulphoxide (DMSO) solution at 75 °C ± 2 °C for 6 h with a frequency of 40 kHz is demonstrated. These fibrils with a diameter of about 450 nm were systematically investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and wide‐angle X‐ray diffraction (WAXD). It was found that the fibrils consisted of microfibrils with about 200 nm diameter, including periodic lamellae with thickness of 30–45 nm perpendicular to the fiber axis. The PAN fiber crystallinity and crystal size slightly decreased under the ultrasonic etching. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 617–619, 2010     

Acoustic emission from cavitating solutions: implications for the mechanisms of sonochemical reactions

The acoustic emission from collapsing cavitation bubbles generated using ultrasound of 20 kHz and 515 kHz frequencies in water has been measured and correlated with sonoluminescence and hydroxyl radical production to yield further information on the frequency dependence of sonochemical reactions. A reasonable correlation was found, and the results suggest differences in the predominant types of cavitation observed under laboratory conditions.     

Effects of pulsed ultrasound on the adsorption of n-alkyl anionic surfactants at the gas/solution interface of cavitation bubbles

Sonolysis of argon-saturated aqueous solutions of the nonvolatile surfactants sodium dodecyl sulfate (SDS) and sodium 1-pentanesulfonate (SPSo) was investigated at three ultrasonic frequencies under both continuous wave (CW) and pulsed ultrasound. Secondary carbon-centered radicals were detected by spin trapping using 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) and electron paramagnetic resonance (EPR) spectroscopy. Following sonolysis, -*CH- radicals were observed for both surfactants under both sonication modes. Under CW at 354 kHz, the maximum plateau -*CH- radical yield was higher for SPSo than for SDS, indicating that SDS, which is more surface active under equilibrium conditions, accumulates at the gas/solution interface of cavitation bubbles to a lesser degree, compared with the less surface active surfactant, SPSo. However, after sonolysis (354 kHz) under pulsed ultrasound with a pulse length of 100 ms and an interval of 500 ms, the -*CH- radical yield at the plateau concentrations was higher for SDS than for SPSo due to increased amounts of SDS accumulation on the bubble surfaces. In contrast to the findings following sonolysis at 354 kHz, sonolysis of aqueous surfactant solutions at 620 kHz and 803 kHz showed a higher -*CH- radical yield for SDS compared with SPSo under CW but lower -*CH- radical yield with increasing pulsing interval, indicating a frequency dependence on accumulation. Results indicate that pulsing the ultrasonic wave has a significant effect on the relative adsorption ability of n-alkyl surfactants at the gas/solution surface of cavitation bubbles.     

DECOMPOSITION OF BLACK LIQUOR BY ULTRASOUND PROCESS

Ultrasound (US)-induced cavitation is an effective way in oxidizing organic contaminants in wastewater either as the independent operation unit or in combination with other oxidation methods. In this paper, black liquor and filtrate after acidifying and settling were sonicated The effect of working parameters on ultrasonic degradation of black liquor, such as different combinationmethods, frequency, power supply, initial concentration, pH, duration time, ionic strength and catalyst were studied The results were as follows: (1) At the conditions of 4OkHz, IOOW, 4h, pH at 6 and temperature 30±2℃,, utilizing US/US-H2O2/US-Fenton, weak-orange filtrate turned to colloid with the increase of time and little sediment produced after settling. Especially filtrate came to be milk white collides and upper water approached to nearly achromatic by US-Fenton. Compared with the US, US-H2O2/US-Fenton COD (Chemical oxidation demand) removal ratio can increase 15%,30% respectively. Because of more hydroxyl radicals produced in tire reaction process; (2) At the condition of lOOW and 4h, the degradation efficiency of black liquor was better at 40kHz over at 20kHz. Moreover black liquor can be biodegraded easily Those based on that the big molecule of contaminants in aqueous solution can be changed into the little molecule with ultrasound (3) At the condition of 40kl-l: and 4h, the COD removal ratio of black liquor was more higher at 60W than at 80W, while the removal ratio of COD at 60W was nearly close to the ratio at 100W,“ (4) The initial concentration of black liquor influenced the effect of sonochemical degradation; (5) The variation of pH had no effect on degradation; (6) The longer the duration time, tire greater the removal ratio of COD. But this ratio increased slowly after 4h; (7) Adding 0.2g/L NaCI to change the ionic strength of the black liquor, the COD removal ratio can increase 10%; (8) The degradation rates increased by the coexistent catalysts of TiO2, Co^+2 and Ag^+.     

Effects of initial concentration of LASs on the rates of sonochemical degradation and cavitation efficiency

The effect of initial concentration of linear alkylbenzene sulfonate (LAS: p-octylbenzene sulfonate (LAS C₈), p-nonylbenzene sulfonate (LAS C₉), p-dodecylbenzene sulfonate (LAS C₁₂)) on the rate of sonochemical degradation was investigated over a wide concentration range under Ar atmosphere by 200 kHz ultrasonic irradiation. The degradation rate of each LAS increased with increasing initial concentration of LAS and then started to decrease with the different behavior depending on the types of LASs. This result indicated that the cavitation efficiency was gradually changed by their concentrations and the optimum LAS concentrations for their effective degradation existed. The maximum degradation rates were observed at 250 μM of LAS C₁₂, 1250 μM of LAS C₉, and 2500 μM of LAS C₈, respectively. These optimum concentrations were found to be about four to six times smaller than these critical micelle concentrations (CMCs). It was also found that the maximum degradation rates at the optimum concentrations were observed to be almost linearly correlated with their CMCs. Based on the obtained results, it could be suggested that the micelle formation occurs in the interfacial region of cavitation bubbles during rectified diffusion and this phenomenon reduces the cavitation efficiency. In addition, from the results of the rate of the sonochemical degradation of LASs and the yield of hydrogen peroxide, the existence of thermal gradient in the interfacial region of cavitation bubbles was also confirmed.     

Ultrasonic degradation of polycaproamide in 40% sulfuric acid solution

The influence of polymer-polymer interactions and ultrasonic parameters on the ultrasonic degradation of polycaproamide in aqueous 40% H₂SO₄ was investigated. It was found that the rate data for the concentrations studied could be represented well by Ovenall's rate equation. However values of the rate constant chosen to fit Ovenall's equation tend to decrease with increasing concentration of polycaproamide from 0.5 to 2.0 g/100 cm³. With increasing ultrasonic power, the degradation rate increases, but it decreases as frequency is increased. This suggests that cavitation has a dominant role.     

超声波辐照和臭氧氧化协同降解废水中的结晶紫

采用超声波辐照、臭氧氧化以及超声波辐照-臭氧氧化降解废水中的结晶紫;考察了废水初始pH、超声波功率和频率、氧气流量、反应温度等因素对降解效率的影响.结果表明:超声波和臭氧对结晶紫的降解具有协同作用;当废水溶液初始质量浓度为200mg.L-1、pH为10.0时,控制超声波功率和频率分别为100 W和30kHz,氧气流量为0.4L.min-1,反应温度为25℃,反应时间为90 min,则总有机碳(TOC)的去除率可达89.2%,相应的一级反应速率常数为2.38×10-2min-1.     

Ultrasonic Degradation of Hydroxypropyl Cellulose Solutions in Water,Ethanol, and Tetrahydrofuran

Ultrasonic degradations of hydroxypropyl cellulose (HPC) have been carried out in water, ethanol, and tetrahydrofuran (THF) solutions. In the HPC-water system, cavitation intensity did not increase linearly with ultrasound intensity because of a lower threshold of ultrasonic intensity below which cavitation does not occur. At 27°C the rate of degradation in the three solvents followed the order water > ethanol > THF which is not in line with their characteristic impedance values. The rate of degradation for 20 kHz, 70 W ultrasound intensity was found to increase with a decrease in solution volumes, concentration of HPC, and temperature. Increased rate of degradation at lower temperatures supports the concept based on sonoluminescence experiments that it is the cavitation in a polymer solution that is responsible for ultrasonic degradations and the dissolved polymer molecules do not act as cavitation nuclei. Increased surface tension and density of the solvent are thought to be responsible for improved cavitation at low temperatures. Infrared spectroscopy and x-ray analysis of HPC subjected to ultrasonic treatments remained unchanged, suggesting that there were no chemical or structural (e.g., degree of order) changes on irradiation. The decreases in molecular weights on irradiation arise due to random chain scission whereas similar decreases in Huggins coefficients can be attributed to physical changes (decrease in molecular weight or branching) in the degraded HPC samples.     

Preparation of Small Particle Sized ZnAl-Hydrotalcite-Like Compounds by Ultrasonic Crystallization

Ultrasonic technology has been intensively studied recently due to its special features. In this paper, an ultrasonic crystallization method was introduced for the preparation of ZnAl-Hydrotalcite-Like compounds (ZnAl-HTLcs). Samples with high crystallinity, small particle size and narrow particle size distribution were obtained and fully characterized using conventional techniques of XRD, FT-IR and TGDTA. The results prove that both ultrasonic frequency and ultrasonic power have effects on the sizes of the product particles. By varying the ultrasonic power from 250 W to 88 W, with the ultrasonic frequency fixed at 59 kHz, the median particle size of the samples increased from 0.37 μm to 0.82 μm. By altering the hydrothermal treatment time from 1 h to 5 h at 110℃, the median particle size of ZnAl-HTLcs synthesized via ultrasonic crystallization increased from 0.88 μm to 1.11 μm.     

Degrade naphthalene using cells immobilized combining with low-intensity ultrasonic technique

In this paper, we studied the naphthalene degradation by using Pseudomonas aeruginosa under low-intensity ultrasonic stimulation. In our experiment, the degradation rate of naphthalene was the main parameter. We found that low-intensity ultrasonic could not only promote the growth of immobilized P. aeruginosa, but also could improve the degradation of naphthalene. In this article, 1% naphthalene was added into MM culture medium as imitation wastewater. The effect of low-intensity ultrasonic parameter and gel-globes size were considered. We found the influence was obvious, and the optimum degradation rate was acquired when the parameters of ultrasonic are: frequency, 24 kHz; power, 8 W; ultrasonic time, interval time, 10 s; total time, 10 m and the gel-globes were made by using injector no. 14. The naphthalene degradation rate of immobilized cells with ultrasonic stimulation is 82%, which is 12.9 and 42.2% higher than that of immobilized cells and suspended cells without ultrasonic stimulation, respectively.     

Effect of 1.7 MHz ultrasound on a gas-vacuolate cyanobacterium and a gas-vacuole negative cyanobacterium

Ultrasonic signals propagated through medium were directly applied to unicellular cyanobacterium cell surfaces to investigate the biological effects induced by ultrasound. The gas-vacuolate cyanobacterium Microcystis aeruginosa and the gas-vacuole negative cyanobacterium Synechococcus PCC 7942 responded differently to ultrasound. When M. aeruginosa was irradiated by 1.7 MHz ultrasound at 0.6 W cm(-2) every day, it showed a decrease of nearly 65% in biomass increment, and this group's generation time increased twice as much as the control. While Synechococcus culture irradiated every day still grew as fast as the control, and its final biomass was as much as the control. The value of the electric conductivity change (Deltasigma) sharply increased in Microcystis suspension during the exposure process, which revealed more ultrasonic cavitation yield in liquid related to the gas-vacuolate cyanobacteria. The relative malondialdehyde (MDA) content, a quantitative indicator of lipid peroxidation, increased by 65% in Microcystis cells and 9% in Synechoccus cells after ultrasonic irradiation. Moreover, the membrane permeability, quantified by measuring the relative amount of electrolyte leaking out of cells, increased to more than 60% in the Microcystis cells. The results indicated that Microcystis cells were susceptible to ultrasonic stress. According to Rayleigh-Plesset's bubble activation theory, 1.7 MHz ultrasound approached the eigenfrequency of gas-vacuolate cells. The present investigation suggested the importance of the cavitational effect relative to intracellular gas-vacuoles in the loss of cell viability. In summary, 1.7 MHz ultrasonic irradiation was effective in preventing water-bloom forming cyanobacteria from growing rapidly due to changes in the functioning and integrity of cellular and subcellular structures.     

Sonolysis of chlorobenzene in the presence of transition metal salts

Sonolysis of aqueous solution of chlorobenzene at 200 kHz frequency in the presence of transition metals chlorides was investigated. Through analyzing the nature and distribution of the products detected in the reaction mixture, a new mechanism of sonodegradation is advanced. Depending on the metals used and their behavior during sonolysis, we were able to discriminate between inside and outside cavitation bubble mechanisms. Iron and cobalt chlorides, which could undergo redox reactions in the presence of HO radicals generated ultrasonically, give higher amounts of phenolic compounds compared with palladium chloride that undergoes a reduction to metal. Palladium reduction takes place in bulk solution and therefore all organic reactions that compete for hydrogen must occur also in bulk solution. Accordingly, palladium can be a useful tool in determining the reaction site and the decomposition mechanism of organic compounds under ultrasonic irradiation.