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Acoustic Cavitation (acoustic + cavitation)
Selected AbstractsUltrasonic Debridement of Root Canals: Acoustic Cavitation and Its Relevance,INTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2009M. Ahmad BDS First page of article [source] An investigation of the mechanisms of ultrasonically enhanced desorptionAICHE JOURNAL, Issue 2 2007Oualid Hamdaoui Abstract In this work, the mechanisms underlying ultrasonic desorption of 4-chlorophenol from granular activated carbon have been explored. Desorption experiments are investigated in the absence and presence of 516 kHz ultrasound of different intensities. Using three regenerating solutions and two temperatures, it has been shown that ultrasonic irradiation considerably improves both the amount and the rate of desorption. Desorption increases with increasing temperature and ultrasound intensity. The addition of sodium hydroxide or a mixture of sodium hydroxide and ethanol to the regenerating medium leads to an enhancement of the desorption, especially in the presence of ultrasound. The mechanisms of ultrasonically enhanced desorption is due both to the thermal and non-thermal (hydrodynamical) effects of ultrasound. Hydrodynamical phenomena are principally produced by the acoustic vortex microstreaming within porous solids as well as at the solid-liquid interface and by the high-speed micro-jets and high-pressure shock waves produced by acoustic cavitation. The thermal effects are evaluated as localized hot spots formed when bubbles cavitated as well as by global heating of the medium and piezoelectric transducer heating-up. Additionally, the non-thermal effect of ultrasound is greater than the thermal effect, and it is more noticeable when the ultrasonic irradiation is carried out in a high temperature regenerating medium. © 2007 American Institute of Chemical Engineers AIChE J 2007 [source] Degradation of Chlorocarbons Driven by Hydrodynamic CavitationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007Z.-L. Wu Abstract To provide an efficient lab-scale device for the investigation of the degradation of organic pollutants driven by hydrodynamic cavitation, the degradation kinetics of chloroform and carbon tetrachloride and the increase of conductivity in aqueous solutions were measured. These are values which were not previously available. Under hydrodynamic cavitation conditions, the degradation kinetics for chlorocarbons was found to be pseudo first-order. Meanwhile, C-H and C-Cl bonds are broken, and Cl2, Cl., Cl, and other ions released can increase the conductivity and enhance the oxidation of KI in aqueous solutions. The upstream pressures of the orifice plate, the cavitation number, and the solution temperature have substantial effects on the degradation kinetics. A decreased cavitation number can result in more cavitation events and enhances the degradation of chlorocarbons and/or the oxidation of KI. A decrease in temperature is generally favorable to the cavitation chemistry. Organic products from the degradation of carbon tetrachloride and chloroform have demonstrated the formation and recombination of free radicals, e.g., CCl4, C2Cl4, and C2Cl6 are produced from the degradation of CHCl3. CHCl3 and C2Cl6 are produced from the degradation of CCl4. Both the chemical mechanism and the reaction kinetics of the degradation of chlorocarbons induced by hydrodynamic cavitation are consistent with those obtained from the acoustic cavitation. Therefore, the technology of hydrodynamic cavitation should be a good candidate for the removal of organic pollutants from water. [source] Spatial Distribution of Acoustic Cavitation Bubbles at Different Ultrasound FrequenciesCHEMPHYSCHEM, Issue 8 2010Muthupandian Ashokkumar Prof. Abstract Images of sonoluminescence, sonophotoluminescence and sonochemiluminescence are recorded in order to semi-quantitatively compare the spatial distribution of the cavitation activity at three different ultrasound frequencies (170 kHz, 440 kHz and 700 kHz) and at various acoustic amplitudes. At all ultrasound frequencies investigated, the sonochemically active cavitation zones are much larger than the cavitation zones where sonoluminescence is observed. Also, the sonochemically active bubbles are observed at relatively lower acoustic amplitudes than that required for sonoluminescence bubbles to appear. The acoustic power required for the observation of the initial cavitation bubbles increases with an increase in the ultrasound frequency. The cavitation bubbles are observed relatively uniformly throughout the reactor at 170 kHz whereas they are located away from the transducer at the higher frequencies used in this study. While these observations highlight the complexities involved in acoustic cavitation, possible reasons for the observed results are discussed. [source] | ||||||||||