Acoustic cavitation in a liquid medium generates several physical and chemical effects. The oscillation and collapse of cavitation bubbles, driven at low ultrasonic frequencies (e.g., 20 kHz), can generate strong shear forces, microjets, microstreaming and shockwaves. Such strong physical forces have been used in cleaning and flux improvement of ultrafiltration processes. These physical effects have also been shown to deactivate pathogens. The efficiency of deactivation of pathogens is not only dependent on ultrasonic experimental parameters, but also on the properties of the pathogens themselves. Bacteria with thick shell wall are found to be resistant to ultrasonic deactivation process. Some evidence does suggest that the chemical effects (radicals) of acoustic cavitation are also effective in deactivating pathogens. Another aspect of cleaning, namely, purification of water contaminated with organic and inorganic pollutants, has also been discussed in detail. Strong oxidising agents produced within acoustic cavitation bubbles could be used to degrade organic pollutants and convert toxic inorganic pollutants to less harmful substances. The effect of ultrasonic frequency and surface activity of solutes on the sonochemical degradation efficiency has also been discussed in this overview.

Complexes of N,N′-bis(salicylidene)-1,3-diaminopropane, an ONNO type ligand, with ZnX₂ (X = AcO⁻, NO_3-, Cl⁻, Br⁻, I⁻) salts were prepared. Molecular structures of these complexes were identified using elemental analyses, IR spectrometry and X-ray diffraction techniques. It has been observed that the reactions between zinc ions and the said ligand tend to produce polynuclear complexes and depending on the anion present either di- or trinuclear complexes are formed. Thus, it can be deduced from the results presented in this article that trinuclear complexes form when the zinc salt used was the acetate or nitrate and dinuclear complexes form if the anion in the zinc salt is a halogen.

We report a sonochemical method for the fabrication of stable TiO ₂ –chitosan hybrid microspheres possessing nanoporous structure and antimicrobial properties.

The initial growth of acoustic cavitation activity is important in some applications such as therapeutic and diagnostic medicine. The initial growth of cavitation activity has been investigated using sonoluminescence and sonochemical activity (sonochemiluminescence) at 358 kHz, 647 kHz and 1062 kHz and at 5 W, 15 W and 30 W applied power levels. The growth of sonochemically active bubble population is found to be much faster than that of sonoluminescence bubble population at 358 kHz and 647 kHz whereas almost similar growth rate is observed at 1062 kHz for both bubble populations. This suggests that the cavitation bubble resonance size ranges of sonoluminescence and sonochemically active bubbles are different at 358 kHz and 647 kHz, whereas they have similar size range at 1062 kHz. At 358 kHz and 647 kHz, relatively smaller bubbles become chemically active. Possible reasons for such observations have been discussed. The data presented and discussed in this study may be useful in controlling the growth of cavitation bubble population in addition to enhancing the knowledge base in cavitation science. (C) 2015 Elsevier B.V. All rights reserved.