Chemical Effects Of Cavitation Research Articles

Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics

Wastewater treatment plants, the last barrier between ever-increasing human activities and the environment, produce huge amounts, of unwanted semi-solid by-product - waste activated sludge. Anaerobic digestion can be used to reduce the amount of sludge. However, the process needs extensive modernisation and refinement to realize its full potential. This can be achieved by using efficient pre-treatment processes that result in high sludge disintegration and solubilization. To this end, we investigated the efficiency of a novel pinned disc rotational generator of hydrodynamic cavitation. The results of physical and chemical evaluation showed a reduction in mean particle size up to 88%, an increase in specific surface area up to 300% and an increase in soluble COD, NH4-N, NO3-N, PO4-P up to 155.8, 126.3, 250 and 29.7%, respectively. Microscopic images confirmed flocs disruption and damage to yeast cells and Epistilys species due to mechanical effects of cavitation such as microjets and shear forces. The observed cell ruptures and cracks were sufficient for the release of small soluble biologically relevant dissolved organic molecules into the bulk liquid, but not for the release of microbial DNA. Cavitation treatment also decreased total Pb concentrations by 70%, which was attributed to the reactions triggered by the chemical effects of cavitation. Additionally, the study confirmed the presence of microplastic particles and fibers of polyethylene, polyethylene terephthalate, polypropylene, and nylon 6 in the waste activated sludge.

Understanding of ultrasound enhanced electrochemical oxidation of persistent organic pollutants

Advanced oxidation processes have gained attention recently due to their effectiveness in mineralizing toxic recalcitrant pollutants. In this paper, studies on combined sonolysis and electroxidation techniques have been reviewed for the degradation of the persistent organic pollutants, and real industrial wastewater. The effects of various parameters such as ultrasonic power, current density, initial pH, and electrolyte concentration have been elucidated. Critical analysis of the studies (1996-2020) on the treatment of various synthetic and real wastewater using the sono-electroxidation process has been considered. Ultrasound, in combination with electrochemical technology, is an attractive option for the treatment of industrial wastewater. The application of ultrasound gives the synergistic effect by virtue of the physical and chemical effects of cavitation. Coupling these two techniques increases the mineralization degree by increasing the mass transport rate and the chemical reaction rate, and reduce the electrode passivation and fouling problem. Woking with an optimized sonoelectrochemical reactor design with low power ultrasound with pulsed mode can remarkably decrease the energy cost and increase the economic viability of the treatment method. Challenges associated with the process are documented in this paper.

Quality-Related Enzymes in Plant-Based Products: Effects of Novel Food-Processing Technologies Part 3: Ultrasonic Processing

High-power ultrasound is a versatile technology which can potentially be used in many food processing applications including food preservation. This is part 2 of a series of review articles dealing with the effectiveness of nonthermal food processing technologies in food preservation focusing on their effect on enzymes. Typically, ultrasound treatment alone does not efficiently cause microbial or enzyme inactivation sufficient for food preservation. However, combined with mild heat with or without elevated pressure (P ≤ 500 kPa), ultrasound can effectively inactivate enzymes and microorganisms. Synergistic effects between ultrasound and mild heat have been reported for the inactivation of both enzymes and microorganisms. The application of ultrasound has been shown to enhance the rate of inactivation of quality degrading enzymes including pectin methylesterase (PME), polygalacturonase (PG), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) at mild temperature by up to 400 times. Moreover, ultrasound enables the inactivation of relatively heat-resistant enzymes such as tomato PG1 and thermostable orange PME at mild temperature conditions. The extent to which ultrasound enhances the inactivation rate depends on the type of enzyme, the medium in which the enzyme is suspended, and the processing condition including frequency, ultrasonic intensity, temperature, and pressure. The physical and chemical effects of cavitation are considered to be responsible for the ultrasound-induced inactivation of enzymes, although the dominant mechanism depends on the structure of the enzyme.

Mathematical Model of Multibubble Cavitation into Sonochemical Reactor

The research described in this paper shows that main parameter of acoustic cavitation which should be used for practical applications this phenomenon, are not the temperatures of plasma into the cavitation bubbles (the intensity of son luminescence), but the power of pressure pulses, which they produce, and which cause destruction of phases existing in a liquid (the intensity of erosion). The distribution of the density power of erosion in space can be the subject of numerically simulated, if it is assumed that process of multibubble cavitation is an ergodic process. For this the integral of pressure superposition from all bubbles of cavitation field at any point in space, must be approximated by the function of the pressure pulse on the surface of a single cavitation bubble, that pulsate with a period equal to the period of oscillations of the harmonic wave. This superposition of pressure can be described using a two metrics of space, which are belongs to this point. The first – the average distance from this a point until all points of the cavitation region. It determines the average time of arrival into this point of a total perturbation of pressure from all bubbles. The second – the average harmonic distance – determines the average coefficient of attenuation of this perturbation. The results of computational and laboratory experiments illustrate the adequacy and the applicability of model. The model makes it possible to quantitatively compare the results of physical and chemical effects of cavitation in the any liquids in the reactors of any size. The model also gives a sufficient degree of accuracy and reliability of performing the technical calculations for the design of such devices and the possibility to make comparative assessments of different reactors.

A study of the ultrasonic preparation of neodymium doped zinc oxide nanoparticles in room temperature ionic liquid

The sonochemical process has been proved to be a useful technique for generating various nanostructured materials. The physical and chemical effects of cavitation are highly dependent on the contents of the collapsing bubble and hence on the choice of solvent. Recently, room-temperature ionic liquid (RTIL) have been developed to a central point of interest in both academia and industry. RTIL are nonvolatile, non-flammable, and thermally stable solvents. These properties make ionic liquids potentially attractive for use in sonochemical reactions. The application of ultrasound to synthesis nanomaterials in conjunction with ionic liquids, however, has been rarely exploited. In this work, a facile approach has been developed for the preparation of neodymium doped zinc oxide nanopaticles in RTIL via an ultrasonic irradiation. The morphology and properties of the products have been characterized by X-ray diffraction and transmission electron microscopy. A possible mechanism is proposed to explain the formation ...

Mathematical Model of the Spatial Distributing of Density of Erosive Power of Multibubble Cavitation

The research described in this paper shows that main parameter of applied researches of acoustic cavitation are not the intensity the temperatures of plasma in the cavitation bubbles (power of sonoluminescence), but the power of pressure pulses, which they produce, and which cause destruction of phases existing in a liquid (power of erosion). The distribution of the density power of erosion in space can be the subject of numerically simulated, if it is assumed that process of multibubble cavitation is an ergodic process. For this the integral of pressure superposition from all bubbles of cavitation field at any point in space, must be approximated by the function of the pressure pulse on the surface of a single cavitation bubble, that pulsate with a period equal to the period of oscillations of the harmonic wave. This superposition can be described using a two metrics of space, which belongs to this point. The first – the average distance from this point until all points of the cavitation region, determines the average time of arrival at this point of the total perturbation of pressure. Second – means harmonic distance and determines the average coefficient of attenuation of this perturbation. The results of computational and laboratory experiments illustrate the adequacy and the applicability of model. The model makes it possible to quantitatively compare the results of physical and chemical effects of cavitation in the any liquids in the reactors of any size and design. The model also gives a sufficient degree of accuracy and reliability of performing the technical calculations for the design of such devices and the possibility to make comparative assessments of the different reactors.

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.

Sonochemical Synthesis of Gold Nanoparticles: Effects of Ultrasound Frequency

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.

Sonochemistry—A demonstration lecture

The potential uses of sonochemistry for the processing and chemical industries of the future have been established already in the chemical laboratory. The driving force for this technology is acoustic cavitation and a deeper understanding of this phenomenon will be required to help sonochemistry achieve more widespread acceptance and implementation in industry. For this reason a coordinated research effort is needed involving not only chemists but engineers, physicists, and mathematicians. In the past interaction between these disciplines has been limited due to the different scientific circles in which they move, but a few conferences, including this one, have sought to bring such disciplines together to promote cooperation. This presentation incorporates a series of demonstrations which illustrate the types of physical and chemical effects of cavitation and ultrasound which interest the chemist. These will include degassing, the generation of free radicals, the effects of cavitation near a surface, the dispersion of solids, emulsification, and particle manipulation in an acoustic field. Hopefully these will serve not only as an introduction to sonochemistry for those whose main discipline is not chemistry, but also as a focus for the powerful effects of cavitation which need deeper coordinated exploration.

Sonoluminescence and the Chemical Effects of Cavitation

It has been suspected for some time that sonoluminescence and the chemical effects of cavitation are caused by the same thermal mechanism. It would seem, however, that the connection is even more intimate, since the existence of certain radicals appears to be essential for both phenomena. This is discussed briefly in the following review.