Abstract:This paper presents the use of hydrodynamic cavitation and ultrasonic cavitation technologies for treating rhodamine B (RhB) in simulated wastewater.
“…In this experiment, there exist many tiny bubbles (cavitation nuclei) in the solution due to the stirring during the solution preparation. These microbubbles in sessile droplet were activated by ultrasound and experienced a dynamic process including oscillation, growth, contraction and explosion, that is, ultrasonic cavitation effect [39] , [40] , [41] . Fig.…”
“…In this experiment, there exist many tiny bubbles (cavitation nuclei) in the solution due to the stirring during the solution preparation. These microbubbles in sessile droplet were activated by ultrasound and experienced a dynamic process including oscillation, growth, contraction and explosion, that is, ultrasonic cavitation effect [39] , [40] , [41] . Fig.…”
“…Although, in principle, it is possible to use pseudo- n th order kinetics, most of the reports describing experimental data on pollutant degradation using hydrodynamic cavitation have used pseudo-first order kinetics. Several studies are published using this approach. − This approach of using a pseudo-first order rate constant for describing the hydrodynamic cavitation process has been shown to not be appropriate by Ranade et al They had clearly shown that this approach would predict two different values of the effective rate constant for the same hydrodynamic cavitation reactors under the same operating conditions for different volume of the holding tank ( k app = 1.06 × 10 –3 min –1 for 0.005 m 3 volume in the holding tank and k app = 2.41 × 10 –4 min –1 for 0.024 m 3 volume in the holding tank). It is unphysical to expect dependence of the effective rate constant on the volume of the holding tank!…”
Section: Current Status Of Modeling Of Hydrodynamic Cavitation
Reacto...mentioning
Hydrodynamic cavitation (HC) is finding ever increasing applications in water, energy, chemicals, and materials sectors. HC generates intense shear, localized hot spots, and hydroxyl radicals, which are harnessed for realizing desired physicochemical transformations. Despite identification of HC as one of the most promising technology platforms, its potential is not yet adequately translated in practice. Lack of appropriate models for design, optimization, and scale-up of HC reactors is one of the primary reasons for this. In this work, the current status of modeling of HC reactors is presented. Various prevailing approaches covering empirical, phenomenological, and multiscale models are critically reviewed in light of personal experience of their application. Use of these approaches for different applications such as biomass pretreatment and wastewater treatment is briefly discussed. Some comments on extending these models for other applications like emulsions and crystallization are included. The presented models and discussion will be useful for practicing engineers and scientists interested in applying HC for a variety of applications. Some thoughts on further advances in modeling of HC reactors and outlook are shared, which may stimulate further research on improving the fidelity of computational models of HC reactors.
“…Also, in various branches of industry, the effect of a magnetic field is widely used to change the properties of water [16][17][18]. The study of cavitation in low-frequency sound fields revealed an analogy in terms of physicochemical effects between low-frequency and ultrasonic cavitation [19,20].…”
The paper presents the results of research into the influence of low-frequency sound and magnetic fields on the change in the properties of water and its purification in a vibrating machine with an eccentric drive, which allows obtaining a constant amplitude of oscillation when the frequency of oscillations of the drive is changed. A method and construction of a vibrating machine for changing the properties of water and cleaning is proposed. Thanks to its reciprocating movement, and in the pulsation chamber and the nozzle, appropriate reactions take place. At certain oscillation frequencies, a cavitation cavity appears in the nozzle and the pulsation chamber, in which the process of splitting water molecules into active radicals takes place. At the same time, during the reciprocating movement of water through a non-magnetic nozzle, which is covered by permanent magnets, an additional effect of a variable magnetic field direction is exerted on water, which strengthens the breaking of hydrogen bonds in water molecules. Visualization of the hydrocavitation process during operation of a vibrating machine with a transparent nozzle was studied. During the experiment, changes in water parameters were studied, i.e. changes in pH, changes in the oxidation-reduction potential of treatment ORP and the total content of mineralization according to the TDS index with treatment time. The total concentration of dissolved salts decreases from 400 to 300 units, which also indicates an improvement in water quality. The rational frequency limits of the vibration drive of the machine are in the range from 18 to 23 Hz with an amplitude of oscillations of 0.002 m, and the ratio of its design parameters is determined: with a piston diameter of 0.1 m, it is recommended to use a diameter of the hole in the piston from 0.006 to 0.008 m.
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