Charged Bubbles Research Articles

Characteristics of Bubble Dispersion under Nonuniform Electric Field in an Up-Flow Bubbling System: From Charged Bubble to Charged Bubble Cluster

Characteristics of Bubble Dispersion under Nonuniform Electric Field in an Up-Flow Bubbling System: From Charged Bubble to Charged Bubble Cluster

Numerical Study on the Dynamics of a Charged Bubble in the Acoustic Field

In this paper, the dynamics of an acoustic bubble with a constant charge in compressible liquid are investigated numerically, which is based on the Gilmore-NASG model to estimate the radial oscillations. The cavitation effects are enhanced due to the presence of the charge on the bubble surface. The obtained results from the present model are compared with that calculated by the previous model within a wide range of parameters (e.g., charge, acoustic pressure amplitude, ultrasound frequency, and liquid temperature). The similar influences of these parameters on bubble collapse intensity can be observed from both models. Since the present model fully considers the compressibility of gas and liquid, it can be applied to a wider parameter range and leads to the larger predicted values. The research in this paper can provide important insights about the effects of charge on bubble dynamics and the acoustic cavitation applications (e.g., sonochemistry, water treatment, and food industry).

Electroflotation Treatment of Industrial Wastewater in a Specially Designed Electroflotator Powered by a Solar Panel

Currently, the anode in existing electroflotators is a dense mesh with small cells, which causes salt deposits to form on its surface during the electrolysis of waste water. In another case, the salt deposits completely cover the cells, which stops the electroflotation process by preventing the passage of electrolytic hydrogen bubbles through them. The use of an anode in the form of a dense mesh with small cells in electroflotators, on the one hand, increases the density of direct current flowing in industrial wastewater during electroflotation of industrial wastewater, and therefore increases the formation of microdispersed electrolytic hydrogen bubbles, which contribute to the successful electroflotation of industrial wastewater. On the other hand, the use of an anode in the form of a dense mesh with small cells in electroflotators sharply reduces the passage through this mesh of electrolytic hydrogen bubbles, formed during electroflotation of industrial wastewater, which sharply slows down electroflotation process. When the author devised electroflotation treatment for industrial wastewater in a specially built electroflotator, powered by a solar panel, this issue was resolved. The article presents a developed method of electroflotation treatment of industrial wastewater in a specially designed electroflotator, powered by a solar panel (solar cell), which includes an electrolysis base and uses negatively charged electrolytic hydrogen bubbles with a calculated dispersion, which release microscopic particles from wastewater in the process of wastewater treatment by floating up in the wastewater of the created by them strong complexes: negatively charged microdispersed electrolytic hydrogen bubbles + microscopic particles of wastewater from industrial wastewater in the process of an elementary act of flotation.

Influence of algal organic matter in the in-situ flotation removal of Microcystis using positively charged bubbles

Positively charged bubbles efficiently capture and remove negatively charged algal cells without relying on coagulation-flocculation. However, the efficiency is notably influenced by the presence of algal organic matter (AOM). This study investigated the impact of AOM composition on flotation performance by analyzing AOM from various growth phases of Microcystis flos-aquae. The results indicated that low-concentration AOM (<5 mg C L-1), particularly the high molecular weight (>30 kDa) fractions containing high percentages of protein during the exponential growth phase, significantly improved the flotation efficiency by >18%. A high-speed camera system illustrates the pivotal role of low-concentration protein-containing AOM in forming network structures that enhance cell capture. These protein-driven network structures, which enhance the flotation efficiency, provide valuable insights into the development of effective in-situ algal bloom prevention techniques.

Charged Cavitation Multibubbles Dynamics Model: Growth Process

The nonlinear dynamics of charged cavitation bubbles are investigated theoretically and analytically in this study through the Rayleigh–Plesset model in dielectric liquids. The physical and mathematical situations consist of two models: the first one is noninteracting charged cavitation bubbles (like single cavitation bubble) and the second one is interacting charged cavitation bubbles. The proposed models are formulated and solved analytically based on the Plesset–Zwick technique. The study examines the behaviour of charged cavitation bubble growth processes under the influence of the polytropic exponent, the number of bubbles N, and the distance between the bubbles. From our analysis, it is observed that the radius of charged cavitation bubbles increases with increases in the distance between the bubbles, dimensionless phase transition criteria, and thermal diffusivity, and is inversely proportional to the polytropic exponent and the number of bubbles N. Additionally, it is evident that the growth process of charged cavitation bubbles is enhanced significantly when the number of bubbles is reduced. The electric charges and polytropic exponent weakens the growth process of charged bubbles in dielectric liquids. The obtained results are compared with experimental and theoretical previous works to validate the given solutions of the presented models of noninteraction and interparticle interaction of charged cavitation bubbles.

Electroflotation Treatment of Industrial Wastewater in a Specially Designed Electroflotator Powered by a Solar Panel

Currently, the anode in existing electroflotators is a dense mesh with small cells, which causes salt deposits to form on its surface during the electrolysis of waste water. In another case, the salt deposits completely cover the cells, which stops the electroflotation process by preventing the passage of electrolytic hydrogen bubbles through them. The use of an anode in the form of a dense mesh with small cells in electroflotators, on the one hand, increases the density of direct current flowing in industrial wastewater during electroflotation of industrial wastewater, and therefore increases the formation of microdispersed electrolytic hydrogen bubbles, which contribute to the successful electroflotation of industrial wastewater. On the other hand, the use of an anode in the form of a dense mesh with small cells in electroflotators sharply reduces the passage through this mesh of electrolytic hydrogen bubbles, formed during electroflotation of industrial wastewater, which sharply slows down electroflotation process. When the author devised electroflotation treatment for industrial wastewater in a specially built electroflotator, powered by a solar panel, this issue was resolved. The article presents a developed method of electroflotation treatment of industrial wastewater in a specially designed electroflotator, powered by a solar panel (solar cell), which includes an electrolysis base and uses negatively charged electrolytic hydrogen bubbles with a calculated dispersion, which release microscopic particles from wastewater in the process of wastewater treatment by floating up in the wastewater of the created by them strong complexes: negatively charged microdispersed electrolytic hydrogen bubbles + microscopic particles of wastewater from industrial wastewater in the process of an elementary act of flotation.

Effect of a modulated acoustic field on the dynamics of a vibrating charged bubble

We investigate the effect of amplitude-modulated acoustic irradiation on the dynamics of a charged bubble vibrating in a liquid. We show that the potential V(x) of the bubble, and the number and stability of its equilibria, depend on the magnitude of the charge it carries. Under high-frequency amplitude-modulation, a modulation threshold, Gth, was found for the onset of increased bubble amplitude oscillations. For some pressure field values, charge can facilitate the control of chaotic dynamics via reversed period-doubling bifurcation sequences. There is evidence for peak-shouldering and shock waves. The Mach number increases rapidly with the drive amplitude G. In the supersonic regime, for G>1.90Pa, the high-frequency modulation raises both Blake’s and the transient cavitation thresholds. We found a decrease in the bubble’s maximum charge threshold, and threshold modulation amplitude for the occurrence Vibrational resonance (VR). VR occurs due to the modulated oscillatory pressure field, and the influence on VR of the electrostatic charge, and other parameters of the system are investigated. In contrast to the cases of VR reported earlier, where the amplitude G of the high-frequency driving is typically much higher than the amplitude of the low-frequency driving (Ps), the VR resonance peaks occur here at relatively low G values (0<G<10Pa) compared to the acoustic driving pressure Ps∼105 Pa. The optimal parameter values for enhanced response could be useful in acoustic cavitation applications.

Electroflotation Treatment of Industrial Wastewater in a Specially Designed Electroflotator Powered by a Solar Panel

Currently, the anode in existing electroflotators is a dense mesh with small cells, which causes salt deposits to form on its surface during the electrolysis of waste water. In another case, the salt deposits completely cover the cells, which stops the electroflotation process by preventing the passage of electrolytic hydrogen bubbles through them. The use of an anode in the form of a dense mesh with small cells in electroflotators, on the one hand, increases the density of direct current flowing in industrial wastewater during electroflotation of industrial wastewater, and therefore increases the formation of microdispersed electrolytic hydrogen bubbles, which contribute to the successful electroflotation of industrial wastewater. On the other hand, the use of an anode in the form of a dense mesh with small cells in electroflotators sharply reduces the passage through this mesh of electrolytic hydrogen bubbles, formed during electroflotation of industrial wastewater, which sharply slows down electroflotation process. When the author devised electroflotation treatment for industrial wastewater in a specially built electroflotator, powered by a solar panel, this issue was resolved. The article presents a developed method of electroflotation treatment of industrial wastewater in a specially designed electroflotator, powered by a solar panel (solar cell), which includes an electrolysis base and uses negatively charged electrolytic hydrogen bubbles with a calculated dispersion, which release microscopic particles from wastewater in the process of wastewater treatment by floating up in the wastewater of the created by them strong complexes: negatively charged microdispersed electrolytic hydrogen bubbles + microscopic particles of wastewater from industrial wastewater in the process of an elementary act of flotation.

Environmentally friendly buff cleaning of ceria nanoparticles using bubbles in gas-dissolved water

Buff cleaning serves as a crucial preparatory step following chemical mechanical polishing, aimed at removing bulk particles from wafer surfaces present in slurries. Most cleaning solutions comprise a variety of complex chemical compounds. Conventional cleaning solutions typically consist of complex chemical compounds, including toxic or carcinogenic substances, which hinder wastewater recycling and exacerbate environmental impacts. Here, an eco-friendly buff-cleaning solution, oversaturated gas-dissolved water, is proposed for effective elimination of colloidal ceria nanoparticles. The growth of inherent bubbles that accompanies heating and shear in buff cleaning is associated with the particle-cleaning process and contributes to particle-removal efficiency (PRE). Various optical methods were employed to examine the size and quantity of bubbles, revealing nitrogen (N2) bubbles to be approximately 1 µm in diameter, while carbon dioxide (CO2) bubbles varied from 1 to 10 µm. Gas-dissolved water demonstrated improved PRE, with CO2 exhibiting superior performance in comparison to N2. Negatively charged bubbles were found to effectively capture positively charged ceria particles from oxide film surfaces, cleaning solutions, and pad asperity surfaces. Additionally, bubbles enhanced particle dispersion, as evidenced by a colloidal ceria slurry displaying an average size of 162.5 nm in water, 158.1 nm in N2 water, and 149.8 nm in CO2 water. Well-dispersed particles can easily be flushed from the pad-wafer gap to minimize the risk of recontamination.

Processing of magnesium alloy by energy-intensive multifunction cavitation in a strong magnetic field with laser light excitation and associated sonoluminescence

This work developed a novel metal processing technique referred to as laser-assisted magnetic energy-intensive multifunction cavitation. This technology employs a strong magnetic field to focus bubble energy while applying sonic radiation around a waterjet cavitation jet. Individual bubbles in the cavitation cloud undergo repeated isothermal expansion and adiabatic compression, raising the temperature and pressure of the bubbles. In addition, the presence of a magnetic field over the region between the nozzle exit and the cavitation cloud in which cavitation primarily occurs greatly increases the number and energy density of charged bubble collisions based on the Lorentz force acting between the bubbles. The application of laser light to the charged bubble cloud provides multiphoton excitation that increases the charges of the ions within each bubble, leading to more active collisions. This enhanced cavitation treatment technology was applied to AZ31B magnesium alloy and was found to improve the functionality of the metal.

Soap bubbles deformation in non-uniform electric field and corona discharge

The paper presents the process of soap bubble development in a strong and highly non-uniform electric field obtained using a needle-plate electrode configuration. Bubbles ca. 43 mm in diameter were investigated in a point-plane electrode system with a 30 mm air gap and potential difference up to 14 kV The work includes a qualitative description of the observed phenomena as well as their quantitative evaluation. It was found that the polarity of the applied voltage has a significant effect on the behavior of the bubble in such electrode configuration. It was observed that changes in bubble height and width for positively charged bubbles are more than two times greater than for negatively-charged ones. The formation of a dimple at the top of the bubble caused by the ionic wind was also observed.

Electrostatic Forces in Control of the Foamability of Nonionic Surfactant

Can the DLVO theory predict the foamability of flotation frothers as MIBC (methyl isobutyl carbinol)? The flotation froth is a multi-bubble system, in which the bubbles collide, thus either coalescing or rebounding. This scenario is driven by the hydrodynamic push force, pressing the bubbles towards each other, the electrostatic and van der Waals forces between the bubbles, and the occurrence of the precipitation of the dissolved air between the bubbles. We studied the foamability of 20 ppm MIBC at constant ionic strength I = 7.5 × 10−4 mol/L at different pH values in the absence and presence of modified silica particles, which were positively charged, thus covering the negatively charged bubbles. Hence, we observed an increase in the foamability with the increase in the pH value until pH = 8.3, beyond which it decreased. The electrostatic repulsion between the bubbles increased with the increase in the pH value, which caused the electrostatic stabilization of the froth and subsequently an increase in the foamability. The presence of the particles covering the bubbles boosted the foamability also due to the steric repulsion between the bubbles. The decrease in the foamability at pH &gt; 8.3 can be explained by the fact that, under such conditions, the solubility of carbon dioxide vanished, thus making the aqueous solution supersaturated with carbon dioxide. This caused the precipitation of the latter and the emergence of microbubbles, which usually make the bubbles coalesce. Of course, our explanation remains a hypothesis.

Development of processing technology using extremely high concentration cavitation energy by strong magnetic field

This work demonstrates a new processing technology termed magnetic energy intensive multifunction cavitation (MEI-MFC). In this technique, a strong magnetic field is used to concentrate the bubble energy while ultrasonic waves are applied from the perimeter of a water-jet cavitation jet. The cavitation bubbles are expanded while generating a swirling flow that increases the temperature and pressure of the bubbles. In addition, the presence of a strong magnetic field at the nozzle outlet and the collisions of charged bubbles induced by the Lorentz force cause a significant increase in the number of bubbles and the energy density. This enhanced cavitation processing technology can be applied to various materials to improve strength and to induce functionalization. The peening of austenitic stainless steel using this technique provides a highly corrosion-resistant surface while suppressing the formation of martensite and preventing sensitization by generating a new surface microstructure with a toughened layer directly underneath.

Removal effect and mechanism of amphiphilic chitosan modified microbubbles on microcystis aeruginosa

Algal blooms in lake and reservoir water lead to water quality problems, including water odors, algal toxins, and disinfection byproducts. A novel dissolved air flotation process that incorporates positively charged bubbles (PosiDAF) can effectively remove algae in lakes and reservoirs. Chitosan, as a modified bubble agent in the PosiDAF process, has attracted extensive attention due to its natural nontoxicity and good flocculation properties. In this paper, three types of amphiphilic chitosan with different lengths of carbon chains were prepared via amphiphilic modification and were used as bubble modifiers to remove microcystis aeruginosa in the PosiDAF process. The effects of algae removal under different dosage of modifiers were compared, and the role of algal organic matter was investigated. Results showed that the water solubility of chitosan was markedly enhanced after amphiphilic modification, while thermal stability were decreased. When using butyl-N-2 hydroxypropyl trimethyl chitosan ammonium chloride (C4-HTCC), the effect of modified air flotation was the best, and the removal ratio of algae was 93.47% when the C4-HTCC dosage was 1.0 mg/L. The presence of AOM enhanced the overall effect of algae removal, and electrostatic attraction was the primary adhesion mechanism of the microbubble-amphiphilic chitosan-algal organic matter-algal cell system. In addition, adsorption bridging and net trapping also have positive effects on algae removal.

ESTIMATION OF NUCLEAR FUSION REQUIREMENTS IN BUBBLES DURING ULTRA-HIGH-PRESSURE, ULTRA-HIGH-TEMPERATURE CAVITATION PROMOTED BY MAGNETIC FIELD

In the present work, a strong magnetic field was applied near the outlet of the water jet nozzle to promote the generation of multifunction cavitation bubbles. Because these bubbles contained charged species, the bubbles experienced a Lorentz force due to the magnetic field and collided with greater force. As such, the internal bubble pressure exceeded the threshold value required for fusion to occur. The expansion of these charged bubbles in response to ultrasonic irradiation affected adjacent charged bubbles so that the energy density of the atoms in the bubbles was greater than the fusion threshold. The results of this work strongly suggest that the formation of bubbles via the UTPC process in conjunction with a strong magnetic field may result in bubble fusion.

Study on the cell-collector-bubble interfacial interactions during microalgae harvesting using foam flotation

Foam flotation is an economical and efficient technology for microalgae harvesting. However, the mechanism of cell-collector-bubble interfacial interactions remains to be elucidated. There are two distinct hypotheses regarding the mechanism of microalgae foam flotation. In this study, the cationic surfactant N-cetyl-N-N-N-trimethylammonium bromide (CTAB), which acts as a partition between Chlorella sorokiniana cells and bubbles, is quantified and the zeta potential response of cells and bubbles after adsorption of CTAB is calculated to reveal the interfacial mechanism of the cells-collector-bubble interfacial interactions. The results indicated that more than 90% of CTAB was preferentially adsorbed on the bubbles, which reversed the surface charge of bubbles from negative (−20 mV) to positive (6.1 mV). However, only 0%–3% CTAB was observed on the microalgae cells, suggesting its limited influence on the negatively charged microalgae cells (from −22.3 to −18.6 mV). During microalgae foam flotation, the nonpolar tails of CTAB were first inserted into the bubble through hydrophobic interactions, leaving the positively charged polar heads outside; further, the CTAB-covered positively charged bubbles captured the negatively charged cells by electrostatic attraction. A feasible mechanism was proposed to understand the interfacial interaction of the microalgae cell-CTAB-bubble. By understanding the mechanism of foam flotation, efficient and cost-effective collectors and devices for microalgae harvesting using foam flotation can be developed.

Thin shells in ( 2+1 )-dimensional F(R) gravity

We study thin shells of matter in (2+1)-dimensional F(R) theories of gravity with constant scalar curvature R. We consider a wide class of spacetimes with circular symmetry, in which a thin shell joins an inner region with an outer one. We analyze the stability of the static configurations under radial perturbations. As examples of spacetimes asymptotically anti-de Sitter, we present a charged bubble and a charged thin shell surrounding a non-charged black hole. In both cases, we show that stable solutions can be found for suitable values of the parameters.

On analytical and experimental aspects of soap bubble stream charging

The paper discusses the applicability and advantages of using electrically charged soap bubbles as a route to produce fine sprays composed of highly charged particles, commonly named as electroaerosols. It is indicated that such low in energy demand process may produce very fine droplets or particulates charged to a level higher than that obtained using classical spray charging techniques, involving no bubbles. A process of a soap bubble electrical charging is thus initially studied on a simple analytical basis pointing out to a possibility of producing air bubbles with charge-to-mass (Q/m) ratio up to 60 mC/kg (constrained by the Rayleigh limit) while just 2 mC/kg is commonly considered as a threshold value for an effective particle charging process. Finite element 3D electrostatic simulation method (3D FEM) is then applied to assess a single bubble charging level achievable in a laboratory setup using a DC high-voltage biased bubble machine producing soap bubbles 23 mm in diameter on average. The 3D FEM simulation results postulate a single bubble maximum charging level approaching 25 nC at 41.5 kV charging voltage (constrained by the Rayleigh limit), corresponding to (Q/m) = 17.6 mC/kg. Finally, a stream of bubbles characterized by (Q/m) = 10.4 mC/kg was produced experimentally in the laboratory setup using a contact charging method at 40 kV DC supply. A discrepancy between 3D FEM-simulated results and experimental data was discussed on a shielding effect basis.Graphic abstract

Ultrasound-induced generation of multielectron bubbles in liquid helium

Multielectron bubbles provide a unique platform to study electrons in two dimensions and on curved surfaces, at densities which cannot be accessed using electrons on bulk helium or in semiconductor interfaces. Usually, MEBs are created by applying a large electric field and thereby inducing electrohydrodynamical instability on a charged surface of liquid helium. In the present study, we describe a method to create instability of the charged surface using ultrasound, in the presence of small electric fields. The ultrasound was applied close to the charged liquid-vapor interface, resulting in the formation of a liquid column, which breaks into liquid droplets. The mechanical impact of the droplets falling back into the bulk liquid resulted in the formation of highly charged multielectron bubbles. We estimated the initial charge density of the bubbles above the lambda point to be close to ${10}^{13}\phantom{\rule{0.16em}{0ex}}\mathrm{electrons}/{\mathrm{m}}^{2}$.

Characteristics of CaCO3 nucleated around cyanobacteria: Implications for calcification process

To evaluate the influences of cyanobacterial extracellular polymeric substances (EPS) on CaCO3 precipitation, calcification experiments were conducted for 48 h (initial values of calcite saturation state and equilibrium CO2 partial pressure were ∼5-fold and ∼600 μatm, respectively) using cultures of four filamentous strains (Leptolyngbya sp. (NIES-2104), Scytonema sp. (NIES-2130), Phormidium ambiguum (NIES-2119), and Spirulina subsalsa (NIES-598)). All cultures induced CaCO3 precipitation mainly by photosynthesis to form mono-/poly crystalline calcite and amorphous calcium carbonate (ACC) around them. These features suggested a CaCO3 nucleation process via an ACC precursor phase on negatively charged substances generated by cyanobacteria (i.e., cell walls, EPS, and oxygen bubbles). The characteristics of the precipitated CaCO3 were strongly influenced by the surface properties of the cyanobacteria. For Leptolyngbya, which lacks EPS, a small number of CaCO3 was nucleated onto the smooth surface of negatively charged cell walls and entire cells were incorporated into a large single crystal of calcite. For Scytonema and Phormidium, which possess EPS sheaths, a relatively large number of CaCO3 was nucleated onto the rough surface of negatively charged sheaths, and their sheaths were encrusted and partially impregnated by calcite crystals. For Spirulina, which possesses a loose EPS matrix, CaCO3 nucleation was scarce and restricted to the surface of negatively charged oxygen bubbles stabilized by the EPS matrix to form hollow calcite crystals. These results suggest that chemical properties (i.e., abundance of dissociated acidic groups) primarily controlled the presence/absence of CaCO3 nucleation around cyanobacteria, while a physical property (i.e., submicron-scale structure of negatively charged substances) primarily controlled the numbers of crystal nuclei provided and stabilized ACC precursors as well as the calcification styles (sheath encrustation or impregnation).