Large Air Bubbles Research Articles

Performance Evaluation of UOWC Systems from an Empirical Channel Model Approach for Air Bubble-Induced Scattering.

Underwater optical wireless communication (UOWC) systems provide the potential to establish secure high-data-rate communication links in underwater environments. The uniqueness of oceanic impairments, such as absorption, scattering, oceanic turbulence, and air bubbles demands accurate statistical channel models based on empirical measurements for the development of UOWC systems adapted to different types of water and link conditions. Recently, generalized Gamma and a mixture of two generalized Gamma probability density functions (PDF) were proposed to describe the statistical behavior of small and large air bubbles, respectively, when considering several levels of particle-induced scattering. In this paper, we derive novel closed-form analytic expressions to compute the bit error rate (BER) and outage performance using both proposed PDFs for various scattering conditions. Furthermore, simple asymptotic expressions are obtained to determine the diversity order of each scenario. Monte Carlo simulation results verify the obtained theoretical expressions. Our results also reveal that UOWC systems present lower BER and outage performance under more turbid water cases with respect to the tap water case due to the higher diversity order and despite the significant increases in pathloss at short link distances. Particle-induced scattering provides an inherent mechanism of turbid waters to mitigate air bubble-induced fluctuations and light blockages.

Anterior Chamber Air Bubble Dynamics With Decreases in Atmospheric Pressure.

To evaluate the effect of decreasing barometric pressure on intracameral bubble size and intraocular pressure (IOP) in eyes with varying air fills in the anterior chamber. A total of 36 human donor eyes received 30%, 50%, or 90% anterior chamber air fill. The eyes were subjected to decreases in atmospheric pressure down to 750 hPa, equal to 2400 m in altitude, and were repeatedly imaged using anterior segment OCT while IOP was measured continuously. Eyes with 30% air fill initially showed moderate increases in IOP yet rising to an average of 30.83 mm Hg at 850 hPa (mimicking 1400 m altitude) and 42.08 mm Hg at 750 hPa. Eyes with larger air bubbles showed more acute increases in IOP with increases to an average of 47.25 mm Hg in eyes with 50% air fill at 850 hPa and 63.33 mm Hg at 750 hPa. In eyes with 90% air fill in the anterior chamber, IOP readings with an average of 113.42 mm Hg were observed already at 850 hPa, at which point additional pressure reduction was not performed. While severe increases in IOP were observed with decreased atmospheric pressure in eyes with large air bubbles in the anterior chamber, small and moderately sized bubbles seem to allow for travel over modest changes in altitude.

Impact of Air Bubbles on the Saltiness Perception of NaCl-Loaded Oleogel-Stabilized Water-in-Oil Emulsions.

Reducing salt intake without affecting the saltiness perception remains a great challenge for the food industry. Herein, the demulsification of water droplets and air bubbles was controlled to modulate the release of sodium from oleogel-stabilized water-in-oil emulsions (OGEs) stabilized by monoglyceride crystals. The effect of monoglycerides with carbon chain length (glycerol monolaurate-GML, glyceryl monostearate-GMS, and glycerol monopalmitate-GMP) and homogenization methods (hand-shaking or high-speed blender) on sodium release and saltiness was investigated by in vitro and in vivo oral processing tests. Milky-white stable emulsions were formed with both water droplets and air bubbles dispersing in the oil phase, regardless of the selected homogenization methods. Air bubbles were more unstable than water droplets during oral digestion. GML OGEs with more and larger air bubbles and the lowest hardness exhibited the highest sodium release rate and the strongest saltiness, independent of homogenization methods. The balance between air bubbles and water droplets in the GMS and GMP OGEs caused slower sodium release and lower saltiness. Overall, the presence of air bubbles in NaCl-loaded W/O oleogel-based emulsions was shown to have important implications for tailoring their sodium release and saltiness.

Reusing biofloc-culture water and microbubble aeration for culturing the white-leg shrimp Litopenaeus vannamei

This study investigated the effects of reusing biofloc-culture water for culturing the white-leg shrimp Litopenaeus vannamei. Experiments were conducted for two continuous cycles without water exchange for 30 days during the nursery stage. The studies were performed with two different aeration systems, namely microbubbles (MB) and large air bubbles (LB). Water quality parameters such as dissolved oxygen (DO), temperature, pH, salinity, alkalinity, total ammonia nitrogen (TAN), nitrite, nitrate, settleable solids (SS), and total suspended solids (TSS) were recorded throughout the culture days. Also, comparisons were performed on parameters of the shrimp growth, i.e., body weight and length, feed conversion ratio (FCR), and specific growth rates (SGR) for the 30-day culture for Cycles 1 and 2. Cycle 2 showed no deterioration in water quality and no significant difference in growth performance compared to Cycle 1 for either aeration method (MB and LB). However, when comparing between aeration methods, MB aeration significantly improved the DO of the water and accelerated the conversion of TAN to nitrate. Shrimps in the MB aeration system were significantly larger (by 39%) with a lower FCR value (reduced by 30%) than in the LB aeration system. Harmful bacteria from the Vibro group were detected. However, they occurred at a minimum level in both cycles and aeration types. Overall, the biofloc-culture water might be reused for the subsequent cycle, while the MB aeration might promote the growth of biofloc and L. vannamei.

Flow and heat transfer characteristics of submerged impinging air-water jets

Flow and heat transfer characteristics of submerged impinging water jets were experimentally investigated. Air was mixed with water using a venturi tube installed before a pipe nozzle. The effects of the volumetric air fraction (β = 0.0–0.7) and jet impingement distance (L/D = 2–8) were studied at a water jet Reynold number, Rew, of 24,000. The air-water flow in the pipe nozzle and impinging air-water jet was recorded using a high-speed camera. An infrared thermal imaging camera measured local heat transfer on the impingement surface. Results show that heat transfer depends strongly on the volumetric air fraction. Impingement distance also affects the behavior of air bubbles in the water jet. Air bubbles can increase the heat transfer on the impingement region by increasing turbulence intensity in the jet with small air bubbles or an intermittent effect of large air bubbles impinging on the surface. Impinging jets where L/D = 4 with β = 0.3 and L/D = 2 with β = 0.2 give the highest heat transfer enhancement, about ∼47% compared to the case of β = 0.0.

Effect of Surfactant Type on Foaming Properties of Milk

The presence of low molecular weight surfactants is suspected as one of the causes of poorly foaming milk, as they can interfere with milk proteins in the formation and stabilization of foam. Here, we explore the effect of various surfactants on the foaming properties of reconstituted skim milk powders. Each surfactant is different in electrical charge and molecular weight, including cleaning O- and E-coded chemicals, Tween 80, sucrose stearate, sodium oleate, sodium dodecyl sulfate, cetyltrimethylammonium bromide, benzalkonium chloride, and lecithin. The results showed that surfactants had different effects on foamability, foam stability, and structure, due to their varied effects on milk properties (e.g., pH, zeta potential, and surface tension). E-coded chemicals and sucrose stearate markedly decreased milk foamability, while the impact of Tween 80 and lecithin was considered detrimental to foam stability, as they mostly induced the production of large air bubbles in the foam.

Novel Slow-Release Defoamers for Concrete Using Porous Nanoparticles as Carriers.

Excess large and unstable air bubbles can reduce the compressive strength of hardened concrete, and traditional defoamers always fail because of adsorption and encapsulation on cement with the progress of cement hydration in later stages. It is necessary to develop a novel defoamer that shows a sustained defoaming ability in fresh concrete. A novel slow-release defoamer for concrete using porous nanoparticles as carriers is reported for the first time. The porous nanoparticles/polyether defoamer composite (SiO2-Def) was prepared via sol-gel method. SiO2-Def is a spherical composite nanoparticle with a size range of 160-200 nm and a uniform pore size distribution. SiO2-Def shows a high load rate of about 16.4% and an excellent release under an alkali and salt environment. It has a weak initial defoaming ability but shows a sustained defoaming ability with time, so that it can avoid the failures of defoamers and eliminate harmful bubbles entrained during the processes of pumping and transportation. Moreover, SiO2-Def produced a higher compressive strength of the hardened cement mortars.

Effect of oil-based emulsion on air bubbles in the spray sheet produced through the air-induction nozzle.

The air-induction spray featured by air bubbles involved in the spray sheet has attracted great attention in applications of agricultural spray due to its advantages of alleviating spray drift and promoting deposition. The objective of the presented study is to deepen the understanding of the mechanism of the air-induction spray through elucidating the effect of sprayed liquid on characteristics of air bubbles in the spray sheet. The air bubbles with relatively large sizes are stable for a long time span. As velocity of the water spray increases from 6.85 m s-1 to 17.87 m s-1 , average size of the air bubbles decreases from 383.21 μm to 236.47 μm. With the introduction of organosilicone surfactant, the surface tension of the sprayed liquid decreases from 67.38 mN m-1 to 31.32mN m-1 ; accordingly, average size of the bubbles decreases from 383.21 μm to 160.9μm. Compared to aqueous solutions spray, the oil-based emulsion spray is responsible for relatively small average size of air bubbles as the surface tension and spray velocity are respectively similar. Low drainage rate of the bubble lamella contributes to high stability of large air bubbles. The decrease of the average size of air bubbles is responsible for small volumetric median diameter of oil-based emulsion spray compared with water spray. Besides the increase of the spray velocity and the decrease of the surface tension, the Marangoni effect caused by dynamics of oil droplets at air-liquid interface also contributes to the decrease of average size of air bubbles. © 2022 Society of Chemical Industry.

Performance of Newly Developed Intermittent Aerator for Flat-Sheet Ceramic Membrane in Industrial MBR System

An intermittent aerator was newly developed to reduce energy costs in a flat-sheet ceramic membrane bioreactor (MBR) for industrial wastewater treatment. Large air bubbles were supplied over a short time interval by the improved aerator technology at the bottom of the flat-sheet membrane. Performance tests for the intermittent aerator were carried out in a pilot system with two cassettes immersed in a membrane tank of the 1-MGD demonstration plant at Jurong Water Reclamation Plant (JWRP) in Singapore. Stable operation was achieved at an average flow of 19–22 LMH with every-2-days MC and peak flow of 27 to 33 LMH with daily MC with reduced air flow for membrane aeration. This indicates that energy costs for membrane aeration can be reduced by using the intermittent aerator. Stable MBR operation with a projected 43% reduction in the overall operating costs could be achieved with an improved aerator together with improved MC regime and membrane cassette.

Особенности формирования «Big Bubble» при проведении глубокой передней послойной кератопластики

Purpose. To determine the optimal channel parameters in the deep layers of the corneal stroma when performing deep anterior lamellar keratoplasty (DALK), providing the maximum frequency of air bubble formation, under the control of intraoperative optical coherence tomography. Material and methods. The study was performed at 30 patients (30 eyes) with a diagnosis of stage III keratoconus. The average age of patients is 31±7 years. All patients were divided into groups consisting of 10 patients, depending on the choice of the topographic orientation of the channel for pneumodissection in the deep layers of the corneal stroma when performing DALK: 1st group – the channel is located towards the center of the cornea; 2nd group – the channel is located paracentral to the temporal side; 3rd group – the channel is located paracentral to the nasal side. In all cases, DALK was performed with a femtosecond laser Femto LDV Z8 (Ziemer, Switzerland). The length of the formed femto channels were variable and amounted to 1.0, 1.5, 2.0, 2.5 and 3.0 mm in each group. Results. The use of intraoperative OCT demonstrated that in all 30 cases the depth of the channel for pneumodissection corresponded to preoperative calculations and amounted to 97±5µm to DM. It was found that the bedding of the channel at a distance of 100µm to the descemet membrane (DM) and its paracentral orientation is characterized by a greater frequency of formation of the «Big Bubble» in comparison with its central orientation: 3rd group – 90% and 2nd group – 80% against 1st group – 60% of cases. The study of the effect of the length of the channel for pneumodissection on the ease of formation of the "Big Bubble" demonstrated that more attempts are required to inject sterile air when channels of 2.0, 2.5, 3.0 mm being used than with short channels of 1.0, and 1, 5 mm (average 3 attempts versus 1.5 attempts, respectively). Conclusion. The paracentral orientation of the location of the channel for pneumodissection is accompanied by a higher percentage of formation of the "Big Bubble" than the central location of the channel. Manual extension of femtochannels having length of 1.0, 1.5 mm, directly with a microsurgical spatula 30G followed by inserting a metal cannula into the channel minimizes the number of attempts to inject sterile air, that facilitates the formation of the "Big Bubble". Performing DALK applying the function of intraoperative OCT allows to control the accuracy of all stages of the operation, including the stage of formation of a large air bubble. Performing DALK with the applying of the function of intraoperative OCT allows to control the accuracy of all stages of the operation, including the stage of formation of a large air bubble. Key words: deep anterior lamellar keratoplasty, Big Bubble, channel for pneumodissection

Bubble breathing is skin deep for anoles

The underwater world is alien to most land animals, a place we only visit briefly before our breath runs out. A few terrestrial animals extend their stay by bringing air with them, such as diving beetles that smuggle bubbles under their wings, or human divers with compressed air tanks. The newest member of the terrestrial SCUBA club are several species of semi-aquatic Anolis lizards, as described by Christopher Boccia, a researcher from the University of Toronto, Canada, and more than a dozen colleagues in their recent study.Spurred on by their own natural history observations of tropical anoles serenely resting at the bottom of streams, the authors rounded up 20 species of anoles (including five considered to be semi-aquatic) at field sites across the Americas and the Caribbean. Using buckets, aquaria or even kiddie pools, they let the anoles dive voluntarily or gently submerged them, paying very close attention to what happened next.When submerged, the anoles took on a silvery sheen, caused by a thin layer of air (a ‘plastron’) forming between the water and their skin. The quicksilver-like coating also invariably connected to a large air bubble around their head to their nostrils. Most species at least occasionally inhaled and exhaled – effectively re-breathing – the bubble while submerged. And when the team compared how many times the different species resorted to re-breathing, the semi-aquatic anoles re-breathed more often and for longer stretches than their non-aquatic cousins. They also stayed underwater longer, with the champion diver of the group staying under for 18 min. Perhaps, the authors mused, the exaggerated re-breathing response in semi-aquatic anoles was an adaptation to their waterfront lifestyle.But that's a hypothesis that only holds if re-breathing serves a physiological function, such as providing oxygen for respiration. To test this idea, the researchers started jabbing an oxygen-measuring probe into the bubbles, looking for evidence that the anoles sucked oxygen out of their bubbles during their dives. They found that the oxygen levels decreased over time in the bubbles and larger anoles consumed oxygen more slowly than smaller ones, which is exactly what they expected from respiring lizards on land. It seems that diving anoles are probably re-breathing the air they take down with them from the surface.There are a few ways that breathing and re-breathing the same bubble of air could help anoles make longer dives. The first is that re-breathing mixed the air inside the anole's body, helping them to extract as much oxygen as possible from the air already in their lungs and throat. The bubble may also help anoles dump carbon dioxide into the water around them, preventing the waste from building up in their bodies. Finally, and most intriguing, the anole might take a page from the book of diving beetles and use bubbles like a physical gill. As the oxygen in the bubble declines, more oxygen is pulled from the water into the bubble, which could allow these air breathers to supplement their breath holding with water breathing!The key to the anole's bubble breathing strategy is probably their waxy skin and the plastron that forms around it, connecting the bubble with their internal respiratory system via the bubble around their nostrils. All anoles get a silvery coating when dunked in water, regardless of their habitat preferences, and so their peculiar skin likely evolved for something other than SCUBA diving, such as keeping clean or dry, and semi-aquatic anoles then co-opted it to create the plumbing of their bespoke underwater breathing apparatus. Anoles may dive deep to keep away from predators or find food, but the trick they use to do it is only skin deep.

Near-wall flow response to large air bubbles rising in inclined water channels

The two-strip electrodiffusion probe is employed to investigate the wall shear rate induced by large air bubbles rising in stagnant or coflowing water within inclined rectangular channels. Synchronized video recordings of bubble movements captured by a high-speed camera provide additional information on the bubble shapes and terminal velocities. The measurements are carried-out in a channel with easily adaptable geometry (three heights and various widths) over a wide range of operation parameters (air volumes and liquid velocities) and inclination angles (from horizontal to vertical arrangement). The main objective of this experimental study is to elucidate the influence of individual operating parameters on the bubble-induced wall shear rate. The typical profile of wall shear rate measured at the center of a flat channel can be characterized by a positive peak at the bubble front location, a negative plateau corresponding to the reverse flow in a liquid film around the bubble, and highly fluctuating values in a wake behind the bubble. Just as the large bubbles in flat channels exhibit a close similarity in their frontal shapes, so do the wall shear rate profiles induced by differently sized bubbles. The magnitude and profile of measured wall shear rate is found to be controlled primarily by the distance between two opposite walls squeezing the rising bubble, thus in flat channels by the channel height. By contrast, widening the channel has no significant effect, even though it contributes to a significant increase in the bubble rise velocity. When the channel is tilted, the rising bubbles are pushed towards the roof wall and thus two distinct wall shear rate profiles are measured at the opposite walls of the channel. The liquid coflow then contributes positively not only to the bubble velocity but also to the magnitude of wall shear rate in the near-wall flow region.

Large air bubble in the Berger space during cataract surgery

For treating retinal or Descemet membrane detachment, an expansive gas is purposefully injected into the vitreous cavity or the anterior chamber. However, it is important to consider the potential complications associated with gas injection, such as intraocular pressure elevation, intraocular lens (IOL) opacification, and gas bubble migration. It is crucial to deal effectively with unexpected intraocular air bubbles. The Berger space is an interspace between the posterior lens capsule and the anterior vitreous hyaloid that provides potential for gas bubble migration. In this study, the features and management during cataract surgery for an individual with a large air bubble in the Berger space is described. A 26-gauge needle was used to puncture the posterior capsule and aspirate the gas bubble; however, this intraoperative strategy was considered inappropriate. Other strategies, such as pars plana aspiration and posterior capsule capsulorhexis before IOL implantation, may be considered in similar cases in the future.

Computational modeling on slug flow phenomenon in inverted siphon and improving its performance

AbstractSlug flow is one of the flow patterns that occur in transmission systems containing two‐phase flow. Large air bubbles trapped in these systems block the flow and expose the structure to undesirable pressures and sharp fluctuations. In this research, numerical modeling has been performed using CFD technique in OpenFOAM software by InterFoam solver. Pressure fluctuations and their magnitude induced by slug flow in inverted siphon have destructive effects on the structure life. Combining the loads exerted by the pressure fluctuations induced on the structures with other loads may exceed the bearing loads of structure. In the inverted siphon, placing the ribs to reduce the damages exerted by slug flow were investigated. Different placements of ribs with different heights on the sloping parts of inverted siphon were modeled numerically. Study of flow characteristics showed that d/Hc ratio (d and Hc represent the rib height and duct height, respectively) can greatly balance the negative pressures and also improve the average pressures in the structure. The results showed that the use of ribs, the probability of forming slugs with pressure drop and severe fluctuations decreased and the maximum and minimum pressures improved about 25% and 20%, respectively.

INFLUENCE OF CORONA AND STREAMER DISCHARGES ON THE BEHAVIOR OF LARGE AIR BUBBLES ARTIFICIALLY FORMED ON/IN A LIQUID

INFLUENCE OF CORONA AND STREAMER DISCHARGES ON THE BEHAVIOR OF LARGE AIR BUBBLES ARTIFICIALLY FORMED ON/IN A LIQUID

Sparged but not stirred: Rapid, ADH-NADH oxidase catalyzed deracemization of alcohols in a bubble column

We investigate in detail both the deracemization reaction rate and maximum conversion of (R,S)-1-phenylethanol in a bubble column and the deactivation rates of both enzymes involved, alcohol dehydrogenase (ADH) and NADH oxidase (nox2). Instead of the predicted ellipsoidal shape of the bubbles, we observe a spherical shape in all our experiments. Calculated values for the area-specific mass transfer coefficient kLa in sparged, but not stirred, solution ranged from 17 to 87 h−1. We find that minimizing the air–liquid interface over time results in the lowest rate of nox2 deactivation. The onset of nox2 dissociation beyond the initial 50 h correlates with a tenfold increase in the observed deactivation rate constant. The highest conversion (99%) for deracemizing 50 mM (R,S)-1-phenylethanol was reached in the shortest reaction time (6 h) if large air bubbles (diameter 2.6 mm) at slow flowrates (5 bubbles/s) were employed. A faster flowrate, which delivers more oxygen per unit time, increased the initial reaction rate but resulted in a slower rate at higher conversions and ultimately incomplete maximum conversion (94%). Reaction rates under sparging were 4–8 times faster than in quiescent solution. Lastly, stirring did not significantly aid conversion (41% vs 37% in quiescent solution after 12 h) but caused increased enzyme deactivation (44 h vs 136 h half-life quiescent solution).

Capturing the impact of nanobubble liquid in enhancing the physical quality of ice cream

Nanobubbles are bubbles of nanometer to micrometer size and are dispersed in a liquid water. In recent years, nanobubbles technology has been used in an extensive range of application such as in drinking water, agriculture, fishery, wastewater treatment and food. In ice cream, air cells are important for the smooth texture of ice cream. In this study, the effects of using nanobubble liquid in ice cream was compared with the one using normal water. Samples were prepared and analysis was conducted to check the physical properties of ice cream. Based on the results obtained, the apparent viscosity of ice cream made using nanobubble liquid (INBL) and normal water (INW) were 0.211 Pa.s and 0.149 Pa.s, respectively. INBL ice cream had higher density and firmness which were 0.77 g/mL and 34.80 gram-force, respectively while INM ice cream had slightly lower density and firmness which were 0.74 g/mL and 29.93 gram-force, respectively. The overrun of INBL ice cream was lower which was 46 % while INW ice cream was 54 %. For both INW and INBL ice creams, the fastest melting rate was recorded between 10-30 min at the rate of 1.491 g/min and 1.558 g/min, respectively. INBL ice cream held its body slightly longer and melted a bit later than INW ice cream. As a conclusion, ice cream with lower overrun is denser and has rich texture. Smaller air bubbles are able to hold the ice cream body better than the ones with larger air bubbles. Nanobubble liquid ice cream has higher firmness value which indicates its ability to better retain its shape.

Investigation on slug flow phenomenon in Alborz morning glory spillway and preventing its destructive effects

Slug flow is a flow pattern which occurs in conveyance systems containing a two phase-fluid flow. Large air bubbles entrapped along these systems interrupt the flow and conduct to undesirable pressures and their fluctuations. Most of the previous concerning studies on slug flow phenomenon were performed in micro-channels with small scales in which the expansion of the air bubbles was negligible. In contrast, we investigated the systems with large pressure drops which conduct to abrupt increases on the volume of air phase. In this research, the verification tests applying CFD techniques were performed in OpenFOAM software by interFoam solver. The performance of morning glory spillways is investigated under steady states. While during the occurrence of flood, by increasing the depth over the spillway crest, the discharge is augmented which conducts to entrap the air pockets with pressure and velocity fluctuations. These fluctuations influence on the life of structures and their performances. This study aimed on unsteady flow in a glory morning spillway and its consequences and proposing the measures for reducing the destructive effects of slug flow. The pressure and velocity fluctuation were considered as the indices for the performance of a hydraulic structure. Spatial and temporal variations of pressure and velocity along the spillway are evaluated. Also, the influences of spillway geometry on slug flow and the measures to attenuate its destructive effects are analyzed. The results showed that the better performances of morning glory spillway are coincided by the diameter of tunnel superior than the height of water above the crest.

Velocity of a large bubble rising in a stagnant liquid inside an inclined rectangular channel

The velocity of large air bubbles rising in an inclined rectangular channel filled up with stagnant water is investigated within the inertial flow regime. The experiments based on bubble observation by means of a high-speed camera are carried-out in a versatile channel with easily adaptable geometry over a wide range of inclination angles. The results obtained in vertical channels of various aspect ratios are confronted with the previous analytical predictions to confirm bubble velocity scaling based on the channel perimeter. The extrapolation of velocity measurements done at very low inclinations then provides the translation velocities of large bubbles corresponding to horizontal channel placements. These velocities agree well with the results of previous channel emptying experiments and suggest velocity scaling based on the channel height. Markedly different dependences of the bubble rise velocity on the channel inclination are observed in flat and tall channels. The analysis of our experimental data provides a simple model for the prediction of the bubble rise velocity in inclined rectangular channels. The effects of leveling and buoyancy, which are jointly acting on bubbles in inclined channels, are incorporated into the model through two principal parameters: the limiting bubble velocities achieved at the horizontal and vertical channel placement. Considering the inertial regime of large Taylor bubbles, these limiting velocities are predictable with a sufficient accuracy.

АДСОРБЦИЯ ПОВЕРХНОСТНО-АКТИВНЫХ ВЕЩЕСТВ НА ВОЗДУШНЫХ ПУЗЫРЬКАХ И ВЛИЯНИЕ СООТНОШЕНИЯ ИХ РАЗМЕРОВ НА ПРОИЗВОДИТЕЛЬНОСТЬ ПУЗЫРЬКОВО-ПЛЕНОЧНОЙ ЭКСТРАКЦИИ

Bubble-film extraction as an improved form of bubbling flotation allows to reduce the concentration of surface-active impurities in water to the level of tenths of a milligram per liter. The use of a polydisperse stream of air bubbles during bubble-film extraction significantly accelerates the process of water purification, when the proportion of large and small air bubbles reaches a certain ratio in their mixed stream. The best case is when air bubbles of different sizes form an integrated structure inside the collecting funnel of the discharge channel of the bubble-film extractor. In the built-in structure, capillary waves accompanying the rupture of large bubbles in the upper part of the critical gasfilling zone inside the funnel of the bubble film extractor transmit their pulses to small-sized bubbles. These pulses overcome the electrostatic repulsion in the boundary menisci of the contacting bubbles and thereby initiate their fusion with the release of more adsorbed surface-active substances into that part of the discharge channel in the bubble-film extractor where a stream of flat liquid films of flotation concentrate appears. As a result, a significant increase in the rate of water purification from its surface-active pollution occurs. The features of bubble-film extraction (enhanced bubble flotation) for water purification are considered from the standpoint of the equilibrium and dynamics of adsorption of surface-active admixtures of water (surfactants) on air bubbles with various sizes. It is shown, that within a certain ratio of dimensions and quantity of air bubbles in their stream transferring surfactants from the water bulk into the bubble-film extractor, the productivity of bubble-film extraction process increases many times. The reason consists in the collective fusion of big and small air bubbles in their embedded structure inside of the bubble-films extractor under the action of capillary waves appearing at the bursting of large bubbles.