Air Bubble Surface Research Articles

Evaluation of separation by high shear mixing for per- and poly-fluoroalkyl substances (PFAS) treatment in water

Widespread per- and poly-fluoroalkyl substances (PFAS) contamination in water, sediments and soils has driven demand for scalable and cost-effective treatments suitable for application across a range of ∑PFAS concentrations from ng/L to mg/L. One promising class of treatment technology is based on PFAS accumulation at the surface of air bubbles. In this study, hydrodynamic cavitation induced by high shear mixing generated colloidal gas aphrons (CGAs) made of different surfactants (cationic, anionic and non-ionic) to facilitate separation of PFAS differing in carbon–fluorine chain length, head group and charge. Separation efficiency was evaluated for a 600 µg/L ∑PFAS mixture of 6 PFAS each at 100 µg/L, and also for a solution spiked to 1 mg/L ∑PFAS with an aqueous film forming foam (AFFF) mixture. The choice of surfactant produced CGAs with different bubble sizes and surface properties; the non-ionic surfactant produced significantly smaller bubbles, while the cationic and anionic surfactant varied principally by charge. The ∑PFAS separation efficiency varied from < 30 % to 86 % using different surfactants after a 30 s process. The non-ionic surfactant was most effective overall, and the cationic surfactant was most efficient for short-chain PFAS, and those with the carboxylic head group due to surface charge compatibility. Zwitterionic precursor PFAS and perfluoroalkyl sulfonic acids species tested in this study were removed with > 90 % efficiency when anionic and non-ionic surfactants formed the CGAs, while short-chain perfluoroalkyl acids PFAA were removed similarly effectively by cationic surfactant-derived CGAs. While separation efficiencies were lower than the > 95 % ∑PFAS reductions reported elsewhere, the effect was achieved with a treatment time of 30 s, in contrast to the significantly longer treatment cycles applied in other studies.

Effects of biodegradable dispersants on the separation flotation of chalcopyrite and serpentine

The presence of serpentine slime coating on the chalcopyrite surfaces severely affects the chalcopyrite floatability. In this study, three biodegradable polymers, namely polyaspartic acid (PASP), polyepoxy succinic acid (PESA), and hydrolyzed polymaleic (HPMA) were used as dispersants to disperse the chalcopyrite and serpentine particles. The micro-flotation experiments demonstrated that the application of dispersants in the flotation effectively reduced the negative impact of serpentine over a wide pH range, restoring the recovery rate of chalcopyrite to about 85%. The XPS analysis revealed that the dispersants could be adsorbed onto the mineral surfaces through the binding of carboxyl groups with the magnesium or copper sites. As a result, the surface potentials of serpentine changed from positive to negative, while that of the chalcopyrite became even more negative, resulting in a strong electrostatic repulsion between them, which effectively eliminated the covering of the serpentine on the chalcopyrite surface. The AFM force measurements indicate a weak interaction of the polycarboxylic acids dispersants with the surface of chalcopyrite. Consequently, the adsorption of dispersants on the chalcopyrite surface has an insignificant impact on the subsequent adsorption of collectors, which is further supported by the adhesion force measurements between the air bubble and mineral surfaces. Therefore, the application of polycarboxylic acid dispersants in the flotation significantly enhanced the floatability of chalcopyrite in the presence of the serpentine fines.

Technology of extraction of fuel mass from ash and slag waste in Ukraine

Purpose. Development of a technological scheme for the processing of ash and slag waste from coal-fired thermal power plants. The methods. The ash and slag dumps of thermal power plants are made up of the main components - slag, ash and unburned coal particles, drawing up an appropriate scheme for the extraction of coal particles allows the development of an effective scheme for the processing of ash and slag outputs of thermal power plants. The slag is separated from the fly ash by classification on a screen. Next, the method of extracting fuel mass from fly ash is used - the flotation method, based on the selective fixation of coal particles on the surface of air bubbles in the flotation chamber, with subsequent extraction of coal particles into a foam product. The mineral part of the ash cleaned from the fuel mass is ready for use in the road construction industry. Findings. A technological scheme for the processing of ash and slag waste of coal-fired thermal power plants has been developed, which makes it possible to obtain slag, high-quality coal concentrate, and the mineral part of ash. The originality. For the first time, a mathematical model was developed for forecasting indicators of enrichment of ash and slag waste of coal-fired thermal power plants by the flotation method. To predict beneficiation indicators, it is necessary to use three disclosure values: the initial ash content of the coal fraction (Aпd), the number of coal grains (PРЗ), the number of rock grains (PНЗ), provided that the separation characteristics of the beneficiation equipment are experimentally determined in advance. On the basis of the developed mathematical model of forecasting indicators of ash slag waste enrichment, an appropriate flotation scheme for effective extraction of fuel mass was drawn up, which made it possible to develop a technological scheme for processing ash slag waste of coal-fired thermal power plants. Practical implementation. The developed technological scheme for the processing of ash and slag waste makes it possible to obtain slag with a yield of 3.11% suitable for filling industrial roads, coal concentrate with a yield of 25.75% with an ash content of 21.80% can be used as a secondary fuel for thermal power plants or as a raw material for production solid fuel briquettes, as well as the mineral part of ash with a yield of 71.14% with an ash content of 98.10%, which can be used in the road construction industry.

Effect of foaming characteristics of air entrained agents on mechanical properties and pore structures of cement-based materials in plateau mountainous regions

Concrete freeze-thaw damage is common in high-altitude regions. Adding an appropriate amount of air-entraining agents (AEA) can improve the flowability of fresh concrete and the frost resistance of hardened concrete, without significantly affecting concrete strength. However, the existing studies of the influence and mechanism of AEAs on concrete mainly focus on conventional environmental tests and simulated conditions, with less consideration to the various environmental factors caused by real altitude changes. In this study, five types of AEAs are utilized according to bubble shaking tests in two different altitude environments: Chengdu, Sichuan (altitude: 300 m; air pressure: 96.7 kPa), and Aba Prefecture, Sichuan (altitude: 3700 m; air pressure: 66.7 kPa). Physical and mechanical properties as well as pore structure tests are also conducted on AEA paste and concrete. The results show that the relationship between air bubble sizes and surface tension of AEA solutions is the closest, with larger bubble sizes, smaller bubble volumes, and poorer foaming properties observed at high-altitude regions. Adding an appropriate amount of AEA can improve concrete workability. In high-altitude and low-temperature regions, AEA concrete exhibits better slump retention. The addition of triterpenoid saponin AEA increases the proportion of small pores (0.5 μm–200 μm) in paste and concrete, with a lower growth rate observed at high altitudes compared to lower altitudes. Additionally, the average pore diameter and bubble spacing coefficient of hardened paste decrease, optimizing the pore structure. Triterpenoid saponin AEA is recommended for improving concrete performance in high-altitude environments, with a recommended dosage of 0.01 %.

AIR BUBBLE ENCAPSULATION OF EUKARYOTIC CELLS AND THERAPY FAILURES

Background: The purpose of this manuscript is to introduce a newly discovered potential dangers of air bubbles used for therapeutic or diagnostic purposes into the human body.At present, the injection of air bubbles into the human body for diagnostic purpose is viewed positively by the medical/scientific community. In Vitro experiments are presented whereby cells isolation by air bubbles could interfere with chemotherapy treatments.Methods: Author’s own saliva sample was spitted out onto the center of a clean 25X75x1mm glass slide. The sample was placed and focused on the viewing platform of a video microscope. A toothpick was used to harvest inner cheek cells and gently transfer onto the spitted out sample. After focusing, areas were selected showing floating cells and air bubbles. Different laminar levels were observed by cells migrating at different levels.While microscopically observing the sample, the glass slide was disturbed by finger tapping, the aim to induce bubble bursting.Results: Deformed cells were observed when adhering to the outer surface of air bubbles. Additionally, undeformed cells seen at two distinct perpendicular layers when trapped within the floating bubbles. Noticed was a selective attraction of cells by the outer edge of the floating bubbles. Cells attached to the bubble’s edge were being deformed and attracted to each other. Cells were also observed passing unattracted when in a separate laminar flow under the floating bubble. The provocative tapping causing air bubbles to cavitate and burst.Conclusions: The bursting of an air bubble is not the only factor in floating eukaryotic cells deformation. In this manuscript video microscopy and still images are introduced demonstrating a newly found horizontal flat parallel energy field in the periphery of the oxygen bubble. This energy is evident in the free-floating air bubble interface as cheek eukaryotic cells adhere only to the flat round edge of a bubble. Cells are attracted, adhered to each other, and deformed by their own intrinsic attraction. Once the bubble bursts, cells and debris are dispersed, with cells adherence partially disturbed. Cell deformations persisting. It could be hypothesized that cancer cells trapped at different laminar layers inside the bubble be refractory to external chemotherapy agents thus retaining their cancer characteristics.

Investigation on the oil bridge between air bubble and glass surface in water: Formation, deformation, mechanical force and implications for froth flotation

In froth flotation, the insoluble oil as a liquid bridge between an air bubble and a solid surface in water is a common and important interface phenomenon. This paper investigated the impact of the oil bridge between an air bubble and a glass plane from aspects of mechanical forces acting on complex interfaces. An air bubble was pulling towards an oil droplet anchored on a flat glass slide under water compulsively. In this process, the high-speed camera was applied to observe the deformation of the interfaces and the mechanical forces were measured using a micro-force sensor. It was found that the air-water-oil (A-W-O) three-phase contact line (TPL) can form, expand and become stable rapidly within 85.0 ms when the bubble is attached to the oil droplet. The expansion of the A-W-O TPL provides an extra adhesion force to the air bubble. The oil formed an oil bridge connecting the bubble and the solid surface which shortened the attachment distance and extended the detachment distance. The mechanical force resulting from the oil bridge acting on the air bubble is equivalent to an air bubble directly adhering to a hydrophobically modified surface. The capillary force and pressure force were calculated and were found to be the major components of the mechanical force in the detaching process. This mechanical force was directly influenced by the interfacial tension vectors, the interface curvatures, and the TPL radius. The deformation on the interface, especially the A-W interface, is significant to the detachment process and related mechanical forces.

Технология использования чернового концентрата в качестве минералов-носителей

Технология использования чернового концентрата в качестве минералов-носителей

Three-phase contact formation between an air bubble and solid surfaces with different hydrophobicity degrees in liquid

Interactions between gas bubbles and solid particles are crucial in numerous industrial processes, including froth flotation, in which particle-bubble attachment plays a vital role. The process efficiency depends on differences in the surface wettability (i.e., hydrophobicity, expressed by the contact angle) of separated particles. This study aimed to investigate the influence of surface hydrophobicity and zeta potential on the formation of a three-phase contact (TPC) between a single air bubble and planar glass surfaces. Different degrees of hydrophobicity were achieved by esterification with a range of alcohols and time. The interaction between the bubble and surface was monitored using a high-speed camera with a time resolution of 1 ms, allowing for measurements of the time of thin liquid film drainage, time and diameter of TPC formation, TPC line expansion velocity, and dynamic contact angles. The observations suggest that TPC formation occurs when the solid surface has a sufficient degree of hydrophobicity (critical contact angle) and is dependent on the differences in zeta potential values between the air bubble and the solid surface in water. When both surfaces are negatively charged, the limiting value of the water contact angle is ca. 35°, whereas for oppositely charged surfaces, the value slightly decreases to ca. 31°. The results show that increasing surface hydrophobicity enhances the bubble adhesion effectiveness by increasing both the propagation velocity of the TPC perimeter and its size (measured by the diameter of the formed TPC). The article also discusses the mechanism of bubble-solid adhesion in relation to the hydrophobicity and zeta potential of the solid surface based on the obtained results.

ОСОБЕННОСТИ РАСЧЕТА ВЕЛИЧИНЫ ФАКТОРА ОБНОВЛЕНИЯ ПОВЕРХНОСТИ ПУЗЫРЬКОВ ВОЗДУХА

The resource intensity of biological wastewater treatment is reduced by increasing the energy efficiency of the pneumatic aeration systems used in the aeration tank. Modernisation of the aeration process is possible with the development of an adequate mathematical model describing the process of mass transfer from air bubble to water the oxygen required for biological oxidation of wastewater pollutants. The analysis of the Lewis- Whitman two-film theory, Higbee's penetration theory, and P. W. Dankwerts' theory of deformed bubble surface renewal describing the process of mass transfer of air oxygen into water showed the peculiarities of their application to gas-liquid systems. The factor of renewal of deformed surface of air bubbles is of great importance for describing the processes of mass transfer of air oxygen to water when using pneumatic aeration system in aeration tanks. In turbulent flow at continuous renewal of interfacial surface created by air bubbles, there is intensification of mass transfer process due to turbulent diffusion, which is reflected in calculated mathematical dependences. The use of mathematical dependences determining the rate of mass transfer of air oxygen to water through the deformable surface of bubbles formed in the aeration volume of the aeration tank will make it possible to take into account the change in their shape. This will increase the accuracy of determining the values of technological characteristics of pneumatic aeration systems.

Effect of mono- and di-valent cations on PFAS removal from water using foam fractionation – A modelling and experimental study

Per- and poly-fluoroalkyl substances (PFAS) are a group of recalcitrant compounds whose widespread use in a variety of consumer products has led to contamination of groundwater and surface water systems. Foam fractionation is a potential remediation technology for treatment of PFAS contaminated water, which takes advantage of the high surface activity imparted by the fluorocarbon chain to remove them from solution by adsorption to the surface of air bubbles. In this study, the effect of mono- and di-valent cations on the performance of a PFAS foam fractionation process where sodium dodecyl sulphate (SDS) is used as a co-foaming agent has been evaluated. The results indicated that the separation of PFAS was improved in an order that followed the charge density of the salts with Mg2+ > Na+ > K+. It was also observed that at salt concentrations above 100 mM for Na+, above 10 mM for K+ and Mg2+ but between 0.1 and 10 mM for Ca2+ in the presence of greater than 4 ppm of SDS, the cations can complex with the SDS in the system and suppress foam formation due to the surfactant precipitation. Foam fractionation was able to remove perfluorohexane sulphonic acid (PFHxS), perfluorooctanoic acid (PFOA) and perfluorooctane sulphonic acid (PFOS) from a sample of Australian groundwater to below the analytical detection limit of 0.1 ppb within 60 min with SDS being used as the co-foaming agent, but was unable to remove the short chain perfluorobutanoic acid (PFBA).

A casting method using contrast-enhanced diethylphthalate for micro-computed tomography of snow

AbstractCasting snow is necessary to prevent metamorphism and deformation prior to X-ray micro-computed tomography (μCT) imaging. Current methods are insufficient for large-scale field sampling of snow due to safety considerations associated with the casting medium and/or lengthy sample preparation times. Here, a casting method using contrast-enhanced diethylphthalate (DEP) for μCT of snow is presented. The X-ray contrast of DEP is enhanced with barium titanate nanoparticles (BaTiO3) and iodine (I2). A partially unsupervised, three-phase segmentation method utilizing traditional Gaussian smoothing followed by a three-step process to address transition voxels is also presented. Synthetic images derived from real snow samples are used to evaluate the segmentation method with various configurations of trapped air bubbles. Real snow samples spanning a range of specific surface areas (SSAs) (8–28 m2kg−1) and densities (135–463 kg m−3) are used to assess the performance of the segmentation method on real, cast samples. The method yields SSA, density and correlation length errors of less than 10% for synthetic images with air bubble surface areas less than 333 m−1per sample volume for eight of the nine snow samples. For eight of the nine cast samples, the method yields errors of less than 10% for all three parameters.

Adhesion forces for water/oil droplet and bubble on coking coal surfaces with different roughness

Surface roughness plays a significant role in floatability of coal. In the present paper, coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements. The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness. The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning. Maximum adhesion forces between water and surfaces were 111.70, 125.48, and 136.42 μN when the roughness was 0.23, 0.98, and 2.79 μm, respectively. In contrast, under a liquid environment, the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water. Maximum adhesion forces of increasing roughness were 97.14, 42.76, and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48, 145.84, and 121.02 μN between oil droplet and surfaces, respectively. Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.

Comparison of the adhesion kinetics between air or oily bubble and long flame coal surface in flotation

Flotation is an effective separation technology with a wide range of applications, and oily bubbles have recently been shown to be more effective than air bubbles at separating low-rank coal. However, the differences in the spreading behaviours of oily and air bubbles at the microscale have not yet been clarified. In this study, high-speed camera technology was used to characterise the interaction process of air and oily bubbles with low-rank coal particles. The three-phase contact (TPC) line formation behaviours of air and oily bubbles on the low-rank coal surface were observed in a deionised solution. At 0–20 ms, the oily bubbles spread more quickly on the low-rank coal surface than the air bubbles; the TPC spreading completion percentages of the oily and air bubbles were 97.58% and 70.73%, respectively. At 20–100 ms, the oily bubbles spread more slowly than the air bubbles because they respectively had 2% and 30% of the TPC spreading process to complete. The results indicated that the oily bubble surface was more hydrophobic than the air bubble surface.

Prevention of Microsphere Blockage in Catheter Tubes Using Convex Air Bubbles.

This paper presents a novel method to prevent blockages by embolic microspheres in catheter channels by using convex air bubbles attached to the channels’ inner wall surface. The clogging by microspheres can occur by the arching of the microspheres in the catheter. A few studies have been done on reducing the blockage, but their methods are not suitable for use with embolic catheters. In this study, straight catheter channels were fabricated. They had cavities to form convex air bubbles; additionally, a straight channel without the cavities was designed for comparison. Blockage was observed in the straight channel without the cavities, and the blockage arching angle was measured to be 70°, while no blockage occurred in the cavity channel with air bubbles, even at a geometrical arching angle of 85°. The convex air bubbles have an important role in preventing blockages by microspheres. The slip effect on the air bubble surface and the centrifugal effect make the microspheres drift away from the channel wall. It was observed that as the size of the cavity was increased, the drift distance became larger. Additionally, as more convex air bubbles were formed, the amount of early drift to the center increased. It will be advantageous to design a catheter with large cavities that have a small interval between them.

Recent Advances in Understanding and Use of Oleofoams

This review aims at presenting recent advancements on the understanding of oleofoams for food applications. Edible oleofoams are currently based on heating a vegetable oil solution containing a high-melting point component, which crystallize upon cooling. After aeration (mostly by whipping), crystals adsorb to air bubble surfaces. The remaining crystals in excess in the continuous phase form an oleogel. Due to both the presence of crystals at the interface and in the bulk, the resulting oleofoams exhibits high stability to drainage, coalescence and disproportionation. The mechanisms leading to the high foam stability are still under investigations to understand and to discriminate between bulk and interfacial rheology effects. The research on edible oleofoams are still scarce in comparison to aqueous food foams even if they present promising applications. In the area of molecular gastronomy, oleofoams are already produced. Oleofoams are a great opportunity for food technologists to develop healthier food products with a low fat content associated to new sensorial properties. However, it is important to better understand these systems in order to help food technologists to use oleofoams and it will contribute to expand this new promising area in food science.

Ultralow Threshold Cavity-Free Laser Induced by Total Internal Reflection.

Total internal reflection is one of the most important phenomena when a propagated wave strikes a medium boundary, which possesses a wide range of applications spanning from optical communication to a fluorescence microscope. It has also been widely used to demonstrate conventional laser actions with resonant cavities. Recently, cavity-free stimulated emission of radiation has attracted great attention in disordered media because of several exciting physical phenomena, ranging from Anderson localization of light to speckle-free imaging. However, unlike conventional laser systems, the total internal reflection has never been implemented in the study of laser actions derived from randomly distributed media. Herein, we demonstrate an ultra-low threshold cavity-free laser system using air bubbles as scattering centers in which the total internal reflection from the surface of air bubbles can greatly reduce the leakage of the scattered beam energy and then enhance light amplification within a coherent closed loop. Our approach provides an excellent alternative for the manipulation of optical energy flow to achieve ultra-low threshold cavity-free laser systems, which should be very useful for the development of high performance optoelectronic devices.

Effect of the ratio between fatty alcohol and fatty acid on foaming properties of whipped oleogels

Oil foams that are based on oleogels are stabilized by the presence of crystalline particles at the air bubble surface and in bulk. The size of crystalline particles is an important parameter in oil foam stabilization. The creation process (cooling and shear rate) can tune its properties. The aim of this study was to determine the effect of altering the weight ratio (R) between long chain fatty acids and fatty alcohols on the oil foam. Two optimal weight ratios R = 7:3 and R = 8:2, for which mixed crystals were present, produced the best foams in terms of overrun, foam firmness and foam stability. R not only affected the crystal size, but also the number of crystalline particles present in the oleogel. Mixed crystals help to produce and stabilize the foams. We highlighted that there is a link between the oleogel stability and hardness with their resulting oleofoam properties.

Influence of interfacial adsorption of glyceryl monostearate and proteins on fat crystallization behavior and stability of whipped-frozen emulsions

The effect of interfacial competitive adsorption of glyceryl monostearate (GMS) with proteins and GMS-fat (anhydrous milk fat; coconut oil) interactions on the fat crystallization behavior and stability of whipped-frozen emulsions were investigated. The results indicated GMS retarded the nucleation of emulsified anhydrous milk fat, but accelerated crystal growth. A contrasting outcome was elicited by emulsified coconut oil. Increasing GMS concentration strengthened and weakened the structural networking within anhydrous milk fat and coconut oil emulsions, respectively, which was evidenced by the oscillatory rheology results. Anhydrous milk fat whipped-frozen emulsions were characterized by increased partial coalescence degree with increasing GMS concentration. However, lower partial destabilization index and insignificant effect of GMS was found in coconut oil systems. Confocal laser scanning micrographs revealed that big clumps of fat globules were present at air bubble surfaces in anhydrous milk fat whipped-frozen emulsions, while only some individual fat globules were observed in coconut oil systems.

An investigation of continuous interaction process between air bubble and various roughness coal surfaces using microbalance

An investigation of continuous interaction process between air bubble and various roughness coal surfaces using microbalance

Measurement of the Attachment Force between an Air Bubble and a Mineral Surface: Relationship between the Attachment Force and Flotation Kinetics.

The interaction forces between air bubbles and mineral surfaces were directly measured during the attachment process using an apparatus developed in our laboratory, and they are defined as the attachment forces. The attachment forces were measured between the air bubble and mineral surfaces modified with surfactants to have different hydrophobicities. Chalcopyrite and galena were used as the mineral surfaces, and their hydrophobicity was controlled by adsorbing xanthates with different hydrocarbon chain lengths. The hydrophobicity is represented by the static contact angle of water on the mineral surface. When the static contact angle was less than 90°, the attachment force increased considerably with increasing static contact angle of the surfaces, irrespective of the mineral type or the hydrocarbon chain length of the adsorbed xanthate. The hydrophobicity of the mineral surface is found to be the dominant factor determining the attachment force. The measured attachment forces agree well with those calculated based on the force balance model derived from the capillary force and Laplace pressure equation. Microflotation experiments to examine the relationship between the attachment force and flotation kinetics were carried out under the same conditions to control surface hydrophobicity. The variation in the flotation kinetic constants and attachment forces with the water contact angle are very similar. As a result, the attachment forces measured by the developed apparatus can provide quantitative information on the interaction between an air bubble and the mineral surface and can be used for predicting the flotation kinetics.