Jan Zawala

• Ph.D. D.Sc., Associate professor
• Professor (Associate) at Polish Academy of Sciences

The dynamics of bubble-wall collision is studied by means of numerical simulations to elucidate the mechanism of bubble rebound at a solid, no-slip wall in viscous liquid. Results obtained are compared with experimental data as well as data re-ported in the literature. Similarities and differences are discussed. Bubble trajectory, shape deformation...

Protein nanoparticles have been proven to be highly effective stabilizers of water-in-water emulsions obtained from a number of different types of aqueous two-phase systems (ATPS). The stabilizing efficiency of such particles is attributed to their affinity to the water/water interface of relevant ATPS, and emulsion formulations with long-term stab...

In recent decades, numerous studies have focused on finding environmentally friendly substitutes for commonly used petrochemical-based compounds. This paper explores the potential use of poly-L-lysine/rhamnolipids and poly-L-glutamic acid/ethyl lauroyl arginate mixtures, for foam formation and stabilization. Two complementary methods were employed...

In recent decades, numerous studies have focused on finding environmentally friendly substitutes for commonly used petrochemical–based compounds. This paper explores the potential use of poly-L-lysine/rhamnolipids and poly-L-glutamic acid/ethyl lauroyl arginate mixtures, for foam formation and stabilization. Two complementary methods were employed...

Introductions Ink based on metallic nanoparticles has been widely used so far for the fabrication of electronic circuits and devices using printing technology. This study aimed at the analysis of the effect of the silver shell thickness of nickel@silver core@shell (Ni@Ag) nanoparticles (NPs) on the fabrication and conductive properties of deposited...

In flotation, a bubble acts as a carrier for attached particles. The properties of the gas–liquid interface of the bubble are one of the main factors determining the bubble motion and flotation efficiency. Monitoring of the bubble motion may deliver interesting information about the state of the gas–liquid interface. In the case of pure liquids, a...

The formation of motion-induced dynamic adsorption layers of surfactants at the surface of rising bubbles is a widely accepted phenomenon. Although their existence and formation kinetics have been theoretically postulated and confirmed in many experimental reports, the investigations primarily remain qualitative in nature. In this paper we present...

The adsorption characteristics of amino acid surfactants, synthesized as substances with different volumes and hydrophilic head properties, have been previously described experimentally, without robust theoretical explanation. A theoretical model enabling the characterization of the adsorption behavior and physicochemical properties of this type of...

Data in the literature on the influence of water temperature on the terminal velocity of a single rising bubble are highly contradictory. Different variations in bubble velocity with temperature are reported even for potentially pure systems. This paper presents a systematic study on the influence of temperature between 5 °C and 45 °C on the motion...

The properties of thin liquid films are usually investigated under static conditions, isolated from external disturbances. Such studies provide vital information about the drainage mechanism of the thin liquid film, but the conditions of these measurements are vastly different from those that occur when a real dispersed system is created. In this p...

Influence of a motion induced dynamic adsorption layer (DAL) at a liquid/air interface on a kinetic of three-phase contact line (TPCL) expansion in solutions of n-cetyltrimethylammonium bromide (CTAB - cationic surfactant) was studied. It was found that, independently of the solid surface hydrophobicity (assessed using determination of the receding...

Cationic alkyltrimethylammonium bromides (C n TAB, with n = 8, 12, 16, 18) and their mixtures with n-octanol as a nonionic surfactant were chosen as a model system to study the synergistic effect on foamability (two-phase system) and floatability (three-phase system) of quartz in the presence of binary mixtures of ionic/nonionic surfactants. The fo...

The dynamics of air bubbles spreading on the underside of solid substrates is an important scientific problem with numerous applications. This work explores the spreading of bubbles against an ultra-thin, porous ultra-high-molecular-weight polyethylene (UHMWPE) film. This polymer film can be used in applications where a solid-liquid-gas interface i...

This paper presents a simple method for determination of synergism in binary surfactant mixtures. A homologous series of cationic alkyltrimethylammonium bromides (CnTAB, with n = 8, 12, 16, 18) mixed with three non-ionic surfactants (n-octanol, methyl isobutyl carbinol, tri(propylene glycol) butyl ether) was chosen as a model system. In addition to...

In this study, foamability of pure solutions of alkyltrimethylammonium bromides (C n TAB with n = 8, 12 and 16) of various concentrations and their mixtures with n-octanol was studied. It was found from the results that n-octanol behaved as a foamability enhancer, depending on the C n TAB solution concentration. Similar foam height was obtained in...

Importance of external conditions and properties of phases creating liquid films, in outcome of the air bubble collisions with liquid/air and liquid/solids interfaces in clean water and in liquid solutions, is critically reviewed. The review is focussed on initial stages of the liquid films formation by bubbles colliding with interfaces, as well as...

It is well known that mixtures of various collectors or collectors and frothers show often a synergetic effect [1-7], i.e. their overall effectiveness is greater than expected from their individual characteristics. This synergetic effect can affect significantly recovery and selectivity of a separation proces, and can also be related to foamability...

The interaction between bubbles and solid particles is an important mechanism in many industrial processes and flotation is a significant component of the most utilized applications. While flotation of mineral ores deals with fine particles and larger bubbles, the aim of this review is to focus on the opposite case; the interaction between smaller...

This paper presents a quite simple, fully automatized single droplet generator, which can be an alternative for more expensive and complicated microfluidic devices. The simple generation nozzle connected to the pressure cells and cheap peristaltic pumps, synchronized via developed software with simple GUI (graphical user interface) implemented into...

The paper presents results of experimental studies on kinetics of the three‐phase contact formation and a bubble attachment to a quartz surface in solutions of cationic surfactant of various concentrations. By tuning the distance between a single bubble formation point and a quartz surface immersed in the solution, the influence of state of dynamic...

The progress in recent years in characterising the properties of the interface between air and water in the presence of commonly used surfactants in mineral flotation (termed frothers) is summarized. The focus of this review is on techniques that provide access to dynamic aspects of frother interactions at the interface between air and water, and t...

Understanding mineral-chemical interactions at the solid-liquid interface is an aim for all scientists and engineers that focus on mineral flotation, a process of mineral beneficiation. This article highlights some recent results and publications that have made use of advanced tools of physical chemistry, materials science, and colloid/interface ch...

In this paper, the kinetic of the three-phase contact (TPC) formation and the flotation recovery of highly hydrophobic solids with different surface roughness were studied in pure water and aqueous solutions of n-octanol. The surface roughness varied between 1 to 100 μm. It was found that there was a strong influence of surface roughness on both ki...

Kinetics of spreading of the three-phase contact hole (dewetting) formed by an air bubble colliding with hydrophobic solid surface, after rupture of intervening liquid film, was studied both experimentally and numerically. During experiments it was found that evolution of the TPC line diameter with time occurs with characteristic S-shaped trend whi...

The paper presents systematic studies on influence of state of dynamic adsorption layer (DAL) induced at the rising bubble interface on time-scale of the bubble attachment to quartz and mica surfaces immersed in pure n-cetyl-trimethylammonium bromide (CTAB) and mixed octanol/CTAB solutions of different concentrations. It was found that in the case...

Influence of initial adsorption coverage at surface of an air bubble (radius 0.74 mm) formed at the capillary orifice, on profiles of its rising velocities and shape variations was investigated in n-octanol, n-octyltrimethylammonium bromide (CTAB) and Tween80 solutions of different concentrations. The bubble formation and degree of adsorption cover...

The paper presents the principles of our new single bubble generator, which allows a precise control of bubble formation in pure liquids and surfactant solutions, i.e., their detachment frequency and the adsorption time at their motionless surface. We show that the bubbles with equilibrium size can be produced at the capillaries of various orifice...

This paper presents the determination of a concentration at the minimum bubble velocity (CMV) for different types of frothers, such as straight and branched alkyl chain aliphatic alcohols, 1,ω-diols, poly(propylene glycol) and poly(ethylene glycol) alkyl ethers, n-alkyltrimethylammonium bromides, commercial frothers and others. The values of termin...

The effect of cationic (n-cetyltrimethylammonium bromide − CTAB) and non-ionic (n-octanol) surface-active substances (SAS) on the kinetics of rising bubble attachment to a quartz surface and flotation recovery of quartz particles was investigated. The measured time of the three-phase contact (TPC) formation (tTPC) and the advancing contact angle (s...

Flotation and single bubble tests were performed to compare the kinetics of flotation and time of a bubble attachment to naturally hydrophobic solids with different degree of hydrophobicity that is highly hydrophobic polytetrafluoroethylene, moderate hydrophobic fluorite and slightly hydrophobic quartz. The paper identifies an important relationshi...

This paper presents an experimental study of the behavior of an ascending air bubble (equivalent radius 0.74 mm) colliding with a solid substrate. The substrate is either motionless or oscillating with a precisely adjusted acceleration, slightly higher than gravity. It is shown that the stability of the liquid film formed between the striking bubbl...

We report results of the experiments and numerical simulations on kinetics of collision, bouncing and coalescence of air bubbles at free surface of pure liquids of different viscosities. The bubble collision and bouncing courses on the stagnant and vibrating (with controlled acceleration), water/air and silicone oil/air interfaces are compared. For...

In this work flotation and single bubble tests were conducted with high purity quartz in water and hexylamine solutions at different pHs. It was found that flotation kinetics and time of the three-phase contact (TPC) formation (tTPC) at the quartz surface by the colliding bubble were affected by the hexylamine concentration and the solution pH. The...

The time of a single bubble attachment to a rough hydrophobic solid surface with contact angle greater than 90° in aqueous solutions at different frothers (n-octanol, α-terpineol and N-octyl-trimethylammonium bromide) in the concentration ranges of 10–6 to 10–3 M was compared with flotation performed under corresponding conditions. A relationship b...

Influence of variations of the bubble surface fluidity on its rising velocity, kinetics of collisions, bouncing and attachment to hydrophobic solid surface was studied experimentally and modeled by means of numerical calculations. A theoretical model was elaborated to describe gradual retardation of the bubble surface fluidity as observed in surfac...

The influence of solid surface roughness (hydrophobic Teflon) on the timescale of the ascending air bubble (Rb = 0.74 mm) attachment and the kinetics of the spreading of the three-phase contact (TPC – gas/liquid/solid) line was studied. The moment of the rising bubble collision with a horizontal Teflon plate immersed in ultrapure water was monitore...

The kinetics of collision and bouncing of an air bubble on hydrophilic and hydrophobic solid surfaces immersed in distilled water is reported. We carried out the experiments and compared the bubble collision and bouncing courses on the stagnant and vibrating, with a controlled frequency and amplitude, solid/liquid interface. For stagnant interface...

Single pore set-up with the drop detachment process observed by high speed CCD camera is a convenient system to study basic processes governing formation of emulsions by cross-flow membrane emulsification. We studied dependence of the droplet size on the volumetric flows of continuous and dispersed phase in square glass cell (10 mm × 10 mm), where...

The total energy balance of a system consisting of a bubble (radius 0.74mm) freely rising in viscous liquid under the action of buoyancy was considered. Values of bubble acceleration, local and terminal velocities, and shape deformations calculated by numerically solving the Navier-Stokes equation are compared with experimentally determined values....

The paper is devoted to kinetics and mechanism of the three-phase contact (TPC) formation by the colliding bubble at model hydrophobic (polytetrafluoroethylene – Teflon) and hydrophilic (muscovite mica) solid surfaces. To determine influence of type of the surfactant polar group the experiments were carried out in solutions of non-ionic (n-hexanol...

Background: The DAL (dynamic adsorption layer) formation, that is, the establishment of uneven distribution of adsorption coverage over the rising bubble surface, with significantly diminished coverage at the upstream pole, is the factor of crucial importance for the bubble motion parameters and kinetic of the bubble collisions with various interf...

Antibubbles are ephemeral objects. Their lifetime is driven by the slow drainage of the air shell from the bottom to the top of the antibubble under the action of hydrostatic pressure. We show in this paper that this argument is only valid if the water used to make the surfactant mixture is saturated in air. Otherwise, two paths are used by the air...

The paper presents fundamentals of a simple physicochemical method (SPMD) and analysis of results obtained when the method was applied for detection of organic contaminations (surface-active substances SAS) in samples of environmental and industrial waters. The method is based on measurements of variations of air bubble local velocities, which can...

Experiments on the coalescence time of submillimeter bubbles colliding with a distilled water/air interface either being at rest (undisturbed) or vibrating vertically (with controlled amplitude and frequency) were carried out. It was found that the outcome of the bubble collision (coalescence or bounce) depends on impact velocity and size of the bu...

We have investigated the influence of concentration of surfactants typically used as flotation frothers (α-terpineol and n-octanol) and roughness of the solid surface on phenomena occurring during rising bubble collisions with a model hydrophobic Teflon surface. The time of three-phase contact (TPC) formation (t(TPC)) and the time of drainage (t(D)...

The paper presents experimental results and numerical simulations on influence of air presence at hydrophilic porous surface (fritted glass filter) on kinetics of the bubble collisions and bouncing. Phenomena occurring during collisions of the rising bubble with surface of the fritted glass filter without and with microbubbles sticking out (protrud...

Phenomena occurring during collisions of the rising bubble with hydrophobic surfaces (Teflon and silanized glass) were monitored using a high-speed camera working with a frequency 1040 Hz. The influence of n-octanol concentration on the bubble impact velocity, bouncing amplitude and frequency, the time of three phase contact (TPC) formation (trpc)...

This paper presents results of studies on structural parameters and settling rates of aggregates formed during bench- and pilot-scale paraffinic froth treatment (PFT) at about 80 °C, during extraction of bitumen from the oil sands. The structures of individual aggregates were investigated using light microscopy, and their composition was estimated...

The bouncing of air bubbles of about 1 mm in diameter on an air/oil interface is reported. We compare the behavior of the bubble when the interface is at rest or when it is vibrated. The results obtained for the interface at rest allowed extracting the key parameter responsible for the outcome of the bubble collision, i.e. bounce or coalescence (bu...

Phenomena occurring during bubble collisions with a water/air interface were studied. The bubble impact velocity was tuned by the following: (i) changing the bubble diameter and (ii) adjusting the distance between the bubble formation point and the water free surface (at the bubble acceleration stage). It was found that the bubble bouncing and the...

Bubble motion is an important problem for mass transfer applications and is encountered in many industrial applications. Recently, Kulkarni and Joshi underlined in their review [1] the importance of the gas bubbles and their rise, due to buoyancy, for various kinds of the gas-liquid reactors. They stated [1] that gas-liquid conBubble and Drop Inter...

Kinetics of the three phase contact (TPC) formation and phenomena occurring during collision of the rising bubble with Teflon plates of different surface roughness were studied in distilled water, α-terpineol and n-octanol solutions, using a high-speed camera of frequency 1040 Hz. Influence of solution concentration and surface roughness on time of...

Influence of adsorption of n-alkyltrimethylammonium bromides (C8, C12, C16) and formation of motion induced dynamic architecture of adsorption layer (DAL) over surface of the colliding bubble on kinetics of three-phase contact (TPC) formation at mica surface was studied. The dynamic phenomena occurring during the bubble collisions were monitored us...

Influence of pH of the BSA solutions on velocity of the rising bubbles, stability of foams, and properties of single foam and wetting films was studied. It was found that the solution pH affected significantly the BSA surface activity and properties of the protein adsorption layer under dynamic and static conditions. At pH close to the isoelectric...

The paper presents the influence of the dynamic adsorption layer (DAL) formation on time of the bubble attachment to mica surface in n-dodecyltrimethylammonium bromide (DDTABr) and n-hexadecyltrimethylammonium bromide (CTABr) solutions. Phenomena occurring during collisions of the single rising bubbles with mica plates, located at different distanc...

This review focuses on the importance of air presence at hydrophobic solid surfaces for wetting film rupture and kinetics of three phase contact formation. Affinity to air is a typical feature of hydrophobic surfaces, but it has been often either overlooked or not taken into consideration. When the hydrophobic surface, contacted earlier with air, i...

Collisions and bouncing of the bubbles with water/gas and water/solid interfaces occurring within a time scale of milliseconds were studied. It was shown that the bubble kinetic energy at the moment of collision has a profound influence on the bubble bouncing prior to the bubble rupture at the liquid/gas interface and attachment to the hydrophobic...

Mechanism of the three-phase contact (TPC) formation and phenomena occurring during collisions of the ascending bubble with a solid and flat surface were studied. Three fluorite samples of different origins and surface roughness and smooth mica plates were investigated. It was found that the time-scale and the mode of air bubble/flat fluorite surfa...

The paper presents a simple physicochemical method (SPMD) elaborated for detection of organic contaminations in water. The SPMD method is based on measurements of lowering the rising bubble velocity by surface active contaminants present in water. A simple set-up consisting of a long glass tube with the capillary in bottom, air container and stop-w...

Phenomena occuring during the bubble motion in the protein solutions were studied. Variations of the bubble local velocity and its shape deformations were determined as a function of distance from capillary orifice and analysed in terms of adsorption coverage at interface of the detaching bubble. The profile of local velocity showed maximum value a...

Initial accelerations, local and terminal velocities, dimensions and shape variations of the bubbles rising in n-pentanol, n-octanol, n-octyltrimethylammonium (OTAB), n-dodecyltrimethylammonium (DDTAB) and n-cetyltrimethylammonium (CTAB) bromides solutions were determined. Single bubbles were formed at the capillary orifice in a so controlled way t...

The free ascending bubble-fluorite surface collision test showed that the three phase contact (TPC) was formed and time of the TPC formation was strongly affected by the roughness of the fluorite surface. The time of the TPC formation varied by an order of magnitude, from ca. 20 to 200ms, depending on the fluorite origin and surface roughness. The...

Influence of n-pentanol, n-octanol and octyl-trimethylammonium bromide on acceleration, local velocities and shape of the bubble detaching from the capillary was studied. The local velocities and shape of the bubble were measured as a function of distance and solution concentration. It was found that bubble acceleration in distilled water was over...