Anomalous thickness variation of the foam films stabilized by weak non-ionic surfactants

Qu, Xuanhui; Wang, Liguang; Karakashev, Stoyan I.; Nguyen, Anh V.

doi:10.1016/j.jcis.2009.05.038

Cited by 38 publications

(34 citation statements)

References 72 publications

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“…A Microelectrophoresis Apparatus Mk II (Rank Brothers Ltd., UK), consisting of a rectangular cell (10 mm Â 1 mm) and platinum electrodes, was used in the measurement of microbubbles. The generation of microbubbles and measurement was adapted from that described by Qu et al (2009). Specifically, nitrogen was dissolved into a Milli-Q solution comprising 0.5 mM NaHCO 3 and made up to an ionic strength of 1.8 mM with NaCl, corrected to pH 7 with 1.6 mg L À1 of polymer, at 450 kPa by leaving overnight.…”

Section: Bubble Charge Measurementsmentioning

confidence: 99%

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

et al. 2014

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Cyanobacteria Flotation PosiDAFWater soluble polymers a b s t r a c t Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed.Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer * Corresponding author.E-mail address: r.henderson@unsw.edu.au (R.K. Henderson). 1 Current address: School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.Available online at www.sciencedirect.com ScienceDirect journal h ome page: www.elsevier.com/loca te/watres w a t e r r e s e a r c h 6 1 ( 2 0 1 4 ) 2 5 3 e2 6 2 http://dx

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Section: Bubble Charge Measurementsmentioning

confidence: 99%

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

et al. 2014

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“…This method has primarily been applied in the study of surfactant-laden films unlike the case of saline liquid films (Exerowa et al, 1979;Karakashev and Manev, 2003;Manev and Pugh, 1991;Qu et al, 2009). To date few studies have been conducted on saline liquid films using the thin liquid micro-interferometric technique (Firouzi and Nguyen, 2014a;Henry et al, 2009;.…”

Section: Thin Liquid Film Micro-interferometrymentioning

confidence: 99%

Drainage and stability of foam films during bubble coalescence in aqueous salt solutions

Firouzi¹

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Bubble coalescence and thin liquid films (TLFs) between bubbles known as foam films, are central to many daily activities, both natural and industrial. They govern a number of important processes such as foam fractionation, oil recovery from tar sands and mineral recovery by flotation using air bubbles. TLFs are known to be stabilized by some salts and bubble coalescence in saline water can be inhibited at salt concentrations above a critical (transition) concentration. However, the mechanisms of the inhibiting effect of these salts are as yet contentious. The aim of this work is to characterise the behaviour of saline liquid films both experimentally and theoretically to better understand the mechanisms.The effect of sodium halide and alkali metal salts including NaF, NaBr, NaI, NaCl, KCl and LiCl on the stability of a foam film was investigated by applying the TLF interferometry method. To mimic realistic conditions of bubble coalescence in separation processes, the drainage and stability of TLFs were studied under non-zero bubble (air-liquid interface) approach speeds (10-300 µm/s) utilizing a nano-pump. For each of the salts studied, a critical concentration (Ccr) above which liquid films lasted for up to 50 s depending on the salt type, concentration and the interface approach speed, was determined. For concentrations below Ccr, the saline liquid films either ruptured instantly or lasted for less than 0.2 s. Ccr follows the order NaF

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“…It is also interesting to note that all films formed from drops with age older than 1 min ruptured at a thickness at around 50 nm or smaller than 50 nm (Figure 4.4). In particular, the DI water films formed from the biconcave drops with the age of 8, 10, 20, 40, and 60 mins ruptured at almost constant thickness of around 35.6 nm which is smaller than the thickness of film rupture for some surfactant systems (Angarska et al, 2004;Qu et al, 2009). …”

Section: Shown Inmentioning

confidence: 85%

Stability and coalescence of bubbles in salt solutions in a bubble column and thin liquid films

Nguyen¹

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Salts are known to inhibit bubble coalescence at the concentration greater than a critical (transition) concentration. The phenomenon of bubble coalescence governs the size distribution of bubbles, which is vital to many natural and industrial processes including mass transfer in the ocean, multiphase reactors and mineral recovery in froth flotation. Despite intensive studies over nearly a century resulting in multiple hypotheses, mechanisms of the coalescence inhibition are still unclear.Researchers have greatly agreed that it is the liquid films between bubbles that control the coalescence and must be firstly understood. Surprisingly, most studies have just focused on the bubble tests, but there was a lack of comprehensive studies about the liquid films in a surfactant-free salt system. This thesis aims to provide experimental evidence and extend the current understanding of the liquid film stability and coalescence in salt solutions.Firstly, the effect of superficial gas velocity (3.5, 10, and 18 mm/s), salt type (NaCl, NaI and CsCl) and concentration (0.001M to 3M) on bubble coalescence and gas holdup in a small bubble column were studied. For the first time, it was found that the transition concentration for coalescence inhibition is not a unique entity of salts as reported but it decreases with increasing gas velocity, which highlights the importance of hydrodynamic conditions. The results also confirmed the ion specific responses of investigated salts to transition concentration and gas holdup.To understand the coalescence, liquid films of the simplest subject, deionised water (DI), were studies using the micro-interferometry method with the Sheludko cell. It was showed that films of DI water drained very fast and ruptured instantly when two bubbles were first brought into contact.However, the film drainage rate and rupture thickness sharply decreased and the film lifetime steeply increased with increasing contact time up to 10 min, but then they levelled off. It was argued that the phenomenon was due to the migration of inherently dissolved gases which act as the long-range hydrophobic attraction. The JC Erickson et al.' theory of the hydrophobic attraction and the extended Stefan-Reynolds models to include the air/water surface mobility were also employed. The liquid film study was then extended for salts without a presence of surfactants. Drainage and stability of liquid films in different salts (LiCl, NaCl, KCl, CsCl, KNO3, NaClO3, CaCl2, and MgSO4) over a wider range of concentration (0.001M -3M) were studied in the close (saturation) Sheludko cell with the strictly controlled saturation level and surface contact time. Films of all salts drained slower and lasted longer with increasing salt concentration. Also, the so-called non-inhibiting ii salt, NaClO3, indeed inhibits coalescence at high concentrations (greater than 1M). The effect of the DLVO forces was totally ruled out. Based on the correlation between the experimental results and the data of oxygen solubility and solution viscosity, i...

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Anomalous thickness variation of the foam films stabilized by weak non-ionic surfactants

Cited by 38 publications

References 72 publications

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

Drainage and stability of foam films during bubble coalescence in aqueous salt solutions

Stability and coalescence of bubbles in salt solutions in a bubble column and thin liquid films

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