A unifying model for concentration polarization, gel-layer formation and particle deposition in cross-flow membrane filtration of colloidal suspensions

Bacchin, Patrice; Si-Hassen, Djaffar; Starov, Victor; Clifton, Michaël; Aimar, Pierre

doi:10.1016/s0009-2509(01)00316-5

Cited by 191 publications

(159 citation statements)

References 20 publications

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“…This situation is quite similar to the formation of a polarization region in dead-end filtration [32,33]. The difference with dead-end filtration is that, since hφ s re- 6) reveals transport mechanisms.…”

Section: The Transition Regionsupporting

confidence: 52%

“…The gradient in volume fraction is associated with a gradient in osmotic pressure. This gradient compensates for the drag force created by the capillary suction and allows the movement of the fluid to become different from that of the particles.This situation is quite similar to the formation of a polarization region in dead-end filtration [32,33]. The difference with dead-end filtration is that, since hφ s re- 6) reveals transport mechanisms.…”

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confidence: 52%

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Drying Dip-Coated Colloidal Films

Cabane

Sztucki

et al. 2011

Langmuir

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We present the results from a Small Angle X-ray Scattering (SAXS) study of lateral drying in thin films. The films, initially 10 µm thick, are cast by dip-coating a mica sheet in an aqueous silica dispersion (particle radius 8 nm, volume fraction φs = 0.14). During evaporation, a drying front sweeps across the film. An X-ray beam is focused on a selected spot of the film, and SAXS patterns are recorded at regular time intervals. As the film evaporates, SAXS spectra measure the ordering of particles, their volume fraction, the film thickness and the water content, and a video camera images the solid regions of the film, recognized through their scattering of light. We find that the colloidal dispersion is first concentrated to φs = 0.3, where the silica particles form a gel with repulsive interactions. Then the particles aggregate until they form a cohesive wet solid at φs = 0.68 ± 0.02. Further evaporation from the wet solid leads to evacuation of water from pores of the film, but leaves a residual water fraction φw = 0.16. The whole drying process is completed within three minutes. An important finding is that, in any spot (away from boundaries), the number of particles is conserved throughout this drying process, leading to the formation of a homogeneous deposit. This implies that no flow of particles occurs in our films during drying, a behavior distinct to that encountered in the iconic coffee-stain drying. It is argued that this type of evolution is associated with the formation of a transition region that propagates ahead of the drying front. In this region the gradient of osmotic pressure balances the drag force exerted on the particles by capillary flow toward the liquid-solid front. INTRODUCTIONCoatings are often made through deposition of liquid colloidal dispersions. Common examples are paints, anticorrosion coatings and ceramic coatings. In most cases, the dispersion is applied as a liquid film, and it changes into a solid film as a result of solvent evaporation. A variety of deposition patterns can be obtained, depending on the evaporation profile over the liquid film and on the flows taking place inside the deposit during drying [1][2][3][4][5][6][7]. The two extreme situations are as follows:(a) Homogeneous film formation: in the simplest case, there is no lateral flow through the liquid film, and all volatile components are evaporated locally. The number of particles at each point of the film is conserved throughout the drying process. Therefore the deposition of a uniform liquid colloidal film leads to a final solid film that has homogeneous composition, thickness and microstructure. Relatively homogeneous films can also be obtained through mechanisms where there is a moving liquid-solid boundary, and there is a flow of liquid phase near this boundary [8,9].(b) Coffee-ring: this process has also been extensively studied [1, 2]. In this situation a macroscopic flow throughout the liquid carries nearly all the particles to the fixed edges of the film, where they pack into a dense rim. At the end o...

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Section: The Transition Regionsupporting

confidence: 52%

supporting

confidence: 52%

Drying Dip-Coated Colloidal Films

Cabane

Sztucki

et al. 2011

Langmuir

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“…This analogy has been underlined by a model [13] for the description of gel and deposit formation from the concentration polarisation where critical flux defines both these transitions. The DCF model developed in this paper could then describe the formation of a gel with heterogeneous properties.…”

Section: Application Of Dcf Model To the Gel Theorymentioning

confidence: 92%

“…• a mass balance with a diffusive term based on an osmotic pressure for suspensions with a critical volume fraction (thermodynamic approach) [13] to describe the aggregation phenomena.…”

Section: Physical Basis For Distribution Of Critical Flux (Dcf)mentioning

confidence: 99%

Distributions of critical flux: modelling, experimental analysis and consequences for cross-flow membrane filtration

Bacchin

Espinasse

Aimar

2005

Journal of Membrane Science

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“…The pressure driven membrane separation can never be performed without mass accumulation (Bacchin et al 2002). In order to predict the transport phenomena through the MF membrane, an estimation of the dye percentages in the permeate, the concentrate and adsorbed by the membrane were given in Table 4, considering the dye amount in the feed of 100 %.…”

Section: Dye Mass Balancementioning

confidence: 99%

New treatment at source approach using combination of microfiltration and nanofiltration for dyeing effluents reuse

Masmoudi

Trabelsi

Ellouze

et al. 2013

Int. J. Environ. Sci. Technol.

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Textile effluents are considered among the most polluted wastewaters all over the world. Among different textile processes, dyeing is the operation that produces the most important amounts of chemical pollution. Many studies have been carried out toward the treatment of these hazardous effluents, and a variety of techniques have been applied for this aim. In this work, the effluents coming from different steps of the dyeing cycle were treated following different mixtures of baths using membrane technology. Nanofiltration (NF) experiments were performed for color removal, but membrane fouling still a major limitation. To enhance NF performances, microfiltration (MF) was carried out as pretreatment to NF. The results showed almost above 99 % of color and turbidity removal and also an important decrease in COD, chloride and salts contents with an improvement in the MF and NF stabilized fluxes of different mixtures compared to that corresponding to the dyeing effluent treated separately. In order to accomplish a full reuse cycle, dyeing experiments were performed using the combined system (MF/NF) permeates. Results were evaluated regarding total color difference between samples and a standard test done with fresh water.

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A unifying model for concentration polarization, gel-layer formation and particle deposition in cross-flow membrane filtration of colloidal suspensions

Cited by 191 publications

References 20 publications

Drying Dip-Coated Colloidal Films

Drying Dip-Coated Colloidal Films

Distributions of critical flux: modelling, experimental analysis and consequences for cross-flow membrane filtration

New treatment at source approach using combination of microfiltration and nanofiltration for dyeing effluents reuse

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