Microdivers to study sedimentation in polydisperse, concentrated colloidal suspensions

Biesheuvel, P.M.; Verweij, H.; Breedveld, Victor

doi:10.1002/aic.690470908

Cited by 5 publications

(15 citation statements)

References 27 publications

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“…Solely the suspension density determines whether these particles move upward ('cream'), or down ('settle') (relative to the solvent velocity). This is a well-known point of view concerning particle sedimentation in engineering fields [11,13,16,17]. Eventually, these particles will stop moving when the gravitational force has vanished, in other words, when their mass density is equal to the local suspension density (the so-called isopycnic point [1]).…”

Section: Forcesmentioning

confidence: 97%

“…Indeed, a simple but elegant experiment with a suspension containing two types of particles, of which one (polystyrene, PS) has a mass density smaller than the suspension, but larger than the pure solvent, and the other (alumina) has a density larger than the suspension, unambiguously shows that the lighter particles initially cream and, only after the heavier particles have settled and the local suspension density has dropped below that of PS, start to settle themselves [17]. Figure 1 summarizes this process clearly.…”

Section: Forcesmentioning

confidence: 99%

“…The proportionality constant is a diffusion coefficient, which can be approximated by . Additional details can be found in [17]. The total height of the flask with cap is 63 mm.…”

Section: Dynamic Sedimentationmentioning

confidence: 99%

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Sedimentation dynamics and equilibrium profiles in multicomponent mixtures of colloidal particles

Spruijt¹,

Biesheuvel²

2014

J. Phys.: Condens. Matter

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In this paper we give a general theoretical framework that describes the sedimentation of multicomponent mixtures of particles with sizes ranging from molecules to macroscopic bodies. Both equilibrium sedimentation profiles and the dynamic process of settling, or its converse, creaming, are modeled. Equilibrium profiles are found to be in perfect agreement with experiments. Our model reconciles two apparently contradicting points of view about buoyancy, thereby resolving a long-lived paradox about the correct choice of the buoyant density. On the one hand, the buoyancy force follows necessarily from the suspension density, as it relates to the hydrostatic pressure gradient. On the other hand, sedimentation profiles of colloidal suspensions can be calculated directly using the fluid density as apparent buoyant density in colloidal systems in sedimentation-diffusion equilibrium (SDE) as a result of balancing gravitational and thermodynamic forces. Surprisingly, this balance also holds in multicomponent mixtures. This analysis resolves the ongoing debate of the correct choice of buoyant density (fluid or suspension): both approaches can be used in their own domain. We present calculations of equilibrium sedimentation profiles and dynamic sedimentation that show the consequences of these insights. In bidisperse mixtures of colloids, particles with a lower mass density than the homogeneous suspension will first cream and then settle, whereas particles with a suspension-matched mass density form transient, bimodal particle distributions during sedimentation, which disappear when equilibrium is reached. In all these cases, the centers of the distributions of the particles with the lowest mass density of the two, regardless of their actual mass, will be located in equilibrium above the so-called isopycnic point, a natural consequence of their hard-sphere interactions. We include these interactions using the Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) equation of state. Finally, we demonstrate that our model is not limited to hard spheres, by extending it to charged spherical particles, and to dumbbells, trimers and short chains of connected beads.

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Section: Forcesmentioning

confidence: 97%

Section: Forcesmentioning

confidence: 99%

See 1 more Smart Citation

Sedimentation dynamics and equilibrium profiles in multicomponent mixtures of colloidal particles

Spruijt¹,

Biesheuvel²

2014

J. Phys.: Condens. Matter

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“…For multicomponent suspensions, more elaborate expressions are available. 37,39,40 As Eqs. (1)- (3) show, to describe the fluid flow, we use a very different expression compared to that for the dispersed particles.…”

mentioning

confidence: 99%

“…31,39,44 Next we consider the equilibrium sedimentation profile of a multi-component molecular or colloidal mixture in a centrifugal or gravity field (e.g., the earth's atmosphere), i.e., all velocities are zero. Interestingly, whether the space (fluid) in between the particles (molecules) is empty, or an incompressible fluid, does not matter when equilibrium is considered (but is very important for transport modeling).…”

mentioning

confidence: 99%

Two-fluid model for the simultaneous flow of colloids and fluids in porous media

Biesheuvel

2011

Journal of Colloid and Interface Science

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Manufacture and optimization of tubular ceramic membrane supports

2008

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Inorganic membranes can be considered an alternative to organic membranes, due to their thermal, chemical and mechanical stability under harsh conditions. Ceramic membranes are used as support structures to increase permeability through composite inorganic membranes in separation processes. Tubular a-alumina membrane supports with smooth inner surfaces can be manufactured by means of the centrifugal casting technique.In this study, the effect of three different AKP powder sizes (0.25, 0.31 and 0.6lpm) and sintering temperatures (1000 to 1400°C) on the properties of the a-alumina supports were investigated in order to determine the optimum particle size and sintering temperature which would yield a porous support with an optimized permeability, while still retaining the smooth inner surface and adequate mechanical strength. A study concerning the possible replacement of the expensive AKP powder range with the less expensive Alcoa CT 3000 SG powder was also undertaken.The supports manufactured by centrifugal casting were characterized in terms of dimensions and by mercury porosimetry, water permeability and SEM. A novel strength testing apparatus was developed in order to determine the mechanical strength from the inside of the tubular structures.The effect of the polymer concentration, which is added to stabilize the colloidal suspension used in the centrifugal casting technique, as well as the influence of the sintering rate during polymer burn-off, was also investigated.A larger particle size resulted in an increased porosity, pore size and permeability, while a decrease in linear shrinkage and mechanical strength was observed. There was a decrease in porosity and permeability with increasing sintering temperature while the linear shrinkage and mechanical strength increased. The AKP-30 (0.31 pm) and AKP-1 S(O.61 pm) had a different particle packing than the AKP-50 (0.25pm) supports and consequently a decrease in pore size with increasing sintering temperature was observed for both the AKP-30 and AKP-15 supports, while the pore size remained constant for the AKP-50 supports. Increased polymer concentration Abstract resulted in an increase in permeability, pore size and porosity, while the mechanical strength of the support decreased. This was due to the evolution of "cracks" during sintering. The sintering rate had no profound influence on the properties of the membrane supports. The powder with the widest particle size distribution (AKP-15 powder) resulted in support structures with the widest pore size distribution. The aim of the study, i.e. the optimization of the supports, was attained when comparing the results in this study to our previous work as well as the available literature.Compared to our own previous study, the permeability increased from 28 to 41 ~.h.-'bar.-'m.-', the porosity from 36 to 37% and the pore radius from 99 to 167nm for the AKP-15 supports sintered at 1200°C.Structural cracking and warping during sintering of the powder compacts made from untreated Alcoa CT 3000 SG powder indicated tha...

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Microdivers to study sedimentation in polydisperse, concentrated colloidal suspensions

Abstract: A small amount of polymer particles with diameters in the 100

Cited by 5 publications

References 27 publications

Sedimentation dynamics and equilibrium profiles in multicomponent mixtures of colloidal particles

Sedimentation dynamics and equilibrium profiles in multicomponent mixtures of colloidal particles

Two-fluid model for the simultaneous flow of colloids and fluids in porous media

Manufacture and optimization of tubular ceramic membrane supports

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