Temperature Dependence of Thermodiffusion in Aqueous Suspensions of Charged Nanoparticles

Putnam, Shawn A.; Cahill, David G.; Wong, Gerard C. L.

doi:10.1021/la700489e

Cited by 137 publications

(206 citation statements)

References 48 publications

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“…[24] On the other hand, S T decreased with the concentration of the colloid and may even switch the sign from positive to negative. [25] Similar results were reported for solutions of molecules.…”

Section: Perikinetic Foulingmentioning

confidence: 99%

Reactor Fouling by Preformed Latexes

Urrutia

Bandrés

Asúa

2016

Macro Reaction Engineering

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Reactor fouling caused by preformed latexes is investigated using 50 wt% solids content latexes of different colloidal stability. In the absence of agitation, a rapid adsorption equilibrium is achieved for pH below the isoelectric point of the stainless steel (pH = 4.3). The equilibrium fouling decreases as solids content decreases and by increasing the pH above the isoelectric point of the stainless steel. The stability of the latex is a major factor determining fouling, which strongly decreases as latex stability increases. Under agitation, fouling increases with time, solids content, and temperature, and it decreases as the colloidal stability of the latex increases. The flow patterns in the reactor determine the distribution of fouling in the baffles. A mechanism for fouling formation is proposed by combining computational fluid dynamics and experimental results.

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Section: Perikinetic Foulingmentioning

confidence: 99%

Reactor Fouling by Preformed Latexes

Urrutia

Bandrés

Asúa

2016

Macro Reaction Engineering

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“…It had been known for a while that in some colloidal suspensions the particles move to the cold, and in others to the warm, corresponding to a positive and negative Soret effect, respectively [5][6][7]. Recent experiments on aqueous solutions of lysozyme protein [8,9], polystyrene beads [9][10][11][12], micelles [11], DNA [13], and Ludox particles [14] revealed a surprisingly similar temperature dependence in the range T = 0...80…”

mentioning

confidence: 99%

Transport in Charged Colloids Driven by Thermoelectricity

2008

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We study the thermal diffusion coefficient DT of a charged colloid in a temperature gradient, and find that it is to a large extent determined by the thermoelectric response of the electrolyte solution. The thermally induced salinity gradient leads in general to a strong increase with temperature. The difference of the heat of transport of co-ions and counterions gives rise to a thermoelectric field that drives the colloid to the cold or to the warm, depending on the sign of its charge. Our results provide an explanation for recent experimental findings on thermophoresis in colloidal suspensions.PACS numbers: 66.10.C, 82.70.-y,47.57.JIntroduction. Colloidal suspensions in a non-uniform electrolyte show a rich and surprising transport behavior. Upon applying an electric field or a chemical or thermal gradient on a macromolecular dispersion, one observes migration of its components and a non-uniform distribution in the stationary state. The physical mechanisms of electrophoresis and diffusiophoresis are well understood [1,2] and widely used in biotechnology and microfluidic applications [3,4].The situation is less clear concerning transport driven by a thermal gradient. There is no complete description for the underlying physical forces, and even the sign of the thermophoretic mobility lacks a rationale so far. It had been known for a while that in some colloidal suspensions the particles move to the cold, and in others to the warm, corresponding to a positive and negative Soret effect, respectively [5][6][7]. Recent experiments on aqueous solutions of lysozyme protein [8,9], polystyrene beads [9-12], micelles [11], DNA [13], and Ludox particles [14] revealed a surprisingly similar temperature dependence in the range T = 0...80• C. In all cases, an inverse Soret effect occurs at low T , changes sign at some intermediate value T * , and seems to saturate above 50 • C. On the other hand, a large negative thermophoretic mobility has been reported for charged latex spheres in a buffered solution at weak acidity and low salinity [10]; adding LiCl or NaCl results in a change of sign and a transport velocity that depends significantly on the cation. These features strongly suggest a single mechanism related to the electric properties of the colloid; the relevance of the thermoelectric effect for colloidal suspensions has been pointed out recently [10].A thermal gradient modifies the solute-solvent interactions and drives the particle at a velocity [15]

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“…We discuss the size dependence of the Soret coefficient of large colloidal particles. For charged polystyrene beads confined in an 10-micron chamber, a quadratic variation S T ∝ R 2 was found for radii ranging from 20 nm to 1 µm [18], whereas subsequent experiments reported a linear dependence S T ∝ R for both solid particles [21][22][23][24] and microemulsion droplets [25] The Gibbs energy of large particles is proportional to the surface area, G ∝ R 2 , resulting in the quadratic law S T ∝ R 2 for Eastman's expression (2), which has been used for fitting the data of Ref. [18].…”

Section: E Comparison With Experimentsmentioning

confidence: 92%

“…On the other hand, since the Einstein coefficient is inversely proportional to the radius and D T independent of the particle size [8,33,36], the ratio (15) results in S T ∝ R, in agreement with the data of Refs. [21][22][23][24][25]. A more complex situation occurs for strongly hydrophobic particles with a finite slip length, where a quadratic dependence is obtained for intermediate particle size [40]; yet this effect can be discarded for micron-sized beads.…”

Section: E Comparison With Experimentsmentioning

confidence: 99%

Is Soret equilibrium a non-equilibrium effect?

Würger

2013

Comptes Rendus. Mécanique

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Recent thermophoretic experiments on colloidal suspensions revived an old debate, namely whether the Soret effect is properly described by thermostatics, or necessarily requires nonequilibrium thermodynamics. Based on colloidal transport theory and the entropy production of the related viscous flow, our analysis leads to the conclusion that the equilibrium approach may work for small ions, yet fails for colloidal particles and polymers. Regarding binary molecular mixtures, our results shed some doubt on the validity of thermostatic approaches that derive the Soret coefficient from equilibrium potentials.

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Temperature Dependence of Thermodiffusion in Aqueous Suspensions of Charged Nanoparticles

Cited by 137 publications

References 48 publications

Reactor Fouling by Preformed Latexes

Reactor Fouling by Preformed Latexes

Transport in Charged Colloids Driven by Thermoelectricity

Is Soret equilibrium a non-equilibrium effect?

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