The controlled flocculation of particulate dispersions using small particles of opposite charge I. Sediment volumes and morphology

Luckham, P.F.; Vincent, Brian; Hart, Connor; Tadros, Th.F.

doi:10.1016/0166-6622(80)80018-7

Cited by 49 publications

(40 citation statements)

References 11 publications

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“…1b and 1c, excess particles located in regions of the aqueous phase between drops at relatively close separations appeared to form bridging structures between the drops. These structures are reminiscent of the particle bridges observed by Luckham and co-workers [32,33] in freezefracture electron microscopy imaging of dispersions of large, negatively charged, polystyrene particles which had been flocculated by the addition of small, positively charged, polystyrene particles. In emulsions prepared here at low sodium chloride concentrations (∼0.001 M), the bridging particles appeared loosely packed (see Fig.…”

Section: Pickering Emulsionsmentioning

confidence: 90%

“…Electrostatic interactions tend to determine whether the particles selectively aggregate (homoaggregation) or the different particles types aggregate (heteroaggregation) [34][35][36]. Where there is a large disparity in size, the heteroaggregates consist of the large particles surrounded by a shell of the small particles [37,38] and bridging flocculation of the large particles may occur [32,33,39,40]. Small particles may be excluded from regions in between larger particles (at close separations) and induce flocculation through attractive depletion interactions [20][21][22][23][24][25][41][42][43][44].…”

Section: Effect Of Diluting Pickering Emulsions In Salt Solutionsmentioning

confidence: 97%

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Effect of adding anionic surfactant on the stability of Pickering emulsions

Whitby

Fornasiero

Ralston

2009

Journal of Colloid and Interface Science

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We investigated the structure and stability of dodecane-in-water emulsions stabilised by partially hydrophobised silica particles after dilution of the emulsions in solutions of sodium dodecyl sulfate and sodium chloride. The emulsions were stable to coalescence on dilution in salt solutions, but did cream over time. The rate and extent of creaming gradually decreased as the salt concentration in the diluted emulsion increased. Dilution in low concentrations of the anionic surfactant did not affect the emulsion stability to coalescence or alter the creaming behaviour of the emulsion. At surfactant concentrations above the critical micelle concentration, however, the rate and extent of creaming and flocculation of the drops were enhanced.

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Section: Pickering Emulsionsmentioning

confidence: 90%

Section: Effect Of Diluting Pickering Emulsions In Salt Solutionsmentioning

confidence: 97%

Effect of adding anionic surfactant on the stability of Pickering emulsions

Whitby

Fornasiero

Ralston

2009

Journal of Colloid and Interface Science

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“…In a series of previous publications (8-11), Vincent and coworkers investigated the interaction between small polystyrene latex particles and larger particles of opposite charge, where each set of particles was covered with a preadsorbed layer of a neutral, water-soluble polymer, such as poly(vinyl alcohol-co-vinyl acetate) (PVA) (8)(9)(10)(11) or an alkyl ethylene oxide (C 14 E 6 or C 14 E 20 ) (8). The results were presented in terms of particles' adsorption isotherms; some of the results were interpreted qualitatively in terms of the DLVO theory (12)(13)(14).…”

Section: Introductionmentioning

confidence: 99%

“…This situation corresponds to low-affinity particle adsorption isotherms. Further work (11,(15)(16)(17) showed that, over a narrow range of concentrations of the small particles and low electrolyte concentrations, the small particles act as (particle) bridging floculants for the larger particles.Hansen and Matijevic (18) studied the adsorption of monodispersed [poly(methyl methacrylate-co-methacrylic acid)] latex particles (40 nm radius) onto much larger (hydrated) metal oxide particles with radii around 250 nm. The thermodynamics and kinetics of the particle adsorption process were analyzed taking into consideration the double-layer properties of both types of particles.…”

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confidence: 98%

Stability in Colloidal Mixtures Containing Particles with a Large Disparity in Size

Uricanu

Eastman

Vincent

2001

Journal of Colloid and Interface Science

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“…More specifically, chainlike aggregates comprised of alternating silica-SAM-NH 3 + and rhodamine-labeled microspheres can be seen in the control suspension, as expected due to the heteroflocculation. [12][13][14][15] A second colloidal suspension was prepared in the same way as the control, except that it was irradiated with UV light for 40 min after mixing. A dramatic change in the colloidal packing efficiency accompanies UV irradiation, which is visually apparent by comparing the light-exposed suspension to the control.…”

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confidence: 99%

Light-Regulated Electrostatic Interactions in Colloidal Suspensions

et al. 2005

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Colloidal suspensions enjoy widespread use in applications ranging from advanced materials to drug delivery. By tailoring the interactions between particles, one can design colloidal fluids, gels, or crystals needed for ceramic, 1 coating, 2 ink, 3 photonic, 4,5 and pharmaceutical materials. 6 One common strategy is to alter their electrostatic interactions by varying either the pH or ionic strength of the solution in which they are suspended. 7 However, problems such as nonuniform mixing and disruption of suspension microstructure arise when acid, base, or electrolyte species are added. The ability to tailor electrostatic interactions between colloids with spatial and temporal control in the absence of chemical additions would not only alleviate these problems but also open new possibilities in colloidal assembly. Here we demonstrate an approach to modulate the surface charge of colloidal particles and, hence, their electrostatic interactions by irradiation with UV light.To generate light-sensitive colloidal particles, we designed a new self-assembled monolayer (SAM) that undergoes charge inversion upon photocleavage (Figure 1). Each molecule of the SAM is initially terminated with a positively charged ammonium (-NH 3 + ) group. Photocleavage of the ortho-nitrobenzyl linker 8 then exposes an underlying negatively charged carboxylate (-COO -) group. Accordingly, silica particles functionalized with this SAM are expected to possess an effective charge (or zeta potential) that can be tuned through a broad range of positive, neutral, and negative values at fixed pH simply by exposure to UV light for varying times. Because their zeta potential ( ) can be regulated by irradiation alone, it should be possible to induce phase changes within colloidal suspensions without externally altering their solution composition.As described in detail in the Supporting Information, chlorosilane 1 is synthesized in three steps from the known 4-(hydroxymethyl)-3-nitrobenzoic acid. 9 Immobilization of 1 on dried silica microspheres (∼1 µm diameter) is accomplished in toluene with triethylamine as an acid scavenger ( Figure 1). Brief exposure to trifluoroacetic acid (TFA) in methylene chloride converts the BOC group to an ammonium cation. This stable colloidal suspension undergoes rapid flocculation upon exposure to TFA. After washing with methylene chloride, the ammonium-terminated microspheres (silica-SAM-NH 3 + ) are washed with benzene and lyophilized.To confirm the expected photochemical transformation, the particles' surface composition was examined via X-ray photoelectron spectroscopy (XPS) before and after irradiation. As shown in Figure 2, the nitrogen 1s photoelectron peak decreases substantially upon exposure of colloidal suspensions to UV light. This observation is consistent with photoinduced cleavage of the bifunctional SAM, which results in a loss of amino and nitro groups from the microsphere surface. From the XPS integrated intensities, it is estimated that 85-95% of the nitrogen has been removed from the silica-SAM af...

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The controlled flocculation of particulate dispersions using small particles of opposite charge I. Sediment volumes and morphology

Cited by 49 publications

References 11 publications

Effect of adding anionic surfactant on the stability of Pickering emulsions

Effect of adding anionic surfactant on the stability of Pickering emulsions

Stability in Colloidal Mixtures Containing Particles with a Large Disparity in Size

Light-Regulated Electrostatic Interactions in Colloidal Suspensions

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