Effect of particle size on stability of monodisperse selenium hydrosols

Joseph-Petit, A.-M; Dumont, F.; Watillon, André

doi:10.1016/0021-9797(73)90411-6

Cited by 21 publications

(10 citation statements)

References 35 publications

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“…Elimelech ( − ) observed similar discrepancies from DLVO theory using Brownian particles and glass beads. Similar discrepancies have also been observed in aggregation experiments ( − ).…”

Section: Introductionsupporting

confidence: 88%

Deposition and Reentrainment of Brownian Particles in Porous Media under Unfavorable Chemical Conditions: Some Concepts and Applications

Hahn

O’Melia

2003

Environ. Sci. Technol.

272

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The deposition and reentrainment of particles in porous media have been examined theoretically and experimentally. A Brownian Dynamics/Monte Carlo (MC/BD) model has been developed that simulates the movement of Brownian particles near a collector under "unfavorable" chemical conditions and allows deposition in primary and secondary minima. A simple Maxwell approach has been used to estimate particle attachment efficiency by assuming deposition in the secondary minimum and calculating the probability of reentrainment. The MC/BD simulations and the Maxwell calculations support an alternative view of the deposition and reentrainment of Brownian particles under unfavorable chemical conditions. These calculations indicate that deposition into and subsequent release from secondary minima can explain reported discrepancies between classic model predictions that assume irreversible deposition in a primary well and experimentally determined deposition efficiencies that are orders of magnitude larger than Interaction Force Boundary Layer (IFBL) predictions. The commonly used IFBL model, for example, is based on the notion of transport over an energy barrier into the primary well and does not address contributions of secondary minimum deposition. A simple Maxwell model based on deposition into and reentrainment from secondary minima is much more accurate in predicting deposition rates for column experiments at low ionic strengths. It also greatly reduces the substantial particle size effects inherent in IFBL models, wherein particle attachment rates are predicted to decrease significantly with increasing particle size. This view is consistent with recent work by others addressing the composition and structure of the first few nanometers at solid-water interfaces including research on modeling water at solid-liquid interfaces, surface speciation, interfacial force measurements, and the rheological properties of concentrated suspensions. It follows that deposition under these conditions will depend on the depth of the secondary minimum and that some transition between secondary and primary depositions should occur when the height of the energy barrier is on the order of several kT. When deposition in secondary minima predominates, observed deposition should increase with increasing ionic strength, particle size, and Hamaker constant. Since an equilibrium can develop between bound and bulk particles, the collision efficiency [alpha] can no longer be considered a constant for a given physical and chemical system. Rather, in many cases it can decrease over time until it eventually reaches zero as equilibrium is established.

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Section: Introductionsupporting

confidence: 88%

Deposition and Reentrainment of Brownian Particles in Porous Media under Unfavorable Chemical Conditions: Some Concepts and Applications

Hahn

O’Melia

2003

Environ. Sci. Technol.

272

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“…Parfitt and Picton ( 22) used graphite particles in aqueous solutions of sodium dodecyl sulfate and determined that those with a primary particle diameter of 25 nm aggregated in primary minima while chemically similar particles with a diameter of 250 nm aggregated in secondary minima. On the basis of experiments using monodisperse selenium sols over a range of particle sizes, Joseph-Petit et al (23) wrote that "the coagulation of small particles, occurring in the primary minimum, is well described by using the simple model of a critical barrier height, and ... that, for large particles, excellent agreement with experiment is obtained when considering a constant secondary minimum". For the selenium sols used by these authors, the transition from primary to secondary attachment occurred at a particle diameter of 55 nm.…”

Section: Discussionmentioning

confidence: 99%

Aquasols: On the Role of Secondary Minima

Hahn

Abadzic

O’Melia

2004

Environ. Sci. Technol.

220

223

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Experiments are presented that test the hypothesis of deposition into and reentrainment from secondary minima during flow through porous media. The release of deposited particles following a decrease in ionic strength is inconsistent with deposition in the primary minimum of either simple DLVO interaction energy curves (which suggest that deposition is irreversible) or Born-DLVO interaction energy curves (which create a finite primary minimum that deepens with decreasing ionic strength). The observed release of particles is, on the other hand, consistent with deposition in the secondary minimum because this energy minimum decreases and can disappear with decreasing ionic strength. The implications for colloid transport of a reversible deposition process in the secondary minimum are very different from those of a process involving irreversible deposition in the primary minimum. First, particles that are continually captured and released will travel much farther in the subsurface than might be expected if the classic irreversible filtration model is applied. Second, and perhaps more significantly, deposition in the secondary well can increase with increasing particle size. Although particle transport by convective diffusion increases as particle size decreases, particle "attachment" in secondary minima decreases with decreasing particle size. Thus, smaller particles (those with diameters in the order of a few tens of nanometers) would be more effective in the facilitated transport of highly sorbing contaminants such as hydrophobic organic molecules, metals, and radionuclides. Other contaminants are themselves particles, such as viruses (tens of nanometers in diameter) and bacteria (near 1 microm in diameter). Due to this difference in size, viruses could be transported over much larger distances than bacteria. Third, the transport of colloids and, hence, the transport of contaminants associated with them, depends on the Hamaker constant of the particle-water-aquifer media system. Colloids of lower Hamaker constant are likely to be transported farther than colloids of higher Hamaker constant. The extent of adsorption of specific contaminants and the Hamaker constant for the particle-aquifer system are both characteristics of the particles and contribute to the effectiveness of colloid-facilitated transport. Finally, the solution chemistry of the pore waters (through pH, ionic strength, types of solutes, and the valence of the ions) ultimately controls the deposition and release of colloidal particles in porous media. The pH determines the charge density and surface potential of the surfaces. When the surfaces are similarly charged, their interaction can be unfavorable, with an energy barrier and secondary minimum. The ionic strength and valence of the ions determines the shape of the interaction energy curve, including the presence and height of the energy barrier and the presence and depth of the secondary well. Since the subsequent release of a particle depends on the mode in which the particle is deposited (prima...

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“…For given chemical conditions, the depth of the secondary minimum increases with particle size and the Hamaker constant of the interacting media. The apparent disparity with respect to particle size effects was observed in numerous coagulation studies (25,(57)(58)(59)(60). This discrepancy was attributed to deposition in primary and secondary minima.…”

Section: Log[kci]mentioning

confidence: 99%