Straining of Nonspherical Colloids in Saturated Porous Media

Xu, Shangping; Qian, Lei; Saiers, James E.

doi:10.1021/es071328w

Cited by 90 publications

(94 citation statements)

References 26 publications

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“…In addition, straining of colloids in the saturated system also depends on solution properties, colloid size, colloid shape, colloid size distribution as well as grain size and heterogeneity [2,3,5,6,71,85,86]. The straining of colloids were more dominant for large, irregular shape, and multi-disperse colloids [84][85][86].…”

Section: Attachment Of Colloid By Strainingmentioning

confidence: 99%

“…The straining of colloids were more dominant for large, irregular shape, and multi-disperse colloids [84][85][86]. Straining of colloids in the unsaturated porous media become very complex due to the presence of gaseous phase.…”

Section: Attachment Of Colloid By Strainingmentioning

confidence: 99%

“…Several mechanisms are responsible for colloid transport in unsaturated zone in addition to that of saturated zone, such as, liquid-gas interface capture, solid-liquid-gas interface capture, liquid-film straining, and storage in immobile liquid zones [13,18,27,44,51,68,70,79,85,87]. The strong force (capillary force) associated with the moving liquid-gas interfaces led to particle mobilization in the natural subsurface environment.…”

Section: Introductionmentioning

confidence: 99%

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Section: Attachment Of Colloid By Strainingmentioning

confidence: 99%

Section: Attachment Of Colloid By Strainingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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“…Extensive observation of platelet movement in interstices of microfilter chips representing PRP filters revealed that platelets do not rotate when passing through filter at creeping/Stokesian flow conditions, i.e., Re<<1 (Javadpour 2006). The nonrotating movement of platelets may be explained by the interesting work of Xu et al (2008). Xu et al (2008) suggested that high contraction ratio (H/r; where H and r are the half-widths of the domain at the widest and narrowest parts of the pore channel, respectively) causes large velocity difference that may rotate spheroids.…”

Section: Platelet Shape Factormentioning

confidence: 99%

“…The nonrotating movement of platelets may be explained by the interesting work of Xu et al (2008). Xu et al (2008) suggested that high contraction ratio (H/r; where H and r are the half-widths of the domain at the widest and narrowest parts of the pore channel, respectively) causes large velocity difference that may rotate spheroids. For example, H/r = 60/0.95 is needed to induce rotation at creeping/Stokesian flow condition.…”

Section: Platelet Shape Factormentioning

confidence: 99%

Modeling Filtration of Platelet-Rich Plasma in Fibrous Filters

Javadpour

Jeje

2011

Transp Porous Med

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Removing leukocytes (white cells) from blood products such as platelet-rich plasma (PRP) prevents serious problems for the PRP recipients. We present a model to study selective separation of leukocytes from a dilute suspension of leukocytes and platelets (PRP) using fibrous filters. A selective PRP filter permits platelets to pass but bars the way for leukocytes. In PRP filters, fine synthetic fibers are packed randomly and interstices are larger than cells. Interactive forces between the suspended cells and fibers determine cell capture yield, i.e., deep-bed filtration process. Our model is based on a hierarchical set of differential equations corresponding to porescale and macroscale. At the porescale, we model movement and interaction of cells with fibers. A single cell entering the interstitial space encounters drag and surface forces. We define a unit bed element (UBE) composed of a fiber and interstitial space, where fiber diameter corrected for the size of the cells. We add measured surface forces between cells and fibers (electrostatic, van der Waals, fluid expression resistance, and biological responses) to the cell velocity equation. We then transform pore scale events into macroscale continuum by imposing periodic boundary conditions for contiguous UBEs and applying macrotransport theory. At macroscale, two independent coefficients: mean cell velocity vector U* and mean cell capture yield constant K*characterize cell filtration efficiency. Our model showed reasonable match with experimental data. Model results showed that diameter of fibers, injection velocity, bed porosity, and bed thickness control selective capture of leukocytes. Our model showed that it is merely impossible to filter out all leukocytes without capturing platelets. Based on our model, an optimized filter can capture 90% of leukocytes and pass through 45% of platelets. Nomenclature a&b Major diagonals of platelet, μm a The radius of a sphere with a volume equivalent to a platelet, μm a Cell radius, μm A A-function (Eq. 26) C Cell concentration, fraction D Fiber diameter, μm D m Diffusion coefficient of particle (cell), m 2 s E Bed porosity, fraction F rep Repulsive surface forces, nN F att Attractive surface forces, nN J ∞ 0 Asymptotic probability flux density, m −2 s −1 H Half width of the domain at the widest part of a pore channel (Sect. 4.2), μm k Boltzmann constant, 1.3805 × 10 −23 JK −1 K* Macroscopic cell capture yield constant, t −1 l UBE length, μm L Filter bed thickness, mm M 0 Moment of 0th order P ∞ 0 Steady-state conditional probability density, fraction rRadial distance from the center of a fiber (Fig. 7a) or narrowest part of a pore channel (Sect. 4.2), μm r Radial vector inside a UBE, μm R Fiber radius, μm R Macroscopic position vector, μm t Time, s T Temperature, K T Torque, Nm U Interfacial fluid velocity, ms −1 U* Macroscopic average cell velocity, ms −1 Greek symbols α Porosity-dependent coefficient in classical theory, dimensionless θ Coordination angle around a fiber, degree γ Perrin factor, dimensionless η cell...

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Predicting colloid transport through saturated porous media: A critical review

et al. 2015

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Understanding and predicting colloid transport and retention in water‐saturated porous media is important for the protection of human and ecological health. Early applications of colloid transport research before the 1990s included the removal of pathogens in granular drinking water filters. Since then, interest has expanded significantly to include such areas as source zone protection of drinking water systems and injection of nanometals for contaminated site remediation. This review summarizes predictive tools for colloid transport from the pore to field scales. First, we review experimental breakthrough and retention of colloids under favorable and unfavorable colloid/collector interactions (i.e., no significant and significant colloid‐surface repulsion, respectively). Second, we review the continuum‐scale modeling strategies used to describe observed transport behavior. Third, we review the following two components of colloid filtration theory: (i) mechanistic force/torque balance models of pore‐scale colloid trajectories and (ii) approximating correlation equations used to predict colloid retention. The successes and limitations of these approaches for favorable conditions are summarized, as are recent developments to predict colloid retention under the unfavorable conditions particularly relevant to environmental applications. Fourth, we summarize the influences of physical and chemical heterogeneities on colloid transport and avenues for their prediction. Fifth, we review the upscaling of mechanistic model results to rate constants for use in continuum models of colloid behavior at the column and field scales. Overall, this paper clarifies the foundation for existing knowledge of colloid transport and retention, features recent advances in the field, critically assesses where existing approaches are successful and the limits of their application, and highlights outstanding challenges and future research opportunities. These challenges and opportunities include improving mechanistic descriptions, and subsequent correlation equations, for nanoparticle (i.e., Brownian particle) transport through soil, developing mechanistic descriptions of colloid retention in so‐called “unfavorable” conditions via methods such as the “discrete heterogeneity” approach, and employing imaging techniques such as X‐ray tomography to develop realistic expressions for grain topology and mineral distribution that can aid the development of these mechanistic approaches.

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Straining of Nonspherical Colloids in Saturated Porous Media

Cited by 90 publications

References 26 publications

Geological Disposal of Nuclear Waste: Fate and Transport of Radioactive Materials

Geological Disposal of Nuclear Waste: Fate and Transport of Radioactive Materials

Modeling Filtration of Platelet-Rich Plasma in Fibrous Filters

Predicting colloid transport through saturated porous media: A critical review

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