Colloid Transport in Saturated and Unsaturated Porous Media PDF Download
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Author: Jun Qi
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 200
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Author: Jun Qi
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 200
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Book Description
Author: Jie Han
Publisher: ProQuest
ISBN: 9780549753995
Category : Colloids
Languages : en
Pages :
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Author: Yuniati Zevi
Publisher:
ISBN:
Category :
Languages : en
Pages : 122
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Author: Chris L. Brueck
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 65
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Book Description
Understanding the mechanisms controlling colloid transport and deposition in the vadose zone is an important step in protecting our water resources. Colloid transport in unsaturated porous media was studied using X-Ray Microtomography (XMT), which is a non-destructive imaging technique that provides three-dimensional images at a resolution on the order of 3 [micro]m/pixel. Under favorable attachment conditions, 5 -15 [micro]m hydrophobic silver coated hollow glass spheres were suspended and drained through sintered glass bead columns at flow rates of 0.5, 5.0 and 50.0 mL/hr. The results show that total colloid deposition was dependent on drainage flow rate and saturation. A positive correlation was found between the total colloid concentration and the number of trapped air bubbles. An image processing algorithm was written to assess the partitioning of colloids to the solid-water interfaces (SWIs), air-water interfaces (AWIs), and air-water-solid (AWS) contact lines, which led to the conclusion that at medium to high water contents, AWIs and AWS contact lines were equally important for colloid attachment and mobilization. Lastly, colloids were shown to be left behind the main drainage front, becoming immobilized in the disconnected wetting phase by attachment to SWIs, or in pendular wetting phase rings.
Author: John T. Crist
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Author: John Matthew Thomas
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 142
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Author: Fritz H. Frimmel
Publisher: Springer Science & Business Media
ISBN: 3540713395
Category : Science
Languages : en
Pages : 294
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Book Description
This book covers the basics of abiotic colloid characterization, of biocolloids and biofilms, the resulting transport phenomena and their engineering aspects. The contributors comprise an international group of leading specialists devoted to colloidal sciences. The contributions include theoretical considerations, results from model experiments, and field studies. The information provided here will benefit students and scientists interested in the analytical, chemical, microbiological, geological and hydrological aspects of material transport in aquatic systems and soils.
Author: Yasemin Mehtap Fertelli
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 170
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The recent study by Crist et al. (2004) attempted to provide pore scale insights into mechanisms responsible for controlling colloid transport in unsaturated porous media. However, because they relied on images obtained along surfaces that were open to the atmosphere, artificial evaporation resulted in 2 more critical artifacts; formation of air-water-solid (AWS) contact lines, and advection/deposition of colloids to AWS contact lines. These evaporation-related artifacts need to be addressed because they account for most of the colloid deposition at AWS contact lines reported in Crist et al. (2004) ... As stated in Crist el al. (2004), '' ... the front panel was removed to avoid light reflections that obscured the view and, thus, exposed one side of the sand column to air''. Although a more recent paper (Crist et al., 2005) also presents results using the same methods and is therefore also affected by evaporation, we will restrict our present comments to Crist et al. (2004). Here, we show that removal of the front panel results in a sequence of three critical artifacts; (1) significant evaporation, (2) drying of thin films and formation of air-water-solid (AWS) contact lines, and (3) advection of colloids to AWS contact lines where they are deposited. As explained below, these artifacts so drastically disturbed their system that the magnitude of their observations are not likely to occur anywhere except within the most superficial few cm of soils. Before explaining these artifacts, we note that although trapping of colloids at AWS contact lines reported in Crist et al. (2004) is largely an artifact of evaporation, colloid filtration within perimeters of pendular rings is in fact a main prediction of the film straining model (Wan and Tokunaga, 1997). In that model, colloid filtration is predicted to be more efficient below a critical water saturation, when capillary connections between pendular rings become separated by adsorbed water films. In that paper we stated that ''Retardation of ideal, nonsorbing colloids can occur at two locations: trapped within individual pendular rings due to exclusion from entry into surrounding thin films and within film ... '' (Wan and Tokunaga, 1997). Thus, while Crist et al. (2004) implied that the film straining model applies only to retardation of colloid transport within thin films, colloid retention within perimeters of pendular rings is a main feature of our model.
Author: Ann Mathew
Publisher:
ISBN:
Category :
Languages : en
Pages : 272
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