Author: Béatrice Harmand
Publisher:
ISBN:
Category :
Languages : fr
Pages : 225
Get Book Here
Book Description
Dans le cadre de la problématique du stockage des déchets radioactifs, une approche du transport de radioéléments par des particules colloïdales à l'aide d'un modèle linéaire a permis de souligner l'effet d'accélération des colloïdes sur la migration des radio polluants dans la géosphère. L’influence des paramètres physico-chimiques (force ionique, pH, charge de surface), géométriques (diamètre de particules, longueur du milieu poreux) et de l'hydrodynamique (vitesse d'écoulement entre 0,8 et 50 m/j) sur le transport des colloïdes a été étudiée dans un système modèle particules de latex (de 0,11 à 0,79 micromètre) - sable quartzeux (dmoyen = 125 micromètre). Il est montré que les courbes de percée des particules sont bien représentées par un modèle à deux sites de capture. Le processus de capture vers chaque site est caractérisé par un temps de transfert optimisé sur les courbes expérimentales, la fraction de site étant fonction de l'accumulation de particules en surface du milieu poreux
Author: Fritz H. Frimmel
Publisher: Springer Science & Business Media
ISBN: 3540713395
Category : Science
Languages : en
Pages : 294
Get Book Here
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: Vladimir Canseco Ruiz
Publisher:
ISBN:
Category :
Languages : fr
Pages : 0
Get Book Here
Book Description
La thèse traite du transport de particules colloïdales en milieu poreux. L'influence des propriétés physico-chimiques et hydrodynamiques sur le dépôt et détachement de particules de latex a été étudiée en réalisant des expériences durant lesquelles des grandeurs macroscopiques (concentration dans les effluents, réduction de perméabilité) et microscopiques (variation de porosité par atténuation gamma) ont été mesurées.
Author: Fritz H. Frimmel
Publisher: Springer Verlag
ISBN: 9783540713388
Category : Science
Languages : en
Pages : 291
Get Book Here
Book Description
Colloids are known to be the often neglected phase for the transport of pollutants in aquatic ecosystems. This book covers the basics of abiotic colloid characterization, of biocolloids and biofilms, the resulting transport phenomena and their engineering aspects. The contributors are leading specialists devoted to colloidal sciences. The discussion reflects their broad scope of viewpoint and depth of expertise. Coverage includes theoretical considerations, results from model experiments, and field studies.
Author: Madeleine Stoll
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Rock fractures can serve as water conducting structures for fluid flow and mass transport within the Earth's crust. Large apertures, which enable high flow velocities, and a rock matrix with several orders of magnitude lower permeability, are accountable that those structures serve as preferential conduits for solutes and colloids. The mechanistic understanding of fundamental transport and retention processes is essential to make reliable predictions of the fate of solutes and colloids in the subsurface. This comprehensive topic is of paramount importance in many areas of geo-engineering, for example disposal of nuclear waste in deep geological formations, enhanced geothermal systems, CO2 sequestration, gas and oil industry, and contaminant transport in groundwater systems. This cumulative Ph.D. thesis deals with the investigation of the impact of flow channel geometry on solute and colloid transport through natural rough fractures. The bottom-up approach used in this thesis helped to investigate separately the mechanisms and the processes on mass transport (solute and colloids) in four steps. All experiments in this thesis were conducted under hydraulic and chemical settings establishing laminar flow and overall unfavorable colloid attachment conditions.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 4
Get Book Here
Book Description
The goal of the DOE project is to identify the chemical and physical factors that control the transport of colloids in fractured formations, and develop a generalized capability to predict colloid attachment and detachment based on hydraulic factors (head, flow rate), physical structure (fracture aperture), and chemical properties (surface properties of colloids and fracture surfaces). The research approach targets multiple scales, including: (a) a theoretical description of colloid dynamics in fractures that extend concepts used for porous media to fracture geometry, with predictions experimentally tested in simplified laboratory fractures; (b) colloid transport experiments in intact geological columns, which provide natural complexity, but mass balance data and experimental control over flow, colloid size, ionic strength and composition; (c) field-scale transport experiments using colloidal tracers to examine realistic scales of fracture connectivity; and (d) modeling of colloid transport in complex fracture networks that include fractures with varying flow rates and permitting colloid diffusion into microfractures. Understanding the processes that control colloid behavior will increase confidence with which colloid-facilitated contaminant transport can be predicted and assessed at contaminated DOE sites. An added benefit is the expectation that this work will yield novel techniques to either immobilize colloid-bound contaminants in-situ, or mobilize colloids for enhancing remedial techniques such as pump-and-treat and bioremediation.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
Get Book Here
Book Description
The goal of this project was to identify the chemical and physical factors that control the transport of colloids in fractured materials, and develop a generalized capability to predict colloid attachment and detachment based on hydraulic factors (head, flow rate), physical processes and structure (fracture aperture, matrix porosity), and chemical properties (surface properties of colloids, solution chemistry, and mineralogy of fracture surfaces). Both aqueous chemistry and physical structure of geologic formations influenced transport. Results of studies at all spatial scales reached consensus on the importance of several key controlling variables: (1) colloid retention is dominated by chemical conditions favoring colloid-wall interactions; (2) even in the presence of conditions favorable to colloid collection, deposited colloids are remobilized over long times and this process contributes substantially to the overall extent of transport; (3) diffusive exchange between water-conducting fractures and finer fractures and pores acts to ''buffer'' the effects of the major fracture network structure, and reduces predictive uncertainties. Predictive tools were developed that account for fundamental mechanisms of colloid dynamics in fracture geometry, and linked to larger-scale processes in networks of fractures. The results of our study highlight the key role of physical and hydrologic factors, and processes of colloid remobilization that are potentially of even greater importance to colloid transport in the vadose zone than in saturated conditions. We propose that this work be extended to focus on understanding vadose zone transport processes so that they can eventually be linked to the understanding and tools developed in our previous project on transport in saturated groundwater systems.
Author: Peter Vilks
Publisher: Pinewa, Man. : Geochemistry Research Branch, Whiteshell Laboratories
ISBN: 9780660168913
Category : Colloids
Languages : en
Pages : 27
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : fr
Pages :
Get Book Here
Book Description
Author: Elisabeth Rodier
Publisher:
ISBN:
Category :
Languages : fr
Pages : 202
Get Book Here
Book Description
Cette thèse a pour objet l'étude du passage et de la rétention de particules colloïdales au sein d'un milieu poreux. Dans un premier temps, on effectue une étude bibliographique, d'une part sur les caractéristiques de base de l'interface liquide-solide, d'autre part sur les études théoriques et expérimentales réalisées au sujet de la déposition des colloïdes sur une surface collectrice. On s'intéresse ici plus particulièrement au cas où l'on est dans des conditions répulsives. Des expériences de migration de suspensions colloïdales dans un milieu poreux sont ensuite présentées. Auparavant, on a choisi un colloïde et un milieu poreux modèles que l'on caractérise d'un point de vue potentiel de surface par des mesures électrophorétiques et des mesures de courant d'écoulement. Ils sont ensuite mis en contact dans diverses conditions physico-chimiques, d'une part en système fermé en l'absence d'hydrodynamique et d'autre part en système ouvert pour lequel les conditions hydrodynamiques varient. On étudie ainsi l'influence de plusieurs paramètres tels que le débit d'entrée, la force ionique, le pH, le temps, etc...
