Colloid-facilitated Transport of Contaminants in Porous Media PDF Download

Author: Sujoy B. Roy
Publisher:
ISBN:
Category :
Languages : en
Pages : 296

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Author: Heecheul Choi
Publisher:
ISBN:
Category :
Languages : en
Pages : 306

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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: Shiyan Jiang
Publisher:
ISBN:
Category : Groundwater flow
Languages : en
Pages : 232

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Author: Tanya Kay Bilezikjian
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 130

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Author: John F. McCarthy
Publisher:
ISBN:
Category :
Languages : en
Pages : 317

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The main purpose of this project was to advance the basic scientific understanding of colloid and colloid-facilitated Cs transport of radionuclides in the vadose zone. We focused our research on the hydrological and geochemical conditions beneath the leaking waste tanks at the USDOE Hanford reservation. Specific objectives were (1) to determine the lability and thermodynamic stability of colloidal materials, which form after reacting Hanford sediments with simulated Hanford Tank Waste, (2) to characterize the interactions between colloidal particles and contaminants, i.e., Cs and Eu, (3) to determine the potential of Hanford sediments for \textit{in situ} mobilization of colloids, (4) to evaluate colloid-facilitated radionuclide transport through sediments under unsaturated flow, (5) to implement colloid-facilitated contaminant transport mechanisms into a transport model, and (6) to improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facili\-tated transport for clean-up procedures and long-term risk assessment. We have previously shown that upon contact with simulated waste tank solutions, Hanford sediments change their mineralogical composition. Certain minerals, i.e., quartz, smectite, and kaolinite, are partially dissolved, and new mineral phases, i.e., the feldspathoids cancrinite and sodalite, are formed. We have characterized these mineral transformations and clarified the mineral transformation pathways. The new minerals were mainly in the colloidal size fraction (diameter less than 2 mum), had a negative surface charge, and were microporous, meaning they contained small pores. When Cs was present during the formation of the minerals, contaminants, like Cs, could be trapped inside the mineral structure. Transport experiments under water saturated and unsaturated conditions showed that the colloids were mobile in Hanford sediments. As the water saturation of the sediments decreased, the amount of colloids transported also decreased. The colloids had the ability to enhance the migration of the radionuclide Cs; however, Cs initially sorbed to colloids was desorbed during transport through uncontaminated Hanford sediments. The finding that Cs was stripped off the colloids during the transport through uncontaminated sediments implies that colloids will likely not be an effective carrier for Cs, unless the Cs is incorporated into the mineral structure of the colloids such that the radionuclide cannot desorb from the colloids. Nevertheless, it appears that the amount of Cs that can be transported by mobile colloids beneath Hanford waste tanks is limited. Colloids will not be able to move the bulk mass of Cs through the vadose zone at Hanford. Colloid stability studies indicate that Hanford sediment form stable colloidal suspensions when suspended in Hanford sediment pore waters. Colloid stability was assessed by determination of the critical coagulation concentration, i.e., the chemical electrolyte concentration at which colloidal suspensions flocculate and settle out (become unstable). Although in the stable mode, Hanford colloids will settle out of solution after extended periods of time (months to years). Given the low recharge rates at Hanford range, which from near 0 to more than 100 mm/year, and the long travel times for rainwater to reach the groundwater of more than 40 years, it appears that colloidal transport is unlikely to occur if colloids are initially to be suspended close to the soil surface by infiltrating rainwater. However, if preferential flow or transient flow occurs, then colloidal transport may become more important. The results of this project have also led to improvements of our fundamental understanding of colloid transport and mobilization under unsaturated flow conditions in porous media. We have found that colloid attachment to the liquid-gas interface is not that relevant and that colloids rather attached near the triple phase interface where air, water, and solid phases meet. We have also found that capillary forces are the most dominant forces governing colloid release in unsaturated porous media. These results help to advance our understanding of colloid fate and transport in unsaturated porous media.

Author: Hesham Bekhit Mohamed Bekhit
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 516

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Author: Veronica L. Morales
Publisher:
ISBN:
Category :
Languages : en
Pages : 169

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Although a wide variety of studies have been conducted to understand the numerous processes responsible for the transport of solutes and particulates through soils in order to prevent groundwater contamination, many gaps remain. This thesis presents the findings of two mechanisms (colloid facilitated transport and development of preferential flow infiltration) by which contaminants are able to expedite their transport through unsaturated soils (i.e., the vadose zone), easily reach deeper groundwater, and lower the filtering capacity of soils. The first study of this thesis bridges the gap between changes in polymeric characteristics of dissolved organic matter-colloid complexes induced by solution composition, and the effect these have on colloid transport through unsaturated soils. The second study presents a semi-empirical approach to improve existing models that predict attachment efficiency ([alpha]) of electrosterically stabilized suspensions moving through a porous medium using direct measurements of polymeric characteristics. The fourth study elucidates the capillary forces responsible for the transition between pinning or allowing particles to slip when they approach an air-water-solid interface. Lastly, bioclogging and soil-water repellency from dehydrated microbial exudates are studied in terms of biotic changes in structure and surface properties that generate points of wetting instability that can result in the formation of persistent preferential flow paths.

Author: K. U. Totsche
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 120

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Book Description

Author: Monzer Fanun
Publisher: Elsevier
ISBN: 0444632840
Category : Science
Languages : en
Pages : 715

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Book Description
The Role of Colloidal Systems in Environmental Protection describes the importance of colloids in many applications that contribute to environmental protection, including drinking water and wastewater treatment, heavy metal remediation, treatment of radioactive materials, corrosion, and energy conversion. Knowledge of the physical and chemical composition of colloids is important to understand and accurately model the relevant processes. The book familiarizes the reader with the technological features of the application of colloids in environmental protection, and provides chemical engineers, researchers, and scientists in academic and corporate communities with the latest developments in this field. Each chapter covers the whole spectrum of the relevant science, from the fundamentals to applications. - Provides the applied technological features of colloids in environmental protection - Gives insight into the use of bio-solid colloids as contaminant carriers - Covers the natural occurrence of biosurfactants in the environment and their applications - Provides information on the use of nanoparticles for environmental applications - Chapters written by recognized and respected experts in the field from all over the world