Transport of formaldehyde in water unsaturated laboratory columns packed with quartz sand: Effect of colloid-sized clay particles.

2020 ◽  
Author(s):  
Theodosia V. Fountouli ◽  
Constantinos V. Chrysikopoulos
Keyword(s):  
Vadose Zone ◽  
Quartz Sand ◽  
Water Saturation ◽  
Packed Column ◽  
Interaction Energies ◽  
Unsaturated Porous Media ◽  
Great Abundance ◽  
Clay Particles ◽  
Colloid Particles ◽  
Colloid Retention

<p>Colloid-sized clay particles are in great abundance in the unsaturated or vadose zone and are capable of binding a variety of contaminants, which in turn either facilitate or hinder their migration in the subsurface. Also, FA has relatively strong affinity for kaolinite colloid particles (Fountouli et al., 2019). This study examines the effects of two representative colloid-sized clay particles (kaolinite, montmorillonite) on the transport of formaldehyde (FA) in unsaturated porous media. Transport experiments were performed in columns packed with quartz sand, under unsaturated conditions. The transport of FA was examined with and without the presence of suspended clay particles under various flow rates and various levels of saturation. DLVO interaction energies and the capillary potential energy associated with colloid retention at air-water and solid-water interfaces were calculated. The experimental results clearly suggested that the presence of suspended clay particles hindered the transport of FA in unsaturated packed columns. Moreover, as expected, it was shown that clay particle retention in the packed column increased with decreasing level of water saturation.</p><p> </p><p>Reference</p><p>Fountouli, T.V., C.V. Chrysikopoulos, and I.K. Tsanis, Effect of salinity on formaldehyde interaction with quartz sand and kaolinite colloid particles: batch and column experiments. Environmental Earth Sciences 78, 152, 2019.</p><p> </p>

scholarly journals Effect of Clay Colloid Particles on Formaldehyde Transport in Unsaturated Porous Media

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3541
Author(s):  
Theodosia V. Fountouli ◽  
Constantinos V. Chrysikopoulos
Keyword(s):  
Porous Media ◽  
Quartz Sand ◽  
Experimental Results ◽  
Low Flow ◽  
Unsaturated Porous Media ◽  
Flow Rates ◽  
Clay Particles ◽  
Colloid Retention ◽  
Clay Colloid

This study examines the effects of two representative colloid-sized clay particles (kaolinite, KGa-1b and montmorillonite, STx-1b) on the transport of formaldehyde (FA) in unsaturated porous media. The transport of FA was examined with and without the presence of clay particles under various flow rates and various levels of saturation in columns packed with quartz sand, under unsaturated conditions. The experimental results clearly suggested that the presence of clay particles retarded by up to ~23% the transport of FA in unsaturated packed columns. Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy calculations demonstrated that permanent retention of clay colloids at air-water interfaces (AWI) and solid-water interfaces (SWI) was negligible, except for the pair (STx-1b)–SWI. The experimental results of this study showed that significant clay colloid retention occurred in the unsaturated column, especially at low flow rates. This deviation from DLVO predictions may be explained by the existence of additional non-DLVO forces (hydrophobic and capillary forces) that could be much stronger than van der Waals and double layer forces. The present study shows the important role of colloids, which may act as carriers of contaminants.

Flagella and their property affect the transport and deposition behaviors of Escherichia coli in quartz sand

2021 ◽  
Author(s):  
Mengya Zhang ◽  
Lei He ◽  
Meiping Tong
Keyword(s):  
Escherichia Coli ◽  
Porous Media ◽  
Quartz Sand ◽  
Packed Column ◽  
High Mobility ◽  
Deposition Process ◽  
Flow Chamber ◽  
Chamber System ◽  
Bacterial Flagella ◽  
Silica Surfaces

<p>The effects of bacterial flagella as well as their property on the transport and deposition of bacteria were examined by using four types of <em>Escherichia coli </em>(<em>E.coli</em>) with or without flagella, as well as with normal or sticky flagella. Packed column, quartz crystal microbalance with dissipation (QCM-D), visible parallel plate flow chamber system, as well as visible flow chamber system packed with porous media system were utilized to investigate the deposition behaviors and the deposition mechanisms of bacteria with different property of flagella. We found that the presence of flagella favored <em>E.coli</em> deposition onto quartz sand/silica surfaces. Moreover, by changing the porous media porosity and directly observing the deposition process of bacteria in porous media, grain-to-grain contacts were found to be major sites for bacterial deposition. Particularly, flagella could help bacteria swim near and then deposit at grain-to-grain contacts. In addition, we found that due to the stronger adhesive forces, sticky flagella could further enhance bacterial deposition onto quartz sand/silica surfaces. Elution experiments showed that the portion of bacteria with flagella depositing onto secondary energy minima was relatively lower than bacteria without flagella, indicating that flagella could help bacteria attach onto sand surfaces more irreversibly. Clearly, flagella and their property would have obvious influence on the transport and deposition behaviors of bacteria in porous media. By removing the flagella or changing their property, the transport and deposition of bacteria in porous media can be altered. Particularly, bacterial flagella can be removed to facilitate the transport of bacteria in remediation system requiring high mobility of bacteria, while in system requiring the immobilization bacteria in porous media, bacteria with sticky flagella can be employed.</p>

Colloid Retention in Unsaturated Porous Media as Impacted by Colloid Size

2009 ◽  
Vol 27 (1) ◽  
pp. 35-49 ◽  
Author(s):  
Gang Chen ◽  
Junliang Liu ◽  
Kamal Tawfiq ◽  
Kai Yang ◽  
Christal Banks
Keyword(s):  
Porous Media ◽  
Unsaturated Porous Media ◽  
Colloid Retention

Geoelectrics Estimating Changes in Water Saturation of the Vadose Zone

2004 ◽  
Author(s):  
S. Mares ◽  
L. Zima ◽  
J. Dohnal ◽  
Z. Jane ◽  
J. Knez
Keyword(s):  
Vadose Zone ◽  
Water Saturation

scholarly journals Application of an ionic stabilizer for reinforcing and ensuring frost resistance of clay soils

2020 ◽  
Vol 220 ◽  
pp. 01037
Author(s):  
V. A. Shorin ◽  
A. Y. Velsovskij ◽  
T R Akhmetov
Keyword(s):  
Water Saturation ◽  
Drainage System ◽  
Reinforced Soil ◽  
Appropriate Technology ◽  
Clay Soils ◽  
Local Clay ◽  
Insulating Layer ◽  
Clay Particles ◽  
Reinforced Soils ◽  
Structural Layer

This work is devoted to the study of applicability of the Underbold stabilizer for clay soils in the Vologda region, Russia. The influence of the stabilizer on maintaining the ultimate compressive strength of reinforced soils is shown. It depends on the content of clay particles (soil type) and can reach 30% if the appropriate technology (recommended by the manufacturer) is used. The use of the Underbold stabilizer according to our technology (treatment with a stabilizer - drying - reinforcing with cement) provides an increase in the strength of the reinforced soil after water saturation up to 2 or more times in comparison with samples without a stabilizer. It is shown that when designing a pavement using local clay soils reinforced by the Underbold stabilizer, it is necessary to make a water-insulating layer, and the necessary drainage system to improve the performance of the structural layer. It is noted that this stabilizer does not reduce the phenomenon of frost heaving.

Determination of Air-Water Interfacial Area for Drainage and Imbibition in Unsaturated Porous Media

1999 ◽  
Author(s):  
Charles E. Schaefer ◽  
David A. DiCarlo ◽  
Paul V. Roberts ◽  
Martin J. Blunt
Keyword(s):  
Porous Media ◽  
Water Saturation ◽  
Pore Space ◽  
Sodium Dodecyl ◽  
Sodium Dodecyl Benzene Sulfonate ◽  
Interfacial Area ◽  
Gravity Drainage ◽  
Unsaturated Porous Media ◽  
Column Adsorption ◽  
Dodecyl Benzene Sulfonate

Abstract A new experimental method was developed to measure air-water interfacial area as a function of capillary pressure and water saturation in unsaturated porous media. The surfactant sodium dodecyl benzene sulfonate (SDBS) was used in equilibrium column adsorption experiments to determine the air-water interfacial area for water saturations (ml water/ml pore space) ranging from 0.05 to 1.0, and pressures ranging from 0 to 20 cm of water. A comparison was made between columns which were equilibrated under gravity drainage, versus columns equilibrated under secondary imbibition. Gravity drainage experiments showed the air-water interfacial area decreased linearly with saturation, while imbibition experiments showed a more complex non-monotonic relation to the saturation.

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