Sensitivity of the transport and retention of stabilized silver nanoparticles to physicochemical factors

Liang, Yan; Bradford, Scott A.; Šimůnek, Jiřı́; Vereecken, Harry; Klumpp, Erwin

doi:10.1016/j.watres.2013.02.025

Cited by 181 publications

(181 citation statements)

References 51 publications

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“…42 In addition, the retained AgNPs could hinder further retention due to the repulsive AgNP−AgNP interactions especially when more particles were retained at higher C o . 33 An observed decrease in k 1 and S max /C o with larger C o supports this hypothesis (SI Table S1). Higher effluent concentrations and less retention were observed in Figure 3 for higher q (flow velocity).…”

Section: ■ Results and Discussionsupporting

confidence: 59%

“…In contrast, blocking caused the RP shapes to transition from hyperexponential, to nonmonotonic, and to uniform in the quartz sand. 33 These differences can partially be ascribed to the higher values of S max /C o in the current work (>1.94 cm 3 g −1 ). In comparison, values of S max /C o were frequently as low as 0.732 cm 3 g −1 in the quartz sand.…”

Section: ■ Results and Discussionmentioning

confidence: 54%

“…In comparison, values of S max /C o were frequently as low as 0.732 cm 3 g −1 in the quartz sand. 33 In addition, as confirmed by the BET surface area analysis, the interacting surface area in the loamy sand (1.7 m 2 g −1 ) is much greater than in the quartz sand (less than 0.2 m 2 g −1 ). Both of these factors tend to diminish the relative importance of blocking in loamy sand in comparison to quartz sand; e.g., it takes more AgNPs to fill a larger value of S max /C o .…”

Section: ■ Results and Discussionmentioning

confidence: 81%

“…The breakthrough curves exhibited blocking behavior (a decreasing retention rate with time) as the maximum retained concentration on the solid phase (S max ) filled. 33 Furthermore, RP shapes transitioned from hyperexponential, to nonmonotonic, and to uniform during blocking as S max was filled by retained AgNPs and free surfactant molecules. 33 Mechanical straining and chemical interactions between AgNPs and the soil surface have also been suggested to play important roles in AgNP retention in a disturbed sandy soil.…”

Section: ■ Introductionmentioning

confidence: 99%

“…33 Furthermore, RP shapes transitioned from hyperexponential, to nonmonotonic, and to uniform during blocking as S max was filled by retained AgNPs and free surfactant molecules. 33 Mechanical straining and chemical interactions between AgNPs and the soil surface have also been suggested to play important roles in AgNP retention in a disturbed sandy soil. 7 Studies on the mobility of micrometer-sized colloids pointed out that the pore structure of undisturbed soil and leaching of naturally occurring particles during infiltration were important processes that affected contaminant migration.…”

Section: ■ Introductionmentioning

confidence: 99%

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Retention and Remobilization of Stabilized Silver Nanoparticles in an Undisturbed Loamy Sand Soil

Liang

Bradford

Šimůnek

et al. 2013

Environ. Sci. Technol.

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114

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Column experiments were conducted with undisturbed loamy sand soil under unsaturated conditions (around 90% saturation degree) to investigate the retention of surfactant stabilized silver nanoparticles (AgNPs) with various input concentration (C o ), flow velocity, and ionic strength (IS), and the remobilization of AgNPs by changing the cation type and IS. The mobility of AgNPs in soil was enhanced with decreasing solution IS, increasing flow rate and input concentration. Significant retardation of AgNP breakthrough and hyperexponential retention profiles (RPs) were observed in almost all the transport experiments. The retention of AgNPs was successfully analyzed using a numerical model that accounted for time-and depth-dependent retention. The simulated retention rate coefficient (k 1 ) and maximum retained concentration on the solid phase (S max ) increased with increasing IS and decreasing C o . The high k 1 resulted in retarded breakthrough curves (BTCs) until S max was filled and then high effluent concentrations were obtained. Hyperexponential RPs were likely caused by the hydrodynamics at the column inlet which produced a concentrated AgNP flux to the solid surface. Higher IS and lower C o produced more hyperexponential RPs because of larger values of S max . Retention of AgNPs was much more pronounced in the presence of Ca 2+ than K + at the same IS, and the amount of AgNP released with a reduction in IS was larger for K + than Ca 2+ systems. These stronger AgNP interactions in the presence of Ca 2+ were attributed to cation bridging. Further release of AgNPs and clay from the soil was induced by cation exchange (K + for Ca 2+ ) that reduced the bridging interaction and IS reduction that expanded the electrical double layer. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, and correlations between released soil colloids and AgNPs indicated that some of the released AgNPs were associated with the released clay fraction.

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Section: ■ Results and Discussionsupporting

confidence: 59%

Section: ■ Results and Discussionmentioning

confidence: 54%

Section: ■ Results and Discussionmentioning

confidence: 81%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Retention and Remobilization of Stabilized Silver Nanoparticles in an Undisturbed Loamy Sand Soil

Liang

Bradford

Šimůnek

et al. 2013

Environ. Sci. Technol.

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120

114

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Modeling the release of E. coli D21g with transients in water content

Bradford

Wang

Torkzaban

et al. 2015

Water Resources Research

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Transients in water content are well known to mobilize colloids that are retained in the vadose zone. However, there is no consensus on the proper model formulation to simulate colloid release during drainage and imbibition. We present a model that relates colloid release to changes in the air-water interfacial area (A aw ) with transients in water content. Colloid release from the solid-water interface (SWI) is modeled in two steps. First, a fraction of the colloids on the SWI partitions to the mobile aqueous phase and airwater interface (AWI) when the A aw increases during drainage. Second, colloids that are retained on the AWI or at the air-water-solid triple line are released during imbibition as the AWI is destroyed. The developed model was used to describe the release of Escherichia coli D21g during cycles of drainage and imbibition under various saturation conditions. Simulations provided a reasonable description of experimental D21g release results. Only two model parameters were optimized to the D21g release data: (i) the cell fraction that was released from the SWI (f r ) and (ii) the cell fraction that partitioned from the SWI to the AWI (f awi ). Numerical simulations indicated that cell release was proportional to f r and the initial amount of retention on the SWI and AWI. Drainage to a lower water content enhanced cell release, especially during subsequent imbibition, because more bacteria on the SWI were partitioned to the AWI and/or aqueous phase. Imbibition to a larger water content produced greater colloid release because of higher flow rates, and more destruction of the AWI (smaller A aw ). Variation in the value of f awi was found to have a pronounced influence on the amount of cell release in both drainage and imbibition due to changes in the partitioning of cells from the SWI to the aqueous phase and the AWI.

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The impact of immobile zones on the transport and retention of nanoparticles in porous media

Molnar

Gerhard

Willson

et al. 2015

Water Resources Research

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Nanoparticle transport and retention within porous media is treated by conceptualizing the porous media as a series of independent collectors (e.g., Colloid Filtration Theory). This conceptualization assumes that flow phenomena near grain-grain contacts, such as immobile zones (areas of low flow), exert a negligible influence on nanoparticle transport and assumes that retention and release of particles depends only on surface chemistry. This study investigated the impact of immobile zones on nanoparticle transport and retention by employing synchrotron X-ray computed microtomography (SXCMT) to examine pore-scale silver nanoparticle distributions during transport through three sand columns: uniform iron oxide, uniform quartz, and well-graded quartz. Extended tailing was observed during the elution phase of all experiments suggesting that hydraulic retention in immobile zones, not detachment from grains, was the source of tailing. A numerical simulation of fluid flow through an SXCMT data set predicted the presence of immobile zones near grain-grain contacts. SXCMT-determined silver nanoparticle concentrations observed that significantly lower nanoparticle concentrations existed near grain-grain contacts throughout the duration of all experiments. In addition, the SXCMT-determined pore-scale concentration gradients were found to be independent of surface chemistry and grain size distribution, suggesting that immobile zones limit the diffusive transport of nanoparticles toward the collectors. These results suggest that the well-known overprediction of nanoparticle retention by traditional CFT may be due to ignoring the influences of grain-grain contacts and immobile zones. As such, accurate prediction of nanoparticle transport requires consideration of immobile zones and their influence on both hydraulic and surface retention.

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Sensitivity of the transport and retention of stabilized silver nanoparticles to physicochemical factors

Cited by 181 publications

References 51 publications

Retention and Remobilization of Stabilized Silver Nanoparticles in an Undisturbed Loamy Sand Soil

Retention and Remobilization of Stabilized Silver Nanoparticles in an Undisturbed Loamy Sand Soil

Modeling the release of E. coli D21g with transients in water content

The impact of immobile zones on the transport and retention of nanoparticles in porous media

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