Transport of engineered nanoparticles in partially saturated sand columns

Transport and Retention of Sulfidized Silver Nanoparticles in Porous Media: The Role of Air‐Water Interfaces, Flow Velocity, and Natural Organic Matter

“…The complete particle retention of S‐Ag‐NP without NOM aging in our study was in contrast to the findings of Yecheskel et al (2016) where sulfidized Cit‐Ag‐NPs behaved like a conservative tracer in sand. The authors used a different sulfidation method to generate the NPs where a higher concentration of citrate was used, the sulfidation was performed by granular pyrite, and no NP washing of surplus citrate and sulfur was described.…”

“…The main difference was the shift in time for initial NOM‐S‐Ag‐NPs breakthrough of 2.5 to 5.2 PV. Most studies reported for stabilized Ag‐NPs an earlier breakthrough at around 1 PV independent of the saturation, for example, for saturated experiments with and without NOM (El Badawy et al, 2013; Kanel et al, 2015; Taghavy et al, 2013), and unsaturated experiments (Liang, Bradford, Šimůnek, Heggen, et al, 2013; Yecheskel et al, 2016). Under the same unsaturated hydraulic conditions, Kumahor et al (2016) observed for Cit‐Ag‐NPs and Cit‐Ag‐NPs aged with soil solution an initial breakthrough between 0.5 and 1.7 PV.…”

“…Hyperexponential and nonmonotonic retention profiles have been observed for Ag‐NPs at various saturation, flow rates, and solution conditions (Degenkolb et al, 2019; Kumahor et al, 2016; Liang, Bradford, Šimůnek, Heggen, et al, 2013). An excessive deposition of NPs at the column inlet have been assigned to chemical particle heterogeneity or NP aggregation (Goldberg et al, 2014; Yecheskel et al, 2016), to different hydrodynamics (Bradford et al, 2011) and straining in the critical zone of the uppermost mm (Kumahor, Hron, et al, 2015). In our study, only the S‐Ag‐NP experiment provided an ideal hyperexponential retention profile.…”

“…The transport of engineered inorganic NPs through porous media is controlled by several key factors (El Badawy et al, 2013): the transport velocity and tortuosity, grain size and grain surface roughness (Liang, Bradford, Šimůnek, Vereecken, et al, 2013; Sagee et al, 2012), solution chemistry of the mobile phase (Makselon et al, 2017), geochemistry of the porous substrate, and the concentration, stability, surface charge, and aggregation behavior of NPs themselves. In quartz sand and natural soils, the presence of dissolved organic matter enhanced the mobility of stabilized Ag‐NP (Sagee et al, 2012; Yecheskel et al, 2016) while low pH, higher ionic strength and divalent cations promoted NP aggregation and retention (Akaighe et al, 2013; Baalousha et al, 2008). In saturated, pure quartz sand with a negative surface charge Ag‐NPs stabilized colloidally often show a high mobility whereas in natural soils, the decreasing grain size, the presence of clay minerals and positively charged iron and aluminum oxides causes enhanced NP retention (Cornelis et al, 2013; El Badawy et al, 2013; Liang, Bradford, Šimůnek, Vereecken, et al, 2013).…”

Transformation and bioavailability of metal oxide nanoparticles in aquatic and terrestrial environments. A review

“…As stated earlier, MeO-NPs surface charge could be reversed due to their interaction with the complex soil components which enhance their mobility in the compartment. For instance, the positively charged ZnO-NPs is immobile in soils, but increased mobility was reported in the presence of HA (Yecheskel et al, 2016).…”