Transport and retention of surfactant- and polymer-stabilized engineered silver nanoparticles in silicate-dominated aquifer material. (May 2018)

• Record Type: Journal Article
• Authors: Adrian, Yorck F.; Schneidewind, Uwe; Bradford, Scott A.; Simunek, Jirka; Fernandez-Steeger, Tomas M.; Azzam, Rafig
• Is Part Of: Environmental pollution. Volume 236(2018)
• Page Start: 195
• Page End: 207
• Publication Date: 2018-05
• Subjects: Engineered silver nanoparticles -- Contaminant transport -- Groundwater -- Column experiments -- Blocking; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.01.011
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Packed column experiments were conducted to investigate the transport and blocking behavior of surfactant- and polymer-stabilized engineered silver nanoparticles (Ag-ENPs) in saturated natural aquifer media with varying content of material < 0.063 mm in diameter (silt and clay fraction), background solution chemistry, and flow velocity. Breakthrough curves for Ag-ENPs exhibited blocking behavior that frequently produced a delay in arrival time in comparison to a conservative tracer that was dependent on the physicochemical conditions, and then a rapid increase in the effluent concentration of Ag-ENPs. This breakthrough behavior was accurately described using one or two irreversible retention sites that accounted for Langmuirian blocking on one site. Simulated values for the total retention rate coefficient and the maximum solid phase concentration of Ag-ENPs increased with increasing solution ionic strength, cation valence, clay and silt content, decreasing flow velocity, and for polymer-instead of surfactant-stabilized Ag-ENPs. Increased Ag-ENP retention with ionic strength occurred because of compression of the double layer and lower magnitudes in the zeta potential, whereas lower velocities increased the residence time and decreased the hydrodynamics forces. Enhanced Ag-ENP interactions with cation valence and clay were attributed to the creation of cation bridging in the presence of Ca 2+ . The delay in breakthrough was always more pronounced for polymer-than surfactant-stabilized Ag-ENPs, because of differences in the properties of the stabilizing agents and the magnitude of their zeta-potential was lower. Our results clearly indicate that the long-term transport behavior of Ag-ENPs in natural, silicate dominated aquifer material will be strongly dependent on blocking behavior that changes with the physicochemical conditions and enhanced Ag-ENP transport may occur when retention sites are filled. Graphical abstract: Image 1 Highlights: Ag-ENP transport depends on the stabilizing agent, fines <63 μm, and background solution. Ag-ENP retention and breakthrough successfully described using Langmuirian blocking. Retention increases with ionic strength and cation valence of background solution. Ag-ENP stabilizing agent has pronounced influence. Even small amounts of aquifer material <63 μm can strongly retard Ag-ENP breakthrough.