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Stability and transport of graphene oxide nanoparticles in groundwater and surface water

Lanphere, Jacob D., Rogers, Brandon, Luth, Corey, Bolster, Carl H., Walker, Sharon L.
Environmental Engineering Science 2014 v.31 no.5 pp. 1-10
calcium chloride, carbon, electrophoresis, groundwater, groundwater flow, ions, nanoparticles, organic matter, porous media, potassium chloride, surface water
A transport study investigating the effects of natural organic matter (NOM) in the presence of monovalent (KCl) and divalent (CaCl2) salts was performed in a packed bed column. The electrophoretic mobility (EPM) and effective diameter of the graphene oxide nanoparticles (GONPs) were measured as a function of NOM concentration. Suwannee River Humic Acid (SRHA) was used as the model NOM and was characterized across an environmentally relevant concentration range of 0.1-10 mg/L. Results suggest that the transport of GONPs is increased in monovalent (KCl) and divalent (CaCl2) salts in the presence of NOM. For NOM concentrations = 1.0 mg/l typically found in surface water environments, steric stabilization occurred and resulted in more stable GONPs. Conversely, in the presence of NOM concentrations (0.1 mg/L) found in some groundwater environments, slightly larger GONP aggregates were formed when compared to conditions in the absence of NOM, suggesting that bridging is occurring. In the absence of NOM, the effect of divalent ions increased GONP retention during transport in a packed bed column at lower salt concentrations (10-3 M CaCl2) compared to that for monovalent salts as reported in previous work. This study confirms that these “carbonaceous-oxide” materials follow traditional theory for stability and transport. This is the first study that identifies sensitivity of this unique carbon material to valence and NOM during transport in porous media that represent surface and groundwater conditions.