Transport, Stability, and Deposition of Gold Nanoparticles in Porous Media
Gold-nanoparticle (AuNP) transport in groundwater is heavily influenced by the intrinsic properties of the nanoparticles and the external parameters of the environment. Batch experimental data indicated that 15 nm AuNP coated by bovine serum albumin (BSA-AuNP) was more stable at high ionic strength compared to citrate-coated AuNP (cit-AuNP) of similar size. It was expected that the stability of these AuNP would be replicated in column studies. Column experiments with varying monovalent and divalent ion concentrations using both types of AuNP yielded breakthrough curves that both adhere and deviate from this hypothesis. BSA-AuNP was found to be more stable relative to cit-AuNP during porous media flow in the presence of increasing concentrations of CaCl2, but the opposite occurred with increasing NaCl concentration. Colloidal filtration theory (CFT) fails to predict and explain this discrepancy. DLVO calculations suggested pore-space destabilization occurred in these experiments that were not accounted by CFT.