Prior research has demonstrated that nanoparticle mobility in porous media is sensitive to the concentrations of aqueous co-constituents, including stabilizing agents and electrolytes. The objective of this research is to investigate the influence of coating polymer residuals on nanoparticle transport and deposition. Column experiments demonstrated that residual aqueous polyacrylic acid-octylamine (PAA-OA) copolymer, a coating molecule designed to facilitate QD suspension stability, inhibited QD deposition. Subsequent PAA-OA and QD transport experiments indicated that sorption of free PAA-OA copolymer blocked nanoparticle attachment sites on the solid phase, thereby enhancing QD transport. A macro-scale nanoparticle transport simulator is developed to model this competition for attachment sites, implementing a modification of classical filtration theory. Here QD and PAA-OA transport are coupled through a Langmuir-type blocking function to account for both QD and PAA-OA interactions with the solid surface. Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/mwrm/uploads/60792__figure1_.jpg' alt='' /> Comparison of model simulations with column experimental observations reveals that the simulator is able to reproduce both the measured QD breakthrough and the anomalous QD retention profile. The utility of the experimentally-validated simulator is further demonstrated by the ability of the model to predict PAA-OA transport in Ottawa Sand columns alone, and enhanced QD transport following a PAA-OA pre-flood. Comparisons between these results and those of traditional particle filtration models reveal that competition between aqueous and nanoparticle constituents can dramatically influence predictions of nanoparticle behavior in field-scale scenarios.

Modeling the influence of secondary constituents on nanoparticle deposition in porous media

248th National Meeting (2014)

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