Understanding the fate and transport of nanomaterials in subsurface environments has far reaching implications for oil reservoir reconnaissance/intervention and environmental remediation. As such, much attention has been directed toward developing coating chemistries that are capable of stabilizing nanomaterials in harsh subterranean environments. Difficulties arise due to charge screening by electrolytes in high salinity brine and due to high temperatures, which can lead to collapse of the steric layer from lower critical solution temperature (LCST) transitions of the polymer coating. These issues, however, may be overcome by leveraging cooperative interactions between functional groups present on the periphery of nanoparticles and ions present in the brine. The work presented here aims to understand how certain divalent ions can synergistically interact with carbohydrate-based coatings to yield colloids with exceptional stability in high ionic strength multicomponent brines. This report details the synthesis of dextran-coated superparamagnetic iron oxide nanoparticles (Dex-SPIONs) and subsequent testing of their colloidal stability in various brine formulations, as well as their transport properties in porous media, i.e. unconsolidated sand pack columns. Our findings suggest that calcium (Ca<sup>2+</sup>) ions can boost the colloidal stability of polysaccharide-coated nanoparticles in concentrated brines, a possible paradigm shift in designing coatings for subsurface applications.

Colloidal stability and transport of polysaccharide-coated magnetic nanoparticles

256th National Meeting (2018)

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