Engineered superparamagnetic nanoparticles (NPs) stabilized using synthetic surfactants have been previously used for removal of targeted contaminants from water. In this study, monodispersed iron oxide NPs (dispersible in apolar solvents) were synthesized by thermal decomposition of iron salt (FeO(OH)) in the presence of oleic acid and 1-octadecene. For aqueous-based applications, these were phase transferred to water by a bilayer ligand addition approach using probe sonicator. Rhamnolipid- a natural biosurfactant, has tremendous potential to remove heavy metals and organic contaminants from water. Due to its biodegradability and lower toxicity, rhamnolipid was explored as the ligand for stabilizing spherical (9 nm) iron oxide NPs. Parameters varied were probe sonication time, sonication amplitude, rhamnolipid concentration and volume of iron oxide NPs. Optimum conditions were selected based on phase transfer efficiency and hydrodynamic diameter of NPs in aqueous phase. Characterization of the resulting suspension was performed using transmission electron microscopy (TEM), total organic carbon (TOC) analysis and zeta (ζ) potential measurements. The stability of the monodispersed aqueous suspension was evaluated through particle-particle aggregation kinetics using time-resolved dynamic light scattering. The aqueous stable NPs were then used for evaluating U(VI) removal from water at environmentally relevant conditions. The impact of pH, initial loading of U(VI), presence and absence of carbonate were systematically observed. The observed equilibrium partitioning was interpreted using surface complexation modeling to account for U(VI) binding to the carboxyl groups in the rhamnolipid. The model was evaluated for its ability to simulate U(VI) adsorption as a function of the pH, total U(VI) loading, and dissolved inorganic carbon concentration.

U(VI) removal using rhamnolipid stabilized iron oxide nanoparticles

2019 Spring National Meeting

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