Complex metal oxides are important nanomaterials for catalysis, energy storage, and water purification. These nanomaterials are being rapidly incorporated into numerous commercial products, however, the potential impact to the environment upon improper disposal is still unknown. A commonly overlooked aspect when assessing the environmental and biological safety of engineered nanomaterials is transformation of these materials in aqueous systems. Such transformations are poorly understood, and yet will dictate the environmental fate and biological impact of these nanomaterials. We present a comprehensive analysis of the interaction of an environmentally relevant oxyanion, phosphate, with complex metal oxide nanomaterial, lithium cobalt oxide (LCO), through the implementation of complementary <i>in situ</i> analytical techniques to probe the reactions occurring at the nanoparticle-liquid interface. We show that adsorption of phosphate at environmentally relevant concentrations on LCO nanoparticle surfaces significantly alters their surface charge through formation of bidentate deprotonated complexes on the surface, which we can discern from Attenuated Total Reflectance-FTIR (ATR-FTIR) and Laser Doppler Microelectrophoresis. This surface charge depression leads to increased colloidal stability, as shown by Dynamic Light Scattering size analysis and UV-Visible Spectroscopy tracking of particle sedimentation. ATR-FTIR and flow adsorption microcalorimetry results show that these interactions are favorable over a broad range of pH values, and therefore across multiple protonation states of the phosphate oxyanion. The implications of this interaction may be increased dispersability and bioavailability of these materials in environmental water systems. Future work will probe the hypothesis that the alteration in LCO surface properties may impact the ion release from these particles in model environmental aqueous systems.<br/>

Phosphate adsorption on lithium cobalt oxide nanoparticles impacts environmental presence and bioavailability

256th National Meeting (2018)

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