Impact of Nanoparticle Surface Properties on the Attachment of Cerium Oxide Nanoparticles to Sand and Kaolin

Soil texture has been found to be a critical factor in regulating the fate and transport of cerium oxide nanoparticles (CeO(2)NPs) in the terrestrial environment. However, the underlying mechanisms for the interactions between CeO(2)NPs and different components of soil are still poorly understood. The attachment of CeO(2)NPs onto two typical components of soil (sand and kaolin) in batch experiments were investigated to provide insights into the retention and bioavailability of CeO(2)NPs in soil. Surface properties of CeO(2)NPs, including surface charge and surface coating condition, had strong impacts on the interactions between CeO(2)NPs and soil particles. Positively charged CeO(2)NPs [CeO(2)NPs(+)] displayed the greatest attachment onto kaolin, whereas the negatively charged CeO(2)NPs [CeO(2)NPs(-)] showed poorest attachment onto sand. The attachment of CeO(2)NPs onto kaolin was significantly greater than onto sand, irrespective of surface charge. Homoaggregation of CeO(2)NPs increased the size of CeO(2)NPs on the surface of sand and kaolin. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) calculations agreed with the experimental observations that surface charge and coating condition of CeO(2)NPs played a vital role in the homoaggregation and adsorption of CeO(2)NPs. For CeO(2)NPs(-) coated with polyvinylpyrrolidone (PVP), the steric repulsion between soil particles and CeO(2)NPs increases rapidly with the increase of maximum surface concentration of PVP. Adsorption isothermal fittings indicated that the adsorption of CeO(2)NPs onto sand and kaolin can be properly described by the Dubinin-Radushkevich isotherm. The results obtained in this study are crucial for the understanding of the fate and transport of engineered nanomaterials in the environment.