Fate and Transport of (FeXNi1-X)yOZ Nanoparticles in Aquatic Environments

Magnetic nanoparticles, such as iron oxide and iron-nickel oxide nanoparticles, have been synthesized because of their useful potential applications including ferrofluids for audio speakers, targeted gene and drug delivery, magnetic storage media, contrasting agents in magnetic resonance imaging, and adsorbents for toxic environmental pollutants. However, few studies investigated the fate and transport of these magnetic nanoparticles in aquatic environments. In this current study, we electrochemically synthesized iron oxide (i.e., maghemite and hematite) and iron-nickel oxide nanoparticles with different electrostatic and magnetic properties to investigate the stability and mobility of these nanoparticles in porous media. The magnetic saturation and isoelectric point of the electrochemically synthesized iron-nickel oxide nanoparticles decreased and increased, respectively, as iron content in the iron-nickel nanoparticles decreased. Stability and transport results indicated that the stability and mobility of nanoparticles were influenced by a combination of electrostatic and magnetic interactions. Specifically, the stability of the particles under varying pH conditions showed that these nanoparticles were more stable as electrostatic repulsion increased and magnetic attraction decreased. In the case of iron-nickel oxide nanoparticles, the relative breakthrough of nanoparticles through the packed bed column increased with nickel content in nanoparticles. Implications for the transport of the magnetic nanoparticles in aquatic environments will be further discussed.