Colloidal stability of Fe3O4 magnetic nanoparticles differentially impacted by dissolved organic matter and cations in synthetic and naturally-occurred environmental waters

Abstract Better understanding of the colloidal behaviors of nanomaterials impacted by aquatic chemistry parameters is needed for appropriate evaluation of the environmental risks posed by nanomaterials in natural waters. In the study, the colloidal stability of Fe 3 O 4 magnetic nanoparticles (Fe-MNPs) was evaluated over a range of chemistry characteristics [e.g., pH, dissolved organic matter (DOM), salt types, cationic strength] in six synthetic water samples. The findings from the synthetic water samples were further examined with eight “real world” environmental water samples. Our results demonstrated that DOM fraction, humic acid (HA), promoted suspension of Fe-MNPs more by hydrophobic interactions in addition to ligand exchange and electrostatic effects compared with fulvic acid (FA). Capability of cations to increase aggregation of Fe-MNPs were in the order of Ca 2+  > Mg 2+ >> Na + because of their different degrees of bridging complexation with DOM molecules on particle surfaces. As a key parameter for indicating Fe-MNPs colloidal stability, Zeta (ζ) potentials of Fe-MNPs in these waters samples were well correlated to (R 2  = 0.880, P