TY - JOUR
T1 - Effects of monovalent and divalent metal cations on the aggregation and suspension of Fe3O4 magnetic nanoparticles in aqueous solution
AU - Wang, Hao
AU - Zhao, Xiaoli
AU - Han, Xuejiao
AU - Tang, Zhi
AU - Liu, Shasha
AU - Guo, Wenjing
AU - Deng, Chaobing
AU - Guo, Qingwei
AU - Wang, Huanhua
AU - Wu, Fengchang
AU - Meng, Xiaoguang
AU - Giesy, John P.
N1 - Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/5/15
Y1 - 2017/5/15
N2 - There has been limited research investigating how the mechanisms of aggregation of magnetic nanoparticles (MNPs) are affected by inorganic ions. In this study, Na+, Mg2 +, Ca2 +, Sr2 + and Ba2 + were selected to systematically study the aggregation mechanisms of Fe3O4 MNPs. The results indicated that divalent cations more significantly affected the stabilities of MNPs than Na+ at low concentrations (e.g., 0.1 mM) in a decreasing order of Ba2 + > Sr2 + > Ca2 + > Mg2 + > Na+. Extended DLVO theory did not offer a satisfactory explanation for the above difference due because it ignores specific ion effects. It was also found that the initial adsorption ratios of these metals by Fe3O4 MNPs were linearly proportional to the hydrodynamic diameter (HDD) of Fe3O4 MNPs before aggregation occurred. In addition to the valence states, the hydration forces and ionic radii of the metal cations were proposed to be other factors that significantly affected the interactions of metal cations with Fe3O4 MNPs based on the excellent linear relationships of the HDD of Fe3O4 MNPs and these three factors. Moreover, a bridging function of divalent cations might develop after aggregation occurred based on the increases in their adsorption amounts and intensities for binding oxygen-containing functional groups. In addition, an increase in the positive ζ potential of MNPs was observed with the addition of divalent cations until 10.0 mM at a pH of 5.0, which potentially enhances the resistance of MNPs to aggregation in aquatic systems compared with Na+. Consequentially, the effects of metal cations on the aggregation of MNPs are determined by the hydration forces, valance states, ionic radii and bond types formed on the MNPs. Thus, the specific ion effects of these cations should be considered in predicting the environmental behaviors of specific nanomaterials.
AB - There has been limited research investigating how the mechanisms of aggregation of magnetic nanoparticles (MNPs) are affected by inorganic ions. In this study, Na+, Mg2 +, Ca2 +, Sr2 + and Ba2 + were selected to systematically study the aggregation mechanisms of Fe3O4 MNPs. The results indicated that divalent cations more significantly affected the stabilities of MNPs than Na+ at low concentrations (e.g., 0.1 mM) in a decreasing order of Ba2 + > Sr2 + > Ca2 + > Mg2 + > Na+. Extended DLVO theory did not offer a satisfactory explanation for the above difference due because it ignores specific ion effects. It was also found that the initial adsorption ratios of these metals by Fe3O4 MNPs were linearly proportional to the hydrodynamic diameter (HDD) of Fe3O4 MNPs before aggregation occurred. In addition to the valence states, the hydration forces and ionic radii of the metal cations were proposed to be other factors that significantly affected the interactions of metal cations with Fe3O4 MNPs based on the excellent linear relationships of the HDD of Fe3O4 MNPs and these three factors. Moreover, a bridging function of divalent cations might develop after aggregation occurred based on the increases in their adsorption amounts and intensities for binding oxygen-containing functional groups. In addition, an increase in the positive ζ potential of MNPs was observed with the addition of divalent cations until 10.0 mM at a pH of 5.0, which potentially enhances the resistance of MNPs to aggregation in aquatic systems compared with Na+. Consequentially, the effects of metal cations on the aggregation of MNPs are determined by the hydration forces, valance states, ionic radii and bond types formed on the MNPs. Thus, the specific ion effects of these cations should be considered in predicting the environmental behaviors of specific nanomaterials.
KW - Aggregation and suspension
KW - Aquatic environment
KW - FeO MNPs
KW - Metal cations
KW - Specific ion effects
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U2 - 10.1016/j.scitotenv.2017.02.060
DO - 10.1016/j.scitotenv.2017.02.060
M3 - Article
C2 - 28202242
AN - SCOPUS:85012031738
SN - 0048-9697
VL - 586
SP - 817
EP - 826
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -