posted on 2015-06-02, 00:00authored byXiaojun Chang, W. Matthew Henderson, Dermont C. Bouchard
To systematically
evaluate how dispersion methods affect the environmental
behaviors of multiwalled carbon nanotubes (MWNTs), MWNTs were dispersed
in various solutions (e.g., surfactants, natural organic matter (NOM),
and etc.) via ultrasonication (SON) and long-term stirring (LT). The
two tested surfactants [anionic sodium dodecyl sulfate (SDS) and nonionic
poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene
glycol) (PEO–PPO–PEO) triblock copolymers (Pluronic)]
could only disperse MWNTs via ultrasonication; while stable aqueous
SON/MWNT and LT/MWNT suspensions were formed in the presence of the
two model NOMs (Suwannee river humic acid and fulvic acid). Due to
the inherent stochastic nature for both methods, the formed MWNT suspensions
were highly heterogeneous. Their physicochemical properties, including
surface charge, size, and morphology, greatly depended upon the dispersant
type and concentration but were not very sensitive to the preparation
methods. Aggregation and deposition behaviors of the dispersed MWNTs
were controlled by van der Waal and electrostatic forces, as well
as other non-DLVO forces (e.g., steric, hydrophobic forces, etc.).
Unlike the preparation method-independent physicochemical properties,
LT/NOM-MWNTs and SON/NOM-MWNTs differed in their fathead minnow epithelial
cell metabolomics profiles.