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Tanapon Phenrat Navid Saleh Kevin Sirk Hye-Jin Kim Robert D. Tilton Gregory V. Lowry 《Journal of nanoparticle research》2008,10(5):795-814
Nanoscale zerovalent iron (NZVI) particles are 5–40 nm sized Fe0/Fe-oxide particles that rapidly transform many environmental contaminants to benign products and are a promising in situ
remediation agent. Rapid aggregation and limited mobility in water-saturated porous media limits the ability to deliver NZVI
dispersions in the subsurface. This study prepares stable NZVI dispersions through physisorption of commercially available
anionic polyelectrolytes, characterizes the adsorbed polymer layer, and correlates the polymer coating properties with the
ability to prevent rapid aggregation and sedimentation of NZVI dispersions. Poly(styrene sulfonate) with molecular weights
of 70 k and 1,000 k g/mol (PSS70K and PSS1M), carboxymethyl cellulose with molecular weights of 90 k and 700 k g/mol (CMC90K
and CMC700K), and polyaspartate with molecular weights of 2.5 k and 10 k g/mol (PAP2.5K and 10K) were compared. Particle size
distributions were determined by dynamic light scattering during aggregation. The order of effectiveness to prevent rapid
aggregation and stabilize the dispersions was PSS70K(83%) > ≈PAP10K(82%) > PAP2.5K(72%) > CMC700K(52%), where stability is
defined operationally as the volume percent of particles that do not aggregate after 1 h. CMC90K and PSS1M could not stabilize
RNIP relative to bare RNIP. A similar trend was observed for their ability to prevent sedimentation, with 40, 34, 32, 20,
and 5 wt%, of the PSS70K, PAP10K, PAP2.5K, CMC700K, and CMC90K modified NZVI remaining suspended after 7 h of quiescent settling,
respectively. The stable fractions with respect to both aggregation and sedimentation correlate well with the adsorbed polyelectrolyte
mass and thickness of the adsorbed polyelectrolyte layers as determined by Oshima’s soft particle theory. A fraction of the
particles cannot be stabilized by any modifier and rapidly agglomerates to micron sized aggregates, as is also observed for
unmodified NZVI. This non-dispersible fraction is attributed to strong magnetic attractions among the larger particles present
in the polydisperse NZVI slurry, as the magnetic attractive forces increase as r6. 相似文献