Comparison of the aggregation behavior of Ti[O.sub.2] nanoparticles exposed to fulvic acid and bacillus subtilis exudates

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered Ti[O.sub.2] nanoparticles (nano-Ti[O.sub.2]). After exposure of nano-Ti[O.sub.2] to varying concentrations of Suwannee River fulvic acid (SRFA...

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Bibliographic Details
Published in:Water, air, and soil pollution air, and soil pollution, 2014-11, Vol.225 (11)
Main Authors: Duster, Thomas A, Fein, Jeremy B
Format: Article
Language:English
Subjects:
Analysis
Humic acid
Nanoparticles
Online Access:Get full text
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Summary:The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered Ti[O.sub.2] nanoparticles (nano-Ti[O.sub.2]). After exposure of nano-Ti[O.sub.2] to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-Ti[O.sub.2] aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-Ti[O.sub.2] exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-Ti[O.sub.2] aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-Ti[O.sub.2] can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-Ti[O.sub.2] in geologic systems. Keywords Bacterial exudate * Fulvic acid * Natural organic matter (NOM) * Nano-Ti[O.sub.2] * Aggregation * Fate and transport
ISSN:0049-6979
DOI:10.1007/s11270-014-2189-1