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The manufacture of significant quantities of nanomaterials will inevitably lead tothe introduction of these materials into the environment. The understanding of thecharacteristics and the fate of these nanomaterials in water is crucial to evaluatetheir environmental implication and potential risk for human exposure. Thisresearch investigated the characteristics, dispersion and stability of two importantcategories of nanomaterials, metal oxide nanoparticles and quantum dots (QDs)in different aquatic environments, as well as their propensity to be removed byportable water treatment. Lab-synthesized hematite was prepared as individualnanoparticles; whereas, all commercial metal oxide nanoparticles wereaggregates as received. Neither sonication nor dispersant could not break upthese aggregates to primary nanoparticles. It may attribute to chemical bondingduring the synthesis or storage. Except silica, metal oxide nanoparticleaggregates aggregated further in 0.01 M KCl solution. The stability of silica maybe related to its low pH value of zero point of charge (pHzpc) and low Hamakerconstant. Addition of 4 mg/L natural organic matter (NOM) could stabilize metal oxide nanoparticles byimparting negative charge to their surface and producing an increase in absolutesurface potential. Compared with metal oxide nanoparticles, most QD particlespresented as individual nanoparticles, but they also contained a few aggregates.Due to carboxyl functional groups bound on QDs surface, QDs remained stableunless divalent or trivalent cations were introduced to form complexes with QDs.Portable water treatment studies showed that these nanoparticles were relativelydifficult to be removed from water only by coagulation, flocculation andsedimentation processes and 0.45 m filtration enhanced their removal. Includes 9 references, tables, figures.

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Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 40File Size: 1 file , 2.4 MB