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Transport of Fluorescently Labeled Hydroxyapatite Nanoparticles in Saturated Granular Media at Environmentally Relevant Concentrations of Surfactants
Citation:
Wang, D., C. Su, C. Liu, AND D. Zhou. Transport of Fluorescently Labeled Hydroxyapatite Nanoparticles in Saturated Granular Media at Environmentally Relevant Concentrations of Surfactants. Colloids and Surfaces A: Physicochemical and Engineering Aspects. Elsevier B.V., Amsterdam, Netherlands, 457:58-66, (2014).
Impact/Purpose:
Submitting to the journal Colloids and Surfaces A: Physicochemical and Engineering Aspects
Description:
Little is known about the mobility of engineered nanoparticles (ENPs) in granular media at environmentally relevant concentration of surfactant, which represents a critical knowledge gap in employing ENPs for in-situ remediation of contaminated groundwater. In this study, transport and retention of alizarin red S (ARS)-labeled hydroxyapatite nanoparticle (nHAP) were investigated in water-saturated sand at environmentally relevant concentrations of surfactants: anionic sodium dodecyl benzene sulfonate (SDBS, 0–50 mg L–1) and cationic cetyltrimethylammonium bromide (CTAB, 0–5 mg L–1). Transport of ARS-nHAP increased with increasing SDBS concentration because of enhanced colloidal stability and reduced aggregate size arising from enhanced electrostatic, osmotic, and elastic-steric repulsions between ARS-nHAP and sand grains. In contrast, transport decreased significantly with increasing CTAB concentration due to reduced surface charge and enhanced aggregation of ARS-nHAP. Osmotic and elastic-steric repulsions played a minor role in enhancing ARS-nHAP colloidal stability in CTAB tests. Retention profiles of ARS-nHAP exhibited hyperexponential-shapes for all conditions tested, and became more pronounced as CTAB concentration increased. The phenomenon was attributed to the aggregation and ripening of ARS-nHAP in the presence of surfactants, particularly CTAB. Overall, the present study suggests that surfactant type and concentration may be important considerations in employing nHAP for engineered in-situ remediation of metal- and radionuclide-contaminated groundwater.
