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DTSTART;TZID=US/Eastern:20100205T150000
DTEND;TZID=US/Eastern:20100205T160000
SUMMARY:Phase Distribution of Solubilized Multiwall Carbon Nanotubes in Aqueous Systems Containing Solid Organic Matter, Qingguo (Jack) Huang -- 
DESCRIPTION:NanoSEC Seminar. Dr. Jack Huang of the University of Georgia Department of Crop and Soil Sciences, Griffin Campus, will  be presenting his talk entitled "Phase Distribution of Solubilized Multiwall Carbon Nanotubes in Aqueous Systems Containing Solid Organic Matter" this week.We are conducting research to investigate the environmental and ecological behavior of water-dispersed
carbon nanotubes, including water-sediment phase distribution, possible degradation and food chain
transport, thereby providing useful information for environmental risk assessment and potential waste
treatment. To unambiguously identify and quantify carbon nanotubes from various natural materials
including water, sediments and organisms, we use C14-labeled carbon nanotubes in our study. Previous
studies indicate carbon nanotube uptake by organisms from soil/sediment media and from aqueous phase
exhibited different behaviors. Thus, information on phase distribution between different environmental
compartments is essential to risk assessment. We conducted experiments to examine phase distribution of
C14 labeled multiwall carbon nanotubes (MWCNTs) in aqueous systems containing peat as a model
organic solid phase under a series of varying pH and ionic strength conditions. Our results suggest that
the solid phase distribution of water-dispersed MWCNTs tends to be governed by three interactive
processes: i) dissolved cations tend to promote CNT aggregation via double layer compression; ii)
dissolved organic matter released from the solid phase tends to stabilize CNTs dispersion via steric
hindrance; and iii) CNTs sorb onto the solid phase. All processes are variously influenced by aqueous
conditions (e.g. pH, electrolytes, dissolved organic matter) and their interplay governs the phase
distribution of MWCNTs. We also characterized MWCNT length distribution by SEM before and after
phase distribution. The results suggest that the shorter nanotubes (
LOCATION:Auditorium, Riverbend Research Laboratory South
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