Characterization of nanoparticles and colloids in aquatic systems:

Speaker:Mamadou S. Diallo, Ph.D.Materials and Process Simulation Center, Beckman Institute 139-74
California Institute of Technology, Pasadena, CA, 91125
and
Department of Civil Engineering
Howard University, Washington DC, 20059Abstract:
Fulvic acids (FA) and humic acids (HA) constitute 30 to 50% of dissolved organic matter in natural aquatic systems. A commonly accepted view in the environmental chemistry literature is that FA and HA exist as soluble macroligands in aqueous solutions at low concentration and as supramolecular aggregates at higher concentration. The size, shape and structure of these aggregates are still the subject of ongoing debate. In this paper, we use small angle neutron scattering (SANS) to assess the effects of solute concentration, solution pH and background electrolyte (NaCl) concentration on the structure and size of Suwannee River fulvic acid (SRFA) aggregates in aqueous solutions. The qualitative features of the SANS curves and data analysis are not consistent with the view points that FA and HA form micelle-like aggregates or random coils in aqueous solutions. We find that SRFA forms fractal aggregates in aqueous solutions with size greater than 242 nm. The SRFA aggregates undergo a significant degree of restructuring in compactness as solution pH, solute concentration and NaCl concentration increase.

Location: Kaprielian Hall (KAP) - rielian Hall, Room 156

Audiences: Everyone Is Invited

Contact: Evangeline Reyes