AVS 50th International Symposium
    Applied Surface Science Thursday Sessions
       Session AS-ThM

Paper AS-ThM4
Application of Electron Based Spectroscopies Combined with Chemical Derivatization for the Characterization of Black Carbon Surfaces

Thursday, November 6, 2003, 9:20 am, Room 324/325

Session: Electron Spectroscopy
Presenter: L.A. Langley, Johns Hopkins University
Authors: L.A. Langley, Johns Hopkins University
T.H. Nguyen, Johns Hopkins University
W.P. Ball, Johns Hopkins University
D.H. Fairbrother, Johns Hopkins University
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Black carbon (BC) is derived from charred plant materials and soot from combustion processes and is ubiquitous in the environment. It is now recognized that remarkably small concentrations of BC can have strong effects on the sorption of hydrophobic organic chemicals (HOCs). Despite the ubiquity of such BC particulates and the importance of sorption to contaminant fate and treatment, little is known about the physical and chemical variability of BC materials or the manner in which their properties can impact the sorption of HOCs in aquatic environments. The surfaces of soots and chars are best described as extended graphene sheets decorated at the edges by various surface oxides. The nature and composition of these surface oxides is believed to play a critical role in determining the sorption properties of BCs towards HOCs. Although X-ray Photoelectron Spectroscopy (XPS) can provide information on the elemental composition of the surface and detect changes in the O/C ratio of different BCs, quantification of the distribution of surface oxides by analysis of the C(1s) and O(1s) lineshapes alone is very difficult. To circumvent this problem XPS augmented by chemical derivatization has been employed in order to provide quantitative information on the distribution of oxide functional groups on the surface of BC. We will also present results on the potential application of bromine as a chemical derivatizing agent capable of titrating the degree of aromatic character in BCs. Additionally, synthetic chars generated from the pyrolysis of wood samples will be characterized as a function of their formation conditions. Results from XPS and chemical derivatization studies of natural chars and synthetic chars will be presented. These results are complemented by sorption studies, where different trends in sorption can be rationalized based on the surface characterization of the BC sorbents.