Synchrotron-based soft X-ray spectromicroscopy was used to probe nanometer-scale chemical heterogeneities of black carbon (BC) materials, including anthracite coal, coke, and activated carbon (AC), and to study their impact on the partitioning of one type of polychlorinated biphenyls (PCB-166: 2,3,4,4, 5,6 hexachloro biphenyl) onto AC particles. Various carbon species (e.g., aromatic, ketonic/phenolic, and carboxylic functional groups) were found in all of the BC materials examined, and impurities (e.g., carbonate and potassium ions in anthracite coal) were identified in nanometer-scale regions of these samples. We show that these chemical heterogeneities in AC particles influence their sorption of hydrophobic organic compounds (HOCs). PCB-166 was found to accumulate preferentially on AC particles with the highest content of aromatic functionalities. These new findings from X-ray spectromicroscopy have the following implications for the role of BC materials in the environment: (1) the functional groups of BC materials vary on a 25-nanometer scale, and so does the abundance of the HOCs; (2) molecular-level characterization of HOC sorption preferences on AC will lead to an improved understanding of AC sorption properties for the remediation of HOCs in soils and sediments.
Stanford Univ, Surface & Aqueous Geochem Grp, Dept Geog & Environm Sci, Stanford, CA 94305 USA; Hanyang Univ, Dept Chem, Seoul 133791, South Korea; CNRS, UMR 7590, Lab Mineral Cristallog, F-75252 Paris, France; Inst Phys Globe, F-75252 Paris, France; Stanford Univ, Dept Civil & Environm Engn, Stanford, CA 94305 USA; Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA; SLAC, Stanford Synchrotron Radiat Lab, Menlo Pk, CA 94025 USAArticleEnglish