Characterization of Sorbent Properties of Soil Organic Matter and Carbonaceous Geosorbents Using n-Alkanes and Cycloalkanes as Molecular Probes
- 11 December 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in Environmental Science & Technology
- Vol. 43 (2), 393-400
- https://doi.org/10.1021/es802277n
Abstract
Nonspecific interactions and modes (i.e., adsorption vs absorption) of sorption by noncondensed, amorphous organic phases (here termed organic matter; OM) in soils and by rigid, aromatic, and condensed phases (termed carbonaceous geosorbents; CGs) were investigated using n-alkanes and cycloalkanes as molecular probes. Sorption isotherms of n- and cyclooctane from water for seven CGs (charcoal, lignite coke, activated carbon, graphite, partially oxidized graphite, diesel soot, bituminous coal), four sorbents with a predominance of OM (lignite, peat, two sapric soils), and two soils containing OM and high amounts of CGs were measured in batch systems. The peat and the sapric soils showed extensively linear sorption, while the CGs exhibited highly nonlinear (Freundlich exponents 0.2−0.7) and strong (Koc values being up to 105 times those for the OM-rich materials at low concentrations) sorption for the alkanes studied, showing that enhanced sorption by CGs can occur to completely apolar sorbates that do not undergo any specific interaction. Sorption by CGs was generally stronger and more nonlinear for n-octane than for cyclooctane, which suggests a strong dependence of sorption on the 3-D structure of sorbate molecules. The n-octane-to-cyclooctane sorption coefficient ratios (Kn/Kc) for adsorption to CGs were ≥1, being distinctly different from those for absorption to the OM-rich materials (Kn/Kc < 1). The measured sorption isotherms and the CG compositions in the soils determined by quantitative petrography analysis suggest, however, that CGs occurring in soils may be far less effective sorbents than the reference CGs used in the sorption experiments at least for nonspecifically interacting sorbates, probably because of competitive sorption and/or pore blocking by natural OM. The presented approaches and results offer a basis for interpreting sorption data for other organic compounds, as nonspecific interactions and sorption modes are relevant for any compound.This publication has 44 references indexed in Scilit:
- Absorption or Adsorption? Insights from Molecular Probes n-Alkanes and Cycloalkanes into Modes of Sorption by Environmental Solid MatricesEnvironmental Science & Technology, 2008
- Effects of added PAHs and precipitated humic acid coatings on phenanthrene sorption to environmental Black carbonEnvironmental Pollution, 2006
- Near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy for mapping nano‐scale distribution of organic carbon forms in soil: Application to black carbon particlesGlobal Biogeochemical Cycles, 2005
- Soot-Carbon Influenced Distribution of PCDD/Fs in the Marine Environment of the Grenlandsfjords, NorwayEnvironmental Science & Technology, 2002
- Evaluation of a protocol for the quantification of black carbon in sedimentsGlobal Biogeochemical Cycles, 2001
- Assessing the Combined Roles of Natural Organic Matter and Black Carbon as Sorbents in SedimentsEnvironmental Science & Technology, 2001
- Preferential Sorption of Planar Contaminants in Sediments from Lake Ketelmeer, The NetherlandsEnvironmental Science & Technology, 2000
- A Revised Physical Concept of Natural Organic Matter as a Sorbent of Organic CompoundsPublished by American Chemical Society (ACS) ,1999
- Quantification of the Dilute Sedimentary Soot Phase: Implications for PAH Speciation and BioavailabilityEnvironmental Science & Technology, 1996
- Adsorption of CO2 and N2 on Soil Organic Matter: Nature of Porosity, Surface Area, and Diffusion MechanismsEnvironmental Science & Technology, 1996