TY - JOUR
T1 - Mineral mesopore effects on nitrogenous organic matter adsorption
AU - Zimmerman, Andrew R.
AU - Goyne, Keith W.
AU - Chorover, Jon
AU - Komarneni, Sridhar
AU - Brantley, Susan L.
N1 - Funding Information:
We thank Bharat Newalkar of the Materials Research Laboratory, The Pennsylvania State University for production of the mesoporous phases, Mary Kay Amistadi, University of Arizona, for assistance with DRIFT analyses, and James Kubicki, Penn State Department of Geosciences, for assistance with molecular modeling. We also appreciate the helpful suggestions of Drs. Larry Mayer and Karen Wilson in their review of this manuscript. This research was partially supported by the Penn State Biogeochemical Research Initiative for Education (BRIE) sponsored by NSF (IGERT) grant DGE-9972759, Materials Research Science and Engineering Center (MRSEC) under grant DMR 0213623 (for S.K.). Acknowledgment is also made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research.
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2004/3
Y1 - 2004/3
N2 - The "mesopore protection hypothesis" [Chem. Geol. 114 (1994) 347; Geochim. Cosmochim. Acta 58 (1994) 1271] proposes that organic matter (OM) may be protected from enzymatic degradation by sequestration within mineral mesopores (2-50 nm diameter). This hypothesis is a leading, though controversial, theory in explaining both the preservation of some extremely labile OM compounds and observed correlations between OM content and mineral surface area in soils and sediments. To test this idea, we carried out batch experiments in aqueous suspensions to examine the adsorption/desorption of amino acid monomers and polymers onto fabricated mesoporous and nonporous alumina and silica. Each mineral pair was of similar surface chemistry and differed only in the presence or absence of intraparticle mesoporosity. All amino acid monomers and polymers smaller than about one-half the pore diameter exhibited significantly greater surface area-normalized adsorption to mesoporous alumina (8.2 nm mean pore diameter) and silica (3.4 nm mean pore diameter) compared to nonporous mineral analogues. Proteins larger than the mesopores exhibited greater adsorption to the nonporous phases indicating their exclusion from internal surfaces of mesoporous minerals. Greater desorption hysteresis for mesopore-sorbed OM indicates that desorption from pores was inhibited. The adsorption/desorption data, as well as Langmuir-Freundlich modeling and adsorption affinity distributions, suggest that capillary condensation, a 'pore-filling' mechanism, may explain the experimental observations. These results provide a potential mechanism for the selective sequestration and preservation of sedimentary OM as well as organic contaminants.
AB - The "mesopore protection hypothesis" [Chem. Geol. 114 (1994) 347; Geochim. Cosmochim. Acta 58 (1994) 1271] proposes that organic matter (OM) may be protected from enzymatic degradation by sequestration within mineral mesopores (2-50 nm diameter). This hypothesis is a leading, though controversial, theory in explaining both the preservation of some extremely labile OM compounds and observed correlations between OM content and mineral surface area in soils and sediments. To test this idea, we carried out batch experiments in aqueous suspensions to examine the adsorption/desorption of amino acid monomers and polymers onto fabricated mesoporous and nonporous alumina and silica. Each mineral pair was of similar surface chemistry and differed only in the presence or absence of intraparticle mesoporosity. All amino acid monomers and polymers smaller than about one-half the pore diameter exhibited significantly greater surface area-normalized adsorption to mesoporous alumina (8.2 nm mean pore diameter) and silica (3.4 nm mean pore diameter) compared to nonporous mineral analogues. Proteins larger than the mesopores exhibited greater adsorption to the nonporous phases indicating their exclusion from internal surfaces of mesoporous minerals. Greater desorption hysteresis for mesopore-sorbed OM indicates that desorption from pores was inhibited. The adsorption/desorption data, as well as Langmuir-Freundlich modeling and adsorption affinity distributions, suggest that capillary condensation, a 'pore-filling' mechanism, may explain the experimental observations. These results provide a potential mechanism for the selective sequestration and preservation of sedimentary OM as well as organic contaminants.
UR - http://www.scopus.com/inward/record.url?scp=1442291172&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=1442291172&partnerID=8YFLogxK
U2 - 10.1016/j.orggeochem.2003.10.009
DO - 10.1016/j.orggeochem.2003.10.009
M3 - Article
AN - SCOPUS:1442291172
SN - 0146-6380
VL - 35
SP - 355
EP - 375
JO - Organic Geochemistry
JF - Organic Geochemistry
IS - 3
ER -