Natural organic matter as a dual-mode (partition-adsorption) sorbent of hydrophobic organic compounds

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:203609

Pignatello, J J; Xing, B ^[1]

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1. Univ. of Connecticut, Storrs, CT (United States)

Evidence is presented that soil natural organic matter (NOM) is a dual-mode sorbent, in analogy to glassy polymers. Dual mode sorption involves sorbate partitioning (dissolution) in the bulk matrix, in parallel with Langmuir-type adsorption at ``sites`` within the matrix. The sorbents of study included soils (2--4% NOM), peat samples (93--98% NOM), soil humic acid particles (99% NOM), and natural and synthetic polymers. The sorbates were halogenated aliphatic and aromatic compounds, chlorinated phenols, and triazine and chloroacetanilide herbicides. Experiments were carried out on aqueous suspensions. Evidence of dual mode behavior exhibited by NOM sorbents includes: (1) isotherm nonlinearity over a wide concentration range; (2) increasing linearity with temperature between 5 and 90 C; and (3) bisolute competitive effects between like compounds. Removing the minor mineral component from peat by HCl/HF treatment had no effect. Glassy polymers, like polyvinyl chloride, showed the same behaviors, while rubbery polymers, like polyethylene and hydrated cellulose, gave linear sorption and no competitive effects. Isotherm nonlinearity in a peat and a soil was greater (Freundlich exponent smaller) for a more slowly equilibrating fraction of sorbate, indicating that many of the Langmuir sites are not in direct contact with bulk solution but exist within the NOM macromolecular structure.

• OSTI ID: 203609
• Report Number(s): CONF-9511137--; ISBN 1-880611-03-1
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADSORPTION ISOTHERMS
AROMATICS
HUMIC ACIDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC MATTER
PEAT
SOIL CHEMISTRY
SORPTIVE PROPERTIES