| Abstract
| - Humic acid was fractionated into eight different molecularsize components using ultrafiltration. Solid-state CPMAS13C NMR demonstrated that fractions larger than 100 000Daltons were primarily aliphatic in character, while fractionssmaller than 30 000 Daltons were predominantly aromaticin character. Solid-state 19F NMR examination of thesorptive uptake of hexafluorobenzene (HFB) by HA andeach of the fractions gave spectroscopic evidence for theexistence of at least three sorption sites in the smallermolecular size fractions, while two predominant sorptionsites could be established in the larger molecular size fractions.Sorbed HFB displayed higher mobility in the smaller,more aromatic fractions while HFB in the larger, morealiphatic fractions displayed lower mobility. The relativemobilities of HFB in each sorption domain suggest that therigid domain may be composed of aliphatic carbonrather than aromatic carbon moieties. In larger sizefractions, this domain may be the result of rigid, glassyregions composed of aliphatic molecules or side chains.
|
