Inhaltszusammenfassung

A bulk humic acid (HA) extracted from a South Moravian lignite was further fractionated by sequential extraction in buffers at different pHs. All samples were analyzed by high performance size exclusion chromatography (HPSEC) and elemental analysis. Weight-averaged molecular weights (Mw) of fractions dissolved at pH 7, 8, and 9 were larger than for the parent bulk HA, thereby indicating that Mw of humic matter is related only to molecular size as affected by sample hydration rather than its m...A bulk humic acid (HA) extracted from a South Moravian lignite was further fractionated by sequential extraction in buffers at different pHs. All samples were analyzed by high performance size exclusion chromatography (HPSEC) and elemental analysis. Weight-averaged molecular weights (Mw) of fractions dissolved at pH 7, 8, and 9 were larger than for the parent bulk HA, thereby indicating that Mw of humic matter is related only to molecular size as affected by sample hydration rather than its molecular mass. Moreover, hydration radius was a function of the specific chemical properties of humic fractions. Addition of small amount of either mineral (HCl) or organic acids (formic, acetic, propionic) to humic solutions induced significant changes in conformational arrangements of the treated sample with respect to control. Also the conformational changes among humic fractions depended on their different molecular composition and suggested a weakly-bound supramolecular association of different humic molecules in solution. » weiterlesen» einklappen

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