Elham A. Ghabbour a,*, Andreas C. Scheinost b,1, Geoffrey Davies( 2007). XAFS studies of cobalt(II) binding by solid peat and soil-derived
humic acids and plant-derived humic acid-like substances
Chemosphere 67 (2007) 285–291
Abstract: This work has examined cobalt(II) binding by a variety of solid humic acids (HAs) isolated from peat, plant and soil sources at temperatures down to 60 K. The results confirm that X-ray absorption near-edge spectroscopy (XANES) measurements cannot distinguish
between aquo and carboxylato ligands in the inner coordination sphere of Co(II). However, between 1 and 2 inner-sphere carboxylate ligands can be detected in all the peat, plant and soil-derived HA samples by extended X-ray absorption fine structure (EXAFS) measurements, indicating inner-sphere coordination of HA-bound Co(II). The precision of C(carboxylate) detection is limited by the extent and quality of the data and the ontribution from inner-sphere O to the Fourier transformed peaks used to detect carbon. Putative chelate ring formation is consistent with a relatively negative entropy change in step A, the stronger Co(II) binding step by HA functional groups, and could relate to ‘non-exchangeable’ metal binding by HSs. _ 2006 Elsevier Ltd. All rights reserved.
Keywords: (Solid humic acids; Metal binding Cobalt (11): XANES ; EXAFS)
