Elham A. Ghabbour, Andreas C. Scheinost, Geoffrey Davies ( 2007). XAFS studies of cobalt(II) binding by solid peat and soil-derived humic acids and plant-derived humic acid-like substancesChemosphere 67 (2007) 285–2910000000000
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 contribution 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(II); XANES; EXAFS.)
