Conformational changes of dissolved humic and fulvic superstructures with progressive iron complexation

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Title: Conformational changes of dissolved humic and fulvic superstructures with progressive iron complexation
Authors: Nuzzo, Assunta | Sanchez Sanchez, Antonio | Fontaine, Barbara | Piccolo, Alessandro
Research Group/s: Química Agrícola
Center, Department or Service: Universidad de Alicante. Departamento de Agroquímica y Bioquímica
Keywords: Metal-complexation | Dissolved humic substances | Supramolecular associations | Heavy metals | Molecular sizes | Size-exclusion chromatography
Knowledge Area: Edafología y Química Agrícola
Issue Date: Jun-2013
Publisher: Elsevier
Citation: Journal of Geochemical Exploration. 2013, 129: 1-5. doi:10.1016/j.gexplo.2013.01.010
Abstract: Conformational changes of a humic acid (HA) and a fulvic acid (FA) induced by iron complexation were followed by high-performance size exclusion chromatography (HPSEC) with both UV–vis and refractive index (RI) detectors. Molecular size distribution was reduced for HA and increased for FA with progressive iron complexation. Since interactions of Fe with humic components are electrostatic, it is likely that the triple-charged Fe ions formed stronger complexes with the more acidic hydrophilic and hydrated FA than with the less acidic and more hydrophobic HA. The large content of ionized carboxyl groups in FA, thus favored the formation of intra- or intermolecular bridges between the negatively charged fulvic acid molecules, and led to more compact and larger size network than for HA. Conversely, iron complexation with HA disrupted the humic conformational arrangements stabilized by only weak hydrophobic bonds into smaller-size aggregates of greater conformational stability due to formation of strong metal complexes. These results confirmed that humic molecules in solution were organized in supramolecular associations of relatively small molecules loosely bound together by dispersive interactions and hydrogen bonds, and they specifically responded to chemical changes brought about by metal additions. The present study revealed the molecular changes occurring in superstructures of natural organic matter when in metal complexes and contributed to understand and predict the environmental behavior in waters and soil of metal complexes with natural organic matter.
ISSN: 0375-6742 (Print) | 1879-1689 (Online)
DOI: 10.1016/j.gexplo.2013.01.010
Language: eng
Type: info:eu-repo/semantics/article
Peer Review: si
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Appears in Collections:INV - Química Agrícola - Artículos de Revistas

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