Ion Binding to Hs

The interaction of metal cations with HS is a topic of great importance both from fundamental and environmental points of view and has attracted the attention of a high number of researchers (Clapp et al. 2001 Senesi and Loffredo 2005 Van Riemsdijk 

FIGURE 10.25 Different metal-humic complexation structures proposed by Senesi and Loffredo. (Reprinted from Senesi, N., and E. Loffredo, Chemical Processes in Soils, Soil Science Society of America, Madison, WI, 563-617, 2005, with kind permission.) 

Other studies of metal-HS interactions include NMR experiments (Kingery et al. 2001 Senesi and Loffredo 2005 and references therein), which have been used to correlate metal-binding structures with metal-binding characteristics, to elucidate binding mechanisms and to determine complexation equilibrium constants. IR experiments are less helpful, but they generally confirm that the carboxylate groups are often the main ligand for complexed metals (Davies et al. 2001). 

Gillam. 1990. Determination of molecular weights of humic substances by colligative property measurements. In Humic Substances II In Search of Structure, ed. M. H. B. Hayes, P. MacCarthy, R. L. Malcolm, and R. S. Swift, chap. 18. 1st ed. New York John Wiley Sons. 

Alvarez-Puebla, R. A., C. Valenzuela-Calahorro, and J. J. Garrido. 2006. Theoretical study on fulvic acid structure, conformation and aggregation a molecular modelling approach. Science of the Total Environment 358, no. 1-3 243-254. 

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