Further Investigations on Fulvic Acid-Cu2+-Montmorillonite Interactions*

H. Kodama and M. Schnitzer
Soil Research Institute, Agriculture Canada, Ottawa, Ontario, Canada
* Contribution No. 467. Dedicated to the memory of Dr. W. F. Bradley.

Abstract: The major mechanism by which fulvic acid removed Cu2+ from Cu2+-montmorillonite was complexation, most likely chelation. This was confirmed by the use of a specific cupric ion electrode which showed that whereas the total Cu2+ concentration in the supernatant solutions increased with rise in pH, about 7 per cent of the total Cu2+ solubilized by fulvic acid occurred in the ‘free’ or ‘uncomplexed’ form at pH 2·5, only 0·6 per cent was similarly distributed at pH 4·5 and 0·0009 per cent at pH 6·5. External surface area measurements by a dynamic BET method showed the following surface areas: 2·5 m2 g−1 for the fulvic acid, 8·0 m2 g−1 for the Cu2+-montmorillonite but 16·1 m2 g−1 for the FA-Cu2+-montmorillonite complex. Electron micrographs of the FA-clay complex confirmed that fulvic acid was adsorbed in interlamellar spaces and on external surfaces of the Cu2+-montmorillonite.

Clays and Clay Minerals; February 1974 v. 22; no. 1; p. 107-110; DOI: 10.1346/CCMN.1974.0220115
© 1974, The Clay Minerals Society
Clay Minerals Society (www.clays.org)