Original scientific paper

Release of Silicon and Aluminum from Montmorillonite Surfaces in Aqueous Systems

Ivan Sondi ; Center for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia
Vlasta Tomašić ; Division of Physical Chemistry, Ruđer Bošković Institute, Zagreb, Croatia
Nada Filipović-Vinceković ; Division of Physical Chemistry, Ruđer Bošković Institute, Zagreb, Croatia

Abstract

The release of silicon and aluminum from purified Na-montmorillonite surfaces in aqueous
systems was investigated in dependence of pH at 25 °C. This study has shown that the dissolution
of montmorillonite solid involves several parallel and sequential physico-chemical processes.
The initial fast exchange of surface cations by hydrogen ions is followed by the release
of aluminum and silicon. The dissolution rate of Si is higher than that of Al and influenced by
the relative ratios of basal siloxane and edge surfaces. It is quantitatively described by the dissolution
rate constants depending on pH. These results are in agreement with the heterogeneity
of montmorillonite surfaces and the dominant presence of the siloxane basal surface. The shift
of pH to more basic values by the ion exchange processes, and the hydrolysis of dissolved species,
induces the formation of secondary amorphous solids, which may serve as precursors for
the formation of amorphous aluminosilicates.

Keywords

aluminum; clay minerals; geochemistry; montmorillonite; pH; silicon; surfaces

Hrčak ID:

31188

URI

https://hrcak.srce.hr/31188

Publication date:

31.12.2008.

Visits: 1.768 *