CHEMICAL MECHANISMS IN THE DISSOLUTION KINETICS OF MINERALS - THE ASPECT OF ACTIVE-SITES

Mechanistic rate laws for the description of mineral dissolution include (often implicitly) the mole fraction of active surface sites. The amount of active sites is first estimated by dissolution experiments in presence of polyvalent cations which inhibit proton-promoted dissolution. The dissolution reactivities of surface Al centers of several minerals and of comparable dissolved polynuclear Al complexes are determined. This comparison offers a second possibility for the indirect estimation of the concentration range of active surface sites. The coordination geometries of surface Al centers, which are given by the crystal lattice network, are considered to determine the reactivity in dissolution processes. © 1990 Birkhäuser Verlag.