Mechanisms of classical crystal growth theory explain quartz and silicate dissolution behavior
Year: 2005
Type: article
Abstract: The central control of mineral weathering rates on biogeochemical systems has motivated studies of dissolution for more than 50 years. A complete physical picture that explains widely observed variations in dissolution behavior is lacking, and some data show apparent serious inconsistencies that cannot be explained by the largely empirical kinetic "laws." Here, we show that mineral dissolution can, in fact, be understood through the same mechanistic theory of nucleation developed for mineral growth. In principle, this theory should describe dissolution but has never been tested. By generalizing nucleation rate equations to include dissolution, we arrive at a model that predicts how quartz dissolution processes change with undersaturation from step retreat, to defect-driven and homogeneous etch pit formation. This finding reveals that the "salt effect," recognized almost 100 years ago, arises from a crossover in dominant nucleation mechanism to greatly increase step density. The theory also explains the dissolution kinetics of major weathering aluminosilicates, kaolinite and K-feldspar. In doing so, it provides a sensible origin of discrepancies reported for the dependence of kaolinite dissolution and growth rates on saturation state by invoking a temperature-activated transition in the nucleation process. Although dissolution by nucleation processes was previously unknown for oxides or silicates, our mechanism-based findings are consistent with recent observations of dissolution (i.e., demineralization) in biological minerals. Nucleation theory may be the missing link to unifying mineral growth and dissolution into a mechanistic and quantitative framework across the continuum of driving force.
Institutions: Lawrence Livermore National Laboratory, Virginia Tech
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Awards: G1101028137, G1702950523, G3177268909, Kinetic and Thermodynamic Controls on Mg and Sr Contents during Calcite Growth: Establishing a Baseline for Biological Mineralization, INVESTIGATION OF THE PHYSICAL BASIS FOR BIOMINERALIZATION, G6445123630, The Kinetics of Silica Dissolution: An Integrated Experimental Investigation of Quartz and Amorphous Silica Reactivity in the Mixed Solute Compositions of Natural Waters
OpenAlex ID: W2067608390