Towards a Fundamental Understanding of Mineral Dissolution Kinetics: An Integrated Experimental and Theoretical Approach

William Marsh Rice University, Houston TX

Investigators

Abstract

Luttge EAR-0125667 Mineral dissolution data obtained by vertical scanning interferometry have formed the basis for a new surface model of the dissolution process. This model has been formalized in a fundamental rate law (Lasaga and Luttge, Science 291, 2400-2404, 2001), with potential relevance to a wide range of minerals and mineral surface problems. In this project, we set forth a plan integrating experimental and theoretical techniques designed to explore the kinetics and dissolution mechanism of (alumino)silicates. We also anticipate that this work will have far reaching implications for other minerals as well. The techniques were chosen to enhance one another and provide complementary information, and include vertical scanning interferometry (VSI), hydrothermal atomic force microscopy (HAFM), Monte Carlo (MC) and solvated ab initio and density functional theory (DFT) quantum mechanical calculations. This approach will also allow us to incorporate results with data taken from previous experiments involving mineral powders and single crystals in batch and flow reactors. By operating over a wide range of length scales, this work has the potential to provide a much-needed, critical link between the atomic-scale observation of surface phenomena and their macroscopic result. The project will produce the following: (1) the dissolution rates of plagioclase as a function of solid composition, temperature and pH; (2) a direct comparison of VSI and HAFM data; (3) the relationship of these data to macroscopic (bulk) rates, as well as ab initio and DFT calculations; (4) the relationship between reaction rate and mineral surface area in terms of total (BET) versus reactive surface area; (5) a detailed understanding of the kinetics and mechanisms of feldspar dissolution from solvated ab initio and DFT calculations, and their relationship to earlier gas-phase calculations.