Abstract

Quantification of the dissolution and precipitation kinetics of minerals is essential in understanding environmental and geological processes and in the application of mineral reactions in industrial uses. Barite (BaSO4) occurs in crustal rocks associated with hydrothermal alteration and in marine sediments. The current research of Luttge's workgroup at Rice is focused on the quantification of the weathering and precipitation rates of important calcium/magnesium (alumino)-silicates, carbonates, and barium sulfate.

The application of VSI allows us to quantify mineral dissolution/precipitation rates experimentally and independently from the so-called surface problem (Luttge et al., 1999, Luttge & Lasaga, 2000a). The near-atomic-scale technique quantifies surface topographies precisely.

Hilary Barelas has focused her research on the dissolution kinetics of barite. A feasibility study completed over the summer lead to preliminary results that can be used as a basis for a more comprehensive study of its fluid solid interactions. We will conduct experiments in flow-through cells. The BaSO4 samples will be exposed to solutions with EDTA-(ethylenediamenetetraacetic acid) concentrations of 0.01M &endash; 0.1M. EDTA is a chelating agent that forms Ba-EDTA complexes and increases the rate of etch pit formation significantly. The temperature dependence of the reaction rates will be studied over a range from 25 &endash; 80 C.

The outcome of this study will provide a direct comparison of results produced by VSI and AFM as complementary analytical techniques. We expect that the study will help us to understand how AFM results obtained on a nanometer to angstrom scale are linked with the bulk rates. This research will lead to a deeper understanding of the dissolution mechanism of barite, and the quantification of dissolution kinetics for a model substance that has importance in a number of natural and industrial processes.