Chemical and Bacterial Reactions at the Surfaces of Environmentally-Important Metal Sulfide Minerals: Linking Atomic and Field Scales

点击翻译按钮获取中文摘要

This award in the Environmental Geochemistry and Biogeochemistry Program is jointly supported by the Divisions of Earth Sciences, Chemistry, and Chemical and Transport Systems Engineering. Jillian F. Banfield, Geology Department, and Robert J. Hamers, Chemistry Department, of the University of Wisconsin-Madison will investigate at an atomic level the nature of reactions occurring at interfaces between aqueous solutions and surfaces of metal sulfide minerals. They will use a multidisciplinary approach, incorporating biological, geological and chemical factors, and integrate results from a wide array of experimental methods, including STM, XPS, and confocal microscopy. Parallel field and laboratory studies will be conducted. Surfaces formed as a consequence of natural inorganically- and organically-mediated weathering will be compared to synthetically-weathered minerals to explore the applicability of laboratory-based studies to natural systems. The goals of the investigation are to determine the mechanisms and rates of dissolution, precipitation, and ion adsorption at metal sulfide surfaces; the effect of electrochemical oxidation and reduction on surface morphology; the role of impurities in modifying rates of electrochemical processes at surfaces; and the role of bacteria in controlling surface microstructural characteristics and dissolution rates. Chemical weathering of minerals is the process by which rocks are converted into the constituents of soils and sediments. Sulfide minerals such as galena, sphalerite, and chalcopyrite are mined as sources of important elements, such as lead, zinc, and copper, releasing the metals and acidifying water. The increase in acidity accelerates weathering of other minerals. Understanding the dissolution and crystallization behavior of metal sulfides, by chemical and bacterial routes, is important to developing predictive models of metal speciation and bioavailability. The goal of this study is to improve understanding of natural systems and to develop accurate laboratory tests and predictive models.