Udo Becker

Almost all environmentally relevant reactions in nature or in technical applications that involve minerals are surface or interface reactions. Be it crystal growth, adsorption reactions, mineral dissolution, redox reactions, or even the growth of crystallites from the melt, the actual reactions take always place at mineral surfaces. This is one reason why I got started to analyze the atomic and electronic structure, the chemistry and reactivity of mineral surfaces. In addition, over the last 20 years, a number of surface-sensitive techniques has been developed to image and analyze surfaces with up to atomic resolution. Thus, it is possible now to resolve reaction mechanisms step by step without relying too much on hypotheses. Furthermore, we can calculate some of these reactions at a quantum mechanical level. This way, it has become much more satisfying to understand environmental reactions, predicting these, or optimize certain reaction types for technological applications or remediation purposes. Among the projects that we are working on right now are:

• the oxidation of sulfide surfaces that plays a role in acid mine drainage and the release of heavy-metal ions
• the adsorption and reduction of noble metal atoms on sulfide surfaces and the role that dopant ions (e.g., arsenic) and surface diffusion play to form nanoparticulates of these metals
• the role of the atomic and electronic structure of oxide surfaces (e.g., hematite) in redox reactions such as the adsorption of manganese which may play a role in the purification of drinking water
• the structure and stability of TiO2 nanoparticules
• the adsorption of pesticides on clay particulates
• the role of jarosites as a secondary mineral for the storage of heavy-metal ions in open mine pits
• biomineralization processes as they occur in the growth of bones, teeth, and organisms such as coccolithopores
• the calculation of the thermodynamics and ordering processes in solid solutions such as
• sulfates (for example barite-celestite or barite hashemite) and carbonates
• oscillatory zoning in garnets
• magnetic ordering in iron and iron-titanium oxides.

This list shows the plethora of applications using the surface-sensitive tools (e.g., STM, AFM, XPS ...) in combination with computer simulations.

Field(s) of Study

• Mineral surface chemistry and nanoscience
• Computational mineralogy