Structural Dynamics of Manganese Oxides during Manganese Redox Cycling

Mengqiang Zhu and Q. Wang

University of Wyominig, USA

mzhu6@uwyo.edu

Manganese (Mn) oxides are metal scavengers and strong oxidizers. These minerals influence fate and transport of trace metals and degrade organic carbon and pollutants. Birnessite is the most common and reactive one among about 30 Mn oxide phases in the environment. It is a layered structure and layers consist of predominantly Mn^IVO₆ with minor Mn^IIIO₆ and structural defects (Mn vacancies). The vacancies and edges of the layers are the adsorption sites for transition and heavy metals. The Mn(III) content in the layers affects oxidizing activity of birnessite. Thus, the structure and Mn oxidation state composition of birnessite strongly affects birnessite reactivity, and is subject to dynamic changes during Mn(II) oxidative precipitation or partial reductive dissolution that commonly occurs in natural waters, soils and sediments. In this presentation, I will give an owv22ww1rview recent progress