The Geochemical Processes Controlling Vacancy and Mn(III) Concentrations in Birnessite Structure

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项目编号	1529937
	The Geochemical Processes Controlling Vacancy and Mn(III) Concentrations in Birnessite Structure
	Mengqiang Zhu
主持机构	University of Wyoming
项目开始年	2015
	2015-08-01
项目结束日期	2018-07-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	273721(USD)
国家	美国
语种	英语
英文摘要	Soils, sediments and natural waters may become contaminated by toxic metals from anthropogenic sources, such as mining and industrial wastes, vehicle emissions, lead-acid batteries, paints, etc., threatening public health and ecosystem. Birnessite, the dominant type of wide-spread manganese (Mn) oxide mineral in the environment, is a metal scavenger and can hold several percentages of toxic metals of its body weight, hence acting as an effective detoxifying agent. The ability of birnessite to scavenge metals, as well as other properties, highly rely on its structure and chemical composition that are affected by unknown geochemical processes. The main objective of this funded research is to identify the geochemical processes and discover how they take place step by step, how rapidly they happen, as well as whether and how they are affected by common environmental conditions. Results will benefit not only the fundamental research on critical geochemical and mineralogical processes, but also industrial applications of Mn oxides, such as fabricating high-performance birnessite as sorbents and oxidizers for pollution control and as semiconductor for harvesting solar energy in the photovoltaic industry. The proposed study will train students at different levels. The PI and a high school teacher will work together to develop a curriculum in earth science for high school students. The extraordinary properties of birnessite are determined by Mn vacancy and Mn(III) concentrations in its structure. There is, therefore, a critical need to identify those geochemical processes that control birnessite vacancy and Mn(III) concentrations. In the absence of such knowledge, assessing contaminant fate and transport particularly in Mn-rich environments will remain challenging. We hypothesize that the reactions of Mn(II) with birnessite control the vacancy and Mn(III) concentrations, and that the reactions are subject to influences of solution chemistry and birnessite formation rates. Both microbially mediated and chemically-synthetic reaction systems will be employed. X-ray absorption spectroscopy, diffraction and atomic pair distribution function analysis, and high resolution transmission electron microscopy will be used to characterize birnessite samples in addition to wet chemical analyses. Results are expected to advance the current understanding while generating new knowledge of Mn oxide mineralogy and geochemistry and their impact on biogeochemical cycles.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/68362
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Mengqiang Zhu.The Geochemical Processes Controlling Vacancy and Mn(III) Concentrations in Birnessite Structure.2015.