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

控制水钠锰矿结构中空位和 Mn(III) 浓度的地球化学过程

• 批准号: 1529937
• 负责人: Mengqiang Zhu
• 金额: $ 27.37万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1529937&HistoricalAwards=false
• 关键词: Geochemical; Processes; Controlling; Vacancy; Mn

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.

土壤，沉积物和天然水可能会受到来自人为来源的有毒金属的污染，例如采矿和工业废物，车辆排放，铅酸电池，油漆等，威胁到公共卫生和生态系统。 Birnessite是环境中主要的大型锰（Mn）氧化物矿物质的主要类型，是一种金属清道夫，可以容纳其体重的有毒金属的几个百分比，因此充当有效的排毒剂。 Birness石材清除金属以及其他特性的能力高度依赖于其结构和化学过程影响的化学过程。这项资助的研究的主要目的是确定地球化学过程，并发现它们是如何逐步进行的，它们发生的速度以及它们是否以及如何受到共同环境条件的影响。结果不仅将受益于关键的地球化学和矿物质学过程的基本研究，还将受益于MN氧化物的工业应用，例如将高性能的birnessite和用于污染控制的高性能Birnessite和用于在光伏工业中收获Solar能量的半导体。拟议的研究将培训不同级别的学生。 PI和一名高中老师将共同为高中生开发地球科学课程。因此，迫切需要确定控制Birnessite空缺和Mn（III）浓度的地球化学过程。在缺乏此类知识的情况下，尤其是在MN丰富的环境中评估污染物的命运和运输将仍然具有挑战性。我们假设Mn（II）与Birnessite的反应控制空位和Mn（III）浓度，并且这些反应受到溶液化学和Birnessite形成速率的影响。将采用微生物介导的和化学合成反应系统。 X射线吸收光谱，衍射和原子配对分布函数分析以及高分辨率透射电子显微镜除湿化学分析外还将用于表征Birnessite样品。预计结果将提高当前的理解，同时产生对MN氧化物矿物学和地球化学的新知识及其对生物地球化学周期的影响。