The Surface Structure and Reactivity of Mn-Oxides and Their Impact on As Transformation in the Environment: A Multi-Scale Approach

锰氧化物的表面结构和反应性及其对环境中砷转化的影响：多尺度方法

• 批准号: 0417830
• 负责人: Donald Sparks
• 金额: $ 5万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0417830&HistoricalAwards=false
• 关键词: Surface; Structure; Reactivity; Mn; Oxides

ABSTRACTResearch is proposed that investigates the chemical and physical properties of the environmentally important oxides of manganese that play an important role in soil redox chemistry. It is well accepted in the soil science community that Mn-oxides exist as coatings and as discrete particles in soils, in part with nano-dimensions. Their rich redox chemistry affects the mobility and bioavailability of environmental toxins including many metals and metaloids. Research will be focused primarily on the surface structure and chemical reactivity of both the bulk birnessite (MnO2) phase of Mn-oxide and also a nano-MnOOH phase under a variety of environmentally relevant conditions. In particular, a selection of advanced surface spectroscopic techniques, including attenuated total reflection infrared and synchrotron-based photoelectron spectroscopy, will be used to develop a picture of the reacting Mn-oxide surface, such as determining the relative surface concentration of different oxidation states, over a range of established soil pH values. These Mn-oxide surfaces will then be probed via reaction with aqueous arsenic oxyanions to establish the control that differences in Mn-oxide structure and reactivity exert on the transformation of As3+ to As5+, one of the central As detoxification pathways in the environment.While birnessite, found in a wide range of soil environments, is a primary target of the proposed research, nanosized Mn-oxides also exist in the environment and are of interest in the current research. Toward developing an understanding of the role that nano-Mn-oxides might play in soil chemistry, research will investigate the reactivity and electronic structure of MnOOH nanoparticles as a function of size. Nano-MnOOH with homogeneous size distributions from 20 to 80 will be prepared and studied in solutions with varying pH and the As oxidation reaction will again be used as a probe for reactivity. This particular phase of the research project will not only develop an understanding of the size-reactivity relationship for Mn-oxide, but will in general contribute to the broader effort in geo- and soil chemical communities to evaluate the importance of nano-chemistry in the environment.Broader Impacts Resulting from the Proposed Activity The proposed study has a significant educational component. First, NSF funds will be used to support and train a postdoctoral associate at the University of Delaware and a graduate student at Temple University. Second, by virtue of this study being strongly interdisciplinary in nature, the scientific breadth of researchers in this project will benefit from the constant exchange of ideas and concepts between groups having expertise in diverse areas of soil and surface chemistry. This collaboration fits into the broader need for interdisciplinary studies to understand complex environmental chemistry. The studies will advance not only the frontiers of environmental geochemistry, but also provide important predictive information on contaminant transformations that will benefit society at large.

提出了Abstractresearch，研究了在土壤氧化还原化学中起重要作用的锰氧化物的化学和物理特性。在土壤科学界被广泛接受，即Mn-氧化物作为涂料和土壤中的离散颗粒的存在，部分部分是纳米二维。它们丰富的氧化还原化学会影响环境毒素的迁移率和生物利用度，包括许多金属和金属素。研究将主要集中在MN-氧化物的大量Birnessite（MNO2）相的表面结构和化学反应性以及在各种与环境相关的条件下的纳米MNOOH相。特别是，将使用晚期表面光谱技术的选择，包括衰减的总反射红外和基于同步加速器的光电子光谱法，用于在建立的土壤pH值的范围内开发反应Mn-氧化物表面的图片，例如确定不同氧化态的相对表面浓度。然后将通过与砷氧水性反应进行探测这些MN氧化物表面，以确定控制Mn-氧化物结构和反应性在AS3+向As5+转化上施加的差异，这是环境中的环境中的广泛范围 - 在环境中存在的范围内，是NIS的范围内，是NIS的范围，是NIS的范围，NIS的范围是NIS的范围，这是NIS的范围，NIS的范围内，是诺斯的范围，nis的范围内，是诺斯的范围。在当前的研究中。为了了解纳米-MN氧化物在土壤化学中可能起的作用的理解，研究将研究MNOOH纳米颗粒的反应性和电子结构，这是大小的函数。将在具有不同pH的溶液中准备并研究具有均匀尺寸分布的纳米 - mnooh，AS氧化反应将再次用作反应性的探针。研究项目的这个特定阶段不仅将对MN氧化物的尺寸反应关系有所了解，而且总体上将为地理和土壤化学界的更广泛的努力做出更广泛的努力，以评估纳米化学在环境中的重要性。拟议的活动造成的影响拟议的活动拟议的研究具有重要的教育成分。首先，NSF资金将用于支持和培训特拉华大学的博士后助理和Temple University的研究生。其次，由于本研究本质上是强烈的跨学科，该项目中研究人员的科学广度将受益于在土壤和表面化学领域具有专业知识的群体之间不断交流的思想和概念。这种合作符合对跨学科研究的广泛需求，以了解复杂的环境化学。这些研究不仅会推进环境地球化学的前沿，而且还提供了有关污染物转变的重要预测信息，这些信息将使整个社会受益。