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Time-Resolved Structural Analysis of Heavy Metal Cation Exchange Reactions in Anionic Clay and Manganese Oxide Nanoparticles

阴离子粘土和氧化锰纳米颗粒中重金属阳离子交换反应的时间分辨结构分析

基本信息

批准号：
0125908
负责人：
Peter Heaney
金额：
$ 22.6万
依托单位：
Pennsylvania State Univ University Park
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2002
资助国家：
美国
起止时间：
2002-01-01 至 2005-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125908&HistoricalAwards=false
关键词：
Time Resolved Structural Analysis Heavy

项目摘要

HeaneyEAR-0125908Anionic clays and manganese oxides occur abundantly as nanocrystalline coatings on soil and sediment particles in surficial environments. They exhibit a remarkable facility for exchanging ions dissolved in aqueous fluids and act as major traps for anions and cations. The investigators of this proposal will apply a novel crystallographic approach to resolve mechanisms of cation exchange in layered double hydroxide and Mn oxide materials. Powdered samples will be monitored by synchrotron X-ray diffraction during the process of cation exchange. These experiments will yield the first time-resolved analyses of the structural distortions that occur to accommodate substitutions by transition metals in low-temperature minerals. Additionally, in concert with high-temperature infrared spectroscopy, synchrotron XRD analyses will be performed as samples are heated, allowing the structural manifestations of thermal decomposition to be correlated with cation exchange capacity.These studies will allow the investigators to capture intermediate transition steps that are overlooked by a more conventional static analysis of final run products. As the structural perturbations that are associated with chemical substitutions tend to stabilize the exchanged phases, these studies will indicate which factors limit the degree of exchange for selected cations. Consequently, these experiments will suggest approaches to the design of new remediation materials with amplified exchange characteristics.

阴离子粘土和锰氧化物在地表环境中以纳米晶体的形式大量存在于土壤和沉积物颗粒上。它们在交换溶解在水溶液中的离子方面表现出非凡的能力，并作为阴离子和阳离子的主要捕集器。本提案的研究人员将应用一种新的晶体学方法来解决层状双氢氧化物和氧化锰材料中阳离子交换的机制。在阳离子交换过程中，粉末样品将被同步x射线衍射监测。这些实验将首次对低温矿物中过渡金属取代所产生的结构扭曲进行时间分辨分析。此外，与高温红外光谱相配合，同步加速器XRD分析将在样品加热时进行，使热分解的结构表现与阳离子交换能力相关联。这些研究将使研究人员能够捕捉到被更传统的最终运行产品静态分析所忽略的中间过渡步骤。由于与化学取代相关的结构扰动倾向于稳定交换相，这些研究将表明哪些因素限制了所选阳离子的交换程度。因此，这些实验将为设计具有放大交换特性的新修复材料提供方法。