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

• 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

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.

HeaneyEAR-0125908阴离子粘土和锰氧化物作为纳米晶体涂层大量存在于地表环境中的土壤和沉积物颗粒上。 它们表现出卓越的交换溶解在水性液体中的离子的能力，并充当阴离子和阳离子的主要陷阱。 该提案的研究人员将应用一种新颖的晶体学方法来解决层状双氢氧化物和氧化锰材料中的阳离子交换机制。 粉末状样品在阳离子交换过程中将通过同步加速器X射线衍射进行监测。 这些实验将首次对低温矿物中过渡金属替代所发生的结构变形进行时间分辨分析。 此外，与高温红外光谱相结合，同步加速器 XRD 分析将在样品加热时进行，从而使热分解的结构表现与阳离子交换容量相关。这些研究将使研究人员能够捕获中间转变步骤，这些步骤是最终运行产品的更传统的静态分析忽略了这一点。由于与化学取代相关的结构扰动往往会稳定交换相，因此这些研究将表明哪些因素限制了选定阳离子的交换程度。 因此，这些实验将为设计具有放大交换特性的新型修复材料提出建议。