Mineral Formation by Cluster Self-Assembly: Schwertmannite as a Partially Crystallized Nanomineral

通过簇自组装形成矿物：施韦特曼石作为部分结晶的纳米矿物

• 批准号: 1451996
• 负责人: Frederick Marc Michel
• 金额: $ 27.17万
• 依托单位: Virginia Polytechnic Institute and State University
• 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 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1451996&HistoricalAwards=false
• 关键词: Mineral; Formation; Cluster; Self; Assembly

Our ability to understand crystallization processes is a key to interpreting the past, present, and future evolution of our planet. Yet our scientific understanding of crystallization - the transformation of dissolved species into solids - is incomplete. Recent research is revealing a diversity of new "nonclassical" pathways and mechanisms by which crystals, particularly nanocrystals, form and grow through attachment of intermediate and precursor particles. However, immense gaps remain in our understanding of these processes. This project will investigate the assembly of clusters to form the ferric oxyhydroxide mineral schwertmannite in order to understand how it forms via nonclassical route. Schwertmannite is pervasive and of broad interest in acidic environments because it exhibits high surface area and an affinity for a variety of potential pollutants. Additionally, because schwertmannite and other poorly crystalline minerals are so abundant and important at and near Earth's surface, understanding their formation is the key to interpreting the geologic record and the interaction between organisms and geologic media. The overarching objective of this research is to document the nature of schwertmannite precursor clusters as a function of solution composition and growth conditions, and then to use that information to construct a general model that shows how dissolved iron and sulfate react in solution forming schwertmannite. Preliminary in situ synchrotron scattering data show the formation of clusters (~1.5 nm) having schwertmannite-like structural characteristics. These clusters are stable in solution as long as the solution remains turbulent (for up to 40 hours), but quickly aggregate and transform to schwertmannite under static fluid conditions. Based on preliminary data, the investigators hypothesize that schwertmannite forms via a nonclassical pathway involving self-assembly of schwertmannite-like precursor particles. They also hypothesize that the composition and properties of schwertmannite should reflect the structure and composition of the particles that aggregate. The investigators will apply a suite of in situ laboratory and synchrotron mineral characterization techniques to study the real-time formation of synthetic schwertmannite precursor clusters in solution and their aggregation into schwertmannite solids. The investigators will also collect and characterize water samples and sediments from an active AMD system and evaluate schwertmannite formation in nature. The structural, chemical, and physical data from these experiments will be used to develop a general crystallization model for schwertmannite that is consistent with thermodynamic and chemical principles, and with observations in the literature and this project of schwertmannite formation in nature.

我们理解结晶过程的能力是解释地球过去、现在和未来演变的关键。然而，我们对结晶的科学理解-溶解物质转化为固体-是不完整的。最近的研究揭示了新的“非经典”途径和机制的多样性，晶体，特别是纳米晶体，形成和生长通过连接的中间体和前体颗粒。然而，我们对这些进程的理解仍然存在巨大差距。这个项目将研究团簇的组装，以形成羟基氧化铁矿物施威特曼石，以了解它是如何通过非经典途径形成的。施威特曼石在酸性环境中是普遍存在的并且具有广泛的兴趣，因为它表现出高的表面积和对各种潜在污染物的亲和力。此外，由于施威特曼石和其他结晶不良的矿物在地球表面和附近非常丰富和重要，因此了解它们的形成是解释地质记录以及生物与地质介质之间相互作用的关键。本研究的首要目标是记录的性质的施氏前驱体集群作为一个功能的溶液组成和生长条件，然后使用该信息来构建一个通用的模型，显示溶解的铁和硫酸盐反应在溶液中形成施氏。初步的原位同步辐射散射数据显示形成的集群（~1.5 nm）具有Schwertmannite样的结构特征。这些团簇在溶液中是稳定的，只要溶液保持湍流（长达40小时），但在静态流体条件下迅速聚集并转化为施韦特曼石。基于初步数据，研究人员假设，Schwertmannite通过非经典途径形成，涉及Schwertmannite样前体颗粒的自组装。他们还假设，施威特曼石的组成和性质应该反映聚集颗粒的结构和组成。研究人员将应用一套原位实验室和同步加速器矿物表征技术来研究溶液中合成施威特曼石前体簇的实时形成及其聚集成施威特曼石固体。研究人员还将收集和表征活跃的AMD系统的水样和沉积物，并评估自然界中的施威特曼石形成。从这些实验的结构，化学和物理数据将被用来开发一个通用的结晶模型，是符合热力学和化学原理，并与文献中的观察和自然界中的施威特曼石形成的这个项目。