Coprecipitation of Pb and As in apatite and applications to environmental remediation

磷灰石中 Pb 和 As 的共沉淀及其在环境修复中的应用

• 批准号: 0952298
• 负责人: John Rakovan
• 金额: $ 24.57万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0952298&HistoricalAwards=false
• 关键词: Coprecipitation; Pb; apatite; applications; environmental

The crystal chemistries of apatite group minerals (a.k.a. apatites) have been widely investigated. They can accommodate numerous substitutions, including cations, polyanions, and monoanions. Thus, they play a significant role in many geochemical and environmental processes such as elemental cycling, availability of nutrients, and contaminant transport and fate. Formation of apatites has been studied as a means for contaminant remediation, especially for heavy metals such as Pb, Zn, Cd, Cu, and Ni, through sequestration by sorption or coprecipitation, and has been shown to be effective due to its high affinity for these metals and its low solubility under earth?s surface conditions. Thus, once co-precipitated in the highly stable apatite structure metals are no longer easily dispersible or bioavailable. However, there is still a great deal to be learned about the sequestration of other metals and the effect of combined metal uptake. One metal of enormous environmental significance and with great potential to be remediated through apatite sequestration is As. However, there are a limited number of studies focused on coprecipitation of As in apatite and the properties of solid solutions involving this metal. Furthermore, Pb and As often occur together in the environment due to natural processes (e.g. weathering of ore deposits) and human activities (e.g. smelting), and even less work on the simultaneous coprecipitation of Pb and As in apatite exists, despite the fact that natural Pb-As apatites occur (mimetite, clinomimetite). This proposal focuses on I) synthesis and elucidation of the chemical and physical properties of apatite group minerals in the Ca-Pb-PO4-AsO4-OH-Cl system for evaluation of their application to simultaneous As and Pb remediation and II) testing the application of Ca-PO4 solutions for sequestration of As, and combined As and Pb, through apatite precipitation in contaminated sediments. PI will investigate the extent of possible solid solutions, the kinetics of crystallization reactions, the possible pathways of formation, the structure and crystal chemistry, and the thermodynamics of synthesis reaction products. He will conduct a site-specific case study at a former smelting facility with known As and Pb contamination of local sediments. Engineered contaminated sediments will also be investigated to help elucidate reactions taking place in the natural samples. The results of this study will greatly increase our knowledge of the fundamental mineralogy of some of the least understood apatite group minerals with wide geologic implications, for example the study of ore deposit petrogenesis, and the general geochemical cycling of As and Pb. Furthermore, the results may lead to the effective application of these minerals to environmental remediation. The broader impacts of this proposal are many. The work has broad environmental implications (heavy-metal sequestration and stabilization) that are of immense importance to society. It may also lead to a more cost effective remediation technology for As and Pb. The proposed research will include the participation and education of undergraduate and graduate students. Outreach and education of the general public, specifically targeting the amateur scientist and mineral enthusiast communities, will be facilitated through talks at museums and amateur societies, and publications in journals for a diverse non-professional audience.

磷灰石族矿物（又称磷灰石）的晶体化学已被广泛研究。它们可以容纳许多取代，包括阳离子、聚阴离子和单阴离子。因此，它们在许多地球化学和环境过程中发挥着重要作用，如元素循环、营养物质的可用性、污染物的运输和命运。磷灰石的形成已被研究作为污染物修复的手段，特别是对重金属，如Pb、Zn、Cd、Cu和Ni，通过吸附或共沉淀的隔离，并已被证明是有效的，因为它对这些金属的高亲和力和在地下的低溶解度？S表面条件。因此，金属一旦在高度稳定的磷灰石结构中共沉淀，就不再容易分散或生物利用。然而，关于其他金属的固存和联合金属吸收的影响，仍有很多东西有待了解。砷是一种具有巨大环境意义的金属，通过磷灰石固存具有很大的修复潜力。然而，关于砷在磷灰石中的共沉淀和涉及该金属的固溶体性质的研究数量有限。此外，由于自然过程（如矿床风化）和人类活动（如冶炼），铅和砷经常在环境中同时存在，尽管存在天然的铅-砷磷灰石（镁铝云母、斜铝云母），但关于铅和砷在磷灰石中同时共沉淀的研究就更少了。本研究的重点是：I)合成并阐明Ca-Pb-PO4-AsO4-OH-Cl体系中磷灰石群矿物的化学和物理性质，以评价其在同时修复As和Pb中的应用；II)测试Ca-PO4溶液在污染沉积物中通过磷灰石沉淀来吸附As和As和Pb的应用。PI将研究可能的固溶体的范围，结晶反应的动力学，可能的形成途径，结构和晶体化学，以及合成反应产物的热力学。他将对当地沉积物中已知的砷和铅污染的前冶炼设施进行具体地点的案例研究。工程污染的沉积物也将被调查，以帮助阐明自然样品中发生的反应。本研究结果将大大增加我们对一些最不了解的磷灰石群矿物的基本矿物学知识，具有广泛的地质意义，例如矿床岩石成因的研究，以及As和Pb的一般地球化学循环。此外，研究结果可为这些矿物在环境修复中的有效应用提供参考。这项提议的广泛影响是多方面的。这项工作具有广泛的环境影响（重金属隔离和稳定），对社会具有巨大的重要性。这也可能导致一种更经济有效的砷和铅的修复技术。建议的研究将包括本科生和研究生的参与和教育。将通过在博物馆和业余协会举行的讲座以及为各种非专业读者在期刊上发表的出版物，促进特别以业余科学家和矿物爱好者社区为对象的一般公众的宣传和教育。