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.

已广泛研究了磷灰石组矿物质（又称磷灰石）的晶体化学。它们可以容纳许多替代品，包括阳离子，多层和单次。因此，它们在许多地球化学和环境过程中起着重要作用，例如元素循环，营养素的可用性以及污染物的运输和命运。已经研究了磷灰岩的形成作为污染物补救的一种手段，尤其是通过通过吸附或共沉淀隔离的重金属，例如Pb，Zn，Cd，Cu和Ni，并且由于其对其高亲和力而被证明是有效的这些金属及其在地球表面条件下的低溶解度。因此，一旦在高度稳定的磷灰石结构中共沉淀，金属将不再容易分散或生物利用。但是，关于其他金属的隔离以及合并金属摄取的效果，仍然可以了解很多。一种具有巨大的环境意义的金属，具有通过磷灰石封存来修复的巨大潜力。但是，有限的研究集中在磷灰石中的AS和涉及该金属的实心溶液的性质。此外，由于自然过程（例如，矿床的风化）和人类活动（例如冶炼），PB和经常在环境中一起发生，甚至在同时对PB的共沉淀和apatite的同时工作，尽管事实也存在天然PB-AS磷灰石发生（MIMETITE，临床石）。该提案的重点是i）在CA-PB-PO4-ASO4-OH-CL系统中磷灰石组矿物质的化学和物理性质的合成和阐明，以评估其对同时应用的应用和PB修复以及II）测试该应用通过污染的沉积物中的磷灰石沉淀，用于隔离AS的CA-PO4溶液，用于隔离AS和AS和Pb。 PI将研究可能的固体溶液的程度，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。他将在以前的冶炼机构进行特定于现场的案例研究，并被称为当地沉积物的PB污染。还将研究工程污染的沉积物，以帮助阐明天然样品中发生的反应。这项研究的结果将大大提高我们对具有广泛地质意义的磷灰石群矿物的基本矿物学的了解，例如对矿石沉积岩石发生的研究以及AS和PB的一般地球化学循环。此外，结果可能会导致这些矿物质在环境修复中的有效应用。该提案的更广泛影响很多。这项工作具有广泛的环境含义（重金属的隔离和稳定）对社会至关重要。这也可能导致AS和PB的更具成本效益的补救技术。拟议的研究将包括本科生和研究生的参与和教育。公众的外展和教育，特别针对业余科学家和矿物爱好者社区，将通过博物馆和业余社会的会谈以及在期刊上的出版物来促进，以供多种非专业观众提供。