Monoclinic Hydroxyapatite

Elliott, J. C.; Mackie, P. E.; Young, R. A.

doi:10.1126/science.180.4090.1055

Cited by 356 publications

(239 citation statements)

References 11 publications

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“…The results per hexagonal cell are plotted in ascending energy order. The mixed configuration (↓↓)(↑↑) monoclinic structure suggested by Elliott [34], yields the lowest energy (structure 1) and is used as the reference energy. The lattice constants are a=9.53Å, b=2a and c=6.91Å.…”

Section: Resultsmentioning

confidence: 99%

“…al. [34] who, following the work by Young [10], prepared a sample consisting of ~30% monoclinic HA and 70% hexagonal phases. They concluded that HA grown in a sufficiently clean experimental environment and having little impurities or vacancies can assume monoclinic symmetry under ambient conditions.…”

Section: B Activation Energy For the Hexagonal To Monoclinic Transitionmentioning

confidence: 99%

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First-principles study of the biomineral hydroxyapatite

2011

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The biomineral hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 is the main mineral constituent of mammal bone. Hydroxyapatite crystallizes in the hexagonal and monoclinic phases, the main difference between them being the orientation of the hydroxyl groups. Using density functional theory we study the energetics of the hexagonal and monoclinic phases along with the several hypothetical crystal structures of hydroxyapatite. The monoclinic phase has the lowest energy, with the hexagonal phase being only 22meV/cell higher in energy. We identify a structural transition path from the hexagonal to monoclinic phase with the activation energy of 0.66 eV per hexagonal cell. At room temperature the transition occurs on a millisecond time scale. The electronic structures of the monoclinic and hexagonal phases are compared. For the hexagonal phase we calculate the phonon frequencies at the Γ-point and elastic constants. Both are in good agreement with available experiment.

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Section: Resultsmentioning

confidence: 99%

Section: B Activation Energy For the Hexagonal To Monoclinic Transitionmentioning

confidence: 99%

First-principles study of the biomineral hydroxyapatite

2011

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“…Citrate is needed to keep calcium in solution long enough (days) to inject into the subsurface because a solution containing Ca 2+ and phosphate only will rapidly form mono-and di-calcium phosphate, but not apatite (Andronescu et al 2002, Elliot et al 1973, Papargyris et al 2002. Relatively slow biodegradation of the Ca-citrate complex (days) allows sufficient time for the reagents to be injected and transported to the areas of the aquifer where treatment is required.…”

Section: Apatite Placement In the Subsurfacementioning

confidence: 99%

100-NR-2 Apatite Treatability Test: High-Concentration Calcium-Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization

Vermeul¹,

Fritz²,

Fruchter³

et al. 2010

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SummaryFollowing an evaluation of potential strontium-90 ( 90 Sr) treatment technologies and their applicability under 100-NR-2 hydrogeologic conditions, the U.S. Department of Energy (DOE), Fluor Hanford, Inc. (now CH2M Hill Plateau Remediation Company [CHPRC]), Pacific Northwest National Laboratory, and the Washington State Department of Ecology agreed that the long-term strategy for groundwater remediation at the 100-N Area should include apatite as the primary treatment technology. This agreement was based on results from an evaluation of remedial alternatives that identified the apatite permeable reactive barrier (PRB) technology as the approach showing the greatest promise for reducing 90 Sr flux to the Columbia River at a reasonable cost. This report documents work completed to date on developing a high-concentration amendment formulation and initial field-scale testing of this amendment solution.The general approach for developing an in situ remedial technology for sequestering 90 Sr in groundwater through the formation of calcium-phosphate mineral phases (i.e., apatite) was documented in a project-specific treatability test plan that provides a detailed discussion of test objectives and outlines the technical approach for developing and deploying the technology. Activities completed to date in support of the 100-NR-2 apatite treatability test that have been reported in previous documents include 1) laboratory-scale studies, 2) pilot-scale field testing with a low-concentration solution, 3) initial treatment of a 91-m (300-ft) -long PRB section with the low-concentration formulation, and 4) analysis of sediment samples collected following low-concentration treatment to determine whether any apatite had formed. A high-concentration amendment solution was formulated to maximize apatite formation within the targeted treatment zone while minimizing the short-term increases in 90 Sr concentration associated with injecting high-ionic-strength solutions.The original concept for field-scale deployment of the apatite PRB technology involved injecting a low-concentration, apatite-forming solution, followed by higher concentration injections as required to emplace sufficient treatment capacity to meet remedial objectives. The low-concentration injections were designed to provide a small amount of treatment capacity, thus stabilizing the 90 Sr residing within the treatment zone while minimizing 90 Sr mobilization because of the injection of high-ionic-strength solutions. In theory, this approach would act to minimize 90 Sr mobilization during subsequent highconcentration injections. However, results from the low-concentration field testing with a formulation containing stoichiometric calcium and phosphate concentrations for apatite precipitation and subsequent laboratory studies aimed at optimizing the amendment formulation determined that modifying the solution to a calcium-poor formulation was a better approach for maximizing apatite formation while minimizing short-term increases in 90 Sr concentration. This m...

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“…Citrate is needed to keep calcium in solution long enough (days) to inject into the subsurface; a solution containing Ca 2+ and phosphate only will rapidly form mono-and di-calcium phosphate, but not apatite (Andronescu et al 2002;Elliot et al 1973;Papargyris et al 2002). Relatively slow biodegradation of the Ca-citrate complex (days) allows sufficient time for injection and transport of the reagents to the areas of the aquifer where treatment is required.…”

Section: Apatite Placement In the Subsurfacementioning

confidence: 99%

Interim Report: 100-NR-2 Apatite Treatability Test: Low Concentration Calcium Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization

Williams¹,

Fritz²,

Mendoza³

et al. 2008

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SummaryEfforts to reduce the flux of strontium-90 ( 90 Sr) to the Columbia River from past-practice liquid waste disposal sites have been underway since the early 1990s in the 100-N Area at the Hanford Site. Termination of all liquid discharges to the ground in 1993 was a major step toward meeting this goal. However, 90 Sr adsorbed on aquifer solids beneath the liquid waste disposal sites and extending beneath the near-shore riverbed remains a continuing source to groundwater and the Columbia River. Researchers realized from the onset that the initial pump-and-treat system was unlikely to be an effective long-term solution because of the geochemical characteristics of 90 Sr; subsequent performance monitoring has substantiated this theory. Accordingly, the first Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) 5-year review re-emphasized the need to pursue alternative methods to reduce impacts on the Columbia River. 1Following an evaluation of potential 90 Sr treatment technologies and their applicability under 100-NR-2 hydrogeologic conditions, U.S. Department of Energy, Fluor Hanford, Inc. (FH), Pacific Northwest National Laboratory, and the Washington State Department of Ecology agreed the long-term strategy for groundwater remediation at the 100-N Area will include apatite sequestration as the primary treatment, followed by a secondary treatment⎯or polishing step⎯if necessary (most likely phytoremediation). Since then, the agencies have worked together to agree on which apatite-sequestration technology has the greatest chance of reducing 90 Sr flux to the Columbia River at a reasonable cost. In July 2005, aqueous injection, (i.e., the introduction of apatite-forming chemicals into the subsurface) was endorsed as the interim remedy and selected for field testing. Studies are in progress to assess the efficacy of in situ apatite formation by aqueous solution injection to address both the vadose zone and the shallow aquifer along the 91 m (300 ft) of shoreline where 90 Sr concentrations are highest. This report describes the field testing of the shallow aquifer treatment that was funded by FH.A low-concentration, apatite-forming solution was injected into the shallow aquifer in 10 injection wells during fiscal years 2006 and 2007, and performance monitoring is underway. The lowconcentration, apatite-forming solution consists primarily of calcium chloride, trisodium citrate, and sodium phosphate. The objective of the low-concentration Ca-citrate-PO 4 injections is to stabilize the 90 Sr in the aquifer at the test site, to be followed by high-concentration injections to provide for long-term 90 Sr treatment. Two pilot test sites at the east and west ends of the barrier, which are equipped with extensive monitoring well networks, were used for the initial injections to develop the injection design for the remaining portions of the barrier. Based on a comparison of hydraulic and transport response data at the two pilot test sites, it was determined the apparent permeability ...

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Monoclinic Hydroxyapatite

Cited by 356 publications

References 11 publications

First-principles study of the biomineral hydroxyapatite

First-principles study of the biomineral hydroxyapatite

100-NR-2 Apatite Treatability Test: High-Concentration Calcium-Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization

Interim Report: 100-NR-2 Apatite Treatability Test: Low Concentration Calcium Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization

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