Dataset Information

Dissolution-Precipitation Synthesis and Characterization of Zinc Whitlockite with Variable Metal Content.

ABSTRACT: In the present work, a series of zinc whitlockite (Ca_xZn_y(HPO₄)₂(PO₄)₁₂) powders was synthesized by a low-temperature dissolution-precipitation process for the first time. The phase conversion from calcium hydroxyapatite to zinc whitlockite occurred in an acidic medium in the presence of Zn²⁺ ions. Variable chemical composition of the synthesis products was achieved by changing Ca-to-Zn molar ratio in the reaction mixture. Investigation of the phase evolution as a function of time demonstrated that phase-pure zinc whitlockite powders can be synthesized in just 3 h. It is also demonstrated that single-phase products can be obtained when the Ca-to-Zn ratio in the reaction medium is in the range from 9 to 30. With higher or lower ratios, neighboring crystal phases such as scholzite or calcium hydroxyapatite were obtained. The morphology of the synthesized powders was found to be dependent on the chemical composition, transforming from hexagonal to rhombohedral plates with the increase of Zn content. Thermal stability studies revealed that the synthesized compounds were thermally unstable and decomposed upon heat treatment.

SUBMITTER: Kizalaite A

PROVIDER: S-EPMC8396804 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Dissolution-Precipitation Synthesis and Characterization of Zinc Whitlockite with Variable Metal Content.

Kizalaite Agne A Grigoraviciute-Puroniene Inga I Asuigui Dane Romar C DRC Stoll Sarah L SL Cho Sung Hun SH Sekino Tohru T Kareiva Aivaras A Zarkov Aleksej A

ACS biomaterials science & engineering 20210728 8

In the present work, a series of zinc whitlockite (CaxZny(HPO4)2(PO4)12) powders was synthesized by a low-temperature dissolution-precipitation process for the first time. The phase conversion from calcium hydroxyapatite to zinc whitlockite occurred in an acidic medium in the presence of Zn2+ ions. Variable chemical composition of the synthesis products was achieved by changing Ca-to-Zn molar ratio in the ...[more]

PMID: 34318657

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Project description:Fossils exposed at the surface are an integral component of the paleontologic record and provide an archive of past life. However, it is widely known that fossils are not stable indefinitely upon exposure to surface conditions such as physical, chemical, and biological processes, and this last phase of taphonomy is poorly understood. Studies regarding the longevity of fossils subject to weathering, such as acidic precipitation, are absent in the literature. The goal of this study was to experimentally determine vertebrate fossil dissolution rates under variable pH conditions in a controlled laboratory setting. It was hypothesized that fossils would dissolve within acidic solutions and do so at an increasing rate when exposed to increasingly acidic solutions. The experiments were conducted on three fossil vertebrae in triplicate in closed reaction vessels at pH 4, 5, and 6. The fossils were completely submerged for 21 days in a tap water solution with the pH adjusted using 0.1N hydrochloric acid (HCl). Fossil dissolution was quantified by changes to: (1) fossil mass; (2) elemental chemistry of water and fossils with inductively coupled plasma mass spectrometry (ICP-MS); (3) fossil mineralogy with X-ray diffraction (XRD); and (4) histologic structures with thin section analyses. All fossils exhibited mass loss, which increased with decreasing pH conditions, and was greatest under pH 4 (477 to 803 mg loss). The elemental analyses with ICP-MS indicated an increase of both calcium (maximum increase of 315 ppm) and phosphorus (increase of 18 ppm) in aqueous solutions with increasing pH and a loss of those same elements from the fossils (maximum loss of 10 ppm Ca and 6 ppm P). XRD revealed loss of gypsum in all post-dissolution samples. Taken together, the results of ICP-MS and XRD suggest dissolution of the primary mineral phases, including hydroxylapatite, and secondary phases, particularly calcite and gypsum, resulting in an estimated mass loss at pH 4 of 23 to 28 mg per day. Thin section analysis showed degradation of both cortical and trabecular bone in all post-dissolution images, demonstrating physical changes to the fossils as a result of water-rock interactions. These findings constitute the first quantitative analysis of fossil dissolution rates and provide insights into this last stage of taphonomy, addressing a largely understudied potential bias in the vertebrate fossil record.

Dataset Information

Dissolution-Precipitation Synthesis and Characterization of Zinc Whitlockite with Variable Metal Content.

Publications

Dissolution-Precipitation Synthesis and Characterization of Zinc Whitlockite with Variable Metal Content.

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