Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite

The unstable compound octacalcium phosphate (OCP) is one of the crystalline precursors of the apatite mineral series composed by hydroxyapatite, fluorapatite and chlorapatite. The feature of OCP to react into apatite, depending on the media conditions, has been mainly exploited for biomedical applic...

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Main Authors: Alfredo Idini, Franco Frau
Format: Article
Language:English
Published: Elsevier 2021-05-01
Series:Heliyon
Subjects:
Online Access:http://www.sciencedirect.com/science/article/pii/S2405844021009853
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spelling doaj-26fc44928e8444e29ef19d4fae33d2bb2021-06-03T14:44:53ZengElsevierHeliyon2405-84402021-05-0175e06882Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatiteAlfredo Idini0Franco Frau1Department of Chemical and Geological Sciences, University of Cagliari, 09042, Monserrato, CA, ItalyCorresponding author.; Department of Chemical and Geological Sciences, University of Cagliari, 09042, Monserrato, CA, ItalyThe unstable compound octacalcium phosphate (OCP) is one of the crystalline precursors of the apatite mineral series composed by hydroxyapatite, fluorapatite and chlorapatite. The feature of OCP to react into apatite, depending on the media conditions, has been mainly exploited for biomedical applications as bone and tooth substitute material. Recently, some important applications of OCP have been documented: e.g. as electrode material for supercapacitors and as fluoride remover reagent for environmental purposes. With the aim of deepening the property of OCP to be the crystalline precursor of apatite and assessing if and how the anionic competition can influence the formation of the different apatite end-members, the OCP → apatite reaction has been here investigated placing 0.223 mmol of OCP in 50 mL aqueous solution with 0.368 mmol of dissolved fluoride, chloride, hydroxyl and carbonate anions (fluoride alone, fluoride with each of the other anions, and all the anions together) at room temperature. The post-experiment analyses of solid and liquid phases, conducted by using XRD, ESEM and ICP-OES, show that fluoride is always the main anion removed from solution during the OCP transformation reaction. The precise mineralogical characterization of solid phases formed, performed using the Rietveld algorithm, shows that fluorapatite is always the main resulting apatitic phase, followed by hydroxyapatite. Taking into account the different application fields of OCP, these results could be significant in better defining the OCP → apatite reaction in aqueous solutions where different competing anions are involved.http://www.sciencedirect.com/science/article/pii/S2405844021009853Octacalcium phosphateAnionic competitionFluorapatite formationFluoride uptake from aqueous solution
collection DOAJ
language English
format Article
sources DOAJ
author Alfredo Idini
Franco Frau
spellingShingle Alfredo Idini
Franco Frau
Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
Heliyon
Octacalcium phosphate
Anionic competition
Fluorapatite formation
Fluoride uptake from aqueous solution
author_facet Alfredo Idini
Franco Frau
author_sort Alfredo Idini
title Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
title_short Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
title_full Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
title_fullStr Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
title_full_unstemmed Mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
title_sort mineralogical-geochemical study of the anionic competition effect on the octacalcium phosphate reaction into fluorapatite
publisher Elsevier
series Heliyon
issn 2405-8440
publishDate 2021-05-01
description The unstable compound octacalcium phosphate (OCP) is one of the crystalline precursors of the apatite mineral series composed by hydroxyapatite, fluorapatite and chlorapatite. The feature of OCP to react into apatite, depending on the media conditions, has been mainly exploited for biomedical applications as bone and tooth substitute material. Recently, some important applications of OCP have been documented: e.g. as electrode material for supercapacitors and as fluoride remover reagent for environmental purposes. With the aim of deepening the property of OCP to be the crystalline precursor of apatite and assessing if and how the anionic competition can influence the formation of the different apatite end-members, the OCP → apatite reaction has been here investigated placing 0.223 mmol of OCP in 50 mL aqueous solution with 0.368 mmol of dissolved fluoride, chloride, hydroxyl and carbonate anions (fluoride alone, fluoride with each of the other anions, and all the anions together) at room temperature. The post-experiment analyses of solid and liquid phases, conducted by using XRD, ESEM and ICP-OES, show that fluoride is always the main anion removed from solution during the OCP transformation reaction. The precise mineralogical characterization of solid phases formed, performed using the Rietveld algorithm, shows that fluorapatite is always the main resulting apatitic phase, followed by hydroxyapatite. Taking into account the different application fields of OCP, these results could be significant in better defining the OCP → apatite reaction in aqueous solutions where different competing anions are involved.
topic Octacalcium phosphate
Anionic competition
Fluorapatite formation
Fluoride uptake from aqueous solution
url http://www.sciencedirect.com/science/article/pii/S2405844021009853
work_keys_str_mv AT alfredoidini mineralogicalgeochemicalstudyoftheanioniccompetitioneffectontheoctacalciumphosphatereactionintofluorapatite
AT francofrau mineralogicalgeochemicalstudyoftheanioniccompetitioneffectontheoctacalciumphosphatereactionintofluorapatite
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