Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions

Jemal, M.

doi:10.5772/13645

Cited by 3 publications

(4 citation statements)

References 42 publications

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“…[7], progressive dissolution of carbonated Caapatites in the same amount of a 19% w/w P 2 O 5 solution (4.5 ml) results in the occurrence of successive phenomena. This appears through the graph representing the energy released as a function of the solid amount.…”

Section: Dissolution Of More Amounts Of Ca-co 3 Apatitesmentioning

confidence: 99%

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Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Jemal¹

2017

Phosphoric Acid Industry - Problems and Solutions

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The principal material in the phosphate ores is composed of calcium fluorapatite Ca 10 (PO 4 ) 6 F 2 , in which the various components have been partially substituted by magnesium, sodium, carbonate, and hydroxyl ions. These substitutions affect the stability of the material and its reactivity toward the acid attack. The present chapter reports the influence of carbonates and magnesium on these properties. Using different calorimeters, dissolution experiments of carbonated and noncarbonated Ca and Ca/Mg apatites were carried out in acid solutions leading to thermochemical quantities. The results show that substitution of carbonate for F ions in the channel (to get A-type carbonate F-apatites) results in increasing the stability of the edifice, while substitution of CO 3 for PO 4 in fluor-or hydroxyapatites (to get B-type apatites) leads to a decrease in stability. The latter phenomenon was also observed when substituting magnesium for calcium in F-apatites. The presence of the former in the apatite structure results in an increase of the speed of dissolution in acid solution that is enhanced when carbonate is also replacing phosphate groups. Dissolution mechanism of synthesized Ca/Mg F-apatites seems to be a one-step process, while dissolution of a Gafsa (TN) natural phosphate to get superphosphate fertilizer is more complex.

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Section: Dissolution Of More Amounts Of Ca-co 3 Apatitesmentioning

confidence: 99%

“…The same calculation procedure has been applied for hydroxy and chlor-apatites containing the metal reported above. All these results are gathered in reference [7]. Substitutions of calcium by alkali earth metals, Cd or Pb have also been considered thermochemically and have been widely published in literature.…”

Section: Introductionmentioning

confidence: 99%

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Jemal¹

2017

Phosphoric Acid Industry - Problems and Solutions

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“…The last decades have produced numerous biomaterials based on apatite, sometimes associated with drugs or biologically active ions (Al-Kattan et al 2010b; Barroug and Glimcher 2002;Benaziz et al 2001;Bohner et al 2008;Drouet et al 2008Drouet et al , 2012Weber et al 2013). Biomimetic apatite-based hybrid systems have been used in cancer diagnosis and therapeutics (Al-Kattan et al 2010a, 2011, 2010bBouladjine et al 2009;Mondejar et al 2007;Yang et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…There remains a lack of understanding of the thermodynamics of formation of apatite compounds that may exhibit various degrees of stoichiometry, crystallinity, particle size, and ionic substitution. Published data almost invariably addresses only well-crystallized stoichiometric apatites (Jemal 2011) (e.g., hydroxyapatite, fluorapatite, and apatites doped with heavy metals or alkaline earth ions), and the thermodynamic effects of lanthanide incorporation into phosphate apatites M 10 (PO 4 ) 6 X 2 do not seem to have been specifically addressed. In a recent study (Rollin-Martinet et al 2013), we investigated by solution calorimetry the energetics of biomimetic apatites corresponding to various stoichiometries, documenting in particular their strongly negative enthalpy-driven Gibbs free energies of formation, and we related the formation energetics to changes in calcium and hydroxide contents, unveiling the importance of ionic substitution on apatite thermodynamics.…”

Section: Introductionmentioning

confidence: 99%

Energetics of lanthanide-doped calcium phosphate apatite

Hosseini

Drouet

Al-Kattan

et al. 2014

American Mineralogist

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International audienceLanthanides “Ln” (rare earths) are critical elements found in natural minerals such as calcium phosphate apatites, in sedimentary and igneous settings as well as in skeletal diagenesis. From a medical point of view, nanoparticles of lanthanide-doped apatites can be produced for conferring luminescence properties of interest in cancer cells detection. However, the impact of the substitution of Ln for Ca on the stability and solubility of related apatite phases is still essentially unknown. To investigate the thermochemical effects of such lanthanide substitution for calcium in apatite, we prepared and analyzed four series of apatites with up to 10% lanthanide substitution for calcium. After thorough physicochemical characterization via complementary techniques (XRD, FTIR, TG/DSC, and IPC-AES), high-temperature oxide melt solution calorimetry in molten sodium molybdate at 973 K was performed to determine their enthalpies of formation from constituent oxides and from the elements, at 298 K. Our results indicate that although enthalpies of formation are strongly exothermic in all cases, Ln-doping has a destabilizing effect, which increases with dopant concentration and with the size of the incorporated Ln3+ ion. After estimating standard entropies, Gibbs free energies of formation and equilibrium constants for Ca2+/Ln3+ exchange reactions in apatite were then evaluated, for the first time allowing access to quantitative thermodynamic data that may be used in various fields for stability calculations or partitioning estimates between fluids and solids

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Low-temperature heat capacity and thermal expansion of synthetic caracolite Na3Pb2(SO4)3Cl

Knyazev¹,

Bulanov²,

Смирнова³

et al. 2014

Thermochimica Acta

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Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions

Cited by 3 publications

References 42 publications

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Energetics of lanthanide-doped calcium phosphate apatite

Low-temperature heat capacity and thermal expansion of synthetic caracolite Na3Pb2(SO4)3Cl

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