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Abstract <p>A comprehensive physicochemical study of fluorwavellite Al<sub>3</sub>(PO<sub>4</sub>)<sub>2.1</sub>(OH)<sub>1.9</sub>F<sub>0.8</sub>⋅5.5H<sub>2</sub>O (from the Ulytau region, Kazakhstan) was carried out using powder X-ray diffraction, electron probe microanalysis, FTIR, Raman and EPR spectroscopy, and thermogravimetry. The enthalpy of formation of the studied fluorwavellite from elements was determined for the first time using high-temperature melt solution calorimetry in a Calvet microcalorimeter (–6606 ± 12 kJ/mol). The value of its standard entropy was estimated and the Gibbs energy of formation was calculated (483.4 J/(mol K) and –5941 ± 12 kJ/mol, respectively). The thermodynamic constants of the end members of the isomorphic series wavellite Al<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>3</sub>⋅5H<sub>2</sub>O–fluorwavellite Al<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>F⋅5H<sub>2</sub>O were estimated: <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({{\Delta }_{f}}H_{{{\text{el}}}}^{0}\)</EquationSource> <!--GeoChem2560107Gritsenko-m1--> </InlineEquation> (298.15 K) = –6328 ± 12 and –6435 ± 12 kJ/mol, <i>S</i><sup>0</sup>(298.15 K) = 464.3 and 463.0 J/(mol K), <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({{\Delta }_{f}}G_{{{\text{el}}}}^{0}\)</EquationSource> <!--GeoChem2560107Gritsenko-m2--> </InlineEquation> (298.15 K) = –5674 ± 12 and –5801 ± 12 kJ/mol, respectively.</p>

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Fluorwavellite: A Physicochemical Study and Thermodynamic Characteristics

  • 期刊论文

  • 发表日期：

    2026年3月1日

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  • Yu. D. Gritsenko,
  • L. P. Ogorodova,
  • S. V. Vyatkin,
  • M. F. Vigasina,
  • D. A. Kalinyuk,
  • L. V. Melchakova,
  • D. A. Ksenofontov

摘要

Abstract

A comprehensive physicochemical study of fluorwavellite Al3(PO4)2.1(OH)1.9F0.8⋅5.5H2O (from the Ulytau region, Kazakhstan) was carried out using powder X-ray diffraction, electron probe microanalysis, FTIR, Raman and EPR spectroscopy, and thermogravimetry. The enthalpy of formation of the studied fluorwavellite from elements was determined for the first time using high-temperature melt solution calorimetry in a Calvet microcalorimeter (–6606 ± 12 kJ/mol). The value of its standard entropy was estimated and the Gibbs energy of formation was calculated (483.4 J/(mol K) and –5941 ± 12 kJ/mol, respectively). The thermodynamic constants of the end members of the isomorphic series wavellite Al3(PO4)2(OH)3⋅5H2O–fluorwavellite Al3(PO4)2(OH)2F⋅5H2O were estimated: \({{\Delta }_{f}}H_{{{\text{el}}}}^{0}\) (298.15 K) = –6328 ± 12 and –6435 ± 12 kJ/mol, S0(298.15 K) = 464.3 and 463.0 J/(mol K), \({{\Delta }_{f}}G_{{{\text{el}}}}^{0}\) (298.15 K) = –5674 ± 12 and –5801 ± 12 kJ/mol, respectively.