Thermodynamic description of Be(II) solubility and hydrolysis in acidic to hyperalkaline NaCl and KCl solutions
Autor: | Xavier Gaona, Christian Adam, N. Cevirim-Papaioannou, Thomas Sittel, Ezgi Yalçıntaş Bethune, M. Böttle, Marcus Altmaier, Dieter Schild |
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Jazyk: | angličtina |
Rok vydání: | 2020 |
Předmět: |
Technology
Chemistry Inorganic chemistry Aqueous two-phase system Context (language use) Solubility equilibrium 010501 environmental sciences 010502 geochemistry & geophysics 01 natural sciences Pollution Hydrolysis Geochemistry and Petrology Ionic strength Phase (matter) Environmental Chemistry Solubility Ternary operation ddc:600 0105 earth and related environmental sciences |
Zdroj: | Applied geochemistry, 117, Article: 104601 |
ISSN: | 0883-2927 1872-9134 |
DOI: | 10.5445/ir/1000120378 |
Popis: | The solubility of Be(II) is investigated in carbonate-free dilute to concentrated HCl–NaCl–NaOH, KCl–KOH, NaOH and KOH solutions. Undersaturation experiments were performed under Ar atmosphere at T= (22 ± 2) °C. XRD, XPS, SEM and quantitative chemical analysis confirm that α-Be(OH)$_{2}$(cr) is the solid phase controlling the solubility in all evaluated systems. No transformation of α-Be(OH)$_{2}$(cr) to β-Be(OH)$_{2}$(cr) or ternary solid phases Na/K–Be(II)–OH(s) is observed in the investigated systems within the timeframe of this study (t ≤ 600 days). An amphoteric solubility behaviour of Be(II) is observed with a solubility minimum at pH$_{m}$ ≈ 9.5 (with [Be(II)] ≈ 10$^{-6.8}$M), regardless of the ionic strength. The combination of solubility data determined in acidic pH$_{m}$ conditions and the hydrolysis scheme reported in the literature for cationic hydrolysis species of Be(II) is used for the determination of the solubility constant of α-Be(OH)$_{2}$(cr), log *K°$_{s,0}$ = (6.9 ± 0.4). Slope analysis of the solubility data in alkaline to hyperalkaline conditions and $^{9}$Be NMR support the predominance of the monomeric hydrolysis species Be(OH)$_{2}$(aq), Be(OH)$_{3}$– and Be(OH)$_{4}$$^{2-}$ within the strongly alkaline pH$_{m}$-conditions relevant in cementitious systems. The comprehensive solubility dataset collected within this study in combination with extensive solid and aqueous phase characterization allow the development of a complete chemical, thermodynamic and (SIT) activity model for the system Be$^{2+}$–Na$^{+}$–K$^{+}$–H$^{+}$–Cl$^{-}$–OH$^{-}$–H$_{2}$O(l). This model provides an accurate and robust tool for the evaluation of Be(II) solubility and speciation in a diversity of geochemical conditions, including source term calculations of beryllium in the context of the nuclear waste disposal Safety Case. |
Databáze: | OpenAIRE |
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