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Thermodynamic characterization of the amphoteriс oxides M2O3 (M─Cr, Fe, Co) and their hydrates in aqueous mediaстатья
Дата последнего поиска статьи во внешних источниках: 1 мая 2024 г.
- Автор: Shkol'nikov E.V.
- Журнал: Russian Journal of Applied Chemistry
- Том: 84
- Номер: 10
- Год издания: 2011
- Издательство: Maik Nauka/Interperiodica Publishing
- Местоположение издательства: Russian Federation
- Первая страница: 1702
- Последняя страница: 1709
- DOI: 10.1134/S107042721110005
- Аннотация: Using thermodynamic data, the solubility constant K 0 Ks and dissolution parameters in aqueous media of difficult to dissolve crystalline metahydroxides CrOOH and .(., .)-FeOOH, oxides .-FeO1.5 and CoO1.5 at O1.5 O1.5 25°C have been calculated for the first time. 2. Solubility of oxides M2O3 (M - Cr, Fe, Co) and 2 O3 of their hydrates in water is very low (10-14-10-5 mol-l-1), 5 is determined by complexes respectively Cg(OH)2 +, 2 +, Fe(OH)3, Co(OH)3 and depends on the composition and structure of Fe(OH)3, Co(OH)3 and depends on the composition and structure of Fe(OH)3, Co(OH)3, ) )3 strongly decreasing in the transition from amorphous to stable crystalline modification (by 5-6 orders of magnitude for Cr(OH)3, .-FeOOH and .-FeO1.5). The molar solubility in water of stable crystals decreases in the series CoOOH > Co(OH)3 > .-CrO1.5 > )3 O1.5 Cr(OH)3 > .-FeOOH > .-FeO1.5 > CrOOH. )3 O1.5 3. The influence of pH value on the molar solubility of M2O3 oxides and their hydra- 2 O3 oxides in aqueous alkaline and acidic media at 25°C has been calculated for the first time using thermodynamic data taking into account the formation of mono- and polynuclear hydroxocomplexes. The p values (8.8, 8.0, 7.6) of the most Nopt of complete precipitation of hydrated oxides of chromium(III), iron(III) and cobalt(III) respectively, as well as the amphoteric parameter A > 1, increasing in the series of amorphous hydroxides Co(OH)3 < Fe(OH)3 < )3 )3 Cr(OH)3 were determined. )3 4. Chromium(III) oxide and its hydrates, unlike Fe(III) and Co(III) compounds, show a negative effect of common OH- ions on solubility upon addition of alkali
- Добавил в систему: Школьников Евгений Васильевич