Magnetite solubility and phase stability in alkaline media at elevated temperatures

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research Pub Date : 1994-05-01 DOI:10.2172/34346

S. Ziemniak, M. Jones, K. Combs

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引用次数: 63

Abstract

AbstractA platinum-lined flowing autocláve facility was used to investigate the solubility behavior of magnetite (Fe3O4) in alkaline sodium phosphate and ammonium hydroxide solutions between 21 and 288°C. Measured iron solubilities were interpreted via a Fe(II)/Fe(III) ion hydroxo-, phosphato-, and ammino-complexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A total of 14 iron ion species were fitted. Complexing equilibria are reported for 8 new species: Fe(OH)(HPO4)−, Fe(OH)2(HPO4)2−, Fe(OH)3(HPO4)2−, Fe(OH)(NH3)+, Fe(OH)2(PO4)3−, Fe(OH)4(HPO4)3−, Fe(OH)2(H2PO4)−, and Fe(OH)3(H2PO4)3−. At elevated temperatures, hydrolysis and phosphato complexing tended to stabilize Fe(III) relative to Fe(II), as evidenced by free energy changes fitted to the oxidation reactions. $$\begin{gathered} Fe(OH)_3^ - + H_2 O_ \leftarrow ^ \to Fe(OH)_4^ - + (1/2)H_2 (g) \hfill \\ Fe(OH)_2^{} (HPO_4 )^{2 - } + H_2 O_ \leftarrow ^ \to Fe(OH)_3 (HPO_4 )^{2 - } + (1/2)H_2 (g) \hfill \\ \end{gathered}$$ For temperatures below 83°C and for a dissolved hydrogen concentration of 234 μmol-kg−1, the activity of ferrous iron in aqueous solution is controlled by a hydrous Fe(II) oxide solid phase rather than magnetite.

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磁铁矿在高温碱性介质中的溶解度和相稳定性

摘要采用铂衬里流动autocláve装置，研究了磁铁矿Fe3O4在碱性磷酸钠和氢氧化铵溶液中21 ～ 288℃的溶解度行为。测量的铁溶解度通过Fe(II)/Fe(III)离子氢氧、磷酸和氨基络合模型解释，这些平衡的热力学函数通过数据的最小二乘分析得到。共拟合了14种铁离子。报道了8种新的络合平衡:Fe(OH)(HPO4)−、Fe(OH)2(HPO4)2−、Fe(OH)3(HPO4)2−、Fe(OH)(NH3)+、Fe(OH)2(PO4)3−、Fe(OH)4(HPO4)3−、Fe(OH)2(H2PO4)−和Fe(OH)3(H2PO4)3−。在高温下，水解和磷酸络合倾向于稳定Fe(III)相对于Fe(II)，这可以从符合氧化反应的自由能变化中得到证明。$$\begin{gathered} Fe(OH)_3^ - + H_2 O_ \leftarrow ^ \to Fe(OH)_4^ - + (1/2)H_2 (g) \hfill \\ Fe(OH)_2^{} (HPO_4 )^{2 - } + H_2 O_ \leftarrow ^ \to Fe(OH)_3 (HPO_4 )^{2 - } + (1/2)H_2 (g) \hfill \\ \end{gathered}$$当温度低于83℃，溶液中氢浓度为234 μmol-kg−1时，亚铁在水溶液中的活性受含水Fe(II)氧化物固相而不是磁铁矿控制。

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来源期刊

Accounts of Chemical Research 化学-化学综合

CiteScore

31.40

自引率

1.10%

发文量

312

审稿时长

2 months

期刊介绍： Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance. Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.