Dissolution of hydrous iron(III) oxides by reductive mechanisms
Dissolution of hydrous iron(III) oxides by reductive mechanisms
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DOI：
10.1021/la00052a033
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发表时间：
1991-04
期刊：
影响因子：
3.9
通讯作者：
D. Suter;S. Banwart;W. Stumm
中科院分区：
文献类型：
--
作者：
D. Suter;S. Banwart;W. Stumm
还原机制在自然界中三价铁（氢）氧化物的溶解过程中起着重要的作用。对于铁（III）（氢）氧化物，还原机制通常比非还原机制更快，因为铁（II）从晶格表面的释放在能量上比铁（III）的释放更有利。我们已经研究了两种不同类型的溶解，它们都涉及还原步骤。第一个反应是通过抗坏血酸还原溶解赤铁矿（a-Fe 20 a），第二个反应是通过铁（II）络合物溶解针铁矿（-FeOOH），其中还原步骤达到快速的总溶解速率。在这两种情况下，溶解速率与溶解固体表面上还原物质的浓度成比例。测定了不同pH值下的溶出速率。pH值的影响是明显的，并给出了所观察到的趋势的解释。铝的存在被证明tofinfluence抗坏血酸在pH 4的赤铁矿的溶解，但不是在pH 3。这一观察结果是由铝在pH 4的吸附表面的阻塞。
Reductive mechanisms play an important role in the dissolution of iron (III)(hydr) oxides in nature. For iron (III)(hydr) oxides, reductive mechanisms are usually faster than nonreductive mechanisms, because release of iron (II) from the surface of the crystal lattice is energetically more favorable than release of iron (III). We have studied two different types of dissolution, which both involve a reductive step. The first reaction is the reductive dissolution of hematite (a-Fe20a) by ascorbate and the second is the dissolution of goethite (-FeOOH) by iron (II) complexes, where a reduction stepleads to a fast overall dissolution rate. In both cases, the dissolution rate is proportional to the concentration of the reducing species on the surface of the dissolving solid. Dissolution rates for different pH values have been determined. The effect of the pH value is pronounced and explanations are given for the trend observed. The presence of aluminum is shown toinfluence the dissolution of hematite by ascorbate at pH 4, but not at pH 3. This observation is explained by the blocking of the surface by adsorption of aluminum at pH 4.