Photoreductive dissolution of colloidal iron oxide: Effect of citrate
Photoreductive dissolution of colloidal iron oxide: Effect of citrate
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DOI：
10.1016/0021-9797(84)90206-6
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发表时间：
1984-11
期刊：
影响因子：
--
通讯作者：
T. Waite;F. Morel
中科院分区：
文献类型：
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作者：
T. Waite;F. Morel
研究了氧化铁锂镁铁石(γ-FeOOH)的光诱导溶解，发现在柠檬酸盐存在下，光诱导溶解作用大大增强。通过柠檬酸盐在锂镁铁矿上的吸附、各种条件下净氧化铁的溶解以及溶液相氧化还原反应的研究，提出了一个溶解过程的概念模型，并对其进行了验证。初始溶解速率与表面结合柠檬酸铁的浓度直接相关，光溶解过程的一级速率常数与可溶性柠檬酸铁光解离的一级速率常数非常相似。溶解很可能是通过直接激发表面结合的柠檬酸铁的电荷转移带来进行的。在低pH(pH 4.0)时，溶出速率恒定，而在高pH(pH 6.5和8.2)时，继续光解时，溶出速率下降。这种减少是由于(1)表面发生的氧依赖的失活过程和(2)胶体氧化铁对可溶的柠檬酸铁络合物的“配位体”吸附而从溶液中损失光生铁。在这些较高的pH值下，溶解过程叠加了一个涉及溶液相铁物种的快速氧化-还原循环，还原步骤由柠檬酸铁络合物的光解引起，氧化步骤由柠檬酸亚铁的生成控制。
The light-induced dissolution of the iron oxide, lepidocrocite (γ-FeOOH), has been investigated and found to be greatly enhanced in the presence of citrate. A conceptual model of the dissolution process is presented and validated through studies of citrate adsorption to lepidocrocite, net iron oxide dissolution under a variety of conditions, and solution phase redox reactions. The initial dissolution rate is directly related to the concentration of the surface bound ferric citrate and the first order rate constant for the photodissolution process is very similar to that found for the photodissociation of soluble ferric citrate. Dissolution most likely occurs through direct excitation of charge transfer bands of the surface bound ferric citrate. At low pH (pH 4.0), a constant rate of dissolution is observed while at higher pH (pH 6.5 and 8.2), the dissolution rate decreases on continued photolysis. This decrease is due to (1) an oxygen-dependent deactivation process occurring at the surface and (2) loss of photo-produced iron from solution by “ligand-like” adsorption of soluble iron citrate complexes by the colloidal iron oxide. Superimposed on the dissolution process at these higher pH is a rapid oxidation-reduction cycle involving solution phase iron species with the reduction step induced by photodissociation of ferric citrate complexes and the oxidation step controlled by the formation of ferrous citrate.