The sequestration of metal ions into the crystal structure of minerals is common in nature. To date, the incorporation of technetium(IV) into iron minerals has been studied predominantly for systems under carefully controlled anaerobic conditions. Mechanisms of the transformation of iron phases leading to incorporation of technetium(IV) under aerobic conditions remain poorly understood. Here we investigate granular metallic iron for reductive sequestration of technetium(VII) at elevated concentrations under ambient conditions. We report the retarded transformation of ferrihydrite to magnetite in the presence of technetium. We observe that quantitative reduction of pertechnetate with a fraction of technetium(IV) structurally incorporated into non-stoichiometric magnetite benefits from concomitant zero valent iron oxidative transformation. An in-depth profile of iron oxide reveals clusters of the incorporated technetium(IV), which account for 32% of the total retained technetium estimated via X-ray absorption and X-ray photoelectron spectroscopies. This corresponds to 1.86 wt.% technetium in magnetite, providing the experimental evidence to theoretical postulations on thermodynamically stable technetium(IV) being incorporated into magnetite under spontaneous aerobic redox conditions.

金属离子螯合到矿物的晶体结构中在自然界中很常见。迄今为止，有关将锝 (IV) 掺入铁矿物的研究主要针对在严密控制的厌氧条件下的系统。导致在有氧条件下掺入锝 (IV) 的铁相转化机制仍然知之甚少。在这里，我们研究了在环境条件下以高浓度还原螯合锝 (VII) 的粒状金属铁。我们报告了在锝存在下水铁矿向磁铁矿的延迟转变。我们观察到，在结构上掺入非化学计量磁铁矿中的一小部分锝 (IV) 对高锝酸盐的定量还原受益于伴随的零价铁氧化转化。对氧化铁的深入剖析显示掺入的锝 (IV) 簇，占通过 X 射线吸收和 X 射线光电子能谱估计的总保留锝的 32%。这对应于磁铁矿中 1.86 wt.% 的锝，为在自发有氧氧化还原条件下将热力学稳定的锝 (IV) 掺入磁铁矿中的理论假设提供了实验证据。