Fe(II)-bearing geologic media are promising agents for the consumption of dissolved oxygen (DO) remaining in geologic formations after the backfilling of radioactive waste repositories, which helps prevent redox-sensitive radionuclides from becoming soluble and mobile in groundwater. A second-order rate law has been proposed to describe DO consumption due to the oxidation of structural Fe(II) at the mineral surface; however, it has only been tested against a few Fe(II)-bearing geologic media via DO consumption experiments. Thus, this study investigates the applicability of the second-order rate law to Fe(II)-bearing geologic media and minerals by reanalyzing data from previous batch experiments of DO consumption. Additional DO consumption experiments were also performed on diatomaceous and siliceous mudstones to examine the influence of clay components and coexisting Fe(II)-bearing minerals on the DO consumption rate constant. The reanalysis results showed that the second-order rate law can effectively describe DO consumption by both natural geologic media and purified minerals. The derived consumption rate constants are relatively similar for natural geologic media and purified minerals, but not for media with a high clay content. In particular, the rate constants for sedimentary rocks with smectite components exhibit large variations and tend to be smaller than the theoretical lower limit for structural Fe(II) on silicate minerals. Conversely, the rate constants for mudstones containing non-swelling chlorite exhibit small variations. This implies that, in batch experiments on powdered samples containing smectite, DO is consumed not only by structural Fe(II) at the external surface but also by Fe(II) in the interlayers of the smectite, which is less accessible to DO in bulk solution. This may explain the prolonged reaction time and relatively small rate constants of sedimentary rocks with smectite components. This study suggests that the second-order rate law can be applied to model DO consumption in a variety of Fe(II)-bearing rocks. However, the rate constants may be underestimated with large variations when testing powdered rocks containing smectite.

含 Fe(II) 的地质介质是消耗放射性废物储存库回填后残留在地质构造中的溶解氧 (DO) 的有希望的试剂，这有助于防止对氧化还原敏感的放射性核素在地下水中溶解和移动。已经提出了二阶速率定律来描述由于矿物表面结构 Fe(II) 氧化引起的 DO 消耗；然而，它仅通过 DO 消耗实验针对少数含 Fe(II) 的地质介质进行了测试。因此，本研究通过重新分析先前批量实验的溶解氧消耗数据，研究二阶速率定律对含 Fe(II) 地质介质和矿物的适用性。还对硅藻土和硅质泥岩进行了额外的 DO 消耗实验，以检查粘土成分和共存的含 Fe(II) 矿物对 DO 消耗速率常数的影响。再分析结果表明，二阶速率定律可以有效地描述天然地质介质和纯化矿物对溶解氧的消耗。自然地质介质和纯化矿物的导出消耗率常数相对相似，但粘土含量高的介质则不然。特别是，具有蒙脱石成分的沉积岩的速率常数表现出很大的变化，并且往往小于硅酸盐矿物上结构 Fe(II) 的理论下限。相反，含有非膨胀绿泥石的泥岩的速率常数变化很小。这意味着，在含有蒙脱石的粉状样品的批量实验中，DO 不仅被外表面的结构 Fe(II) 消耗，而且被蒙脱石夹层中的 Fe(II) 消耗，而在本体溶液中，DO 较难吸收。这可以解释具有蒙脱石成分的沉积岩的反应时间延长和速率常数相对较小的原因。该研究表明，二阶速率定律可用于模拟各种含 Fe(II) 岩石中的 DO 消耗。然而，当测试含有蒙脱石的粉状岩石时，速率常数可能会被低估，变化很大。这可以解释具有蒙脱石成分的沉积岩的反应时间延长和速率常数相对较小的原因。该研究表明，二阶速率定律可用于模拟各种含 Fe(II) 岩石中的 DO 消耗。然而，当测试含有蒙脱石的粉状岩石时，速率常数可能会被低估，变化很大。这可以解释具有蒙脱石成分的沉积岩的反应时间延长和速率常数相对较小的原因。该研究表明，二阶速率定律可用于模拟各种含 Fe(II) 岩石中的 DO 消耗。然而，当测试含有蒙脱石的粉状岩石时，速率常数可能会被低估，变化很大。