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Anaerobic Corrosion Reaction Kinetics of Nanosized Iron

机译：纳米铁的厌氧腐蚀反应动力学

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Nanosized Fe~0 exhibits markedly different anaerobic corrosion rates in water compared to that disseminated in moist quartz sand. In water, hydrogen production from corrosion exhibits an autocatalytic style, attaining a maximum rate of 1.9 mol kg~(-1) d~(-1) within 2 d of reaction. The rate then drops sharply over the next 20 d and enters a period of uniformly decreasing rate, represented equally well by first-order or diffusion-controlled kinetic expressions. In quartz sand, hydrogen production exhibits a double maximum over the first 20 d, similar to the hydration reaction of Portland cement, and the highest rate attained is less than 0.5 mol kg~(-1) d~(-1). We ascribe this difference in early time corrosion behavior to the ability of the released hydrogen gas to convect both water and iron particles in an iron/water system and to its inability to do so when the iron particles are disseminated in sand. By 30 d, the hydrogen production rate of iron in quartz sand exhibits a uniform decrease as in the iron/water system, which also can be described by first-order or diffusion-controlled kinetic expressions. However, the corrosion resistance of the iron in moist sand is 4 times greater than in pure water (viz. t_(1/2)of 365 d vs 78 d, respectively). The lower rate for iron in sand is likely due to the effect of dissolved silica sorbing onto iron reaction sites and acting as an anodic inhibitor, which reduces the iron's susceptibility to oxidation by water. This study indicates that short-term laboratory corrosion tests of nanosized Fe~0/ water slurries will substantially underestimate both the material's longevity as an electron source and its potential as a long-term source of hydrogen gas in groundwater remediation applications.
机译：纳米Fe〜0在水中的厌氧腐蚀速率与湿石英砂中的厌氧腐蚀速率明显不同。在水中，腐蚀产生的氢表现出自催化方式，在反应后2 d内最大速率达到1.9 mol kg〜（-1）d〜（-1）。然后，速率在接下来的20 d内急剧下降，并进入一个速率均匀降低的时期，该速率由一阶或扩散控制的动力学表达式表示得同样好。在石英砂中，氢的产生在最初的20 d内显示出两倍的最大值，这与硅酸盐水泥的水化反应相似，并且最高产率低于0.5 mol kg〜（-1）d〜（-1）。我们将这种早期腐蚀行为的差异归因于释放的氢气对铁/水系统中的水和铁颗粒进行对流的能力，以及当铁颗粒散布在沙子中时无法做到的。到30 d时，石英砂中铁的氢产生速率表现出与铁/水系统相同的均匀降低，这也可以通过一阶或扩散控制的动力学表达式来描述。但是，铁在潮湿的沙子中的耐腐蚀性是纯水的4倍（分别是365 d和78 d的t_（1/2））。沙子中铁的比率较低可能是由于溶解的二氧化硅吸附到铁反应位点上并起阳极抑制剂的作用，从而降低了铁对水氧化的敏感性。这项研究表明，纳米级Fe〜0 /水浆液的短期实验室腐蚀测试将大大低估该材料作为电子源的寿命以及在地下水修复应用中作为长期氢气源的潜力。

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