Reardon Eric J, Fagan Randal, Vogan John L, Przepiora Andrzej
Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
Environ Sci Technol. 2008 Apr 1;42(7):2420-5. doi: 10.1021/es0712120.
Nanosized Fe0 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. t1/2 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 Fe0/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.
与分散在潮湿石英砂中的纳米级零价铁相比，其在水中表现出明显不同的厌氧腐蚀速率。在水中，腐蚀产生氢气呈现出自催化模式，在反应2天内达到最大速率1.9 mol kg⁻¹ d⁻¹。然后在接下来的20天内速率急剧下降，并进入速率均匀下降阶段，用一级动力学表达式或扩散控制动力学表达式都能很好地描述。在石英砂中，氢气产生在前20天呈现出双最大值，类似于波特兰水泥的水化反应，达到的最高速率小于0.5 mol kg⁻¹ d⁻¹。我们将早期腐蚀行为的这种差异归因于释放的氢气在铁/水体系中对水和铁颗粒的对流能力，而当铁颗粒分散在沙子中时则无法做到这一点。到30天时，石英砂中铁的产氢速率如在铁/水体系中一样呈现出均匀下降，这也可以用一级动力学表达式或扩散控制动力学表达式来描述。然而，潮湿沙子中铁的耐腐蚀性比纯水高4倍（即半衰期分别为365天和78天）。沙子中铁的较低腐蚀速率可能是由于溶解的二氧化硅吸附到铁反应位点上并作为阳极抑制剂起作用，从而降低了铁被水氧化的敏感性。这项研究表明，纳米级零价铁/水浆体的短期实验室腐蚀试验将大大低估该材料作为电子源的寿命及其在地下水修复应用中作为长期氢气源的潜力。
