Characterization and Reactivity of Iron Nanoparticles prepared with added Cu, Pd, and Ni
Characterization and Reactivity of Iron Nanoparticles prepared with added Cu, Pd, and Ni
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DOI：
10.1021/es903278e
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发表时间：
2010-07-01
影响因子：
11.4
通讯作者：
Penn, R. Lee
中科院分区：
文献类型：
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作者：
Chun, Chan Lan;Baer, Donald R.;Penn, R. Lee
二次金属与铁颗粒的缔合影响工程修复系统中的氧化还原反应性。然而，金属添加剂的结构特征和反应性变化的机制尚未完全阐明。在这里，我们合成了铁纳米粒子与Cu，Pd，和Ni含量范围从0-2摩尔%，通过溶液沉积过程（SDP），氢还原过程（HRP），或氢还原的水铁矿共沉淀的金属阳离子（HRCO）。从固态表征的结果表明，合成方法产生类似的铁芯/磁铁矿壳颗粒，但产生的金属添加剂的分布方面的实质性差异。在SDP中，金属添加剂不均匀地分布在颗粒的表面上。金属添加剂在TEM图像中作为HRP和HRCO颗粒上的球形纳米颗粒（5-20 nm）清晰可辨。由于金属是合成过程中不可或缺的，我们假设金属添加剂作为溶质存在于HRCO颗粒的铁芯内。四氯化碳（CT）降解的动力学批实验进行定量比较的颗粒的氧化还原反应性。总体而言，金属添加剂导致CT降解的增强的伪一级速率常数（k（O，CT））相比，铁纳米粒子。对于SDP法和HRP法制备的纳米铁，k（O，CT）随金属添加剂浓度的增加而增加。氯仿产率（Y-CF）的值是独立的身份和金属添加剂的量。然而，HRCO铁颗粒的k（O，CT）和Y-CF均显著增加。结果表明，它是最强烈地影响反应性和产物分布的金属添加剂的分布。例如，对于具有ca的材料。0.9 mol% Ni、反应性和Y-CF变化显著（HRCO > SDP > HRP），并且HRCO-NiFe导致最低的最终氯仿浓度，因为氯仿快速脱氯。此外，长期反应性的连续加标实验表明，金属添加剂的存在通过使得能够更大地利用Fe-0而促进还原。
The association of a secondary metal with iron particles affects redox reactivity in engineered remediation systems. However, the structural characteristics of the metal additives and mechanism responsible for changes in reactivity have not been fully elucidated. Here, we synthesized iron nanoparticles with Cu, Pd, and Ni content ranging from 0-2 mol % via a solution deposition process (SDP), hydrogen reduction process (HRP), or hydrogen reduction of ferrihydrite coprecipitated with the metal cations (HRCO). Results from solid-state characterization show that the synthesis methods produced similar iron core/magnetite shell particles but produced substantial differences in terms of the distribution of the metal additives. In SDP, the metal additives were heterogeneously distributed on the surface of the particles. The metal additives were clearly discernible in TEM images as spherical nanoparticles (5-20 nm) on the HRP and HRCO panicles. Because the metals were integral to the synthesis process, we hypothesize that the metal additive is present as solute within the iron core of the HRCO particles. Kinetic batch experiments of carbon tetrachloride (CT) degradation were performed to quantitatively compare the redox reactivity of the particles. Overall, metal additives resulted in enhanced pseudo-first-order rate constants of CT degradation (k(O,CT)) compared to that of the iron nanoparticles. For the bimetallic iron nanoparticles prepared by SDP and HRP, k(O,CT) increased with the concentration of metal additives. The values of chloroform yield (Y-CF) were independent of the identity and amount of metal additives. However, both k(O,CT) and Y-CF of the HRCO iron particles were significantly increased. Results suggest that it is the distribution of the metal additives that most strongly impacts reactivity and product distribution. For example, for materials with ca. 0.9 mol% Ni, reactivity and Y-CF varied substantially (HRCO > SDP > HRP), and HRCO-NiFe resulted in the lowest final chloroform concentration because chloroform was rapidly dechlorinated. In addition, sequential spike experiments for long-term reactivity demonstrated that the presence of the metal additives facilitated reduction by enabling greater utilization of Fe-0.