School of Civil and Environmental Engineering, University of Technology, Sydney (UTS), Post Box 129, Broadway, NSW 2007, Australia.
Water Res. 2013 Sep 1;47(13):4585-99. doi: 10.1016/j.watres.2013.04.029. Epub 2013 May 9.
Iron nanoparticles are becoming increasingly popular for the treatment of contaminated soil and groundwater; however, their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Assessing their stability under environmental conditions is crucial for determining their environmental fate. A multi-method approach (including different size-measurement techniques and the DLVO theory) was used to thoroughly characterise the behaviour of iron oxide nanoparticles (Fe2O3NPs) under environmentally relevant conditions. Although recent studies have demonstrated the importance of using a multi-method approach when characterising nanoparticles, the majority of current studies continue to use a single-method approach. Under some soil conditions (i.e. pH 7, 10 mM NaCl and 2 mM CaCl2) and increasing particle concentration, Fe2O3NPs underwent extensive aggregation to form large aggregates (>1 μm). Coating the nanoparticles with dissolved organic matter (DOM) was investigated as an alternative "green" solution to overcoming the aggregation issue instead of using the more commonly proposed polyelectrolytes. At high concentrations, DOM effectively covered the surface of the Fe2O3NPs, thereby conferring negative surface charge on the particles across a wide range of pH values. This provided electrostatic stabilisation and considerably reduced the particle aggregation effect. DOM-coated Fe2O3NPs also proved to be more stable under high ionic strength conditions. The presence of CaCl2, however, even at low concentrations, induced the aggregation of DOM-coated Fe2O3NPs, mainly via charge neutralisation and bridging. This has significant implications in regards to the reactivity and fate of these materials in the environment.
铁纳米颗粒在污染土壤和地下水的处理中越来越受欢迎；然而，它们在地下环境中的迁移性和反应性受到其聚集倾向的显著影响。评估其在环境条件下的稳定性对于确定其环境归宿至关重要。本研究采用多方法（包括不同的粒径测量技术和 DLVO 理论）对氧化铁纳米颗粒（Fe2O3NPs）在环境相关条件下的行为进行了全面表征。尽管最近的研究表明，在纳米颗粒的表征中使用多方法方法非常重要，但大多数当前的研究仍然使用单一方法。在某些土壤条件下（即 pH 7、10 mM NaCl 和 2 mM CaCl2）和增加颗粒浓度下，Fe2O3NPs 会发生广泛聚集，形成大的聚集物（>1 μm）。将纳米颗粒用溶解的有机物（DOM）进行涂层处理，被视为克服聚集问题的一种替代“绿色”解决方案，而不是使用更常见的高分子电解质。在高浓度下，DOM 有效地覆盖了 Fe2O3NPs 的表面，从而在很宽的 pH 值范围内赋予颗粒负表面电荷。这提供了静电稳定作用，并大大减少了颗粒聚集的效果。DOM 涂层的 Fe2O3NPs 在高离子强度条件下也表现出更高的稳定性。然而，即使在低浓度下，CaCl2 的存在也会诱导 DOM 涂层的 Fe2O3NPs 聚集，主要是通过电荷中和和桥接。这对这些材料在环境中的反应性和归宿具有重要意义。
