School of Civil and Environmental Engineering, University of Technology, Sydney, Post Box 129, Broadway, NSW 2007, Australia.
Sci Total Environ. 2013 Sep 1;461-462:19-27. doi: 10.1016/j.scitotenv.2013.04.083. Epub 2013 May 25.
Iron oxide nanoparticles are becoming increasingly popular for various applications including the treatment of contaminated soil and groundwater; however, their mobility and reactivity in the subsurface environment are significantly affected by their tendency to aggregate. One solution to overcome this issue is to coat the nanoparticles with dissolved organic matter (DOM). The advantages of DOM over conventional surface modifiers are that DOM is naturally abundant in the environment, inexpensive, non-toxic and readily adsorbed onto the surface of metal oxide nanoparticles. In this study, humic acid (HA) and Suwannee River natural organic matter (SRNOM) were tested and compared as surface modifiers for Fe2O3 nanoparticles (NPs). The DOM-coated Fe2O3 NPs were characterised by various analytical methods including: flow field-flow fractionation (FlFFF), high performance size exclusion chromatography (HPSEC) and Fourier transform infrared spectroscopy (FTIR). The stability of the coated NPs was then evaluated by assessing their aggregation and disaggregation behaviour over time. Results showed that both HA and SRNOM were rapidly and readily adsorbed on the surface of Fe2O3 NPs, providing electrosteric stabilisation over a wide range of pH. HPSEC results showed that the higher molecular weight components of DOM were preferentially adsorbed onto the surface of Fe2O3. As SRNOM consists of macromolecules with a higher molecular weight than HA, the measured size of the SRNOM-coated Fe2O3 NPs was 30% larger than the HA-coated Fe2O3 NPs. FTIR results indicated the occurrence of hydrogen bonding arising from electrostatic interaction between the DOM and Fe2O3 NPs. Finally, a stability study showed that after 14 days, small agglomerates and aggregates were formed. The HA-coated Fe2O3 NPs formed agglomerates which were easily disaggregated using a vortex mixer, with the coated NPs returning to their initial size. However, SRNOM-coated Fe2O3 NPs were only partially disaggregated using the same method, which indicates that these aggregates have a more compact structure.
氧化铁纳米粒子在各种应用中越来越受欢迎，包括受污染土壤和地下水的处理；然而，它们在地下环境中的迁移性和反应性受到其团聚倾向的显著影响。克服这个问题的一个解决方案是用溶解的有机物（DOM）来包裹纳米粒子。与传统的表面改性剂相比，DOM 的优势在于 DOM 在环境中天然丰富、廉价、无毒且易于吸附到金属氧化物纳米粒子的表面。在这项研究中，腐殖酸（HA）和苏万尼河天然有机物（SRNOM）被测试并比较作为 Fe2O3 纳米粒子（NPs）的表面改性剂。用各种分析方法对 DOM 包裹的 Fe2O3 NPs 进行了表征，包括：流场分离（FlFFF）、高效尺寸排阻色谱（HPSEC）和傅里叶变换红外光谱（FTIR）。然后通过评估涂层 NPs 的团聚和分散行为随时间的变化来评估其稳定性。结果表明，HA 和 SRNOM 都能迅速且容易地吸附在 Fe2O3 NPs 的表面，在广泛的 pH 值范围内提供静电稳定作用。HPSEC 结果表明，DOM 的高分子量组分优先吸附在 Fe2O3 的表面。由于 SRNOM 由比 HA 具有更高分子量的大分子组成，因此测量的 SRNOM 包裹的 Fe2O3 NPs 的尺寸比 HA 包裹的 Fe2O3 NPs 大 30%。FTIR 结果表明，DOM 和 Fe2O3 NPs 之间的静电相互作用导致氢键的发生。最后，稳定性研究表明，14 天后，形成了小的团聚体和聚集体。HA 包裹的 Fe2O3 NPs 形成的团聚体很容易通过涡旋混合器分散，涂层 NPs 恢复到初始尺寸。然而，使用相同的方法，只有部分 SRNOM 包裹的 Fe2O3 NPs 被分散，这表明这些聚集体具有更紧凑的结构。
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