Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin Street, 119991, Moscow, Russia.
National University of Science and Technology 'MISIS', 4 Leninsky prospect, 119049, Moscow, Russia.
Anal Bioanal Chem. 2021 Jun;413(15):3999-4012. doi: 10.1007/s00216-021-03351-2. Epub 2021 Apr 24.
Natural nanomaterials, which play a very important role in environmental processes, are so far poorly studied. Firstly, the separation of nanoparticles from the bulk sample is a challenge. Secondly, the absence of reference natural nanomaterials makes it impossible to compare the results obtained by different researchers and develop a unified methodology for the separation and characterization of natural nanomaterials. Therefore, the development of reference natural nanomaterials is an urgent need of the environmental analytical chemistry. In this work, mineral nanoparticles (kaolinite, montmorillonite, muscovite, and quartz) have been studied as potential reference natural nanomaterials. A set of analytical methods including coiled-tube field-flow fractionation, scanning electron microscopy, dynamic light scattering, laser diffraction, inductively coupled plasma atomic emission, and mass spectrometry are applied to the separation and characterization of nanoparticles. It has been shown by laser diffraction that 93-98% of separated mineral nanoparticles are in the size range from about 40 to 300 nm, while 2-7% have size up to 830 nm. The size range of particles is confirmed by electron microscopy. Major (Al, Na, K, Ca, Fe), trace (Ti, Co, Cu, Zn, Tl, Pb, Bi, etc.), and rare earth elements have been determined in the suspensions of kaolinite, montmorillonite, and muscovite nanoparticles. Based on Al content, the concentration of mineral nanoparticles in suspensions is estimated. Agglomeration stability (consistency of size distribution) of nanoparticles at pH 6-8 is assessed. It has been shown that muscovite nanoparticles are stable at pH 7-8, whereas montmorillonite nanoparticles are stable only at pH 8 for at least 4 weeks. A noticeable agglomeration of kaolinite nanoparticles is observed at pH 6-8. Due to the low concentration of quartz nanoparticles, their characterization and stability assessment are hindered. The challenges of the development of reference natural nanomaterials are discussed.
天然纳米材料在环境过程中起着非常重要的作用，但迄今为止研究甚少。首先，从大量样品中分离纳米颗粒是一个挑战。其次，由于缺乏参考天然纳米材料，无法比较不同研究人员获得的结果，并为天然纳米材料的分离和特性制定统一的方法。因此，开发参考天然纳米材料是环境分析化学的迫切需要。在这项工作中，研究了矿物纳米颗粒（高岭土、蒙脱石、云母和石英）作为潜在的参考天然纳米材料。应用了一系列分析方法，包括盘管式场流分级法、扫描电子显微镜、动态光散射、激光衍射、电感耦合等离子体原子发射光谱和质谱法，对纳米颗粒进行分离和特性研究。激光衍射表明，分离出的矿物纳米颗粒中 93-98%的颗粒尺寸在 40-300nm 左右，而 2-7%的颗粒尺寸高达 830nm。电子显微镜证实了颗粒的尺寸范围。在高岭土、蒙脱石和云母纳米颗粒的悬浮液中测定了主要（Al、Na、K、Ca、Fe）、痕量（Ti、Co、Cu、Zn、Tl、Pb、Bi 等）和稀土元素。基于 Al 含量，估算了悬浮液中矿物纳米颗粒的浓度。在 pH 6-8 下评估了纳米颗粒的团聚稳定性（粒径分布的一致性）。结果表明，云母纳米颗粒在 pH 7-8 下稳定，而蒙脱石纳米颗粒在 pH 8 下至少 4 周稳定。在 pH 6-8 下观察到高岭土纳米颗粒明显的团聚。由于石英纳米颗粒的浓度较低，其特性和稳定性评估受到阻碍。讨论了开发参考天然纳米材料所面临的挑战。
