Amarasinghe Priyanthi M, Katti Kalpana S, Katti Dinesh R
Department of Civil Engineering, North Dakota State University, Fargo, North Dakota 58105, USA.
Appl Spectrosc. 2008 Dec;62(12):1303-13. doi: 10.1366/000370208786822269.
Understanding the rates at which fluid flows into clay interlayers at the molecular level is fundamental to designing an effective clay barrier system. In this work, molecular interactions at the Na-montmorillonite (MMT)-water interface, emphasizing the flow properties of the clay interlayer, have been studied at the molecular and nanoscale level using polarized Fourier transform infrared (FT-IR) spectroscopic and X-ray diffraction (XRD) techniques. Clay-water slurries were smeared on inert gold-coated metal substrates for FT-IR experiments and slurries were smeared on quartz plates for XRD experiments. By analyzing the O-H stretching and H-O-H bending vibrations in clay slurries, it was concluded that the molecular behavior of interlayer water is significantly different from the molecular behavior of bulk water. With increasing clay-water interaction time, it was also seen that the Si-O stretching bands of clay are being significantly altered by the water molecules in the interlayer. Using these spectroscopic techniques we have estimated the time required for water to flow into the clay interlayer. Further, by analyzing the particle size of the clay using atomic force microscopy (AFM) imaging, we were able to estimate the flow velocity of the water in the clay interlayer. This velocity is found to be 3.23 x 10(-9) cm/s. This flow velocity was found to be of the same order of magnitude as the hydraulic conductivity of smectite-type clay reported elsewhere. Also described in this work is the correct positioning of the Si-O out-of-plane vibration band of MMT at the two-layer saturation level in the interlayer. This band was only observed in p-polarized spectra at 1211 cm(-1). Thus, we attribute this band to the Si-O out-of-plane vibration band.
在分子水平上了解流体流入粘土层间的速率是设计有效的粘土屏障系统的基础。在这项工作中，使用偏振傅里叶变换红外（FT-IR）光谱和X射线衍射（XRD）技术，在分子和纳米尺度上研究了钠蒙脱石（MMT）-水界面处的分子相互作用，重点是粘土层间的流动特性。将粘土-水浆料涂抹在惰性金涂层金属基板上进行FT-IR实验，将浆料涂抹在石英板上进行XRD实验。通过分析粘土浆料中的O-H伸缩振动和H-O-H弯曲振动，得出层间水的分子行为与 bulk 水的分子行为有显著差异的结论。随着粘土-水相互作用时间的增加，还可以看到粘土的Si-O伸缩带被层间的水分子显著改变。使用这些光谱技术，我们估计了水流入粘土层间所需的时间。此外，通过使用原子力显微镜（AFM）成像分析粘土的粒径，我们能够估计粘土层间水的流速。发现该流速为3.23×10^(-9) cm/s。发现该流速与其他地方报道的蒙脱石型粘土的水力传导率处于同一数量级。这项工作还描述了MMT的Si-O面外振动带在层间两层饱和水平处的正确位置。该带仅在1211 cm^(-1)的p偏振光谱中观察到。因此，我们将该带归因于Si-O面外振动带。
