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Smectite in bentonite: Near infrared systematics and estimation of layer charge
Applied Clay Science ( IF 5.6 ) Pub Date : 2018-08-01 , DOI: 10.1016/j.clay.2018.01.022
C. Tsiantos , V. Gionis , G.D. Chryssikos

Abstract The facile and accurate measurement of the layer charge of dioctahedral smectite has been demonstrated recently by means of the O-D method, an infrared-based technique capable of recording the exact position of a dangling O-D (O H) bond stretch of interlayer water. The present work attempts to transfer this know-how to the near-infrared (NIR) spectra of natural bentonites in anticipation of even higher throughput capabilities. For this reason, the NIR systematics of ~ 70 bentonites in both natural and Na-exchanged form have been analyzed against the mid-infrared-derived layer charges of the same samples. The as determined layer charges were not biased by the nature of the interlayer cations (Ca2 +, Mg2 +, Na+). A linear correlation between the (ν + δ) combination modes of H2O and Al2OH at ~ 5250 and 4525 cm− 1, respectively, was established, confirmed on a broader collection of bentonite samples, and discussed in terms of interlayer and layer chemistry. The (ν + δ) H2O wavenumber was found to correlate linearly with layer charge, but the slope was dependent on interlayer cation due to the cation-dependence of the bending δ Η2Ο fundamental mode. Additionally, PLS chemometric modeling of the NIR spectra was employed successfully to provide layer charge predictive algorithms, desensitized from the effect of interlayer cation (Ca2 +, Mg2 +, Na+).

中文翻译:

膨润土中的蒙脱石:近红外系统学和层电荷估计

摘要 最近通过 OD 方法证明了双八面体蒙脱石层电荷的简便和准确测量,OD 方法是一种基于红外的技术,能够记录层间水悬空 OD (OH) 键拉伸的确切位置。目前的工作试图将这种专有技术转移到天然膨润土的近红外 (NIR) 光谱中,以期获得更高的吞吐量能力。出于这个原因,已经针对相同样品的中红外衍生层电荷分析了约 70 种天然和 Na 交换形式的膨润土的 NIR 系统学。所确定的层电荷不受层间阳离子(Ca2+、Mg2+、Na+)的性质影响。H2O 和 Al2OH 的 (ν + δ) 组合模式分别在 ~ 5250 和 4525 cm− 1 处线性相关,成立,在更广泛的膨润土样品集合中得到证实,并在层间和层化学方面进行了讨论。发现(ν+δ)H2O波数与层电荷线性相关,但由于弯曲δH2O基模的阳离子依赖性,斜率取决于层间阳离子。此外,NIR 光谱的 PLS 化学计量模型成功地用于提供层电荷预测算法,不受层间阳离子(Ca2+、Mg2+、Na+)的影响。
更新日期:2018-08-01
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