Adsorption of Lysine on Na-Montmorillonite and Competition with Ca2+: A Combined XRD and ATR-FTIR Study

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• 作者：Yanli Yang ; Shengrui Wang ; Jingyang Liu ; Yisheng Xu ; Xiaoyun Zhou
• 刊名：Langmuir
• 出版年：2016
• 出版时间：May 17, 2016
• 年：2016
• 卷：32
• 期：19
• 页码：4746-4754
• 全文大小：601K
• 年卷期：0
• ISSN：1520-5827

文摘

Lysine adsorption at clay/aqueous interfaces plays an important role in the mobility, bioavailability, and degradation of amino acids in the environment. Knowledge of these interfacial interactions facilitates our full understanding of the fate and transport of amino acids. Here, X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) measurements were used to explore the dynamic process of lysine adsorption on montmorillonite and the competition with Ca²⁺ at the molecular level. Density functional theory (DFT) calculations were employed to determine the peak assignments of dissolved lysine in the solution phase. Three surface complexes, including dicationic, cationic, and zwitterionic structures, were observed to attach to the clay edge sites and penetrate the interlayer space. The increased surface coverage and Ca²⁺ competition did not affect the interfacial lysine structures at a certain pH, whereas an elevated lysine concentration contributed to zwitterionic-type coordination at pH 10. Moreover, clay dissolution at pH 4 could be inhibited at a higher surface coverage with 5 and 10 mM lysine, whereas the inhibition effect was inconspicuous or undetected at pH 7 and 10. The presence of Ca²⁺ not only could remove a part of the adsorbed lysine but also could facilitate the readsorption of dissolved Si⁴⁺ and Al³⁺ and surface protonation. Our results provide new insights into the process of lysine adsorption and its effects on montmorillonite surface sites.