Mechanism Associated with Kaolinite Intercalation with Urea: Combination of Infrared Spectroscopy and Molecular Dynamics Simulation Studies.
Mechanism Associated with Kaolinite Intercalation with Urea: Combination of Infrared Spectroscopy and Molecular Dynamics Simulation Studies.
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DOI：
10.1021/acs.jpcc.6b10533
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发表时间：
2017-01-12
期刊：
影响因子：
--
通讯作者：
Teppen BJ
中科院分区：
文献类型：
--
作者：
Zhang S;Liu Q;Gao F;Li X;Liu C;Li H;Boyd SA;Johnston CT;Teppen BJ
采用红外光谱和分子动力学模拟研究了尿素在高岭石中的插层行为。红外光谱分析结果表明，高岭石的硅氧烷/氧化铝表面与脲形成了氢键。尿素的羰基（-C=O）作为氢受体的氧化铝表面上的羟基。脲的胺基（-NH 2）作为H-供体与硅氧烷表面上的基础氧和/或氧化铝表面上的羟基的氧相互作用。由分子动力学模拟直接计算的脲与高岭石表面形成的氢键与红外光谱结果一致。此外，分子动力学模拟进一步提供了深入了解尿素与高岭石层间环境的相互作用能。计算的脲分子与高岭石、氧化铝和硅氧烷表面的相互作用能表明，脲在高岭石层间的插层在能量上是有利的。脲与氧化铝表面的相互作用能大于脲与硅氧烷表面的相互作用能，表明氧化铝表面在脲插层高岭石中起主要作用。硅氧烷表面作为H-受体，以促进脲的插层。本研究提供了一个直接的看法，具体的驱动力在高岭土中的尿素插层。所获得的结果可以帮助开发适当的协议，以插入和分层粘土层的粘土为基础的应用和产品。
Intercalation of urea in kaolinite was investigated using infrared spectroscopy and molecular dynamics simulation. Infrared spectroscopic results indicated the formation of hydrogen bonds between urea and siloxane/alumina surfaces of kaolinite. The carbonyl group (–C=O) of urea acted as H-acceptors for the hydroxyl groups on alumina surfaces. The amine group (–NH2) of urea functioned as H-donors interacting with basal oxygens on siloxane surfaces and/or the oxygens of hydroxyl groups on alumina surfaces. The H-bonds of urea formed with kaolinite surfaces calculated directly from molecular dynamics simulation was consistent with the infrared spectroscopic results. Additionally, MD simulations further provided insight into the interaction energies of urea with the kaolinite interlayer environment. The calculated interaction energies of urea molecules with kaolinite alumina and siloxane surfaces suggest that the intercalation of urea within kaolinite interlayers is energetically favorable. The interaction energy of urea with alumina surfaces was greater than that with siloxane surfaces, indicating that the alumina surface plays a primary role in the intercalation of kaolinite by urea. The siloxane surfaces function as H-acceptors to facilitate the intercalation of urea. The present study offers a direct view of the specific driving force involved in urea intercalation in kaolinite. The results obtained can help develop appropriate protocol to intercalate and delaminate clay layers for clay-based applications and products.
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