Dynamics of Sodium and Lithium Counter-Ions and Water Molecules in Cation-Exchange Resins as Shown by NMR Spectroscopy
Dynamics of Sodium and Lithium Counter-Ions and Water Molecules in Cation-Exchange Resins as Shown by NMR Spectroscopy
复制标题
核磁共振波谱显示阳离子交换树脂中钠和锂反离子以及水分子的动力学
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
K. Furihata
中科院分区：
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作者：
M. Ohuchi;Peter Meadows;Hiroharu Horiuchi;Y. Sakaki;K. Furihata
通过测量1H、7Li和23Na核磁共振弛豫时间和自扩散系数，研究了阳离子交换树脂中水分子和阳离子（锂和钠反离子）的动力学。研究了五种不同由交联聚苯乙烯磺酸共聚物组成的凝胶型阳离子交换树脂在水和盐水溶液中的膨胀。对大孔型树脂进行了比较研究。从自旋-晶格弛豫时间T1的Arrhenius图中得到的锂离子和钠离子的活化能与树脂的交联有很好的相关性。由于每种树脂中阳离子的T1都比对应水溶液中的T1短，因此树脂中阳离子旋转运动的相关时间更长。树脂交联度越高，阳离子的旋转运动就越慢，越受限制。采用脉冲场梯度核磁共振法直接测定了凝胶型树脂中水分子和锂、钠反离子的自扩散系数。这些物种的平移扩散与类似T1的树脂交联密切相关。在高交联树脂中，水分子和阳离子的扩散变慢。Li+离子和水分子的表观扩散系数随扩散时间的变化而变化。这可以解释为凝胶-杂孔型离子交换树脂在三维网络结构中的扩散受限。
The dynamics of water molecules and cations (lithium and sodium counter-ions) in cation-exchange resins were investigated by measuring relaxation time and self-diffusion coefficients of 1H, 7Li, and 23Na NMR. Five gel-type cation-exchange resins with different by the crosslinked poly(styrene sulfonic acid) copolymer swollen in water and salt aqueous solution were studied. A macroporous-type resin was studied for comparison. Activation energy for the lithium and sodium ions obtained from the Arrhenius plots of spin-lattice relaxation times T1 correlated well with the cross-linking of resins. Since T1 of the cations in every resin are shorter than in corresponding aqueous solution, the correlation time of the rotational motion of cations is longer in the resins. With higher cross-linking of the resin, the rotational motion of the cations becomes slower and more restricted. Self-diffusion coefficients of water molecules and lithium and sodium counter-ions in the gel-type resin were directly measured by pulsed field-gradient NMR methods. Translational diffusion of these species was closely related to the cross-linking of resin similar to T1. The diffusion of water molecules and cations becomes slower in higher cross-linked resin. Apparent diffusion coefficients of Li+ ions and water molecules were dependent on diffusion time. This may be explained by restricted diffusion in a three dimensional network structure of gel-heteroporous type ion-exchange resins.