Structural and electronic characteristics of molecular models of swollen polyacrylic and sulfostyrene-type cation exchangers in sodium and potassium ionic forms are calculated within the non-empirical HF/basis set method using the MINI Huzinaga basis set and the Firefly program. The obtained data are compared with those for water clusters of a comparable size. The molecular models include four and two monomeric units of corresponding polymers with ten water molecules per functional group; the water clusters contain 20 and 40 water molecules. The following characteristics of the model structure are obtained: the number and the types of the nearest neighbors of cations and water molecules; the distances between the interacting ions and the atoms; the orders of interionic and ion-molecular bonds; binding energy distribution of water molecules in the systems; number and length distributions of hydrogen bonds; the number and character of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text{RCO}_{2}^{-}\cdots {{\text{I}}^{+}},\ \text{RSO}_{3}^{-}\cdots {{\text{I}}^{+}}\ \text{and}\ {{\text{H}}_{\text{2}}}\text{O}\cdots {{\text{I}}^{+}}$$\end{document} bonds. The lengths of hydrogen bonds and the total number of intermolecular and ion-molecular bonds per water molecule in water clusters are established to be similar to those in Na+ and K+ molecular models of ion exchangers. The first coordination layer around both ions is filled with oxygen atoms of water molecules and fixed anions. The coordination numbers of Na+ and K+ are almost equal to those in aqueous solutions. The calculations indicate that direct interaction of Na+ and K+ with the anionic groups is responsible for the difference between their ion exchange selectivities on carboxylic and sulfostyrene ion exchangers. The Na+ ion forms direct largely covalent chemical bonds with the fixed carboxylate anion. The K+ ion forms long electrostatic bonds with the carboxylate group. This accounts for a higher selectivity of Na+ on carboxylic ion exchangers than that of K+. The K+ ion forms long direct electrostatic bonds with the fixed sulfonate anion. The Na+ ion does not form direct bonds with the sulfonate due to strong hydration of the former. This accounts for a higher selectivity of K+ on sulfonic acid resins that that of Na+.

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钠和钾离子在羧酸和磺酸阳离子交换剂上的水合和离子交换选择性之间基本差异的量子化学证据

钠和钾离子形式的溶胀聚丙烯酸和磺基苯乙烯型阳离子交换剂的分子模型的结构和电子特性是在非经验 HF/基组方法中使用 MINI Huzinaga 基组和 Firefly 程序计算的。将获得的数据与具有可比大小的水簇的数据进行比较。分子模型包括对应聚合物的四个和两个单体单元，每个官能团有十个水分子；水簇包含 20 和 40 个水分子。得到模型结构的以下特征：阳离子和水分子最近邻的数量和类型；相互作用的离子与原子之间的距离；离子间键和离子-分子键的顺序；系统中水分子的结合能分布；氢键的数量和长度分布；\ documentclass [12pt] {minimal} \ usepackage {amsmath} \ usepackage {wasysym} \ usepackage {amsfonts} \ usepackage {amssymb} \ usepackage {amsbsy} \ usepackage {mathrsfs} \ usepackage {upgreek} \ setlength 的数量和字符{\oddsidemargin} {- 69pt} \ begin {document} $$ \ text {RCO} _ {2} ^ {-} \ cdots {{\ text {I}} ^ {+}}, \ \ text {RSO} _ {3} ^ {-} \ cdots {{\ text {I}} ^ {+}} \ \ text {and} \ {{\ text {H}} _ {\ text {2}}} \ text { O} \ cdots {{\ text {I}} ^ {+}} $$ \ end {document} 债券。水簇中每个水分子的氢键长度和分子间和离子-分子键的总数被建立为类似于离子交换剂的 Na + 和 K + 分子模型中的那些。两个离子周围的第一个配位层充满了水分子和固定阴离子的氧原子。Na + 和K + 的配位数几乎等于水溶液中的配位数。计算表明 Na + 和 K + 与阴离子基团的直接相互作用是导致它们在羧基和磺基苯乙烯离子交换剂上的离子交换选择性差异的原因。Na + 离子与固定的羧酸根阴离子形成直接的大部分共价化学键。K + 离子与羧酸盐基团形成长静电键。这些解释了 Na + 在羧酸离子交换剂上的选择性高于 K + 的选择性。K + 离子与固定的磺酸根阴离子形成长的直接静电键。由于前者的强水合作用，Na + 离子不与磺酸盐形成直接键。